Patent Application
20090191999
The present invention relates to a dust shield for a bearing and to a pulley with a bearing with a dust shield. More specifically, the present invention relates to a dust shield to prevent the ingress of foreign materials into the bearing of a pulley and to a pulley equipped with a dust shield.
Flexible drives, in particular belt-driven accessory drives in vehicular engine compartments, typically include one or more tensioners or idlers which include pulleys that contact the drive. Due to the rotational speed of these pulleys and the loads they carry, the pulleys typically rotate on bearings, such as roller or ball bearing races, to carry their loads, reduce frictional losses and to reduce operating noise.
While the use of such bearings is widespread and generally satisfactory, vehicular engine compartments and other environments are exposed to a variety of foreign materials such as dirt and water. As a result, the bearings in the flexible drive pulleys can suffer from the ingress of the foreign materials into their bearing surfaces. Such ingress can increase the friction in the bearing and/or can abrade the bearing surfaces reducing the operating lifetime of the bearing. While many bearings include seals to inhibit the ingress of foreign materials, such seals are not perfect and degrade over time, leading to the ingress of foreign material and ultimately failure of the bearings.
Previous attempts to reduce the ingress of foreign materials have consisted of the provision of oversized washers on the mounting bolt attaching the pulley to its mounting surface, the washers being located on one or both sides of the bearing to act as a physical barrier between the bearing and foreign materials.
While such washers can reduce the ingress of foreign materials into the bearing, they are not fully effective as they merely abut the bearing and foreign material, in particular water and water-borne particles, can infiltrate behind the edges of the washer and into the bearing. Further, the provision of the washers requires additional assembly/installation steps when assembling or installing the pulley, increasing the assembly/installation expense. Further, washers can be inadvertently omitted from assembly/installation, resulting in increased expenses for defective parts and/or premature failure of a pulley installed without a washer.
It is an object of the present invention to provide a novel dust shield for a pulley bearing which obviates or mitigates at least one disadvantage of the prior art. It is a further object of the present invention to provide a novel pulley with a dust shield which obviates or mitigates at least one disadvantage of the prior art.
According to a first aspect of the present invention, there is provided a dust shield to inhibit the ingress of foreign materials into a pulley bearing and a pulley. The dust shield is press fit to one side of the bearing such that it is captive during assembly and/or installation of the pulley. A second dust shield can be provided on the opposite side of the bearing to further inhibit the ingress of foreign materials. Preferably, at least one of the dust shields includes a bolt retention feature which holds an installation bolt captive to the pulley prior to installation. The dust shields can be fabricated from selected materials with desired thermal characteristics to insulate the bearing from sources of undesired heat and/or to assist the removal of waste heat from the bearing.
Preferred embodiments of the present invention will now be described, by way of example only, with reference to the attached Figures, wherein:
As used herein, the term dust shield is intended to comprise a barrier member which inhibits the ingress of foreign materials such as water, water-borne particles or dry particulate materials into a bearing.
Pulley 20 includes a pulley member 24 which includes a cylindrical outer surface 28 configured to engage the flexible drive means and further includes a centered cup-shaped raceway 32 to receive a bearing 36. Bearing 36 can be any suitable bearing, such as a roller bearing assembly or ball bearing assembly having an outer race 40 which frictionally engages pulley member 24 and an inner race 44 which receives a bolt 48 that mounts pulley 20 to the surface or member on which it is installed. A series of ball bearings are interposed between the outer race 40 and the inner race 44, as is well known in the art. Bearing 36 defines an axis of rotation about which the pulley 20 rotates.
As best seen in
In the present invention, a dust shield 56, best seen in
Unlike prior art washers that were employed as dust shields in front of bearings, dust shield 56 includes an inner axial lip 60 whose outer diameter, in combination with the thickness (gauge) of the material from which dust shield 56 is formed, allows dust shield 56 to be press fit into the inner radial surface of inner race 44 of bearing 36 such that the resulting interference fit retains dust shield 56 in position on bearing 36, as shown in
As is best seen in
Optionally as shown in
As should now be apparent, when press fit to bearing 36, dust shield 56 is held captive in this position and acts as a barrier to inhibit the ingress of foreign material into the interior of bearing 36. By being held captive to bearing 36, the inadvertent omission of dust shield 56 during assembly and/or installation of pulley 20 is prevented.
In a present embodiment of the invention, dust shield 56 is formed by stamping galvanized steel, approximately 0.58 mm in thickness, and the exposed outer and inner radial edges of dust shield 56 are preferably treated with an anti-corrosion coating. However, as will be apparent to those of skill in the art, dust shield 56 can be fabricated from a variety of other materials, including zinc, tin, other metal alloys or suitable plastic materials.
An additional contemplated advantage of dust shield 56 being fabricated from metal is the enhanced removal of waste heat from bearing 36. In operation, pulley member 24 can rotate at high speeds and be subject to significant loads which result in a significant amount of heat being generated within bearing 36. As the operating lifetime of bearing 36 is adversely affected by operation at high temperature levels, it is generally desired that as much waste heat be removed from bearing 36 as reasonably possible.
However, for cost reasons, pulley member 24 is often fabricated from materials, such as plastics, which do not assist in dissipating the waste heat produced in bearing 36. Even when pulley member 24 is fabricated from metal, it can still be difficult to remove desired amounts of waste heat from bearing 36.
By employing dust shield 56 which is fabricated from a material with reasonably good thermal transfer characteristics, such as the above-mentioned galvanized steel, an additional surface is provided over which the transfer of the waste heat from bearing 36 to the surrounding atmosphere can occur.
Further, whether metal or plastic, it is contemplated that dust shield 56 can be treated to enhance its thermal transfer capabilities, if desired. For example, a coating, such as the thermal dispersant coating sold by Tech Line Coatings, Inc. of Murrieta Calif. under the brand name TLTD, can be applied to dust shield 56 to enhance its thermal transfer capabilities thus enhancing the removal of waste heat from bearing 36.
While not necessary, it is preferred that dust shield 56 further include a bolt retention feature. As best seen in
In this manner, dust shield 56 is captive to bearing 36 and bolt 48 is captive to dust shield 56 and pulley 20 can be assembled into the configuration illustrated in
Tabs 72 of the bolt retention feature can accommodate bolts 48 of different sizes, without modification, should an embodiment of pulley 20 be used with different sized bolts. For example, if a single embodiment of pulley 20 is installed on different engines, pulleys 20 for installation on one engine will have the appropriate sized bolts, e.g. M6, inserted into dust shield 56 while pulleys 20 for a different engine will have the appropriate sized bolts, e.g. M8, inserted into dust shield 56.
Similarly, it is contemplated that a single dust shield 56 design and/or size can be used with different embodiments of pulley 20, provided that the inner radial and outer radial dimensions of bearing 36 are similar in each embodiment.
Depending upon where pulley 20 is installed, foreign material may still be able to reach the interior of bearing 36 from the back (the lower side in the orientation illustrated in
Dust shield 100, which is best seen in
Dust shield 100 further includes a generally planar annular portion 108 which overlies and protects a portion of resilient seal 52 on the back of bearing 36 when dust shield 104 is installed on bearing 36 and further includes a raised outer lip 112 which extends radially outwardly over the remainder of resilient seal 52 and bearing 36 and extends over the outer radial edge of raceway 32, presenting a serpentine or labyrinth path between the pulley member 24 and the dust shield 100.
As should now be apparent, when press fit to bearing 36, dust shield 56 is held captive in this position and acts to inhibit the ingress of foreign material into the interior of bearing 36. By being held captive to bearing 36, the inadvertent omission of dust shield 56 during assembly and/or installation of pulley 20 is also prevented.
In a present embodiment of the invention, dust shield 100 is stamped from the same material as dust shield 56, although it is contemplated that dust shield 100 can be fabricated from a different material than dust shield 56 if desired.
As with dust shield 54, dust shield 100 can also assist in managing the thermal operating conditions of bearing 36. For example, if dust shield 100 is fabricated from a material with good thermal transfer characteristics, such as the above-mentioned galvanized steel, dust shield 100 can serve as another surface over which waste heat from bearing 36 can be transferred to the surrounding air. If desired, the above mentioned thermal dispersant coating or the like can also be applied to dust shield 100.
However it is also contemplated that, in many circumstances, pulley 20 will be installed on a surface or object, such as an internal combustion engine, which itself produces heat which could be transferred to bearing 36. In such a case, dust shield 100 can act to insulate bearing 36 from this source of undesired heat by fabricating dust shield 100 from a material with relatively good thermal insulating properties and/or by applying a thermal barrier coating, such as the thermal barrier coating sold by Tech Line Coatings, Inc. of Murrieta Calif. under the brand name TLLB. In such a case, the combination of a thermally insulating dust shield 100, between the source of undesired heat, and thermally conductive dust shield 56, providing a surface from which waste heat from bearing 36 can be radiated, can provide a thermal management system for bearing 36.
While in the illustrated embodiment bolt 48 is shown as being installed extending from front (the upper surface in the orientation illustrated in
The present invention provides a dust shield to inhibit the ingress of foreign materials into a pulley bearing. The dust shield is press fit to one side of the bearing such that it is captive during assembly and/or installation of the pulley. A second dust shield can be provided on the opposite side of the bearing to further inhibit the ingress of foreign materials. Preferably, at least one of the dust shields includes a bolt retention feature which holds an installation bolt captive to the pulley prior to installation. The dust shields can be fabricated from selected materials with desired thermal characteristics to insulate the bearing from sources of undesired heat and/or to assist the removal of waste heat from the bearing.
The above-described embodiments of the invention are intended to be examples of the present invention and alterations and modifications may be effected thereto, by those of skill in the art, without departing from the scope of the invention which is defined solely by the claims appended hereto.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CA2007/000974 | 5/31/2007 | WO | 00 | 11/25/2008 |
| Number | Date | Country | |
|---|---|---|---|
| 60809871 | Jun 2006 | US |
