Abstract:
A torque transmission device for starting an internal combustion engine using a permanently engaged starter motor for a start-stop system. An annular gear connected with the starter motor includes a bearing for decoupling the starter motor from the engine based upon the rotational speed difference between the internal combustion engine and the starter motor. The device includes a freewheel for the speed-controlled coupling of the starter motor to the internal combustion engine so that torque is transmitted between the annular gear and the engine crankshaft. An annular gear carrier is arranged between the annular gear and the freewheel. The bearing and the freewheel are arranged radially relative to each other so that at least the freewheel and the bearing are in communication with an oil chamber of the engine. First and second seal elements are provided for sealing the engine oil chamber of the internal combustion engine.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is the U.S. national phase application under 35 U.S.C. §371 of International Application Ser. No. PCT/DE2012/001090, having an international filing date of 14 Nov. 2012, and designating the United States, the entire contents of which are hereby incorporated by reference to the same extent as if fully rewritten. 
     BACKGROUND OF THE INVENTION 
     The invention concerns a torque transmission device and particularly concerns a permanently engaged starter (PES) for a start-stop system with a change-of-mind function. Already known PES systems include a bearing and a freewheel disposed outside of the engine oil chamber, i.e., in the dry area of the engine. PES systems located in the wet chamber of the engine have also been described, for example in EP 1 748 202 B1. 
     An object of the present invention is to provide an improved solution to offer advantages with regard to leak tightness, lubrication, assembly, and costs. 
     SUMMARY OF THE INVENTION 
     For achieving that object, the invention proposes various solutions that include the following features: 
     The invention uses a ball bearing for decoupling the differences in rotational speed between the engine and the starter, a freewheel for the speed-controlled coupling of the PES to the drive train of the engine, and two sealing elements for sealing the wet chamber of the engine from the transmission housing. Furthermore, the freewheel outer ring (FRAX) and the bearing inner ring are configured in one piece with each other and are preferably made out of a refinished drawn part. The bearing outer ring and the junctional region with the annular gear (intermediate ring) are likewise configured in one piece with each other and are made preferably out of a refinished blank. 
     The following features can be additionally or alternatively provided: 
     The component freewheel outer ring/bearing inner ring is connected by positive engagement and in a leak-proof manner with help of a flange element screwed on the crankshaft (KW), e.g., partially laser welded, and centered with respect to each other through radial surfaces. 
     In order to avoid refinishing because of distortion of the bearing raceways during welding, the weld seam is preferably made only partially. 
     A sealing element preferably made of an elastomer is arranged on the inner diameter of the bearing inner ring between the component freewheel outer ring/bearing inner ring and the flange element. 
     The component freewheel outer ring/bearing inner ring and the flange element are connected through the flex plate by positive engagement, for example riveted, and joined substantially without spacing at least in the region of the flange element. 
     The centering of the composite component freewheel outer ring/bearing inner ring and the flange element on the crankshaft is thus achieved with help of the flex plate. The flange element has a radial clearance to the crankshaft seat. 
     The annular gear is cold rolled and connected directly to the intermediate ring. 
     The connection of the annular gear is realized through positive engagement, optionally by riveting as a low-cost variant. In the case of a positive engagement through a weld joint, it is advantageous that the annular gear can be centered on the outside by welding so that a precise circular running is obtained. For this purpose, it is necessary to provide a spacing between the intermediate ring and the inner diameter of the annular gear carrier. 
     The different variants of the embodiment can be combined at least partially with one another. 
     An optimized lubricant supply at the freewheel can be achieved through suitable apertures on the component that forms the bearing outer ring and the freewheel inner ring. 
     In a torque transmission device using a starter motor for starting an internal combustion engine having an annular gear cooperating with the starter motor, and including a bearing for decoupling the difference in rotational speed between the internal combustion engine and the starter motor. The device further includes a freewheel for the speed-controlled coupling of the starter motor to the internal combustion engine, such that torque transmission takes place between the annular gear and a crankshaft of the internal combustion engine. The device includes still further an annular gear carrier arranged between the annular gear and the freewheel. 
     The above-described object is achieved by the fact that the bearing and the freewheel are arranged radially on top of each other such that at least the freewheel and the bearing communicate with an engine oil chamber of the internal combustion engine, and such that a first sealing element and a second sealing element are provided for sealing the engine oil chamber of the internal combustion engine. The freewheel is preferably arranged radially outside of the bearing, this bearing preferably being a rolling bearing, for example a ball bearing. The bearing serves to decouple the differences in rotational speed between the internal combustion engine and the starter motor. The freewheel serves for the speed-controlled coupling of the starter motor to a drive train in which the internal combustion engine comprising the torque transmission device of the invention is arranged. The two sealing elements serve to seal from a transmission housing the engine oil chamber that is also designated as a wet chamber. 
     A preferred example of an embodiment of the torque transmission device is characterized in that a bearing outer ring of the bearing and a freewheel inner ring of the freewheel are made in one piece with each other and form an outer bearing freewheel unit. The bearing outer ring and the freewheel inner ring are preferably constituted by a common race ring body. The common race ring body preferably includes radially on an inner side at least one running surface for rolling elements of the bearing. Radially on an outer side, the common race ring body preferably includes at least one running surface for freewheeling elements of the freewheel. Advantageously, the common race ring body is connected particularly integrally to an intermediate ring that constitutes a junction region for the annular gear. 
     A further preferred example of an embodiment of the torque transmission device is characterized in that, further, a bearing inner ring of the bearing and a freewheel outer ring of the freewheel are made in one piece with each other and form an inner bearing freewheel unit. The bearing inner ring preferably includes radially on an outer side at least one running surface for rolling elements of the bearing. Radially on an inner side the freewheel outer ring body includes at least one running surface for the freewheeling elements of the freewheel. The freewheel outer ring is made preferably in one piece with the bearing inner ring. The inner bearing freewheel unit preferably possesses a substantially U-shaped cross-section including a base from which two legs protrude at an angle. A radially inner leg of the inner bearing freewheel unit constitutes the bearing inner ring of the bearing. A radially outer leg of the inner bearing freewheel unit constitutes the freewheel outer ring. 
     A further preferred example of an embodiment of the torque transmission device is characterized in that a flex plate for torque transmission is provided between the internal combustion engine and a drive train, while being arranged directly adjacent to the inner bearing freewheel unit in an axial direction. The flex plate is preferably configured as a flexible component and serves for torque transmission between the crankshaft of the internal combustion engine and a clutch or a transmission. For this purpose, the flex plate is connected through a radially inner peripheral edge region to the crankshaft. 
     A further preferred example of an embodiment of the torque transmission device is characterized in that a radially widening gap is provided between the inner bearing freewheel unit and the flex plate. The flex plate can bear against the inner bearing freewheel unit in a radially inner region. In a radially outer region, the radially widening gap is deliberately arranged between the inner bearing freewheel unit and the flex plate. The radially widening gap is open in a radially outward direction. 
     A further preferred example of an embodiment of the torque transmission device is characterized in that the gap is filled at least partially with a material having a low modulus of elasticity, in particular with an elastomer. The material with the low modulus of elasticity advantageously enables the flex plate to be deformed or to move in a limited manner relative to the inner bearing freewheel unit. In this way, if necessary, an offset between the crankshaft and the clutch or the transmission can be compensated for. 
     A further preferred example of an embodiment of the torque transmission device is characterized in that the inner bearing freewheel unit is connected to a flange element that is fixed on the crankshaft. The flange element is fixed on the crankshaft with a radially inner peripheral edge region, for example with the help of a fixing means like screws. With a radially outer peripheral edge region the flange element is preferably fixed on the inner bearing freewheel unit. 
     A further preferred example of an embodiment of the torque transmission device is characterized in that the inner bearing freewheel unit is centered on an outer periphery of the flange element. For this purpose, the inner bearing freewheel unit is configured, as viewed in cross-section, for example with a step-like shoulder. 
     A further preferred example of an embodiment of the torque transmission device is characterized in that the inner bearing freewheel unit is connected to the flange element by fusion of material. The connection by fusion of material is preferably made as a welded joint. However, this welded joint is preferably not made as a continuous but only as a partial weld seam. In this way, an undesired refinishing of the bearing raceways because of distortion caused by welding can be avoided. 
     A further preferred example of an embodiment of the torque transmission device is characterized in that a further sealing element is arranged between the bearing inner ring of the inner bearing freewheel unit and the flange element. The further sealing element is preferably made of an elastomeric plastics material. The further sealing element is preferably arranged radially on the inside on the bearing inner ring. 
     A further preferred example of an embodiment of the torque transmission device is characterized in that a flex plate, or the flex plate, is fixed on the flange element. Advantageously, the flex plate is connected through positive engagement, for example by riveting on the flange element. A centering of the torque transmission device on the crankshaft is achieved in this case preferably through the flex plate. As a result, the flange element has a radial clearance relative to a crankshaft seat used for centering. A sealing element can be provided between the flange element and the bearing inner ring. 
     A further preferred example of an embodiment of the torque transmission device is characterized in that the annular gear is connected through positive engagement to an intermediate ring. In this case, however, attention must be paid to the fact that the concentric running of the annular gear follows the radial tolerances during riveting. Although this is relatively inexact, it has the advantage of being less expensive. 
     A further preferred example of an embodiment of the torque transmission device is characterized in that the annular gear is connected by fusion of material to an intermediate ring. The connection of the annular gear to the intermediate ring is realized preferably by welding, particularly by laser welding or by metal active gas welding. The connection by fusion of material offers the advantage that the annular gear, for example during welding, can be centered on the outside. In this way, an exact concentricity of running can be assured. This however makes it necessary to provide a certain spacing between the intermediate ring and an inner diameter of the annular gear carrier. 
     A further preferred example of an embodiment of the torque transmission device is characterized in that a further sealing element is arranged between a bearing inner ring of the bearing or the outer bearing freewheel unit and the crankshaft. In this way the sealing of the engine oil chamber relative to the transmission housing is improved. 
     A further preferred example of an embodiment of the torque transmission device is characterized in that the bearing and the freewheel are arranged radially within the first sealing element and the second sealing element. As a consequence, both the bearing and the freewheel preferably have a smaller diameter than the first and the second sealing element. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further advantages, features and details of the invention result from the following description in which different examples of embodiment are described in detail with reference to the appended drawings. The drawing figures show: 
         FIGS. 1 a  to 6 b   , altogether six variants of the torque transmission device of the invention, wherein the figures referenced with b are all reduced to PES parts and a flex plate, and 
         FIGS. 7, 8   a ,  8   b ,  9 , and  10 , five further variants of the torque transmission device of the invention, in a semi-section. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In  FIGS. 1 to 10  a torque transmission device of the invention is represented in different variants. The torque transmission device shown in  FIGS. 1 a  and 1 b    and in  FIG. 7  includes an annular gear  1 ;  41  that is firmly connected to an annular gear carrier  2 ;  42  by a weld  15 , as seen in  FIGS. 1 a  and 1 b   . In  FIGS. 7, 8   a , and  10  it can be seen that a starter annular gear  62  of a starter motor  61  is meshed with the annular gear  41 . 
     A freewheel  3 ;  43  and a bearing  4 ;  44  are integrated in the torque transmission device. The torque transmission device further includes a flex plate  5 ;  45  that is non-rotatably connected to a crankshaft  6 ;  46 . Through the flex plate  5 ;  45  torque can be transmitted from the crankshaft  6 ;  46  to a transmission (not shown) arranged further downstream in a drive train of an automotive vehicle, or to an intermediately arranged clutch (not shown). 
     The bearing  4 ;  44  includes a bearing inner ring  7 ;  47  and a bearing outer ring. The bearing outer ring of the bearing  4 ;  44  is combined with a freewheel inner ring of the freewheel  3 ;  43  in an outer bearing freewheel unit  8 ;  48 . In an inner bearing freewheel unit  9 ;  49  the bearing inner ring  7 ;  47  is combined with a freewheel outer ring  14 ;  54 . 
     The inner bearing freewheel unit  9 ;  49  has a substantially U-shaped cross-section with a base from which two legs extend at an angle. The base of the U-shaped cross-section extends substantially in the radial direction. The term radial relates to an axis of rotation of the torque transmission device that is indicated through a chain-dotted line. 
     The radially inner leg of the U-shaped cross-section is constituted by the bearing inner ring  7 ;  47 . The radially outer leg of the U-shaped cross-section is constituted by the freewheel outer ring  14 ;  54 . The two legs of the U-shaped cross-section extend parallel to each other in axial direction, i.e., parallel to the axis of rotation of the torque transmission device. 
     A radially outward extending gap  10 ;  50  is formed between the base of the inner bearing freewheel unit  9 ;  49  and the flex plate  5 ;  45  that includes a matched pot-shaped section. Radially within the gap  10 ;  50 , the flex plate  5 ,  45  bears directly, or indirectly with interposition of a further element, against the inner bearing freewheel unit  9 ;  49 . 
     A sealing element  11 ;  51  is arranged radially on an inner side on the inner bearing freewheel unit  9 ;  49 . The sealing element  11 ;  51  serves to seal the bearing inner ring  7 ,  47  of the inner bearing freewheel unit  9 ;  49  and the crankshaft relative to each other. 
     Further, the bearing inner ring  7 ;  47  is combined with a covering disk/a covering sheet metal/a flange element  17   a ;  17   b ;  17   c  or a flange element  57 , into a unit  12 ;  52 . As can be seen for example in  FIG. 7 , the flange element  57  is connected through a riveted joint  74  by positive engagement to the flex plate  45 .  FIGS. 3 a  and 3 b    show that the freewheel outer ring  14  can also be combined by a weld joint  15  into a unit  12  made up of bearing inner ring/covering disk. 
     A gap filling is indicated at  16   a  in  FIGS. 3 a  and 3 b   . In  FIGS. 6 a  and 6 b    the gap filling is referenced as  16   b.    
     The annular gear carrier  2 , as can be seen for example in  FIGS. 1 a  and 1 b   , is fixed by a weld joint  15  to an intermediate ring that forms a part of the outer bearing freewheel unit  8 .  FIGS. 4 a  and 4 b    show that the attachment of the annular gear carrier  2  with the intermediate ring of the outer bearing freewheel unit  8  can also be realized through riveted joints  18 . 
     For sealing the engine oil chamber from the transmission housing two sealing elements  19 ,  20 ;  59 ,  60  are integrated in the torque transmission device. The sealing element  20 ;  60  is arranged radially outside of the outer bearing freewheel unit  8 ;  48 . The sealing element  19 ;  59  is arranged in the radial direction between the inner bearing freewheel unit  9 ;  49  and the outer bearing freewheel unit  8 ;  48 . 
     In  FIGS. 5 a  and 5 b    it is indicated at  21  that the covering disk  17   c  can be connected by positive engagement through a toothed connection to the inner bearing freewheel unit  9 . A sealing element  22  serves for sealing between the crankshaft  6  and the inner bearing freewheel unit  9 . 
     In  FIGS. 6 a  and 6 b    it can be seen that the bearing inner ring  7  is connected with help of a toothed connection  21   b  by positive engagement to the flex plate  5 . Moreover, the bearing inner ring  7  is connected by the weld joint  15   b  by fusion of material to the freewheel outer ring  14 . 
     In the variant V 1  of  FIG. 1 a    and  FIG. 1 b   , the bearing outer ring and the freewheel inner ring are made in one piece with each other, and the annular gear carrier and the annular gear are made in two pieces and connected to each other by welding. The sealing in the direction of the crankshaft is achieved through a press fit on the bearing inner ring without additional sealing elements. 
     In the variant V 2  of  FIG. 2 a    and  FIG. 2 b   , the bearing outer ring and the freewheel inner ring are configured in one piece with each other. The bearing inner ring and the freewheel inner ring are likewise made in one piece with each other, with a gap to the flex plate widening in a radially outward direction. The covering disk under the flex plate, the annular gear, and also the annular gear carrier are formed by rolling in one piece with one another and are subsequently welded-on. The sealing in the direction of the crankshaft is achieved through a sealing element (in this case, an O-ring) between bearing inner ring/flex plate/covering disk. The torque of the PES is supported solely through a press fit on the bearing inner ring. 
     Variant V 3 , represented in  FIG. 3 a    and  FIG. 3 b   , corresponds substantially to variant V 2  except that the bearing inner ring and the covering disk are made in one piece with each other. The freewheel outer ring is connected by fusion of material (in this case, by welding), or by positive engagement to the bearing inner ring/covering disk, the sealing in the direction of the crankshaft being realized with help of a sealing element (here, an O-ring) on the element made up of bearing inner ring/covering disk. The gap between the freewheel outer ring and the flex plate is filled with a material having a low modulus of elasticity, for example an elastomer which can be deformed in correspondence to a movement of the flex plate. The torque of the PES is supported on the screw connection of the crankshaft. 
     Variant V 4  of  FIG. 4 a    and  FIG. 4 b    corresponds substantially to variant V 2  except that, in this case, the covering disk is omitted. It is solely the flex plate that is screwed to the crankshaft. The annular gear and the annular gear carrier are made in one piece with each other by rolling and are attached by riveting (or by screwing). A sealing element in the direction of the crankshaft (here an O-ring) is arranged between the flex plate and the bearing inner ring. The annular gear carrier secures the sealing from migrating to the exterior. 
     Variant V 5  shown in  FIG. 5 a    and  FIG. 5 b    corresponds substantially to variant V 2  except that the covering sheet metal for supporting the torque is connected to the bearing inner ring through positive engagement (here in form of a toothed connection). The sealing in the direction of the crankshaft is realized through a sealing element (here an annular ring) arranged on the end of the bearing inner ring facing the engine. The annular gear carrier and the annular gear are made in two pieces and are welded-on. 
     Variant V 6  of  FIGS. 6 a  and 6 b    corresponds substantially to variant V 3  except that the flex plate is connected directly to the crankshaft and, for supporting the torque, also by positive engagement (here in the form of a toothed connection) to the bearing inner ring. The sealing in the direction of the crankshaft is realized through a sealing element (here an O-ring) that is arranged radially between the bearing inner ring and the crankshaft screw connection of the flex plate. The gap between the freewheel outer ring and the flex plate is filled up with a material having a low modulus of elasticity (for example an elastomer) which can deform in correspondence to movements of the flex plate. 
     The different individual structural variants of embodiments V 1 -V 6  can be combined with one another with regard to the embossing of the annular gear carrier with the starter annular gear and its connection, and also for the sealing of the wet chamber of the engine in the direction of the crankshaft connection geometry. This is indicated in the foregoing text for example, optionally, annular gear carrier and annular gear made to standard in two pieces, or in one piece by shaping through rolling or, for example, optionally, the fixing of the annular gear carrier through a weld joint or by riveting or screwing etc. 
     An optimized lubricant supply on the freewheel can be achieved through suitable apertures provided in the component which forms the bearing outer ring and the freewheel inner ring. 
     In the exemplary embodiment represented in  FIG. 7 , the annular gear  41  is provided with cold-rolled teeth. The annular gear carrier  42  is fixed on the intermediate ring  56  through the riveted joints  55 . The flex plate  45  is provided with a matched pot-shaped section. The inner bearing freewheel unit  49  is made as a refinished drawn part. One point  71  indicates a transition fit between the bearing inner ring  47  and the crankshaft  46 . The transition fit simplifies mounting and demounting. 
     At one point  72 , the flex plate  45  bears against the flange element  57 . At one point  74  a riveted joint is indicated between the flex plate  45  and the flange element  57 . The riveted joint  74  serves for the pre-assembly prior to or after a partial welding-on of the flange element  57  to the inner bearing freewheel unit  49 . The partial welding-on is indicated at one point  73 . 
     At one point  75 , it is indicated that the centering of the torque transmission device on the crankshaft  46  is achieved through the flex plate  45 . An associated centering diameter is indicated through an arrow  76 . At one point  77 , it is indicated that for sealing between the bearing inner ring  47 , or the flange element  57 , and the crankshaft  46 , a special sealing element made out of an elastomeric plastics material is used. 
     It is indicated at one point  81  in  FIG. 8 a    that the annular gear carrier  42  is connected through fusion of material by a welded joint to the intermediate ring  56 . At one point  82 , is represented a centering gap for the radial centering of the annular gear carrier  42  prior to welding. The connection through fusion of material, for example by laser welding or MAG welding, is made after the external centering when the concentric running of the annular gear  41  is found to be satisfactory. 
     In  FIG. 8 b    is represented a detail out of  FIG. 8 a    of a further variant. At one point  85  it can be seen that the annular gear carrier  42  bears against the intermediate ring  56 . At one point  86 , is represented a centering gap for the radial centering of the annular gear carrier  42  prior to the welding step. At one point  87  is indicated a weld seam for the connection through fusion of material between the annular gear carrier  42  and the intermediate ring  56 . 
     In the exemplary embodiment illustrated in  FIG. 9 , it can be seen that the flex plate  45  bears directly against the inner bearing freewheel unit  49  at one point  91 . At one point  92 , it is indicated that the flex plate  45  is connected through fusion of material by a welded joint  51  to the inner bearing freewheel unit  49 . The connection through fusion of material is advantageously configured as a partial weld joint with a low heat input. 
     In the exemplary embodiment represented in  FIG. 10 , similar to the exemplary embodiment represented in  FIG. 9 , the torque transmission device is centered on the crankshaft  46  through the flex plate  45  at the point  75 . At one point  101 , the flex plate  45  bears against the inner bearing freewheel unit  49 . At one point  102 , it is indicated that for a pre-assembly, the flex plate  45  can be riveted to the inner bearing freewheel unit  49 . For the purpose of sealing, a sealing element made of a suitable plastics material can be arranged at one point  103  between the inner bearing freewheel unit  49  and the flex plate  45 .