Hydraulic Pump Control System for Excavator Shock Reduction
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Solution Overview
Problem
The switching between connected and unconnected states of hydraulic pumps in work machines, such as excavators, causes pressure fluctuations in hydraulic cylinders, leading to operator felt shocks, especially when the working unit is not in contact with an object, resulting in significant pressure changes and discomfort.
Innovation Solution
A control system that manages the connection between a first and second hydraulic pump using an opening/closing device, ensuring the pumps remain connected when the distributed flow rates are below a predetermined supply flow rate and the pressure difference between the rod-side and cap-side spaces of the hydraulic cylinders is within a defined value, thereby minimizing shock.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the opening/closing device switches between connected and unconnected states of hydraulic pumps, then the hydraulic system can operate in different configurations, but pressure fluctuations occur causing operator shock
Solution Approach 1:
The control device determines switching timing in advance by monitoring flow rates and pressure differences before actual state changes occur. This preliminary detection allows the system to prepare for smooth transitions by ensuring conditions are appropriate for switching, thereby preventing pressure fluctuations and operator shock.
Solution Approach 2:
The control device continuously monitors flow rates and pressure differences between rod-side and cap-side spaces, using this feedback information to determine the optimal timing for switching between connected and unconnected states. This feedback mechanism ensures transitions occur only when conditions minimize pressure fluctuations and operator discomfort.
2Productivity
If the pumps are switched to unconnected state when flow rates are high, then system efficiency improves, but pressure instability occurs when flow rates are low
Solution Approach 1:
The control device dynamically adjusts the connection state between pumps based on real-time flow rate conditions. When flow rates are high, the system operates in unconnected state for efficiency; when flow rates drop below thresholds or pressure differences indicate instability risk, the system transitions to connected state. This dynamic adaptation maintains both efficiency and stability across varying operating conditions.
Solution Approach 2:
The system changes operational parameters (connection state) based on flow rate and pressure difference thresholds. By monitoring these parameters and switching states when they cross defined boundaries, the system optimizes efficiency during high-flow conditions while maintaining stability during low-flow conditions, preventing pressure fluctuations that would occur with fixed configuration.
3Stability of the object's composition
If the passage is kept open for pump connection, then pressure stability is maintained, but system complexity increases
Solution Approach 1:
The control device automatically determines and executes switching decisions based on pre-established criteria involving flow rates and pressure differences. This self-service approach eliminates the need for complex manual control systems or intricate switching mechanisms, as the control device independently manages the connection state transitions based on real-time system conditions.
Data Source
AI summary
A control system includes: first and second hydraulic pumps; an opening/closing device provided in a passage connecting the first and second hydraulic pumps and configured to open and close the passage; a control device controlling the opening/closing device to switch between connected and unconnected states of the first and second hydraulic pumps; a first hydraulic cylinder to which hydraulic fluid from the first hydraulic pump is supplied in the unconnected state; and a second hydraulic cylinder to which hydraulic fluid from the second hydraulic pump is supplied in the unconnected state. The control device controls the opening/closing device to be in the connected state when distributed flow rates of the hydraulic cylinders are a predetermined supply flow rate or lower and a difference between a pressure in a rod-side space and a pressure in a cap-side space of the hydraulic cylinder is a defined value or smaller.