Study and Development of the Torque Compensation Cam

  Masao Nishioka, Nishioka Mechanism Laboratory

1 Introduction
The high integration technology and high-speed production technology of the micro parts for such as portable phone and personal computer are the key of base industries in Japan. Most of the production/assembling machines for those parts equip cams, thus the speed of production becomes three to four times faster than the previous speed in the past ten years. It becomes public known that the cam has the torque compensation function besides the motion and signal transmitting functions. The said improvement of production rate is realized by equipping the torque compensation cam (TCC) that embodied the new function.

2 Contents of technologies
Most of the motion pattern of the end effecter of industrial machine is the dwell-rise-dwell cycle. It consists the acceleration in the first half and deceleration in the later half. This produces a big fluctuation of input-shaft torque. By this, the speed of input shaft changes and the desired motion is not be achieved, thus the higher speed could not be obtained. By installing a TCC that compensates the fluctuating torque onto the same shaft, the input shaft torque becomes minimum, the speed of the input shaft becomes constant, as the result the vibration is inhibited.

TCC can be universally used for many industrial machines. The most suitable machines are that has a bottleneck for high-speed operation. TCC heightens the dramatic effect for the container machines, the plastic bottle injection machines, the glass molding machines and the high speed IC-chip mounting machines. The ratio of the high speed IC-chip mounter that equips TCC is more than 90% in 2000. For the big industrial machines, the rated motor torque becomes small, the feature of energy saving is another merit.

The specific type of the TCC family that are developed are the inertia type TCC that fits to speed-varied machines, the helical spring type TCC for universal use and the air spring type TCC that fits to big machine. As the summary, the advantages of TCC are as follows,

(1) cancel or minimize the fluctuating input shaft torque
(2) keep the rotational speed of input shaft constant
(3) minimize the vibration and shorten the settlement time
(4) as a result, it becomes possible to reach higher speed
(5) the required motor torque is small, then the energy consumption becomes small

3 Conclusion
To keep the speed of input shaft, conventionally the governor and flywheel are used. Comparing with those devices, TCC is cheep and compact and the time constant is short. Therefore TCC becomes a key device to reach higher speed. It is expected that TCC have more applications in the future.

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