September 28, 2011
Development of “Space-saving and High Performance Angular Contact Ball Bearings for Air Oil Lubrication” for Main Shaft of Machine Tools
(“Angular Contact Ball Bearing with Outer Ring Refueling Hole”)
[Contributing to greater lubrication reliability and more compact main shaft by feeding lubrication oil directly from the outer ring]
NTN Corporation (hereafter, NTN) has developed “Space-saving and High Performance Angular Contact Ball Bearings for Air Oil Lubrication” for main shaft of machine tools, featuring a new layout that allows lubrication oil to be fed directly within the bearing via a lubrication hole on the outer ring.
In addition to high-speed and high-rigidity, the main shafts of machine tools need to be designed to be more compact and deliver reliable machining, even under various operating conditions. With air-oil lubrication, which is one method for lubricating the bearings of main shafts, small quantities of lubricating oil are fed into internal bearing structure with compressed air via bearing spacer (hereafter, spacer) adjacent to the bearing itself and lubrication holes. Yet this method suffers from the following problems.
|(1)||Limited miniaturization||:||the addition of a lubrication hole in the space means the spacer needs to be of a minimum width, limiting the extent to which the bearing can be miniaturized.|
|(2)||Stagnation of lubrication oil||:||changes to the bearing position under a range of machining conditions and the formation of an air curtain across rotating sections of the bearing within increasing main shaft speeds can cause lubrication oil around lubrication hole area (piping circuits) of the spacer to stagnate. This results in an unreliable supply of lubrication oil within the shaft bearing.|
|(3)||Noise||:||there is an increase in noise when feeding lubrication oil through the spacer.|
The “Space-saving and High Performance Angular Contact Ball Bearings for Air Oil Lubrication” developed by NTN eliminates the need for a lubrication hole in the spacer, which allows for a reduction in the width of the spacer and an overall more compact main shaft. Feeding lubrication oil directly within the bearing itself limits fluctuations in lubrication conditions, enables a more reliable supply of lubrication oil and limits noise. The design of the outer ring oil groove and lubrication hole have been optimized and o-rings installed on either side of the lubrication hole to prevent oil leaking from the outer diameter surface of the shaft bearing. The elimination of piping circuits within the spacer reduces the number of cases where lubrication capabilities are lost, thereby reducing the quantity of lubrication oil and air required and leading to a more compact supply unit.
The newly developed product was displayed at “EMO Hannover 2011 (the world's premier trade fair for the metal working technology)” held in Hannover, Germany from September 19 to 24, and will be proposed to manufacturers of machine tools as the next-generation type of bearing.
[ Features ]
|(1)||Compact: reduction in width of bearing spacer|
|→ 20% reduction in length of front spindle (for shaft diameter φ100, 4-row bearing layout)|
|(2)||Less noise: up to 6 dBA reduction (compared to standard air-oil spacer)|
|(3)||2/3 reduction in air-oil quantity, 1/2 reduction in lubrication oil quantity (compared to standard air-oil spacer)|
[ Application ]
Main shaft of machine tools (such as machining centers and complex machining equipment)
[ Inquiries about this release ]
Business Planning Department, Industrial Business Headquarters +81-594-24-2478
[ Product Photo ]
[ Structure and example of application ]
[ Applications ]
- Example of application of main shaft of machine tool (machining center)