Variable-Displacement Hydraulic Motor Speed-Based Torque Control
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Solution Overview
Problem
Current hydraulic motor control systems used in forestry equipment are slow to respond to changing loads, often requiring operators to stop and wait for inertia to build back up, making them less suitable for smaller tractors, even with two-speed motors.
Innovation Solution
A variable displacement hydraulic motor system with a controller and speed sensor that adjusts motor displacement based on rotational speed, allowing for continuous adjustment between infinite volumes and optimizing acceleration and torque distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a two-speed motor with fixed displacement settings is used, then the motor can provide higher torque at lower speeds, but the system is slow to respond to changing loads and requires operators to stop and wait for inertia to build back up
Solution Approach 1:
The patent applies dynamics by replacing fixed displacement settings with a continuously variable displacement mechanism. The swash plate assembly allows the motor displacement to be dynamically adjusted in real-time based on operating conditions, enabling smooth transitions between high-torque and high-speed modes without the lag associated with fixed two-speed systems. This dynamic adjustment resolves the contradiction by making the displacement adaptive rather than static.
Solution Approach 2:
The patent changes the displacement parameter continuously rather than in fixed steps. By varying the swash plate angle, the motor can achieve any displacement value between minimum and maximum, allowing optimal torque and speed parameters to be maintained across varying load conditions. This continuous parameter change eliminates the responsiveness delays inherent in fixed two-speed systems.
2Force
If the motor shifts between large volume and small volume modes, then torque can be increased to reduce deceleration, but the drum speed must be reduced and operators must stop feeding the drum and wait for speed and inertia to build back up
Solution Approach 1:
The continuous variable displacement mechanism allows the motor to dynamically adjust torque output without discrete mode shifts. Instead of abruptly switching between large and small volume modes, the displacement can be smoothly varied to maintain optimal torque throughout operation, eliminating the need to stop feeding the drum and wait for inertia to rebuild.
Solution Approach 2:
The patent enables continuous adjustment of motor displacement, ensuring that useful action (drum rotation and cutting) continues without interruption. The smooth transition between displacement settings maintains continuous torque delivery and drum speed, preventing operational downtime where operators would otherwise need to stop and wait for inertia to build back up.
3Force
If a weighted drum operating on inertia is used, then momentum is carried as the drum rotates at speed, but the system is not well-suited for smaller tractors even when a two-speed motor is employed
Solution Approach 1:
The continuous variable displacement capability allows the motor to adapt its torque and speed output to match the capabilities of smaller tractors. By adjusting displacement in real-time, the system can optimize performance for lighter-duty applications without requiring a heavily weighted drum, making it compatible across a wider range of tractor sizes and power levels.
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 system improves responsiveness and efficiency by proactively adjusting motor displacement to maintain optimal speed and torque, reducing deceleration and enhancing performance across a range of loads, particularly beneficial for smaller tractors.
Implementation Method 1
a speed sensor configured to measure the rotational speed of the operative element and output a speed signal representative of the measured speed
Implementation Method 2
A variable displacement hydraulic motor receives pressurized hydraulic fluid from a hydraulic pump
Data Source
AI summary
A hydraulically powered implement is designed for use in connection with a tractor that has a hydraulic pump that supplies pressurized hydraulic fluid to the implement. The implement includes a variable displacement hydraulic motor, an operative element driven by the hydraulic motor, a speed sensor configured to measure the rotational speed of the operative element and output a speed signal representative of the measured speed, a shift module that adjusts the displacement of the hydraulic motor in response to a shift command signal, and a controller. The controller sends the shift command signal to the shift module in response to speed signal output by the speed sensor.