Brake Booster Spindle Nut Segmentation
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Solution Overview
Problem
Existing brake boosters for motor vehicles face challenges in extending the service life of spindle nuts and ensuring operational reliability, particularly in converting rotary motion into translational motion with minimal friction and high drive force transmission.
Innovation Solution
The spindle nut is designed as two pieces with an outer part made of high-strength material and an inner part made of low-friction material, featuring an axial form-locked connection and an outer toothing that allows direct drivability by another gear wheel, enhancing service life and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the spindle nut is made of a single material, then the manufacturing is simple, but the service life and efficiency are limited due to inability to optimize both strength and friction properties
Solution Approach 1:
The spindle nut is divided into two separate components: an outer part made of high-strength material (such as steel) and an inner part made of low-friction material (such as polyoxymethylene, polytetrafluorethylene, or polyamide). These two parts are axially connected in a form-locked manner, allowing each part to be optimized for its specific function while working together as a unified spindle nut assembly.
Solution Approach 2:
The spindle nut combines two different materials with complementary properties: a high-strength material for the outer part to withstand mechanical loads and a low-friction material for the inner part to reduce friction with the male thread. This composite structure enables simultaneous optimization of strength and friction properties that cannot be achieved with a single material.
2Reliability
If the spindle nut uses only a female thread for motion conversion, then the structure is simple, but the operational reliability and versatility are reduced
Solution Approach 1:
The spindle nut is equipped with both a female thread for converting rotary motion to translational motion and an outer toothing for direct engagement with gear wheels. This multi-functional design allows the spindle nut to serve multiple purposes: motion conversion through the female thread and direct drivability through the outer toothing, thereby improving operational reliability and versatility.
Solution Approach 2:
The spindle nut can operate in different modes depending on the driving mechanism used: it can be driven through the female thread for precise motion control or through the outer toothing for high-torque direct engagement. This dynamic adaptability enhances the reliability of the brake booster system under varying operational conditions.
3Force
If high-strength material is used for the spindle nut, then the drive force transmission is improved, but the friction with the male thread increases
Solution Approach 1:
The spindle nut is segmented into an outer part made of high-strength material for optimal drive force transmission and an inner part made of low-friction material for minimal friction with the male thread. This segmentation allows each material to be optimized for its specific function, achieving both high force transmission and low energy loss.
Solution Approach 2:
Different regions of the spindle nut have different material properties tailored to their specific functions: the outer part has high strength for force transmission, while the inner part has low friction for efficient thread engagement. This local optimization of material properties resolves the contradiction between force transmission and friction loss.
4Force
If the outer part and inner part are connected by friction fit, then the assembly is simple, but the axial load absorption and torque transmission are insufficient
Solution Approach 1:
The connection between the outer part and inner part is achieved through segmented form-locked elements such as bent holding sections or coupling bolts. These elements create mechanical interlocking that provides strong axial load absorption and torque transmission while maintaining relatively simple assembly and disassembly procedures.
Solution Approach 2:
The form-locked connection elements are pre-designed and pre-positioned on either the outer part or inner part before assembly. The bent holding sections are pre-bent to engage with corresponding features on the other part, ensuring proper alignment and secure connection during assembly without requiring complex adjustment procedures.
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 design significantly increases the service life and operational reliability of the brake booster by reducing friction and enabling efficient conversion of rotary motion into translational motion, while ensuring reliable high-torque transmission and axial load absorption.
Implementation Method 1
the gear unit includes a rotatable spindle nut including a female thread and an axially displaceable, rotatably fixed spindle rod including a male thread, the female thread being engaged with the male thread in order to convert a rotary motion of the drive motor into a translational motion of the spindle rod
Implementation Method 2
the inner part is made of a low-friction and/or low-wear material, in particular of polyoxymethylene, polytetrafluorethylene, and/or polyamide. As a result, in particular, the friction between the female thread and the male thread is reduced
Data Source
AI summary
A brake booster for a main brake cylinder of a motor vehicle includes a drive motor connected or connectable to a pressure piston for the main brake cylinder via a gear unit, where the gear unit includes a rotatable spindle nut, including a female thread and an axially displaceable, but rotatably fixed, spindle rod that includes a male thread, the male and female threads engaging into each other in order to convert a rotary motion of the drive motor into a translational motion of the spindle rod for actuating the pressure piston. The spindle nut is formed as two pieces and includes an inner part including the female thread and an outer part including an outer toothing, the inner and outer parts being made of different materials.