Abstract:
A transmission noise attenuation device for a bearing assembly of a belt-driven conical-pulley transmission having a chain that serves as an endless torque-transmitting device. A shaft is rotatably supported in a bearing that includes a bearing outer ring with a cylindrical outer surface, wherein the bearing is supported in a bearing housing. At least one cam ring is positioned between the bearing housing inner surface and the bearing outer ring outer surface. The cam ring is elastically deformable to allow limited radial movement between the bearing housing inner surface and the bearing outer ring outer surface.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a belt-driven conical-pulley transmission, such as a continuously variable transmission, having an endless torque-transmitting means in the form of a drive chain, as well as to a noise attenuation device for a shaft bearing supported in a bearing housing. The invention also relates to a cam ring structure for a noise attenuation arrangement. 
     2. Description of the Related Art 
     The requirement for comfort in automobiles is generally very high, also particularly with regard to acoustics. Especially for luxury automobiles, the driver and passengers wish to prevent any disturbing noise originating as a result of operation of the automobile power train. However, internal combustion engines and other power train components, such as transmissions, do create noises that can generally be perceived as constituting a disturbance. In continuously variable transmissions, the use of a plate-link chain can lead to the production of noise, because a plate-link chain, by virtue of its structure with links and pins, creates a repetitive knocking noise during operation of the transmission when the pins strike the conical disks of the transmission. 
     Belt-driven conical-pulley transmissions with a continuously variable transmission ratio include two pairs of conical disks located on shafts that are spaced from each other and around which an endless torque-transmitting means frictionally engages the conical surfaces of the pairs of conical disks. The transmission ratio of the transmission can be continuously modified by opposite changes of the spacings between the pairs of conical disks. Metallic chains are particularly used as endless torque-transmitting means in transmissions in which high torques can be transmitted, for example torque levels in the range of 300 Nm and higher. 
     Radially-undulating springs are currently used for vibration isolation of loaded rotation bearings. However, they have the disadvantage that as a result of their spring deflection, a displacement of the shaft as a function of the load is induced. That can lead on the one hand to loads that are so great as to damage components in contact with it, and on the other hand to an increase in noise production. 
     An additional disadvantage is the fact that the cam height on the inner radius and the perimeter of such radially-undulating springs are different. Manufacturing conditions result in tolerances. The addition of the tolerances is superimposed on the load-dependent displacement resulting from the spring deflection as a static positioning error, whereby the total tolerance in the position of the shaft relative to the housing becomes very large. 
     An object of the invention is the reduction of noise transmission, especially structure-borne noise transmission from the conical disks in a motor vehicle by the elimination of the load-dependent displacement of the shafts, while keeping the necessary manufacturing costs required for that purpose as low as possible. 
     SUMMARY OF THE INVENTION 
     Briefly stated, in accordance with one aspect of the present invention, the object is achieved by means of a noise attenuation device for a shaft bearing supported in a bearing housing of a belt-driven conical-pulley transmission having a chain as an endless torque-transmitting means. This noise attenuation device includes a bearing outer ring having an outer surface defined by a circular cylinder and within which a shaft is supported. The bearing outer ring is rigidly positioned within the bearing housing, wherein the inner surface of the bearing housing surrounds the outer surface of the bearing outer ring. Between the inner surface of the bearing housing and the outer surface of the bearing outer ring at least one cam ring is arranged that by elastic deformation allows limited radial movement between the inner surface and the outer surface. 
     Advantageous embodiments and further developments of the inventive noise attenuation device are set forth below by way of example, whereby the examples are not to be considered as limiting. 
     At least two adjacent cam rings are axially spaced from each other. After a predetermined radial relative movement between the outer surface and the inner surface, the cam rings rest on the inner surface or the outer surface and prevent any further radial relative movement. 
     The cam ring is provided, on the inside and outside, with support protuberances or cams, which are brought into contact, with a certain amount of play, with the outer surface and/or the inner surface. The height of the cams or the support protuberances is identical. That results under operating conditions in a reduced shaft offset, whereby the bearing application area of the bearing isolation is significantly increased. In addition, that solution, involving a cam ring, makes possible more economical manufacturing. 
     The play lies within a tolerance of 0.02 millimeters to 0.1 mm, whereby it should preferably be less than or equal to 0.1 mm. 
     Advantageously, all of the support protuberances have an identical amount of play relative to the respective outer surface and/or inner surface. 
     A radially-extending side surface is formed on at least one axial wall of the outer surface, and on at least one axial wall of the inner surface. And at least one support component is provided by means of which the side surfaces are supported opposite to each other. 
     On the outer surface and radially positioned relative to its radially-extending side surfaces is a sleeve with a basically U-shaped cross section, between which and the outer surface at least one cam ring is arranged. 
     The radial side surfaces of the outer surface rest against radial side surfaces of the inner surface, in an elastic and resilient manner and in an axial direction, by means of the basically radially running, arched sidewalls of the sleeve. 
     Attached to the outer surface and radially positioned relative to its radially-extending side surfaces is a spring sleeve that forms the cam ring, the spring sleeve having a basically U-shaped cross-section. The wall of the spring sleeve, which runs basically parallel to the axis, bulges radially outward. 
     The wall of the spring sleeve has at least two axially-spaced, circumferential radial undulations, and with an axial wavelength direction. 
     An annular region between the radial undulations extends as a circumferential recess in the outer surface. 
     The wall of the spring sleeve has at least one radial undulation with a wavelength direction running in the circumferential direction. 
     The radial undulations of the wall, the wavelength directions of which run axially and/or in the direction of the circumference, are of equal height. 
     The cam ring is formed of segments that extend over parts of the circumference of the inner surface and/or the outer surface. 
     Examples of advantageous embodiments of cam rings in accordance with the invention, and which can be used in the noise attenuation device in accordance with the invention, are described below. 
     A cam ring to surround at least a partial periphery of a circular cylindrical outer surface has spaced cams in the circumferential direction that are formed on the radial exterior and the radial interior, for permanent contact with the outer surface, and an inner surface that is concentric with the outer surface and is surrounded by it. 
     A cam ring with cams has a slit or a gap. 
     The cam ring can be produced by stamping and subsequent bending, which is extremely advantageous for economical manufacturing. 
     A further advantage for economical manufacturing is when a cam ring is composed of rectangular or round wire material. 
     In addition, it is advantageous for the support protuberances to be produced having an exact size by means of a transverse impact extrusion process. 
     The belt-driven conical-pulley transmission with the noise attenuation device in accordance with the invention, and the cam ring or rings in accordance with the invention, can be used for any kind of bearing application. They are advantageously used for roller bearings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The structure, operation, and advantages of the present invention will become further apparent upon consideration of the following description, taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a cross-sectional view of a portion of a belt-driven conical-pulley transmission; 
         FIG. 2  is a fragmentary cross-sectional view of an embodiment of a bearing support; 
         FIG. 3  is a cross-sectional view taken along the line  3 - 3  of  FIG. 2 ; 
         FIG. 4  is a fragmentary cross-sectional view of another embodiment of a bearing support; 
         FIG. 5  is a cross-sectional view taken along the line  5 - 5  of  FIG. 4 ; 
         FIG. 6  is a fragmentary cross-sectional view of an embodiment of a cam ring; 
         FIG. 7  is a fragmentary cross-sectional view of another embodiment of a cam ring; 
         FIG. 8  is a fragmentary cross-sectional view of another embodiment of a bearing support and associated cam ring; and 
         FIG. 9  is an elevational view of a cam ring. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows only one part of a belt-driven conical-pulley transmission, specifically the part of the belt-driven conical-pulley transmission  1  that is driven by a drive motor, such as an internal combustion engine, and is located on the drive side or the input side. In a completely implemented belt-driven conical-pulley transmission, the input side part is associated with a complementary output side part of the continuously-variable, belt-driven conical-pulley transmission, whereby both parts are connected to each other by means of an endless torque-transmitting means, for example in the form of a plate-link chain  2  for transmitting torque. The belt-driven conical-pulley transmission  1  has a shaft  3 on the input side thereof, which, in the design shown is integrally formed with a fixed conical pulley  4 . This axially-fixed conical pulley  4  is adjacent, in the axial longitudinal direction of the shaft  3 , to an axially-displaceable conical pulley  5 . 
     In the representation according to  FIG. 1 , the plate-link chain  2  is shown in a radially outer position, relative to the input side pair of conical pulleys  4 ,  5 , which is achieved when the axially-displaceable conical pulley  5  in the drawing is displaced toward the right, which shifting movement of the axially-displaceable conical pulley  5  results in a radially outward movement of the plate-link chain  2 , producing a change in the transmission ratio of the transmission to high speed. 
     The axially displaceable conical pulley  5  can also be displaced toward the left in the plane of the drawing, in a known manner, whereby in that position the plate-link chain  2  is at a radially inner position (which is represented by reference numeral  2   a ), which produces a transmission ratio of the belt-driven conical-pulley transmission  1  of low speed. 
     The torque provided by a drive motor (not shown) is introduced to the input side part of the belt-driven conical-pulley transmission shown in  FIG. 1  by means of a gear  6  supported on the shaft  3 . Gear  6  is supported on the shaft  3  by means of a rolling body in the form of a ball bearing  7 , which receives axial and radial forces and which is secured to the shaft  3  by means of a disk  8  and a shaft nut  9 . A torque sensor  10  is arranged between the gear  6  and the axially-displaceable conical pulley  5  and is associated with a spreader disk unit  13  provided with an axially-fixed spreader disk  11  and an axially-displaceable spreader disk  12 . Arranged between the two spreader disks  11 ,  12  are rolling bodies, for example in the form of the balls  14  as shown. 
     A torque introduced through the gear  6  leads to the development of an angle of rotation between the axially-stationary spreader disk  11  and the axially-displaceable spreader disk  12 , which leads to an axial displacement of the spreader disk  12  that is based on the presence of inclined ramps arranged thereon, on which the balls  14  roll, thus causing an axial offset of the spreader disks relative to each other. 
     The torque sensor  10  has two pressure chambers  15 ,  16 , of which the first pressure chamber  15  is provided for the purpose of pressurizing with a pressure medium as a function of the transferred torque, and the second pressure chamber  16  is provided with a pressure medium as a function of the transmission ratio of the transmission. 
     For the production of the contact pressure for applying a normal force to the plate-link chain  2  between the axially-stationary conical pulley  4  and the axially-displaceable conical pulley  5 , a piston/cylinder unit  17  is provided that has two pressure chambers  18 ,  19 . The first pressure chamber  18  serves to increase or reduce the contact pressure that is applied to the plate-link chain  2  between the conical pulleys  4 ,  5 , and is connected with the pressure chamber  15  of the torque sensor  10 . The second pressure chamber  19  serves to change the force applied to the plate-link chain  2  as a function of the transmission ratio. 
     The shaft  3  has three channels  20  for supplying the pressure chambers with pressure medium from a pump (not shown). By means of an outlet side channel  21 , the pressure medium can flow out of the shaft  3  and return to the circuit. 
     The pressurization of pressure chambers  15 ,  16 ,  18 ,  19  leads to a torque- and transmission-ratio-dependent displacement of the axially-displaceable conical pulley  5  on the shaft  3 . For the purpose of accepting the displaceable conical pulley  5 , the shaft  3  has centering surfaces  22  that serve as a sliding fit for the displaceable conical pulley  5 . 
     As can readily be seen in  FIG. 1 , the belt-driven conical-pulley transmission  1  has a silencing device  23  in the region of each of the bearings of the conical pulley  4  on the shaft  3 . For that purpose the silencing device can have an annular body with an attenuation lining, or it can be composed of only an attenuation liner. 
     In accordance with  FIG. 2 , a bearing inner ring  22  surrounds a shaft (not shown) of a pair of conical pulleys in a belt-driven conical-pulley transmission. Between it and a bearing outer ring  44 , that is arranged concentrically with it, roller bodies  66  are arranged so that components  22 ,  44 , and  66  jointly form a roller bearing. It is to be understood that the outer surface of the bearing inner ring  22 , on which the roller bodies  66  roll, can be formed directly by a suitably machined outer surface of the shaft (not shown). The bearing outer ring  44  is received in an annular recess of a bearing housing  88 , for example a transmission housing, which, as shown on the right side of  FIG. 2 , is closed by a removable annular cover  110 . 
     The outer surface of the bearing outer ring  44  is not directly supported by the wall of the annular recess, but by an intermediate arrangement of various annular components and a shell  112  that can optionally be set into the annular recess. More precisely, in the example shown four annular cam rings  118  are arranged between the outer surface  114  of the bearing outer ring  44  and the inner surface  116  of the shell  112 , with stop rings  220  arranged between the cam rings  118  in order to ensure that an axial distance is maintained between them. Positioning rings  222  are provided on both axially outer sides. 
     The rigidity of the cam rings  118  is such as to enable the achievement of the desired rigidity of the bearing against radial displacement of the bearing shaft (not shown) by means of the four cam rings  118 . As follows from  FIG. 3 , which is a detail view of  FIG. 2  in the direction  3 - 3 , the cam rings  118  are formed in such a way that they are constantly in contact with outer surface  114  and inner surface  116 . The shell  112 , which can be made of steel, for example, is optional and serves to prevent wear of the recess and/or bore of the bearing housing  88  and can be made of a light metal. 
     In the embodiment according to  FIG. 2 , positioning rings  222  are provided in the peripheral direction, axially outside the cam rings  118 . 
     As is apparent from  FIG. 3 , the cam rings  118  are provided with inner and outer support protuberances  224 , which are spaced from each other in the circumferential direction and are in constant contact with outer surface  114  and inner surface  116 . The cam rings  118  are supported by the bearing housing  88 , which gives rise to an identical support of the roller bearing. 
       FIGS. 4 and 5  show a structure corresponding substantially with that Of  FIGS. 2 and 3  of the support or the uncoupling of the outer bearing ring  44  from bearing housing  88 , by means of which the noise transmission from the roller bearing to the foundation is reduced. Adjacent outer protuberances  224  of cam ring  118   a  are circumferentially spaced along an arc defined by the angle φ. 
     In the embodiments in accordance with  FIGS. 6 and 7 , the outer surfaces of the bearing outer ring  44  have no recess or groove. The sidewalls of the cam ring  118   b  extend parallel to the sidewalls of the bearing outer ring  44 , so that the cam ring, which is in the form of a spring sleeve, does not have the function of an axial spring. The cam ring  118   c  in  FIG. 7 , which is also in the form of a spring sleeve, has the additional function of an axial spring. 
     In  FIG. 8 , the left half of the figure is in longitudinal cross section and the right half of the figure shows a side view of an additional embodiment of a cam ring  118   d  in the form of a spring sleeve. The bearing outer ring  44   a  is surrounded by a spring sleeve  118   d  in the form of a thin-walled, spring steel sheet, with an essentially U-shaped overall cross section. The radially-extending sidewalls  666  are radially supported by a ring-shaped step  668  that is formed on the side surfaces of the outer ring  44   a . Radial resilience is achieved by a crown or radially-outward bulge of the end wall  770  of the spring sleeve  118   d . The basic rigidity can be controlled by the thickness of the sheet. The spring characteristic can usefully be chosen by selecting the nature of the curvature of the end wall, if necessary with several waves, and/or the contour of the sidewalls  666 . For example, the spring characteristic can be controlled in such a way that the end wall  770  comes into contact with the outer surface of the outer ring  44   a  after a certain radial deformation. Furthermore, an axial resilience of the spring sleeve  118   d  can be controlled by appropriate formation of the sidewalls  666  and the adjacent side surfaces of the outer bearing ring  44   a . By asymmetrical bending in their plane, the radial sidewalls  666  can also affect the radial resilience of the spring sleeve  118   d.    
     By having the radial sidewalls  666  extend far over and/or around the outer ring  44   a , on one hand the radial requirement for space is minimized, and on the other hand a relatively great degree of axial resilience is made possible. If necessary, slippage of the sidewalls  666  from the ring-shaped step  68  can be prevented by a suitable undercut. The spring sleeve  118   d  need not extend as a single piece over the entire circumference of the outer ring  44 . It can be made in the form of two circumferential segments. Retention of the spring sleeve  118   d  in the assembled condition is ensured by the included boring or recess in the bearing housing  88 , whereby through the crowned shape of the spring sleeve its mounting is facilitated. 
     For the axial support of the bearing, a circumferentially-extending radial protuberance  774  of the spring sleeve  118   d  can be provided, which is received in an annular groove  776  in the bearing housing  88 . The annular groove  776  can be formed by a gradation on the inner surface  116  of the bearing housing  88 , which is closed on the side by the annular cover  110   a.    
       FIG. 9  shows a possible embodiment of a cam ring in which the inner and outer protuberances  224  are arranged to lie opposite each other. An additional advantageous solution can also be that the protuberances  224  are arranged opposite each other, but offset at a specified distance. A gap  332  is provided to facilitate assembly of the cam ring over the bearing outer ring. 
     Although particular embodiments of the present invention have been illustrated and described, it would be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit of the present invention. It is therefore intended to encompass within the appended claims all such changes and modifications that fall within the scope of the present invention.