# US 11,111,650 B2 · Hydraulic drive system for construction machine

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- Number: US 11,111,650 B2
- Document ID: US11111650B2
- Status: Granted
- Kind: B2
- Application number: 16/492,482
- Filed: 2018-05-23
- Published: 2021-05-06
- Granted: 2021-09-07
- Earliest claimed: 2017-09-29
- Assignees: Hitachi Construction Machinery Tierra Co., Ltd.
- Applicants: Hitachi Construction Machinery Tierra Co., Ltd.
- Inventors: Kiwamu Takahashi; Taihei Maehara; Takeshi Ishii; Yoshifumi Takebayashi; Natsuki Nakamura; Daisuke Oka
- Web page: https://patentgrep.com/patent/US11111650B2

## CPC

- E02F 9/2235: {including an electronic controller}
- E02F 9/22: Hydraulic or pneumatic drives {(for dipper or bucket arm position control E02F3/43, for blade position control for graders E02F3/844; for turntables E02F9/121; for fork-lift trucks B66F9/22)}
- E02F 9/2285: {Pilot-operated systems}
- E02F 9/2292: {Systems with two or more pumps}
- E02F 9/2296: {Systems with a variable displacement pump}
- F15B 11/17: using two or more pumps
- F15B 2211/20553: with pilot circuit, e.g. for controlling a swash plate
- F15B 2211/20576: with multiple pumps
- F15B 2211/6346: representing a state of input means, e.g. joystick position
- F15B 2211/6652: Control of the pressure source, e.g. control of the swash plate angle
- F15B 2211/7051: Linear output members
- F15B 2211/7058: Rotary output members
- F15B 2211/7135: Combinations of output members of different types, e.g. single-acting cylinders with rotary motors
- E02F: DREDGING; SOIL-SHIFTING (winning peat E21C49/00)
- 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

When a swing motor and a boom cylinder are driven simultaneously, a hydraulic drive system appropriately adjusts a distribution of torques between hydraulic pumps and feeds back a torque actually consumed by the hydraulic pump for actuating the swing motor accurately to the hydraulic pump for actuating the boom cylinder. To that end, when boom raising and swinging are performed simultaneously, the hydraulic drive system corrects an allowable torque of a hydraulic pump 302 that supplies a hydraulic fluid to a swing motor 3c so as to be lowered by a certain ratio, reducing allowable torques of hydraulic pumps 102 and 202 that supply a hydraulic fluid to a boom cylinder 3a by torques consumed by the hydraulic pumps 102 and 202 that supply a hydraulic fluid to the swing motor 3c.

## Claims

### Claim 1

A hydraulic drive system for a construction machine, the hydraulic drive system comprising:
a plurality of hydraulic pumps including variable-displacement first and second hydraulic pumps driven by a prime mover;
a plurality of actuators driven by hydraulic fluids delivered from the plurality of hydraulic pumps;
a first regulator to which a delivery pressure of the first hydraulic pump is introduced and that controls a displacement volume of the first hydraulic pump such that a torque consumed by the first hydraulic pump does not exceed a first allowable torque;
a second regulator to which a delivery pressure of the second hydraulic pump is introduced and that controls a displacement volume of the second hydraulic pump such that a torque consumed by the second hydraulic pump does not exceed a second allowable torque; and
a first valve device that generates a first output pressure to feed back the torque consumed by the second hydraulic pump to the first regulator based on the delivery pressure of the second hydraulic pump,
wherein the first regulator includes a first operation drive section to which the first output pressure is introduced and with the first operation drive section, the first regulator corrects a horsepower control starting pressure for securing the first allowable torque so as to be smaller by the first output pressure thereby to control the displacement volume of the first hydraulic pump such that a sum of the torques consumed by the first and second hydraulic pumps does not exceed a predetermined value, and
the plurality of actuators include a boom cylinder for driving a boom of a front work implement and a swing motor for driving an upper swing structure, the boom cylinder being driven by a hydraulic fluid delivered by the first hydraulic pump, and the swing motor being driven by a hydraulic fluid delivered by the second hydraulic pump, and
wherein the hydraulic drive system further comprises:
a controller that, when the swing motor and the boom cylinder are driven simultaneously, calculates a correction value for the horsepower control starting pressure for reducing the second allowable torque of the second hydraulic pump so as to be smaller than a maximum allowable torque at a time when the swing motor is driven independently;
a second valve device for generating a second output pressure corresponding to the correction value calculated by the controller;
a second operation drive section included in the second regulator and to which the second output pressure is introduced for correcting the horsepower control starting pressure for securing the second allowable torque so as to be smaller by the second output pressure; and
an output pressure corrector for limiting the first output pressure of the first valve device such that the first output pressure of the first valve device does not exceed the horsepower control starting pressure for securing the second allowable torque corrected by the second operation drive section.

### Claim 2 (depends on 1)

The hydraulic drive system for a construction machine according to claim 1, wherein
the first valve device is a variable pressure reducing valve disposed in a hydraulic line to which the delivery pressure of the second hydraulic pump is introduced for generating the first output pressure,
the second valve device is a proportional solenoid valve operable based on an output current corresponding to the correction value generated by the controller for generating the second output pressure, and
the output pressure corrector comprises a pressure receiving section included in the variable pressure reducing valve and to which the second output pressure of the proportional solenoid valve is introduced for correcting a set pressure of the variable pressure reducing valve so as to be smaller by the second output pressure.

### Claim 3 (depends on 1)

The hydraulic drive system for a construction machine according to claim 1, wherein
the controller calculates the correction value for the horsepower control starting pressure by multiplying the horsepower control starting pressure for securing the maximum allowable torque of the second hydraulic pump by a magnification ranging from 0 inclusive to 1 exclusive.

### Claim 4 (depends on 3)

The hydraulic drive system for a construction machine according to claim 3, further comprising:
a plurality of directional control valves for controlling flows of the hydraulic fluid supplied to the plurality of actuators; and
a plurality of operation devices for commanding respective drives of the plurality of actuators for shifting the directional control valves corresponding thereto,
wherein the controller inputs an operation signal from one of the plurality of operation devices that commands the drive of the swing motor, and based on the operation signal, calculates the magnification as a value that increases as the operation amount of the operation device increases.

### Claim 5 (depends on 1)

The hydraulic drive system for a construction machine according to claim 1, wherein
the output pressure corrector is implemented as a function of the controller,
the controller selects, as the correction value for the horsepower control starting pressure for securing the first allowable torque of the first hydraulic pump, a smaller one of a value obtained by subtracting the correction value from the horsepower control starting pressure for securing the maximum allowable torque of the second regulator when the swing motor is driven independently and a detected value of the delivery pressure of the second hydraulic pump, and outputs a first current corresponding to the selected value,
the controller also outputs a second current corresponding to the correction value for the horsepower control starting pressure for securing the second allowable torque,
the first valve device is a first proportional solenoid valve operable based on the first current output from the controller for generating the first output pressure, and
the second valve device is a second proportional solenoid valve operable based on the second current output from the controller for generating the second output pressure.