Method and device for controlling pump torque for hydraulic construction machine

• US 20050160727A1
• Filed: 11/18/2003
• Published: 07/28/2005
• Est. Priority Date: 12/11/2002
• Status: Active Grant

• Current Assignee: Hitachi Construction Machinery Company Limited (Hitachi, Ltd.)
• Original Assignee: Hitachi Construction Machinery Company Limited (Hitachi, Ltd.)
• Inventors: Ishikawa, Kouiji, Nakamura, Kazunori, Arai, Yasushi, Kowatari, Yoichi
• Granted Patent: US 8,162,618 B2
• Time in Patent Office: Days
• US Class Current: 60/431
• CPC Class Codes: E02F 9/2235 including an electronic controller
• CPC Class Codes: E02F 9/226 Safety arrangements, e.g. hydraulic driven fans, preventing cavitation, leakage, overheating
• CPC Class Codes: E02F 9/2292 Systems with two or more pumps
• CPC Class Codes: E02F 9/2296 Systems with a variable displacement pump
• CPC Class Codes: F04B 17/05 driven by internal-combustion engines
• CPC Class Codes: F04B 23/06 the pumps being all of reciprocating positive-displacement type
• CPC Class Codes: F04B 49/002 Hydraulic systems to change the pump delivery
• CPC Class Codes: F04B 49/065 and making use of computers
• CPC Class Codes: F04B 49/08 Regulating by delivery pressure

Abstract

A current load rate of an engine 10 is computed and a maximum absorption torque of at least one hydraulic pump 1, 2 is controlled so that the load rate is held at a target value. Engine stalling can be prevented by decreasing the maximum absorption torque of the hydraulic pump under a high-load condition. When an engine output lowers due to environmental changes, the use of poor fuel or other reasons, the maximum absorption torque of the hydraulic pump can be decreased without a lowering of the engine revolution speed. Further, the present invention is adaptable for any kinds of factors causing a lowering of the engine output, such as those factors that cannot be predicted in advance or are difficult to detect by sensors. In addition, because of no necessity of sensors, such as environment sensors, the manufacturing cost can be reduced.

Claims

1. A pump torque control method for a hydraulic construction machine comprising an engine, a fuel injector for controlling a revolution speed and an output of said engine, a fuel injector controller for controlling said fuel injector, and at least one variable displacement hydraulic pump driven by said engine and driving actuators, wherein the control method comprises the steps of computing a current load rate of said engine and controlling a maximum absorption torque of said hydraulic pump so that the load rate is held at a preset target value when said load rate exceeds the preset target value.

2. A pump torque control method for a hydraulic construction machine according to claim 1, wherein the step of computing the load rate is performed by setting in advance a relationship between a target fuel injection amount computed by said fuel injector controller and an engine torque margin rate (ENGTRRT), and determining the load rate as the engine torque margin rate corresponding to the target fuel injection amount at that time.

3. A pump torque control method for a hydraulic construction machine according to claim 1, wherein the step of controlling the maximum absorption torque is performed by computing a deviation (Δ

TRY) of the load rate from the target value thereof, modifying a pump base torque (TR0) based on the computed deviation, and controlling the maximum absorption torque of said hydraulic pump to be matched with a modified pump base torque (TR1).

4. A pump torque control method for a hydraulic construction machine according to claim 1, wherein the control method further comprises the steps of, at the same time as controlling the maximum absorption torque of said hydraulic pump so that the load rate is held at the target value thereof, computing a deviation (Δ

N) of an actual revolution speed from a target revolution speed of said engine, and controlling the maximum absorption torque of said hydraulic pump so that the deviation reduces.

5. A pump torque control system for a hydraulic construction machine comprising an engine, a fuel injector for controlling a revolution speed and an output of said engine, a fuel injector controller for controlling said fuel injector, and at least one variable displacement hydraulic pump driven by said engine and driving actuators, wherein the control system further comprises first means for computing a current load rate of said engine, and second means for controlling a maximum absorption torque of said hydraulic pump so that the load rate is held at a preset target value when said load rate exceeds the preset target value.

6. A pump torque control system for a hydraulic construction machine according to claim 5, wherein said first means gets in advance a relationship between a target fuel injection amount computed by said fuel injector controller and an engine torque margin rate (ENGTRRT), and determines the load rate as the engine torque margin rate corresponding to the target fuel injection amount at that time.

7. A pump torque control system for a hydraulic construction machine according to claim 5, wherein said second means compute a deviation (Δ

TRY) of the load rate from the target value thereof, modifies a pump base torque based on the computed deviation, and controls the maximum absorption torque of said hydraulic pump to be matched with a modified pump base torque.

8. A pump torque control system for a hydraulic construction machine according to claim 7, wherein said second means integrate the deviation to determine a pump base torque modification value, and add the determined pump base torque modification value to the pump base torque, thereby modifying the pump base torque.

9. A pump torque control system for a hydraulic construction machine according to claim 5, wherein the control system further comprises third means for computing a deviation (Δ

N) of an actual revolution speed from a target revolution speed of said engine, and controlling the maximum absorption torque of said hydraulic pump so that the deviation reduces.