Hydraulic Pump Torque Control for Engine Lug-Down
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Solution Overview
Problem
The quick operation of hydraulic actuators in hydraulic work machinery leads to a sudden increase in pump absorption torque and discharge flow rate variations, causing engine lug-down and deterioration in operability due to existing control methods that maintain a constant minimum pump absorption torque regardless of engine rotational speed.
Innovation Solution
An engine lug-down suppressing device that includes detection means to differentiate between operating and non-operating states, adjusting pump absorption torque based on target engine rotational speed during non-operation and actual engine rotational speed during operation, ensuring the torque remains within a range that approaches the maximum absorption torque as the engine speed increases, and incorporates temperature correction for optimal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the operating lever device is quickly operated from non-operated state to maximum manipulated variable, then the hydraulic actuator responds quickly, but the pump absorption torque suddenly increases causing engine lug-down and deterioration in operability
Solution Approach 1:
The control device increases pump absorption torque in advance during the transient period when the operating lever is quickly operated, before the engine rotational speed decreases. This preliminary action prevents the sudden torque deficiency that causes lug-down, allowing the hydraulic actuator to respond quickly while maintaining engine stability and operability.
Solution Approach 2:
The control device acts as an intermediary between the operating lever device and the variable displacement hydraulic pump, mediating the torque transmission. When quick operation is detected, the control device adjusts the pump absorption torque to bridge the gap between the sudden operator input and the engine's rotational speed response, preventing lug-down while maintaining responsive actuator operation.
2Stability of the object's composition
If the pump absorption torque is held at a preset minimum value when the operating lever device is non-operated, then the engine operates stably, but the pump discharge flow rate varies greatly when the actuator starts operation quickly
Solution Approach 1:
The control device dynamically adjusts the pump absorption torque based on the operational state. When the operating lever is quickly operated, the control device transitions from holding minimum torque to increasing torque during the transient period, then returns to minimum torque after stabilization. This dynamic adjustment maintains engine stability while reducing pump discharge flow rate variation during quick starts.
3Reliability
If the speed control increases fuel injection quantity to restore engine rotational speed, then the target engine rotational speed is recovered, but there is a delay in response causing lug-down phenomenon
Solution Approach 1:
The control device performs preliminary action by increasing pump absorption torque before the engine rotational speed decreases during quick operation. This anticipatory control prevents the speed drop that triggers the delayed fuel injection response, eliminating lug-down while maintaining reliable speed control. The normal speed control mechanism remains intact for non-transient conditions.
Data Source
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AI summary
To provided an engine lug-down suppressing device for hydraulic work machinery, capable of suppressing deterioration in operability of a hydraulic actuator when the hydraulic actuator is caused to operate quickly from a stopped state. Pilot pressure to a tilting control unit 25 of a variable displacement hydraulic pump 23 is controlled by a solenoid valve 54. A controller 55 controls the solenoid valve 54 in accordance with a target rotational speed signal from an input unit 40. This control differs according to whether or not a detector 51 detects the pilot pressure created by an operating lever device 34. In an entire range of the target engine rotational speed, pump absorption torque at the time when the pilot pressure is not detected, falls within a range equal to or smaller than pump absorption torque at the time when the pilot pressure is detected, and is set to approach the pump absorption torque at the time when the pilot pressure is detected with an increase in the target engine rotational speed.