Variable Valve Device Roller Abrasion via Localized Laser Hardening

The patent applies selective laser hardening to specific regions of the internal teeth (tooth top and tooth surfaces) while maintaining lower hardness in the tooth root and body portions. This creates a gradient hardness distribution where the contact surfaces have high hardness for abrasion resistance, while the interior maintains ductility to prevent roller abrasion. The laser hardening is applied only to the regions that require wear resistance, avoiding excessive hardness throughout the entire tooth structure.

The patent changes the physical and mechanical parameters of the internal teeth by applying laser hardening treatment. This process modifies the hardness parameter locally, creating a hardened surface layer with different mechanical properties than the base material. The laser hardening transforms the microstructure of the tooth surfaces, increasing surface hardness while preserving the toughness of the underlying material, thereby resolving the contradiction between abrasion resistance and roller protection.

The selective laser hardening of tooth surfaces creates a harder, more wear-resistant contact surface that maintains better dimensional stability under alternating torque. This localized hardening prevents the tooth profiles from deforming or wearing down, thereby maintaining precise roller engagement and preventing circumferential roller movement that would generate noise.

The laser hardening treatment is applied in advance to the tooth surfaces before the components are assembled and subjected to operating conditions. This preliminary hardening action prepares the surfaces to withstand the alternating torque and roller loads, preventing wear and dimensional changes that would lead to noise generation during operation.