Slewing drive apparatus for construction machine

Patent metadata

Field	Value
Publication number	US-9920780-B2
Application number	US-201514747233-A
Country	US
Kind code	B2
Filing date	Jun 23, 2015
Priority date	Jul 30, 2014
Publication date	Mar 20, 2018
Grant date	Mar 20, 2018

Abstract

Provided is a slewing drive apparatus for a construction machine capable of satisfactory pump-flow-rate control regardless of change in engine speed, including a variable displacement hydraulic pump, a slewing motor, a slewing operation device, a control valve, a relief valve, and a pump-flow-rate control device that performs a relief cut control and includes: a section for detecting an engine revolution number Ne and a slewing speed of a slewing body; a section for determining a target pump flow rate Qo that is a sum of a slewing-speed correspondence flow rate Q 1 and a minimum required relief flow rate Qmin; a section for determining a target pump-tilt-angle qtg obtained by dividing the target pump flow rate Qo by the detected engine revolution number Ne; and a section for adjusting an actual pump-tilt-angle of the hydraulic pump so as to bring the actual pump-tilt-angle to the target pump-tilt-angle qtg.

First claim

The invention claimed is:

1. A slewing drive apparatus to be installed on a construction machine including a slewing body to slew the slewing body, the slewing drive apparatus comprising:
an engine;
a variable displacement hydraulic pump that is driven by the engine to thereby discharge a hydraulic fluid;
a slewing motor that slews the slewing body;
a slewing operation device that receives an operation for actuating the slewing motor and outputs a slewing command corresponding to the operation;
a control valve that makes a valve opening action so as to control the actuation of the slewing motor, in response to the slewing command output by the slewing operation device;
a relief valve that defines a maximum pressure of the slewing motor; and
a pump-flow-rate control device that controls a pump-tilt-angle determining a pump flow rate that is a discharge flow rate of the hydraulic pump, characterized in that
the pump-flow-rate control device performing a relief cut control and including: a section for detecting an engine revolution number Ne and a slewing speed of a slewing body; a section for determining a target pump flow rate Qo that is a sum of a slewing-speed correspondence flow rate Q 1 that is a flow rate of a hydraulic fluid actually flowing to the slewing motor, the flow rate corresponding to the detected slewing speed, and a minimum required relief flow rate Qmin that is a flow rate of a hydraulic fluid flowing in the relief valve and is a minimum flow rate for securing a pressure required for starting slewing of the slewing body; a section for determining a target pump-tilt-angle qtg that is a value obtained by dividing the target pump flow rate Qo by the detected engine revolution number Ne; and a section for adjusting an actual pump-tilt-angle of the hydraulic pump so as to bring the actual pump-tilt-angle to the target pump-tilt-angle qtg,
wherein the pump-flow-rate control device further includes: a section for determining a plurality of target pump flow rates based on respective different kinds of controls including the relief cut control; and a section for selecting a minimum target pump flow rate out of the plurality of target pump flow rates, as a final target pump flow rate, the pump-flow-rate control device obtaining the target pump-tilt-angle qtg by dividing the selected target pump flow rate by the engine revolution number Ne.

2. The slewing drive apparatus for a construction machine according to claim 1 , wherein the plurality of kinds of controls include: the relief cut control; a positive control using a target pump flow rate corresponding to an amount of operation applied to the slewing operation device; and a PQ control using a target pump flow rate corresponding to a pump pressure that is a discharge pressure of the hydraulic pump.

Assignees

• Kobelco Constr Mach Co Ltd

Inventors

• Ueda Koji
• Izuka Takaaki

Classifications

• F15B2211/405

  characterised by the type of flow control means or valve · CPC title

• F15B2211/50518

  using pressure relief valves · CPC title

• F15B2211/7058

  Rotary output members · CPC title

• F15B13/0401

  Valve members; Fluid interconnections therefor · CPC title

• F15B2211/20523

  Internal combustion engine · CPC title