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The structural principle of the loader-transmission system
Jul 18 , 2022

The air-conditioning system and anti-rollover and falling object protection devices are not available in the first generation, but are newly added in the second product, mainly to increase safety and comfort. Other components such as steering system, braking system, cab, working device, frame, etc. have also undergone major changes. On the basis of the first generation, more than ten advanced technologies and selected structures have been adopted. Therefore, compared with the first generation, the second generation has a considerable improvement in reliability, safety and comfort, work efficiency, etc., and the appearance is also much more beautiful.
Transmission system
The transmission system of a typical wheel loader in my country currently consists of a transmission (also called a torque converter gearbox assembly), a drive axle, and a drive shaft.
(1) Transmission
The transmission consists of a torque converter and a gearbox. One end of the torque converter is directly connected with the other end of the diesel engine and the gearbox, which is compact in structure and reliable in connection. It is the most widely used and common connection method for wheel loaders at home and abroad. Others include the transmission as a whole and separate from the diesel engine, or the torque converter is directly connected with the diesel engine and separated from the gearbox, and the transmission shaft is used between them. At present, SEM's ZL50D type and Changlin's ZLM50E type are the structural types in which the torque converter, including the transfer case, is directly connected to the diesel engine, separated from the gearbox, and connected to the drive shaft.
Liugong ZL50C transmission is composed of twin-turbo hydraulic torque converter and planetary power shift gearbox. The gearbox has one forward and one backward two planetary rows, plus a direct gear (block), a total of two forward and one backward three gears. The structure is simple, the gears are few, and the single lever operation is completely realized. The torque converter has two turbines, and the second turbine is directly transmitted to the transmission input shaft (gear), which is a light-load speed change state for each gear. One turbine is transmitted to the input shaft of the gearbox through the overrunning clutch. When the torque of each corresponding gear increases and the speed decreases to the point where the overrunning clutch is engaged, the two turbines work at the same time, which is the low-speed and high-torque state of the corresponding gear. It is automatically realized by the overrunning clutch through the speed. In fact, the transmission has 4 forward gears and 2 reverse gears, because each gear has a high and low speed automatic shift. Therefore, the transmission shows its advantages in this aspect, and the handling performance is better than that of the ordinary multi-speed multi-lever control transmission. But it also has a major disadvantage, the twin-turbo torque converter is less efficient and loses more power than a simple three-element torque converter. At present, this fixed-shaft gearbox has not adopted electronic technology, so it is an ordinary multi-lever operation.
CAT950B type and Komatsu's WA380-3 type are all four-in and four-reverse transmissions, single-lever electro-hydraulic shifting or computer integrated control. The torque converters are all three-element simple type, the gearbox CAT is a multi-row planetary type, and the Komatsu is a fixed-shaft type.
At present, the third-generation products, such as Liugong's ZL50G, use a transmission composed of a three-element torque converter and a four-speed forward and three-speed reverse fixed-shaft gearbox produced by "ZF" company. The three-element torque converter has high efficiency, adopts a single-handle electro-hydraulic gear shift controlled by a microcomputer semi-automatic, and adds a second gear quick switch button (KD button) during operation. Each operation cycle only needs to move the handle back and forth once and press the KD button once, which is simple, fast, comfortable and labor-saving to operate, thus greatly improving the work efficiency. The product is selected for its variable speed control system.
(2) Drive axle
The drive axle consists of a front axle and a rear axle. Since the loader requires a large tractive force, the front and rear axles of modern wheel loaders are all drive axles. The front axle is directly fixed on the front frame, and the rear axle is a swing axle, which is connected with the rear frame through the subframe. Modern wheel loaders basically use the connected steering, so the front and rear drive axles are all common except for the rotation direction of the main drive spiral bevel gear. In the third generation, the center swinging type of the rear axle appeared, instead of using the subframe, but connecting the swinging frame to the rear frame. It appeared that the rear axle housing was not common to the main transmission bracket and the front axle, and the rest were still connected to the front axle. The bridge is completely generic.
At present, the drive axles of wheel loaders in my country basically use integral axle housings, fully floating axle shafts, and drive axles with main drive and two-stage deceleration at the wheel side. The main drive generally adopts the first-level spiral bevel gear to reduce the speed, and the wheel edge generally adopts the planetary wheel speed reducer. Figure 4 shows Liugong ZL50C drive axle, its structure is generally representative. The drive axles of the 8 domestic products listed in Table 1 above are all of this type of structure.
At present, the drive axle of the third-generation ZL50 wheel loader has a drive axle with built-in wet multi-disc road control device and anti-skid differential, which improves the braking performance and the passing performance and operation performance under harsh working conditions. The "ZF" AP400 drive axle used by Liugong's third-generation product ZL50G is this drive axle. The "ZF" AP400 drive axle housing is an integral type, with a built-in wet multi-disc brake on the inner side of the wheel reducer inside the axle. There is also a three-section axle housing, the wheel side reducer and the built-in wet multi-disc brake are concentrated in the middle of the axle, close to both sides of the main drive. This kind of structure has good performance, but it is difficult to manufacture. CAT's 950B type and Komatsu's WA380-3 type drive axle are all of this structure. There is another kind of drive axle similar to "ZF" AP400, the only difference is that the built-in wet multi-disc brake is on the outside of the wheel reducer. This kind of structure is not very good and rare.
(3) Transmission shaft
The drive shaft is basically evolved from the car drive shaft. my country's first-generation ZL50 six-carrying machine drive shaft is basically modified from "Jiefang" and "Dongfeng" automobile drive shafts. At present, there are still a large number of ZL50 wheel loaders, including the ZL50C-I of Xiagong and Longgong, which still use the "Dongfeng brand" modified transmission shaft. Take Liugong ZL50C
The second-generation product headed by the company, due to the increase in strength and torque, is not suitable for the reliability of this kind of transmission shaft. The transmission shaft of heavy-duty vehicles is specially designed as a special transmission shaft for wheel loaders, and its bearing capacity is higher than that of "Dongfeng". ", "Jiefang" drive shaft is more than double the height, and the reliability is greatly improved. Except for Liugong ZL50C, it has been widely used in the second and even third generation ZL50 wheel loader products.

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