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附錄1
變速箱齒輪的設(shè)計(jì)準(zhǔn)則：
由于汽車變速箱各擋齒輪的工作情況是不相同的，所以按齒輪受力、轉(zhuǎn)速、噪聲要求等情況，應(yīng)該將它們分為高擋工作區(qū)和低擋工作區(qū)兩大類。齒輪的變位系數(shù)、壓力角、螺旋角、模數(shù)和齒頂高系數(shù)等都應(yīng)該按這兩個(gè)工作區(qū)進(jìn)行不同的選擇。
高擋工作區(qū)：通常是指三、四、五擋齒輪，它們在這個(gè)區(qū)內(nèi)的工作特點(diǎn)是行車?yán)寐瘦^高，因?yàn)樗鼈兪瞧嚨慕?jīng)濟(jì)性擋位。在高擋工作區(qū)內(nèi)的齒輪轉(zhuǎn)速都比較高，因此容易產(chǎn)生較大的噪聲，特別是增速傳動(dòng)，但是它們的受力卻很小，強(qiáng)度應(yīng)力值都比較低，所以強(qiáng)度裕量較大，即使削弱一些小齒輪的強(qiáng)度，齒輪匹配壽命也在適用的范圍內(nèi)。因此，在高擋工作區(qū)內(nèi)齒輪的主要設(shè)計(jì)要求是降低噪聲和保證其傳動(dòng)平穩(wěn)，而強(qiáng)度只是第二位的因素。
低擋工作區(qū)：通常是指一、二、倒擋齒輪，它們在這個(gè)區(qū)內(nèi)的工作特點(diǎn)是行車?yán)寐实停ぷ鲿r(shí)間短，而且它們的轉(zhuǎn)速比較低，因此由于轉(zhuǎn)速而產(chǎn)生的噪聲比較小。但是它們所傳遞的力矩卻比較大，輪齒的應(yīng)力值比較高。所以低擋區(qū)齒輪的主要設(shè)計(jì)要求是提高強(qiáng)度，而降低噪聲卻是次要的。
在高擋工作區(qū)，通過選用較小的模數(shù)、較小的壓力角、較大的螺旋角、較小的正角度變位系數(shù)和較大的齒頂高系數(shù)。通過控制滑動(dòng)比的噪聲指標(biāo)和控制摩擦力的噪聲指標(biāo)以及合理選用總重合度系數(shù)、合理分配端面重合度和軸向重合度，以滿足現(xiàn)代變速箱的設(shè)計(jì)要求，達(dá)到降低噪聲、傳動(dòng)平穩(wěn)的最佳效果。而在低擋工作區(qū)，通過選用較大的模數(shù)、較大的壓力角、較小的螺旋角、較大的正角度變位系數(shù)和較小的齒頂高系數(shù)，來增大低擋齒輪的彎曲強(qiáng)度，以滿足汽車變速箱低擋齒輪的低速大扭矩的強(qiáng)度要求。以下將具體闡述怎樣合理選擇這些設(shè)計(jì)參數(shù)。
變速箱各擋齒輪基本參數(shù)的選擇：
1 合理選用模數(shù)：
模數(shù)是齒輪的一個(gè)重要基本參數(shù)，模數(shù)越大，齒厚也就越大，齒輪的彎曲強(qiáng)度也越大，它的承載能力也就越大。反之模數(shù)越小，齒厚就會(huì)變薄，齒輪的彎曲強(qiáng)度也就越小。對于低速擋的齒輪，由于轉(zhuǎn)速低、扭矩大，齒輪的彎曲應(yīng)力比較大，所以需選用較大的模數(shù)，以保證其強(qiáng)度要求。而高速擋齒輪，由于轉(zhuǎn)速高、扭矩小，齒輪的彎曲應(yīng)力比較小，所以在保證齒輪彎曲強(qiáng)度的前提下，一般選用較小的模數(shù)，這樣就可以增加齒輪的齒數(shù)，以得到較大的重合度，從而達(dá)到降低噪聲的目的。
在現(xiàn)代變速箱設(shè)計(jì)中，各擋齒輪模數(shù)的選擇是不同的。例如，某變速箱一擋齒輪到五擋齒輪的模數(shù)分別是：3.5；3；2.75；2.5；2；從而改變了過去模數(shù)相同或模數(shù)拉不開的狀況。
2合理選用壓力角：
當(dāng)一個(gè)齒輪的模數(shù)和齒數(shù)確定了，齒輪的分度圓直徑也就確定了，而齒輪的漸開線齒形取決于基圓的大小，基圓大小又受到壓力角的影響。對于同一分度圓的齒輪而言，若其分度圓壓力角不同，基圓也就不同。當(dāng)壓力角越大時(shí)，基圓直徑就越小，漸開線就越彎曲，輪齒的齒根就會(huì)變厚，齒面曲率半徑增大，從而可以提高輪齒的彎曲強(qiáng)度和接觸強(qiáng)度。當(dāng)減小壓力角時(shí)，基圓直徑就會(huì)變大，齒形漸開線就會(huì)變的平直一些，齒根變薄，齒面的曲率半徑變小，從而使得輪齒的彎曲強(qiáng)度和接觸強(qiáng)度均會(huì)下降，但是隨著壓力角的減小，可增加齒輪的重合度，減小輪齒的剛度，并且可以減小進(jìn)入和退出嚙合時(shí)的動(dòng)載荷，所有這些都有利于降低噪聲。因此，對于低速擋齒輪，常采用較大的壓力角，以滿足其強(qiáng)度要求；而高速擋齒輪常采用較小的壓力角，以滿足其降低噪聲的要求。
例如：某一齒輪模數(shù)為3，齒數(shù)為30，當(dāng)壓力角為17.5度時(shí)基圓齒厚為5.341；當(dāng)壓力角為25度時(shí)，基圓齒厚為6.716；其基圓齒厚增加了25%左右，所以增大壓力角可以增加其彎曲強(qiáng)度。
3 合理選用螺旋角：
與直齒輪相比，斜齒輪具有傳動(dòng)平穩(wěn)，重合度大，沖擊小和噪聲小等優(yōu)點(diǎn)?，F(xiàn)在的變速箱由于帶同步器，換擋時(shí)不再直接移動(dòng)一個(gè)齒輪與另一個(gè)齒輪嚙合，而是所有的齒輪都相嚙合，這樣就給使用斜齒輪帶來方便，因此帶同步器的變速箱大多都使用斜齒輪。
由于斜齒輪的特點(diǎn)，決定了整個(gè)齒寬不是同時(shí)全部進(jìn)入嚙合的，而是先由輪齒的一端進(jìn)入嚙合，隨著輪齒的傳動(dòng)，沿齒寬方向逐漸進(jìn)入嚙合，直到全部齒寬都進(jìn)入嚙合，所以斜齒輪的實(shí)際嚙合區(qū)域比直齒輪的大。當(dāng)齒寬一定時(shí)，斜齒輪的重合度隨螺旋角增加而增加。承載能力也就越強(qiáng)，平穩(wěn)性也就越好。從理論上講，螺旋角越大越好，但螺旋角增大，會(huì)使軸向分力也增大，從而使得傳遞效率降低了。
在現(xiàn)代變速箱的設(shè)計(jì)中，為了保證齒輪傳動(dòng)的平穩(wěn)性、低噪聲和少?zèng)_擊，所有齒輪都要選擇較大的螺旋角，一般都在30°左右。對于高速擋齒輪由于轉(zhuǎn)速較高，要求平穩(wěn)，少?zèng)_擊，低噪聲，因此采用小模數(shù)，大螺旋角；而低速擋齒輪則用較大模數(shù)，較小螺旋角。
4合理選用正角度變位：
對于具有良好潤滑條件的硬齒面齒輪傳動(dòng)，一般認(rèn)為其主要危險(xiǎn)是在循環(huán)交變應(yīng)力作用下，齒根的疲勞裂紋逐漸擴(kuò)張?jiān)斐升X根斷裂而失效。變速箱中齒輪失效正是屬于這一種。為了避免輪齒折斷，應(yīng)盡量提高齒根彎曲強(qiáng)度，而運(yùn)用正變位，則可達(dá)到這個(gè)目的。一般情況下，變位系數(shù)越大，齒形系數(shù)值就越小，輪齒上彎曲應(yīng)力越小，輪齒彎曲強(qiáng)度就越高。
在硬齒面的齒輪傳動(dòng)中，齒面點(diǎn)蝕剝落也是失效原因之一。增大嚙合角，可降低齒面間的接觸應(yīng)力和最大滑動(dòng)率，能大大提高抗點(diǎn)蝕能力。而增大嚙合角，則必須對一副齒輪都實(shí)行正變位，這樣既可提高齒面的接觸強(qiáng)度，又可提高齒根的彎曲強(qiáng)度，從而達(dá)到提高齒輪的承載能力效果。但是，對于斜齒輪傳動(dòng)，變位系數(shù)過大，又會(huì)使輪齒總的接觸線長度縮短，反而降低其承載能力。同時(shí)，變位系數(shù)越大，由于齒頂圓要隨之增大，其齒頂厚度將會(huì)變小，這會(huì)影響齒頂?shù)膹?qiáng)度。
因此在現(xiàn)代變速箱的設(shè)計(jì)中，大多數(shù)齒輪均合理采用正角度變位，以最大限度發(fā)揮其優(yōu)點(diǎn)。主要有以下幾個(gè)設(shè)計(jì)準(zhǔn)則：
對于低速擋齒輪副來說，主動(dòng)齒輪的變位系數(shù)應(yīng)大于被動(dòng)齒輪的變位系數(shù)，而對高速擋齒輪副，其主動(dòng)齒輪的變位系數(shù)應(yīng)小于被動(dòng)齒輪的變位系數(shù)。
主動(dòng)齒輪的變位系數(shù)隨擋位的升高而逐漸xiajiang。這是因?yàn)榈蛽鯀^(qū)由于轉(zhuǎn)速低、扭矩大，齒輪強(qiáng)度要求高，因此需采用較da的變位系數(shù)。
各擋齒輪的總變位系數(shù)都是正的（屬于角變位修正），而且隨著擋位的升高而逐漸減小?？傋兾幌禂?shù)越小，一對齒輪副的齒根總的厚度就越薄，齒根就越弱，其抗彎強(qiáng)度就越 低，但是由于輪齒的剛度減小，易于吸收沖擊振動(dòng)，故可降低噪聲。而且齒形重合度會(huì)增加，這使得單齒承受最大載荷時(shí)的著力點(diǎn)距齒根近，使得彎曲力矩減小，相當(dāng)于提高了齒根強(qiáng)度，這對由于齒根減薄而消弱強(qiáng)度的因素有所抵消。所以總變位系數(shù)越大，則齒根強(qiáng)度越高，但噪聲則有可能增大。因此高速擋齒輪要選擇較小的總變位系數(shù)，而低速擋齒輪則必須選用較大的總變位系數(shù)。
5 提高齒頂高系數(shù)：
齒頂高系數(shù)在傳動(dòng)質(zhì)量指標(biāo)中，影響著重合度，在斜齒輪中主要影響端面重合度。由端面重合度的公式可知，當(dāng)齒數(shù)和嚙合角一定時(shí)，齒頂圓壓力角是受齒頂高系數(shù)影響的，齒頂高系數(shù)越大，齒頂圓壓力角也越大，重合度也就越大，傳動(dòng)也就越平穩(wěn)。但是，齒頂高系數(shù)越大，齒頂厚度就會(huì)越薄，從而影響齒頂強(qiáng)度。同時(shí)，從最少不根切齒數(shù)公式來看，齒頂高系數(shù)越大，最少不根切齒數(shù)就會(huì)增加，否則的話，就會(huì)產(chǎn)生根切。因此，在保證不根切和齒頂強(qiáng)度足夠的情況下，增大齒頂高系數(shù)，對于增加重合度是有意義的。
因此在現(xiàn)代變速箱的設(shè)計(jì)中，各擋齒輪的齒頂高系數(shù)都選擇較大的值，一般都大于1.0，稱為細(xì)高齒，這對降低噪聲，增加傳動(dòng)平穩(wěn)性都有明顯的效果。對于低速擋齒輪，為了保證其具有足夠的齒根彎曲強(qiáng)度，一般選用較小的齒頂高系數(shù)；而高速擋齒輪，為了保證其傳動(dòng)的平穩(wěn)性和低噪聲，一般選用較大的齒頂高系數(shù)。
以上是從模數(shù)、壓力角、螺旋角、變位系數(shù)和齒頂高系數(shù)這五個(gè)方面去獨(dú)立分析齒輪設(shè)計(jì)趨勢。實(shí)際上各個(gè)參數(shù)之間是互相影響、互相牽連的，在選擇變速箱的參數(shù)時(shí)，既要考慮它們的優(yōu)缺點(diǎn)，又要考慮它們之間的相互關(guān)系，從而以最大限度發(fā)揮其長處，避免短處，改善變速箱的使用性能。
附錄2
Gearbox design criteria:
As the automobile gearbox stall the work gear is not the same, so according to gear force, speed, noise requirements, etc., they should be divided into high and low-end work area work area two broad categories. Gear modification coefficient, pressure angle, helix angle, modulus and Addendum coefficient and so on should be based on the work areas of these two different options.
High-grade work area: usually refers to the three, four, five-speed gears, they work in this area is characterized by a higher utilization rate of traffic, because they are economical car stalls. In the high-end gear working area than the higher speed, so easy to have a greater noise, especially the growth rate of transmission, but their force was small, the intensity of stress values are relatively low, so strength margin, so even after weaken the strength of some small gear, gear matching is also applicable within the framework of life. Therefore, in high gear the work of the major design requirements for the region is to reduce noise and ensure a smooth transmission, while the intensity is only the second factor.
Low-grade work area: usually refers to the first, second and reverse gears, they work in this area is characterized by low utilization rate of traffic, working time is short, and their speed is relatively low, so the noise generated due to rotational speed is relatively small. But the moment they are transmitted is larger, tooth stress values are relatively high. Therefore, the main gear low area design requirements is to improve the strength, while the noise reduction is secondary.
In the high-end work area, through the use of smaller modulus, the smaller the pressure angle, the larger the helix angle, the smaller is the angle variable coefficient and a larger Addendum coefficient. Noise ratio by controlling the sliding friction of indicators and control of noise indicators, and a reasonable selection of the total coincidence coefficient, reasonable distribution of end-of coincidence degree and axial coincidence degree, in order to meet the design requirements of modern transmissions, to reduce the noise, transmission of the most stable good results. In the low-grade work area, through the selection of the larger modulus, the larger pressure angle, the smaller helix angle, the larger is the angle variable coefficient and a smaller Addendum coefficient,
To increase the low-end gear bending strength to meet the low-speed auto gearbox gear high-torque low strength requirements. The following will specifically set out what a reasonable selection of these design parameters.
Transmission gear basic parameters of the file options:
A reasonable choice Modulus:
Modulus is an important basic parameters of gears, the greater the modulus, the greater the tooth thickness, the greater the gear bending strength, the greater its carrying capacity. On the contrary modulus smaller tooth thickness will be thinner, thus the smaller the gear bending strength. For the low-profile gear, due to the low rotational speed, torque, gear bending stress relatively large, so we need to use a larger module in order to ensure its strength demands. The high gear gear, due to high speed, torque is small, gear bending stress is relatively small, so ensure that the premise of gear bending strength, generally use a smaller modulus, so that you can increase the number of teeth in order to obtain a larger coincidence degree
So as to achieve noise reduction purposes.
In modern transmission design, each gear module file option is different. For example, a transmission gear to file a five-speed gear module are: 3.5; 3; 2.75; 2.5; 2; thus changing the modulus of the same or a module over the past few pull not open situation.
2 rational selection pressure angle:
When a gear tooth modulus and determined, gear pitch circle diameter also identified, while the gear involute base circle depends on the size of the base circle size of the impact angle under pressure again. For the same pitch circle of gear, if it is the pressure angle of its sub-degree circle is different from the base circle is different. When the pressure angle, the larger, the base circle diameter of the smaller, more curved involute, tooth tooth root will be thicker and larger radius of curvature of tooth surface, which can increase the tooth bending strength and contact strength. When reducing the pressure angle, the base circle diameter will be larger, the involute tooth profile will change some of the flat, tooth root thinning, tooth surface radius of curvature smaller,
Which makes the tooth bending strength and contact strength will decrease, but as the pressure angle decreases, increase the degree of coincidence gears, reducing the tooth stiffness, and can reduce the time of entry and exit mesh dynamic load, All of these are beneficial to reduce the noise. Therefore, for low-profile gear, often with a larger pressure angle, in order to meet the strength requirements; while the high gear gear often used a smaller pressure angle, in order to meet their noise reduction requirements.
For example: a gear module 3, teeth 30, when the pressure angle of 17.5 degrees tooth thickness of 5.341 base circle; when the pressure angle of 25 degrees, the base circular tooth thickness of 6.716; its base circle tooth thickness increased about 25%, so increase the pressure angle can increase its bending strength.
A reasonable choice of three helix angle:
Compared with the spur gear, helical gear with a transmission smooth, coincidence degree, the impact of small and low noise advantages. As with the current transmission synchronizer, the shifter is no longer directly moving a gear meshing with another gear, but all of the gears are meshing phase, disturbing the convenient use of helical gears, so the transmission with a synchronizer Most of all use helical gears.
Because the characteristics of helical gears and decided the entire tooth width is not the same time, all entered the mesh, but first be entered at one end of tooth meshing with the tooth of the drive, along the tooth width direction is gradually enter the mesh, until the entire tooth width have to enter into mesh, so the actual meshing helical gear spur gear than a large area. When the tooth width is constant, helical gear with helix angle degree of coincidence increases. Carrying capacity of the stronger, the better smoothness. In theory, the helix angle the bigger the better, but the helix angle increases, the axial pitch will also increase, making the transfer efficiency decreased.
In modern transmission design, in order to ensure smooth gear drive, low noise and low impact, all the gears should choose a larger helix angle, generally in about 30 °. For high-speed stall speed due to a higher gear, for a stable, low impact, low-noise, so a small modulus, large helical angle; while low-profile gear you use a larger modulus, the smaller spiral angle.
4 is a reasonable choice of the angle deformation:
For the good of the hardened gear lubrication condition is generally believed that the main danger is in the loop under the action of alternating stress, the tooth root fatigue cracks caused by the gradual expansion of the tooth root fracture and failure. Transmission in gear failure is a part of this. In order to avoid tooth fracture, it should enhance tooth root bending strength, while the use of positive deflection, you can achieve this goal. Under normal circumstances, variable coefficient the greater the coefficient the smaller the tooth, tooth bending stress on the smaller, the higher the tooth bending strength.
In the hardened gear transmission, the tooth surface pitting peel off one of the reasons is also a failure. Increased engagement angle, which reduces the contact between the tooth surface stress and maximum slip rates, can greatly enhance the pitting corrosion resistance capabilities. The increased pressure angle, it must be practiced on a gear is changed bits, thereby enhancing the tooth surface contact strength, but also improve the bending strength of tooth roots to achieve the effect of improving the carrying capacity of gears. However, for helical gear drive, variable coefficient is too large, but also the total tooth will shorten the length of contact line, but reduce its carrying capacity. Meanwhile, the variable coefficient greater, due to tooth tip should be even greater, the tooth tip thickness will be smaller,
This will affect the strength of the top gear.
Therefore, in modern transmission design, most of the gears are a reasonable angle of deflection is used in order to maximize its advantages. Mainly in the following design guidelines:
For the low-profile gear pair, the active gear variable coefficient should be larger than the passive gear modification coefficient, while for high-speed file gear pair, which take the initiative to gear modification coefficients should be less than the passive gear modification coefficient.
Active gear modification coefficient increases gradually with stalls xiajiang. This is because the low-grade area due to the low rotational speed, torque, gear strength with high requirements, therefore need to adopt a more da variable coefficient.
Gear of the total variation of all files coefficient is positive (of the angle deflection amended), and along with the increase of stalls gradually decreased. The smaller the total variation coefficient, a pair of gear pairs of the total thickness of the tooth root more thin, tooth root more weak, its lower bending strength, but because of reduced tooth stiffness, easy to absorb shock and vibration, so can reduce the noise. And the degree of tooth overlap will increase, which makes a single tooth to withstand the maximum load when the focus on pitch near the tooth root, making bending moment decrease is equivalent to increasing strength of the tooth root, which is due to thinning and weakening of tooth root strength factor has been offset. Therefore, the greater the total variation coefficient, then the tooth root strength of the higher
But the noise is likely to increase. So high gear gear to choose a smaller total variation coefficient, while the low-profile gear, you must use a larger total variation coefficient.
Addendum 5 to the factor:
Addendum coefficient of transmission quality index, the impact of focus on adaptation, the main impact in the helical gear face of coincidence degree. End coincidence degree from the formula we can see, when the number of teeth and meshing a certain angle, the tooth tip pressure angle is subject to the impact of Addendum coefficient, Addendum coefficient the greater the addendum circle the greater the pressure angle, coincidence degree also The larger drive is also more stable. However, Addendum coefficient the greater the thickness of the top teeth will be thinner, thereby affecting the intensity of the top teeth. At the same time, from at least a few formula Cutting is not the root point of view, the greater the Addendum coefficient, at least not the root Cutting the number will increase, otherwise, it will generate the root cutting. Therefore,
In the guarantee not to cut the root and the tooth top of the case of sufficient strength, increasing the Addendum coefficient, for increasing the degree of coincidence is meaningful.
Therefore, the design of a modern gearbox, each gear tooth profile the top choice of high coefficients are greater value, generally greater than 1.0, known as fine a high-tooth, which is to reduce noise, increase the transmission has a significant effect of Stationarity . For the low-profile gear, in order to ensure that it has enough tooth root bending strength, generally choose the smaller Addendum coefficient; while the high gear gear, in order to ensure its smooth transmission and low noise, generally choose the larger Addendum factor.
The above is from the module, pressure angle, helix angle, addendum modification coefficient and the coefficient of these five areas to an independent analysis of gear design trends. In fact between the various parameters influence each other mutually implicated, the choice of transmission parameters, it is necessary to take into account their strengths and weaknesses, but also take into account the relationship between them in order to maximize its strengths and weaknesses and to improve the use of transmission performance.
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