COMPENSATION SHAFT

Description

[0001] The invention relates to a balance shaft for balancing inertial forces and / or inertial moments of a reciprocating internal combustion engine. It is a built embodiment comprising the following components: an unbalanced shaft with an unbalanced section and an adjacent bearing journal with a partially cylindrical circumference, the cylindrical part of which is oriented towards the shaft unbalance, a bearing ring surrounding the bearing journal, which rests on the cylindrical part of the circumference and defines a free space with a radially opposite bearing journal back, and a clamping element clamped in the free space, which clamps the bearing ring radially against the cylindrical part of the circumference.

[0002] A generic balance shaft comprising an unbalanced shaft and a bearing ring, the attachment of which to the bearing journal of the unbalanced shaft is effected by an elastic clamping element between the bearing ring and the bearing journal back, is known from DE 10 2016 210 480 A1 and DE 20 2017 102 212 U1.

[0003] Another constructed balance shaft is known from EP 2 459 899 B1. There, an axially outer edge region of the bearing ring is connected to an axial side surface in the region of the cylindrical partial circumference.

[0004] The present invention is based on the objective of providing a built balance shaft with an alternatively joined bearing ring.

[0005] The solution to this problem is achieved by the features of claim 1. Accordingly, the clamping element is intended to secure the bearing ring against axial displacement on both sides on the bearing journal, wherein the clamping element is axially positively connected on one side to the unbalanced shaft and on the other side to the bearing ring.

[0006] In other words, the axially positive connection of the bearing ring to the unbalanced shaft is established indirectly, namely via the clamping element.

[0007] In an advantageous embodiment, the cylindrical partial circumference and consequently also the inner surface of the bearing ring can be radially recessed relative to the adjacent unbalanced sections. This makes it possible to increase the ratio of shaft unbalance to shaft mass, thus promoting lightweight shaft construction.

[0008] The axial positive fit between the clamping element and the unbalanced shaft can be formed by a groove in the bearing journal back, with the groove walls axially enclosing axial end faces of the clamping element. Conversely, it is possible for the clamping element to have a recess that axially encloses a projection arranged on the bearing journal back.

[0009] The axial positive locking between the clamping element and the bearing ring can be formed by either the bearing ring axially enclosing the clamping element or, conversely, by the clamping element axially enclosing the bearing ring.

[0010] Optionally, the bearing ring should be positively connected to the clamping element both axially and circumferentially. The circumferential positive connection can be formed, in particular, by a radially outward projection on the clamping element that engages in a transverse bore in the bearing ring and secures it (also) against rotation relative to the clamping element and thus relative to the bearing journal. The projection and the transverse bore are advantageously positioned in the load-free circumferential area of ​​the bearing journal.

[0011] Further features of the invention will become apparent from the following description and from the drawing, which shows an embodiment of a balance shaft according to the invention. The drawing shows: Figure 1: a longitudinal section of an end section of the balance shaft; Figure 2: the unbalance shaft according to Figure 1 as a single part; Figure 3: detail X according to Figure 1 .

[0012] The Figures 1 to 3Figure 1 shows the components and assembly of a balance shaft according to the invention. This shaft comprises an unbalance shaft 1, manufactured as a cast or forged part, with an end drive journal 2 for a drive wheel (not shown) to be mounted thereon, and with unbalance sections 9, 10, 11 and 12, as well as with bearing journals 3 and 4, each connecting two of the unbalance sections 9 to 12. The bearing journals 3 and 4 are only partially cylindrical, and their cylindrical partial circumference 7 is shaped to maximize the shaft unbalance (see arrow in Figure 1). Figure 3) oriented such that the imbalance of the unbalance sections 9 to 12 and the imbalance of the bearing journals 3, 4 are essentially parallel and in the same direction, and load the cylindrical partial circumference 7 essentially at its center. The radially opposite (non-cylindrical) partial circumference of the bearing journal 3, 4, hereinafter referred to as the bearing journal back 8, is free from the circular arc of the cylindrical partial circumference 7 as referenced to the shaft axis of rotation 18.

[0013] The balance shaft further comprises, for each bearing journal 3, 4, a surrounding bearing ring 5, a clamping element 15 that (non-destructively) detaches the bearing ring 5 to the bearing journal 3, 4, and a needle roller bearing 6 for radial needle bearing of the balance shaft in a housing of an internal combustion engine. The inner raceway of the needle roller bearing 6 is formed by the bearing ring 5.

[0014] The circular circumference of the cylindrical partial circumference 7 is smaller than the circular circumference of the adjacent unbalanced sections 9 and 10, and 11 and 12, respectively. Both the cylindrical partial circumference 7 and the inner raceway on the bearing ring 5 are radially recessed relative to the axial shoulders 13 and 14 of the unbalanced sections 9 to 12. The width of each bearing ring 5 is smaller than the distance between the axial shoulders 13 and 14, which extend circumferentially only partially and essentially symmetrically to the load zone on the cylindrical partial circumference 7 and the adjacent bearing ring 5, with a circumferential angle of significantly less than 180°. Each bearing ring 5 is mounted between the axial shoulders 13 and 14 at approximately equal distances on both sides. Figure 3 The bearing rings 5 ​​are mounted by threading them onto the unbalance shaft 1 and then positioning them on the bearing journals 3 and 4.

[0015] The imbalance of the unbalance sections 9 to 12 and the imbalance of the adjacent bearing journals 3, 4 are to be maximized in order to maximize the shaft imbalance (see arrow in Figure 3 ) essentially parallel and aligned, wherein each cylindrical partial circumference 7 is oriented circumferentially such that it is loaded essentially centrally around its circumference.

[0016] The clamping elements 15, which are made of plastic or, alternatively, of spring-hardened metal sheet, have an approximately crescent-shaped cross-section and are inserted under elastic deformation in the radial clearance that is bounded by the bearing journal back 8 and the inner surface of the bearing ring 5. The radial preload force of the clamping element 15 acts on the bearing ring 5 in the direction opposite to the shaft imbalance direction, so that the bearing ring 5 is held in a static contact with the cylindrical partial circumference 7.

[0017] The axial fastening of the bearing rings 5 ​​to the bearing journals 3, 4 is achieved (beyond the clamping force-induced static friction) by axial positive locking between the clamping element 15 and the unbalanced shaft 1 on the one hand, and between the clamping element 15 and the bearing ring 5 on the other. This secures the clamping element 15 against axial displacement in both directions relative to the unbalanced shaft 1, and each bearing ring 5 is secured against axial displacement in both directions relative to the clamping element 15 and, consequently, also relative to the unbalanced shaft 1 by means of the clamping element 15. There is no direct axial positive locking connection between the bearing ring 5 and the unbalanced shaft 1.

[0018] In the illustrated embodiment, the axial positive locking between the clamping element 15 and the unbalanced shaft 1 is formed by a groove 16 in the bearing journal back 8 with groove walls extending transversely to the shaft's axis of rotation 18, which axially enclose the end faces 20 of the clamping element 15 with virtually no play. The axial positive locking between the clamping element 15 and the bearing ring 5 is formed by radially outward projections 17 on the clamping element 15, which also axially enclose the end faces of the bearing ring 5 with virtually no play.

[0019] The term 'axially practically free of play' refers either to an axially free-of-play mounting or to an axially free-play mounting whose axial play is dimensioned to a maximum extent that axial contact of the bearing ring 5 directly with the unbalanced shaft 1 is excluded.

[0020] The projections 17 are designed as snap hooks with insertion chamfers to allow them to deflect elastically in a radially inward direction when the clamping element 15 is clipped between the bearing journal backs 8 and the bearing ring 5.

[0021] In an alternative version, the snap hooks can be replaced by a Figure 3 The dotted projection 17' on the clamping element 15 can be added or replaced. This projection engages in a transverse bore 19 in the bearing ring 5, thus securing it against rotation relative to the bearing journal 3, 4 – in addition to the static friction of the bearing ring 5 on the cylindrical partial circumference 7. The projection 17', and therefore also the transverse bore 19, are positioned diametrically opposite to the load zone in the unloaded circumferential area of ​​the bearing journal 3, 4.

Claims

1. A balance shaft, comprising: - an unbalance shaft (1) having an unbalance section (9, 10, 11, 12) and an adjacent bearing pin (3, 4) with an only partially cylindrical circumference, the cylindrical part-circumference (7) of which is oriented towards the unbalanced shaft mass, - a bearing ring (5) surrounding the bearing pin (3, 4), which bears against the cylindrical part-circumference (7) and delimits a free space with a radially opposite bearing pin back (8), - and a clamping element (15) clamped in the free space, which clamps the bearing ring (5) radially against the cylindrical part-circumference (7), characterized in that the clamping element (15) secures the bearing ring (5) against axial sliding on the bearing pin (3, 4) on both sides, the clamping element (15) being connected in an axially interlocking manner to the unbalance shaft (1) on one side and to the bearing ring (5) on the other side.

2. The balance shaft according to claim 1, characterized in that the cylindrical part-circumference (7) is radially recessed relative to the unbalance section (9, 10, 11, 12).

3. The balance shaft according to claim 1 or 2, characterised in that the interlocking connection between the clamping element (15) and the unbalance shaft (1) is formed by a groove (16) in the bearing pin back (8), the groove walls of which axially enclose axial end faces (20) of the clamping element (15).

4. The balance shaft according to any one of the preceding claims, characterized in that the interlocking connection between the clamping element (15) and the bearing ring (5) is formed by radially outward projections (17) on the clamping element (15), which axially enclose the end faces of the bearing ring (5).

5. The balance shaft according to any one of the preceding claims, characterized in that the interlocking connection between the clamping element (15) and the bearing ring (5) is formed by a radially outward projection (17') on the clamping element (15), which engages in a transverse bore (19) in the bearing ring (5) and secures this in an interlocking manner against rotation relative to the bearing pin (3, 4).