Basic Knowledge of Bulldozers 1 KomatsuG25(Left) & G40(Right) farm tractor a competitive demonstration event held in Manchuria in early 1930s The largest bulldozer, D575A-3, launched in 2001 The first unit of the D50-1 bulldozer produced in 1947 D80A produced in 1963 after many stringent quality control tests 2 D21 Machine weight Engine horsepower 3,940 kg 32.4 kW (44 HP) D575 Machine weight Engine horsepower 152,600 kg 858 kW (1,150 HP) 3 JCB Liebherr Ingersoll-Rand Terex Kobelco Volvo CNH Hitachi John Deere Caterpillar Komatsu Large bulldozers Large excavators Large wheel loaders Mining Large dump trucks Large motor graders Bulldozers Excavators Wheel loaders Construction Dump trucks Articulated dump trucks Motor graders Mini excavators Mini wheel loaders Utility Backhoe loaders Skid steer loaders Telescopic handlers Forestry equipment Others Recycling equipment Compactors 4 5 6 7 8 9 Outline of Structure Operation Lever, Pedal, Switch, etc Power Train Control Speed, Traction, Steering Hydraulic System for W/E Control the W/E(Blade Ripper) System Overview of the Bulldozer Machine Operation Input device Operator Fuel Dial PCCS lever PPC lever Decel pedal Break pedal PT controller Work Equipment Hyd. Pump Control valve Hyd. Actuator Blade & Ripper control Final Drive Travelling & Steering control ECM Engine Power Line Torque Converter Transmission Steering System Machine Work 13 Technical Map of Bulldozer(D21~D575A) 14 Power Line 15 History of Bulldozers power train Tier3 Generation Direct drive T/M Transfer engine power to T/M directly by clutch disc & plate engagement None (Improve Engine toughness , controllability) Torque Flow T/M Transfer engine power to T/M indirectly through Torque converter oil Middle & Large class (Improve power transfer efficiency) Hydro Shift T/M Transfer engine power to T/M directly through damper. Vibration & shock are absorbed and transferred to T/M. Only D21 (Improve controllability--- Step less transmission) Hydro Static T/M (HST) Engine power rotate Hyd pump and power transfer to Hyd motor. By hyd motor rotation speed , machine can travel as stepless shift. Small Class 16 Direct drive T/M Merit ・High efficiency of power transferring Engine Main clutch Transmission Torque Flow T/M Engine Torque Converter Torque flow transmission ・Easy operation ・Less gear shift shock ・No engine stall under heavy load (load escape in T/C) ・High engine toughness under heavy load ・Easy operation ・Less gear shift shock ・High efficiency of power transferring Hydro Shift T/M Demerit ・Complicated operation ・Engine stall under heavy load (load can’t escape) ・Engine power fluctuate depend on load ・Power transfer efficiency is low ・Engine power fluctuate depend on load ・High production cost compared with direct T/M ・Engine stall under heavy load (load can’t escape in T/C) ・Engine power fluctuate depend on load Engine Damper Hydro shift T/M Hydro Static T/M (HST) Engine PTO Hyd motor Hyd pump ・Gear shift operation is not ・Power transfer efficiency is low required. ・Oil contamination control is ・No power cut by stepless T/M strictly required. ・No engine stall under load. (load escape by hyd relief) ・Max engine power can be used constantly 17 Type of Transmission & Steering system Steering : Making Difference of speed between the Left and Right trucks. Transmission Large Middle Small Small D575A D475A D375A D275AX D155AX D85EX D65EX D61EX D51EX/PX D39EX/PX D37EX/PX D31EX/PX Steering System Clutch & Brake Output for one side track is split by Clutch and is held by Brake. HSS Hydro Static Steering System Both side tracks are connected by differential gear. Hydraulic motor makes Difference of speed between both tracks via differential gear. Torque Flow Transmission HST Hydro Static Transmission Both side tracks have each set of Hydraulic Pump and motor. Each tracks are controlled individually. Power Train Skelton (Sample:D65A Torque Flow T/M) Sprocket Track Shoe Transmission Torque Converter Steering Clutch Engine Final Drive Universal Joint Steering Brake 19 Torque Converter Turbine Pump Turbine Stator Pump Rotated by oil flow comes from Pump. Change direction of return oil flow from turbine to pump. Driven by engine. It makes oil flow. Stator Output Shaft Torque Converter Cut-away model Pump Turbine From Engine (Input) To T/M (Output) Stator Lock-Up Clutch Stator Clutch 21 Ref. : Performance Curve of Torque Converter *with Fixed Stator Traction Output Engine Output Torque Ratio Convert to the Heat Efficiency Traction Output Feature of Torque conveter -No Engine stall (Fluid Coupling) -Torque multiplied effects The Traction force is increased when vehicle speed is decreased due to external load. -Low efficiency during high speed travel(fixed stator) (Improvement of efficiency by lock-up, stator control) Speed Ratio 22 Disc Clutch ディスククラッチ From control valve 1. 2. 3. 4. 5. 6. Clutch housing Clutch piston Disc Plate Return spring Pin A. Sun Gear B. Planetary Pinion C. Ring Gear D. Carrier Clutch “Disengaged” Clockwise rotation Input in Sun Gear [A] Planetary Gear[B] start rotation toward counter clockwise Ring Gear[C] start rotation toward clockwise (Same direction as Sun gear) Clutch “Engaged” クラッチ”入”の場合 (Ring gear Fixed) Clockwise rotation Input in Sun Gear [A] Planetary Gear[B] start rotation toward counter clockwise Since Ring Gear[C] is not rotated, Planetary Gear [B] rotate Carrier [D] toward clockwise (Same direction as Sun gear) Inside of Disc [3] and outside of Ring Gear [C] are meshed each other, and rotate together. Plate [4] is fixed in Clutch Housing [1] by Pin [6], slightly move only axial direction. 23 Planetary Type Transmission Directional Clutches Speed Clutches D155A-2 T/M Structure (Power transmission route) 3rd 2nd 1st Double Structure Input Shaft To PTO To Output Shaft Forward/Reverse Group Either “F” or “R” clutch ON Power from Input shaft is output from “Carrier” -> Input to Carrier of 3rd clutch pack. Speed shift Group ECMV installed machine has possibility of occurrence of “Double clutch engagement. And cause serious T/M damage Either 3rd, 2nd, 1st clutch is engaged, speed is reduced depend on gear shift. -> Power is transferred to output shaft. 25 Modulating Valve Function When shift F&R, 1st to 2nd , prevent sudden engagement of clutch, moderate shift shock. Comfort riding, improve durability of power train system Clutch pressure [Graph] Relation of time progress and clutch pressure increasing A: Filling time B: Build up time C: Modulating time Time (Sec) 26 Control of Clutch engaging pressure Type Outline Merit Demerit Modulating Valve ECMV (Mechanical Type) (Electric control type) It consists of a modulating valve and a speed valve. By mechanical operation, a modulating valve raises clutch oil pressure gradually at the time of a gear shift. The transmission has only one modulating valve. The speed valve changes the direction of oil flow and then it changes speed range and F-R.(directional valve) (Electronic Control Modulation Valve) -Each clutch pack has independent ECMV. -Output oil pressure is controlled proportionally to solenoid current. -the Oil pressure is increase gradually by control of the PT controller. -Clutch oil pressure is detected by the fill-switch. -Simple structure -No risk for double engagement -Individual control for each clutch pack is possible. -The smooth engaging of clutch by pressure control. -Smooth speed shifting by cooperative control for each ECMV. (Power transmitting is not cut during shifting) - Individual pressure control for each clutch is impossible - Power transmitting is cut a momentarily when shifting. -Risk of double engagement due to trouble of the fill switch. - Oil management is severe. 27 HST(Hydro Static Transmission) Ex) D31-22 There are 2 sets of Hydraulic pump & motor. Capacity of Pump & Motor are controlled individually Left and Right. *Include Steering function. The basic structure of the HST Bulldozer is common. -Size of pump and motor. -Type of changing capacity in motor (3 stage type or variable). are different depend on model and generation. Type of Steering System Clutch & Brake ・・・ Middle & Large Size Bulldozers, Old machines Disengage the clutch of turning side, power transmit to opposite side. After clutch disengaged, engage brake disc & plate, sharp turn is possible. Spin turn is not possible. There are 2 categories by steering brake type. ・Multiple disc clutch + Band brake ・Multiple disc clutch + Multiple disc brake HSS(Hydro-Static Steering) ・・・Small & Middle Size (-EX, -AX) No clutch structure, only brake disc & plate are installed for stopping machine. Steering for LHS&RHS is controlled by rotating direction of HSS motor. Spin turn and dozing during steering is possible. HST(Hydro-Static Transmission) ・・・Small size bulldozers (-EX) As same as Hyd excavators, steering is controlled by rotation difference of both LHS&RHS travel motors. Spin turn and dozing during steering is possible. 29 Steering Clutch & Brake Bevel gear shaft Output shaft LHS Steering Brake LHS Steering Clutch Bevel gear Output shaft RHS Steering Clutch RHS Steering Brake HSS System Hydro- Static Steering System HSS (Hydro Static Steering System) HSS Motor The idler for left axes (inverse rotation) Sun Gear (Input) Carrier (Input) Ring Gear(Output) : HSS Motor : Bevel Gear : Final drive Input Bevel gear shaft Output 32 HSS control system The steering spool in the control valve is driven by the EPC output pressure. Both side EPC valve is controlled by command current from T/M, Steering controller. HSS pump pressure oil flows to HSS motor and HSS gear train makes LH steering, RH steering or counter rotation. 33 Final Drive 34 Final Drive (Ex. D375A-6) [ 16 ] [ 26 ] [ 68 ] [ 79 ] [ 15 ] 35 Floating seal O-Ring Seal ring prevent dirt and water intrusion from outside. Sealing surface: Both seal slip each other, but oil is not leaked since both faces adhere. Seal ring Seal ring prevent oil leakage from inside of case Rotation side (sprocket) No Rotation side (Case) Notes; 1. Never adopt oil on the O-Rings when assembling 2. Never hit floating seal when installing 36 Undercarriage 37 Undercarriage 1) Track frame Track frame Oscillate type Track frame can oscillate around pivot shaft. Mainly employed for mediumand large-sized. <Features> When the track of either side rides over an obstacle, shocks are reduced. Pivot shaft Rigid type Single structure made by welding track frame and main frame together and used for small-sized models mainly. <Features> High rigidity and simple structure. Oscillatable ●Track frame Equalizer bar Pivot shaft Idler Track frame Carrier roller Track roller State after track frame is installed Sprocket Track roller guard 38 Undercarriage 2) Idler cushion Adjusting to optimum tension High tension Loose 39 Type of Sprockets Solid type Supply parts Segment type 40 Undercarriage 3) Link assembly Bushing is meshed with tooth bottom of sprocket Grease-lubricated type (Dry type) Oil-lubricated type (Wet type) The space between the pin and bushing is filled with grease for lubrication. <Features> ○Simple structure and low cost. ○If grease decreases, the bushing and pin come in contact, and that can cause elongation of the link pitch. The space between the pin and bushing is filled with oil for lubrication. <Features> ○Early wear of the pin and bushing is prevented and the link pitch is not elongated. ○Oil may leak. ○Structure is complicated and cost is higher than grease-lubricated type. PLUS Type (Parallel Link Undercarriage System) Since the pin and center bushing rotates, the outside of the bushing is worn less. <Features> ○The wear life of the bushing is elongated greatly. (The wear life of the bushing is elongated to about twice, although that depends on the jobsite) ○R & M cost can be reduced. 41 Hydraulic System for Working Equipment HSS motor Type of Valves Present models of bulldozers employ CLSS system Small Class Feature Middle & Large Class -There are many type of valves Only D475 -The CB valve is used only for the bulldozer. -Steering priority valve is installed (The machine with HSS system) -Hydraulic drive fan system is employed widely in bulldozers. Small Class : Fan system is included with W/E system Middle & Large : Set of Pump & motor are installed : DB valve : CB valve : CA valve