Balance shaft

Abstract

The invention relates to a balance shaft, comprising: an unbalanced shaft (1) with a centre of mass (9) at a distance from the rotational axis (8) thereof, which spans an unbalance plane (10) with the rotational axis, and a bearing pin (6, 7) with an only semi-cylindrical perimeter, wherein the cylindrical partial perimeter (11) is directed towards the shaft imbalance; a bearing ring (13) surrounding the bearing pin, which rests on the cylindrical partial perimeter and borders a free space together with a radially opposing bearing pin back (12); and a sheet metal spring (14) which is tensioned against the bearing pin back on one side and the bearing ring on the other side in the free space and which tensions the bearing ring radially against the cylindrical partial perimeter, characterised in that the sheet metal spring is tensioned against two supporting points (20, 21) on the bearing pin back, running on both sides of the imbalance plane and with orthogonal projections running on the imbalance plane relative to the centre of mass on this side of the rotational axis.

Description

[0001] balance shaft

[0002] The invention relates to a balance shaft comprising:

[0003] - an unbalanced shaft with a center of mass spaced from its axis of rotation, which forms an unbalance plane with the axis of rotation, and a bearing journal with only a partially cylindrical circumference, the cylindrical partial circumference of which is aligned towards the shaft unbalance,

[0004] - a bearing ring surrounding the bearing journal, which rests on the cylindrical part of the circumference and, together with a radially opposite bearing journal back, defines a free space,

[0005] - and a sheet metal spring which is tensioned in the free space against the bearing journal back on the one hand and the bearing ring on the other hand and tensions the bearing ring radially against the cylindrical part circumference.

[0006] A generic balance shaft with an unbalanced shaft and a bearing ring, which is attached to the bearing journal of the unbalanced shaft by means of a sheet metal spring clamped between the bearing ring and the bearing journal back, is known from DE 10 2019 101 319 A1. A stiffening rib runs along the bearing journal back in the direction of the rotation axis, counteracting the operational shaft deflection, and the sheet metal spring is tensioned against the ridge line of the stiffening rib.

[0007] The present invention is based on the object of providing a balance shaft of the type mentioned above with an improved clamping of the bearing ring.

[0008] The solution to this problem is provided by the features of claim 1. Accordingly, the sheet metal spring is to be clamped against two support points on the bearing journal back, which extend on either side of the unbalance plane, and whose orthogonal projections onto the unbalance plane with respect to the center of mass extend on this side of the rotation axis. Compared to the cited prior art, no rotational degree of freedom remains for the sheet metal spring clamped in the free space, whose rotational installation position is clearly defined and stabilized due to the position of the two support points on the bearing journal back, on the one hand, and the clamping against the bearing ring, on the other. Consequently, the sheet metal spring can no longer twist in an undefined manner or rotate with the bearing ring in the event of rotational slippage of the bearing ring during operation.Depending on the contact situation between the sheet metal spring and the back of the bearing journal, the term 'support point' refers to its contact point or, in the case of line or surface contact, its line or surface center of gravity.

[0009] Further features of the invention will become apparent from the following description and the drawings, which illustrate exemplary embodiments of balance shafts according to the invention. Unless otherwise stated, identical or functionally equivalent components or features are provided with the same reference numerals. They show:

[0010] Figure 1 shows the balance shaft known from the prior art cited at the beginning in a perspective view;

[0011] Figure 2 shows a bearing journal of a first balance shaft according to the invention as a perspective section;

[0012] Figure 3 shows a bearing journal of a second balance shaft according to the invention as a perspective section;

[0013] Figure 4 shows the bearing journal according to Figure 3 in a longitudinal section;

[0014] Figure 5 shows an alternative sheet metal spring to Figures 3 and 4 as a perspective individual part.

[0015] The known balance shaft according to reference figure 1 comprises an unbalanced shaft 1 manufactured as a cast or forged part with an end drive pin 2 for a drive wheel (not shown) to be mounted thereon and with unbalanced sections 3, 4 and 5 as well as with bearing pins 6 and 7, which each connect two of the unbalanced sections 3 and 4 or 4 and 5. The unbalanced shaft 1 has a center of mass 9 spaced from its axis of rotation 8, which, according to figure 2, spans an unbalance plane 10 with the axis of rotation 8. In order to maximize the shaft unbalance, the bearing journals 6, 7 are only partially cylindrical and their cylindrical partial circumference 11 (see dashed area in Figure 2) is oriented such that the unbalance of the unbalance sections 3 to 5 and the unbalance of the bearing journals 6, 7 are essentially parallel and aligned in the same direction and load the cylindrical partial circumference 11 essentially in the center of the circumference.The (non-cylindrical) partial circumference of the bearing journal 6, 7 radially opposite the cylindrical partial circumference 11 is referred to below as the bearing journal back 12 and is free from the orbit of the cylindrical partial circumference 11 relative to the rotation axis 8.

[0016] The balance shaft further comprises a bearing ring 13 surrounding each bearing journal 6, 7, a sheet metal spring 14 releasably attaching the bearing ring 13 to the bearing journal 6, 7 (non-destructively), and a needle roller and cage assembly 15 for radial needle bearing support of the balance shaft in a housing of an internal combustion engine. The inner raceway of the needle roller and cage assembly 15 is formed by the bearing ring 13. The sheet metal springs 14, made of spring-hardened sheet metal, have an approximately crescent-shaped cross-section and are each inserted, subject to elastic deformation, into the radial free space defined by the bearing journal back 12 on the one hand and the inner surface of the bearing ring 13 on the other. The radial preload force of the sheet metal spring 14 acts on the bearing ring 13 in the direction opposite to the shaft imbalance direction, so that the bearing ring 13 is clamped against the cylindrical partial circumference 11.In the known balance shaft according to Figure 1, the sheet metal spring 14 is open in the area of ​​the bearing journal back 12, with the spring ends 16 and 17 defining the opening being tensioned against the ridge line 18 of a longitudinally extending stiffening rib 19 of the unbalanced shaft 1. There is no further contact between the sheet metal spring 14 and the bearing journal back 12, so that the sheet metal spring 14 can rotate with the bearing ring 13 in the event of rotational slippage.

[0017] Such uncontrolled rotation of the bearing ring 13 is prevented in the balance shaft shown in Figure 2 by the contact geometry of the sheet metal spring 14 with the bearing journal back 12, explained below. According to the invention, the sheet metal spring 14 is tensioned against two support points 20 and 21 of the bearing journal back 12, which extend on either side of the unbalance plane 10 and, in this case, next to the stiffening rib 19, and whose orthogonal projections onto the unbalance plane 10 extend on this side of the rotation axis 8 with respect to the center of mass 9. An orthogonal projection is known to be the perpendicular mapping of a point onto a plane. Figure 3 shows the orthogonal projection of the support point 21 as a point drawn in black below the rotation axis 8.These support conditions and the opposing clamping of the sheet metal spring 14 against the bearing ring 13 determine the rotational position of the sheet metal spring 14 relative to the rotation axis 8, so that the aforementioned twisting or co-rotation of the sheet metal spring 14 is excluded. In the embodiment of Figure 2, the cylindrical partial circumference 11 springs back radially relative to shoulders 22 and 23 of the unbalanced shaft 1, with the shoulders 22, 23 enclosing the end faces 24 of the bearing ring 13 with tight axial play and thus securing the bearing ring 13 against displacement on both sides on the bearing journal 6 and / or 7.

[0018] Figures 3 and 4 show detailed views of the second balance shaft according to the invention. The axial fastening of the bearing ring 13 on the bearing journal 6 and / or 7 is achieved exclusively by the sheet metal spring 14, which is axially positively connected to the bearing ring 13 on the one hand and to the bearing journal back 12 on the other. The axial positive connection of the sheet metal spring 14 with the bearing ring 13 is formed in this case by four projections 25 of the sheet metal spring 14, which, as cut and radially outwardly formed sheet metal tabs, axially enclose the bearing ring 13 at its end faces 24.The axial positive connection of the sheet metal spring 14 with the bearing journal back 12 is formed by interlocking projections and / or recesses of the sheet metal spring 14 and the bearing journal back 12, and in this case by the bearing journal back 12 having either one or two grooves 26 extending on both sides of the stiffening rib 19, the groove walls of which enclose the axial end faces 27 of the sheet metal spring 14 with minimal axial play. Alternatively, the grooves 26 can be replaced by a single groove on the ridge line 18 of the stiffening rib 19.

[0019] The sheet metal spring 14 of the third balance shaft according to the invention, shown as an individual part in Figure 5, has recesses 28 into which projections (not shown) on the bearing journal back 12 engage and thus produce the axial positive connection of the sheet metal spring 14 with the bearing journal back 12.

[0020] All of the sheet metal springs 14 shown above are open around their circumference, with the opening 29 of each sheet metal spring 14 being located in a circumferential region of the bearing ring 13 which is diametrically opposite the cylindrical partial circumference 11.

Claims

Patent claims balance shaft, comprising: - an unbalanced shaft (1) with a center of mass (9) spaced from its axis of rotation (8), which defines an unbalance plane (10) with the axis of rotation (8), and a bearing journal (6, 7) with only a partially cylindrical circumference, the cylindrical partial circumference (11) of which is aligned towards the shaft unbalance, - a bearing ring (13) surrounding the bearing journal (6, 7), which bears against the cylindrical part circumference (11) and, together with a radially opposite bearing journal back (12), defines a free space, - and a sheet metal spring (14) which is tensioned in the free space against the bearing journal back (12) on the one hand and the bearing ring (13) on the other hand, and tensions the bearing ring (13) radially against the cylindrical partial circumference (11), characterized in that the sheet metal spring (14) is tensioned against two support points (20, 21) of the bearing journal back (12), which extend on either side of the unbalance plane (10) and whose orthogonal projections onto the unbalance plane (10) with respect to the center of mass (9) extend on this side of the axis of rotation (8). Balance shaft according to claim 1, characterized in that the sheet metal spring (14) secures the bearing ring (13) against displacement on both sides on the bearing journal (6, 7), wherein the sheet metal spring (14) is connected in an axially positive manner on the one hand to the bearing journal back (12) and on the other hand to the bearing ring (13).Balance shaft according to claim 2, characterized in that the axial positive connection of the sheet metal spring (14) with the bearing ring (13) is formed by radial projections (25) of the sheet metal spring (14), which axially enclose the bearing ring (13) at its end faces (24). Balance shaft according to claim 2 or 3, characterized in that the axial positive connection of the sheet metal spring (14) with the bearing journal back (12) is formed by interlocking projections and / or recesses in the sheet metal spring (14) and the bearing journal back (12). Balance shaft according to one of the preceding claims, characterized in that the sheet metal spring (14) is circumferentially open, wherein the opening (29). the sheet metal spring (14) is located in a circumferential region of the bearing ring (13) which is diametrically opposite the cylindrical partial circumference (11).

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