The Calculation Method And Testing Technic Of The Hy-vo Chain Shafting Center Distance

Tooth chain is an important basic mechanical part which is widely used.usually,it can be classified into two categories:tooth chain with round pin and tooth chain with rocker pin.If the tooth profile of wheel is involute, tooth chain with rocker pin can be called Hy-Vo chain,which can drive more smoothly.compared with roller chain,as the changeable pitch reduces the chordal effect remarkably,So the impact and vibration can be reduced.that's why the Hy-Vo chain is used when the speed is very high,the load is very heavy,or the distance between shaft is very long. Hy-Vo chain is usually used as drive device in oil drilling machine,metallurgical machine,chemical engineering machine,generator set and so on.These years the timing chain and drive chain of gearbox used widely in the engine of new sedan.So the Hy-Vo chain have a good prospect of application.The chain length accuracy not only affect the shaft distance,but also the transmission performance and service life,so it's an important index which must be checked while foreign chain company asks us to manufacture.The chain length accuracy is the embodiment of pitch accuracy in nature,and the pitch accuracy is determined by the accessories accuracy of the chain.So,it has practical value to study the internal relation between the chain length accuracy and the parts accuracy.The project is supported by the national science foundation,it studies the calculation and testing method of the shaft center distance of the Hy-Vo chain.In accordance with machine capacity of national chain enterprise,we have manufactured the test model of Hy-Vo chain.studies shows the factors which affect the Hy-Vo chain pitch accuracy include the accuracy of the plates hole pierce,guide plate pierce and the drawing accuracy of the pin. The roller chain has a constant pitch,so the chordal effect is inevitable.when the roller chain service at a high speed,the chordal effect will result in vibration,noise,impact load ,so the chain strength will be lowed.If the changeable pitch chain was adopted,the center line of the chain keeps tangent with the pitch circle,the transversal vibration caused by chordal effect will be weakened obviously.Thus the chain can be used under high speed.The Hy-Vo chain that appeared now is a kind of changeable pitch chain,which can weaken the transversal vibration notablely.The figure 1 shows the basic theory how the changeable pitch decreases the chodal effect.Here,the joint A is meshing,and the joint B has finished meshing.It means the center line of link 2 and link 3 have turned the angle of 2π/z .because special joint mechanism has been designed,as the increase of rotary angle of joint A,the pitch of link 2 elongates correspondingly,which means the joint A can avoid the transverse descend so that the center line of the chain keeps tangent with the pitch circle.Thus,so long as the joint mechanism can make the joint A keep tangent with the pitch circle,it can compensate the chordal effect.With this method,we can abtain the target of non-transverse fluctuation.The biggest factor which affects the shaft center distance is the pitch accuracy.so,in order to lower the fluctuation of shaft center distance,special attention should be paid to improve the accuracy of plate piercing and pin drawing.The following is chain length formula of the assembly of n pieces of plates and m pieces of guiding plates.The accuracy of accessories and chain length can be linked up with the formula above,and it can be connected with the distance between shaft furtherthe caliper diameter reflect the pitch diameter indirectly,and the pitch diameter affect the shaft center distance linearly.The smaller the actual pitch diameter is,the larger the shaft center distance is.the radial fluctuation of the chain wheel will result in the shaft center distance fluctuation.if two chain wheel are manufactured in couple,the speed ratio is one to one,and the chain wheel installed in-phase,the shaft center distance fluctuation will be reduced dramatically.when the machining accuracy reache IT8,the fluctuation can be neglected.Just as follow table:Table 1 the effect of wheel accuracy to the The new type Hy-Vo chain also suffers from chordal effect,but our theoretical model and experimental result show that the fluctuation is so small that it can be neglect during designing progress.There is linear relation between the chain length and the loading force,the analytic function can be found from experiment.Figure 1 is the effect of loading force to the distance between shaft.In the figure,we can consider the AB and CD as straight line respectively.In figure 1,the coordinate of A,B,C are A( 5 0,235.75),B (1 50,235.87),C (4 00,235.99).It's easy to conclude that when the loading force is F( F≤150),the elongation of shaft distance is 0.0012 ? (1 50-F); when the loading force is F( F >150),the elongation of shaft distance is 0.00048 ? ( F-150).we put forward a hypothesis for every factor above,from which the analytic function was deduced.then,two type problem canbe solved.first,given the dimension distribution of all parts,we can get the shaft center distance;second,given the shaft center distance,we can deduce the dimension distribution of all parts.So,our research provide not only the guidance for the standadization of Hy-Vo chain.