Hydraulic Motor Speed Control With Closed-Loop Flow Regulation
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Solution Overview
Problem
Hydraulic systems with fixed displacement pumps and motors face challenges in accurately controlling motor speed due to varying fluid flow rates caused by engine speed variations, mechanical and volumetric inefficiencies, and fluid temperature/viscosity changes, leading to undesired motor speed fluctuations.
Innovation Solution
Implementing a hydraulic system with fixed displacement pumps and motors, utilizing rate-control valves and pressure regulation valves, along with solenoid-operated proportional valves and engagement valves, to adjust fluid flow rates and maintain consistent motor speed through closed-loop control systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a fixed displacement pump and fixed displacement motor are used, then cost is reduced and hydraulic efficiency is improved, but motor speed control precision deteriorates due to varying flow rates from engine speed changes, mechanical/volumetric inefficiencies, and fluid temperature variations
Solution Approach 1:
The patent applies dynamics by making the hydraulic system adjustable through variable displacement mechanisms. The pump or motor can change their displacement volume dynamically based on operating conditions, allowing the system to adapt flow rates to maintain consistent motor speed despite engine speed variations or load changes, thereby resolving the contradiction between using simple fixed displacement components and achieving precise speed control.
Solution Approach 2:
The patent utilizes parameter changes by modifying the displacement volume of the hydraulic pump or motor as a controllable parameter. By adjusting the displacement parameter in response to feedback from speed sensors or control systems, the flow rate to the motor is regulated to maintain desired speed performance while still using fundamentally simple displacement components, thus improving speed control precision without completely abandoning the simplicity of fixed displacement architecture.
2Loss of energy
If a fixed displacement pump is used, then hydraulic efficiency is improved, but motor speed stability deteriorates due to flow rate variations from mechanical and volumetric efficiency changes over time
Solution Approach 1:
The patent implements feedback control by incorporating speed sensors that monitor actual motor speed and feeding this information back to a control system. The control system compares the measured speed with the desired speed and adjusts the hydraulic flow rate accordingly by modifying pump or motor displacement, thereby maintaining motor speed stability despite changes in mechanical or volumetric efficiency over time while preserving the energy efficiency of fixed displacement components.
3Device complexity
If a fixed displacement motor is used, then device complexity is reduced, but motor speed precision deteriorates due to downstream flow variability from pump output fluctuations
Solution Approach 1:
The patent introduces an intermediary component, such as a flow control valve or variable displacement mechanism, between the fixed displacement pump and the fixed displacement motor. This intermediary acts as a mediator that regulates the flow rate reaching the motor, compensating for pump output fluctuations and ensuring consistent motor speed, thereby achieving precise speed control without increasing the complexity of the motor itself or replacing the simple fixed displacement architecture.
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 achieves precise and consistent motor speed control by adjusting fluid flow rates using proportional valves and closed-loop control, mitigating the effects of varying engine speeds and load conditions.
Implementation Method 1
a first rate-control valve fluidly coupled to the first pump and the first motor and movable through a range of positions to adjust a flow rate to the first motor
Implementation Method 2
utilizing rate-control valves and pressure regulation valves, along with solenoid-operated proportional valves
Implementation Method 3
pressure regulation valves, along with solenoid-operated proportional valves and engagement valves, to adjust fluid flow rates and maintain consistent motor speed
Implementation Method 4
solenoid-operated proportional valves and engagement valves
Implementation Method 5
maintain consistent motor speed through closed-loop control systems
Data Source
AI summary
An electrohydraulic system for a work machine includes a pump, a motor fluidly coupled to the pump, a subassembly driven by the motor, and a rate-control valve fluidly coupled to the pump and the motor. The rate-control valve is movable through a range of positions. A present speed of the motor is proportional to a present position of the rate-control valve. The present position of the rate-control valve is adjustable by varying a current supplied to the rate-control valve. The supply of current to the rate-control valve is adjusted based on the difference between the present speed of the motor and a target speed of the motor.