Plastic Master Cylinder Piston with Metal Insert for Noise Damping
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Solution Overview
Problem
Existing master cylinders experience noise due to sudden brake fluid surges when the push rod is rapidly released, and the production of complex aluminum pistons is costly and inefficient.
Innovation Solution
A molded plastic primary piston with a metal insert is used, allowing for increased mechanical resistance and reduced material thickness, enabling easier production and noise damping, while the metal insert accommodates the push rod and enhances mechanical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aluminum pistons with specific complex shapes are used to improve performance, then the master cylinder performance is improved, but the production cost increases significantly
Solution Approach 1:
The invention uses a composite structure combining plastic material for the piston body with a metal insert (aluminum or stainless steel) for the forward cavity. This allows the piston to benefit from the cost-effectiveness and ease of molding of plastic while incorporating the mechanical strength and resistance to deformation of metal in the critical area where the push rod applies force, thereby resolving the contradiction between performance and manufacturing cost.
2Speed
If the push rod is rapidly released, then the pistons return to rest position quickly, but fluid hammer noise is generated
Solution Approach 1:
The invention changes the material parameters of the piston by using plastic material with specific viscoelastic properties. This material characteristic dampens the sudden fluid surge that occurs during rapid piston return, thereby reducing fluid hammer noise while still allowing quick return of the pistons to rest position.
3Ease of manufacture
If plastic material is used for the primary piston, then production is easier and more economical, but mechanical resistance is reduced
Solution Approach 1:
The invention combines plastic material (providing ease of manufacture through injection molding) with a metal insert in the forward cavity (providing high mechanical resistance). The metal insert is specifically positioned where the push rod applies force, ensuring that the area subject to highest mechanical stress has sufficient strength while the rest of the piston benefits from the manufacturing advantages of plastic.
Solution Approach 2:
The invention applies different material qualities to different parts of the piston: the forward cavity (subject to high mechanical stress from the push rod) is made of metal insert for strength, while the rest of the piston body is made of plastic for ease of manufacture. This local differentiation of material properties resolves the contradiction between mechanical resistance and ease of manufacture.
Data Source
AI summary
A primary piston is described of molded plastic and equipped with a functional metallic insert and at least one groove. The primary piston is installed in a master cylinder comprising at least the primary piston and a secondary piston, these being mounted in the bore hole of a master cylinder. These pistons can create pressure in a primary pressure chamber and a secondary pressure chamber, respectively, due to the action of a push rod on the primary piston.