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ZL05装载机总体及其工作装置设计
装载机总体设计
装载机工作装置设计
装载机工作装置总体设计
装载机工作装置
ZL05装载机
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ZL05装载机总体及其工作装置设计,ZL05装载机总体及其工作装置设计,装载机总体设计,装载机工作装置设计,装载机工作装置总体设计,装载机工作装置,ZL05装载机
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本科生毕业设计（论文）开题报告 学生姓名：李鑫 学 号：14020926 班 级：140209 专 业：机械工程及自动化 指导教师：李 风 毕业设计（论文）开题报告一、课题介绍1.课题名称：ZL05微型轮式装载机总体设计2.课题背景：设计课题的意义 ZL系列轮式装载机是一种高效率的工程机械，具有结构先进，性能可靠，机动性强，操纵方便等优点。广泛应用于矿山，建筑工地，道路修建，水利工程，港口，货场，电站以及其他工业部门，进行装载、推土、铲挖、起重、牵引等多种作业。对加快工程建设速度减轻劳动强度提高工程质量降低工程成本都发挥着重要作用，因此近几年来无论在国内还是国外装载机品种和产量都得到迅速发展，成为工程机械的主导产品之一。为适应工程施工，市政建设及农用水利工地的砂石、灰土等各种散装物料的装运需要，提出设计小型轮式装载机的任务。 设计课题的目的轮式装载机总体设计是机械制造，机械设计和机械电子（机电一体化）等专业的一个重要的教学环节，是学完技术基础课及有关专业课以后的一次专业课程内容的综合设计。通过设计提高学生的机构分析与综合的能力，机械构造设计的能力，机电一体化系统设计能力，掌握实践生产过程自动化的设计方法。通过设计把有关课程（机械原理，机械设计，理论力学，材料力学，液压与气动技术，工程材料，材料成型，自动控制理论，测试技术，数控技术，微型计算机原理及应用，自动机械设计等）中所获得的理论知识在实际中综合的加以运用，使这些知识得到巩固和发展，并使理论知识和生产密切的结合起来。轮式装载机总体设计是机械设计及机械制造专业和机械电子专业的学生一次比较完整的整机设计。通过设计，培养学生独立的机械整机设计的能力，树立正确的设计思想，掌握机械产品设计的基本方法和步骤。通过设计使学生能熟练的应用有关参考资料，计算图表，手册，图册和规范；熟悉有关国家标准，以完成一个工程技术人员在机械整体设计方面所必须具备的基础技能训练。 轮式装载机的发展现状1）国外轮式装载机的发展现状1 新产品不断推出近年来，轮式装载机以围绕提高效率、降低成本为核心，继续向大型化、微型化发展，不断推出新产品，加速更新换代。卡特彼勒公司90年代初推出Cat966F轮式装载机，时隔1年又推出Cat980F轮式装载机，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轮式装载机，根据物料体积质量不同而选配l8 30m3的铲斗，机重170t；装有涡轮增压后冷的Cat3516型柴油发动机牵引力大、加速性能好；加长的工作动臂增加了卸载高度，能对载重量218t的大型自卸汽车装载。马拉松勒图尔勒(Marathon Letourneau)公司1990年和1994年在LI100的基础上分别推出LI400和LI800型轮式装载机。l998年9月在美国塔克癣(Tucson)召开的Longding 2000年会上，该公司宣布正在开发的斗容204m3的L1350型轮式装载机将于21世纪初投放市场，供载重量150200t自卸汽车装载。德雷塞(Dresser)公司90年代初推出4000型轮式装载机，斗容1030m3、机重1518t，采用模块结构的传动系统，大功率、敏感按钮控制的液压系统z型单摇臂工作装置。优化的整体结构和湿式盘式制动器，具有自动调节和自动密封性能。目前，全世界约有400台(功率大于750kw)大型轮式装载机应用在露天矿山和建筑工程，与大型自卸汽车配套使用。在发展大型轮式装载机的同时，微型轮式装载机以机动灵活、效率高、多功能和价格低廉赢得市场，发展甚快。如：日本古河公司生产的FL30-1型轮式装载机斗容034m3、机重23t；小松公司的WA30-1型斗容034rn3、柴油机功率20kW；丰田织机公司的斗容017m3、机重1t等这些微型装载机适用于建筑工地和地下矿山挖沟、平地、堆料等。2 新结构不断涌现21 工作机构卡特技勒公司推出组合式八杆机构。从地面到整个举升高度范围内具有平行移动的特点。它将快速连接器和塔架式机构设计成整体式工作装置，通过快速更换不同的辅助机构完成装卸、堆垛、扫雪、平地、清扫路面、推土、吊装、搬运和地表钻孔等作业，实现一机多能，减少用户设备投资。德雷塞公司开发Z型单臂工作机构并与高压液压系统相结台，为铲斗提供更大的掘起力；缩短装载工作循环，增加铲斗装满系数，大幅度提高劳动生产率。由于铰点少、杆件少，便于维修保养，降低维修费用。22 传动机构以卡特彼勒公司为代表的轮式装载机采用液力机械传动系统，其自动动力换档变速箱自动选择档位传动比，使换档在变速箱最佳效率点进行。该公司最近推出的STIC(转向变速集成)系统，将转向和换档功能集成于一操纵手柄上，使操纵更加省力、轻便，换档更加平稳，可大幅度提高生产率。以日本小松公司WA系列中小功率(小于125kW)为代表的轮式装载机采用新型集中式结构的驱动桥。它将主传动制动器和行星轮式终传动都集中在桥的中部，桥壳断面变化连续、平缓，内应力分布台理，从根本上防止因传统结构桥壳在轮边支承轴段应力集中断裂。轮端采用浮动密封结构，安装简便，有自动补偿功能，密封性能良好。该结构设计合理、基本零件少、工艺性好、性能好、可靠性高。马拉松勒图尔勒公司的轮式装载机采用柴油机一发电机一电动轮传动，比液力机械传动系统简单。在整个作业中柴油发动机以恒定转速运转，减少燃油消耗，延长发动机寿命；无变速箱、传动轴等许多部件，提高了传动效率，操作维修方便，费用低；独立电动牵引马达为固态控制，反应迅速，减少车轮打滑和轮胎过渡磨损；设置了电动缓行器，不用工作制动停机，装料对位准确；整机重心低，行驶稳定性好，可靠性高。23 液压系统德雷塞公司轮式装载机液压系统用传感器接受柴油机转速信号，当转速下降时柱塞式变量泵便自动增加转向系统流量，以保持恒定的转向速度，在最大挖掘工况时可减少流量，减慢液压元件动作，以保持液压系统的动力平衡，减少液压系统热损耗，节省功率。卡特彼勒轮式装载机转向液压系统用负荷传感式溢流阀，使液压泵在负载决定压力下溢流，降低系统压力，提高了液压元件寿命。工作装置液压系统采用举升限位装置和下放自动定位装置，避免了机械限位时液压缸行程终了产生高压和冲击；装设的蓄能器能吸收冲击载荷，并对整机的纵向摇摆起阻尼作用；液压缸导向套处有三重密封，防止泄漏和肪尘。24 司机室新型轮式装载机司机室的设计充分考虑了人的生理需求，对仪表位置排列、操作手柄和踏板、司机座椅、能见度、防噪和隔振、温度调节等均符台人机工程学，使司机在舒适、轻松、安全环境下操作，提高工作效率。如卡特彼勒轮式装载机的司机室设有微机监控装置和可调悬挂式座椅，先导液压阀操纵铲斗控制手柄及流量放大转向系统等，使操作轻便、灵活，采用防滚翻保护结构(ROPS)和落体撞击保护结构(FOPS)符台ISO标准要求。3自动化水平不断提高微电子技术的突破性进展为轮式装载机自动控制、状态监测及视线范围内遥控技术的发展创造了条件。柴油发动机自动控制喷油系统、变速箱自动控制换档、性能参数和状态监测均取得重大进展，在视线内遥控作业已进入实用阶段，从而改善了性能，提高了可靠性，缩短了停机时间，增加了生产能力，降低了燃油消耗，取得了更大的经济效益。31 柴油发动机自动控制喷油系统卡特彼勒Cat994D型装载机采用了Cat3516B型柴油发动机，装有HEUI型电控喷油系统，根据外载荷有效控制功率和转速，发动机喷油泵随调速器动作，精确地对燃油进行调节、加压和供油，降低初始喷油速率，减少NO 和HC，噪声小，燃油效率高。32 变速箱自动控制换档日本川崎重工公司的KLD97Z型轮式装载机采用自动控制换档的变速箱，可按装载机运转工况自动选择最佳档位，用微机控制离台器，从而简化操作、提高作业效率、减少冲击，实现平稳换档；电子控制装置、传感器等使用可靠，一旦控制系统发生故障，可用手动换档，不影响工作。33 设备状态监测卡特彼勒开发的电子监控(EMS)系统对轮式装载机主要系统出现故障或潜在问题提出警告和显示，有三种不同的警告级别和信号，每种信号表明系统的状态和司机应采取的适当措施。34 机载电子称重系统目前，许多大型轮式装载机都装设机载电子称重系统，能清楚地显示出需再装的物料量，从而使心中有数，以防止过载或欠载，减少无效跑车次数，节省作业时间，提高生产效率。并可对质量累计计算显示仪表以彩色数码显示，清楚明了，校准简便，误差为3以内。2）国内轮式装载机的发展现状在今后相当长的时间内，轮式装载机仍将是工程建设机械中最重要的机种之一，国内年需求量持续稳定地保持在一较高水平，但国内装载机生产厂家也在急剧膨胀，竞争更趋激烈，各生产厂家纷纷开发新产品，来迎接市场的挑战。3t以下装载机3t以下产品主要以ZL10、ZL15、ZL16为代表，还有一些利用拖拉机底盘改装的小型装载机，主要与日益增多的农用运输车辆配套使用。主要零部件均采用一般性能及质量的发动机、驱动桥、变速箱、液压件。技术较先进的静液压传动产品，液压件国内不易配套，产品成本居高不下，制约了该类产品在国内的发展。ZL30装载机ZL30装载机主要生产厂家有成工、常林、徐工、宜工、山工等。该产品零部件配置较零乱，生产厂家具有自制的桥箱，风格各具特色，质量及性能上相对稳定，技术先进性一般。徐工最近开发的ZL30F装载机，采用电换挡变速箱，使3t级装载机技术上有了新的突破。ZL40ZL50装载机ZL40ZL50装载机，主要装载机生产厂家均拥有该产品。第一代产品几十年来沿续至今，全国几乎使用同一套图纸，有些技术力量薄弱的厂家，仍把其当作主导产品推向市场。第二、三代产品主要是对工作装置进行优化，改变外观造型。如柳工ZL40BZL50C、徐工ZL40EZL50E。第四代产品是在第三代的基础上，进一步优化整机的性能及配置，电控箱、湿式制动器等新技术得到应用，并形成了各企业的专有技术及专利技术，使产品以崭新的面貌推向市场。ZL60及6t以上装载机6t以及6t以上的装载机，这是国内潜在市场最大的产品，1998年以前大多数生产厂家均开发了ZL60装载机，但由于受传动件的制约，ZL60装载机没能成功地推向市场。在1999年北京国际工程机械博览会上，各厂家推出了新一代ZL60装载机，多数厂家选择柳州ZF合资生产的箱或桥，液压元件也有新配置，发动机可选用斯太尔或上柴6121(Cat3306)，整机可靠性得到很大提高，给国内大吨位装载机带来发展机遇。 产品在生产中的作用及使用范围ZL05装载机是一种单桥驱动、整体车架、机械传动的小型装载机。该机适用于市政工程、城市环卫、公路养护、车站码头、中小煤矿等单位装载松散物料。可与翻斗车、轻型汽车、中小型拖拉机和农用汽车配套使用，可明显提高工作效率，降低工人劳动强度，而且使用、维修简单、方便，价格低廉。3.工作内容和要求：题目的内容总体参数的确定，总体布置。工作装置及液压系统设计。典型零部件设计、选取。整机合理性分析。工作量译文6000字。开题报告。说明书20000字。4张A0图。读参考文献15篇以上。程序设计及典型零件工艺分析。4.课题的重点和难点：ZL05轮式装载机的结构组成传动系统。工作液压系统。工作装置。该机工作装置由铲斗、动臂、摇臂和拉杆构成，安装在车架的支架上。其他。（1）该机采用了增加前桥桥荷和整机配重的措施，明显地增加了前轮的附着力。（2）与全液压装载机相比，该机结构简单，操作容易，维修方便、价格低廉。ZL05轮式装载机的主要技术参数：额定装载质量(kg)： 500额定斗容量(m3)： 0.25最大卸载高度(mm)： 大于1900相应卸载距离(mm)： 大于800轴距(mm)： 1540轮距(mm)： 1150最小离地间隙(mm)： 245车速(kmh)： 前进： 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最大牵引力（N）： 9000发动机额定功率(kW)： 15机重（kg）： 18005.可能用到的主要知识和技能：机械原理，机械设计，理论力学，材料力学，液压与气动技术，工程材料，材料成型，自动控制理论，测试技术，数控技术，微型计算机原理及应用，自动机械设计等本科期间学到的课程。6.需要自学的知识和技能：SolidWorks,AUTOCAD,CATIA等绘图仿真软件。二、工作计划2006.022006.03 调研，译文，开题报告2006.04.012006.04.15 总体布置及草图2006.04.152006.05.01 总体设计，总装图2006.05.012006.05.15 零部件设计，说明书2006.05.152006.06.01 绘图，论文2006.06.012006.06.20 修改，完善图纸、论文，准备答辩三、参考文献1 刘慧斌，装载机工作装置优化设计方法的研究，硕士，浙江大学，2000.2 吉林工业大学工程机械教研室.轮式装载机设计.北京：中国建筑工业出版社，1982.3 李建成.矿山装载机设计.北京：机械工业出版社，1989.4 高梦熊.地下装载机结构设计与使用.北京：北京冶金工业出版社，1987.5 王国彪，杨力夫.装载机工作装置优化设计.北京：机械工业出版社，1996.6 机械设计手册联合编写组.机械设计手册.北京：化学工业出版社，1982.7 房斌，张文中，胡其颖.ZL05装载机.徐州：徐州工程机械集团公司，1997.8 赵昱东.国外轮式装载机的新进展. 马鞍山：马鞍山矿研究院，2000. 8Applied Ergonomics 34 (2003) 265271 Aspects to improve cabin comfort of wheel loaders and excavators according to operators L.F.M. Kuijt-Eversa,*, F. Krausea, P. Vinka,b aTNO Work and Employment, P.O. Box 718, Hoofddorp 2130 AS, The Netherlands bIndustrial Design, TU Delft, The Netherlands Received 19 April 2002; received in revised form 25 November 2002; accepted 29 December 2002 Abstract Comfort plays an increasingly important role in interior design of earth moving equipment. Although research has been conducted on vehicle interiors of wheel loaders and excavators, hardly any information is known about the operators 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 vehicle interior. The results show that almost half of the operators rate the comfort of their cabin average 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. r 2003 Elsevier Science Ltd. All rights reserved. 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 sometimes even more than 8h a daycomfort 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 frequently in awkward posturesexposure 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 musculos- keletaldisordersamongoperators:minimizingof magnitude and frequency of vibration reaching the operator; locating controls optimally to minimize reach distances, trunk fl exion and trunk rotation; providing maximum operator visibility from an upright supported seated posture; and taking regular breaks to minimize the effects of sustained postures. Improvements of cab comfort are very often based on reducing the risk factorsforwork-relatedmusculoskeletaldisorders (Zimmerman et al., 1997; Attebrant et al., 1997). Only a few studies have mentioned aspects which operators wish to 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. *Corresponding author. Tel.: +31-23-55-49-938; fax:+31-23-55-49- 305. E-mail address: l.kuijtarbeid.tno.nl (L.F.M. Kuijt-Evers). 0003-6870/03/$-see front matter r 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0003-6870(03)00032-2 Unfortunately,theoperatorsopinionscannotbe distinguished in Nakadas 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 experience may be of great help designing a more comfortable vehicle interior. The aim of the current study is to fi nd aspects mentioned by wheel loader and excavator operators, 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 ap- proaching operators visiting Bauma (the worlds largest exhibition for construction equipment). Most of the participants 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 excavator 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 ques- tionnaire was divided into three parts: (1) characteristics of the population, (2) evaluation of the current machine being operated, and (3) future demands on earth moving machinery. In the fi rst part we asked the operators age, years of experience as operator, the kind of machinery being operated and its age. In the second part of the questionnaire, operators evaluated their machine by rating overall comfort and their opinion of specifi c parts of the machine on a four-point scale (very good, good, average, poor). Finally, two open questions asked about the operators future demands: what improvements would make the machine more comfortable and what aspects are the most important to work well with the machine. Fig. 1. Excavator. L.F.M. Kuijt-Evers et al. / Applied Ergonomics 34 (2003) 265271266 2.3. Data analysis Data were sorted by machine type, after which the responses of wheel loader operators and excavator operatorswereseparatelyanalyzed.Withinthese groups, operators of older machinery (X4 years old) were separated from operators of newer machinery (o4 years old). In addition, the categories very good and good were combined (very good/good) and the categoriesaverageandpoorwerecombined (average/poor). Frequencytablesweremadeoftheoperators opinions about overall machine comfort and about their opinions about specifi c parts of their machines. Chi-square was calculated between age of machine and overall comfort and between age of machine and the operators opinion of specifi c parts of the machine. We assumed that if fewer than 80% of the operators rated a part of the machine good/very good, improvement of this part could contribute to a more comfortable vehicle interior. In part three of the questionnaire, the operators indicated aspects to improve machine comfort and aspects they found necessary to work well with the machine. We classifi 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: 36.579.4 years) and the excavator operators (mean age: 36.379.3 years) who participated in this study, were experienced with a mean of 12.3 (78.1) and 13.4 (79.2) 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; see Fig. 3). 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. Fig. 4 shows that operators of newer machinery (o4 years old) rated the overall cab comfort as good/very good more often than operators of older Fig. 2. Wheel loader. Age of machines Percentage of machines per category 0 10 20 30 40 50 60 ExcavatorsWheel loaders Machines (%) less than 4 years old4 years or more Fig. 3. The participants machines are divided into two categories: machines o4 years old and machines =4 years old. L.F.M. Kuijt-Evers et al. / Applied Ergonomics 34 (2003) 265271267 machines (X4 years old). This was found both among wheel loaders (w21 8:5; po0:04) and among excava- tors (w21 23:0; po0:001). 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 fi gure was 81%. These results show that during recent years the experienced cab comfort of excavators and wheel loaders has improved. Fig. 5 illustrates the opinion of the operators about specifi c parts of the machines less than 4 years old. As seen in Table 1, fewer aspects of wheel loaders are rated average/poor by more than 20% of the operators, than excavators. Common aspects which can contribute to increase of cab comfort are dashboard and displays, adjustabilityofseatsandcontrols,vibrationand damping, noise reduction, and seat comfort. Excavator operators would also like to see improvement of climate General opinion about comfort of the cab Percentage of operators rating “good/very good“ 0 20 40 60 80 100 ExcavatorsWheel loaders Operators (%) less than 4 years old4 years or more Fig. 4. Percentage of operators rating their machines good and very good on cab comfort. Excavators less than 4 years old Percentage operators rating “good“ and “very good“ 020406080100 020406080100 Seat comfort Adjustablility of seat and controls Way controls work Pedals Dashboard and displays View Climate control Cab dimension/interior space Machines appearance Noise reduction Vibration and damping Operators (%) GoodVery good GoodVery good Wheel loaders less than 4 years old Percentage operators rating “good“ and “very good“ Seat comfort Adjustablility of seat and controls Way controls work Pedals Dashboard and displays View Climate control Cab dimension/interior space Machines appearance Noise reduction Vibration and damping Operators (%) Fig. 5. Opinion of excavator and wheel loader operators about specifi c parts of the machines. L.F.M. Kuijt-Evers et al. / Applied Ergonomics 34 (2003) 265271268 control, 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 machines comfort. We classifi ed these aspects into 15 categories (see Table 2). Fig. 6 shows which features should be improved according to the operators. Seat comfort, climate control and accessories are often mentioned for both wheel loaders (20%, 12%, 15%, resp.) and excavators (21%, 19%, 12%, resp.). Excavator operators also mention cab design (including dimensions, ingress/egress; 19%). The aspects considered most important to work well with the machine are summarized in Table 3. 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. Table 2 Classifi cation of aspects mentioned by operators CategoriesExamples TCO (total cost of ownership)Costs of machine (procurement, service costs, rest value) Machine performancePerformance, hydraulics, gear ServiceabilityCleaning of the machine, manufacturer service ReliabilityReliability Seat comfortSeat pan, lumbar support, arm rests, curvature of back support Adjustability of seat and controlsAdjustability of seat height, adjustability of controls OperabilityJoystick, steering wheel, interaction joystick and beam ViewView of work, dead angles, position of mirrors Dashboard and displaysUsability of dashboard/controls, readability, absent information, position of displays Climate control Temperature, dust fi lters, ventilation, blower position Design/dimensions/ingress and egress Design and dimensions of cabin and machine, position of steps, grab rails Noise and vibrationNoise, vibration, damping AccessoriesRadio, fridge, storage space, cup holder Safety and stabilityFeelings of safety, stability of machine EnvironmentNoise outside the machine, exhaust fumes Table 1 Aspects rated average or poor by more than 20% of the operators for both wheel loaders and excavators less than 4 years old Wheel loadersExcavators AspectOperators (%)AspectOperators (%) Dashboard and displays32.0Seat comfort*29.5 Adjustability of seat and controls31.2Vibration and damping*27.0 Vibration and damping*28.1Dashboard and displays26.0 Noise reduction28.1Climate control*24.1 Seat comfort24.9Machines appearance24.0 Cab dimensions, interior space, ingress and egress*22.3 Noise reduction*21.9 View21.9 Adjustability of seat and controls*21.0 Reliability20.9 Aspects marked by* are rated by signifi cantly more operators of newer machinery (less than 4 years old) as good or very good compared to machines older machinery (4 years or more). Fig. 6. Aspects which need improvement according to excavator and wheel loader operators. L.F.M. Kuijt-Evers et al. / Applied Ergonomics 34 (2003) 265271269 4. Discussion The aim of the current study was to fi 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 fi nd these aspects, we asked questions about three issues. * about comfort of specifi 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, climate control and accessories as ways to increase cab comfort. Excavator operators alsomentionedcabdesign(includingdimensions, ingress/egress).Theseaspectswerealsoratedas average/poor by more than 20% of the operators (except accessories because this was not an item in the second part of the questionnaire). Other aspects which 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 average/poor by more than 20% of the operators, they need special 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 response, which would normally be very diffi cult. A disadvantage might be that the vast majority of respondents were German which could mean that the results have a limited validity among operators in other countries. The German operators may have other ideas about cab comfort than operators, who work in other countries. The demands 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 operators opinion might vary according to the brand. The most common brands would therefore infl 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 opinion. The open questions gave the operators the opportunity to think open-minded which may render valuable information. Open questions are less suitable for data analysis, 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 loaders 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 average/poor by more than 20% of the operators and they are also mentioned as aspects which need improve- ment in order to increase cab comfort. 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 average/poor. Besides, whole body vibra- tion is a serious health hazard (Houtman et al., 2001). 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,unclearwhyoperators did notmention vibration. When comparing excavators and wheel loaders, improving seat comfort is an issue fo
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