Pump Unit And Hydrostatic Transmission

Abstract

There is provided a pump unit configured to be capable of transmitting a rotational per from a driving power source which is operatively connected thereto to an actuator through a pair of hydraulic fluid lines. The pump unit includes: an input shaft; a hydraulic pump main body; a PTO shaft; a PTO clutch mechanism; and auxiliary pump main body; a suction line; a discharge line; a charge line; a PTO hydraulic fluid line; a pressure-reducing valve; and a resistance valve. The PTO hydraulic fluid line and the charge line are fluidly connected to the primary side and a secondary side of the pressure-reducing valve, respectively.

1 . A pump unit for vehicle traveling configured to be capable of transmitting a rotational power through a pair of first hydraulic fluid lines and a pair of second hydraulic fluid lines from a driving power source which is operatively connected thereto to first and second hydraulic motor units for driving right and left driving wheels, the pump unit comprising:
 an input shaft which is operatively connected to the driving power source;   first and second hydraulic pump main bodies which are operatively driven by the input shaft and are fluidly connected to the first and second motor units through the pair of first hydraulic fluid lines and the pair of second hydraulic fluid lines;   a housing main body which surrounds the first and second hydraulic pump main bodies;   a port block which abuts and supports the first and second hydraulic pump main bodies, and defines the accommodating space for the first and second hydraulic pump main bodies in cooperation with the housing main body; and   a communication line which communicates between a forward-movement high-pressure side first hydraulic fluid line, which is brought into higher pressure during forward movement, out of the pair of first hydraulic fluid lines and a forward-movement high-pressure side second hydraulic fluid line, which is brought into higher pressure during forward movement, out of the pair of second hydraulic fluid lines, the communication line having an orifice inserted therein.   
     
     
         2 . The pump unit according to  claim 1 , wherein
 the port block is provided with a pair of first hydraulic fluid passages and a pair of second hydraulic fluid passages which form a part of the pair of first hydraulic fluid lines and the pair of second hydraulic fluid lines, respectively, and   the communication line is configured to communicate between a forward-movement high-pressure side first hydraulic fluid passage, which is brought into higher pressure during forward movement, out of the pair of first hydraulic fluid passages and a forward-movement high-pressure side second hydraulic fluid passage, which is brought into higher pressure during forward movement, out of the pair of second hydraulic fluid passages.   
     
     
         3 . The pump unit according to  claim 2 , wherein
 the pair of first hydraulic fluid passages and the pair of second hydraulic fluid passages are formed to be substantially parallel to each other, and   the communication line has a communication fluid passage formed in the port block such that it is orthogonal to the pair of first hydraulic fluid passages and the pair of second hydraulic fluid passages.   
     
     
         4 . The pump unit according to  claim 3 , wherein
 the forward-movement high-pressure side first hydraulic fluid passage and the forward-movement high-pressure side second hydraulic fluid passage are placed adjacent to each other.   
     
     
         5 . The pump unit according to  claim 2 , wherein
 the communication line has a conduit which is detachably connected to the port block such that it communicates the forward-movement high-pressure side first hydraulic fluid passage and the forward-movement high-pressure side second hydraulic fluid passage to each other.