Patent Application
20150147198
The present invention generally relates to automotive and other vehicles, and more specifically, to a wheel for such a vehicle which includes a pump for automatically inflating a pneumatic tire mounted on the wheel.
Low tire pressure is a major cause of excessive fuel consumption, tire wear, and impaired steerability. A typical pneumatic tire will leak about 25 percent of its pressure per year due to rubber's inherent permeability. It is thus good practice to check/maintain tire pressure on a regular basis.
However, even checking tire pressure every few weeks may not prevent these adverse affects when a slow leak is present, and the leak may go undetected unless a careful record is maintained of how frequently the pressure in each tire has to be replenished. A fast leak or flat condition may rapidly cause damage to the tire and even render it unusable in a short period of time even though this condition may go unnoticed by an inexperienced driver until it is too late.
It is thus desirable to have some mechanism that automatically replenishes the tire pressure when it is lower than its optimal amount. Conventional tire pumps may be mounted on vehicle wheels and utilize centrifugal force to automatically pump air from the atmosphere into a tire cavity and thereby maintain the tire pressure at a predetermined value.
These pumps may be two-stage pumps with a piston radially movable in a cylinder to draw air from the atmosphere into a primary chamber and pump air from a secondary chamber into the tire cavity when the piston is moved outward by centrifugal force resulting from movement of the vehicle and rotation of the wheels. The piston may be moved inward by a spring when the vehicle stops to transfer air from the primary chamber into the secondary chamber. In order to keep the mass of the piston and the force and size of the spring within practical limits, the piston and spring may be made small enough that the piston may begin to move outward in response to a small centrifugal force resulting from a low vehicle speed.
This causes a problem when the vehicle is operated at low speed in the rain, and/or on terrain including loose particulate matter such as dirt or sand. If the pump does not have an inlet filter, operation under such adverse conditions may cause contaminants to be drawn into the pump and clog the inlet and outlet valves and/or even be pumped into the tire. If the pump does have an inlet filter, the filter may become clogged. These conditions may render the pump inoperable.
Friction between the piston and the wall of the cylinder when the pump is operating also may cause wear and reduction of the service life of the pump. Since pneumatic tires typically leak slowly, an automatic tire pump may only be required to operate during a fraction of the time the vehicle is running to maintain the pressure at the optimal value. Conventional tire pumps may operate continuously, and are thereby subjected to more wear than is necessary.
Another conventional pump may be mounted to a vehicle's wheel and be powered by the wheel's motion during normal vehicle operation thereby maintaining an optimal tire inflation pressure. The pump may be a positive displacement, piston-type compressor wherein the piston responds to the centrifugal force generated by the wheel's rotation or to the vertical acceleration generated by the wheel's response to bumps in the road. The piston may be a small diameter, but may include an upper extension made of dense material. Thus, there may be sufficient mass responding to rotation or the motion from bumps to move the piston and create the necessary pressure for inflation. The piston may be returned by a spring once the forces acting upon the piston decline due to a slow vehicle speed, a smooth driving surface, or both.
The pump may include inlet and outlet check valves. The pump/inflator may be mounted to the wheel either within the tire cavity or external to the tire. If the centrifugal forces of rotation are to propel the piston, the axis of the cylinder may be oriented radially. If the pump is designed to be energized by the wheel's reaction to bumps in the road, it may be oriented tangential to a circle centered at the wheel axis. It may also have a double acting piston. Compression would then take place when the compressor would be approximately at 3:00 o'clock or 9:00 o'clock in its rotation with the wheel as a bump would be hit by the wheel.
For the case of centrifugal force for piston action, there may be one compression stroke for each excursion of automobile speed from stationary or some minimum speed up to the automobile speed which translates into adequate rotational speed to generate the needed piston force to create air flow into the tire cavity. For the case in which bumps in the road actuate the piston, the compression strokes may be more random than the bumps themselves since the strokes would only occur when the axis of the compressor would be aligned in its rotation to a direction more or less parallel with the wheel motion caused by the bump.
Pressure regulation may be provided by designing the pump's compression ratio to limit the delivery pressure to that desired to be the maximum tire inflation pressure. Compression ratio may be the ratio of cylinder volume at the start of a piston stroke to the volume remaining in the cylinder at the end of the piston's stroke. Compression ratio for a given basic design may be set at the time of manufacture by either limiting the piston travel or by providing additional “dead” volume within the piston. One method for this may be to drill a hole in the bottom of the piston at the time of manufacture, the depth of the hole being set to obtain the desired pressure development.
When the pump is actuated by centrifugal force, the pump may work with the piston gradually progressing along the cylinder against the compressed charge of air in the cylinder as the vehicle accelerates and the wheel rotation rate increases. Once the charge of air exceeds the existing tire pressure plus the discharge valve cracking differential pressure, any increased vehicle speed causes additional stroke movement of the piston and discharge of the compressed air into the tire cavity. As the vehicle slows or stops, the piston return spring may have returned the piston to its location at the beginning of its stroke and the pumping process may begin again with new vehicle motion. With typical passenger car operation including many stops and starts, the pump may deliver a small charge of air each time the vehicle accelerates from a speed low enough to allow the piston return spring to return the piston to a speed high enough to force the piston to compress air and discharge compressed air into the tire cavity.
In order to maximize the force available for driving the piston to compress the air in the cylinder, the piston may have an enlarged end made of dense material. The enlarged end may be opposite the end of the piston that fits into the cylinder, with its diameter being larger than the piston diameter. The enlarged end may be constructed of brass, lead, and/or other high density material(s). This conventional pump may eliminate extra tire wear and fuel consumption caused by underinflated tires. Where only a small leak occurs, this pump may extend mileage before the tire becomes completely uninflated or flat.
A pumping device in accordance with the present invention is used with a pneumatic tire mounted on a tire rim to keep the pneumatic tire from becoming underinflated. The pumping device includes a housing attached to the tire rim, a dynamic mass mechanically confined to radial movement relative to the housing and the tire rim, an intake port for ambient to enter the housing, and an exhaust port for forcing air into a tire cavity of the pneumatic tire for restoring air loss from an inflation volume within the tire cavity.
According to another aspect of the present invention, the dynamic mass is mechanically confined to radial movement within the housing.
According to still another aspect of the present invention, the dynamic mass changes position corresponding to a rotational speed of the tire rim.
According to yet another aspect of the present invention, a plane about which the dynamic mass moves is coplanar with a rotational plane of the tire rim.
According to still another aspect of the present invention, movement of the dynamic mass transfers work energy to air pressure in the housing.
According to yet another aspect of the present invention, a first check valve is disposed proximate to the intake port for preventing air from flowing out of the housing.
According to still another aspect of the present invention, a second check valve disposed proximate to the exhaust port for preventing air from flowing out of the tire cavity and into the housing.
According to yet another aspect of the present invention, a biasing element returns the housing from a high volume intake condition to a low volume exhaust condition.
According to still another aspect of the present invention, the first check valve and the second check valve are self checking ball-type check valves.
According to yet another aspect of the present invention, a bladder receives ambient air from within the housing and forces pressurized air into the tire cavity.
According to still another aspect of the present invention, the housing receives ambient air from an exterior of the housing and exhausts pressurized air to the tire cavity simultaneously.
According to yet another aspect of the present invention, a lever arm is pivoted by radial movement of the dynamic mass.
According to still another aspect of the present invention, a biasing member restores the dynamic mass to an initial position.
According to yet another aspect of the present invention, a mechanical fastener fixes the pumping device to the tire rim.
According to still another aspect of the present invention, an adhesive fixes the pumping device to the tire rim.
According to yet another aspect of the present invention, a second housing is attached to the tire rim diametrically opposite the first housing.
According to still another aspect of the present invention, the pumping device also restores air loss from an inflation volume within a second tire cavity of a second pneumatic tire.
According to yet another aspect of the present invention, the biasing member is attached to two tabs on the pumping device.
According to still yet another aspect of the present invention, additional biasing members are added to additional tabs to increase the force restoring the dynamic mass to the initial position.
The pump housing 70 may have one or more chambers and corresponding valves 80. A biasing element 90, such as a spring, may be incorporated to return the chamber volume from a high volume condition (
The device 220 may provide generally radially outward movement of the dynamic mass 260 to sequentially affect a simultaneous intake and exhaust stroke, thereby eliminating a need for a biasing element to affect either an intake or exhaust stroke. The device 220 may include multiple and/or reversing RPM changes (such as an initial acceleration, deceleration and/or second acceleration) to affect one full intake/exhaust cycle of the device 220. To affect this simultaneous stroke, the dynamic mass 260 may move radially inward thereby drawing air into the pump housing 270 and also compressing a bladder 290 to force air into the tire cavity 50. The pump housing 270 may have one or more chambers and corresponding valves 280. The valves 280 may be configured to allow the pump housing 270 to intake air from the exterior and to exhaust the inspired air from the bladder 290 to the tire cavity 50.
Another variation of the devices 20, 220, 520, 620 may be electro-mechanical in nature. Harvesting of mechanical energy from the movement of the dynamic masses 60, 260, 560, 660 may be converted to stored electrical energy in a capacitive device (not shown) utilizing an electro-mechanical device, then released by the same or a different electro-mechanical device to affect the operation of the devices. Further, the assemblies 10, 200, 500, 600 may be mounted to a rim 30 in several ways. The devices 20, 220, 520, 620 may be configured to utilize existing rim features and eliminate the need to modify the rim 30 in any way. One such mounting may utilize an inflation valve access hole in the rim wall to provide both a fastening point an ambient air intake port. Such a mounting may integrate the inflation valve function in the structure of the devices 20, 220, 520, 620, or interface with an industry standard inflation valve. The devices 20, 220, 520, 620 may be configured to be mounted at any position on a rim 30 and within the tire cavity 50, generally, but not necessarily, requiring modification of the rim 30 for structurally fixing the devices to the rim and providing an access port for the intake of ambient air.
While the rim mounted assemblies 10, 200, 500, 600 have been shown in
While a certain representative examples and details have been shown for the purpose of illustrating the present invention, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit or scope of the present invention.
