# US 2019/0376535 A1 · Liquid-pressure driving system

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- Number: US 2019/0376535 A1
- Document ID: US20190376535A1
- Status: Published application
- Kind: A1
- Application number: 16/476,782
- Filed: 2018-01-26
- Published: 2019-12-12
- Earliest claimed: 2017-02-01
- Assignees: Kawasaki Jukogyo Kabushiki Kaisha
- Applicants: Kawasaki Jukogyo Kabushiki Kaisha
- Inventors: Hiroaki MITSUI; Akihiro KONDO
- Web page: https://patentgrep.com/patent/US20190376535A1

## CPC

- F16H 61/4104: Flushing, e.g. by using flushing valves or by connection to exhaust
- F15B 7/006: {Rotary pump input}
- F15B 11/08: with only one servomotor
- F15B 13/0401: {Valve members; Fluid interconnections therefor}
- F15B 21/0423: Cooling
- F04B 39/06: Cooling; Heating; Prevention of freezing
- F15B 7/008: {with rotary output}
- F15B 13/042: operated by fluid pressure {(F15B13/0401, F15B13/0416 take precedence)}
- F15B 2211/20515: Electric motor
- F15B 2211/20546: variable capacity
- F15B 2211/20561: reversible
- F15B 2211/27: Directional control by means of the pressure source
- F15B 2211/40515: with variable throttles or orifices
- F15B 2211/41581: being connected to an output member and a return line
- F15B 2211/428: actuated by fluid pressure
- F15B 2211/611: Diverting circuits, e.g. for cooling or filtering
- F15B 2211/613: Feeding circuits
- F15B 2211/615: Filtering means
- F15B 2211/62: Cooling or heating means
- F15B 2211/7054: Having equal piston areas
- F15B 2211/7058: Rotary output members
- F16H: GEARING
- F15B: SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F04B: POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS (machines for liquids, or pumps, of rotary-piston or oscillating-piston type F04C; non-positive-displacement pumps F04D; pumping of fluid by direct contact of another fluid or by using inertia of fluid to be pumped F04F)

## Abstract

A liquid-pressure driving system includes: a pump connected to an actuator through two pressure liquid passages; pressurizing mechanisms interposed on the passages and applying pressure to the operating oil returning from the actuator; a low pressure selector valve connected to parts of the passages and introducing to a cooling passage the operating liquid having lower pressure between the operating liquids flowing through the two pressure liquid passages; a restrictor mechanism interposed on the cooling passage; a cooler apparatus interposed on the cooling passage downstream of the restrictor mechanism, the cooler apparatus cooling the operating liquid flowing through the cooling passage; and a pressure liquid returning mechanism connected to parts of the two pressure liquid passages, each of the parts being at one side of the corresponding pressurizing mechanism close to the pump, the pressure liquid returning mechanism returning the cooled operating liquid to the two pressure liquid passages.

## Claims

### Claim 1

A liquid-pressure driving system in which a main circuit thereof forms a liquid-pressure closed circuit together with a liquid-pressure actuator,
the liquid-pressure driving system comprising:
a liquid-pressure pump connected to the liquid-pressure actuator through two pressure liquid passages and configured to suck a pressure liquid through one of the two pressure liquid passages and eject the pressure liquid through the other of the two pressure liquid passages;
pressurizing mechanisms interposed on the respective two pressure liquid passages and configured to apply pressure to the operating oil returning from the liquid-pressure actuator;
a low pressure selector valve connected to parts of the two pressure liquid passages, each of the parts being located at one side of the corresponding pressurizing mechanism which side is close to the liquid-pressure actuator, the low pressure selector valve being configured to introduce to a cooling passage the operating liquid having lower pressure between the operating liquids flowing through the two pressure liquid passages;
a restrictor mechanism interposed on the cooling passage;
a cooler apparatus interposed on the cooling passage so as to be located downstream of the restrictor mechanism, the cooler apparatus being configured to cool the operating liquid flowing through the cooling passage; and
a pressure liquid returning mechanism connected to parts of the two pressure liquid passages, each of the parts being located at one side of the corresponding pressurizing mechanism which side is close to the pressure liquid pump, the pressure liquid returning mechanism being configured to return the operating liquid, cooled by the cooler apparatus, to the two pressure liquid passages.

### Claim 2 (depends on 1)

The liquid-pressure driving system according to claim 1, wherein:
the pressure liquid returning mechanism includes a returning passage connected to the two pressure liquid passages; and
the returning passage is connected to the cooler apparatus.

### Claim 3 (depends on 2)

The liquid-pressure driving system according to claim 2, further comprising an accumulator connected to the returning passage, wherein
the accumulator maintains the operating liquid, flowing through the returning passage, at preset set pressure.

### Claim 4 (depends on 1)

The liquid-pressure driving system according to claim 1, wherein the restrictor mechanism includes a variable restrictor configured such that an opening degree thereof is changeable.

### Claim 5 (depends on 1)

The liquid-pressure driving system according to claim 1, wherein:
the pressurizing mechanism includes a first check valve and a second check valve;
the first check valve is opened by the operating liquid flowing from the liquid-pressure pump to the liquid-pressure actuator; and
the second check valve opens when pressure of the operating liquid flowing from the liquid-pressure pump to the liquid-pressure actuator becomes equal to or higher than predetermined pressure.

### Claim 6 (depends on 1)

The liquid-pressure driving system according to claim 1, wherein:
when differential pressure between liquid pressures of the two pressure liquid passages becomes zero, the low pressure selector valve is located at a neutral position; and
at the neutral position, the low pressure selector valve connects the two pressure liquid passages to each other and also connects the two pressure liquid passages to the cooling passage.