Abstract:
A machine includes, but is not limited to at least one first shaft, which is mounted so it is rotatable in a housing, a lubricant duct extending in the first shaft along its axis, and at least one lubrication point, which is supplied with lubricant via a supply line comprising the lubricant duct. A section of the supply line runs in a first wall of the housing between an outlet opening of the lubricant duct and the lubrication point.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to German Patent Application No. 102010005749.5, filed Jan. 27, 2010, which is incorporated herein by reference in its entirety. 
       TECHNICAL FIELD 
       [0002]    The technical field relates to the lubrication of a machine, in particular a shift transmission for a motor vehicle. 
       BACKGROUND 
       [0003]    Diverse technologies are typical for lubricating surfaces of moving parts of such a machine which are endangered by friction wear. In order to lubricate gearwheels which mesh with one another, it is sufficient if one of these gearwheels immerses at least a part of its circumference in a lubricating oil reservoir. Lubricating oil entrained upon immersion is distributed over the entire circumference of the immersed wheel and also the circumference of a wheel meshing therewith. Oil which is spun off of these wheels forms a mist in the interior of the machine, which is deposited on other gearwheels and thus ensures their lubrication. Surfaces of bearings moving against one another are generally not suitable for such immersion or spray mist lubrication because of their protected placement. In order to lubricate such a bearing, providing a shaft extending through the bearing with a lubricant duct, which extends along the shaft and from which spur holes extend to the bearing, in order to flush through the bearing using lubricating oil, is known from DE 33 20 086 C2, for example. An outlet opening is formed on one end of the shaft, via which the oil returns into the reservoir. 
         [0004]    If a machine according to this prior art has still further lubrication points that are not situated around the shaft, these must be supplied with lubricant independently of the lubrication points of the shaft, or branching lines must lead from a common lubricant source to the lubricant duct of the shaft and the other lubrication points. Both solutions result in a significant space requirement for the lubricant circuit, and the necessity of providing supply lines for the lubrication points makes placing the remaining components of the machine more difficult. 
         [0005]    In view of the foregoing, at least on object is to specify a machine that allows even poorly accessible lubrication points to be supplied with lubricant via a compact system of supply lines, which causes little obstruction of the placement of other machine components. In addition, other objects, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background. 
       SUMMARY 
       [0006]    The at least one object is achieved in that, in a machine having at least one first shaft mounted so it is rotatable in a housing, a lubricant duct extending in the first shaft along its axis, and at least one lubrication point, which is supplied with lubricant via a supply line comprising the lubricant duct, a section of the supply line runs in the wall of the housing between an outlet opening of the lubricant duct and the lubrication point. This allows a supply of the lubrication point via a short supply line even if it can be reached poorly or not at all using a supply line fixed in place on the housing. The lubricant duct preferably extends between opposing front ends of the first shaft, i.e., the outlet opening of the lubricant duct on a first front end is opposite to an intake opening on the opposing front end. 
         [0007]    If the shaft is sufficiently linear, the hole can also be linear, so that the lubricant can flow through with little resistance even in the case of a small cross-section. This allows more efficient lubricant supply than a line which must follow a possibly complex three-dimensional contour of a wall. 
         [0008]    The lubrication point which is supplied via the lubricant duct and the supply line section adjoining thereon can particularly be a bearing of a second shaft. If the lubrication point is situated in the first wall, solely the line section running in the first wall is sufficient to supply it with lubricant. If the lubrication point is located in a second wall of the housing, the lubricant circuit expediently additionally also comprises a lubricant duct extending in the second shaft at least up to the lubrication point. 
         [0009]    Since the second wall is not required to guide sections of the supply line therein, it can be contoured strongly three-dimensionally. In particular, the second wall can have a projection facing toward the first wall, which is hollow on an outer side facing away from the first wall, in order to house other parts of a motor vehicle drivetrain, in particular a clutch, therein. Above all a double clutch has a high space requirement, so that the hollow projection is particularly useful for a space-saving housing of the double clutch. 
         [0010]    The bearing, which is supplied with lubricant via the supply line, preferably engages in a recess of the first or second wall and delimits a lubricant chamber together with this wall. This allows a direct supply of the bearing with lubricant through contact with the lubricant chamber, without a spur line being required in the second shaft. 
         [0011]    The lubricant duct can be fed via a drop catcher situated on an end of the first shaft, which is used to catch lubricant sprayed in the machine, in particular lubricant atomized upon immersion of a splashing part of the machine in a reservoir. Furthermore, it is preferable for the lubricant duct to comprise at least one section on the shaft, which is parallel to the rotational axis of the shaft, having ribs which extend warped to the rotational axis and protrudes radially inward. These ribs promote the movement of the lubricant in the supply line. Such a lubricant duct can be implemented simply, in that said section parallel to the shaft is formed by a hollow body inserted into the lubricant duct. 
         [0012]    A preferred area of application is a stepped transmission for motor vehicles. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The embodiments will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and: 
           [0014]      FIG. 1  shows a double-clutch transmission in an axial section; 
           [0015]      FIG. 2  shows the double-clutch transmission in a schematic cross-section; 
           [0016]      FIG. 3  shows a detail view of a housing wall of the transmission having a drop catcher fastened on the housing wall; 
           [0017]      FIG. 4  shows a section through a recess of the housing wall and a shaft mounted therein; 
           [0018]      FIG. 5  shows a perspective view of a turbine for conveying lubricant oil; 
           [0019]      FIG. 6  shows a section through the turbine in a plane shifted parallel to the axis of the turbine; and 
           [0020]      FIG. 7  shows a section through the turbine along plane VII-VII from  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    The following detailed description is merely exemplary in nature and is not intended to limit application and uses. Furthermore, there is no intention to be bound by any theory presented in the preceding background or summary or the following detailed description. 
         [0022]      FIG. 1  shows a schematic section through a double-clutch transmission for a motor vehicle. A double clutch  1 , which is known per se, is situated between the output shaft  2  of an engine, which is not shown, and two input shafts  3 ,  4 , which are situated concentrically to one another on the same axis, of the transmission, in order to alternately apply torque to the input shaft  3  or the input shaft  4 . 
         [0023]    Multiple gearwheels  5 ,  6 ,  7  are installed rotationally fixed on the input shafts  3 ,  4 , which in turn mesh with gearwheels  8  to  11  on two parallel lay shafts  12 ,  13 . The gearwheels  8  to  11  of the lay shafts  12 ,  13  are fixable in a rotationally fixed manner on the lay shafts  12 ,  13  via locking synchronization devices  14  to  17 . A third lay shaft  18  carries gearwheels  19 ,  20 , which mesh with gearwheels  21 ,  22  of the lay shaft  12 . In that, for example, the locking synchronization device  15  couples the gearwheel  22  to the lay shaft  12 , a first gear of the transmission can be implemented by torque transmission between the gearwheels  5 ,  8 ,  21 ,  19 ,  20 ,  22 . 
         [0024]    In order to allow shifting between the gears without torque interruption, the second gear, like all even-numbered gears, is assigned to the hollow input shaft  4 , while the odd-numbered gears are produced via the inner input shaft  3 , which extends through the hollow input shaft  4 . Since the principles of such double-clutch transmissions have been previously published in various forms, they do not need to be explained in detail here. 
         [0025]    Every lay shaft  12 ,  13 ,  18  carries a pinion  23 ,  24 ,  25 , which meshes with a ring gear  26  of a differential  27 . In that a locking synchronization device  28  locks the gearwheels  19 ,  20  on the lay shaft  18 , a reverse gear can be generated via its pinion  25 . The shafts  3 ,  4 ,  12 ,  13 ,  18  are received in a housing  29 , on whose floor an oil sump  30  is located. The housing has walls  35 ,  53  oriented transversely to the shafts. The walls  35 ,  53  each have multiple cup-like or shell-like recesses  37 ,  38 ,  39  or  60 ,  61 ,  62 , respectively, in which roller bearings  45 ,  58  or  46 ,  59 , which bear the shafts  13 ,  12 ,  18 , are inserted. 
         [0026]      FIG. 2  illustrates the location of the axes of the differential  27 , the input shafts  3 ,  4 , and the lay shafts  12 ,  13 ,  18  in a housing  29 , which encloses the transmission. Some of the gearwheels of the transmission are shown as circles concentric to the axes in  FIG. 2   
         [0027]    The ring gear  26  of the differential  27  extends furthest down of all gearwheels and is immersed on a part of its circumference in the oil sump  30 . In order to keep splashing losses small, the oil level  31 , which is indicated as a dot-dash line, is set when the transmission is stationary so that the gearwheels of the shafts  3 ,  4 ,  12 ,  13 ,  18  are not immersed and their teeth which mesh with one another are lubricated by oil mist swirled up by the ring gear  26 . When the transmission is running, the oil from the sump  30  is distributed everywhere in the housing  29 . Oil which runs off of the shafts  3 ,  4 ,  12 ,  13  and their gearwheels first reaches a temporary store  34 , which lies somewhat higher than the oil sump  30  in the housing  29  and is separated from the oil sump  30  by an inner wall  32 . A narrow gap  33  at the lower end of the inner wall  32  allows a delayed backflow of the oil into the sump  30 . This has the result that in operation, the oil level of the sump  30  drops to a level  31 ′, which is still sufficient to wet the teeth of the ring gear  26 . The splashing losses of the transmission in continuous operation are thus close to zero. 
         [0028]      FIG. 3  shows a perspective detail view of an inner side of the wall  35  of the housing  29  enclosing the transmission. A roomy recess  36 , which is provided to accommodate a part of the differential  27 , fills up a majority of the lower area of the wall  35 . The recesses  37 ,  38 ,  39  are shown all around the recess  36 , which each accommodate an end section of the lay shafts  13 ,  12 , or  18 , respectively, and the roller bearings  45  or  58  bearing this end section. While the recesses  37 ,  38  are essentially delimited by ribs  40  protruding from the wall  35 , the recess  39  is indented in the wall  35 , and the end of a hole  41  can be seen on its floor, which extends within the wall  35  to a drop catcher  42 . The drop catcher  42  has a cross-section curved like a horn having an open end  43 , which faces toward the ring gear  26  (not shown in  FIG. 3 ) to catch oil, which the teeth of the ring gear  26  entrains from the oil sump  30  during its rotation and subsequently spins off. The collected oil reaches the recess  39  via the drop catcher  42  and the hole  41 . The recess  39 , a front end of the lay shaft  18  engaging therein, and a flank of the roller bearing  45  delimit a chamber containing oil here. The roller bearing  45  is lubricated with the oil of the chamber by contact. 
         [0029]    As shown in  FIG. 1 , a duct  44  extends over the entire length of the lay shaft  18  up to the recess  62 , corresponding to the recess  39 , which, together with the front end of the lay shaft  18  engaging therein and the roller bearing  46 , delimits a chamber, from which the roller bearing  46  acquires lubricant oil. A line  52  originating from this chamber extends in the wall  53  to the other recesses  61 ,  62  of the wall  53 . The line  52  can be applied in a star shape, or it can connect the recesses  60 ,  61 ,  62  to one another in a row. The recesses  61 ,  62  in turn delimit, together with the roller bearings  59  inserted therein and the front ends of the shafts  12  or  13 , respectively, oil chambers, via which the bearings  59  are supplied with oil. 
         [0030]      FIG. 4  shows the above-described state of affairs in a uniform illustration for the shafts  12 ,  13 ,  18 . The chamber, which is delimited by the recess  60 ,  61 , or  62 , the shaft  12 ,  13 , or  18 , and the roller bearing  46  or  59 , is identified by  63 . In the case of the recess  62 , oil flows from the duct  44  of the shaft  18  through the chamber into the line  52 ; in the case of the recesses  60 ,  61 , the oil passes from the line  52  via the chamber  63  into ducts  54  or  56  of the shaft  12  or  13 , respectively. 
         [0031]    The ducts  54 ,  56  open into oil chambers in the recesses  38  or  37 , respectively, which in turn adjoin the bearings  58  and supply them with oil. In order to convey the oil throughput through the duct  44 , a turbine  47  is inserted into a widened area on the end of the lay shaft  18  facing toward the receptacle  39 .  FIG. 4 ,  FIG. 5 , and  FIG. 6  show this turbine  47  in a perspective view or in section. 
         [0032]    The turbine  47  is, as shown in  FIG. 5 , a one-piece metal body essentially having the form of a flat cylinder, through which a passage  48  extends in the axial direction. The passage  48  is obtained by multiple drilling or milling steps. Multiple holes  49 , five here, are advanced at uniform angular intervals to one another warped to the axis of symmetry through the body of the turbine  47 ; i.e., each rotation of the turbine  47  by 2π/5 around its axis of symmetry transfers the turbine  47  into itself. The diameter of the holes  49  is selected so that they fuse into a single passage  48 .  FIG. 6  shows a section through the turbine  47  along an axis—identified by  50  here—of such a hole  49 , a second hole  49  may be seen in the section. 
         [0033]      FIG. 7  shows the turbine in section along the plane VII-VII, which is perpendicular to the hole axis  50 , from  FIG. 6 . In this section, walls  51 , which remain between the individual holes  49  and protrude radially inward into the passage  48 , may be seen, which give oil penetrated therein an impulse in the axial direction when the turbine  47  rotates. As also shown in the section of  FIG. 6 , the holes  49  approach closer and closer to the outer circumference of the turbine on the downstream side of the turbine  47 . Therefore, not only the warped orientation of the holes  49  and walls  51 , but rather also the centrifugal force acting in the rotating turbine  47  drive the oil through the turbine  47 . A dynamic pressure can thus be built up downstream from the turbine  47  in the duct  44 , which ensures a sufficient oil supply of the roller bearings  45 ,  46 ,  58 ,  59 . 
         [0034]    To increase the oil pressure in the ducts  54 ,  55 ,  56 , the shafts  3 ,  12 ,  13  can also be provided with turbines  47  on the input side, i.e., on their end facing away from the double clutch  1 . 
         [0035]    It is also conceivable to only provide the shafts  3 ,  12 ,  13  located downstream with turbines  47 , in order to ensure a lubrication of the roller bearings, which is qualitatively equivalent to the lubrication of the roller bearings  45 ,  46 . 
         [0036]    The embodiments have been described above especially with reference to a transmission having double clutch, since such transmissions represent a preferred area of application. The increased space requirement of the double clutch  1  in comparison to a typical single clutch results in strong contouring of the wall  35 , having a projection  57  protruding far into the transmission housing  29  around the input shafts, which makes the oil supply of the roller bearings  58 , which bear the shafts  3 ,  4 ,  12 ,  13  on the side of the wall  35 , via lines guided in the wall  35  difficult. However, it is obvious that the invention is also usable in other constructions of transmissions or in general for the oil supply of any desired lubrication points in diverse types of machines. Thus, for example, supplying lubrication points via a lubricant duct which extends along a camshaft in an internal combustion engine comes into consideration. 
         [0037]    While at least one exemplary embodiment has been presented in the foregoing summary and detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents.