Patent Publication Number: US-2017350495-A1

Title: Final drive housing

Description:
FIELD OF THE INVENTION 
     The present disclosure relates to a housing for a final drive, the housing being configured for housing a deceleration mechanism for decelerated transmission of a rotation speed of a driving motor, and to a final drive equipped with the same. 
     BACKGROUND 
     Conventionally, a driving device for use in a crawler vehicle such as a hydraulic excavator is equipped with a final drive, which functions to perform decelerated transmission of a rotation speed of a driving motor to a crawler track (while increasing torque). The final drive is constituted by a deceleration mechanism such as a planetary gear arrangement inside a housing including a stationary-side housing fixed to a crawler track frame and a rotation-side housing freely rotatable with respect to the stationary-side housing. 
     In such a configuration, a sliding portion between the stationary-side housing and the rotation-side housing is provided with a floating seal for preventing leakage of lubricant oil from the deceleration mechanism. Configurations for avoiding damage to the floating seal due to clogging of the crawler track with foreign materials such as mud are known, such as a labyrinth channel communicating with the area outside the floating seal, in order to reduce the invasion of foreign materials. Japanese Patent Application Publication No. 50-258, discloses a discharge ditch for discharging out fine foreign materials invaded into the labyrinth channel provided around the whole periphery of the stationary-side housing. An upper portion of the stationary-side housing is covered with an arc-shaped wall portion in order to reduce the invasion of foreign materials, such as small stones, falling down from the crawler track located above the stationary-side housing. However, this configuration is not sufficient to reduce foreign materials conveyed from the crawler track located below the final drive. Other known configurations include forming a slope in the stationary-side housing in a range of +/−30° to provide a tapered entry to the labyrinth channel, or forming the the labyrinth channel such that the gap in the lower portion is larger than a gap in the upper portion, in order to facilitate the discharge of foreign material invaded therein. 
     However, these configurations are not sufficient to reduce the invasion of foreign materials, because the labyrinth channel itself is the only configuration for hampering the invasion of foreign materials. 
     As such, there is a demand for a simpler configuration that can more effectively reduce the invasion of foreign materials and the seal destruction caused by the invading foreign materials. 
     SUMMARY 
     A housing for a final drive is provided, the housing being configured to be positioned at one end of a driving device of a crawler vehicle in a driving direction and for housing a deceleration mechanism for decelerated transmission of a rotation of a driving motor to a crawler track, comprising: a stationary-side housing; a rotation-side housing provided rotatably with respect to the stationary-side housing and configured such that the crawler track of the driving device is to be wound around the rotation-side housing; a seal portion for sealing a gap between the stationary-side housing and a rotation-side housing; and a labyrinth channel provided at a position corresponding to the seal portion, the stationary-side housing having: a cylinder-shaped housing main body located coaxially with a rotation shaft of the rotation-side housing; and a plurality of openings for discharging foreign materials, the plurality of openings being provided in a lower half portion of the housing main body. 
     According to the disclosed embodiment, the plurality of openings for discharging foreign materials are provided only in around an outer periphery portion of the lower half portion of the cylindrical-shaped housing main body of the stationary-side housing so as to communicate with the labyrinth channel, whereby it becomes possible to reduce invasion of foreign materials into the labyrinth channel by such a simple configuration and to easily discharge, via the openings, foreign materials invaded into the labyrinth channel. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1( a )  is a side view illustrating one embodiment of a final drive according to the present invention, and  FIG. 1( b )  is a cross-sectional view illustrating part of the final drive. 
         FIG. 2  is a front view illustrating the housing. 
         FIG. 3  is a perspective view illustrating part of a driving device provided with the final drive housing. 
         FIG. 4  is a side view illustrating a crawler vehicle provided with the housing. 
     
    
    
     DETAILED DESCRIPTION 
     In the following, the present disclosure is described in detail, referring to one embodiment illustrated in  FIGS. 1 to 4 . 
     As illustrated in  FIG. 4 , a hydraulic excavator serving as a working machine is a crawler vehicle and includes an upper rotatable body  12  rotatably mounted on a driving device  11  provided below the rotatable body, and a working device  13  for construction work or the like device mounted on the upper rotatable body  12 . 
     The driving device  11  includes a sprocket  15   a  of a final drive  15  on one end (rear) of a crawler frame  14  in a driving direction, the crawler frame  14  being provided on each of a right side and a left side of the vehicle, and the final drive being configured to be driven by a driving hydraulic motor, that is, a driving motor M ( FIG. 1( a ) ). At each of the other ends (front), an idler wheel  16  is rotatably supported by a shaft. In a lower portion of the crawler frame, a plurality of lower rollers  17  are rotatably supported by respective shafts. In an upper portion of the crawler frame a plurality of upper rollers  18  are rotatably supported by respective shafts. A crawler track  19  is wound on the sprocket  15   a , the idler wheel  16 , the plurality of lower rollers  17 , and upper rollers  18  on either of left and right sides of the vehicle. Note that  FIGS. 1 to 4  illustrate only the left side of the vehicle and illustration of the right side of the vehicle is omitted here as the right and left sides are symmetrical. 
     As illustrated in  FIGS. 1 to 4 , the final drive  15  includes a housing  21  and a deceleration mechanism  22  housed in (built in) the housing  21 . 
     The housing  21  includes a rotation-side housing  25  serving as one side, a stationary-side housing  26  serving as the other side, a bearing  27  being mounted on the stationary-side housing  26  and receiving the rotation-side housing  25  rotatably, and a seal mechanism  28  provided at a sliding portion between the rotation-side housing  25  and the stationary-side housing  26 . 
     The rotation-side housing  25  includes an attachment flange  32  integrated with the rotation-side housing  25  by a plurality of bolts  31 , and a ring gear  33 , and a cover  35  integrated with the ring gear  33  by a fixing bolt (not illustrated). The rotation-side housing  25  is provided with cylinder-shaped rotation-side protrusion portion  36  protruding toward the stationary-side housing  26  at an edge facing the stationary-side housing  26 . The rotation-side housing  25  is also provided with, at an attachment flange  32 , the sprocket  15   a  for driving the crawler track  19  of the crawler vehicle. Therefore, around the rotation-side housing  25 , the crawler track  19  of the driving device  11  is wound. 
     The stationary-side housing  26  is fixed to the crawler track frame  14  of the hydraulic excavator. To the stationary-side housing  26 , the driving motor M is mounted. The stationary-side housing  26  includes a housing main body  38  formed in a cylinder shape, and has slits  39  on an outer periphery portion of the housing main body  38 , the slits  39  being a plurality of notched openings. 
     At a center portion thereof, the housing main body  38  is provided with an engagement recess portion  41 , in which an output shaft of the driving motor M is inserted. Moreover, the housing main body  38  integrally includes a cylindrical-shaped main body portion  43  having the engagement recess portion  41 , and a flange portion  44  flanged from an outer periphery portion of the main body portion  43 . The flange portion  44  is provided with cylindrical-shaped stationary-side protrusion portion  44   a  at an edge portion facing and protruding toward the rotation-side housing  25 . The stationary-side protrusion portion  44   a  is provided at a position located outwardly away from the rotation-side protrusion  36 . That is, the rotation-side protrusion portion  36  is inserted inwardly with respect to the stationary-side protrusion portion  44   a , so that the stationary-side protrusion portion  44   a  and the rotation-side protrusion portion  36  face each other in a diameter direction of the housing  21  without touching each other. 
     The slits  39  are provided within the stationary-side protrusion  44   a  of the flange portion  44  of the housing main body  38 . The slits  39  are provided radially in the diameter direction and communicate between an inside and an outside of the housing main body  38  (the stationary-side protrusion portion  44   a ). The slits  39  are provided in an area located in a lower half portion of the housing main body  38  (within stationary-side protrusion portion  44   a ) and preferably primarily along the rear edge in the driving direction. That is, the slits  39  are located at a position lower than a horizontal virtual line L 1  passing through a center of the housing main body  38 , and in a range of about 90° defined between the horizontal line L 1  and a lower part of a vertical virtual line L 2  passing through the center of the housing main body  38 . In the other words, the slits  39  are located in a position near that part of the crawler track  19  which is wound around the rotation-side housing  25  (and sprocket  15   a ). Among the slits  39 , a slit(s) located in the lower part of the housing main body  38  may be located forwardly with respect to the virtual line L 2 . That is, some slits  39  located in the lower portion may be located slightly forward of the vertical center of a lower edge portion of the housing main body  38 . More specifically, in the present embodiment, the slits  39  are located in a range of the 3 o&#39;clock position to the 7 o&#39;clock position when viewed from the left hand side in the case of the final drive  15  on the left side of the hydraulic excavator. Thus, the slits  39  are preferably located in a range of the 5 o&#39;clock position to the 9 o&#39;clock position when viewed from the right hand side in the case of the final drive  15  on the right side of the hydraulic excavator. 
     The deceleration mechanism  22  is configured to perform decelerated transmission of rotation outputted from the driving motor M mounted in the stationary-side housing  26 , to the crawler track  19  wound around the sprocket  15   a  attached to the rotation-side housing  25 . The deceleration mechanism  22  may be a planetary gear-type deceleration mechanism, and is connected with the output shaft of the driving motor M, the output shaft being inserted in the engagement recess  41 . Moreover, in the deceleration mechanism  22 , lubricant oil is sealed inside the ring gear  33 . 
     The seal mechanism  28  is configured to facilitate prevention of oil leakage from the inside to the outside of the rotation-side housing  25 , and foreign material invasion from the outside to the inside of the housing  21 , and includes a floating seal  51  serving as a seal portion, and a labyrinth channel  52  constituting a labyrinth seal portion. 
     The floating seal  51  is configured to seal a gap between the rotation-side housing  25  and the stationary-side housing  26 . The floating seal  51  includes metal rings  54   a  and  54   b  made of a metal and O rings  55   a  and  55   b  made of, for example, synthetic resin. 
     The metal rings  54   a  and  54   b  have fine-fabricated and highly rigid sliding surfaces  57   a  and  57   b , respectively, and hold the O rings  55   a  and  55   b  on their outer periphery sides. 
     The floating seal  51  is configured such that the fine-fabricated sliding surfaces  57   a  and  57   b  inside the metal rings  54   a  and  54   b  closely contact with each other due to pressing pressure of the O ring  55   a  pressed into a gap between the metal ring  54   a  and the rotation-side housing  25  (an internal circumferential surface of the rotation-side protrusion portion  36 ), and due to pressing pressure of the O ring  55   a  pressed into a gap between the metal ring  54   b  and the stationary-side housing  26  (an internal circumferential surface of the flange portion  44 ), and seal function is realized by the close contact, thereby preventing the leakage of the oil contained inside the rotation-side housing  25 . 
     The labyrinth channel  52  is a space portion bent in a zigzag configuration back and forth between the rotation-side protrusion portion  36  of the rotation-side housing  25  and the stationary-side protrusion portion  44   a  of the stationary-side housing  26 . The labyrinth channel  52  communicates with a position outside of the floating seal  51 . The labyrinth channel  52  prevents relatively large foreign materials from invading to reach the floating seal  51  and reduces invasion of relatively small foreign materials reaching the floating seal  51 . Moreover, the labyrinth channel  52  communicates with each slit  39  of the stationary-side housing  26 , and with the outside of the housing  21  via the slits  39 . 
     INDUSTRIAL APPLICABILITY 
     Next, an effect of the embodiment thus illustrated. With the configuration in which the labyrinth channel  52  communicates with a position facing the floating seal  51  sealing the gap between the rotation-side housing  25  and the stationary-side housing  26 , it becomes difficult for materials such as muddy water, mud, and small-particle soils to invade to reach floating seal  51  located at a far end of the labyrinth channel  52 , even if the driving device  11  of the hydraulic excavator HE splashes the materials such as muddy water, mud, and small-particle soils up when running on a road with such materials. 
     Moreover, even if such materials such as muddy water, mud, and small-particle soils reach the far end of the labyrinth channel  52 , the slits  39  communicating the labyrinth channel  52  and the outside of the stationary-side housing  26  facilitates the discharge of the materials, thereby reducing tendency of damaging the floating seal  51 . 
     However, the configuration in which the slits for communicating the labyrinth channel  52  with the outside of the stationary-side housing  26  are simply provided does not eliminate a case of invasion of small stones or the like. 
     To solve this problem, according to the embodiment, the slits  39  for discharging out foreign materials are provided primarily only in the rear edge portion in the driving direction in the lower half of the housing main body  31 . Foreign materials, for example, small stones carried from below the front edge portion by the crawler track  19 , and mud or rigid foreign materials falling from the crawler track  19  located thereabove can be reduced without using an additional protecting member, or the like. Thus, the invasion of foreign materials into the labyrinth channel  52  can be reduced by using such a simple configuration, and foreign materials invaded into the labyrinth channel  52  can be easily discharged out via the slits  39 . 
     Moreover, the slits  39  extended radially in the diameter directions of the housing main body  31  make it easier to discharge out foreign materials invaded into the labyrinth channel  52 . Therefore, seal damage to the floating seal  51  associated with foreign material invasion into the labyrinth channel  52  can be reduced effectively. 
     Thus, by housing the deceleration mechanism  22  in the housing  21 , the seal damage to the floating seal  51  associated with the foreign material invasion can be reduced, thereby reducing oil leakage resulted from such seal damage and consequently securing reliability of the final drive  15 . 
     According to the embodiment, the driving device  11  is also applicable to any crawler vehicles, for example, ones for agricultural use, apart from the hydraulic excavator HE.