Constant Velocity Drive Shaft Factory—

As energy conservation and consumption reduction have become the “new green trend,” people’s demand for vehicles that are green, environmentally friendly, comfortable, and safe is steadily increasing. Consequently, vehicle NVH (noise, vibration, and harshness) performance indicators are receiving ever greater attention. As critical, safety-related, and essential components of automobiles, constant-velocity drive shafts naturally need to evolve toward lower vibration, lower noise, longer service life, lighter weight, higher torque capacity, and enhanced efficiency.

The low-vibration, long-life constant-velocity shaft is a new product developed by the company for D Company’s Q and X models. Compared with conventional constant-velocity drive shafts, this shaft features a lighter weight, higher transmission efficiency, lower axial forces, and reduced high-frequency slip resistance. It effectively addresses customer demands for vehicle lightweighting, improved NVH performance, and enhanced fuel economy. At the same time, it boasts a longer service life, greater flexibility and reliability, a more compact structure, smoother power transmission, superior shock resistance, and strong torque-carrying capacity. All of its technical performance indicators are at the leading level among similar products both domestically and internationally, and it has obtained two technical specifications and seven utility model intellectual property rights. In 2022, the low-vibration, long-life constant-velocity shaft assembly project was awarded the Third Prize in Science and Technology of Zhejiang Mechanical Industry.

Behind the project’s success lie one challenge after another: high customer expectations, emerging technological frontiers, and insufficient experimental and R&D conditions... In October 2018, the factory began assembling its R&D team and established the CFT group, led by the general manager and headed by the project engineer. Throughout the tortuous R&D journey, team members tackled one issue at a time, rolled out solutions in an orderly manner, and steadily advanced through each milestone, uniting their efforts and innovating to overcome difficulties.

To help reduce the vehicle’s fuel consumption, the customer requested a lightweight design for the drive axle. How could we achieve this weight reduction without compromising the strength of the drive axle joint? After careful consideration of various design options, the project team decided to adopt a lightweight GI87M constant-velocity universal joint and optimize the three-slot housing geometry by eliminating excessively large or unnecessary structural features. This approach successfully reduced the housing weight by more than 20%. However, this change also brought about a new challenge: the narrowing of the ball raceways could potentially affect the joint’s durability performance. To address this issue, the project team engaged in an intensive brainstorming session, comparing experimental data and evaluating different design alternatives. They ultimately modified the original surface-contact structure of the ball raceways into a dual-point contact configuration. As a result, the stress distribution previously spread across the entire spherical surface was now concentrated on just two contact points after optimization. Experimental results showed that, following the optimization, each ball raceway exhibited only two small, well-defined polished areas instead of extensive wear marks across the entire surface. This innovative redesign significantly enhanced the joint’s durability, greatly extending its service life.

The path of new product R&D is far from smooth sailing. Starting from scratch and independently designing and building a fixed-joint bending moment test bench was yet another major challenge that gave the entire project team a headache. This test bench is used to simulate the impact of transmission vibrations—transmitted through the drive shaft to the tire side—on the vehicle’s NVH performance under idle conditions. “This is a domestic first, and we had absolutely no prior experience or resources to draw upon,” said Wang Ruiqing, the project progress manager. The test bench consists of a fixed end and a moving end, connected by a shaft in the middle. During experiments, they found that simply adding vibration dampers to the moving end wasn’t enough to obtain accurate test data. So, the project team added rigid shims and six-component force sensors to both the shaft and the fixed end, enabling the test bench to collect force changes with greater precision. “At the time, we could only make the most of the materials provided by the customer. Since the customer had very high requirements for the experimental data, we had to keep adjusting and refining our approach, making repeated modifications along the way.” Throughout the process of building the test bench, team members would dive headfirst into the project at 8 a.m. every day and return home under the glow of streetlights in the evening. After countless experiments, the team successfully identified the optimal dimensions for components within the constant-velocity joint, reduced the dynamic bending moment in the fixed-end joint, and thereby optimized the vehicle’s vibration characteristics under idle conditions, significantly improving its overall NVH performance.

In addition, customers have very high requirements for low-temperature abnormal noises in fixed-joint assemblies. To meet these requirements, a dedicated testing protocol was developed specifically for this project, stipulating that all tests must be conducted under constant temperature conditions of -40°C. When no suitable conditions were available, the project team overcame the challenge by retrofitting existing equipment with cooling devices. At the same time, the team collaborated closely with lubricant suppliers to conduct extensive experimental verification on current lubricants, identifying the key lubricant parameters that significantly influence low-temperature noise. As a result, they successfully developed a low-temperature noise-reducing lubricant tailored precisely to the customer’s project needs. This low-temperature noise-reducing lubricant effectively reduces frictional resistance within the CV joint components, enabling the drive shaft to operate more flexibly even under low-temperature conditions, thereby minimizing friction-induced vibrations and extending the product’s service life.

“No matter how tough the hurdles may be, we’ll always get through them.” The low-vibration, long-life constant-velocity drive shaft—whose total cost project successfully passed the approval of Company D’s Technical Center and Quality Assurance Department—entered mass production in April 2020 and has received positive feedback from users. “Although it was exhausting and challenging, the product finally passed inspection, and we feel incredibly accomplished!” Wang Ruiqing feels that at the moment the product gained recognition, all the hard work and fatigue simply vanished. “Because this project had extremely high requirements and involved many intricate details, we learned a great deal and further enhanced our ability to develop products in sync with high-end clients.”

The road ahead is long yet bright. The new series of low-vibration, long-life constant-velocity drive shafts not only enriches the company’s product portfolio but also meets OEMs’ growing demands for reducing vehicle weight, minimizing the installation space for chassis components, enhancing energy conversion efficiency, and improving overall vehicle NVH performance. This not only effectively boosts the company’s product competitiveness and opens up new opportunities for supplying to major automakers, increasing the company’s visibility and establishing it as a new growth engine—but also underscores the company’s firm commitment, as a traditional manufacturing enterprise, to vigorously implement the nation’s energy and environmental protection policies. Looking ahead, the company will further intensify its innovative efforts, pool its strengths to overcome challenges, and use concrete actions in technological innovation to accelerate green development.