One-way roller clutches: one idea, many applications

• Roller clutches transfer a torque in one direction and move freely in the opposite direction. In neutral, they have a low frictional torque, which prevents drive system losses and saves energy.
•     Drawn cup roller clutches are used in a variety of industrial and automotive applications, including e-bikes, motorcycles, overrunning clutches and speed compensation devices

Bearing manufacturer company has seen an increase in demand for its one-way roller clutches, including applications on e-bikes (electric bikes) and motorcycles, as well as industrial applications in overrunning clutches for packaging machines and speed compensation devices for conveyor systems.

Roller clutches transfer a torque in one direction and move freely in the opposite direction. In neutral, they have a low frictional torque, which prevents drive system losses and saves energy.

Drawn cup roller clutches are high precision machine elements consisting of thin-walled, drawn outer rings (drawn cups) with a series of ramps on the inside diameter, plastic cages, springs and needle rollers. They can be used in a wide range of applications as backstops or overrunning clutches. Drawn cup roller clutches have extremely compact radial dimensions and carry out indexing from the locking direction in the freewheel direction. Roller clutches with bearing supports can also support radial forces.

Due to their low mass and the resulting low moment of inertia of the clamping elements, drawn cup roller clutches from Schaeffler are characterised by their high indexing frequencies. They also have a low overrunning frictional torque. As the needle rollers are individually spring retained, the shaft, needle roller and clamping surface remain in contact with each other at all times, which enables a high indexing accuracy to be achieved.

One-way clutches for e-bikes

Drawn cup roller clutches bearings are used as reliable one-way clutches for e-bikes, where they transmit high torques from the drive to the output components, for example, from the bottom bracket spindle to the chain ring. In central motor drives for e-bikes, drawn cup roller clutches perform an overrunning or locking function to decouple the central motor from the drive train. This is needed if the cyclist doesn’t require the assistance of the drive system, i.e. on a flat stretch of road or if the drive is deliberately switched off.

The HF, HFL and FRAX series of drawn cup roller clutches are particularly popular in bicycle applications. HF one-way clutches have an extremely compact design but have no bearing supports and so can only transmit torques. HFL series one-way clutches can also support radial forces due to the integral plain or rolling bearings. Both one-way clutch series are suitable for aluminium housings. Roller clutches with a knurled outside surface have the suffix ‘R’ and are suitable for use with plastic housings.

Protecting motorcycles

The FRAX series of roller clutches have a sleeve design with outer rings and integrated clamping ramps manufactured using forming methods, which improves manufacturing process reliability. Compared to drawn cup roller clutches with needle rollers, FRAX series roller clutches are capable of transferring much higher levels of torque. The compact design provides excellent power density, while simplifying assembly and mounting.

The most common application of the FRAX roller clutch is the E-starter one-way clutch for motorcycles. This forms the connection between the electric starter and the crankshaft. The one-way clutch safeguards the starter components from damage when the combustion engine is started and the engine speed exceeds that of the starter.

Roller clutches are also finding applications in automotive passenger cars, where they are used as one-way clutch discs for decoupling from irregularities in the powertrain drive, as well as automatic transmission converters, torque converters and hybrid transmissions.

Design calculation and simulation

In the automotive industry, minimising energy loss during the ‘engine idle’ phase has become increasingly important in reducing vehicle fuel consumption and CO2 emissions. The friction torque from the roller clutch can be minimised by optimal spring loading: if the outer ring rotates, the rollers can even lift off from the inner ring, eliminating roller clutch friction.

What is a Ball Bearing?

From small and large motors to car axles to electric fans and hard disc drives (HDDs), ball bearings are used in a wide array of machines for rotary motion. Ball bearings support rotary parts and reduce friction to facilitate the smooth operation of machines. The size of ball bearings can range from smaller than a grain of rice — small enough to fit inside a wristwatch—to over one meter in diameter for factory and power plant applications., 

Ball Bearing Components

Ball bearings are comprised of four major parts: a large ring (outer ring), a small ring (inner ring), balls between the rings (steel balls), and a cage to prevent the balls from hitting each other. The modern structure dates back to around 1500, when Leonardo da Vinci invented ball bearings to reduce friction against the axles of horsedrawn carts. For more than 500 years, the ball bearing has been defined by this simple structure.

The Precision of a Ball Bearing

The main function of a ball bearing is to reduce friction and facilitate smooth rotation of an axis. Modern ball bearings test the very limits of precision. As an example, one of the key elements to making an ultra-precise ball bearing is the degree to which the groove where the balls roll can be made into a perfect circle.
The most important performance measure in judging a ball bearing is the extent to which it reduces friction and facilitates smooth and easy rotation. Ball bearings may end up in aircraft, automobiles, precision medical equipment and many other end products, but no matter the application, it is important to maintain smoothness and minimize friction. Changes in the times brings diversification and complexity in end products and machine types along with new performance requirements for ball bearings, including miniaturization, higher rotation speeds, durability and duration, as well as noise reduction.
 
 The world’s largest manufacturer of miniature precision ball bearingsand a volume leader in the design and manufacturing of precision electro-mechanical components, including cooling fans and blowers, precision small motors and mechanical bearing assemblies, as well as a total solutions supplier of backlight, and LED programmable drivers. products can be found in the personal computing, networking, telecommunications, home entertainment, home electronics, and automotive, medical and industrial markets.

Bearings has much to gain from new auto emission rules

Implementation of stricter emission rules may pinch those who want to buy new vehicles, but for bearings companies, it is turning into an incremental revenue driver.

India’s largest supplier of bearings to the passenger car segment, is well poised to benefit from increased demand for next-generation bearings which contribute to lower emissions by improving vehicle performance.

promoted by Germany’s Schaeffler Group, may outpace the industry as well as its own historical performance in revenue growth in the next few years. Between 2010 and 2015, its annual growth was 10% with revenue expanding to Rs 1,707 crore, as per company’s annual report.

With the deadlines on the emission rules — April 2017 for BS-IV and April 2020 for BS-VI — drawing closer, automakers are expected to shift to next generation bearings, opening up a revenue opportunity for the component makers. All Bearings Company is expected to reap the highest benefit since it is the market leader in the passenger car segment where volume visibility is the highest among all the automobile segments — its market share in the passenger car segment is expected to increase to 18.9% in 2020 from 16.7% in the last fiscal, according to Kotak Institutional Equities. All Bearings companies’ overall revenue market share was nearly 15% in the last fiscal year.

Its financial year ends in December. Since the new generation of bearings are almost 2.5-3 times expensive than the conventional ones, the changes will help the company better its average realisation as well as margins.

According to analysts, the bearings content will increase to Rs 4,000 per car in 2020 from Rs 3,000 currently, another factor that bodes well for the segment. the Bearings enjoys superior market position compared to its peers due to lower sourcing of goods from the parent to sell in the local market and better margins on traded goods.

Bearings has commissioned a new plant at Savli in Gujarat with an investment of Rs 400 crore and it has potential to generate Rs 1,000 crore in revenue at peak utilisation. With higher utilisation of the new plant and increased proportion of the newgeneration bearings in its product mix could help the company boost its margins. Last year, its operating margin was 17.7%.

Also, the company would benefit from an expected increase in the use of technologically better bearings in trucks and the railways. The government’s plan to upgrade railway infrastructure by projects such as dedicated freight corridors, high-speed trains and metros in major cities can nearly double the demand for bearings from the railways. This may bode well for companies in the sector.

At Friday’s closing price of Rs 4,182.85 on the BSE, the stock is trading at 23 times its FY18 projected earnings. This is at par with tier one automakers and appears justified due to the company’s superior earnings growth and market position to capture the changing trends in the industry.

Roller Bearing for Large Gear Boxes

Combination of special heat treatment and material for superior life expectancy

Designed to improve the reliability of large gearboxes used in wind power generators and other industrial machines, NSK has introduced a long-life, large-size roller bearing. The principal innovation of the new bearing is a combination of special heat treatment technology and proprietary NSK material that delivers superior flaking resistance, including that of white structure flaking. The result is seven times longer service life than that provided by a standard steel (SUJ2) bearing.

The gearboxes found in wind power generators and mining, steelmaking and construction equipment, require roller bearings that are able to support heavy loads. In addition, such bearings must demonstrate excellent reliability in order to cope with the increasing size of wind power generators being produced, and the harsh operating conditions of industrial machinery.

It was these factors that prompted NSK to create a robust, large bearing capable of class-leading reliability. This task demanded the development of a special heat treatment process that was able to delay the occurrence and propagation of cracks.

As a result of these innovations, NSK’s roller bearings for large gearboxes demonstrates seven times longer white structure flaking life than a conventional standard steel bearing. Furthermore, surface originated flaking life is three times as long, while substrate originated flaking life and fracture toughness are both double. As an additional benefit, the rate of dimensional change offered by NSK’s roller bearing for large gearboxes is 50 times less than that of conventional alternatives.

In conclusion, today’s large gearbox designers should consider the use of NSK’s long-life large roller bearing for improved reliability in harsh environments. NSK is anticipating global annual sales for this product of around €8 million by 2017.