the hydraulic drive technology in the engineering mechanical travel drive system

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the hydraulic drive technology in the engineering mechanical travel drive system travel drive system is an important part of the construction machinery. Compared with the systems of work, travel drive system not only need to transfer more power, the device has a higher efficiency and longer life, but also hope in the v ariable speed governor, differential, change the output shaft rotation direction and the reverse transmission power and other aspects of good ability. So, what transmission, how to better meet the needs of the various engineering mechanical travel drive, has been the subject of construction machinery industry have to face. Especially in recent years, with the rapid development of China\\ s transportation, energy and other infrastructure construction process, the scale of construction and resource development continues to expand, engineering machinery market demand for greatly enhanced, while also facing the more demanding operating environment, working conditions conditions are more complex challenges posed by in-depth study to further promote its travel drive system.

Here attempt to investigate the hydraulic drive technology in the engineering machinery the development of the travel drive system and its laws from the perspective of the composition and performance characteristics.

2, based on a single drivehydraulic hose assemblies

Construction Machinery walking system initially used mainly to mechanical transmission and hydraulic mechanical transmission (other than hydraulic excavator) way. Now, the transmission mode of the hydraulic and electric drive also appeared in the travel drive device of construction machinery, fully demonstrates the great role in promoting scientific and technological development in this area.

2.1 Mechanical Transmission

Low average load factor of purely mechanical drive engine, it is generally only stepped speed, and the layout is restricted. However, because of its advantage in the steady-state, high transmission efficiency and manufacturing costs low regard, so far in the speed range relatively small general passenger and freight cars and demanding a constant operating speed on the economy of agricultural tractors areas continues to occupy a dominant position.

2.2 The hydraulic transmission

Hydraulic transmission with torque converter replaced the clutch, the mechanical transmission of segmented stepless capacity. Its prominent advantage is close to the hyperbolic output torque - speed characteristics, mechanical transmission line with the rear power shift can automatically match the load and prevent the overload of the power transmission device. The converter power density but low load stress, a large number of production cost is not high so that it can be widely used in large and medium-sized shovel earth moving machinery, lifting and transport machinery and cars, tanks and other high-speed vehicles. But restricted its characteristics match and layout, a smaller range of variable torque, dynamic braking is poor, not suitable for the requirements of speed an d stability of the occasion.

2.3 The hydraulic drive

Compared with mechanical transmission. The hydraulic drive is easier to implement the motion parameters (flow) and dynamic parameters (pressure) control, hydraulic transmission compared to a hydraulic transmission with good low-speed load characteristics. With the high transfer efficiency, constant power output control, access to adequate power system structure is simple, the output speed variable speed, forward and reverse operation, speed rigid, easy action to achieve outstanding advantages, hydraulic transmission engineering The machinery has been widely used. Almost all engineering machinery and equipment could be seen the traces of hydraulic technology, many of which have become the main drive and control. The limit load regulation, closed loop engine speed control, constant pressure, the combination of constant power adjustment variable system develop ment to the hydraulic drive used in engineering machinery walking system provides a broad development prospects.

Compared with the purely mechanical and hydraulic transmission, hydraulic transmission of the main advantage of the convenience and flexibility of the layout of its regulation, according to the form of construction machinery and working conditions and the needs of the various components of the engine, wheel, work organizations are arranged in a reasonable place under any scheduling speed, the engine, transmission can play a greater traction, and transmission in a wide range of output speed to maintain a higher efficiency, and can easily access The powertrain features a variety of optimization to adapt to various operating load conditions. With closed oil walking speed higher operating machinery, hydraulic drive variable speed, the vehicle soft start, rapid speed change and the impact of changing the direction of travel. Very valuable in the job require frequent starting and variable speed, often shuttle moving vehicles performance. Compared with the open loop and closed loop design, installation and commissioning, and maintenance have a high degree of difficulty and technical requirements.

With the combination of electronic and hydraulic technology, can easily achieve the regulation and control of the hydraulic system. The introduction of computer-controlled components and various types of sensing applications, but also greatly expands the range of hydraulic components. Vehicles, a variety of sensors to monitor the project status parameters, after computing the output control target instruction, so that the automated control of vehicles within the entire scope of work, the machine\\ s fuel economy, power, operating production rates to achieve the best value. Therefore, the use of hydraulic drive allows construction machinery is easy to implemen t intelligent, energy-saving and environmental protection, which has become the development trend of the current and future construction machinery.

2.4 Power Drives

Power transmission is by the internal combustion engine driven generators to produce electric motor-driven vehicles can walk part of the movement, through electronic adjustment system to adjust the motor shaft speed and direction, with wide withered speed, the input components (generators), and output components (motor) and control devices can be divided into the installation advantages. Electric drive for diesel electric ship and diesel locomotives, the first, and then extended to large-tonnage mining trucks and some large-scale construction machinery, has emerged in recent years small and medium-sized lifting and transport of diesel-electric drive forklifts and tractors vehicles. However, some of the reasons of the technical an d economic aspects of the power components used in mobile machinery far as fixed equipment as prevalent in electric drive only \"future technology\" for the majority of mobile machinery.

3, the development of composite drive technology

Can be seen from the foregoing analysis, used in construction machinery travel drive system based on a single drive way constitute a simple, reliable transmission, applicable to certain situations and areas. In most practical applications, the drive technology is often not exist in isolation of each other with mutual penetration and binding, such as more or less hydraulic, hydraulic and electric power transmission device includes mechanical transmission links, and new mechanical and hydraulic gear set of electrical and hydraulic control system. In other words, the use of the targeted compound and integrated manner, can give full play to the various transmission mode on their respective strengths, weaknesses, and to get the best benefits. It is noteworthy that both regulation and layout flexibility and high power density of hydraulic transmission device which acts as an important role.

3.1 composite hydraulic and mechanical and hydraulic transmission

(1) series

The tandem is the most simple and common complex way, set the mechanical transmission between the output of a hydraulic motor or hydraulic transmission and drive axle in order to expand the efficient area of ??the governor, segmented continuously variable transmission. Has been widely used loaders, combine harvester and some special vehicles. Its development is to transform the driving force transmission ratio will be in the road between the shifting planetary gear installed directly in the driving wheel to realize the great changes the speed ratio of the wheel side hydraulic drive, which canceled the drive axle, more user-friendly layout.

(2) parallel

Is commonly referre d to as \"hydro-mechanical power split transmission\", understood as a hydraulic and mechanical devices in parallel, respectively, the transmission power flow transmission system, that is, multiple degrees of freedom of the planetary differential output of the engine hydraulic power is divided into two shares of machinery \"power flow\", with the hydraulic power flow controllability, these two power flow in the re-convergence can be adjusted total output speed. In this way will combine the advantages of the stepless speed regulation performance of the hydraulic drive and mechanical transmission of the steady state high efficiency in these two areas, an existing Continuously Variable performance, variable speed and a relatively high efficiency and wide efficient area device.

Gear according to the structure of this compound can be divided into two categories: the first category the outside of the planetary gear differential shunt and shunt type, common shunt transmission can be divided into input shunt type and output shunt type basic forms; second category is the use of differential movement between the hydraulic pump or motor rotor and the housing shunt shunt type.

Komatsu of Japan this complex mode of hydraulic drive transmission, has been applied on the loaders, bulldozers and other construction machinery. Fendt tractor production in Germany Vario type continuously variable transmission equipment, agricultural tractors, 2003, total sales of more than 30,000 units.

It can be seen, this new type of gear has become an increasingly large and medium-sized power hydraulic transmission and power shift transmission of powerful competitors.

(3) time-sharing manner

Operating speed and non-operating state transfer Kongshi speed difference between the special vehicles, using the traditional mechanical transmission for high-speed driving, additional hydraulic power units for low sp eed operation can satisfy the contradictions of these two conditions. Machinery - Hydraulic timeshare driven applications are very common on these vehicles, this technology has been used in aircraft deicing vehicle and field transplanting machines and other vehicles and equipment on the need to \"crawl speed\".

(4) mode

The hydraulic motor mounted directly on the wheel within the wheel side hydraulic drive an auxiliary hydraulic drive, you can solve the construction machinery need to improve the traction performance, but not all-wheel drive, it is difficult to arrangement of the traditional mechanical transmission problem. Stepless speed regulation performance of the hydraulic drive to coordinate the synchronization between the transmission of the driving wheel in different ways, in a sense also be regarded as a power split transmission: the power of the power machine is assigned to several groups of driving wheels, promote the movement of veh icles after the ground-coupled traction. Currently, many engineering machinery manufacturers of this technology is used on the part of the self-propelled drive capability, such as construction machinery such as self-propelled motor graders and scrapers.

3.2 Hydraulic and electric drive compound

Due to the development of modern technology, electronic technology is a significant advantage in signal processing capability and speed, and hydraulic and electric drive components in their respective power characteristics have their own strengths. Therefore, in addition to is now a common electronic nerve + hydraulic muscle \"of this model, both in the power flow of the composite transmission there are many successful examples, such as: by the inverter or DC speed motor and high efficiency, low ripple quantitative hydraulic pump to a variable flow hydraulic oil source, using the integrated installation of electric pump - electric hydraulic actuator unit con sisting of hydraulic cylinders or low speed high torque hydraulic motors, and industrial vehicles hybrid drive system and so on.

3.3 secondary regulation hydrostatic transmission

Secondary regulation hydrostatic transmission technology is through the regulation of hydraulic components, hydraulic and mechanical energy conversion. In general, its implementation is pressure-coupled systems using fixed-pressure coupling between the components (pump) and the secondary components (motor), rely on real-time adjustment of the motor displacement to balance the load torque. At present, the starting point for research on secondary regulation of the hydrostatic transmission technology to drive the process of energy recovery and re-use of energy, a reasonable allocation of the overall structure of the hydrostatic transmission from a macro point of view, and to improve its hydrostatic transmission control features.

In order to do not have bi-directional st epless variable capacity hydraulic motor and the reciprocating motion of the hydraulic cylinder can also be run in the constant pressure of the secondary-conditioning systems network, use of secondary regulation technology \"hydraulic transformer, which is similar to the power transformer used to match the different needs of users of the system pressure and flow, in order to match the power of the hydraulic system.

Secondary regulation compared to the hydrostatic transmission with conventional hydrostatic transmission, its advantages are easier to control, able to work in the four quadrants, in the case does not change the form of energy for energy recovery, energy storage, the use of hydraulic accumulator acceleration greatly improve acceleration power and system pressure peak, the primary element and secondary components are installed separately, can be a source of oil pumping station to the multiple hydr aulic power components, reducing cooling costs, manufacturing costs of the equipment reduced system efficiency.

Secondary regulation compared to the hydrostatic transmission and electric drive, with fast dynamic response of closed-loop control, high power density, light weight, installation space, etc..

Secondary regulation hydrostatic transmission has many advantages, making it widely used in many fields. Abroad has been successfully applied in the field of shipbuilding industry, steel industry, large-scale test-bed vehicle transmission. Mercedes-Benz car company has secondary regulation technology driving drive for driverless transport system.

4, Conclusion

Since 2O century 9O\\ s, engineering machinery has entered a new period of development and extensive application of new technology makes new structures and new products are emerging. With the penetration of micro-electronics technology to the engineering machinery, engineering machinery increasingly to the direction of intelligence and mechatronics development, increasingly demanding requirements of the travel drive device for construction machinery. In recent years, hydraulic technology rapid development, is getting more sophisticated hydraulic components, hydraulic transmission in the engineering and mechanical transmission application by leaps and bounds, the advantages of hydraulic transmission are increasingly apparent. Can be confident that, with the hydraulic technology and microelectronic technology, computer-controlled technology and sensor technology is closely integrated with the hydraulic drive technology will play an increasingly important role in the development of construction machiner