Abstract
Toyota Motor Corporation has applied machining technology such as welding, drilling, cutting and surface modification using CO2 and YAG lasers to vehicle parts since the middle of the 1980s. In the 2000s, diode and LD pumped YAG lasers that offer efficiency advantages in terms of energy and space were marketed as new types of laser resonator. These are expected to bring in a new phase of laser technology.
Currently, Toyota Motor Corporation has been promoting the use of diode lasers for plastic welding and the use of LD pumped YAG lasers for body welding. In recent years, it has become imperative to reduce CO2 emissions, and the development of technology to reduce fuel consumption in passenger cars has also been given higher priority. One way to achieve this purpose is to reduce the weight of the bodyshell. More specifically, body weight can be lowered by reducing the thickness of panels and simplifying structures. Continuous welding is one method for joining panels that enables panel rigidity to be improved, but it is hampered by problems such as heat distortion and low productivity. These problems can be overcome by using lasers. Laser welding involves low heat input, thereby enabling the application of continuous welding to thin panels. In addition, by combining a small head with a highly efficient LD pumped YAG laser capable of beam transmission by fiber, laser welding can be applied to portions that have been conventionally difficult to access.
CAE was used to investigate portions that allow the advantages of laser welding to be fully utilized. As a result, the greatest effect was found by applying laser welding to the vicinity of the room partition panel and upper back panel. It was confirmed that body torsional rigidity could be improved by constraining the area around the partition panel by continuous laser welding. The adoption of continuous laser welding in this way allows body weight to be reduced while still meeting the target value for body torsional rigidity. Several ideas related to a 4.5-kw output LD pumped YAG laser and a laser head with pressure roller have been adopted related to application of continuous laser welding.
Continuous laser welding was first applied to interior structure members to lower body weight by reducing the steel gauge. Subsequent application of laser welding from one side has contributed to simplification and weight reduction of structures.
Keywords: Laser, Continuous welding, Rigidity, Bodyshell, Weight reduction