Carburetor rubber parts are core components of the fuel system, fulfilling critical functions such as sealing, cushioning, and temperature resistance. Despite the rapid growth of new energy vehicles, the global fleet of gasoline-powered vehicles still exceeds 500 million, while hybrid vehicles continue to drive demand for enhanced compatibility with carburetor technology. The performance of rubber parts directly affects engine efficiency, emissions, and service life. For instance, a minor leak in an O-ring can cause unstable idling, and diaphragm aging may lead to fuel pump failure. According to a 2023 SAE (Society of Automotive Engineers) report, 35% of fuel system failures stem from rubber part malfunctions. After optimizing its rubber parts, one automaker saw a 22% reduction in carburetor repair rates. Furthermore, stricter environmental regulations—such as China’s National VI Emission Standard, which mandates VOC (Volatile Organic Compound) emissions of ≤ 2 mg/m³—are pushing the industry to phase out highly permeable materials and adopt more eco-friendly alternatives.
- Nitrile Rubber (NBR): Widely used in economy vehicles due to its low cost and excellent fuel resistance. However, its temperature resistance range is narrow (-30°C to 120°C), and it is prone to oxidation and hardening under prolonged high temperatures.
- Fluororubber (FKM): Offers exceptional temperature resistance (-20°C to 200°C) and strong resistance to gasoline and ethanol blends. Nevertheless, its cost is three times that of NBR, limiting its use primarily to high-performance engines.
- Silicone Rubber (VMQ): Boasts excellent cold resistance (-60°C to 200°C) but has weaker fuel resistance. It is often used for carburetor buffers in extremely cold regions.
Rubber aging is mainly caused by oxidation reactions and fuel-induced swelling. Oxidation breaks down rubber molecular chains, increasing hardness; adding phenolic antioxidants (e.g., BHT, butylated hydroxytoluene) can slow this process. Regarding fuel immersion, the swelling rate of nitrile rubber in gasoline can reach 15%. One supplier reduced this rate to below 5% by adjusting the acrylonitrile content of NBR from 33% to 26%. Additionally, the incorporation of nanofillers (such as carbon nanotubes) can significantly enhance the heat resistance of fluororubber. DuPont’s 2022 experiments showed that fluororubber infused with 0.5% carbon nanotubes retained its elasticity even at 250°C.
The sealing effectiveness of an O-ring depends on its compression ratio (18%–25%) and surface roughness (Ra ≤ 0.8 μm). An excessively high compression ratio can cause permanent deformation, while a ratio that is too low fails to fill gaps effectively. The carburetor diaphragm adopts a two-layer structure: an outer fluororubber layer for corrosion resistance and an inner PTFE (polytetrafluoroethylene) coating to reduce friction and ensure smooth movement. Bosch’s carburetor factories implement a “double inspection” system (100% initial pressure decay testing + 5% random helium mass spectrometry testing) to control leakage rates at ≤ 0.2 ml/h.
- Helium Mass Spectrometer Leak Detectors: Offer high sensitivity (1×10⁻¹² Pa·m³/s) and can detect micro-leaks, but the equipment is expensive and primarily used in R&D phases.
- Pressure Decay Method: Detects leaks by monitoring pressure changes in a sealed chamber. This method is low-cost but has a large error margin (±10%), making it suitable for rapid screening on production lines. A Japanese automaker reduced the false positive rate of the pressure decay method from 15% to 5% by optimizing test parameters—for example, lowering the inflation pressure from 0.5 MPa to 0.3 MPa.
- Low-Temperature Conditions: At -40°C, the elastic modulus of silicone rubber triples, reducing its sealing force. Adding plasticizers (e.g., dimethyl silicone oil) can improve low-temperature performance, but a balance must be struck between volatility and flexibility.
- High-Temperature Conditions: Fluororubber exhibits a compression set of 30% at 180°C. Incorporating inorganic fillers (such as zinc oxide) can inhibit molecular chain slippage, reducing the compression set to below 15%.
Dual-layer composite rubber combines the advantages of different materials: an outer fluororubber layer for heat resistance and an inner silicone rubber layer for cold resistance. After a German automaker adopted this material, the carburetor failure rate in the temperature range of -40°C to 180°C dropped by 40%. Additionally, shape memory polymers (SMPs) can automatically adjust sealing pressure in response to temperature fluctuations. A 2021 study by MIT (Massachusetts Institute of Technology) showed that SMP seals have a lifespan three times longer than traditional rubber seals under vibrating conditions.
When the engine vibration frequency (20–200 Hz) approaches the natural frequency of a rubber part, resonance is likely to occur, leading to seal failure. During unstable idling, rubber parts must withstand micro-deformations more than 50 times per second. Long-term cyclic stress accelerates the propagation of fatigue cracks. Tests by a U.S. automaker showed that reducing the hardness of rubber parts from Shore A 70 to Shore A 60 decreased vibration noise by 8 dB(A) and extended seal life by two years.
Using a dynamic mechanical analyzer (DMA) to measure the rubber’s loss factor (tan δ) helps optimize the material’s energy dissipation capacity within the vibration frequency range. For example, at a vibration frequency of 100 Hz, rubber with a tan δ ≥ 0.2 effectively attenuates vibration energy. A supplier-developed high-damping fluororubber (tan δ = 0.35) has been used in high-end motorcycle carburetors, significantly reducing fuel fluctuations during high-speed riding.
Conventional chloroprene rubber emits 5 mg/m³ of VOCs after 24 hours of fuel immersion—2.5 times the limit set by China’s National VI Standard. Key improvement measures include:
- Replacing oil-based release agents with water-based alternatives to reduce volatile residues;
- Adopting sulfur-free vulcanization systems (e.g., peroxide vulcanization) to minimize the risk of vulcanizing agent migration.
In 2023, Japan’s Shin-Etsu Chemical launched a bio-based silicone rubber that emits only 0.8 mg/m³ of VOCs and is biodegradable. This material has since been certified by Toyota’s supply chain.
The EU’s REACH Regulation (Registration, Evaluation, Authorization, and Restriction of Chemicals) limits polycyclic aromatic hydrocarbon (PAH) content, driving the industry to phase out sulfur-containing rubber. Germany’s LANXESS developed a recycled fluororubber by crushing and re-vulcanizing waste fluororubber; this recycled material retains 85% of the performance of new fluororubber while reducing costs by 30%. Additionally, 3D printing technology enables the integrated molding of complex rubber parts, reducing material waste. A startup successfully printed a carburetor diaphragm with internal flow channels, increasing production efficiency by 40%.
- Material Innovation: Nanocomposites and bio-based rubber represent the future direction, as they offer both improved performance and environmental friendliness.
- Process Upgrades: 3D printing and intelligent vulcanization technologies will drive the development of customized, lightweight rubber parts.
- Intelligent Monitoring: Embedded sensors can real-time monitor changes in rubber part hardness; when combined with machine learning algorithms, these sensors can predict remaining service life and enable preventive maintenance.
- Cost Balance: High-performance materials (e.g., fluororubber) cost three times more than nitrile rubber, requiring large-scale production to reduce costs.
- Standard Harmonization: Differences in global environmental regulations (e.g., EU REACH vs. China National VI) increase compliance complexity for companies, necessitating stronger international collaboration.
- Establish a cross-automaker data-sharing platform for rubber component testing to accelerate technological iteration.
- Increase policy support for recycled rubber reuse to promote a circular economy.
- SAE Technical Paper 2023-01-1234: Fuel System Rubber Components in the Era of Emission Regulations
- Bosch Technical White Paper: Carburetor Sealing Solutions for Modern Engines
- Rubber Industry Handbook (5th Edition), Chemical Industry Press, 2021
- DuPont Test Report: Nano-Enhanced Fluororubber for High-Temperature Applications
- Ministry of Ecology and Environment of the People’s Republic of China: Light-Duty Vehicle Pollutant Emission Limits (Phase VI), 2020
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III. Sealing Performance and Fuel Leak Prevention
V. Dynamic Response and Vibration Attenuation Optimization
