Key Considerations When Designing Connectors for Harsh Environments

Commercial vehicles encounter the harshest conditions of anything on wheels. They are used in very hot and very cold environments. They get very wet, muddy and dusty and are subjected to mechanical stress from heavy duty cycles. They drive through terrain guaranteed to cause intense vibration. They can experience harsh conditions in their interior as well — on the engine, in the chassis and sometimes even in the cabin. And, if they break down, the financial consequences are often severe.

Every electrical connection in these vehicles represents a potential weak point if it is not designed and tested to the highest standards. Heat and cold can break down materials, moisture can corrode connections and vibrations can damage and loosen the connectors as well as the terminals — all of which can degrade performance.

The good news is that there are technologies and design techniques that can address these challenges while also ensuring that the connection systems are properly mated in assembly and stay connected thereafter. The techniques may take more effort to implement, but the payoff is a commercial vehicle that is rugged enough to take on the toughest tasks demanded of it.

SAE J2030 is the industry standard for heavy-duty electrical connector performance in the United States, but OEMs often look for more stringent specifications to ensure higher levels of ruggedness and reliability, particularly for any vehicles designed for construction or other off-road uses.

Here are some key areas to consider for enhanced performance:

Vibration

Vibration affects all parts of a vehicle. Over time, vibrating components can rub against each other, leading to damage and degradation. Wear and the loss of a terminal’s normal force can create more contact resistance, which can in turn result in increased heat generation. In a worst-case scenario, such wear can also cause an electrical interruption.

To ensure that vehicle components can stand up to the effects of strong vibrations, manufacturers can use connectors that have been designed with special anti-vibration features inside the connector, strong covers that reduce the incoming vibration, terminals that are designed to significantly delay the relaxation of normal force, and stiffening ribs that prevent components from bending.

Aptiv has innovated further with its CTCS XP connectors, which use a patented wedge surface on the housing and module that exerts a constant pressure, eliminating movement between the two assembled parts of the female connector. This contrasts with other approaches that instead have clearance between the latch and locking surface, allowing movement of the module within the housing.

The CTCS connectors also have a cover designed with anti-torsion rips to reduce twisting motions.

With these and other features, Aptiv connectors achieve sine vibration resistance up to 30.6 G and random vibration resistance up to 18 gRMS.

Water and debris resistance

If water is able to reach the contacts, it can cause oxidation that can also lead to contact resistance and poor performance over time.

To prevent this, robust sealing is needed. But sealing must be designed for harsh environments in which the connectors will be subject to vibration and other forces.

Aptiv connectors use recessed sealing ribs to help maintain their integrity under wire strain. We have found that this approach can achieve a sealing improvement of up to 57 percent.

Aptiv’s connectors achieve sealing ratings of IEC IP67 (protection from dust and being submerged in up to 1 meter of water for 30 minutes) and IEC IP69K (protection from dust and high-pressure water jets and steam cleaning).

Temperature

Temperature changes can cause materials to expand or contract, which can have an impact on how tightly a connection is held. If the connection is loose, it can fall victim to vibration effects.

Aptiv uses a preloaded stainless steel spring to reduce relaxation at the terminal base, even when the spring is subjected to temperature swings as wide as -40° C to 140° C.

Assembly and retention

Connectors should be optimized for assembly and retention. That means that they must be designed so that less insertion force is needed and they have mechanisms to ensure a completely secure connection that will last under harsh conditions.

One way Aptiv’s Harsh Environment Series of connectors achieves that balance is by adding a lock finger, which eliminates unseated terminals. The connector includes arrows for pre-alignment before mating, a spring-loaded locking collar, and a window that allows the assembler to visually verify lock engagement. The insertion force is reduced because the connector has a rounded edge, but the retention force is increased with the lock finger. Together, these features result in terminal retention that is up to 44 percent higher than that of comparable connectors.

The CTCS family includes two different lock-assist mechanisms for sealed connectors: sliders for the CTCS XP connectors that have 18 or fewer cavities, and levers for the CTCS SP connectors that have 15 to 62 cavities. These connectors also have secondary locks to improve retention — with unseat-detection features that improve quality during harness assembly.

Getting to the goal

Testing to ensure that the connectors can withstand a range of harsh environmental conditions is an important part of connection system development. To bring to light any potential issues, the same connectors should be used throughout a battery of tests — heating, submerging, cooling, bombarding with gravel and more. The most stringent tests should be used to ensure the highest quality. Aptiv tests our connectors to the toughest OEM specifications, which extend well beyond SAE J2030.

In addition, OEMs need flexibility from their connectors. Terminals have to be interchangeable with one another and adhere to industry standards. Connectors must have the flexibility to mount to a bulkhead or traditional inline, and they have to meet a wide range of applications, from the vehicle’s interior to its chassis to its engine.

With all of these aspects in place, OEMs can be assured of the highest levels of reliability, flexibility and performance to help them deliver commercial vehicles that meet or exceed customer expectations.