Benefits of the motor
The MW motor itself features high-capacity bearing supports - a more compact assembly if external bearings support the load. Integrated static or dynamic brakes - or both - add to the compactness of the direct-drive motor.
The bearing support is designed to accommodate the wide variations of loads and orientations encountered in the field applications. This is especially important as machine weights and speeds increase.
The motor's Dyna+ brake is integrated around the bearing support and can perform three braking functions - parking, emergency, service. This feature has enabled agricultural machinery manufacturers to achieve international TUV compliance for dynamic braking. The brake keeps its braking characteristics after 25,000 dynamic operations. And because the brake is continuously flushed by hydraulic oil, it maintains a constant temperature. Again, a single grade of hydraulic oil is used for the entire hydrostatic transmission.
Furthermore, brake torque is applied directly to the wheel rim, so torque is not transmitted through the shaft splines, thereby eliminating the potential for shaft fatigue that can occur with conventional designs. To further reduce potential maintenance, life of the brake discs exceeds that of the motor. So the downtime otherwise needed to replace brake disks is eliminated.
Finally, the external design of bearing supports and integral brakes prevents any fibrous material from the field from wrapping around the wheel shaft, which otherwise could damage the motor's seal.
Electronic transmission control
For traditional equipment designs, the MW motors can be used with manual control pumps. In such cases, speed control will occur in steps - operation similar to that of three- or four-speed transmissions. This characteristic is typical of cam lobe motor technology. However, leading tractor manufacturers have already initiated a trend in agricultural machinery - continuously variable transmissions (CVTs).
Operators have become accustomed to greater convenience, easier use, and less operator fatigue offered by CVTs. And managers and operators alike understand the benefits that electronically managed transmissions bring to their businesses in terms of overall man-machine productivity.
Consequently, what they have come to expect in tractors, they also want in more specialized self-propelled agricultural machinery. Electronics offer great flexibility in customizing machines. From identical hardware, one can easily achieve completely different machine performance and behavior, just by adjusting control parameters or by reprogramming on-board software functions.
Electronics improve the vehicle safety thanks to continuous monitoring and safety programs. electronics also protect the machine from improper use that could damage or destroy sensitive components. Fast on line diagnostic programs help solve any issues in an efficient and professional manner.
On-board computers and software can be specifically designed to control hydrostatic transmissions that use cam lobe motors. Moreover, the controls can simultaneously manage the diesel engine, pump displacement, and displacement of each wheel motor. This allows incorporating useful automatic functions, such as:
* automatic speed shift with continuously variable speed from 0 to 65 Km/hr, which ensures the best transmission configuration under any circumstance,
* dynamic braking management, which can vary the ratio between hydrostatic and mechanical braking, and
* traction control management to achieve independent wheel-to-wheel drive control.
On-board electronics can interface with any cabin controls, such as a brake pedal, joysticks or both, and communicate through CAN bus. Electrically controlled Series SA pumps contain a non-contact sensor that provides continuous output of the the swashplate position. This allows closed-loop pressure and flow control. The pump also achieves fast response - a 75-cc/rev pump can go from neutral to full stroke in 200 msec.
Such performance is key to an efficient CVT. The instant the on-board computer executes a command to change motors displacement, it simultaneously executes a command to change pump displacement accordingly, so vehicle speed does not change.
For more information, contact Poclain Hydraulics, Sturtevant, Wis., at (262) 321-0676, or visit www.poclain-hydraulics.com.