[机械模具数控自动化专业毕业设计外文文献及翻译]【期刊】利用差动轮系实现机械压力机混合输入的研究-外文文献

Science in China Series E: Technological Sciences 2007 Science in China Press Springer-Verlag Received November 19, 2004; accepted October 17, 2006 doi: 10.1007/s11431-007-0003-7 Corresponding author (email: H). Current address: Mechanical and Electrical Engineering College, Henan Agriculture University, Zhengzhon 450002, China Supported by the National Natural Science Foundation of China (Grant No. 50575175) Sci China Ser E-Tech Sci | February 2007 | vol. 50 | no. 1 | 69-80 Study of utilizing differential gear train to achieve hybrid mechanism of mechanical press HE YuPeng1, ZHAO ShengDun2, ZOU Jun2& ZHANG ZhiYuan2 1 School of Mechanical Engineering, Nanjing University of Science & Technology, Nanjing 210094, China; 2 School of Mechanical Engineering, Xian Jiaotong University, Xian 710049, China The problems of hybrid input of mechanical press are studied in this paper, with differential gear train as transmission mechanism. It is proposed that “adjust-able-speed amplitude” or “differential-speed ratio” is the important parameters for the hybrid input mechanism. It not only defines the amplitude of the adjustable speed, but also determines the ratio of the power of the servomotor to the power of the conventional motor. The calculating equations of the ratio of transmission in all axes, the power of two motors, and the working load distribution are deduced. The two kinds of driving schemes are put forward that the servomotor and the conven-tional motor simultaneously drive and the servomotor and the conventional motor separately drive. The calculating results demonstrate that the latter scheme can use much lower power of the servomotor, so this scheme makes manufacture and use cost much lower. The latter scheme proposes a feasible way to apply the hybrid mechanism of mechanical press in practice engineering. mechanical press, hybrid mechanism, differential gear train, adjustable-speed 1 Introduction At present there are many research papers about the hybrid mechanism of mechanical press, and it has become a hot research topic. The hybrid mechanism is a mechanism with 2-degree-of freedom (also called differential speed mechanism), and when two independent motions are input at the same time, the output that can satisfy some motion requirements is obtained through the motion composition of the mechanism. The hybrid mechanism is also called controllable mechanism, or hybrid machine. The purpose of research on hybrid mechanism of mechanical press is using con-ventional motor with big power carrying flywheel to finish stamping work pieces; and uses ser- 70 HE YuPeng et al. Sci China Ser E-Tech Sci | February 2007 | vol. 50 | no. 1 | 69-80 vomotor with low power to adjust the slider speed. The advantages of the hybrid mechanism ap-plied in the mechanical press are that it not only can reduce much lower manufacturing cost than servo press, but also has a flexible working velocity of slider1. So the mechanical press of hybrid mechanism arouses many researchers interest in working on it; and these studies are mainly fo-cused on the multi-bar hybrid mechanism. Du and Guo1, 2have comprehensively discussed the seven-bar hybrid mechanism of mechanical press, including the feasible conditions of composition of the linkage mechanism, the slider motion analysis, and the torque and power distribution be-tween the two motors as well as the optimal design. The trajectory planning based on polynomial interpolation is also investigated, and the computer simulation shows that the result is indeed at-tractive. In addition, Meng3 has also investigated the kinematical analysis of the seven-bar mechanism, and the optimal design has been completed based on the minimum power of the ser-vomotor motor, and Meng has proposed that the hybrid mechanism is a research direction of the mechanical press. Tokuz4 first put forward of the hybrid mechanism and analyzed the velocity synthesis by using the differential gear train. His experiment confirmed the feasibility of his con-ception. The concepts of the adjustable-speed amplitude and differential-speed ratio are not mentioned in their works, and the relationship between the velocity variation and the power of the two motors were not clearly given5 8. But these concepts are very important and absolutely necessary for the hybrid mechanism to select the two motors power and determine the working load distribution between conventional motor and the servomotor. In refs. 1 3 they used linkage mechanism to implement the hybrid input of mechanical press. The method is very complex because the change of the length and position of the each bar in linkage mechanism will have an effect on the motion of the slide of the mechanical press. So some principal problems are usually ignored in research hy-brid mechanism course, and the research results don not always coincide with the practice engi-neering conditions9 11. The gear differential train has two freedoms, and the ratios of transmission between arbitrary two axes are a constant. In order to simplify the mechanical model and make the problems much projected, the differential gear train is used as transmission mechanism to study the hybrid problems of the mechanical press in this paper. This paper addresses the relationship be-tween the adjustable-speed amplitude and the power of the two motors, the working load distri-bution between the two motors, and puts forward two drive schemes of the conventional motor and the servomotor simultaneously working, and two motors separately working. With the 200-ton mechanical press as the engineering background, a drive system of the hybrid mechanism of the mechanical press is designed, and the feasibility of the two drive schemes in mechanical press is analyzed. 2 The principle of the hybrid mechanism The working principle of the hybrid mechanism of the mechanical press with differential gear train is illustrated in Figure 1. The system consists of conventional motor (also called AC machine with constant speed), servomotor, reducing unit I, reducing unit II, differential gear train, and crank slide mechanism. The output axis of the differential gear train is connected with the crankshaft of the crank slide mechanism. One of the two input axes links the conventional motor through the re-ducing unit ; the other input axis links the servomotor through the reducing unit II. Therefore the motion of the crankshaft is completely controlled by the motions of the conventional motor and the HE YuPeng et al. Sci China Ser E-Tech Sci | February 2007 | vol. 50 | no. 1 | 69-80 71 servomotor. The reducing unit and the reducing unit II are respectively installed between the two motors and the differential gear unit in the way of serial in order to bear a part of reducing velocity task of the all transmission system, because too big drive ratio of the differential gear train will make its driving efficiency decreased. The angular velocity of the conventional motor is constant, so its price is cheaper. The angular velocity of the servomotor is adjustable, so its price is expensive. In the system of the hybrid mechanism the constant speed of the output axis is provided by high power conventional motor; and the servomotor provides its adjustable speed. Therefore, in this way, it not only makes the output motion of the crankshaft of the mechanical press flexible, but also avoids using high power servomotor. Hence it could save 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 change12. The dis-placement 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 comes 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 1V , slow working velocity 2V , and high back velocity 3V . The velocity 1V and velocity 3V should be as possible as high and the velocity 2V 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. 72 HE YuPeng et al. Sci China Ser E-Tech Sci | February 2007 | vol. 50 | no. 1 | 69-80 4 The nomenclatures and equations of the hybrid mechanism 4.1 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 1n , 2n and 0n . The torques of the three axes are respectively expressed as 1M , 2M and 0M . 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 sub-script. 4.1.1 The conventional motors influence on the output motion. When the servomotor stops, 20n = , only the angular velocity of the conventional motor affects the output angular velocity 0n , 2 10210nni= , (1) where 20n represents axis 0 angular velocity, and 210i represents total drive ratio from axis 1 to axis 0 including differential gear train and re-ducing unit I when axis 2 (servomotor axis) is fixed. 4.1.2 The servomotors influence on the output motion. When the conventional motor stops, 10n = , only the angular velocity of the servo-motor affects the output angular velocity 0n , 1 20120nni= , (2) where 10n represents axis 0 angular velocity, and 120i 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. 4.1.3 The conventional motors and servomotors influence on the output motion. When the conventional motor and the servomotor run at the same time through the composition of the dif-ferential gear train, the output velocity can be expressed as 12 210001220 10nnnnnii=+=+. (3) Because the servomotor can run at arbitrary angular velocity between the zero and specific ve-locity in both positive and negative directions, 2n can be expressed as 22enKn= , (4) Figure 2 Ideal displacement cure of the slide. HE YuPeng et al. Sci China Ser E-Tech Sci | February 2007 | vol. 50 | no. 1 | 69-80 73 where K is the ratio of the actual angular velocity to the specific angular velocity of the servomotor; the value is arbitrary between 1 and +1, including zero. 2en is the specific angular velocity of the servomotor. So eq. (3) can be rewritten as 2102110 20eKnnnii=+ . (5) 4.2 Adjustable-speed amplitude and differential-speed ratio 4.2.1 Adjustable-speed amplitude. In order to correctly denote the variable velocity of the differential gear train of the hybrid mechanism, the concept of adjustable-speed amplitude is in-troduced. As shown in Figure 1, adjustable-speed 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 adjustable-speed 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 motor13. 211 220 20 2 10211110 20210eenninimnni=. (6) In the differential gear train of the hybrid mechanism, the adjustable-speed amplitude is the most basic and the most important technology parameter. It not only determines the matching relation-ship of the speed of the two input axes, but also decides the matching relationship of the installed capacity of the servomotor and the conventional motor. 4.2.2 Differential-speed ratio. The differential-speed ratio is usually used to express adjustable speed technology performance in the differential gear train. It is an important technology parameter of the differential effect in the differential system. The differential-speed ratio equals the reciprocal value of the adjustable-speed amplitude. It can be expressed as 120122 101einRmn i= =. (7) According to the fact that the angular velocity is in inverse proportion to its torque and that the same load is driven by conventional motor and servomotor, an equation expressed with the powers of the two motors can be deduced, 11 122 2eM nPRM nP=, (8) where 1P is the power of the conventional motor,111P Mn= . 2P is the power of the servomotor, 222eP Mn= . 4.3 The working load power distribution Supposing that the working load power of the mechanical press is 0P , the power relationship between the conventional motor, the servomotor and working load can be expressed as below: 10RPPRK=+, (9) 74 HE YuPeng et al. Sci China Ser E-Tech Sci | February 2007 | vol. 50 | no. 1 | 69-80 20KPPRK=+, (10) 012P PP= + . (11) From eqs. (9) (11), the output powers of the conventional motor and the servomotor are de-termined by the value of factor K, which is ac-tually equal to the change ratio of angular ve-locity 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. 4.3.1 The output axis running at the basic speed. When the output angular velocity of the servo-motor equals zero, that is, 0K = ,20P = , from eq. (9), we have 10P P= . (12) Here the conventional motor bears all the loading power. 4.3.2 The output axis running in the increasing speed region. The servomotor runs in the positive direction, 0 1K , and both 1P and 2P are positive values, so both the conventional motor and the servomotor bear a part of the working load. The load borne by conventional motor is 10 01RP PPR=+. (13) The load borne by servomotor is 20101P PR=+. (14) For example, if the adjustable-speed amplitude 0.1m = (10%) , that is 10R = , then 10 00.909P PP= , (15) 2000.091P P= . (16) Thus the conventional motor bears 90.9% 100% working load and the servomotor bears only 0 9.1% working load. The value of the adjustable-speed and the differential-speed ratio deter-mine the load distribution between the two motors. 4.3.3 The output axis running in the decreasing speed region. In the decreasing speed re-gion, the servomotor runs in negative direction, and the range value of K is 1 0K . By eqs. (9) and (10), the 1P is positive, and the 2P 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, 10 2 0P PPP= +. (17) When the angular speed is in the region 0 n2e, the load of the conventional motor is Figure 3 Physical sense of the adjustable-speed amplitude. HE YuPeng et al. Sci China Ser E-Tech Sci | February 2007 | vol. 50 | no. 1 | 69-80 75 10 01RP PPR= . (18) Thus when the output angular speed is in the decreasing region, the conventional motor con-sumes 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. 4.4 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; and (ii) the conventional motor and the servomotor are separately driven. 4.4.1 The conventional motor and the servomotor being simultaneously driven. This scheme shows that the angular velocity of the crankshaft of the mechanical press is composed of the an-gular velocity of the conventional motor as the basic speed and the angular velocity of the ser-vomotor as the adjustable speed (Figure 3). The angular velocity and the powers can be calculated by using eqs. (1) (18). 4.4.2 The conventional motor and the servomotor being separately driven. This scheme shows that only one motor is driven in the hybrid input course and at the same time another motor