【正文】 ： 1．單斗液壓挖掘機應(yīng)有較大的牽引力，使挖掘機在濕軟地面或高低不平的地面上行走時具有良好的越野性能，并有較強的爬坡和轉(zhuǎn)彎能力。但履帶式行走裝置制造成本高，運行速度低，運行和轉(zhuǎn)向時功率消耗大，零件磨損快，因此，挖掘機長距離運行時需借助于其他運輸車輛。 液壓挖掘機履帶式行走裝置的結(jié)構(gòu)和構(gòu)造履帶式行走裝置(—1)由連接回轉(zhuǎn)支承裝置的行走架通過支重輪4，履帶2將載荷傳至地面。為了克服上述缺點，提高質(zhì)量，目前有關(guān)部門已將挖掘機、推土機和裝載機的“四輪一帶”圖紙統(tǒng)一，逐步做到標準化、通用化和系列化，為提高產(chǎn)品質(zhì)量、而速發(fā)展工程機械創(chuàng)造條件。履帶、支重輪等零部件采用工業(yè)拖拉機的標準件，因而可降低成本，質(zhì)量也有保證。整體式是履帶板上帶嚙合齒，直接與驅(qū)動輪嚙合，履帶板本身成為支重輪等輪子的滾動軌道。 所以：b=(~)209=~ 為了取標準節(jié)距的履帶，這里取b=400mm 履帶支撐面長度根據(jù)經(jīng)驗公式 L0=KL=（~）=~ （） 這里初取2500mm。當鏈軌繞過驅(qū)動輪時可借助輪齒白動清除鏈軌節(jié)上的淤泥。（3）校核軌鏈節(jié)的抗拉強度對于鋼制履帶，履帶板應(yīng)驗算其拉伸應(yīng)力，危險截面是銷孔的最窄處： ()——取自《工程機械底盤構(gòu)造與設(shè)計》P314式中：——履帶銷套半徑，； ——履帶銷半徑，； ——一塊履帶板一端的各銷孔寬度之和。因此驅(qū)動輪應(yīng)選用淬透性好的鋼材，通常用50Mn，45SiMn，中頻淬火、低溫回火，硬度應(yīng)達到HRC55～58。所以名義齒數(shù)Z=。a) 支重輪外形尺寸的選擇挖掘機重量通過支重輪傳給地面，工作時如地面不平它將經(jīng)常受到?jīng)_擊，所以支重輪所受載荷較大。支重輪內(nèi)壓裝有軸套3，這種軸套是雙金屬式的，既耐磨強度又高?！?支重輪1—輪體 2—軸 3—螺塞 4—墊圈 5浮動油封環(huán) 6—浮動油封座 7—O型膠圈 8—銷 9軸套根據(jù)《工程機械底盤構(gòu)造與設(shè)計》：安裝尺寸外形尺寸配合尺寸特性尺寸ABCELKDd1d2FD1300240120323352101885565180155確定支重輪個數(shù)：軸間距 （）——取自《工程機械底盤設(shè)計》P231取=290mm。 托鏈輪的設(shè)計托輪用來承托上部履帶，防止其過度下垂，減少上方履帶的跳動和下垂量，并防止履帶從側(cè)向滑脫。導(dǎo)向輪的中間擋肩環(huán)應(yīng)有足夠的高度，兩側(cè)邊的斜度要小。 張緊裝置的設(shè)計 張緊裝置的功用主要是保證適當?shù)穆膸埦o力，當導(dǎo)向輪受到前方的沖擊載荷時，緩沖彈簧回縮以吸收振動，防止履帶和驅(qū)動輪損壞。緩沖彈簧工作行程終了時的壓縮力：40=(60~80)KN緩沖彈簧工作行程需考慮履帶和驅(qū)動輪卡入石塊時能脫離嚙合，即工作行程為： （） ——取自《工程機械底盤構(gòu)造與設(shè)計》P320式中：驅(qū)動輪齒頂圓直徑，； 驅(qū)動輪齒根圓直徑?！八妮喴粠А卑惭b尺寸 驅(qū)動輪一般置于機械后方，因為機器前進的時間多，而且牽引力大，這樣履帶驅(qū)動段的長度小，可以減小功率損失。~3176。牽引平衡方程為： （—1）式中 —為驅(qū)動輪的扭矩 —驅(qū)動輪的半徑 —履帶的牽引力 —運行時各阻力之和 ——《單斗液壓挖掘機》P2001．土壤的變形阻力土壤對履帶行走裝置在運行時的阻力是由于履帶使土壤擠壓變形而引起的。因此履帶上比壓基本上可寫作均勻分布。39。驅(qū)動輪的摩擦阻力 一般根據(jù)經(jīng)驗公式，履帶的內(nèi)阻力 =（~）G(N) () 以上四種運行阻力中，以坡度阻力和轉(zhuǎn)彎阻力為最大。是正確的解，=176。=176。則 [Pmin +(PmaxPmin)]dx=G (1)由O（F）=0。=式中一馬達轉(zhuǎn)速(r／min)。從上式可看出，L／B值又不能太大，否則將增大轉(zhuǎn)彎阻力值，降低原地轉(zhuǎn)彎能力，因此L／B的比值應(yīng)恰當選擇。 Houston, May 1993.[16] McCloy D, 《Discharge Characteristics of Servo Valve Orifices》, 1968 Fluid International Conference.[17] . Binder, 《“Fluid Mechanics”. 3rd Edition, 3rd Printing. PrenticeHall, Inc.》, Englewood Cliffs,NJ. 1956.[18] Patton . 《Mechanical Power Transmission》. New Jersey: Printice—Hall, 1980科技論文翻譯Theory of fluid propertiesWe will concentrate mainly on three fluid properties in this chapter: ? The density which leads to mass and hence to hydraulic inertia effects.? The viscosity which leads to the hydraulic friction effects.? The pressibility and thus the bulk modulus which leads to the hydraulic system stiffness. Notice that the pressibility effect can be modified by air release, cavitation phenomena and by expansion of a pipe, hose or chamber containing the hydraulic fluid.1 Density and pressibility coefficient The density is the mass of a substance per unit volume:Density has dimensions of [M/L] and is expressed in kilograms per cubic meter [kg/m]. As mentioned previously the density is a function of the pressure and the temperature:This function can be approximated by the first three terms of a Taylor series:This can also be expressed as:WithAndThis equation is the linearized state equation for a liquid. Using the definition of the density, the two coefficients α and B can also be expressed as:B is known as the isothermal bulk modulus or for simplicity the bulk modulus and α is known as the cubical expansion coefficient. Since fluid density varies with the applied pressure, this implies that a given mass of fluid submitted to a pressure change changes its volume. This phenomenon leads to the definition of the pressibility coefficient β: where β is expressed in units Pa (or m/N). Considering the relation for a closed hydraulic circuit the mass is constant, and hence: it follows that Using the definition of the pressibility coefficient β we obtain: More usually we use the bulk modulus B also known as the volumetric elasticity modulus: The relation between ρ and B implies mass conservation. This relation must be RIGOROUSLY RESPECTED in the calculations. In the modeling and simulation context of fluid energy systems, disregarding the relation between ρ and B leads to abnormal evolutions of pressure in the closed circuit submitted to pression and expansion cycles. This phenomenon is strongly accentuated if aeration occurs in the circuit (when dissolved air in the fluid reappears in the form of bubbles). We shall approach this point by examining the phenomena of aeration and cavitation. The air can also have adverse consequences on a fluid pressibility. In liquid air can be present in two forms: entrapped and dissolved. Entrapped air When the return pipe is not submersed in the tank the liquid jet can entrain some air bubbles in the tank. Another phenomenon that affects the quantity of air in liquid is the leakage. Figure 1: Liquid leakageFigure 2: Air is entrainedThis air stays in the liquid as cavities and can modify the fluid pressibility. In this context we talk about effective bulk modulus. Figure 3 shows the bulk modulus of a diesel fuel at 40 176。當S2．3時，原地轉(zhuǎn)彎不能實現(xiàn)；2．1S2．3時，原地轉(zhuǎn)彎可能實現(xiàn)；S2．1時，原地轉(zhuǎn)彎性能良好。 接地長度、軌距校核以及最小離地間隙的確定 挖掘機行走裝置的接近角和離開角一般較小，可近似認為導(dǎo)向輪與驅(qū)動輪中心距離即軸距A等于履帶接地長度L。根據(jù)、T和驅(qū)動輪節(jié)圓直徑Dq，可求出減速機三個主要參數(shù)、和：(1)減速機輸出扭矩MgMg=式中T—一側(cè)最大牽引力(N)； 一驅(qū)動輪機械效率。原地轉(zhuǎn)彎的行走阻力可用下式計算：W=（—）μG+ =6000+6000 =27783N （）式中——轉(zhuǎn)彎阻力系數(shù)，取=挖掘機的牽引力TW 故在一般路面能實現(xiàn)原地轉(zhuǎn)彎，滿足設(shè)計要求。附著力為Gcos=6000176。 目前大多數(shù)履帶式液壓挖掘機的行走牽引力T與機重G取下列比例，即T=(~)G （）初步取T==48000N履帶行走裝置一個顯著特點就是爬坡能力大，一般為50%~80%。39。 履帶轉(zhuǎn)彎阻力履帶寬為b，長為L，且=5則一條履帶的微面積bdx繞履帶中心點o轉(zhuǎn)動時的力矩可表示為。土壤的變形阻力推倒過程復(fù)雜，只是實際計算時可采用簡化為： （） ——稱運行比阻力，此值與道路種類等有關(guān)，—1選取。為了不和它們的運動發(fā)生干涉，支重輪的位置應(yīng)保證當導(dǎo)向輪在緩沖彈簧達到最大變形時相互不發(fā)生干涉，后支重輪的輪緣外徑與驅(qū)動輪齒頂圓之間應(yīng)保留一定的間隙。在導(dǎo)向輪與驅(qū)動輪的中心距離一定的情況下，當2太大時，會減少接地長度，造成接地面積減少，接地比壓提高；而且支重輪處履帶折彎角度增大，會影響傳動效率。由《機械設(shè)計》P386表166常用旋