[New Product] Unit Products for Office Equipment - NTN

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Unit Products for Office Equipment 2.2 Operating principle of lock-type torque diodes A torque diode is essentially a reverse-input blocking clutch on which rotation on the input side is transmitted to the output side, but rotation on the output side is not transmitted to the input side. If the revolution on the output side is not transferred to the input side because the output shaft is locked, then the torque diode is defined as a lock type. If the revolution on the output side is not transferred to the input side because the output shaft rotates freely, then the torque diode is defined as a free type. The operating principle of the lock-type torque diode is illustrated in Figs. 5 through 7. When the input shaft is at a standstill, the rollers are forced by the spring to the wedge-shaped space between the inner ring cam surface, which is integrated with the output shaft, and the outer ring sliding surface. As a result, even when an attempt is made to turn the inner ring (integrated with the output shaft), the inner ring and outer ring are locked together and the inner ring does not turn (Fig. 5). The input shaft and the cage rotate together, so when the input shaft rotates, the cage also rotates in the same direction. Then, the cage comes into contact with the roller to force the roller toward the larger side of the cam surface (toward the spring), releasing the lock (Fig. 6). When the input shaft is further turned, the two surfaces on the input shaft come into contact with the two surfaces in the hole of the inner ring and force the inner ring (integrated with the output shaft) to rotate (Fig. 7). Outer ring Outer ring sliding surface Inner ring cam surface Input shaft rotates Rollers Fig. 5 Fig. 6 Spring Cage Inner ring (integrated with the output shaft) Input shaft Lock is released Rotation direction of the cage Rotation direction of the input shaft 2.3 Structure of the TDL16 compact, lightweight torque diode The structure of the newly developed TDL16 compact, lightweight torque diode is illustrated in Fig. 8. Contact point Fig. 7 Housing (resin) Outer ring Roller Spring Input shaft 1) Output shaft (resin) 25 Cage Lid (resin) Inner ring 34.8 Note 1) The input shaft is not built into the torque diode. Fig. 8 Structure of TDL16 -71-
NTN TECHNICAL REVIEW No.742006 2.3.1 Compact design The structure of the old TDL28 is characterized in that the roller at each end of the spring is forced to the cam surface. In contrast, the TDL16 has a novel structure in which multiple rollers at each end of the spring are forced to the cam surface. Because of this arrangement, the outer diameter of the TDL16 is smaller than that of the TDL28 though both designs have the same number of rollers. Thus, the TDL16 has succeeded in minimizing the loss of load bearing capacity on the clutch. In Table 2, the dimensions and limiting torque of the TDL16 are compared with those of the TDL28. 2.3.2 Lightweight design By incorporating the resin components (output shaft, housing, lid) shown in Fig. 8, the authors’ TDL16 compact, lightweight torque diode achieved weight reduction of 50% relative to the TDL28 (Fig. 9). Table 2 Size and limiting torque of TDL16 and TDL28 2.3.3 Durability Under the test conditions summarized in Table 3, the TDL16 has successfully endured 300,000 cycles of load applications. Running speed Load torque One cycle Table 3 Test condition of endurance test 3. Conclusion 250min -1 0.5 N-m (constant loading in one direction) Forward rotation for 2.5 sec.standstill for 10 sec. reverse rotation for 2.5 sec.standstill for 10 sec. NTN believes that their NTB14 ultra-compact torque limiter unit and TDL16 compact, lightweight torque diode positively contribute to space and energy conservation in photocopying machines and printers. NTN will further develop unit products to satisfy future market needs. Shape TDL16 25 OD x 35.8 L (mm) (Note that the shape of the resin housing can be altered upon customer request.) TDL28 30 OD x 38.2 L (mm) Limiting torque 2) 2.5Nm 4.9Nm Note 2) These limiting torque values have been calculated based on the maximum surface pressures occurring on the cam surfaces. The useful operating life of a torque diode can vary depending on operating conditions. Weight g 70 60 50 40 30 20 10 0 TDL16 TDL28 Fig. 9 Weight of TDL16 and TDL28 Photos of authors Shoji ITOMI Industrial Engineering Dept. Industrial Sales headquarters Atsushi MOROOKA Industrial Engineering Dept. Industrial Sales headquarters -72-
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