Variable Displacement Hydraulic Motor Smooth Shifting Control
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Solution Overview
Problem
Shifting a two-speed axial piston drive motor in power machines, such as utility vehicles, results in jolts to the operator due to discrete displacement changes between high-torque low-speed and high-speed modes, causing an uncomfortable ride and negative operator perception.
Innovation Solution
Implementing a drive system with a variable displacement drive motor controlled by a shift actuator and a controller that smoothly transitions between minimum and maximum displacements based on travel speed, allowing for continuous variable displacement and eliminating abrupt shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If discrete displacement changes are used in two-speed drive motor, then torque output and travel speed are provided in two distinct modes, but jolts occur to the operator during shifting
Solution Approach 1:
The drive motor displacement is made dynamically variable rather than fixed at two discrete values. The system continuously adjusts displacement between minimum and maximum values based on operating conditions, eliminating abrupt transitions and providing smooth power delivery while maintaining operator comfort
Solution Approach 2:
The displacement parameter of the drive motor is changed from discrete fixed values to continuously variable values. By controlling displacement as a variable parameter rather than fixed setting, the system achieves smooth transitions between operating modes and eliminates jolts during shifting
2Adaptability or versatility
If discrete displacement changes are used in two-speed drive motor, then high torque and high speed modes are provided, but abrupt shifts cause negative operator perception
Solution Approach 1:
The system provides dynamic adaptability through continuous displacement variation rather than fixed speed modes. This allows the drive motor to smoothly adapt to different operating requirements while maintaining positive operator perception through imperceptible transitions
Solution Approach 2:
The displacement adjustment is made continuous rather than discrete, ensuring uninterrupted and smooth power delivery. This continuous adjustment eliminates abrupt shifts and maintains consistent operator comfort across the entire operating range
3Speed
If two-speed axial piston drive motor is used, then different displacements provide different speeds and torque, but shifting causes jolts during operation
Solution Approach 1:
The drive motor operates with dynamically variable displacement rather than fixed two-speed settings. This dynamic control allows smooth transitions between speed ranges by continuously adjusting displacement, eliminating jolts during what would traditionally be abrupt shifting events
Solution Approach 2:
The displacement parameter is changed from discrete fixed values to continuously variable values. This parameter transformation eliminates the harmful jolts associated with discrete shifting while maintaining the ability to provide different speed and torque outputs
Data Source
AI summary
Disclosed are power machines, and drive systems for use thereon, as well as methods of controlling the displacement of a hydraulic drive motor. The drive system includes a drive pump capable of providing a hydraulic power output and a drive motor operably coupled to the drive pump that receives the hydraulic power output from the drive pump. The drive motor has an operating displacement that is variable between a minimum displacement and a maximum displacement and it provides a rotational output member. A shift actuator is operably coupled to the drive motor and it is configured to vary the displacement of the drive motor between the minimum displacement and the maximum displacement. A controller controls the shift actuator to cause the drive motor to provide infinitely variable displacement between the minimum and maximum displacements.