【正文】 uring fluid distribution process. One new structured valve plate with nosymmetrical kidney bores is developed [12]. This valve plate 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 parison of pressure condition inside piston chamber between valve plates with difference angle and without difference angel.Fig. 11. Output pressure of the pump 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 plex. With the virtual prototype of piston pump, the force on the backside of the pistons can be investigated. With different angle of swash plate (including 0176。. Fig. 12. Fluid force on the pistons Fig. 13. Pressure with the angle of swashplate changing 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 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 shows the stress and strain when the simulation time is at s. The maximum stress at this state is about 196 MPa and the maximum strain is about mm. The most serious deformation region appears nearby the spline.(a) Stress of the middle shaft at s (MPa)(b) Strain of the middle shaft at s (10–4)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 mm. So the result is in a proper range. Besides, the stress also can be used for analyzing the friction on the outside of the piston.(a) Stress of the pistons (MPa) (b) Strain of the pistons (10–8)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 (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 reduce 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 plex hydraulic ponents, so the modeling and simulation also need several hypotheses to simply modeling.(4) Compared with the traditional simulation 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, it is difficult and plicated to make the effective interface. But with the development of the modeling and putation, the VPT has the potential to help to develop the new generation piston pump prototype with higher performance.References[1] ZHANG B F. Dynamic simulation of transmission system of mobile power station based on virtual prototype technology[D]. Luoyang: Henan University of Science and Technology, 2004. (in Chinese)[2] ZHENG J R. ADAMS——Introduction and application of virtual prototype technology[M]. Beijing: People’s Medical Publishing House, 2002. (in Chinese)[3] YANG Z W, XU B, ZHANG B. Simulation of axial piston pump based on virtual prototype[J]. Hydraulics Pneumatics amp。所以，在計(jì)算機(jī)上，虛擬樣機(jī)柱塞泵可以工作就像一個(gè)真正的柱塞泵,流量紋波、壓力脈動(dòng)、運(yùn)動(dòng)原理、應(yīng)力等的部分,可以調(diào)查。和簡(jiǎn)化帶來(lái)相當(dāng)大的偏差。由于有復(fù)雜的結(jié)構(gòu)和液壓固體耦合的非線(xiàn)性的特點(diǎn)，它是耗時(shí)和昂貴的，具有嘗試和錯(cuò)誤的傳統(tǒng)設(shè)計(jì)方法,傳統(tǒng)方法的分析結(jié)果都不夠準(zhǔn)確。所有這些研究證明該技術(shù)的有效性,但這些模型仍然是簡(jiǎn)單的，需要進(jìn)一步改善。一些配件的模型,如變量機(jī)構(gòu)和滑靴壓緊,被忽略?；デ蜚q中心的運(yùn)動(dòng)可以由B點(diǎn)的軌跡來(lái)描述。 泵零件轉(zhuǎn)動(dòng)慣量 質(zhì)量 體積 中間軸 0 斜盤(pán) 0 柱塞 5 滑靴 8 缸體 0 泵零件 泵殼軸缸體柱塞滑靴斜盤(pán)軸剛性連接缸體剛性連接圓柱副柱塞圓柱副球面副滑靴球鉸副平面副斜盤(pán)轉(zhuǎn)動(dòng)副平面副配流盤(pán)剛性連接軸承剛性連接轉(zhuǎn)動(dòng)副此外,給中軸增加一定量的速度，然后活柱泵基本模型的可以驅(qū)動(dòng)所有部件運(yùn)動(dòng)，就像一個(gè)真正的沒(méi)加油的泵。而當(dāng)活塞向左移動(dòng),柱塞推動(dòng)液體驅(qū)動(dòng)負(fù)載。 分布式流控制缸孔開(kāi)放面積大小,這是顯示在圖4(b)中。中間軸的模型用相同的方式來(lái)做。柱塞泵的虛擬樣機(jī)是通過(guò)將所有這些模型組裝在一起而建造的。流量脈動(dòng)振幅隨著斜盤(pán)傾角的增加而越來(lái)越大。斜盤(pán)的不同角度(包括0176。這個(gè)力的振動(dòng)振幅隨著斜盤(pán)角增加而上升。最嚴(yán)重的變形區(qū)域出現(xiàn)在花鍵附近。這個(gè)角度有助于減少壓力