Patent Publication Number: US-7211023-B2

Title: Variator and variator arrangement

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation of International Application PCT/EP2004/008669, filed on Aug. 3, 2004. This application is hereby incorporated by reference in its entirety. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a variator for a toroidal transmission, with a driving disk and with a driven disk, between which is set up a toroidal space which defines a toroidal reference circle, and with at least two rollers which are arranged in the toroidal space for torque transfer between the driving disk and the driven disk, the rollers being in each case mounted rotatably on a roller carrier, the roller carriers being in each case spatially adjustable by means of a piston/cylinder arrangement, in order to adjust the transfer ratio of the variator, and the pistons of the piston/cylinder arrangements being in each case adjustable along a stroke axis. 
   The present invention relates, furthermore, to a variator arrangement consisting of two or more variators of the type mentioned. 
   2. Description of the Related Art 
   In the field of transmissions, in particular of transmissions for motor vehicles, there is a trend toward continuously variable transmissions. Continuously variable transmissions, in general, make it possible to operate the internal combustion engine that is arranged in series with the transmission in motor vehicles, in a favorable rotational speed range independently of the respective vehicle speed. The efficiency of the drivetrain formed by the internal combustion engine and the continuously variable transmission is thereby improved. Furthermore, continuously variable transmissions afford a particularly high degree of driving comfort. 
   Among continuously variable transmissions, toroidal transmissions, as they are known, have particular importance, specifically especially because of their higher torque capacity, as compared with continuously variable wrap-around transmissions (CVTs). 
   Among toroidal transmissions, the Torotrak™ system is of particular significance (cf. www.torotrak.com). This transmission manages without an input-side starting clutch or a hydrodynamic torque converter. It is a full-toroidal transmission which is generally constructed in the manner of a countershaft transmission. The variator ensures a continuous adjustment of the ratio. A planet wheel set serves as a summing transmission. 
   The core of the toroidal transmission is the variator of the type initially mentioned or an arrangement consisting of a plurality of such variators. 
   In transmission designs put forward at the present time, the piston/cylinder arrangements for the spatial adjustment of the roller carriers are arranged tangentially with respect to the toroidal reference circle and spatially well outside the maximum diameter of the toroidal disks (driving and driven disk). As a result of this arrangement, the cylinders project well beyond the actual contour of the variator, the consequence of this being that the toroidal transmission, overall, has a large build in the radial direction (unfavorable package). On account of this, the designs of toroidal transmissions known at the present time can be fitted only with difficulty to the tunnel contour of vehicles having standard longitudinal drive trains. 
   SUMMARY OF THE INVENTION 
   Against the above background, the object of the present invention is to specify an improved variator for a toroidal transmission and a variator arrangement based on this. 
   In the variator initially mentioned, the above object is achieved in that the piston/cylinder arrangements are connected to the roller carriers via respective levers. 
   By virtue of the measure of providing a specific piston/cylinder arrangement for each roller, the cylinder surface of the individual piston/cylinder arrangements can be smaller than in the case of a single piston/cylinder arrangement for all the rollers. Furthermore, by means of the levers, it is possible to arrange the individual piston/cylinder arrangements more favorably, so that the construction space of the variator is reduced especially in the radial direction. 
   These advantages also apply to a variator arrangement with a plurality of such variators and to a toroidal transmission constructed thereby. 
   The above object is consequently achieved in full. 
   The lever systems of the respective rollers are preferably designed identically in kinematic terms, so that the stroke transfer ratios are the same, with the result that the division of the roller supporting forces is distributed uniformly over the circumference of the variator. 
   It is especially preferred if the levers are pivotably mounted in the toroidal transmission fixedly with respect to the housing. 
   A fixed reference point for the levers is thereby set up, so that the lever systems can be controlled more simply. 
   Furthermore, it is advantageous if the stroke axes of the piston/cylinder arrangements are in each case oriented approximately parallel to a tangent of the toroidal reference circle. 
   A short axial type of construction is thereby possible. 
   In this case, it is especially advantageous if the piston/cylinder arrangements are arranged in the region of the outer circumference of the driving or driven disk. 
   What is achieved thereby is that the variator also has a compact build in the radial direction. 
   It is, of course, in this case particularly preferred if the piston/cylinder arrangements are arranged between the driving and the driven disk, that is to say lie at least partially within the toroidal space. 
   In this embodiment, it is advantageous, furthermore, if the stroke axes of the piston/cylinder arrangements are arranged approximately perpendicularly with respect to the axis of the driving or driven disk. 
   As a result, once again, a particularly short axial and radial type of construction is achieved. In this case, the piston/cylinder arrangements preferably lie on a circular line which is arranged concentrically with respect to the toroidal reference circle. Particularly preferably, the circle formed by the piston/cylinder arrangements lies in the same plane as the toroidal reference circle. 
   Alternatively to this, however, it is also possible to arrange the stroke axes of the piston/cylinder arrangements approximately parallel to the axis of the driving or driven disk. 
   This form of construction, as a rule, leads to a somewhat more complicated lever system, but may likewise contribute to a significant reduction in construction size in the radial direction. 
   It is particularly preferred, overall, if the cylinders of the piston/cylinder arrangements are mounted on a common system carrier. 
   The outlay in structural terms is thereby reduced. 
   This applies likewise when the pistons are mounted on a common system carrier. 
   In this case, it is especially advantageous if the cylinders or pistons are produced in one piece with the system carrier. 
   The number of parts is thereby further reduced. Moreover, a compact type of construction is obtained. 
   According to a further exemplary embodiment preferred overall, the levers are mounted pivotably on a common system carrier. 
   The system carrier is in this case preferably mounted within the toroidal transmission fixedly with respect to the housing. The system carrier may be the same one on which the cylinders of the piston/cylinder arrangements are also secured. 
   As a result, once again, the outlay in structural terms is reduced. 
   It is advantageous, furthermore, if the roller carriers are connected to the associated lever in each case via a cardan or ball joint. 
   What is achieved thereby is that the roller carriers are movable spatially in a plurality of degrees of freedom (in particular, in an axial direction and rotatably about this axis). As a result, the necessary kinematic degrees of freedom of the roller carrier can consequently be implemented simply in structural terms in spite of the lever systems. 
   Overall, it is advantageous, furthermore, if the piston/cylinder arrangements and the roller carriers are articulated on the respective levers in such a way that the actuating force generated by the piston/cylinder arrangements is transferred, reinforced, to the respective roller carriers. 
   In this embodiment, the lever principle of mechanics is utilized to ensure that the roller carriers are movable with comparatively low actuating forces. The piston/cylinder arrangements can thereby be designed with a further reduced cross section. The construction space necessary for the variator is thereby further diminished. 
   According to a further preferred embodiment, a system carrier as a variator component fixed with respect to the housing is provided. 
   As already mentioned above, the system carrier may serve as a carrier for the cylinders and/or the levers. It may, however, also fulfill further tasks. 
   It is especially advantageous, in this case, if the system carrier is multipart. 
   What is achieved thereby is that the system carrier can possess higher functionality. 
   It is especially preferred if the system carrier has at least one fluid duct. 
   It is thereby possible to utilize the system carrier for the transportation of fluid, in particular oil. 
   In this case, it is especially advantageous if, in the case of a multipart system carrier, the fluid duct is formed by at least one groove which is located in one system carrier part and which is closed by another system carrier part. 
   The outlay in terms of the production of the fluid ducts is thereby markedly reduced. 
   According to a further preferred embodiment, the system carrier has a bearing point for a variator shaft. 
   It is thereby possible to utilize the system carrier for a further function. Thus, in a variator arrangement with two variators arranged next to one another, what can be achieved is that reaction forces arising from the drive power or driven power of the inner variator disk are not introduced into the variator. The variator shaft then remains free of transverse forces. A flexion of this shaft is avoided. 
   For comparable reasons, it may be advantageous if the system carrier has a bearing point for a countershaft. 
   According to a further preferred embodiment, the kinematics of the connection of the piston/cylinder arrangements to the respective levers are utilized to reduce the transverse movement of the rollers for achieving the ratio transfer. 
   As a result, the “stroke” can be reduced, specifically by a pivoting or tilting movement being superposed. 
   Alternatively to this, it is possible to utilize the kinematics of the connection of the piston/cylinder arrangements to the respective levers to increase the transverse movement of the rollers for achieving the ratio transfer. 
   This affords better regulatability. 
   In the variator arrangement according to the invention, it is especially advantageous if the two variators each have a system carrier, said system carriers being connected to one another by means of a connecting element. 
   The variator arrangement, overall, can thereby be constructed as a module, this simplifying mounting into the transmission. 
   The features mentioned above and those yet to be explained below can be used not only in the combination specified in each case, but also in other combinations or alone, without departing from the scope of the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Exemplary embodiments of the invention are illustrated in the drawing and are explained in more detail in the following description. In the drawing: 
       FIG. 1  shows a diagrammatic view of a toroidal transmission; 
       FIG. 2  shows a partially cut away diagrammatic perspective view of a variator according to the invention; 
       FIG. 3  shows a side view of a further embodiment of the variator according to the invention; and 
       FIG. 4  shows a longitudinal sectional view through a variator arrangement according to the invention with two variators. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In  FIG. 1 , a diagrammatically illustrated toroidal transmission is designated in general by  10 . 
   The toroidal transmission has a transmission input shaft  12 , a countershaft  14  and a transmission output shaft  16 . 
   A variator arrangement of the toroidal transmission  10  is shown at  20 . The variator arrangement  20  has a variator main shaft  22  and a variator secondary shaft  24 . The variator arrangement  20  contains, furthermore, two variators  26 A,  26 B. 
   Each variator has a driving disk  28 A,  28 B and a driven disk  30 A,  30 B. 
   The driving disks  28 A,  28 B enclose, together with the respective driven disks  30 A,  30 B, in each case a toroidal space  32 A,  32 B. 
   A plurality of rollers  34 , as a rule three rollers  34  in each case, are arranged in each case in the toroidal spaces  32 A,  32 B so as to be distributed circumferentially over the toroidal space. 
   The rollers  34  can be adjusted spatially within the toroidal space  32  by means of an actuator mechanism, not illustrated in any more detail, as is shown diagrammatically at  36 , in order to vary the transfer ratio of the variator arrangement  20 . In this case, it goes without saying that all the rollers  34  of the variators  26 A,  26 B are adjusted codirectionally, so that the reaction forces occurring can be absorbed uniformly over the circumference of the variator arrangement  20 . 
   At  38 , a wheel set is shown, which connects the countershaft  14  in the manner of a constant to the variator secondary shaft  24  to which the driving disks  28 A,  28 B are secured. The driven disks  30 A,  30 B are secured to the variator main shaft  22  which is connected to a summing transmission  40 . 
   The summing transmission  40  has a planet wheel set  42 . The variator main shaft  22  is connected to the sun wheel of the planet wheel set  42 . The countershaft is connected to the planet carriers of the planet wheel set  42  via a further wheel set (not designated. 
   The sun wheel is connectable to the transmission output shaft  16  via a high-regime clutch  44 . The ring wheel of the planet wheel set  42  is connectable to the transmission output shaft  16  via a low-regime clutch  46 . 
   The functioning of the toroidal transmission  10  is generally known and is not described in detail here for the sake of compact illustration. 
     FIG. 2  shows a partially cut away diagrammatic perspective view of part of a variator  26  according to the invention. The variator  26  may be used as the variators  26 A,  26 B of the variator arrangement  20  in the toroidal transmission  10  of  FIG. 1 . 
   The variator  26  has a driving disk  28  (not illustrated) and a driven disk  30  which enclose a toroidal space  32 . Furthermore, three rollers  34 , of which one roller  34  is illustrated in  FIG. 2 , are arranged in the toroidal space  32  so as to be distributed circumferentially. 
   The roller  34  is mounted rotatably on a fork-like roller carrier  50 . The longitudinal axis of the roller carrier  50  is designated by  51 . The axis of rotation of the roller  34  on the roller carrier  50  is designated by  52 . 
   A toroidal reference plane  54  of the toroidal space  32  is oriented perpendicularly with respect to the variator main shaft  22  which is illustrated diagrammatically in  FIG. 2  as an axis. 
   The variator  26  has, furthermore, an adjusting device, designated in general by  60 , for the roller carrier  50 . The adjusting device  60  is arranged on a system carrier  62  which is fixed with respect to the housing and which is arranged parallel to the toroidal reference plane  54 . Only part of the system carrier  62  is illustrated in  FIG. 2  for the sake of a clearer illustration. 
   A piston/cylinder arrangement  64  is arranged on the system carrier  62 . The piston/cylinder arrangement  64  lies approximately in the region of the circumference  65  of the driven disk  30  in the radial direction. 
   The piston/cylinder arrangement  64  has a cylinder  68  secured to the system carrier  62  and a piston  66  which is displaceable along a stroke axis  70 . In the illustration of  FIG. 2 , the stroke axis  70  is oriented approximately tangentially with respect to the circumference  65  of the driven disk  30  and runs approximately perpendicularly with respect to the axis  22 . 
   The piston  66  is connected to a lever  72 . The lever  72  is mounted on the system carrier  62  pivotably about a lever axis  73 . The lever axis  73  is generally oriented approximately parallel to the axis  22 . The pivotability of the lever  72  is indicated diagrammatically at  74 . 
   Approximately in a middle region of the lever  72 , the latter has arranged on it a ball joint  76 , on which one end of the roller carrier  50  is mounted in an articulated manner. 
   The piston  66  is articulated approximately in the region of the free end of the lever  72 , specifically by means of a guide  78  indicated diagrammatically. 
   The adjusting device  60  or the lever mechanism formed thereby is designed such that a castor angle α is set up between the toroidal reference plane  54  and the longitudinal axis  51  (roller pivot axis) of the roller carrier  50 . 
   The lever  72  can be deflected about the lever axis  73  as the result of an actuation of the piston/cylinder arrangement. This gives rise to a spatial adjustment of the roller carrier  50  which is composed of linear movements, as are illustrated diagrammatically at  80 , and of rotational movements about an axis  52   b  of the roller carrier  50 , as shown diagrammatically at  82 . The axis  52   b  runs approximately parallel to the axis  22 . 
   The lever ratios during the adjustment operation can be set up by suitable choice of the location of the ball joint  76  (or of a corresponding cardan joint) and of the location of articulation of the piston  66  on the lever  72  in such a way that force intensification can be achieved. It is thereby possible for the cylinder surface of the piston/cylinder arrangement  64  to be small, so that the piston/cylinder arrangement can easily be integrated into the variator  26  in structural terms. 
   It goes without saying that corresponding adjusting devices  60  for the other two rollers (not illustrated) of the variator  26  are similarly arranged, distributed circumferentially, on the system carrier  62 . 
   The three piston/cylinder arrangements  64  of the variator  26  are activated parallel to one another and codirectionally by means of a control device, not illustrated in any more detail. Furthermore, the lever ratios in all three adjusting devices  60  are designed identically. The stroke transfer ratios are likewise selected identically. 
   By the piston/cylinder arrangements  64  being arranged tangentially around the outer circumference of the disks  28 ,  30  of the variator  26 , the piston/cylinder arrangements  64  enclose approximately a circle which is arranged concentrically with respect to the outer circumference  65 . Ideally, the piston/cylinder arrangements  64  may be arranged directly between the disks  28 ,  30  of the variator  26 . For structural reasons, however, it is necessary, where appropriate, for the piston/cylinder arrangements  64  to extend slightly beyond the circumference  65 . In this case, the stroke axes  70  run in each case parallel to a tangent of the outer circumference  65 . 
   Although it is naturally preferred if the piston/cylinder arrangements  64  are arranged on a common system carrier  62 , they may also in each case be individually arranged fixedly with respect to the housing via suitable means. 
   In an alternative embodiment, the piston/cylinder arrangements are arranged in the region of the circumference  65  of the disks  28 ,  30  of the variator  26 , but rotated through 90°, as indicated diagrammatically at  64 ′. The corresponding stroke axis  70 ′ of this modified piston/cylinder arrangement  64 ′ then runs approximately parallel to the axis  22 . In this case, it may be necessary to provide a multimembered lever mechanism for adjusting the roller carrier  50 . 
     FIG. 3  illustrates an implementable embodiment of a variator module  90  for a variator  26 . The variator module  90  is constructed according to the principles which were explained in relation to the variator  26  of  FIG. 2  or its adjusting device  60 . Only differences from this are dealt with below. 
   The variator module  90  has a system carrier  62 . The system carrier  62  has an annular disk to which the levers  72  are articulated and the cylinders  68  of the piston/cylinder arrangements  64  are secured. The cylinders  68  may be secured to the system carrier  62  in any desired way. They may also be produced in one piece with this. 
   The annular disk of the system carrier  62  is connected via three radial webs to a hub  92  of the system carrier  62 , said hub being arranged around the variator main shaft  22 . The variator main shaft  22  is mounted within the hub  92  rotatably in relation to the system carrier  62  fixed with respect to the housing. 
   The variator module  90  contains, furthermore, the three roller carriers  50  with the rollers  34  mounted in each case on them. 
   The variator module  90  can be preassembled before being fitted into the variator  26 . If suitable hydraulic fluid connections are provided, it is even possible to test the variator module  90  for functioning capacity and to vent it before it is fitted into the variator  26 . Furthermore, the assembly of the variator  26  is simplified. 
     FIG. 4  shows a variator arrangement  20  (cf.  FIG. 1 ) with two variators  26 A,  26 B arranged next to one another on a variator main shaft  22 . 
   The variators  26 A,  26 B are constructed according to the same basic principles as the variator  26  of  FIG. 2 . Furthermore, the variators  26 A,  26 B contain in each case a variator module  90 A and  90 B according to  FIG. 3 . 
   It is illustrated, at  94 , that the variator secondary shaft  24  is mounted on the system carriers  62 A,  62 B, and the variator main shaft  22  is also mounted indirectly above that. 
   In the embodiment illustrated, the system carriers  62 A,  62 B are constructed in two parts and consist of a first carrier  95  and of a further carrier  96 . The first carrier  95  possesses the same function as the system carrier  62  described with reference to  FIG. 3 . That is to say, the first carrier  95  supports the levers  72  and the piston/cylinder arrangements  64 . 
   The further carrier  96  is arranged adjacent to the first carrier  95 . The carriers  95 ,  96  bear closely one against the other. On the further carrier  96  (and/or on the first carrier  95 ), one or more grooves are formed, which, in conjunction with the other carrier  95  or  96  in each case, serve as hydraulic fluid ducts (oil ducts)  98 . Consequently, the system carriers  62 A,  62 B may also be used for the routing of hydraulic fluid into the interior of the toroidal space  32 . 
   Finally, it is shown that the system carriers  62 A,  62 B are connected rigidly to one another via a connecting element  100 . 
   In this embodiment, it is possible to produce the variator arrangement  20  as a prefabricated module which is subsequently fitted into the toroidal transmission  10 . 
   The following additionally applies, in general, to the variator according to the invention and the variator arrangement according to the invention: 
   The adjusting devices  60  are identical, in particular with regard to the piston-travel transfer function. As a result, deviations in ratio transfer during adjustment operations are minimal, and consequently the efficiencies are improved, as compared with the prior art. 
   By virtue of a suitable arrangement of the levers  72 , the tilting of the roller axis  52  generated by their pivoting movement may be designed such that the transfer ratio adjustment is reinforced. The required pivoting movement of the levers  72  for covering the entire transfer ratio range can thereby be reduced. This diminishes the construction space requirement of the adjusting device  60 . 
   The tilting of the roller axis  52  generated by the pivoting movement of the levers  72  may likewise be designed such that it counteracts the transfer ratio adjustment. As a result, the transfer ratio adjustment by means of the adjusting device  60  becomes more sluggish, and therefore regulation can be designed to be less dynamic. This affords advantages in terms of the regulation/control of the transmission. 
   As regards the abovementioned hydraulic fluid ducts  98 , it must be mentioned that the ducts may also be sealed off by means of an intermediate plate  105  between the system carrier parts  95 ,  96 . 
   The system carriers  62  may have in each case bearing points for a variator main shaft  22 . As a result, reaction forces arising from the drive power or driven power of the inner variator disks  28 A and  28 B are not introduced into the variator  26 . The variator main shaft  22  is then free of transverse forces. Furthermore, a flexion of the variator main shaft  22  is avoided. 
   Furthermore, the system carriers  62  may have (not illustrated) bearing points for the countershaft  14 . The flexion of the countershaft  14  can thereby be reduced. The bearing reactions of the drive power or driven power of the respective variator are then absorbed by the system carrier  62  and load the housing of the toroidal transmission  10  to a lesser extent. 
   The position of the rollers  34  within the toroidal space (cavity)  32  of the full-toroidal variator  26  according to the invention determines the transfer ratio of the variator  26  via geometric relations. If the position of the rollers  34  in the toroidal space  32  is changed, then the transfer ratio also changes via the kinematics and the geometry. In the prior art with radially oriented piston/cylinder arrangements, the rollers  34  and the roller carriers  50  are displaced tangentially with respect to the toroidal reference circle  54  by means of these piston/cylinder arrangements. The transfer ratio change is thereby initiated. The hydraulic pressure and consequently the force of the piston/cylinder arrangements then determine the torque transmittable in the variator  26 . 
   In the embodiment according to the invention, the roller carriers  50  are no longer connected directly to the piston/cylinder arrangements, but, instead, via the respective levers  72 . When a movement is imparted to the pistons  66  of the piston/cylinder arrangements  64 , this movement is transferred to the roller carriers  50  via the levers  72  and a transfer ratio change likewise results. The kinematics of the roller carriers  50  are in this case designed such that they adapt to the movement of the roller carriers of the prior art. In this case, a resulting tilting movement about the axis  52   b  of the rollers  34  is utilized to reduce the transverse movement of the rollers  34 , as compared with the known solution, in order to achieve a specific transfer ratio. 
   The guides  78  of the pistons  66  on the levers  72  may be achieved, for example, by means of a slotted link, the required groove being arranged on the piston and the sliding element being arranged on the lever, or vice versa. 
   Alternatively, the tie-up may also take place by means of a joint between piston and lever. In this case, the cylinder is then tied to the housing or to the system carrier in an articulated manner. The joint may be designed as a ball joint in the piston.