Ljudreduktion för maskiner som arbetar i flera kvadranter 17/ Liselott Ericson

Introduction The combustion engine’s noise level has been reduced Makes the hydraulic system noise level more apparent Increased pressure levels and reduced weight of the hydraulic system Increases the noise level 2

General Noise Excitation Emitted noise Response 3

Noise in Fluid Power Systems Force and moment pulsation Excitation System Response Emitted noise Mechanical vibration Pressure pulsation Flow pulsation Noise 4 Hydraulic resonance response Mechanic resonance response Mechanic resonance response

Noise in Fluid Power Systems Force and moment pulsation Mechanical vibration Pressure pulsation Flow pulsation Noise 5 Hydraulic resonance response Mechanic resonance response Mechanic resonance response Excitation System Response Emitted noise

> Reduce Noise in Fluid Power Systems Force and moment pulsation Mechanical vibration Pressure pulsation Flow pulsation Noise Screening Isolation Geometry Material Pipe clamping Pipes Volumes Orifices Reducing the excitation energy from pump/motor System developer Pump/motor designer Hydraulic resonance response Mechanic resonance response Mechanic resonance response 6 Excitation System Response Emitted noise

Flow Pulsations 7

8

9 Note: The kinematic flow ripple is changed

PumpMotor Pump vs. Motor 10

Pump vs. Motor 11 PumpMotor

Cross-angle Cross-angle,  12 The Cross-angle varies the dead centre at displacement changes.

13 PUMP Displacement Rotational direction Counter-clockwise Clockwise Negative Positive PUMP MOTOR Left port pressurised Right port pressurised Displacement Rotational direction Counter-clockwise Clockwise Positive PUMPMOTOR PUMP Negative Different Driving Modes

Common Noise Reduction Features Pre-compression and decompression angle  Very sensitive for changes of operational conditions Pressure relief groove Pre-compression filter volume 14

Pre-compression filter volume Pressure relief groove Sound Pressure at pump housing vs. Flow Ripple 15 Small volume Large volume

System knowledge 16 Noise reduction System knowledge

Pump/motor working space 17 Noise reduction Pump/motor working space

Variable pressure with fix displacementConstant pressure with fix displacement Fix pre-compressionGradual pressurisation 18 The choice of noise reduction feature

Constant pressure with variable displacement Fix pre-compression and Cross-angle Gradual pressurisation and Cross-angle Variable pressure with variable displacement 19

Variable pressure with variable displacement fixed pressure port Gradual pressurisation and Cross-angle Variable pressure with variable displacement changed pressure port Gradual pressurisation ??? The choice of noise reduction feature 20

Fix pre-compression Gradual pressurisation Fix pre-compression and Cross-angle Gradual pressurisation and Cross-angle Gradual pressurisation and Cross-angle Gradual pressurisation??? The choice of noise reduction feature 21

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