Boots – shoes – and leggings
Patent
1995-04-07
1997-12-16
Trammell, James P.
Boots, shoes, and leggings
36455101, G01M 1500
Patent
active
056992521
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FILED AND INDUSTRIAL APPLICABILITY
This invention relates to internal combustion engines and more specifically to the removal of acceleration effects and the correction of cyclical errors that occur in the detection of misfits/roughness in an internal combustion engine. The methods according to the invention can also be applied to the determination of speed and acceleration measures corrected for cyclic errors for other purposes, such as, for example, precision spark advance control, adaptive braking control, and automatic transmission control.
BACKGROUND ART
In the recent past, Federal regulations have restricted the amount of pollutants that may be emitted into the atmosphere by an automobile. One method of meeting these restrictions is the use of a catalytic converter in the exhaust system which converts harmful exhaust emissions into harmless products. However, when a cylinder does not fire properly, raw fuel may be dumped into the exhaust system and thus into the catalytic converter. Due to the temperatures in the exhaust/catalyst, the raw fuel may ignite and cause irreparable damage to the converter's ability to reduce exhaust emissions. Even should burning not occur, the catalyst's ability to function properly may be inhibited if the air/fuel mixture deviates substantially from stoichiometry. To protect the catalyst, it is advantageous then to be able to detect when cylinders misfire so that appropriate steps can be taken.
In the course of normal operation of an internal combustion engine, engine torque fluctuations about a mean level occur as a result of the summed effect of the torque production in individual cylinders and the mechanics of the torque production process. These torque fluctuations give rise to engine speed fluctuations which can be monitored and used, on a cylinder by cylinder basis, to gain a measure of the mean torque produced by the engine. Also available on a cylinder by cylinder basis is a separate measure of the average net torque over the firing interval of any cylinder. Net torque, as used herein, means the difference between the torque produced by the engine and the load on the engine. With an accurate measure of the average net torque over a cylinder firing interval, a misfiring cylinder can be detected.
In Citron et al, U.S. Pat. No. 4,532,592, an index of performance, IP, is calculated for each cylinder. The IP is the difference in measures of the speed at top dead center, TDC, for two successive cylinders. An acceleration measure is formed from these two speed measures to normalize the result with respect to engine speed. It is shown that the index of performance is directly proportional to the integrated net torque over the firing interval of the first cylinder. The method disclosed in U.S. Pat. No. 4,532,592 provides for use of the index of performance in an engine performance monitor and control system. The method assumes that the engine is operating at steady state. When the engine is not at steady state the contribution of the acceleration to each speed measure at TDC must be removed.
To obtain the sharpest measure of the associated steady state speed at TDC, and hence the best measure of the mean pressure torque variation on a cylinder by cylinder basis, not only must acceleration effects be removed, but account must be taken of the fact that measurement errors exist. For example, tooth spacing error on the toothed wheel from which raw IP data is obtained must be taken into account. U.S. Pat. No. 4,532,592 assumes that digital filtering of the speed waveform will be employed, if required, to remove such effects. That the magnitude of these errors is significant is demonstrated by FIG. 1, which shows results from rotating an 18 tooth speed measurement wheel from a vehicle on a lathe at a constant 2500 rpm. Note that the tooth spacing errors cause a 2% peak to peak error in the calculated speed. The calculated speed is determined by assuming position measures of the 18 teeth are evenly spaced 20 degrees apart, and counting the clock counts that occur b
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Armfield Jeffrey S.
Citron Stephen J.
Miller Craig Steven
Purdue Research Foundation
Trammell James P.
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