Tailgate Actuator Spring Composition for Compact Quiet Operation
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Solution Overview
Problem
Existing actuators for opening and closing car tailgates face challenges in achieving compact size, high compressive force resistance, low spring relaxation, fatigue resistance, and noise reduction, particularly due to stringent requirements for helical steel wire springs used in SUVs with large tailgates.
Innovation Solution
A helical compression spring actuator using a coated steel wire with a drawn lamellar pearlitic microstructure and a metallic coating layer, comprising a steel core with specific alloy composition and a zinc-aluminum coating, which eliminates the need for post-coating operations and flock layers, providing enhanced mechanical properties and noise attenuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a helical steel wire spring with small diameter is used to make the actuator compact, then the actuator size is reduced, but the spring must withstand high compressive forces consistently which increases manufacturing difficulty
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters of the steel wire (carbon: 0.45-0.65%, silicon: 0.70-1.50%, manganese: 0.50-2.00%, chromium: 0.50-1.50%) and heat treatment parameters (tempering temperature: 150-250°C, stress relieving temperature: 200-400°C) to achieve the required mechanical properties in a compact spring design
Solution Approach 2:
The patent uses composite material approach by creating a multi-element steel alloy composition that combines carbon, silicon, manganese, and chromium to achieve superior mechanical properties including high tensile strength (>2300 N/mm²), low relaxation (<10% after 1000 cycles), and adequate ductility (reduction of area >40%) in a compact spring geometry
2Volume of moving object
If the spring is made compact with small diameter, then the actuator is more compact, but fatigue resistance must be maintained under high load conditions
Solution Approach 1:
The patent changes material parameters by optimizing the steel composition (particularly carbon 0.45-0.65% and silicon 0.70-1.50%) and heat treatment parameters (tempering at 150-250°C followed by stress relieving at 200-400°C) to achieve a microstructure that provides both high strength and fatigue resistance in compact springs
Solution Approach 2:
The patent applies preliminary action through pre-stress relieving heat treatment at 200-400°C after coiling and shot peening treatment before final assembly, which pre-establishes the internal stress state and surface compressive stresses to enhance fatigue life under high load conditions
3Ease of manufacture
If hard drawn steel wire is used, then manufacturing is simpler, but noise generation occurs during actuator operation
Solution Approach 1:
The patent changes the material state by replacing hard drawn wire with patented steel wire that undergoes specific heat treatment parameters (tempering 150-250°C, stress relieving 200-400°C) to achieve a microstructure that reduces operational noise while maintaining manufacturing simplicity
Solution Approach 2:
The patent converts the potential harm of noise generation into a benefit by using shot peening treatment that creates beneficial compressive surface stresses, which not only reduce noise during operation but also enhance fatigue resistance and extend spring life
4Strength
If martensitic microstructure is used to achieve high strength, then tensile strength increases above 2300 N/mm², but ductility and toughness are reduced
Solution Approach 1:
The patent applies parameter changes by controlling the tempering temperature (150-250°C) and stress relieving temperature (200-400°C) to transform the microstructure from brittle martensite to a tempered structure that maintains high tensile strength (>2300 N/mm²) while achieving adequate ductility (reduction of area >40%)
Solution Approach 2:
The patent uses composite material approach by creating a multi-element alloy (carbon, silicon, manganese, chromium) that forms a tempered microstructure combining strength and ductility, achieving tensile strength >2300 N/mm² with reduction of area >40% through synergistic element interactions
5Object-generated harmful factors
If flock layers and adhesive coatings are added to reduce noise, then noise attenuation is achieved, but device complexity and manufacturing steps increase
Solution Approach 1:
The patent extracts and eliminates the complex flocking and adhesive coating operations by using shot peening treatment alone to achieve noise attenuation, simplifying the manufacturing process while maintaining noise reduction effectiveness
Solution Approach 2:
The patent converts the shot peening process, originally intended for strength enhancement, into a dual-purpose treatment that simultaneously provides noise attenuation through surface compression and stress relief, eliminating the need for separate noise control measures
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
The solution satisfies the demanding mechanical and noise requirements for tailgate actuators by offering high strength, ductility, and extended lifetime without noise generation, while reducing the need for additional coatings and noise-dampening layers.
Implementation Method 1
The steel wire is metal coated, in particular hot dip coated, with a metallic coating layer
Implementation Method 2
The microstructure of the steel core is drawn lamellar pearlite
Data Source
AI summary
An actuator for opening and closing a door or a tailgate of a car contains a helical compression spring and a motor. The helical compression spring is provided for opening a door or the tailgate of a car when compressive forces of the helical compression spring are released. The motor is provided for compressing the helical compression spring in order to close the door or the tailgate of the car. The helical compression spring contains a helically coiled coated steel wire. The helically coiled coated steel wire contains a steel core and a metallic coating layer. The steel core contains a steel alloy. The steel alloy contains 0.8 to 0.95 wt % carbon, 0.2 to 0.9 wt % manganese; 0.1 to 1.4 wt % silicon; optionally one or more micro-alloying element. The microstructure of the steel core is drawn lamellar pearlite. The metallic coating layer contains at least 84% by mass of zinc.