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Frontiers of Mechanical Engineering

ISSN 2095-0233

ISSN 2095-0241(Online)

CN 11-5984/TH

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Front. Mech. Eng.    2022, Vol. 17 Issue (1) : 1    https://doi.org/10.1007/s11465-021-0657-z
RESEARCH ARTICLE
Integrated slipper retainer mechanism to eliminate slipper wear in high-speed axial piston pumps
Qun CHAO1,2, Junhui ZHANG2(), Bing XU2, Qiannan WANG2, Fei LYU2, Kun LI3
1. State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
2. State Key Laboratory of Fluid Power and Mechatronic Systems, School of Mechanical Engineering, Zhejiang University, Hangzhou 310027, China
3. Qing’an Group Co., Ltd, Xi’an 710077, China
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Abstract

The power density of axial piston pumps can greatly benefit from increasing the speed level. However, traditional slippers in axial piston pumps are exposed to continuous sliding on the swash plate, suffering from serious wear at high rotational speeds. Therefore, this paper presents a new integrated slipper retainer mechanism for high-speed axial piston pumps, which can avoid direct contact between the slippers and the swash plate and thereby eliminate slipper wear under severe operating conditions. A lubrication model was developed for this specific slipper retainer mechanism, and experiments were carried out on a pump prototype operating at high rotational speed up to 10000 r/min. Experimental results qualitatively validated the theoretical model and confirmed the effectiveness of the new slipper design.
Keywords axial piston pump      high speed      slipper wear      slipper design      retainer      lubrication model     
Corresponding Author(s): Junhui ZHANG   
Just Accepted Date: 19 November 2021   Online First Date: 26 January 2022    Issue Date: 28 January 2022
 Cite this article:   
Qun CHAO,Junhui ZHANG,Bing XU, et al. Integrated slipper retainer mechanism to eliminate slipper wear in high-speed axial piston pumps[J]. Front. Mech. Eng., 2022, 17(1): 1.
 URL:  
https://academic.hep.com.cn/fme/EN/10.1007/s11465-021-0657-z
https://academic.hep.com.cn/fme/EN/Y2022/V17/I1/1
Fig.1  Schematic of a swash plate type axial piston pump.
Fig.2  Configuration of the new slipper retainer mechanism for a high-speed axial piston pump.
Fig.3  Illustration of the sliding plate/bearing plate interface.
Fig.4  (a) Lubricating interface between sliding and bearing plates; (b) tribological surface of the bearing plate.
Fig.5  Program structure of the simulation algorithm for the sliding plate/bearing plate interface.
Variable Value Variable Value
Angular span of kidney-shaped pocket, α/(° ) 28 Casing pressure, pc/MPa 0.05
Swash-plate angle, β/(° ) 5 Outlet pressure, pH/MPa 20
Fluid dynamic viscosity, μ/(Pa·s) 0.012 Inlet pressure, pL/MPa 0.5
Fluid density, ρ/(kg·m?3) 837 Pitch radius of kidney-shaped pockets, R/mm 20.35
Spring force, Fs/N 320 Piston pitch radius, Rp/mm 20
Piston’s moment of inertia, Jp/(kg·mm2) 0.16 Inner radius of internal sealing land, R1/mm 16.3
Piston length, L/mm 26 Outer radius of internal sealing land, R2/mm 17.8
Initial contact length of the first piston, l0/mm 14.5 Inner radius of external sealing land, R3/mm 23
Mass of piston-slipper assembly, m/g 16.5 Outer radius of external sealing land, R4/mm 24.5
Piston mass, mp/g 12 Piston ball radius, rb/mm 3.75
Number of pistons, N 9 Piston radius, rp/mm 5
Tab.1  Main geometrical dimensions and fluid properties of the high-speed axial piston pump
Fig.6  Gap height at the three points at different rotational speeds (discharge pressure = 20 MPa).
Fig.7  Gap height and pressure distributions across the sliding plate/bearing plate interface (discharge pressure = 20 MPa, rotational speed = 10000 r/min). (a) Gap height distribution at 90°; (b) pressure distribution at 90°; (c) gap height distribution at 270°; and (d) pressure distribution at 270°.
Fig.8  Tilting angle of the sliding plate relative to the bearing plate interface (discharge pressure = 20 MPa).
Fig.9  (a) Minimum gap height and (b) its azimuth angle in the sliding plate/bearing plate interface (discharge pressure = 20 MPa).
Fig.10  (a) High-speed pump prototype; (b) test rig; (c) hydraulic circuit schematic. Reproduced from Ref. [26] with permission from Springer Nature.
Fig.11  Pump prototype equipped with (a) traditional slipper retainer device and (b) new slipper retainer device.
Fig.12  Comparison of the sliding wear between two types of slipper retainer mechanisms. (a) Sliding plate and bearing plate in the new mechanism; (b) slippers in the new mechanism; (c) slippers and bearing plate in the traditional mechanism.
Abbreviations
BDC Bottom dead center
DLC Diamond-like carbon
DLC + WC W-doped DLC coating
HP High-pressure
LP Low-pressure
Variables
ap Acceleration of the piston along its centerline
fb Friction coefficient between the piston ball and slipper socket
fp Friction coefficient between the piston and cylinder bore
Fa Reciprocating inertial force of the piston-slipper assembly
Fb Contact force between the piston ball and slipper socket
Fd Pressure force from the displacement chamber
Ff Friction force between the piston and cylinder bore
Fs Spring force exerted by the spherical cup
Fc Total clamping force
Fh Separating force generated by the fluid film
h Gap height
h1, h2, h3 Gap heights at three points
hmax Maximum gap height
hmin Minimum gap height
Jp Piston’s moment of inertia about its axis
l Contact length of the piston within the cylinder bore
l0 Initial contact length of the first piston
L Piston length
m Mass of one piston-slipper assembly
mp Piston mass
Mx Moment component of Mc in the x direction
My Moment component of Mc in the y direction
Mc Moment generated by the total clamping force
Mh Moment generated by the separating force
N1, N2 Contact forces between the piston and cylinder bore at two engaging ends
p Fluid pressure
pc Casing pressure of the pump
p(φi) ith displacement chamber pressure as a function of the angular displacement
r Radial distance from the coordinate origin
rb Piston ball radius
rp Piston radius
R Pitch radius of the kidney-shaped pockets in the sliding plate
R1 Inner radius of internal sealing land
  
R2 Outer radius of internal sealing land
R3 Inner radius of external sealing land
R4 Outer radius of external sealing land
Rp Piston pitch radius
t Time
vp Velocity of the piston along its centerline
Vp Resultant velocity of the piston relative to the cylinder block
α Angular span of the kidney-shaped pocket in the sliding plate
β Swash-plate angle
θ Angular distance from the y axis
θa Azimuth angle of the minimum or maximum gap height
φ Angular displacement of the piston from the BDC
μ Fluid dynamic viscosity
ρ Fluid density
ω Rotational speed of the pump
ωp Spinning speed of the piston
ωs Rotational speed of the sliding plate
  
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