H. V \ ^ ^^ SOCIETY OF AUTOMOTIVE ENGINEERS, INC. 485 Lexington Avenue, New York, N. Y. 10017 Electric Controls for Powershift Transmissions R. L. Black R. H. Schaefer Allison Division of General Motors SOCIETY OF AUTOMOTIVE ENGINEERS Earthmoving Industry Conference Central Illinois Section Peoria, Illinois April 9-10, 1968 680261 Downloaded from SAE International by North Carolina State Univ, Sunday, September 16, 2018680261 Electric Controls for PovN^ershift Transmissions R. L. Black R. H. Schaefer Allison Division of General Motors During the past twenty years, a great many charges have been made inthedes^n concepts of heavy-duty vehicles. Some of the most sig­ nificant changes have been in the following areas: All vehicles have increased in size; the multiple power principle is used in scrapers; and the articulated concept is being applied to material-handling vehicles. For example, in the vehicle growth area, the payload of earth- movii^ dumptrucks has been increased to 120 tons; the bowl capacity of scrapers has been expanded to 50 yards; the capacity of loaders has been increased to 15 yards. In scraper applications the use of two or even three engines (multiple power principle) has become very popular. Additional power packages provide economical means of getting the extra power needed for faster loading and increased gradeability. The articulation con­ cept has provided many different vehicles with vastly improved maneuverability. This con­ cept has found wide acceptance in scrapers and loaders, and now the principle is beii^ applied to trucks. ABSTRACT In the past twenty years there have been extensive changes in the design concepts of heavy-duty vehicles. For instance, vehicle size has been increased, some vehicles are articulated, and some are multi-powered. These new vehicle designs with their complex geometry and often remotely-located power plants have made the rai^e selection of the Powershift transmission difficult. Mechani­ cal shift control systems have shown certain limitationsin controllii^the new vehicles and are being replaced with other system types which are controlled by air, hydraulics, or electricity. A new electric shift control system is pre­ sented in this paper. This control is easily adaptable to the new vehicle concepts and offers the additional advantages of shift in- hibitii^ and increased transmission dura­ bility. Because of its flexibility and built-in safeguards, this system offers many advan­ tages that should lead to its wide acceptance in future vehicle designs. Downloaded from SAE International by North Carolina State Univ, Sunday, September 16, 2018TYPICAL MECHANICAl LINKAGE | \ . \ .-■ .-- -Vf Figure 1 Figure 2 These changes in heavy-duty vehicle de­ sign concepts — because of vehicle geometry, location of driver and transmission, etc. — make it increasii^ly difficult for the vehicle manufacturer to adapt a rar^e selection con­ trol system. By virtue of the increases in vehicle size, drivers are being moved further away from the transmissions. See Figure 1. This increased distance makes the mechanical shift linkage more lei^hy and complex. From Figure 2 it can be seen that there may be several dis­ advantages in a mechanical shift linkage sys­ tem when applied to larger vehicles. • Exposure to ice, mud, rocks, etc., may interfere with movement or cause damage. • Increased complexity makes it more difficult to maintain proper adjustment. • Increased number of parts makes it more difficult to control lost motion and deflection in the system. Any of these conditions may cause prob­ lems. Ice, mud, rocks, etc., produce the most common problem — inability to shift. Misadjustment of linkage can result in the Powershift transmission operating in a range other than that indicated on the shift tower. Linkage deflection is the most serious be­ cause it may result in the manual range selec­ tion valve getting i