電主軸的機械設(shè)計【含9張圖紙】

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畢 業(yè) 設(shè) 計（論 文）任 務(wù) 書 　　機械工程 系（院） 20 08 屆 題 目 電 主 軸 的 設(shè) 計 學生姓名 專業(yè)班級 指導教師 職 稱 填寫日期： 2008 年 3月12日 設(shè)計（論文）依據(jù) 國內(nèi)電主軸的研究始于 2 0世紀 6 0年代 ,主要用于零件內(nèi)表面磨削 ,這種電主軸的功率低 ,剛度小。并且它采用無內(nèi)圈式向心推力球軸承 ,限制了高速電主軸的生產(chǎn)社會化和商品化。 2 0世紀 70年代后期至 80年代 ,隨著高速主軸軸承的開發(fā) ,研制了高剛度、高速電主軸 ,它被廣泛應(yīng)用于各種內(nèi)圓磨床和各個機械制造領(lǐng)域。在 2 0世紀 80年代末以后 ,由磨用電主軸轉(zhuǎn)向銑用電主軸 ,它不僅能加工各種形體復雜的模具 ,而且開發(fā)了用于木工機械用的風冷式高速銑用電主軸 ,推動了高速電主軸在銑削中的應(yīng)用。目前國內(nèi)研究高速電主軸的科研機構(gòu)有我國河南省洛陽軸承研究所 ,他們能自行研究開發(fā)電主軸 ,其DmN值達到了很高的水平 ;廣州鉅聯(lián)高速電主軸有限公司研發(fā)的大功率靜壓軸承電主軸曾獲得日內(nèi)瓦國際專利技術(shù)博覽會金獎 ;廣東工業(yè)大學高速加工和機床研究所也開發(fā)了數(shù)控銑床高速電主軸。在我國的安陽市 ,有一家中外合資的電主軸生產(chǎn)廠家———安陽萊必泰機械有限公司 ,它擁有先進的電主軸、機床主軸設(shè)計和制造技術(shù)。該公司研制生產(chǎn)的加工中心電主軸 ,采用先進技術(shù) ,配有矢量閉環(huán)控制系統(tǒng) ,能對主軸實行恒功率調(diào)速 ,準停制動?！? 國外高速電主軸技術(shù)的研究現(xiàn)狀國外高速電主軸技術(shù)由于研究較早 ,技術(shù)水平也處于領(lǐng)先地位 ,電主軸已越來越多地應(yīng)用到工業(yè)制造業(yè)中。著名的有瑞士的Fisher公司、Ibag公司、德 國的GMN公司、Hofer公司、Siemens公司、意大利Faemat公司、Gamfior公司及美國Ingersoll公司、日本Okuma公司和Fanuc公司等,它們的技術(shù)水平代表了這個領(lǐng)域的世界先進水平。并在此基礎(chǔ)之上,這些外國廠家已生產(chǎn)了多種商品化高速機床。如瑞士米克朗公司 ,就是世界上著名的精密機床制造商。它生產(chǎn)的機床配備最高達 6 0 0 0 0r/min的高速電主軸 ,可以滿足不同的切削要求 。 隨著機床技術(shù)、高速切削技術(shù)的發(fā)展和實際應(yīng)用的需要，人們對機床電主軸的性能也提出了越來越高的要求，電主軸技術(shù)的發(fā)展趨勢主要表現(xiàn)在以下幾個方面：向高速大功率和低速大轉(zhuǎn)矩方向發(fā)展，向高精度、高剛度方向發(fā)展，向精確定向（準停）方向發(fā)展，向快速起、停方向發(fā)展，向超高速方向發(fā)展，向標準化方向發(fā)展 任務(wù)要求 根據(jù)設(shè)計課題所要完成的設(shè)計任務(wù)要求，確定具體的任務(wù)要求如下： 1、熟悉設(shè)計內(nèi)容，對所要設(shè)計的課題進行分析，確定方案； 2、根據(jù)設(shè)計課題任務(wù)，要求對高速電主軸機械部分進行設(shè)計； 3、根據(jù)初步設(shè)計完成電主軸結(jié)構(gòu)草圖，在此基礎(chǔ)上完成零件圖設(shè)計； 4、要求對所要設(shè)計的電主軸軸身進行校核，使機身結(jié)構(gòu)合理具有一定的穩(wěn)定性； 5、軸身部分設(shè)計要體現(xiàn)良好的工藝性和經(jīng)濟性； 6、論文必須符合要求，不少于10000字。 進度計劃 3月23日—3月30日 熟悉設(shè)計內(nèi)容及設(shè)計要求； 3月31日—4月13日 查閱各類相關(guān)資料，進行初步設(shè)計，結(jié)構(gòu)分析，確定總體方案； 4月14日—5月4 日 進行各類設(shè)計工作并完成，同時完成論文草稿； 5月5日—5月14 日 完成設(shè)計論文，最終完成設(shè)計任務(wù)書所要求的內(nèi)容； 5月15日—5月17日 進行最后審核，準備畢業(yè)答辯工作。 任務(wù)下達人（指導教師）簽字： 年 月 日 任務(wù)接受人（學生）簽字： 年 月 日 教研室主任簽字： 年 月 日 說明：該任務(wù)書每生一式兩份，簽字有效，一份系（院）存檔，一份學生留存。 畢業(yè)設(shè)計（論文）外文參考文獻翻譯 機械工程 系（院） 20 08 屆 題 目（中文） 電主軸的機械設(shè)計 （英文）the mechanic designs of electric spindles 學生姓名 專業(yè)班 完成日期： 2008 年 3月 23 日 目 錄 1. 電主軸技術(shù)水平分析………………………………………………（8） 2. 高速電主軸單元…………………………………………………（14） The electrical technical level of main shaft is analysed Abstract: Electrical main shaft is the processing machine tool of numerical control " heart parts ", this paper has introduced typical structure and the working principle of electrical main shaft , has elaborated the crucial technology of electrical main shaft , has summarized it to develop tendency. Keyword: The electrical porcelain ball of main shaft mix the bearing lubrication of oil gas 1, it is general to state the processing quality that can not only raise processing efficiency substantially because of high speed processing and can still raise workpiece apparently, so, its application field is very extensive , is especially in aerospace , the manufacturing industries such as automobile and mould in. It is spoilt recently that so, the machine tool of numerical control that has high speed process capability has become market. Now, the domestic and international each famous manufacturer of machine tool adopts the electrical structure of main shaft extensively in the machine tool of numerical control , is especially being compound to process machine tool and much axle to unite to move , polyhedron processing machine tool and the machine tool of parallel connection in. Electrical main shaft is the processing machine tool of numerical control " heart parts ", its performance index direct decision the level of machine tool, it is that machine tool realizes basic condition and the prerequisite of high speed processing. 2 the working principle electrical main shaft of the working principle, typical structure and 2.1 advantage electrical main shafts of electrical main shaft is the direct motor rotor of be hollow pack in main shaft on, stator knows super-cooling but cover fixes , form a complete unit of main shaft in the casing hole of main shaft, after starting eclectricity rotor directly drive the operation of main shaft. The typical structural layout way of the typical structural electrical unit of main shaft of 2.2 electrical main shafts is that generator sets up before main shaft , rear axle Cheng between ( as picture show ), its advantage is that the axial size of the unit of main shaft is the big, medium-sized machine tool of numerical control short comparatively, the rigidity of main shaft big, power suits comparatively; It is insufficient to be the naturally scattered hot condition in the generator in the casing of main shaft that encloses to differ from , has higher temperature rise. The 1 casings of main shaft the 2 cooling sets of 3 4 5 import stator rotors of cooling water the 6 sets of 7 8 9 10 former 11 can export feedback installation bearing rear axles of cooling water of runner shaft of main shaft of main shaft Cheng the advantage electrical province of main shaft of 2.3 electrical main shafts have gone to take ship or positive drive, the 0 transmissions that have realized machine tool have raised transmission efficiency. The rigidity of electrical main shaft good, rotary precision is sex high respond fast good, can realize very high rotational speed and add and slow down degree and decide angle stop fast definitely ( C axle control ), the scope of speed adjustment is wide. 3, the crucial technical concept of " electrical main shaft " of electrical main shaft should not be simple to understand for the merely a sleeve of main shaft , and should be a set of assembly, include: Stator, rotor, bearing, the high speed installation of frequency conversion and lubrication install and cool installation. Therefore electrical main shaft is the with high speed bearing technical, lubrication technical, cooling technical technical, precise production of dynamic balancing with the technologies such as assembly technology as well as generator high speed drive synthesize to utilize. The with high speed bearing technology of 3.1 electrical main shafts realizes the electrical high speed of main shaft to melt, is precise and crucial to be the application of high speed precise bearing. Now the bearing that applied in high speed precise electrical main shaft have precise roll bearing and liquid movement press bearing and gas press bearing and magnetic suspension bearing quietly, but it is precise angle contact porcelain ball bearing and precise cylinder roller bearing mainly. It is high that liquid movement press the standardization level of bearing; Gas presses bearing quietly to be improper for in the rate occasion of great merit; Magnetic suspension bearing because of control system complex, price is expensive , its practicality gets restriction. Angle contact ball bearing can not only at the same time bear radial and axial load, and rigidity high, high speed performance good, structural simple compact, kind specifications numerous repair easily to change, thus in electrical main shaft, get extensive application. Now along with the development of porcelain bearing technology, the electrical bearing of main shaft of the most application is to mix porcelain ball bearing, roll body use Si3N4 porcelain ball, with the structure of " little pearl dense pearl ", bearing ferrule encloses for GCr15 steel. Is this kind of to mix bearing to pass to reduce little centrifugal force and top moment , reduce the friction between little ball and raceway groove , so get lower temperature rise and better high speed performance. Porcelain ball mix bearing and steel ball bearing compare , advantage is as follows: ( 1 ) the porcelain ball bearing friction performance of porcelain and steel composition very good, can reduce the stress of material and lubricant. ( 2 ) because of porcelain density low , can reduce the centrifugal force in operation. ( 3 ) the heat with lower porcelain coefficient of expansion have reduced bearing efficiently add the change of load in advance. ( 4 ) the flexible mould of porcelain quantity higher, can raise the rigidity of bearing. Above-mentioned factor have prolonged the life of bearing substantially with have promoted the operation limit speed of bearing. The lubrication technical with high speed electrical main shaft of 3.2 electrical main shafts the temperature rise that must control bearing with reasonable, controallable bearing lubrication way , in order to guarantee stability and the precision of the machining complex of numerical control of machine tool. Adopt to roll the lubrication way of the electrical main shaft of bearing now have the waies such as fat lubrication, oil fog lubrication and the lubrication of oil gas mainly. Fat lubrication in the electricity with relatively lower rotational speed main shaft in is more common lubrication way. The lubrication system of fat lubrication type electrical main shaft is simple , uses convenience and free from contamination , has strong versatility. Oil fog lubrication has lubrication and cooling double role, it is taking compressed air as power , mixes oil liquid atomization into air through oil fog ware to flow , then transports it to need the location of lubrication. The equipment needed by oil fog lubrication is simple , maintenance convenience has more cheap price , is a kind of with high speed electrical lubrication way of main shaft that used generally. But it has pollutive environment, oil consume more higher shortcoming. Along with the raising that people ask for environmental protection, oil fog lubrication way must be superseded gradually. The lubrication technology of oil gas is use compressed air the lubricating oil of be trace difference succession continuously land provide each set of bearing of main shaft accurately, small oil drop in roll with , outside raceway between form the flexible oil membrane of dynamic pressure, and reduce air can take the partial heats produced by bearing operation. Practice shows that the fuel delivery in lubrication is been harmful for too much less , and former two lubrication waies can not control the amount of fuel delivery accurately , disadvantage in the raising of the bearing rotational speed and life of main shaft. And develop the lubrication way of oil gas of geting up recently the lubricating oil that can control the point of every friction accurately quantity, reliability is very high. Practice proof and the lubrication of oil gas are the most ideal method of lubrication of great merit of the rate electrical bearing of main shaft, but the equipment needed by it is complex , cost is high. Because of the lubrication way lubrication effect ideal of oil gas, now have become international the last most popular lubrication way. Its cooling electrical main shaft and the analysis of thermal source of 3.3 electrical main shafts have two major internal thermal sources: Built-in motor give out heat with the bearing of main shaft give out heat. If not control , from the heat that this arouses warp can the serious processing precision and bearing service life that reduces machine tool , so, the service life that causes electrical main shaft shortens. Electrical main shaft because of the depository type configuration of main shaft in adopting, locate in the generator in the unit of main shaft can not break up with fan heat, therefore naturally, scattered hot condition is lacked comparatively. Generator is realizing energy transition , is internal to produce power loss , so makes generator give out heat. Study to show , is under generator with high speed operation condition , have near 1/3 generator give out heat quantity from generator rotor produce , and the absolutely most of heats that rotor produces are passed through the air gap between rotor and stator in stator; Others 2/3 the stator that heat produces in generator. So produce the major solution method of giving out heat for generator is the cycle for that generator stator adopts cooling fluid flow to carry out force to cool. Typical cooling system is to cool generator stator with the water type cooling installation of outer circulation , goes to the heat tape of generator. What angle contact ball bearing give out heat , is roller mainly under high speed and the rolling friction between raceway, the etc. that receive the top sliding friction that moment produces as well as the viscous friction of lubricating oil produce. Reduce little bearing to give out heat the major measure of quantity: ( 1 ) reduce the diameter of little ball properly reduce little ball diameter can reduce little centrifugal force and top moment, so, reduce little friction, quantity decreases to give out heat. ( 2 ) adopt new material for example adopt porcelain material do ball, porcelain ball bearing and steel quality angle contact ball bearing are compared with , when high speed turns around ball and raceway between roll with sliding friction reduce little, give out heat to measure reduction. ( 3 ) the lubrication way oil gas of reasonable adopting and the lubrication waies such as oil fog for bearing not only have lubrication role, still have certain cooling role. Service life and the performance of 3.4 electrical main shafts that design and assembly electrical main shaft will get must carry out elaborate design and production for the electrical every part of main shaft. The stator of electrical main shaft from have is high Dao the high quality flat of silicon steel of magnetic rate press repeatedly, in stator cavity have to rush system inlay line groove. Rotor from rotor core, squirrel cage and runner shaft 3 partial groups become. Location precision and the size precision of the case of main shaft will also directly affect the comprehensive precision of main shaft. Usually directly design bearing hole in the case of main shaft on, to add to pack generator stator must open at least one end. When the high speed of main shaft spins , any unbalanced quality of Xiao De arouses the vibration of high frequency of big electrical main shaft. Therefore the precision requirement of dynamic balancing of precise electrical main shaft reach G1 G0. 4 levels. For the dynamic balancing of this kind of grade, with conventional method, it is the insufficient dynamic balancing that need to still carry out whole after assembling to carry out dynamic balancing only respectively before assembling for every element on main shaft, even still design special voluntarily balanced system to realize the online dynamic balancing of main shaft. Additionally, when designing electrical main shaft must comply with structural symmetrical principle, key coupling and thread coupling strictly in electrical main shaft on have been prohibited use, and have adopted profit coupling generally, realize torque with this transmit. After profit coupling and thread coupling or key coupling compare have: Will not produce curved and torsion stress on main shaft, as the revolving precision of main shaft does not affect; the sport control of 3.5 little electrical main shafts in the machine tool of numerical control in, electrical main shaft usually adopts the method of frequency control. Now, there are the ordinary drive and control of frequency conversion mainly , direct torque and control as well as the drive of vector control actuator control 3 kinds of control way. Ordinary frequency conversion is scalar drive and control, it drives to control property, export power and rotational speed for permanent torque drives into direct ratio. It is thought of that the development performance of the ordinary control of frequency conversion is not enough to manage , in low speed, control performance is not good, export power is not enough to stabilize , also does not have C axle function. But price is cheap , has simple structure , is used in grinding machine and ordinary with high speed milling machine etc. normally. Vector control technology imitate the control of the motivation of direct current, with rotor magnetic field it is directional , use vector the method of alternating come to realize drive and control, have good development performance. Vector control actuator has great torque value when just starting , besides, electrical main shaft has simple structure and very little inertia, so, it is big to start acceleration, can realize to start after instant reach promise limit speed. It is two that this kind of actuator also have open loop and closed circuit, the latter can realize the feedback of location and speed , not only has better development performance , can still realize C axle function; And the development performance of the former is lacked , also does not have C axle function , but has relatively cheap price. Directly torque control develops after being then vector control technology, is another as geting up to grow the new high performance alternating technology of speed adjustment, its control thought is novel , construction of system is succinct and clear , more suits the drive of high speed electrical main shaft , can more satisfy the with high speed electrical high rotational speed of main shaft, the wide scope of speed adjustment and high speed instant to allow the requirement of development property and the property of static quiet that stops , has become a hot technology of alternating transmission field. 4 electrical main shaft develop tendency along with the high speed and technology of machine tool cut the needs of actual application and the development of technology, people have also put forward more and more high requirement for the performance of the electrical main shaft of machine tool, the technology of electrical main shaft develop tendency major expression in some following aspects: ( 1 ) to the at low speed big torque direction development and rate of great merit ( 2 ) to high accuracy and high rigidity direction development ( 3 ) to accurately directional( stop definitely) direction development ( 4 ) to fast from , stop direction development ( 5 ) to exceed with high speed direction development ( 6 ) to standardization direction development 。 電主軸技術(shù)水平分析 摘要：電主軸是高速數(shù)控加工機床的“心臟部件”，本文介紹了電主軸的工作原理、典型結(jié)構(gòu)，闡述了電主軸的關(guān)鍵技術(shù)，總結(jié)了其發(fā)展趨勢。 關(guān)鍵詞：電主軸 陶瓷球混合軸承 油氣潤滑 1、概述 由于高速加工不但可以大幅度提高加工效率，而且還可以顯著提高工件的加工質(zhì)量，所以其應(yīng)用領(lǐng)域非常廣泛，特別是在航空航天、汽車和模具等制造業(yè)中。于是，具有高速加工能力的數(shù)控機床已成為市場新寵。目前，國內(nèi)外各著名機床制造商在高速數(shù)控機床中廣泛采用電主軸結(jié)構(gòu)，特別是在復合加工機床、多軸聯(lián)動、多面體加工機床和并聯(lián)機床中。電主軸是高速數(shù)控加工機床的“心臟部件”，其性能指標直接決定機床的水平，它是機床實現(xiàn)高速加工的前提和基本條件。 2、電主軸的工作原理、典型結(jié)構(gòu)及優(yōu)點 2.1 電主軸的工作原理 電主軸就是直接將空心的電動機轉(zhuǎn)子裝在主軸上，定子通過冷卻套固定在主軸箱體孔內(nèi)，形成一個完整的主軸單元，通電后轉(zhuǎn)子直接帶動主軸運轉(zhuǎn)。 2.2電主軸的典型結(jié)構(gòu) 電主軸單元典型的結(jié)構(gòu)布局方式是電機置于主軸前、后軸承之間，其優(yōu)點是主軸單元的軸向尺寸較短，主軸剛度大，功率大，較適合于大、中型高速數(shù)控機床；其不足是在封閉的主軸箱體內(nèi)電機的自然散熱條件差，溫升比較高。 2.3電主軸的優(yōu)點 電主軸省去了帶輪或齒輪傳動，實現(xiàn)了機床的“零傳動”，提高了傳動效率。電主軸的剛性好、回轉(zhuǎn)精度高、快速響應(yīng)性好，能夠?qū)崿F(xiàn)極高的轉(zhuǎn)速和加、減速度及定角度的快速準停（C軸控制），調(diào)速范圍寬。 3、電主軸的關(guān)鍵技術(shù) “電主軸”的概念不應(yīng)簡單理解為只是一根主軸套筒，而應(yīng)該是一套組件，包括：定子、轉(zhuǎn)子、軸承、高速變頻裝置、潤滑裝置、冷卻裝置等。因此電主軸是高速軸承技術(shù)、潤滑技術(shù)、冷卻技術(shù)、動平衡技術(shù)、精密制造與裝配技術(shù)以及電機高速驅(qū)動等技術(shù)的綜合運用。 3.1電主軸的高速軸承技術(shù) 實現(xiàn)電主軸高速化精密化的關(guān)鍵是高速精密軸承的應(yīng)用。目前在高速精密電主軸中應(yīng)用的軸承有精密滾動軸承、液體動靜壓軸承、氣體靜壓軸承和磁懸浮軸承等，但主要是精密角接觸陶瓷球軸承和精密圓柱滾子軸承。液體動靜壓軸承的標準化程度不高；氣體靜壓軸承不適合于大功率場合；磁懸浮軸承由于控制系統(tǒng)復雜，價格昂貴，其實用性受到限制。 角接觸球軸承不但可同時承受徑向和軸向載荷，而且剛度高、高速性能好、結(jié)構(gòu)簡單緊湊、品種規(guī)格繁多、便于維修更換，因而在電主軸中得到廣泛的應(yīng)用。目前隨著陶瓷軸承技術(shù)的發(fā)展，應(yīng)用最多的電主軸軸承是混合陶瓷球軸承，即滾動體使用Si3N4陶瓷球，采用“小珠密珠”結(jié)構(gòu)，軸承套圈為GCr15鋼圈。這種混合軸承通過減小離心力和陀螺力矩，來減小滾珠與溝道間的摩擦，從而獲得較低的溫升及較好的高速性能。 陶瓷球混合軸承與鋼球軸承相比，優(yōu)點如下： （1）陶瓷與鋼組成的陶瓷球軸承摩擦性能非常好，能降低材料與潤滑劑的應(yīng)力。 （2）因陶瓷密度低，可降低運轉(zhuǎn)時的離心力。 （3）陶瓷較低的熱膨脹系數(shù)有效降低了軸承預(yù)加負荷的變化。 （4）陶瓷的彈性模量較高，可以提高軸承的剛性。 上述因素大幅度地延長了軸承的壽命和提升了軸承的運轉(zhuǎn)極限速度。 3.2電主軸的潤滑技術(shù) 高速電主軸必須采用合理的、可控制的軸承潤滑方式來控制軸承的溫升，以保證數(shù)控機床工藝系統(tǒng)的精度和穩(wěn)定性。采用滾動軸承的電主軸的潤滑方式目前主要有脂潤滑、油霧潤滑和油氣潤滑等方式。 脂潤滑在轉(zhuǎn)速相對較低的電主軸中是較常見的潤滑方式。脂潤滑型電主軸的潤滑系統(tǒng)簡單、使用方便、無污染、通用性強。 油霧潤滑具有潤滑和冷卻雙重作用，它以壓縮空氣為動力，通過油霧器將油液霧化并混入空氣流中，然后把其輸送到需要潤滑的位置。油霧潤滑所需設(shè)備簡單，維修方便，價格比較便宜，是一種普遍使用的高速電主軸潤滑方式。但它有污染環(huán)境，油耗比較高等缺點。隨著人們對環(huán)保要求的提高，油霧潤滑方式必將逐漸被淘汰。 油氣潤滑技術(shù)是利用壓縮空氣將微量的潤滑油分別連續(xù)不斷地、精確地供給每一套主軸軸承，微小油滴在滾動和內(nèi)、外滾道間形成彈性動壓油膜，而壓縮空氣則可帶走軸承運轉(zhuǎn)所產(chǎn)生的部分熱量。 實踐表明在潤滑中供油量過多或過少都是有害的，而前兩種潤滑方式均無法準確地控制供油量多少，不利于主軸軸承轉(zhuǎn)速和壽命的提高。而新近發(fā)展起來的油氣潤滑方式則可以精確地控制各個摩擦點的潤滑油量，可靠性極高。實踐證明，油氣潤滑是高速大功率電主軸軸承的最理想潤滑方法，但其所需設(shè)備復雜，成本高。由于油氣潤滑方式潤滑效果理想，目前已成為國際上最流行的潤滑方式。 3.3電主軸的熱源分析及其冷卻 電主軸有兩個主要的內(nèi)部熱源：內(nèi)置電動機的發(fā)熱和主軸軸承的發(fā)熱。如果不加以控制，由此引起的熱變形會嚴重降低機床的加工精度和軸承使用壽命，從而導致電主軸的使用壽命縮短。 電主軸由于采用內(nèi)藏式主軸結(jié)構(gòu)形式，位于主軸單元體中的電機不能采用風扇散熱，因此自然散熱條件較差。電機在實現(xiàn)能量轉(zhuǎn)換過程中，內(nèi)部產(chǎn)生功率損耗，從而使電機發(fā)熱。研究表明，在電機高速運轉(zhuǎn)條件下，有近1/3的電機發(fā)熱量由電機轉(zhuǎn)子產(chǎn)生，并且轉(zhuǎn)子產(chǎn)生的絕大部分熱量都通過轉(zhuǎn)子與定子間的氣隙傳入定子中；其余2/3的熱量產(chǎn)生于電機的定子。所以，對電機產(chǎn)生發(fā)熱的主要解決方法是對電機定子采用冷卻液的循環(huán)流動來實行強制冷卻。典型的冷卻系統(tǒng)是用外循環(huán)水式冷卻裝置來冷卻電機定子，將電機的熱量帶走。 角接觸球軸承的發(fā)熱主要是滾子與滾道之間的滾動摩擦、高速下所受陀螺力矩產(chǎn)生的滑動摩擦以及潤滑油的粘性摩擦等產(chǎn)生的。減小軸承發(fā)熱量的主要措施： （1）適當減小滾珠的直徑 減小滾珠直徑可以減小離心力和陀螺力矩，從而減小摩擦，減少發(fā)熱量。 （2）采用新材料 比如采用陶瓷材料做滾珠，陶瓷球軸承與鋼質(zhì)角接觸球軸承相比，在高速回轉(zhuǎn)時，滾珠與滾道間的滾動和滑動摩擦減小，發(fā)熱量降低。 （3）采用合理的潤滑方式 油氣和油霧等潤滑方式對軸承不但具有潤滑作用，還具有一定的冷卻作用。 3.4電主軸的設(shè)計和裝配 電主軸要獲得好的性能和使用壽命，必須對電主軸各個部分進行精心設(shè)計和制造。電主軸的定子由具有高導磁率的優(yōu)質(zhì)矽鋼片迭壓而成，定子內(nèi)腔帶有沖制嵌線槽。轉(zhuǎn)子由轉(zhuǎn)子鐵芯、鼠籠和轉(zhuǎn)軸三部分組成。主軸箱的尺寸精度和位置精度也將直接影響主軸的綜合精度。通常將軸承座孔直接設(shè)計在主軸箱上，為加裝電機定子，必須至少開放一端。 主軸高速旋轉(zhuǎn)時，任何小的不平衡質(zhì)量即可引起電主軸大的高頻振動。因此精密電主軸的動平衡精度要求達到G1~G0.4級。對于這種等級的動平衡，采用常規(guī)的方法即僅在裝配前對主軸上的每個零件分別進行動平衡是遠遠不夠的，還需在裝配后進行整體的動平衡，甚至還要設(shè)計專門的自動平衡系統(tǒng)來實現(xiàn)主軸的在線動平衡。另外，在設(shè)計電主軸時，必須嚴格遵守結(jié)構(gòu)對稱原則，鍵聯(lián)接和螺紋聯(lián)接在電主軸上被禁止使用，而普遍采用過盈聯(lián)接，并以此來實現(xiàn)轉(zhuǎn)矩的傳遞。過盈聯(lián)接與螺紋聯(lián)接或鍵聯(lián)接相比有：不會在主軸上產(chǎn)生彎曲和扭轉(zhuǎn)應(yīng)力，對主軸的旋轉(zhuǎn)精度沒有影響；主軸的動平衡易得到保證等優(yōu)點。轉(zhuǎn)子與轉(zhuǎn)軸之間的過盈聯(lián)接分為兩類，一類是通過套筒實現(xiàn)的，此結(jié)構(gòu)便于維修拆卸；另一類是沒有套筒，轉(zhuǎn)子直接過盈聯(lián)接在轉(zhuǎn)軸上，此類聯(lián)接轉(zhuǎn)子裝配后不可拆卸。由于內(nèi)孔與轉(zhuǎn)軸配合面之間有很大的過盈量，所以轉(zhuǎn)子與轉(zhuǎn)軸可以采用轉(zhuǎn)軸冷縮和轉(zhuǎn)子熱脹法裝配。帶有套筒的聯(lián)接拆卸時，需向轉(zhuǎn)子套筒上預(yù)留的油孔中高壓注油，迫使轉(zhuǎn)子的過盈套筒漲開，即可順利拆卸下電機的轉(zhuǎn)子。電機定子通過一個冷卻套固定裝在電主軸的箱體中。 3.5電主軸的運動控制 在數(shù)控機床中，電主軸通常采用變頻調(diào)速方法。目前主要有普通變頻驅(qū)動和控制、矢量控制驅(qū)動器的驅(qū)動和控制以及直接轉(zhuǎn)矩控制三種控制方式。 普通變頻為標量驅(qū)動和控制，其驅(qū)動控制特性為恒轉(zhuǎn)矩驅(qū)動，輸出功率和轉(zhuǎn)速成正比。普通變頻控制的動態(tài)性能不夠理想，在低速時控制性能不佳，輸出功率不夠穩(wěn)定，也不具備C軸功能。但價格便宜、結(jié)構(gòu)簡單，一般用于磨床和普通的高速銑床等。 矢量控制技術(shù)模仿直流電動機的控制，以轉(zhuǎn)子磁場定向，用矢量變換的方法來實現(xiàn)驅(qū)動和控制，具有良好的動態(tài)性能。矢量控制驅(qū)動器在剛啟動時具有很大的轉(zhuǎn)矩值，加之電主軸本身結(jié)構(gòu)簡單，慣性很小，故啟動加速度大，可以實現(xiàn)啟動后瞬時達到允許極限速度。這種驅(qū)動器又有開環(huán)和閉環(huán)兩種，后者可以實現(xiàn)位置和速度的反饋，不僅具有更好的動態(tài)性能，還可以實現(xiàn)C軸功能；而前者動態(tài)性能稍差，也不具備C軸功能，但價格較為便宜。 直接轉(zhuǎn)矩控制是繼矢量控制技術(shù)之后發(fā)展起來的一種新型的高性能交流調(diào)速技術(shù)，控制思想新穎，系統(tǒng)結(jié)構(gòu)簡潔明了，適合于高速電主軸的驅(qū)動，能滿足高速電主軸高轉(zhuǎn)速、寬調(diào)速范圍、高速瞬