Product category:
Springs, dampers, latches, locks and small components
News Release from: Rencol Tolerance Rings | Subject: Tolerance Rings
Edited by the Engineeringtalk Editorial
Team on 14 February 2008
Tolerance rings keep magnets in place
Simple and cost-effective alternative to the more traditional mounting methods, such as heat to press and the use of adhesives.
Rencol Tolerance Rings has developed a new way of mounting the magnet for a position sensor accurately and rigidly using a tolerance ring The new approach presents a simple and cost-effective alternative to the more traditional mounting methods, such as heat to press and the use of adhesives
Position sensors are widely used in modern cars, not least in electric power assisted steering (EPAS) systems.
In such restricted locations, these sensors must have exact positioning while at the same time be able to withstand severe rates shock and vibration.
To complicate matters further, they often incorporate magnets manufactured from powdered metal that are brittle and therefore difficult to fix in place.
Conventional press fitting is unsatisfactory, due to the high press forces involved and the need for close toleranced components.
An alternative sensor mounting method that is less likely to cause mechanical damage is the use of adhesives.
On the face of it, gluing the sensors into position looks like an attractive option and even allows the metal holders to be replaced by plastic, reducing the overall weight of the assembly.
In practice however it's difficult to achieve accurate sensor positioning consistently.
There's also the added curing time and, once the glue is cured, reworking the assembly is practically impossible.
Thanks to Rencol, there is now a cost-effective alternative for sensor mounting - the use of tolerance rings.
In simple terms, the tolerance ring is a radial spring ring with corrugation that is press fitted between two mating components, generating a retention force that fixes the components together securely.
Assembly is quick and simple; by gently closing-up the tolerance ring ends and pushing it into the plastic magnet housing until it's located squarely within the groove.
Once positioned, release the ring whereby the spring properties will retain the ring within the housing.
Then simply press the shaft into the magnet housing and tolerance ring assembly to the desired vertical location.
Accurate alignment of the poles can be achieved easily by simply rotating the holder.
"Accurate, reworkable and cost effective, tolerance rings can provide low assembly forces across a specified tolerance range", says Chris Needes, Automotive Product Manager at Rencol.
"They provide an accurate holder rotatable 360 degrees after assembly".
As the fitting force is low and can be accurately determined by the design of the ring, the assembly can be press fitted without risk of damage to brittle magnet materials.
Also, because of the resilient nature of the tolerance ring, this arrangement provides the sensor with a useful degree of protection against vibration and shock.
In addition, the ring gives consistent performance over a wide range of temperatures.
Another key benefit of using a tolerance ring is that the poles of the magnet can be aligned after assembly.
Overall cost savings achieved with this new assembly method are significant and measurable.
Tolerance rings allow the use of low assembly forces without the need to hold tight mating component tolerances.
This enables the traditional machined metal magnet holders to be replaced by lighter and less expensive moulded plastic alternatives.
The ability to rework a component can save time and money.
And, unlike glue, the stainless steel ring has no curing time and does not react with the magnet's surface. Request a free brochure from Rencol Tolerance Rings ...
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