1、Hydraulic and pneumatic pressure transmission9.1 The Approach for Design of Hydrostatic Circuits9.2 A Design Example of Hydraulic SystemsChapter list Introduction The design of hydrostatic transmission systems is an important part of the whole mechanical design and also a summarizing and comprehensi
2、ve 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 requirements9.1.2 Analy
3、sis for working conditions and determination of main parameters9.1.3 Determination of hydraulic system diagram9.1.4 Calculation and selection of hydraulic components9.1.5 Performance check for a hydraulic system designed9.1.6 Drawing of working diagrams and technical documentsFig.9-1 General design
4、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
5、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 effic
6、iency,safety,reliability,cost,etc.1.Analysis of working conditions 1 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.dynamic parameters(Fig.9-2a)Includes tw
7、o parts ofmovement parameters(Fig.9-2b)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
8、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 beLfaFFFF(9-1)1)The working load LF2)The
9、 friction resistance force fFfNFf F(9-2)3)The inertia load aF Besides three loads mentioned above,an actuator stands also viscosity resistance force,sealed resistance force and back pressure resistance etc.(9-3)aGvFmagt2.Determination of main parameters The working pressure for actuators can be sele
10、cted 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:minminqvAminminMqVFor cylinders For moto
11、rs minminminmin(2/60)vnorTab.9-1 Working pressure selected for an actuator according to loadLoadF（N）50000 Working pressure p（MPa）0.81 1.52 2.53 3445 57 Tab.9-2 Working pressure selection for an actuator according to mainframe typeMainframe type Machine tools Agricultural machinery,small-sized engine
12、ering machinery,auxiliary devices for engineering machinery Hydraulic press,large-sized excavator,heavy machinery,lifting and conveying machinery Grin-derModular machine toolsPlaner Drawing benchWorking pressurep（MPa）235 8810 1016 2032 3.Drawing of working condition chart of the actuators After the
13、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 condit
14、ion chart of actuators 1-Startup acceleration 2-Quick feed 3-Working feed 4-Brake 9.1.3 Determination of hydraulic system diagram1.Analysis and selection of the hydraulic scheme2.Analysis and selection of the hydraulic circuits3.Determination of hydraulic system diagram9.1.4 calculation and selectio
15、n of hydraulic components1.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
16、 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 valvesTab.9-3 Experiential values of the pressure loss in the inlet oil line System configuration Overall pressure loss(MPa）Simple system with general throttle
17、 speed-regulating components and pipelines 0.20.5Complex system with speed-regulating valves and pipelines 0.51.5p3.Selection of valve arrangementsThere 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 hydr
18、aulic system designed1.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
19、,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 nq2nn()qppq （9-4）2.Checking of the temperature rise caused by heat generation according to heat balance principle,when the dim
20、ension 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,then2o3210(C)QTV（9-5）Once the checked oil temperature rise surpasses the allowable value,a proper cooler must be set in the sy
21、stem.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 com
22、ponents 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,ove
23、rall table of outsourcing parts,etc.9.2.1 Analysis of working conditions9.2.2 Determination of main parameters of the actuator9.2.3 Design of hydraulic systems9.2.4 Selection of hydraulic components9.2.5 Performance check for hydraulic systems This section is to study the hydraulic system of a singl
24、e 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 Mech
25、an-ical efficienc-y of the cylinder 3000095001005050.050.20.20.10.9mdfsf()t s2(m/min)v13(m/min)vv、2(mm)lLtNFF（）1mml()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 conditionsThe axial
26、 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 followsa9500 5N404N9.8 0.2 60vGvFmtgtfssN0.2 9500N1900NFf FfddN0.1 9500N950NFf FTab.9-4 Loads on the cylinder in
27、 each work step Working conditionLoad combinationLoad F（N）Thrust Startup 19002111Acceleration 13541504Deceleration 9501056Work feed 3095034389Rapid retract 9501056fsFFfdmFFFfdFFfdtFFFfdFFm(N)F The loads on the cylinder in each work step are listed in Tab.9-4,where the back pressure in the oil return
28、ed 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 actuator11122112m2AFA pA pA pp1）system pressure3）area of cylinder2）back pressure The cylinder area c
29、an be calculated from the thrust at work feed period:Then22162m1343890.0096m96cm0.8(4)10()22FApp1411.06cm,0.7077.82cmADdD 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 are11cm,8cmDd2222212()95.00cm,44.75c
30、m44DDdAA 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 stepFig.9-5 Working conditions diagram 9.2.3 Design of hydraulic systems1.Selection of hydraulic cir
31、cuits2.Design of hydraulic systems3.Selection of the hydraulic valvesFig.9-6 Principle chart of hydraulic systemFig.9-7 Principle chatr of hydraulic system with modular valves9.2.4 Selection of hydraulic components1.Pumps1）pressure2）flow rate The maximum flow rate provided by the two pumps is 25.13L
32、/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 isp1.1 25.13L/min27.64L/minq 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
33、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 elementsThe valves and auxiliary elements can be selected according to the system working pressure and the practical flow rate through the
34、m,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.NumberNameFlow rate estimated（L.min-1）Type and specification1Filter 30XU-J63X80 2Pair vane pump5.1+22PV2R-6/263Pre
35、ssure gauge switch-KF3-E3B4Check valve 25AF3-Ea10B 5Pressure relief valve5YF3-E10B 6Five-way,three-position solenoid valve6035DY-E10B 7Check valve 60AF3-Ea10B 8Pressure switch-PF-B8L 9Stroke valve50AXQ-E10B 10Speed control valve0.511Check valve 6012Check valve 25AF3-Ea10B 13Back pressure valve0.5YF3
36、-E10B 14Hydraulic-controlled sequence valve 25XF3-E10B Tab.9-6 Types and specification of the components NumberNameFlow rate estimated（L.min-1）Type and specification1Filter 30XU-J63X80 2Pair vane pump5.1+22PV2R-6/263Soleplate block 27.1EDKA-10 4Pressure gauge Y-100T 5Pressure gauge switch-4K-F10D3 6
37、Pressure switch-PD-F10D3-A 7Hydraulic-controlled sequence valve 25X-F10D3-P/T(P1)8Pressure relief valve5Y1-F10D3-P/T 9Electromagnetic speed control check valve-Q1AD-F6/10D3-B 10Check valve 25A-F10D3-T 11Back pressure valve0.5PA-Fa6/10D3-B(A)12Check valve 25A-F10D3-T 13Check valve 60A-F10D3-T 14Five-
38、way,three-position solenoid valve6035DY-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.NoImageNoImagep727.1L189.7LVq9.2.5 Performance checking of this hydraulic systems1.Pressure loss2.Oil temperature rise
