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第53頁(yè),共52頁(yè)。根據(jù)以上設(shè)計(jì)滾齒刀的理論,我們可以確保擺線—弧機(jī)器的旋轉(zhuǎn)部分滾齒加工出正確的輪廓。當(dāng)我們知道關(guān)于機(jī)械的旋轉(zhuǎn)部分分開的曲線等式后,我們可以通過(guò)圖7,弄清楚在滾齒刀螺旋部分末端機(jī)械的旋轉(zhuǎn)部分分開的等式,如下: (2)等式里β1是機(jī)械旋轉(zhuǎn)部分的螺旋角,β2是滾齒刀螺旋部分的螺旋角。圖6 齒軌上分開的曲線結(jié)構(gòu)齒軌上分開的曲線可以由下面的等式很容易的得出: (1)等式中r是轉(zhuǎn)子節(jié)距圓的半徑,ρ是直線od的長(zhǎng)度,φ是直線oe和縱坐標(biāo)Y的夾角。兩個(gè)坐標(biāo)點(diǎn)d1和d2可以很容易的由d1(x1,y1)和d2(x2,y2)表示出,顯然,當(dāng)齒軌和機(jī)械的旋轉(zhuǎn)部分捏合時(shí),機(jī)械的旋轉(zhuǎn)部分輪廓圍繞齒軌移動(dòng)的尖端d形成齒軌輪廓分開的曲線結(jié)構(gòu)。根據(jù)齒輪嚙合定理,我們可以很容易的理解機(jī)械旋轉(zhuǎn)部分中間的齒軌嚙合。圖3螺桿旋轉(zhuǎn)部分末端 圖4 滾刀的軸向輪廓 圖5 凹形曲線 (3) 準(zhǔn)確的計(jì)算出中間曲線的最好方法這里我們利用中間的齒軌來(lái)推算分開的邊沿曲線中間曲線。一種方法是延長(zhǎng)曲線cd和直線de,如圖3所示,這種方法可以防止?jié)L刀邊沿刃口出現(xiàn)獨(dú)立的曲線,但是滾刀輪廓將變成圖4所示,這種滾刀即不能生產(chǎn)也不能可能使用。擺線延長(zhǎng)線cd和直線de的交點(diǎn)處存在一個(gè)尖端d,也就是說(shuō),也就是說(shuō)在交點(diǎn)d出存在一個(gè)共同的切點(diǎn)。在本文里,我們將對(duì)用于滾齒加工不對(duì)稱具有尖端外形的擺線—弧輪廓的滾刀的設(shè)計(jì)原理進(jìn)行深入研究。由于不對(duì)稱的擺線—弧輪廓螺旋壓縮機(jī)比對(duì)稱的弧輪廓有很多優(yōu)越之處,目前,我們國(guó)家的工廠都采用前者。但是,實(shí)現(xiàn)滾齒加工螺桿壓縮機(jī)機(jī)械旋轉(zhuǎn)部分的主要問題是,螺桿壓縮機(jī)機(jī)械旋轉(zhuǎn)部分的輪廓必須適合于滾齒加工。因此,目前相對(duì)于銑削加工的方法,滾齒加工變的越來(lái)越普遍。目前,我國(guó)制造螺旋轉(zhuǎn)子的機(jī)加工方法是銑削,但缺陷是生產(chǎn)效率和加工精度都比較低。通過(guò)實(shí)際的設(shè)計(jì)、生產(chǎn)和測(cè)試證實(shí)這種這種理論對(duì)滾齒刀刀具和滾齒刀擺線—弧機(jī)械的旋轉(zhuǎn)部分的設(shè)計(jì)有很大的作用。當(dāng)設(shè)計(jì)用來(lái)加工這種機(jī)器旋轉(zhuǎn)部分的滾齒刀刀具時(shí),這種滾刀的刃口將出現(xiàn)分離的現(xiàn)象。 it has a tip on it. When design the hob cutter used for machining this kind of rotors, the profile of hob edge will appear separation. In this paper, the author made researches on the design theory of hob cutter for hobbing the cycloidarc rotor with tip profile, and got the best way for design this kind of hob cutter with a separate edge. It is good practice to design the hob cutter and hob the cycloidarc rotor according to practical design, manufacture and test.(1) INTRODUCTIONThe efficiency and reliability of screw pressor mainly depend on manufacturing technology of screw rotors. At present, the machining method of our country for machining screw rotors is milling the shorting of milling is low productivity and machining accuracy. Hobbing characteristic is high productivity and machining accuracy, so the machining method for hobbing instead of milling screw pressor rotors is now being more and more popular.Hobbing instead of milling for machining screw pressor rotors has much more advantage, but the key problem for carrying out hobbing the screw pressor rotors is that the profile of screw pressor rotors must be suited to hobbing. Our national standard profile for screw pressor rotors have nosymmetric cycloidarc profile and symmetric are profile [1], since nosymmetric cycloidarc profile screw pressor has much more advantage than symmetric are profile screw pressor, our national factory all adopt the former at present. The property of nosymmetric cycloidarc profile is that the conjoint curve of profile isn’t slick curve, it has a tip on the profile, it is still a great difficult for hobbing instead of milling this kind of screw rotors in our country as the design problem of hob cutter. In this paper, we’ll make researches on the design theory of hob cutter for hobbing the nosymmetric cycloidarc rotor with tip profile.(2 ) EXISTING PROBLEM shows the end section of nosymmetric cycloidarc rotors, its end profile is posed of radial line ab, arc bc, prolonged cycloid cd and radial line de. The point of intersection of prolonged cycloid cd and radial line de exist a tip d, that is, the d point of intersection hasn’t mon tangent. As we calculate the corresponding axial profile of hob cutter according to cutting tool design handbook or other cutting tool design data, we’ll find that the axial profile of hob cutter bees two separate curves, like the one shown in . The end profile of screw rotor The axial profile of hobIn order to machining the required rotor profile and insure the tip not being cut out, people can usually take following two ways to solve this problem. One way is to prolong curve cd and radial line de as shows, this way can avoid appearing separate curve of hob edge, but hob profile will bee shows, this kind of hob edge can neither be machined nor be used. Another way is to make a concave curve to link the separate hob edge as shows. The end profile of screw rotor The axial profile of hob The concave curveThis way can avoid the tip being cut out, but it will produce two new tips on hob edge. This kind of hob is not only difficult to be machined but also easy to be worn on the tips. Form above discussing we can see that above two ways is not the best way to solve this problem. The best way to solve this kind of problem is to figure out the intermediate curve between separate edge curves accurately.(3) THE BEST WAY FOR CALCULATING INTERMEDIATE CURVE ACCURATELYHere we make use of the intermediate rack to calculate the intermediate curve between separate edge curves. That is, in the first place, we figure out the intermediate profile of rack according to the mesh of intermediate rack and rotor, in the second place, we figure out the intermediate profile of hob edge curve according to the mesh of intermediate rack and hob worm. According to gear mesh theorem, we can figure out the profile of intermediate rack mesh with rotor easily. As the tip exists on the profile of rotor, calculated profile of rotor will be two separate curves as shows. The two coordinates points d1 and d2 can easily figure out as following d1(x1, y1) and d2(x2, y2), obviously, the formation of separate curve of rack profile is that the tip d on rotor profile move around the rack to form when rack meshes with rotor. According to we can see, the mesh of rack and rotor is equal to pitch circle of ro