牵引传动机械变速器英文翻译文献_图文

1、Research and Development of Cone to Cone Type CVT H. Komatsubara*T. YamazakiS. KuribayashiYamagata University Yamagata University Kuribayashi Steamship Yamagata, Japan Yamagata, Japan Tokyo, JapanAbstract Traction drive CVT is a low noise and a low vibration. But most of traction drive CVT have comp

2、lex structure. One of the authors invented a new type of traction drive CVT. As for this new CVT, the structure is simple, and transfer efficiency is high. This new CVT is called Cone to Cone Type CVT(CTC-CVT. The purpose of this research aimed at practical use of CTC-CVT In this report, first the s

3、tructure and the speed changing mechanism of CTC-CVT is examined. Secondly, the design of CTC-CVT is described. Finally, the mechanical efficiency of power transmission is examined.Keywords: machine element, tribology, lubrication, CVT, traction drive, efficiencyI. IntroductionIn the traction drive,

4、 mechanical power is transmitted between two rotors via an elastohydrodynamic lubrication (EHL oil film. The traction oil intervening between the rotors forms an oil film when it experiences a pressing force, and it transmits mechanical power by the shear force (traction force of this oil film. The

5、traction drive is low vibration and low noise and has the feature of being able to make up a continuously variable transmission (CVT. For the traction drive type CVT, various structures have been developed. Ring-corn type CVT 1 and kopp type CVT 2 have been applied to industrial machine. Half-toroid

6、al CVT has been practically used for automobiles 3. Power transmission efficiency of this CVT is over 92 % 4. In addition, shaft drive CVT 5 and full-toroidal CVT 6 have been studied. However, the CVT of this traction drive type has a narrow range of reduction ratio and the structure is complex.Thus

7、, Kuribayashi, one of the authors, devised a CVT using cones in the traction drive type CVT, whose structure is simple and from which a high reduction ratio is available7. Figure 1 shows a schematic of the power transmission portion of the devised CVT. Figure 2 shows an exploded perspective view of

8、the power transmission portion. In this CVT, intermediate rolling elements are placed between the input and output shafts to transmit mechanical power. The input and output shafts have a concave conical form, and the intermediate rolling elements have a convex conical form. Because mechanical power

9、is transmitted from cone to cone, this new CVT is *E-mail: hkomatsuyz.yamagata-u.ac.jp E-mail: am01137dipfr.dip.yz.yamagata-u.ac.jp E-mail: a.kotanikuribayashi.co.jp called the cone-to-cone type CVT (CTC-CVT. On the input and output shafts, gears are attached at the shaft end as shown in Figure 2. B

10、y attaching the gears, the number of mating parts of the input and output shafts and the rolling elements can be increased. By increasing the number of mating parts of the input and output shafts and the rolling elements, high torque can be transmitted.This study aims at practical development of CTC

11、-CVT which simple structure parts and power transmission efficiency is about 90 %. This time, to know the basic characteristics of the CTC-CVT, one set of input and output shafts and rolling elements was examined without attaching gears at the input and output shaft ends.First the structure and spee

12、d-changing mechanism of the CTC-CVT are described. Finally, the design and power transmission efficiency examination of a prototype are presented.Fig. 1. Schematic of CTC-CVT Fig. 2. Exploded perspective view of CTC-CVT (a e=2.0 (b e=1.0 (c e=0.5Fig. 5. Reduction ratio change mechanism of CTC-CVTII.

13、 Basic Structure A. Structure of CTC-CVTFigure 3 shows a schematic of the power transmission portion of the CTC-CVT. This CTC-CVT is composed of input and output shafts and an intermediate rolling element inscribed between them. The input and output shafts have a concave conical form, and the interm

14、ediate rolling element has a convex conical form. An offset of E is given between the input and output shafts. Traction oil intervenes between the concave cone at the end of each shaft and the convex cone of the intermediate rolling element, and it forms an oil film when a pressing force is applied

15、from the input shaft side. A traction force is produced by the oil film, and the rotation of the input shaft is transmitted to the output shaft via the intermediate rolling element. Speed changes are effected by changing the contact radius of the intermediate rolling element, and the radius change i

16、s in turn effected by translating the intermediate rolling element obliquely along the cone angle.B. Speed-changing MechanismThe CTC-CVT changes the speed smoothly by translating the intermediate rolling element obliquely along the cone angle. Figure 4 shows the geometry of the power transmission po

17、rtion. Letting r 1 be the corotation radius of the input shaft, r 2 be the corotation radius of the convex cone on the input side, 1 be the angular velocity of the input shaft, and 2 be the angular velocity of the rolling element, then the following relationship is obtained on the input side.2211r r

18、 = (1Letting r 3 be the corotation radius of the convex cone on the output side, r 4 be the corotation radius of the output shaft, and 3 be the angular velocity of the output shaft, then the following relationship is obtained on the output side.3423r r = (2The reduction ratio, e , is the ratio of th

19、e angular velocity of the input shaft to that of the output shaft and is given by the following equation using Equations 1 and 2.1342322131r r rr e = (3If the corotation radii, r 1 and r 4, of the input and outputshafts are equal, the following equation is obtained.32r r e = (4If the convex cone is

20、translated, the corotation radii r 2 and r 3 of the intermediate rolling element at the points of contact respectively with the input and output shafts change. As shown in Figure 5(a, the reduction ratio is 2.0 if the length of r 2 is twice the length of r 3. It is 1.0 if the length of r 2 is equal

21、to the length of r 3 (Figure 5(b. Likewise, the reduction ratio is 0.5 if the length of r 2 is half the length of r 3 (Figure 5(c. Thus, when the corotation radii of the intermediate rolling element change, the reduction ratio changes according to Equations 3 and 4. Fig. 3. Schematic of power transm

22、ission portion Fig. 4. Geometrical parameters of CTC-CVTIII. Design of CTC-CVT PrototypeTo verify the operation and performance of the CTC-CVT, a CTC-CVT prototype was designed. Figure 6 shows a sectional view of the designed CTC-CVT. Table 1 shows the specifications for the designed CTC-CVT prototy

23、pe.As a design condition, a motor with a rated capacity of 15 kw and a rotational speed of 1500 rpm was used as the input power source. The design was done on the design concept of attaining a prototype with high power transmission efficiency.For changing the speed, a mechanism to translate ther 2=2

24、r 3r 2=r 3r 2=r 3/2 Fig. 6. Schematic view of CTC-CVT intermediate rolling element along the cone angle byturning a handle was used. Figure 7 shows a schematic ofthe transmission mechanism. A case supports theintermediate rolling element, and a slider is attached to thecase. A groove is cut in the f

25、rame at the same angle as theconvex cone. A handle is attached on the top of the case,and turning the handle translates the case along the grooveand can effect stepless speed changes.The pressure force necessary for the traction drive isgiven by the loading cam on the input shaft side. Theloading ca

26、m is a device to produce a pressing forceaccording to the input torque. For the bearings on theinput and output shafts, a duplex angular bearing androller bearing are used. The bearings of the CTC-CVTexperience radial and thrust loads. These bearings areused as a combination that can carry these loa

27、ds and causelittle power loss at the bearings. The CVT was designedso that the duplex angular bearing will carry radial andthrust loads and the roller bearing will carry a large radialload. The distance between the bearings was decided inconsideration of the allowable angle and efficiency of thebear

28、ings.For the lubrication of the various parts of the CVT,forced lubrication using a CVT lubrication hydraulic unit(pump, filter, cooler and tank was used, and this unit isinstalled separately from the CVT prototype. Labyrinthseals are used, in consideration of the power loss by thesealing devices. F

29、ig. 7. Schematic of Transmission MechanismOutput Torque T2(Nm 95.5Reduction ratio e0.5 - 2.0Input speed N1(min-1 1500Output speed N2(min-1 750 - 3000Cone angle (deg 46Contact radius r1,r4(mm 46Offset E(mm 13TABLE I. Design specification of CTC-CVTIV. Examination of Power Transmission EfficiencyPower

30、 transmission efficiency is most important asperformance of the transmission and an examination aboutthis was performed. The power loss by the traction drivetype CVT includes the loss by the support bearing, theloss occurring at the contact surface of the powertransmission portion, the loss by agita

31、tion of traction oiland the loss by oil seals and other sealing devices. Theprototype fabricated this time employs forced lubrication,which sprays traction oil onto the CVT by the externalhydraulic unit. Thus it is thought that there is no powerloss by agitation of traction oil. Because labyrinth se

32、alsare used for the sealing devices, it is considered that thereis no power loss by the sealing devices. Therefore, theloss by the support bearing and the loss at the contactsurface of the power transmission portion were examined.A. Effect of Bearing LossBy the pressure force from the loading cam, a

33、 radialload acts on the roller bearing on the input and outputshafts, and radial and thrust loads occur on the duplexangular bearing. Due to these loads, a torque loss occursat each bearing. This torque loss is expressed as kineticfriction torque, M t. The kinetic friction torque, M t,occurring at e

34、ach bearing is expressed by the followingequation:vltMMM+=(5where M l is the load term and M v is the velocity term.B. Effect of SpinAround the normal to the contact surface of the power transmission portion, relative rotary motion of the oil film occurs in the elliptic contact area, and this motion

35、 is called spin. The traction oil is heated by this spin, increasing the slippage and reducing the shear force. The loss due to the spin was theoretically found by an analytical method by using the elastoplastic model of Johnson and Tevaarwerk 8 and taking into account the oils shear force reduction

36、 accompanying the heating. C. Power Transmission Efficiency The power transmission efficiency P can be expressed by the following equation using the speed transmission efficiency S and torque transmission efficiency T .T S P = (6 The speed transmission efficiency represents the relationship of the a

37、ctual rotational speed to the rotational speed of the ideal transmission free from slippage under point contact condition. The speed transmission efficiency can be found theoretically from the slippage rate (creep on the input and output sides. The creep can be found from the traction curve as the m

38、agnitude of creep for the set traction coefficient. The traction curve represents the relationship between creep and traction coefficient. The traction coefficient represents the ratio of the traction force to the normal force, which is the normal component of the pressure force acting on the interm

39、ediate rolling element. Figure 8 shows the traction curve of the CTC-CVT for the design specifications given in Table 1. The temperature of the traction oil was taken at 60 °C.The torque transmission efficiency represents the relationship of the actually transmitted torque to the ideally transm

40、itted torque free from slippage under point contact condition. The torque transmission efficiency can be found from the loss at each bearing and the loss due to spin. Figure 9 shows the calculated power transmission efficiency versus input torque for reduction ratios of 2.0, 1.0 and 0.5.The power tr

41、ansmission efficiency decreases as the input torque increases. The power transmission efficiency also decreases as the reduction ratio decreases, that is, the output speed is increased. The torque loss at the bearings increases as the input torque increases. When the output speed is increased, a tor

42、que loss occurs at the bearings. Moreover, the surface pressure in the contact area becomes large and the slippage increases, so the power loss becomes large. The power transmission efficiency was 93% at a reduction ratio of 2.0 for the design specifications given in Table 1. V. Conclusion(1 Aiming

43、at practical development of a CTC-CVT which is a continuously variable transmission using cones,we designed a prototype and examined its power transmission efficiency.(2 We found the bearing loss and spin loss in the traction area, which contribute to a reduction of power transmission efficiency. As a result, the calculated efficiency of the designed CTC-CVT is 93%.The CTC-CVT designed this time is now in the process of fabrication, and we will do a trial run to measure the efficiency and compare it with the theoretical value.00.020.040.060.080.10123456 Creep Cr%T r a c t i o n c o e f f