Excavator Hydraulic Pump Control for Variable Motor Speed
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Solution Overview
Problem
Conventional shovels with negative control type hydraulic systems experience deteriorating operability when the operating state of the motor changes, such as variations in rotational speed, leading to inefficiencies and reduced performance.
Innovation Solution
A shovel with a hydraulic system that includes a controller to adjust the discharge flow rate of the hydraulic pump based on a preset flow rate control characteristic, allowing for adaptive control at different rotational speeds of the motor, thereby maintaining operability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single flow rate control characteristic is used for all motor rotational speeds, then the control system is simple, but operability deteriorates when motor rotational speed varies
Solution Approach 1:
The patent applies dynamics by making the flow rate control characteristic changeable according to motor rotational speed. The control device selects between a first flow rate control characteristic (for normal rotational speeds) and a second flow rate control characteristic (for reduced rotational speeds), allowing the system to adapt dynamically to operating conditions rather than using a fixed control characteristic.
Solution Approach 2:
The patent changes the control parameter (flow rate control characteristic) based on the motor rotational speed parameter. When rotational speed drops below a threshold, the system switches to a different control characteristic that accounts for the reduced speed, thereby maintaining proper hydraulic pump discharge flow rate control under varying operational parameters.
2Loss of energy
If hydraulic pump discharge flow rate is not optimized for varying motor speeds, then energy waste increases, but implementing optimization adds control complexity
Solution Approach 1:
The control device monitors the actual motor rotational speed and uses this feedback to determine which flow rate control characteristic to apply. This feedback mechanism allows the system to automatically adjust the hydraulic pump discharge flow rate based on real-time operating conditions, preventing energy waste without requiring complex manual intervention.
Solution Approach 2:
The system performs self-adjustment by automatically selecting the appropriate flow rate control characteristic based on motor rotational speed. The control device autonomously manages the hydraulic pump discharge flow rate optimization without external intervention, reducing energy waste while maintaining manageable control complexity through automated decision-making.
Data Source
AI summary
A shovel includes a lower traveling body, an upper swing body swingably mounted on the lower traveling body, a motor mounted on the upper swing body, a hydraulic pump driven by the motor, and processing circuitry configured to control the discharge flow rate of the hydraulic pump in accordance with a flow rate control characteristic that is preset. The flow rate control characteristic is a characteristic indicating a correspondence between the displacement of the hydraulic pump and a negative control pressure. The flow rate control characteristic includes a first flow rate control characteristic adopted when the motor rotates at a first rotational speed and a second flow rate control characteristic adopted when the motor rotates at a second rotational speed lower than the first rotational speed.