The A6VG is a swashplate-type axial piston variable motor designed for hydrostatic transmissions in closed-circuit applications. Engineered for high-power density, the unit features a rotating group consisting of a cylinder block with nine pistons, allowing for high-speed operation and significant torque output. The variable displacement capability is achieved through an integrated hydraulic control system that adjusts the swashplate angle, enabling a wide control range from maximum displacement to zero. This motor is particularly suited for heavy-duty mobile machinery, such as excavators, forestry equipment, and agricultural harvesters, where precise speed control and high starting torque are critical operational requirements.
Technical Specifications and Performance Parameters
The following table outlines the standard performance metrics for the A6VG series. These values are based on mineral oil with a viscosity of 30 mm²/s at an operating temperature of 50°C.
| Parameter | Unit | Typical Value |
|---|---|---|
| Displacement (Max) | cm³/rev | 28 to 250 |
| Nominal Pressure | bar | 400 |
| Peak Pressure | bar | 450 |
| Max Speed (at Vg max) | rpm | 3000 – 4500 |
| Mounting Interface | – | ISO 3019-2 |
| Fluid Compatibility | – | HLP Mineral Oil / HFD |
Fluid Cleanliness and Filtration Requirements
The operational longevity of the A6VG is fundamentally dependent on the cleanliness of the hydraulic medium. Due to the tight tolerances between the piston-to-bore interface and the valve plate-to-cylinder block interface, particulate contamination can lead to accelerated adhesive wear and spool silting in the control valves.
To maintain the integrity of the rotating group, the system must adhere to ISO 4406 cleanliness standards. For most closed-circuit applications, a cleanliness level of 18/16/13 or better is required. Filtration should be implemented on the charge pressure circuit to ensure that fluid entering the motor meets these specifications. Failure to maintain these levels increases the risk of cavitation-induced erosion on the valve plate and scoring of the swashplate bearing surfaces.
Seal Elastomer Compatibility and Thermal Management
The A6VG is typically equipped with either Nitrile Butadiene Rubber (NBR) or Fluoroelastomer (FKM/Viton) seals, depending on the application’s thermal profile and fluid chemistry.
- NBR (Nitrile): Suitable for standard mineral-based hydraulic fluids (HLP) within a temperature range of -20°C to +80°C.
- FKM (Viton): Mandatory for applications involving synthetic ester-based fluids or high-temperature environments exceeding +80°C.
When selecting seals, engineers must account for the chemical compatibility with the specific fluid additives, as certain anti-wear (AW) and extreme-pressure (EP) additives can degrade NBR elastomers over time. Furthermore, the housing pressure must be monitored to ensure it does not exceed the shaft seal’s rating, as excessive case pressure—often caused by restricted case drain lines—will lead to premature seal extrusion and external leakage.
Control Systems and Integration
The A6VG utilizes various control interfaces, including hydraulic proportional control, electric proportional control, and pressure-dependent displacement control. Integration must comply with DIN 24340 and ISO 4401 standards for mounting patterns. When configuring the control logic, it is essential to account for the response time of the swashplate adjustment mechanism. In high-inertia loads, the use of integrated pressure relief valves or anti-cavitation valves is recommended to prevent pressure spikes during rapid deceleration phases, ensuring the motor remains within its design envelope as defined by ISO 1219-1 symbology.