Bearings – Rotary bearing – Antifriction bearing
Reexamination Certificate
2001-03-30
2004-04-27
Lavinder, Jack (Department: 3683)
Bearings
Rotary bearing
Antifriction bearing
C384S477000
Reexamination Certificate
active
06726367
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a rolling apparatus having low heat conductivity, in particular to such a rolling apparatus to be used to systems transporting within furnaces at high temperatures such as ceramic kiln cars, conveyors for continuously heating treatment or paint baking trolleys, otherwise to usage under conditions where heat is conducted to the rolling apparatus via a housing or a shaft from a heat source outside of the rolling apparatus as an iron-steel equipment, resulting to have high temperatures (hereafter called as “the rolling apparatus used in the vicinity of the heat source”).
The invention also relates to a rolling bearing for supporting a main shaft of a motor of air blowing fan used as a cooling fan of micro processor (IC, MPU) to be incorporated into air conditioning fans, ventilating fans, personal computers or servers (hereafter called as “the rolling bearing for fan motor”).
Further, the invention relates to a rolling bearing to be suitably used to copiers (PPC: white-black, color, analog, digital or other kinds), laser beam printer (LBP), facsimile (FAX), or office machinery such as compound machines of them (hereafter called as “the rolling bearing for office machinery”).
In the rolling bearing, members as a movable member, a supporter and rolling elements are composed with metallic members as steel. At the interior of the rolling bearing, a lubricant as a grease is circulated or charged for effecting lubrication. Such rolling bearings are used without any problems under ordinarily using conditions.
On the other hand, in the systems transporting within furnaces at high temperatures such as ceramic kiln cars, conveyors for continuously heating treatment or paint baking trolleys, as the inside of the furnace is at high temperature, the heat is conducted mainly from the housing, that is, from the outer ring into the inside of the rolling bearing to heighten temperatures thereof. The inner ring, outer ring, and rolling elements are mainly composed with a steel for bearing (SUJ2).
As motors of cooling fans of micro processors to be incorporated in personal computers or servers are demanded to be small sized or quiet, a so-called brushless DC motor is employed, where a rotor is furnished with a permanent magnet and an electromagnetic field is formed by the core and coil of a stator to rotate the rotor. In motors for air blowing of a middle sized type, AC motor by an inverter control is used, and also similarly to the above, the electromagnetic field is formed at the stator side to rotate the rotor.
Such rolling bearings for fan motor are structured with a duplex bearing effected with a normal position or constant load—pre load for securing rigidity of a main shaft. In the rolling bearing, a bearing ring and rolling elements are composed with a bearing steel or heat resistant steel, and a holder is a metal-made press holder, and in particular, for the small sized bearing, resin-made crown holder is used. In these bearing units, depending on attachment of the rotor, there are cases of the outer ring rotating and the inner ring rotating.
The office machinery such as copiers, LBP, FAX or these compound machines has been demanded to have more advanced high performance (heightening the treating speed per sheet of paper) and to be more compact. The office machinery has always been demanded to be improved as such. For satisfying these requirements, the rolling bearing used at a sheet sending part of the office machinery has been more reduced in size, faster working conditions and trended to be higher load.
Especially, the rolling bearing used to heat rolls at a toner fixing part or pressure rolls is worked at high temperatures as 200 to 250° C., since a step of using the rolling bearing heats to fuse a toner on a sheet to fix thereon, and the working conditions are more severer (parts other than the toner fixing part are at 100 to 150° C.).
The rolling bearing used to heat rolls at the toner fixing part or the pressure rolls has been demanded to be lower in a consumed energy when the rolling bearing is rotated, that is, to be low torque of the rolling bearing for saving the energy.
Besides, as recycling use of units of the heat roll parts has been advanced for curtailing resources, the rolling bearing used therefor is requested to be a longer life under circumstances at high temperatures.
In addition, it has been required for the heat roll to have characteristic less to escape heat at high temperature outside therefrom for saving the energy.
At first, explanation will be made to problems of the prior art rolling bearing used in the vicinity of the heat source as transporting systems within furnaces at high temperatures or the iron-steel equipment.
The inner rings, outer rings and rolling elements of the rolling bearings as above are often composed with a steel for bearing (SUJ2) having high heat conductivity as 50 W/m·K. Therefore, in case the rolling bearing is disposed nearly to the heat source, the heat therefrom is easy to conduct to the interior of the rolling bearing, and in particular, either near to the heat source of the inner ring and the outer ring, that is, saying in the above example, the temperature of the outer ring faster goes up.
Accordingly, there were risks that a lubricant existing on the raceway surface of the outer ring (for example, silicone grease or fluorine based grease) was oxidized and worsened in a short time, separated an oil content or dissolved, so that the lubricity of the lubricant was deteriorated to extremely shorten the life of the rolling bearing.
Next reference will be made to problems involved with the conventional rolling bearing for fan motors.
Recently, accompanied with miniaturization of electric or electrical machinery, the miniaturization has been progressed also as to fans for internal cooling or blowing air. Particularly, as microprocessors to be incorporated in personal computers, servers or the like also increase heating values together with heightening of calculation processing speed, the cooling fans to be used in this technical field have been demanded, together with the miniaturization, to increase an air quantity and to lower the air blowing temperature.
An air blowing capacity of the fan is determined by the size and rotation number of the fan, and for increasing the air blowing capacity while miniaturizing the size, it is necessary to increase the rotor rotation number of the motor.
In air blowers of air conditioners, the fan has been advanced to have a high output for realizing rapidly cooling or warming. For these fan motors, AC motors by the inverter control are employed, but for making the high output, a carrier frequency from an inverter electric source should be made high frequency.
However, if the electric energy to be supplied to the stator is increased by making the high speed rotation (heightening the rotation number) and the high output of the fan motor, the heat value becomes large, which is generated in the coil or core forming the magnetic field of the stator. Then, if, like the conventional rolling bearing, the composing members of the rolling bearing for supporting a main shaft of the fan motor are fabricated with such materials having high heat conductivity as bearing steels, the heat occurring in the stator is easily transmitted to the rotor to heighten the temperature of the fan. So, although the air quality is increased, the air blowing temperature goes up, so that the increase of the fan cooling effect is probably hindered.
Since the temperature of the rolling bearing itself also goes up, the viscosity of the lubricant charged in the rolling bearing goes down to cause bad lubricity, and therefore if a bearing ring and rolling elements are both composed with a metal, there appear problems of adhesion or fine seizure to bring about a deterioration in the acoustics in the bearing in an early period of service.
Problems with the conventional rolling bearings for office machinery will be explained.
The reduction in size, high speed of serving conditions, hig
Ikeda Norifumi
Yamamoto Toyohisa
Kramer Devon
Lavinder Jack
NSK Ltd.
Sughrue & Mion, PLLC
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