As we all know, bulldozers are a major type of earthmoving machinery. Due to the small number of tire bulldozers, the commonly used bulldozers are crawler and tire. The following article mainly describes the structure and working principle of the crawler bulldozer.
Most of the crawler bulldozers with a power greater than 120KW use hydraulic-mechanical transmission. This type of bulldozer comes from the introduction of three basic types of bulldozer manufacturing technology, D155, D85 and D65, introduced by Komatsu Japan. After localization, the basic model is TY320, TY220 and TY160. In order to meet the needs of users in various working conditions, the bulldozer manufacturers in China have expanded the product variety on the basis of the above three basic bulldozers and formed three series of bulldozers. TY220 bulldozer series 名媛直播 include TSY220 wetland bulldozer, TMY220 desert bulldozer, TYG220 plateau bulldozer, TY220F forest logging bulldozer, TSY220H sanitation bulldozer and DG45 pipe hoist, etc. TY320 and TY160 series bulldozers are also expanding similar series of 名媛直播. In the TY160 series, there are TSY160L type ultra-wet bulldozer and TBY160 type bulldozer.
The development and expansion of bulldozer product types must not only meet the work adaptability of different working conditions, but also maintain the maximum component versatility (or interchangeability) with the basic model, which brings great convenience to the majority of users. Great convenience. In order to facilitate users to purchase parts, the production plants have kept the part numbers of Komatsu Corporation of Japan. Only the parts designed by themselves during the modification are labeled with their own manufacturer's number.
Crawler bulldozer is mainly composed of engine, transmission system, working device, electrical part, cab and hood, etc. Among them, the mechanical and hydraulic transmission systems include hydraulic torque converter, coupling assembly, planetary gear type power shift transmission, center transmission, steering clutch and steering brake, final drive and walking system.
The power take-off mechanism (PTO) 10 drives the working pump P1 in the hydraulic system of the working device by means of gear transmission and spline connection, variable speed torque converter hydraulic system variable speed pump P2, steering brake hydraulic system steering pump P3; sprocket 8 represents the second stage Straight gear drive final drive mechanism (including left and right final drive assembly); track shoe 9 includes track system, track frame and suspension device assembly, including the walking system. This article will focus on the structure, working principle of hydraulic torque converter, planetary gear type power shift transmission, steering clutch and steering brake in the above transmission system, as well as the failure and elimination of the hydraulic system.
Domestic bulldozers under 102KW, such as T140, T120, T70 and other low-power bulldozers, are all mechanically driven transmission systems, including clutches and mechanical transmissions. This type of bulldozer is also sold in China; its structure is relatively simple, the production time is early, the user is familiar with it, and it is relatively easy to use and maintain.
1. Hydraulic torque converter
The torque converter is a three-element centripetal turbine type with simple structure and high transmission efficiency. The torque converter is composed of three parts: pump wheel assembly, turbine assembly and guide wheel assembly.
The pump wheel in the pump wheel assembly is connected by the bolt and the drive shell, and the drive gear is connected by the bolt and the drive shell. The driving gear is inserted directly into the flywheel ring gear of the engine, so the pump wheel rotates with the engine. The guide wheel is connected to the guide wheel hub by a bolt, and the guide wheel hub is connected to the guide wheel seat by a spline, and the guide wheel seat is connected to the torque converter shell by a bolt, so the guide wheel and the torque converter shell together do not rotate. The turbine and the turbine hub are riveted together by rivets, and then connected to the turbine output shaft by splines. The turbine output shaft is connected by splines and couplings to transmit power to the subsequent transmission system. The pump wheel rotates with the engine to input power, the guide wheel does not rotate, and the turbine rotates to output power. The three are independent of each other, and the gap between the wheels is about 2mm.
The pump wheel, turbine, and guide wheel themselves are composed of many blades, called cascades, and the blades are composed of curves and have a complicated shape. When the torque converter is working, the cascade needs to be filled with oil. When the pump wheel rotates at high speed, the oil in the cascade of the pump wheel moves outward along the curved surface under the action of centrifugal force and shoots at the outlet of the cascade To the outlet of the turbine cascade, and then to perform centripetal movement along the curved surface of the turbine cascade, then from the outlet of the turbine cascade to the inlet of the guide cascade, through the guide cascade and back to the pump wheel. The circular space composed of the pump wheel, turbine and guide wheel cascade is called the circulation circle. The design of the curved surface of the turbine cascade determines that the turbine and pump wheel rotate in the same direction. In this way, the oil in the circulation circle of the torque converter cascade, on the one hand, rotates in the circulation circle, and on the other hand, rotates with the pump wheel and turbine, thus forming a complex spiral motion. In this motion, the energy is pumped from the pump The wheel passes to the turbine.
The turbine load is determined by the bulldozer load. The load of the bulldozer is transferred to the crawler walking system by the blade, then to the final drive, steering clutch, center drive, transmission and coupling assembly, and finally to the torque converter turbine. When the turbine load is small, the rotation speed is fast; when the load is large, the rotation speed is slow. When the bulldozer is unable to move due to overload, the rotation speed of the turbine also drops to 0 and becomes the braking state of the turbine. At this time, because the turbine stops rotating, the oil jetted from the pump cascade passes through the turbine cascade with the greatest impact to the guide wheel, and is converted into pressure in the non-rotating guide cascade. The turbine increases the torque of the turbine. The increased torque is consistent with the direction of rotation of the turbine. At this time, the turbine output torque is the largest, which is 2.54 times the pump wheel torque. With the increase of the load, the speed of the turbine gradually decreases, and the torque gradually increases. This is equivalent to a continuously variable transmission gradually reducing the speed and increasing the torque. This stepless torque-changing performance is matched with the planetary gear type power shift transmission which is easy to operate and has fewer gears, so that the bulldozer obtains excellent traction performance.
The torque converter is hydraulically operated. When the oil is moving in the cascade, due to impact and friction, it consumes energy and heats up the oil, so the transmission efficiency of the torque converter is low. At present, the highest efficiency of the best torque converter at home and abroad is 88%. When the turbine of the torque converter stops rotating due to the overload of the bulldozer, all the energy transmitted by the pump wheel is converted into heat and consumed, and the efficiency of the torque converter is 0 at this time. To improve the transmission efficiency of the torque converter, it is necessary to grasp the load of the bulldozer, so that the turbine has the appropriate speed and the bulldozer has the appropriate speed; that is, when the bulldozer cannot move due to excessive load, the load must be reduced in The blade may be changed from II gear to I gear.
Knowing from the structure and working principle of the torque converter, the oil will leak internally and heat when the torque converter is working. This requires that the oil inside the torque converter be replenished in time, and the heated oil is replaced and cooled to form a cycle.
Models TY320 and TY220 have completely similar torque converters, only with geometric enlargement. Type TY160 and TY220 have basically similar torque converters, and the structure is somewhat changed. Their failure and maintenance are basically the same.
2. Planetary gear type power shift transmission
The transmission is mainly composed of four planetary rows and a rotary lockup clutch. "I", "II", "III", and "IV" are the four planetary rows, and "V" is the rotation lock-up clutch. The "I", "II" and "IV" planetary rows are fixed ring gears, which are output by the planetary carrier rotating in the same direction.
An additional planetary gear is installed on the planet carrier of the "II" planet row. If the ring gear C is fixed by a clutch, when the sun gear A turns right, the planet gear B turns left, the planet gear E turns right, and the planet carrier D turns left. Then, a planetary gear reduction mechanism with sun gear input and planetary carrier reverse rotation output is formed. The TY220 bulldozer transmission uses the second planetary row as the reverse gear.
There are 5 clutches. The cylinder bodies of the first to fourth clutches are all connected to the end cover by bolts, they are not moving. When the pressure oil is filled between the cylinder block and the piston, the pressure oil will build up the oil pressure under the seal that the oil exceeds the plan, and push the piston to press the friction plate, then the ring gear can be fixed.
The structure of No. 5 rotation lockup clutch is special. It has no planetary mechanism and rotates as a whole during operation. When supplying oil to the rotating cylinder, it is necessary to supply oil to the central shaft first. During operation, the pressure oil passes through the oil passage in the fixed casing 19 of the fifth clutch, enters into the rotating oil cylinder, and pushes the piston to work. To prevent leakage, use a rotating seal ring to seal. After the working oil is rotated, the rotating cylinder keeps rotating, and the centrifugal force is thrown outward, and cannot be discharged through the oil supply channel, which will increase the wear of the friction plate. To solve this problem, the discharge in the rotating oil passage will increase the friction plate wear. To solve this problem, a steel ball check valve is added to the rotating cylinder block. Under the action of pressure oil, it seals the oil hole to establish the oil pressure. When the oil supply is stopped, it will be thrown away and the oil return hole is opened to return oil.
The TY220 bulldozer transmission has many structural features. Using these features, maintenance can be performed more easily. For example, the friction plates and discs of the first to fourth clutches are common; the pistons and sealing rings of the second to fourth planetary rows are the same, the guide pins of the planetary clutches are the same, the disc separation springs are the same, and the clutch piston separation springs are the same; The same planetary carrier is used for the first to third planetary rows; the planetary carrier for the fourth planetary row is inserted into the third planetary row ring gear with an external ring gear, and the spring ring is used to prevent axial movement and so on.
The TY320 and TY220 bulldozer series 名媛直播 have completely similar transmissions, only the geometric size is enlarged. In the TY160 bulldozer transmission, the clutch arrangement is different. The first clutch is forward gear, the second clutch is reverse gear, the third rotation lock-up clutch is I gear, the fourth clutch is III gear, and the fifth clutch is II gear. Anmen has the same use and maintenance features.
3. Steering clutch and steering brake
After the power of the transmission is transmitted into the center transmission, it changes from longitudinal transmission to lateral transmission, and is transmitted to the left and right steering clutches separately from the horizontal shaft.
The steering clutch of this machine is of spring compression, hydraulic separation, constant meshing, and temperature-type friction plate structure. It includes outer drum 1, inner drum 5, pressure plate 2, outer friction plate 3, inner teeth 4, piston 15, bolt 13, sleeve 14 and piston 15 are connected as a whole, large and small springs support inner drum 5 On the upper side, the installation load of the spring pushes the piston 15 to move to the right, driving the pressure plate 2 to press the friction plate 3 and the tooth plate 4 together to realize the joint force transmission. There are 8 sets of springs with a total installed load of 3.2T. There is enough pressure to press the friction plates to transmit torque.
When the bulldozer needs to turn (such as pulling the left steering rod), Huai pressure oil is filled into the oil chamber between the steering clutch piston 15 and the hub 6, the oil pressure pushes the piston, and the pressure plate moves to the left, and the friction plate and the tooth plate are released , No longer transmitting torque, the left side of the bulldozer loses power, and turns to the left under the push of the right track. At the end of the steering, the lever is released, the hydraulic oil flows back under the push of the piston, the steering clutch re-engages the force transmission, and the bulldozer resumes straight travel.
The TY220 bulldozer steering brake is a hydraulically assisted, floating wet brake band type. It includes the brake band 15, the booster piston 8, the connecting rod 10, the floating rod 11, the connecting rod 14 and other parts installed on the outer drum of the steering clutch. Due to the superior performance of the floating mechanism, regardless of whether the outer drum of the clutch rotates forward or reverse, the braking is smooth and there will be no braking shock.
When the brake band lining 16 on the brake band 1.5 wears out, the gap between the brake band and the outer drum becomes larger, the brake springboard stroke increases, and when the stroke increases to a certain limit, braking becomes unreliable. Therefore, it is necessary to constantly adjust the brake band clearance.
Method for adjusting the gap of the brake band: After removing the cover of the adjustment bolt, turn the adjustment bolt to the right, tighten the brake band to hug the outer drum (tightening torque about 90N · m), and then loosen the bolt (TY160 type Loosen 15/6 turns, TY320 loosens 11/6 turns), so that a standard gap of 0.3mm appears between the brake band and the outer drum, and the adjustment is completed.
The TY320, TY160 and TY220 bulldozer series 名媛直播 have similar steering clutches and brakes, and they have the same use and maintenance characteristics.
