Structure Design The newly developed clutch structure adopts the same design as the original design and the imported sample. Under the premise of ensuring the performance of the assembly meets the requirements, the design of the parts is self-designed. In this design, the friction plate material of imported parts cannot be obtained at home and the import cost is high. The friction plates need to be reselected. At the same time taking into account that some parts and components have similar parts in China, in order to expand the scale of production and reduce costs, some of the parts using the company's standard parts (such as platen rivets, transmission film) or other product borrowed parts (such as cover). Determination of basic structural parameters The calculation of the sliding work is due to the frequent engagement and slip grinding of the clutch, which will accelerate the friction plate wear and reduce the service life of the clutch. In particular, the skidding during start-up is much more serious than when shifting gears. The severity of clutch slip grinding is often measured by the sliding work. Therefore, the slipping work of the clutch in this design is first checked. Calculated according to empirical formula (1), the slipping work per unit area is shown in Table 2. A = M × m × n 2 × 0.0548 / U / [0.95 × M × U-G × (tan α + f)] (1) where, M: engine maximum torque; m: quality; n: starting speed (take 1000); G: gravity; α: slope (take 0.15); f: road frictional resistance coefficient (take 0.02); U = i/r = (i G × i H)/r (i G: 1st gear or 2nd gear ratio; i H: main reduction ratio; r: wheel dynamic radius). According to experience, the sliding work per unit area is not more than 50. It can be seen that the domestically designed clutch slip grinding work satisfies the actual vehicle demand. Backup factor estimation The backup factor β is an important parameter of the clutch. It can reflect the reliability of the maximum torque transmitted by the clutch. When selecting β, the following considerations should be taken into account: After the friction plate wears during use, the clutch can also ensure the maximum torque transmitted by the engine, and it must be possible to prevent the clutch itself from slipping excessively large; Design sample 1 Actual measurement sample 2 Measure localization design F m2 3236 3510 3309 3400μ=0.27 Transfer capacity 142.19 154.230 145.398 150.197 Backup factor 1.42 1.54 1.45 1.50μ=0.25 Transfer capacity 131.66 142.806 134.628 139.071 Backup rate 1.31 1.42 1.35 1.39 Prevention Driveline overload. In order to reliably transmit the maximum torque of the engine and prevent the clutch from slipping too much, β must not be too small; in order to prevent the clutch size from becoming too large, preventing serious overloading, and ensuring that the operation is light, β cannot be too large. According to the formula (2), the torque M c can be calculated and divided by the maximum engine torque to obtain the reserve factor. Table 3 shows the calculated reserve factor. M c = 2 × F m2 × μ × rm (2) where: rm: the average friction radius of the friction plate; μ: friction coefficient, usually taken 0.25 (or 0.27); M c: torque value; F m2: initial compression force. According to the empirical value, the reserve factor generally takes 1.3 ~ 1.7. From Table 3, it can be seen that the selection of reserve factor can meet the basic requirements of clutch design. 3 Selection of friction plate materials and selection of friction plate materials Due to the fact that the friction plate materials of the imported parts cannot be obtained at home, the import cost is high and the friction plates need to be reselected. According to the requirements of the maximum torque of the engine and the inner and outer diameter of the friction plate, Rebestow's friction material B8805 with properties similar to those of imported materials was selected. B-8805 features: It does not contain toxic heavy metals and heavy metal compounds, stable friction coefficient, excellent attenuation, minimal wear, good start comfort, high burst strength. This friction coefficient is smaller than that of imported materials. Therefore, with the same friction area and the pressure of the pressure plate, the torque transmission capacity and the backup coefficient of the localized clutch are smaller than those of the imported parts. The torque reserve coefficient is higher than the specific power of the entire vehicle compared with the import. Small pieces. The load characteristics are determined because the conventional friction coefficient of B8805 is smaller than that of imported materials in order to improve the transfer ability and reserve factor. The localization design adopts a program to increase the pressing force of the pressure plate. The imported parts are designed for 2981-3236N; the domestic design is 3500-4000N. The clutch pedal force is installed in the vehicle according to the prototype submitted by the first design and the pedal force test is performed. The test results are shown in Table 4. From the test results, it can be seen that the force of the clutch pedal for installing domestically produced parts is on average 1 kg larger than the pedal force for installing the imported parts, and there are two test values ​​that exceed the specification values ​​set by the manufacturer. If you enter the market at this level, customers will complain. Since the clutch pedal force depends on the clutch pressure plate separation force, the maximum pedal force is the maximum separation force multiplied by the transmission lever ratio (a pedal lever ratio x a separation lever ratio). The calculated vehicle transmission leverage ratio is 10.2, which corresponds to the depot manufacturer's pedal force specifications. The maximum separation force of the clutch pressure plate should be controlled within the range of 1226 to 1278N. Under the premise of ensuring that the clutch lift does not change and the pressing force does not change (Fm2=3500 ～ 4000N), the maximum separation force is required to be controlled below 1278 N. From the actual situation, it is difficult; through the discussion, due to the clutch The load characteristics and the separation characteristics, the lift of the pressure plate and the stroke of the separation are linear, and there is a certain correspondence between the compression load of the pressure plate and the separation load. By adjusting the pressing force (F m2 = 3400 ~ 3900N), the maximum separation force can be controlled below 1278N. Conclusion After the improved prototypes are assembled by real vehicles, the pedal force test, and the vehicle endurance verification, the localization design development meets the actual application needs and can be transferred to the approval process of production parts. It can be seen from the above localization cases that, after choosing a friction material with lower friction coefficient than the original design, in order to ensure that the backup coefficient and transmission capacity are equivalent to the original design, the localization design adopts a countermeasure to increase the pressure force of the pressure plate. Because there is a certain corresponding relationship between the separation force of the clutch and the pressing force of the pressure plate, the separation force of the clutch is accordingly increased. Because of the linear relationship between the clutch pedal force and the clutch separation force (lever ratio), the operating force of the clutch pedal also increases. The improvement scheme appropriately lowers the platen pressing force to reduce the separation force so that pedal operation comfort is improved.
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