What is the structural principle of hydraulic torque converter of Komatsu bulldozer?

Bulldozer 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 with the drive housing by bolts, and the drive gear is connected with the drive housing by bolts. The drive gear is directly inserted into the flywheel ring gear of the engine, so the pump wheel rotates with the engine. The guide wheel is connected with the guide wheel hub by bolts, the guide wheel hub is connected with the guide wheel seat by splines, and the guide wheel seat is connected with the torque converter housing by bolts, so the guide wheel and the torque converter housing do not rotate together. The turbine and the turbine hub are riveted together, and then connected with the turbine output shaft through splines. The turbine output shaft is connected with the coupling through splines 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 clearance between wheels is about 2mm.

The impeller, turbine and guide wheel themselves are composed of many blades, which are called cascades. The blades are composed of curved blades with complex shapes.

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 pump wheel cascade moves outward along the curved surface under the action of centrifugal force, shoots at the outlet of the cascade to the outlet of the turbine cascade, then moves centripetally along the curved surface of the turbine cascade, shoots from the outlet of the turbine cascade to the inlet of the stator cascade, passes through the stator cascade and flows back to the pump wheel. The circular space composed of pump wheel, turbine and guide wheel cascade is called circular circle. Because the design of turbine cascade curved surface shape determines that the turbine and pump wheel rotate in the same direction. In this way, the oil in the torque converter cascade circle rotates in the circle on the one hand, and rotates with the pump wheel and turbine on the other hand, forming a complex spiral movement. In this movement, energy is transferred from the pump wheel to the turbine.

The turbine load is determined by the bulldozer load. The load of the bulldozer is transferred from the blade to the crawler traveling system, then to the final drive, steering clutch, central drive, transmission and coupling assembly, and finally to the torque converter turbine. When the turbine load is small, its 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 0, becoming the braking state of the turbine. At this time, because the turbine stops rolling, the oil shot from the pump impeller cascade passes through the turbine cascade and rushes to the guide wheel with the maximum impact, which is converted into pressure in the non rotating guide wheel cascade. The pressure is back pressed to the turbine, increasing the turbine torque. The increased torque is consistent with the turbine rotation direction. At this time, the turbine output torque is the largest, 2.54 times of the pump impeller torque. As the load increases, the speed of the turbine gradually decreases and the torque gradually increases, which is equivalent to a stepless transmission gradually reducing speed and increasing torque. This kind of infinitely variable torque function is matched with the planetary gear power shift transmission which is easy to operate and has fewer gears, making the bulldozer obtain excellent traction function.

The hydraulic torque converter works by hydraulic force. When the oil moves in the cascade, it will consume energy and heat the oil due to impact and friction, so the transmission efficiency of the hydraulic torque converter is low. At present, the highest efficiency of the best hydraulic torque converter at home and abroad is 88%. When the turbine of the torque converter stops rolling due to the overload of the bulldozer, all the energy transmitted from the pump wheel is converted into heat and consumed. At this time, the efficiency of the torque converter is 0. 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, reduce the load in time, lift the blade or shift from gear II to gear I.