The extended shaft and double-row ball bearing of Denison's M5B vane motor line provide a sturdy mounting for the cooling fan and accommodate radial and axial loading.
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Last year Denison Hydraulics expanded its vane motor line with the introduction of the M5B. One version of the new vane unit, the M5BF, is designed specifically for application in fan drive systems on off-highway equipment. The M5B, manufactured at Denison's Vierzon, France, facility, is a significant advancement in vane motor technology, particularly in terms of pressure capability, volumetric efficiency, starting torque, and noise level. The unit is rated for pressures up to 32 MPa (4650 psi), has a speed range of 100-6000 rpm, and is available with a choice of five cartridges providing displacements up to 45 cm3 /rev (2.75 in3 /rev).
The heart of the new motor is its replaceable cartridge assembly with several key design features, including a 12-vane configuration. Hydraulic pins and light springs hold the vanes radially against the cam ring contour, ensuring a seal at zero speed so that the motor can develop a high starting torque. Centrifugal force at higher speeds augments the pins and springs.
Radial grooves and holes through the vane balance radial hydraulic forces on the vanes. With the rotor and cam rings also pressure balanced, motor life is increased over the full speed range.
The use of a modified version of the M5B as a fan drive motor has been successful, particularly in Europe where more than 1500 M5BF units are now in the field. To meet the demands of this type of application, the motor has a reinforced, double-row, reversed-contact ball bearing that supports an extended tapered shaft. The fan mounts directly on the shaft and the heavy-duty bearing accommodates radial and axial loading.
The largest user in Europe to date is Volvo, which uses the new technology on its wheel loaders. One of the incentives for using a hydraulic fan drive is the need to reduce noise levels on construction equipment. For example, Volvo now offers machines that have the entire engine encapsulated. The belt that would normally drive the fan has been replaced by a hydraulic drive system.
A load-sensing piston pump on the loader drives an M5BF motor with the fan directly mounted on its shaft. The pump gets a signal from the engine computer to increase or decrease the speed of the fan motor. Oil- and water-temperature sensors and an engine speed sensor provide the appropriate signals. A major advantage of this system is that the fan only runs when cooling is needed and can stop when it is not required. Previously, the fan was directly connected to the engine with a belt and ran continuously.
Other promising potential applications of the M5BF in fan-drive systems include combine harvesters, trains, and mining machines. All of these installations can benefit from reduced engine power consumption and quieter operation.
