New Technology for Powershift Transmissions in Hydrostatik Driven Wheel Excavators and Wheel Loaders

Hydrostatic drives are winning ever-greater preference in fast-moving construction machines vith speeds approaching 40 km/h and a high proportion of reverse-gear operation. A very important precondition to achieving optimum, effective technical solutions is the cooperation of engine, hydrostatic system, multi-ratio powershift transmissions and axles as a complete drive system. The function and complexity of open and closed-loop control systems are also of major influence.

Operation of the vehicle must be made simpler for the driver while improving driving comfort, and the speed with which the drive system responds to the drivers commands must be increased. For this to be achieved, the way in which drive power is utilized under constantly changing operational conditions must involve a high degree of automated functions in addition to the manual commands.

To meet these demands a new design concept for 2-speed powershift transmissions has been developed with the 2 HL 100 and 2 HL 110, for applications primarily in wheel excavators from 10 to 22 metric tons service weight and in wheel loaders up to 12 metric tons. Design considerations essentially concentrated on the following requirements:

• Powershift transmissions
• Using the powershift clutches as auxiliary and parking brakes, thus obviating the need for a separate multi-disc safety brake
• Higher power-to-weight ratio and improved technology
• Rating and design as a standard transmission for use in open and closed hydraulic circuits
• Improved efficiency
• Improved driving comfort and shift quality
• Independent lubrication of the transmission
• Hydraulic or electrical overspeed protection for the hydraulic motor
• Reducing transmission noise
• Standard control block containing the shift and brake valves for the transmission
• Useable with single and dual circuit braking systems