【導(dǎo)讀】本課題是進(jìn)行輕型越野車轉(zhuǎn)向驅(qū)動(dòng)橋的設(shè)計(jì)。橋，包括驅(qū)動(dòng)半軸，萬向節(jié)，橋殼，車輪等部件，協(xié)調(diào)設(shè)計(jì)車輛的全局。降低整車生產(chǎn)的總成本，推動(dòng)汽車經(jīng)濟(jì)的發(fā)展。向驅(qū)動(dòng)橋的各個(gè)部件，選出最佳的方案?？?，成本降低，適合本國路面的行駛狀況和國情。任務(wù)是傳遞發(fā)動(dòng)機(jī)的動(dòng)力，使之適應(yīng)于汽車行駛的需要。還得由驅(qū)動(dòng)橋的差速器來解決左、右驅(qū)動(dòng)車輪間的轉(zhuǎn)矩分配問題和差速要求。因此，要想使汽車驅(qū)動(dòng)橋的設(shè)計(jì)合理，首先必須選。好傳動(dòng)系的總傳動(dòng)比，并恰當(dāng)?shù)貙⑺峙浣o變速器和驅(qū)動(dòng)橋。器比應(yīng)能滿足汽車在給定使用條件下具有最佳的動(dòng)力性和燃料經(jīng)濟(jì)性。驅(qū)動(dòng)橋的噪聲主要來自齒輪及其他傳動(dòng)機(jī)。提高它們的加工精度、裝配精度，增強(qiáng)齒輪的支承剛度，是降低驅(qū)動(dòng)橋工作。噪聲的有效措施。驅(qū)動(dòng)橋各零部件在保證其強(qiáng)度、剛度、可靠性及壽命的前提下。單級(jí)驅(qū)動(dòng)橋的使用比例越來越高；技術(shù)方面，輕量化、舒適性的要求將逐步提高。

　　

【正文】 large overlap coefficient to assure the number of mating gears is between 2 to 3 or more。 2 using the small number of teeth of the small gear to obtain large drive ratio and save space。 3 assembling exactly to make the mating surface exceed 50 percent. Partition of finite element mesh The material of rear axle housing is fed iron and its density 7850 kg/m3, Young39。s modulus of elasticity , Poisson ratio , shear modulus , of drive gear is 20GrMnTi steel and its density 7800 kg/m3, Young39。s modulus of elasticity , Poisson ratio , shear modulus , using solid164 element. Fig 2 FEM but gears and drive axle housing Fig 3 The set assembling of rear axle The determination of boundary conditions The boundary conditions of vibration analysis of rear axle include: the drive gear’s speed, the follower gear’s initial speed load, the constraint condition of the rear axle housing. The deduction of drive gear’s speed 1 The type of drive wheel is 155R13 and the diameter of airfilled 576 mm. 2 Assuming the wheel’line speed is 90km/h, be equal to 25 m/s, so the angular velocity is As the drive ratio of follower gear and drive gear is 41:8, so the angular velocity of drive gear is: *41/8 and output shaft is: w2 output angular velocity, w1 input constant angular velocity, a1 angle between input shaft and connection shaft, a2 angle between output shaft and connection shaft, φ1 is the rotate speed of input shaft. a1 a2 a , The follower gear’s initial speed load The vehicle’s speed can’t be 90km/h at the start point actually, but gradually increase into steady state. If the initial speed is not applied or applied inaccurately, the gears may generate great impact. Only when applying accurate initial speed load, the gears’ deform can be appropriate. The constraint condition of rear axle housing The load that the housing bears es from the impact when the gears mate. The impact is passed to the housing by the axle and bearing, and result in the housing’s vibration. Fig 4 The constraint of rear axle housing 2. EXTRACTING THE DATE OF REAR AXLE TRANSIENT ANALYSIS The main purpose of transient analysis is to extract the load data of rear axle housing. The method to deal with the bearing and housing is nodepasted. So the nodes of exterior of surface fig2 C, D, E are the points needed to analyze. All of the nodes amount to 552. According to the analysis of bearing axial and circumferential different nodes, we can find that the nodes’ response are almost the same. So when dealing with the load data, we can regard the timedomain curve of the nodes of the same bearing equally. This simplified representation is proper and also reduces the amount of work. After obtaining the timedomain vibration signals, it is needed to transform them to frequencydomain signals: 1 to find which frequency can cause wide vibration, and then do some major research on it to reduce the vibration in the frequency finally, 2 to use them as load data in SYSNOISE software. From the diagram below, we can find there is great vibration at frequencies followed as , , 200Hz and . So the load data of the three different frequencies should be imported to SYSNOISE software for harmonic response analysis. As the response of D and E are very much alike, so only the response of D is listed below Fig 5 The frequencydomain response in 2021Hz at C Fig 6 The frequencydomain response in 2021Hz at D 3. ANALYSIS OF REAR AXLE’S NOISE Firstly, we import the displacement result of the harmonic response and corresponding frequency. And then we can use Boundary Element Method BEM to solve the noise problem. The purpose is to find the main noise source and to provide some proof for later improvement. Some documents have pointed out that the rear axle noise is resulted from the structural surface’s vibration, such as rear axle housing. Referred to the research result of FEM, we know the housing’s vibration focus on housing rear cover and main reducing gear shell, both of which are located in the middle of the housing. So when set the field points, we should consider emphatically the noise radiation condition in the middle place Fig 7 Field collocation At frequency , the result of sound pressure level SPL is below: Fig 8 The SPL of back housing Fig 9 The SPL of up housing From the figure, we can find the main noise source locate at main reducing gear shell and back housing. A great amount of faint yellow appears at these places and the SPL of these places is between and . For the sake of parison, we list the calculation result of all frequencies as follows: By parison, we can conclude: housing main radiation area nclude: back housing shell, main reducing gear shell and housing shell abdominal area. And back housing shell is the main area. So any measure to reduce the housing noise must aim at back housing shell. 4. MODIFIED STRUCTURE OF REAR AXLE As the back housing shell is always the main source of radiation noise, this paper controls the housing shell’s vibration by cross shank and rice character shank. And it aims at two frequencies and 592 Hz at which the noise is imizing. Fig10 The cross shank on rear axle housing’s cap Fig11 The rice shank on rear axle housing’s cap Taking cross shank for example, we pare the noise result with that before at . And we set the indication range as before. To our surprise, the SPL imum of the rear axle housing turns to dB by , reducing about 4 dB. And the SPL imum of the rear axle housing turns to dB by dB, the same result as the method of rice character shank. 5. CONCLUSIONS Based on the research of the rear axle housing’s vibration and noise analysis, this paper identifies the main radiation noise resource and improves the structure that reduces the response of th