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Engineers at Saint-Gobain Performance Plastic Rencol are able to design tolerance rings for the electronic throttle control (ETC) in cars, as well as other applications.

Electric motors are being used to drive an increasing number of devices in cars.

One such application is within the throttle body to control the butterfly valve, commonly known as the ETC.

Because of the demanding environment where this assembly is mounted, automotive engineers are confronted with a number of issues.

Operating temperatures of up to 150C are commonplace; if dissimilar materials are used – steel and aluminium alloy, for example – the differential thermal expansion between the motor and housing can have a detrimental effect on the large tolerances.

The alignment of pinion gear can also be problematic.

There is also the vibration of the car’s engine to consider, which in turn vibrates the motor and can cause failure of the electrical connectors, via fretting corrosion of the terminals.

Saint-Gobain Performance Plastics Rencol said the tolerance ring is a solution to all of these problems, and is also inexpensive, reliable and straightforward.

These radially sprung steel fasteners are capable of handling direct torque transfer, predictable and repeatable torque slip, axial retention, controlled collapse and radial loading between the mating components, and can help reduce noise and vibration, avoid resonance frequencies and overcome differences in thermal expansion.

Depending on the specific requirements of the throttle-body application, engineers at Saint-Gobain Performance Plastics Rencol can design the tolerance ring to provide the right combination of properties needed.

In many applications, the motor is only fixed at the front.

As the rear of the motor is not supported, engine vibration can lead to fatigue failure or fretting corrosion of the electrical terminals.

To solve this problem, engineers have taken advantage of the properties of a crown ring used to mount the electric motor within the throttle housing.

The crown ring is a radial spring fastener with several sprung fingers, which, while deflected, give a required load.

The height and number of sprung fingers can be altered to cope with specific system tolerances, thermal expansion and support of the motor weight.

This system is said to combine the benefit of large diametrical tolerance compensation (in excess of 1mm is possible) with the additional benefit of low assembly forces.

Where engineers are restricted by physical component sizes, other solutions are available.

A tolerance ring comprising a series of waveforms can be used to create an interference fit, securely holding the motor in position.

The waveforms and other important criteria, such as ring thickness and hardness are designed by engineers at Rencol working closely with the component manufacturer.

Where physical space is restricted further, a miniature ring can be used to secure the motor.

Here, the tolerance ring is located on the bushing/bearing housing.

Upon assembly, the tolerance ring is aligned within the rear of the housing, generating an interference fit and locking the motor in position.

Saint-Gobain Performance Plastics Rencol

With 15 sites and six R&D centres globally, we at the Bearings and Tolerance Rings Group, a division of Saint-Gobain Performance Plastics, provide ‘engineer-to-engineer solutions-in-motion’ to high-volume international OEMs in the automotive, leisure, energy, industrial, and other markets. Backed by a heritage of product innovation, technology, advanced materials and market leadership, we are dedicated to working with customers using their extensive engineering expertise to deliver standard and custom solutions in NORGLIDE® bearings, RENCOL® tolerance rings, SOLGLIDE® bearings, JOINSHIM® rings, and NORSLIDE® cable liners that meet the most demanding applications.

The Saint-Gobain Performance Plastics, Bearings and Tolerance Rings Group provides product expertise to six key markets:

  • Automotive (steering systems, powertrain, electric motors, seats and hinges)
  • Bicycles 
  • Solar 
  • Appliances 
  • Industrial valves 
  • Hard disk drives 

Saint-Gobain is a global leader in the design, production and distribution of innovative, high-performance materials for industry and employs more than 195,000 people. With operations in more than 64 countries, Saint-Gobain is the 60th largest employer and among the top 50 global industrial companies worldwide. Saint-Gobain is listed on the stock exchanges of Paris, London, Frankfurt, Zurich, Brussels and Amsterdam. Saint-Gobain’s global strategy is focused around three core markets: 

  • Construction products
  • Innovative materials
  • Building distribution

The company is committed to playing a leading role in developing energy efficient innovations for the housing and construction sectors, protecting the environment, and managing growth in a sustainable fashion.

Saint-Gobain maintains 12 research centres and 101 development units and invests more than €400m in R&D. Saint-Gobain has been at the forefront of innovation for more than 300 years. Last year, Saint-Gobain achieved global sales of almost €42.1bn.

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