Fluid Pressure Control Device with Conduction Path for Air Removal
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Solution Overview
Problem
The existing fluid pressure control devices for hydraulic shovels face issues with air mixing in the pilot chamber, leading to response delays and instability in the movement of the boom cylinder, especially during slight operations, due to the drainage of pilot pressure through orifices or gaps, which affects the responsiveness and operability.
Innovation Solution
A fluid pressure control device with a load retaining mechanism that includes a check valve, a bypass passage, and a switching valve with a pilot chamber and a conduction path that allows pilot pressure to be directed to a drain passage only when the switching valve moves by a predetermined stroke amount or more, preventing pilot pressure variation during slight operations and effectively removing air from the pilot chamber without compromising responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an orifice or gap is provided between the pilot chamber and the drain passage to remove air, then air removal capability is improved, but pilot pressure stability deteriorates
Solution Approach 1:
The conduction path is designed to activate automatically when the switching valve moves by a predetermined stroke amount or more, allowing air to be drained from the pilot chamber in advance before it causes operational problems. This preliminary air removal prevents response delays while maintaining pilot pressure stability during normal operation.
Solution Approach 2:
The system transitions from a static drainage structure (constant orifice) to a dynamic one where the conduction path opens only when the switching valve moves sufficiently. This dynamic activation ensures air is removed when needed (during valve movement) while preventing continuous drainage that would destabilize pilot pressure.
2Object-affected harmful factors
If the switching valve moves to open the bypass passage, then air can be removed from the pilot chamber, but responsiveness deteriorates due to pilot pressure drainage
Solution Approach 1:
The conduction path provides partial drainage capability - it removes air from the pilot chamber when the switching valve moves by a predetermined stroke amount, but does not continuously drain pilot pressure. This partial action is sufficient to remove air while maintaining enough pilot pressure for rapid valve response.
Solution Approach 2:
The conduction path acts as an intermediary drainage route that activates only under specific conditions (when switching valve moves sufficiently). It mediates between the need to remove air and the need to maintain pilot pressure for responsiveness, allowing air removal without compromising response speed.
3Object-affected harmful factors
If pilot pressure is constantly drained to remove air, then air removal is improved, but operability deteriorates due to response delay and variable response
Solution Approach 1:
Instead of continuous drainage, the system uses periodic action where the conduction path opens only when the switching valve moves by a predetermined stroke amount. This periodic activation removes air effectively while maintaining pilot pressure stability during normal operation, ensuring smooth and predictable operability without response delays or variable responses.
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 allows for the removal of air from the pilot chamber while maintaining the responsiveness of the fluid pressure control device, ensuring stable and consistent operation by preventing pilot pressure instability during both slight and large movements of the switching valve.
Implementation Method 1
a check valve configured to allow the working fluid to flow only from the control valve to the load-side pressure chamber
Implementation Method 2
a biasing member configured to bias the spool in a valve-closing direction
Implementation Method 3
a spool configured to move in a valve-opening direction in accordance with the pilot pressure in the pilot chamber
Data Source
Figure 1
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Figure 3
AI summary
A switching valve (22) of a fluid pressure control device (100) includes a pilot chamber (22a) to which pilot pressure is leaded via the pilot valve (10), a spool (36) configured to move in a valve-opening direction in accordance with the pilot pressure in the pilot chamber (22a), a biasing member (41) configured to bias the spool (36) in a valve-closing direction, and a conduction path (46) configured to lead one part of a pilot pressure fluid leaded to the pilot chamber (22a) to a drain passage (40). The conduction path (46) is configured to communicate with the drain passage (40), when the switching valve (22) moves by a predetermined stroke amount or more in the valve-opening direction.