Virtual Simulation Engine Mounting System Part i i 2

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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

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• Introduction

• Vehicle Development Process

• Methods of Ride Comfort Analysis

• Engine Mount Design

• Conclusion

Content

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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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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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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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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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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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Figure 3: Test car on the 4 poster bench

Source: fka, Aachen

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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.


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.

(Source : LMS)


Figure 4: Result of Transfer Path Analysis (TPA)

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.

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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.

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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.

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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.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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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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.

++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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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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CBA

Figure 9: Engine Mounts in different designs and dimensions

Engine Mount Design

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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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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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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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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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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)

Documents

Virtual Simulation Engine Mounting System Part i i 2