機械式前置汽車變速器實驗臺設(shè)計,機械式,前置,汽車,變速器,實驗,試驗,設(shè)計 Introduction to Mechanical Design The Design Process A machine is a combination of mechanism and other components which transforms, transmits ,or utilizes energy, force ,or motion for a useful purpose .Examples are engines ,turbines ,vehicle ,hoists, printing presses, washing machines ,and movie cameras. Many of the principle and methods of design that apply to machines also apply to manufactured articles that are not true machines, from hub caps and filing cabinets to instruments and nuclear pressure vessels. The term “mechanical design” is used in a broader sense than “mechanical design” to include their design. For some apparatus, the thermal and fluid aspects that determine the requirements of heat, flow path, and volume are separately considered. However, the motion and structural aspects and the provisions for retention and enclosure are considerations in mechanical design. Applications occur in the field of mechanical engineering, and in other engineering fields as well, all of which require mechanical devices, such as switches, cams, valves, vessels, and mixers. Designing starts with a need, real or imagined. Existing apparatus may need improvements in durability, efficiency, weight, speed, or cost. New apparatus may be needed to perform a function previously done by men, such as computation, assembly, or servicing. With the objective wholly or partly defined, the next step in design is the conception of mechanisms and their arrangements that will perform the needed functions. For this, freehand sketching is of great valve, not only as record of one’s thoughts and as an aid in discussion with others, but particularly for communication with one’s own mind, as a stimulant for creative ideas. Also, a broad knowledge of components is desirable ,because a new machine usually consists of a new arrangement or substitution of well-known types of components ,perhaps with changes in size and material .Either during or following this conceptual process, one will make quick or rough calculations or analyses to determine general size and feasibility. When some idea as to the amount of space that is needed or available has been obtained, to-scale layout drawing may be started. When the general shape and a few dimensions of the several components become apparent, analysis can begin in earnest. The analysis will have as its objective satisfactory or superior performance, plus safety and durability with minimum weight, and a competitive cost. Optimum proportions and dimensions will be sought for each critically loaded section, together with a balance between the strengths of the several components. Materials and their treatment will be chosen. These important objectives can be attained only by analysis based upon the principles of mechanics, such as those of static’s for reactions forces and for the optimum utilization of friction; of dynamics for inertia, acceleration, and energy; of elasticity and strength of materials for stress and deflection; of physical behavior of materials; and of fluid mechanics for lubrication and hydrodynamic drives. The analyses may be made by the same engineer who conceived the arrangement of mechanisms, or, in a large company, they may be made by a separate analysis division or research group. As a result of the analyses, new arrangements and new dimensions may be required .Design is reiterative and cooperative process, whether done formally or informally, and the analyst can contribute to phases other than his own. Finally, a design based upon function and reliability will be completed, and a prototype may be built. If its tests are satisfactory, and if the device is to be produced in quantity, the initial design will undergo certain modifications that enable it to be manufactured in quantity at a lower cost. During subsequent years of manufacture and service, the design is likely to undergo changes as new ideas are conceived or as further analyses based upon tests and experience indicate alterations . Sales appeal, customer satisfaction, and manufacturing cost are all related to design, and ability in design is intimately involved in the success of an engineering venture. Some rule for design In the section it is suggested that, applied with a creative attitude, analyses can lead to important improvements and to the conception and perfection of alternate, perhaps more functional, economical, and durable products. The creative phase need not be an initial and separate one. Although he may not be responsible for the whole design, an analyst can contribute more than the numerically correct answer to a problem that he is asked to solve- more than the values of stress, dimensions, or limitations of operation. He can take the broader view that the specifications or the arrangements may be improved. Since he will become familiar with device and its conditions of operation before or during hid analysis, he is in a good position to conceive of alternatives. It is better that he suggest a change in shape that will eliminate a moment or a stress concentration than to allow construction of a mechanism with heavy sections and excessive dynamic loads. It is better that he scrap his fine analysis, rather than that he later see the mechanism scrapped. To stimulate creative thought, the following rules are suggested for the designer and analyst. The first six rules are particularly applicable for the analyst, although he may become involved with all ten rules. 1. Apply ingenuity to utilize desired physical properties and to control undesired ones. 2. Recognize functional loads and their significance. 3. Anticipate unintentional loads. 4. Devise more favorable loading conditions. 5. Provide for favorable stress distribution and stiffness with minimum weight. 6. Use basic equations to proportion and optimize dimensions. 7. Choose materials for a combination of properties. 8. Select carefully between stock and integral components. 9. Modify a functional design to fit the manufacturing process and reduce cost. 10. Provide for accurate location and noninterference of parts in assembly. Journal of Beijing Institute of Technology, 1998, Vol.7, No.2 Automatic Control of Automobile Transmission Performance Test Stand Abstract Aim to realize automatic control of automobile transmission performance test stand. Methods The automatic control technique of the lubricant temperature, the program-controlled automatic shifting of the transmission, the continuous adjusting of revolution speed and load, data –acquisition and data real-time processing were adopted. Results The lubricant temperature was controlled at the set temperature .The automatic shifting of the transmission is simple, reliable and accurate. The automatic adjusting of load and rotation speed is rapid and accurate, the torque divergence is, and the rotation speed divergence is. Conclusion The four kinds of techniques are applied into the automobile transmission performance test stand successfully. The profound study of test and theory about every part of automobile for improving the performances of national products is of very important meaning for developing the national automobile industry. Gear box is a key part of automobile transmission systems. Its properties have effects on the performance directly. The main performance parameters are: the transmission efficiency, the lubricant, the noise and so on. So it is necessary to do the performance test rapidly and accurately. In this paper, automatic-control techniques are applied to the multifunction test stand of the automobile transmission performance. Lubricant automatic constant temperature control, program-controlled automatic shifting, infinitely variable adjusting rotation speed and load, automatic acquisition and processing of the test data, and automatic outputting test reports and curves are fulfilled. The test conditions, accuracy and speed are provided strictly. 1 AUTOMATIC CONSTANT TEMPERATURE CONTROL TECHNIQUE The lubricant temperature should be controlled strictly under the performance test. In the whole process of the test, the temperature should be guaranteed at the set temperature. Otherwise, the test of the gear box performance would be affected. In this paper, mixing cool oil and hot oil by PID automatic-control technique is used to realize the lubricant constant temperature. The system consists of the lubricant force-circulating system and the PID electric automatic-control with feedback system. Fig.1 shows the lubricant force-circulating system. Fig.2 illustrates the PID electric automatic-control with feedback system. Fig. 1 lubricant force-circulating system 1-motor 2-oil pump 3-pressure manometer 4-discharge valve 5-slide valve 6-filter 7-auxiliary oil tank 8. Stop-valve 9-cooling apparatus 10-electric heater and hot oil tank 11.three-port electric-drive valve 12-hydraulic tube The PID automatic control with feedback system is used to control the motor of the three-port electric-adjusting valve. If the feedback temperature valve is lower than the set temperature valve, the valve’s motor will rotate clockwise, and then the hot oil flow will rise. Otherwise, the valve’s motor will rotate counter-clockwise, and then the cool oil flow will rise. The cool lubricant comes from the cooling apparatus. The hot lubricant comes from the hot-lubricant tank with electric heaters. The temperature meter monitors the box’s oil temperature, and provides the basic set number for the PID temperature controller. The auxiliary temperature controller keeps the temperature of the oil in the hot lubricant tank in some range of the PID set temperature. Fig.2 PID automatic-control principle diagram 1-PID temperature controller 2- temperature meter 3- Auxiliary temperature controller 4-electric heater 5-hot oil case temperature transducer 6- transmission oil temperature transducer 7-feedback temperature transducer 8- the motor of the three-port electric-adjusting valve 2. COMPUTER-CONTROL SYSTEM Fig.3 illustrates the computer automatic control flow chat. System functions are as follows: 1. Monitoring performance parameters: the input rotation speed and torque, the output rotation speed and torque, the lubricant temperature, the position of shifting. 2. Adjusting main variable frequency motor’s rotation speed and eddy current electro-dynamometer’s load. 3. Automatic selecting shift position. Fig.3 Computer automatic control flow chart 2.1 Shifting Control The cylinder position crank mechanism of shifting and positioning controls the shifter lever’s motion. Piston stroke is controlled by magnetic switches. Shifting steps are completed by 1-oil-water dividing filter 2-gas source 3- gas manometer 4, 5, 10, 11-magnetic slide valve 6-one-way valve 7-shifting cylinder 8- magnetic switch 9- positioning cylinder Fig.4 shifting pneumatics system schematic diagram 1, 2, 3, 4-solid relay 5, 6, 7, 8-slide valve magnet 9- main computer 10-computer on slice 11-position switch Fig.5 Shifting control electric circuit schematic diagram the computer on slice. The shifting pneumatics system is shown as Fig.4 .The shifting control electric circuit demonstrating chart is shown as Fig.5. The computer sends shifting commands to the computer on slide for switching-on corresponding relay to control the magnetic slide valve. The different pneumatics circuits are switched on to realize different shifting and positioning motion. 2.2 Controlling of Rotation Speed and Load The frequency of crystal oscillator is 1.8432MHz. The first grade dividing frequency time constant is 2. Then the frequency divider’s freq2uency is 921.6 kHz. Later, the system control software sets sequential time constant for next frequency divider to get sequential voltage. The relation between time constant and frequency is time constant=921.6frequency. The automatic controllers of rotation speed and load have voltage access ports with computer. By F/V transducer control voltage is obtained. Corresponding relations among the input frequency, the output voltage, the motor rotation speed and the electrodynamometer magnetizing current are as follows: Input frequency/kHz Output voltage/V Motor-rotation speed(r/min) electrodynamometer magnetizing current/A 0 0 0 0 5 5 6000 5 3. COMPUTER DATA REAL-ACQUISITION AND PROCESSING 3.1 Data Real-Acquisition The signals of transducers are changed into the same signal – the linear frequency signal by high precision V/F and I/F transducers before they transmitted to the computer. Then by 8253 time-counter and corresponding calculations, the valve of the tested engineering variable is obtained. Corresponding relation is A=cN, A is the engineering valve, N is the number of pulses of time-counter, and c is the calibrated coefficient of transducer. 3.2 Data Real-Time Processing On the basic of original data acquired from transducers, the input power, the output power, the ratio and the efficiency are calculated immediately. At the same time, the efficiency curves are showed on the computer screen. 4. THE CONSTRUCTION OF THE TEST STAND This performance test stand is a power open-circuit test stand, and consists of the frame, the electric control system, the computer system, the lubricant automatic constant temperature system, and the program-controlled automatic shifting system. Fig.6 shows the frame of the test stand. The power set is a high rotation speed frequency-changing motor of 55KW, and able to realize infinitely variable speed adjusting from 0-6000r/min, thus, the transmission input doesn’t need a speeder, the noise of the test stand itself id lowered on a large scale .The loading set is an eddy current electrodynamometer of 160KW, the power could be input from one side or double sides, so as to meet the requirements of the transmission with a differential gear or without a differential gear. The synchronous belt is adopted at the transmission output side, thus, the construction id very simple and the noise is low. 1-55KW frequency changing motor 2-input torque, rotation speed transducer 3- tested transducer 4-output torque, rotation speed transducer 5- synchronous belt 6-160KW eddy current electrodynamometer 7-lubricant pump station 8-shifting mechanical system Fig.6 The construction of the test stand frame 5. THE EXAMPLE OF THE TEST The performance test of ALTO transmission is done on the test stand. By original data processing, the efficiency curves are shown as Fig.7 During the test process, monitor parameters are controlled in the range of the test stand, the data are as follows: Fig.7 Efficiency curve Input rotation speed :(( 1000, 2000, 3000)) r/min Input torque ((28, 56)) Nm Lubricant temperature (80) 6. CONCLUSIONS (1) By the technique of mixing the cool and the hot oil, the transmission lubricant constant temperature control could be realized. (2) By the technique of program-control automatic shifting, adjusting rotation speed and load, and data real-time acquisition and processing, the automobile transmission property test could be completed automatically. (3) Computer gives test report and curves. REFERENCE 1. Lu J F Transducer port and test apparatus circuit (in China). Beijing: Beijing institute of Aero-technics Publishing House, 1994 12