High speed bearing cage

A bearing cage is disclosed that includes a first ring and a second ring with a plurality of crossbars extending therebetween to define a plurality of rolling element pockets. The first ring and the second ring each include a plurality of radially outward protrusions, a plurality of reliefs, and a plurality of axially extending protrusions extending into the plurality of rolling element pockets. The plurality of crossbars each include a plurality of retention tabs configured to engage rolling elements in the plurality of rolling element pockets.

FIELD OF INVENTION

The present disclosure relates to a high speed bearing cage.

BACKGROUND

Bearing assemblies are used in a wide range of applications. In particular, electric vehicles rely on bearing assemblies that have high speed capabilities. As used herein, the term high speed with respect to bearing assemblies means speeds of 20,000 rpm to over 50,000 rpm. The cages used in these high speed bearing applications present a variety of challenges regarding durability and friction losses.

It would be desirable to provide a high speed bearing cage that can withstand high performance demands regarding durability and also reduce friction losses.

SUMMARY

A bearing cage is disclosed that includes a first ring and a second ring with a plurality of crossbars extending therebetween to define a plurality of rolling element pockets. The first ring and the second ring each include a plurality of radially outward protrusions, a plurality of reliefs, and a plurality of axially extending protrusions extending into the plurality of rolling element pockets. The plurality of crossbars each include a plurality of retention tabs configured to engage rolling elements in the plurality of rolling element pockets.

In one aspect, the plurality of reliefs each have a profile including a first round end, a second round end, and an elongated slot connecting the first round end and the second round end. The first round end and the second round end extend radially inward from the elongated slot. The reliefs can have a telephone-shaped profile.

The plurality of retention tabs can be formed via a plurality of fingers and a plurality of slots. The plurality of slots in the plurality of crossbars are oriented in a radially outward direction, and a radial extent of the plurality of slots is at least 50% of a total radial extent of the plurality of crossbars.

In one aspect, the plurality of radially outward protrusions are circumferentially aligned and overlapping with the plurality of rolling element pockets.

The plurality of retention tabs can be only provided in regions directly adjacent to a respective one of the first ring and the second ring.

The plurality of reliefs are positioned radially outward from a pitch diameter in one aspect.

The bearing cage can be formed from a high heat polyamide or a thermoplastic polymer. In one embodiment, the bearing cage has a thickness greater than 0.5 mm throughout each of the components of the bearing cage.

Circumferential areas defined between the plurality of radially outward protrusions can be configured to define lubrication channels to the rolling elements held within the bearing cage.

A bearing assembly is also disclosed herein.

Additional embodiments are disclosed herein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Certain terminology is used in the following description for convenience only and is not limiting. “Axially” refers to a direction along an axis (X) of an assembly. “Radially” refers to a direction inward and outward from the axis (X) of the assembly. “Circumferentially” refers to a direction extending along a curve or circumference of a respective element relative to the axis (X) of the assembly.

A reference to a list of items that are cited as “at least one of a, b, or c” (where a, b, and c represent the items being listed) means any single one of the items a, b, or c, or combinations thereof. The terminology includes the words specifically noted above, derivatives thereof and words of similar import.

A bearing cage10is illustrated inFIGS. 1-15. The bearing cage10includes a first ring20and a second ring30with a plurality of crossbars40extending therebetween to define a plurality of rolling element pockets50.

The first ring20and the second ring30each include various features. In one aspect, the first ring20and the second ring30are identical to each other. One of ordinary skill in the art would understand that the first ring20and the second ring30can be different from each other.

In one embodiment, the first ring20and the second ring30each include a plurality of radially outward protrusions22,32, a plurality of reliefs24,34, and a plurality of axially extending protrusions26,36extending into the plurality of rolling element pockets50.

The term relief is used herein to refer to a hole, opening, gap, or other lack of material in rings20,30.

The plurality of crossbars40each include a plurality of retention tabs28,38configured to engage with rolling elements6. The plurality of retention tabs28,38are each formed via a plurality of fingers29,39and a plurality of slots42a,42b(i.e. cutouts) such that the plurality of fingers29,39provide a circumferentially extending portion to secure the rolling elements6. In one embodiment, the plurality of retention tabs28,38are only provided in regions directly adjacent to a respective one of the first ring20and the second ring30. In other words, the crossbars40do not include retention tabs28,38along an entire axial extent of the crossbars40. This design ensures that the rolling elements6do not contact the crossbars40in medial regions of the crossbars40. In one aspect, the crossbars40are flat and uniform between the retention tabs28,38.

The retention tabs28,38reduce the impact effect and high stress at corners of the rolling element pockets50. The fingers29,39and slots42a,42balso provide a degree of flexibility to absorb shocks from heavy roller impact during high speeds.FIG. 15is provided to specifically show the interface between the retention tabs28,38and the rolling elements6. This design also allows for a smaller clearance between the rolling elements6and the retention tabs28,38, and helps control a tighter or more limited rolling element drop limit. As shown inFIG. 7, the rolling element drop is a distance between 6′ and 6″. The arrangement disclosed herein provides retention tabs28,38such that the rolling elements can be load in with an interference that is greater than 0.01 mm, or greater than 0.1 mm in one embodiment. This configuration reduces the rolling element drop and makes the bearing assembly more stable.

The plurality of slots42a,42bin the plurality of crossbars40are oriented in a radially outward direction. The plurality of slots42a,42bextend from a radially inner surface of the crossbars40in the radially outward direction. In one aspect, the slots42a,42bare identical to each other.

A radial extent (E1) or depth of the plurality of slots42a,42bis at least 50% of a total radial extent (E2) or depth of the plurality of crossbars40. One of ordinary skill in the art would understand that the depth of the slots42a,42bcan vary.

In one embodiment, the plurality of reliefs24,34each have a profile including a first round end24a,34a, a second round end24b,34b, and an elongated slot24c,34cconnecting the first round end24aand the second round end24b. In one aspect, the first round end24a,34aand the second round end24b,34bextend radially inward from the elongated slot24c,34c. In one embodiment, each of the reliefs24,34extend for at least 10 degrees in a circumferential direction. In one aspect, the reliefs24,34have a “telephone-shaped” profile, i.e. a generally curved body with enlarged ends oriented in the same direction. The reliefs24,34reduce the impact effect between the bearing cage10and the cage guidance (i.e. the outer ring4or an outer housing), which helps damp vibrations of the bearing cage10and makes the bearing cage more dynamically stable. This design helps reduce cage friction losses during high speeds.

The plurality of axially extending protrusions26,36each are formed as circular bumps or protrusions. The axially extending protrusions26,36establish a single point of contact between the rolling elements and the ends of the rolling element pockets50. This design helps reduce friction losses. In other words, this design helps reduce the overall size of contact surfaces between the rolling elements6and the bearing cage10.

In one embodiment, the plurality of radially outward protrusions22,32are circumferentially aligned or overlap with the plurality of rolling element pockets50. One of ordinary skill in the art would understand from the present disclosure that the location of the protrusions22,32can vary. The protrusions22,32generally help reduce a contact area of the bearing cage10with an outer component. This also helps reduce friction losses due to the reduction in contact area and thus reduces friction. Spaces defined circumferentially between the radially outward protrusions22,32also act as channels43for improving lubrication flow, which improves durability and the life cycle for the bearing cage10. In the assembled state, the protrusions22,32define points of contact between the bearing cage10and the outer ring4.

The bearing cage10disclosed herein can be formed from any suitable material. In one aspect, the bearing cage10is formed from a high heat polyamide or a thermoplastic polymer. In one embodiment, the bearing cage10is formed from PA46-GF30, PA66-GF30 or polyether ether ketone (PEEK).

In one aspect, the bearing cage10maintains a thickness of each of the components described herein of 1.0 mm or thicker. In one aspect, each of the bearing cage components have a thickness greater than 0.5 mm.

The bearing cage10disclosed herein can be implemented in any bearing application and is particularly well suited for high speed bearing applications. For example, the bearing cage10can be used in an electric motor axle. The bearing cage10is suitable for operation in bearing applications having speeds of 20,000 rpm to over 50,000 rpm.

FIGS. 9-15illustrate various views of a bearing assembly2that includes the bearing cage10, as well as the rolling elements6and the outer ring4. During assembly, as shown inFIG. 10, the rolling elements6can be inserted in a radially outward direction to snap into the rolling element pockets50defined by the bearing cage10. As shown inFIG. 12, the reliefs24,34are arranged radially outward from the pitch diameter (P) of the bearing assembly2. One of ordinary skill in the art would understand that the position of the reliefs24,34can vary. As shown inFIG. 15, the slots42a,42bextend radially outward at least to a pitch diameter (P) of the bearing assembly.

FIG. 7illustrates two relative positions of the rolling elements6. As shown inFIG. 7, position6′ of the rolling elements6corresponds to a running position. In other words, position6′ illustrates the rolling elements6being relatively radially outward to a resting position due to centrifugal force. Position6″ corresponds to a drop limit position for the rolling elements6. These positions are controlled by the degree of flexibility in the retention tabs28,38, which is a result of the fingers29,39and slots42a,42b. Based on the configuration of the bearing cage and flexible fingers29,39, the drop of the rolling element (i.e. distance between 6′ and 6″) is limited to 0.3 mm.

Having thus described the present disclosure in detail, it is to be appreciated and will be apparent to those skilled in the art that many physical changes, only a few of which are exemplified in the detailed description of the embodiments, could be made without altering the inventive concepts and principles embodied therein.

It is also to be appreciated that numerous embodiments incorporating only part of the preferred embodiment are possible which do not alter, with respect to those parts, the inventive concepts and principles embodied therein.

The present embodiment and optional configurations are therefore to be considered in all respects as exemplary and/or illustrative and not restrictive, the scope of the embodiments being indicated by the appended claims rather than by the foregoing description, and all alternate embodiments and changes to this embodiment which come within the meaning and range of equivalency of said claims are therefore to be embraced therein.

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