Why are most power shift transmissions used with hydraulic torque converters in construction machinery?
A non-rigid Torque Converter using liquid as the working medium is one of the types of hydraulic transmission. The hydraulic torque converter has a closed working chamber in which the liquid circulates. The pump wheel, turbine wheel and guide wheel are respectively connected with the input shaft, output shaft and housing. When the power machine (internal combustion engine, electric motor, etc.) drives the input shaft to rotate, the liquid flows out of the centrifugal pump wheel, passes through the turbine, the guide wheel and then returns to the pump wheel in sequence, and circulates again and again. The pump wheel transfers the mechanical energy of the input shaft to the liquid. The high-speed liquid drives the turbine to rotate, transferring energy to the output shaft. The torque converter transmits torque by generating a change in momentum moment by the interaction of liquid and blades. The main feature of the hydraulic torque converter different from the hydraulic coupling is that it has a fixed guide wheel. The guiding effect of the guide wheel on the liquid makes the output torque of the torque converter higher or lower than the input torque, so it is called a torque converter. The ratio of the output torque to the input torque is called the torque conversion coefficient. The zero-speed torque conversion coefficient when the output speed is zero is usually about 2-6. The torque conversion coefficient decreases with the increase of output speed. The input shaft and output shaft of the hydraulic torque converter rely on liquid connection, and there is no rigid connection between the working components. The characteristics of the hydraulic torque converter are: it can eliminate shock and vibration, overload protection performance and start performance; the speed of the output shaft can be greater or less than the speed of the input shaft, and the speed difference between the two shafts varies with the size of the transmitted torque; Good automatic transmission performance, the output speed will automatically decrease when the load increases, and vice versa; the power machine has a stable working area, and the transient changes of the load will not be reflected on the power machine. The hydraulic torque converter has higher efficiency near rated working conditions, with the highest efficiency being 85%~92%
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China is the world's largest excavator sales market. Due to its harsh working environment, there are many new performance requirements for variable frequency motors. The core technology has been monopolized by foreign companies, making China's AC drive excavators always rely on import and joint venture production. . Until August 2005, this situation was broken with the completion of the trial production of the first 10 cubic meters AC drive excavator in China to support the variable frequency speed control asynchronous motor of Yongji Factory.
At present, Yongji Motor has been equipped with a series of large-scale AC drive excavators of 10 cubic meters, 20 cubic meters, 27 cubic meters, 35 cubic meters and 55 cubic meters. The core technology has reached the advanced level of international similar products and successfully operated on China's large-scale coal mines such as Huaneng Yimin, China Power Investment Huolinhe, Shenhua Zhugeer, and China Coal Pingyi have gradually made China's AC drive excavators rank among the world's leading AC excavator manufacturers.
In October 2004, as a major manufacturing enterprise of China's large excavator, Taizhong Group started a strong cooperation with China's locomotive electric drive development leading company, North Vehicle Group Yongji Motor Factory, and determined to independently develop and develop China's AC drive excavator, breaking Foreign technical barriers to achieve localization of key technologies. In just over 4 months, Yongji Plant has developed four kinds of variable frequency drive motors for lifting, turning, pushing and running the first 10 cubic meters excavator in China, replacing the traditional DC motor system.
Subsequently, in the development of 20 cubic meters AC drive excavator motor, Yongji Motor is aiming at the international advanced level according to the needs of the national excavator market, continuously optimizing the design, successfully solving the matching of working conditions, frequent overload multiples and large vibration in the use environment. Technical problems such as dust and dust have made the core technology of 20 cubic meters of excavators reach the advanced level of international similar products. In April last year, the 20-cubic-meter excavator was at the acceptance ceremony of Shenhua Bieneng Company's Heiqigou open-pit mine. Yongji Motor can compete with foreign products for superior performance, so that Shenhua Group's Zhuneng Company immediately said that if Yongji Motor is in There will be no quality problems during the 12-month warranty period. In the future, the excavators we purchase will all be equipped with the company's motors instead of purchasing foreign products.
It is reported that in June this year, Yongji Electric will also supply three sets of 12 cubic meters AC drive excavators to Peru for the first time, thus creating a precedent for China's exchange excavators to go abroad.
North Car Yongji boosts the development of China's AC drive excavator
Recently, the “Development of Variable Frequency Speed ​​Control Asynchronous Motor Unit for WK-20 Electric Shovel Car†declared by CNIC Yongji Motor Factory was included in the 2007 Shanxi Science and Technology Research Project. This is the first WK-20 (20 m3) large excavator with complete independent intellectual property rights in China, which was equipped with Yongji Electric on June 27 last year. It was first listed in Taiyuan after being successfully evaluated by experts and users. Entering the province's scientific and technological research projects has effectively promoted China's AC drive excavators to enter the "time" of independent research, so that China has truly achieved a leap from a large importing country to an independent research and development power.