Hydraulic circuit of hydraulically driven vehicle

Claim 2

A hydraulic circuit of a hydraulically driven vehicle, comprising: a driving source; a closed circuit which comprises a hydraulic pump driven by said driving source, a hydraulic motor driven by pressurized oil supplied by said hydraulic pump, a high pressure side oil conduit connecting a discharge side of said hydraulic pump to an input side of said hydraulic motor, and a low pressure side oil conduit connecting a suction side of said hydraulic pump to an output side of said hydraulic motor; a booster pump; means for driving said booster pump; an oil source; a first hydraulic oil supply conduit having one end opening into said oil source and the other end connected to a suction side of said booster pump; a second hydraulic oil supply conduit having one end connected to a discharge side of said booster pump and the other end to said low pressure side oil conduit; valve means having an inlet port and an outlet port for discharging excess oil in said low pressure side oil conduit; a hydraulic oil cooling radiator having an inlet and an outlet; a first hydraulic oil discharge conduit having one end connected to said low pressure side oil conduit and the other end connected to the inlet port of said valve means; a second hydraulic oil discharge conduit having one end connected to the outlet port of said valve means and the other end connected to the inlet of said hydraulic oil cooling radiator; and a third hydraulic oil discharge conduit having one end connected to the outlet of said hydraulic oil cooling radiator and the other end opening into said oil source, wherein an improvement comprises an auxiliary hydraulic motor which is driven by the pressurized oil discharged from said booster pump and a fan rotated by said auxiliary hydraulic motor for cooling said hydrauliC oil cooling radiator.

Claim 3

A hydraulic circuit as defined in claim 1, wherein said auxiliary hydraulic motor is interposed in said second hydraulic oil supply conduit.

Claim 4

A hydraulic circuit as defined in claim 1, wherein said auxiliary hydraulic motor is interposed between the other end of said second hydraulic oil supply conduit and said low pressure side oil conduit.

Claim 5

A hydraulic circuit as defined in claim 3, which further comprises a third hydraulic oil supply conduit connecting the outlet of said auxiliary hydraulic motor with said low pressure side oil conduit, a bypass conduit having one end connected to said second hydraulic oil discharge conduit and the other end to said third hydraulic oil supply conduit, and second valve means adapted in said by-pass conduit to prevent the pressurized oil from flowing from said first valve means in said by-pass conduit and to communicate said by-pass conduit with said second hydraulic oil discharge conduit when the oil pressure in said third hydraulic oil supply conduit becomes higher than a preset value.

Claim 6

A hydraulic circuit as defined in claim 1, wherein said auxiliary hydraulic motor is interposed between the other end of said second hydraulic oil discharge conduit and the inlet of said hydraulic oil cooling radiator.

Claim 7

A hydraulic circuit as defined in claim 1, wherein said auxiliary hydraulic motor is interposed between the other end of said third hydraulic oil discharge conduit and said oil tank.

Claim 8

A hydraulic circuit of a hydraulically driven vehicle, comprising a driving source; an oil source; at least two closed circuits each of which comprises a hydraulic pump driven by said driving source, a hydraulic motor driven by pressurized oil supplied from said hydraulic pump, a high pressure side oil conduit connecting a discharge side of said hydraulic pump to an input side of said hydraulic motor, and a low pressure side oil conduit connecting a suction side of said hydraulic pump with the output side of said hydraulic motor; at least two devices each provided in correspondence to each of said closed circuits and comprising a booster pump, means for driving said booster pump, a first hydraulic oil supply conduit having one end opening into said oil source and the other end connected to a suction side of said booster pump, a second hydraulic oil supply conduit having one end connected to the discharge side of said booster pump and the other end to said low pressure side oil conduit, valve means having an inlet port and an outlet port for discharging excess oil in said low pressure side oil conduit, and a first hydraulic oil discharge conduit having one end connected to said low pressure side oil conduit and the other end to the inlet port of said valve means; a hydraulic oil cooling radiator having an inlet and an outlet; a first main hydraulic pressure discharge conduit having one end connected to the outlet ports of the respective valve means and the other end connected to the outlet of said hydraulic oil cooling radiator; and a second main hydraulic oil discharge conduit having one end connected to the outlet of said hydraulic oil cooling radiator and the other end opening into said oil source, wherein an improvement comprises an auxiliary hydraulic motor driven by the pressurized oil discharged from each of said booster pumps and a fan driven by said booster pump for cooling said hydraulic oil cooling radiator.

Claim 9

A hydraulic circuit of a hydraulically driven vehicle, comprising a driving source; an oil source; at least two closed circuits each of which comprises a hydraulic pump driven by said driving source, a hydraulic motor driven by pressurized oil supplied from said hydraulic pump, a high pressure side oil conduit connecting a discharge side of said hydraulic pump to an input side of said hydraulic motor, and a low pressure side oil conduit connecting a suction side of said hydraulic pump with the output side of said hydraulic motor; at least two devices each provided in correspondence to each of said closed circuits and comprising a booster pump, means for driving said booster pump, a first hydraulic oil supply conduit having one end opening into said oil source and the other end connected to a suction side of said booster pump, a second hydraulic oil supply conduit having one end connected to the discharge side of said booster pump and the other end to said low pressure side oil conduit, valve means having an inlet port and an outlet port for discharging excess oil in said low pressure side oil conduit, and a first hydraulic oil discharge conduit having one end connected to said low pressure side oil conduit and the other end to the inlet port of said valve means; a hydraulic oil cooling radiator having an inlet and an outlet; a first main hydraulic pressure discharge conduit having one end connected to the outlet ports of the respective valve means and the other end connected to the outlet of said hydraulic oil cooling radiator; and a second main hydraulic oil discharge conduit having one end connected to the outlet of said hydraulic oil cooling radiator and the other end opening into said oil source, wherein an improvement comprises an auxiliary hydraulic motor driven by the pressurized oil discharged from each of said booster pumps and a fan driven by said booster pump for cooling said hydraulic oil cooling radiator.

Claim 10

A hydraulic circuit as defined in claim 6, wherein said auxiliary hydraulic motor has an inlet port and an outlet port for hydraulic oil and said inlet port is opened into the other end of said second hydraulic oil supply conduit in each of said closed circuits, while said outlet port is connected to said low pressure side oil conduit in each of said closed circuit.

Claim 11

A hydraulic circuit as defined in claim 7, which further comprises a third hydraulic oil supply conduit connecting the outlet port of said auxiLiary hydraulic motor with the low pressure side oil conduit in each of said closed circuits, a by-pass conduit having one end connected to said first main hydraulic oil discharge conduit and the other end to each of said third hydraulic oil supply conduits, and second valve means adapted to block the hydraulic oil flowing from each of said first valve means into said by-pass conduit and to communicate said by-pass conduit with said first main hydraulic oil discharge conduit when the oil pressure in each of said third hydraulic oil supply conduits becomes higher than a preset value.

Claim 12

A hydraulic circuit as defined in claim 6, wherein said auxiliary hydraulic motor is interposed between the other end of said first main hydraulic oil discharge conduit and the inlet of said hydraulic oil cooling radiator.

Claim 13

A hydraulic circuit as defined in claim 6, wherein said auxiliary hydraulic motor is interposed between the other end of said second main hydraulic oil discharge conduit and said oil source.

Claim 14

A hydraulic circuit of a hydraulically driven vehicle, comprising a hydraulic pump having a suction port and a discharge port, which pump sucks a predetermined quantity of oil from the suction port and discharges the same from the discharge port; a hydraulic motor having an input side and output side; a first pressurized oil conduit for connecting the discharge port of said hydraulic pump and the input side of said hydraulic motor; a second pressurized oil conduit for connecting the output side of said hydraulic motor to the suction port of said hydraulic pump, so that said hydraulic motor is driven by the pressurized oil discharged from said pump; an oil tank; a first conduit starting from said oil tank and terminating at a point in said second pressurized oil conduit; a second conduit starting from a point upstream from the terminating point of said first conduit in said second pressurized oil conduit and terminating at said oil tank; an auxiliary pump provided in said first conduit for constantly supplying from said oil tank to the suction port of said pump a predetermined quantity of oil smaller than that sucked by said hydraulic pump; a radiator provided in said second conduit for cooling the oil passing therethrough; an auxiliary motor provided in at least one of said first and second conduits so as to be driven by the oil passing therethrough; and a fan driven by said auxiliary motor for cooling said radiator.

Claim 15

A hydraulic circuit of a hydraulically driven vehicle, comprising a hydraulic pump having a suction port and a discharge port, which pump sucks a predetermined quantity of oil from the suction port and discharges the same from the discharge port; a hydraulic motor having an input side and output side; a first pressurized oil conduit for connecting the discharge port of said hydraulic pump and the input side of said hydraulic motor; a second pressurized oil conduit for connecting the output side of said hydraulic motor to the suction port of said hydraulic pump, so that said hydraulic motor is driven by the pressurized oil discharged from said pump; an oil tank; a first conduit starting from said oil tank and terminating at a point in said second pressurized oil conduit; a second conduit starting from a point upstream from the terminating point of said first conduit in said second pressurized oil conduit and terminating at said oil tank; an auxiliary pump provided in said first conduit for constantly supplying from said oil tank to the suction port of said pump a predetermined quantity of oil smaller than that sucked by said hydraulic pump; a radiator provided in said second conduit for cooling the oil passing therethrough; an auxiliary motor provided in at least one of said first and second conduits so as to be driven by the oil passing therethrough; and a fan driven by said auxiliary motor for cooling said radiator.