Bulldozers use mechanical transmission or hydraulic mechanical transmission systems with hydraulic torque converters, and a few use hydraulic transmission systems.
(1) Hydraulic torque converter
The pump wheel in the pump wheel assembly is connected by a bolt and a drive housing, and the drive gear is connected by a bolt and a drive housing. The drive gear is inserted directly into the ring gear of the engine flywheel, so the pump wheel rotates with the engine. The guide wheel is connected by a bolt and a guide hub, and the guide hub is connected by a spline and a guide wheel seat, and the guide wheel seat is connected by a bolt and a torque converter case, so that the guide wheel and the torque converter case are not rotated together. The turbine and turbine hub are riveted together with rivets and connected to the turbine output shaft. The turbine output shaft is connected to the subsequent drive train via splines and couplings. The pump wheel rotates with the engine, the power is input, the guide wheel does not rotate, the turbine rotates, and the power output is independent of each other, and the gap between the wheels is about 2 mm.
The pump wheel, the turbine and the guide wheel are themselves composed of a plurality of blades, which are called cascades, and the blades are composed of curved pieces 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 a high speed, the oil in the pump wheel cascade flows outward along the curved surface under the action of centrifugal force, and is directed at the exit of the cascade. The turbine cascade exits then flows centripetally along the turbine cascade surface and from the turbine cascade exit to the guide vane inlet, through the guide vane cascade and back to the pump impeller. The circular space composed of the pump wheel, the turbine and the guide vane cascade is called a circular circle. Due to the design of the shape of the turbine cascade surface, it is determined that the turbine and the pump wheel rotate in the same direction. In this way, the oil in the circle of the converter cascade is rotated on the one hand in the cycle circle and on the other hand with the pump wheel and the turbine, thus forming a complex spiral motion, in which the energy is pumped from the pump. The wheel is passed to the turbine.
The turbine load is determined by the dozer load. The load of the bulldozer is transferred by the blade to the track travel system and then to the final drive, steering clutch, central drive, transmission and coupling assembly, which is ultimately passed 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 speed of the turbine also drops to zero, which becomes the braking state of the turbine. At this time, because the turbine stops rotating, the oil injected by the pump vane cascade passes through the turbine cascade to drive the guide wheel with the greatest impact, and is converted into pressure in the non-rotating guide vane cascade, and the pressure is reversed. The turbine increases the torque of the turbine. The increased torque is in the same direction as the turbine. At this time, the turbine output torque is the maximum, which is 2.54 times the pump torque. As the load increases, the speed of the turbine gradually decreases and the torque gradually increases. This is equivalent to a stepless speed change in a continuously variable transmission. This stepless torque-changing performance is matched with a planetary gear-type power shift transmission that is easy to handle and has fewer gears, enabling the bulldozer to achieve superior traction performance.
The torque converter works on hydraulic power. When the oil flows in the cascade, energy is consumed due to impact and friction, and the oil is heated, so the transmission efficiency of the torque converter is low. At present, the best torque converter at home and abroad has a maximum efficiency of 88%. When the turbine of the torque converter stops rotating due to the overload of the bulldozer, all the energy transmitted from the pump wheel is converted into heat and consumed, and the torque converter efficiency is zero. In order to improve the transmission efficiency of the torque converter, it is necessary to grasp the load of the bulldozer so that the turbine has an appropriate speed and the bulldozer has an appropriate speed; that is, when the bulldozer is unable to move due to excessive load, it is necessary to reduce the load in time. Cut the blade or change from II to I.
It is known from the structure and working principle of the torque converter that the oil will leak and heat when the torque converter is working. This requires timely replenishment of the oil inside the torque converter, and replace the heated oil to cool down to form a cycle.
The TY320 and TY220 models have completely similar torque converters, but only undergo geometric amplification. The TY160 type and the TY220 type have basically similar torque converters, and the human structure is somewhat changed. Their failures and repairs are basically the same.
(2) Planetary gear type power shift transmission
The transmission consists essentially of four planetary rows and a rotary lock clutch. The "I", "II", "III" and "IV" in Fig. 3 are four planetary rows, and "V" is a rotary locking clutch.
The "I", "II" and "IV" planetary rows are fixed ring gears that are output in the same direction as the planet carrier.
The planet carrier of the "II" planetary platoon is equipped with a planetary gear. If the ring gear C is fixed by the clutch, when the sun gear A turns right, the planetary gear B turns left, the planetary gear E turns right, and the carrier D turns left. Then, a planetary gear reduction mechanism that inputs the sun gear and reversely rotates the carrier is formed. The TY220 bulldozer transmission uses the II planetary row as a reverse gear.
There are 5 clutches. The cylinder bodies of the first to fourth clutches are all bolted to the end caps, and they are not moving. When the pressure oil is filled between the cylinder block and the piston, the pressure oil can be fixed when the oil exceeds the planned seal, the oil pressure is established, and the piston is pressed against the friction plate.
The No. 5 rotary lock clutch has a special structure. It has no planetary mechanism and is rotated as a whole during operation. When supplying oil to the rotary cylinder, first supply oil to the center shaft. During operation, the pressurized oil passes through the oil passage in the stationary casing 19 of the fifth clutch, enters the rotary cylinder, and pushes the piston to work. To prevent leakage, seal with a rotating seal ring. After the working oil is continuously rotated due to the rotating cylinder, the centrifugal force is pulled out and cannot be discharged through the oil supply passage, which increases the wear of the friction plate. In order to solve this problem, the discharge of the rotating oil passage increases the wear of the friction plate. In order to solve this problem, a steel ball check valve is added to the rotary cylinder block. Under the action of the pressure oil, it seals the oil hole to establish the oil pressure. When the oil supply is stopped, it will open and open the oil return hole to return. oil.
The TY220 bulldozer transmission has many features in its structure, and the use of these features makes maintenance easier. For example, the friction plates and the optical discs of the first to fourth clutches are common; the pistons of the second to fourth planetary rows are the same as the seal ring, the guide pins of the planetary row clutch are the same, the separation springs of the optical disc are the same, and the clutch piston separation spring is the same; The 1st to the 3rd planetary platoons use the same planet carrier; the planet carrier of the 4th planetary platoon uses the outer ring gear to insert into the 3rd planetary gear ring gear, and uses a spring retainer to prevent axial swaying and the like.
The TY320 and TY220 bulldozers have a completely similar transmission, just magnifying the geometry. In the TY160 type bulldozer transmission, the arrangement of the clutches is different. The first clutch is the forward gear, the second clutch is the reverse gear, the third rotary lock clutch is the first gear, the fourth clutch is the third gear, and the fifth clutch is the second gear. Ans have the same use and maintenance features.
(3) Steering clutch and steering brake
After the power of the transmission is transmitted to the central transmission, it is changed from the longitudinal transmission to the lateral transmission, and the horizontal shaft is transmitted to the left and right steering clutches respectively.
The 220 hp and 230 hp steering clutches are spring-loaded, hydraulically separated, normally meshed, and wet friction lining configurations. The utility model comprises an outer drum, an inner drum, a pressure plate, an outer friction plate, an inner tooth, a piston, a bolt, a sleeve and a piston connected as a whole, and a large and a small spring are supported on the inner drum, and a spring installation load pushes the piston to the right. Move, drive the pressure plate to press the friction plate and the tooth piece together to achieve the joint force. There are 8 sets of springs with a total installation load of 3.2T. There is enough pressure to compress the friction plates to transmit torque. When the bulldozer needs to turn (such as pulling the left steering rod), the hydraulic oil is filled into the oil chamber between the steering clutch piston and the hub, the oil pressure pushes the piston, drives the pressure plate to move to the left, the friction plate and the tooth piece are loosened, no longer The torque is transmitted and the bulldozer loses power on the left side 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 is regurgitated under the push of the piston, the steering clutch re-engages the force, and the bulldozer resumes straight travel.
The steering brake of the TY220 bulldozer is a hydraulic assisted, floating wet brake belt. It includes brake bands, booster pistons, connecting rods, floating rods, connecting rods, etc., mounted 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 is forward or reverse, the braking is smooth and does not cause a brake shock.
When the brake band lining on the brake band wears, the gap between the brake band and the outer drum becomes larger, and the brake spring stroke increases. When the stroke increases to a certain limit, the brake becomes unreliable. Therefore, it is necessary to constantly adjust the brake band gap. The standard stroke and limit stroke of the bulldozer brake pedal are shown in the table.
Brake belt clearance adjustment method: After removing the cover of the adjusting bolt, turn the adjusting bolt port to the right, tighten the brake band to hold the outer drum (tightening torque about 90N·m) and then loosen the bolt (TY160 type) Loosen 15/6 turns and TY320 loosen 11/6 turns), so that the standard gap of 0.3mm between the brake band and the outer drum is achieved.
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