裝配圖ZL05微型輪式裝載機總體設計,裝配,zl05,微型,輪式,裝載,總體,整體,設計 本科生畢業(yè)設計（論文） 開題報告 學生姓名：李鑫 學 號：14020926 班 級：140209 專 業(yè)：機械工程及自動化 指導教師：李 風 畢業(yè)設計（論文）開題報告 一、課題介紹 1.課題名稱： ZL05微型輪式裝載機總體設計 2.課題背景： ⑴ 設計課題的意義 ZL系列輪式裝載機是一種高效率的工程機械，具有結構先進，性能可靠，機動性強，操縱方便等優(yōu)點。廣泛應用于礦山，建筑工地，道路修建，水利工程，港口，貨場，電站以及其他工業(yè)部門，進行裝載、推土、鏟挖、起重、牽引等多種作業(yè)。對加快工程建設速度減輕勞動強度提高工程質量降低工程成本都發(fā)揮著重要作用，因此近幾年來無論在國內還是國外裝載機品種和產(chǎn)量都得到迅速發(fā)展，成為工程機械的主導產(chǎn)品之一。 為適應工程施工，市政建設及農用水利工地的砂石、灰土等各種散裝物料的裝運需要，提出設計小型輪式裝載機的任務。 ⑵ 設計課題的目的 輪式裝載機總體設計是機械制造，機械設計和機械電子（機電一體化）等專業(yè)的一個重要的教學環(huán)節(jié)，是學完技術基礎課及有關專業(yè)課以后的一次專業(yè)課程內容的綜合設計。通過設計提高學生的機構分析與綜合的能力，機械構造設計的能力，機電一體化系統(tǒng)設計能力，掌握實踐生產(chǎn)過程自動化的設計方法。通過設計把有關課程（機械原理，機械設計，理論力學，材料力學，液壓與氣動技術，工程材料，材料成型，自動控制理論，測試技術，數(shù)控技術，微型計算機原理及應用，自動機械設計等）中所獲得的理論知識在實際中綜合的加以運用，使這些知識得到鞏固和發(fā)展，并使理論知識和生產(chǎn)密切的結合起來。 輪式裝載機總體設計是機械設計及機械制造專業(yè)和機械電子專業(yè)的學生一次比較完整的整機設計。通過設計，培養(yǎng)學生獨立的機械整機設計的能力，樹立正確的設計思想，掌握機械產(chǎn)品設計的基本方法和步驟。通過設計使學生能熟練的應用有關參考資料，計算圖表，手冊，圖冊和規(guī)范；熟悉有關國家標準，以完成一個工程技術人員在機械整體設計方面所必須具備的基礎技能訓練。 ⑶ 輪式裝載機的發(fā)展現(xiàn)狀 1）國外輪式裝載機的發(fā)展現(xiàn)狀 1 新產(chǎn)品不斷推出 近年來，輪式裝載機以圍繞提高效率、降低成本為核心，繼續(xù)向大型化、微型化發(fā)展，不斷推出新產(chǎn)品，加速更新?lián)Q代。 卡特彼勒公司90年代初推出Cat966F輪式裝載機，時隔1年又推出Cat980F輪式裝載機，它增加了斗容和功率。改善了性能、提高了可靠性。不久又推出更大的Cat994輪式裝載機，根據(jù)物料體積質量不同而選配l8～ 30m3的鏟斗，機重170t；裝有渦輪增壓后冷的Cat3516型柴油發(fā)動機牽引力大、加速性能好；加長的工作動臂增加了卸載高度，能對載重量218t的大型自卸汽車裝載。 馬拉松?勒圖爾勒(Marathon Letourneau)公司1990年和1994年在LI100的基礎上分別推出LI400和LI800型輪式裝載機。l998年9月在美國塔克癬(Tucson)召開的Longding 2000年會上，該公司宣布正在開發(fā)的斗容20．4m3的L1350型輪式裝載機將于21世紀初投放市場，供載重量150～200t自卸汽車裝載。 德雷塞(Dresser)公司90年代初推出4000型輪式裝載機，斗容10～30m3、機重151．8t，采用模塊結構的傳動系統(tǒng)，大功率、敏感按鈕控制的液壓系統(tǒng)．z型單搖臂工作裝置。優(yōu)化的整體結構和濕式盤式制動器，具有自動調節(jié)和自動密封性能。 目前，全世界約有400臺(功率大于750kw)大型輪式裝載機應用在露天礦山和建筑工程，與大型自卸汽車配套使用。在發(fā)展大型輪式裝載機的同時，微型輪式裝載機以機動靈活、效率高、多功能和價格低廉贏得市場，發(fā)展甚快。如：日本古河公司生產(chǎn)的FL30-1型輪式裝載機斗容0．34m3、機重2．3t；小松公司的WA30-1型斗容0．34rn3、柴油機功率20kW；豐田織機公司的斗容0．17m3、機重1t等這些微型裝載機適用于建筑工地和地下礦山挖溝、平地、堆料等。 2 新結構不斷涌現(xiàn) 2．1 工作機構 卡特技勒公司推出組合式八桿機構。從地面到整個舉升高度范圍內具有平行移動的特點。它將快速連接器和塔架式機構設計成整體式工作裝置，通過快速更換不同的輔助機構完成裝卸、堆垛、掃雪、平地、清掃路面、推土、吊裝、搬運和地表鉆孔等作業(yè)，實現(xiàn)一機多能，減少用戶設備投資。 德雷塞公司開發(fā)Z型單臂工作機構并與高壓液壓系統(tǒng)相結臺，為鏟斗提供更大的掘起力；縮短裝載工作循環(huán)，增加鏟斗裝滿系數(shù)，大幅度提高勞動生產(chǎn)率。由于鉸點少、桿件少，便于維修保養(yǎng)，降低維修費用。 2．2 傳動機構 以卡特彼勒公司為代表的輪式裝載機采用液力機械傳動系統(tǒng)，其自動動力換檔變速箱自動選擇檔位傳動比，使換檔在變速箱最佳效率點進行。該公司最近推出的STIC(轉向變速集成)系統(tǒng)，將轉向和換檔功能集成于一操縱手柄上，使操縱更加省力、輕便，換檔更加平穩(wěn)，可大幅度提高生產(chǎn)率。 以日本小松公司W(wǎng)A系列中小功率(小于125kW)為代表的輪式裝載機采用新型集中式結構的驅動橋。它將主傳動制動器和行星輪式終傳動都集中在橋的中部，橋殼斷面變化連續(xù)、平緩，內應力分布臺理，從根本上防止因傳統(tǒng)結構橋殼在輪邊支承軸段應力集中斷裂。輪端采用浮動密封結構，安裝簡便，有自動補償功能，密封性能良好。該結構設計合理、基本零件少、工藝性好、性能好、可靠性高。 馬拉松?勒圖爾勒公司的輪式裝載機采用柴油機一發(fā)電機一電動輪傳動，比液力機械傳動系統(tǒng)簡單。在整個作業(yè)中柴油發(fā)動機以恒定轉速運轉，減少燃油消耗，延長發(fā)動機壽命；無變速箱、傳動軸等許多部件，提高了傳動效率，操作維修方便，費用低；獨立電動牽引馬達為固態(tài)控制，反應迅速，減少車輪打滑和輪胎過渡磨損；設置了電動緩行器，不用工作制動停機，裝料對位準確；整機重心低，行駛穩(wěn)定性好，可靠性高。 2．3 液壓系統(tǒng) 德雷塞公司輪式裝載機液壓系統(tǒng)用傳感器接受柴油機轉速信號，當轉速下降時柱塞式變量泵便自動增加轉向系統(tǒng)流量，以保持恒定的轉向速度，在最大挖掘工況時可減少流量，減慢液壓元件動作，以保持液壓系統(tǒng)的動力平衡，減少液壓系統(tǒng)熱損耗，節(jié)省功率?？ㄌ乇死蛰喪窖b載機轉向液壓系統(tǒng)用負荷傳感式溢流閥，使液壓泵在負載決定壓力下溢流，降低系統(tǒng)壓力，提高了液壓元件壽命。工作裝置液壓系統(tǒng)采用舉升限位裝置和下放自動定位裝置，避免了機械限位時液壓缸行程終了產(chǎn)生高壓和沖擊；裝設的蓄能器能吸收沖擊載荷，并對整機的縱向搖擺起阻尼作用；液壓缸導向套處有三重密封，防止泄漏和肪塵。 2．4 司機室 新型輪式裝載機司機室的設計充分考慮了人的生理需求，對儀表位置排列、操作手柄和踏板、司機座椅、能見度、防噪和隔振、溫度調節(jié)等均符臺人機工程學，使司機在舒適、輕松、安全環(huán)境下操作，提高工作效率。如卡特彼勒輪式裝載機的司機室設有微機監(jiān)控裝置和可調懸掛式座椅，先導液壓閥操縱鏟斗控制手柄及流量放大轉向系統(tǒng)等，使操作輕便、靈活，采用防滾翻保護結構(ROPS)和落體撞擊保護結構(FOPS)符臺ISO標準要求。 3自動化水平不斷提高 微電子技術的突破性進展為輪式裝載機自動控制、狀態(tài)監(jiān)測及視線范圍內遙控技術的發(fā)展創(chuàng)造了條件。柴油發(fā)動機自動控制噴油系統(tǒng)、變速箱自動控制換檔、性能參數(shù)和狀態(tài)監(jiān)測均取得重大進展，在視線內遙控作業(yè)已進入實用階段，從而改善了性能，提高了可靠性，縮短了停機時間，增加了生產(chǎn)能力，降低了燃油消耗，取得了更大的經(jīng)濟效益。 3．1 柴油發(fā)動機自動控制噴油系統(tǒng) 卡特彼勒Cat994D型裝載機采用了Cat3516B型柴油發(fā)動機，裝有HEUI型電控噴油系統(tǒng)，根據(jù)外載荷有效控制功率和轉速，發(fā)動機噴油泵隨調速器動作，精確地對燃油進行調節(jié)、加壓和供油，降低初始噴油速率，減少NO 和HC，噪聲小，燃油效率高。 3．2 變速箱自動控制換檔 日本川崎重工公司的KLD97ZⅢ型輪式裝載機采用自動控制換檔的變速箱，可按裝載機運轉工況自動選擇最佳檔位，用微機控制離臺器，從而簡化操作、提高作業(yè)效率、減少沖擊，實現(xiàn)平穩(wěn)換檔；電子控制裝置、傳感器等使用可靠，一旦控制系統(tǒng)發(fā)生故障，可用手動換檔，不影響工作。 3．3 設備狀態(tài)監(jiān)測 卡特彼勒開發(fā)的電子監(jiān)控(EMS)系統(tǒng)對輪式裝載機主要系統(tǒng)出現(xiàn)故障或潛在問題提出警告和顯示，有三種不同的警告級別和信號，每種信號表明系統(tǒng)的狀態(tài)和司機應采取的適當措施。 3．4 機載電子稱重系統(tǒng) 目前，許多大型輪式裝載機都裝設機載電子稱重系統(tǒng)，能清楚地顯示出需再裝的物料量，從而使心中有數(shù)，以防止過載或欠載，減少無效跑車次數(shù)，節(jié)省作業(yè)時間，提高生產(chǎn)效率。并可對質量累計計算顯示儀表以彩色數(shù)碼顯示，清楚明了，校準簡便，誤差為±3％以內。 2）國內輪式裝載機的發(fā)展現(xiàn)狀 在今后相當長的時間內，輪式裝載機仍將是工程建設機械中最重要的機種之一，國內年需求量持續(xù)穩(wěn)定地保持在一較高水平，但國內裝載機生產(chǎn)廠家也在急劇膨脹，競爭更趨激烈，各生產(chǎn)廠家紛紛開發(fā)新產(chǎn)品，來迎接市場的挑戰(zhàn)。 ①3t以下裝載機 3t以下產(chǎn)品主要以ZL10、ZL15、ZL16為代表，還有一些利用拖拉機底盤改裝的小型裝載機，主要與日益增多的農用運輸車輛配套使用。主要零部件均采用一般性能及質量的發(fā)動機、驅動橋、變速箱、液壓件。技術較先進的靜液壓傳動產(chǎn)品，液壓件國內不易配套，產(chǎn)品成本居高不下，制約了該類產(chǎn)品在國內的發(fā)展。 ②ZL30裝載機 ZL30裝載機主要生產(chǎn)廠家有成工、常林、徐工、宜工、山工等。該產(chǎn)品零部件配置較零亂，生產(chǎn)廠家具有自制的橋箱，風格各具特色，質量及性能上相對穩(wěn)定，技術先進性一般。徐工最近開發(fā)的ZL30F裝載機，采用電換擋變速箱，使3t級裝載機技術上有了新的突破。 ③ZL40／ZL50裝載機 ZL40／ZL50裝載機，主要裝載機生產(chǎn)廠家均擁有該產(chǎn)品。第一代產(chǎn)品幾十年來沿續(xù)至今，全國幾乎使用同一套圖紙，有些技術力量薄弱的廠家，仍把其當作主導產(chǎn)品推向市場。第二、三代產(chǎn)品主要是對工作裝置進行優(yōu)化，改變外觀造型。如柳工ZL40B／ZL50C、徐工ZL40E／ZL50E。第四代產(chǎn)品是在第三代的基礎上，進一步優(yōu)化整機的性能及配置，電控箱、濕式制動器等新技術得到應用，并形成了各企業(yè)的專有技術及專利技術，使產(chǎn)品以嶄新的面貌推向市場。 ④ZL60及6t以上裝載機 6t以及6t以上的裝載機，這是國內潛在市場最大的產(chǎn)品，1998年以前大多數(shù)生產(chǎn)廠家均開發(fā)了ZL60裝載機，但由于受傳動件的制約，ZL60裝載機沒能成功地推向市場。在1999年北京國際工程機械博覽會上，各廠家推出了新一代ZL60裝載機，多數(shù)廠家選擇柳州ZF合資生產(chǎn)的箱或橋，液壓元件也有新配置，發(fā)動機可選用斯太爾或上柴6121(Cat3306)，整機可靠性得到很大提高，給國內大噸位裝載機帶來發(fā)展機遇。 ⑷ 產(chǎn)品在生產(chǎn)中的作用及使用范圍 ZL05裝載機是一種單橋驅動、整體車架、機械傳動的小型裝載機。該機適用于市政工程、城市環(huán)衛(wèi)、公路養(yǎng)護、車站碼頭、中小煤礦等單位裝載松散物料?？膳c翻斗車、輕型汽車、中小型拖拉機和農用汽車配套使用，可明顯提高工作效率，降低工人勞動強度，而且使用、維修簡單、方便，價格低廉。 3.工作內容和要求： ⑴題目的內容 ①總體參數(shù)的確定，總體布置。 ②工作裝置及液壓系統(tǒng)設計。 ③典型零部件設計、選取。 ④整機合理性分析。 ⑵工作量 ①譯文6000字。 ②開題報告。 ③說明書20000字。 ④4張A0圖。 ⑤讀參考文獻15篇以上。 ⑥程序設計及典型零件工藝分析。 4.課題的重點和難點： ⅠZL05輪式裝載機的結構組成 ①傳動系統(tǒng)。 ②工作液壓系統(tǒng)。 ③工作裝置。 該機工作裝置由鏟斗、動臂、搖臂和拉桿構成，安裝在車架的支架上。 ④其他。 （1）該機采用了增加前橋橋荷和整機配重的措施，明顯地增加了前輪的附著力。 （2）與全液壓裝載機相比，該機結構簡單，操作容易，維修方便、價格低廉。 ⅡZL05輪式裝載機的主要技術參數(shù)： 額定裝載質量(kg)： 500 額定斗容量(m3)： 0.25 最大卸載高度(mm)： 大于1900 相應卸載距離(mm)： 大于800 軸距(mm)： 1540 輪距(mm)： 1150 最小離地間隙(mm)： 245 車速(km／h)： 前進： V1=1.9, V2=4.4 V3=5.97, V4=7.1 V5=13.9, V6=22.2 后退： VR1=4.58 掘起力（KN）： 1100 最大牽引力（N）： 9000 發(fā)動機額定功率(kW)： 15 機重（kg）： 1800 5.可能用到的主要知識和技能： 機械原理，機械設計，理論力學，材料力學，液壓與氣動技術，工程材料，材料成型，自動控制理論，測試技術，數(shù)控技術，微型計算機原理及應用，自動機械設計等本科期間學到的課程。 6.需要自學的知識和技能： SolidWorks,AUTOCAD,CATIA等繪圖仿真軟件。 二、 工作計劃 2006.02——2006.03 調研，譯文，開題報告 2006.04.01——2006.04.15 總體布置及草圖 2006.04.15——2006.05.01 總體設計，總裝圖 2006.05.01——2006.05.15 零部件設計，說明書 2006.05.15——2006.06.01 繪圖，論文 2006.06.01——2006.06.20 修改，完善圖紙、論文，準備答辯 三、參考文獻 [1] 劉慧斌，裝載機工作裝置優(yōu)化設計方法的研究，碩士，浙江大學，2000. [2] 吉林工業(yè)大學工程機械教研室.輪式裝載機設計.北京：中國建筑工業(yè)出版社，1982. [3] 李建成.礦山裝載機設計.北京：機械工業(yè)出版社，1989. [4] 高夢熊.地下裝載機結構設計與使用.北京：北京冶金工業(yè)出版社，1987. [5] 王國彪，楊力夫.裝載機工作裝置優(yōu)化設計.北京：機械工業(yè)出版社，1996. [6] 機械設計手冊聯(lián)合編寫組.機械設計手冊.北京：化學工業(yè)出版社，1982. [7] 房斌，張文中，胡其穎.ZL05裝載機.徐州：徐州工程機械集團公司，1997. [8] 趙昱東.國外輪式裝載機的新進展. 馬鞍山：馬鞍山礦研究院，2000. 8 Aspects to improve cabin comfort of wheel loaders and excavators according to operators Abstract Comfort plays an increasingly important role in interior design of earth moving equipment. Although research has been conducted on vehicle interiors of wheel loa- ders and excavators, hardly any information is known about the operator’s opinion. In this study a questionnaire was completed by machine operators to get their opinion about aspects which need to be improved in order to design a more comfortable vehi- cle interior. The results show that almost half of the operators rate the comfort of th- eir cabin‘‘a(chǎn)verage’’ or ‘‘poor’’. According to the operators, cab comfort of wheel loaders can be increased by improving seat comfort. Besides improving seat comfort, cabin comfort of excavators can be improved by changing the cab design (including dimensions, ingress/egress), view, reliability, and climate control. Keywords: Cabin comfort; Operators’ opinion; Earth moving equipment. 1. Introduction Comfort plays an increasingly important role in vehicle design. As machine operators of earth moving equipment often spend long hours in their vehicle— some- times even more than 8 h a day—comfort is a major issue in interior design of these machines.Operating earth-moving machinery is not a physically heavy job and can be sustained for long periods.Nevertheless, operating such a machine appears to be a risk factor for musculoskeletal disorders, especially when the task is not interrupted by other working activities or breaks. Zimmerman et al. (1997) showed that the main problems of earth-moving machinery operators concern physical complaints in the neck/ shoulder and low back region, general fatigue and feelings of discomfort. This might be attributed to a combination of static load during prolonged sitting— frequ- ently in awkward postures—exposure to whole body vibrations, and handling and steering the machine(Zimmerman et al., 1997; Tola et al., 1988; de Looze et al., 2000). A comfortable well-designed vehicle interior may reduce awkward postures and provide an environment that stimulates optimal operator performance. Based on a literature review about musculoskeletal disorders and their risk factors, Zimmerman et al. (1997) made four recommendations for reducing work-related musculoskeletal disorders among operators: minimizing of magnitude and frequency of vibration rea- ching the operator; locating controls optimally to minimize reach distances, trunk ?exion and trunk rotation; providing maximum operator visibility from an upright supported seated posture; and taking regular breaks to minimize the effects of sus- tained postures. Improvements of cab comfort are very often based on reducing the risk factors for work-related musculoskeletal disorders (Zimmerman et al., 1997; Attebrant et al., 1997). Only a few studies have mentioned aspects which operators wishto see improved. Nakada (1997) describes the desirability ranking for dump trucks and wheel loaders given by product creators, designers, design engineers, operators and young people. Nakada, (1997) shows that much design attention has been paid to instrument panel/monitors and meters and the operator seat. Unfor- tunately, the operators’ opinions cannot be distinguished in Nakada’s study (1997). However, in order to design a comfortable vehicle interior, the opinion of the operators is important as they are the end-users of the machines. Their user expe- rience may be of great help designing a more comfortable vehicle interior. The aim of the current study is to ?nd aspects mentioned by wheel loader and excavator ope- rators, which can be used to improve the comfort of vehicle interiors in the future. In this article we describe the results of a questionnaire given to 273 machine operators. They were asked their opinion about their current machine, their future demands and aspects they considered important to work well with the machine. This allowed us to identify aspects that need improvement in machine design. 2. Method 2.1. Subjects A convenience sample was obtained through approaching operators visiting Ba- uma (the world’s largest exhibition for construction equipment). Most of the parti- cipants were wheel loader operators (n = 61) and excavator operators (n=212). The others (n = 65) were operators of several construction machines (e.g., mobile cranes, dozers, tower cranes, off-road trucks). Only the results for wheel loader and excava- tor operators are presented in this article, as they account for 18% and 62.7% of the total number of respondents respectively. Figs. 1 and 2 show a typical wheel loader and excavator. 2.2. Questionnaire Data were collected by means of a questionnaire which was completed during an interview. The questionnaire was divided into three parts: (1) characteristics of the population, (2) evaluation of the current machine being operated, and (3) future de- mands on earthmoving machinery. In the ?rst part we asked the operator’s age, years of experience as operator, the kind of machinery being operated and its age. In the se- cond part of the questionnaire, operators evaluated their machine by rating overall comfort and their opinion of speci?c parts of the machine on a four-point scale (very good, good, average, poor). Finally, two open questions asked about the operator’s f- uture demands: what improvements would make the machine more comfortable and what aspects are the most important to work well with the machine. 2.3. Data analysis Data were sorted by machine type, after which the responses of wheel loader operators and excavator operators were separately analyzed. Within these groups, operators of older machinery (≥4 years old) were separated from operators of newer machinery (〈4 years old). In addition, the categories ‘‘very good’’ and‘‘good’’ were combined (‘‘very good/good’’) and the categories ‘‘a(chǎn)verage’’ and ‘‘poor’’ were com- bined(‘‘a(chǎn)verage/poor’’). Frequency tables were made of the operators opinions about overall machine comfort and about their opinions about speci?c parts of their machines. Chi-square was calculated between age of machine and overall comfort and between age of ma- chine and the operators’ opinion of speci?c parts of the machine. We assumed that if fewer than 80% of the operators rated a part of the machine ‘‘good/very good’’, im- provement of this part could contribute to a more comfortable vehicle interior. In part three of the questionnaire, the operators indicated aspects to improve machine com- fort and aspects they found necessary to work well with the machine. We classi?ed these aspects into categories and calculated the percentage responses. 3. Results 3.1. Characteristics of the population Both the wheel loader operators (mean age: 36.5±9.4 years) and the excavator operators (mean age: 36.3±9.3 years) who participated in this study, were experien- ced with a mean of 12.3 (±8.1) and 13.4 (±9.2) years of service, respectively. Half of the operators operate machines less than 4 years old (53% of the wheel loader and 50% of the excavator operators). 3.2. Evaluation of current machine 57.4% of wheel loader operators and 55.9% of the excavator operators rated the overall cabin comfort‘‘good/very good’’. It shows that operators of newer machinery (<4 years old) rated the overall cab comfort as ‘‘good/very good’’ more often than operators of older machines (≥4 years old). This was found both among wheel load- ers (χ2(1)=8.5,p<0.04) and among excavators (χ2(1)=23.0,p<0.001).Seventy-eight percent of the operators driving wheel loaders less than 4 years old, rated the comfort of their machine as ‘‘good/very good’’.With excavator operators this ?gure was 81%. These results show that during recent years the experienced cab comfort of excavat- ors and wheel loaders has improved.It illustrates the opinion of the operators about speci?c parts of the machines less than 4 years old.Fewer aspects of wheel loaders are rated‘‘a(chǎn)verage/poor’’ by more than 20% of the operators, than excavators. Com- mon aspects which can contribute to increase of cab comfort are dashboard and dis- plays, adjustability of seats and controls, vibration and damping, noise reduction, and seat comfort. Excavator operators would also like to see improvement of climate co- ntrol, improved machine appearance, and better cab dimensions (including interior space, ingress/egress),view, and reliability. 3.3. Future demands The participants generated 467 items desired to improve the machine’s comfort. We classi?ed these aspects into 15 categories (see Table 2). It shows which features should be improved according to the operators. Seat comfort, climate control and ac- cessories are often mentioned for both wheel loaders (20%, 12%,15%, resp.) and ex- cavators (21%, 19%, 12%, resp.).Excavator operators also mention cab design (inc- luding dimensions, ingress/egress; 19%). The aspects considered most important to work well with the machine are sum- marized . Machine performance is by far the most important issue if we look at the averages. Other aspects like view and reliability play less important roles. 4. Discussion The aim of the current study was to ?nd aspects mentioned by wheel loader and excavator operators which can be used to improve the comfort of vehicle interiors in future. In order to ?nd these aspects, we asked questions about three issues. ?about comfort of speci?c aspects of the cab (rating on a four-point scale); ?about aspects necessary to improve the cab comfort (open question); ?about aspects important to work well with the machine (open question). Excavator and wheel loader operators mentioned improved seat comfort, clim- ate control and accessories as ways to increase cab comfort. Excavator operators also mentioned cab design (including dimensions, ingress/egress). These aspects were al- so rated as‘‘a(chǎn)verage/poor’’ by more than 20% of the operators (except accessories be- cause this was not an item in the second part of the questionnaire). Other aspects wh- ich can be taken into account with cab design are those which operators mention as most important aspects to work well with the machine. Especially when these aspects are also rated as ‘‘a(chǎn)verage/poor’’ by more than 20% of the operators, they need spec- ial attention.Improving these aspects have priority in designing a more comfortable cab. In our study, we collected our data among visitors to the Bauma exhibition in 2001. The advantage of this collection method is that it is possible to reach a large group of operators within a short period of time, at the same time getting a large re- sponse, which would normally be very dif?cult. A disadvantage might be that the va- st majority of respondents were German which could mean that the results have a li- mited validity among operators in other countries. The German operators may have other ideas about cab comfort than operators, who work in other countries. The de- mands of the operators on their machine depend on the working environment (e.g., climate, landscape, dust) and their tasks (e.g., driving off road, driving on the main road), which can be different between countries. Besides, the operators based their opinion on their current machine. It is possible that in Germany certain brands are overrepresented compared to other countries and that the operator’s opinion might vary according to the brand. The most common brands would therefore in?uence the results of our study as many operators use one of these machines (Excavators: brand A 22.6%, brand B 22.2%;Wheel loaders: brand A 21.3%, brand B 18%, brand C 11.5 %). Since we used a short questionnaire to collect the data, no detailed information could be asked. The goal of our study was to get a global view on the operators’ opi- nion. The open questions gave the operators the opportunity to think open-minded which may render valuable information. Open questions are less suitable for data an- alysis, because we needed to categorize answers. Inevitably information is lost in this process, but the goal of obtaining a global view was nevertheless achieved. Our results show that seat comfort, climate control, accessories (for wheel load- ers and excavators) and cab design (including dimensions, ingress/egress), view, and reliability (for excavators only) are the aspects which can improve cab comfort. All these aspects are rated‘‘a(chǎn)verage/poor’’ by more than 20% of the operators and they a- re also mentioned as aspects which need improvement in order to increase cab com- fort. In our opinion designers should give priority to these items when redesigning cabs. It is interesting that operators did not mention vibration as an aspect which can improve comfort, as it was ranked high on the list of machine parts rated ‘‘a(chǎn)verage/p- oor’’. Besides, whole body vibration is a serious health hazard (Houtman et al., 200 1). It is possible that the operators did not mention vibration because they may see vibration as an engine property or an inevitable consequence of working on earth- moving equipment. Operators might have the idea that vibration cannot be reduced by redesigning only the cab. It is,however, unclear why operators did not mention vibration. When comparing excavators and wheel loaders, improving seat comfort is an is- sue for both wheel loaders and excavators. Although seat comfort in excavators has been improved during recent years (see Table 1), improvements are still necessary. However,this is not easy as sitting comfort depends on many other factors more or less related to seat design: e.g., adjustability of seat and controls, vibration and dam- ping, and view. For example, a bad view from the cabin can result in awkward body postures, which reduces comfort in spite of a comfortable seat. Beyond the common aspect seat comfort, many differences exist between wheel loaders and excavators. One difference we found between the excavator and the wh- eel loader was that excavator cab design (including dimensions and ingress/egress) needs improvement. This difference may be explained by access and space. Firs- t,there is a difference in machine access with grips generally quite wide apart and steps to the cabin far from optimal, being either too high or too narrow. Operators could experience this as a problem. Secondly, there is a fundamental difference be- tween wheel loaders and excavators in the space available for the cab. With the pre- sent design, excavators have a limited width available for the cab as it must be posi- tioned between the boom and the left machine side, leaving approximately 1 m for the cab. Another difference is that improving view can increase the cab comfort of the excavator. View is a very important aspect to work well with the excavator. The boo- m of the excavator has a wide range of motion and the operator needs to see the bu- cket for the full range. A comfortable cab provides a clear view of the work place and the bucket, without necessitating awkward postures. In the introduction, we stated that comfort plays an important role in cab design. It is therefore interesting to ?nd that the operators did not mention comfort as one of the most important aspects to work well with the machine. They mentioned aspects such as the machine’s performance, reliability, view and operability. It seems that operators think ?rst about the basic requirements needed to perform their task and apparently do not see comfort as one of them. If we compare our results with the results of Nakada, (1997), in both studies the operator seat is ranked as important. Instrument panel, monitors and meters are also ranked as important in Nakada’s study. In our study vibration, dashboard and disp- lays are high on the list of parts rated as ‘‘a(chǎn)verage/poor’’ by more than 20% of the operators, but they are not seen as aspects that can improve cab comfort. Nakada’s study did not mention vibration at all. A reason for this may be that in our study, ex- perienced operators played a larger role than in Nakada’s and because that study was focused on interior design. An increase in cab comfort has been achieved during recent years. From Table 1 it seems that wheel loaders have made progress on fewer aspects than excavators. But in fact, the improvements of speci?c aspects of wheel loaders (i.e., machine’s ap- pearance, climate control, and view) were of such a high level that these aspects were rated as ‘‘a(chǎn)verage/poor’’ by fewer than 20% of the operators and are therefore not m- entioned in this table. However, 27.7% of the excavator operators and 25.0% of the wheel loader operators of machinery less than 4 years old rate the cabin’s comfort ‘‘a(chǎn)verage/ poor’’. These results show that improvement of cab comfort is still needed. In our study, we found some important aspects which can contribute to improvement of cab comfort. Unfortunately, these aspects do not represent detailed information, and we can not say how they should be changed to get a more comfortable cab. The- refore, further research is necessary to indicate speci?c improvements for each mac- hine individually. 5. Conclusion Operators do not mention cabin comfort as one of the most important aspects to work well with the machine, yet when asked about it almost half of the wheel loader and excavator operators rate their cabin’s comfort as ‘‘a(chǎn)verage/poor’’. Cab comfort of wheel loaders can be increased by improving seat comfort. Besides seat comfort, cab comfort of excavators can be improved by changing the cab design (including dimensions,ingress/egress), view, reliability, and climate control, according to the operators. Because we cannot say speci?cally how these aspects should be changed to get a more comfortable cab, further research is necessary to indicate speci?c impr- ovements for excavators and wheel loaders individually.