Bosch Rexroth. The Drive & Control Company - · PDF file09.10.2014 | Yinuo Shi, Advanced Engineering Pumps and Motors | © Bosch Rexroth AG 2014. All rights reserved, also regarding

09.10.2014 | Yinuo Shi, Advanced Engineering Pumps and Motors | © Bosch Rexroth AG 2014. All rights reserved, also regarding any disposal, exploitation, reproduction, editing, distribution, as well as in the event of applications for industrial property rights.

SIMPACK User Meeting – Augsburg / 8. + 9. October 2014

Bosch Rexroth. The Drive & Control Company

Modeling Axial Piston Pumps of Swashplate Type in SIMPACK Yinuo Shi Advanced Engineering Pumps and Motors Bosch Rexroth AG / Mobile Applications

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1. Introduction to swashplate axial piston pumps

2. Challenges in the modeling as multi-body system 3. Modeling in SIMPACK

4. Simulation results 5. Conclusion and next steps

Contents

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Rotary group Splined gearing connection between

the cylinder and the drive shaft

Pistons and cylinder bores arranged to be coaxial to the drive shaft

Support of the slippers and the retaining plate on the swashplate (tilted plate)

Support of the swashplate on the housing through bearing (no contact to the drive shaft)

Introduction to swashplate axial piston pumps

Swashplate Cylinder

Drive shaft Piston

Slipper

∎ High pressure ∎ Low pressure

∎ Housing pressure

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Principle of function Rotation of the cylinder with the drive

shaft through the splined gearing

Stroke of pistons within the cylinder bores during the rotation of the cylinder (depending on the swashplate angle)

Intake of hydraulic fluid on the inlet side (low pressure)

Discharge of hydraulic fluid on the outlet side (high pressure)

Efficient transmission of hydraulic power

Introduction to swashplate axial piston pumps

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Contents

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Tribologic aspects for swashplate design Lubrication for main contact positions

Slipper swashplate contact Slipper retaining plate contact

Cylinder port plate contact Piston cylinder (bushing) contact

Solid contact due to asperity

Elastic and thermal effects

Challenges in the modeling as multi-body system

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2. Challenges in the Modeling as multi-body system 3. Modeling in SIMPACK


Contents

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Potential methods Method 1:

Calculation of hydraulic pressure in external software Input in SIMPACK Interpolation for different operating states (rotating speed, swash angle, etc.)

Simplified force elements via expression in SIMPACK

Method 2: Cosimulation Method 3: User routines for simultaneous computation of hydraulic pressure

User routines for mixed lubrication (hydrodynamic lubrication plus asperity)

Adoption of method 3 for the current modeling and simulation in SIMPACK

Modeling in SIMPACK

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Modeling of mechanical parts Substructures

Piston & slipper Cylinder

Retaining parts: retaining ball, retaining plate …

Swashplate Control and counter pistons

Drive shaft (with force element “Massless Beam Cmp”)

Model assembly by the “sender” & “receiver”

Modeling in SIMPACK

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User routine for hydraulic pressure

Modeling in SIMPACK

User force element (SimUMST)

Input parameters: fluid data, nominal pressure, area profile,

geometric data, reference marker, …

Output parameters: pressure, force, flow rate, …

Pressures in piston chamber and slipper inner range as dynamic states

Leakage of tribologic contacts

De-/activation of slipper pressure mode

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User routine for thrust bearing Application on slipper swashplate contact,

slipper retaining plate contact and cylinder port plate contact

Discretization of contact area to involve the rotation of the bodies

Solution of Reynolds equation for parallel lubrication film (1D-solution1) for each subarea (without elastic deformation) Simultaneous kinematic parameters – film thickness and its velocity –

obtained by SIMPACK access functions

Contact due to asperity Approach according to Patir2 (contact force due to surface roughness

if the film thickness is less than the reference value)

Modeling in SIMPACK

1: Derivation by Eric Quetel, Robert Bosch GmbH 2: N. Patir, Effects of surface roughness on partial film lubrication using an average flow model based on numerical simulation, PhD Thesis, Northwestern University, Illinois, 1978

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User routine for thrust bearing

Modeling in SIMPACK

User force element (squeeze force)

Input parameters: fluid data, boundary pressure, geometric data, parameters for mixed lubrication, …

De-/activation of mixed mode (due to asperity)

Output parameters: pressure, force, flow rate, …

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0

0.005

0.01

0.015

0.02

0.025

050

100150200

250300

350400

1

1.5

2

2.5

3

x 10-5


Journal bearing Application on piston cylinder (bushing) contact

Method 1: constraint for parallel approach Method 2: user routine

Unwrapped lubrication film Discretization of Reynolds equation for

nonparallel lubrication film (without elastic deformation)

Simultaneous kinematic parameters – eccentricities and velocities – obtained by SIMPACK access functions

Contact due to asperity (surface roughness)

Modeling in SIMPACK

eccentricities

contact length

Film

thic

knes

s [m

]

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User routine for journal bearing

Modeling in SIMPACK

User force element

De-/activation of mixed mode (due to asperity)

Output parameters: force, torque, kinematic parameters (for

reconstruction of pressure field), …

Kinematic parameters

Discretization in circumferential and translational directions

Boundary pressure, geometric and fluid data

front rear

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Friction force Hydrodynamic friction force1

Piston cylinder (bushing): Couette-term due to viscosity and relative velocity (obtained by SIMPACK access function); Poiseuille-term due to boundary pressure difference Slipper swashplate: Couette-term due to

viscosity and relative velocity (obtained by the SIMPACK access function)

Mixed friction force due to asperity

Slipper swashplate: application of the friction coefficient and the surface contact force

Modeling in SIMPACK

1: Derivation by Eric Quetel, Robert Bosch GmbH

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Contents

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Hydraulic pressure profile Computation of simultaneous

pressure profile, depending on

Geometry of control plate and piston-slipper throttle Kinematics, such as

translational and rotating speed, swash angle, etc.

Dynamic behavior due to elastic drive shaft (with force element “Massless Beam Cmp”)

Simulation results

Pressure in piston chamber and in the inner range of slipper

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Thrust bearing (slipper contact) Squeeze force in outer and

inner range, depending on

Geometry of slipper Simultaneous film thickness,

velocity and boundary pressure

Solid contact force due to asperity, depending on

Material properties Surface roughness

Film thickness

Simulation results

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+ +

Segment 1

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Journal bearing (piston bushing contact) Test for shaft speed run-up, instantaneous piston pressure, constant

eccentricities, but regardless of solid contact and friction

Resulting force, application point, and resulting torque

Simulation results

0

0.005

0.01

0.015

0.02

0.025

050100150200250300350400

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

x 107

simultaneous pressure distribution (unwrapped lubrication film)

Cir. dir. (0 – 2π)

Tran

sl. d

ir. (c

onta

ct le

ngth

[m])

[Pa]

19


Friction (hydrodynamic friction) Test for piston cylinder (bushing) friction considering shaft speed run-up

Couette-term due to viscosity and relative velocity Poiseuille-term due to boundary pressure difference

Simulation results

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Contents

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Conclusion Development of MBS-models for axial piston units of swashplate design

in SIMPACK

Computation of pressure profile with respect to simultaneous kinematics of each part of the pump model

Description of hydrodynamic film lubrication by Reynolds equation

Solution for parallel film (thrust bearing, analytically for 1D case) Solution for non-parallel film (journal bearing, numerically for 2D case

through discretization) Description of solid contact force due to asperity

Integration of contact and friction forces into MBS-models by user routines

Conclusion and next steps

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Next steps Application of numerical solution of

Reynolds equation for nonparallel film in the case of thrust bearing

Slipper swashplate contact Cylinder control plate contact

Integration into MBS by user routines Description of hydrodynamic and solid friction at all contact positions Reduction of simulation time by optimization of user routines and

solver settings

Elastic aspects (besides drive shaft)

Conclusion and next steps

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User experience – Suggestion to SIMPACK pre/communicators: override index, e.g., “SUBSTR_ID”, not only for receiver but also for sender.

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Documents

Bosch Rexroth. The Drive & Control Company - · PDF file09.10.2014 | Yinuo Shi, Advanced Engineering Pumps and Motors | © Bosch Rexroth AG 2014. All rights reserved, also regarding