RENCOL® Tolerance Ring Applications Study
Standard Tolerance Ring
Miniature Tolerance Ring
Electric motors are being used to drive an increasing number of devices in motor vehicles. One such application is the use of electric motors within the throttle body to control the butterfly valve, commonly known as ETC (Electronic Throttle Control).
Engineers are confronted with a number of issues including:
- Operating temperatures of up to 150° C
- Tolerances of motor and housing up to 0.8 mm in total
- Vibration of the engine/movement of the motor
- Failure of the electrical connections due to vibration
- Alignment of pinion gear
- Mounting between dissimilar materials
- Control of NVH / rattle / play of motor
- Prevention of premature motor failure
- Easy to assemble
- Allows for lighter weight design
In many applications, the motor is only fixed at the front and the engine vibration can lead to fatigue failure or fretting corrosion of the electrical terminals, as the rear of the motor is not supported.
The Crown Ring is the latest in a series of cost-effective, problem solving innovations that RENCOL® tolerance rings has to offer the automotive engineer. 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 is altered specific to each customer requirements to cope with system tolerances, thermal expansion and support of the motor weight. This system combines the benefit of the large diametrical tolerance compensation (in excess of 1 mm is possible) with the additional benefit of low assembly forces.
When engineers are restricted by physical component sizes, other solutions are available. A RENCOL® tolerance ring comprising a series of waveforms is 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 with ring specialists and component manufacturers working closely together.
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 locking the motor in position.
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