Abstract:
A pulley device comprising a rolling bearing including an inner ring defining a central bore, and outer ring and rolling elements mounted between the inner ring and the outer ring, a pulley secured in rotation with the outer ring and provided with a feature for engaging with a transmission member. The pulley additionally includes a screw comprising a head and a shank housed in the central bore of the inner ring, the screw being configured to fix the pulley device to a motor support. The pulley device also comprises a first sleeve arranged between the inner ring and the screw, on the side of the motor support. The first sleeve includes an inner surface that has a frustoconical portion having an increasing diameter toward the head of the screw.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is a Non-Provisional Patent Application, filed under the Paris Convention, claiming the benefit of France (FR) Patent Application Number 1462046, filed on 8 Dec. 2014, which is incorporated herein by reference in its entirety. 
     FIELD OF THE INVENTION 
     The invention relates to a pulley device. The field of the device is that of tension rollers for stretching a chain or belt for transmitting movements, rollers, winders, loose pulleys and any other means for support and transmitting rotation. 
     BACKGROUND OF THE INVENTION 
     In a known manner, such a pulley device may comprise a rolling bearing and a fixing screw. The rolling bearing comprises an inner ring and an outer ring in relative rotation. The screw comprises a head end and a threaded end. The screw crosses through the inner ring of the rolling bearing, such that its threaded end penetrates inside a tapped orifice arranged in a support, for example an engine block. To the extent possible, mechanical contact should be avoided between the rotating elements of the rolling bearing and the support, which can in particular be positioned in the engine compartment of a motor vehicle and subject to frequent vibrations. 
     To that end, it is known to use a spacer to axially separate the rolling bearing from the support. To produce this spacer, a first approach consists of integrating the spacer into the inner ring of the rolling bearing. One drawback of this approach is that it makes the manufacturing and assembly of the pulley devices equipped with such spacers more complex. 
     According to a second approach, the spacer is a separate part from the rolling bearing. The pulley device is then equipped with a metal sleeve that is secured to the inner ring of the rolling bearing. One drawback of this approach relates to the weight and cost of the sleeve. 
     In this respect, it is known, for example from DE-A-198 50 157, to provide a sleeve made from a plastic material that is overmolded or fitted on the inner ring of the rolling bearing. Such a pulley device is simple and cost-effective to manufacture. 
     It is also known, for example from DE-A-10 200 60 19 538, to provide two sleeves with a reduced size and that define an axial interstice between them. When the fixing screw is inserted through the sleeves, this screw is often inserted at an angle and then collides with an edge of the sleeve positioned against the support. Using two sleeves makes it possible to reduce the weight and cost of the pulley device, but complicates the insertion of the screw into the support. 
     SUMMARY OF THE INVENTION 
     The present invention more particularly aims to resolve these drawbacks, by proposing a new pulley device that facilitates the insertion of the screw. 
     To that end, the invention relates to a pulley device, comprising a rolling bearing including an inner ring defining a central bore, an outer ring and rolling elements mounted between the inner ring and the outer ring. The pulley device also comprises a pulley, secured in rotation with the outer ring and provided with means for engaging with a transmission member, as well as a screw comprising a head and a shank housed in the central bore of the inner ring, the screw being configured to fix the pulley device to a motor support. The pulley device also comprises a first sleeve arranged between the inner ring and the screw, on the side of the motor support. According to the invention, the sleeve includes an inner surface that has a frustoconical portion having an increasing diameter toward the head of the screw. 
     Thus, the invention makes it possible to prevent the screw from being jammed against the second sleeve during its insertion through the device. The shank of the screw passes in the inner central bore of the inner ring, then through the frustoconical portion of the sleeve without any risk of colliding with one of its edges, before penetrating the support. Furthermore, providing a frustoconical portion on the sleeve makes it possible to reduce the weight, and therefore cost, of the device. 
     According to advantageous, but optional aspects of the invention, such a pulley device may incorporate one or more of the following features, considered in any technically admissible combination:
         The pulley device further comprises a second sleeve arranged between the inner ring and the screw.   An axial gap is defined between the first sleeve and the second sleeve arranged in the bore of the inner ring, the axial gap having a length greater than or equal to half of the length of the bore.   The second sleeve has an inner surface that has a frustoconical portion having a diameter increasing toward the first sleeve.   The first and second sleeves have an identical construction.   The inner surface of at least one of the first and second sleeves has a frustoconical portion having an increasing diameter and emerging opposite the other sleeve.   At least one of the first and second sleeves has a cylindrical outer surface provided with at least one rib positioned bearing against the inner ring of the rolling bearing.   The minimum diameter of the inner surface of the first sleeve is smaller than the diameter of the shank of the screw.   The inner surface of the first sleeve is frustoconical over more than 80% of its axial length.   The frustoconical portion of the first sleeve extends over its entire inner surface.   At least one of the first and second sleeves is provided with an outer bevel, and an end oriented toward the other sleeve.   The first sleeve is mounted on the inner ring by overmolding, gluing or pressing.   The first sleeve is made from a synthetic material, in particular polyamide reinforced with glass fibers.       

    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The invention will be better understood and other advantages thereof will appear more clearly in light of the following description, provided solely as a non-limiting example and done in reference to the appended drawings, in which: 
         FIG. 1  is an elevation view of a pulley device according to a first embodiment of the invention, comprising a pulley, a rolling bearing, two sleeves and a fixing screw, which is not shown for simplification reasons; 
         FIG. 2  is a sectional view, along plane II-II of  FIG. 1 , of the pulley device of  FIG. 1  when it is mounted on a motor support using its screw, the second sleeve being inserted between the screw head and the rolling bearing, the first sleeve being inserted between the rolling bearing and the motor support; 
         FIG. 3  is a perspective view of the second sleeve shown in  FIG. 2 ; 
         FIG. 4  is an elevation view of the second sleeve along arrow IV in  FIG. 3 ; 
         FIG. 5  is a sectional view of the second sleeve along plane V-V in  FIG. 4 ; 
         FIG. 6  is a perspective view of the first sleeve shown in  FIGS. 1 and 2 ; 
         FIG. 7  is an elevation view of the first sleeve along arrow VII in  FIG. 6 ; 
         FIG. 8  is a sectional view of the first sleeve along plane VIII-VIII in  FIG. 7 ; 
         FIG. 9  is a view similar to  FIG. 2  of a pulley device according to a second embodiment of the invention, and 
         FIG. 10  is a view similar to  FIG. 2  of a pulley device according to a third embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       FIGS. 1 and 2  show a pulley device  1  according to the invention, of the tension roller type. 
     The pulley device  1  is designed to be mounted on a motor support  100 , partially shown in  FIG. 2 . This pulley device  1  comprises a ball bearing  2 , a pulley  3 , a fastening screw  4 , and two sleeves  5  and  6 . Reference X 1  denotes a central axis of the pulley device  1 . The pulley device  1  defines a central bore  10  centered on the axis X 1 . Reference L denotes the length of the bore  10  measured parallel to the axis X 1 . 
     Hereinafter, the terms “axial” and “radial” are defined in relation to the axis X 1 . Thus, an axial direction is parallel to the axis X 1  and a radial direction is perpendicular to the axis X 1  and secant to that axis. An axial surface is perpendicular to an axial direction and a radial surface is perpendicular to a radial direction. 
     The ball bearing  2  includes an inner ring  22 , an outer ring  24  and rolling elements  26  mounted between the inner ring  22  and the outer ring  24 . In the non-limiting example of  FIG. 2 , the rolling elements  26  are made up of two rows of balls  26 . Alternatively, the rolling elements  26  can be rollers or needles. 
     The pulley  3  is fixed on the outer ring  24 , for example by gluing, overmolding, tight mounting or crimping. The pulley  3  is secured in rotation, around the axis X 1 , with the outer ring  24 . The pulley  3  is provided with an outer peripheral surface  30 , i.e., the surface of the pulley  3  oriented radially outward relative to the axis X 1 . This surface  30  is provided to receive, by bearing, a belt  32  shown in mixed lines in  FIG. 2 . The surface  30  forms means for engagement of the pulley  3  with the belt  32 , which forms a torque transmitting member. In place of the belt  32 , the device  1  can receive a chain mounted around the surface  30 , whose geometry is then adapted. References  34  and  36  respectively denote the opposite annular surfaces of the pulley  3 , which are parallel to one another and perpendicular to the axis X 1 , the surface  36  being turned toward the motor support  100 . 
     The fastening screw  4  is received in the bore  10  of the device  1 . The screw  4  comprises a head  42  and a shank  44 , which extends from the head  42  to a threaded end  46 . Reference D 44  denotes the constant diameter of the shank  44 . Reference X 4  also denotes a longitudinal axis of the screw  4 , which is superimposed on the axis X 1  when the screw  4  is received in the bore  10 . 
     The pulley device  1  comprises a first sleeve  6  and a second sleeve  5  that delimit the bore  10  with the inner ring  22 . The sleeves  5  and  6  are made from a synthetic material, for example polyamide reinforced with glass fibers. The sleeves  5  and  6  are mounted on the inner ring  22  by overmolding, gluing or pressing. 
     The second sleeve  5 , shown in detail in  FIGS. 3 to 5 , is arranged radially between the inner ring  22  and the screw  4  on the side of its head  42 . In practice, the sleeve  5  is designed to receive, by bearing, the head  42  of the screw  4  when it is tightened in a corresponding tapping  102  of the motor support  100 . 
     The sleeve  5  is centered on an axis X 5  that is combined with the axes X 1  and X 4  in the mounted configuration of the pulley device  1 . Reference L 5  denotes the axial length of the sleeve  5 . 
     The sleeve  5  comprises an inner axial portion  52 , which is positioned radially between the inner ring  22  and the shank  44  of the screw  4 , and an outer axial portion  54  that is positioned axially between the inner ring  22  and the head  42  of the screw  4 . The portion  52  includes a cylindrical outer surface  520 , provided to come into contact with the inner ring  22 . In the example of  FIGS. 4 and 5 , the surface  520  is provided with four ribs  55  designed to bear against the inner ring  22  of the rolling bearing  2 . Alternatively, the surface  520  can be provided with a different number of ribs  55 . When the portion  52  of the sleeve  5  is inserted into the inner ring  22 , the ribs  55  exert a maintaining force on the inner ring  22 . The portion  54  includes a radial and outer cylindrical surface  540 , oriented toward the pulley  3 . 
     The sleeve  5  further comprises an inner radial surface  500  which, in the assembled configuration, is oriented toward the axis X 1  and the screw  4 . The surface  500  is frustoconical over the majority of its length L 5 . The surface  500  comprises a cylindrical portion  57 , in contact with the shank  44  in the mounted configuration of the pulley device  1 , and a frustoconical portion  58 . The frustoconical portion  58  has a diameter D 58  that increases toward the first sleeve  6 . Reference D 52  denotes the maximum inner diameter of the sleeve  5 , measured on the side of the portion  52 , and reference D 54  also denotes the minimum inner diameter of the sleeve  5 , measured on the side of the portion  54 . The diameter D 52  is strictly greater than the diameter D 54 . In particular, the diameter D 54  is the diameter of the cylindrical portion  57 . Before the shank  44  of the screw  4  is inserted in the bore  10 , the diameter D 54  is slightly smaller than the diameter D 44  of the shank  44  of the screw  4 , such that, when the screw  4  is received in the bore  10  of the pulley device  1 , the sleeve  5 , in particular its cylindrical portion  57 , is radially expanded and exerts a retaining force on the screw  4 . 
     The portion  52  of the sleeve  5  includes an end  53 , which is oriented toward the first sleeve  6  and includes an annular surface  530  perpendicular to the axis X 5 . The end  53  of the sleeve  5  is provided with a bevel  56  arranged at the junction between the surfaces  520  and  530 . The bevel  56  is provided to facilitate the mounting of the sleeve  5  in the inner ring  22  of the rolling bearing  2 . 
     The frustoconical portion  58  extends, from the annular surface  530 , over more than 80% of the lengths L 5  of the sleeve  5 . In practice, the portion  58  extends over more than 90% of the lengths L 5 . 
     According to one alternative of the invention that is not shown, the frustoconical portion  58  can extend over the entire length L 5 . In that case, the surface  500  does not comprise a cylindrical portion. 
     The first sleeve  6 , shown in detail in  FIGS. 6 to 8 , is arranged radially between the inner ring  22  and the screw  4  on the side of the motor support  100 . In practice, the sleeve  6  is designed to receive the motor support  100  by bearing when the threaded end of the screw  4  is tightened in the corresponding tapping  102  of this motor support. 
     The sleeve  6  is centered on an axis X 6  that is combined with the axes X 1 , X 4  and X 5  in the mounted configuration of the device  1 . Reference L 6  denotes the axial length of the sleeve  6 . 
     The sleeve  6  comprises an inner axial portion  62 , which is positioned radially between the inner ring  22  and the shank  44  of the screw  4 , and an outer axial portion  64 , which is positioned axially between the inner ring  22  and the motor support  100 . The portion  62  includes a cylindrical outer surface  620  provided to come into contact with the inner ring  22 . In the example of  FIGS. 6 and 7 , the surface  620  is provided with four ribs  65  designed to bear against the inner ring  22  of the rolling bearing  2 . Alternatively, the surface  620  can be provided with a different number of ribs  65 . When the portion  62  of the sleeve  6  is inserted into the inner ring  22 , the ribs  65 , like the ribs  55  of the sleeve  5 , exert a maintaining force on this inner ring  22 . The portion  64  includes a radial and outer cylindrical surface  640 , oriented toward the pulley  3 . 
     The sleeve  6  further comprises an inner radial surface  600  which, in the assembled configuration, is oriented toward the axis X 1  and the screw  4 . The surface  600  is frustoconical over most of its length L 6 . The surface  600  comprises a cylindrical portion  67 , bearing on the shank  44  in the mounted configuration of the pulley device  1 , and a frustoconical portion  68 . The frustoconical portion  68  has a diameter D 68  that increases toward the second sleeve  5 . Reference D 62  denotes the maximum inner diameter of the sleeve  6 , measured on the side of the portion  52 , and reference D 64  also denotes the minimum inner diameter of the sleeve  6 , measured on the side of the portion  64 . The diameter D 62  is strictly larger than the diameter D 64 . In particular, the diameter D 64  is the diameter of the cylindrical portion  67 . Before insertion of the shank  44  of the screw  4  in the bore  10 , the diameter D 54  is slightly smaller than the diameter D 44  of the shank  44  of the screw  4 , such that, when the screw  4  is received in the bore  10  of the pulley device  1 , the sleeve  6 , in particular the cylindrical portion  67 , is radially expanded and exerts a retaining force on the screw  4 . 
     The portion  62  of the sleeve  6  includes an end  63 , which is turned toward the second sleeve  5  and includes an annular surface  630  perpendicular to the axis X 6 . The end  63  of the sleeve  6  is provided with a bevel  66  arranged at the junction between the surfaces  620  and  630 . The bevel  66 , like the bevel  56  of the second sleeve  5 , is provided to facilitate the mounting of the sleeve  6  in the inner ring  22  of the rolling bearing  2 . The frustoconical portion  68  extends, from the annular surface  630 , over more than 80% of the length L 6  of the sleeve  6 . In practice, the portion  68  extends over more than 90% of the lengths L 6 . 
     According to one alternative of the invention that is not shown, the frustoconical portion  68  extends over the entire length L 6 . In this case, the surface  600  does not comprise a cylindrical portion. 
     As shown in  FIG. 2 , an axial gap E is defined parallel to the axis X 1  between the surface  530  of the second sleeve  5  and the surface  630  of the first sleeve  6 . Reference  1  denotes the length of the gap E measured parallel to the axis X 1 . The length l is greater than or equal to half of the length L of the bore  10 . 
     At this gap E, the inner ring  22  directly delimits the bore  10  radially to the axis X 1 . This allows a significant reduction in the weight of the pulley device  1 . Furthermore, owing to the frustoconical portion of the surface  600 , the insertion of the screw  4  is facilitated, since the end  46  of the screw  4  does not abut against a junction edge of the surfaces  600  and  630 . The frustoconical nature of the surface  58  also facilitate the insertion of the shank  44  of the screw into the bore  10  while allowing angular play between the parts  4  and  5 , during this insertion. 
     Other embodiments of the invention are described below in reference to  FIGS. 9 and 10 . In these embodiments, the component elements of the pulley device  1  are comparable to those of the first embodiment described above and, for simplification reasons, bear the same numerical references. Only the differences with respect to the first embodiment are described below. 
     According to the second embodiment, shown in  FIG. 9 , the second sleeve  5  and the first sleeve  6  have an identical construction, in practice the same as that of the sleeve  5  of the first embodiment. This makes it possible to reduce the manufacturing costs of the parts  5  and  6 . 
     According to the third embodiment, shown in  FIG. 10 , the sleeves  5  and  6  have an identical construction and have inner radial surfaces  500  and  600  made up of three portions. In particular, the surface  500  of the sleeve  5  has a cylindrical portion  57  axially surrounded by two frustoconical portions  58  and  59 , while the surface  600  of the sleeve  6  has a cylindrical portion  67  axially surrounded by two frustoconical portions  68  and  69 . Among these frustoconical portions, the first portions  58  and  68  have a diameter D 58  and D 68 , respectively, increasing and emerging toward the other sleeve  5  or  6 . On the contrary, the second frustoconical portions  59  and  69  have a diameter D 59  and D 69 , respectively, increasing and emerging opposite the other sleeve  5  or  6 . 
     According to one embodiment not shown in the figures, the sleeve  6  is as described above, while the sleeve  5  does not include a frustoconical portion and its surface  500  is cylindrical over its entire length L 5 . 
     According to another alternative not shown in the figures, the frustoconical portions  58  and  68  extend over the entire inner surfaces  500  and  600  of the sleeves  5  and  6 . 
     Furthermore, the pulley device  1  can be configured differently from  FIGS. 2 to 10  without going beyond the scope of the invention. Furthermore, the technical features of the different embodiments and alternatives mentioned above can be combined with one another in whole or in part. Thus, the device  1  can be adapted in terms of cost, functionalities and performance.