# US 2014/0196448 A1 · Hydraulic control apparatus and method

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- Number: US 2014/0196448 A1
- Document ID: US20140196448A1
- Status: Published application
- Kind: A1
- Application number: 14/217,678
- 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/US20140196448A1

## CPC

- F16H 61/4061: Control related to directional control valves, e.g. change-over valves, for crossing the feeding conduits
- E02F 3/32: working downwardly and towards the machine, e.g. with backhoes
- E02F 9/2203: {Arrangements for controlling the attitude of actuators, e.g. speed, floating function}
- E02F 9/2235: {including an electronic controller}
- E02F 9/2296: {Systems with a variable displacement pump}
- F15B 11/165: {for adjusting the pump output or bypass in response to demand}
- F15B 2211/3116: the pump port being open in the centre position, e.g. so-called open centre
- F16H: GEARING
- 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

A hydraulic control apparatus is disclosed 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 a position of the directional control valve is changed according to an operation amount of an operation member. The hydraulic control apparatus includes a virtual negative control pressure calculating part configured to calculate, based on the operation amount of the operation member and a discharge pressure of the hydraulic pump, a virtual negative control pressure when a negative control system is assumed; and a part configured to calculate a control command value for the hydraulic pump based on the virtual negative control pressure.

## 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 a position of the directional control valve is changed according to an operation amount of an operation member, the hydraulic control apparatus comprising:
a virtual negative control pressure calculating part configured to calculate, based on the operation amount of the operation member and a discharge pressure of the hydraulic pump, a virtual negative control pressure when a negative control system is assumed; and
a part configured to calculate a control command value for the hydraulic pump based on the virtual negative control pressure.

### Claim 2 (depends on 1)

The hydraulic control apparatus of claim 1, wherein the virtual negative control pressure calculating part calculates a virtual bleed opening area from a given virtual bleed opening area characteristic based on the operation amount of the operation member, and then calculates the virtual negative control pressure based on the calculated virtual bleed opening area and the discharge pressure of the hydraulic pump.

### Claim 3 (depends on 1)

The hydraulic control apparatus of claim 1, wherein the construction machine has an unloading valve connecting to a tank, the unloading valve being provided between the directional control valve and the hydraulic pump, and
the hydraulic control apparatus includes a correcting part configured to correct the control command value for the hydraulic pump based on an actual viscosity and a reference viscosity, wherein the actual viscosity is estimated based on the discharge pressure of the hydraulic pump when an command value of a predetermined discharge flow rate is applied to the hydraulic pump during idling, and the reference viscosity is estimated based on an oil temperature when the command value of the predetermined discharge flow rate is applied to the hydraulic pump during idling.

### Claim 4 (depends on 1)

The hydraulic control apparatus of claim 1, wherein the construction machine has an unloading valve of a proportional control valve type connecting to a tank, the unloading valve being provided between the directional control valve and the hydraulic pump,
the hydraulic control apparatus includes a correcting part configured to correct the control command value for the hydraulic pump based on an actual discharge flow rate and a predetermined discharge flow rate, wherein the actual discharge flow rate is estimated based on the discharge pressure of the hydraulic pump when an command value of the predetermined discharge flow rate is applied to the hydraulic pump and an opening position of the unloading valve is kept at a predetermined opening position between 0 and a maximum value during idling.

### Claim 5

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 a position of the directional control valve is changed according to an operation amount of an operation member, the method comprising:
calculating, based on the operation amount of the operation member 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.