Travel Pump Pilot Pressure Control Under Variable Engine Load
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Solution Overview
Problem
Conventional work machines face challenges in reducing the output of hydraulic instruments due to various loads, leading to inefficiencies in travel pump operation.
Innovation Solution
A hydraulic system for work machines is designed with a travel motor, travel pump, hydraulic pump, pilot oil path, travel operation device, additional pilot oil path, drain oil path, pressure selection valve, and pressure adjustment valve, which together control the flow direction of hydraulic oil based on generated pilot and additional pilot pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the output of hydraulic instruments is reduced due to various loads, then the engine load is managed, but the operational efficiency of travel pump deteriorates
Solution Approach 1:
The system divides the single pilot oil path into two separate paths: a first pilot oil path for normal operation and a second pilot oil path for additional pressure control. This segmentation allows independent control of pressure sources, enabling the travel pump to maintain efficiency while the engine load is managed through selective activation of the second path only when needed.
Solution Approach 2:
A pressure selection valve is introduced as an intermediary component that selectively connects either the first pilot oil path or the second pilot oil path to the travel pump based on operating conditions. This mediator enables smooth transition between different pressure sources without direct interference, maintaining travel pump efficiency while accommodating varying engine load conditions.
2Device complexity
If a single pilot oil path is used, then the system structure is simple, but the control flexibility under varying loads deteriorates
Solution Approach 1:
The system transitions from a static single pilot oil path to a dynamic dual-path configuration where the pressure selection valve actively switches between the first and second pilot oil paths based on real-time load conditions. This dynamic adaptation provides flexible control while maintaining relatively simple overall structure through the use of a single switching valve.
3Productivity
If the pilot pressure is increased to maintain travel pump output, then the travel pump efficiency is maintained, but the engine load increases
Solution Approach 1:
Instead of continuously increasing pilot pressure through a single high-capacity path, the system uses the second pilot oil path with an additional pressure generating device only when and to the extent needed to maintain travel pump output. This partial action approach maintains travel pump efficiency while avoiding unnecessary engine load increase during normal operating conditions.
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 system effectively controls the hydraulic oil flow direction, enhancing the operational efficiency of travel motors and pumps, even under varying load conditions.
Implementation Method 1
The hydraulic pump is to supply pilot hydraulic oil. The pilot oil path connects the hydraulic pump and the travel pump to supply the pilot hydraulic oil to the travel pump.
Implementation Method 2
The pressure selection valve is provided in the first coupling oil path to select a selected pressure of the pilot hydraulic oil from the pilot pressure and the additional pilot pressure to apply the selected pressure to the pilot hydraulic oil in the second coupling oil path.
Implementation Method 3
The pressure adjustment valve is provided in the second coupling oil path and is configured to control the selected pressure to be an adjusted pilot pressure.
Implementation Method 4
The travel pump is configured to control a flow direction of the hydraulic oil supplied to the travel motor based on the pilot pressure and the additional pilot pressure.
Data Source
AI summary
A hydraulic system in a work machine includes a travel operation device provided in a pilot oil path between a hydraulic pump a travel pump and including an operation member and configured to generate a pilot pressure supplied via the pilot oil path and an additional pilot pressure in accordance with an operation amount of the operation member. The travel pump is to control a flow direction of hydraulic oil supplied to a travel motor based on the pilot pressure and the additional pilot pressure. A pressure selection valve is provided in a first coupling oil path to select a selected pressure from the pilot pressure and the additional pilot pressure to apply the selected pressure to the pilot hydraulic oil in the second coupling oil path. A pressure adjustment valve is provided in a second coupling oil path to control the selected pressure to be an adjusted pilot pressure.