March 11, 2019, Shanghai—Among the number of problems per 100 vehicles (PP100) calculated by JDPower, although the number of complaints about odor problems in cars dropped from 16% in 2017 to 12% in 2018, compared to Other problems, complaints about the smell problem in the car are still high. In order to find the “culprit” that causes the odor in the car, JD Power conducted odor tests under normal temperature and high temperature conditions. The test took five days, tested five best-selling SUV and sedan models, simulated consumer complaints about the smell in the car, and tested the gas components released by the vehicle and seats after being exposed to normal temperature and high temperature. Cai Ming, general manager of JD Power China’s automotive product division, and Cai Weicheng, director, pointed out that to improve the odor performance in the car, finding the vehicle design details that affect the user’s perception of smell is the key. Manufacturers need onion-peeling research to discover user needs for scents and factors that affect user experience one by one.
Research process of car interior odor, data source: JD Power China
Odor analysis at room temperature is not representative
At present, manufacturers only conduct the VOC test of the whole vehicle under normal temperature conditions. However, according to the feedback from consumers, the smell they complain about is often produced under high temperature or exposure to sunlight, so the normal temperature test does not meet the requirements. usage scenarios in most cases. In addition, in the seat odor skin and cover test, the manufacturer usually seals the sample and places it in a drying oven at 80°C for 2 hours, then takes it out, and then places it at room temperature for 1 hour before evaluating the taste. However, in consumer usage scenarios, in most cases they do not have the conditions to stand at room temperature for 1 hour, and there is also a big gap with consumers’ usage habits.
Gas Composition and Complaint Correlation
According to the national standard GB/T27630-2011, the country currently only clearly stipulates the gas content of pentaphenyltrialdehyde in the car. JD Power found through the analysis of experimental data that there is no difference between pentaphenyltrialdehyde and the results of JD Power’s new car quality study (IQS). There is no reasonable correlation, and substances other than pentylenetrialdehyde are contributing to user complaints.
Under normal temperature conditions, only styrene and acetaldehyde were positively correlated with IQS, and the correlation coefficients of other gases were very low or even negatively correlated. Under high temperature conditions, only styrene, acetaldehyde and acrolein are positively correlated with IQS, which means that pentaphenyltrialdehyde is not the main reason for consumers to complain about the odor in the car, but other substances that cause customers complaints.
Correlation between gas substances and new car quality study (IQS), data source: JD Power China
Comparative analysis of normal temperature and high temperature gas groups
After 16 hours of normal temperature sampling and 6 hours of high temperature exposure sampling, JD Power detected 92 substances in a car, including ketones, aldehydes, esters, alcohols, aroma Group, naphthenes, nitriles, alkanes.
In general, the content of the substance will increase with the increase of temperature. No matter it is normal temperature or high temperature, the content of dimethyl heptane is significantly higher than that of other substances. Under high temperature conditions, the content of this substance is almost double that of DMH, need to focus on interior materials that generate dimethylheptane.
The composition of the Top 20 gases at room temperature VS high temperature sudden increase, unit: micrograms per cubic meter, data source: JD Power China
where the smell is produced
After evaluating the seats, JD Power found that, except for high temperature and low temperature factors, the odor contribution of the front seats is much greater than that of the rear seats, which is due to the fact that the front seats are equipped with more other parts such as wiring harnesses, Plastic parts, etc., a variety of materials lead to more odors. Among them, the content of cyclohexanone and formaldehyde in the front seat is relatively high at high temperature, and the content of propylene glycol diacetate in the rear seat is higher than that in the front seat. Crucial role. (The change of vehicle interior materials and seat materials will directly affect the contribution of front and rear seats to vehicle odor.)
In short, analyze the scene and reason of customer complaints, understand their expectations for the smell in the car, identify the gas components that affect user satisfaction, determine which materials these substances come from, and finally analyze which parts or production processes in the car produce Only by removing negative substances can the problem of peculiar smell in the car be fundamentally solved.
The steps to determine important substances are:
Confirmation steps of important gas substances, data source: JD Power China
Production Quality Evaluation and Improvement (MFG) – Assess and improve the factory’s mass production capabilities
JD Power’s production quality assessment uses “quality ring” and “MFG scoring mechanism”, from the perspective of consumers, through 19 aspects in 6 dimensions (automation, quality management, flexible labor system, personnel, supply chain management and support system) The 310 inspection items can effectively point out the deficiencies and gaps in the manufacturer’s internal quality control system, provide corresponding answers and guidance (clarify and solve specific customer problems), and take reasonable measures to narrow the gap.