The piston ring is one of the most important parts in the internal combustion engine. It plays the role of support, sealing, guiding and heat transfer in the internal combustion engine. Its free-form profile and its machining accuracy directly affect the engine's power, fuel consumption, noise and Service life. For decades, high-efficiency, high-precision piston ring processing equipment has been the goal of people's pursuit, and introduced a variety of machine tools and equipment with different structures and characteristics. This paper will analyze the requirements of the piston ring inner and outer circular cutting machining equipment from the piston ring free state contour line. According to the characteristics and existing deficiencies of the existing piston ring processing equipment, a piston ring numerical control lathe is being developed by the author. Structural plan.
1 Piston ring free profile processing characteristics Analysis of the piston ring free state profile curve determines its performance after loading into the engine cylinder, affecting the circumferential radial pressure distribution, sealing and service life. The free-state profile of the piston ring is closely related to its radial pressure distribution. The design of the piston ring is firstly selected according to its working conditions: the appropriate radial pressure distribution formula, and then the corresponding free state is calculated by mathematical and mechanical methods. The profile line, and then use a variety of special equipment to machine the required inner and outer contour lines.
At present, there are ten formulas for the radial pressure distribution of piston rings commonly used in China: there are many kinds, such as the Genzbull format w, Arnold, long-gang, x-type, constant-pressure and so on. The same type of piston ring is calculated by different pressure distribution formulas, and free-form lines of different shapes can be obtained. Although the difference is not very large, only in the range of lmm, the piston ring free-form line is extremely sensitive to its working pressure distribution. Therefore, in order to obtain the ideal piston ring pressure distribution, it is necessary to machine a precise contour curve of the free state of the piston ring.
Regardless of the pressure distribution formula used, the resulting piston ring is free: division. Research direction: Numerical control technology, mechatronics technology, won the third prize of the provincial scientific and technological progress 2, the city's second prize for scientific and technological progress. E-mai: cimsyzu.edu.cn: The shapes are similar.
It is a typical piston ring medium-diameter free-form curve, which is symmetrically distributed with respect to the opening, and its maximum median diameter is generally at 11 120°, and the opening width is generally performed on the piston ring at a uniform rotational speed n (r/min). For cutting, the radial cutting speed and acceleration of the piston ring can be calculated as follows: the free-form line of a typical piston ring of the double-ring piston ring company and its analyzed velocity curve and acceleration curve.
As can be seen from the figure, when the workpiece rotation speed is n=180r/rain, the maximum acceleration can be calculated from equation (2) to be 14.66m/s2. This requires the piston ring processing equipment to have high feed acceleration and fast system. The frequency response function, which is difficult to satisfy for the usual CNC systems and servo motors.
2 Piston ring inner and outer circular cutting processing equipment At present, the domestic piston ring inner and outer circular free line processing is dominant in the mainstream is the pl which is realized by the mold, which uses the master control tool to make the radial displacement to process the required piston. Ring shape inside and outside the circle, this equipment structure Xiao line motor L! ! J丨1 spindle system? Jf servo motor-*1z axis high efficiency high precision piston ring CNC machining machine structure scheme The encoder is simple, the price is moderate, the work is reliable However, the mold manufacturing cycle li, j processing precision is low. Can not be timely and flexible according to piston ring model and parameter requirements!
It is difficult to meet changing market demands by changing the model.
In the Song Dynasty in the 1990s, the National University of Defense Technology developed a numerically controlled profiled piston ring lathe 1MI using a stepper motor and a sinusoidal feed mechanism. It can process various piston ring pressure distribution curves and improve the piston ring: processing efficiency. The production cycle of the live cold ring is greatly shortened. The machine and milling compound vertical full CNC piston ring machine of a Japanese machine tool has also been applied in a few piston ring production enterprises: but the cutting process of the equipment is still based on imitation. The working principle of the shape requires a sinusoidal cam machine to drive the cutting tool to complete the feed motion, so there is still a problem of wear and replacement of the cam. The stepping motor has a low response frequency and cannot meet the requirements of high-speed machining. In Japan, a machine tool company introduced a vertical and full CNC piston ring machine in the 1990s. The right half is the turning part. The left part is the milling part, the turning part and the milling part each have 4R servo feed motor, and one R automatic detection motor, which consists of 9 servo motors. The whole machine has a complicated structure and is expensive, up to more than 600,000 US dollars. For most of the piston ring manufacturers, its expensive price is unbearable. 3 High-efficiency and high-precision piston ring internal and external machining strategy From the current analysis of the existing equipment in the piston ring internal and external circular machining, the trend of piston ring cutting is CNC machining, relying on the model to obtain the free-curve shape of the piston ring is difficult to adapt to today's ever-changing market requirements. The biggest problem facing the piston ring CNC machining comes from two aspects: ~ is the CNC system that needs high-speed processing function Second, there must be a tool feed drive mechanism that meets the requirements of acceleration characteristics. With the development of microelectronics cooking, in recent years, the numerical control system The calculation speed: the degree is greatly improved. The high-speed CNC system of 32-bit or even 64-bit chips has been widely used in industrial applications. The motion controller based on digital signal processor (DSP) has also gradually matured, thus meeting the requirements of piston ring processing. The high-speed CNC system has a large selection space: for the drive, if it is still through the combination of the traditional i servo motor and a ball screw, it is difficult to meet the high acceleration requirement 'soft master' working principle, the ball screw The acceleration is usually only 0.50.6g, even if the large lead ball screw can only reach about lg. In recent years, linear motors have developed rapidly and are gradually applied in various industrial fields. Linear servo motors can directly provide linear motion without Any mechanical connection, no backlash, fast moving speed (up to 58m/s), high acceleration (510f and fast response capability), ideal for piston ring machining feed drive system: Yangzhou University Electromechanical Research Institute and Yizheng Shuanghuan Piston Ring Co., Ltd. is cooperating to develop a new type of high-efficiency and high-precision piston ring CNC machining machine for this machine The structural scheme adopts an ordinary AC servo motor and a linear servo motor to control the axial feed and the radial feed motion of the piston ring machining, the angle information collected by the spindle rotary encoder and the diameter of the linear motor Coordinating the displacement to the displacement, constructing a "soft master" through the high-performance CNC system, which replaces the normal hard master to complete the machining of the piston ring free profile: for the working principle of this "soft master": The piston ring machining machine solution constructed by linear servo motor and high-performance numerical control can solve the high-speed response and high acceleration characteristics required for free-form line processing of piston rings, and has the characteristics of high response frequency and fast product modification. Is a development direction of today's piston ring machine tools
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