Variable Charge and Flushing in Hydrostatic Circuits
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Solution Overview
Problem
Current hydrostatic transmission systems suffer from inefficient flushing due to unintelligent control of flush valves and relief valves, leading to excessive energy consumption and system losses, as the flushing flow is not optimized for varying operating conditions, causing frictional losses and premature fluid degradation.
Innovation Solution
A closed hydrostatic circuit with a variable charge system and a variable flushing system, featuring an electronically controlled pressure regulating valve, bidirectional variable displacement motor, and a flush valve connected to both input/output lines, allowing for controlled fluid flow through a flush orifice and relief valve based on the charge pump's capacity, optimizing flushing flow according to operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the circuit flushing system is sized to flush adequate flow under worst case operating conditions, then the flushing effectiveness is improved, but the charge pump size increases and energy consumption increases
Solution Approach 1:
The patent applies dynamics by making the charge pump variable displacement, allowing it to adjust its output dynamically based on operating conditions. The controller modulates the pump displacement to provide adequate flushing flow only when needed (high speed operation) and reduces flow at low speeds, eliminating the need for a continuously large pump while maintaining flushing effectiveness when required.
Solution Approach 2:
The system changes the parameter of charge pump output flow based on operating conditions. The controller monitors circuit conditions and adjusts the charge pump displacement to change the flushing flow parameter dynamically, providing high flow when temperature rise is a concern and low flow when operating at low speeds, thereby resolving the contradiction between maintaining flushing effectiveness and reducing energy consumption.
2Temperature
If circuit flushing flow is maximized to prevent fluid overheating, then fluid temperature control is improved, but parasitic losses and fuel consumption increase at low speeds
Solution Approach 1:
The system implements periodic or conditional action by activating high-level flushing only during high-speed operation when heat generation is significant. The controller monitors operating conditions and periodically adjusts the charge pump output, providing maximum flushing flow when needed and minimizing or eliminating flushing flow during low-speed operation, thereby controlling temperature without continuous parasitic losses.
Solution Approach 2:
The patent applies partial action by providing flushing flow at only the necessary levels and times. Instead of continuous maximum flushing, the system provides partial flushing (reduced flow) at low speeds and excessive flushing (maximum flow) only when required at high speeds, optimizing the balance between temperature control and energy loss reduction.
3Reliability
If the charge pump operates at full capacity continuously, then adequate charge flow is maintained, but system efficiency decreases due to constant parasitic losses
Solution Approach 1:
The system implements self-service through the controller that automatically monitors circuit conditions and adjusts the charge pump output accordingly. The controller determines when full charge flow is needed versus when reduced flow suffices, allowing the system to self-regulate and eliminate the need for continuous full-capacity operation, thereby maintaining charge flow adequacy while improving overall system efficiency.
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 solution minimizes power losses at low speeds while maintaining adequate flushing and charge flow at high speeds, ensuring the hydrostatic fluid's viscosity remains within optimal limits, reducing energy consumption and extending fluid lifespan.
Implementation Method 1
a variable displacement charge pump configured to supply charge fluid and pilot control fluid to the hydrostatic circuit
Implementation Method 2
an electronically controlled pressure regulating valve in communication with an output of the charge pump
Implementation Method 3
a bidirectional variable displacement hydrostatic motor. The hydrostatic motor is connected to two input/output lines
Implementation Method 4
The flush valve is configured to select the lower pressure line of the two hydrostatic circuit pressure lines
Data Source
AI summary
A closed hydrostatic circuit with variable charge and variable flushing systems is disclosed. A variable displacement charge pump is configured to supply charge fluid and pilot control fluid to the hydrostatic circuit. An electronically controlled pressure regulating valve is in communication with an output of the charge pump and is linked to a controller. When the hydrostatic control system detects a high hydraulic temperature condition, the electronically controlled pressure regulating valve, that is in communication with an output of the charge pump and that is linked to a controller, increases the charge pump flow. A bidirectional variable displacement hydrostatic motor is connected in parallel to two input/output lines. A flush valve is in communication with the hydrostatic motor and both input/output lines. The flush valve and hydrostatic motor are both in communication with the flush orifice and a flush relief valve. When the pressure regulating valve causes the charge pump to operate at or near a full capacity, fluid exits the flush valve and passes through both the flush orifice and the flush relief valve. In contrast, when the pressure regulating valve causes the charge pump to operate at a lower or near minimum capacity, fluid exits the flush valve and passes through the flush orifice only without passing through the flush relief valve.