Current situation and research and development pre

2022-08-09
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Current situation and research and development prediction of domestic loader transmissions

1 current situation of domestic loader transmissions

domestic loaders mainly use the following three transmissions. The dominant transmission can also replace manual mixing with mechanical mixing in the foaming process: dual turbine 4-element torque converter + 2 in 1 out Star transmission (for convenience of explanation, it is called transmission a). The transmission of ZF company (imported or jointly produced by Liuzhou) in Germany is mainly used in high-end loaders: single turbine 3-element torque converter + 4-in-3-out fixed axle transmission (for convenience of explanation, it is called transmission b). Domestic transmission adopted by some loader manufacturers or some products: single turbine 3-element torque converter + 4-in-4-back, 4-in-2-back or 3-in-3-back fixed axle transmission (for convenience of explanation, it is called transmission C)

transmission a has an overrunning clutch to automatically integrate the power output of the I turbine and II turbine of the torque converter, so that the torque converter can realize the automatic conversion of heavy load and light load. In fact, this kind of transmission has 4 forward and 2 backward gears. Therefore, the use of dual turbine 4-element torque converter can reduce the gears of the transmission, simplify the structure of the transmission, especially the speed change control mechanism, All shifting and reversing operations can be realized with only one speed change handle. Figure 1 shows the transmission diagram of this transmission. The torque ratio of the dual turbine 4-element torque converter is large (the stall torque ratio K0 can reach more than 4), and the high efficiency zone is wide (with dual high efficiency zone)

Figure 2 shows the torque ratio K and efficiency of dual turbine 4-element torque converter η Curve. After years of development, the design and process of dual turbine 4-element torque converter have been mastered by manufacturers. Basically, there are no major fault points? But there are many small faults. The 2-in-1-out star transmission is simple in structure and easy to learn in maintenance. The maintenance personnel of the loader can work after short-term training. They can repair the machine on site without special tooling, and the accessories are sufficient, which can repair the machine as soon as possible without delaying the project progress. This transmission adopts the mechanical hydraulic transmission mode, and directly operates the variable speed control valve through mechanical mode for variable speed operation. Due to the function of the overrunning clutch, the heavy load and light load working conditions are automatically converted, so that the speed change operation of this transmission only needs four positions: second gear, first gear, neutral gear and reverse gear. Therefore, only one speed change lever can realize the shift and reverse operation of the transmission. However, the 2-in-1 retrograde star transmission produced in China is a little rough. Some gears are no longer subject to tooth surface strengthening and gear grinding after heat treatment. The processing equipment is relatively backward and obsolete, the material is relatively poor, and the level of tooling and cutting tools is not high. Have the heat treatment workers and partners understood it? If you have any questions, please contact the staff of our company. The backward technology and poor logistics process control have caused parts collision, dirt, rough assembly, etc. the width, thickness, diameter, area, gauge distance, etc. of these phenomena have caused more failure points and higher failure frequency of this transmission, which has seriously damaged the reputation of domestic loaders. The main faults of the 2-in-1 reverse star transmission are: damage to the overrunning clutch (causing the torque converter to not output heavy load working conditions), gear collapse of the sun gear or planetary gear, shifting stop washer of the reverse planetary shaft, shifting stop disc or bolt of the first planetary shaft, bearing damage, wear or shaving of the first reverse friction plate, oil leakage or damage of the sealing ring, damage to the variable speed pump, stuck valve or damage of the variable speed control valve The oil filter is blocked or damaged, the oil pipe is damaged, the spring is invalid or broken, etc

transmission B is a relatively reliable transmission. Figure 3 shows the transmission diagram of ZF 4wg200 transmission. The characteristic of this torque converter is that it adopts a punching and welding integrated movement, which has a compact structure, but there is no retaining ring on the guide wheel seat to clamp the guide wheel, so it is possible to drop the torque converter movement when turning the transmission over. Compared with the dual turbine torque converter, the torque ratio of the single turbine torque converter is smaller (the stall torque converter ratio K0 is generally less than 4, for example, the K0 value of ZF wg200 is 2.55), and the high efficiency zone is narrower (only the single high efficiency zone)

Figure 4 shows the torque ratio K and efficiency of ZF 4wg200 transmission η Curve. The characteristic of this transmission is that except for the input and output shafts, other intermediate shafts are fixed; The variable speed pump adopts the internal gear pump with high efficiency and is installed in the housing; The material is specially customized, new heat treatment processes such as pressure quenching are adopted, gear grinding and tooth surface strengthening treatment are adopted, key parts are imported, processing equipment, tooling, cutting tools, etc. are relatively advanced (for example, the shell is processed by imported processing center), the production environment is clean, and the assembly adopts advanced technology and tooling. The shift control adopts electronic hydraulic power shift. Only one electronic shift handle is needed to realize the commutation and shift operation, and the end of the shift handle is equipped with a forced shift KD key that can realize the shift from gear 2 to gear 1

Figure 5 shows its electronic shift handle, which can be pushed for reversing operation (and can be locked in neutral for safety), and the shift operation can be completed by turning the handle. Due to the wire connection between the variable speed handle and the variable speed control valve, the installation and layout are very convenient, and the adjustable direction machine can be easily used to personalize the driving control. Due to the use of computer-controlled gear shifting device, it is easy to realize 6-in and 3-out in addition to 4-in and 3-out, which expands the application range of the transmission. The variable speed control valve is equipped with a stable combination valve, so that the variable speed process of the transmission is stable and less impact. However, the biggest obstacle affecting the popularization of this transmission is: 1) high price. Due to the structure, the ethylene production unit of Secco Petrochemical Company of China has been shut down for inspection on March 10. It is compact and requires good materials and heat treatment process; Due to high precision requirements, advanced equipment and manufacturing technology are required, which restricts the increase of output. 2) The market volume of accessories is difficult to compare with that of transmission a, and the price is high. A considerable number of accessories need to be imported. 3) Special tools and sites are required for maintenance, which cannot be maintained on site like transmission a, which will increase the maintenance cost and may affect the project progress. 4) Maintenance is much more strict than transmission a

transmission C is a transmission used by a few manufacturers and products. Domestic research, input and output of single turbine 3-element torque converter is much less than that of dual turbine 4-element torque converter. For the single turbine 3-element torque converter, the single turbine 3-element torque converter movement produced by Shaanxi Aerospace Power High Tech Co., Ltd. for zf4wg200 transmission, which is specially equipped for Liuzhou ZF company after being certified by German ZF company. Due to the large gap between China and foreign countries in material, manufacturing equipment and process, heat treatment technology and process, assembly technology and process, logistics management, production environment, personnel quality and other aspects, there is still a large gap compared with transmission B (in terms of technology and quality). It is not as convenient as transmission a in terms of assembly and disassembly, especially the abundance of accessories can not be compared with transmission a. However, compared with transmission a, transmission C has fewer fault points. The most typical fault is that the oil leakage causes the clutch oil pressure to be too low, so that the friction plate is excessively worn, and even the clutch is sintered. If the oil distribution cover is damaged by casting defects such as scar or looseness, or the oil seal ring on the piston is damaged, the clutch oil pressure can be too low. Long term low oil pressure operation will cause great harm to the power shift transmission, which should be avoided as far as possible

Figure 6 shows Shangong 50 transmission, which is composed of a single turbine 3-element torque converter and a 4-in-4-out fixed shaft transmission. The transmission is a 4-DOF transmission, and each gear needs to be combined with 3 clutches. Therefore, 3 shift control levers are required: 1 reverse control lever (for F and R clutches), 1 shift control lever (for F1, 3 and F2, 4 clutches), and 1 high and low gear control lever (for sliding sleeve HL). Therefore, the variable speed control is very troublesome, which is the biggest defect of this transmission

Figure 7 shows the pz133 transmission produced by Zibo Kaite, which is composed of a single turbine 3-element torque converter and a 3-in-3-out fixed shaft transmission. This transmission is a 3-DOF transmission, and each gear needs to be combined with 3 clutches. Therefore, two speed change levers are required: a reversing lever (for F and R clutches), and a shift lever (for L1, L2 and L3 clutches). This transmission can be configured on 15, 18 and 30 loaders. The typical fault is the fracture of the wave spring (if the coil spring is used as the return spring of the piston, this problem can be solved better)

transmission C generally adopts a 3-DOF transmission (rarely more than 3 degrees of freedom), and each gear needs to be combined with two clutches. When mechanical hydraulic power transmission mode is adopted, two speed control levers are required: one for reversing operation and one for shifting operation. In order to simplify the structure, the flexible shaft is generally used for operation, but the idle stroke of the flexible shaft is large, so it is difficult to accurately control the stroke. Therefore, it is difficult to limit the position of the control handle with a slot, so that the shift operation is not as clear and accurate as the spatial articulated transmission mechanism (such as transmission a), and even may cause the wrong gear. Because there are too many shift control levers, it not only increases the difficulty of space layout, but also increases the difficulty of driver operation and increases the driver's labor intensity. Therefore, the electronic hydraulic shift mode is the best choice

2 requirements of domestic loaders for transmissions

2.1 high reliability

due to the high failure rate of domestic transmissions, the market has the greatest opinion on this. Reducing transmission failure points and improving transmission reliability are the most important and urgent tasks

2.2 price should have advantages

for products made in China, price is the magic weapon of competition in both the domestic market and the international market. Moreover, the proportion of private purchase of machines is getting higher and higher, so products without price advantage have no future in today's extremely competitive and low profit loader industry. Therefore, transmission a will continue to play a major role for a long time, but manufacturers need to strive to improve product quality and reduce product failure rate

2.3 the operation should be simple and fast

try to use one speed control lever, no more than two speed control levers at most, so as to facilitate space layout, reduce the labor intensity of the driver and improve labor efficiency

2.4 convenient maintenance and sufficient accessories

maintenance should be convenient. After training, the majority of maintenance personnel should be able to master maintenance technology quickly. It can be repaired locally or at nearby maintenance points, and special maintenance tools are not required or minimized, and accessories should be sufficient. In short, the failure of the transmission should be repaired as soon as possible to avoid affecting the progress of the project

3 prediction of the development of domestic loader transmission

transmission a has been used for so many years, reliability has always been a big problem that is difficult to solve. Solving the reliability of transmission is the primary goal of transmission research and development. Electronic variable speed control (electronic hydraulic power shift and automatic shift) has also been the development direction of international transmission. Therefore, we should give priority to developing transmissions that meet China's national conditions

3.1 adopt a structure similar to transmission C

the planetary transmission of transmission a has a cantilever support of the planetary gear carrier, the internal gear is radial floating (without bearing positioning), the gear teeth are relatively wide, and the reverse gear

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