# US 10,370,825 B2 · Hydraulic drive system of construction machine

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- Number: US 10,370,825 B2
- Document ID: US10370825B2
- Status: Granted
- Kind: B2
- Application number: 15/573,497
- Filed: 2016-04-28
- Published: 2018-05-03
- Granted: 2019-08-06
- Earliest claimed: 2015-05-11
- Assignees: Kawasaki Jukogyo Kabushiki Kaisha
- Applicants: Kawasaki Jukogyo Kabushiki Kaisha
- Inventors: Akihiro Kondo; Hideyasu Muraoka
- Web page: https://patentgrep.com/patent/US10370825B2

## CPC

- E02F 9/2235: {including an electronic controller}
- E02F 3/425: {Drive systems for dipper-arms, backhoes or the like}
- E02F 9/2004: {Control mechanisms, e.g. control levers (control levers per se G05G)}
- E02F 9/2246: {Control of prime movers, e.g. depending on the hydraulic load of work tools}
- E02F 9/2282: {Systems using center bypass type changeover valves}
- E02F 9/2292: {Systems with two or more pumps}
- E02F 9/2296: {Systems with a variable displacement pump}
- F02D 29/04: peculiar to engines driving pumps
- F02D 41/0205: {using an auxiliary engine speed control (engine speed control per se F02D31/00)}
- F02D 41/3005: {Details not otherwise provided for}
- F04B 1/295: by changing the inclination of the swash plate
- F04B 49/06: Control using electricity (regulating by means of floats actuating electric switches F04B49/04)
- F15B 11/028: for controlling the actuating force (F15B11/024 takes precedence)
- F15B 11/17: using two or more pumps
- E02F 3/32: working downwardly and towards the machine, e.g. with backhoes
- F02D 31/001: {Electric control of rotation speed}
- F02D 2200/101: Engine speed
- F15B 11/08: with only one servomotor
- F15B 13/0442: {with proportional solenoid allowing stable intermediate positions}
- F15B 2211/20523: Internal combustion engine
- F15B 2211/20546: variable capacity
- F15B 2211/20576: with multiple pumps
- F15B 2211/6316: the pressure being a pilot pressure
- F15B 2211/633: representing a state of the prime mover, e.g. torque or rotational speed
- F15B 2211/6346: representing a state of input means, e.g. joystick position
- F15B 2211/6651: Control of the prime mover, e.g. control of the output torque or rotational speed
- F15B 2211/6652: Control of the pressure source, e.g. control of the swash plate angle
- E02F: DREDGING; SOIL-SHIFTING (winning peat E21C49/00)
- F02D: CONTROLLING COMBUSTION ENGINES (vehicle fittings, acting on a single sub-unit only, for automatically controlling vehicle speed B60K31/00; conjoint control of vehicle sub-units of different type or different function, road vehicle drive control systems for purposes other than the control of a single sub-unit B60W)
- 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)
- F15B: SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR

## Abstract

Pump controller: when operation device receives neither first or second operation, outputs standby rotation speed as command rotation speed to engine controller, standby rotation speed being lower than selected reference rotation speed; when operation device receives first operation, changes command rotation speed from standby rotation speed to first target rotation speed in such a manner that as an amount of first operation increases, increasing rate of command rotation speed decreases gradually; when operation device receives second operation, changes command rotation speed from standby rotation speed to second target rotation speed in such a manner that as an amount of second operation increases, increasing rate of command rotation speed increases gradually; and feeds command current to a solenoid proportional valve that outputs secondary pressure to regulator that adjusts tilting angle of a pump, such that a discharge flow rate of the pump is proportional to amount of first and second operation.

## Claims

### Claim 1

A hydraulic drive system of a construction machine, the hydraulic drive system comprising:
an operation device that receives a first operation for moving an actuator in a first direction and receives a second operation for moving the actuator in a second direction, in which a load on the actuator is lower than the load on the actuator moved in the first direction;
a variable displacement pump that supplies hydraulic oil to the actuator and that is driven by an engine;
a solenoid proportional valve that outputs a secondary pressure corresponding to a command current;
a regulator that adjusts a tilting angle of the pump in accordance with the secondary pressure outputted from the solenoid proportional valve;
an engine controller that controls a fuel injector of the engine;
a rotation speed selector that receives a selection of a reference rotation speed of the engine; and
a pump controller that outputs a command rotation speed to the engine controller and feeds the command current to the solenoid proportional valve, wherein
the pump controller:
when the operation device receives neither the first operation nor the second operation, outputs a standby rotation speed as the command rotation speed, the standby rotation speed being lower than the selected reference rotation speed;
when the operation device receives the first operation, changes the command rotation speed from the standby rotation speed to a first target rotation speed lower than or equal to the selected reference rotation speed in such a manner that as an amount of the first operation increases, an increasing rate of the command rotation speed decreases gradually;
when the operation device receives the second operation, changes the command rotation speed from the standby rotation speed to a second target rotation speed lower than or equal to the selected reference rotation speed in such a manner that as an amount of the second operation increases, the increasing rate of the command rotation speed increases gradually; and
feeds the command current to the solenoid proportional valve, such that a discharge flow rate of the pump is proportional to the amount of the first operation and the amount of the second operation.

### Claim 2 (depends on 1)

The hydraulic drive system of a construction machine according to claim 1, wherein
the actuator is at least one of a boom cylinder, an arm cylinder, and a bucket cylinder.

### Claim 3 (depends on 2)

The hydraulic drive system of a construction machine according to claim 2, wherein
the second target rotation speed is lower than the first target rotation speed.

### Claim 4 (depends on 3)

The hydraulic drive system of a construction machine according to claim 3, wherein
the pump controller feeds the command current to the solenoid proportional valve, such that a maximum value of the tilting angle of the pump when the amount of the first operation is at its maximum is the same as a maximum value of the tilting angle of the pump when the amount of the second operation is at its maximum.

### Claim 5 (depends on 1)

The hydraulic drive system of a construction machine according to claim 1, wherein
the second target rotation speed is lower than the first target rotation speed.

### Claim 6 (depends on 5)

The hydraulic drive system of a construction machine according to claim 5, wherein
the pump controller feeds the command current to the solenoid proportional valve, such that a maximum value of the tilting angle of the pump when the amount of the first operation is at its maximum is the same as a maximum value of the tilting angle of the pump when the amount of the second operation is at its maximum.