KD1150型載貨汽車設計（變速器總成設計）
KD1150型載貨汽車設計（變速器總成設計）,kd1150,載貨,汽車,設計,變速器,總成
TRANSMISSION
Of all transmission technologies, the manual gearbox is the most efficient; around 96 per cent of the energy that is put in comes out of the other end. But not everyone can drive one or wants to. Because you have to dip the clutch pedal, it is less comfortable to drive in heavy traffic. It makes the driver tired and the torque interruptions’ head-nod effect on passengers can be wearing.
The driver's clutch control and corresponding torque interruptions are also the manuals weak point. When accelerating up through the gearbox, each up-shift requires the driver to cut the torque momentarily by lifting the gas pedal and dipping the clutch. It may just take a second to complete the operation, but during this time the vehicle is losing speed and acceleration.
At the opposite end of the spectrum is the traditional automatic. The modern transmission is by far, the most complicated mechanical component in today’s automobile. It is a type of transmission that shifts itself .A fluid coupling or torque converter is used instead of a manually operated clutch to connect the transmission to the engine.
There are two basic types of automatic transmissions based on whether
the vehicle is rear wheel drive . On a rear wheel drive car , the transmission is usually mounted to the back of the engine and is located under the hump in the center of the floorboard alongside the gas pedal position . A drive shaft connects the rear of the transmission to the final drive which is located in the rear axle and is used to send power to the rear wheel. Power flow on this system is simple and straight forward going from the engine, through the torque converter , then through the transmission and driver shaft until it reaches the final driver where it is split and sent to the two rear wheel .
On a front wheel drive car, the transmission is usually combined .With the final drive to from what is called a transaxle. The engine on a front wheel driver car is usually mounted sideways in the car with the transaxle tucked under it on the side of the engine facing the rear of the car. Front axles are connected directly to the transaxle and provide power to the front wheels. In this example, power flows from the engine through the torque converter to a large chain that sends the power through a 180 degree turn to the transmission that is along side the engine. From there，The power is routed through the transmission to the final drive where it is split and sent to the two front wheels through the drive axles.
There are a number of other arrangements including front drive vehicles where the engine is mounted front to back instead of sideways and there are other systems that drive all four wheels but the two systems described here are by far the most popular. A must less popular rear drive arrangement has the transmission mounted to the final drive at the rear and is connected by a drive shaft to the torque converter which is still mounted on the engine. This system is found on the new corvette and is used in order to balance the weight evenly between the front and rear wheels for improved performance and handling. Another rear drive system mounts everything, the engine, transmission and final drive in the rear. This rear engine arrangement is popular on the Porsche.
The modern automatic transmission consists of many components and systems that are designed to work together in a symphony of planetary gear sets, the hydraulic system, seals and gaskets, the torque converter, the governor and the modulator or throttle cable and computer consider being an art form.
On the automobile planet gear mainly uses in two places, one is the driving axle reduction gear, two is the automatic transmission. Very many net friends all want to know that, the planet gear has any function, why automobile must have it
. We knew very well the gear major part all rotates the spool thread fixed gear. For example mechanical type clock and watch, above all gears although all in make the rotation, but their rotation center (with center of a circle position superposition) often installs through the bearing on the cabinet, therefore, their rotating axis all is the relative cabinet fixed, thus also is called "dead axle gear"
. Has must have surely moves, the corresponding place, some kind of not that manner knows very well is called "planet gear" the gear, their rotation spool thread is not fixed, but is installs the support which may rotate in (blue color) on (in chart black part is shell, yellow expression bearing). The planet gear (green) besides can look like the dead axle gear such to revolve own rotating axis (B-B) to rotate, their rotating axis also (is called planet) along with the blue color support to circle other gears the spool thread (A-A) to rotate. Circles oneself spool thread the rotation to be called "rotation", circles other gear spool threads the rotation to be called "revolution", looks like in solar system planet such, therefore acquires fame.
The spool thread fixed gear drive principle is very simple, meshes mutually in a pair in the gear, some gear takes the driving pulley, the power spreads from its there, another gear takes the driven wheel, the power outputs from it toward outside. Also some gears only take the stopover station, at the same time meshes with the driving pulley, one side meshes in addition with the driven wheel, the power passes from its there.
In contains the planet gear in the gear system, the situation was different. Because has the planet frame, in other words, may have three rotating axes permissions power input/Output, but also may use the coupling or the brake and so on method. in needs time limits axis the rotation, is left over two axes to carry on the transmission, as the matter stands, meshes mutually between the gear relations may have the many kinds of combinations: The power from sun gear input, outputs from other sun gear, the planet put through brake mechanism has checked dies; Power from sun gear input, from planet output, moreover a sun gear ecks dies; The power from a planet input, outputs from sun gear, moreover a sun gear checks dies; Two powers separately from two sun gears inputs, after synthesis from planet output; Two powers separately from the planet and sun gear input, after the synthesis output from other sun gear; The power from sun gear input, divides two groups outputs from other sun gear and the planet frame; The power from a planet input, divides two groups to output from two sun gears;
Its shift quality is good thanks to its torque converter, but efficiency is relatively poor despite recent advances. Because of this, a lot of the current research is trying to find an efficient alternative to the conventional automatic.
The main technologies are continuously variable transmissions (CVTs); dual clutch transmissions (DCTs) and automated manual transmission (AMTs).They all offer different benefits over the conventional planetary automatic.
The CVT uses a belt chain or torodial shaped dish drive to vary an infinite number of gear ratios. It has improved efficiency and cost when compared to conventional automatics. Its advantage comes from its simplicity. It consists of very few components；usually a rubber or metal-link belt；a hydraulically operated driving pulley, a mechanical torque-sensing driving pulley, microprocessors and some sensors.
The transmission works by varying the distance between the face of the two main pulleys. The pulleys have V－shaped grooves in which the connecting the belt rides. One side of the pulley is fixed axially; the other side moves, actuated by hydraulics.
When actuated, the cylinder can increase or reduce the amount of space between the two sides of the pulley. This allows the belt to ride lower or higher along the walls of the pulley, depending on driving conditions. This changes the gear ratio. A torodial-type design works in a similar way but runs an discs and power- rollers
The "step less" nature of its design is CVT's biggest draw for automotive engineers .Because of this, a CVT can work to keep the engine in its optimum power range, thereby increasing efficiency and mileage. A CVT can convert every point on the equine’s operating curve to a corresponding point on its own operating curve.
The transmission is most popular with Japanese carmakers and Japanese supplier JATCO is a major producer. But in the US and Europe driving styles are different. Uptake has been slow despite Audi and other manufacturers having Offered CVT operations on their ranges.
The DCT is, in effect, two manual gearboxes coupled together. Gear shifts are made by switching from one clutch on one gearbox to another clutch on the other. The shift quality is equal to a conventional automatic, but slip, fluid drag and hydraulic losses in the system result in only slightly improved efficiency and acceleration over the conventional planetary automatic. Developing the control strategy is costly too.
"Resent advances in conventional automatic technology have weakened the argument to develop and set up production for CVT or DCT," says Bill Martin, managing director of transmission firm Zeroshift "Some carmakers have cancelled DCT projects because of the cost."
The cheapest way to build an automatic is with an AMT. AMTs use actuators to replace the clutch pedal and gear stick of a conventional manual. They keep the high efficiency and acceleration of a manual gearbox, but the shift quality on some models is lacking. Torque interruptions and the head-nod effect are the most common complaint.
SO what is the alternative? There are always new ideas in transmissions, but Zeroshift says that its technology has efficiency benefits over a manual, delivering fuel economy improvements to city driving. Shift quality can also be equal to that of a refined automatic.
Zeroshift's approach is an upgrade to the AMT. The synchromesh is replaced with an advanced dog engagement system.
Dog engagement has been used for many years in motor sport to allow fast shifts. Conventional dog Boxes are unsuitable for road use as the large spaces between the drive lugs or 'dogs" create backlash, an uncomfortable shunt caused by the sudden change in torque direction.
Zeroshift's technology solves this problem by adding a second set of drive dogs. It has also made each of The two sets of dogs only capable of transmitting torque in one or other opposing directions.” By controlling the engagement and disengagement of the two sets you can shift into the new gear before disengaging the previous gear," says Martin "The shift quality is smoother than a typical modern six-speed automatic luxury car"
The shift is instant and the torque is not interrupted. This philosophy is used for both up and down shifts.
"In conventional AMT there is an emissions spike during a shift due to the need to back off and reintroduce throttle, this is eliminated by going seamless," says Martin.” This also reduces fuel consumption. “
It is a relative newcomer to the transmission sector, but the firm says that it is already attracting the attention of major European and US carmakers. The big draw is as a low-cost alternative to DCT, says Martin.
Because the manual gearbox architecture is largely maintained, production costs and complexity are not greater than for a conventional AMT. Development of tile controls side is also considerably cheaper. Music to the ears of engineers trying to cut emissions and costs.
"Most of the carmakers have seen the system at least once," says Martin "Some signed us up immediately some have said not yet. None have said no." That may be the clearest sign yet that when it comes to power train developments, carmaker are starting to focus on the transmission.
How zeroshift works? The hardware consists of two sets of bullets mounted and actuate on two independent bullet rings. Both set of bullets run on the common hub, which is attached to the shaft with splints.
Each bullet has a special profile. On one side they have an angled face for engagement. These are diagonally opposed, allowing the bullet to have a drive function for one gear and an overrun function for the other gear. The engagement faces taper backwards slightly to ensure the bullet latches onto the engaged under load.
The opposite corners have a ramp, which pushes the bullet out of the previous gear once the new gear has been engaged.
In neutral both bullet rings are positioned midway between the ratios. To select first gear, the bullets are moved into mesh with the engagement dogs. The bullets are actuated via shift forks connected to the shift actuators.
變速器
所有變速箱技術中，手動變速器的效益最高，輸出功率可達到輸入功率的96%，但并不是所有的人都能駕馭手動變速箱，也不是所有人愿意用它。因為用手動變速器需要踩離合器，這是在交通繁忙的時候很不舒服，駕駛員容易疲勞，而由扭矩中斷導致的“點頭”效應也會使乘客很難受。
由駕駛員操縱離合器而產生的扭矩中斷是手動變速器主要的缺點。在換檔加速時，駕駛員都必須通過松開油門并踩下離合器來使扭矩中斷，完成整個過程大概需要一秒，但在這段時間里車輛會暫時停止加速，速度也會降低。
與此截然不同的是自動變速箱，到目前為止現(xiàn)代汽車自動變速器是汽車上最復雜的元件。它是一種可以自己換擋的變速器。力矩轉換器或流體聯(lián)合器被用來代替手動離合器連接發(fā)動機。
汽車上變后輪驅動或前輪驅動是車輛自動變速器的兩種基本類型。在一個后輪驅動的速器通常放在發(fā)動機后面凸起后長板旁邊氣體踏板下方的位置。駕駛桿連接變速器后端，最終駕駛的準確位置在后軸，用操縱力控制后輪。發(fā)動機的動力簡單連續(xù)的在這個系統(tǒng)中循環(huán)，在通過變速器時改變力矩，通過傳動軸后在主減速器分流到兩后輪。
在前輪驅動汽車中，變速器常常兼有最終驅動叫做變速驅動橋。前輪驅動汽車通常在發(fā)動機的后下方安裝有橫向變速驅動橋。前橋直接連接在發(fā)動機的變速驅動橋上為前輪提供動力，動力從發(fā)動機出發(fā)轉過一個大鏈條后經180°轉變傳給變速器。從而，將主動力通過變速器后分流傳到驅動軸再送到兩前輪。
也有一些其他方式的前輪驅動車輛，車架前方代替另一邊的其他系統(tǒng)驅動四輪，但在這兒僅對其中的兩個系統(tǒng)進行說明。相對于前輪驅動來說最流行的是后輪驅動，在發(fā)動機上連接一個輸出軸，將改變后的力矩傳給后驅動輪。這個系統(tǒng)是探尋前后軸實施改進的新的節(jié)能動力平衡裝置。另一個驅動系統(tǒng)是把所有的驅動零件都按在后輪上。這種排列方式發(fā)動機通常后置。
現(xiàn)代自動變速器由許多的部件和系統(tǒng)組成，它們有行星齒輪組、液壓系統(tǒng)、密封圈和密封襯墊、變矩器、油壓調節(jié)器、調制器、節(jié)氣門拉線、電子控制裝置等，經精心設計運轉協(xié)調，其中的電子控制裝置經歷了多年的發(fā)展，已經以巧妙的形式溶入了許多人性化的設計。
汽車上的行星齒輪主要用在兩個地方，一是驅動橋減速器、二是自動變速器。很多網友都想知道，行星齒輪有什么功能，為什么汽車少不了它。
我們熟知的齒輪絕大部分都是轉動軸線固定的齒輪。例如機械式鐘表，上面所有的齒輪盡管都在做轉動，但是它們的轉動中心（與圓心位置重合）往往通過軸承安裝在機殼上，因此，它們的轉動軸都是相對機殼固定的，因而也被稱為"定軸齒輪"。 軸線固定的齒輪傳動原理很簡單，在一對互相嚙合的齒輪中，有一個齒輪作為主動輪，動力從它那里傳入，另一個齒輪作為從動輪，動力從它往外輸出。也有的齒輪僅作為中轉站，一邊與主動輪嚙合，另一邊與從動輪嚙合，動力從它那里通過。
在包含行星齒輪的齒輪系統(tǒng)中，情形就不同了。由于存在行星架，也就是說，可以有三條轉動軸允許動力輸入/輸出，還可以用離合器或制動器之類的手段，在需要的時候限制其中一條軸的轉動，剩下兩條軸進行傳動，這樣一來，互相嚙合的齒輪之間的關系就可以有多種組合：動力從其中一個太陽輪輸入，從另外一個太陽輪輸出，行星架通過剎車機構剎死；動力從其中一個太陽輪輸入，從行星架輸出，另外一個太陽輪剎死；動力從行星架輸入，從其中一個太陽輪輸出，另外一個太陽輪剎死；兩股動力分別從兩個太陽輪輸入，合成后從行星架輸出；兩股動力分別從行星架和其中一個太陽輪輸入，合成后從另外一個太陽輪輸出；動力從其中一個太陽輪輸入，從另外一個太陽輪和行星架分兩路輸出；動力從行星架輸入，分兩路從兩個太陽輪輸出。
由于采用了變矩器，這種變速器的換檔質量不錯但效率相對較差雖然目前有所改進。因此，目前進行了許多研究，試圖發(fā)現(xiàn)傳統(tǒng)變速器的有效的代替方案。
主要的技術還是無級變速器（CVT）、雙離合變速（DCT）和手自一體（AMT）變速器。它們在不同的方面優(yōu)于傳統(tǒng)的行星齒輪式自動變速器。
無級變速器采用帶、鏈或錐盤滾輪來產生無限多種速比，與傳統(tǒng)自動變速器相比其效率和成本都有所改善。之所以有這些優(yōu)點，是因為它結構簡單，這種變速器的零部件很少，通常只有一根橡膠或金屬傳動帶、一個液壓作用的驅動帶輪、一個機械扭矩感應式驅動帶輪、一些微處理器和傳感器等。
這種變速器的工作原理是改變兩個主帶輪表面之間的距離，帶輪上掛傳動帶的地方開了V形槽，一側的帶輪沿軸向固定，另一側的帶輪可在液壓的作用下移動。
在驅動輪后，液壓缸可增加或減少帶輪兩側之間的距離，這樣會使傳動帶在帶輪側壁上的位置上下變動，變動的方式取決于駕駛情況。這樣就會使變速比改變。錐盤滾輪型變速器的工作原理與此類似但用的是驅動盤和動力滾輪。
CVT（無極）變速器的特點對技術人員最具有吸引力。因為這樣沒有檔位，CVT可使發(fā)動機保持在最佳的功率范圍內。這樣可以使效率提高并在相同的油耗下增加行駛里程。CVT可將發(fā)動機工作曲線上的每一點轉變?yōu)槠浔旧砉ぷ髑€上相應的點。
這種變速器最受日本汽車制造商青睞，并且日本變速器生產商JACTO是主要生產者，但在歐美國家，情況就有所不同。盡管奧迪和其它一些制造商在一些車型上推出了CVT，但在這方面他們追趕的步伐仍然很緩慢。
DCT實際上是將兩臺手動變速器合在一起，換檔過程是通過兩臺變速器的離合器之間的相互切換來實現(xiàn)的。這種變速器的換檔質量和傳統(tǒng)的自動變速器相同，但由于系統(tǒng)會發(fā)生滑動、液體阻力和液壓損失，其效率和加速性只比傳統(tǒng)行星齒輪自動變速器稍有提高，開發(fā)控制系統(tǒng)的成本也很高。
“最近在傳統(tǒng)自動變速器技術上所取得的進展，使開發(fā)和生產CVT或DCT的呼聲有所降低?！弊兯倨魃a企業(yè)Zeroshift公司的執(zhí)行總裁比爾馬丁說，“由于成本過高，有些汽車廠已經取消了DCT項目。”
AMT是成本最低的自動變速器技術，AMT用執(zhí)行器來代替?zhèn)鹘y(tǒng)的離合器踏板和換檔桿，這種變速器保留了手動變速器的高效率和加速性能，但某些型號的變速器換檔質量不高，扭矩中斷和“點頭”效應仍是主要的缺點。
那么什么是最好的代替方案？變速器方面的新技術是層出不窮的，但Zeroshift公司聲稱其變速器的效率優(yōu)于手動變速器，提高失去駕駛的燃油經濟性，同時，其換檔效率可以和改進后的自動變速器相媲美。
Zeroshift公司采用的是一種改進版的AMT技術，這種技術用先進的犬牙嚙合系統(tǒng)代替同步器。
犬牙嚙合技術許多年前就已經在賽車運動中采用，目的是為了加快換檔速度。傳統(tǒng)的犬牙式變速器并不適合在公路上，因為驅動環(huán)或犬牙之間的空隙很大，會產生后坐——由扭矩突然轉向而產生的一種不舒適的竄動。
Zeroshift公司通過增加第二套驅動犬牙來解決這一問題，這種技術還使每組犬牙只能傳遞兩種相反方向扭矩中的一種。“通過對兩套犬牙的嚙合和分離，可在上一個檔位沒有分離的情況下?lián)Q入新的檔位?！瘪R丁說，“換檔質量超過采用現(xiàn)代化的6檔變速器的豪華轎車?！?
換檔可在瞬間完成，而扭矩不發(fā)生中斷，而且這種方法既可用于升檔又可用于降檔。
“在使用傳統(tǒng)的AMT變速器時，由于需要關閉并重新打開油門，換檔過程中排放會達到高峰，而通過這種無過渡的換檔方式可以消除這種現(xiàn)象。”馬丁說，“這樣還能降低燃油消耗。”
“盡管在技術上變速器領域還比較新，但公司稱已經引起了歐美各大汽車制造商的注意，最大的吸引力在于其成本比DCT低”，馬丁說。
由于可以保留大部分手動變速器的結構，這種變速器的成本和復雜性都不會高于傳統(tǒng)的AMT變速箱?？刂葡到y(tǒng)的成本也會大大降低，這對試圖減少排放和削減成本的工程師來說是個好消息。
“大部分制造商都來參觀過，”馬丁說，“有些公司馬上就和我們簽合同，另一些未作決定，拒絕的一個都沒有?！边@再清楚不過的表明了汽車制造商現(xiàn)在正在將動力系統(tǒng)開發(fā)的重點轉移到變速箱上。
Zeroshift公司的變速系統(tǒng)是怎樣工作的呢？它的硬件部分包括兩套犬牙，安裝在兩個獨立的犬牙環(huán)上并受其驅動，兩套犬牙有一個共同的蓋，蓋和一個花鍵軸相連。
每個犬牙都有特殊的輪廓。在一側是用于嚙合的直角面。這些直角面是沿對角線相對的，這樣的犬牙在對某一個檔位具有驅動功能的同時，對另一個檔位具有超越傳動的功能。嚙合面有輕微的后向錐度，以保證犬牙能在加載時鎖定在嚙合齒輪上。
相對角上有一個斜坡，可在新檔位嚙合后將犬牙從前一個檔位推離。
在空檔時，兩個犬牙環(huán)處于變速比的中間位置。選一檔時，犬牙會發(fā)生移動并和犬牙嚙合面發(fā)生嚙合。犬牙通過與換檔執(zhí)行器相連的換檔撥叉驅動。
驅動犬牙將一檔齒輪與輸出軸鎖定在一起，將扭矩從齒輪傳遞到輸出軸。一檔的超越傳動犬牙也會移動并將齒輪以相反的方向和輸出軸鎖定。這樣可以在油門關閉且發(fā)動機倒拖時將扭矩從齒輪傳遞到輸出軸。這樣就消除了犬牙嚙合式變速器常見的后坐現(xiàn)象。
在加大油門換檔時，一檔齒輪的超越傳動犬牙卸載后和二檔齒輪嚙合。然后換入二檔時，前一個驅動環(huán)卸載。
如果犬牙之間不能完全嚙合，即實現(xiàn)兩個犬牙面之間的嚙合，由于相對速度差的存在，二檔齒輪會打開一個嚙合缺口。在犬牙抵住嚙合面后，在撥叉和執(zhí)行器的共同作用下，儲存的能量會將犬牙送入缺口內。
此時，一檔超越傳動犬牙成為二檔的驅動犬牙。在換入二檔后，一檔的驅動犬牙隨即卸載。這時候，這些犬牙不再受其固定面固定，可以被執(zhí)行器或犬牙上的斜面推離檔位。
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