A6VE28EP1/63W-VAL020B Rexroth Motor | 450 Bar Plug-in

Product Overview

The A6VE28EP1/63W-VAL020B is a 28 cm³/rev displacement model from Bosch Rexroth’s A6VE series 63 generation of bent-axis axial tapered piston variable motors, featuring EP1 electric proportional control and an integrated plug-in design specifically engineered for direct integration into mechanical gearboxes of mobile machinery. The Rexroth identification number is 9604360.

The core design philosophy of the A6VE series is to plug the motor directly into the mechanical gearbox—the mounting flange is positioned at the center of the housing, allowing the motor to be almost fully inserted into the gearbox for maximum space savings. The motor requires no additional mounting tolerance adjustment; it simply slides into the mechanical gearbox, significantly simplifying machine layout and assembly. The A6VE series is suitable for hydrostatic drives in both open and closed circuits, with displacement infinitely variable from Vg max to Vg min = 0. The wide control range enables the variable motor to deliver both high rotational speed and high torque.

The model code breaks down as follows: A6VE identifies the A6VE series bent-axis variable plug-in motor; 28 denotes the 28 cm³/rev displacement; EP1 is the electric proportional control type (proportional solenoid controlled, displacement proportional to control current); 63W indicates series 63, with W being the shaft and mounting configuration code; VAL020B is the port configuration, control device and additional option combination code. EP1 electric proportional control achieves stepless displacement modulation through a proportional solenoid, with control current proportional to displacement—ideal for travel drive systems requiring precise speed control and power matching.

Every A6VE28EP1/63W-VAL020B unit undergoes 100% simulated operating-condition bench testing prior to shipment, covering pressure cycling, displacement response, control signal calibration and thermal shock. Plug-in interface dimensions, control signal interface and port configuration comply with Rexroth original specifications and are identical to the original Rexroth A6VE28 series, ensuring true drop-in interchangeability with zero modification to the gearbox interface or hydraulic piping required.

Technical Specifications

A6VE Series Frame Size Specifications:

• A6VE28 (This Model): Displacement 28.1 cm³/rev, nominal pressure 400 bar, max pressure 450 bar, max speed at Vg max 5,550 rpm, max speed at Vg < Vg max 8,750 rpm, max flow 156 l/min, torque at Δp=350 bar 179 N·m, weight ~16 kg

• A6VE55: Displacement 54.8 cm³/rev, nominal pressure 400 bar, max pressure 450 bar, max speed at Vg max 4,450 rpm, max speed at Vg < Vg max 7,000 rpm, max flow 244 l/min, torque at Δp=350 bar 349 N·m, weight ~26 kg

• A6VE80: Displacement 80 cm³/rev, nominal pressure 400 bar, max pressure 450 bar, max speed at Vg max 3,900 rpm, max speed at Vg < Vg max 6,150 rpm, max flow 312 l/min, torque at Δp=350 bar 509 N·m, weight ~34 kg

• A6VE107: Displacement 107 cm³/rev, nominal pressure 400 bar, max pressure 450 bar, max speed at Vg max 3,550 rpm, max speed at Vg < Vg max 5,600 rpm, max flow 380 l/min, torque at Δp=350 bar 681 N·m, weight ~47 kg

• A6VE160: Displacement 160 cm³/rev, nominal pressure 400 bar, max pressure 450 bar, max speed at Vg max 3,100 rpm, max speed at Vg < Vg max 4,900 rpm, max flow 496 l/min, torque at Δp=350 bar 1,019 N·m, weight ~64 kg

• A6VE250: Displacement 250 cm³/rev, nominal pressure 350 bar, max pressure 400 bar, max speed at Vg max 2,700 rpm, max speed at Vg < Vg max 3,600 rpm, max flow 675 l/min, torque at Δp=350 bar 1,391 N·m, weight ~90 kg

A6VE28EP1/63W-VAL020B Additional Specifications:

• Model Code: A6VE28EP1/63W-VAL020B

• Rexroth Identification Number: 9604360

• Type: Bent-axis axial tapered piston variable motor

• Maximum Displacement: 28.1 cm³/rev (1.71 in³/rev)

• Minimum Displacement: 0 cm³/rev (infinitely adjustable to zero)

• Nominal Pressure (Continuous): 400 bar (5,800 psi)

• Maximum Pressure (Intermittent): 450 bar (6,525 psi)

• Maximum Speed (Vg max): 5,550 rpm

• Maximum Speed (Vg < Vg max): 8,750 rpm

• Maximum Flow: 156 l/min

• Torque (at Δp=350 bar): 179 N·m

• Control Type: EP1 electric proportional, proportional solenoid driven, displacement proportional to control current

• Control Signal: Current control, 12V or 24V system compatible

• Rotation: Bidirectional (reversible)

• Circuit Compatibility: Open circuit / closed circuit universal

• Mounting Type: Plug-in, mounting flange positioned at center of housing for direct insertion into mechanical gearbox

• Operating Temperature Range: -40°C to +115°C

• Hydraulic Fluid: Mineral oil (ISO VG46/68), synthetic oil, water glycol

• Weight: ~16 kg (35 lbs)

• Original Design: Bosch Rexroth, Germany

Key Technical Advantages

1. Plug-In Design for Direct Integration into Gearbox

The A6VE28 features Rexroth’s unique plug-in design with the mounting flange positioned at the center of the housing, allowing the motor to be almost fully inserted into the mechanical gearbox. This architecture maximizes space savings, making it particularly suitable for travel drive gearboxes, wheel-end gearboxes and other space-constrained applications. The motor simply slides into the gearbox for assembly, requiring no complex mounting tolerance compliance, significantly reducing assembly difficulty and labor cost. The plug-in design also creates a rigid connection between motor and gearbox, improving overall drivetrain rigidity and vibration resistance.

2. EP1 Electric Proportional Control for Precise Stepless Displacement Modulation

This model is configured with EP1 electric proportional control, achieving stepless displacement modulation through a proportional solenoid. Control current is proportional to displacement, with displacement continuously variable from Vg max to Vg min = 0. Compared to hydraulic pilot control, electric proportional control offers faster response, higher control precision and easier integration with machine electronic control systems. The wide control range enables the motor to deliver both high rotational speed and high torque, enabling efficient switching between machine startup acceleration and high-speed cruising.

3. Bent-Axis Tapered Piston Design for High Starting Torque and High Power Density

The A6VE28 employs a bent-axis axial tapered piston rotary group design, with the cylinder block angled relative to the output shaft and tapered pistons transmitting torque through a thrust plate. The bent-axis architecture delivers high torque at startup with favorable starting efficiency. At Δp=350 bar pressure differential, torque reaches 179 N·m. The compact construction and weight of only about 16 kg deliver class-leading power density among variable motors of comparable displacement. Tapered pistons with precision-ground cylinder bores minimize internal leakage, maintaining high volumetric efficiency across the entire displacement range.

4. High Speed Capability and Zero Displacement Function

The A6VE28 achieves maximum speed of 5,550 rpm at maximum displacement and up to 8,750 rpm at partial displacement, leading among variable motors of comparable displacement. The zero displacement function allows the output shaft to idle, reducing hydraulic system power loss and heat generation in transport mode, further improving machine transport speed and fuel efficiency.

5. 100% Simulated Load Testing & Drop-In Interchangeability

Each A6VE28EP1/63W-VAL020B unit is bench-tested under simulated operating conditions prior to dispatch, covering pressure cycling, displacement response, control signal calibration and thermal variation. Plug-in interface dimensions, control interface and port configuration comply with Rexroth original specifications, matching the original Rexroth A6VE28 series exactly, enabling direct replacement without modification to gearbox interface or hydraulic piping.

Application Areas

The A6VE28 series variable plug-in motors are widely deployed in hydrostatic travel drive systems of mobile machinery, combined with A4VG series variable pumps in closed-circuit drivetrains:

• Excavator Travel Drives: track excavator travel gearbox integration, e.g. Volvo EC series, Caterpillar 300 series

• Wheel Loader Travel Drives: wheel-end gearbox integration

• Road Roller Travel Drives: vibratory roller travel systems

• Aerial Work Platforms: self-propelled aerial work platform drive systems

• Agriculture: tractor front axles, combine harvester travel drives

• Mining: subsurface loaders, mining truck travel drives

• Industrial: hydrostatic transmission systems requiring compact installation space

Expert Maintenance Tips

1. Control Signal Calibration and Displacement Verification: The EP1 electric proportional control requires control signal calibration after installation to confirm minimum displacement position (0 cm³/rev) and maximum displacement position match the technical manual. Control current range should be set per Rexroth technical manual to ensure linear proportional relationship between displacement and control current. If displacement response exhibits lag or drift, inspect proportional solenoid operating condition, control spool for sticking and pilot circuit for air entrainment. Establish a displacement-current calibration curve in the machine electronic control system to ensure travel drive speed control accuracy.

2. Plug-In Interface Seal Inspection: The A6VE28 employs plug-in mounting, with the sealing surface between motor and gearbox being a potential leak point. Clean the plug-in interface mating surface before installation and inspect O-rings and seals for integrity. After insertion, confirm flange bolts are evenly tightened in a diagonal sequence to Rexroth technical manual torque values. Periodically inspect the plug-in interface for leakage, especially under frequent pressure cycling conditions.

3. Drain Line Management: The drain port must return to the reservoir independently—housing back pressure must not exceed 2 bar. For A6VE plug-in motors, the case drain port is typically located on the gearbox housing—ensure drain line diameter is sufficient and free of back pressure obstruction. The drain line end must remain submerged to prevent air ingestion. Confirm the housing is filled with clean hydraulic oil before first startup.

4. Oil Cleanliness and Temperature Control: Maintain system oil cleanliness at ISO 4406 18/16/13 or better. Case drain temperature is affected by pressure and speed and is always higher than circuit temperature—system temperature must not exceed 115°C at any point. Replace hydraulic oil and filter after the first 500 hours, then follow a 2,000-hour or annual replacement cycle. VG 46 is recommended at 60°C operating temperature.

5. Zero Displacement Function and Transport Mode Maintenance: The A6VE28’s zero displacement function significantly increases machine transport speed. In transport mode with displacement near zero, verify that the gearbox lubrication system remains operational (some gearboxes rely on motor case drain for lubrication). Inspect system pressure, flow and temperature parameters in zero displacement mode every 500 hours to confirm proper operation and gearbox lubrication.

6. Periodic Tapered Piston Group and Bent-Axis Bearing Inspection: The A6VE28’s tapered pistons, piston rings and bent-axis bearings are primary wear components. Inspect tapered piston-to-cylinder bore clearance, piston ring wear and bent-axis bearing clearance every 2,000 hours. Abnormal efficiency loss, noise or vibration requires immediate shutdown and service. Use Rexroth original specification parts when replacing piston groups to ensure fit accuracy and assembly torque per technical manual requirements.