【正文】 d is driven by conventional motor and servomotor, an equation expressed with the powers of the two motors can be deduced, where P1 is the power of the conventional motor, P1 = M1n1 . P2 is the power of the servomotor, P2 = M2n2e . The working load power distribution Supposing that the working load power of the mechanical press is P0 , the power relationship between the conventional motor, the servomotor and working load can be expressed as below: Figure 3 Physical sense of the adjustablespeed amplitude. From eqs. (9)― (11), the output powers of the conventional motor and the servomotor are determined by the value of factor K, which is actually equal to the change ratio of angular velocity of the servomotor. Hence when the output angular velocity runs in different working region, the ratio of bearing load of the two motors is different, too. The output axis running at the basic speed. When the output angular velocity of the servomotor equals zero, that is, K = 0 , P2 = 0 , from eq. (9), we have .Here the conventional motor bears all the loading power. The output axis running in the increasing speed region. The servomotor runs in the positive direction, 0≤ K≤ 1 , and both P1 and P2 are positive values, so both the conventional motor and the servomotor bear a part of the working load. Thus the conventional motor bears %― 100% working load and the servomotor bears only 0― % working load. The value of the adjustablespeed and the differentialspeed ratio determine the load distribution between the two motors. The output axis running in the decreasing speed region. In the decreasing speed region, the servomotor runs in negative direction, and the range value of K is ?1≤ K≤ 0 . By eqs. (9) and (10), the P1 is positive, and the P2 is negative. The negative value of the servomotor power shows that the servomotor power is already the working resistance. Hence the conventional motor is not only doing work to the working load, but also doing work to the servomotor power, When the angular speed is in the region 0― n2e, the load of the conventional motor is Thus when the output angular speed is in the decreasing region, the conventional motor consumes more energy than in the other regions. The decrease of the output speed is at the price of consuming the servomotor input power. In order to save energy, the output angular speed should avoid or reduce running in the decreasing region. The two drive schemes of the hybrid mechanism of the mechanical press According to eq. (3), the output angular velocity of the hybrid mechanism is equal to the reduced value of their sum of the angular velocities of both the conventional motor and the servomotor. As shown in Figure 1, the output angular velocity of the differential gear train is connected with the crank axis of the mechanical press, so the two axes have the same angular velocity. When either of the conventional motor or the servomotor is driven, or when both of them are driven, the different angular velocity of the crankshaft of the mechanical press can be obtained. Therefore, two kinds of the schemes of the hybrid mechanism of the mechanical press are proposed: (i) the conventional motor and the servomotor are simultaneously driven。 therefore it is flexible. Figure 4 Physical sense of the parison of the two output angular speed. Because drive ratios 2 i10 and 1 i20 are independent of each other, and the operation and the servomotor operation of the conventional motors are independent of each other too, the values of the two drive ratios can be assigned a very different value (one is very small, and the other is very big), so the two output angular velocities may differ greatly. So doing can satisfy the motion requirements of the mechanical press slide in different stages. The physical sense of parison of the two output angular speed is illustrated as in Figure 4. 5 Conclusion According to the velocity characteristics of the mechanical press, the differential gear train is applied in the hybrid mechanism of the mechanical press. Through the above analysis and calculation, the following conclusions can be reached: (1) The adjustablespeed amplitude and differentialspeed ratio are important parameters of the hybrid mechanism. They are not only the ratio of the adjustable speed to the basic speed, but also the ratio of the power of the servomotor to the power of the conventional motor. (2) With the scheme of the conventional motor and the servomotor being simultaneously driven, the power of the two motors has to be assigned high value in order to satisfy the velocity requirements of the mechanical press. So doing increases the manufacturing cost and the operation cost of the mechanical press, and therefore i