轴向柱塞泵英文文献及翻译

1、Modeling and Simulation on Axial Piston Pump Based on Virtual Prototype TechnologyAbstract: A particular emphasis is placed on the virtual prototype technology (VPT) of axial piston pump. With this technology it is convenient and flexible to build a complicated 3D virtual based on real physical mode

2、l. The actual kinematics pairs of the parts were added on the model. The fluid characters were calculated by hydraulic software. The shape of the parts, the flexible body of parts, etc. were improved in this prototype. So the virtual prototype of piston pump can work in computer like a real piston p

3、ump, and the flow ripple, pressure pulsation, motion principle, stress of parts, etc. can be investigated. The development of the VPT is introduced at the beginning, and the modeling process of the virtual prototype is explained. Then a special emphasis is laid on the relationship between the dynami

4、cs model and the hydraulic model, and the simulations on the flow ripple, pressure pulsation, motion principle, the stress and strain distribution of the middle shaft and piston are operated. Finally, the advantages and disadvantages of the VPT are discussed. The improved virtual prototype of piston

5、 pump more tally with the real situation and the VPT has a great potential in simulation on hydraulic components.Key words: virtual prototype, axial piston pump, dynamics1 IntroductionAxial piston hydrostatic pump is an important hydraulic component, which is widely applied both in industry and mobi

6、le machine. As the piston pump has complicated structure and composite high-speed motion, so it is difficult to do exactly research on the pump. The pump model is always simplified to a great degree. And the simplifications bring considerable deviation. With the development of computer and multi-bod

7、y dynamics, the virtual prototype technology (VPT) is used for studying hydraulic system and components. Virtual prototype technology is a new engineering technology. With the VPT complex mechanism system model can be made and its dynamics characteristic can be simulated at a very real condition by

8、integrating modeling tools from several different fields and simulation methods. The core of VPT is the dynamics model, which have several interfaces to connect other models, such as hydraulic model and fitness element method (FEM) model. So the virtual prototype built based on VPT can simulate most

9、 of the pump performances, and the simulation results of the virtual prototype are very close to the test results of the physics prototype. Sometimes the simulation can even replace physics test and save the development cost1. Hydraulic virtual prototype technology integrate the advanced 3D CAD mode

10、ling method and hydraulic simulation technology to predict performance and study characteristics of a machine1. Because of the complicated structure and nonlinear characteristics of the hydraulic-solid coupling, it is time-consuming and expensive with traditional try-and-error design way, and the an

11、alysis results of traditional way are not accurate enough2. The virtual prototype of hydraulic machine, such as the axial piston pump, is a better way to predict the performance of hydraulic component3. With the commercial hydraulic and dynamic softwares, a virtual prototype of piston pump was made

12、by Aachen Technique University, Germany, in 20024. The hydraulic characteristics and frictions between the key tribo-pairs were analyzed56. In order to optimize the incline angle of the swash plate, a virtual prototype of a bent axis piston pump was made in 20037. The concept of virtual prototype of

13、 piston pump was proposed in 2004, the output pressure and flow ripple, the strain and stress of the key parts were all analyzed8. It is very useful for the optimization of pump. The flow ripple of a swash plate piston pump was studied using VPT in 20069. All these researches proved the effectivity

14、of this technology, but these models are still simple and need further improving.In this research, a virtual prototype of axial piston pump is developed, which combines 3D model, flexible FEM model and hydraulic modeling together. The performance of the pump is analyzed, and the optimization of the

15、index angle of swash plate by VPT shows the potential of improving products.2 Modeling of the Piston PumpThe validity of the simulation results lay on the rationality of its model, so the modeling of piston pump is crucial. The virtual prototype of piston pump connects several different models, incl

16、uding hydraulic system, 3D structural model and FEM parts model, which are built respectively and connected each other in simulation.2.1 Analysis of dynamic relationshipsBefore building the dynamic model and making the interfaces to connect other models, the real kinetic relationships and motion par

17、ameters of the necessary parts should be analyzed. There are several hypotheses as follows.(1) In order to simply the simulation, only necessary parts are considered. Some accessories models, such as mechanism of variable displacement and slipper hold-down, are ignored.(2) The rotation of middle sha

18、ft is stable and the speed is defined as constant.(3) The angle of swash plate changes in a defined work range by rotation drive.(4) The oil film between piston and cylinder, swash plate and slipper, cylinder and valve plate is stable, and its friction coefficient is constant.As shown in Fig. 1, the

19、 middle shaft of swash plate type piston pump rotates around its axis and drives the cylinder, pistons and correspond slippers rotating at a same speed1011.The coordinates of point B of intersection between the center line of piston and the surface of swash plate is described as follows: (1)From Eq.

20、 (1), it is shown that piston moves along z-axis and rotates around the middle shaft. The track of point B can describe the motion of the piston. Based on Eq. (1), the speed and accelerate of point B are as follows: (2)The slipper is connected with piston by spherical joint. The track of point B in

21、the spherical joint can describe the motion of slipper. The coordinates of the point B are (3)The motion track of the slipper is ellipse, the vector diameter is (4)The angle between and the Lang-axis of ellipse is (5)The rotation speed of the point B around the point O is (6)The velocity of the poin

22、t B is (7)Based on the equations above, the motion of basic parts can be defined.2.2 Structural and dynamic modelAs for swash plate type piston pump, showed in Fig. 2(a), the 3D structural model (Fig. 2(b) was made in a comerical CAD software. To simplify the analysis, only necessary parts model wer

23、e made. The joints and constraints between connecting parts were added. According to the real dynamic relationship between different parts, the proper joints and motion parameters are shown in Table 1 and Table 2. In the dynamic software, all these joints and motions were added to corresponding part

24、s. Then the basic dynamic model was finishied with a 3D structural model adding dynamic relationships.Besides, the ration speed of the middle shaft should be added, then the basic model of piston pump can be drove and all parts can move just like a real pump without oil.2.3 Hydraulic model of piston

25、 pumpAs there is no fluid force and motion in the basic dynamic model, so the dynamic model can only simulate the motion of piston pump and dont have the function of sucking oil and charging oil to drive load. In order to build the hydraulic model, there are some hypotheses as follows, (1) The pisto

26、n pump works stably and the rotation speed of middle shaft is defined constant.(2) The oil film in the gap between piston and cylinder, slipper and swash plate, cylinder and valve plate is stable. And there is only leakage of laminar flow.(3) There is hydrostatic balance in the gap between cylinder

27、and valve plate, slipper and swash plate, and the pressure ratio is constant (=0.9).(4) The viscidity of the fluid oil is invariable.Based on the motion relationship between the pump parts and the flow influence on the pump, the hydraulic model of the piston pump starts with the basic flow model.As

28、shown in Fig. 3, the low pressure oil is sucked to the cylinder bore when the piston moves to the right. While the piston moves to the left, the piston charges the oil out to drive loads.The model shown in Fig. 3 is the basic unit of one piston. And this unit including three important leakages, qv1

29、between piston and cylinder, qv2 between slipper and swash plate and qv3 between cylinder and valve plate, which are described in Eqs. (8)(10)11:, (8), (9), (10)where dr Diameter of piston,hr1Gap height between piston and cylinder,lr Contact length between cylinder and piston, Dynamic viscidity of t

30、he fluid, Eccentricity ratio of piston,p1 Pressure inside piston chamber,p0 Environment pressure inside pump, Pressure ratio,hr2Gap height between the swash plate and slipper,r1, r2 Structural parameters of slipper,hr3Gap height between valve plate and cylinder,1, 2, R1,R2, R3, R4 Structural paramet

31、ers of valve plate.The input oil and output oil in the cylinder bore are supplied through the valve plate, so the open area of the kidney bore in valve plate is used for controlling oil sucking and charging. Fig. 4(a) shows the open area coefficient curves with changing of rotation angle. Because th

32、e angle difference of the two different bore is 180 (Fig. 4(b), so it can be modeled with a throttle valve controlled by the open area size. The distributed flow is controlled by the cylinder bore open area size, which is shown in Fig.4(b).Fig. 4. Model of valve plateTo simplify the modeling, the fl

33、ow model and the valve plate model were combined to an integrated unit (Fig. 5). As one pump has nine pistons, so the whole pump model includes nine integrated piston models, which is shown in Fig. 6.Fig. 5. Encapsulation of the flow model and valve plate modelFig. 6. The whole hydraulic model of th

34、e pump2.4 Finite element method of the key partsThe stress and deformation of some key parts in pump working process should be researched by flexible body analysis8. The middle shaft and the piston are two typical parts needed to consider the flexibility character. It is necessary to analyze the mod

35、el with FEM and to convert the rigid body to flexible one. In an FEM software environment, the flexible body of piston can be read to the dynamic model and be assembled to the whole pump model. Fig. 7 shows the finite element model of the piston with flexible characteristics. The middle shaft model

36、was also made in the same way. Fig. 8 shows the two flexible parts in the assemble pump. Then the solver can simulate the pump and get the stress results and deformation results of the piston and the shaft. The intensity of corresponding parts is analyzed in this way. Fig. 7. Flexible body model of

37、the pistonFig. 8. Assemble pump with flexible bodyof piston and middle shaftAccording to the above analysis, the virtual prototype of piston pump includes several different models. So interfaces are needed to connect these models into one unit. Thereby, the hydraulic interface, the dynamic interface

38、 and flexible body interface are built according to the working environment. Fig. 9 shows the relationship of these models. The virtual prototype of piston pump are built by assembling all these models together.Fig. 9. Models relationship of pump virtual prototype3 Results and DiscussionMany aspects

39、 of the piston pump can be investigated based on the pump virtual prototype, such as the output characters, the force of pistons, the stress and deformation of the pistons and the middle shaft, etc.3.1 Output characters of pumpThe output flow and pressure of pump are used directly for driving loads

40、in the hydraulic system. So the output character is one of the most important performances of the pump. With the virtual prototype of piston pump, it is easily to get the output characters. Fig. 10 shows the output flow changing with angle of the swash plate. The flow ripple is clearly shown in the

41、result curves. The cycle time of flow ripple is the same based on the rotation speed. The flow ripple amplitude is getting higher with the swash plate angle increasing. Besides, the flow condition in each piston chamber can also be presented with the simulation.Fig. 10. Output flow with angle of swa

42、sh plateAs there are gaps between the two kidney bores in the valve plate, the output flow is discontinues. So the pressure ripple and corresponding noise are produced during fluid distribution process. One new structured valve plate with no-symmetrical kidney bores is developed 12. This valve plate

43、 has a difference angle (index angel) between the two kidney bores. With this structure, the pressure ripple of the pump can be reduced obviously, shown in Fig. 11. Fig. 11 presents the comparison of pressure condition inside piston chamber between valve plates with difference angle and without diff

44、erence angel.Fig. 11. Output pressure of the pump3.2 Force on the pistonsIn the piston pump, the pistons are used for sucking and charging oil. So the fluid force on the pistons is variable and complex. With the virtual prototype of piston pump, the force on the backside of the pistons can be invest

45、igated. With different angle of swash plate (including 0, 2.5, 5, 7.5, 10, 12.5, 15) at the same load condition, the force on each of the nine pistons is different and the force presents a periodic change with time, shown in Fig. 12. The vibration amplitude of force is getting higher with the swash

46、plate angle increasing.In order to analyze the influence of the swash plate angle, the fluid force was simulated with the angle changing continuously. The curve in Fig. 13 shows the trend of the force. It starts with a very small value, and the value of the force rises quickly while the angle of swa

47、sh plate reaches 5. Fig. 12. Fluid force on the pistons Fig. 13. Pressure with the angle of swashplate changing3.3 Stress and deformation of the pistons and middle shaftWith the FEM technology, the middle shaft and pistons model are improved from rigid body to flexible body, which is more tally with

48、 the actual situation. In dynamic environment, the stress and strain of the flexible body can be simulated when the virtual prototype is running. And the intensity of the flexible body parts can be investigated.The stress and strain can describe the intensity and deformation to a degree. Fig. 14 sho

49、ws the stress and strain when the simulation time is at 0.135 s. The maximum stress at this state is about 196 MPa and the maximum strain is about 0.002 mm. The most serious deformation region appears nearby the spline.(a) Stress of the middle shaft at 0.135 s (MPa)(b) Strain of the middle shaft at

50、0.135 s (104)Fig. 14. Stress and strain of the middle shaftFig. 15 gives the simulation result of the piston. The maximum stress in the piston is about 222 MPa and the maximum strain is about 0.005 mm. So the result is in a proper range. Besides, the stress also can be used for analyzing the frictio

51、n on the outside of the piston.(a) Stress of the pistons (MPa) (b) Strain of the pistons (108)Fig. 15. Stress and strain of the piston4 Conclusions(1) On the basis of different models and the interfaces, it is feasible to make the virtual prototype of piston pump. According to the type of the model

52、(such as the dynamic model and hydraulic model), corresponding simulation results are shown to predict the performance of the piston pump, so more characteristics can be studied by VPT.(2) When the valve plate is mounted on the end cap, a difference angle (index angle) is set. This angle helps to re

53、duce the pressure ripple. And the effect of the virtual prototype is also proved based on the simulation results.(3) The piston pump is one of the most complex hydraulic components, so the modeling and simulation also need several hypotheses to simply modeling.(4) Compared with the traditional simul

54、ation on piston pump, the VPT concentrated on more factors, such as the shape of the parts, the flexible body of parts, etc. So simulation model more tally with the actual situation and the result is more effective and useful to optimize the structure.(5) Because of the connection of so many models,

55、 it is difficult and complicated to make the effective interface. But with the development of the modeling and computation, the VPT has the potential to help to develop the new generation piston pump prototype with higher performance.References1 ZHANG B F. Dynamic simulation of transmission system o

56、f mobile power station based on virtual prototype technologyD. Luoyang: Henan University of Science and Technology, 2004. (in Chinese)2 ZHENG J R. ADAMSIntroduction and application of virtual prototype technologyM. Beijing: Peoples Medical Publishing House, 2002. (in Chinese)3 YANG Z W, XU B, ZHANG

57、B. Simulation of axial piston pump based on virtual prototypeJ. Hydraulics Pneumatics & Seals, 2006, 3: 3336. (in Chinese)4 DEEKEN M. Simulation of the reversing effects of axial piston pumps using conventional CAE toolsJ. lhydraulik und Pneumatik (O+P), 2002, 46: 612.5 YU X K, WANG J. Virtual proto

58、type of a hydraulic system based on ADAMSM. Beijing: Construction Machinery and Equipment, 2003. (in Chinese)6 DEEKEN M. Simulation of the tribological contacts in an axial piston machineJ. lhydraulik und Pneumatik (O+P), 2003, 47: 1112.7 PETER A, MARTIN P. Simulation of a hydraulic variable axial piston double pump of bent axis design with subsystemsC/The 1st MSC.ADAMS European User Conference, London, November 1314, 2002: 1017.8 ZHANG H, KASPER L, RICH K. Develop