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Saint-Gobain RENCOL® Tolerance Ring solutions for powered door systems
Motor vehicle liftgates or closure panels act to open, close and seal a rear cargo area of a van, minivan, or sport utility type motor vehicle. Typically, these closure panels are mounted in a frame located at the rear of the vehicle within the body in white.
Technological innovation for doors and closures has mainly been concentrated around automation with the introduction of automatic liftgates and side door open and closure mechanisms. The most common system used for powered liftgates are spindle drives. Why? Because they can be easily designed to be mounted into the frame using the same connecting pivots, unlike a passive gas-strut which is an alternative solution. Automatic liftgates and side doors share a common requirement to have an overload or safety mechanism integrated into the system.
Powered liftgates are already quite common. Powered side doors are becoming increasingly popular and are currently being incorporated into higher end vehicles.
How powered door systems work
The powered system is operated by a wireless signal that connects to an actuator. Within the actuator, a tiny electrical motor turns a series of gears that drive a rack and pinion gear. This is connected to the actuator rod, which, when activated, unlocks the door and the motor opens the side door or tailgate.
In these applications there are a number of small gears that need to be protected if the door opens onto a fixed structure/body or anything that may get trapped between the door and the car body. This is where each system requires overload protection that will allow for the motor to slip thus protecting any components and obstacles from being damaged.
The RENCOL® Tolerance Ring fits between the worm gear hub and the spindle drive either directly or via an adaptor hub in the worm gear to protect the system from overload. So if, for example, the output drives against an obstruction, or receives a shock load, the RENCOL® Tolerance Ring will allow a momentary slip between the worm gear and the spindle drive, protecting the system from damage. After this slip the RENCOL® Tolerance Ring will automatically reset and allow for the door to work as normal.
How does overload protection work?
Whether operated manually or through a powered spindle drive the mechanical components that allow tailgates and vehicle side doors to open and close can be subject to human error, shock inputs and system overload; where the system’s torque level is surpassed. A slip clutch or overload clutch prevents damage by slipping between the mating components when the torque threshold is exceeded.
The RENCOL® Tolerance Ring is a custom designed, space saving mechanical slip clutch that offers torque protection at the desired level your system requires. Visit our page RENCOL® Tolerance Ring as a slip clutch to understand more.
Why use a RENCOL® Tolerance Ring as an overload clutch in powered door systems
There are a number of advantages to using a tolerance ring in powered spindle drive systems, these are:
- Protects the motor and gears from damage caused by input shocks, unexpected blocks or end user error.
- Reduces packaging space because they can be implemented between the worm gear hub and spindle drive. A tolerance ring can be installed in-line with mating components reducing the overall design space compared with typical friction clutches.
- The ring can be engineered so slip (protection) occurs at a torque level suited to the weight of the tailgate or side door, using the same mating components. Typical nominal torques required for these type of systems range from 1.0Nm to 6.0Nm.
- When used as an in-line clutch they reduce the number of components in the system and therefore reduces the weight and packaging space of the system.
- A tolerance ring provides stable torque value over the system’s lifetime.
- Our solution can provide a consistent feel to the user by holding a flat torque level during an individual cycle. This removes any “notchy” behaviour and provides a smooth quality feel to the user.
- A RENCOL® Tolerance Ring is easy to install into systems by press fitting the mating female and male components together with the tolerance ring mounted at the interface.
- The RENCOL® Tolerance Ring is custom designed to the optimal torque level, rather than having to compromise to a standard level. This allows the diameter and length to remain constant while covering a range of torque levels.
- Reduces system inertia and increases responsiveness.
- A RENCOL® Tolerance Ring automatically resets after each slip event, removing the need for manual intervention thus saving time and cost.
A tolerance ring isn’t just a stand-alone component – it’s part of a larger system. RENCOL® Tolerance Rings are designed by our engineers to suit your individual application. Although simple by design, a tolerance ring is a complex engineered component. Visit our page dedicated to explaining how a tolerance ring works to understand how these rings operate.
Design capabilities
Each slip clutch is specifically designed for its unique purpose and tested in-house using our comprehensive testing facilities which are located globally. We use the production mating components and the precise test conditions to ensure that it is 100% compatible with your system. Offering you complete confidence in every component we create for you both in development, test and production.
Some applications require consistent torque over a large number of slip cycles. The RENCOL® Tolerance Ring can be designed to reduce torque-drop over multiple slip cycles, giving a consistent performance over the life of the system.
Figure 1: These are theoretical guidance values for typical tolerance ring configurations. It is possible to have applications outside these limits – please contact us to discuss.
The RENCOL® Tolerance Ring slips at consistent repeatability over its lifetime. This can be achieved utilizing the correct choice of mating components. A 500 slip cycles test run is shown in figure 2, and represents a typical torque slip level for spindle drive overload protection system. In large scale production, a torque stability of up to +/- 15% can be achieved.
Figure 2: This graph shows 500 slip cycles of the system. Only seven run in cycles were required for the torque to stabilize and give a consistent system.
Collaborative working
Our engineer to engineer approach to design means that each tolerance ring is created to its customer’s unique system and specifications. RENCOL® engineers will work with you to design a tolerance ring for your system. As a one-piece solution, it reduces the space, weight and packaging of your system and because each ring is custom designed, the torque threshold can be specified to your requirements. Off-the-shelf solutions are often heavier, larger and more expensive and do not always fit perfectly into the motor or system. This is why, at Saint-Gobain Bearings, we make components custom designed to your specifications.
Speak to the team at Saint-Gobain
If you are facing an engineering challenge, talk to us at Saint-Gobain. Our experience, comprehensive testing facilities and multi-industry knowledge can offer a fresh perspective to shape future solutions. You can contact us using the contact us form or email us at: makingabigdifference@saint-gobain.com