Work Machine Hydraulic Pressure Control Under Engine Load
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Solution Overview
Problem
Conventional hydraulic systems in work machines experience reduced output due to engine load, leading to inefficient operation and difficulty in maintaining smooth functioning of hydraulic actuators.
Innovation Solution
The hydraulic system incorporates a travel pump, pilot oil paths, additional pilot oil paths, pressure selection valves, pressure adjustment valves, and differential pressure generation valves to control hydraulic oil flow direction and pressure, ensuring smooth operation of travel motors and hydraulic actuators even under varying engine loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the output of travel pump is reduced due to engine load, then energy consumption is saved, but hydraulic actuator performance deteriorates
Solution Approach 1:
The hydraulic system is divided into multiple independent pump units (travel pump and hydraulic pump) that can operate independently. The travel pump is controlled by pilot pressure from the hydraulic pump, allowing the hydraulic pump to maintain actuator performance while the travel pump adjusts to engine load conditions, resolving the contradiction between energy saving and performance maintenance.
Solution Approach 2:
Pilot pressure serves as an intermediary control mechanism. The hydraulic pump generates pilot pressure that controls the travel pump's operation. This intermediary allows the system to respond to engine load changes while maintaining sufficient hydraulic pressure for actuators, balancing energy consumption with actuator performance.
2Strength
If the output of travel pump is reduced due to engine load, then mechanical stress on engine is reduced, but operation smoothness deteriorates
Solution Approach 1:
The system dynamically adjusts the travel pump output based on real-time engine load conditions through pilot pressure control. When engine load is high, the travel pump output is automatically reduced, preventing overload while maintaining smooth operation through proportional control rather than abrupt changes.
3Reliability
If multiple pressure control valves are added to maintain actuator performance, then hydraulic actuator performance is improved, but system complexity increases
Solution Approach 1:
The hydraulic pump serves multiple functions: it supplies hydraulic oil to actuators, generates pilot pressure to control the travel pump, and maintains system pressure. This multi-functionality reduces the need for additional dedicated pressure control valves, maintaining actuator performance while limiting system complexity growth.
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
The system maintains consistent hydraulic actuator performance by adjusting pilot pressures, allowing for smooth operation across a wide range of engine loads, enhancing ease of use and efficiency.
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 differential pressure generation valve is provided in the second coupling oil path to generate differential pressure upstream or downstream relative to the pressure adjustment valve. The differential pressure generation valve includes at least one of a check valve and a relief valve.
Data Source
AI summary
A hydraulic system in a work machine includes a travel operation device to generate a pilot pressure and an additional pilot pressure in accordance with an operation amount of the operation member. A 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 a second coupling oil path. A pressure adjustment valve is provided in the second coupling oil path to control the selected pressure to be an adjusted pilot pressure. A differential pressure generation valve is provided in the second coupling oil path to generate differential pressure upstream or downstream relative to the pressure adjustment valve.