Gear Chain Industrial B.V.
a Tarasconweg 13
5627 GB Eindhoven
The Netherlands
t +31 (0) 40 2906801
f +31 (0) 40 2906804

GCI's Servo-Actuation System

For many years already Gear Chain Industrial is active in the field of advanced CVT actuation systems. Various concepts have been devised and tested, with low energy consumption always being the highest priority.

Conventional CVT actuation systems for passenger vehicles rely on a large hydraulic pump, which is permanently connected to the engine crankshaft. All hydraulic components are supplied with sufficient oil pressure and flow by means of this pump, under all circumstances. However, since the engine speed rarely matches the required oil flow of the transmission, the pump is over-dimensioned in such a way that it supplies enough flow even at very low RPM. The resulting excess of pressurized oil flow is consequently returned to the oil reservoir, without having had any actual function. So, this concept suffers from a principal disadvantage resulting in too much fuel consumption. On a typical driving cycle, around 3-4 % of total fuel usage is needed for driving this particular pump.

A second drawback is the dependency of the transmission: the combustion engine has to run for the CVT to function. With the advent of new driving modes, such as “Stop-Start”, “Sailing” and “Electric-Only”, it is of crucial importance that the CVT can stand on its own whilst the engine is off. Concluding, something has to change to keep up with the newest developments in automotive drive trains.

In order to mitigate the above mentioned disadvantages, engineers at Gear Chain Industrial have invented and developed the so-called “Servo-Actuation-System” (SAS), for application in CVT’s. This concept makes use of two small electrically-driven oil pumps. One pump takes oil from the reservoir and pressurizes the hydraulic part of the variator. A second oil pump is placed in between the two variator pulley pistons, and displaces oil from one pulley piston to the other, thereby controlling the variator speed ratio.

Because these servo-pumps can deliver a variable and precise amount of oil flow, a “Power-on-Demand” system is created. This means that just the right amount of hydraulic effort is being done for operating the CVT, and hardly any energy is wasted when doing so. On top of that, the CVT is now able operate on its own, and the low energy consumption (< 50W) results in a minimal discharging of the batteries.

In the past years Gear Chain Industrial has equipped a number of CVT prototypes and test setups with the Servo-Actuation-System. These include (self-developed) CVT’s for a Ford F250 pick-up truck and a DAF LF45 urban delivery truck.

With GCI’s extensive experience on this subject, a new version of this actuation system can be developed for various variator applications in no-time. It offers a very high level of variator controllability, which in term presents new possibilities with regard to drive train speed control and functionality. These include super-fast “Tip-Shifting” and even more precise tracking of optimal drive train operating points under dynamic conditions.

In the following movie, operation of a 24 Volt Servo-Actuation-System is demonstrated in combination with a chain variator test setup.

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