Roller bearing and a mechanical system comprising such a roller bearing

Abstract

A roller bearing configured to be mounted on a balancing shaft. The rolling bearing having an outer ring, a cage axially protruding beyond at least one side of the outer ring, and rollers mounted in the cage and in rolling contact with the outer ring. The cage provides at least one boss on a side that axially protrudes beyond the outer ring, the boss being dedicated to come into abutment against the outer ring in case of relative axial displacement between the cage and outer ring.

Claims

1. A combination of a roller bearing and a balancing shaft on which the roller bearing is mounted comprising: an outer ring having a cylindrical inner surface centered on a central axis, and two annular lateral outer ring surfaces extending radially toward the central axis and defining a ring width parallel to the central axis, a cage having a plurality of pockets circumferentially distributed around the central axis, and two annular lateral cage surfaces extending radially to the central axis and defining a cage width parallel to the central axis, the cage width being greater than the ring width, the cage axially protruding beyond at least one of the annular lateral surfaces of the outer ring, and rollers that are mounted in the pockets of the cage, extend parallel to the central axis, and are disposed between the inner surface of the outer ring and a circumferential groove extending axially along the balancing shaft such that all of the contact between the rollers and the balancing shaft is located in the circumferential groove and such that all contact between the cage and the balancing shaft is located outside of the circumferential groove, the circumferential groove being configured to maintain an elongated axis of each of the rollers parallel to the central axis, wherein contact between the cage and the balancing shaft is at a different radial distance from the contact between the rollers and the balancing shaft, the cage comprises: at least one boss that radially outwardly protrudes from an axially extending radial surface on a side of the cage that axially protrudes beyond the outer ring, the boss being dedicated to come into abutment against the outer ring in case of relative axial displacement between the cage and outer ring, the axially extending radial surface having a first axial end and a second axial end, the at least one boss being axially spaced from the first axial end and from the second axial end, and wherein the outer ring comprises an annular chamfer on at least on axial side, the chamfer being dedicated to form an abutting surface for at least one boss of the cage.

2. The roller bearing according to claim 1, wherein the cage axially protrudes beyond both annular lateral outer ring surfaces of the outer ring.

3. The roller bearing according to claim 2, wherein the cage comprises at least one boss on each axial side, the bosses being dedicated to come into abutment against the outer ring in case of relative axial displacement between the cage and outer ring in both axial directions.

4. A mechanical system for a vehicle engine, comprising: a balancing shaft having an axial part centered on a central axis and at least one radial part extending radially outwardly to the central axis, a second member secured to the balancing shaft, and a roller bearing according to claim 1, the outer ring being axially located between the radial part and the second member, the rollers being disposed in rolling contact with the axial part of the balancing shaft, the radial part and the second member forming axial guidance means for the cage disposed therebetween.

5. The mechanical system according to claim 4, wherein the outer ring is mounted in a housing.

6. The mechanical system according to claim 4, wherein an axial clearance is defined parallel to the central axis on at least one side of the cage from a lateral surface of the cage up to a lateral surface of the radial part or of the second member, the axial clearance providing a greater width compared to the axial distance between the boss and the outer ring.

7. The mechanical system according to claim 6, wherein axial clearances are defined on both sides of the cage.

8. The mechanical system according to claim 4, wherein the second member is a gear.

9. The mechanical system according to claim 4, wherein lateral edges of the circumferential groove form axial guidance means for the rollers.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be explained in correspondence with the annexed figures, as an illustrative example, without restricting the object of the invention. In the annexed figures:

(2) FIG. 1 is a sectional view of a mechanical system according to the invention, equipped with a roller bearing also according to the invention,

(3) FIG. 2 is a sectional view, at a larger scale, showing detail II of FIG. 1, and

(4) FIG. 3 is a perspective view of a roller bearing according to the invention.

DETAILED DESCRIPTION

(5) FIGS. 1 and 2 partly show a mechanical system 1 according to the invention, for example a vehicle engine.

(6) System 1 comprises a balancing shaft 2 including an axial part 3 and a radial part 4, a gear 6 secured to the shaft 2 by a screw 7, and a housing 8 axially located between radial part 4 and gear 6. In the present case, radial part 4 is a counterweight or unbalanced mass. A lateral surface 43 or radial part 4 and a lateral surface 64 of gear 6 are axially facing each other. Housing 8 comprises a cylindrical inner bore 82 and two lateral surfaces 83 and 84 defining a housing width w8.

(7) Moreover, system 1 comprises a roller bearing 10 also defined according to the invention. Roller bearing 10 is mounted radially on axial part 3 of shaft 2 and in bore 82 of housing 8, and axially between surface 43 of radial part 4 and surface 64 of gear 6. Roller bearing 10 is centered on a central axis X10 and comprises rollers 12, an outer ring 20 and a cage 30. Rollers 12 are needles extending parallel to central axis X10. Part 4 and gear 6 form axial guidance means for roller bearing 1, in particular axial guidance means for cage 30 disposed therebetween.

(8) As shown on FIG. 1, constitutive elements of system 1 are also centered on axis X10. In the concept of the invention, axially means parallel to axis X10, while radially means perpendicular to axis X10.

(9) Outer ring 20 has a cylindrical outer surface 21 and a cylindrical inner surface 22 centered on axis X10. Surface 21 is fitted in bore 82 of housing 8, while surface 22 is in rolling contact with rollers 12. Outer ring 20 also has two annular lateral surfaces 23 and 24 extending radially to axis X10. Outer ring 20 has a ring width w20 defined parallel to axis X10 between the lateral surfaces 23 and 24.

(10) Cage 30 is radially spaced from outer ring 20. Cage 30 is in contact with axial part 3 and with a corner 45 formed between part 3 and 4 of shaft 2. Cage has an inner surface 32 in contact with axial part 3. As an alternate not shown, the cage does not contact parts of the shaft 2.

(11) Cage 30 has two annular lateral surfaces 33 and 34 extending radially to axis X10. Surface 33 faces surface 43 of radial part 4 of shaft 2, while surface 34 faces surface 64 of the gear 6. Part 4 and gear 6 form axial guidance means for cage 30 disposed therebetween. Cage 30 has a cage width w30 defined parallel to axis X10 between lateral surfaces 33 and 34.

(12) Cage 30 comprises pockets 38 distributed around axis X10. Rollers 12 are mounted in pockets 38 and disposed in rolling contact, on the one hand, with inner surface 22 of outer ring 20 and, on the other hand, with axial part 3 of shaft 2.

(13) More precisely, an outer cylindrical surface of the axial part 3 of shaft 2 comprises an annular groove 35 forming a rolling surface for the rollers 12 of bearing 10. Lateral edges 36, 37 on each axial side of the groove 35 are axial guiding means for the rollers 12. As an alternate not shown, the axial part 3 of shaft 2 comprises an outer cylindrical surface without groove, the cylindrical surface forming a rolling surface for the rollers 12. In that case, the lateral edges of pockets 38 of cage 30 form axial guidance means for the rollers 12.

(14) As shown on FIGS. 1 and 2, widths w8 and w20 are substantially equal. Surface 23 of outer ring 20 is aligned with surface 83 of housing 8, while surface 24 of outer ring 20 is aligned with surface 84 of housing 8, radially to axis X10.

(15) Parallel to axis X10, several distances a3, b3, c3 are defined on a first side of bearing 10 near surfaces 23, 33 and 43, while several distances a4, b4, c4 are defined on a second side of bearing 10 near surfaces 24, 34 and 64. An axial overstepping a3 is defined from surfaces 23 up to surface 33. An axial clearance b3 is defined from surface 23 up to surface 43. An axial clearance c3 is defined from surface 24 up to surface 34. An axial overstepping a4 is defined from surface 24 up to surface 34. An axial clearance b4 is defined from surface 24 up to surface 64. An axial clearance c4 is defined from surface 34 up to surface 64.

(16) In other words, cage 30 protrudes axially beyond at least one lateral surface 23 or 24 of outer ring 20 and beyond corresponding lateral surface 83 or 84 of housing 8. Preferably, as shown on FIGS. 1 and 2, cage 30 protrudes beyond both lateral surfaces 23 and 24 of outer ring 20 and beyond both lateral surfaces 83 and 84 of housing 8.

(17) According to the invention, the cage 30 comprises a first boss 301 on a first axial side, the first boss 301 radially outwardly protruding from the cage 30 and being dedicated to come into abutment against the lateral surface 23 of outer ring 20 in case of relative axial displacement between the cage 30 and outer ring 20.

(18) In the embodiment of FIG. 2, the cage 30 further a second boss 302 on a second axial side, the second boss 302 radially outwardly protruding from the cage 30 and being dedicated to come into abutment against the lateral surface 24 of outer ring 20 in case of relative axial displacement between the cage 30 and outer ring 20.

(19) Bosses 301, 302 are discrete, e.g. circumferentially extend along a limited angular sector, preferably between 2 and 5.

(20) Bosses 301, 302 radially extend beyond the inner cylindrical bore 22 of outer ring 20. Bosses 301, 302 partly axially face the lateral surfaces 23, 24 respectively of outer ring 20, the surfaces 23, 24 forming abutment surfaces for the bosses 301, 302.

(21) In the embodiment of FIG. 2, lateral surfaces 23, 24 of outer ring 20 comprise each a chamfer 231, 241 respectively. By this way, the axial arrangement of the roller bearing 10 is of reduced width and can be implemented in reduced widths between radial part 4 and gear 6. In this embodiment, chamfers 231, 241 define each a slope surface but may have any other suitable shape. As an alternate not shown, the lateral surfaces 23, 24 of outer ring do not comprise any chamfer, bosses abutting directly against lateral surfaces.

(22) As an alternate not shown, only one side of the cage may comprise at least one boss.

(23) In the embodiment of FIG. 3, the cage 30 comprises only one boss on each axial side. As an alternate not shown, a plurality of bosses can be circumferentially distributed on the circumference of at least one axial side of the cage 30.

(24) In the embodiment of FIGS. 2 and 3, the bosses are of substantial half-spherical shape. Alternatively, bosses may have any other suitable shape protruding from the cage 30.

(25) Advantageously, axial clearances c3 and c4 are each of higher width compared to the axial distance between each boss 301, 302 and the contact surface with outer ring 20, here the chamfers 231, 241 respectively. Such a design rule prevents the lateral surfaces 33, 34 of cage 30 to contact the lateral surfaces 43, 64 of radial part 4 and gear, respectively.

(26) The cage is centered between part 4 of shaft 2 and gear 6, thus reducing the shocks and vibrations due to axial cage displacements. In operation or during transport, the axial movement of cage 30 is stopped either by boss 301 against the chamfer 231 on one side of outer ring 20 or by boss 302 against the chamfer 241 on the other side of outer ring 20.

(27) Other non-shown embodiments can be implemented within the scope of the invention. In particular, shaft 2, housing 8 and roller bearing 10 can have different shapes or arrangements to be adapted to the specific requirements of the application, still within the scope of the invention.