Hydraulic Piston Unit Displacement Control Without a Servo Unit
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Solution Overview
Problem
Existing hydraulic piston units require a separate servo unit for adjusting displacement volume, leading to increased costs, construction space usage, wear, and leakage issues.
Innovation Solution
A hydraulic piston unit with a tiltable displacement element between end positions, controlled by a control valve with high and low pressure ports, eliminating the need for a servo unit by using working pistons to adjust the displacement volume based on fluid pressure differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a servo unit with servo cylinder and movable servo piston is used to adjust displacement volume, then the displacement volume can be controlled, but the device complexity increases and construction space is consumed
Solution Approach 1:
The invention extracts and eliminates the separate servo unit (servo cylinder and servo piston) from the hydraulic piston unit. Instead, the working pistons themselves are used to directly adjust the displacement element, removing the unnecessary intermediate assembly and simplifying the overall structure while maintaining the displacement control function.
Solution Approach 2:
The working pistons are given a dual function: they not only convey hydraulic fluid but also serve to adjust the displacement volume by tilting the displacement element. This multi-functionality eliminates the need for dedicated servo components, reducing device complexity while maintaining operational capability.
2Ease of operation
If a servo unit is used to adjust displacement volume, then displacement control is achieved, but manufacturing costs increase
Solution Approach 1:
By removing the servo unit components (servo cylinder, servo piston, associated seals and mounting structures), the bill of materials is reduced, leading to lower manufacturing costs. The existing working pistons are repurposed to perform the displacement adjustment function, eliminating the need for additional expensive components.
Solution Approach 2:
The invention merges the displacement adjustment function into the existing working piston assembly. By combining multiple functions into existing components rather than adding separate assemblies, the overall part count decreases, reducing both manufacturing and assembly costs.
3Ease of operation
If a servo unit is used to adjust displacement volume, then displacement control is achieved, but the reliability decreases due to wear and leakage
Solution Approach 1:
By eliminating the servo unit, the invention removes additional sealing interfaces and moving parts that are susceptible to wear and leakage. Fewer components mean fewer potential failure points, thereby improving overall system reliability.
Solution Approach 2:
The working pistons self-adjust the displacement element based on the hydraulic pressure differential across them. This self-regulating mechanism eliminates the need for external servo control, reducing the number of active control components that could fail and improving system reliability.
4Ease of operation
If a servo unit is used to adjust displacement volume, then displacement control is achieved, but the quantity of parts increases
Solution Approach 1:
The invention removes the servo unit assembly (servo cylinder, servo piston, seals, mounting hardware) from the system. This extraction significantly reduces the total number of parts while the working pistons continue to perform their primary function and additionally control the displacement element.
Solution Approach 2:
The working pistons serve multiple purposes: conveying hydraulic fluid and adjusting the displacement volume. This multi-functionality reduces the need for dedicated components, thereby decreasing the overall quantity of parts in the system.
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
Simplifies displacement volume adjustment, reduces part count, saves space, and enhances reliability by eliminating the need for a servo unit, while maintaining efficient operation in both pump and motor modes.
Implementation Method 1
the hydraulic fluid pressure difference between these two control ports and the hydraulic fluid pressure in the cylinder bores determines the tilt angle of the displacement element
Data Source
AI summary
A hydraulic piston unit including a rotational group for driving or being driven by a driving shaft, and having a tiltable displacement element for adjusting the displacement volume of the rotational group between a minimum or a maximum displacement, wherein, on t valve segment between a kidney-shaped inlet port and a kidney-shaped outlet port at respective dead end positions of reciprocally moveable working pistons first and second control ports are located in fluid connection with cylinder bores in the cylinder block, for controlling the position of the displacement element. The hydraulic piston unit further includes a control valve with a shiftable control valve spool fluidly connected via a high pressure port to a high pressure side of the hydraulic piston unit. The control valve spool is configured to conduct hydraulic fluid from the high pressure side to one of the first or the second control port.