There is a need for a vehicle chassis in many engineering jobs to run working devices along with the vehicle chassis while the working devices implement various jobs, for example, a sweeping car, a reaping machine and so on. The power transmission of some working devices is to drive the vehicle to run and drive the working device to work synchronously by one engine via one mechanical transfer case, for example, a transmission device of the reaping machine. However, the sweeping car and the like need to change their running speed during running and the rotation speed of the engine will be changed when the running speed is changed, which results in decrease of working quality. Therefore, the sweeping car and the like working devices can not use this kind of power transmission method.
At present, the power transmission similar to the working device of the sweeping car has two solutions. One solution is to configure two engines of which one engine is used to drive the vehicle to run and the other engine is used to drive the working device to work. The other solution is to configure a single engine connected with hydraulic transmission. The engine is used to drive a plurality of serially connected hydraulic pumps so as to drive the vehicle to run and drive the working device to work respectively by controlling the plurality of hydraulic pumps and hydraulic motors. Both of the above two solutions have deficiencies. The double engines configuration solution has higher gasoline consumption and more exhaust emissions. Large space in a special vehicle must be occupied to install the double engines. This configuration always uses high power to drive a low load. The solution of the single engine configured hydraulic transmission has lower total transmission efficiency. The efficiency of the hydraulic transmission system is 15%-25% lower than the efficiency of the mechanical transmission system, the transmission efficiency is low and the gasoline consumption is high.
When driving a camion driven by mechanical transmission means on a rough road in mining area, the damage of the engine, the mechanical clutch, the transmission and the driving axle is several times larger than driving on a flat road. Under this circumstance, the car driven by the hydraulic transmission means and having a characteristic of stepless variable speed runs with less power and cost. However, when the camion runs on the flat road, the mechanism of the mechanical transmission means is better so that the transmission efficiency is high and the speed is fast. The market needs parts of vehicles to have a transmission characteristic suitable for different road conditions in one same vehicle. Some domestic and foreign companies are studying and producing an automobile chassis transmission device having good running performance suitable for running on the road such as mining areas, deserts, the icy and snowy roads and swampy fields.
The Hydraulic Transmission Discussion (Author, W U Kejin, “The Hydraulic Industry”, hosted by the hydraulic and pneumatic industry of the Mechanical Industry Department, published in total volume 26, May 15, 1987) publishes a hydraulic-mechanical double power flow transmission device of a camion of a foreign company. The hydraulic power flow of this mechanism is achieved by driving a constant displacement hydraulic motor by an axial piston two-way variable displacement hydraulic pump transmission. The mechanical power flow is achieved by a simple planetary transmission system. The duty of the mechanical power branch is as follows: in this mechanism, the power imported by a component is divided into two lines of power to be exported, and the energy of two parts of the power flows transmitted from the hydraulic transmission and the mechanical transmission are converged, then the converged power is exported by an output component. Main operating elements of this transmission are three as follows: a variable rod of a variable displacement pump and clutches L1 and L2. The transmission process of this solution has the following three stages: The first stage is to run forward and backward at a low speed. The clutch L2 is disengaged to cut off the mechanical power branch. The clutch L1 is engaged to make a planetary row gyre as a whole. This stage achieves running forward and backward by operating the variable rod. This stage is hydraulic transmission. The second stage is to increase the speed of the vehicle. Under the circumstance of running forward at a low speed, after the output volume of the pump is adjusted to the maximum position, the clutch L1 is disengaged and the clutch L2 is engaged so that the planetary row starts to work. Then the variable rod of the variable displacement pump is adjusted gradually from a plus maximum position towards the direction of reducing the output volume. This stage is hydraulic-mechanical composite transmission. In the third stage, the speed of the vehicle is further increased and the adjusting method is that the variable rod of the pump is adjusted from the zero position towards minus direction of the output volume. Then inclination of a sloping cam plate of the pump is changed, therefore, the hydraulic motor also rotates reversely. The adjustment is proceeding gradually until the variable rod of the pump reaches to the minus maximum position of the output volume. Then the camion obtains the maximum running forward speed. The third stage is also hydraulic-mechanical composite transmission. The hydraulic-mechanical composite transmission solution has the following deficiencies: (1) The first stage operating in this solution is the hydraulic transmission so the transmission efficiency is low; (2) Based on analysis to the direction of the power flow passing in the second stage, there is recurrent power; (3) In the operation of the third stage, the ratio of the hydraulic power flow to the mechanical power flow is changed continually so that the total converged transmission efficiency is not steady; (4) The operating method of this solution is complex and difficult to master, which is not compatible with general operating main essentials of common vehicles, and when a driver is driving the vehicle, he is easy to have operating errors causing accidents because of a habitual action.
Both of the blast furnace and the mine need to be blasted or aired by high-power blowers. Some continuous equipment, such as large scale equipment or a conveyor, need to be driven by high-power electric motors. When these equipment start, a lot of start-up drag torque should be overcome, and the power-supply network of the equipment should avoid being attacked by start-up current. Some equipment need good speed adjusting performance during running. The Application of Fluid-flywheel Clutch and Energy Saving Technology (written by LIU Yingcheng and YANG Naiqiao, published by chemical industry press, the first edition of January, 2006) publishes a selection of transmission means of a speed-adjusting-type fluid-flywheel clutch (Chapter 6, Section 7, Subsection 3, Tables 6-8). In many kinds of speed adjusting transmission means listed in the above tables, when a single electric motor is connected with the speed-adjusting-type fluid-flywheel clutch in series, the transmission efficiency of this mechanism is low and the power configured for the fluid-flywheel clutch is large. When several electric motors are connected with the speed-adjusting-type fluid-flywheel clutch in series or in parallel, the structure of this mechanism is complex and the investment is high.
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