Piston-Cylinder Elastic Guide Element for Hydraulic Clutch
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Solution Overview
Problem
Existing piston-cylinder arrangements in hydraulic clutch actuation devices face issues with axial guidance due to tolerances and lateral forces, particularly at low temperatures, which compromise the seal's functionality by allowing radial movement and play.
Innovation Solution
An elastic guide element made of a material that hardens before the seal, such as an elastomer with a higher glass transition temperature, is used parallel to the seal to absorb shape errors and protect the seal from harmful movements by 'freezing' deformation at low temperatures, ensuring play-free axial movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a rigid guide bushing is used to guide the piston and absorb transverse forces, then the piston can be guided axially, but radial movement of the piston occurs at low temperatures due to radial clearance, compromising seal function
Solution Approach 1:
The guide element's material parameters change with temperature: at operating temperature it remains elastic to accommodate transverse forces and tolerances, but at low temperatures it hardens (glass transition) to freeze form defects and prevent radial piston movement, thereby protecting the seal
Solution Approach 2:
The system uses a composite approach combining the rigid guide bushing with an elastic guide element made of temperature-sensitive material (elastomer with specific glass transition temperature), creating a composite guidance system that adapts its properties based on temperature conditions
2Ease of manufacture
If radial clearance is increased in the guide bushing to compensate for tolerances, then assembly is easier, but axial guidance precision deteriorates
Solution Approach 1:
The guide element transitions from a soft elastic state during assembly (allowing tolerance compensation) to a hardened state at low temperatures (providing precise axial guidance), dynamically changing its mechanical properties to satisfy both requirements at different stages
3Adaptability or versatility
If the seal material is made softer to accommodate transverse movements, then sealing flexibility improves, but at low temperatures the seal cannot accommodate transverse movements, causing radial piston movement
Solution Approach 1:
The elastic guide element acts as an intermediary between the piston and the seal, absorbing transverse forces and preventing them from reaching the seal at low temperatures, while allowing the seal to remain soft and flexible for sealing purposes at operating temperatures
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 solution allows for unimpeded, play-free axial piston movement while protecting the seal from transverse forces, maintaining effective sealing across varying temperatures and operational conditions.
Implementation Method 1
The elastic guide element is made of a material that hardens earlier upon cooling than the seal material. The glass transition temperature is understood to be the ambient temperature below which the elastomer gradually becomes brittle and ceases to function as a spring.
Implementation Method 2
Because the guide element hardens earlier than the seal material, the seal is protected from harmful transverse movements in its hardened state. Due to its elasticity, the guide element can compensate for form defects in the piston and housing components without interference.
Data Source
Figure 1
Figure 2~3
AI summary
The invention relates to a piston-cylinder arrangement for a disengagement unit, in particular for a master cylinder of a hydraulic clutch actuation device, comprising a cylinder which is in the form of a housing (2) and which spans an annular pressure chamber (3) in which a piston (4) is mounted in axially movable fashion, wherein the piston (4) is sealed off with respect to the pressure chamber (3) by means of at least one seal (5). In the case of a piston-cylinder arrangement which can be guided without play at all operating temperatures and in the presence of adverse tolerances, an elastic guide element (7) is arranged in parallel with the seal (5) in the direction of motion of the piston (4), which guide element is composed of a material which, during a cooling process, hardens earlier than a material of the seal (5).