Battery Pack assembly and fastening

Battery Pack assembly and fastening

In Pack assembly, module fastening generally refers to fixing the module to the box with bolts. The module not only occupies a large space, but also a large mass. The performance and safety of the entire Pack are directly determined by the fastening of the module. . In Pack assembly, not only the modules are fastened by bolts, but also the box structure, charging and discharging connectors, safety valves, MSD switches, BMS, high-voltage cables, etc. also need to be bolted tightly. Pack assembly mainly focuses on bolt fastening. The use of bolt fastening has the following four advantages: convenient assembly; convenient disassembly; high efficiency; low cost.

In the process of bolt tightening, it is generally controlled by the torque value. The tightening methods include: torque control method, rotation angle control method, and torque slope method. The actual selection needs to combine factors such as the fastening level of the workpiece, the accuracy of the clamping force, the cost efficiency, the operability, and the maintainability.

(1) Bolt tightening control method
In the domestic Pack industry, there are more torque control methods. No matter how you choose, the goal is to obtain reliable and stable tightening quality. The torque control method is mainly used to explain how to tighten bolts. Torque means that external force must be applied to tighten the screw or nut. Torque T=F×L, in N.m. Rotating the bolt or nut with an external torque makes the screw force extended, and the clamping force generated by the thread interlocking to tighten the workpiece, and the clamping force converted from the external torque is the inevitable element for tightening. Generally speaking, 90% of torque energy is consumed by friction, and only 10% of energy is converted into clamping force.

(2) Realization of bolt tightening
Choice of tightening tools.
①Satisfy the requirements of monitoring parameter functions during the tightening process, such as not only torque requirements but also angle requirements and time requirements during the tightening process.
②To meet the requirements of accuracy and process capability, it is necessary to meet the requirements of products and customers.
③Meet other requirements, such as production capacity and cost requirements.

(3) Tightening operation methods and requirements.
①Manual/semi-automatic tightening method. During the tightening process, manual assistance is needed to complete the tightening requirements. Note during operation: the tightening tool should be held tightly during operation to avoid large swings or skewing; a certain pressure should be applied to the screwdriver head to avoid tightening during the rotation process. The head and the nut are loose.
②Automatic tightening method. In the tightening process, the tightening equipment is completed in vain, and it can be completed without manual assistance. When selecting equipment and processes, you need to pay attention to: according to product characteristics, flexibly choose single-axis or multi-axis tightening methods; priority is given to automatic screw feeding; screws The bit can be automatically corrected when the screw is deflected; the tightening speed setting should be reasonable.

(4) Inspection of tightening tools.
①Internal inspection. It is mainly suitable for tightening tools with no feedback. Adjust the target value before using the tool, and then periodically confirm it with a spot inspection instrument. The spot inspection instrument requires periodic internal calibration or external calibration.
②External measurement. Mainly applicable to tightening tools that cannot be inspected and evaluated internally, such as tools with real-time monitoring of torque and angle.

Common improper tightening: In actual production, various bolts are often improperly tightened, such as missing or forgotten tightening in the common improper tightening, the dislocation of the workpiece causes the bolt to be slanted down, and the screw slips.

In order to reduce improper tightening, it is generally necessary to conduct random inspections by quality inspection staff after tightening, and then draw a riding stitch after passing the test to prevent improperly tightened products from flowing to the client.