Hydraulic Load Pressure Bleed Path for Cold-Start Responsiveness
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Solution Overview
Problem
The responsiveness of working machines is delayed due to increased viscosity of hydraulic fluid at low temperatures, caused by resistance in the load pressure selection valve and throttle, leading to inefficiencies in hydraulic actuator control.
Innovation Solution
Incorporating a bleed path in the hydraulic system to allow a portion of hydraulic fluid to escape to a destination other than the regulator, along with a passage throttle and a bleed throttle, to improve responsiveness by reducing pressure buildup and fluid viscosity effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a load pressure selection valve and throttle are used to control hydraulic pressure, then pressure control precision is improved, but responsiveness deteriorates at low temperatures due to increased fluid viscosity
Solution Approach 1:
The hydraulic system is divided into multiple independent pressure control circuits, each with its own pressure control valve. This segmentation allows each circuit to respond independently to pressure changes, reducing the overall system response time while maintaining precise pressure control in each branch.
Solution Approach 2:
Pressure control valves are pre-positioned close to the hydraulic actuators (cylinders and motors) before fluid delivery. This preliminary positioning reduces the length of high-pressure fluid passages, minimizing the time for pressure waves to travel and reducing the impact of fluid viscosity on system responsiveness.
2Reliability
If hydraulic fluid viscosity increases at low temperature, then fluid sealing and pressure maintenance are improved, but system responsiveness and actuator control efficiency deteriorate
Solution Approach 1:
The system changes the physical parameters of pressure control by using multiple independent pressure control valves with lower pressure drops compared to a single throttle. This parameter change reduces the overall resistance to fluid flow, improving responsiveness while the sealed pressure chambers maintain reliable pressure holding capability.
Solution Approach 2:
Pressure control valves act as intermediaries between the hydraulic pump and actuators, providing controlled pressure regulation with minimal flow restriction. These intermediary devices maintain the beneficial pressure-holding effect of viscous fluid while reducing the harmful impact on responsiveness through their valve design.
3Stability of the object's composition
If a throttle is provided in the load pressure transmission passage, then pressure regulation stability is improved, but pressure transmission speed deteriorates due to flow resistance
Solution Approach 1:
The single throttle is segmented into multiple pressure control valves distributed in parallel across different circuits. This segmentation eliminates the bottleneck effect of a single throttle, allowing pressure regulation stability to be maintained in each circuit while significantly reducing overall pressure transmission time.
Solution Approach 2:
The pressure control approach transitions from a single-series throttle configuration to a multi-parallel valve configuration. This dimensional change in system architecture allows pressure stability to be achieved through multiple independent control points rather than a single flow restriction, reducing transmission delays.
Data Source
AI summary
A working machine includes first and second outlet ports to allow hydraulic fluid to flow out, first hydraulic actuators supplied with hydraulic fluid from the first outlet port, second hydraulic actuators supplied with hydraulic fluid from the second outlet port, a load pressure selection valve to receive load pressures and output a highest load pressure which is higher of the load pressures on the first and second hydraulic actuators, a regulator to receive the highest load pressure and control discharge rates of hydraulic fluid from the outlet ports according to the highest load pressure, a passage throttle in a load pressure transmission passage between the regulator and the load pressure selection valve, and a bleed path to allow hydraulic fluid in a segment passage of the load pressure transmission passage between the load pressure selection valve and the passage throttle to partially escape to a destination other than the regulator.