This document is a shop manual for the Komatsu PC20MR-2 mini hydraulic excavator, covering its structure, function, maintenance, testing, and assembly.
Function Description
The Komatsu PC20MR-2 is a mini hydraulic excavator designed for various construction and excavation tasks. It features a compact design, making it suitable for work in confined spaces. The machine is equipped with a work equipment that includes a boom cylinder, allowing for digging, dumping, and other earthmoving operations. It also has a blade for leveling and backfilling. The hydraulic system provides power for the work equipment, travel, and swing functions, utilizing a variable displacement piston pump for the main hydraulic functions and a gear pump for auxiliary functions. The control system is hydraulic assist, ensuring smooth and precise operation.
Important Technical Specifications
Model and Serial Number:
- Machine Model: PC20MR-2
- Serial Number: 15001 and up
Dimensions and Weight:
- Operating Weight: 2,220 kg (Canopy specification), 2,385 kg (Cab specification). Values in brackets [ ] are for rubber shoe specification, while values in parentheses ( ) are for steel shoe specification.
- Overall Length (for transport): 3,810 mm
- Overall Height (for transport): 2,520 mm [2,515 mm]
- Overall Width: 1,450 mm
- Shoe Width: 250 mm
- Tail Swing Radius: 805 mm (Canopy), 865 mm (Cab)
- Minimum Ground Clearance: 285 mm [280 mm]
- Overall Length of Track: 1,880 mm
- Distance between Tumbler Centers: 1,440 mm
- Track Gauge: 1,200 mm
- Blade Width x Height: 1,450 x 300 mm
- Machine Cab Height: 1,380 mm
Engine:
- Model: Komatsu 3D76E-5N Diesel engine
- Type: 4-cycle, water-cooled, in-line direct injection type, swirl chamber type
- No. of Cylinders - Bore x Stroke: 3 - 76 x 82 mm
- Piston Displacement: 1.115 l {1,115 cc}
- Rated Engine Output: 15.5 kW {20.8 HP} / 2,500 rpm
- Maximum Torque: 66.7 Nm {6.8 kgm} / 1,600 rpm
- High Idling Speed: 2,680 rpm
- Low Idling Speed: 1,450 rpm
- Minimum Fuel Consumption Ratio: 265 g/kWh {198 g/HPh}
Performance:
- Bucket Capacity: 0.066 m³
- Max. Digging Depth: 2,350 mm
- Max. Vertical Wall Depth: 1,950 mm
- Max. Digging Reach: 4,300 mm
- Max. Reach at Ground Level: 4,170 mm
- Max. Digging Height: 4,100 mm
- Max. Dumping Height: 2,820 mm
- Bucket Offset: 525 mm (L.H.), 770 mm (R.H.)
- Max. Blade Lifting Height: 340 mm
- Max. Blade Lowering Depth: 230 mm
- Max. Digging Force (Bucket): 18.8 kN {1,920 kg}
- Continuous Swing Speed: 8.9 rpm
- Swing Max. Slope Angle: 19.0 deg.
- Travel Speed (Low / High): 2.8 / 4.6 km/h
- Gradeability: 30 deg.
- Ground Pressure: 27.3 kPa {0.28 kg/cm²} [28.5 kPa {0.29 kg/cm²}] (Rubber shoe), 29.3 kPa {0.30 kg/cm²} [30.5 kPa {0.31 kg/cm²}] (Steel shoe)
Hydraulic System:
- Hydraulic Pump: Variable displacement piston type x 1, gear type x 1 (Total capacity: 22 + 6.4 cm³/rev)
- Set Pressure (Travel, Work Equipment): 24.5 MPa {250 kg/cm²}
- Set Pressure (Swing): 16.2 MPa {165 kg/cm²}
- Set Pressure (Blade): 21.6 MPa {220 kg/cm²}
- Control Valve: 8-spool type x 1, Hydraulic assist type
- Travel Motor: Variable-displacement piston motor (with counterbalance valve, parking brake) x 2
- Swing Motor: Fixed-displacement piston motor (with brake valve, swing shaft brake) x 1
- Hydraulic Tank: Box-shaped, open type
- Hydraulic Oil Filter: Tank return side
- Hydraulic Oil Cooler: Air cooled (Drawn-CUP)
- Boom Cylinder: Double acting piston, Ø70 mm (inside diameter), Ø40 mm (piston rod outside diameter), 454 mm (stroke), 1,187 mm (max. distance between pins), 733 mm (min. distance between pins)
Electrical System:
- Starting Motor: 12V, 1.4 kW
- Alternator: 12V, 40A
- Battery: 12V, 45Ah x 1 (50B24L) (5-hour rate)
- Radiator Core Type: AL louver type fin
Undercarriage:
- Carrier Roller: 2 on each side
- Track Roller: 3 on each side
- Track Shoe (Rubber Shoe): Unit-type rubber crawler
- Track Shoe (Steel Shoe): Assembly-type double grouser: 44 each side
Usage Features
The PC20MR-2 is designed for ease of operation and maneuverability. Its compact dimensions and tail swing radius allow it to operate effectively in tight job sites. The hydraulic assist control system provides responsive and smooth control of the work equipment, enhancing operator comfort and precision. The machine's travel speed, with both low and high settings, allows for efficient movement across different terrains. The blade provides versatility for grading and backfilling tasks, complementing its primary excavation functions. The robust undercarriage, available with either rubber or steel shoes, offers stability and traction.
Maintenance Features
The manual emphasizes the importance of proper service and repair for safe operation. It outlines various safety precautions to be followed during maintenance, including wearing appropriate personal protective equipment, ensuring the work area is clean and free of hazards, and using correct tools and lifting equipment.
Key maintenance aspects highlighted:
- Tightening Torques: Specific tightening torques are provided for various bolts, nuts, flared nuts, and O-ring boss piping joints to ensure proper assembly and prevent loosening.
- Coating Materials: A list of recommended coating materials, such as adhesives, gasket sealants, and greases, is provided for disassembly and assembly procedures.
- Hydraulic System Maintenance: Instructions for releasing residual pressure from the hydraulic tank before disconnecting hoses are given, along with precautions for handling hydraulic oil.
- Component Handling: Heavy parts (25 kg or more) are identified with a symbol, and instructions for safe hoisting using wire ropes are detailed, including allowable load values and proper slinging techniques.
- Electrical System: A wire code table is included to aid in understanding wiring diagrams for electrical system maintenance.
- General Precautions: Emphasizes reading the Operation and Maintenance Manual, using "UNDER REPAIR" signs, and ensuring all parts are reassembled in their original places with new damaged parts.
- Fluid Management: Instructions for draining oil and water, and preventing spills, are provided.
- Engine Maintenance: The manual refers to the 68E-88E Series Engine Shop Manual for detailed engine maintenance procedures, indicating that the PC20MR-2 uses the 3D76E-5N engine.
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