International Journal of Engineering Trends and Technology (IJETT) – Volume 32 Number 3- February 2016
Design, Development and Analysis of
Variable Displacement Pump by Application
of Linkage Motion Adjuster
Neelam M. Kamthe#1, Manmohan M. Bhoomkar#2, Ganesh E. Kondhalkar#3
#1Department of Mechanical Engineering, Pune University / ABMSP’s APCOER , Pune,India.
#2Department of Mechanical Engineering, Pune University / PVG COET, Pune, India
#3Department of Mechanical Engineering, Pune University / ABMSP’s APCOER , Pune,India.
Abstract— Axial piston pumps with constant
pressure and variable flow have extraordinary
possibilities for controlling the flow by change of
pressure. The major obstacle in application of the
bent axis piston pump is extremely high cost over
that of the radial piston pump; it ranges in the range
of 5to 6 times the cost of radial piston pump. Hence
there is a need to develop a modification in the
radial piston pump design that will offer a variable
discharge configuration in addition to the
advantages of high efficiency and maximum
pressure. Thus objective of project is defined to
develop a variable displacement linkage that will
enable to vary the stroke of a single cylinder axial
piston pump, thereby offering to vary the discharge
of the pump using manual control. The solution
offered is in form of the linkage motion adjuster
pump where this mechanism is to convert rotary
motion of crank element into oscillatory output of
the output element. The angle of oscillation of the
output is a function of the position of pivot element.
The pivot element position can be varied as it is
placed on a slide. Thus adjustment of the stroke can
be done by varying the position of the pivot element.
CAE of critical component and meshing using Ansys
has done. The experimental validation part of the
pump will be done using a test rig developed to
evaluate the performance characteristics of the
pump.
Keywords — pump, control link, pivot, crank.
I. INTRODUCTION
Variable displacement hydraulic pumps and motors
have significant energy savings than throttling valve
control [1]. But at low displacement the efficiency of
variable displacement machines decreases. So it
limits use of these pumps for partial load
application. Thus, it is need to develop hydraulic
pump/motors with high efficiency across the full
displacement range. There are three designs are
available currently for variable displacement pump.
Figure1 shows Swash-plate type axial-piston pump,
which is used as the fluid power- source for
hydraulic circuitry. These devices are used to
transmit power in many engineering applications
such as aircrafts, earthmoving equipment, and shop
tools. The advantages of these machines have been
ISSN: 2231-5381
high effort and low inertia, flexible routing of power,
and continuously-variable power transmission. By
varying the angle of swash plate it is possible to vary
the stroke of the pistons hence the discharge can be
varied in this configuration of pump. Bent axis pump
consist of cylinder block which is inclined to the
drive shaft. The disk connected inline to the drive
shaft on which the piston bases are mounted and
heads of pistons are in line with cylinders. When
drive shaft start to rotate the pistons reciprocates in
cylinders because of bent axis. Vane Pump Figure3
consists of rotor having vanes which rotates inside
ring. Rotor is eccentric with ring. Vanes tensioned to
keep the contact with walls of ring. Vanes are slide
into ring and creates the chambers, volume of these
chamber decreases due to eccentricity. Due to which
the fluid from chambers forces out the pump.
Eccentricity between rotor and ring decides the
displacement. [2] All designs which are discussed
above utilizes planar joints which having high
mechanical friction and high leakage to maintain
hydrodynamic bearings. In [3-6] work has been done
to enhance the efficiency of these machines. But this
work is for maximize efficiency only for high
displacement; they have not improve poor efficiency
at low displacement. So it is necessary to consider
other methods to improve efficiency at lower
displacement. In [7-8] alternative mechanisms
suggested to create adjustable crank slider linkage,
which are able to vary the stroke and so the
displacement. They developed the graphical
synthesis technique for generating adjustable
mechanisms with variable coupler curves. Zhou and
Ting presented a method of generating adjustable
slider-crank mechanisms for multiple paths by
adjusting the distance between the slider axis and the
crank [9] Adjustable linkage mechanisms for
controlling piston displacement have been
previously described and patented for internal
combustions engines to vary the compression ratio
to meet the power demand.[10] These engine
linkages, however, do not go to zero displacement.
Shoup developed a technique for the design of an
adjustable spatial slider-crank mechanism for use in
pumps or compressors [11]. This spatial mechanism
requires the repositioning of the axis of slide relative
to the crank. None of these mentioned techniques
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International Journal of Engineering Trends and Technology (IJETT) – Volume 32 Number 3- February 2016
and examples provides both a constant top dead
center (TDC) regardless of displacement and the
ability to reach zero displacement. A preliminary
kinematic synthesis technique was previously
described by the authors validation.[12]
This paper describes the design, synthesis, analysis of
can be closely and precisely monitored .By
application of kinematic overlay method the plots of
the input and output link position are determined to
derive the desired speed change at a given location
of the control link. The figure below illustrates the
phenomenon of speed change
mechanism to convert rotary motion of crank
element into oscillatory output of the output element.
The angle of oscillation of the output is a function of
the position of pivot element. The pivot element
position can be varied as it is placed on a slide. Thus
adjustment of the stroke can be done by varying the
position of the pivot element. Also includes testing
of the pump to plot characteristics of pump.
II. SYSTEM DESIGN
The system design comprises of development of the
mechanism so that the given concept can perform
the desired operation. The mechanism is basically an
inversion of four bar kinematic linkage. A very
important consideration when designing a
mechanism to be driven by a motor, obviously to
ensure that the input crank can make complete
revolution. Mechanism in which no link makes a
complete revolution would not be useful in such
applications. For the four bar linkage, there is a very
simple test of whether this is the case, hence the
mechanism is suitably designed using Grashoff’s
law. Grashof’s law states that for a planar four bar
linkage, the sum of the shortest and longest link
lengths cannot be greater than the sum of the
remaining two link lengths if there is to be
continuous relative motion between two members.
Grashof’s law
Where, s is length of shortest link, l is length of
longest link, p and q are lengths of remaining two
links. If this inequality is not satisfied no link will
make a complete revolution relative to another.The
synthesis of the output to be derived from the
linkage mechanism is derived by application of
Graphical method of kinematic design named the,
kinematic overlay method’. It is the easiest and
quickest of all method to use. The input link is
rotated through 180 degree to plot the locations of
the output link at start and end of cycle to determine
the output from the linkage. In this case the desired
output is derived by moving the control pivot in two
positions namely
Control link position –A
Control link position- B
To achieve the desired rated output the linkage
control link is moved from Control link position–A
to control link position –B. The Control link pivot
thereby changes the degree of oscillation of the
output link which is further rectified using one way
clutches to get a uni-directional output. Another
unique feature of the drive being that the speed
changes are step-less and hence the speed changes
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Fig. 1 The input and output link position for
control kink Position -A
Fig. 1 The input and output link position
for control kink Position -B
Desired speed ratio of 1:2 and 1:4 speed
reductions have been achieved by design of
kinematic linkage.
Simple and robust speed change
mechanism with advantage of step less
speed change is derived.
Single lever speed control with precise
speed changes is achieved.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 32 Number 3- February 2016
III. MECHANICAL DESIGN
For design parts detail design is done and
dimensions thus obtained are compared to next
highest dimension which are readily available in
market this simplifies the assembly as well as post
production servicing work. Following table gives the
dimensions and material of designed parts.
TABLE 1
Design of parts
Sr.
No.
1
Name of part
Material
Input shaft
EN24(40N;2cr1Mo
28)
2
Input crank
C45
d = 16 mm
3
Output yoke
C40
d = 16 mm
4
Output shaft
EN 24 (40 N; 2 cr 1
Mo 28)
d = 16 mm
5
connecting
pin
Yoke pin
6
Design
Dimension
d = 16 mm
Fig4. Total Deformation of connecting rod
d=8mm
D=16
Shaft bearing will be subjected to purely medium
radial loads; hence we shall use ball bearings for
this application. Bearing 6004ZZ, 6005ZZ, 6006ZZ,
6201ZZ are selected after checking for the dynamic
capacity. The UD one way clutch CSK-20 is a clutch
with dimensions same as that of single row deep
groove ball bearing of medium duty series 6204zz
Series 62 is selected after checking for dynamic
capacity. Connecting rod, output yoke, Control link
are checked for failure under direct tensile failure.
Eccentric or cam has checked for the torsional shear
failure.
Fig.5 Equivalent (von-mises) stresses of output yoke.
IV. ANALYSIS OF PARTS
A. Analysis
The analysis of critical parts which designed in
previous chapter. Modelling is done in solid works
and analysis in Ansys. The results of analysed parts
are as following.
Fig 6.Total Deformation of output yoke
Fig.3. Equivalent (von-mises) stresses of connecting
rod
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International Journal of Engineering Trends and Technology (IJETT) – Volume 32 Number 3- February 2016
B. Discussion of analysis.
TABLE 2
Comparison of design and analysis
VonTotal
Part Name Maximum
theoretical
mises
deforma
stress
stress
tion
(N/mm2)
N/mm2
Mm
Connecting
rod
Output
yoke
Control link
0.33
0.4
0.0001
Safe
0.48
0.495
1.24e-5
Safe
0.66
0.86
3.97 e-5
Safe
Eccentric
0.14
7.3427e5
-
safe
V. RESULTS AND DISCUSSION
Fig.7 Equivalent (von-mises) stresses of control link
Fig. 8 Total Deformation of control link
Fig. 10Linkage motion adjuster pump
Observations are taken for maximum and minimum
discharge condition of control link and discharge are
taken at different speeds. Then graphs plotted for
volumetric efficiency for both condition.
TABLE 2
Result table of volumetric efficiencies for
maximum discharge condition
Sr.
No.
Speed
( rpm)
Fig.9 Equivalent (von-mises) stresses of eccentric.
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Result
01
02
03
04
05
100
200
300
400
500
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Actual
flow
rate
(LPM)
0.0317
0.063
0.092
0.122
0.15
Theoretical
flow rate
(LPM)
Volumetric
efficiency
0.036
0.073
0.11
0.147
0.183
86.35
86.82
83.7
83.2
81.65
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International Journal of Engineering Trends and Technology (IJETT) – Volume 32 Number 3- February 2016
element into oscillatory output of the output element.
The angle of oscillation of the output is a function of
the position of pivot element. The pivot element
position can be varied as it is placed on a slide. Thus
adjustment of the stroke can be done by varying the
position of the pivot element. So conclusions from
this paper are as following.
1.
Fig.11 Graph of volumetric efficiency for
maximum discharge condition
For the maximum and minimum discharge
condition the average volumetric efficiency
are 84.34 and 84.06 respectively for the
Fig11. Shows the graph of volumetric efficiency
versus speed of pump. From graph it concludes that
Pump gives almost constant volumetric efficiency
for different speeds at minimum discharge position
of control link.
TABLE 3
Result table of volumetric efficiency for
minimum discharge condition
various speeds.
2.
Pump gives the good volumetric efficiency
at both minimum and maximum discharge
condition,
3. The cost of the pump is much less than
variable displacement pumps available in
market.
REFERENCES
[1]
[1] Williamson, C., Zimmerman, J., and Ivantysynova,
M., 2008, “Efficiency Study of an Excavator
Hydraulic System Based on Displacement-Controlled
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Bath/ASME
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[2]
Ivantysyn,
J.,
and
Ivantysynova,
M.,
2001,
“Hydrostatic Pumps and Motors”, Academic Books
International, New Delhi.
[3]
Manring, N. D., 2003, “Valve-Plate Design for an
Axial Piston Pump Operating at Low Displacements,”
Fig.12 Graph of volumetric efficiency for
minimum discharge condition
Fig.12 shows the graph of volumetric efficiency
versus speed of pump. From graph it concludes that
Pump gives almost constant volumetric efficiency
for different speeds at minimum discharge position
of control link.
ASME J. Mech. Des., 125(1), pp. 200–205.
[4]
Wang, S., 2012, “Improving the Volumetric Efficiency
of the Axial Piston Pump,” ASMEJ. Mech. Des., 134,
p. 111001.
[5]
Grandall, D. R., 2010, “The Performance and
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[6]
Seeniraj, G. K., and Ivantysynova, M., “Impact of
VI. CONCLUSIONS
This paper discussed design analysis of variable
Valve Plate Design on Noise,Volumetric Efficiency
displacement linkage that will enable to vary the
2006 International Mechanical Engineering Congress
and Control Effort in an Axial Piston Pump,” ASME
and Exposition, Fluid Power Systems and Technology,
stroke of a single cylinder axial piston pump,
Chicago, IL, ASME Paper No. IMECE2006- 15001,
thereby offering to vary the discharge of the pump
Nov. 5–10, New York, pp.
using manual control. The solution offered is in form
of the linkage motion adjuster pump where in
mechanism to convert rotary motion of crank
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77–84.
[7]
[7] Tao, D. C., and Krishnamoorthy, S., 1978,
“Linkage
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Mechanism
Adjustable
for
Variable
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International Journal of Engineering Trends and Technology (IJETT) – Volume 32 Number 3- February 2016
Symmetrical Coupler Curves With a Double Point,”
Mech. Mach. Theory, 13(6), pp. 585–591.
[8]
Tao, D. C., and Krishnamoorthy, S., 1978, “Linkage
Mechanism Adjustable for Variable Coupler Curves
With Cusps,” Mech. Mach. Theory, 13(6), pp. 577–
583.
[9]
Zhou, H., and Ting, K.-L., 2002, “Adjustable SliderCrank Linkages for Multiple Path Generation,” Mech.
Mach. Theory, 37(5), pp. 499–509.
[10] Soong, R.-C., and Chang, S.-B., 2011, “Synthesis of
Function-Generation Mechanisms Using Variable
Length Driving Links,” Mech. Mach. Theory, 46(11),
pp. 1696–1706.
[11] Shoup, T. E., 1984, “The Design of an Adjustable,
Three Dimensional Slider Crank Mechanism,” Mech.
Mach. Theory, 19(1), pp. 107–111.
[12] Wilhelm, S., and Van de Ven, J. DD., 2011,
“Synthesis of a Variable Displacement Linkage for a
Hydraulic Transformer,” Proceedings of the ASME
2011 International DesignWashington, DC, ASME,
New York, p. 8.
[13] Wilhelm, S., and Van de Ven, J. DD., “Design and
Testing of an Adjustable Linkage fora Variable
Displacement Pump” Journal of Mechanisms and
Robotic of the ASME,NOVEMBER 2013, Vol. 5 /
041008-1
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