1. Basic Definition
The BM6 series is a domestically produced low-speed high-torque cycloidal hydraulic motor adopting end-face plate flow distribution design. It serves as a counterpart to Danfoss OMS/OMT series. As a heavy-duty, large-displacement model in the BM lineup, it relies on cycloid pin gear meshing and end-face oil distribution to deliver high torque output, which can directly drive loads without additional reduction gears.
2. Core Structure & Working Principle
2.1 Key Components
It consists of a front cover, double-row tapered roller bearings, a connecting shaft, a meshing pair of 6-tooth cycloidal rotor and 7-tooth stator, a valve plate, preload compensation springs, an output shaft and a housing.
2.2 Operating Mechanism
The meshing of the 6-tooth rotor and 7-tooth stator forms 7 sealed volume chambers. Synchronously rotating with the rotor, the valve plate switches oil passages. High-pressure hydraulic oil drives the rotor to rotate both rotationally and revolutionarily, and the rotational torque is transmitted to the output shaft via the connecting shaft. The end-face flow distribution structure can automatically compensate for wear on the flow distribution pair, maintaining high volumetric efficiency over long service periods.
3. Structural Advantages
1. End-face plate flow distribution: Ensures ultra-smooth low-speed operation and high volumetric efficiency, with automatic wear compensation to greatly extend service life.
2. Heavy-duty bearing configuration: Equipped with double-row tapered roller bearings to withstand heavy radial loads, suitable for heavy-load and shock-prone working conditions.
3. High backpressure-resistant sealing: Special rotary shaft seals allow a maximum backpressure of 10 MPa; an external drain port is required for stable operation under high backpressure.
4. Modular mounting: Compatible with multiple flange types, splined or parallel-key output shafts, offering excellent interchangeability for replacement.
5. Higher torque rating than BM5: Produces larger output torque under identical pressure, making it more suitable for heavy-duty applications.
4. Model Naming Convention
Take the format BM6-XXX-shaft type-flange-oil port for breakdown:
- BM: General code for cycloidal hydraulic motors
- 6: Code for the 6th series, heavy-duty specification with end-face plate flow distribution
- XXX: Displacement code (e.g. 195/390/800/985, unit: mL/r)
- Suffixes in sequence: output shaft form (P for parallel key / H2 for spline), mounting flange standard, thread specification of inlet & outlet ports
5. Main Technical Parameter Range
5.1 Displacement Coverage
195~1187 mL/r, mainstream specifications: 195, 245, 310, 390, 490, 630, 800, 985, 1000, 1250 mL/r
5.2 Pressure Specifications
- Continuous operating pressure difference: 14~16 MPa; intermittent peak pressure difference: 20.5~31 MPa
- Maximum inlet pressure: 20.5 MPa for continuous operation, 31 MPa for intermittent operation
5.3 Rotational Speed & Torque
- Continuous rotating speed: 5~750 rpm (the upper speed limit decreases as displacement rises)
- Continuous torque: 575~2650 N·m, with short-term peak torque up to around 40% higher
5.4 General Application Requirements
- Recommended medium: No.46 / No.68 anti-wear hydraulic oil, operating oil temperature ≤ 80℃
- Oil cleanliness: ISO 18/13 or higher
- Optimal working range: 1/3~2/3 of rated parameters; long-term full-load operation with maximum pressure and maximum speed is prohibited
6. Typical Application Scenarios
Construction Machinery
Travel & slewing drives of mini excavators, skid steer loaders, aerial work platforms, drilling rigs, snow sweepers, hydraulic winches
Agricultural & Fishery Equipment
Harvesters, tractor accessory drives, marine anchor winches, fishing net winding mechanisms
Industrial Equipment
Plasticizing & mold-adjusting units of injection molding machines, mine conveyors, shearer traction systems, machine tool feed spindles, hoisting winches, light port handling equipment
7. Installation & Replacement Guidelines
1. Two mainstream flange types are available: SAE-C 4-hole flange and domestic standard 4-M12 square flange with positioning shoulder.
2. Common output shafts: φ63 parallel key, 6×45 rectangular spline.
3. For series circuits or backpressure exceeding 5 MPa, a G3/8 external drain port must be connected to avoid seal damage caused by internal overpressure.
4. Run new motors in at 40% of rated pressure for 1 hour before full-load operation.
