汽車差速器的建模和仿真設計【說明書+CAD+SOLIDWORKS+仿真】
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附 錄
Take Between Shaft Differential Thansfer Characteristic Analysis
In many of the drive shaft car, it is a thansfer transmission and between axles in the transmission chain of used to increase output, transmission torque, to enlarge the scope of change, and torque distribution to driving axle.
Thansfer types and characteristics
From the structure and function to see, can be divided into two kinds big. Thansfer
The first kind is gear type thansfer. General gear type thansfer drive, rear axle before two of output shaft in joints front drive meshing set for when the rigid connection. This kind of simple structure, the past in thansfer all kinds of full wheel drive car widely used, its shortcoming is no guarantee that the place before, rear wheel speed is equal, in the course of driving inevitably will generate the power cycle phenomenon. This will make the drive wheels load, a substantial increase in the tire and wear parts intensifies, fuel economy down. Therefore, should be in a separation of thansfer front axle drive device, in car through the gliding paragraph can engage front axle. In addition, general gear type thansfer assigned to the former, rear axle torque ratio between. So this will add to the adhesive condition good driving axle driving force, but may make the bridge for overload and damage. Therefore, currently USES this kind of thansfer car less and less.
Another kind is to take between shaft differential thansfer. This kind of thansfer in before and after the output shaft is between a planetary gear shaft type between differential. It's just overcome the shortcomings, two of the output shaft can be different speed rotation, and according to certain proportion will be assigned to torque, before and after driving axle, already can make the front axle often in driving conditions, and can keep the wheel motor coordination, so don't need a pick up front axle drive from the device. In selecting a belt between shaft differential thansfer, try to make before, rear axle shaft torque distribution close to Hollywood, and to make RenYiQiao distribution of the maximum input torque not more than the bridge's allow input torque. In order to avoid a bridge in the wheels skid completely lost when driving force, this kind of thansfer needs to set between shaft differential locks, so that in a bridge in the wheel slippage will thansfer before and after the output shaft for an organic whole, improve the lock by sex.
Take between shaft differential thansfer characteristic analysis
Take axis of the differential between general set apart in thansfer differential planetary mechanism, can exercise decomposition and synthesis; And make thansfer compact structure, carrying capacity, stable, the noise is small, the life is long. The differential between shaft thansfer is essentially a two degrees of freedom differential linear, of which planet shelf to active parts, surface wheel and tooth lap is center follower, respectively with the before and after the output shaft drive connected. Two follower influenced by certain external conditions, thus make the constraints of the planet reliable transmission line.
(1) Torque distribution characteristics
This illustration shows the belt between shaft differential transmission schemes, among them, thansfer respectively, the sun wheel, tooth circle and planet shelf rotation velocity;For the sun, respectively, and the circle and planet shelf rotation radius.
Thansfer in before and after the output shaft speed operation, have =. The planet round 4 revolution and not only rotation, the planet round on A, B, C, respectively, linear velocity at three V1 = r1w1 V2 = r2w2 V3 = (V1 + V2) / 2 so at this moment, the whole planet
similar row A whole participate in transmission, differential doesn't work.
(2)Differential property
Thansfer output shaft rotation speed before and after the car in the actual operation of the rare. Due to the differences between road conditions and radius, the turning of the car driving, and other factors, the shaft will work between differential. Here in the shaft of the differential between biaxial car as an example:
Before and after the car wheels that bridge rolling radius, making for a greater than driving axle wheels, before and after the wheel axis of the translation of the actual speed and driving speed, will produce consistent before sliding of the rear wheel turn skaters movement, thus cause to the trend and produce different direction wheel additional cut to force. These additional cut to force reaction to thansfer planet round, will make the planet wheel lock by torque no longer balance, and happen, the rotation angular velocity for
rotation. Due to the rotation of the planet round, the A and B two points on the linear velocity will also take place corresponding velocity increment. The show that at any time in the differential between shaft thansfer can be the law, so that it can avoid running all the wheel drive power cycle when phenomenon. Due to differential output shaft of two speed maintain these relations, so as to make the translation speed control of the wheel, tend to be equal to keep up the pure rolling and no sliding state.
(3) Thansfer characteristics of the car through the sexual influence
Take shaft differential between two thansfer shaft torque always maintain certain relation, the car through the difficult road is very harmful. For example when a car is unnecessary wheel in the pavement, other smaller adhesion wheels in a good road, the car driving resistance of much bigger, because the shaft of the differential effect between thansfer, in good road wheels stop and do not move, and the output shaft before thansfer to certain speed rotation, drive wheels skid, car can't front axle road, this kind of circumstance, such as in time, make thansfer self-locking differential output shaft is two shaft into the shaft, rigid connection between differential doesn't work, the output shaft after thansfer torque increases, which make full use of the wheel and the surface, make good adhesive condition car pulled out of difficult sections.
帶軸間差速器的分動器特性分析
在多軸驅動的汽車上設有分動器,它位于變速器和驅動橋之間的傳動鏈中,用來增大變速器輸出的轉矩,以擴大變范圍,并將轉矩分配給驅動橋。
分動器類型及其特點
從結構和功能來看,分動器可分為兩大類。
第一種是齒輪式分動器。一般齒輪式分動器驅動前,后橋的兩根輸出軸在接合前驅動嚙合套時為剛性連接。這類分動器結構簡單,過去在各類全輪驅動的汽車上廣泛使用,其缺點是不能保證前、后輪的地方速度相等,在行駛過程中不可避免地要產(chǎn)生功率循環(huán)現(xiàn)象。這將使驅動輪載荷大幅度增加,輪胎及機件磨損加劇,燃油經(jīng)濟性下降。為此,需在分動器中另設分離前橋驅動的裝置,在汽車通過滑溜段時可以接合前橋。另外,一般齒輪式分動器分配給前、后橋的轉矩比例不定。這樣雖然會增加附著條件較好的驅動橋的驅動力,但可能使該橋因超載而損壞。為此,目前采用這類分動器的汽車越來越少。
另一種是帶軸間差速器的分動器。這類分動器在前、后輸出軸之間有一個行星齒輪式軸間差速器。它正好克服了上述缺點,兩根輸出軸可以不同的轉速旋轉,并按一定的比例將轉矩分配給前、后驅動橋,既可使前橋經(jīng)常處于驅動狀態(tài),又可保證各車輪運動協(xié)調(diào),所以不需要另設接離前橋驅動的裝置。在選用帶軸間差速器的分動器時,盡量使前、后橋轉矩分配接近于軸荷分配,并使任一橋的最大輸入轉矩不超過該橋的允許輸入轉矩。為了避免在某一橋的車輪打滑時完全喪失驅動力,這類分動器需設軸間差速鎖,以便在某一橋車輪出現(xiàn)打滑的情況下將分動器前、后輸出軸鎖為一體,提高通過性。
帶軸間差速器的分動器特性分析
帶軸間差速器的分動器中一般設置單排行星機構差速器,可進行運動分解和合成;并使分動器結構緊湊,承載能力大,工作平穩(wěn),噪聲小,壽命長。分動器中的軸間差速器實質(zhì)上是一個二自由度的差動輪系,其中行星架為主動件,面中心輪及齒圈為從動件,分別與前、后驅動橋的輸出軸相連。兩從動件受一定的外界條件的約束,從而使行星排可靠地傳動。
(1)轉矩分配特性
下圖為帶軸間差速器的分動器傳動示意圖,其中、、分別為太陽輪、齒圈及行星架的轉動角速度;、、分別為太陽 、齒圈及行星架的轉動半徑。
在分動器前、后輸出軸等速運轉時,有 =。行星輪4只有公轉而無自轉,行星輪上A、B、C三點的線速度分別為:V1= r1w1 V2=r2w2 V3=(V1+V2)/2,所以此時整個行星排類同于一個整體參與傳動,差速器不起作用。
(2)差速特性
分動器前后輸出軸等速轉動的情況在汽車實際運行中很少發(fā)生。由于車輪半徑差異、路面狀況及汽車轉彎行駛等原因,軸間差速器將起作用。下面以雙軸汽車的軸間差速器為例:
假設汽車前后橋車輪的滾動半徑大于后橋車輪,為使前、后車輪輪軸的實際平移速度與汽車行駛速度相一致,必將產(chǎn)生前輪滑轉后輪滑移的運動趨勢,因而引起地面對前后車輪產(chǎn)生不同方向的附加切向反力。這些附加切向反力反應到分動器行星輪上,將使行星輪鎖受轉矩不再平衡,而發(fā)生自轉,其自轉角速度為。由于行星輪的自轉,其上A、B兩點的線速度也將發(fā)生相應的速度增量。其表明在任何時候分動器中的軸間差速器都能被此規(guī)律運轉,這樣就可以避免全輪驅動時的功率循環(huán)現(xiàn)象。由于差速器兩輸出軸的轉速保持上述關系,從而使前后輪輪軸的平移速度趨于相等,各車輪也能保持純滾動而無滑動狀態(tài)。
(3)分動器特性對汽車通過性的影響
帶軸間差速器的分動器兩軸輸出轉矩始終保持一定的比例關系,這對汽車通過困難路段是很不利的。例如當汽車某一車橋的車輪處于附著力較小的路面,其它車輪處于良好的路面時,則汽車的行駛阻力較大的情況下,由于分動器的軸間差速器作用,處于良好路面上的車輪停止不動,而分動器的前輸出軸將以一定的轉速旋轉,帶動前橋車輪打滑,汽車無法行駛,這種情況下,如及時鎖差速器,使分動器兩軸輸出軸則成剛性連接,使軸間差速器不起作用,則分動器后輸出軸上的轉矩增大,從而充分利用了車輪與地面的良好附著條件,使汽車駛出困難路段。
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