微型轎車五菱宏光手動變速箱設(shè)計(jì)[三軸五檔汽車變速器],三軸五檔汽車變速器,微型,轎車,五菱宏光,手動,變速箱,設(shè)計(jì),五檔,汽車,變速器 Effects of gear selection of an agricultural tractor on transmission andPTO load during rotary tillageYong-Joo Kima, Sun-Ok Chungb,*, Chang-Hyun ChoicaMachinery Technology Group, Advanced R&D Center, LS Mtron Ltd., Anyang, Republic of KoreabDepartment of Biosystems Machinery Engineering, Chungnam National University, Daejeon, Republic of KoreacDepartment of Bio-mechatronic Engineering, Sungkyunkwan University, Suwon, Republic of Korea1. IntroductionAgricultural tractors are used as a power source for various fieldoperations such as tillage, planting, chemical application, harvest-ing, transportation, through driving axles, power take off (PTO)devices, and hydraulic lines. The number of agricultural tractors isincreasing in many countries in the world. For example, theutilization ratio of a tractor in Korea has been increased to 71.8% ofagricultural working days during the spring and autumn seasons in2010 (Park et al., 2010a,b). A tractor has various levels of drivingand PTO gear settings, and different combinations of the gearsettings are used to provide the required power suitable for anoperation type and field condition.Optimum gear setting for operation type is important since theload acting on the tractor, part durability and working performanceare determined by the gear setting (Park et al., 2010c). Durability oftractor parts is one of the important concerns (Rotz and Bowers,1991). Simens and Bowers (1999) reported that American farmersspent about 40% of the total maintenance costs to repair the tractorand about 30% to repair the failure of powertrain parts due toexcessively high operating speeds. Also, working performanceaffects fuel consumption of the tractor. In the case of the Republicof Korea, annual fuel consumption by tractors was 345 ML/year,accounting for about 48.5% of the total annual fuel consumption ofagricultural machinery (KAMICO and KSAM, 2010). Therefore, itwould be meaningful to analyze effects of gear selection on tractorload during field operations.Kichler et al. (2011) analyzed the effects of the transmissiongear selection on the tractor performance and reported a 105%increase in fuel consumption rate, a 28% increase in implementdraft, and a 255% increase in required power when the gear settingwas changed from 3.0 km h?1to 8.3 km h?1in plow tillage. SeveralSoil & Tillage Research 134 (2013) 9096A R T I C L E I N F OArticle history:Received 15 December 2012Received in revised form 26 July 2013Accepted 27 July 2013Keywords:Agricultural tractorGear selectionTransmissionPTO (power take off)Load severenessRotary tillageA B S T R A C TFor better performance and durability of a tractor during field operations, it is necessary to select theoptimal gear setting for the operation. The purpose of this study was to analyze effects of the gearselection on load acting on the transmission and PTO shafts of a 75 kW agricultural tractor during rotarytillage with a 20-cm tillage depth. In order to measure the loads acting on the transmission and PTO inputshafts, a load measurement system was installed on the tractor. The system consisted of strain-gaugesensors to measure the torque on the transmission and PTO input shafts, a radio telemetry I/O interfaceto acquire the sensor signals, and embedded software to acquire the data. Rotary tillage was conducted atthree ground speeds and three PTO rotational speeds under upland field sites with the same soilconditions. The load data was converted to a load spectrum using the rain-flow counting and SWT (SmithWatson Topper) equations. Sum of damage due to the load was calculated using the Modified Minersrule for each gear selection, and then the load severeness was calculated as the relative magnitude of thedamage sum. The average torque on the transmission input shaft increased significantly as the groundspeed increased from L1 (1.87 km h?1) to L3 (3.77 km h?1) at the same PTO rotational speed. Also, theaverage torque on the PTO input shaft increased as the PTO rotational speed increased at the sameground speed. Rotary tillage exerted significantly greater loads on the PTO input shaft than on thetransmission input shaft. The severeness of the load on the transmission and PTO shafts increased,indicating possible decreased fatigue life, as both the ground and PTO rotational speeds increased.Results of the study might provide information useful for optimum gear selection for rotary tillage,considering not only field efficiency, but load severeness on the transmission and PTO input shafts.? 2013 Elsevier B.V. All rights reserved.* Corresponding author at: Department of Biosystems Machinery Engineering,Chungnam National University, Daejeon 305-764, Republic of Korea.Tel.: +82 42 821 6712; fax: +82 42 823 6246.E-mail address: sochungcnu.ac.kr (S.-O. Chung).Contents lists available at ScienceDirectSoil & Tillage Researchjou r nal h o mep age: w ww.els evier .co m/lo c ate/s till0167-1987/$ see front matter ? 2013 Elsevier B.V. All rights reserved.http:/dx.doi.org/10.1016/j.still.2013.07.013studies have analyzed tractor load during field operations (Gerlach,1966; Van et al., 2009) for efficient and optimum design of a tractor(Han et al., 1999). Most studies on the load analysis have focusedon the transmission since it makes up about 30% of the total tractorcosts (e.g., Kim, 1998). For analysis of the transmission load,researchers analyzed torque load acting on the transmission inputshaft and the driving axle shafts of the tractor during fieldoperations such as plow tillage (Kim et al., 2001; Nahmgung,2001). The load on the transmission input shaft and the drivingaxle shafts increased with plowing speed in most of the fieldconditions.Some research considered load on PTO shafts during rotarytillage and baling operations. Kim et al. (2011b) analyzed powerconsumption of a tractor with a rated engine power of 75 kWduring baler operation and reported that ratios of the powerconsumption to the engine power were 5075% for all PTO gearlevels. Also, Kim et al. (2011a) analyzed power requirement ofmajor components (driving axles, PTO shaft, and hydraulic pumps)of a 30 kW agricultural tractor during plow tillage, rotary tillage,and loader operations. Rotary tillage required the greatest power,and the PTO shaft experienced the greatest amount of the poweramong the components during the process. Summarizing thefindings above, considerable amount of the load was applied onPTO shaft during rotary tillage. However, research related to theeffects of transmission (i.e., operation speed) and PTO gearselection on the tractor load during field operations has not beenreported.This study was an attempt to provide guidelines for theoptimum gear setting, considering both field efficiency and loadsevereness of the major power transmission parts. The purpose ofthis study was to analyze effects of gear selection on loads actingon the transmission and PTO shafts of a 75 kW agricultural tractorduring rotary tillage.2. Materials and methods2.1. Measurement systemA 75-kW agricultural tractor (L7040, LS Mtron Ltd., Korea) wasused in this study. The tractor had a total mass of 3260 kg anddimensions of 4077 mm ? 2000 mm ? 2640 mm(length ? width ? height). The rated engine power and the PTOpower of the tractor at an engine revolution speed of 2300 rpmwere 75 kW and 65 kW, respectively. The tractor was equippedwith a Synchro-mesh type manual transmission composed of twodirection-gears, four main-gears, and four sub-gears. The 16forward and 16 backward ground speeds of the tractor weredetermined by combination of the gear settings. The PTO rotationalspeeds of the tractor at P1, P2, and P3 settings were 540 rpm,750 rpm, and 1000 rpm, respectively. Fig. 1 shows the torquetransducers and radio telemetry systems fitted on the transmissionand PTO input shafts for load measurement. The transmission andPTO input shafts were connected directly to the engine crankshaft;therefore, the speed ratio between the engine crankshaft and theshaft was 1:1. The load measurement system was installed insideof the clutch housing. The load measurement system wasconstructed with strain-gauge sensors (CEA-06-250US-350,MicroMeasurement Co., USA) to measure torque, radio telemetryI/O interfaces (R2, Manner, Germany) to acquire the sensor signals,and an embedded system to analyze the load. For load measure-ment of the transmission, a strain-gauge with a rotor antenna wasinstalled on the transmission input shaft, and a stator antenna wasinstalled on the shaft case. For PTO load measurement, a strain-gauge was installed on the flywheel-sleeve, and a rotor antennaand a stator antenna were installed on the flywheel and enginecase, respectively. The embedded system had the maximumresolution of 24 bits. Load signal from the strain gauges of thecalibrated torque transducers was digitized with a sampling rate of19.2 kHz at a 24-bit resolution and stored in the embedded system(MGC, HMB, Germany). A program to measure the load signal wasdeveloped based on Labview software (version 2009, NationalInstrument, USA).2.2. Experimental methodsThe load acting on the tractor during field operation depends onmany factors such as soil condition and driver skill. Because takingall of these factors into consideration was not practical (Nahm-gung, 2001), effects of these factors were minimized in the study tofocus on effects of ground speed and PTO rotational speed on theload through gear selection.Rotary tillage was conducted at three ground speeds and threePTO rotational speeds in upland field sites located at 3585902300and3585902600North and 12781205600and 1278130300East. The soil typewas sandy, the average water content was 22.3%, and the averagecone index was 1236 kPa, over the depths of 0250 mm.The tillage depth was set as 20 cm. The transmission gear wasset to at L1, L2, and L3 gears to match with PTO gears of P1, P2, andP3, respectively. The gear settings were selected based on theresults of a survey for the annual usage ratio of tractor reported byKim et al. (2011a). The ground speeds of the tractor at L1, L2, and L3were 1.87 km h?1, 2.64 km h?1, and 3.77 km h?1and the PTOrotational speeds at P1, P2, and P3 were 540 rpm, 750 rpm, and1000 rpm, respectively. The rotary tillage tool was a heavy dutyrotavator (WJ220E, WOONGJIN, Korea), and the required ratedpower, total mass, tillage width, and dimensions were 75 kW,750 kg, 2220 mm, and 1050 mm ? 2390 mm ? 1380 mm(length ? width ? height), respectively.2.3. Load analysisProcedures to analyze the tractor load would be different,depending on the purpose. Many researchers have used simplestatistics such as average, maximum, and minimum values in orderto represent the load. This method extracts representative valuesto show the difference of amplitude, but this simplificationprohibits characterizing the whole load profiles since the field loadis irregular. Effects of gear setting on the transmission and PTOload, One-Way ANOVA and the least significant difference test(LSD) were conducted with SAS (version 9.1, SAS Institute, Cary,USA). Also, it is difficult to represent effects of the load on thetractor since the load causes damages to the tractor, and fatigue ofthe tractor parts also needs to be investigated. Fatigue of a tractor isdefined as the damage sum from repeated loadings (Lampman,1997).Severeness, another method of load representation proposed byKim et al. (1998, 2000), is defined as the ratio of the damage sum ateach operation to the minimum damage sum from all theoperations. Severeness would be inversely proportional to fatiguelife. When load severeness is greater, fatigue life would be shorter.Kim et al. (1998) measured the loads acting on the transmissioninput shaft and analyzed the load severeness during plow tillage,rotary tillage, and transportation operations. They found that thesevereness during transportation operation was similar to thatduring plow tillage, but the severeness during rotary tillage wasabout 63 times greater than that during the transportationoperation. Later, Kim et al. (2000) analyzed the severeness ofthe transmission input shaft during rotary tillage at four speedcombinations of the tractor ground speeds (2.9 km h?1and4.1 km h?1) and PTO rotational speeds (588 and 704 rpm) usinga tractor with a rated engine power of 30 kW. The load severenessincreased by 2.32.6 times when the PTO speed increased with theY.-J. Kim et al. / Soil & Tillage Research 134 (2013) 9096 91same ground speed, while the severeness decreased by 0.20.3times when the ground speed increased with the same PTO speed.Fig. 2 is a block diagram explaining the procedures ofsevereness calculation. The measured torque data was convertedfrom time domain to frequency domain using the rainflow cyclecounting method since the torque data was irregular (Xiong andShenoi, 2005). The rainflow cycle counting technique is commonlyrecognized as a good cyclic counting method in fatigue lifeprediction (Hong, 1991). It decomposes a variable amplitude loadhistory into a series of simple events equivalent to individualcycles of constant load amplitude (Glinka and Kam, 1987). Inaddition, the Smith-Waston-Topper uniaxial method was used forcalculation of spectrum magnitude to remove effects of the meantorque using Eq. (1) (Dowling, 1972).Teffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffita tmtap(1)where Teis equivalent torque (Nm), tais torque amplitude (Nm),and tmis mean of torque (Nm).Since the recorded time of the measured load data wasrelatively short (180200 s), it was necessary to extend thenumber of cycles to the total usage time of rotary tillage of thetractor. In order to calculate the total number of cycles at themagnitude of the load, the entire life of the test tractor wasassumed. The total number of cycles of the load was calculated inEq. (2).NT 3600NLh (2)where NTis total number of cycles of the load (cycles), N is numberof calculated cycles of the measured load (cycles s?1), L is entire lifeof the used tractor (year), and h is annual usage time of the tractorfor the operation (h year?1).The annual usage time of the used tractor was 204 hours forrotary tillage in Korea (Lee, 2011). The entire life of the used tractorwas assumed as 10 years, which was normal in Korean agriculturalconditions. The load spectra for the entire life of the used tractor atdifferent gear settings for rotary tillage were represented by theratio of the measured loads to the rated engine torque load, whichwas 275 Nm. The ratios greater than 1 indicates unfavorable loadlevels greater than the rated engine torque load.The damage sum was calculated using measured load and SN(bending stress vs. number of cycle) curve to estimate the numberof cycles of loading to failure (Fatemi and Yang, 1998). The SNcurve was converted to a torque-cycle curve because of the damagecaused by torque signal (Graham et al., 1962; Nguyen et al., 2011).The SN curve was obtained for the material of the input shaft, SCM420H, using the ASTM standard (2004) in Eq. (3). The ASTMstandard has been widely used for fatigue analysis of materials(Wannenburg et al., 2009; Mao, 2010).N 106?6:097logS=223(3)where N is the number of cycles, S is shear stress (MPa).To calculate damage sum, equivalent torque of loadspectrum was converted to stress (Rahama and Chancellor,Fig. 1. Strain-gauges and radio telemetry systems for torque measurement on the transmission and PTO input shafts.Fig. 2. Schematic diagram explaining the procedures of severeness evaluation.Y.-J. Kim et al. / Soil & Tillage Research 134 (2013) 9096921994; Petracconi et al., 2010). The diameters of the transmissionand the PTO input shafts were 28 mm and 26.5 mm, respectively.S 16Tpd3(4)where S is stress (MPa), T is equivalent torque (Nm), and d isdiameter of the shaft (mm).The damage sum was calculated based on the Miners rule(Miner, 1945) in Eq. (5). Miners rule is a procedure for estimatingthe number of cycles of loading to failure (Miner, 1945; Robson,1964; Renius, 1977). The number of cycles (n) was derived from anequivalent torque of the load spectrum. The fatigue life cycles (N)was derived from the SN of SCM 420H. The damage (D) wascalculated by dividing the number of the fatigue life cycles into thenumber of cycles.DtXki1niNi(5)where Dtis damage sum, niis number of cycles, and Niis fatigue life(cycles).3. Results and discussion3.1. Transmission and PTO loads by gear selectionFig. 3 shows examples of torque loads on the transmission andPTO input shafts for the ground speed at L1 and the PTO rotationalspeed at P2 during the rotary tillage operation. The rotary tillageoperation consisted of a preparing period to descend the 3-pointhitch, an operating period to till the soil, and a completion period toascend the 3-point hitch. The measured torque on the transmissionand PTO input shafts showed steep increasing in the preparingperiod and decreasing in the completion period, and torque onthese components showed irregular fluctuation patterns in theoperating period. The magnitude and range of the measured torqueon the PTO input shaft were greater than those on the transmissioninput shaft in the operating period.Table 1 shows torque levels on the transmission and PTO inputshafts by speed combination of the ground speeds (L1, L2, L3) andthe PTO rotational speeds (P1, P2, P3). The average torque wascalculated only for the operating period data, not for the preparingand completion periods. The averaged torque levels of the PTOinput shaft were greater than those of the transmission input shaftat all gear levels during the rotary tillage. These results weresimilar to the results by Kim et al. (2011a) that the PTO requiredthe greatest amount of power among the major componentsduring rotary tillage.The average torque on the transmission input shaft wasconsiderably and significantly increased as the ground speedincreased from L1 to L3 at the same PTO rotational speeds. Loadincreases on the transmission and driving shafts with the speedincrease of plow tillage were also found by Kim et al. (2011a,b) andNahmgung (2001). Also, the averaged load on the transmissioninput shaft increased as the PTO rotational speed increased, exceptthat the load values were not significantly different between L1P2and L1P3. The average torque on the PTO input shaft increased asthe ground speed and PTO rotational speed increased. Theincreases were statistically significant for the PTO rotationalspeed, but not significant for the ground speed.3.2. Severeness evaluationFigs. 4 and 5 show load spectra of the transmission and the PTOinput shafts by gear setting during the rotary tillage, respectively.The spectra were constructed considering the entire life of thetractor, and the numbers of cycles were in the ranges from 103to107. The range of the maximum torque ratio of the transmissioninput shaft was 0.71.5 for the speed-combinations and thegreatest torque ratio was found at L3P1 as shown in Fig. 4. InFig. 3. Example of torque loads on the transmission and PTO input shafts torque at the L1P2 selection during rotary tillage.Table 1Average torque (Nm) on the transmission and PTO input shafts by gear setting during rotary tillage.Transmission input shaft PTO input shaftP1 P2 P3 P1 P2 P3L1 29.8 ? 2.8Aa 1,2,335.9 ? 4.2Ba38.7 ? 4.7Ba105.0 ? 3.6Aa(3.52)4148.7 ? 3.7Ba(4.14) 175.8 ? 4.2Ca(4.54)L2 43.5 ? 4.7Ab51.3 ? 3.3Bb58.5 ? 3.1Cb114.7 ? 3.9Ab(2.64) 151.7 ? 4.1Ba(2.95) 177.7 ? 3.4Ca(3.03)L3 64.9 ? 3.2Ac71.5 ? 3.5Bc82.1 ? 4.9Cc118.7 ? 4.0Ab(1.83) 151.9 ? 3.8Ba(2.12) 182.9 ? 4.2Cb(2.23)1Average ? standard deviation.2Means with different superscript (A, B, C, D) in each row are significantly different at p 0.05 by LSDs multiple range tests3Means with different superscript (a, b, c, d) in each column are significantly different at p 0.05 by LSDs multiple range tests.4Values in the parentheses are the ratios of the torque on the PTO input shaft to the torque on the transmission input shaft at the speed combinations.Y.-J. Kim et al. / Soil & Tillage Resea