Variable Displacement Hydraulic Motor Piston Retainer
Solution Overview
Problem
Previous variable displacement motors and pumps face issues with wear and degradation in their variable displacement assemblies, leading to reduced longevity and increased service intervals.
Innovation Solution
A variable displacement hydraulic motor with a swash plate having a fixed tilt angle and piston assemblies with inner and outer pistons, where the axial movement of the outer piston is controlled by a retainer device, such as a hydraulically actuated pin, to alter motor displacement without the need for adjustable angle swash plates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If variable angle swash plates are used to alter motor displacement, then motor efficiency can be adapted to match working conditions, but the displacement assembly becomes prone to wear and degradation
Solution Approach 1:
The piston assembly is segmented into an inner piston and an outer piston that can move independently. The inner piston interacts with the swash plate while the outer piston is constrained by retainer devices, allowing displacement control without requiring a variable angle swash plate. This segmentation isolates the wear-prone elements and improves reliability while maintaining adaptability.
Solution Approach 2:
The retainer devices dynamically constrain the outer piston at different axial positions to alter motor displacement. By selectively engaging or disengaging the retainer devices, the system can switch between different displacement modes (e.g., full displacement, reduced displacement) without mechanical wear on the swash plate angle adjustment mechanism.
2Adaptability or versatility
If bushings are used to allow angular adjustment of the swash plate, then displacement can be altered, but the bushings are susceptible to wear and degradation
Solution Approach 1:
The invention extracts the displacement control function from the swash plate angle adjustment mechanism. Instead of adjusting the swash plate angle via bushings, the system uses retainer devices that constrain the outer piston axially. This removes the bushings and their associated wear problems while maintaining the ability to alter motor displacement.
3Adaptability or versatility
If variable angle swash plate mechanisms are used, then motor displacement can be adjusted, but the axial length of the motor increases
Solution Approach 1:
The inner piston is nested within the outer piston, with the inner piston interacting with the swash plate and the outer piston constrained by retainer devices. This nested configuration allows both pistons to share the same axial space, enabling displacement control without increasing the overall axial length of the motor.
4Productivity
If reduced swash plate angle mode is used, then displacement is reduced, but motor efficiency decreases
Solution Approach 1:
By segmenting the piston into inner and outer components with independent movement capabilities, the system can maintain optimal swash plate angle interaction through the inner piston while the outer piston's constrained movement provides displacement control. This segmentation prevents the efficiency loss that occurs in traditional systems when operating in reduced displacement mode.
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 solution enhances motor reliability and efficiency, reduces complexity, and allows for a reduction in axial length, while minimizing wear and degradation, thus improving longevity and operational efficiency.
Implementation Method 1
The pin may be hydraulically actuated such that the pin extends and retracts based on hydraulic line pressure
Data Source
AI summary
Systems and methods for a variable displacement hydraulic motor. The hydraulic motor, in one example, includes a swash plate with a tilt angle, multiple piston assemblies configured to rotate about a drive shaft. In the motor, each of the piston assemblies includes an inner piston slideably coupled to an outer piston that mates with a cylinder in a cylinder block and a retainer device configured to inhibit axial movement of the outer piston in a first position and permit axial movement of the outer piston in a second position.