Polymer bearings thrive in automotive applications

Although plain polymer bearings have been a common choice in the machine tool industry for many years, they are also becoming widely accepted in the automotive industry.

Although plain polymer bearings have been a common choice in the machine tool industry for many years, they are also becoming widely accepted in the automotive industry.

The demands on the plain bearing in this case include wear resistance, minimum maintenance and thermal stability.

Igus polymer plain bearings possess these characteristics and can therefore often directly replace steel backed PTFE bushes and roller bearings.

They are also able to provide a significant cost advantage and many technical benefits.

Currently, they are used in many different applications, from simple seat systems, to applications subject to high thermal stress in under bonnet applications, eg in transmission linkages and throttle valves.

In addition to the standard range of plain bearings, Igus can offer special Iglidur materials developed for specific applications.

Results obtained at Igus in Germany, on test benches specifically developed for this purpose, serve as a basis for material selection.

Each year, more than 4000 tests are carried out in the Igus laboratory and more than 100 new materials tested.

Selecting the relevant Iglidur sliding bearing for a specific application is always supported by the use of empirical lifetime data.

Whenever test data are not available for a particular application, Igus can carry out tests on a short-term basis.

This year, for instance, Igus developed a new sliding bearing material for an application with a thermo set shaft for vehicle lighting systems.

This took less than 8 weeks.

The first and foremost requirement to be met with vehicle seat systems is cost.

These seat systems are often required to work with low cost stock bar and metal pressings.

However, the bearing system must possess low clearance to ensure proper reduction of noise.

One possibility to resolve these contrary demands is to install Iglidur polymer sliding bearings prior to the e-coat paint process and give a transition fit between the bearing and shaft.

The advantage of this solution is that - following the paint process - the bearings are calibrated during the drying process by the high temperature (up to 220C), which results in a bearing system with ease of movement and minimum clearance.

Furthermore, due to the transition fit of the shaft, a large contact surface of bearing to shaft is achieved, so that the e-coat paint process of the entire component is guaranteed - whenever conductive sliding bearings, such as Iglidur RN89, are used.

Whenever other component connections give a conductive path, lower cost insulating materials, such as Iglidur G, GLW or RN56, can be used.

This method has been used successfully in metal fittings, seat systems and convertible roof systems.

Further advantages of Iglidur sliding bearings are: high static pressures up to 140N/mm2 are possible; they are quiet running; they require minimum installation space, weight; and "plain" and low-priced shafts are possible.

With the introduction of the new Iglidur H4 sliding bearing, Igus has unveiled a material which offers a long term operating temperature of 200C and is resistant to synthetic transmission oils and fuels.

Igus polymer plain bearings can also offers considerable cost benefits compared to metal plain bearings.

In tests carried out by a major German car manufacturer, transmissions with shift forks, usually fitted with roller bearings, were retrofitted with Iglidur H4 plain bearings.

Although the test drivers did not notice any significantly higher operating force, they praised the improved damping properties.

Another application is in rattle-free bearings for pedal box applications.

For this type of application, plain tubes or plastic bolts, which often consist of glass-fibre reinforced polyamide materials, are usually used due to cost implications.

What both solutions have in common is that they only possess roughly specified tolerances.

However, a bearing system with minimum play must be achieved in order to exclude noise effectively and to obtain good operational properties.

The new pretensioned Iglidur JVSM bearings overcome both these challenges.

Sprung elements at both ends of the sleeve bearing result in a system without play, even when not subjected to load.

The material Iglidur J also offers good friction and wear values even against abrasive glass-fibre-reinforced PA materials.

Glass-fibre reinforced PA or PPS materials can be used as shaft materials.

Plastic-plastic bearing systems are becoming increasingly important in the automotive sector in particular.

In addition to cost, weight reduction and chemical resistance, the economical production of complex design parts is the main reason for the preferred use of plastic materials.

In inlet manifolds, PA materials have been tested for reliability and efficiency for many years.

Now aluminum die-cast housings, eg in the case of throttle valves, are increasingly being replaced with plastic housings.

Here Iglidur sliding bearings are overmoulded with PA or PPS materials at approximately 340C.

In addition to the tribological combination of plain bearing materials, a high thermal stability is necessary.

The Iglidur Z bearing combines all these properties It is important to co-operate with OEMs and to have an exact knowledge of the application's specific requirements as early as possible.

An innovative solution can then be developed, based on the many years of experience gained by Igus engineers in a wide range of applications.

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