ANALYSIS OF THE PLANETARY GEAR OF RAVIGNEAUX TYPE AND ITS APPLICATION IN AGRICULTURAL TRACTORS

Transcription

1 TEKA Kom. Mot. Energ. Roln. OL PAN, 7, 7, ANALYSIS OF THE PLANETARY GEAR OF RAVIGNEAUX TYPE AND ITS APPLICATION IN AGRICULTURAL TRACTORS Jery śebrowsk*, Zbgnew śebrowsk** Unversty of Warma and Maury n Olstyn, Ocapowskego Str., -79 Olstyn, Poland, e-mal: jery.ebrowsk@uwm.edu.pl The Techncal Unversty of Warsaw, Narbutta Str. 84, -54 Warsawa, Poland, e-mal: bgnew.ebrowsk@smr.pw.edu.pl Summary. Ths paper presents two varants of the planetary gear of Ravgneaux type. An analyss of the power flux through the gear on the partcular speeds was derved and ts usefulness n the agrcultural tractors was dscussed Key words: agrcultural tractor, planetary gear, power flux analyss INTRODUCTION The planetary gear unt Ravgneaux [Studńsk 97] n the standard verson (two varants) conssts of one full planetary seres wth the rng gear toothed nternally, and the second non full planetary seres, whch contans the nput sun gear and the planet long pnon nterpenetrated wth the pnon of the full planetary seres. Vew of the planetary gear unt Ravgneaux s presented n Fg. [Berger ], and knematcs dagram n Fg.. Fg.. Vew of the planetary gear unt Ravgneaux

2 ANALYSIS OF THE PLANETARY GEAR OF RAVIGNEAUX TYPE... Fg.. Ravgneaux gear system n the two basc varants: A and B The system enables to obtan four speeds forward and one speed reverse. It s controlled by a system of three clutches and two brakes. Durng the shftng of the speeds (Table ) from the frst to the thrd durng drvng forwards, all the tme one of the clutches (S ) s closed and the followng are swtched successvely: two brakes (H ) and (H ) and the clutch (S ). The fourth speed (wth the rato lower than one) s obtaned by closng of the clutch (S ) and the brake (H ), whch are not used on the lower speeds (necessty of swtchng two elements at the same tme). On the reverse speed one brake (H ) and one clutch (S ) are closed. The power s taken from the rng gear. Ths type of unt s used wdely n automatc gearboxes n passenger cars. Table Speed Speed Speed Speed 4 Reverse Clutch S X X X Clutch S X (B) X Clutch S X (A) X Brake H X X Brake H X X ANALYSIS OF THE PLANETARY GEAR OF RAVIGNEAUX TYPE In the result of stoppng and couplng of varous elements n the gear on the partcular speeds, the power flux has dfferent character for the successve speeds and t has an nfluence on ts mechancal effcency [Müller 97]. For that reason the power flux was determned for partcular speeds wth takng nto account the separaton for the part transmtted by the transportaton movement (no losses) and the part transmtted by the relatve movement, so by the gears (wth losses) [śebrowsk, śebrowsk 987]. The power transmtted by an element x can be noted as (): N wx = M x ω wx ()

3 Jery śebrowsk, Zbgnew śebrowsk and ts component transmtted wth the transportaton movement: and ts component transmtted wth the relatve movement: N ux = M x ω () N x = M x ω x () M x torque transmtted by the element x, ω x angular velocty of the element x, ω transportaton angular velocty of the element x (angular velocty of the cage of the planetary gear, n whch the element x s mounted), ω wx = ω x ω relatve angular velocty of the element x. The ratos of the gearbox wth the partcular speeds were determned wth the Wlls formula: On the frst speed (the gearbox operates analogcally to the cylndrcal gear) the rato can be noted as follows: = (4) and the effcency: = = w (5) effcency of the external gear, w effcency of the nternal gear. On the second speed the rato s equal to: ω = ω = =, ( ) (6) = (7) The power flux on the second gear s the most complcated among the cases of all the speeds. The determned scheme of the powerflux s presented n Fgure. Fg.. Power flux scheme for the second speed

4 ANALYSIS OF THE PLANETARY GEAR OF RAVIGNEAUX TYPE... On the bass of the ntroduced scheme of the power flux the followng formula of the effcency was derved: N = = = N + (8) =, = (9) w On the thrd speed the closed clutches block the planetary system whch mples that the rato s = and no power losses n the gears occur. The rato of the fourth speed can be noted as: ω = = 4 ω () Fgure 4 presents the scheme of the power flux wth the fourth speed Fg. 4. Power flux scheme on the fourth speed The effcency on the fourth speed s as follows: ( ) = = () 4 = w () The rato of the reverse speed (cylndrcal gear case) can be noted as: and the effcency: ω ω W = () N = = = (4) W N The descrbed Ravgneaux systems are used also n the agrcultural tractor s gearboxes.

5 4 Jery śebrowsk, Zbgnew śebrowsk APPLICATION OF THE PLANETARY GEAR RAVIGNEAUX TYPE IN AGRICULTURAL TRACTORS The Ravgneaux systems n the tractor s garboxes have many applcatons [śebrowsk and śebrowsk ]. In Fgure 5 an example of the system s presented, whch was used by the Case manufacturer [Materals of CASE IH]. Fg. 5. Scheme of the Ravgneaux system used by Case manufacturer The power nput s on the gear and the output s from the gear or on the planetary cage wth the assstance of the clutches S and S. Wth the help of the brakes H and H the gears and can be stopped. Effectvely, the system can provde three speeds forward and one speed reverse. Table shows whch elements are closed on the partcular speeds. Table Speed Speed Speed Reverse Clutch S X X X Clutch S X X Brake H X X Brake H X The rato of the frst speed can be noted as: ω = ω = (5) = (6)

6 ANALYSIS OF THE PLANETARY GEAR OF RAVIGNEAUX TYPE... 5 And the effcency formula can be derved on the bass of the presented power flux scheme (Fg. 6): ( ) N O = = (7) N = (8) Fg. 6. The scheme of the power flux n the system on the frst speed On the second gear the rato, the power flux scheme and the effcency formula are dentcal wth the second speed of the Ravgneaux system, descrbed prevously (8), (9), (Fg. ). On the thrd speed the closed clutches block the planetary system, whch results n the rato = and results n no mechancal losses on the gears. The gear rato of the reverse speed can be noted as: W ω = ω = (9) The scheme of the power flux on the reverse speed s showed n Fgure 7, and the mechancal effcency of the reverse speed effcency derved on ts bass can be noted as: N = = = () W N Fg. 7. Scheme of the reverse gear power flux

7 6 Jery śebrowsk, Zbgnew śebrowsk The determned, wth the derved formulas, values of the ratos and effcences on the partcular speeds (dependently on the teeth number and the gear effcency) were put nto Table. Table Speed Speed Speed Reverse Rato Effcency The modfed Ravgneaux system s also a part of a 9 speed gearbox powershft type appled by John Deere manufacturer n the tractors of seres 7 (part III) [John Deere Trans. 99]. Fgure 8 represents the scheme of the part of ths gearbox. The power nput element for the system Ravgneaux (part III) for all the speeds s the planetary cage and the output element s the shaft on whch the frst sun gear s postoned ( 7 larger). In comparson to the classcal Ravgneaux system, n the newest verson of the gearbox was added the rng gear 8 (n the prevous verson there was no gear n ths place and the system had a classcal confguraton). The gears 8 and 9 can be stopped wth the wet multple dscs brakes and the clutch enables connectng the planetary cage wth the gear. Ths soluton enables to get three speeds forward and one speed reversed, but n each confguraton only one frcton element was closed. Ths feature makes the control of the whole unt smpler as the changes of the speeds requre only swtchng between the frcton elements. Fg. 8. Scheme of the modfed Ravgneaux system as a part of a 9-speed gearbox powershft type appled by John Deere [99] manufacturer n the tractors of the seres 7 part III Table 4 presents whch elements are requred to be closed for the partcular speeds.

8 ANALYSIS OF THE PLANETARY GEAR OF RAVIGNEAUX TYPE... 7 Clutch S 4 Brake H 4 Brake H 5 Brake H 6 Table 4 Speed Speed Speed Reverse X X X X The ratos of the partcular speeds, the determned schemes of the power fluxes and the derved formulas of the effcency (dependently on the gear s teeth numbers and the gears effcences) are presented below [śebrowsk ]: Frst speed: Rato = ; No mechancal losses occur n the gears (drect speed) Second speed: 97 = 97 Rato 97 = 97 () s = 9s5 () The scheme of the power flux s presented n Fgure 9. Effcency Fg. 9. Power flux scheme on the second speed ( ) = () = (4) 79 Thrd speed: Rato = (5) 78

9 8 Jery śebrowsk, Zbgnew śebrowsk 8 78 = (6) 7 The scheme of the power flux s presented n Fgure. Fg.. Power flux scheme on the thrd speed Effcency ( ) = (7) = 78 w (8) Reverse speed: Rato = W 7 (9) s5 7 = () 7 s6 The scheme of the power flux s presented n Fgure. Fg.. Power flux scheme on the reverse speed

10 ANALYSIS OF THE PLANETARY GEAR OF RAVIGNEAUX TYPE... 9 Effcency 7 ( ) 7 = 7 () w 7 7 = w () Values of the ratos and effcences on the partcular speeds determned wth the presented formulas are presented n Table 5. Table 5 Speed Speed Speed Reverse Rato Effcency On the bass of the presented examples t can be concluded that n the gearboxes for tractors not all the possble speeds are used. Both manufacturers: Case and John Deere, use three speeds forward and one speed reversed but obtaned n dfferent ways. The power nput s always, whchever speed s realed, on the same element (gear Case, planetary cage John Deere). In the gearbox from Case two clutches and two brakes are used. On each speed two of the frcton elements must be closed but gear shftng s obtaned va swtchng only one frcton element. The Ravgneaux system s utled n the way that the frst and the second gears are reducng and the thrd gear s drect. On the reversed gear the obtaned rato s equal mnus one (durng the work of the planetary seres), whch s accompaned by the crculatng power phenomenon and decreases the effcency of the gearbox on that speed n comparson to the nternal effcency of the planetary seres. On the forward speeds the total effcency of the gearbox s hgher than the nternal effcency of the planetary seres n work. In the John Deere s gearbox, because of dfferent applcaton of the modfed Ravgneaux system, there exst three brakes and one clutch (the desgn s better from the pont of vew of the used frcton elements). Shftng the speeds s obtaned va swtchng only one frcton element. In ths case the frst speed s drect the rato s equal to the one. The rest of the speeds have the ratos lower than one. Ths soluton requres an mplementaton of the reducton gears n the further part of the transmsson system, whch have hgher ratos than the reducton gears used n the case of the Case manufacturer. Also on the reversed speed the rato s lower than one, whch provokes the occurrence of the crculatng power phenomenon. Accordng to ths fact the total effcency of the gearbox on the reverse gear s lower than the nternal effcency of the planetary seres workng nsde. On the forward speeds the total effcency of the gearbox s hgher than the nternal effcency of the planetary seres n work. CONCLUSIONS. The presented and analyed systems of Ravgneaux type gears are transmssons of the power-shft type. Because of the number of speeds and the range of the ratos of the partcular speeds (. and.5 Case or.79 and.79 John Deere) they play

11 Jery śebrowsk, Zbgnew śebrowsk the role of prmary or fnal part of the whole gearbox. In the Case s gearbox the Ravgneaux system s the prmary part of the whole transmsson system that transmts the power to the tradtonal stepped gear after openng of the clutch (operaton ranges). In the case of the John Deere (JD) gearbox, the Ravgneaux system s the fnal part of the transmsson system, whch s fed wth the power by a power-shft gear. The JD gearbox enables shftng of all the speed under the load.. As t was presented n the analyss of the Ravgneaux systems used n tractors, the realaton of the speeds n terms of the proper ratos and control of the speeds shftng s dfferent to the solutons used n the passenger cars (wth the excepton of the second speed n the Case s system).. In the terms of the control, n both of the desgns, three forward speeds are used and one reversed speed. The speeds shftng are realed va swtchng only one frcton element. 4. The effcences of the systems comng from the losses n the gears, on the forward speeds wth the rato not equal to one, are not lower than.98. On the reversed speed both of the gearboxes are charactered by the crculatng power, whch gves as the result an ncrease n the planetary gear load and decrease n the effcency of the systems (.9 Case and.95 John Deere). 5. The most complcated power flux occurs n the case of the second speed n the Case gearbox. However, the effcency on that speed s hgh and ts value s equal to.98. REFERENCES Berger K. : Technologe Kraftfahreugtechnk. Forthe Polsh edton REA, Warsawa. Fachkunde Kraftfahreugtechnk. Verlag Europa-Lehrmttel. Nourney,Vollmer GmbH & Co. Düsselberger Straβe. 478 Haan-Gruten. John Deere Transmsson HO 958 A 99. Materals of CASE IH. Müller H. W. 97: De Umlaufgetrebe Berechnung Anwendung Auslegung. Sprnger Verlag, Berln, Hedelberg, New York. Studńsk K. 97: Teora konstrukcja oblcane samochodu. Warsawa, WNT. śebrowsk J. : Analyse der Lestungsvertelung m Power-Shft-Wechselgetrebe von Ackerschleppern John Deere 7. XIV Polsh-German Semnar: Development Trends n Desgn of Machnes and Vehcles., TU Warschau/FH Köln (UASC) Warsawa. śebrowsk J., śebrowsk Z. 987: Model matematycny prepływu mocy w prekładn planetarnej o dwóch stopnach swobody, Scentfc Conference: Rowój podstaw budowy, eksploatacj badań masyn robocych cęŝkch w tym budowlanych. Sekcja Podstaw Konstrukcj sekcja Podstaw Eksploatacj Komtetu Budowy Masyn PAN. śebrowsk J., śebrowsk Z. : Rowój planetarnych skrynek begów w cągnkach kołowych. XII Scentfc Conference Napęd, sterowane, automatyacja masyn robocych pojadów. Instytut Budowy Masyn Wydału Mechancnego WAT, Sekcja Podstaw Konstrukcj Masyn KBM PAN, 8 October.