Hydrostatic stepless transmission

Abstract

A hydrostatic stepless transmission ( 1 ) comprising axial piston type hydraulic pump ( 30 ) and hydraulic motor ( 40 ) is constructed that a pump side plunger block ( 31 ) faces to a motor side plunger block ( 41 ) through their rotary sliding surfaces ( 33 and 44 ), a plurality of communication passages are formed which communicate cylinders ( 31 a and 41 a ) formed in the plunger blocks with each other fluidally, a separation element is interposed in the communication passages, and in each of the pump and motor side plunger blocks, the separation element divides the communication passages into that of a suction area and that of a discharge area.

1 . A hydrostatic stepless transmission comprising axial piston type hydraulic pump and hydraulic motor, constructed that 
 a pump side plunger block faces to a motor side plunger block through their rotary sliding surfaces,    a plurality of communication passages are formed which communicate cylinders formed in the plunger blocks with each other fluidally,    a separation element is interposed in the communication passages, and    in each of the pump and motor side plunger blocks, the separation element divides the communication passages into that of a suction area and that of a discharge area,    characterized in that:    the separation element is constructed in each of the plunger blocks by spool valves of the same number as the cylinders of the plunger block,    the spool valves are arranged slidably radially centering on a rotary shaft of the plunger block,    outer ends of the spool valves touch an inner peripheral surface of an inner ring of a bearing arranged eccentrically against the rotary shaft,    the spool valves are slid following rotation of the plunger block along radial direction of the rotary shaft so as to open and close the oil passages communicating the cylinders of the plunger blocks with each other, and    by closing the oil passages by the spool valves, each of the plunger blocks is divided into the suction area or the discharge area.    
   
   
       2 . The hydrostatic stepless transmission as set forth in  claim 1 , wherein the rotary shaft of the pump side plunger block and the rotary shaft of the motor side plunger block are disposed coaxially, and the rotary shaft and a planetary gear are combined so as to construct an input separation type hydro mechanical stepless transmission.  
   
   
       3 . The hydrostatic stepless transmission as set forth in  claim 1 , wherein the rotary shaft of the pump side plunger block and the rotary shaft of the motor side plunger block are disposed coaxially, and the rotary shaft and a planetary gear are combined so as to construct an output separation type hydro mechanical stepless transmission.  
   
   
       4 . The hydrostatic stepless transmission as set forth in  claim 1 , wherein the inner peripheral surface of the inner ring of the bearing is slanted against the axis of the rotary shaft.  
   
   
       5 . The hydrostatic stepless transmission as set forth in  claim 1 , wherein the sliding direction of the spool valves is slanted against the axis of the rotary shaft.  
   
   
       6 . The hydrostatic stepless transmission as set forth in  claim 1 , wherein a charge oil supply mechanism is disposed between a connection point to the charge pump provided in a case housing of the hydrostatic stepless transmission and the hydraulic circuit in the motor or pump side plunger block.  
   
   
       7 . The hydrostatic stepless transmission as set forth in  claim 1 , wherein a check mechanism is disposed between a connection point to the charge pump provided in a case housing of the hydrostatic stepless transmission and the hydraulic circuit in the motor or pump side plunger block.  
   
   
       8 . The hydrostatic stepless transmission as set forth in  claim 1 , wherein a case housing of the hydrostatic stepless transmission is divided near the separation element.  
   
   
       9 . The hydrostatic stepless transmission as set forth in  claim 1 , wherein a case housing of the hydrostatic stepless transmission is divided, the hydraulic motor and hydraulic pump are housed in a first housing, and an opening of the first housing is closed by the other housing.  
   
   
       10 . A hydrostatic stepless transmission comprising axial piston type hydraulic pump and hydraulic motor constructed that 
 a pump side plunger block faces to a motor side plunger block through their rotary sliding surfaces,    a plurality of communication passages are formed which communicate cylinders formed in the plunger blocks with each other fluidally,    a separation element is interposed in the communication passages, and    in each of the pump and motor side plunger blocks, the separation element divides the communication passages into that of a suction area and that of a discharge area, wherein the separation element is constructed that the rotary shafts arranged eccentrically support respectively the pump side plunger block and the motor side plunger block,    a pump side port and a motor side port respectively communicated with the cylinders formed in the plunger blocks are formed so as to face to a relative rotary sliding surface between the plunger blocks,    an oil passage is formed which communicates the ports of the plunger blocks, which are shifted by the eccentric arrangement, with each other by overlapping the ports of the plunger blocks with each other,    the oil passage is closed by not overlapping the ports of the plunger blocks with each other on an extension of a line connecting the axes of the rotary shafts, and    the closed oil passage of the oil passages divides the oil passages of each of the plunger blocks into that of the suction area and that of the discharge area.    
   
   
       11 . The hydrostatic stepless transmission as set forth in  claim 10 , wherein an oil passage plate rotated integrally with one of the plunger blocks is provided, and the oil passage plate touches the other plunger block slidably rotatively relatively so as to demarcate the relative rotary sliding surface between the plunger blocks, 
 a plurality of oil passages are penetratively formed axially in the oil passage plate,    an arrangement of the oil passages is substantially the same as that of the ports of the rotary sliding surface of the plunger block rotated integrally with the oil passage plate, and    the rotary shaft of the plunger block rotated integrally with the oil passage plate is supported by the oil passage plate.    
   
   
       12 . The hydrostatic stepless transmission as set forth in  claim 10 , wherein a charge oil supply mechanism is disposed between a connection point to the charge pump provided in a case housing of the hydrostatic stepless transmission and the hydraulic circuit in the motor or pump side plunger block.  
   
   
       13 . The hydrostatic stepless transmission as set forth in  claim 10 , wherein a check mechanism is disposed between a connection point to the charge pump provided in a case housing of the hydrostatic stepless transmission and the hydraulic circuit in the motor or pump side plunger block.  
   
   
       14 . The hydrostatic stepless transmission as set forth in  claim 10 , wherein a case housing of the hydrostatic stepless transmission is divided near the separation element.  
   
   
       15 . The hydrostatic stepless transmission as set forth in  claim 10 , wherein a case housing of the hydrostatic stepless transmission is divided, the hydraulic motor and hydraulic pump are housed in a first housing, and an opening of the first housing is closed by the other housing.