Design and Modeling of Fluid Power Systems
ME 597/ABE 591
Lecture 5
Dr. Monika Ivantysynova
MAHA Professor Fluid Power Systems
MAHA Fluid Power Research Center
Purdue University
Displacement Machines
Study different design principles and learn about the following topics
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
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
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
Dr. Monika Ivantysynova
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Displacement Machines
Swash Plate Machines
Axial Piston Machines
Piston Machines
F
In-line Piston Machines
Bent Axis machines
with external piston support
Radial Piston Machines
with internal piston support
External Gear
F
Gear Machines
Internal Gear
Annual Gear
F
Screw Machines
Vane Machines
Fixed displacement machines
Dr. Monika Ivantysynova
others
Variable displacement machines
3
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Bent axis axial piston pumps
Synchronization of cylinder block
Driving flange
Cylinder block
Using a bevel gear
Using a universal joint
Dr. Monika Ivantysynova
18
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Bent axis axial piston pumps
Synchronization of cylinder block
connecting rod
piston
Piston rod
Cardan joint
Synchronization by piston rod
Synchronization by pistons
Dr. Monika Ivantysynova
19
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Kinematics of bent axis pumps
Four link 3D mechanism
Frame (1)
Five link 3D mechanism
Frame (1)
Cylinder (4)
Cylinder (4)
Piston rod (5)
Piston (3)
Piston (3)
Driving flange (2)
Driving flange (2)
Assuming a fixed connection between link 2 and link 4, achieved by
synchronization
the mechanism has finally three
mechanism has finally two degrees degrees of freedom
of freedom
Piston can rotate about z -axis and
3
Piston can rotate about z 3 -axis
Dr. Monika Ivantysynova
piston rod can rotate about z5-axis
6
20
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Piston Design
Long piston with piston rod
Short piston with piston rod
Synchronization by
universal joint or bevel gear
Synchronization by
pistons or piston rods
Spherical piston with piston ring
Conical piston with piston rings
Dr. Monika Ivantysynova
16
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Design Examples
Pump control device
Driving flange bearings
Spherical valve plate
Dr. Monika Ivantysynova
22
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Design Examples
Driving flange bearings
Fixed displacement pump
Conical piston
Spherical valve plate
Dr. Monika Ivantysynova
23
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Radial Piston Pumps
with external piston support
with internal piston support
Rotating cylinder body
Stroke ring
Suction
Stationary cylinder body
Delivery
Suction
Delivery
eccentricity
Rotating cam or crankshaft
Displacement volume adjustable by changing eccentricity e
Dr. Monika Ivantysynova
10
29
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Radial Piston Pumps
Multiple stroke radial piston pumps
with external piston support
with internal piston support
Rotating cylinder body
Stationary cylinder body
Rotating cam
Stationary stroke ring
Only fixed displacement pumps realizable!
Dr. Monika Ivantysynova
11
30
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Piston support on outer stroke ring
Plane valve plate
Stroke ring
Stroke ring
Piston
Rotating cylinder body
Dr. Monika Ivantysynova
12
16
Piston rotation enforced
by friction force Ff
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Piston support on outer stroke ring
Stroke ring
Piston
Piston roller guide
Stroke ring borne in roller bearings
Dr. Monika Ivantysynova
Piston sliding bearing
13
17
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Piston support on outer stroke ring
Stroke ring
Slipper support
Hydrostatically
balanced slipper
Hydrodynamically
balanced slipper
Slipper pocket
Ball joint inside the piston
Dr. Monika Ivantysynova
14
18
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Stroke ring support
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
Dr. Monika Ivantysynova
15
19
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Design Example
Pump control system
Slipper
Piston
Control journal
Dr. Monika Ivantysynova
16
Stroke ring
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
External gear pump
Basic principle
Radial gaps between teeth addendum circle and housing
Housing
Inlet
Outlet
Driving gear
Qe = V n -Qs
Driven gear
Axial gaps between housing and the gear pair must be very small to seal the
displacement chamber
Dr. Monika Ivantysynova
17
13
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Two stage gear pump
Inlet 1
p1
Driven gear
Outlet 2
p4
p2
p3
Outlet 1
Driving gear
Driven gear
Inlet 2
Outlet 1 and inlet 2 can be connected
or the pump can have two separate outlets
p2 = p3
p1 = p3
the driving gear is pressure balanced!
Dr. Monika Ivantysynova
18
14
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Internal gear pump
Internal gear (ring gear)
Pinion
Advantages:
Better suction ability
Higher efficiency
More compact design
Less noise emission
Suction zone
Pressure 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.
Longer duration of teeth meshing leads to better sealing function
Dr. Monika Ivantysynova
19
15
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Internal gear pump
Crescent shaped divider
Many different tooth profiles have been applied in the recent past.
Dr. Monika Ivantysynova
20
16
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
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.
Ring gear (z2)
Outlet
Inlet
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
Pinion (z1)
quiet operation and long
service life
Gerotor pump
Dr. Monika Ivantysynova
21
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Annular gear pump Orbit principle
2 Pressure port
Ring gear (z2) fixed
Rotating pinion (z1)
1 Suction port
Outlet
Inlet
Multiple delivery of
each tooth space
Rotating
distributor
Dr. Monika Ivantysynova
Displacement volume is
given by z1 times z2 tooth
spaces
22
18
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Pressure compensated axial gaps
Sealing ring
Pressurized area A
Sliding bearing
Shaft seal
Gear pair
Axial gap
FZ FZ
End cap
Bearing bushings housing Front cover
Only one direction of shaft rotation possible!
Dr. Monika Ivantysynova
23
18
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Pressure compensated axial gaps
Driving gear
Axial gap pressure compensated
Pressurized area
Sealing
2FZ
Sliding bearings
Dr. Monika Ivantysynova
Driven gear
24
19
Improved volumetric efficiency
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Pressure compensated radial gaps
Radial gap compensation
Axial gap compensation
Pressurized area
Bearing bushing
Small pressure zone achievable
Dr. Monika Ivantysynova
25
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Gear pump design example
Driving gear
Shaft seal
inlet
outlet
Driven gear
Bearing bushing performing a radial and axial gap compensation
Dr. Monika Ivantysynova
26
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Internal gear pump- design example
Internal gear pump with axial and radial gap compensation
Pinion
Ring gear
special shaped divider
inlet
Pressurized area
outlet
Moveable bearing shell
Radial gap compensation
Dr. Monika Ivantysynova
27
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Screw Pumps
With two meshing screws
outlet
inlet
Dr. Monika Ivantysynova
28
22
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Screw Pumps
outlet
tthread pitch
inlet
outlet
With three meshing screws
Dr. Monika Ivantysynova
29
23
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Vane Pumps
Classification of vane pumps
Unbalanced vane pump
Stator
Rotor
Balanced vane pump
Only fixed displacement pump
Fixed and variable pump design
Dr. Monika Ivantysynova
30
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Vane pumps- basic working principle
Single stroke vane pump variable
displacement volume
inlet
Overcenter pump the direction of flow can be reversed 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
outlet
Large radial forces exerted on the rotor
inlet
Limitation of max. operating pressure (20 MPa)
Dr. Monika Ivantysynova
31
37
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Vane pumps- classification
Multiple stroke vane pump
Rigid vane pump
Rotor
Dr. Monika Ivantysynova
32
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Fluid distribution
External fluid distribution
Internal fluid distribution
outlet
stator
rotor
Distributor - fixed control journal
inlet
Dr. Monika Ivantysynova
33
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
Rigid vane pump
Stator ring
Displacement volume:
Rotor
Pulsation free flow
1st rotor
Dr. Monika Ivantysynova
2nd rotor
34
vane
Design and Modeling of Fluid Power
Systems, ME 597/ABE 591
