NewTechnology

Product Introduction of Compact Torque Diode(TDL8)

Masayuki OHARA *NTN manufactures a “torque diode” that transmits rotation torque fromthe input shaft to the output shaft. But does not transmit the torquefrom the output shaft, which is the reverse input, to the input shaft.Thisarticle introduces the technology of the compact and lightweight torquediode “TDL8” which has an outer ring diameter of 1/3 (10 mm) and aweight of 1/14 (5 g) as compared with conventional product “TDL28”.

1. Introduction

2. Torque diode structure and features

NTN produces a torque diode used in reverse
input prevention mechanisms and drop prevention
mechanisms. This product is used between two powertransmission shafts such as a motor and transmission.
This is a reverse input blocking clutch that transmits
the running torque from the input shaft to the output
shaft and locks the running torque from the output
shaft, preventing it from being transmitted to theinput shaft. Due to this ability, it has been given thename “torque + diode” from the rectifying action ofthe torque. Since it does not require electric power
when compared with an electromagnetic brake, thisenables energy to be saved at mounted machinery.
It is also unaffected by power outages which is anexcellent safety feature. The torque diode (hereafter,TDL) is introduced below (Fig. 1).
Running torquetransmission
direction

Input shaft

Running torquetransmission
direction

TDL comprises an outer ring, inner ring, cage, rollers,
spring and side plate, and is used with an input shaft
prepared by the user (Fig. 2). The running torque of theinput shaft is transmitted to the output shaft integrated
with the inner ring (hereafter, output shaft). The rollers
and spring lock the output shaft when the input shaft isnot rotating to block reverse input.
Side plateRollers
SpringOuter ring

Output shaft(Integrated withinner ring)

Cage

Input shaft(Produced by user)

Input shaft

Output shaft

Output shaft

Running torque from theinput shaft is transmitted
to the output shaft for
both forward and reverse
rotational directions.

When attempting to rotate
the output shaft, theoutput shaft will not rotate
and running torque is nottransmitted to the input shaft.

B-O-B cross-sectional drawing

A-A cross-sectional drawing

Fig. 2 TDL structure

Fig. 1 TDL function* Product Design Dept., Industrial Business Headquarters

NTN TECHNICAL REVIEW No.89

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Product Introduction of Compact Torque Diode (TDL8)
3. Operating principle

4. TDL8 structure and features

This section explains the operating principle of how
TDL transmits running torque from the input shaft tothe output shaft. It also uses a structural drawing of aconventional product “TDL28” to show how the rollers
lock the output shaft (Fig. 3).
When the input shaft is motionless and not rotating,there is clearance between the input shaft and output
shaft. The rollers are making contact with the outerring bore diameter and the output shaft so there is norotation (Fig. 3 (a)).
When the input shaft rotates from a motionlessstate, 1) the cage connected to the input shaft pushes
the rollers to release the lock. Then 2) the input shaft
and output shaft make contact, and 3) the output
shaft rotates (Fig. 3 (b)).
When attempting to rotate from the output shaft,the spring pushes two rollers against a wedge formedby the outer ring bore diameter and output shaft
cam surface. This locks rotation in both the forward
and reverse directions and prevents the shaft fromrotating (Fig. 3 (c)).
Contact (lock)
Outer ring

Rollers Clearance

Fig. 4 shows the structure of the compact andlightweight torque diode “TDL8”. “TDL8” uses a
proprietary shaped C-type spring that enables it
to save more space than “TDL28”, a conventional
product that uses a coiled spring. This enables
smaller rollers to be used because many rollers canbe inserted. This achieves a 10 mm outer ring outer
diameter that is 1/3 the size and a 5 g weight that is
1/14 that of the conventional product “TDL28”, whilestill maintaining the allowable load torque.
The structure and features of the compact andlightweight torque diode “TDL8” are listed below
against the conventional product “TDL28”.
1. Changed from a coiled spring to a proprietary
shaped C-type spring.
2. Many rollers are inserted, enabling smaller roller
sizes, which reduces the overall size and weightof TDL.
RollersC-typespring

Cage
Outputshaft

Coiled spring

Clearance
Input shaft
2-sidedwidthsection

Input shaft(a) When motionless
1) Lock released

2) Contact

3) Rotation(b) When transmitting runningtorque from the input shaft
Contact (lock)
Wedge formedby outer ring bore
diameter andoutput shaft

Clearance

Rotation notpossible

Fig. 3 TDL operating principle

NTN TECHNICAL REVIEW No.89

5. Example of application
TDL is used in as applications like reverse input
prevention mechanisms. This will prevent unintended
rotation from the output shaft and drop prevention
mechanisms (Fig. 5) for the purpose of maintaining
safety when stopping rotation from the input shaft atthe time of a power outage, etc.
It is also installed in automobile seat lifter
mechanisms (Fig. 6). These systems are used to lift orlower an automobile seat surface by operating a leverwhen adjusting the height of the seat. It will also allow
a user to maintain the height of the seat when notoperating the lever.
Point of application

HandleClearance(c) When running torque from the output shaft is blocked

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Fig. 4 TDL8 structure

WeightWeight Weight
When the handle (input shaft) isrotated, the output shaft rotates
and the weight rises.

If the handle is not
rotated, the output shaft
locks so the weight does
not fall.

Fig. 5 Example of application in drop prevention mechanism

Point ofapplication
Load due toweight ofpassenger
Seat surface

Link gear section

Seat movement

LinkThe torque diode prevents the link from fallingover to maintain the seat position.

Fig. 6 Example of application on automobile seat

6. Summary
The compact and lightweight torque diode “TDL8”
achieves a significantly smaller and lighter product incomparison with the conventional product “TDL28”,
and is a product that contributes towards making
mounted machinery smaller, lighter and require lessenergy.
In the future, NTN will continue to aim to make thisproduct more compact, lightweight and provide higher
efficiency, and also achieve a sustainable “NAMERAKA
Society” by saving energy.
References

１） NTN Catalog Clutch Related Products CAT.
No.6405/J．

Photo of author

Masayuki OHARA
Product Design
Dept.,
Industrial Business
Headquarters

NTN TECHNICAL REVIEW No.89101