Bearings – Rotary bearing – Antifriction bearing
Reexamination Certificate
2002-09-23
2004-09-14
Footland, Lenard A. (Department: 3682)
Bearings
Rotary bearing
Antifriction bearing
C324S174000
Reexamination Certificate
active
06789948
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a magnetic encoder used in, for example, a rotation detecting device for detecting the rotational speed of bearing elements rotatable relative to each other and a wheel bearing assembly utilizing such magnetic encoder. In particular, the present invention relates to the magnetic encoder that forms one of component parts of a bearing sealing device that can be mounted in the rotation detecting device employed in an anti-skid control system for a motor vehicle for detecting the rotational speed of front and rear vehicle wheels.
2. Description of the Prior Art
The rotation detecting device for use in association with an anti-skid control system generally used in, for example, motor vehicles has hitherto been available in various types. Of them, the rotation detecting device has been known which includes a toothed rotor and a rotation detecting sensor that are separated from each other by means of a sealing device used to seal a bearing assembly. This known rotation detecting device is separate from and independent of the sealing device used in the bearing assembly.
This known rotation detecting device is of a structure wherein the rotational speed (the number of revolutions) of the toothed rotor mounted on a rotatable shaft is detected by the rotation detecting sensor mounted on a knuckle, and the bearing assembly used is protected from any possible ingress of water and/or any other foreign matter by means of the sealing device independently provided laterally of the rotation detecting device.
A different type is disclosed in, for example, the Japanese Patent No. 2816783, in which for reducing the space for mounting of the rotation detecting device to thereby drastically increase the sensing performance of the rotation detecting device, the rotation detecting device for detecting the rotational speed of a wheel is incorporated in a bearing seal unit. This bearing seal unit is of a structure in which an elastic member mixed with a powdery magnetic material is bonded radially by vulcanization to a slinger used therein so as to extend circumferentially, which elastic member has a plurality of opposite magnetic poles alternating with each other in a direction circumferentially thereof.
The Japanese Laid-open Patent Publication No. 6-281018 (U.S. Pat. No. 5,431,413) discloses the structure in which for reducing the dimension in an axial direction to increase the sealability between a rotatable member and a stationary member and also to facilitate mounting, a space between the rotatable member and the stationary member is sealed with a rotary disc mounted on the rotatable member while the rotary disc is provided with a coder magnetized to a plurality of opposite magnetic poles, to thereby complete a coder incorporated sealing structure. The coder used therein is made of an elastomer added with magnetic particles and has its side surface rendered to be a sealing means that is in flush with a side surface of the stationary member.
The coder made of a plastic material (plastomer) containing a powdery magnetic material or magnetic particles is shaped using a mold assembly adapted to the shape of a final product, that is, molded to the shape defined by the molding cavity within the mold assembly such as performed with the conventional injection molding or the compressive molding, or molded to the shape of a final product by means of an extrusion molding technique using a T-shaped die, or is first prepared by a sheet molding technique such as a calendaring technique in the form of a sheet that is then shaped by means of a blanking technique to the shape of a final product, which final product may be subsequently fixedly bonded to a metallic substrate with the use of a bonding agent. In such case, while a metallic substrate is incorporated in the mold assembly such as an insert molding, molten resin may be subsequently poured into the mold assembly so that a bonding step can be performed simultaneously.
However, of the various prior arts discussed above, the bearing seal device disclosed in any one of the Japanese Patent No. 2816783 and the Japanese Laid-open Patent Publication No. 6-281018 (U.S. Pat. No. 5,431,413) requires the use of an elastomer or an elastic material component that serves as a binder for retaining the powdery magnetic material or the magnetic particles. This is particularly true where the elastic material mixed with the powdery material is bonded radially by vulcanization to the slinger so as to extend circumferentially thereof or the coder defining the coder equipped sealing structure equipped with the coder magnetized to the opposite magnetic poles is rendered to be an elastomer added with the magnetic particles. However, where the elastomer or the elastic material component is used as a binder, it is always necessary to use a dispersing step in which prior to the shaping to the shape of the coder the powdery magnetic material or the magnetic particles are kneaded with the elastomer or the elastic material. Since during this step the relative content by percent (the percent by volume) of the powdery magnetic material or the magnetic particles relative to the binder component is difficult to increase, the coder must have a large thickness in order to secure the magnetic force sufficient to allow the magnetic sensor to perform sensing.
The molding of the coder made of the elastic material or the elastomer containing the powdery magnetic material or the magnetic particles, is performed by shaping with the use of a mold assembly appropriate to the shape of a product by means of, for example, an injection molding technique or a compressive molding technique and, in the case where a vulcanizing step is needed, the elastic material or the elastomer should be retained within the molding assembly for a vulcanizing time needed, thereby posing a problem in that a relatively large number of processing steps are needed.
Also, the coder made of the elastic material or the elastomer containing the powdery magnetic material or the magnetic particles, requires the detecting sensor to be positioned at a location in the vicinity of and relative to the slinger used therein in a direction axially of such slinger so that, for example, in the bearing seal device utilizing the rotation detecting device for detecting the rotational speed of the wheel, the space for mounting thereof can be reduced and the detecting performance can be drastically increased. In such case, when particulate matter such as sand particles are trapped in and bitten within a gap delimited between the bearing seal surface on a rotating side and a detecting sensor surface on a stationary side during run of a motor vehicle, it is often observed that the surface of the coder made of the elastic material or the elastomer will be damaged considerably due to, for example, frictional wear.
In the case of the coder made of the plastic material (plastomer) containing the powdery magnetic material or the magnetic particles, when an attempt is made to mold the coder by the use of the conventional injection molding technique, the compressive molding technique, the extrusion molding technique using the T-shaped die, the sheet molding technique such as the calendaring technique, or the insert molding technique as hereinbefore discussed, the use of a synthetic resin component that serves as a binder for retaining the powdery magnetic material or the magnetic particles is needed after all. However, even where the synthetic resin component is used as the binder, as is the case with the elastomer, the dispersing step has hitherto been required in which prior to the shaping to the shape of the coder, the powdery magnetic material or the magnetic particles are kneaded together with the plastomer or the elastic material. After all since, during this dispersing step, it is difficult to increase the relative percent content (the percent by volume) of the powdery magnetic material or the magnetic particles relative to the binder component, the thic
Footland Lenard A.
NTN Corporation
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