design and modeling of fluid power systems - purdue … · dr. monika ivantysynova maha professor...

Dr. Monika Ivantysynova

MAHA Professor Fluid Power Systems

Design and Modeling of Fluid Power SystemsME 597/ABE 591 Lecture 5

MAHA Fluid Power Research Center

Purdue University

SICFP’05, June 1-3, 2005, Linköping

© Dr. Monika IvantysynovaDesign and Modeling of Fluid Power

Systems, ME 597/ABE 5912

Axial piston pump design solutions (swash plate and bent axis)

Radial piston pumps and motors – piston support

Gear Pumps – internal and external – axial and radial gap compensation

Vane pumps – advantage and disadvantage of this design

Displacement Machines

Study different design principles and learn about the following topics

Aim: - To be able to select the right design for your system application!

- Knowledge about limitations of each basic design

- To apply models on system level for each design

Please study the appropriate chapters in

Ivantysyn, J. and Ivantysynova, M. (2001), Hydrostatic Pumps and Motors.

Akademia Books International. New Dehli. ISBN-81-85522-16-2




Bent axis axial piston pumps

18

Synchronization of cylinder block

Using a universal joint

Using a bevel gear

Cylinder block

Driving flange




Bent axis axial piston pumps

19

Cardan joint

Synchronization of cylinder block connecting rod

Synchronization by pistons

piston

Piston rod

Synchronization by piston rod




Kinematics of bent axis pumps

20

Frame (1)

Driving flange (2)

Piston (3)

Cylinder (4)

Four link 3D mechanism

Assuming a fixed connection between link 2 and link 4, achieved by

synchronization

mechanism has finally two degrees

of freedom

Five link 3D mechanism

Frame (1)Cylinder (4)

Piston (3)

Driving flange (2)

Piston rod (5)

the mechanism has finally three

degrees of freedom

Piston can rotate about z 3 -axis

Piston can rotate about z3-axis and

piston rod can rotate about z5-axis




Piston Design

16

Short piston with piston rod

Spherical piston with piston ring

Long piston with piston rod

Conical piston with piston rings

Synchronization by

universal joint or bevel gearSynchronization by

pistons or piston rods




Design Examples

22

Driving flange bearings

Spherical valve plate

Pump control device




Design Examples

23

Conical piston

Spherical valve plate

Driving flange bearingsFixed displacement pump




Radial Piston Pumps

with external piston support with internal piston support

eccentricity

Suction

Delivery

Stroke ring

Rotating cylinder body

29

Stationary cylinder body

Rotating cam or crankshaft

Suction

Delivery

Displacement volume adjustable by changing eccentricity e




Radial Piston Pumps

30

with external piston support

Multiple stroke radial piston pumps

Stationary stroke ring


with internal piston support

Stationary cylinder body

Rotating cam

Only fixed displacement pumps realizable!




Piston support on outer stroke ring

16

Stroke ring

Stroke ringPlane valve plate


Piston

Piston rotation enforced

by friction force Ff





17

Stroke ring borne in roller bearings

Stroke ring

Piston roller guide

Piston

Piston sliding bearing





18

Ball joint inside the piston

Slipper support Stroke ring

Hydrostatically

balanced slipper

Hydrodynamically

balanced slipperSlipper pocket




Stroke ring support

19

Using a sliding carriage supported using line contact

Stroke ring mounted on a pivot

Change of eccentricity by pivoting

the stroke ring about pivot axis




Design Example

20

Control journal

Slipper

Stroke ring

Piston

Pump control system




External gear pump

13

Basic principle

Inlet Outlet

Driving gear

Driven gear

Housing

Axial gaps between housing and the gear pair must be very small to seal the

displacement chamber

Radial gaps between teeth addendum circle and housing

Se QnVQ




Two stage gear pump

14

Driving gear

Driven gearDriven gear

Inlet 1

Inlet 2

Outlet 2

Outlet 1

Outlet 1 and inlet 2 can be connected

or the pump can have two separate outlets

p1

p2

p4

p3

121 ppp

342 ppp

p2 = p3

p1 = p3

21 pp the driving gear is pressure balanced!




Internal gear pump

15

PinionInternal gear (ring gear)

Suction zonePressure zone

Crescent shaped divider

Using teeth of standard involute design requires a combination where the

pinion has two or more fewer teeth than the ring gear! Pinion and ring gear

are then separated by a crescent shaped divider.

Advantages:

Better suction ability

Higher efficiency

More compact design

Less noise emission

Longer duration of teeth meshing leads to better sealing function




Internal gear pump

16

Many different tooth profiles have been applied in the recent past.

Crescent shaped divider




Annular gear pumps

Applying specially generated tooth curves it can be achieved, that the inner

rotor (the pinion) has only one tooth less than the ring gear, thus eliminating the

crescent-shaped divider.

Gerotor pump

Each tooth of the pinion maintains

continuous sliding contact with a

tooth of the ring gear, providing

fluid tight engagement.

Relative sliding velocity between

pinion and ring gear is very small

quiet operation and long

service life

Outlet Inlet

17

112 zz

Ring gear (z2)

Pinion (z1)

1

1

1

2

1

2

1

12

11

11

zn

zn

z

znn




Annular gear pump – Orbit principle

Ring gear (z2) fixed112 zz

Displacement volume is

given by z1 times z2 tooth

spaces

Multiple delivery of

each tooth spaceRotating

distributor

InletOutlet

Rotating pinion (z1)

2 Pressure port

1 Suction port

18




Pressure compensated axial gaps

Sealing ring

Sliding bearing

Gear pair

Bearing bushings

Shaft seal

End cap Front coverhousing

Pressurized area A

Only one direction of shaft rotation possible!

2

3.11.1p

FA z

FZ FZ

Axial gap




Pressure compensated axial gaps

19

Pressurized area

Driving gear

Driven gearSliding bearings

Sealing

Axial gap – pressure compensated

Improved volumetric efficiency

2

23.11.1

p

FA z

2FZ




Pressure compensated radial gaps

Radial gap compensation

Pressurized area

Axial gap compensation

Bearing bushing

Small pressure zone achievable




Gear pump – design example

20

Shaft seal

Bearing bushing performing a radial and axial gap compensation

Driving gear

Driven gear

inletoutlet




Internal gear pump- design example

Ring gear Pinion

special shaped divider

Internal gear pump with axial and radial gap compensation

inlet

outletMoveable bearing shellPressurized area

Radial gap compensation




Screw Pumps

With two meshing screws

inlet

outlet

With two meshing screws




Screw Pumps

With three meshing screws

outlet

t…thread pitch

inletoutlet




Vane Pumps

Classification of vane pumps

Unbalanced vane pump

RotorStator

Balanced vane pump

Only fixed displacement pumpFixed and variable pump design




Vane pumps- basic working principle

37

inlet

inlet

outlet

Single stroke vane pump – variable

displacement volume

Large radial forces exerted on the rotor

Limitation of max. operating pressure (20 MPa)

Overcentre pump – the direction of flow can be re-

versed by change of eccentricity, i.e. without

changing the direction of rotation of the drive shaft outlet

no flow!Relatively high friction between

axial moveable vanes and rotor

&

between vanes and stator




Vane pumps- classification

Multiple stroke vane pump

Rotor

Rigid vane pump




Fluid distribution

Internal fluid distributionExternal fluid distribution

inlet

outlet

Distributor - fixed control journal

rotor

stator




Rigid vane pump

20

vane

Rotor

Stator ringDisplacement volume:

bcdD

bdD

Vg22

2180

180

42

22

1st rotor 2nd rotor

Pulsation free flow

design and modeling of fluid power systems - purdue … · dr. monika ivantysynova maha professor...

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