Hydraulic circuit of construction machine

• US 7,878,770 B2
• Filed: 02/26/2007
• Issued: 02/01/2011
• Est. Priority Date: 02/27/2006
• Status: Active Grant

• Current Assignee: Kobelco Construction Machinery Company Limited (Kobe Steel Limited)
• Original Assignee: Kobelco Construction Machinery Company Limited (Kobe Steel Limited)
• Inventors: Oka, Hidekazu
• Primary Examiner(s): Kramer; Devon C
• Assistant Examiner(s): LETTMAN, BRYAN MATTHEW
• Application Number:
  US11/678,795
• Publication Number:
  US 20070204607A1
• Time in Patent Office: 1,436 Days
• Field of Search: 417/278
• US Class Current: 417/278
• CPC Class Codes: E02F 9/2228 including an electronic controller
• CPC Class Codes: E02F 9/2285 Pilot-operated systems
• CPC Class Codes: E02F 9/2296 Systems with a variable displacement pump
• CPC Class Codes: F15B 11/163 for sharing the pump output equally amongst users or groups of users, e.g. using anti-saturation, pressure compensation
• CPC Class Codes: F15B 19/002 Calibrating
• CPC Class Codes: F15B 21/08 Servomotor systems incorporating electrically operated control means F15B21/02, F15B21/065 take precedence
• CPC Class Codes: F15B 2211/40515 with variable throttles or orifices
• CPC Class Codes: F15B 2211/428 actuated by fluid pressure
• CPC Class Codes: F15B 2211/45 Control of bleed-off flow, e.g. control of bypass flow to the return line
• CPC Class Codes: F15B 2211/6303 using input signals
• CPC Class Codes: F15B 2211/6309 the pressure being a pressure source supply pressure
• CPC Class Codes: F15B 2211/6654 Flow rate control
• CPC Class Codes: F15B 2211/855 Testing of fluid pressure systems

Abstract

A hydraulic circuit for actuating an electromagnetic proportional pressure reducing valve by a command current outputted from a controller based on an operation amount of a remote control valve, and by a secondary pressure of the pressure reducing valve, actuating a common bleed-off valve which is a hydraulic pilot type spool valve is provided. In the controller, as a correction processing for correcting characteristics of a proportional valve command value which is a current value given to the pressure reducing valve and the opening area of the spool valve, at an inflection point at which the degree of change of a pump pressure increases, an actual proportional valve command value at a time of obtaining the pump pressure is compared to a theoretical proportional valve command value of a case of no tolerance, and a correction to compensate for a difference between the both command values is performed.

Claims

1. A hydraulic circuit of construction machine comprising:

operation means;

a controller for outputting a command current based on an operation amount of the operation means;

an electromagnetic proportional pressure reducing valve actuated by the command current outputted from the controller; and

a hydraulic spool valve actuated by a secondary pressure from the electromagnetic proportional pressure reducing valve, the spool valve being configured to change a pump pressure in response to a change in an opening area of the spool valve, wherein a degree of change in the pump pressure by the hydraulic spool valve to a change in the proportional valve command value exhibits at least one inflection point at which there is an inflection in the degree of change in the pump pressure for a predetermined change of the proportional valve command value;

the controller having correction processing means for correcting the proportional valve command value, comprising;

means for comparing, at the at least one inflection point, a detected actual proportional valve command value to a theoretical proportional valve command value at which the set pump pressure is to be obtained in the case that a tolerance of the secondary pressure with respect to the proportional valve command value does not exist, and

means, based on the comparison, for performing a correction to compensate for a difference between the detected and theoretical command values at the inflection point.

2. The hydraulic circuit of construction machine according to claim 1, wherein said at least one inflection point comprises a plurality of the inflection points, and the controller performs the correction based on a comparison of proportional valve command values at the plurality of inflection points.

3. The hydraulic circuit of construction machine according to claim 1, wherein the controller performs the correction based on a comparison of proportional valve command values at the at least one inflection point and a point at which the tolerance of the secondary pressure with respect to the proportional valve command value becomes a minimum value.

4. The hydraulic circuit of construction machine according to claim 1, wherein the controller obtains the at least one inflection point from a differential pressure between steps of the pump pressure which changes stepwise.