High-Performance Leaf Springs for Commercial Vehicles New Generation Design

Transcription

1 ARISTOTLE UNIVERSITY OF THESSALONIKI LABORATORY OF MACHINE ELEMENTS & MACHINE DESIGN G. Savaidis, M. Malikoutsakis MAN TRUCK & BUS SA Chr. Ertelt, F. Schwaiger High-Performance Leaf Springs for Commercial Vehicles New Generation Design 8 th International Congress of Spring Industry (ESF 8) September 2015, Prague, Czech

2 Outline 1. Introduction - Targets and aspects of modern suspension design - Scope 2. Theoretical investigations - Serial and new leaf spring suspension design - FE analyses (kinematics, stresses) 3. Driving tests - performance verification 4. Conclusions ESF 8 25 th September, 2015 Slide 2/21

3 Introduction Overall targets of the new MAN TGX-Generation 1. Economical 2. Body-friendly 3. Maximum Comfort 4. Reliable ESF 8 25 th September, 2015 Slide 3/21

4 Introduction Contribution of the SUSPENSION team 1. Economical 2. Body-friendly 3. Maximum Comfort 4. Reliable Reduction of number of leaves, reduction and unification of components for driver and cargo Spring rate High kinematics/steering performance, high durability performance ESF 8 25 th September, 2015 Slide 4/21

5 Introduction Principals of leaf spring suspension determines the performance of the vehicle in terms of suspension and guidance Driving direction Steering gear Drop arm Drag link FRAME Shock Absorber Steering lever Track rod ESF 8 25 th September, 2015 Slide 5/21 S-buffer Middle Leaf spring buffer (stretched) Clamped area Wheel joint Shackle

6 Introduction ESF 8 25 th September, 2015 Slide 6/21

7 Introduction Kinematics of leaf spring suspension Design requirements Schematic representation of the wheel joint s orbits Drop arm Drag link BRAKING MAXIMUM UNLOADED VERTICAL CONDITION LOAD o Requirement: Compatibility of the two orbits ESF 8 25 th September, 2015 Slide 7/21

8 Introduction Design requirements o Specific dimensions introduced by the vehicle setting o Reduction of number of leaves o Spring rate R=Force/Displacement within a specific range (comfort) o Compatibility between joint s orbit due to leaf-spring and joint s orbit due to steering rod o Durability: Acting stresses < permissible stresses ESF 8 25 th September, 2015 Slide 8/21

9 Introduction Suspension - Technical targets MAN TGX New Generation Front Axle Suspension For payloads 7.5to, 8to and 9.2to Reduction of number of leaves Reduction / unification of components High kinematics/steering performance High durability performance ESF 8 25 th September, 2015 Slide 9/21

10 Introduction Suspension - Technical scope Front axle payload 7.5to Serial Monoleaf, stepped eye type, eye lever e=17mm, Rate R serial 288±7% One new buffer New Proposals ESF 8 25 th September, 2015 Slide 10/21 1: Monoleaf, berliner eye, e=10mm, R 1 R serial 2:... R 2 = 0.88 R serial

11 Introduction Suspension - Technical scope Front axle payload 8.0to Serial 2-leaf spring, stepped eye, e=17mm, R serial =260±7% [N/mm] One new buffer New Proposals One new buffer Monoleaf, stepped eye, e=17mm, R=1.16 R serial 2-leaf spring, stepped inclined eye, e=0mm, R=R serial ESF 8 25 th September, 2015 Slide 11/21

12 Introduction Suspension - Technical scope Front axle payload 9.2to Serial 3-leaf spring, stepped eye, e=15mm, R serial =300±7% [N/mm] New Proposal One new buffer 2-leaf spring, stepped eye, e=17mm, R R serial ESF 8 25 th September, 2015 Slide 12/21

13 FE Analysis Geometric non-linear analysis: - Original clamping components included (hats, U-bolts, middle plates) k elements/leaf, typical element length ~5mm - Bushings modeled as steel cylinders (further investigations needed) - Rubber silencers modeled with hyperelastic material data - Contact modeling with friction (steel-steel μ=0.1, steel-rubber μ=0.8) - U-bolts pretension considered - Buffer modeled as spring element (non-linear F-s curve) ESF 8 25 th September, 2015 Slide 13/21

14 Wheel joint kinematics Coordinate z (mm) Wheel Joint Kinematics Comparison wheel joint curve maximum vertical load maximum braking load nominal load (payload) empty load ESF 8 25 th September, 2015 Slide 14/ Coordinate x (mm)

15 Kinematics results ARISTOTLE UNIVERSITY ESF 8 25th September, 2015 Slide 15/21

16 Stress results - 7.5to ESF 8 25 th September, 2015 Slide 16/21

17 Driving tests TGX-driving tests in Papenburg with serial and new (prototype) springs test drivers, test engineers, 19 criteria covering the areas of: - driving comfort - straight-ahead driving behavior - cornering behavior - steering behavior 05X-5278, Grades from 1 to 10 ESF 8 25 th September, 2015 Slide 17/21

18 Driving test 7.5to Grades normalized, series = 1.00 A: Serial 7,5t single leaf spring, Rate 288N/mm, front eye at z=-100mm driving comfort 1,20 1,15 1,10 B: Serial 7,5t single leaf spring, Rate 288N/mm, front eye at z=-140mm C: New berlin eye type 7.5t single leaf spring, Rate 288 N/mm, front eye at Z=-140mm cornering 1,05 1,00 0,95 0,90 straight driving behaviour D: New berlin eye type 7.5t single leaf spring, Rate 260 N/mm, front eye at Z=-140mm steering behaviour ESF 8 25 th September, 2015 Slide 18/21

19 Driving test 8.0to Grades normalized, series = 1.00 E: Serial 8.0t 2-leaf spring, Rate 260N/mm, front eye at Z=-100mm driving comfort 1,20 1,15 1,10 1,05 F: Serial 8.0t 2-leaf spring, Rate 260N/mm, front eye at z=-140mm cornering 1,00 0,95 0,90 straight driving behaviour G: New 8.0t 2-leaf spring, Rate 260N/mm, front eye at z=-140mm steering behaviour ESF 8 25 th September, 2015 Slide 19/21

20 Summary / Conclusions Systematic ( ICEAF III, IJSI) design of new front axle suspension for the new TGX-Generation, for 3 axle payloads: 7.5to, 8to, 9.2to Achievement of better driving performance by: - Optimized Adjustment of steering gear/front leaf eye position - Adjustment of eye type (berliner, stepped) and eye lever e - Reduction of spring rate Reduction of components: - 1 wind-up buffer for all axle loads - Reduction of number of leaves for 9.2to (proposal for 8.0to) One steering configuration throughout all axle payloads ESF 8 25 th September, 2015 Slide 20/21

21 Acknowledgements MAN Truck & Bus is gratefully acknowledged for the financial support of the theoretical investigations BETA CAE is gratefully acknowledged for the provision of pre- and post-processing software ESF 8 25 th September, 2015 Slide 21/21