Measuring and testing – Rotor unbalance – Dynamic
Reexamination Certificate
1999-12-23
2001-09-25
Moller, Richard A. (Department: 2856)
Measuring and testing
Rotor unbalance
Dynamic
C700S279000, C340S870160, C073S146300, C073S146400, C073S146500
Reexamination Certificate
active
06293147
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to wheel balancers with the capability of monitoring and setting pneumatic tire pressure.
BACKGROUND OF THE INVENTION
Wheel balancers reduce operational vibrations of vehicular tire and wheel assemblies by the calibrated placement of correction weights. An example of such a wheel balancer is the Hunter GSP 9700 Vibration Control System; for which the Operation Instructions, Software Version 1.3, Form 4202T, O7-99© Copyright 1997 Hunter Engineering Company, is expressly incorporated herein by reference. Referring to Section 5 of the GSP 9700 Operating Instructions, vibrations in tire and wheel assemblies can be caused by: imbalance; non-uniform sidewall stiffness (force variation); bent or out-of-round rims; out-of-round tires and combinations thereof. The theory, analysis and correction of these factors with wheel balancers and the GSP 9700 in particular is described in the afore cited GSP 9700 Operating Instructions.
As described in a note of emphasis from Sect 2.2 OEM-Matching™ of the GSP 9700 Instructions: “It is important that the air pressure of the tire is set to specifications prior to the Road Force Measurement™. Incorrect tire pressure will affect the results.” It is also well known in the art that extreme tire pressure errors can cause imbalance measurement errors. Most importantly, tires which arc either over inflated or under inflated are likely to have premature failures resulting in possibly serious injuries.
Accomplishing pneumatic vehicle tire vibration reduction with a wheel balancer thus requires an accurate tire inflation pressure. To accomplish this during a balancing procedure introduces challenges: The optimization of pressure for the characteristics of the tire, vehicle, environmental conditions and operational circumstances may require frequent or exacting adjustments. The wide range of tire sizes and variations in construction stiffness make it difficult during a balancing procedure to prejudge how long to fill or release gas to reach a desired pressure, thereby involving costly time investments for precision.
Some common automatic pressure adjustment systems use mechanical valving/setting devices. Because the pressure reading instrument used by such devices is not located in the tire but rather upstream in the relatively restricted passages of the filling apparatus, a correct pressure reading can not be made during the actual filling. Hence, gas filling is performed in pulses to allow pressure reading between pulses. These systems operate by brute force trial and error without provision to compensate for differing degrees of mispressurization and are hence time wasting. The inability to improve efficiency by not learning from prior attempts or adjusting for differing tire volumes and stiffnesses can impose further delays. The mechanical nature of these devices also causes a substantial increase in the amount of time between fill stages as the tire pressure approaches the dialed in pressure. Finally, the accuracy of such systems is typically marginal, requiring continuous rechecking with a separate gauge.
Some prior art computer controlled pressure adjustment systems incorrectly assume a constant, linear relationship between the gasflow rate and the tire's physical characteristics. The tire's rate of pressurization vs. gasflow rate can vary, depending on the tire's pressure at a given moment. Such systems also assume constant gas supply pressure. Within a vehicle service center there are often multiple demands being put on a compressed gas supply system simultaneously. A computer controlled system can be greatly slowed in setting the pressure or inhibited from doing so accurately without the capacity to account for these changing conditions.
SUMMARY OF THE INVENTION
The present invention provides for a wheel balancer with an integrated, time-efficient, attention sparing system for the automatic, accurate gas pressurization of pneumatic vehicle tires that are being balanced. The system may include in combination with the wheel balancing apparatus a pneumatic device, an electronic computer in control of the pneumatic device and a graphic display interface also in connection with the computer. The interface serves to show the current pressure reading, the target pressure reading, the mode of operation, whether the pressure is unstable and the user's input.
The pneumatic device includes a connecting passage for a governed flow of gas, a source of pressurized gas, a pressure transducer, one or more exhaust ports and an attachment that connects to and opens a pneumatic tire valve stem. The pressure source, exhaust ports, and tire valve connection are connected to the gas flow through the passage by one or more governors, such as valves, which are selectively operated under the computer's direction. The governors may operate individually or in various combinations, as well as allow bidirectional, unidirectional or prevent gas flow. The governors all normally operate under the computer's direction, except for safety provisions in advent of a power failure to allow for the venting of potentially dangerous pressures.
The present invention can utilize the graphic interface, in one variation a CRT, to provide the user with ongoing measurement results, input control settings and current status in a single image to enhance comprehension speed and control ease. The graphic interface may be selected to appear immediately upon attachment of the device to the tire valve or after a flexibly chosen delay following removal of the tire valve attachment from its home storage position, thereby eliminating another demand on the user's attention. The interface can also selectively depict pressure in U.S. or International units, thus removing unnecessary visual clutter while still maintaining flexibility of worldwide utility.
The electronic computer enables the invention to quickly correct the tire pressure without user attention. Among the computer program's features are a “hands-off” control process where merely attaching the pneumatic system to the tire valve triggers the system to automatically determine if the pressure is correct and, if not, determine if the tire requires inflation or deflation and initiate the appropriate correction procedure. Additionally, the program accomplishes the pressure adjustment by a learning algorithm that can account for the current measured pressure, the target pressure, system criteria, pressurization history, the tire's gas temperature and available individual vehicle and wheel data to minimize the pressure adjustment time.
A nearby tire changer, for example, may cause a momentary source pressure drop to where a resulting next filling pulse duration is too long, or a pressure source compressor shutoff in filling mid-pulse will cause an irregularly increasing gas supply pressure and thus a first pulse overshooting the pressure target. Continuous learning by adjustment of the fill interval after each pulse allows real time adaptation to fluctuating pressure sources. The system learns from misses and typically hits the pressure target accurately on the next interval.
The learning capacity also compensates for nonlinear fill or deflation characteristics of the tire and the gas components. Most notably, when filling from a low tire pressure, most tire designs cause tire pressure rates of increase, with a constant source pressure, that are less than when the tire body is stretched by the tire's higher internal pressure. To make an assumption of a constant fill interval in these cases, therefore, would cause an error on the high side and likely cause the fill pulse to overshoot the desired pressure. At pressures near tire manufacturer ratings, most tires cause pressure to increase linearly with input gas flow rate as the tire behaves akin to a rigid vessel, and compensation is rarely required. However, the learning algorithm is still applied in event of unanticipated tire designs and particularly, to adjust for possible error in a long previous interva
Colarelli, III Nicholas J.
Douglas Michael W.
Parker Paul Daniel
Hunter Engineering Company
Moller Richard A.
Thompson & Coburn LLP
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