Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Electrical signal parameter measurement system
Reexamination Certificate
2001-03-27
2003-08-19
Shah, Kamini (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Electrical signal parameter measurement system
C073S146000, C451S254000
Reexamination Certificate
active
06609074
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to methods of measuring pneumatic tire uniformity and, more particularly, to methods of predicting high speed tire uniformity.
BACKGROUND OF THE INVENTION
In the art of manufacturing pneumatic tires, rubber flow in the tire mold or minor differences in the dimensions of the belts, beads, liners, treads, plies of rubberized cords, etc., sometimes cause non-uniformities in the final tire. Non-uniformities of sufficient amplitude will cause force variations on a surface, such as a road, against which the tires roll producing vibration and noise. When such force variations exceed an acceptable maximum level, the ride and handling of a vehicle utilizing such tires will be adversely affected. It is known that the magnitudes of the force variations change with the speed of tire rotation, generally (but not always) increasing in magnitude with speed, therefore a vehicle operator's perception of tire quality (and vehicle ride) will be most influenced by the force variations occurring at high speeds such as “highway speeds” of, for example, 100 kilometers per hour (Kph) and higher. Accordingly, purchasers of tires, especially large volume purchasers such as vehicle manufacturers (“OEMs”), would prefer to know and specify maximums for high speed force variations on purchased tires. Unfortunately, direct measurement of high speed force variations on tires is difficult and expensive, therefore the industry has devised a variety of equipment and methods for predicting high speed tire performance (uniformity, force variations) based on statistical sampling and on simpler measurements primarily including “low speed” tire uniformity measurements, and possibly also measurements of tire balance.
During the typical tire manufacturing process, factory floor measurements of tire uniformity are performed on tire uniformity machines (“TUMs”) which are used to monitor the quality of the tire production process and may guide or incorporate corrective measures such as grinding to improve the balance and uniformity of a tire. A factory floor TUM is a low speed unit, typically operated at 60 rpm (revolutions per minute) which corresponds to less than 10 Kph for a typical passenger car tire. The low speed TUM is also known in the industry as a “low speed uniformity machine” or “LSU”. In general, a tire uniformity machine subjects a tire to normal conditions of mounting, inflation, load, and rotation (at low speed) while collecting measurement data on variations of force, and sometimes also deflection (e.g., “runout”), and instantaneous angular velocity. A tire uniformity machine typically includes an assembly for rotating a test tire against the surface of a freely rotating loading wheel. In such an arrangement, the loading wheel is acted upon in a manner dependent on the forces exerted by the rotating tire and those forces are measured by appropriately placed measuring devices, connected to the supporting structure of the loading wheel. When a tire being tested yields unacceptable results, shoulder and center rib grinders are used to remove a small amount of the tire tread at precisely the location of non-uniformities detected by the measuring devices. As the tire is rotated, it is measured and ground simultaneously. In a sophisticated, low speed production tire uniformity machine, such as a Model No. D70LTX available from the Akron Standard Co. of Akron Ohio, the force measurements are interpreted by a computer and rubber is removed from the tire tread using grinders controlled by the computer.
Once a tire undergoes correction for force variations in a TUM, it is common manufacturing practice to remove the tire from the TUM and place the tire in a balance machine to measure the amount of imbalance of the tire. Typically, the tires are mounted in the balance machine in a manner similar to that of the tire uniformity machine and inflated to a preset pressure. Then, the static (single-plane) and couple (two-plane) imbalances are measured by one of a variety of well-known methods. When a tire is found to be imbalanced to an unacceptable level, the tire is ordinarily scrapped.
The assumption generally made in the art is that the factory floor measurements of tire quality are reasonably related to high speed tire performance, so that placing “suitable” limits on tire imbalance and on low speed force variations will produce tires that have acceptable high speed performance. A common technique for establishing the suitable limits is to measure individual tires at both high speed and low speed and then mathematically relate the two measurements. In this technique's simplest conceptual form, a tire is found which exhibits the maximum allowable high speed force variation, and then the magnitude of the low speed force variation measured for the same tire is used as the suitable limit. It is known that the relationship between high speed force variation and low speed force variation can be different for different tire constructions (designs) and for different low and high speed tire uniformity machines, so this technique must be repeated for each variation of tire and machine. In many cases, it is desired to be able to predict the magnitude of high speed force variations from factory floor measurements, and so inventive effort, detailed hereinbelow, has been applied to the determination of mathematical equations (including “transfer functions”) to relate various combinations of factory floor measurements to predicted high speed force variations.
Before discussing transfer functions and prediction methods, it is important to understand the various measurements that are involved. Tire performance in terms of vibration (and noise caused by tire vibration) at any given tire rotational speed is substantially determined by tire uniformity and is directly indicated by the magnitude of force variations which occur as the tire rolls under load on a surface. If the surface is a tire uniformity machine load wheel that is instrumented to measure forces, then the forces can be measured to report a direct measurement of the tire's vibration performance (i.e., uniformity) for the tire speed at which it is measured. Since high speed tire uniformity measurements are impractical for large volume factory floor use, low speed TUM measurements must be utilized to predict high speed measurements. The problem is that with low speed TUMs, certain force variations are either too small to be accurately measured at low speeds, or else a measurement of a particular low speed force variation is not sufficient to predict the high speed variation of that force. For these certain force variations, low speed force measurements must be supplemented or replaced with other measurements including, for example, measurements of: other types of force variation, tire imbalance, tire surface displacement (runout), tire stiffness variation, tire angular velocity variation and load wheel angular velocity variation.
In the art, forces on a tire which is rolling under load on a load bearing surface are commonly broken down into three orthogonal components which will be primarily referred to herein as: radial, lateral, and tangential. Radial forces act in the tire's radial direction, i.e., perpendicular to the tire's axis of rotation. Radial forces are strongest in the vertical direction (e.g., wheel “hop”) as the tire interacts with the load bearing surface, but may also have a horizontal (fore-aft, or “surge”) component due to, for example, the radial centrifugal force of a net mass imbalance in the rotating tire. Lateral forces act in a direction parallel to the tire's axis of rotation, and generally occur where the tire's surface touches the load bearing surface. Lateral force causes either tire wobble or a constant steering force. Tangential force, or fore-aft force is experienced at the surface of contact between tire and load bearing surface in a direction both tangential to the tire's outer circumference (e.g., tread surface) and perpendicular to the ti
Cohn Howard M.
The Goodyear Tire & Rubber Company
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