Dual action device ensures both ride comfort and vibration-free idling
01 December 2009
Improved road-shake damping, enhanced engine vibration isolation and optimised idle isolation are all available from just one device, thanks to an innovative development from Trelleborg’s automotive acoustic and vibration damping system division
Trelleborg Automotive’s new Hydromount mechanical shock and vibration isolation system, which features a vacuum switchable bypass and de-coupler all in the one device, is believed to be the only type of its kind on the market. The new mount fulfils the conflicting requirements of having enough damping to mitigate powertrain shake and provide comfort, while being soft enough to ensure isolation during engine idling.
Although it may be a relatively new development, this innovative product has already been proven in terms of performance and durability following a demanding programme of customer tests. One customer – BMW - is currently using the mount on its 5, 6 and 7 Series diesel vehicles.
The vacuum switchable Hydromount (VSH) offers a number of advantages over passive de-couplers, which are typically used to obtain a better compromise between the idle isolation and road shake damping capabilities of hydraulic mounts. It comprises a main channel between two hydraulic chambers to dampen road shake, a switchable de-coupler for improved engine vibration isolation during driving and a switchable secondary channel (the bypass) for optimum idle isolation.
During engine idling, the bypass opens and restricts the de-coupler motion to provide perfect isolation in the main engine excitation frequency range. When driving, the mount switches the de-coupler back on for better isolation of high rpm engine vibrations, simultaneously closing the bypass for comfortable road shake damping.
As well as affording quiet and fast operation, the VSH is designed to avoid a loss of damping during sudden shock loads – such as those originating from impacts with pot holes and sleeping policemen. In addition, the mount is fail-safe in that, in the eventuality of vacuum loss, it still provides damping by reverting back to a ‘safe ride state’. Enrico Kruse, advanced engineering manager at Trelleborg Automotive takes up the story.
“Our durable vacuum switchable Hydromount improves idle smoothness while preserving damping during driving and, to the best of our knowledge, is the only type in production that switches both a bypass and a de-coupler. This system really comes into its own with diesel engines, which 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 systems.”
Trelleborg Automotive also supplies a non-switchable variant of this Hydromount for a number of BMW’s petrol engine vehicles. Thanks to its modular component construction, many parts can be used in each variant, which ensures manufacturing costs remain low – a saving that Trelleborg is able to pass on to its customers. Additionally, the new VSH 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.
The performance of the unit is also independent of the vacuum hose length, thus differentiating it from certain other systems that require short vacuum leads.
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