Swing drive controlling system for construction machine

• US 9,022,749 B2
• Filed: 03/30/2009
• Issued: 05/05/2015
• Est. Priority Date: 03/31/2008
• Status: Active Grant

• Current Assignee: Komatsu Ltd.
• Original Assignee: Komatsu Ltd.
• Inventors: Akiyama, Teruo, Asada, Hisashi, Maruta, Kazuhiro, Ichihara, Masashi, Kitajima, Jin, Ooi, Takeshi
• Primary Examiner(s): Freay, Charles
• Assistant Examiner(s): Pekarskaya, Lilya
• Application Number:
  US12/935,641
• Publication Number:
  US 20110020146A1
• Time in Patent Office: 2,227 Days
• Field of Search: 417/212, 417/213, 417/218, 417/222.1, 417/270, 604/52, 604/68, 180/52.1, 180/53.2, 180/53.3, 180/53.4, 180/53.5, 180/53.6, 180/53.7, 180/53.8
• US Class Current: 417/212
• CPC Class Codes: E02F 9/123 Drives or control devices specially adapted therefor E02F9/125 and E02F9/128 take precedence
• CPC Class Codes: E02F 9/2235 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 11/055 by adjusting the pump output or bypass
• CPC Class Codes: F15B 2211/20546 variable capacity
• CPC Class Codes: F15B 2211/26 Power control functions
• CPC Class Codes: F15B 2211/3052 Shuttle valves
• CPC Class Codes: F15B 2211/3116 the pump port being open in the centre position, e.g. so-called open centre
• CPC Class Codes: F15B 2211/31576 having a single pressure source and a single output member
• CPC Class Codes: F15B 2211/329 actuated by fluid pressure
• CPC Class Codes: F15B 2211/50518 using pressure relief valves
• CPC Class Codes: F15B 2211/6309 the pressure being a pressure source supply pressure
• CPC Class Codes: F15B 2211/6316 the pressure being a pilot pressure
• CPC Class Codes: F15B 2211/6333 representing a state of the pressure source, e.g. swash plate angle
• CPC Class Codes: F15B 2211/6346 representing a state of input means, e.g. joystick position
• CPC Class Codes: F15B 2211/7058 Rotary output members

Abstract

The system includes: a variable displacement hydraulic pump supplying pressure oil to a hydraulic actuator; a pressure detector detecting a pump discharge pressure from the hydraulic pump; a control valve controlling a supply of the pressure oil to the hydraulic actuator; a controller controlling a pump displacement of the hydraulic pump; a hydraulic motor rotating an upper structure of the construction machine; a swing relief valve defining a relief pressure of the hydraulic motor; and a control lever switching a control valve for the hydraulic motor. The controller includes: an adjuster that, when a pump discharge pressure detected by the pressure detector exceeds a first set value, conducts an adjustment to reduce the pump displacement; and a canceller that cancels the adjustment when the pump discharge pressure falls below a second set value. The second set value is equal to or larger than the first set value.

Claims

1. A swing drive controlling system of a construction machine, comprising:

a variable displacement hydraulic pump that is driven by an engine, the variable displacement hydraulic pump supplying a pressure oil to a hydraulic actuator;

a pressure sensor that detects a pump discharge pressure from the variable displacement hydraulic pump;

a control valve that controls a supply of the pressure oil discharged by the hydraulic pump to the hydraulic actuator;

a controller that controls a pump displacement of the variable displacement hydraulic pump;

a hydraulic motor provided by a part of the hydraulic actuator, the hydraulic motor rotating an upper structure of the construction machine;

a swing relief valve that defines a relief pressure of the hydraulic motor; and

a control lever that switches a first control valve for the hydraulic motor that is provided by a part of the control valve,

wherein the controller determines, while the control lever is operated, whether or not an adjustment of a pump absorption torque defined by a product of the pump displacement and the pump discharge pressure is to be conducted and whether or not the adjustment of the pump absorption torque of the variable displacement hydraulic pump is to be cancelled, based on the pump discharge pressure detected by the pressure sensor, and

wherein the controller comprises;

an adjuster that, when the controller determines that the pump discharge pressure detected by the pressure sensor exceeds a first set value, conducts the adjustment to reduce the pump displacement in accordance with the pump discharge pressure and to adjust the pump absorption torque to be set at a value less than a predetermined value; and

a canceller that cancels the adjustment by the adjuster when the controller determines that the pump discharge pressure detected by the pressure sensor falls below a second set value that is larger than the first set value.

2. The swing drive controlling system of the construction machine according to claim 1, wherein:

the swing drive controlling system further comprises a lever operation amount detector that detects a lever operation amount of the control lever;

the swing relief valve is a two-stage swing relief valve that is adapted to set a first relief pressure and a second relief pressure higher than the first relief pressure;

the swing drive controlling system further comprises a solenoid switch that switches a set pressure of the two-stage swing relief valve;

the controller further comprises;

a determining unit that determines that the upper structure is accelerating based on the lever operation amount detected by the lever operation amount detector and the pump discharge pressure detected by the pressure sensor; and

a swing relief pressure switch that;

(i) when the pump discharge pressure detected by the pressure sensor exceeds a third set value, switches the set pressure of the two-stage swing relief valve from the first relief pressure to the second relief pressure, and (ii) when the pump discharge pressure detected by the pressure sensor falls below a fourth set value, switches the relief pressure of the two-stage swing relief valve from the second relief pressure to the first relief pressure;

the third set value is smaller than the first set value,

the fourth set value is equal to or smaller than the second set value; and

the solenoid switch switches the set pressure of the two-stage swing relief valve based on a switching signal from the swing relief pressure switch.

3. The swing drive controlling system of the construction machine according to claim 1, wherein, when a second control valve other than the first control valve for the hydraulic motor is switched while the adjuster of the controller is reducing the pump displacement in accordance with the pump discharge pressure detected by the pressure sensor and adjusting the pump absorption torque of the variable displacement hydraulic pump to be set at the value less than the predetermined value, the controller cancels the adjustment by the adjuster.

4. The swing drive controlling system of the construction machine according to claim 2, wherein the controller further comprises a lever-return determining unit that judges whether or not the control lever for switching the first control valve for the hydraulic motor is returned in a neutral direction while the control lever is operated, and when the lever-return determining unit judges that the control lever for switching the first control valve for the hydraulic motor is returned in the neutral direction while the control lever is operated, the swing relief pressure switch switches the set pressure of the two-stage swing relief valve that is set at the second relief pressure to the first relief pressure.

5. The swing drive controlling system of the construction machine according to claim 2, wherein the controller further comprises a lever-shift-back determining unit that judges whether or not the control lever for switching the first control valve for the hydraulic motor is operated beyond a neutral position in an opposite direction while the control lever is operated, and when the lever-shift-back determining unit judges that the control lever for switching the first control valve for the hydraulic motor is operated beyond the neutral position in the opposite direction while the control lever is operated, the swing relief pressure switch switches the set pressure of the two-stage swing relief valve that is set at the second relief pressure to the first relief pressure.

6. The swing drive controlling system of the construction machine according to claim 2, wherein, when a second control valve other than the first control valve for the hydraulic motor is switched while the adjuster of the controller is reducing the pump displacement in accordance with the pump discharge pressure detected by the pressure sensor and adjusting the pump absorption torque of the variable displacement hydraulic pump to be set at the value less than the predetermined value, the controller cancels a switching from the first relief pressure to the second relief pressure by the swing relief pressure switch.

7. The swing drive controlling system of the construction machine according to claim 1, wherein the adjuster comprises:

an elapsed time judging unit that judges whether or not a time elapsed since the pump discharge pressure exceeded the first set value is within a predetermined time; and

a response characteristics setting unit that sets response characteristics of the pump displacement in response to the pump discharge pressure, wherein the response characteristics setting unit sets the response characteristics in a direction for reducing the pump displacement in response to a change in the pump discharge pressure so that the response characteristics are delayed after the predetermined time has elapsed relative to the response characteristics before the predetermined time has elapsed.