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Chapter 9 Design of Hydraulic Transmission systems,单击此处编辑母版文本样式,单击此处编辑母版标题样式,40,Chapter 9 Design of Hydraulic Transmission System,9.1 The Approach for Design of Hydrostatic Circuits,9.2 A Design Example of Hydraulic Systems,Chapter list,Introduction,The design of hydrostatic transmission systems is an important,part of the whole mechanical design and also a summarizing and,comprehensive application of knowledge in previous chapters.,The aim of this chapter is,to show through an example how,hydrostatic transmission circuits can be designed to satisfy,a given set of requirements.,9.1 The Approach for Design of Hydrostatic systems,9.1.1 Determination of design requirements,9.1.2 Analysis for working conditions and determination of main parameters,9.1.3 Determination of hydraulic system diagram,9.1.4 Calculation and selection of hydraulic components,9.1.5 Performance check for a hydraulic system designed,9.1.6 Drawing of working diagrams and technical documents,Fig.9-1 General design process for a hydraulic transmission system,9.1.1 Determination of design requirements,Before a hydraulic system is designed, the working conditions of the mainframe in the mechanical equipment must be analyzed.,1. The purpose of the mainframe, the overall arrangement, the limitations to the position of the hydraulic devices and their sizes.,2. The mainframe work cycle, the system actions, their sequence, interlock function, automatization.,3. The load on actuators and the ranges of speed, motion stability, position accuracy, conversion accuracy, etc.,4. Working environment and working conditions,.,5. Working efficiency, safety, reliability, cost, etc.,1.Analysis of working conditions,1）,Dynamic parameters analysis,A load diagram can be drawn out based on the determined,extrinsic loads, see Fig.9-2a, which is load chart. The load chart is,actually a load-displacement （,F-l,）curve .,9.1.2 Analysis for working conditions and determination of main parameters,a) Load chart,b) Speed chart,Fig.9-2 Load chart and speed chart of actuators,1- Startup acceleration,2- Quick feed,3- Working feed,4- Brake,5- Friction,6- Cutting force,7- Seal and back pressure resistance,8- Inertia force,(2),Movement parameters analysis,Fig.9-2b is a speed-displacement （,v-l,）curve drawn to express the,speed of each actuator in different phases, it is called speed chart.,When the actuator works in line reciprocating, the extrinsic load will be,(9-1),1) The working load,2) The friction resistance force,(9-2),3) The inertia load,Besides three loads mentioned above, an actuator stands also viscosity resistance force, sealed resistance force and back pressure resistance etc.,(9-3),2. Determination of main parameters,The working pressure for actuators can be selected according to the,largest load in the load chart (see Tab.9-1) or the mainframe type (see,Tab.9-2). However the largest flow rate must be calculated by the,highest speed shown in the speed chart.,The lowest working speed must satisfy the following requirements:,For cylinders,For motors,Tab.9-1 Working pressure selected for an actuator according to load,Load,F（,N,）,50000,Working pressure,p,（MPa）,0.81,1.52,2.53,34,45,57,Tab.9-2 Working pressure selection for an actuator according to mainframe type,Mainframe type,Machine tools,Agricultural machinery, small-sized engineering machinery, auxiliary devices for engineering machinery,Hydraulic press, large-sized excavator, heavy machinery, lifting and conveying machinery,Grin-der,Modular machine tools,Planer,Drawing,bench,Working pressure,p,（MPa）,2,35,8,810,1016,2032,3. Drawing of working condition chart of the actuators,After the structure parameters of the actuators are determined, the practical working pressure, the flow rate and the power can be calculated according to the design task and its requirements. Then pressure (flow rate, or power)time (or displacement) curves can be drawn out, as shown in Fig.9-3.,Fig.9-3 Working condition chart of actuators,1-Startup acceleration,2- Quick feed,3- Working feed,4- Brake,9.1.3 Determination of hydraulic system diagram,1.Analysis and selection of the hydraulic scheme,2. Analysis and selection of the hydraulic circuits,3. Determination of hydraulic system diagram,9.1.4 calculation and selection of hydraulic components,1. Selection of pumps,According to maximum working pressure and provided flow rate calculated above, a proper pump can be selected from product samples. For the sake of safety, the chosen pump must be with a rated pressure 20%60% higher than the maximum working pressure (described above) for pressure reserve , but with a rated flow rate just meeting the maximum flow rate to avoid an exceeding loss of power.,2. Selection of valves,Tab.9-3 Experiential values of the pressure loss in the inlet oil line,System configuration,Overall pressure loss,(MPa）,Simple system with general throttle speed-regulating components and pipelines,0.20.5,Complex system with speed-regulating valves and pipelines,0.51.5,3. Selection of valve arrangements,There are three types of arrangements for hydraulic equipments,(1) Modular type,(2) Manifold plate type,(3) Integrated block,9.1.5 Performance check for a hydraulic system designed,1. Checking of the system pressure loss,The pressure loss includes frictional loss along the pipelines, local loss in the pipelines and to a less produced by the valve components. The pressure loss of along or local can be calculated from the involved expressions shown in Chapter 2, while the local loss of the valve components can be obtained from the product samples.,When the practical flow rate,q,of a valve component doesnt equal the nominal flow rate,（9-4）,2. Checking of the temperature rise caused by heat generation,according to heat balance principle, when the dimension ratios of,three sides of the reservoir are between 1:1:1 and 1:2:3, the oil lever is,80% that of the reservoir height, and the reservoir is in good ventilation,Condition,then,（9-5）,Once the checked oil temperature rise surpasses the allowable value, a proper cooler must be set in the system. The allowable oil temperature rise in the reservoir is different for different mainframes,9.1.6 Drawing of working diagrams and technical documents,The working diagrams usually incorporate hydraulic,system figure, assembly drawing and the assembly and part,Drawings.,There must exist a list of components attached to the hydraulic system figure. The system assembly figure is the construction and erection drawing for the hydraulic system. Generally, the technical documents include the explanations of design calculation, manual to use and maintain, content of parts, standard parts, universal parts, overall table of outsourcing parts, etc.,9.2 A Design Example of Hydraulic Systems,9.2.1 Analysis of working conditions,9.2.2 Determination of main parameters of the actuator,9.2.3 Design of hydraulic systems,9.2.4 Selection of hydraulic components,9.2.5 Performance check for hydraulic systems,This section is to study the hydraulic system of a single side multi-spindle drill machine tool.,axial cutting force,overall gross weight,G（N）,Distanc-es covered at rapid speed,Distanc-es covere-d at work speed,the rapid feed and retract velocity,work feed velocity,time for acceleration and deceleration,friction coeffici-ent of rest,friction of motion,Mechan-ical efficienc-y of the cylinder,30000,9500,100,50,5,0.05,0.2,0.2,0.1,0.9,The dynamic slipway is required to achieve such a work cycle:,rapid feed,work feed,block dwell,rapid retract,stop,at the original position.,9.2.1 Analysis of working conditions,The axial cutting force which is also the only force whose direction is horizontal. Then the inertia force, the friction of rest and the friction of motion against the guide way can be calculated as follows,Tab.9-4 Loads on the cylinder in each work step,Working condition,Load combination,Load,F,（N）,Thrust,Startup,1900,2111,Acceleration,1354,1504,Deceleration,950,1056,Work feed,30950,34389,Rapid retract,950,1056,The loads on the cylinder in each work step are listed in Tab.9-4, where the back pressure in the oil returned chamber is neglected. The load and speed diagrams are indicated in Fig.9-4a and Fig.9-4b.,a) Load,b) Speed,Fig.9-4 Load and speed diagrams of the cylinder,9.2.2 Determination of main parameters of the actuator,1）system pressure,3）area of cylinder,2）,back pressure,The cylinder area can be calculated from the thrust at work feed period:,Then,D,and d must be corrected to standard values according to GB 23481997： , then the practical effective areas of the two chambers of the cylinder are,The pressure, flow rate and power at each work step as shown in Tab.9-5. The working conditions chart can then be drawn, as indicated in Fig.9-5.,Tab.9-5 The pressure, flow rate and power at each step,Fig.9-5 Working conditions diagram,9.2.3 Design of hydraulic systems,1. Selection of hydraulic circuits,2. Design of hydraulic systems,3. Selection of the hydraulic valves,Fig.9-6 Principle chart of hydraulic system,Fig.9-7 Principle chatr of hydraulic system with modular valves,9.2.4 Selection of hydraulic components,1. Pumps,1）pressure,2）flow rate,The maximum flow rate provided by the two pumps is 25.13L/min. If the leakage in the return line is supposed 10% the input flow rate of the cylinder, then the overall flow rate of the two pumps is,From the pressure and flow rate calculated above,the PV2R12-,6/26 type pair vane pump,can be adopted, The deliveries of the,small pump and the large pump are 6mL/r and 26mL/r respectively.,3）motor,According to involved motor product contents, we can select the,Y100L-6,type motor.,2. Valves and auxiliary elements,The valves and auxiliary elements can be selected according to the system working pressure and the practical flow rate through them, see Tab.9-6 and Tab.9-7 .,3. Pipelines,According to YB 231-1970, we can choose the 15-sized cold-drawn seamless steel tube which has an inner diameter of 15mm and outer diameter of 18.2mm.,Number,Name,Flow rate estimated （L.min,-1,）,Type and specification,1,Filter,30,XU-J63X80,2,Pair vane pump,5.1+22,PV2R-6/26,3,Pressure gauge switch,-,KF3-E3B,4,Check valve,25,AF3-Ea10B,5,Pressure relief valve,5,YF3-E10B,6,Five-way, three-position solenoid valve,60,35DY-E10B,7,Check valve,60,AF3-Ea10B,8,Pressure switch,-,PF-B8L,9,Stroke valve,50,AXQ-E10B,10,Speed control valve,0.5,11,Check valve,60,12,Check valve,25,AF3-Ea10B,13,Back pressure valve,0.5,YF3-E10B,14,Hydraulic-controlled sequence valve,25,XF3-E10B,Tab.9-6 Types and specification of the components,Number,Name,Flow rate estimated （L.min,-1,）,Type and specification,1,Filter,30,XU-J63X80,2,Pair vane pump,5.1+22,PV2R-6/26,3,Soleplate block,27.1,EDKA-10,4,Pressure gauge,Y-100T,5,Pressure gauge switch,-,4K-F10D3,6,Pressure switch,-,PD-F10D3-A,7,Hydraulic-controlled sequence valve,25,X-F10D3-P/T(P1),8,Pressure relief valve,5,Y1-F10D3-P/T,9,Electromagnetic speed control check valve,-,Q1AD-F6/10D3-B,10,Check valve,25,A-F10D3-T,11,Back pressure valve,0.5,PA-Fa6/10D3-B(A),12,Check valve,25,A-F10D3-T,13,Check valve,60,A-F10D3-T,14,Five-way, three-position solenoid valve,60,35DY-E10B,Tab.9-7Types and specification of the components (modular valves),Tab.9-8 Input and output flow rate of the cylinder,4. Reservoirs,The volume of the reservoir can be estimated from , where is by experience, then：,V,can be corrected to a standard value of 250L according to GB 28761981.,9.2.5 Performance checking of this hydraulic systems,1. Pressure loss,2. Oil temperature rise,your suggestions are welcome!,The End,
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