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NORGLIDE® PTFE Bearings for automotive door hinges
How to improve performance and longevity of door hinges through bearing selection
Often, the first interaction a person will have with a vehicle is opening the door and as first impressions are everything, it is very important to not let the action of opening the door detract from the look and feel of the vehicle. A pleasurable door opening starts with a well-designed hinge. It’s the door hinge that will regulate the operation of the car’s doors and closures.
Torque, along with other parameters, directly influences the operational feel. If the torque is too high the effort to close the door might not feel as smooth as it should, and in extreme cases, the end user would have to use more force or slam the door closed.
Other factors that affect the perceived quality of the door hinge include:
The growth of electric cars has accelerated or re-prioritized some of these factors and automotive suppliers, like Saint-Gobain Bearings, are continuously developing new products and materials to overcome these challenges. A good example is the charger cap on electric vehicles (EV’s). Depending on their range EV’s generally need to be charged more regularly than combustion engines. The charger cap hinge will have to withstand more open/close cycles throughout the lifetime of the vehicle, the impact of this will need to be factored in by EV engineers and may influence the choice of hinge material, type of hinge and door hinge bearing.
Here we’ll look at the main issues impacting door hinges and how the choice of bearing can offer solutions to the factors effecting the performance and longevity of the door hinge.
Corrosion
Reducing corrosion is a primary concern for many types of door hinges. Red rust is the primary focus but the prevention of white rust is also a concern. The continual exposure to everyday dirt, debris and the weather all have an impact on the life span of hinge systems. Pivot points are known to have the weakest resistance. This is due to the permanent movement and unavoidable gaps between the components in the hinge system. Here, the choice of bearing and bearing materials can play a huge role in the prevention of corrosion.
To prevent galvanic corrosion, components need to be designed to work together. The mating components of the hinge system; the shaft, housing, bearing and type of plating (bronze and graphite are known drivers of galvanic corrosion when in contact with (coated) steel) will need to be harmonized to achieve optimum performance and reduce contact corrosion.
Industry standard tests have been introduced to tackle corrosion and demonstrate high corrosion resistance. At a component level, which includes a single bearing, the Salt Spray test (ISO 9227) is one standard. Depending on the hinge type and position this test can last for 720 hours or more proving the hinge’s resistance to corrosion. Understanding how different materials can impact the bearings ability to withstand corrosion is explained more in our blog corrosion resistant bearings.
Noise and Vibration (N.V.H.)
Noise can be unpleasant and irritating for vehicle drivers and passengers. Unexpected noise, for example, an abrasive sound when opening or closing the driver’s door, can give the impression of poor performance or quality, impacting the users experience and perception of the brand.
The choice of assembly process is one factor that could result in unwanted high torque at the pivot points; another is over-tightening that can lead to unfavourable loads on the hinge system. Both of these issues result in noise and vibrations that can be easily reduced or removed by using the right door hinge bearings and selecting the right materials. Introducing a thick PTFE-compound layer on the bearing softens the movement improving the feel for the user and eliminating some NVH issues. A precise fit assembly process removes free play in the hinges preventing vibration and rattling noises. NVH tests on door hinges can be carried out at our own semi-anechoic chamber to help identify areas of improvement.
Torque
Torque controls the position of the door in the frame and the hinge controls the torque. The hinge’s torque determines the fit of the door into the car body. Doors are fitted as an automated process completed by robots. To regulate this process all doors have a predefined mounting position. If the hinge’s torque isn’t correct the door cannot be fixed into position. Manually adjusting the hinge torque is an option, but should the hinge’s torque be extremely high (>4Nm) manual adjustment becomes difficult.
The position of the hinge can also create problems and, like the hinge torque, it needs to sit within a predefined range. If the relative position of the hinge changes it cannot be properly tightened onto the car body.
Controlling torque in door hinges
To manage the torque variation of the hinge a decrease in the disparity of tolerance during press fit assembly is required. As an example, figure 1 shows a sizing pin with a sizing mandrel that is bigger than the inner diameter of the installed bearing. By pushing the pin through the bearing, the inner diameter of the bearing increases due to a certain percentage of plastic (permanent) deformability of the bearing's structure.
Changing the material of the hinge bearing can prevent deformability, compensate tolerances and decrease torque variation. Aluminium based materials offer good sizing capabilities when compared with DU-type or plastic alternatives. Both NORGLIDE® SALC and SMALC materials with a stretched aluminium-cladded base metal and thick PTFE layer provide the sizing capabilities needed to compensate bearing wall thickness tolerances as well as housing diameter tolerances by choosing the right sizing pin.
Figure 1: Sizing pin in sizing mandrel
This results in a decrease in the tolerance field of max. vs min. press fit possibilities. The images in figure 2 show the worst case scenarios.
Figure 2: Theoretic worst case fit conditions in a typical bearing assembly
Sizing or calibration of the bearing within the hinge assembly is important as this gives a consistent process within the hinge assembly that enhances the quality feel of the hinge for both the OEM and end user. Additionally, it significantly reduces / eliminates scrap and rework in production.
Managing torque, or protecting doors and closures from overload is another consideration. Systems such as a slip clutch, torque limiter or overload clutch are used to protect the hinge from damage. The RENCOL® Tolerance Ring is a space-saving, in-line slip clutch giving a smooth consistent feel and protection for the hinge.
Paint defects
Paint defects are caused when paint debris sticks to the surface of the car during the e-coating process. Paint defects are a particular problem around pivot points when the bearing is fully conductive. A fully conductive bearing allows each layer of the e-coating process to adhere to all of the hinge’s components. These layers flake off when the hinge (or pivot point) is moved during the next stage of the painting process, causing defects.
Using a bearing made from non-conductive material with added conductivity notches allows the electric charge to pass through the hinge during the e-coating process but prevents the paint from sticking to it. This prevents build-up of the various layers of paint and reduces/eliminates paint flake - consequently, it reduces rework during the e-coating process. Explored in more detail, the blog How NORGLIDE® Bearings reduce e-coating paint defects, explains the challenges of paint defects.
Figure 3: Paint bridge caused by fully conductive bearing
Figure 4: Reduction of paint on pivot point using a non-conductive bearing with notches
NORGLIDE® Bearing solutions
On-going developments in bearing materials and technology can help solve some of the challenges for automotive hinges.
NORGLIDE® Bearings are custom-designed to satisfy the performance requirements of each individual system. The location, the loads on the bearing and the environment it needs to withstand are considered during the design phase and contribute to material selection. Recent developments in NORGLIDE® technology optimize the electrochemical potential of the bearing and facilitates the best fit solutions for typical hinge applications.
Corrosion resistance can be improved by selecting the right materials. NORGLIDE® Bearings are available in a wide variety of materials; steel with a zinc coating, stainless steel, aluminium and aluminium cladded materials all provide high corrosion resistance. Selecting the right material to improve corrosion resistance will depend on the boundary conditions. Our engineers have the knowledge and experience to advise on choosing the right material for the right situation.
To overcome NVH issues the combination of advanced materials and a layer of PTFE along with a correctly designed fit can help to deliver noise-free performance. The optimized materials of NORGLIDE® Bearings help reduce and absorb vibrations contributing to a smooth operational feel of any door or closure for the end user.
NORGLIDE® Bearings can also be used to reduce the need for precision manufacturing of the mating components. Our unique materials can compensate for manufacturing tolerances. This is due to the thick layer of PTFE incorporated in our bearings.
Figure 5: Tolerance compensation -- Torque vs. interference fit
For example, in this stamped door hinge there are two bores (blue part) that are not aligned. With the thick PTFE compound layer misalignment can be compensated and tolerances caused by misalignment are counteracted.
NORGLIDE® Bearings can be used for all types of hinges
Our bearings are versatile and offer many benefits for all hinge types, including:
- Side door hinge (forged, stamped or profile version)
- Trunk hinge (liftgate stamped hinge, liftgate forged hinge, gooseneck hinge)
- Hood hinge (single pivot hinge, multibar hinge, multibar hinge with active passenger safety function)
- Sliding door hinges (manual and powered)
- Fuel cap/electric charger caps
- Door handles
- Hinges for convertibles, spoiler
- Hinge systems for (powered) running board
Overall NORGLIDE® Bearings provide a great experience for the end-user. The high quality movement for the life of the door or closure improves the brand reputation of the vehicle and it is why NORGLIDE® Bearings have a strong reputation being recognized as a leader in the automotive market.
Talk to the experts at Saint-Gobain
With over 40 years of experience in door hinges, Saint-Gobain have a detailed knowledge of manual and powered doors and closures. On-going product development supported by R&D experts and world-class testing facilities create products that adapt to changing market conditions and increasing customer demands.
Our tailor-made products for hinge applications can solve common problems and overcome difficult challenges. If you’re facing an engineering challenge get in touch and speak to our experts.