China is a large coal-producing country in the world. In order to meet the rapid increase in coal demand, the installed power of many coal mining machinery has doubled. Therefore, the requirements for the mechanical transmission part are getting higher and higher. New job requirements require the use of planetary gears for coal mining machinery. The planetary gear transmission of the planetary reducer has the characteristics of power splitting, and its center wheels can form a coaxial transmission, and the internal meshing gear pair is reasonably applied, so it can achieve small size, light weight, compact structure and strong load carrying capacity. Features. In addition, the symmetry of the planetary gear transmission structure also balances the reaction forces acting on the center wheel and the boom bearing, which is conducive to improving the transmission efficiency, and the efficiency value can reach 0.97 to 0.99. The planet wheels are evenly distributed around the center wheel, so that the inertial forces of the planet wheels and the swing arms can be balanced with each other, the number of gears participating in the meshing can be increased, the planetary transmission can run smoothly, and the ability to resist shock and vibration is enhanced. Reliability is higher; and as long as the appropriate planetary gear transmission type and gear matching scheme are selected, a small number of gears can be used to obtain a large transmission ratio.
PWZW900 reducer adopts three-stage deceleration (speed ratio can reach 1000: 1), and the deceleration of each stage adopts the method of stepwise increase in shape (the input power is constant, the speed decreases and the torque increases). This can limit the input power and meet the output torque When required, avoid excessive input power and waste. The input planetary mechanism shown in Figure 1 consists of sun gear 1, three planet gears 2, ring gear 3, and planet carrier 4. The planet carrier and sun gear are floating (the speed is high, and the end bearing of the sun gear uses a clearance fit. For axial positioning); intermediate stage planetary mechanism is composed of sun gear 5, 3 planetary gears 6, internal ring gear 7 and planet carrier 8, where the planet carrier and sun gear are floating; output stage planetary mechanism consists of sun gear 9, The four planetary gears 10, the ring gear 11 and the output shaft 12 are composed of which the sun gear is floating. The torque of the power motor is transmitted to the sun gear 1 through the input shaft of the speed reducer. The sun gear 1 and the multiple planet gears 2 generate external meshing (torque shunt). The planet gear 2 meshes with the inner ring gear 3, and the inner ring gear 3 is fixed. The torque Transformed to the planet carrier 4; the planet carrier and the second-stage sun gear 5 are connected by a spline, and are sequentially transmitted to the output shaft 12. The output end cap is positioned by a cylindrical pin and a stop, and is fastened to the machine's casing by screws to withstand torque. The planetary mechanism has a large bearing capacity, a compact structure, and a large transmission ratio, which meets the development needs of excavation machinery. It can also be used in construction machinery such as tunneling machinery and pipe jacking machinery.
The structural performance analysis of PWZW900 planetary reducer for coal mining is as follows:
(1) The output bearings are distributed at both ends of the output shaft to maximize the bearing distance and achieve maximum radial force. The bearing series are spherical roller bearings, which not only meet the bearing capacity, but also realize the compensation of processing and installation errors.
(2) The output method adopts internal spline output (usually the main cutter head of the excavation machinery is transmitted through the transmission shaft transition). This method meets the maximum radial force output by the transmission shaft reducer, and the supporting point is approximately on the output bearing. .
(3) Multi-stage deceleration; In order to improve the efficiency at work, mechanical friction should be avoided as much as possible. This reducer adds a bearing in front of the intermediate sun gear at all levels to prevent mechanical friction between the planet carriers and reduce noise and Temperature rise.
(5) The planetary cage adopts a split cage structure, which effectively avoids uneven force. The connection between the split structure and the sun wheel is made of forged alloy steel, and the non-main force components are made of ordinary cast steel, which can reduce the casting cost. It can also ensure the quality. The joints between the splits use screws and co-existing pins.
(6) The planet carrier and the intermediate sun gear are splined to ensure sufficient torque transmission. The connection with the intermediate sun gear enhances the axial positioning of the pin and prevents the overall axial of the planet carrier caused by uneven centrifugal force during high-speed operation of the reducer. Rigging.
(7) In order to reduce the weight of each flange part, process holes are added without affecting the force, which increases the volume of the inner cavity space, and can more effectively lubricate each part.
(8) The maximum size of the reducer is 900mm, and the maximum torque is 340,000Nm, which effectively saves installation space and reduces the weight of the machine.
(9) Due to the harsh working environment of the excavating machinery, according to the sealing requirements, an “O” -shaped sealing ring is added to the end face of the output / input flange to ensure the seal level inside the reducer after installation. When the working temperature is -35 ～ 200 ℃ and the working medium is water, steam and oil, the shaft can be sealed with a square ring GSI (pressure resistance range 0 ～ 40MPa). When the components are fixedly connected, “O” is added. "-Shaped seal.
In order to make the design of planetary reducer more reasonable and better performance, low-carbon alloy steel is used on the gear material. The external gear has a precision level of 6 and the tooth surface is treated with carburizing to maintain the toughness of the core while increasing the hardness of the tooth surface (surface HRC58-62, core HRC33-42), and the internal gear has also undergone special quenching and tempering treatment. .
In the coal roadheader, planetary transmission is mainly used in the widely used external telescopic cantilever working mechanism. In this mechanism, the reduction gear needs to be installed in the telescopic frame together with the electric device. This requires the transmission device to be small. Compact structure. At the same time, due to the underground operation, the working conditions are relatively harsh, and new challenges have been imposed on the seal, lubrication and cooling of the reducer. The planetary reducer designed uses a combination of grease and thin oil for lubrication. Arbitrary choice (thin oil lubrication is recommended for higher speeds).