With the continuous improvement of modern vehicle power performance, people are paying increasing attention to vehicle safety and comfort, thus placing higher demands on vehicle deceleration and braking performance. Hydraulic reducers, due to their advantages such as high high-speed braking torque, smooth braking, low noise, long lifespan, and small size, have been widely used in diesel locomotives, heavy-duty trucks, military vehicles, and engineering machinery.
Structure and Working Principle of Hydraulic Reducer: The hydraulic reducer structure consists of a driving wheel 2 and a fixed wheel 6, which together form the working chamber. The driving wheel is connected to the rotating components of the transmission system via a drive shaft 1, while the fixed wheel is connected to a stationary component. During operation, the hydraulic reducer's control system regulates the oil filling mechanism to fill the working chamber with oil. Driven by the blades of the driving wheel, the oil circulates and impacts within the working chamber, causing a change in momentum. The oil exerts a reaction force on the driving wheel, generating a braking torque. The impact and friction losses of the oil within the working chamber are converted into heat energy, which is dissipated through the cooling system.
When the hydraulic reducer is filled with oil, its braking torque is calculated as follows: 1/3 is the density of the working fluid, rm/m is the rotational speed of the hydraulic reducer's working wheel, and Z is the effective diameter of the hydraulic reducer's circulating circle, m. [br] 1. Drive shaft 2. Driving wheel 3. Reducer housing 4. Oil inlet 5. Oil outlet 6. Fixed wheel 7. Valve plate 8. Bearing As can be seen from Equation 1, 7 is proportional to and related to the amount of oil filling. To improve the braking efficiency of the hydraulic reducer, it can be achieved by increasing and improving. Placing the hydraulic reducer on the high-speed link of the transmission chain can achieve higher braking performance with a smaller radial dimension. The disadvantage of the hydraulic reducer is that its braking torque decreases faster when the speed decreases, so it is often used as an auxiliary brake in conjunction with other braking methods to form a combined braking mechanism. [br] The braking torque generated by the hydraulic reducer is related to the volume of the working fluid in the working chamber.
In practical engineering, hydraulic reducers are not completely filled with liquid, but are in a partially filled state. The volume of the fluid typically refers to only about 90% of the working chamber volume, leaving room for components such as the fixed chamber, test specimen inertia flywheel assembly, data acquisition system, and auxiliary systems. [br] The air and water vapor that escape are separated. 3. [br] The relative filling volume is defined as the ratio of the working liquid volume to the working chamber volume, i.e., the volume.
The torque test curve generated when the liquid filling amount is 1. Medium speed ratio; 0 The magnitude of the torque, from which the braking torque generated by the hydraulic reducer under partial liquid filling conditions can be approximately derived, that is, the braking torque of the hydraulic reducer is approximately proportional to the liquid filling amount, and the magnitude of the braking torque can be controlled by controlling the liquid filling amount of the reducer. [br] When the hydraulic reducer is in a partially liquid filling state, there will be a free surface with zero pressure in the core of the liquid circulation, 3. At this time, the pressure at the oil outlet of the hydraulic reducer is related to the liquid flow velocity at the drive wheel outlet and the thickness of the liquid ring. Under the same working conditions, the thicker the ring, the higher the part.
A throttle valve is installed at the oil outlet of the hydraulic reducer. When the opening of the throttle valve decreases and the flow area decreases, the flow rate discharged through the throttle valve decreases, falling below the flow rate pumped into the hydraulic reducer by the oil supply pump, thus disrupting the balance. The inlet flow rate of the hydraulic reducer then exceeds the outlet flow rate, causing the fluid volume in the reducer chamber to increase. The liquid ring gradually thickens, and the flow rate discharged through the throttle valve also gradually increases. When the flow rate equals the flow rate pumped into the hydraulic reducer by the oil supply pump, a new balance is reached, and the fluid volume no longer changes. Conversely, when the throttle valve opening increases, the fluid volume decreases. Therefore, adjusting the throttle valve is the purpose of regulating the output characteristics of the hydraulic reducer.
3.1 Experimental Equipment The experimental equipment and performance parameters are as follows: a) The test piece is a certain type of hydraulic reducer suitable for a certain vehicle, with a circulation circle diameter of 375 mm, 20 blades on the driving wheel, 24 blades on the fixed wheel, and axial surface area of the driving wheel inlet and outlet ports of 4 mm, both 4 mm and 4 mm being 0.0375 mm. 5) is the hydraulic reducer used for the test.
The maximum output power of the power unit is 330, the maximum torque is 1320, and the maximum speed is 2400. The C-type transmission box is used to match the speed and torque of the power unit and the test piece. The inertia flywheel assembly is converted to 33.16 based on the inertia of the whole vehicle. [br]6. Elbow 020 type throttle valve, nominal diameter 2, 1. [br]1g. The cooling system adopts a plate heat exchanger with a heat dissipation area of . The working oil is No. 8 hydraulic transmission oil. i. The data acquisition system includes industrial control computer data acquisition and processing software, temperature, pressure, speed and torque sensors, and flow meters, etc.
1. Oil tank 2. Oil filter 3. Gear pump 4. Overflow valve 5. Hydraulic reducer 6. Throttle valve 7. Flow meter 8. Inlet pressure before the heat exchanger. Its function is to automatically adjust the flow rate of the oil supply system through the reducer according to the internal fluid pressure change law under different working conditions of the reducer; by adjusting the different openings of the throttle valve 6 in the outlet oil circuit, different filling amounts are achieved in the hydraulic reducer. 3.2 Test content and data analysis 3.2.1 Basic performance test of hydraulic reducer During the basic performance test, the inertia flywheel assembly is not connected temporarily. [br] Start the pump station, adjust the throttle valve to the maximum opening, and start the power unit after the oil filling state is stable. In the test, the oil filling amount of the hydraulic reducer is adjusted by adjusting the opening of the throttle valve.
Under operating conditions of 650-700, the opening of the throttle valve was adjusted to change the amount of oil in the reducer, and the rotational speed of the hydraulic reducer wheel and the corresponding braking torque, as well as the inlet oil pressure, outlet oil pressure, oil temperature and flow rate of the reducer were recorded at different stable speeds and with different amounts of oil. [br] Based on the test data measured at different speeds, the torque coefficient of the test piece at different amounts of oil was calculated using Equation 1. When the input speed is constant, the amount of oil in the hydraulic reducer cavity is related to the outlet pressure, and the outlet pressure is related to the cavity pressure. When the speed is constant, the outlet pressure is proportional to the cavity pressure of the hydraulic reducer. According to the test data, when the working speed of the hydraulic reducer wheel is 560rZmiru, 600rZmiru, 650rZmiru, 700rZmiru, the cavity pressure of the hydraulic reducer and the torque coefficient are fitted curves. It can be seen from the curves that the torque coefficient of the hydraulic reducer increases with the cavity pressure. As the cavity pressure continues to increase, the critical cavity pressure is different due to different speeds, and the torque coefficient does not increase, but remains at around the maximum value. When the speed of the driving wheel of the hydraulic reducer is constant, the pressure inside the hydraulic reducer cavity is directly proportional to the amount of liquid filling.
Therefore, it can be considered that during the filling process, as the filling amount of the hydraulic reducer increases, the value of 7 also increases; when fully filled, the value of the hydraulic reducer reaches its maximum range, with the working speed of the upper drive wheel being 60 and the working speed of the upper drive wheel being 650 rpm. 3.2.2 Hydraulic reducer braking performance test: An inertia flywheel assembly is added to the test system. Without filling the reducer with oil, the power unit is started to remove the residual oil in the reducer. Then, the speed of the reducer drive wheel is adjusted to 80, the oil supply pump station is started, and the power is cut off while supplying oil to the reducer. The dynamic speed of the reducer and the corresponding braking torque generated at the dynamic speed are recorded under the conditions of the throttle valve being fully open and half open. [br] The speed of the reducer drive wheel is adjusted to the above test, and the test data is recorded. [br] Time s6 The initial braking speed is 120, the throttle valve is fully open, the sampling frequency of the data acquisition system is 50 Hz, and the filling amount is larger when the throttle valve is half open than when it is fully open. Figure 8 shows the curves of the change in speed of the hydraulic reducer wheel and braking torque over time when the initial braking speeds are 500 rpm, 800 rpm and 1200 rpm, and the throttle valve is fully open and half open.
It can be seen that the higher the speed of the driving wheel, the greater the braking torque; at the same initial braking speed, the greater the oil filling of the hydraulic reducer, the greater the braking torque generated, and the faster the speed of the driving wheel of the reducer decreases. [br]200 Adjusting the opening of the throttle valve with the curve of the change of speed and torque over time by using the throttle valve half-open 8 is to adjust the oil filling of the hydraulic reducer. When the throttle valve is half-open, the oil filling of the hydraulic reducer should be greater than the oil filling when the throttle valve is fully open. As can be seen from Figure 8, when the initial braking speed is 500, the maximum braking torque when the throttle valve is half-open is approximately 190 N·m, and the time for the driving wheel speed to drop to zero is approximately 5.3 s; when the throttle valve is fully open, the maximum braking torque is approximately 180.1 N·m, and the time for the driving wheel speed to drop to zero is approximately 6.188 s. When the initial braking speed is 80, the maximum braking torque when the throttle valve is half-open is approximately 340 N·m, and the time for the driving wheel speed to drop to zero is approximately 6.068 s; when the throttle valve is fully open, the maximum braking torque is approximately 280 N·m, and the time for the driving wheel speed to drop to zero is approximately 7.488 s. When the value is 12001, the maximum braking torque when the throttle valve is half open is approximately 550 N·m, and the time for the driving wheel speed to drop to zero is approximately 6.588 seconds; when the throttle valve is fully open, the maximum braking torque is approximately 370 N·m, and the time for the driving wheel speed to drop to zero is approximately 7.88 seconds. [br] Analyzing the above data, it can be concluded that under the same initial braking speed, the larger the fluid volume of the hydraulic reducer, the greater the braking torque generated, and the faster the speed of the reducer's driving wheel drops. Moreover, the higher the initial braking speed, the more obvious this effect is. This also shows that the hydraulic reducer has a good braking effect when used at high speed and with a large fluid volume.
The test results, through the basic performance test and braking performance test of the hydraulic reducer completed on the test bench, yielded the following conclusions: a. The torque coefficient of the tested hydraulic reducer increases with the increase of the oil filling amount. Under the full state, the torque coefficient of the hydraulic reducer reaches the maximum value range, which is 6.4, 106.6, 105. [br] Automotive Technology 1 Braking initial speed of 500 with throttle valve half opening time sc Braking initial speed of 800 rmin with throttle valve fully opening time s3 Braking initial speed of 50, throttle valve fully, i Luxury light gasoline vehicle working condition emission test method correlation study Peng Meichun 1 Zhou Guitian 2 Wang Wentao 1 Liu Dunxiong 2 Lin Yongjie 2 Zhao Xinze 3 Xu Zhigang 3 Jiang Baicheng 31. Guangdong University of Technology; 2. Guangzhou Honda Automobile Co., Ltd.; 3. Shenzhen Huiyin Industrial Development Co., Ltd. 18352.12001 requirements full working condition, 818352.12001 urban working condition and the first cycle working condition of urban working condition, a total of 5 different emission test methods.
The emission characteristics of three Honda Accord vehicles under these five emission testing methods were tested and analyzed. The results show that transient emission testing methods can more comprehensively reflect the technical condition of vehicles than steady-state methods. The transient IM195 method shows a high correlation with the urban driving condition testing methods in GB18352.1-2001, with HC and NO exceeding 90 and CO reaching over 57. [br]Keywords: Light-duty gasoline vehicle emission testing methods, correlation. In the face of increasingly serious motor vehicle exhaust pollution in my country, raising motor vehicle pollutant emission standards is urgent. Successful international experience shows that, in addition to implementing new vehicle emission regulations and controlling pollutant emission levels, the most important way to effectively control vehicle pollution is to supervise the emissions of in-use vehicles and implement the testing and treatment of in-use vehicle emissions. Recently, the State Environmental Protection Administration, in its draft for public comment on emission limits and measurement methods for exhaust pollutants from spark-ignition engines in in-use vehicles, proposed a series of optional testing methods, such as the dual-idle speed method, steady-state loading method, transient condition method, and simplified transient condition method for gasoline vehicles, and the free acceleration method and loaded deceleration method for diesel vehicles. These emission regulations are expected to be officially promulgated and implemented in 2005. Because this new standard includes multiple testing methods, local governments can choose to promote and use them according to their actual conditions and set local standard limits.
Therefore, various regions urgently need to conduct research on the selection of new standard methods and standard limits to provide a scientific basis for the government's scientific and systematic decision-making. [br] Several key technologies for clean vehicles proposed in the draft of the new emission standards for in-use vehicles were supported by the Ministry of Science and Technology's "Research and Development and Application of Key Technologies for Clean Vehicles" project, 2003, 4029. Under high speed and large oil volume conditions, the hydraulic reducer [1 Zhu Jingchang et al.]. Vehicle hydraulic transmission.
