14.10.2007 1
Computer Simulation in Automobile IndustryVehicle Comfort – Engine Mounting Concept
Virtual Simuation of Engine Mounting Concept
to improve Noise & Vibration Performance
Part II
Le The Hung
October 2007
14.10.2007 2
Computer Simulation in Automobile IndustryVehicle Comfort – Engine Mounting Concept
• Introduction
• Vehicle Development Process
• Methods of Ride Comfort Analysis
• Engine Mount Design
• Conclusion
Content
14.10.2007 3
Computer Simulation in Automobile IndustryVehicle Comfort – Engine Mounting Concept
Optimization of engine mounting system concerning engine mount position and
mount characteristics is important for the vehicle vibration and noise.
Part I of the paper was focused on the virtual simulation of the engine mount system
in full car model to achieve better vehicle comfort.
Part II of this paper will show you how to transfer the virtual engine mounting
concept into the prototype car.
Due to global competition the new vehicles have to be developed in very short time
frames for a growing variety of new car models, increasing customer demands on
comfort, performance and quality, reducing costs . During the last ten years, the
development cycles have been reduced from about five years to about three years.
.
Introduction
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Computer Simulation in Automobile IndustryVehicle Comfort – Engine Mounting Concept
The typical vehicle development process is shown in Figure 1.
Vehicle Development Process
Structure Integration Validation PilotMuleVehicle
Hardware
Engineering Engineering
StartStartStyl. / Pack. Styl. / Pack.
FreezeFreezeReleaseRelease Start Start
ProductionProduction
Initial Concept Structure ValidationintegrationVirtual VehicleSimulation
Concept Development Phase Production Development PhaseStart of
Production
(SOP)
Engine Mount System
DevelopmentFigure 1
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Computer Simulation in Automobile IndustryVehicle Comfort – Engine Mounting Concept
The vehicle development process consists of two major phases: the concept
development phase and the product development phase.
The most important milestone is at the transition from the concept phase to the
production phase. In concept phase the prototype hardware is only partially
available, the virtual simulation is very important for the concept decision.
The development of the engine mount system has to be integrated in vehicle
development process and starts in very early phase (Initial / Concept ).
Vehicle Development Process
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Computer Simulation in Automobile IndustryVehicle Comfort – Engine Mounting Concept
To develop of engine mounting system related to vehicle comfort / ride comfort
modern techniques and tools can be used for concept development and matching
of the riding comfort (Figure 2)
• Virtual simulation (Part I of this paper)
• Bench Test in Laboratory
• Ride Test on Road
Virtual Simulation
For the conceptual development of the engine mounting system the virtual
simulation using finite element method can effectively applied in early vehicle
development phase.
Bench Test
The simulated engine mount concept has to be verified and validated in Bench Test
(Figure 3). The 4 poster (cylinder) hydropuls test bench is normally used for a
vibration analysis of complete vehicle. The laboratory test has a lot of advantages,
such short conversion span, reproductivity of test results and the vehicle has not to
be ready for driving.
Methods of Ride Comfort-Analysis
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Computer Simulation in Automobile IndustryVehicle Comfort – Engine Mounting Concept
Methods of Ride Comfort-Analysis
Simulation
Bench Test
Engine mounting Concept
• Engine mount location
• Engine mount stiffness and damping
(Conventional Mount or Hydromount)
Goals: Improving Front End Shake, Idle Shake, Tip In/Tip Off
Vehicle Test on Hydropuls• Measurement seat acceleration
• Effect of different mount characteristics
• Transfer Path Analysis
• Eigenmode Analysis
Ride Test
Ride Test on Road
• Measurement seat acceleration
(objective evaluation)
• Subjective evaluation
• Fine tuning for Prototype Car
Figure 2: Three methods from simulation to road test
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Computer Simulation in Automobile IndustryVehicle Comfort – Engine Mounting Concept
Methods of Ride Comfort-Analysis
Figure 3: Test car on the 4 poster bench
Source: fka, Aachen
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Computer Simulation in Automobile IndustryVehicle Comfort – Engine Mounting Concept
For Front End Shake Test the vehicle is harmonically excited by a signal with 2,5
mm displacement amplitude at front tires in phase or out-of-phase.
The simulation results can be validated with test results for improving the simulation
model.
For Idle Shake Test engine is excited by engine at idle speed (700 rpm -1000 rpm).
In order to identify the contribution of each engine mount to total accelleration at
seat the Transfer Patch Analysis (TPA)method can be used. Figure 4 shows a
typical TPA result.
RideRide Test ( Test on Road)Test ( Test on Road)
A ride test on road is very important test method to get a impression of the vibration
of the full car in reality environment (subjective evaluation). To improve the engine
mount system measured data such as seat accelerations are needed.
Methods of Ride Comfort-Analysis
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Computer Simulation in Automobile IndustryVehicle Comfort – Engine Mounting Concept
.
(Source : LMS)
Methods of Ride Comfort-Analysis
Figure 4: Result of Transfer Path Analysis (TPA)
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Computer Simulation in Automobile IndustryVehicle Comfort – Engine Mounting Concept
.
Engine Mount Design
Simulation tools provide uns important information for developing the engine
Mounts. Dimension, Stiffness and Damping are physical parameters of a mount.
The engine mount must satisfy following essiential but conflicting criteria:
1. First, it should be stiff and high damped for
- supporting the engine
- reducing large engine motions during extreme driving manoveurs
for avoiding contact of the engine with body
- reducing vertical motion due to road excitation for improving Front End
Shake Behaviour
2. Second, it should be soft to isolate the vibration transmitted from engine mount
to the body for reducting vehicle vibration in low frequency range up to 30 Hz
(to improve Idle Shake behaviour) and reducing vehicle noise in higher
frequency range from 80 Hz to 200 Hz (to improve Engine Boom Noise).
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Computer Simulation in Automobile IndustryVehicle Comfort – Engine Mounting Concept
.
Engine Mount Design
The conflict between the high damping required for reducing engine mount motion
and the low damping for dealing with noise had led to the development of the
hydromount. Figure 5 shows a schematic of this type of mount. A fluid is pumped
from one chamber into the another chamber through a long spiral tube. This result
is an increase damping in the mount. A hydromount also contains a decoupler ,
which is a plate that for small motion allows the fluid to go around the plate and
avoid going through the tube. Thus, for rough road shake, the mount adds
considerable damping while for idle shake the mount reacts like a conventional
rubber mount ( small damping at low frequeny).
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Computer Simulation in Automobile IndustryVehicle Comfort – Engine Mounting Concept
.
Engine Mount Design
Figure 5: Hydromount and mount characteristics
Mount Stiffness and damping (loss angle)
___Simulation-----Testfor 1 mm excitationdispalcement
___ Simulation------Testfor 0.1 mm excitationdispalcement
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Computer Simulation in Automobile IndustryVehicle Comfort – Engine Mounting Concept
.Before getting started on design an engine mounting sytem, following basic
questions have to be answered:
1. What engines are to be mounted ?
Engine Volume :1.0 Liter,1.2 Liter,1.4 Liter, 1.6 Liter,1.8 Liter,2.0 Liter …?
Petrol engine or Diesel engine ? 4 cylinder engine or 6 cylinder engine …?
Gear boxes ?
2. Is there a carry over location system?
3. Are there carry over mount designs?
4. Limit on cost of the mounting system.
Can you use hydromounts, hydrobushings or need to stay with rubber mounts?
(convetional rubber mounts are cheaper than hydrolmounts).
5. For each engine you need :
- Engine loads , idle speed, idle and full load, maximum engine moment
(torque)
- Mass, Inertia, Engine Location ( Center of Gravity in Engine Compartment)
- Potential location of mounts (location and space for location)
Engine Mount Design
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Computer Simulation in Automobile IndustryVehicle Comfort – Engine Mounting Concept
Engine Mount right
Strut Mount Front
Var. A Var. B
Var. C Var. D
Engine Mount leftStrut Mount Rear
Figure 6: Engine Mounting System with different mount designs
for diffrent engines
Engine Mount Design
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Computer Simulation in Automobile IndustryVehicle Comfort – Engine Mounting Concept
.
++0Crash Performance
+00NVH Performance
+-0Mount Design
+00Cost
Concept CConcept BConcept ACriteria
0 not good/ not bad
- bad
- good /acceptable
Figure 7: Decision Matrice
Engine Mount Design
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Computer Simulation in Automobile IndustryVehicle Comfort – Engine Mounting Concept
Kriterien der Lagerentwicklung
• Mount position
• Space
• Easy of fitting
• Cost
• Weight
Constraints
• Function
• Durability
• Thermal reability
• Resistance to
corosion
Requirement
Figure 8: Component development
Engine Mount Design
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Computer Simulation in Automobile IndustryVehicle Comfort – Engine Mounting Concept
CBA
Figure 9: Engine Mounts in different designs and dimensions
Engine Mount Design
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Computer Simulation in Automobile IndustryVehicle Comfort – Engine Mounting Concept
Basic plat
Clamping ring
Balance membrane
Throttle-membrane
Throttle-plate
Mount Box
Box retainer
Fluid
V6 Engine
Diesel
Petrol
Engine mount brackets
Figure 10: Hydromount Design
Engine Mount Design
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Computer Simulation in Automobile IndustryVehicle Comfort – Engine Mounting Concept
Fluid
Mount Body
Elastomere
Mount Box
Screw
Engine Mount Bracket
Version B
Engine mount bracket Version A
Figure 11: Hydromount Design
Engine Mount Design
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Computer Simulation in Automobile IndustryVehicle Comfort – Engine Mounting Concept
Fluid
3%DP600
6%
St
28%
Elastomer
10%
Al
53%
Gewichtsanteil [%]
Matreial used for weight reduction
Figure 12: Engine Mount Brackets
Engine Mount Design
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Computer Simulation in Automobile IndustryVehicle Comfort – Engine Mounting Concept
Conclusion
• Application of virtual simulation of engine mount system to improve
vehicle comfort was discussed
• Simulation results provided import information for defining a suitable
engine mounting system
• Validated simualtion model car help to get more understanding of physical
system behaviour and to solve problems encounted during testing
• Engine mounting system with Torque roll axis has a lot of advantages
for improving vehicle comfort
• Hydromount helps to solve conflict problems of vibration and noise
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Computer Simulation in Automobile IndustryVehicle Comfort – Engine Mounting Concept
References
[1] G. Dödlbacher: Rechnerische Ermittlung des Schwingungsverhaltens des
elastisch gelagerten Motors. Automobil-Industrie Nr. 1, S. 57-61 (1982)
[2] H. Demant, J. Roos und D.F. Wolko: Schwingungstechnische Anforderung an
Triebwerklagerungssysteme. ATZ Automobiltechnische Zeitschrift 92
S. 116-118 (1990)
[3] H. Le the, E. Dornauf: Auslegung von Motorlagerungssystemen, Seminar im
Haus der Technik,Essen (1993)
[4] R., Singh: Linear analysis of an automotive hydro-mechanical mount
with emphasis on decoupler characteristics., J. Sound Vibr. 158,
219-243 (1992)
[5] M., Hofmann: Antivibrationssysteme: Grundlagen, Ausführungen, Anwendungen,
in der Reihe von Bibiliothek der Technik (2001)