Transmission lip seal performance testing is key step toward product certification.After all laboratory tests are complete, basic design configurations proven and material properties verified, the next step is to witness the performance of a lip seal "in action." Automatic transmission builders, in the past, relied on inhouse verification programs; or they contacted private testing laboratories to help predict performance and durability of the six to eight lip seals found in modem transmissions. But with new customer/supplier concepts, such as partnering, single source supply and product certification Product certification or product qualification is the process of certifying that a certain product has passed performance and/or quality assurance tests or qualification requirements stipulated in regulations such as a building code and nationally accredited test standards, , the old way is not enough. Acadia is the first elastomer elastomer (ĭlăs`təmər), substance having to some extent the elastic properties of natural rubber. The term is sometimes used technically to distinguish synthetic rubbers and rubberlike plastics from natural rubber. products supplier to the automotive industry The automotive industry is the industry involved in the design, development, manufacture, marketing, and sale of motor vehicles. In 2006, more than 69 million motor vehicles, including cars and commercial vehicles were produced worldwide. to provide supplierbased performance testing Performance Testing covers a broad range of engineering or functional evaluations where a material, product, or system is not specified by detailed material or component specifications: Rather, emphasis is on the final measurable performance characteristics. of lip seals in their natural habitat. Their transmission seal tester (TST TST 1 Toxic shock toxin 2 Treadmill stress test, see there ) puts lip seals through their operational paces, installed in the customer's own clutch housings. The bottom line: Accelerated life testing confirms that lip seals will perform reliably and provide durability over the operational life of the transmission. Automatic transmission designers and manufacturers continually pursue new designs that advance automatic transmission state-of-the-art. From the outside, it does not look like much has changed., But inside, servos, pistons Pistons can mean:
adj. Having or showing shrewdness and discernment, especially with respect to one's own concerns. See Synonyms at shrewd. [Latin ast purchasers of automobiles and heavy duty equipment with components and parts that will outlive out·live tr.v. out·lived, out·liv·ing, out·lives 1. To live longer than: She outlived her son. 2. the vehicle. Extremely crucial components, such as elastomeric seals, and in particular, lip-seals for clutch-applied pistons that regulate transmission functions, have met the developmental challenge. Original automatic transmission designs, dating back to the early 1940s, required only a few lip seals for clutches that provided just forward, reverse and neutral. Today's typical transmission requires approximately eight lip seals to power additional features such as low forward, overdrive (processor) Overdrive - An Intel Pentium processor which fits into a socket designed to accomodate an Intel 486, or into a special upgrade socket on the motherboard. , coast, etc.; all packaged in basically the same housing envelope. A lip seal holds in place eight or more quarts of automatic transmission fluid Automatic transmission fluid (ATF) is the fluid used in vehicles with a self shifting or automatic transmission. It is typically colored red to distinguish it from motor oil and other fluids in the vehicle. (ATF ATF Molecular virology Activating transcription factor A cellular protein that stimulates transcription of adenovirus E4 transcription unit, which acts early in infection at any of several 'enhancer' binding sites ) at approximately 300 [degree] F and assures that all functions are performed as intended. They perform in an environment that grows more hostile due to various additives in the ATF, higher temperatures, closer proximity designs and the need for faster, smooth response of apply/release clutch piston functions. Lip seal variations Space is not available to provide a complete dissertation dis·ser·ta·tion n. A lengthy, formal treatise, especially one written by a candidate for the doctoral degree at a university; a thesis. dissertation Noun 1. on lip seal form, fit and function. But briefly, probably the most widespread use of lip seals is on accumulators, servos and clutch pistons in automatic transmissions. In terms of vehicle operation and customer awareness, the lip seal is the most critical component. Each clutch piston has an inner and outer lip seal that seals the piston as it strokes to apply the clutch. Seal design alternatives vying vy·ing v. Present participle of vie. vying vie for transmission applications include molded and machined seals, long lip and short lip seals and the newer design, one-piece piston/seal combinations. Lip seals permit relaxed tolerances on piston groove diameter and width, bore diameter and finish, out of round, etc., which translates into lower manufacturing costs. The lip deflects to conform as needed as needed prn. See prn order. . The full permissible per·mis·si·ble adj. Permitted; allowable: permissible tax deductions; permissible behavior in school. per·mis tolerance range is usually not used because close fit is often required for piloting and other purposes not associated with sealing. Also, lip seals will compensate for a range of relative temperature changes in the piston and the bore. A key feature of lip seals is their ability to provide zero leakage LEAKAGE. The waste which has taken place in liquids, by their escaping out of the casks or vessels in which they were kept. By the act of March 2, 1799, s. 59, 1 Story's L. U. S, 625, it is provided that there be an allowance of two per cent for leakage, on the quantity which shall appear , where only a minute amount of leakage is desirable and needed for lubrication lubrication, introduction of a substance between the contact surfaces of moving parts to reduce friction and to dissipate heat. A lubricant may be oil, grease, graphite, or any substance—gas, liquid, semisolid, or solid—that permits free action of of the contact area of the lip. It is apparent that configuration, leak characteristics, along with elastomer material selection and performance are all critical issues when designing or modifying a lip seal. The availability of the TST equipment accelerates analysis of all components of design, so that the optimum seal for the specific application can be selected with the confidence that it will perform as intended. The Acadia TST The Acadia lip seal test machine provides a cyclic cyclic /cyc·lic/ (sik´lik) pertaining to or occurring in a cycle or cycles; applied to chemical compounds containing a ring of atoms in the nucleus. cy·clic or cy·cli·cal adj. 1. pressure input of heated automatic transmission fluid into automatic transmission clutch housings. Fluid migration into the closed system is through "one-way" check valves (Mech.) a valve in the feed pipe of a boiler, or other conduit, to prevent the return of the feed water or other fluid. - Knight. See also: Check installed in-line with each clutch housing. The test chamber contains six clutch housings and provides an enclosure for liquid nitrogen Noun 1. liquid nitrogen - nitrogen in a liquid state atomic number 7, N, nitrogen - a common nonmetallic element that is normally a colorless odorless tasteless inert diatomic gas; constitutes 78 percent of the atmosphere by volume; a constituent of all living , the cooling medium for the clutch housings. ATF expelled during testing is collected in stainless steel stainless steel: see steel. stainless steel Any of a family of alloy steels usually containing 10–30% chromium. The presence of chromium, together with low carbon content, gives remarkable resistance to corrosion and heat. reservoirs and then weighed. A computer program converts the weight measurement into an equivalent volume value, and then produces tabular tab·u·lar adj. 1. Having a plane surface; flat. 2. Organized as a table or list. 3. Calculated by means of a table. tabular resembling a table. and graphic representations for leak rate analysis. Basic operating constraints CONSTRAINTS - A language for solving constraints using value inference. ["CONSTRAINTS: A Language for Expressing Almost-Hierarchical Descriptions", G.J. Sussman et al, Artif Intell 14(1):1-39 (Aug 1980)]. of the TST are an operating temperature range of -40 [degree] F to +250 [degree] F, a maximum ATF pressure of 400 psi PSI - Portable Scheme Interpreter and a maximum ATF flow rate of 16 gallons per minute. The clutch piston cycle rate can be as high as 60 cycles per minute, but this rate is highly dependent on fluid viscosity and controlling orifice orifice /or·i·fice/ (or´i-fis) 1. the entrance or outlet of any body cavity. 2. any opening or meatus.orific´ial aortic orifice sizes. To facilitate filling of the clutch housings and reducing transient pressure spikes, the slowest feasible cycle rate is established for most testing. Leak rate analysis The TST has six analytical weighing balances with 0.1 gram resolution and a maximum capacity of 6,100 grams. The balances are transducers that monitor leak rate by weight; weight is subsequently converted into volume by the computer program. Hard copy tabular and graphic representations of ATF leak rates are produced. In operation, after all bench mark calibrations have been locked in, the clutch pistons are cycled in accordance with the needs of the specific tests. Typically, test cycles are from 100,000 to 250,000. However, for testing of transmissions used on heavy duty equipment, over a million cycles may be required. A monitor screen displays test status information including environmental conditions, cycles, status, current weights, leak rates, cycle rates and abort (1) To exit a function or application without saving any data that has been changed. (2) To stop a transmission. (programming) abort - To terminate a program or process abnormally and usually suddenly, with or without diagnostic information. parameters. The test operator can easily observe all critical parameters and respond if corrective action A corrective action is a change implemented to address a weakness identified in a management system. Normally corrective actions are instigated in response to a customer complaint, abnormal levels if internal nonconformity, nonconformities identified during an internal audit or is needed. Using set-up parameters, the computer calculates current weight by dividing the grams indication on each balance by the density of the specific ATF. Leak rate is the product of current weight, minus the weight from five minutes ago, all divided by five minutes. Leak rate calculation, for the production of the graphs, is a differential five point moving average. This filtering of the data results in a reduction of large leak rate spikes, while still providing a very good indication of actual leak rate. TST in action A test program completed on the TST will provide data for leak rate analysis, and will also furnish fur·nish tr.v. fur·nished, fur·nish·ing, fur·nish·es 1. To equip with what is needed, especially to provide furniture for. 2. , for visual inspection, used lip seals that have performed for the equivalent of 100,000 miles or more. A program may be requested either by the manufacturer of the transmission, the seal design team, or Acadia's engineers. The subject seals may be based on entirely new design concepts, or may have just a slight modification, such as a change in shape that is intended to simplify installation. Tests are conducted: * When comparison of performance of molded versus machined lip seals is required; * To verify material changes that are made to lower cost or improve function; * When configuration modifications are made to solve installation problems; * On prototype bonded piston seals, proposed to replace standard loose lip seals; * When failure analysis is required; * During prototype development work. The following examples, abstracted from actual test programs, document obtainable results. Example I Five sets of short lip seals were obtained to determine the leak rate of the seals over the 100,000 cycle life of the test, and to provide for a visual inspection to determine wear and/or deterioration de·te·ri·o·ra·tion n. The process or condition of becoming worse. of the seals. ATF supplied by the customer was heated and cycled through clutch housings at 300 psi [+ or -] 15 psi at a rate of 25 cycles per minute, for 100,000 cycles. Then the lip seals and housings were removed and inspected. Only two seals exhibited any leakage with approximately 0.12 mi/min. being the maximum encountered (see accompanying graphs). Final visual inspection showed minimal wear to the lip or heels of any of the seals. Two OD seals had small cuts on the sealing lip and two other seals showed slight abrasions on the sealing lip. One of each of the parts leaked, but neither exceeded 0. 12 ml/min. The last seal showed no abrasions and no leakage. The tests determined that it was likely that the abrasions and cuts occurred while installing the seals in the fixtures, since some difficulty was encountered during the process. The short lip seals worked well with no seal exceeding the 1.0 mi/leak failure criteria, even with the damage to the sealing lips. The test results support the claim that the short lip seals should perform well under similar conditions in actual application. Exmaple 2 This test program analyzed an·a·lyze tr.v. an·a·lyzed, an·a·lyz·ing, an·a·lyz·es 1. To examine methodically by separating into parts and studying their interrelations. 2. Chemistry To make a chemical analysis of. 3. performance of prototype adhesives for one-piece seals used in transmissions for heavy duty equipment. After a total accumulation of 400,000 cycles, all adhesives were performing satisfactorily and all seals were exhibiting no leakage, except one bonded piston seal. which was removed. Test parameters were: Temperature: 194 [degree] F [+ or -] 1.5 [degree] F Pressure: 400 psi [+ or -] 15 psi Cycles/minute: 14.3 The leak rate history on the seal where the adhesive adhesive, substance capable of sticking to surfaces of other substances and bonding them to one another. The term adhesive cement is sometimes used in place of adhesive, especially when referring to a synthetic adhesive. failed fluctuated between 3 and 10 ml/minute. The seal was removed, cleaned and reinstalled, but continued to leak until it was rotated rotated turned around; pivoted. rotated tibia see rotated tibia. at approximately 160,000 cycles. The leak rate continued to fluctuate after a brief period of low leakage that occurred immediately following rotation. The leak rate then stabilized sta·bi·lize v. sta·bi·lized, sta·bi·liz·ing, sta·bi·liz·es v.tr. 1. To make stable or steadfast. 2. at an average of less than 1.0 ml/minute until the adhesive failed at 350,000 cycles. Inspection of the failed bond revealed that the OD sealing lip had split resulting in a tear that opened the lip approximately 50 mm. The split was near the center of a fracture found in the stress concentration area at the base of the lip on the sealing side. The fracture existed for about a 140 degree arc on the part. The rubber tore back, exposing the adhesive. Example 3 This test program was conducted to provide data on the comparative leak rate of molded and machined outer forward clutch lip seals. Six transmission clutch housings, and machined lip seals and molded lip seals for the outer forward clutches were delivered by the transmission builder. The six clutch housings were provided with fittings and check valves to allow migration of an ATF into and out of the housings. The ATF was transmitted to the clutch housings at a temperature of 250 [+ or -] 5 [degree] F and a pressure of 300 [+ or -] 10 psi. The cycle rate was 60 [+ or -] I cycles per minute allowing the clutch housings to experience a pressure of from 0 [+ or -] 10 psi to 300 [+ or -] 10 psi. Throughout the cycle test, the clutch housings were fixtured at 30 [+ or -] 10 degrees from horizontal to facilitate ATF draining into a stainless steel reservoir. Each reservoir was independently positioned on a 0.1 gram resolution analytical balance analytical balance n. A balance for chemical analysis. Noun 1. analytical balance - a beam balance of great precision used in quantitative chemical analysis chemical balance in order to record the fluid leak rate. The approximate conversion of weight of ATF to volume is: 1.0 grams is equivalent to 1.15 ml. The leak rate analyses (see table) consisted of evaluating three machined lip seals in housings designated as #1. #2 and #3, and three molded lip seals in housings #4, #5 and #6. Following the predetermined pre·de·ter·mine v. pre·de·ter·mined, pre·de·ter·min·ing, pre·de·ter·mines v.tr. 1. To determine, decide, or establish in advance: test duration of 150.000 cycles, the lip seals were removed and molded lip seals were subsequently installed in housings #1, #2 and #3 and machined lip seals were utilized in #4. #5 and #6. The cyclic test was again performed for a duration of 150,000 cycles. The greatest leak rate attained for any hourly collection period was 39.5 grams (45.4 ml) during cycle test 2 for a molded lip seal. Conclusion Automatic transmission state-of-the-art continues to advance as new elastomer materials and new, more effective seal configurations meet performance challenges. The Transmission Seal Tester allows accelerated testing of all aspects of lip seal design so that transmission designers can select, with confidence, the optimum seal for each specific application. Accelerated life testing confirms that lip seals will perform reliably and provide durability over the operational life of the transmission.
Table 1 - cycle test number 1 - accumulated
leak data (grams of AFT)
Machined Molded
housing housing
Time designation designation
(hrs.) Cycles 1 2 3 4 5 6
0.5 1,880 0.0 0.2 0.0 0.6 6.5 5.2
1.5 5,310 0.0 0.5 0.0 1.3 15.5 13.1
2.5 8,910 0.0 0.8 0.0 2.3 23.8 22.3
3.5 12,540 0.3 0.8 0.0 3.6 29.7 29.0
4.5 16,510 0.3 0.8 0.0 4.3 34.2 33.7
5.5 19,880 0.3 0.8 0.0 4.8 37.1 36.4
6.5 23.610 0.3 0.8 0.0 5.3 39.1 39.0
7.5 27,390 0.3 0.9 0.0 5.9 40.7 40.7
8.5 34,410 0.7 1.1 0.5 6.7 42.4 42.2
10.5 37,950 0.7 1.1 0.5 7.4 42.6 42.2
20.5 73,900 1.0 1.1 0.5 11.5 45.7 44.3
30.5 109,700 1.0 1.1 0.5 12.9 53.5 49.3
40.5 145,180 1.0 2.0 0.5 14.0 59.3 60.8
41.5 148,750 1.0 2.0 0.5 14.0 59.4 61.9
41.8 150,000 1.0 2.0 0.5 14.1 59.4 62.3
Table 2 - cycle test number 2 - accumulated
leak data (grams of AFT)
Molded Machined
housing housing
Time designation designation
(hrs.) Cycles 1 2 3 4 5 6
1.0 3,590 0.0 37.1 2.1 0.0 0.0 13.4
2.0 7,200 0.0 67.6 5.1 0.0 0.0 17.6
3.0 10,800 0.0 96.9 7.9 0.0 0.0 21.7
4.0 14,400 0.0 126.8 10.7 0.0 0.0 25.5
5.0 18,000 0.3 159.6 13.5 0.0 0.0 29.6
6.0 21,600 1.4 196.0 16.0 0.0 0.0 33.7
7.0 25,200 2.4 235.5 18.5 0.0 0.0 37.8
8.0 28,200 3.4 271.4 20.7 0.0 0.0 41.8
9.0 32,400 4.3 305.3 22.9 0.0 0.0 45.8
10.0 36,000 5.2 336.2 24.7 0.0 0.0 53.6
11.0 39,600 6.0 364.0 26.6 0.0 0.0 53.6
12.0 43,200 6.8 391.5 28.4 0.0 0.0 57.4
13.0* 46,800 7.5 422.4 30.1 0.0 0.0 61.2
14.0 50,400 8.1 439.2 30.1 0.0 0.0 61.3
15.0 54,000 8.6 443.7 30.1 0.0 0.0 61.3
16.0 57,600 8.7 444.6 30.1 0.0 0.0 61.5
17.0 61,200 8.8 444.6 30.1 0.0 0.0 61.5
18.0 64,800 8.9 444.6 30.1 0.0 0.0 61.6
19.0 68,400 9.0 444.6 30.1 0.0 0.0 62.5
20.0 72,000 9.0 444.6 30.1 0.0 0.0 63.1
30.0 108,000 9.0 444.6 30.1 0.0 0.0 73.2
40.0 144,000 21.3 444.6 30.1 0.0 0.0 87.2
41.0 147,600 22.5 444.6 30.1 0.0 0.0 88.6
41.7 150,000 23.2 444.6 30.1 0.0 0.0 889.2
*Short interruption in tesst to change flow rate of pump to
cause more pronounced pulsing of piston and clutch
plates.
|
|
||||||||||||||||
Printer friendly
Cite/link
Email
Feedback
Reader Opinion