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譯文題目： Transmission design
汽車變速器設(shè)計(jì)
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Transmission design
As we all know automobile engine to a certain speed can be achieved under the best conditions, when compared issued by the power, fuel economy is relatively good. Therefore, we hope that the engine is always in the best of conditions to work under. However, the use of motor vehicles need to have different speeds, thus creating a conflict. Transmission through this conflict to resolve.
Automotive Transmission role sum up in one sentence, called variable speed twisting, twisting or slow down the growth rate by increasing torsional. Why can slow down by twisting, and the growth rate but also by twisting? For the same engine power output, power can be expressed as N = WT, where w is the angular velocity of rotation. When N fixed, w and T is inversely proportional to the. Therefore, the growth rate will reduce twisting, twisting slowdown will increase. Automotive Transmission speed gear based on the principle of variable twisted into various stalls of different transmission ratio corresponding to adapt to different operational conditions.
General to set up a manual gearbox input shaft, intermediate shaft and output shaft, also known as the three-axis, as well as Daodang axis. Three-axis is the main transmission structure, input shaft speed is the speed of the engine, the output shaft speed is the intermediate shaft and output shaft gear meshing between different from the speed. Different gears are different transmission ratio, and will have a different speed.
When drivers choose a launch vehicle stalls, Plectrum will be 1 / 2 file synchronization engagement with a back stall gear and output shaft lock it, the power input shaft, intermediate shaft and output shaft gear of a stall, a stall the output shaft gear driven, and the output shaft power will be transmitted to the drive shaft (red arrow). A typical stall Biansuchilun transmission ratio is 3:1, that is to say three laps to the input shaft and output shaft to a circle.
When the growth rate of car drivers choose two stalls, Plectrum will be 1 / 2-file synchronization and file a joint separation after 2 stall and lock the output shaft gear, power transmission line similar, the difference is that the output shaft gear of a stall 2 stall replaced by the output shaft gear driven. 2 stall Biansuchilun typical transmission ratio is 2.2:1, 2.2 laps to the input shaft and output shaft to a circle than a stall speed increase, lower torque.
When refueling vehicle drivers growth stalls option 3, Plectrum to 1 / 2 back to the free file-synchronization position, and also allows the 3 / 4 file synchronization Mobile stall until 3 in the output shaft gear lock, power can be into the shaft axis - intermediate shaft - the output shaft of the three stalls Biansuchilun, led through three stalls Biansuchilun output shaft. 3 stalls typical transmission ratio is 1.7:1, 1.7 laps to the input shaft and output shaft to a circle is further growth.
When car drivers Option 4 refueling growth stalls, Plectrum will be 3 / 4 from the 3-file synchronization stall gear directly with the input shaft gear joint initiative, and power transmission directly from the input shaft to the output shaft, the transmission ratio at 1:1, that the input shaft and output shaft speed the same. The driving force without intermediate shaft, also known as direct file, the file transmission than the maximum transmission efficiency. Most cars run-time files are used directly to achieve the best fuel economy.
Shift into the first interval when, in a free transmission when Biansuchilun output shaft is not locked in, they cannot rotate the output shaft driven, not power output.
General automotive manual transmission than the main 1-4 stalls, usually the first designers to determine the minimum (one stall) and maximum (4 files) transmission ratio, the middle stall drive by geometric progression than the general distribution. In addition, there are stalls Daodang and speeding, speeding file is also known as the five stalls.
When the car to accelerate to more than car drivers with the choice of five stalls, and a typical five-transmission ratio is 0.87:1, which is driven by a pinion gear, the gear when the initiative to 0.87 zone, passive gear have been transferred to a circle of the End.
Dao Dang, the opposite direction to the output shaft rotation. If one pair of meshing gears when we reverse rotation, with a middle gear, it will become the same to the rotation. Use of this principle, we should add a gear Daodang the "media" will be rotational direction reversed, it will have a Daodang axis. Daodang installed in the transmission shaft independent crust, and the intermediate shaft parallel axis gear with the intermediate shaft and output shaft gear meshing gears, will be contrary to the output shaft.
Daodang usually used for the synchronization control also joins five stalls, stalls and Daodang 5 position in the same side. As a middle gear, the general transmission Daodang transmission ratio greater than 1 file transmission ratio, by twisting, steep slope with some vehicles encountered on the progress stalls falters with a Daodang boost.
Ride from the driver of the considerations, better transmission stall, stall adjacent stall more than the transmission changes the ratio of small, and easy to shift smoothly. However, the short comings of the stalls is more transmission structure is complicated, bulky, light vehicle transmission is generally 4-5 stalls. At the same time, transmission ratio is not integral, but with all of the decimal point, it is because of the gear teeth meshing is not caused by the whole multiples of two gear teeth can lead to the whole multiples of two meshing gears of uneven wear, making the tooth surface quality have a greater difference.
Manual transmission and synchronizer
Manual transmission is the most common transmission, or MT. Its basic structure sum up in one sentence, is a two-axle shaft, where input shaft, the shaft axis and intermediate shaft, which constitute the main body of the transmission and, of course, a Daodang axis. Manual transmission known as manual gear transmission, which can be in the axial sliding gears, the gears meshing different variable speed reached twisting purpose. Typical manual transmission structure and principles are as follows.
Input shaft also said that the first axis, and its front-end spline driven directly with the clutch disc sets with the spline , by the transfer of torque from the engine. The first axis of the intermediate shaft and gears meshing gears often, as long as the shaft axis to a turn, the intermediate shaft and gear also will be rotating. Vice also said intermediate shaft axis, the axis-even more than the size gear. Also known as the second output shaft axis, the axis of various sets of gear stall progress can be manipulated at any time in the role of the device and the corresponding intermediate shaft gear meshing, thus changing its speed and torque. With the end of the output shaft spline associated with the drive shaft through the drive shaft torque transmitted to the drive axle reducer.
Thus, progress stalls drive transmission path is: input shaft gear often rodents - often rodents intermediate shaft gear - corresponding intermediate shaft gear - the second axis corresponding gear. Reversing the gear shaft can be manipulated by the device pick in the axis movement, and the intermediate shaft and output shaft gear meshing gears, to the contrary to the direction of rotation output.
Most cars have five stalls and a Daodang forward, a certain degree of each stall transmission ratio, the majority of stalls transmission ratio greater than 1, 4 file transmission ratio of 1, known as direct stalls, and transmission ratio is less than 1 No. 5 stall called accelerated stall. Free at the output shaft gear in a position of non-engagement, unacceptable power transmission.
The transmission input shaft and output shaft rotational speed to their own, transform a stall when there is a "synchronous". Two different rotational speed gear meshing force will impact the collision occurred, damage gear. Therefore, the old transmission shift to a "feet-off" approach, or stall on the location of the free stay for a while by stalls in the free position refueling doors, in order to reduce the speed differential gear. However, this operation is relatively more complicated and difficult to grasp accurate. So designers create a "synchronized," and allows synchronization through the meshing of gears to be consistent speed and smooth meshing.
At present Synchronous Transmission is based on the synchronization of inertia, mainly from joint sets, synchronous lock ring, and so on, it is characterized by friction on the role of synchronization. Splice sets Genlock engagement ring gear and the ring gear when it had Chamfer (Lock angle), Genlock within the cone ring gear engagement with the question of cone ring gear contact friction. Lock and cone angle has been made in the design of an appropriate choice to be made friction cone of the teeth meshing with the ring gear quickly sets pace at the same time will have a Lock role and to prevent the gears meshing in sync before. When synchronization lock cone ring gear engagement with the question of cone ring gear after contact in the effects of friction torque gear speed quickly lower (or higher) with the same speed synchronous lock ring, the two synchronous rotation of the gear Genlock Central zero speed, thus moment of inertia also disappear, then in force under the impetus of engagement sets unhindered and synchronization lock ring gear engagement, and further engagement with the question of gear engagement and the completion Gear Shift Process.
The automatic gearbox
The automatic gearbox chooses to block the pole the equal to moving the stick shift of the gearbox, having generally below several blocks:P( parking), R( pour to block), N( get empty to block), D( go forward), S( or2, namely for 2 block soon), L.( or1, namely for 1 block soon)This several an usage for blocking a right usages coming driver the automatic gearbox is automotive of person to say particularly important, underneath let us very much familiar with once automatic gearbox eachly blockings main theme.
The usage of the P ( the parking blocks)
The launches the luck turns as long as choose to block the pole in driving the position, automatic gearbox car run about very easily.But park, choose to block the pole must pull into of P, from but pass the internal parking system in gearbox moves the device will output the stalk lock lives, combining to tense the hand system move, preventing the car ambulation.
The usage of the R( pour to block)
R a control for is pouring blocking, using inside wanting slicing recording, automatic gearbox car unlike moving gearbox car so can using half moving, so while reversing the car wanting special attention accelerating pedal.
The usage of the N( get empty to block)
The N is equal to get empty to block, can while starting or hour of trailer usage.At wait for the signal or block up the car will often often choose to block the pole keeps in the of D, trampling at the same time the next system move.If time is very short, do like this is an admission of, but if stop the time long time had better change into of N, combine to tense the hand system moves.Because choose to block the pole in driving the position, the automatic gearbox car has generally and all to drive the trend faintly, long hours trample the system move same as a deterrent this kind of trend, make gearbox oil gone up, the oil liquid changes in character easily.Particularly in the air condition machine work, launch the soon higher circumstance in machine bottom more disadvantageous.Some pilots for the sake of stanza oil, at made good time or go down slope will choose to block the pole pull the of N skids, this burn the bad gearbox very easily, launching the machine to revolves soon in the however because the gearbox outputs at this time the stalk turns soon very high,, the oil pump provides the oil shortage, lubricating the condition worsen, burn the bad gearbox easily.
The usage of the D( go forward to block)
Will choose to block when is normal to drive the pole put in the of D, car can at 1 ～ 4 block( or 3 block) its change to block automatically.The of D drives the position most in common usely. What demand control is: Because the automatic gearbox is soon high and low with car to come to make sure to block according to the accelerator size a, so accelerate the pedal operation method is different, changing to block the hour of the car is soon too not same alike.If start hour quick accelerate the pedal tramples the bottom, rising to block the night, accelerating the ability is strong, arriving certain car soon behind, then will accelerate the pedal loosen to open very quickly, car can rise to block immediately, launch like this the machine voice is small, comfortable good.
The another characteristics of the D is a compulsory low blocking, easy to high speed the hour overtakes a car, will accelerate quickly in of D drove the pedal trample after all, connect the compulsory low fend off the pass and then can reduce to block automatically, the car accelerates very quickly, after overtaking a car loosen to open the pedal of acceleration to can rise to block automatically again.
The usage of the S, of L low the usage that block
The automatic gearbox in in is placed in the low blocking the scope on of S or of Ls, can usage under an etc. circumstance.It change to can make use of to launch well into of S or of Ls the mechanism move, avoiding the car wheel system move the machine over hot, cause the system move the effect descent while going down slope.But change into from the of D of S or of L, car soon can't higher than rise to block the car homologously soon, otherwise strong vibration in opportunity to launch, make gearbox oil hoicked, even will damage the gearbox.
The is another at rain fog weather hour, if the road adheres to the term bad, can change into a position for or of L, fixing at somely first lowly blocking driving, doing not use can automatically changing blocking, in order to prevent the car beats slippery.Must keep firmly in mind at the same time, beat the slippery hour can will choose to block the pole pushes into a motive for, cutting off launching machine, toing guarantee a car the safety.
汽車變速器設(shè)計(jì)
正如我們所知道的汽車發(fā)動(dòng)機(jī)在一定的速度下才能達(dá)到最佳的狀態(tài)，相比之下發(fā)出的動(dòng)力比較大，燃油經(jīng)濟(jì)性也比較好。因此，我們總是希望發(fā)動(dòng)機(jī)能始終處于最佳狀態(tài)下工作。然而，使用汽車時(shí)需要有不同的速度，從而與之產(chǎn)生沖突，這些沖突要通過變速器才能解決。
汽車變速器的作用用一句話來總結(jié)，稱為變速扭矩，就是速度增加扭矩減小或速度減小扭矩增大。為什么可以速度增加扭矩減小，速度減小扭矩增大呢？對(duì)于發(fā)動(dòng)機(jī)輸出功率相同，功率可以表示為N = wT，其中w是轉(zhuǎn)動(dòng)角速度。當(dāng)N相同時(shí)，T和w是成反比的。因此，速度增加扭矩減小，速度減小扭矩增大。對(duì)于變扭原理的汽車變速器變速器，各種檔位對(duì)應(yīng)于不同的傳動(dòng)比，并且能適應(yīng)不同的運(yùn)行工況。
一般一個(gè)手動(dòng)變速箱里設(shè)有輸入軸、中間軸和輸出軸，也被稱為三軸式，以及還有倒檔軸。三軸是傳動(dòng)部分的主要結(jié)構(gòu)，輸入軸的轉(zhuǎn)速就是發(fā)動(dòng)機(jī)的轉(zhuǎn)速，中間軸與輸出軸之間的嚙合，從而產(chǎn)生的速度就是輸出軸的轉(zhuǎn)速。不同的齒輪嚙合產(chǎn)生的傳動(dòng)比也是不同的，從而產(chǎn)生不同的速度。
司機(jī)們?cè)谶x擇啟動(dòng)車檔1檔時(shí)，撥叉將1 / 2檔齒輪和1檔同步嚙合并且鎖定在輸出軸上，1檔齒輪上的動(dòng)力輸入軸、中間軸和輸出軸，1檔齒輪帶動(dòng)輸出軸，然后將輸出軸上的動(dòng)力傳遞到驅(qū)動(dòng)軸上（紅色箭頭）。一個(gè)典型的1檔變速齒輪傳動(dòng)比是3:1，也就是說輸入軸轉(zhuǎn)三圈和輸出軸轉(zhuǎn)一圈。
當(dāng)汽車加速的時(shí)候司機(jī)選擇2檔，撥叉將1 / 2檔齒輪同步器和1檔分離后與2檔齒輪相連接并鎖定輸出軸上，功率傳輸線相同，不同的是，輸出軸齒輪從原來的1檔變?yōu)?檔，然后2檔來使輸出軸齒輪轉(zhuǎn)動(dòng)。典型2檔變速齒輪傳動(dòng)比為2.2:1，輸入軸轉(zhuǎn)2.2圈時(shí)，輸出軸轉(zhuǎn)一圈，相對(duì)于比1檔轉(zhuǎn)速增加，扭矩減小。
當(dāng)汽車加速的時(shí)候司機(jī)選擇3檔，撥叉將1 / 2檔同步器回到空檔，并且還允許3 / 4檔同步器移動(dòng)直到3檔在輸出軸齒輪上鎖定，可以在輸入軸、中間軸、輸出軸中輸出動(dòng)力，3檔變速齒輪帶動(dòng)輸出軸轉(zhuǎn)動(dòng)。典型3檔變速齒輪傳動(dòng)比為1.7:1，輸入軸轉(zhuǎn)1.7圈，輸出軸只要轉(zhuǎn)1圈，是速度進(jìn)一步增加。
當(dāng)汽車加速的時(shí)候司機(jī)選擇4檔，撥叉將3 / 4檔齒輪同步器與3檔脫離直接與輸入軸主動(dòng)齒輪相連接，動(dòng)力直接從輸入軸傳遞到輸出軸，在傳動(dòng)比1:1，即輸入軸和輸出軸轉(zhuǎn)速相同。因?yàn)閯?dòng)力不經(jīng)過中間軸，也被稱為直接檔，直接檔輸出比中間檔輸出大。大多數(shù)汽車運(yùn)行時(shí)使用直接檔，從而來實(shí)現(xiàn)最佳的燃油經(jīng)濟(jì)性。
當(dāng)變速齒輪輸出軸不能被鎖定時(shí)換檔要先掛入空檔，他們不能帶動(dòng)輸出軸轉(zhuǎn)動(dòng)，從而就沒有動(dòng)力輸出。
一般汽車手動(dòng)變速器傳動(dòng)比主要分1-4檔，通常設(shè)計(jì)者首先確定最?。?檔）和最大（4檔）的傳動(dòng)比，中間各檔傳動(dòng)比一般按等比級(jí)數(shù)分配。此外，還有倒檔和超速檔，超速檔也被稱為5檔。
當(dāng)汽車加速的時(shí)候司機(jī)選擇五檔，一個(gè)典型的5檔傳動(dòng)比為0.87:1，這是由一個(gè)小齒輪帶動(dòng)，當(dāng)主動(dòng)齒輪轉(zhuǎn)0.87圈，被動(dòng)齒輪已經(jīng)轉(zhuǎn)完1圈結(jié)束。
倒檔，是相反方向旋轉(zhuǎn)的輸出軸。如果一對(duì)齒輪嚙合時(shí)，大家反向旋轉(zhuǎn)，加一個(gè)中間齒輪，它將變成相同方向的旋轉(zhuǎn)。利用這一原理，我們要添加一個(gè)齒輪倒檔的“媒體”將旋轉(zhuǎn)方向改變成相反的，然后就有樂一個(gè)倒檔軸。倒檔軸獨(dú)立裝在變速器殼里面，平行于中間軸，平行軸齒輪與中間軸和輸出軸齒輪嚙合，將與輸出軸相反。
通常倒檔用的同步器也控制5檔，5檔與倒檔在同一邊兒。作為一個(gè)中間齒輪，一般變速器倒檔傳動(dòng)比大于1檔傳動(dòng)比大，扭矩增大，一些車輛遇到陡坡的時(shí)候使用前進(jìn)檔沒用，就用倒檔來使車子前進(jìn)。
從駕駛者乘坐的考慮，變速器檔位越多越好，相鄰的檔位比變速器的變速率小，且易于換擋平順。然而，檔位越多的缺點(diǎn)就是傳動(dòng)結(jié)構(gòu)復(fù)雜，體積龐大，輕型汽車變速器一般是4-5檔。同時(shí)，傳動(dòng)比不是整數(shù)，而是帶有小數(shù)點(diǎn)，它是因?yàn)辇X輪嚙合不是由齒輪的整倍數(shù)造成的，2個(gè)齒輪齒數(shù)如果是整倍數(shù)，那么就會(huì)導(dǎo)致不均勻的磨損，使齒輪表面質(zhì)量有更大的差異。
手動(dòng)變速器與同步器
手動(dòng)變速器是最常見的變速器，簡(jiǎn)稱MT。用一句話來概括就是兩軸一中，就是輸入軸、軸出軸和中間軸，它們構(gòu)成了變速器的主體，當(dāng)然還有一個(gè)倒檔軸。手動(dòng)變速器稱為手動(dòng)齒輪式變速器，有軸向滑動(dòng)的齒輪，不同齒輪嚙合從而來改變速度和轉(zhuǎn)矩。典型的手動(dòng)變速器的結(jié)構(gòu)和原理如下。
輸入軸也叫第一軸，其前端花鍵直接與離合器盤套與花鍵配合，通過從發(fā)動(dòng)機(jī)轉(zhuǎn)矩的傳遞。第一軸的中間齒輪和齒輪的常嚙合，只要把輸入軸轉(zhuǎn)動(dòng)，中間的軸和齒輪也會(huì)轉(zhuǎn)動(dòng)。中間軸也稱為副軸，中間軸上有著不同大小的齒輪。輸出軸也被稱為第二軸，軸上有各個(gè)前進(jìn)檔齒輪，可以在任何時(shí)間操縱設(shè)備和相應(yīng)的中間齒輪嚙合，從而改變其速度和轉(zhuǎn)矩。輸出軸端部有傳動(dòng)軸和花鍵的連接，通過傳動(dòng)軸扭矩傳遞到驅(qū)動(dòng)橋減速器。
因此，前進(jìn)檔驅(qū)動(dòng)變速器路徑是：輸入軸常嚙齒輪－中間軸常嚙齒輪－相應(yīng)的中間軸齒輪－第二軸相應(yīng)的齒輪。倒車的齒輪軸可以通過在軸運(yùn)動(dòng)的裝置上來進(jìn)行操作，與中間軸和輸出軸齒輪嚙合，向相反方向旋轉(zhuǎn)輸出。
大多數(shù)汽車有五個(gè)前進(jìn)檔和一個(gè)倒檔，每個(gè)檔位有一定的傳動(dòng)比，大多數(shù)檔位傳動(dòng)比大于1，4檔傳動(dòng)比為1稱為直接檔，傳動(dòng)比小于1的5檔稱為加速檔?？諜n時(shí)的齒輪在非接觸的位置，不可以接受動(dòng)力輸出。
變速器輸入軸和輸出軸轉(zhuǎn)速為自己的，換檔時(shí)有一個(gè)“同步”的問題。兩個(gè)不同轉(zhuǎn)速齒輪嚙合會(huì)發(fā)生齒輪碰撞，從而損壞齒輪。因此，舊的變速器換檔要采用“兩腳離合”的辦法，加檔時(shí)在空檔位置停留一段時(shí)間，減檔在空檔位置加油門，以減少齒輪的旋轉(zhuǎn)差。然而，這種操作相對(duì)更為復(fù)雜和難以把握準(zhǔn)確。因此，設(shè)計(jì)師創(chuàng)造了一個(gè)“同步器”，并允許同步通過齒輪嚙合，以保持一致的速度和順利嚙合。
目前同步變速器是基于慣性同步的，主要有接合套、同步鎖環(huán)等組成，其特點(diǎn)是利用摩擦對(duì)同步的作用。接合套、同步鎖相環(huán)齒輪和環(huán)形齒輪嚙合時(shí)有倒角（鎖止角），同步鎖環(huán)的內(nèi)錐面與錐齒輪嚙合齒輪有著摩擦接觸的問題。在設(shè)計(jì)中有了鎖止角和錐角的合理選擇，使摩擦錐與齒環(huán)嚙合的齒輪快速同步，將有一個(gè)鎖止的作用，并防止齒輪在同步之前嚙合。當(dāng)同步鎖環(huán)內(nèi)錐面與錐齒輪嚙合，在摩擦力矩的作用下時(shí)齒輪轉(zhuǎn)速迅速減?。ɑ蛟龃螅┲敝僚c同步鎖相環(huán)有著相同的速度，齒輪相對(duì)于同步鎖環(huán)的轉(zhuǎn)速為零，兩者同步轉(zhuǎn)動(dòng)，從而轉(zhuǎn)動(dòng)慣量也消失了，然后在力的作用下接合套和同步鎖環(huán)齒輪嚙合，與還沒有嚙合的齒輪嚙合從而完成換檔過程。
自動(dòng)變速器
自動(dòng)變速器的選擋桿相當(dāng)于變速器的變速桿，一般有以下幾個(gè)檔位：P（停車）、R（倒擋）、N（空檔），D（前進(jìn)）、S（2，即2速檔），L（1，即1速檔）。這幾檔的正確使用來對(duì)駕駛自動(dòng)變速器汽車的人來說尤其重要，下面讓我們非常熟悉一下自動(dòng)變速器各檔位的使用要領(lǐng)。
P(停車)的使用
當(dāng)發(fā)動(dòng)機(jī)工作時(shí)只要選擋桿在行駛位置上，自動(dòng)變速器汽車很容易行駛。但停車時(shí)，選擋桿必須扳到P，從而通過變速器內(nèi)部的停車制動(dòng)裝置將輸出軸鎖住，并拉緊手剎，防止汽車移動(dòng)。
R(倒檔)的使用
R是倒檔，使用中要牢記，自動(dòng)變速器的車與手動(dòng)變速器的車不同，不可以采用半聯(lián)動(dòng)，所以在倒車時(shí)要特別注意控制加速踏板。
N(空檔)的使用
N時(shí)空檔，可以在啟動(dòng)或拖車時(shí)使用。在等待信號(hào)或堵車時(shí)常常將選檔桿保持在D，同時(shí)踩下腳剎。如果時(shí)間很短，這樣做是允許的，但若停止時(shí)間長(zhǎng)時(shí)最好換入N，并拉緊手剎。因?yàn)檫x檔桿在行駛位置上，自動(dòng)變速器的汽車一般都有微弱的行駛趨勢(shì)，長(zhǎng)時(shí)間踩住制動(dòng)等于強(qiáng)行制止這種趨勢(shì)，使變速器油溫上升，油液容易變質(zhì)。尤其在空調(diào)機(jī)工作時(shí)，發(fā)動(dòng)機(jī)怠速較高的情況更不利，有些駕駛員為了節(jié)油，在加速行駛或走下坡時(shí)將選檔桿扳到N滑行，變速器很容易被燒壞，發(fā)動(dòng)機(jī)在怠速運(yùn)轉(zhuǎn)但是因?yàn)檫@時(shí)變速器輸出軸轉(zhuǎn)速很高，油泵供油不足，潤滑狀況惡化，變速器容易被燒壞。
D(前進(jìn)檔)的使用
汽車正常行駛時(shí)選檔桿放在D，汽車可以在1～4檔（或3檔）之間自動(dòng)變化，D驅(qū)動(dòng)器的位置最常用。需要掌握的是：由于自動(dòng)變速器是由速度高低和油門大小來確定檔位的，所以加速踏板操作方法不同，換擋時(shí)的車速也不相同。如果起步時(shí)迅速將加速踏板踩下，升擋晚，加速能力強(qiáng)，到一定車速后，再將加速踏板很快松開，汽車就能立即升擋，這樣發(fā)動(dòng)機(jī)發(fā)出的噪聲小，舒適性好。
D位的另一個(gè)特點(diǎn)是強(qiáng)制低檔，便于高速時(shí)超車，在D檔位開車時(shí)迅速將加速踏板踩到底，接通強(qiáng)制低擋開關(guān)就能自動(dòng)減檔，汽車很快加速，超車之后松開加速踏板又可自動(dòng)升擋。
S、L位低檔的使用
自動(dòng)變速箱中S、L是低檔，可以在坡道等情況下使用，S、L可以利用發(fā)動(dòng)機(jī)來進(jìn)行制動(dòng)，避免車輪制動(dòng)機(jī)器過熱，導(dǎo)致制動(dòng)性能下降。但從D位換入S或L，車速不能高于相應(yīng)的升擋車速，否則發(fā)動(dòng)機(jī)會(huì)強(qiáng)烈振動(dòng)，使變速器油急劇上升，甚至?xí)p壞變速器。
如果在雨霧天氣時(shí)，若路面附著條件差，可以掛入S或L檔，固定在某一低擋行駛，不要使用自動(dòng)換擋，以防止汽車打滑。同時(shí)必須切記，打滑時(shí)可將選擋桿推到N檔，切斷啟動(dòng)機(jī)，以保證行車安全。