Plastic Connecting Rods in Motor Pump Units for Brake Systems
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Solution Overview
Problem
Existing motor-pump units for brake actuating devices in motor vehicles, particularly those with pneumatic brake boosters, face issues of high friction, lubrication requirements, and power expenditure, especially in vehicles with electric or hybrid drives, where traditional vacuum pumps are inefficient and costly to maintain.
Innovation Solution
The use of plastic connecting rods that encapsulate tappets and bearings, forming a diaphragm unit, reduces component count and assembly complexity, and introduces sintered components for cost-effective production, enabling a low-noise, cost-effective motor-pump unit with improved vibration characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional vane-cell pumps or swing-vane pumps are used, then vacuum can be provided for the brake booster, but friction increases and lubrication is required leading to higher maintenance costs
Solution Approach 1:
The patent replaces the traditional vane-cell pump mechanism with a diaphragm pump mechanism. The diaphragm pump uses a flexible diaphragm element that is actuated by a piston or plunger to create vacuum, eliminating the need for sliding vanes and associated friction. This substitution of mechanical principles resolves the contradiction by maintaining vacuum generation capability while eliminating friction and lubrication requirements.
Solution Approach 2:
The patent employs a flexible diaphragm as the core vacuum-generating element. This thin film component replaces the rigid vane structure, allowing for seal-less operation without friction. The diaphragm flexes to create volume changes for vacuum generation, eliminating the need for sliding contacts and lubrication, thus resolving the friction-reliability contradiction.
2Adaptability or versatility
If an electrically driven vacuum pump is used in vehicles with electric or hybrid drive, then the pump can operate independently of the internal combustion engine, but the pump requires dry-running capability which increases manufacturing complexity
Solution Approach 1:
The patent extracts the lubrication system entirely from the vacuum pump design, creating a dry-running pump. By removing the lubrication circuit and oil-related components, the pump becomes suitable for electric and hybrid vehicles where lubrication is impractical. This extraction simplifies the overall system while maintaining operational independence, resolving the contradiction between adaptability and manufacturing complexity.
Solution Approach 2:
The diaphragm pump design inherently provides self-lubrication through the use of self-lubricating materials for the diaphragm and moving parts. The material selection and design allow the pump to operate without external lubrication, making it self-sufficient and suitable for electric vehicle applications. This self-service approach resolves the contradiction by enabling dry-running operation without complex lubrication systems.
3Device complexity
If the connecting rods are made of plastic with encapsulated tappets and bearings, then the component count is reduced and assembly is simplified, but the structural strength must be maintained
Solution Approach 1:
The patent merges multiple components (connecting rod, tappet, and bearing) into a single integrated plastic component. The connecting rod is manufactured as one piece with the tappet and bearing encapsulated within it, eliminating the need for separate parts and assembly steps. This merging reduces device complexity while the encapsulation technique ensures structural strength is maintained through proper material selection and design.
Solution Approach 2:
The patent uses composite material construction for the connecting rod, combining plastic material with embedded metallic or self-lubricating elements for the bearing and tappet functions. This composite approach allows the single-piece component to achieve both the complexity reduction benefits of integration and the strength requirements through material properties, resolving the contradiction between simplified assembly and structural strength.
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 configuration results in a more cost-effective, lightweight motor-pump unit with reduced assembly expenses and improved vibration characteristics, suitable for electrically driven brake systems without the need for lubrication, enhancing operational efficiency and noise reduction.
Implementation Method 1
the connecting rods are in each case formed in one piece with the tappet and are provided as sintered components
Data Source
AI summary
A motor-pump unit, for providing pressure for a brake actuating device having a pneumatic brake booster including a pump and an electric motor driving the pump, the pump being a dual diaphragm pump having two opposed working diaphragms, each of which is clamped between a pump casing and a working chamber cover and delimits a working chamber, and moveable by a crank drive having connecting rods and bearings, the working diaphragm connected firmly to a tappet and, together with the connecting rod, in each case forming a diaphragm unit. In order to provide a low-noise motor-pump unit which is more cost-effective and requires reduced expenditure on assembly, the connecting rods are made of plastic, wherein in each case one tappet and one bearing are encapsulated with the material of the connecting rod. Alternatively, the connecting rods can be formed in one piece with the tappet and provided as sintered components.