Patent Publication Number: US-2021180683-A1

Title: Gear transmission unit with a  forced lubrication system  including one or more lubricant distribution boxes

Description:
FIELD OF THE INVENTION 
     The invention relates to a gear transmission unit, particularly for a motor-vehicle, of the type comprising:
         a supporting casing,   a plurality of shafts rotatably supported within the supporting casing by means of respective rolling bearings,   a plurality of toothed wheels carried by said shafts and meshing with each other,   a forced lubrication system for lubricating said rolling bearings and/or further internal components of the transmission unit, said forced lubrication system including:   a supply pump for supplying lubricant, and   a plurality of channels formed within walls of said supporting casing of the transmission unit, for bringing the lubricant up to the internal components to be lubricated.       

     PRIOR ART 
     Transmission units of the above indicated type (such as gearshift units and reducer units for motor-vehicles) are old and have been used since long. The use of a forced lubrication system provides a relevant reduction of friction inner losses with respect to more conventional solutions of wet-type transmissions in which the lubricant is displaced inside the casing of the transmission by the movable members themselves which are provided inside the unit (such as a differential crown). In modern transmissions, an improved efficiency is obtained by relying on a dry-type lubrication, in which the lubricant is supplied by a pump, preferably electrically actuated, to a network of channels formed within the casing of the transmission unit. 
     In some known transmissions, in order to reduce the complexity of the network of channels for the lubricant, a forced lubrication is provided only for the components which are located uppermost inside the casing of the transmission unit, whereas the components located in the bottom part are reached by the lubricant due to gravity, after that the lubricant has wet the components in the upper part. Naturally, this solution represents a compromise and has the drawback that it does not insure a proper and controllable lubrication of the components which are located in the bottom part of the transmission. 
     OBJECT OF THE INVENTION 
     A main object of the present invention is that of overcoming the above-mentioned drawbacks. 
     In particular, the object of the invention is that of providing a transmission unit which allows a proper and controllable lubrication of all its components and which can be obtained with simple and quick operations even starting from a transmission unit originally configured for operating with a forced lubrication of the components in the upper part and a lubrication by gravity of the components located in the bottom part of the transmission. 
     More in general, it is an object of the invention that of simplifying the configuration of the network of channels which must be provided within the structure of the transmission unit for the purpose of supplying a controllable flow of lubricant under pressure to all the components to be lubricated inside the transmission. 
     SUMMARY OF THE INVENTION 
     In view of achieving one or more of the above indicated objects, the invention provides a gear transmission unit having the features which have been indicated at the beginning of the present description, and further characterized in that it is provided with one or more accessory elements in the form of lubricants distribution boxes, in that the, or each, distribution box has a hollow body rigidly connected to the supporting casing adjacent to a respective channel outlet which supplies a forced flow of lubricant, and in that said hollow body defines an inner lubricant distribution chamber and has one inlet connected to said channel outlet and two or more outlets connected to further conduits or channels or chambers for supplying a flow of lubricant under pressure in parallel to various components to be lubricated inside the supporting casing. 
     Due to the provision of the above-mentioned lubricant distribution boxes, the operations which are necessary for adapting a transmission unit to operate with a proper and controllable lubrication of all the inner components of the unit are rendered extremely simple, quick and inexpensive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features and advantageous of the invention will become apparent from the description which follows, with reference to the annexed drawings, given purely by way of non-limiting example, in which: 
         FIG. 1  is a diagram of the lubrication system of a transmission unit, 
         FIG. 2  is a perspective view of a detail of a gear transmission unit (namely a reducer unit for an electric motor unit of a motor-vehicle), 
         FIG. 3  shows the same detail of  FIG. 2  with the toothed wheels removed, in order to show the rolling bearings for supporting the shafts on which the toothed wheels are mounted, 
         FIG. 4  is a further perspective view and at an enlarged scale of a detail of  FIG. 3 , with a rolling bearing removed, in order to show the outlets of the channels for supplying a flow of lubricant under pressure, 
         FIG. 5  shows the same detail of  FIG. 4 , in the case of a transmission unit according to the invention, in which two the outlets of the channels for supplying the lubricant there have been associated connecting members for connection to a lubricant distribution box, 
         FIG. 6  shows the same detail of  FIG. 5 , with the distribution box mounted at the connecting members for the lubricant, 
         FIG. 7  is a perspective view of the transmission box, including a box body and a lid secured thereto, 
         FIG. 8  is a perspective view of the body of the distribution box, on the side opposite to that of  FIG. 7 , and 
         FIG. 9  is a perspective view in cross-section of the distribution box. 
     
    
    
     DETAILED DESCRIPTION OF ONE EMBODIMENT 
     In  FIG. 1 , reference  1  generally designates a gear transmission unit, such as a motor-vehicle gearshift or a gear reducer unit for a motor-vehicle electric motor. Unit  1  includes a supporting casing  2  in which there are rotatably mounted, by means of rolling bearings, two or more shafts carrying toothed wheels meshing with each other. The transmission unit  1  is provided with a forced lubrication system  3  including a supply pump  4  driven by electric model  5  for supplying a flow of lubricant (oil) under pressure to a network of inner channels  5  formed in the walls of the supporting casing  2 . 
     The example shown herein relates to a transmission unit originally configured with a network of channels  5  provided for supplying a flow of lubricant under pressure directly to the rolling bearings, and/or other inner components of the unit, which are located in the uppermost part inside the casing  2 . In the known solution, the components located in the lowermost part are reached by the lubricant, due to gravity, after that the lubricant has wet the components in the uppermost part. As indicated in the foregoing, this solution does not insure a proper and controllable lubrication of all the inner components of the unit. The idea at the basis of the present invention is that of transforming a transmission unit configured as described with extremely simple and inexpensive operation, in order to obtain a direct forced lubrication also of the components located in the lowermost part inside the unit. 
       FIG. 2  shows a detail of toothed wheels R 1 , R 2 , R 3 , R 4  arranged inside of the unit  1 . The toothed wheels R 1 -R 4  are mounted on shafts A 1 , A 2 , A 3 , which are parallel to each other and are rotatably supported inside of the supporting casing  2  of the unit  1  by means of rolling bearings B 1 , B 2 , B 3  ( FIG. 3 ). 
     By way of example, in a transmission unit according to the prior art, the lubrication of the rolling bearing B 1  is obtained by supplying a flow of lubricant under pressure up to the surface of the seat which receives the bearing. For this purpose, a channel  5  for supplying the flow of lubricant coming from the pump  4  opens out at a channel outlet  5 A at the surface of seat  13  for the bearing ( FIG. 4 ). 
     In a transmission unit according to the known art, the forced flow of lubricant which exits from the outlet  5 A wets the bearing B 1 , after which it continues to flow by gravity towards the lowermost part inside the supporting casing, so as to lubricate the bearings and/or other components located in the lowermost part inside the casing  2 . 
     In one exemplary embodiment of the transmission unit according to the invention, at the seat of the rolling bearing B 1  there is provided a lubricant distribution box S. In the illustrated example, the box S comprises a hollow body of plastic material, defined and by a box element S 1  and a lid S 2  secured in any known way (such as by welding or glue) to the box element S 1 . 
     Also with reference to the illustrated example, the box element S 1  incorporates two connecting portions  6  having holes  7  for engagement of securing screws for securing the distribution box S to the structure of the transmission unit (in which holes  14  are formed for engagement of the screws— FIG. 5 ). 
     The inner chambers C defined between the box element S 1  and of the lid S 2  constitutes a lubricant distribution chamber. The main wall of the box element S 1  has three apertures  8 , surrounded by necks  9  projecting from the outer surface of element S 1 . 
     One of the holes  8  is used as an inlet aperture communicating with the channel outlet  5 A which brings the lubricant flow coming from the supply pump. A hole  12  formed in the lid S ( FIG. 7 ) is used as an outlet for lubrication of the seat of the bearing B 1 . Other two holes  8  are used as outlets which supply the flow of lubricant under pressure to other channels or conduits (one of which is designated by  5 B in  FIG. 4 ) which bring the lubricant to other components to be lubricated, for example located in the lowermost part of the unit. With reference to  FIG. 5 , there are provided that connecting members  11  for connection of outlets  8  of the distribution box to channels which lead the lubricant in parallel to different users. The connecting members  11  have outer portions  10  mounted around the necks  9  of box S. 
     Naturally, the configuration of the distribution box S may widely vary with respect to what is shown purely by way of example. Similarly, the position of one or more transmission boxes S inside the transmission casing can be selected and optimized on the basis of the specific configuration of the transmission casing, on the basis of the position of the inner components to be lubricated and on the basis of the need to obtain the greatest possible simplification of the network of channels which must be formed within the walls of the casing of the transmission unit. 
     Also in the case of the illustrated example, the material constituting the distribution box S is a plastic material, but the use of metal material is not excluded. The number and dimension of holes  8  to be used for defining the inlet and at the outlets of each distribution box are of course determined as a function of the specific needs. 
     In the illustrated example, the holes  8  have axes orthogonal with respect to the general plane of the distribution box S, but they could be also provided on the lateral wall of the box, for defining one radial inlet and/or radial outlets. 
     As it is clearly apparent from the present description, the distribution box S has preferably a substantially flattened configuration, so that it can be housed within the seat of a rolling bearing of a transmission unit. However, it is to be understood that the configuration of the body of the box is predetermined as a function of the mounting position and the space which is available. 
     Naturally, while the principle of the invention remains the same, the embodiments may widely vary with respect to what has been described and illustrated purely by way of example, without departing from the scope of the invention as defined in the annexed claims.