JP2006071028A - Toroidal-type continuously variable transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive toroidal-type continuously variable transmission capable of miniaturizing a variator without increasing control oil pressure and providing stable synchronization. <P>SOLUTION: This toroidal-type continuously variable transmission is provided with a plurality of power rollers 11 nipped and held between an input side disc and an output side disc, a plurality of trunnions 6 swinging centered on a pair of pivots 5 being at twist positions for central axes of the input side disc and the output side disc and provided concentrically for each other and supporting each power roller 11 rotatably, and a driving piston 43 for displacing each trunnion 6 in the axial direction of the pivot 5. Each trunnion 6 is supported by a plurality of driving pistons 43 having the same structure mutually. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a toroidal continuously variable transmission that can be used in transmissions of automobiles, motorcycles, and various industrial machines.

  The use of a toroidal type continuously variable transmission as schematically shown in FIGS. 5 and 6 is partially implemented as a transmission for an automobile. This toroidal continuously variable transmission supports an input side disk 2 concentrically with an input shaft 1, and an output side disk 4 is fixed to an end of an output shaft 3 disposed concentrically with the input shaft 1. Inside the casing containing the toroidal-type continuously variable transmission, trunnions 6 and 6 are provided that swing around pivots 5 and 5 that are twisted with respect to the input shaft 1 and the output shaft 3. A power roller 11 is rotatably supported on each trunnion 6, 6, and each power roller 11, 11 is sandwiched (rolled) between both the input side and output side disks 2, 4. .

  The cross sections of the inner side surfaces 2a and 4a facing each other of the input and output side disks 2 and 4 each form a concave surface obtained by rotating an arc centering on the pivot 5 or a curve close to such an arc. ing. And the peripheral surface 11a, 11a of each power roller 11, 11 formed in the spherical convex surface is contact | abutted to each inner surface 2a, 4a.

  Between the input shaft 1 and the input side disk 2, a loading cam type pressing device 12 is provided. The pressing device 12 elastically presses the input side disk 2 toward the output side disk 4. The pressing device 12 includes a cam plate 13 that rotates together with the input shaft 1 and a plurality of (for example, four) rollers 15 held by a cage 14. Further, a cam surface 16 that is an uneven surface is formed on one side surface (the left side surface in FIGS. 5 and 6) of the cam plate 13 in the circumferential direction, and the outer surface (see FIGS. 5 and 5) of the input side disk 2. A similar cam surface 17 is also formed on the right side surface of FIG. The plurality of rollers 15 are supported so as to be rotatable about an axis extending in the radial direction with respect to the input shaft 1.

  In the toroidal type continuously variable transmission having such a configuration, when the input shaft 1 is rotated, the cam plate 13 is rotated along with the rotation of the input shaft 1, and the plurality of rollers 15, 15 are connected to the input side disk by the cam surface 16. 2 is pressed by the cam surface 17 provided on the outer side surface of the head. As a result, the input side disk 2 is pressed against the plurality of power rollers 11, 11, and at the same time, based on the pressing between the pair of cam surfaces 16, 17 and the rolling surfaces of the plurality of rollers 15, 15. The input side disk 2 rotates. Then, the rotation of the input side disk 2 is transmitted to the output side disk 4 via the power rollers 11 and 11, and the output shaft 3 fixed to the output side disk 4 rotates.

  When the rotational speeds of the input shaft 1 and the output shaft 3 are changed, and when deceleration is performed between the input shaft 1 and the output shaft 3, the trunnions 6 and 6 are swung around the pivot shafts 5 and 5. As shown in FIG. 5, the peripheral surfaces 11 a and 11 a of the power rollers 11 and 11 are arranged near the center of the inner surface 2 a of the input side disk 2 and the outer periphery of the inner side surface 4 a of the output side disk 4. The displacement shafts 9 and 9 are inclined so as to abut each other.

  On the other hand, when the speed is increased, the trunnions 6 and 6 are swung so that the peripheral surfaces 11a and 11a of the power rollers 11 and 11 have the inner surface 2a of the input side disk 2 as shown in FIG. Each of the displacement shafts 9 and 9 is inclined so as to come into contact with the outer peripheral portion and the central portion of the inner side surface 4 a of the output side disk 4. If the inclination angle of each of the displacement shafts 9 and 9 is set intermediate between those shown in FIGS. 5 and 6, an intermediate gear ratio can be obtained between the input shaft 1 and the output shaft 3.

  7 and 8 show an example of a more specific double cavity type toroidal continuously variable transmission. In addition, about the structural member which is common in FIG.5 and FIG.6, the same code | symbol is attached | subjected below and the detailed description or illustration is abbreviate | omitted.

  As shown in FIG. 7, the input shaft 1 is rotatably supported inside the casing 101. First and second input-side disks 2 and 2 are rotatably supported at both ends of the input shaft 1. In this case, the first and second input side disks 2 and 2 are concentrically arranged with their inner side surfaces 2a and 2a facing each other, and can rotate in synchronization with each other inside the casing 101. .

  Around the intermediate portion of the input shaft 1, first and second output side disks 4, 4 are supported via a sleeve 109. An output gear 110 is integrally provided on the outer peripheral surface of the intermediate portion of the sleeve 109. The output gear 110 is disposed concentrically with the input shaft 1 and has an inner diameter larger than the outer diameter of the input shaft 1. The output gear 110 is rotatably supported by a support wall (intermediate wall) 111 provided in the casing 101 via a pair of rolling bearings 112.

  The first and second output side disks 4 and 4 are splined to both ends of the sleeve 109. In this case, the output side disks 4 and 4 are arranged with their inner side surfaces 4a and 4a facing in opposite directions. Accordingly, the input side disk 2 and the output side disk 4 have their inner side surfaces 2a, 4a facing each other.

  As shown in FIG. 8, a pair of yokes 113a and 113b are supported inside the casing 101 and laterally of the output side disks 4 and 4 with both the disks 4 and 4 sandwiched from both sides. . The pair of yokes 113a and 113b are formed in a rectangular shape by pressing or forging a metal such as steel. In order to support the pivots 5 provided at both ends of the trunnion 6 to be described later in a swingable manner, circular support holes 118 are provided at the four corners of the yokes 113a and 113b, and the width direction of the yokes 113a and 113b. A circular locking hole 119 is provided at the center of the.

  The pair of yokes 113a and 113b are supported so as to be slightly displaceable by support posts 20a and 20b formed on portions of the inner surface of the casing 101 facing each other. These support posts 20a and 20b are respectively provided so as to face the first cavity 21 and the second cavity 22 between the inner side surface 2a of the input side disk 2 and the inner side surface 4a of the output side disk 4, respectively. Yes.

  Accordingly, the yokes 113 a and 113 b are supported by the support posts 20 a and 20 b, and one end thereof faces the outer peripheral portion of the first cavity 21 and the other end faces the outer peripheral portion of the second cavity 22. is doing.

  Since the first and second cavities 21 and 22 have the same structure, only the first cavity 21 will be described below.

  The first cavity 21 is provided with a pair of trunnions 6. Concentric shafts 5 are provided concentrically at both ends of the trunnion 6, and these pivots 5 are supported by one end portions of a pair of yokes 113a and 113b so as to be swingable and axially displaceable. That is, the pivot 5 is supported by the radial needle bearing 26 inside the support hole 118 formed at one end of the yokes 113a and 113b. The radial needle bearing 26 includes an outer ring 27 whose outer peripheral surface is a spherical convex surface and whose inner peripheral surface is a cylindrical surface, and a plurality of needles 28.

  A circular hole 30 is provided in each intermediate portion of the trunnion 6. A displacement shaft 31 is supported in each circular hole 30. Each of the displacement shafts 31 includes a support shaft portion 33 and a pivot shaft portion 34 that are parallel to each other and eccentric. Among these, the support shaft portion 33 is supported inside the circular hole 30 via a radial needle bearing 35. The power roller 11 is supported around the pivot shaft 34 via another radial needle bearing 38.

  A pair of displacement shafts 31 provided for each of the first and second cavities 21 and 22 is provided at a position 180 degrees opposite to the input shaft 1 for each of the first and second cavities 21 and 22. It has been. In addition, the direction in which each pivot shaft 34 of the displacement shaft 31 is eccentric with respect to each support shaft 33 is the same as the rotational direction of the input disks 2, 2 and the output disks 4, 4. The eccentric direction is a direction substantially orthogonal to the direction in which the input shaft 1 is disposed. Therefore, the power roller 11 is supported so that it can be slightly displaced along the longitudinal direction of the input shaft 1. As a result, when the power roller 11 tends to be displaced in the axial direction of the input shaft 1 due to fluctuations in the amount of elastic deformation of the constituent members based on fluctuations in torque transmitted by the toroidal continuously variable transmission. However, an excessive force is not applied to the constituent members, and the displacement can be absorbed.

  A thrust ball bearing 39 and a thrust bearing 40 such as a slide bearing or a needle bearing are provided between the outer peripheral surface of the power roller 11 and the inner peripheral surface of the trunnion 6 in order from the outer surface of the power roller 11. It has been. Among these, the thrust ball bearing 39 allows rotation of the power roller 11 while supporting a load in the thrust direction applied to the power roller 11. The thrust bearing 40 allows the pivot shaft 34 and the outer ring 41 to swing around the support shaft 33 while supporting a thrust load applied to the outer ring 41 of the thrust ball bearing 39 from the power roller 11. .

  A drive rod 42 is coupled to one end of the trunnion 6. A drive piston 43 is fixed to the outer peripheral surface of the intermediate portion of these drive rods 42. The drive piston 43 is oil-tightly fitted in the drive cylinder 44. The drive piston 43 constitutes an actuator for displacing the trunnion 5 in the axial direction.

  As shown in FIG. 7, a loading cam type pressing device 45 is provided between the drive shaft 200 that receives power from the engine and the one input side disk 2. The pressing device 45 includes a cam plate 46 and a plurality of rollers 48, and rotates one input side disk 2 while pressing it toward the other input side disk 2 based on the rotation of the drive shaft 200. The plurality of rollers 48 are held by a holder 47 so as to be freely rollable.

  During operation of the toroidal continuously variable transmission configured as described above, the rotation of the drive shaft 200 is transmitted to one input side disk 2 via the pressing device 45, and this input side disk 2 and the other input side disk are transmitted. The disk 2 and the input shaft 1 rotate in synchronization with each other. The rotation of the input side disks 2 and 2 is transmitted to the output side disks 4 and 4 via the power roller 11. The rotation of the output side disks 4 and 4 is taken out by the output gear 110 and transmitted to the output shaft 201.

  When the rotational speed ratio between the input shaft 1 and the output gear 110 is changed, a pair is provided corresponding to the first and second cavities 21 and 22 based on switching of control valves (not shown). The drive piston 43 thus moved is displaced by the same distance in the opposite directions for each of the cavities 21 and 22. Along with the displacement of these drive pistons 43, a total of four trunnions 6 are displaced in the opposite direction, and one power roller 11 is displaced downward and the other power roller 11 is displaced upward. As a result, the tangents acting on the abutting portions between the peripheral surfaces of the power rollers 11 and 11a, 11a, the inner side surfaces 2a, 2a of the input side disks 2, 2, and the inner side surfaces 4a, 4a of the output side disks 4, 4 The direction of the direction force changes. As the direction of the force changes, the trunnion 6 swings in the reverse direction around the pivot shaft 5 pivotally supported by the yokes 113a and 113b. As a result, the contact position between the peripheral surface of the power roller 11 and the input side disks 2 and 2 and the output side disks 4 and 4 changes, and the rotational speed ratio between the input shaft 1 and the output gear 110 changes. .

  FIG. 9 is a cross-sectional view showing an example of a single cavity type toroidal continuously variable transmission. The input side disk 2 and the output side disk 4 are rotatably supported around the input shaft 1 via needle bearings 116 and 116, respectively. Further, the cam plate 46 of the loading cam type pressing device 45 is spline-engaged with the outer peripheral surface of the end portion of the input shaft 1, and is prevented from moving in a direction away from the input side disk 2 by the end plate 117. An output gear 110 is coupled to the output side disk 4 by a key 120, and the output side disk 4 and the output gear 110 rotate in synchronization. Other configurations are the same as those shown in FIGS.

  By the way, in recent years, demands for miniaturization and weight reduction of transmissions for automobiles and motorcycles have become more severe. Therefore, also in the above-described toroidal-type continuously variable transmission, for example, the variator is reduced in size, that is, the diameters of the cavities 21 and 22 are reduced.

  In relation to this, Patent Document 1 discloses a three-roller toroidal type in which a trunnion and a double-acting drive piston are coupled by a link and the drive piston is efficiently arranged to reduce the size and weight. A continuously variable transmission is disclosed.

Patent No. 3480034

  As described above, when the diameters of the cavities 21 and 22 are reduced in response to the demand for reduction in size and weight, it is necessary to prevent the transmission torque from being lowered. Since the distance to the traction contact point (contact point between the disks 2 and 4 and the power roller 11) is shortened, it is necessary to increase the tangential force. Specifically, the driving piston 43 is coupled to the trunnion 6 and supports a force twice the tangential force (the sum of the force by which the power roller 11 is pulled by the input disk 2 and the force by which the output disk 4 is pulled). It is necessary to increase the operating pressure, that is, the control hydraulic pressure. This is because only one drive piston 43 is generally provided for one trunnion 6, and the drive piston 43 is also reduced by the size of the variator.

  However, when the control oil pressure is increased, the pump loss increases, and the power transmission efficiency of the transmission may decrease. Moreover, since the ratio of the torque used in order to accelerate a vehicle body among the torque which an engine generate | occur | produces will reduce, acceleration performance will also be deteriorated.

  In addition, as in Patent Document 1 described above, in the three-roller structure in which the trunnion and the driving piston are coupled by a link, the configuration of the driving pistons of the three rollers is not the same, so the pressure of each driving piston can be changed, It is necessary to match the thrust of the drive piston by changing the cross-sectional area of the drive piston. In this case, the number of items to be managed (pressure, dimensions, etc.) increases, which causes an increase in cost. Furthermore, even if the management is performed, the number of friction generation points is different, so that there is a possibility that the force for supporting the trunnion is different and the synchronization becomes unstable.

  The present invention has been made in view of the above circumstances, and provides an inexpensive toroidal continuously variable transmission that can reduce the size of the variator without increasing the control hydraulic pressure and can achieve stable synchronization. For the purpose.

  In order to achieve the above object, the toroidal continuously variable transmission according to claim 1 includes an input side disk and an output side that are supported concentrically and rotatably in a state where the inner side surfaces thereof face each other. A disc, a plurality of power rollers sandwiched between the two discs, and a pair of pivots provided concentrically with each other at a twisted position with respect to a central axis of the input side disc and the output side disc A toroidal continuously variable transmission that includes a plurality of trunnions that swing around the center and rotatably support the power rollers, and a drive piston that displaces the trunnions in the axial direction of the pivot. Each trunnion is supported by a plurality of the drive pistons having the same structure.

  In the first aspect of the present invention, each trunnion is supported by a plurality of drive pistons, and therefore each trunnion is displaced in the axial direction by the plurality of drive pistons, so that the pressure receiving area of the entire drive piston increases. . Therefore, it is possible to reduce the size of the variator without increasing the control hydraulic pressure. Further, since the structure of the drive piston that supports each trunnion is the same, the number of sliding friction occurrence portions of the drive piston is the same, and there is no possibility that the synchronization becomes unstable. Further, since it is not necessary to make the thrusts of the pistons coupled to the same trunnion coincide with each other, it is possible to avoid an increase in cost (a cheap toroidal-type continuously variable transmission can be provided).

  Further, the toroidal continuously variable transmission according to claim 2 is the toroidal continuously variable transmission according to claim 1, wherein the drive pistons are provided on both sides of each trunnion, or each trunnion The plurality of drive pistons are provided on one side.

  In the invention described in claim 2, since the degree of freedom of arrangement of the drive piston is increased, the variator space can be effectively used, and the layout of the variator is facilitated. As a result, the mountability of the transmission is improved and a substantial reduction in size is possible.

  A toroidal continuously variable transmission according to claim 3 is the toroidal continuously variable transmission according to claim 1 or 2, wherein at least one of the plurality of drive pistons supporting each trunnion is provided. One is characterized by being connected to the trunnion via a link.

  In the invention described in claim 3, since the amplification factor of the control pressure (operating pressure of the drive piston) can be changed by the link, it is possible to control with a lower pressure pump.

  The toroidal continuously variable transmission according to claim 4 is the toroidal continuously variable transmission according to any one of claims 1 to 3, wherein the drive piston receives a hydraulic pressure from a hydraulic source. Acting through a hydraulic line, an accumulator is provided in the middle of the hydraulic line.

  In the invention described in claim 4, since an accumulator is provided in a hydraulic line for supplying pressure oil to the drive piston, for example, an insufficient discharge flow rate of a hydraulic source (for example, a pump) at the time of a sudden shift is detected. It can be compensated by accumulating pressure. That is, the increase in the pressure receiving area associated with the configuration of claim 1 increases the flow rate required at the time of sudden shift, so that the discharge flow rate of the hydraulic power source may be insufficient at the time of sudden shift, but as in the configuration of this claim If an accumulator is inserted in the hydraulic circuit and accumulated in a steady state, an insufficient discharge flow rate of a hydraulic source (for example, a pump) can be compensated by accumulated pressure in the accumulator. Therefore, the invention according to claims 1 to 3 can be realized without increasing the size of the pump. In addition, since it is almost impossible that the sudden shift continues continuously, it is possible to sufficiently cope with the shortage of the discharge flow rate of the hydraulic power source only by inserting the accumulator.

  According to the toroidal type continuously variable transmission of the present invention, each trunnion is supported by a plurality of the drive pistons having the same structure, so that the variator can be reduced in size without increasing the control hydraulic pressure. Stable synchronization can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The feature of the present invention lies in the trunnion support structure by the drive piston, and other configurations and operations are the same as the conventional configurations and operations described above. Therefore, only the features of the present invention will be described below. The other parts are simply described with the same reference numerals as in FIGS.

  FIG. 1 schematically shows a first embodiment of the present invention. As shown in the figure, for example, each pair of trunnions 6 existing in the same cavity is supported by a plurality (two in the figure) of drive pistons 43 via a drive rod 42. In this case, a pair of drive pistons 43 that support each trunnion 6 are provided on both sides of the trunnion 6, respectively. In the present embodiment, all of the drive pistons 43 have the same structure.

  Further, the hydraulic pressure from the hydraulic pump 300 as a hydraulic source acts on each drive piston 42 via a hydraulic circuit 310. More specifically, the pressure oil from the hydraulic pump 300 is guided to the hydraulic circuit 310 via the control valve 304, and the corresponding drive cylinder 44 is connected via the corresponding hydraulic line 306 constituting the hydraulic circuit 310. It is supplied to both sides. The hydraulic line 306 also connects the chambers of the drive cylinder 44 in the same trunnion 6 and different trunnions 6 to each other. Further, an accumulator 302 is provided in the middle of the hydraulic line connecting the hydraulic pump 300 and the control valve 304.

  Thus, in the present embodiment, each trunnion 6 is supported by the plurality of drive pistons 43, and thus each trunnion 6 is displaced in the axial direction by the plurality of drive pistons 43, so that the pressure receiving area of the entire drive piston 43 is increased. Will increase. Therefore, it is possible to reduce the size of the variator without increasing the control hydraulic pressure. Moreover, since the structure of the drive piston 43 that supports each trunnion 6 is the same, the number of sliding friction generation portions of the drive piston 43 is the same, and there is no possibility that the synchronization becomes unstable.

  In this embodiment, since the accumulator 302 is provided in the hydraulic line that supplies the pressure oil to the drive piston 43, for example, the insufficient discharge flow rate of the hydraulic pump 300 at the time of sudden shift is compensated by the accumulated pressure of the accumulator 302. be able to. That is, the increase in the pressure receiving area associated with this configuration increases the flow rate required at the time of a sudden shift, so that the discharge flow rate of the hydraulic pump 300 may be insufficient at the time of a sudden shift. If the accumulator is inserted and accumulated in the steady state, the insufficient discharge flow rate of the hydraulic pump 300 can be compensated by the accumulated pressure of the accumulator 302. Therefore, the present invention can be realized without increasing the size of the pump 300. In addition, since it is almost impossible that the sudden shift continues continuously, it is possible to sufficiently cope with the shortage of the discharge flow rate of the hydraulic pump 300 only by inserting the accumulator 302.

  FIG. 2 schematically shows a second embodiment of the present invention. As shown in the figure, in the present embodiment, a plurality (two in the figure) of drive pistons 43 are provided on one side of each trunnion 6. Other configurations are the same as those in the first embodiment. Accordingly, the same operational effects as those of the first embodiment can be obtained, and the degree of freedom of arrangement of the drive piston 43 including the arrangement form of the first embodiment is increased, so that the variator space can be effectively used. Also, the layout of the variator becomes easy. As a result, the mountability of the transmission is improved and a substantial reduction in size is possible.

  FIG. 3 schematically shows a third embodiment of the present invention. As shown in the figure, in this embodiment, one of the two drive pistons 43 that support each trunnion 6 is coupled to the trunnion 6 (drive rod 42) via a link 312. The link 312 is swingable around a fulcrum 316 and is relative to the drive rod 42 of one drive cylinder 43 (drive rod coupled to the trunnion) and the drive rod 42 ′ of the other drive cylinder 43. It is pivotally connected. In this case, in order to reduce tilting friction, it is preferable that the drive rod 42 and the link 312 are connected via a rolling bearing (spherical bearing) 318. In order to reduce offset friction, it is preferable that the drive rod 42 ′ and the link 312 are connected via a rolling bearing 320.

  Thus, in this embodiment, since the drive piston 43 and the trunnion 6 are coupled via the link 312 that swings around the fulcrum 316, the control pressure (by adjusting the position of the fulcrum 316 as appropriate) The amplification factor of the operating pressure of the drive piston 43 can be changed. Therefore, it becomes possible to control with a lower pressure pump.

  FIG. 4 schematically shows a fourth embodiment of the present invention. As illustrated, in the present embodiment, all of the two drive pistons 43 that support each trunnion 6 are coupled to the trunnion 6 (drive rod 42) via a link 312. Other configurations are the same as those of the third embodiment. Therefore, the same operational effects as those of the third embodiment can be obtained, and the amplification factor can be changed in all the drive pistons 43, so that the torque transmission efficiency can be further improved.

  Needless to say, the present invention is not limited to the above-described embodiments, and can be variously modified without departing from the scope of the invention. For example, in the above-described embodiment, there are two drive pistons that support each trunnion, but each trunnion may be supported by three or more drive pistons.

  The present invention can be applied to various toroidal type continuously variable transmissions such as the single cavity type shown in FIG. 9 and the double cavity type shown in FIG.

It is a model diagram which shows the principal part of the 1st Embodiment of this invention. It is a model diagram which shows the principal part of the 2nd Embodiment of this invention. It is a model diagram which shows the principal part of the 3rd Embodiment of this invention. It is a model diagram which shows the principal part of the 4th Embodiment of this invention. It is a side view which shows the fundamental structure of the toroidal type continuously variable transmission conventionally known in the state at the time of maximum deceleration. It is a side view which shows the basic structure of the toroidal type continuously variable transmission conventionally known in the state at the time of maximum acceleration. It is sectional drawing which shows an example of the conventional concrete structure. It is sectional drawing which follows the AA line of FIG. It is sectional drawing which shows an example of a single cavity type toroidal type continuously variable transmission.

Explanation of symbols

2 Input side disk 4 Output side disk 5 Axis 6 Trunnion 11 Power roller 43 Drive piston

Claims (4)

An input side disk and an output side disk that are supported concentrically and rotatably with each inner surface facing each other, a plurality of power rollers sandwiched between these two disks, and the input side disk And a plurality of trunnions that pivot about a pair of pivots that are concentrically provided to each other and are twisted with respect to the central axis of the output side disk, and that rotatably support the power rollers, A toroidal continuously variable transmission comprising a drive piston for displacing each trunnion in the axial direction of the pivot;
Each of the trunnions is supported by a plurality of the drive pistons having the same structure, and the toroidal continuously variable transmission.   2. The toroidal continuously variable transmission according to claim 1, wherein the drive pistons are provided on both sides of each trunnion, or the plurality of drive pistons are provided on one side of each trunnion.   3. The toroidal continuously variable transmission according to claim 1, wherein at least one of the plurality of drive pistons supporting each trunnion is coupled to the trunnion via a link. .   The hydraulic pressure from a hydraulic pressure source acts on the drive piston via a hydraulic line, and an accumulator is provided in the middle of the hydraulic line. The toroidal type continuously variable transmission described in the item.

Images