Tailgate Actuator Spring Material for Fatigue Life and Noise Control
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Solution Overview
Problem
Existing actuators for opening and closing SUV tailgates face challenges in achieving compact size, high compressive force resistance, low spring relaxation, sufficient fatigue life, and noise reduction, which are not adequately met by traditional helical steel wire springs with martensitic microstructure.
Innovation Solution
A helical compression spring made from a coated steel wire with a drawn lamellar pearlite microstructure, featuring a steel core alloy with specific composition and a metallic coating layer comprising at least 84% zinc, which provides enhanced strength, ductility, and noise attenuation without the need for post-coating or flocking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a helical 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 the risk of relaxation and reduces fatigue life
Solution Approach 1:
The patent changes the microstructural parameters of the steel wire from martensitic to drawn lamellar pearlite through controlled cooling during wire drawing. This parameter change allows the spring to maintain small diameter while achieving the required fatigue life and relaxation resistance, as the pearlitic structure provides better ductility and fatigue performance under high compressive loads
Solution Approach 2:
The patent uses a composite approach by combining specific steel alloy composition (0.5-0.9% C, 1-2.5% Si, 0.3-1.5% Mn, 0.5-1.5% Cr) with a drawn lamellar pearlite microstructure. This composite material design enables the spring to withstand high compressive forces in a compact form while maintaining low relaxation and high fatigue resistance
2Strength
If steel wire with martensitic microstructure is used to achieve high strength, then tensile strength is improved, but noise generation increases and ductility is reduced
Solution Approach 1:
The patent changes the microstructural parameter from martensitic to drawn lamellar pearlite through controlled cooling rates during wire drawing. The pearlitic structure with its layered morphology provides inherent noise dampening characteristics while maintaining sufficient strength, eliminating the need for flocking and reducing actuator noise during operation
Solution Approach 2:
The patent eliminates the flocking layer (a temporary noise-dampening coating) by using the drawn lamellar pearlite microstructure itself for noise attenuation. This removes the need for post-coating operations and provides lasting noise reduction throughout the spring's service life
3Force
If steel wire diameter is increased to withstand high compressive forces, then force resistance is improved, but the actuator becomes less compact and spring relaxation increases
Solution Approach 1:
The patent changes the microstructural parameters to drawn lamellar pearlite with specific alloy composition, which provides superior strength-to-diameter ratio. This allows the spring to withstand high compressive forces with a smaller diameter, maintaining actuator compactness while improving force resistance and reducing relaxation
4Strength
If hardening and tempering heat treatment is applied to achieve martensitic microstructure, then tensile strength is improved, but manufacturing complexity increases and ductility is reduced
Solution Approach 1:
The patent changes the manufacturing parameter by controlling the cooling rate during wire drawing to produce drawn lamellar pearlite directly, eliminating the need for separate hardening and tempering heat treatment operations. This simplifies the manufacturing process while maintaining high strength and improving ductility
Solution Approach 2:
The patent extracts the complex heat treatment steps (hardening and tempering) from the manufacturing process by achieving the desired microstructure (drawn lamellar pearlite) through controlled cooling during wire drawing alone, reducing manufacturing complexity
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 properties and lifetime requirements while preventing noise generation, offering improved fatigue life and reduced spring relaxation, making it suitable for high-cycle operations in SUV tailgate actuators.
Implementation Method 1
The microstructure of the steel core is drawn lamellar pearlite
Implementation Method 2
The microstructure of the steel core is drawn lamellar pearlite
Implementation Method 3
the metallic coating layer comprises at least 84% by mass of zinc; and preferably aluminum... which provides enhanced strength, ductility, and noise attenuation
Data Source
Figure 1~2
Figure 3
AI summary
An actuator for opening and closing a door or a tailgate of a car comprises 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 comprises a helically coiled coated steel wire. The helically coiled coated steel wire comprises a steel core and a metallic coating layer. The steel core comprises a steel alloy. The steel alloy comprises between 0.8 and 0.95 wt% carbon, between 0.2 and 0.9 wt% manganese; between 0.1 and 1.4 wt% silicon; optionally one or more than one of the micro-alloying elements chromium, vanadium, tungsten, molybdenum, niobium or boron; optionally aluminum; unavoidable impurities; and iron. The microstructure of the steel core is drawn lamellar pearlite. The metallic coating layer comprises at least 84% by mass of zinc; and preferably aluminum.