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Leakage of hydraulic pump Because most of the relative moving parts in the hydraulic pump are sealed by the clearance seal, the hydraulic pump works When, the high pressure oil of the oil pressure chamber must flow to the oil suction chamber and other low pressure places through this gap, thus forming a drain Leak. This not only reduces the volumetric efficiency of the pump, the flow of the pump is reduced, and limits the rating of the hydraulic pump An increase in stress. Therefore, controlling leakage and reducing leakage is the basic condition to ensure the normal operation of hydraulic pump One of them. The leakage condition of hydraulic pump is the existence of gap and pressure difference, and its leakage and gap value three times Is proportional to the first power of the pressure difference. Analysis of pump leakage is mainly from seal clearance size, Clearance pressure difference and whether the movement increases leakage three aspects. The main leakage clearance of the plunger pump is the annular clearance between the plunger and the cylinder hole, followed by the axial column The end clearance between the piston pump cylinder block and the valve plate, and the plane clearance between the sliding shoe and the swash plate. For radial column In addition to the annular clearance between the plunger and the cylinder hole, the radial clearance between the cylinder and the valve shaft, Clearance between the shoe and the inner ring of the stator. Because the precision of the ring clearance between the plunger and the cylinder hole is easy to control, And other gaps are easily compensated, so the volume efficiency and pressure rating of the plunger pump are higher. In leaf The main leakage clearance in vane pump is the end clearance between the rotor and the valve plate, followed by the blade and the rotor The clearance between the blade slots, between the top of the blade and the inner ring of the stator. Medium and high pressure double acting vane pump to reduce leakage Leakage, some will be designed as a floating valve plate, to achieve automatic end clearance compensation. External meshing tooth The main clearance of the wheel pump is the end clearance between the gear end face and the front and back pump cover or the left and right side plates, followed by And the radial clearance between the tooth tip and the pump body circle, the meshing clearance between the two meshing gear teeth. Medium-high pressure gear The end clearance of the pump is compensated by an automatic floating compensation mechanism.

Hydraulic pump as a power component in the hydraulic system, to the whole hydraulic system to provide high pressure hydraulic oil, to drive other hydraulic components to complete the expected action requirements, is the power source of hydraulic system. When the hydraulic system problems, the first to think of the hydraulic pump. Through the analysis of various hydraulic pump failures, listed the common failures and causes, and finally find out the solution. Although there are many types of hydraulic pumps, the working principle and function of hydraulic pumps are the same, so the hydraulic pump can be studied as a separate object. After the investigation and analysis of the faults that often occur in the work of various hydraulic pumps, the common faults that often occur in hydraulic pumps are summarized as follows: 1.1 No oil or no pressure is absorbed by hydraulic pump Hydraulic pump suction oil or no pressure, the whole hydraulic system will not work, affecting the efficiency of the system. The reasons are: 1. The prime mover and oil pump rotation is inconsistent; 2. Oil pump transmission key falls off; 3. Oil inlet and outlet are reversed; 4. The oil level in the tank is too low, and the suction pipe mouth is exposed; 5. The speed is too low and the suction is insufficient; 6 oil viscosity is too high, so that the blade movement is not flexible; 7. The oil temperature is too low, so that the oil viscosity is too high; 8. Blockage of suction pipe or filter device causes poor oil absorption; 9. High filtering accuracy of suction inlet filter causes poor oil absorption; 10. Low filtration accuracy of the system oil leads to the blade getting stuck in the groove; 11. Insufficient suction of small displacement oil pump; 12. Air leakage in suction pipe. Corresponding solutions: 1. Correct the turning direction of the prime mover; 2. Reinstall the transmission key. 3. Select the correct connection according to the instructions; 4. Fill the oil to the lowest oil mark; 5. Increase the speed to above the minimum speed of the oil pump; 6. Choose working oil with recommended viscosity; 7. Heat to recommended normal working oil temperature; 8. Clean the pipeline or filter device, remove the blockage, replace or filter the oil in the tank; 9. Select the filter correctly according to the instructions; 10. Disassemble, repair and grind the internal parts of the oil pump, reinstall them carefully, and replace the oil; 11. Fill the pump with oil; 12. Check the joints of the pipeline and seal them firmly. 1.2 The flow rate of hydraulic pump is not up to the rating When the hydraulic pump flow is insufficient, the speed and pressure of the actuator are unstable, and the external work can not be achieved. The common reasons are: 1. The speed does not reach the rated speed; 2. There is leakage in the system; 3. Because the oil pump works for a long time and vibrates, the screw of the pump cover loosens; 4. Leakage of suction pipe; 5. The oil level in the tank is too low; 6. The inlet oil filter is blocked or the flow is over; 7. The suction pipe is blocked or the diameter is small; 8. Oil viscosity is too high or too low; 9 variable pump flow regulation is improper. The corresponding solutions: 1. Choose the motor speed according to the rated speed specified in the manual; 2. Check the system and repair the leakage point; 3. Tighten the screws properly. 4. Check the joints and seal and tighten them; 5. Fill the oil to the lowest oil mark; 6. Clean the filter or choose an oil filter with a flow rate more than 2 times that of the oil pump; 7. Clean the pipe, choose suction pipe not less than the inlet diameter of the oil pump; 8. Use recommended viscosity working oil; 9. Adjust to the required flow rate. 1.3 The pressure of the hydraulic pump cannot rise The common reasons are: 1. The oil pump is not filled with oil or the flow is insufficient; 2. The adjustment pressure of the relief valve is too low or faulty; 3. There is leakage in the system; 4. Because the oil pump vibrates for a long time, the screw of the pump cover loosens; 5. Leakage of suction pipe; 6. Insufficient oil absorption; 7. Variable pump pressure adjustment is improper. Corresponding solutions: 1. Same as the above-mentioned exclusion method; 2. Adjust the relief valve pressure or repair the relief valve; 3. Check the system and repair the leakage point; 4. Tighten the screws properly. 5. Check the joints and seal and tighten them; 6. Same exclusion method as above; 7. Adjust to desired pressure. 1.4 Serious noise and pressure fluctuation Serious noise and pressure fluctuation have a great impact on the performance and working environment of the hydraulic system. The reasons are: 1. Suction tubing or oil filter is partially blocked; 2. The oil suction end connection is not tightly sealed, air enters, and the oil suction position is too high; 3. Air enters from the oil seal of the pump shaft; 4. The screw on the pump cover is loose. 5. The pump and the shaft connecting device are different or loose; 6. The oil viscosity is too high, and there are bubbles in the oil; 7. The passing capacity of suction oil filter is too small; 8. The rotational speed is too high; 9. Pump body cavity obstruction; 10 gear pump tooth shape precision is not high or poor contact, pump parts damaged; 11. The axial clearance of the gear pump is too small, and the vertical degree of the inner hole and the end face of the gear or the parallelism of the two holes on the pump cover is blocked. 12. Pipeline vibration. The corresponding solution is: 1. Remove dirt, make suction pipe smooth; 2. Oil at the oil sucking end connection, if there is better, tighten the connector, or replace the seal, reduce the oil sucking height; 3. Replace the seal. 4. Tighten properly; 5. Reinstall it to make it concentric and tighten the connector; 6. Change the hydraulic oil with appropriate viscosity to improve the quality of oil; 7. Use oil filters with larger passing capacity; 8. Make the speed of rotation lower than the maximum allowable speed; 9. Clean or replace the pump body; 10. Replace gear or grind dressing, replace damaged parts; 11. Check and repair related parts disassembly relief valve cleaning; 12. Take isolation and vibration mitigation measures. 1.5 Overheating The main reasons for the failure of hydraulic pump overheating are as follows: 1. Oil viscosity is too high or too low; 2. 2. Serious friction between side plate and shaft sleeve and gear end face; 3. Poor cleanliness of oil, aggravated internal wear, so that the volume efficiency decreases, oil leakage from the internal clearance throttling and generate heat; 4. Too small tank volume, poor heat dissipation; 5 system overload, mainly in the pressure or speed is too high; The corresponding solution is: 1. Replace with a suitable viscosity of hydraulic oil; 2. Repair or replace the side plate and shaft sleeve; 4. Increase the fuel tank to expand the heat dissipation area; 5. Adjust the pressure and speed. 1.6 Leakage The leakage of the hydraulic pump directly determines the output flow of the hydraulic pump, which will affect the stability of the hydraulic system speed and the output power. The main reasons for the failure: 1. The center spring of the plunger pump is damaged, so that the cylinder block and the oil distribution cross lose the sealing; 2. Oil seal or sealing ring damage; 3. Poor sealing surface; 4 pump parts wear, clearance is too large. The corresponding solution is: 1. Replace the spring; 2. Replace the oil seal or sealing ring; 3. Check and repair; 4. Replace or rematch the parts. 1.7 Inspection and repair of hydraulic pump bearings 1. Service life of bearings The most important part of the plunger pump is the bearing. If the bearing clearance is out of whack during use, the normal clearance between the piston rod and the cylinder body hole, the slipper and the swash plate, the valve plate and the cylinder body distribution surface cannot be guaranteed. At the same time, the hydrostatic oil film thickness of the friction pair will be destroyed, and the service life of the piston pump bearing will be reduced. In the process of use, bearings should be regularly repaired and replaced according to the provisions of the manual. According to the manufacturer's data, the average service life of the bearing is about 10h, if it exceeds this value, a new bearing needs to be replaced. 2. Bearing detection Bearing detection items are mainly bearing clearance, bearing clearance detection to use professional testing instruments, therefore, in the maintenance process, can only use the visual method for simple inspection, such as the roller surface of the bearing is found to have scratches or discoloration, the bearing must be replaced. 3. Precautions when replacing bearings When replacing bearings, attention should be paid to the English letter of the original bearing (representing the accuracy grade) and the model. Bearings used on the plunger pump mostly use large load capacity bearings. It is best to buy the original manufacturer and the original specification products when replacing the bearings. If you can not buy, need to replace, should look up the table replacement, the purpose is to maintain the accuracy of bearing grade and load capacity, otherwise it will affect the use of the pump effect, serious will reduce the service life of the pump.

With the improvement of our agricultural mechanization, especially the spread of small farm machinery in hilly areas south of the Yangtze River, our agricultural modernization has developed rapidly. And the application of hydraulic technology is more powerful to promote the degree of automation of agricultural machinery, further promote the popularization of agricultural machinery. The application of hydraulic technology in agricultural machinery is many, for agricultural machinery to provide adjustment, power, help and other technical support. There are three main aspects: First, agricultural machinery used in the production of bulk food crops, such as tractors, reapers, planters and so on. In the harvester, the hydraulic system mainly plays the role of controlling the height of the harvester and the opening and closing of the granary. In the cultivator, the hydraulic system can also provide driving force for the control of tillage depth and lifting when crossing the ditch. In farm tractors, the application of hydraulic technology optimizes the connection process between the tractor and the supporting farm tools. The second is the research and development of agricultural machinery. With the progress of science and technology, agricultural machinery is also developing in the direction of automation and intelligence, and the scientific application of hydraulic system can not only provide enough power for agricultural machinery, but also effectively improve the operation efficiency of agricultural machinery. For example, electro-hydraulic control technology conveniently realizes a variety of complex hydraulic function requirements. There are hydraulic suspension technology, to solve the combined operation of agricultural machinery folding, flipping and other functions of the power drive problem. Third, agricultural machinery used by cash crops. The use of hydraulic system in this kind of agricultural machinery mainly involves large translational sprinkler, cotton interset machinery and so on. However, agricultural machinery often work outdoors, is easily affected by vibration, sunlight, rainfall and other factors, so the daily maintenance of agricultural machinery hydraulic system, maintenance is very important. The common faults of agricultural machinery hydraulic system are four aspects, which are insufficient operating power of hydraulic system, unstable hydraulic driving process, hydraulic system leakage or component damage, and high temperature of hydraulic system. What about these failures? If the operating power of the hydraulic system is insufficient, the reason may be that the pressure of the main oil circuit is too low, then it is necessary to check whether the setting value of the safety valve of the hydraulic system and the working condition meet the actual requirements of the hydraulic system, but also to check whether the parts joint is tightened, if necessary to replace the high sealing components. If the hydraulic drive is unstable and abnormal noise occurs, it is necessary to check whether the hydraulic pump bearing, blade and other components are aging, and whether the axial clearance wear is serious. If it is the abnormal sound of the control valve, it is necessary to grind the control valve seat to restore its sealing performance or replace it, and check the deformation and failure of the internal pressure regulating spring to restore the pressure regulating function. If it is the leakage of hydraulic system, it is necessary to find out the cause of leakage according to the leakage location, and focus on checking the status of joints, tubing, as well as the clearance of the moving parts of valve and cylinder matching components, and timely replacement of severely worn parts. If the temperature of the hydraulic system is too high, the reason may be that the viscosity of the hydraulic oil is too high, or that the mechanical tubing and cooler are blocked, or that the pressure value of the system is too large, the internal leakage of the hydraulic system, and the parts are worn seriously. So when the temperature of the hydraulic system is too high, you can start to check from these aspects. In addition, there are intermittent movement of hydraulic cylinder, high viscosity of hydraulic oil and other failures, which need to be carefully checked and accumulated experience in the use of operation and maintenance personnel to improve the understanding of the operation principle of agricultural machinery hydraulic system.

The main technical parameters of hydraulic pump (1) Pump displacement (mL/r) The volume of liquid that can be discharged by the pump per rotation. (2) The theoretical flow of the pump (L/min) at the rated revolution, the maximum flow rate of the pump can be discharged within the unit time obtained by the calculation method. (3) the rated flow of the pump (L/min) under normal working conditions; Ensure the pump for a long time to run the maximum output flow. (4) the rated pressure of the pump (MPa) under normal working conditions, can ensure that the pump can run for a long time. (5) the maximum pressure of the pump (MPa) allows the pump to exceed the maximum pressure of the rated pressure in a short time. (6) the rated revolution of the pump (r/min) under the rated pressure, can ensure the maximum number of revolutions for a long time normal operation. (7) the maximum revolution of the pump (r/min) at the rated pressure, allow the pump to exceed the maximum revolution of the rated speed in a short time. (8) pump volumetric efficiency (%) pump actual output flow and theoretical flow ratio. (9) pump total efficiency (%) pump output hydraulic power and input mechanical power ratio. (10) the driving power of the pump (kW) can drive the mechanical power of the hydraulic pump under normal working conditions. Performance parameters of hydraulic pump and hydraulic motor Hydraulic pump and hydraulic motor performance parameters are: pressure, flow, efficiency, power, torque and so on. (1) pump pressure Pump pressure includes rated pressure, working pressure and maximum pressure. The rated pressure of hydraulic pump (motor) refers to the maximum working pressure allowed when the pump (motor) runs continuously under standard conditions. It is related to the structural form of the pump (motor) and the volumetric efficiency; Hydraulic pump (motor) working pressure pB(pM) refers to the pump (motor) working from the pump (motor) outlet actual measured pressure, its size depends on the load; The maximum pressure of the pump refers to the limit pressure of the overload operation allowed by the pump in a short time, which is limited by the sealing performance of the pump itself and the strength of the parts and other factors; Working pressure less than or equal to the rated pressure, rated pressure less than the maximum pressure. (2) pump flow Pump flow is divided into displacement, theoretical flow, actual flow and instantaneous flow. Pump (motor) displacement VB (VM) refers to the volume of oil output (input) when the shaft of the pump (motor) turns around without considering leakage; The theoretical flow qBt(qMt) of the pump (motor) refers to the volume of oil output (input) per unit time without considering the leakage; The actual flow qB(qM) refers to the pump (motor) working when the actual output (input) flow; Rated flow qBn(qMn) refers to the pump (motor) at rated speed and rated pressure when the output (input) flow. The instantaneous flow qBin of the pump is the flow value of the hydraulic pump at a moment, generally referring to the theoretical (geometric) flow rate of the pump moment. The actual flow rate of the pump (motor) is less than (greater than) or equal to the rated flow rate, allowing for leakage, and the theoretical flow rate of the pump (motor) is greater than (less than) the actual flow rate. (3) The power and efficiency of hydraulic pump and hydraulic motor The power and efficiency of hydraulic pump and hydraulic motor mainly refers to input power, output power, mechanical efficiency, volumetric efficiency and total efficiency. For hydraulic pump, the input is the mechanical power PBI, the output is the hydraulic PBT, the ratio of two power is the total efficiency of the pump ηB, the pump output power is less than the input power, the difference between the two is the power loss, including volume loss and mechanical loss, these losses are respectively expressed by the total efficiency ηB, volume efficiency ηBv, mechanical efficiency ηBm. Due to the leakage loss and friction loss, the actual flow qB of the pump is less than the theoretical flow qBt, and the theoretical torsional TBt moment is less than the actual torque TB. The calculation formula related to the pump is: For hydraulic motor, the input is mechanical power PMI, the output is hydraulic PMT, the ratio of two power is the total efficiency of the pump ηM, the output power of the motor is less than the input power, the difference between the two is power loss, power loss is divided into volume loss and mechanical loss, these losses are respectively expressed by the total efficiency ηM, volume efficiency ηMv, mechanical efficiency ηMm. The actual flow qM of the motor is greater than the theoretical flow qMt, and the theoretical torsional TMt moment is greater than the actual torque TM.

Agricultural machinery hydraulic pump has the advantages of compact structure, small size, light weight, agricultural machinery hydraulic pump has been widely used in the walking hydraulic system of harvesting machinery, harvesting machinery, silage machinery and other industries, the East China Sea steam towing and gradually accumulate design and operation experience. With the application market of agricultural machinery and equipment gradually transferred to the high-end market, the development of the high-end market will also put forward higher requirements for the performance of agricultural machinery hydraulic pump, and after the introduction of the East China Sea steam towing agricultural machinery hydraulic application field, I hope you have a new understanding of agricultural machinery hydraulic pump, it represents the development direction of agricultural machinery hydraulic pump in the 21st century. Donghai Auto towing Parts Factory is a set of hydraulic design and development, manufacturing, maintenance and after-sales in one of the high-tech enterprises. East China Sea steam towing products are: hydraulic pump, hydraulic gear pump, hydraulic pump test bench, hydraulic tester, agricultural machinery hydraulic assembly supporting, hydraulic pump maintenance, hydraulic pump accessories, the company has a strong technical development ability, sound scientific management talent system and automatic product manufacturing, testing equipment. The company is located in Taizhou, Zhejiang Province, the use of Zhejiang transportation convenience, leading to all parts of the country, the factory is located in Yuhuan Kanmen Liao Industrial Park.