Trelleborg introduces vacuum-switchable hydromount

Edited by the Engineeringtalk editorial team Sep 22, 2009

Trelleborg Automotive has launched a hydromount with a vacuum-switchable bypass and a decoupler.

This is intended to improve road-shake damping, enhance engine vibration isolation and optimise idle isolation.

The company claims that its new mount fulfils the conflicting requirement of having enough damping to mitigate powertrain shake and provide comfort, while being soft enough to ensure isolation during engine idling.

The vacuum-switchable hydromount offers durability characteristics; having been developed in accordance with BMW's specific criteria, the mount has satisfied stringent customer testing and is already in use on the BMW 5, 6 and 7 Series diesel vehicles.

The hydromount also offers increased advantages over passive decoupler solutions, which are typically used to obtain a better compromise between the idle isolation and the road-shake damping of hydraulic mounts.

It comprises a main channel between two hydraulic chambers to dampen road shake, a switchable decoupler for improved engine vibration isolation during driving and a switchable secondary channel (the bypass) for optimum idle isolation.

During engine idling, Trelleborg's solution opens the bypass and restricts decoupler motion to provide isolation in the main engine excitation frequency range.

When driving, the mount switches the decoupler back on for the better isolation of high revolutions-per-minute engine vibrations, simultaneously closing the bypass for comfortable road-shake damping.

As well as affording quiet and fast operation, the new vacuum-switchable hydromount has been engineered to avoid a loss of damping during sudden impact loads, such as with pot holes and sleeping policemen, for example.

The mount is failsafe in that, in the eventuality of vacuum loss, it still provides damping by reverting back to the safe 'ride state'.

Enrico Kruse, advanced engineering manager at Trelleborg Automotive, said: 'This system really comes into its own with diesel engines, which, due to higher noise and vibration levels, require particular attention to reduce noise, vibration and harshness.

'At the same time, ever-tightening emissions standards are driving the development of smaller petrol engines with direct injection or turbo charging.

'With these engines invariably producing more vibrations, we are finding an increasing requirement for switchable mounting solutions,' he added.

The company also supplies a non-switchable variant of this hydromount for a number of BMW's petrol-engine vehicles.

Thanks to a modular component construction, this allows many parts to be used in each variant, which ensures that manufacturing costs remain as low as possible.

The vacuum-switchable hydromount has been engineered with space saving in mind and offers a compact design that requires only the same space as that of the passive version.

A further benefit is derived from performance that is independent of the vacuum hose length.

This differentiates Trelleborg's vacuum-switchable hydromount from certain other solutions that necessitate short vacuum leads.

The switching mechanism design of the company's new hydromount currently has patents pending in a number of countries.