# US 2014/0196793 A1 · Hydraulic control apparatus and method

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 2014/0196793 A1
- Document ID: US20140196793A1
- Status: Published application
- Kind: A1
- Application number: 14/217,721
- Filed: 2014-03-18
- Published: 2014-07-17
- Earliest claimed: 2011-09-21
- Assignees: Sumitomo Heavy Industries, Ltd.
- Applicants: Sumitomo Heavy Industries, Ltd.
- Inventors: Eisuke MATSUZAKI
- Web page: https://patentgrep.com/patent/US20140196793A1

## CPC

- F15B 1/033: with electrical control means
- E02F 3/32: working downwardly and towards the machine, e.g. with backhoes
- E02F 9/2228: {including an electronic controller}
- E02F 9/2235: {including an electronic controller}
- E02F 9/2267: {Valves or distributors (position of valves arrangements on upper-structures E02F9/0875)}
- E02F 9/2296: {Systems with a variable displacement pump}
- F15B 11/165: {for adjusting the pump output or bypass in response to demand}
- F15B 2211/3111: the pump port being closed in the centre position, e.g. so-called closed centre
- F15B 2211/50536: using unloading valves controlling the supply pressure by diverting fluid to the return line
- F15B 2211/526: electrically or electronically
- F15B 2211/6309: the pressure being a pressure source supply pressure
- F15B 2211/6346: representing a state of input means, e.g. joystick position
- F15B 2211/665: Methods of control using electronic components
- F15B 2211/6652: Control of the pressure source, e.g. control of the swash plate angle
- Y10T 137/0318: Processes
- Y10T 137/86027: Electric
- F15B: SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- E02F: DREDGING; SOIL-SHIFTING (winning peat E21C49/00)
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A hydraulic control apparatus is disclosed which includes an unloading valve controlling part; an command value calculating part configured to calculate, based on an operation amount of an operation member for changing a position of the directional control valve and a discharge pressure of the hydraulic pump, a virtual negative control pressure, and calculates a control command value for the hydraulic pump based on the virtual negative control pressure; and a correcting part configured to operate under the situation where the directional control valve is in such a state that the fluid path to the hydraulic actuator is closed, wherein the correcting part corrects the control command value or a parameter, which is used in calculating the control command value, such that a discharge flow rate of the hydraulic pump is a predetermined flow rate.

## Claims

### Claim 1

A hydraulic control apparatus that controls a hydraulic pump in a construction machine in which a hydraulic actuator is connected to the hydraulic pump via a directional control valve of a closed center type, and in which an unloading valve, which is connected to a tank, is provided between the directional control valve and the hydraulic pump, the hydraulic control apparatus comprising:
an unloading valve controlling part configured to control the unloading valve such that fluid communication between the hydraulic pump and the tank is blocked in a situation where the directional control valve is in such a state that a fluid path to the hydraulic actuator is opened, and such that the fluid communication between the hydraulic pump and the tank is established in a situation where the directional control valve is in such a state that a fluid path to the hydraulic actuator is closed;
an command value calculating part configured to operate under the situation where the directional control valve is in such a state that the fluid path to the hydraulic actuator is opened, wherein the command value calculating part calculates, based on an operation amount of an operation member for changing a position of the directional control valve and a discharge pressure of the hydraulic pump, a virtual negative control pressure when a negative control system is assumed, and calculates a control command value for the hydraulic pump based on the virtual negative control pressure; and
a correcting part configured to operate under the situation where the directional control valve is in such a state that the fluid path to the hydraulic actuator is closed, wherein the correcting part corrects the control command value or a parameter, which is used in calculating the control command value, such that a discharge flow rate of the hydraulic pump is a predetermined flow rate.

### Claim 2 (depends on 1)

The hydraulic control apparatus of claim 1, wherein the predetermined flow rate corresponds to a minimum discharge flow rate of the hydraulic pump.

### Claim 3

A method of controlling a hydraulic pump in a construction machine in which a hydraulic actuator is connected to the hydraulic pump via a directional control valve of a closed center type, and in which an unloading valve, which is connected to a tank is provided between the directional control valve and the hydraulic pump, the method comprising:
controlling the unloading valve such that fluid communication between the hydraulic pump and the tank is blocked, calculating, based on an operation amount of an operation member for changing a position of the directional control valve and a discharge pressure of the hydraulic pump, a virtual negative control pressure when a negative control system is assumed, and calculating a control command value for the hydraulic pump based on the virtual negative control pressure, under the situation where the directional control valve is in such a state that the fluid path to the hydraulic actuator is opened; and
controlling the unloading valve such that fluid communication between the hydraulic pump and the tank is established, and calculating a control command value for the hydraulic pump such that a discharge flow rate of the hydraulic pump is a predetermined flow rate, under the situation where the directional control valve is in such a state that the fluid path to the hydraulic actuator is closed.