【机械类毕业论文中英文对照文献翻译】悬架几何
收藏
资源目录
编号：77690342
类型：共享资源
大小：743.85KB
格式：RAR
上传时间：2020-05-07
上传人：柒哥
认证信息
个人认证
杨**（实名认证）
湖南
IP属地：湖南
6
积分
- 关 键 词：
-
机械类毕业论文中英文对照文献翻译
机械类
毕业论文
中英文
对照
文献
翻译
悬架
几何
- 资源描述：
-
【机械类毕业论文中英文对照文献翻译】悬架几何,机械类毕业论文中英文对照文献翻译,机械类,毕业论文,中英文,对照,文献,翻译,悬架,几何
- 内容简介：
-
附录A悬架几何引言无论设计乘用车还是赛车的悬架系统都需要各种学科的知识。这一章只涉及到其中的一方面，悬架几何的学习，没有设涉及到悬架元件在载荷变化下，产生位移与变形所产生的影响。这些影响将在23章讨论。当我们谈论悬架几何时，它表示的是怎样把整车的非簧载质量与簧载质量联系起来。这些联系不仅决定着它们之间的相对运动也影响着它们之间力的传递。每种悬架几何结构的设计必须满足你对应的车型的要求。所以不会存在唯一的最好的悬架几何结构。17.1自由度与运动路径对于独立悬架，不管前悬架还是后悬架，其控制臂的作用就是控制车轮相对车身的运动在一个理想的路径。由于设计者的设计，外倾角，内倾角，前束角在这个路径中会产生各种变化，但是当上下运动时，悬架运动仍然遵循这个路径。换句话说，车轮相对车架有一个固定的运动路径。相对这个路径不会发生前后或水平方向的改变。转向节不会随意转动，而是由这个路径决定.悬架在弹簧减震器的作用下上下运动时，通过悬架横臂的相互连接来精确控制，转向节在各个方向上的位置。在前悬架中，只有在人为的控制转向器的是时候，才有一定转向的自由度。在空间上对于任何一物体相对于另一物体的运动而言，它的相对运动可分为三个位移运动的组成合三个转动运动的组成（见图17.1）。在三维的空间里一个物体拥有6个自由度。我们以上所说的任何一种独立悬架上的转向节相对于车架只有一种运动路径，换句话说，限制了悬架的五个方向上的自由度。实际上，机械元件提供的约束就限制自由度方面而言并不是完美的。因此独立悬架几何的学习是来控制怎样约束转向节来限制其他五个方向上的自由度。在设计悬架几何中，如果你所能用的为唯一的元件是带有杆端轴承的杆件的话，便能够提供五个自由度当中的一个约束，换句话说，提供五个自由度的约束需要五个张紧受力的杆件。为了联系概念，以便更了解的更加清楚，我们需要明白，典型的悬架原件是怎样提供约束的。通过图17.2我们可以看到，一个A臂是由两个带有杆端的球铰副的直杆组成。一个麦弗逊的支柱是以是一个滑动运动机构，在一定的角度滑动行程内，它等同于一个A臂。现在，带着这种思想，我们来看一下大多数的独立悬架，想出五个杆件的连接的各种方案。（见图17.3）。标准的赛车的双横臂悬架有两个A臂，再加上一个横拉杆。如此每个A臂有两个杆，一个横拉杆总共5个。一个麦弗逊的滑柱看做有两个杆，下横臂有两个，加上横拉杆也是五个。有一些悬架用的杆件比较少可能不是那么明显，但是最终的目的是达到对运动的约束。其中一个例子是拖曳臂式后悬架。只有一个横臂起到五个杆的作用，为了达到要求，必须足够结实以承受三个转动方向上的转矩与扭矩。对于非独立悬架的后轴来说，两个车轮联系在一起，所以其中一个车轮运动会影响到另一个（见图17.4）。当两个车轮联系在一起，它们相对于车身有两种不同的运动，它们可以一起上下运动，也可以反方向一个向下一个向上运动。在运动过程中，这个轴相对车身有两个自由度。在空间中，总共有六个自由度，当我们设计非独立悬架时，我们需要限制其中的四个。可以通过一个梁代表四个受力的杆来实现。17.2 瞬时中心的定义在接下来的这一章里，瞬时中心将用来描述和决定一些悬架的基本参数。为了清楚地明白这些讨论，关于瞬时中心的定义将按顺序来说明。“瞬时”的意思是杆的连接在那一确切的位置。“中心”代表的是假想的，杆的连接处的瞬时转动点的有效投影点。图17.5表明了怎样一个长杆代替两个短杆。随着杆的连接时移动的，瞬时中心也是动的，所以合适的几何设计不仅建立在所有的瞬时中心随离地间隙的变化出现在它们期望的位置，也要随悬架的行程的变化，控制瞬时中心位置的变化与变化的快慢。瞬时中心来源于在二维平面内的动态的学习。这样形象的表达出了两个物体之间的运动关系。在悬架设计中，将三维问题转化为二位问题可以变得很方便。这样我们讨论前视图和侧视图。我们做出经过车轮中心的铅垂面，一个平行于汽车的中心线，另一个垂直于汽车中心线。然后我们把悬架的关键点投影到这两个平面上。当我们用一条线连接球铰接点和控制臂之间的轴套，把它投影到包含上下横臂的平面，然后这两条先将在某点相交，这个交点便是杆的瞬时连接点。如果在前视图里做投影，得到的瞬时中心影响着外倾角的变化率、侧倾中心的某些信息、磨胎运动和一些决定着转向特性的某些数据。如果你在侧视图里作投影，得到的瞬时中心，将影响着车轮的运动路径，抗俯仰特性，主销后倾角的变化率。在三维空间里，三个正交视图中，俯视图得到的有关轮胎路径变化的信息是最少的。瞬时轴线在真正的三维空间里瞬时中心被瞬时轴线所代替。如果我们把前视图和后视图的瞬时中心相连，便得到一条线。这条线可以看做相对车身的瞬时转动轴线（见图17.6）。独立悬架有一个运动的瞬时轴线，这是因为它们有五个约束：当然，这条瞬时轴线随离地间隙的变化而变化。后轴有两个瞬时轴心，一个对应悬架的上下跳动，一个对应侧倾运动。它们也随着离地间隙的变化而运动。所以无论何时我们学习一个悬架系统，都需要完成它的瞬时中心和瞬时轴先。这章的余下部分将涉及到常见的前后悬架类型的这些轴线的决定因素，此外也设计到它们的一些调整，来满足赛车的需求。17.3独立悬架对于所有的独立悬架它们都有两个瞬时中心，来完成悬架特性的设计。侧视图的瞬时中心控制与前后加速度有关的力与运动，前视图的瞬时中心控制与水平方向的加速度有关的力与运动。前视图中的等视摆臂几何。前视图中控制臂瞬时中心的位置控制着侧倾中心的高度，外倾角变化率，轮胎水平方向上的磨胎运动。瞬时中心可以在车轮的内侧，也可以在车轮的外侧。它可以在水平面以上或水平面以下。它确切的位置取决于设计者的要求。侧倾中心高度侧倾中心的高度是在前视图中，由轮胎的接地点与瞬时中心的连线与汽车中心线的投影的交点测量而得的（见图17.7（a）。通过在汽车的两侧作图而得，这两条线的交点便是车的簧载质量相对地面的转动中心。这也并不一定是在汽车的中心线，尤其是对于非对称的悬架几何结构（见图17.7（b），或者是汽车在转弯的时候。很显然瞬时中心距离地面的高度，与轮胎的距离，在车轮的内侧还是外侧决定着侧倾中心的位置。现在你知道怎样找到侧倾中心，那它代表什么意思呢？在簧载质量与非簧载质量之间，由侧倾中心建立了离心力的作用点。当一辆车转弯时，作用于中心的离心力，被轮胎与地面的摩擦力所抵消。如果适当的力与力矩（有关侧倾中心的）被显示出来，作用于CG的水平力可以转移到侧倾中心上来。侧倾中心越高围绕侧倾中心的侧倾力矩就越小。侧倾中心越低的话，侧倾力矩就越大。你也会注意到，侧倾中心越高的话，作用于侧倾中心的水平力，也就力地面越高。这种水平作用力与它到地面的距离的乘积被认为是非侧倾力矩。所以侧倾中心的高度是权衡侧倾力矩与非侧倾力矩的相对影响的结果。（见18章关于这些影响的另一个解释）以上部分简单而直接。然而在建立一个期望的侧倾中心高度的时候有另外一个影响因素，那就是横纵向的耦合效应。如果侧倾中心高于水平面，来自于轮胎的横向力形成了关于瞬时中心的力矩。这个力矩向下压轮胎，向上抬升簧载质量，叫做千斤顶效应。（见图17.8（a）。如果侧倾中心低于水平面，这个力矩将会向下压簧载质量。无论哪种情况，由于水平力的作用，将会使簧载质量收到垂直方向上的力的作用。在带有非独立悬架的老式车上很常见。另一个分析这种方案的方法见图17.8（b）。这里作用与接触点的所有力在瞬时中心这个作用点被分解成水平方向与垂直方向上的力，图中所示的垂直力将会抬升簧载质量。外倾角变化率侧倾中心与等效摆臂的长度与高度有关。外倾角的变化率仅与等效摆臂的长度有关（见图17.9）当我们可以把悬架的横臂简化为一个摆动的杆时，这个轮胎外倾角的变化率就可以由这个式子求出了arctan(l/fvsa length) ，即车轮每运动一英寸对应的车轮外倾角变化。由图2-3我们可知，短的臂长会造成大的外倾变化，长的臂长造成小的外倾变化。注：这个是不同于静态车轮外倾设置和定位的。附录BSuspension GeometryIntroductionDesigning suspension systems for production or racing cars requires technical knowledge in several disciplines. This chapter will cover only one of those disciplines-the study of suspension kinematics or geometry.This chapter does not cover the effects of compliance or deflections of structural components under load ; these effects are discussed in Chapter 23.When we talk about suspension geometry it means the broad subject of how the unsprung mass of a vehicle is connected to the sprung mass. These connections not only dictate the path of relative motion, they also control the forces that are transmitted between them. Any particular geometry must be designed to meet the needs of the particular vehicle for which it is to be applied. There is no single best geometry.17. 1 Degrees of Freedom and Motion Path For an independent suspension, be it front or rear, the assemblage of control arms is intended to control the wheel motion relative to the car body in a single prescribed path. That path may have camber gain, caster change, and toe change as prescribed by the designer but it still follows only one path as it moves up and down. In engineering terms we could say that the wheel has a fixed path of motion relative to the car body. It is not allowed to move fore and aft laterally relative to this path. The knuckle is not allowed to rotate other than as determined by this fixed path (of course the wheel is allowed to roll around the spindle axis). The suspension linkages are expected to position the knuckle (wheel) very accurately in all directions while allowing it to move up and down against the spring and shock. In front suspension we do have a steer rotation degree of freedom but only when it is demanded from the steering system. For any body moving in space relative to another body. Its motion can be completely defined by three components of linear motion and three components of rotational motion (see Figure 17. 1). A single body is said to have six degrees of freedom of motion in a three-dimensional world. We said above that any independent suspension allows only one path of motion of the knuckle relative to the body. Another way to say the same thing is that the suspension provides five degrees of restraint (D. O. R.), i. e. It severely limits motion in five directions. In the real world, the mechanical components that supply the restraints are not perfect” in the sense of restraining the motion to a particular degree of freedom. Therefore the study of independent suspension geometries is to determine how to restrain the knuckle to limited motion in live directions.If the only components you could use to design a suspension geometry were straight links with rod ends (spherical joints) on each end, the required restrains can be provided with five of them. In other words to obtain five degrees of restrains requires exactly five tension-compression links.To relate this concept to more familiar hardware, we need to understand how typical suspension components provide their restraining function. Looking at Figure 17.2 You can see that an A-arm is really equivalent to two straight links with their outer ends coming together at the ball joint. A Macpherson Strut is kinematically a slider” mechanism which is equal to an A arm that is infinitely long at right angles to the slider travel.Now, with this in mind, we can look at most independent suspensions and come up with a count of five links in every case(see Figure 17. 3), The standard racing double wishbone suspension has two A-arms plus a tie rod Thus two links for each A-arm and one link for the tie rod adds up to five. A Macpherson Strut suspension has two for the strut, two for the lower A arm and the tie rod makes live. There are some suspensions that are less obvious because they have fewer links, but what they are usually doing is introducing a bending requirement to achieve restraint of motion. An example of this is a semi trailing arm rear suspension. There is one arm that does the job of live links, but in order to do it, it must be strong in bending and torsion in the three directions of rotation. For solid axle (or beam type) rear (and occasionally front) axles, the two wheels are tied together, so motion of one affects the other (see Figure 17. 4). When two wheels are tied together, they have two different motions relative to the body ; they can go up and down together (parallel bump motion) or they can move in opposite directions one up and one down (roll motion). In kinematic terms the axle has two degrees of freedom of motion relative to the body. There is a total of six degrees of motion in space ; we must restrain four when we design a beam-type rear suspension. This can be accomplished with a linkage having just four tension-compression links.17. 2 Instant Center Definedthroughout the rest of this chapter the term instant center (IC) will be used in describing and determining several common suspension parameters, To help achieve clarity in these discussions some comments about what is an instant center, are in order. The word “instant means at that particular position of the linkage. “Center” refers to a projected imaginary point that is effectively the pivot point of the linkage at that instant. Figure 17. 5 suggests how two short links can be replaced with one longer one. AB the linkage h moved, the center moves, so proper geometric design not only establishes all the instant centers in their desired position at ride height, but also controls how fast and in what direction they move wide suspension travelInstant centers come from the study of kinematics in two dimensions (in a plane). They are a convenient graphic aid in establishing motion relationships between two bodies. In suspension design it is convenient to break down this three-dimensional problem into two, two-dimensional problems. We talk about the front view and the side view geometry. What we are doing is cutting vertical planes (9oe to the ground) through the wheel center, one parallel to the centerline of the car, and the other at a right angle to the vehicle centerline. We then project all the suspension points onto these planes. when we connect a line between the ball joint and the control arm bushing and project it across e plane both for the upper and lower control arms they will usually intersect at some point This intersect is an instantaneous linkage center. If you do the projection in the front view the instant center defines the camber change rate, part of the roll center information scrub motion, and data needed to determine the steer characteristics. If you are working with the side view, the instant center will define the wheel fore and aft path, anti-lift and anti-dive/squat information, and caster change rate. As with any three-dimensional objects, three orthogonal views are possible : because the third view (top view) is approximately along the single (ride) degree of freedom it contains little useful information about the path of the wheel. Instant Axis In true three dimensional space, instant centers are replaced by instant axes. If we take the instant centers defined in the side view and the rear view and connect them together we get a line. This line can be thought of as the instant axis of motion of the knuckle relative to the body (see Figure 17. 6). Independent suspensions have one instant axis of motion because they have five restraints ; of course, this instant axis moves with changes in ride height. Rear axles have two instant axes, one for parallel bump and one for roll ;these also may move with changes in ride height So whenever we are studying a particular suspension system we need to establish the instant centers and/or the instant axes. The remainder of this chapter will be devoted to the determination of these axes for many common types of front and rear suspensions, with additional comments in regard to their adjustability to meet the needs of race cars. 17. 3 Independent SuspensionsFor all independent suspensions there are the two instant centers (which change with bump and droop) that establish the properties of that particular design. The side view instant center controls force and motion factors predominantly related to fore and aft accelerations, while the front view instant (or swing) center controls force and motion factors due to lateral accelerations.Front View Swing Arm Geometry The front view swing arm (fvsa) instant center location controls the roll center height (RCH), the camber change rate, and tire lateral scrub. The IC can be located inboard of the wheel or outboard of the wheel. It can be above ground level or below ground. The location is up lo the designers performance requirements.Roll Center Height The roll center height is found by projecting a line from the center of the tire-ground contact patch through the front view instant center shown in Figure 17. 7 (a). This is repeated for each side of the car, where these two lines intersect is the roll center of the sprung mass of the car, relative to the ground. It is not necessarily at the centerline of the car, especially with asymmetric suspension geometry (Figure 17. 7 (b) or once the car assumes a roll angle in a turn. It is obvious that the roll center location is controlled by the instant center heights above or below ground, the distance away from the tire that the instant center is placed, and whether the instant center is inboard or outboard of the tire contact patch.Now that you know how to find the roll center, what does it mean? The roll center establishes the force coupling point between the unsprung and sprung masses. When a car comers, the centrifugal force at the center of gravity is reacted by the tires. The lateral force at the CG can be translated to the roll center if the appropriate force and moment (about the roll center) are shown. The higher the roll center the smaller the roll moment about the toll center (which must be resisted by the springs) ; the lower the roll center tile larger the rolling moment. You will also notice that with higher roll centers the lateral force acting at the roll center is higher off the ground. This lateral force the distance to the ground can be called the nonrolling over moment. So roll center heights are trading off the relative effects of the rolling and nonrolling moments. (See Chapter 18 f
- 温馨提示:
1: 本站所有资源如无特殊说明，都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
2: 本站的文档不包含任何第三方提供的附件图纸等，如果需要附件，请联系上传者。文件的所有权益归上传用户所有。
3.本站RAR压缩包中若带图纸，网页内容里面会有图纸预览，若没有图纸预览就没有图纸。
4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
5. 人人文库网仅提供信息存储空间，仅对用户上传内容的表现方式做保护处理，对用户上传分享的文档内容本身不做任何修改或编辑，并不能对任何下载内容负责。
6. 下载文件中如有侵权或不适当内容，请与我们联系，我们立即纠正。
7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
人人文库网所有资源均是用户自行上传分享，仅供网友学习交流，未经上传用户书面授权，请勿作他用。
川公网安备: 51019002004831号