6. Hydraulic Cylinders Construction & design features of hydraulic cylinders Hydraulic cylinder mountings Load-carrying capacity, speed, & power Operation & features of double-rod cylinders Max. pressure developed by cushions Telescoping cylinders Hydraulic shock absorbers Analysis of hydraulic cylinder piston rod forces -1-
유압액츄에이터 -2-
액츄에이터 (Actuator) 의기능상분류 실린더 Linear Actuator 피스톤형램형 액츄에이터 기어모터 모터 Rotary Actuator 베인모터 Continuous Rotation 피스톤모터요동형모터 Limited Rotation -3-
선형액츄에이터 (Linear Actuators) 의응용 지게차 Motion Simulator Press 비행기조종익 Robot -4-
Rough terrain forklift driven by hydraulic cylinders -5-
유압실린더의종류 단동형 (Single acting) 복동형 (Double acting) 플런저램형 ( 단동식 ) 피스톤형 ( 단동식 ) 단로드형 (Single rod) 양로드형 (Double rod) 단로드형 ( 복동식 ) 양로드형 ( 복동식 ) 축심고정형 / 축심회전형 foot type flange type trunnion type clevis type 속도는일반적으로 10m/min 이내, 5m/min 이상이면쿠션장치필요 -6-
Double-acting Cylinder Design -7-
Cylinder Construction -8-
Cylinder Selection -9-
Various Cylinder Mounting -10-
Universal Alignment Mounting Accessory Benefits Freer range of mounting positions Reduced cylinder binding and side loading Allowance for universal swivel Reduced d bearing and tube wear Elimination of piston blow-by caused by misalignment -11-
Typical Mechanical Linkages -12-
Cylinder Force, Velocity, and Power F = ext p Ap F ret = p ( Ap Ar ) Qin vext = Qin A vret = p A A p r -13-
Special Cylinders Double-rod Cylinder This is typically used when the same task is to be performed at either end. Telescopic Cylinder They are used where long work strokes are required but the full retraction length must be minimized. High lift fork truck -14-
Cylinder loading through mechanical linkages First-class Lever System Counterclockwise moment = clockwise moment Fixed hinge Fcyl ( L1cos θ ) = Fload ( L2cos θ ) L2 Fcyl = Fload L 1 Clevis mount F ( L cosθ cos φ) F cyl cyl 1 = F ( L cos θ ) = load 2 L2 cos F L1 φ load -15-
Cylinder loading through mechanical linkages Second-class Lever System Counterclockwise moment = clockwise moment Clevis mount F cos φ ( L + L )cos θ = F ( L cos θ ) F cyl cyl = 1 2 1 2 load 2 L2 F ( L + L )cos φ load Using a second-class lever rather than a first-class lever reduces the required cylinder piston area for a given application. -16-
Cylinder loading through mechanical linkages Third-class Lever System Counterclockwise moment = clockwise moment Clevis mount Fcyl cos φ( L2)cos θ = Fload( L1+ L2)cosθ L1+ L2 Fcyl = cos Fload L2 φ The third-class lever system can produce a load stroke that is greater than the cylinder stroke, at the expense of requiring a large cylinder diameter. -17-
Hydraulic Excavator -18-
건설작업용유압굴삭기 -19-
Operation of cylinder cushions -20-
Cylinder Cushions -21-
Example: Cylinder cushion problem Q D D S pump piston cushion cushion = 18.2 gpm Wcylinder = 1500 lb = 3in Prelief = 750 psi = 1in C friction = 0.12 = 0.75in -22-
Hydraulic Shock Absorber -23-
Crane Applications of Hydraulic Shock Absorbers -24-
Automotive Application -25-
예제 1: 실린더구동시스템 단로드형복동실린더를이용하여테이블을구동하고자한다. 피스톤직경은 150mm, 로드직경은 85mm이다. 피스톤속도 12m/min, 가속시간은 0.4s 이다. 2 실린더배압은 5 kgf / cm 이다. 피스톤행정은 1000mm이다테이블의중량은 1 ton, 마찰계수는 0.22 이다. 실린더의압력효율은 90% 이다. 위의조건에서테이블을전진시키는데필요한압력과유량을구하라. p, Q (1) 압력 p (2) 소요유량 Q 2 [ 답 ] (1) 5.48 kgf / cm (2) 211.9 l/min table -26-
예제 2: 실린더구동시스템 압력보상밸브를설치한 meter-in 회로를이용하여실린더의속도를 f = 100 N 제어하는시스템이있다. F = 6000 N 피스톤직경은 60mm, 로드직경은 25mm이다. 피스톤부하와마찰력의크기는회로도와같다. Q 1 Q 2 v = 600 mm/s 펌프의용량은 20 ml/rad, 회전수는 C 1000rev/min 이다. PC 펌프의체적효율은 92%, 기계효율은 to rest of 80% 이다. A circuit B 전진동작의정상상태에서, (1) 펌프구동에필요한동력 L in 과 (2) 회로의전효율 η 를구하라. C =20 η p ml/rad n p =1000rev/min Q 3 set at 150bars Q e [ 답 ] (1) 39.4 KW (2) 9 % -27-
Basic Modeling of Dynamic Cylinder Generalized Flow - Continuity equation dv1 0 = + dt V1 β dp dt 1 Q1 0 0 dv dt e V2 + β dp dt 2 2 Q 2 = e + 부호를그림과같이설정하고, 위의식을단순화함. Q 1 = A u 1 + V1 β e dp dt 1 Q 2 = A u 2 + V2 β e dp dt 2 Equation of motion dv P A1 P2 A2 = m + bv + dt f L Q Q 1 2 P P 1 2 V 2 1 1 V load mass m A 1 A 2 v f L -28-
Report Text Problems 6-17 6-26 Due date: 2 주후 -29-