The wheel loader, as a walking machine, is widely used in the transportation of earthwork and the loading, lifting and transportation of loose goods and piles. On the one hand, it has great mobility as a large traction tire loader. On the other hand, it has the characteristics of rapidly changing the working site at high speed. Therefore, it is a good combination of power and maneuverability, and thus determines its economy and practicality.
The hydrostatic transmission driving scheme (with the subsequent load shifting transmission) has many advantages over the hydraulic dynamic torque converter drive scheme. It has been successfully applied to the production of wheel loaders that drive power up to 60 kilowatts.
The application of hydrostatic transmission of high-power tire loaders is similar to that of hydraulic torque converter, because the large torque range of such hydrostatic transmission requires an additional shift transmission, resulting in the drawback of traction during shifting. In spite of this, the walking system is still tending to be static pressure in the tyre loader driven from 60 kW to 100 kW.
However, up to the above power range, engine power of 200 kilowatts, no load weight of 25000 kg and maximum speed of 45 km / h, so far, almost all hydraulic torque converters are used.
The advantage of hydrostatic transmission is relative to the dynamic pressure transmission. On the one hand, its large control range can be stepless or only a few stages shift in the additional shift transmission. On the other hand, its structural form can realize the comprehensive transmission plan, and it can be installed in the modern tire loader tilted or transverse in the direction of travel. In a closed loop, the torque can be transmitted in two directions. Therefore, during braking process, a supporting device that can act on driving machinery can be generated, so that brake power and brake wear can be reduced, which will bring down the operation cost of tire loaders. Working hydraulics at the same time at the same time, the reflux energy can be added to another hydraulic pump and the actuator. The decisive advantage of hydrostatic transmission is that it has all kinds of open loop control and closed loop control, and can accept the power of the disposable engine at any speed. Therefore, in the current and future research and development, the optimization design of the driving device of the tire loader has become an inevitable trend.
The torque converter and the hydraulic pressure device provides traction and speed than the engine power available for all running drive, hydraulic traction reduction of about 80% of the weight of the loader under normal conditions, the traction force can not only meet the requirements, and can be cut in order to avoid slippage of the drive wheel loading goods the phenomenon of. This is the typical wheel loader working condition and often occurs during the loader cut into the cargo heap. At this point, the tire wear of the static pressure drive is obviously reduced compared to the dynamic pressure drive with rapid rising of the traction force. The hydrostatic drive provides the maximum traction when working at the same time. Especially in loading large goods, the static pressure loader can improve the working efficiency. In dynamic pressure transmission, only about 50% of the original traction force can be provided due to the decrease of the speed of the driving motor.
The torque carrying capacity of the torque converter is the two equation of a rotational speed. This means that when the torque converter is at a certain speed, it generally accepts all torque at the speed of the load. At the speed below this speed, the ability to accept a sharp decline, thus causing a drop in traction and speed. In the application of static pressure transmission, because it can freely distribute speed transformation and torque transformation, it can theoretically cover the characteristic curve family of the whole engine. And combined with various open loop and closed loop control, the optimization of noise and energy consumption can be realized. In this way, as long as the speed of the driving motor is regulated at a best working point, the driver can only raise the requirement of acceleration, traction or speed through the position of the accelerator pedal.
The purpose of optimization is to reduce the burden of drivers, improve their working conditions on the one hand, and enable them to concentrate on decisive tasks. In addition to its performance advantages, the modern hydrostatic transmission scheme that is compatible with the specialized driving power is also highly competitive in terms of the price of the torque converter drive.