Pilot Line Pressurization for Cold-Start Hydraulic Excavators
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Solution Overview
Problem
Large-type hydraulic excavators face challenges in starting the engine in low-temperature environments due to delayed opening of unloading valves, leading to increased hydraulic pump load and potential engine stalling, which is costly to address with existing solutions that require multiple unloading and main relief valves.
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 pilot line is pressurized by the electric pump when the key is turned on in low temperatures, ensuring the unloading valve opens before engine startup, thus relieving the hydraulic working fluid to the tank and reducing engine load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a unloading valve is provided to relieve the minimum delivery rate at stand-by time, then energy consumption is suppressed, but the opening of the unloading valve is delayed at low temperature due to increased viscous friction
Solution Approach 1:
The patent applies preliminary action by providing a heating device that pre-heats the hydraulic working fluid in the pilot line before the unloading valve needs to open. This prevents the viscous friction delay at low temperature by raising the fluid temperature in advance, ensuring the unloading valve opens promptly when needed while maintaining energy efficiency during stand-by operation.
2Power
If the number of hydraulic pumps is increased to 6-12 times for large-type excavators, then the hydraulic system capacity is increased, but the cost and device complexity increase significantly when applying multiple unloading and main relief valves
Solution Approach 1:
The patent applies universality by designing a common heating device that can be shared across multiple hydraulic pumps in large-type excavators. Instead of providing separate unloading and main relief valves for each pump, the single heating device serves all pumps by pre-heating the pilot line fluid, thereby maintaining the required hydraulic system capacity while significantly reducing the number of components and control lines needed.
3Reliability
If a main relief valve with lowered set pressure is used for low-temperature starting, then the hydraulic pump load is reduced, but the cost and mountability are lowered when multiple such valves are required
Solution Approach 1:
The patent applies universality by replacing multiple individual main relief valves with a single common main relief valve that serves all hydraulic pumps. Combined with the heating device that pre-heats the pilot line, this configuration ensures that the hydraulic pump load is reduced during low-temperature starting without requiring multiple relief valves, thereby improving engine starting property while reducing device complexity and mounting requirements.
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 allows for stable engine starting 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, and allows for common use of electric pumps and motors across multiple hydraulic pumps.
Implementation Method 1
a temperature sensor for measuring a temperature of a hydraulic working fluid delivered from the pilot pump
Implementation Method 2
the pilot line is pressurized by the electric pump when the key is turned on in low temperatures, ensuring the unloading valve opens before engine startup
Data Source
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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.