HST

Abstract

There is provided an HST in which a hydraulic pump unit operatively driven by a driving power source and a hydraulic motor unit arranged spaced apart from the hydraulic pump unit and operatively driving a driving-wheel are fluidly connected by way of operation fluid lines so as to form a closed circuit; wherein the hydraulic motor unit is provided with motor-side operation fluid passages forming one part of the operation fluid lines; a motor-side charge fluid passage having a first end opened to an outside to form a motor-side charge port and a second end fluidly connected to at lease one of the motor-side operation fluid passages; and a check valve interposed in the motor-side charge fluid passage so as to allow the fluid to flow from the motor-side charge port to the one motor-side operation fluid passage while preventing the reverse flow.

Description

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings.

FIG. 1 is a schematic side view of a working vehicle to which an HST according to an embodiment 1 of the present invention is applied.

FIG. 2 is a hydraulic circuit diagram of the HST according to the embodiment 1.

FIG. 3 is a partial longitudinal side view of the vicinity of a hydraulic pump unit of the HST according to the embodiment 1.

FIG. 4 is a longitudinal side view of the hydraulic pump unit shown in FIG. 3.

FIG. 5 is a cross sectional view taken along line V-V in FIG. 4.

FIG. 6 is a cross sectional view taken along line VI-VI in FIG. 4.

FIG. 7 is a longitudinal side view of a hydraulic pump unit modified from that shown in FIG. 4.

FIG. 8 is a partial longitudinal side view of the vicinity of a hydraulic motor unit of the HST according to the embodiment 1.

FIG. 9 is a side view of the hydraulic motor unit shown in FIG. 8.

FIG. 10 is a cross sectional view taken along line X-X in FIG. 9.

FIG. 11 is a cross sectional view taken along line XI-XI in FIG. 10.

FIG. 12 is a hydraulic circuit diagram of an HST according to an embodiment 2 of the present invention.

FIG. 13 is a hydraulic circuit diagram of an HST according to an embodiment 3 of the present invention.

FIG. 14 is a hydraulic circuit diagram of an HST according to an embodiment 4 of the present invention.

Claims

1. An HST in which a hydraulic pump unit operatively driven by a driving power source and a hydraulic motor unit arranged spaced apart from the hydraulic pump unit and operatively driving a driving-wheel are fluidly connected by way of operation fluid lines so as to form a closed circuit; wherein the hydraulic motor unit is provided with motor-side operation fluid passages forming one part of the operation fluid lines; a motor-side charge fluid passage having a first end opened to an outside to form a motor-side charge port and a second end fluidly connected to at lease one of the motor-side operation fluid passages; and a check valve interposed in the motor-side charge fluid passage so as to allow the fluid to flow from the motor-side charge port to the one motor-side operation fluid passage while preventing the reverse flow.

2. An HST according to claim 1, wherein the motor-side charge passage is fluidly connected to a motor-side first operation fluid passage, out of the motor-side operation fluid passages, which has a negative pressure when the driving-wheel rotates in the forward direction.

3. An HST according to claim 2, wherein the motor-side charge fluid passage includes a motor-side common charge fluid passage having a first end opened to an outside to form the motor-side charge port; a motor-side first charge fluid passage for fluidly connecting the motor-side common charge fluid passage to the motor-side first operation fluid passage; and a motor-side second charge fluid passage for fluidly connecting the motor-side common charge fluid passage to a motor-side second operation fluid passage, out of the pair of motor-side operation fluid passages, which has a negative pressure in a time when the driving-wheel rotates in the rearward direction, andthe check valve is inserted into each of the motor-side first and second operation fluid passages.

4. An HST according to claim 1, wherein the hydraulic pump unit is provided with pump-side operation fluid passages forming one part of the pair of operation fluid lines; a pump-side charge fluid passage having a first end opened to an outside to form a pump-side charge port and a second end fluidly connected to at lease one of the pump-side operation fluid passages; and a check valve interposed in the pump-side charge fluid passage so as to allow the fluid to flow from the pump-side charge port to the one pump-side operation fluid passage while preventing the reverse flow, andthe flow path resistance of a motor-side charge line for replenishing the operation fluid from a fluid source to the one motor-side operation fluid passage through the motor-side charge fluid port is set to be smaller than that of a pump-side charge line for replenishing the operation fluid from the fluid source to the one pump-side operation fluid passage through the pump-side charge fluid port.

5. An HST according to claim 4, wherein the check valve includes a check valve main body and a biasing member for biasing the check valve main body to a valve seat, andthe biasing member of the check valve provided in the hydraulic motor unit has a biasing force less than the biasing member of the check valve provided in the hydraulic pump unit.

6. An HST according to claim 4, wherein a conduit for fluidly connecting the fluid source and the motor-side charge fluid port has a length shorter than a conduit for fluidly connecting the fluid source and the pump-side charge fluid port.

7. An HST according to claim 4, wherein a throttle is inserted in the pump-side charge line.

8. An HST according to claim 4, wherein the fluid source is a charge pump main body mounted at the hydraulic pump unit.

9. An HST according to claim 1, wherein the hydraulic motor unit includes a motor shaft operatively connected to the driving-wheel; a motor main body that is fluidly connected to a pump main body of the hydraulic pump unit through the operation fluid lines and drives the motor shaft around its axis line; and a motor case that is capable of storing fluid and accommodates the motor main body, the motor case being provided with the motor-side operation fluid passages and the motor-side charge fluid passage; andthe motor case is further provided with a self-suction passage having a first end opened into an inner space of the motor case and a second end fluidly connected to the motor-side charge fluid passage, and a check valve for allowing the fluid to flow from the first end to the second end of the self-suction fluid passage while preventing the reverse flow.

10. An HST in which a hydraulic pump unit operatively driven by a driving power source and a hydraulic motor unit arranged spaced apart from the hydraulic pump unit and operatively driving a driving-wheel are fluidly connected by way of operation fluid lines so as to form a closed circuit; wherein the hydraulic motor unit includes a motor shaft operatively connected to the driving-wheel; a motor main body that is fluidly connected to a pump main body of the hydraulic pump unit through the operation fluid lines and drives the motor shaft around its axis line; and a motor case that is capable of storing fluid and accommodates the motor main body; andthe motor case is provided with motor-side operation fluid passages forming one part of the operation fluid lines; a self-suction passage having a first end opened into an inner space of the motor case and a second end fluidly connected to the motor-side charge fluid passage, and a check valve for allowing the fluid to flow from the first end to the second end of the self-suction fluid passage while preventing the reverse flow.