Measuring and testing – Tire – tread or roadway
Reexamination Certificate
2001-12-10
2003-07-01
Williams, Hezron (Department: 2855)
Measuring and testing
Tire, tread or roadway
Reexamination Certificate
active
06584836
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to the measurement of tire uniformity with a tire uniformity machine, and more specifically to an improvement in prediction made possible by the removal of machine contributions to the measurement data.
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 completed tire. Non-uniformities of sufficient amplitude will cause force variations on a road surface against which the tires roll, producing vibration and noise. When such variations exceed an acceptable maximum level, the ride and handling of a vehicle utilizing such tires will be adversely affected.
Tire uniformity machines 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. In general, a tire uniformity machine subjects a tire to normal conditions of mounting, pressurization, rotation and load while collecting measurement data on variations of deflection, forces, moments, and velocity. A tire uniformity machine typically includes an assembly for rotating a tire against the surface of a rotating loading wheel. In this testing arrangement, the loading wheel is moved in a manner dependent on the forces exerted by the rotating tire and those forces are measured by appropriately placed measuring devices. When a tire being tested yields unacceptable results, shoulder and/or center rib grinders are used to remove a small amount of the tire tread at precisely the location of the non-uniformities detected by the measuring devices. In a sophisticated tire uniformity machine, the measurements are stored and interpreted in digital form by a computer, and rubber is removed from the tire tread using grinders controlled by the computer. Examples of machines utilizing these methods are disclosed in U.S. Pat. Nos. 3,739,533; 3,946,527; 4,914,869 and 5,263,284.
Unavoidably, tire uniformity machines are not themselves perfectly uniform, and tire uniformity measurement signals may include an erroneous contribution from the tire uniformity machine itself. In effect, minor variations in the design, construction and operation of a tire uniformity machine contribute to variations of deflection, forces, moment or velocity, which contaminate the tire uniformity measurements with a machine contribution.
As noted by U.S. Pat. No. 4,404,848 ('848), it is often the case that measured values contain errors due to rotation deflections of the rims that grip the inspected tire and/or the load wheel of the tire uniformity machine. In addition, small deflections occur due to the deterioration of parts, for example, by rust or by bruises that occur during use of the inspecting machines. A method to correct these types of errors is disclosed by the '848 patent wherein the radial runout of the load wheel is measured without a tire in place, to obtain an erroneous deflection signal. The erroneous deflection signal is then multiplied by the spring constant of the measured tire and subtracted from the measured value of the radial force obtained from the tested tire.
U.S. Pat. No. 4,404,849 describes a method for correcting errors of measurement due to variations in tire pressure in a tire uniformity inspecting operation.
U.S. Pat. No. 5,614,676 ('676) describes a method of vibration analysis for tire uniformity machines by using signals from load cells when the machine idles. The signals are sent to a computer that outputs an alarm signal when the amplitude of vibration at selected frequencies exceeds acceptable levels.
U.S. Pat. No. 6,257,956, incorporated herein by reference, teaches a method for correcting errors of measurement made on tire uniformity machines by identifying and removing machine contributions from tire uniformity measurements. The method of the patent includes calculating the effect of the average machine contribution to the measured values of production tire uniformity as measured by a tire uniformity machine. The machine contribution signal is subtracted from the production tire measurement signals to provide a more accurate basis to evaluate the uniformity of a production tire and guide, as necessary, corrective measures. The method primarily includes the steps of performing one or more tire uniformity measurements on a test tire, and storing the average test tire uniformity measurement data to use as an indicator of the average machine contribution to tire uniformity measurements. When a production tire is measured on the same tire uniformity machine, the stored machine contribution data/signal is subtracted from the production tire data/signal to produce a corrected production tire uniformity measurement.
U.S. Pat. No. 5,396,438 (K. L. Oblizajek, assigned to General Motors Corporation), incorporated in its entirety by reference herein, discloses a method of manufacturing tires which preferably includes measurement of two or more low speed tire parameters, by determining transfer functions which are used to calculate predicted highway speed (high speed) force variations, and then comparing high speed values predicted for production tires to predetermined criteria for controlling manufacture of the production tires.
As described in application Ser. No. 09/817,983 filed Mar. 27, 2001, incorporated herein by reference, 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”. 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. 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 scrapped.
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 or fore-aft force is experienced at the surface of contact between the tire and the load bearing surface in a direction both tangential to the tire's outer circumference (e.g., tread surface) and
Johanning Gregory Scott
Shteinhauz Gregory David
O'Planick Richard B
The Goodyear Tire & Rubber Company
Wheeler David E
Williams Hezron
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