Automotive Air Conditioning Piping Layout Design
When routing the tubing, position it as far as possible from high-temperature components in the front compartment (such as the exhaust manifold), maintaining a minimum clearance of 100 mm. If this requirement cannot be strictly met, the minimum clearance must be no less than 40 mm, and the surface of the tubing must be wrapped with heat-insulating aluminum foil.
Assembly and After-Sales Maintenance
① Ideally, the layout of the compressor's suction and discharge ports should be designed to facilitate the smooth connection of the associated tubing *after* the cooling fan has been installed. This approach paves the way for designing the evaporator-to-compressor line as a single, continuous tube assembly. This design eliminates the need for a pair of clamping plates, a dedicated assembly fixture/gauge, and various standard fasteners, thereby reducing overall assembly time. Furthermore, consolidating the line into a single piece eliminates one potential leak point.
② The tubing section near the compressor typically incorporates a flexible hose. Conventionally, a single-tube clamp is used immediately downstream of this hose to secure the rigid aluminum section of the line; this clamp is typically pre-tightened to the subframe during the powertrain assembly stage. During the final vehicle assembly line process, aligning the tubing's clamping plate with the condenser interface often proves difficult; to achieve a proper connection, the tubing is frequently subjected to severe deformation from being pulled into place. It is recommended that-provided the overall tubing routing remains geometrically sound-the use of this intermediate tube clamp be eliminated. (Note: Currently, for systems utilizing non-subcooling condensers, the condenser inlet is situated relatively far from the compressor, resulting in a longer connecting line; in these specific cases, eliminating the tube clamp is not advisable. This design optimization can be implemented in future projects, particularly those utilizing subcooling condensers.)
③ Currently, in AC systems utilizing "F-type" expansion valves, the clamping plates for the evaporator's inlet and outlet lines are split into two separate components; conversely, systems utilizing "H-type" expansion valves employ a single, monolithic clamping plate for both lines. When a single clamping plate is used, the tubing retains a degree of rotational freedom within the clamp. Consequently, once the clamping plate bolts are tightened, the alignment of the intermediate tube clamps (which attach to welded studs on the vehicle body) often exhibits significant deviation. In other words, when securing this type of single-piece clamping plate, the installer must simultaneously verify that the intermediate tube clamps remain properly aligned-a process that demonstrates that the positional stability and accuracy of a single-piece clamp are inferior to those of a split-clamp design (two separate plates).
Selection and Mounting Methods for Tube Clamps
1) The tube clamps currently in use consist of two primary types: single-tube clamps and double-tube clamps. A double-pipe clamp is initially secured to a single pipeline; during final assembly, the second pipeline-along with its rubber liner-is inserted into the clamp. This process requires prying the clamp open, inevitably causing it to deform. Furthermore, the rubber liner tends to slip out while the second pipeline is being inserted into the clamp. Even if both pipelines are successfully seated within the clamp during vehicle assembly, the liners may not be held securely, as the clamp has already been deformed during the installation process. When production volumes are high, this assembly method can also negatively impact assembly line speed. If the use of double-pipe clamps is unavoidable, the routing of the two pipelines should ideally be arranged to prevent tangling, thereby avoiding complications for assembly line workers. It is recommended to utilize single-pipe clamps instead. To prevent the rubber liner from dislodging, a slot can be cut into the center of the clamp bracket; this allows the outer edge of the liner to protrude through the clamp while the inner surface remains pressed firmly against the pipeline, thereby ensuring it stays securely in place. This type of clamp has already been successfully implemented in vehicle models produced by other manufacturers, and we can adopt this design as well.
2) The installation position and assembly orientation of pipeline clamps are closely tied to the location of weld studs on the vehicle body. The feasibility of the clamp assembly process must be verified using the actual assembly tools available in the workshop; ideally, the design should avoid the need for additional welding guns or specialized gun tips, and-where possible-standardized pipeline components should be utilized consistently. Additionally, the ergonomic aspects of the assembly process-specifically, whether the operation requires workers to bend over-should be taken into consideration.
Pipeline Cost Optimization
Cost factors must be carefully considered during the pipeline routing process, with particular attention paid to the following points:
① Provided that all routing requirements are met, pipelines should be kept as short as possible; after all, saving material translates directly into cost savings. In instances where the overall length of the pipeline system cannot be reduced, the length of the flexible rubber hoses can be trimmed where appropriate, given that rubber hoses typically represent a higher cost component.
② During the routing process, designers should anticipate the need to accommodate various powertrain configurations and strive for maximum component commonality. This approach allows for a reduction in the variety of pipeline components stocked in the spare parts inventory, thereby saving warehouse space and reducing inventory management costs. Even if the entire pipeline assembly cannot be carried over unchanged, efforts should be made to design the rigid aluminum sections as carry-over components. This strategy also benefits the manufacturer by reducing the number of unique pipeline tooling sets required, thereby lowering development costs.
Aesthetics of Pipeline Routing
Once the aforementioned functional requirements have been fully satisfied, consideration should be given to the aesthetic appeal of the pipeline routing layout and its visual harmony with the overall arrangement of components within the engine compartment. For instance, it is best to route tubing in a somewhat concealed manner, avoiding the impression that-the moment the engine hood is opened-the air conditioning lines are the first thing one sees. The routing of the lines should not result in a chaotic crisscrossing pattern with other components (such as rubber hoses, wire harnesses, etc.). Not only does this detract from the aesthetic appeal, but-more importantly-it creates significant difficulties for the assembly workshop. It requires assembly workers to memorize the intricate paths-how lines wind around and thread through various spaces-leading to a final assembly result that is inevitably suboptimal and highly prone to errors during the process.
Tubing Trial Assembly and Review
Once the tubing has passed inspection and is verified to be free of defects, a trial assembly can be conducted. It is crucial to closely monitor the assembly process during these initial trials, as unexpected issues may arise at any moment. For example, if the tubing interferes with other components after installation-assuming our own parts have already been verified as sound-the next step is to inspect the actual clearance between the tubing and adjacent parts. This physical clearance is then compared against the clearance specified in the digital CAD models to pinpoint the root cause of the problem.
Rubber Hose Costs
Since the cost of rubber hoses constitutes a significant portion of the total tubing system cost, cost optimization is a priority. Therefore-provided that all performance requirements are met-rubber hoses should be avoided whenever possible; if they must be used, they should be kept as short as possible.
Current Production Status of Key Rubber Hose Suppliers: Codan (Denmark) currently manufactures in Zhuozhou, Hebei Province; Nichirin (Shanghai) manufactures in Shanghai; Plant 7425 manufactures in Nanjing; and Bridgestone currently continues to import its products from Japan. The unit prices for Codan and Nichirin hoses are likely quite comparable, as they are primarily determined by the volume of large-scale purchase orders placed by the tubing manufacturers.
