Patent Application
20150147199
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 linear movement relative to the housing and the tire rim, the dynamic mass moving in response to shock loads transferred from the tire rim to the dynamic mass and pumping ambient air into the housing, an intake port for ambient air to enter the housing, and an exhaust port for forcing pressurized 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 relative to the pneumatic tire.
According to still another aspect of the present invention, the dynamic mass changes position corresponding to a shock loads from a contact surface to the pneumatic tire.
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 is 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 gear rotates to pump pressurized air from the housing and forcing 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 into the tire cavity simultaneously.
According to yet another aspect of the present invention, a gear rotates by movement of the dynamic mass.
According to still another aspect of the present invention, a biasing member restores an actuation cam to an initial position.
According to yet another aspect of the present invention, a slot arm rotates by movement of the dynamic mass.
According to still another aspect of the present invention, two coaxial gears rotate by movement of the dynamic mass.
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, two springs return the dynamic mass to a neutral position.
According to still another aspect of the present invention, an additional spring returns a cam to an initial position.
According to yet another aspect of the present invention, two slot arms rotate an actuation cam in a single direction.
An air pumping device in accordance with the present invention may be utilized with a tire rim and pneumatic tire. The pumping device may affixed to the tire rim for the purpose of restoring air loss from an inflation volume of the pneumatic tire. The pumping device may include a dynamic mass mechanically confined to movement about a transmission mechanism and a pumping chamber.
The dynamic mass may change position in response to shock loads created between the pneumatic tire and the road surface as the pneumatic tire travels along a road having raised or depressed features (e.g., potholes, speed bumps, unevenness, etc.). The plane about which the dynamic mass moves may be coplanar with respect to the rotational plane of the tire rim, or only slightly askew, so as to be most responsive to the shock loads and vibration generated by traveling along the road. The change in position of the dynamic mass may in turn transfer work energy to an input element of a transmission device. The transmission device may in turn apply mechanical advantage to the work energy in any number of ways determined to be desirable to operate the pumping device, which is dynamically linked to an output element of the transmission device.
A shock sensitive air pumping device in accordance with the present invention may not rely on changes in tire rim rotation speed and may therefore harvest energy from a tire rim that is accelerating, decelerating, and/or at constant rotation speed as long as provided adequate road imperfection or unevenness is present to yield or produce a shock to the tire rim. By comparison, a device dependent upon RPM changes is limited in energy harvesting potential where vehicle driving routine is predominately constant velocity travel with few speed changes (such as in long haul trucking).
The dynamic mass may be configured with one or more biasing elements design to return the mass to a neutral position upon the cessation of shock loads. The neutral position may be substantially within the range of motion allowed by the mounting of the dynamic mass, about which the dynamic mass may move in either of two opposing directions in response to a shock acting generally in the rotational plane of the tire rim. The transmission element may be designed to harvest the work energy generated by the shock unrelated to the direction of movement of the dynamic mass, thereby increasing the efficiency of the air pumping device to harvest available energy from shock producing features available on the road surface. The movement path of the dynamic mass relative to the tire rim may be radial, tangential, axial, and/or a combination thereof. The movement path direction may define the rotational angular positions, relative to the tire contact patch, at which the most efficient energy harvesting may be expected.
The biasing means, specifically the means that returns the dynamic mass to a neutral position in the absence of shock loads, may be tuned relative to the mass, and vise versa, to establish an appropriate resonant frequency. Such a frequency may be established to increase or decrease the sensitivity of the bias-mass system to particular shock load profiles. Of particular interest may be the potential to tune the air pumping device to shock profiles offering a maximum energy to the air pumping device under nominal road conditions and vehicle driving routines.
The air pumping device may include one or more chambers and multiple valves. The chamber volume may be altered by the mechanical motion of the dynamic mass. One or more biasing elements, such as springs, may be incorporated to return the chamber volume from a high volume to a low volume, or vise versa. The valves may be configured to allow the chamber to intake air from the exterior of the inflation space and to exhaust the inspired air to the interior of the inflation space (e.g., a tire cavity). The valves may be selfchecking, or may be mechanically opened and closed under the influence of an auxiliary mechanism (e.g., electrical, pneumatic, hydraulic, etc.). A pressure regulating element may be included for the purpose of limiting the ability of the air pumping device to elevate the pressure of the inflation space beyond a preferred level. Upon sensing a target pressure, or as the target pressure is approached, the regulating element may suddenly or progressively disable the air pumping device by locking, releasing, closing, opening, etc. any number of functional elements such as ports, valves, mechanical linkages, etc.
The transmission device may allow various interaction modes between the dynamic mass and the air pumping device. One such transmission device may result in the mechanical integration of numerous movement reversals of the dynamic mass to affect a single intake and exhaust cycle, thereby allowing a wide degree of shock magnitudes to be captured, stored, and/or periodically released to drive operation of the air pumping device. Another transmission device may allow a variable mechanical advantage profile to exist over a full range of movement of the dynamic mass, thereby allowing work energy from the dynamic mass to be balanced with the variable energy requirement of the air pumping device. Still another transmission device, particularly one in which a biasing element is present in the air pumping device, may utilize the work energy of the dynamic mass to affect the exhaust of air from the air pumping device or, alternatively, the intake of air into the air pumping device.
The air pumping device may be mounted to the tire rim in several ways. First, the air pumping device may utilize existing rim features and eliminate the need to modify the rim in any way. For example, the air pumping device may utilize the inflation valve access hole in the tire rim wall to provide both a fastening point and an ambient air intake port. Such a mounting may integrate the inflation valve function into its structure, or interface with an industry standard inflation valve. Second, the device may be configured to be mounted at any position on the tire rim and within the inflation space or tire cavity, generally, thereby not requiring modification of the tire rim to structurally ground the air pumping device to the tire rim and providing an access port for the intake of ambient air.
The air pumping device in accordance with the present invention may lead to lower operating costs for vehicle owners and provide tire manufacturers additional options for achieving government mandated performance measures.
The pump housing 70 may have one or more chambers and corresponding valves 80. Biasing elements 90, such as springs, may be incorporated to return the chamber volume from a high volume condition (
The device 320 may provide generally radially movement of the dynamic mass 360 to sequentially affect an intake stroke or an exhaust stroke, thereby eliminating a need for a biasing element to affect either an intake or exhaust stroke. The device 320 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 320. To affect this full stroke, the dynamic mass 360 may move in one direction or an opposite direction thereby rotating an actuation cam 380 that enacts linear movement of the pump shaft 370 for the intake/exhaust stroke of a pump chamber 390 to force air into the tire cavity 50. The pump housing 370 may have one or more chambers and corresponding valves (not shown), similar to the arrangement of
The dynamic mass 360 may transfer linear shock energy to a first gear 361 in one linear direction and a second gear 362 in a second opposite linear direction, each rotating the actuation cam 380 incremental amounts in a single rotational direction. Biasing elements, such as the springs 365 may return the dynamic mass 360 to its neutral position. A biasing element 375 may bias the shaft 370 in a single linear direction.
The device 420 may provide generally radially movement of the dynamic mass 460 to sequentially affect an intake stroke or an exhaust stroke, thereby eliminating a need for a biasing element to affect either an intake or exhaust stroke. The device 420 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 420. To affect this full stroke, the dynamic mass 460 may move in one direction or an opposite direction thereby rotating an actuation cam 480 that enacts linear movement of the pump shaft 470 for the intake/exhaust stroke of a pump chamber 490 to force air into the tire cavity 50. The pump housing 470 may have one or more chambers and corresponding valves (not shown), similar to the arrangement of
The dynamic mass 460 may transfer linear shock energy to a first slot arm 461 in one linear direction and a second slot arm 462 in a second opposite linear direction, each rotating the actuation cam 480 incremental amounts in a single rotational direction. Biasing elements, such as the springs 465 may return the dynamic mass 460 to its neutral position. A biasing element 475 may bias the shaft 470 in a single linear direction.
The device 520 may provide generally radially movement of the dynamic mass 560 to sequentially affect an intake stroke or an exhaust stroke, thereby eliminating a need for a biasing element to affect either an intake or exhaust stroke. The device 520 may include multiple and/or reversing RPM changes (such as an initial acceleration, deceleration and/or second acceleration) to affect one full single directional intake/exhaust cycle of the device 520. To affect this full stroke, the dynamic mass 560 may move in one direction or an opposite direction thereby rotating an actuation cam 580 that enacts linear movement of the pump shaft 570 for the intake/exhaust stroke of a pump chamber 590 to force air into the tire cavity 50. The pump housing 570 may have one or more chambers and corresponding valves (not shown), similar to the arrangement of
The dynamic mass 560 may transfer linear shock energy to a single gear 561 in one linear direction and in a second opposite linear direction, only one direction rotating the actuation cam 580 incremental amounts in a single rotational direction. Biasing elements, such as the springs 565 may return the dynamic mass 560 to its neutral position. A biasing element 575 may bias the shaft 570 in a single linear direction.
The device 620 may provide generally radially movement of the dynamic mass 660 to sequentially affect an intake stroke or an exhaust stroke, thereby eliminating a need for a biasing element to affect either an intake or exhaust stroke. The device 620 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 620. To affect this full stroke, the dynamic mass 660 may move in one direction or an opposite direction thereby rotating an actuation cam 680 that enacts linear movement of the pump shaft 670 for the intake/exhaust stroke of a pump chamber 690 to force air into the tire cavity 50. The pump housing 670 may have one or more chambers and corresponding valves (not shown), similar to the arrangement of
The dynamic mass 660 may transfer linear shock energy to a single slot arm 661 in one linear direction and in a second opposite linear direction, only one direction rotating the actuation cam 680 incremental amounts in a single rotational direction. Biasing elements, such as the springs 665 may return the dynamic mass 660 to its neutral position. A biasing element 675 may bias the shaft 670 in a single linear direction.
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While the rim mounted assemblies 10, 300, 400, 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.
