英文翻译
TRANSMISSION TYPES AND OPERATION
Travel-speed-changing systems found in tractors vary considerably particularly with respect to the number of speeds, kinds of gears, and methods of shifting. Based on these factors, transmission types can be classified as (1) sliding spur gear, (2) constant-mesh with shifting collars, (3) Synchromesh, and (4) hydrostatic. Also with respect to changing speeds, it can be done manually with a hand-lever or automatically by hydraulic pressure. These variations will be explained in connection with the descriptions of different makes of tractor transmissions. In general, the smaller sizes of tractors, 20 to 40 PTO hp use simpler transmissions with fewer travel speeds, while the larger sizes have speeds ranging from six or eight to twelve or sixteen. In such cases, provision is made for shifting from the "low-range" to the "high-range" speeds or vice versa while the tractor is in motion, and without disengaging the master clutch and coming to a dead stop. These advantages, in turn, permit a closer and more convenient adjustment and a quicker response of power, torque, and tractive ability of the tractor to the specific drawbar-load conditions and requirements.
Plain Spur-Gear Transmission Figure 18-7 illustrates the design and operation of the type of transmission originally used in earlier tractors and still used in some small, current models. As shown, the different speeds are obtained by sliding gears of a certain size into me h with others of another size. Reverse requires an additional single gear on a separate short shaft. The entire mechanism operates in an oil bath in a special housing. The bearings may be plain or antifriction type. The different speeds are obtained by a manually operated lever attached to certain gears in such a manner as to slide them into mesh with others that are stationary. These changes can only be made with the main clutch disengaged and the tractor stationary. Figure 18-8 shows a similar transmission used in a high-clearance row-crop tractor.
Deere Horizontal Two-Cylinder Transmission Figure 18-9 shows a two-cylinder, horizontal engine equipped with a four-speed sliding gear transmission and spur-gear final drive for the axles and wheels.
Allis-Chalmers Dual-Range Transmission The AUis-Chalmers dual-range (Fig. 18-10) consists of an eight-speed, constant-mesh unit with helical gears and shifting collars. A special double-unit, hand-lever-operated disk clutch that runs in oil has three positions: "Low-range," "High-range," and "Neutral." The change from one range to the other can be made by means of this clutch and a hydraulic assist mechanism while the tractor is moving.
Ford Dual-Power Transmission Figure 18-11 illustrates a manual shift transmission, which normally has eight forward speeds and two reverse speeds. However, if the tractor must operate at slower speeds and under heavier draft conditions, this transmission can be equipped with an optional gear assembly that will provide eight additional forward and four additional reverse speeds. The shift is made by a single lever without stopping the tractor. The travel speed is reduced, but the pulling power is increased to permit the handling of unexpected or difficult situations.
Deere Hydraulic Hi-Lo Range Tractor Figure 18-12 is a six-cylinder, 80 hp tractor having a two-range transmission with twelve forward and three reverse speeds. Table 18-1 gives the travel speeds for each range.
International Harvester 60 hp Tractor Figure 18-13 shows the complete power transmission train for an International Harvester 60 hp tractor having two travel speed ranges with four forward speeds for each one. This is a constant-mesh synchronized transmission. A Hi-Lo-Reverse range lever permits shifting between forward and reverse for shuttle-type operation on back-and-forth operations. The entire power train is pressure lubricated. The wet-disk brakes are hydraulic actuated and self-adjusting.
Deere Four-Wheel-Drive Tractor Figure 18-14 illustrates the power train and transmission design for a four-wbeel-drive tractor. Power is first transmitted to two sets of primary master gears. These gears, in turn, transmit power to two sets of change-speed gears by which the different
ravel speeds are obtained. These gears then transmit the power to the front and rear final-drive gears and axles. Hydraulically operated front and rear differential locks simultaneously lock both axles. Both locks are operated by a single foot pedal which can be engaged or disengaged on the go.
Track-Type Tractor Transmissions The transmissions for the track-type tractors are not unlike those in wheel machines except that the steering mechanism is incorporated in them. That is, the ordinary wheel tractor
s propelled by the rear wheels and guided by means of the front wheels, whereas the conventional track-type tractor, having but two traction members, must be both propelled and guided through them.
Caterpillar Transmission Figure 18-15 shows the change-gear set for the Caterpillar tractor. The power is transmitted to a countershaft by means of bevel gears; then, through two steering clutches located on this countershaft on each side of the bevel gear, to the spur-type final-drive gears; and then to the sprocket. Steering is accomplished through the multiple-dry-disk steering clutches; that is, by means of hand levers, either clutch can be disengaged, which obviously cuts off the power to that particular track and causes the tractor to make a turn. Each clutch is equipped with a foot-operated brake that acts on the outside of the clutch drum carrying the driven plates. If a quick, short turn is desired, not only is the clutch released but the brake for that particular clutch is actuated and the track movement virtually stopped on the one side. With all the power going to the other track, the machine obviously will turn very short. By pressing on both brakes at the same time, the machine can be stopped almost instantly. It should be noted that a differential is unnecessary in the Caterpillar transmission.
Caterpillar Planetary Transmission Figure 18-16 shows a planetary transmission and power train for a track-type tractor. Power from the engine is first transmitted to the torque converter by the crankshaft, then to the planetary power-shift transmission. This unit consists of a certain number of planetary units that vary in size. Large clutch packs surround each gear set and engage with special hydraulic modulation for smooth, cushioned shifting. The clutch plates and gears are cooled by oil. For operations that do not require frequent direction changes this tractor can be equipped with a gear-type transmission.
Hydrostatic Drives and Power Transmission The basic principles involved in the operation of hydrostatic drives are explained in Chap. 20. A hydrostatic drive mechanism consists essentially of two major units, namely, a positive displacement pump driven by the original power unit and a positive displacement motor, which receives its energy from the pump. In other words, the tractor engine develops and transfers mechanical energy to the pump. The pump unit then converts this mechanical energy into hydraulic energy, which operates the motor unit and thus, in turn, produces mechanical energy to propel the tractor.
传输方式和操作
传输系统发现在拖拉机类型相差很大的情况下，尤其是对其速度，各种齿轮及传输方法方法的转变。基于这些因素,传输形式可分为(1)滑动滑移齿轮传递(2)转移项圈传递(3)同步器传递和(4)压力传递。也就是说要改变速度可以自动手动或者是利用液体的压力。这些变化可以解释和说明为什么有不同类型的拖拉机取力器。总的来说,小功率拖拉机使用更简单的传输方式,同时，其传输速度从6或8到12或16。在这种情况下,是为从工作状态向较高的速度变化或反之亦然，而拖拉机在运动时并没有脱离主离合器而停下。小功率拖拉机的这些优点,允许其更方便的调整和较快的响应的力量、扭矩、拖拉机叶轮能力的具体条件和要求。
Spur-Gear传输数字说明了设计和传输的操作类型。最初是用在更早的拖拉机,和一些小型的，电流模拟程序的机械上。不同的速度的转换需要具有一定规不同速度的转换的实现是由一对齿轮或多对齿轮相啮合来实现的。当需要反向操作时，则需要增加一个惰轮，一对齿轮中间，只改变力的方向，不改变力的大小。整个传动机构安装在一个壳体里，其中，装有大量的润滑油来保证润滑。轴承也轴承的选择既可以是承受力的也可以只起支承座用。不同的速度，通过手动操纵杆的控制有一个固定的传动比。每一个转速的传动比是固定的，不同转速的传动比是不同的。当转速发生变化是，离合器要断开传力，使发送几所传出的动力到不了变速箱，变速箱内的转速有一个相对的静止。见原文图18 - 8展示了一个用于high-clearance row-crop拖拉机上的类似的传输方式。
见原文图18 - 9 显示一个双轮缸传输数字迪尔水平,横向引擎装有四滑动齿轮传动,利用双联齿轮和轴传递力。
见原文图18- 10示的是一个有可变速功能的双向离合器控制的，圆柱斜齿轮传动的取力器。因为有一个特别的双向的盘式离合器,手动取力器可以控制其实现三个功能:工作状态，挂高速档和脱离啮合，处于空挡位。通过这样一个离合器，就可以使传输的速度发生一定的变化，并利用液压辅助装置，是拖拉机实现一定的牵引能力。
见原文图18-11中的数字说明福特Dual-Power传输系统的情况,这个传输系统，拥有八个前进挡，两个倒退档。然而,当拖拉机必须实现较慢的转速较大的功率的情况下,在主变速箱总体情况不变的情况下,这种传输会配备一个起落架组件作为副变速箱使前进挡和倒退档的转速变化范围提高一倍。这一变化是由一个单一的杠杆来控制的，而不要求拖拉机动力断开。当拖拉机转速降低时，拖拉机的扭矩就会增加，增大其爬坡能力。
见原文图18-12显示的事林韵梅液压高低变化范围,拖拉机是表六，这种拖拉机是双齿轮传输，她可以有十二种传输速度的变化，和提供三种扭矩。速度和三个扭转。表1给出了速度为18m/s的变化范围。
见原文图18 - 13国际收割拖拉机，展示完整的电力传输列车。每一个国际收割拖拉机都有两种速度变化范围，其中每一种速度变化范围都有四个前进挡，和一个倒退档。这是一个利用同步器的同步传输。利用一个杠杆来控制整个变速箱的前进和倒退，以及各个转速之间变化的操作。整个变速箱采用的是压力润滑。压力润滑的实现是靠一个压力系统和自我压力调节控制器的控制。
见原文图18 – 14显示的是由迪尔公司设计的四轮驱动的拖拉机传动机构。发动机功率首先通过传动轴传递到两个后轮上，再由两个后轮传递到两个前轮上。变速箱可以提供两种不同的速度。从齿轮中发出的力矩，经过轴承，轴，以及其他传出装置的传递，最后传递到四个车轮上来控制拖拉机的前进与倒退。液压装置可以控制两个锁销同时锁紧。这些传递动力的过程都是由一个脚踏板式的操纵机构来控制完成的。
拖拉机牵引的履带式推土机,不像其他履带式推土机那样是一个有独立的传输机构的机器。也就是说,普通的传统的轮拖拉机用后轮作为驱动轮带领前轮转动,但两履带推土机拖拉机既是被牵引机构又起积极的引导作用。
见原文图18-15显示的是履带推土机拖拉机传输。(由个别公司不能履带式拖拉机通讯器)。电力传递到中间轴上的渐开线齿轮;然后,通过两个转向离合器，和位于副传动轴上的每一个渐开线齿轮;最后传递到最终传力机构。转向的实现是靠转向离合器;也就是说,通过手操纵杠杆,离合器,可自动切断电源,同时，运动时需要的特殊的运动轨迹也是由拖拉机完成的。每一个制动离合器都会配备一个简便的从动盘鼓。如果一个快速的，短时间的变速,是理想情况，那么不仅是制动离合器,而且离合器的释放与转动都是与特定的轨迹相符合的。要所有的力量去完成另一个轨迹的传递,显然会很苦难。按下两个刹车的同时,机器可以几乎立刻就停止。值得注意的是,一个模拟毛毛虫运动的传输的方式。
见原文图18 – 16（卡特彼勒行星传动）利用行星轮传递力的履带式推土拖拉机。先从发动机功率传输到变矩器的曲轴,然后到行星传动机构。组成本单元的行星的单位数大小不等。大离合器齿轮组,液压调质的润滑为高级润滑。离合器盘、齿轮需要用冷却油来冷却润滑。因为工作需要,这台拖拉机不需要经常转变传递力的方向，可以用一个齿轮型传力机构传递力。
静压驱动运行中说明了静压驱动和动力传动与控制技术的基本原理。一个静压驱动机制有两个主要的单元,也就是说,一个容积式泵驱动单元,有最初的容积电机,其能量从泵中获得。换句话说,拖拉机引擎开发、转换机械能和液压能。然后利用液压泵降级系能转换成液压能,为液压马达提供动力。因此,反过来,产生的机械能推动拖拉机。
