【導(dǎo)讀】橋式起重機(jī)運(yùn)行小車中最主要的結(jié)構(gòu)有：電動(dòng)機(jī)，減速器，聯(lián)軸器，等等。橋式起重機(jī)的小車設(shè)有起升機(jī)構(gòu)和小車運(yùn)行機(jī)構(gòu)，為使小車輪壓呈均勻分布，高度等因素進(jìn)行選擇。公稱傳動(dòng)比及齒輪參數(shù)的選擇應(yīng)遵守原則和注意事項(xiàng)。相結(jié)合的設(shè)計(jì)計(jì)算方法，其設(shè)計(jì)計(jì)算結(jié)果在該系列試驗(yàn)中得到證實(shí)。maximumtorque、dutyfator、startupfrequency、typeofcontrol、rangeofspeed. machinery，Redueer，Design，Principle，Hydrauliccoupling

　　

【正文】 定子上的旋轉(zhuǎn)磁極，這樣就增加電動(dòng)機(jī)轉(zhuǎn)子的速率直至與旋轉(zhuǎn)磁場(chǎng)同步旋轉(zhuǎn)為止。 (2)轉(zhuǎn)子不需要?jiǎng)?lì)磁的同步電機(jī) 轉(zhuǎn)子不勵(lì)磁的同步電動(dòng)機(jī)能夠運(yùn)用于單相電源上，也能運(yùn)用于多相電 源上。這種電動(dòng)機(jī)中，有一種的定子繞組與分相電動(dòng)機(jī)或多相電動(dòng)機(jī)的定子相似，同時(shí)有一個(gè)鼠籠轉(zhuǎn)子，而轉(zhuǎn)子的表面切成平面。所以是屬于顯極轉(zhuǎn)子，轉(zhuǎn)子磁極是由一種磁化鋼做成的，而且能夠經(jīng)常保持磁性。鼠籠繞組是用來產(chǎn)生啟動(dòng)轉(zhuǎn)矩的，而當(dāng)電動(dòng)機(jī)旋轉(zhuǎn)到一定的轉(zhuǎn)速時(shí)，轉(zhuǎn)子顯極就跟住定子線圈的電流頻率而達(dá)到同步。顯極的極性是由定子感應(yīng)出來的，因此它的數(shù)目應(yīng)和定子上極數(shù)相等，當(dāng)電動(dòng)機(jī)轉(zhuǎn)到它應(yīng)有的速度時(shí)，鼠籠繞組就失去了作用，維持旋轉(zhuǎn)是靠著轉(zhuǎn)子與磁極跟住定子磁極，使之同步。 綜上所訴，由于起重機(jī)的工作環(huán)境與工作條件的特殊性， 為了滿足 這些條件，使起重機(jī)能再工作中更好的發(fā)揮作用，在不浪費(fèi)功率的同時(shí)，能以最大的效率來進(jìn)行工作，同時(shí)不僅提高起重機(jī)的工作效率，更能使生產(chǎn)得到更高的保證，故， 本設(shè)計(jì)應(yīng)該選擇三相異步交流電動(dòng)機(jī) 作為電動(dòng)機(jī)。 結(jié)論 以上是本人對(duì)橋式起重機(jī)的設(shè)計(jì)及計(jì)算的全過程。在該設(shè)計(jì)中和計(jì)算過程中涉及、運(yùn)用了許多基礎(chǔ)及專業(yè)知識(shí)，如：起重運(yùn)輸機(jī)械，起重機(jī)課程設(shè)計(jì)，機(jī)械設(shè)計(jì)，機(jī)械原理，理論力學(xué)，材料力學(xué)等。并且通過文獻(xiàn)對(duì)起重機(jī)這部分也有了比較深的了解，擴(kuò)展了我的知識(shí)面，提高了自己查閱資料， 整理資料的能力。計(jì)算機(jī)繪圖和說明書使我對(duì)這些工作軟件有更加熟練的掌握、對(duì)今后的工作、學(xué)習(xí)有很大的幫助。但由于知識(shí)水平有限，在計(jì)算、設(shè)計(jì)及繪圖過程中不可避免地出現(xiàn)錯(cuò)誤，請(qǐng)各位師長(zhǎng)和專家們給予批評(píng)指正。 致謝 通過本次的畢業(yè)設(shè)計(jì)，使握對(duì)四年所學(xué)的知識(shí)有了深刻的理解。同時(shí)，通過實(shí)習(xí)，親身體驗(yàn)到理論于實(shí)際相結(jié)合的重要性。在與同學(xué)的共同討論設(shè)計(jì)過程中懂得了“團(tuán)結(jié)就是力量“和“自力更生”更深層的內(nèi)涵。 本設(shè)計(jì)在內(nèi)容上，雖然也對(duì)主要關(guān)鍵部分作了詳細(xì)分析及計(jì)算，但某些環(huán)節(jié)如超載限制器設(shè)計(jì)方面， 由于種種原因，沒有對(duì)其加深研究，并不一定適應(yīng)現(xiàn)代生產(chǎn)的要求。但我們渴望達(dá)到一定精度。對(duì)于延長(zhǎng)使用壽命，減少成本有一定幫助。但在某種程度上依然存在著失陷，所以要不斷的學(xué)習(xí)，研究，才能提高，突破。 該設(shè)計(jì)受到劉寶權(quán)，紀(jì)宏，寧曉霞，朱克剛等諸位師長(zhǎng)的精心指導(dǎo)，才使該設(shè)計(jì)得以順利完成。在此表示衷心的感謝！ 編者：李鵬 二 零零八年六月六日 參考文獻(xiàn) ［ 1］羅文新《起重運(yùn)輸機(jī)械》 冶金工業(yè)出版社 ［ 2］《起重機(jī)設(shè)計(jì)手冊(cè)》機(jī)械工業(yè)出版社 ［ 3］《起重機(jī)課程設(shè)計(jì)》冶金工程出版社 ［ 4］《機(jī)械零件設(shè)計(jì)手冊(cè)》 (下 )(第三版 )冶金工業(yè)出版社 ［ 5］《機(jī)械零件設(shè)計(jì)手冊(cè)》國(guó)防工業(yè)出版社 ［ 6］《機(jī)械零件設(shè)計(jì)手冊(cè)》 (第二版 )冶金工業(yè)出版社 附錄 Heat Transfer During the Rolling Process 1 WORKPIECE TEMPERATURE CHANGE IN HOT STRIP MILL After reheating a slab to a desired temperature, it is subjected to rolling. A rolling cycle in a typical hot strip mill includes the following main steps: Descaling of the slab prior to flat rolling by using highpressure water descaling system in bination, in some cases, with edging. Rough rolling to a transfer bar thickness which may vary from 19 to 40 mm. The rough rolling is usually acpanied by edging and inter pass descaling. Transfer of the transfer bar from roughing mill to a flying shear installed ahesd of finishing mill. The shear is usually designed to cut both head and tail ends of the bar. Descaling of the transfer bar prior to entering the finishing mill. Finish rolling to a desired thickness with a possible use of interstand descaling and strip cooling. Air and water cooling of the rolled product on runout table. Cliling of the rolled product. Various types of heat transfer from the rolled workpiece to its surrounding matter occur during the rolling cycle. Some of the lost heat is recovered by generating heat inside the workpiece during its deformation. The main ponents of the workpiece temperature loss and gain in hot strip mill are usually identified as follows: loss due to heat radiation, loss due to heat convection, loss due to water cooling, loss due to heat conduction to the work rolls and table rolls, gain due to mechanical work and friction. The analytical aspects of these ponents are briefly described below. 2 TEMPERATURE LOSS DUE TO TADIATION Two methods have been employed to derive equations for temperature loss due to radiation. In the first method, the temperature gradient within the material is assumed to be negligible. The amount of heat radiated to the environment is then calculated using the StefanBoltzmann law: d q39。r=S dtTTA ar )( 44 ?? Where rA — surface area of body subjected to radiation, m2。] d q39。r — amount of heat radiated by a body,J。 S— StefanBoltzmann constant。 T— temperature of rolled material at time,K。 Ta— ambient temperature,K。 t— time,s。 ? — emissivity. The amount of heat lost by a body d q39。r is give by: d q39。r = dTcVr? Where c— specific heart of rolled material, J/（ kgK） 。 Vr— volume of body subjected to radiation, m3 ? — density of rolled material, kg/m3。 The rate of temperature loss ar can be calculated by considering the heat balance condition d q39。r=d q39。r , and and 12: ar= )( 44arr TTcVASdtdT ?? ?? Equations for the rate of temperature loss due to radiation which have been obtained by reducing some of the known equations to a patible form with an assumption that TaT are summarized in Table 11. In the derivation of these equations, the dependency of the parameters S、 ? 、 ? and c on temperature is not taken into account. However, the variations of these constants with temperature may be significant and,therefore, the final from of 13 will depend on the average values selected for these constants. The temperature loss cT? during radiation time tr can be calculate by intergrating the differential equation: rT? =?tr rdta0 The second method of calculating temperature loss due to radiation takes into account the heat transfer along the thickness of the material. If z is the distance from the center of the body toward its surface, then from a Fourier equation we obtain: 22dzTdadtdT ? Where a— thermal diffusivity of rolled material ,m2/s The differential equation 15 can be solved numerically by the method of finite differences. The goal of these calculations is to establish a relationship between the average temperature of the material Tave which would affect the rolling deformation process and the material surface temperature Tsurface which could be measured. 3 TEMPERTURE LOSS DUE TO CONVECTION In the hot strip mill, heat transfer by convection is related to the motion of air surrounding a workpiece. This motion continuously brings new particles of air into contact with the workpiece. Depending upon whether this internal motion is forced, or free, the heat transfer is referred to as either forced or free convection. The latter is a usual case in the hot strip mills. A key factor in t