大众DSG双离合器变速箱简介

大众DSG双离合器变速箱简介 大众DSG双离合器变速箱技术简介 1 前言 DSG变速箱，又叫直接换档变速箱(Direct Shift Gearbox，DSG)。大众公司根据其工作原理，把它命名为双离合变速箱，即(Double Clutch Transmission，DCT)。2003年，大众汽车推出了全球第一款双离合自动变速箱——6档DSG变速箱，并获得巨大成功。在不到五年的时间里，大众汽车就销售了100多万台装备DSG双离合自动变速箱的轿车。而在2008年北京国际车展上，大众汽车带来了其最新产品——7档DSG变速箱。目前，大众集团已经在其国产的迈腾车上已经开始采用6档DSG变速箱并将在其旗下的更多车型上搭载双离合自动变速箱。双离合自动变速箱以其降低油耗、换档快速、驾乘舒适等优点已经成为变速箱技术的一个发展趋势。现就大众集团的6档DSG变速箱和7档DSG变速箱的结构原理和优势作一简单介绍。 2 大众6档DSG DSG变速器的结构主要由多片湿式双离合器、三轴式齿轮变速器、自动换档机构、电子控制液压控制系统组成。其中最具创意的核心部分是双离合器和三轴式齿轮箱，如下图1所示。因为湿式离合器具有更好的调节能力和优异的热容性，因此能够传递比较大的扭矩。6档DSG双离合自动变速器可匹配最大扭矩350牛米的发动机。目前在国产的迈腾1.8TSI和2.0TSI两款车型上就装备了这款6档DSG。 the public to participate in, in imperceptible provided L people's cultural quality. To built use "Juxian issued on the micro channel," civilized Juxian "micro channel, Ju, networks and other mainstream network media continued to push send online is energy information, and create a good network environment. Deepen the action of the beautiful countryside civilization, to carry out a wide range of" new countryside, new life "training, give full play to the village population culture courtyard, Park Street, cultural square and other positions the role of publicity and education, promote rural way of life more civilized. This year the province's urban and rural sanitation integration of the rural masses satisfaction telephone survey, significantly improved performance in our county, respectively, than the end of last year, years to improve the 5.2,17.5 percentage points. The township streets. Relevant departments of counties units should conscientiously sum up experience, adhere to the problem oriented, people are not satisfied with the village as the focus of the work, insist on grasping both ends, with the middle, to consolidate and improve, expand further effort, in the realization of the normal long-term efforts, to ensure that the end of this year to obtain better results. Third, we need to accelerate the voluntary service system. To actively promote the party members and members and cadres normalization of volunteer service, do a good job in public places, window units and community volunteer service station construction, establishment of covering the whole (a) (b) 图1 2.1 DSG变速器的内部结构 多片湿式双离合器是DSG双离合自动变速器最重要的核心部件，其结构和液压式自动变速器中的离合器相似，但是尺寸要大很多，如下图2所示。双离合器为一大一小2组同轴安装在一起，分别通过输入轴1和输入轴2连接1、3、5档以及倒档和2、4、6档齿轮，如图3所示。利用液压缸内的油压和活塞压紧离合器，油压的建立是由ECU指令电磁阀来控制的，2个离合器的工作状态是相反的，不会发生2个离合器同时接合的情形。 the public to participate in, in imperceptible provided L people's cultural quality. To built use "Juxian issued on the micro channel," civilized Juxian "micro channel, Ju, networks and other mainstream network media continued to push send online is energy information, and create a good network environment. Deepen the action of the beautiful countryside civilization, to carry out a wide range of" new countryside, new life "training, give full play to the village population culture courtyard, Park Street, cultural square and other positions the role of publicity and education, promote rural way of life more civilized. This year the province's urban and rural sanitation integration of the rural masses satisfaction telephone survey, significantly improved performance in our county, respectively, than the end of last year, years to improve the 5.2,17.5 percentage points. The township streets. Relevant departments of counties units should conscientiously sum up experience, adhere to the problem oriented, people are not satisfied with the village as the focus of the work, insist on grasping both ends, with the middle, to consolidate and improve, expand further effort, in the realization of the normal long-term efforts, to ensure that the end of this year to obtain better results. Third, we need to accelerate the voluntary service system. To actively promote the party members and members and cadres normalization of volunteer service, do a good job in public places, window units and community volunteer service station construction, establishment of covering the whole 图2 DSG变速器有2根同轴心的输入轴，输入轴1装在输入轴2里面。输入轴1和离合器1相连，输入轴1上的齿轮分别和1档齿、3档齿、5档齿相啮合;输入轴2是空心的，和离合器2相连，输入轴2上的齿轮分别和2档齿、4档齿、6档齿相啮合;倒档齿轮通过中间轴齿轮和输入轴1的齿轮啮合。通俗地讲，离合器1管1档、3档、5档和倒档，在汽车行驶中一旦用到上述档位中任何一档， 、4档和6档，当使用2、4、6档中的任一离合器1是接合的;离合器2管2档 档时，离合器2接合，如图3所示。 图3 the public to participate in, in imperceptible provided L people's cultural quality. To built use "Juxian issued on the micro channel," civilized Juxian "micro channel, Ju, networks and other mainstream network media continued to push send online is energy information, and create a good network environment. Deepen the action of the beautiful countryside civilization, to carry out a wide range of" new countryside, new life "training, give full play to the village population culture courtyard, Park Street, cultural square and other positions the role of publicity and education, promote rural way of life more civilized. This year the province's urban and rural sanitation integration of the rural masses satisfaction telephone survey, significantly improved performance in our county, respectively, than the end of last year, years to improve the 5.2,17.5 percentage points. The township streets. Relevant departments of counties units should conscientiously sum up experience, adhere to the problem oriented, people are not satisfied with the village as the focus of the work, insist on grasping both ends, with the middle, to consolidate and improve, expand further effort, in the realization of the normal long-term efforts, to ensure that the end of this year to obtain better results. Third, we need to accelerate the voluntary service system. To actively promote the party members and members and cadres normalization of volunteer service, do a good job in public places, window units and community volunteer service station construction, establishment of covering the whole DSG变速器的档位转换是由档位选择器来操作的，档位选择器实际上是个液压马达，推动拨叉就可以进入相应的档位，由液压控制系统来控制它们的工作。在液压控制系统中有6个油压调节电磁阀，用来调节2个离合器和4个档位选择器中的油压压力，还有5个开关电磁阀，分别控制档位选择器和离合器的工作。 当然快速的换档离不开DSG变速箱的核心控制系统，包括:一个机电控制模块、带有多个独立传感器的控制阀组件以及执行机构。机电控制模块收集并处理传感器的信号数据，对双离合器、换档齿轮、液压系统压力等进行控制。另外，该系统还应用了调节阀、转换阀等许多液压阀。DSG变速箱的数据信息通过一个插入式通讯接口在机电控制模块和整车电气系统之间进行交换;通过这个接口，整车和发动机的数据信息也传递到DSG变速箱的控制系统。 2.2 DSG变速器的工作过程 DSG变速器的工作过程比较特别，在1档起步行驶时，动力传递路线如图1(a)中直线和箭头所示，离合器1接合，通过输入轴1到1档齿轮，再输出到差速器。同时，图中虚线和箭头所示的路线是2档时的动力传输路线，由于离合器2是分离的，这条路线实际上还没有动力在传输，是预先选好档位，为接下来的升档做准备的。当变速器进入2档后，退出1档，同时3档预先结合，如图1 所以在DSG变速器的工作过程中总是有2个档位是(b)中动力传递路线所示。 结合的，一个正在工作，另一个则为下一步做好准备。 DSG变速器在降档时，同样有2个档位是结合的，如果4档正在工作，则3档作为预选档位而结合。DSG变速器的升档或降档是由ECU进行判断的，踩油门踏板时，ECU判定为升档过程，作好升档准备;踩制动踏板时，ECU判定为降档过程，作好降档准备。 一般变速器升档总是一档一档地进行的，而降档经常会跳跃地降档，DSG变速器在手动控制模式下也可以进行跳跃降档，例如，从6档降到3档，连续按3下降档按钮，变速器就会从6档直接降到3档，但是如果从6档降到2档时，变速器会降到5档，在从5档直接降到2档。在跳跃降档时，如果起始档位和最终档位属于同一个离合器控制的，则会通过另一离合器控制的档位转换一下，如果起始档位和最终档位不属于同一个离合器控制的，则可以直接跳跃降至所定档位。 3 大众7档DSG 7档DSG双离合自动变速器不管在结构上还是在工作原理上与6档DSG双离合自动变速器相似，除了齿轮传动机构多了一对7档齿轮外，最大的区别在于双离合器的结构，如图4所示。7档DSG双离合器自动变速器采用干式双离合器。 双离合器由3个尺寸相近的离合器片同轴相叠安装组成。位于两侧的2个离合器片分别联接1、3、5、7档和2、4、6档以及倒档齿轮，中间盘在其间移动，分别与2个离合器片“结合”或“分离”，通过切换来进行换挡，如图5所示。相比湿式双离合器，干式双离合器结构简单，效率更高。但是干式离合器能够承受的最大扭矩比湿式离合器要低。所以，7档DSG可匹配最大扭矩为250牛米的“较小”的发动机。 the public to participate in, in imperceptible provided L people's cultural quality. To built use "Juxian issued on the micro channel," civilized Juxian "micro channel, Ju, networks and other mainstream network media continued to push send online is energy information, and create a good network environment. Deepen the action of the beautiful countryside civilization, to carry out a wide range of" new countryside, new life "training, give full play to the village population culture courtyard, Park Street, cultural square and other positions the role of publicity and education, promote rural way of life more civilized. This year the province's urban and rural sanitation integration of the rural masses satisfaction telephone survey, significantly improved performance in our county, respectively, than the end of last year, years to improve the 5.2,17.5 percentage points. The township streets. Relevant departments of counties units should conscientiously sum up experience, adhere to the problem oriented, people are not satisfied with the village as the focus of the work, insist on grasping both ends, with the middle, to consolidate and improve, expand further effort, in the realization of the normal long-term efforts, to ensure that the end of this year to obtain better results. Third, we need to accelerate the voluntary service system. To actively promote the party members and members and cadres normalization of volunteer service, do a good job in public places, window units and community volunteer service station construction, establishment of covering the whole 图4 图5 与6档DSG相比，7档DSG具有自己的特色: (1)双离合器系统结构得到简化。由于采用了干式双离合器结构，7档DSG变速箱就省去了吸滤器、油冷器以及变速箱壳体中的高压油管。与普通手动变速箱一样，变速箱油只用于变速箱齿轮和轴承的润滑和冷却。7档DSG变速箱油仅需要1.7升变速箱油，而6档DSG变速箱则需要6.5升。 the public to participate in, in imperceptible provided L people's cultural quality. To built use "Juxian issued on the micro channel," civilized Juxian "micro channel, Ju, networks and other mainstream network media continued to push send online is energy information, and create a good network environment. Deepen the action of the beautiful countryside civilization, to carry out a wide range of" new countryside, new life "training, give full play to the village population culture courtyard, Park Street, cultural square and other positions the role of publicity and education, promote rural way of life more civilized. This year the province's urban and rural sanitation integration of the rural masses satisfaction telephone survey, significantly improved performance in our county, respectively, than the end of last year, years to improve the 5.2,17.5 percentage points. The township streets. Relevant departments of counties units should conscientiously sum up experience, adhere to the problem oriented, people are not satisfied with the village as the focus of the work, insist on grasping both ends, with the middle, to consolidate and improve, expand further effort, in the realization of the normal long-term efforts, to ensure that the end of this year to obtain better results. Third, we need to accelerate the voluntary service system. To actively promote the party members and members and cadres normalization of volunteer service, do a good job in public places, window units and community volunteer service station construction, establishment of covering the whole (2)动力性和经济性得到进一步提高，排放和舒适性得到改善。由于增加了一个前进档，7档DSG变速箱的动力传输更加平顺。采用7个前进挡后，车辆的1档起步变得更短(减速比更大)，从而改善了车辆的起步性能。新增加的7档做为超速档，具有更小的减速比，对于降低油耗和排放、降低噪音及改善舒适性都产生积极作用。 (3)具有独立的电液控制系统，即液压系统独立于变速箱油的循环系统之外。这一设计大幅减小了液压系统的渗漏并改善了机电控制模块的低温工作性能。另外，这种模块化的设计使其便于进一步研发，以提高性能。 4 DSG双离合自动变速器的优势 (1)彻底消除了换档冲击，不仅可实现快速换档、平顺换档，而且有利于提高乘坐舒适性和汽车加速性能和最高车速。双离合变速器的换挡时间非常短，比手动变速箱的速度还要快，这使得驾驶者几乎感觉不到换档时所产生的顿挫感。。 (2)既没有液力自动变速器中的变矩器，又没有手动变速器中的离合器，所以双离合自动变速器的传动效率要高于液力自动变速器，并且在换档过程中没有动力中断，也就是让发动机的动力一直在利用，而且始终处于最佳的工作状态。与传统手动变速箱相比，在某些车型上，DSG变速箱可降低油耗达12%，而和采用变矩器的传统自动变速箱相比，降低油耗则高达20%。 (3)从制造工艺上看，双离合自动变速器属于定轴轮系自动变速器，可以基于现有的生产工艺，因此继承性要优于行星轮系自动变速器。 5 小结 DSG变速箱已经成为变速器技术的一个发展方向。DSG变速器既具有传统的有级式自动变速器的舒适性，又继承了手动变速器传动效率高、结构简单、加速性能好等优点，而且可以利用手动变速器的生产设备和技术，因而这种新的变速器类型特别适合我国手动变速器占主导地位的国情。 the public to participate in, in imperceptible provided L people's cultural quality. To built use "Juxian issued on the micro channel," civilized Juxian "micro channel, Ju, networks and other mainstream network media continued to push send online is energy information, and create a good network environment. Deepen the action of the beautiful countryside civilization, to carry out a wide range of" new countryside, new life "training, give full play to the village population culture courtyard, Park Street, cultural square and other positions the role of publicity and education, promote rural way of life more civilized. This year the province's urban and rural sanitation integration of the rural masses satisfaction telephone survey, significantly improved performance in our county, respectively, than the end of last year, years to improve the 5.2,17.5 percentage points. The township streets. Relevant departments of counties units should conscientiously sum up experience, adhere to the problem oriented, people are not satisfied with the village as the focus of the work, insist on grasping both ends, with the middle, to consolidate and improve, expand further effort, in the realization of the normal long-term efforts, to ensure that the end of this year to obtain better results. Third, we need to accelerate the voluntary service system. To actively promote the party members and members and cadres normalization of volunteer service, do a good job in public places, window units and community volunteer service station construction, establishment of covering the whole DSG变速器与有级式自动变速器相比，不仅具有同样的舒适性，而且其传动效率高，加速性能好，有利于继承现有有的生产工艺，所以DSG变速箱已经成为变速器技术的一个发展方向，也必将成为今后汽车市场上一个重要的增长点。我国的手动变速器厂可充分利用现有手动变速箱生产能力。 大众集团在中国大连投资4亿多美元的变速箱工厂已经动工。 昨天(3月11日)，记者获悉，该工厂由大众独资，预计将于2009年正式投产，其产品为大众DSG变速箱，届时将搭载在迈腾、TIGUAN等车型上。 该工厂设在大连市，将主要供应其与中国汽车制造商的合资企业一汽集 技术背景 1940年，Darmstadt大学教授Rudolph Franke第一个申请了双离合器变速器专利，该变速器曾经在卡车上试验过，但是没有投入批量生产。随后保时捷也发明了专用于赛车的双离合变速器 (PDK)。 然而，在那个时代，未能成功将DCT/PDK技术投入批量生产。到了20世纪90年代末期，大众公司和博格华纳携手合作生产第一个适用于大批量生产和应用于主流车型的双离合变速器。 双离合DualTronic?技术使得手动变速箱具备自动性能，同时大大改善了汽车的燃油经济性。应用该技术可以保证变速箱在换挡时消除汽车动力中断现象。博格华纳的核心技术:湿式离合器与干式离合器相比更具有竞争力，它能提供更好的稳定性和可控性，同时具有更长的使用寿命。该技术更因其具有的电子变速控制能力，即在任意驾驶条件下优化换档功能而显示其独特的优势。由于双离合变速器是基于平行轴设计的，因此，手动变速器厂可充分利用现有手动变速箱生产能力。 技术应用 大众汽车公司对外所命名为DSG技术，其实就是技术产品供应商博格华纳公司惯称为DualTronic?双离合自动变速器技术。 博格华纳为双离合自动变速箱开发的DualTronic?双离合自动变速湿式离合器和控制系统已于2003年批量生产，配套于大众奥迪革新产品DSG(直接换档变速器) ，最先应用于2003款大众高尔夫R32和奥迪TT上。博格华纳的双离合自动变速器因其产品创新和加工精细而赢得了2005年度北美供应商超级大奖。 随着DSG产品系列进入第三年的批量化生产，大众公司继续推广该技术的应用，现在已用于多款大众，奥迪车上，包括柴油车，燃油直喷涡轮增压汽油车。 在2006年，DSG产品系列将为至少10个汽油和柴油车型配套，包括:大众高尔夫, 大众葆来, 大众捷达, 大众途安, 大众帕萨特, 奥迪A3, 奥迪 TT, 西雅特Toledo和 Altea, 斯柯达的欧雅。 博格华纳的DualTronic?是业内第一个为自动变速箱配套湿式离合器和控制系统。此技术使传统的手动变速箱具有自动变速箱的功能，同时，根据不同的应the public to participate in, in imperceptible provided L people's cultural quality. To built use "Juxian issued on the micro channel," civilized Juxian "micro channel, Ju, networks and other mainstream network media continued to push send online is energy information, and create a good network environment. Deepen the action of the beautiful countryside civilization, to carry out a wide range of" new countryside, new life "training, give full play to the village population culture courtyard, Park Street, cultural square and other positions the role of publicity and education, promote rural way of life more civilized. This year the province's urban and rural sanitation integration of the rural masses satisfaction telephone survey, significantly improved performance in our county, respectively, than the end of last year, years to improve the 5.2,17.5 percentage points. The township streets. Relevant departments of counties units should conscientiously sum up experience, adhere to the problem oriented, people are not satisfied with the village as the focus of the work, insist on grasping both ends, with the middle, to consolidate and improve, expand further effort, in the realization of the normal long-term efforts, to ensure that the end of this year to obtain better results. Third, we need to accelerate the voluntary service system. To actively promote the party members and members and cadres normalization of volunteer service, do a good job in public places, window units and community volunteer service station construction, establishment of covering the whole 用，与自动变速箱相比，可减少排放并节省燃油高达15%。另外，它消除了手动变速箱在换挡时的扭矩中断感，使驾驶更灵敏，同时又充满乐趣。据预测到2015年欧洲乘用车市场对此技术的需求会增至20%。博格华纳在电液控制系统上的专长和在湿式摩擦材料，离合器系统方面的经验可为用户提供节能，高效的驾驶体验。此技术所带来的优越性已被越来越多的用户认可。 工作原理 双离合自动变速器(简称DCT)基于手动变速箱基础之上。而与手动变速箱所不同的是，DCT中的两幅离合器与二根输入轴相连，换挡和离合操作都是通过一集成电子和液压元件的机械电子模块来实现。而不再通过离合器踏板操作。就像tiptronic液力自动变速器一样，驾驶员可以手动换挡或将变速杆处于全自动D挡(舒适型，在发动机低速运行时换挡)或S挡(任务型，在发动机高速运行时换挡)模式。此种模式下的换挡通常由挡位和离合执行器实现。两幅离合器各自与不同的输入轴相连。如果离合器1通过实心轴与挡位1、3、5相连，那么离合器2则通过空心轴与挡位2、4、6和倒挡相连。 发动机的输入轴通过缓冲器与两幅离合器外片相连。发动机启动后自动挂1挡。由于离合器1处于打开状态，因而没有扭矩传到驱动轮。当离合器1关闭时，离合器1的外片逐渐贴合内片并开始通过第一挡的实心轴、齿轮组和同步器传动发动机扭矩至差速器，最终至驱动轮。同时，由于离合器2此时并不传递扭矩，因此第二挡已被预先选定。从第一挡换到第二挡时，由于第一挡的解除和第二挡的挂挡在同一速度，车辆有足够的前冲力。当第离合器2完全接合后，第三挡已被预先选定，因为此时离合器1没有接合，不传导扭矩，挂挡原理依次类推。此时驾驶员仅感觉到离合器转换。对快速换挡操作来说，换下一挡即意味着与之相连的离合器开放，但此挡位预先选定。通过变速箱控制软件的复杂算法，根据驾驶员各自的需要调整换挡类型和换挡速度确保了选定正确挡位。通过设计，双离合变速器中的最大差速小于传统的液力自动离合器，该类离合器操作起来简便快速，与传统的液力自动离合器相比，其舒适感也更高，或不低于液力自动变速器。通过简单的控制软件即可实现从运动型到高舒适型驾乘体验的改变，因此可有效的控制成本以满足不同层次市场、客户的需求。下图是装有湿式双离合器变速箱的大众高尔夫 R32与同一型号的装有6速手动变速箱的车型操作性能的比较: 装备了DCT的汽车也能达到装备手动变速箱汽车同样高的速度。同时，与传统的手动变速箱相比，它具有更好的加速性能， 因为它消除了扭矩中断并且经过欧洲节能循环测试证明(MVEG)，可节省燃油10%，因为其优化的换挡系统可使发动机在最佳效率下连续运转。目前市场上尚未有其他变速箱能具有同样的性能。由于取消了变矩器作为启动装置，车辆的驾驶性，灵敏度和节油性均有很大提高。与众不同的是，DCT的湿式离合器同时采用换挡离合和发动装置。而取消变扭器则极大的减低了重量和惯性。更重要的是驾驶员可独立选择控制车辆。变扭器具有特定的性能(各种扭矩设定、爬行和震动缓解等作用)。一旦设计选定，性能就固定。除了具有取消变扭器的好处外，湿式DCT离合器与无级变速器(CVT)和行星液力自动变速器相比，具有节省燃油和提高驾驶性能的优势。因为它的设计基于具有良好机械性能的平行轴变速器，同时又减少了离合器数量和相关阻力，并可控制离合压力和油供给，具有优化的齿轮传动比和比例扩展。与无级变速器和液力自动变速器不同的是，齿轮传动比和传动比范围可以轻松简the public to participate in, in imperceptible provided L people's cultural quality. To built use "Juxian issued on the micro channel," civilized Juxian "micro channel, Ju, networks and other mainstream network media continued to push send online is energy information, and create a good network environment. Deepen the action of the beautiful countryside civilization, to carry out a wide range of" new countryside, new life "training, give full play to the village population culture courtyard, Park Street, cultural square and other positions the role of publicity and education, promote rural way of life more civilized. This year the province's urban and rural sanitation integration of the rural masses satisfaction telephone survey, significantly improved performance in our county, respectively, than the end of last year, years to improve the 5.2,17.5 percentage points. The township streets. Relevant departments of counties units should conscientiously sum up experience, adhere to the problem oriented, people are not satisfied with the village as the focus of the work, insist on grasping both ends, with the middle, to consolidate and improve, expand further effort, in the realization of the normal long-term efforts, to ensure that the end of this year to obtain better results. Third, we need to accelerate the voluntary service system. To actively promote the party members and members and cadres normalization of volunteer service, do a good job in public places, window units and community volunteer service station construction, establishment of covering the whole 便的予以改变。与手动变速箱相同的是，基于一种变速箱，可以有多种传动比设 置，并且一种传动比范围设置可以超过7个，以最小的成本增加实现为每种特定 发动机和车辆的最佳匹配。在大扭矩柴油机、高转速汽油机、小货车或跑车上使 用同种传动比和传动比范围的液力自动变速箱，会牺牲整车性能和效率。而安装 DCT的车辆并不存在此问题。 the public to participate in, in imperceptible provided L people's cultural quality. To built use "Juxian issued on the micro channel," civilized Juxian "micro channel, Ju, networks and other mainstream network media continued to push send online is energy information, and create a good network environment. Deepen the action of the beautiful countryside civilization, to carry out a wide range of" new countryside, new life "training, give full play to the village population culture courtyard, Park Street, cultural square and other positions the role of publicity and education, promote rural way of life more civilized. This year the province's urban and rural sanitation integration of the rural masses satisfaction telephone survey, significantly improved performance in our county, respectively, than the end of last year, years to improve the 5.2,17.5 percentage points. The township streets. Relevant departments of counties units should conscientiously sum up experience, adhere to the problem oriented, people are not satisfied with the village as the focus of the work, insist on grasping both ends, with the middle, to consolidate and improve, expand further effort, in the realization of the normal long-term efforts, to ensure that the end of this year to obtain better results. Third, we need to accelerate the voluntary service system. To actively promote the party members and members and cadres normalization of volunteer service, do a good job in public places, window units and community volunteer service station construction, establishment of covering the whole