1、附录 1 The Original English THE KEY TECHNOLOGY OF DESIGN HOB FOR HOBBING SCREW COMPRESSOR ROTORS WITH CUCLOID-ARC PROFILE ABSTRCT The profile of cycloid-arc screw compressor rotors is not a smooth profile； it has a tip on it. When design the hob cutter used for machining this kind of rotors, the profi
2、le of hob edge will appear separation. In this paper, the author made researches on the design theory of hob cutter for hobbing the cycloid-arc 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 t
3、he cycloid-arc rotor according to practical design, manufacture and test. (1) INTRODUCTION The efficiency and reliability of screw compressor mainly depend on manufacturing technology of screw rotors. At present, the machining method of our country for machining screw rotors is milling the shortcomi
4、ng 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 compressor rotors is now becoming more and more popular. Hobbing instead of milling for machining screw compresso
5、r rotors has much more advantage, but the key problem for carrying out hobbing the screw compressor rotors is that the profile of screw compressor rotors must be suited to hobbing. Our national standard profile for screw compressor rotors have no-symmetric cycloid-arc profile and symmetric are profi
6、le 1, since no-symmetric cycloid-arc profile screw compressor has much more advantage than symmetric are profile screw compressor, our national factory all adopt the former at present. The property of no-symmetric cycloid-arc profile is that the conjoint curve of profile isnt slick curve, it has a t
7、ip 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, well make researches on the design theory of hob cutter for hobbing the no-symmetric cycloid-arc rotor with tip profile. (2 ) E
8、XISTING PROBLEM Fig.1 shows the end section of no-symmetric cycloid-arc rotors, its end profile is composed 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 has
9、nt common tangent. As we calculate the corresponding axial profile of hob cutter according to cutting tool design handbook or other cutting tool design data, well find that the axial profile of hob cutter becomes two separate curves, like the one shown in Fig.2. Fig.1 The end profile of screw rotor
10、Fig.2 The axial profile of hob In 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 Fig.3 shows, this way can avoid appearing separate curve of hob
11、 edge, but hob profile will become Fig.4 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 Fig.5 shows. Fig.3 The end profile of screw rotor Fig.4 The axial profile of hob Fig.5 The concave curve This way can avo
12、id 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 probl
13、em is to figure out the intermediate curve between separate edge curves accurately. (3) THE BEST WAY FOR CALCULATING INTERMEDIATE CURVE ACCURATELY Here 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 th
14、e 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 ra
15、ck mesh with rotor easily. As the tip exists on the profile of rotor, calculated profile of rotor will be two separate curves as Fig.2 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
16、is that the tip d on rotor profile move around the rack to form when rack meshes with rotor. According to Fig.6 we can see, the mesh of rack and rotor is equal to pitch circle of rotor rolling on the pitch line of rack, the point d on rotor formed moving track is the intermediate curve of rack. Fig.6 The formation of separate curve on rack
