초록 ▼

The present invention provides a pump unit including at least one hydraulic pump with inlet and outlet ports, a pump case for accommodating the hydraulic pump having an opening through which the hydraulic pump is insertable, and a lid, called a center section, closing the pump case. The center secti

The present invention provides a pump unit including at least one hydraulic pump with inlet and outlet ports, a pump case for accommodating the hydraulic pump having an opening through which the hydraulic pump is insertable, and a lid, called a center section, closing the pump case. The center section forms a pair of inlet/outlet passages communicating an end with the inlet and outlet ports of the hydraulic pump and an end opening through a pump case abutting surface of the center section, and a first charging passage by which hydraulic fluid is fed through the pump case abutting surface of the center section. At least one of the pump case and the center section communicates the first charging passage with the pair of inlet/outlet passages via a first hydraulic fluid feeding valve preventing the reverse flow into said first charging passage.

대표청구항 ▼

What is claimed is: 1. A pump unit for operation in association with first and second hydraulic motors that respectively drive first and second driving wheels comprising: a first hydraulic pump and a second hydraulic pump respectively connected to said first and second hydraulic motors, which are a

What is claimed is: 1. A pump unit for operation in association with first and second hydraulic motors that respectively drive first and second driving wheels comprising: a first hydraulic pump and a second hydraulic pump respectively connected to said first and second hydraulic motors, which are apart from said first and second hydraulic pumps, via a first pair of hydraulic lines and a second pair of hydraulic lines; a center section supporting said first hydraulic pump and said second hydraulic pump; a housing accommodating said first hydraulic pump and said second hydraulic pump, said first hydraulic pump, said second hydraulic pump, said first pair of hydraulic lines, said second pair of hydraulic lines, said center section and said housing being integrally connected together to constitute a single unit; and a reservoir tank, which is separated from said single unit by a clearance, for storing hydraulic fluid to be replenished to said first pair of hydraulic lines and said second pair of hydraulic lines; wherein said reservoir tank is fluidly communicated with an internal space of said housing via a first conduit extending through said clearance and forming a fluid communication passage, and is also fluidly communicated with an inlet port for charging to said first pair of hydraulic lines and said pair of hydraulic lines via a second conduit extending through said clearance and forming a hydraulic fluid replenishing passage. 2. A pump unit according to claim 1, wherein: said reservoir tank is supported by said single unit. 3. A pump unit according to claim 2, wherein: said center section is formed as a single unit for supporting both said first and second hydraulic pumps; said center section forms a first pair of hydraulic passages respectively having first ends communicating with said first hydraulic pump and second ends opening to the outside of said center section to form connection ports for connection with said first pair of hydraulic lines, a second pair of hydraulic passages respectively having first ends communicating with said second hydraulic pump and second ends opening to the outside of said center section to form connection ports for connection with said second pair of hydraulic lines, and a charging passage having a first end opening to the outside of said center section to form an inlet port for charging, serving as an inlet for the hydraulic fluid to be replenished and a second end communicating with said first pair of hydraulic passages and said second pair of hydraulic passages via check valves; said charging passage is connected to a pressure relief line communicating with said housing via a relief valve; and said inlet port for charging is connected to said reservoir tank via a hydraulic fluid replenishing passage. 4. A pump unit according to claim 3, wherein: a cooling fan is provided near said single unit, said cooling fan adapted to be driven in synchronism with said first and second hydraulic pumps; said reservoir tank is connected to said single unit in such a manner as to form a clearance therebetween into which a cooling air stream is drawn from said cooling fan; and said hydraulic fluid communication passage and said hydraulic fluid replenishing passage are disposed in such a manner as to traverse said clearance. 5. A pump unit according to claim 2, wherein: said center section includes a first center section and a second center section respectively supporting said first hydraulic pump and said second hydraulic pump; said first center section forms a first pair of hydraulic passages respectively having first ends communicating with said first hydraulic pump and second ends opening to the outside of said first center section to form connection ports for connection with said first pair of hydraulic lines; said second center section forms a second pair of hydraulic passages respectively having first ends communicating with said second hydraulic pump and second ends opening to the outside of said second center section to form connection ports for connection with said second pair of hydraulic lines; at least one of said first and second center sections forms a charging passage having a first end opening to the outside of said at least one of said first and second center sections to form an inlet port for charging, serving as an inlet for the hydraulic fluid to be replenished, and a second end communicating with said first pair of hydraulic passages and said second pair of hydraulic passages via check valves; said charging passage is connected to a pressure relief line communicating with the inside of said housing via a relief valve; and said inlet port for charging is connected to said reservoir tank via a hydraulic fluid replenishing passage. 6. A pump unit for operation in association with first and second actuators comprising: a first hydraulic pump and a second hydraulic pump respectively connected to said first and second actuators via a first pair of hydraulic lines and a second pair of hydraulic lines; a center section supporting said first hydraulic pump and said second hydraulic pump; a housing accommodating said first hydraulic pump and said second hydraulic pump, said housing adapted to be used as a hydraulic fluid tank; a reservoir tank fluidly communicated with an internal space of said housing so as to form a hydraulic fluid tank together with the housing, said reservoir tank being apart from said housing; a charge pump that sucks the hydraulic fluid stored within the hydraulic fluid tank and discharges the same to a charge line fluidly communicated with said first pair of hydraulic lines and said second pair of hydraulic lines; a hydraulic fluid circulation mechanism for taking the hydraulic fluid from the hydraulic tank, and again returning the same to said hydraulic tank; and said hydraulic fluid circulation mechanism designed to return hydraulic fluid drained from a relief valve for regulating the hydraulic pressure of the charge line to the reservoir tank while cooling the same via a cooling conduit that has at least portion extending through the outside air. 7. A pump unit according to claim 6, wherein: said cooling conduit has at least a portion provided thereon with cooling fins. 8. A pump unit according to claim 7, wherein: said center section is a unitary member on which said first and second hydraulic pumps are supported in parallel relationship with one another; said housing forms an opening in a side thereof, through which said first and second hydraulic pumps can pass; said center section and said housing are integrally connected together to form a single unit, so that said opening of the housing can be sealed in a liquid tight manner by said center section with said first and second hydraulic pumps supported thereon; said center section forms a first pair of hydraulic passages respectively having first ends communicating with said first hydraulic pump and second ends opening to the outside of said center section to form connection ports for connection with said first pair of hydraulic lines, a second pair of hydraulic passages respectively having first ends communicating with said second hydraulic pump and second ends opening to the outside of said center section to form connection ports for connection with said second pair of hydraulic lines, and a charging passage having a first end communicating with said hydraulic fluid tank to form an inlet port for charging, serving as an inlet for the hydraulic fluid to be replenished and a second end communicating with said first pair of hydraulic passages and said second pair of hydraulic passages via check valves; and said pump unit further comprises: a charge pump for sucking the hydraulic fluid stored within said hydraulic fluid tank and then discharging the same into said inlet port for charging; a pressure relief line having a first end connected to said charging passage via said relief valve and a second end forming a drain port through which the hydraulic fluid from said relief valve is drained; and a pipe connecting said second end of the pressure relief line with said hydraulic fluid tank; wherein said pipe constitutes said conduit, and said charge pump constitutes a part of said hydraulic fluid circulation mechanism. 9. A pump unit according to claim 8, further comprising a reservoir tank, wherein: said reservoir tank is supported by said single unit; and said inlet port for charging communicates with said reservoir tank via a hydraulic fluid replenishing passage. 10. A pump unit according to claim 9, wherein cooling fins are provided on said hydraulic fluid replenishing passage and said hydraulic fluid communication passage. 11. A pump unit according to claim 9, wherein: a cooling fan adapted to be driven in synchronism with said first and second hydraulic pumps is provided near said single unit; said reservoir tank is connected to said single unit in such a manner as to form a clearance therebetween, into which a cooling air stream from said cooling fan is drawn; and said hydraulic fluid communication passage and said hydraulic fluid replenishing passage are disposed to transverse said clearance. 12. A pump unit according to claim 11, wherein a cooling air duct is provided so that a cooling air stream from said cooling fan is drawn into said clearance along said cooling air duct. 13. A pump unit according to claim 7, wherein: said center section includes a first center section and a second center section respectively supporting said first and second hydraulic pumps; said housing has first and second sidewalls facing one another and respectively forming a first opening and a second opening through which said first hydraulic pump and said second hydraulic pump can respectively pass; said first and second center sections are integrally connected to said housing to form a single unit, so that said first and second openings of said housing are sealed in a liquid tight manner by said first and second center sections respectively supporting said first and second hydraulic pumps thereon; said first center section forms a first pair of hydraulic passages respectively having first ends communicating with said first hydraulic pump and second ends opening to the outside of said first center section to form connection ports for connection with said first pair of hydraulic lines; said second section forms a second pair of hydraulic passages respectively having first ends communicating with said second hydraulic pump and second ends opening to the outside of said second center section to form connection ports for connection with said second pair of hydraulic lines; at least one of said first and second center sections forms a charging passage having a first end communicating with said hydraulic fluid tank to form an inlet for the hydraulic fluid to be replenished and a second end communicating with said first pair of hydraulic passages and said second pair of hydraulic passages via check valves; and said pump unit further comprises: a charge pump for sucking the hydraulic fluid stored within said hydraulic fluid tank and then discharging the same into said inlet port for charging; a pressure relief line having a first end connected to said charging passage via said relief valve and a second end forming a drain port through which the hydraulic fluid from said relief valve is drained; and a pipe connecting said second end of the pressure relief line with said hydraulic fluid tank; wherein said pipe constitutes said conduit, and said charge pump constitutes a part of said hydraulic fluid circulation mechanism.