Pilot Line Pressure Assist for Cold-Start Excavator Hydraulics
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Solution Overview
Problem
Large-type hydraulic excavators face increased costs and reduced mountability due to the need for multiple unloading and main relief valves to improve low-temperature engine starting properties, and existing solutions delay the opening of unloading valves at low temperatures, leading to engine stalling issues.
Innovation Solution
A construction machine equipped with a selector valve, unloading valve, pilot pump, pilot control valve, electric pump, motor, and temperature sensor, where the electric pump raises pilot line pressure when the key is switched from OFF to ON in low temperatures, ensuring the unloading valve opens before engine startup, thereby stabilizing engine rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the unloading valve is designed to relieve minimum delivery rate at stand-by time, then energy consumption is suppressed, but the valve opening is delayed at low temperature due to increased viscous friction
Solution Approach 1:
The heating element is activated before the engine starts (when the key switch transitions from OFF to ON) to pre-heat the hydraulic working fluid in the pilot line. This preliminary heating action reduces the fluid's viscosity in advance, ensuring the unloading valve can open promptly when needed for engine starting, thus resolving the delay caused by low-temperature viscous friction while maintaining energy efficiency during normal operation
2Reliability
If multiple unloading valves and main relief valves are provided for each hydraulic pump, then low-temperature starting property is improved, but cost increases and mountability is lowered
Solution Approach 1:
A single unloading valve is introduced as an intermediary component in the common pilot line that serves all hydraulic pumps. This intermediary valve responds to pilot pressure changes and simultaneously controls the opening of multiple pump unloading valves, eliminating the need for individual unloading valves on each pump while maintaining reliable low-temperature engine starting performance and reducing overall system complexity
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 configuration enhances engine starting properties in low-temperature environments at a lower cost by ensuring the hydraulic working fluid is discharged to the tank immediately, reducing pump load and preventing engine stalling.
Implementation Method 1
a temperature sensor for measuring a temperature of a hydraulic working fluid delivered from the pilot pump
Implementation Method 2
the electric pump raises pilot line pressure when the key is switched from OFF to ON in low temperatures
Implementation Method 3
an unloading valve that is provided in a line branched from a delivery line of the hydraulic pump and connecting to a tank and that is opened according to a pilot pressure acting on a pilot pressure receiving section
Implementation Method 4
a motor that drives the electric pump
Data Source
AI summary
It is an object of the present invention to provide a construction machine having a good engine starting property in a low temperature environment.The construction machine of the present invention includes: an electric pump having a delivery port connected to a line part of a pilot line, the line part connecting a pilot pump with a pilot control valve; a motor that drives the electric pump; and a temperature sensor that measures a temperature of a hydraulic working fluid delivered from the pilot pump. A controller starts driving of the motor in the case where a key switch is operated from a key OFF state to a key ON state and where the temperature of the hydraulic working fluid measured by the temperature sensor is lower than a predetermined temperature.