Hydraulic Pump Torque Feedback for Excavator Swing and Boom Control
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Solution Overview
Problem
Existing hydraulic drive systems for construction machines, such as hydraulic excavators, face challenges in maintaining optimal torque distribution between swing motors and boom cylinders, leading to impaired operability when performing simultaneous swinging and boom raising operations, especially when the torque setting of the swing motor is large, resulting in reduced flow rates to the boom cylinder and lagging boom raising.
Innovation Solution
A hydraulic drive system with variable-displacement pumps and a controller that adjusts the torque distribution between the swing motor and boom cylinder hydraulic pumps, using feedback mechanisms to accurately reflect the actual torque consumption of the swing motor and adjust the horsepower control starting pressure, ensuring the sum of torques consumed by both pumps does not exceed a predetermined value, thereby optimizing the distribution of torques and maintaining stable operability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the torque setting of the swing motor is increased to improve swing performance, then swing operability is improved, but the flow rate to the boom cylinder is reduced causing boom raising to lag
Solution Approach 1:
The patent introduces a feedback mechanism where the delivery pressure of the swing motor hydraulic pump is fed back to the boom cylinder hydraulic pump regulator. This feedback loop enables the system to automatically adjust torque distribution based on actual swing motor torque consumption, ensuring that boom raising speed is maintained even when swing motor torque setting is high. The feedback pressure modifies the regulator setting of the boom pump to compensate for torque allocation imbalances.
Solution Approach 2:
The system dynamically changes the operating parameters of the hydraulic pumps by adjusting displacement volumes based on feedback pressure. The regulator for the boom cylinder pump modifies its displacement volume control in response to the feedback pressure from the swing motor pump, thereby changing the flow rate parameter to maintain boom raising speed while allowing high swing motor torque.
2Ease of operation
If the delivery pressure of the swing motor hydraulic pump is limited by a pressure reducing valve, then combined operability is improved, but the flow rate to the boom cylinder is greatly reduced
Solution Approach 1:
The patent uses the delivery pressure of the swing motor hydraulic pump as an intermediary signal to control the boom cylinder hydraulic pump. Instead of directly limiting flow rate or using a simple pressure reducing valve, the system uses the swing pump's delivery pressure as a feedback signal that modifies the regulator setting of the boom pump. This intermediary mechanism enables coordinated control of both pumps to achieve good combined operability while maintaining adequate flow rate.
3Reliability
If the sum of torques consumed by multiple hydraulic pumps is controlled not to exceed a predetermined value, then the prime mover is prevented from stalling, but the flow rates of individual pumps are reduced to extremes
Solution Approach 1:
The patent implements dynamic torque distribution among multiple hydraulic pumps by continuously adjusting each pump's displacement volume based on feedback pressures. Instead of static torque allocation or simple sum control, the system dynamically balances torque consumption to prevent prime mover stalling while maintaining adequate flow rates to all actuators. The regulator settings are continuously modified in response to changing load conditions and feedback signals.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables effective torque management, ensuring that the boom raising operation is synchronized with swinging, preventing excessive torque reduction and maintaining efficient use of the prime mover's output, thereby enhancing combined operability and swing performance.
Implementation Method 1
a variable pressure reducing valve (12) whose set pressure is reduced by a second output pressure (ΔP3) introduced to a pressure receiving section (12b)
Implementation Method 2
a proportional solenoid valve (15) whose output pressure (ΔP3) is introduced to the pressure receiving section (12b) of the variable pressure reducing valve (12)
Data Source
Figure 1
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AI summary
When a swing motor and a boom cylinder are driven simultaneously, a hydraulic drive system appropriately adjusts a distribution of torques between hydraulic pumps and feeds back a torque actually consumed by the hydraulic pump for actuating the swing motor accurately to the hydraulic pump for actuating the boom cylinder. To that end, when boom raising and swinging are performed simultaneously, the hydraulic drive system corrects an allowable torque of a hydraulic pump 302 that supplies a hydraulic fluid to a swing motor 3c so as to be lowered by a certain ratio, reducing allowable torques of hydraulic pumps 102 and 202 that supply a hydraulic fluid to a boom cylinder 3a by torques consumed by the hydraulic pumps 102 and 202 that supply a hydraulic fluid to the swing motor 3c.