【正文】 both the machine manufacturing costs and the machine operating costs. Figure 1 Working principle of hybrid mechanism of differential gear train. 3 The velocity characteristics of the mechanical press slide The work of the mechanical press presents the regularity of the periodic change[12]. The displacement and velocity changes of the mechanical press slide in an ideal work circulation are illustrated in the Figure 2. The slide starts to move from top dead center to the working start point at high velocity (called quick feeding stage). When the slide of mechanical press approaches the working point, its high velocity is shifted to slow velocity and then it begins to stamp work piece at low velocity (called low working stage). The low velocity of the slide is to avoid great impact on the die, and benefit the plastic shaping of the work piece. After the slide finishes the stamping work and reaches the bottom dead center, the slide es back at high velocity and stops at the top dead center (called quick back stage). Hence, the motion velocity of the mechanical press slide can be divided three kinds: high down velocity V1 , slow working velocity V2 , and high back velocity V3 . The velocity V1 and velocity V3 should be as possible as high and the velocity V2 should be slow and flexible in order to ensure high working times of the mechanical press per minute and satisfy the requirements of different technologies. Actually the mechanical press only works in a very short course before the bottom dead center, and in the other courses it does not do work to the work piece. 4 The nomenclatures and equations of the hybrid mechanism The relationship of the angular velocity in all axes There are three external axes in the differential gear train as illustrated in Figure 1. In order to conveniently express the relationship of the three axes, the axis connected with the conventional motor is called axis 1, the axis connected with servomotor is called axis 2, and the axis connected with crankshaft is called axis 0. The angular velocities of the three axes are respectively expressed as n1 , n2 and n0 . The torques of the three axes are respectively expressed as M1 , M2 and M0 . Because there are two freedoms in the differential gear train, only the third axis is fixed, such that the drive ratio of the other two axes can be determined. So the relationships of drive ratio and angular velocity of the three axes need to be expressed as the character with superscript and subscript. Figure 2 Ideal displacement cure of the slide. The conventional motor’s influence on the output motion. When the servomotor stops, n2 = 0 , only the angular velocity of the conventional motor affects the output angular velocity n0 . The servomotor’s influence on the output motion. When the conventional motor stops, n1 = 0 , only the angular velocity of the servomotor affects the output angular velocity n0 , where 1 n0 represents axis 0 angular velocity, and 1 i20 represents total drive ratio from axis 2 to axis 0 including differential gear train and reducing unit II when axis 1 (servomotor axis) is fixed. The conventional motor’s and servomotor’s influence on the output motion. When the conventional motor and the servomotor run at the same time through the position of the differential gear train, the output velocity can be expressed as . Because the servomotor can run at arbitrary angular velocity between the zero and specific velocity in both positive and negative directions, n2 can be expressed as .where K is the ratio of the actual angular velocity to the specific angular velocity of the servomotor。 中文 4340 字 出處： Science in China Series E: Technological Sciences February 2020, Volume 50, Issue 1, pp 6980 Study of utilizing differential gear train to achieve hybrid mechanism of mechanical press HE YuPeng1?, ZHAO ShengDun2, ZOU Jun2 amp。 the value is arbitrary between ?1 and +1, including zero. n2e is the specific angular velocity of the servomotor. Adjustablespeed amplitude and differentialspeed ratio Adjustablespeed amplitude. In order to correctly denote the variable velocity of the differential gear train of the hybrid mechanism, the concept of adjustablespeed amplitude is introduced. As shown in Figure 1, adjustablespeed amplitude is the ratio (or percentage) of absolute value of up and down adjustable amount to the base speed. In the differential gear train of the hybrid mechanism, the adjustablespeed amplitude equals the ratio value of axis 0 output speed of operating a single servomotor at the specific speed to axis 0 output speed of operating a single conventional motor[13]. In the differential gear train of the hybrid mechanism, the adjustablespeed ampl