GB2156036A

GB2156036A - Tensioning pulley

Info

Publication number: GB2156036A
Application number: GB08407380A
Authority: GB
Inventors: Trevor Martin Stocks; Derek James Hoult
Original assignee: INA Bearing Co Ltd; INA Bearing Co Inc
Current assignee: Schaeffler UK Ltd; Schaeffler Group USA Inc
Priority date: 1984-03-21
Filing date: 1984-03-21
Publication date: 1985-10-02
Also published as: GB2156036B; GB8407380D0

Abstract

A tensioning pulley for a belt drive comprises an inner bearing element (22) on which an outer bearing element (18) rotates about a pulley axis (24). The inner element (22) is an integral component and comprises a cylindrical portion and an end wall (50). The pulley is mounted on an engine block (8) by a bolt (28), the head of which is situated within the cylindrical portion. Tension adjustment is made by slackening the bolt (28), rotating the inner bearing element (22) about the axis (34) of the boil, and re-tightening the bolt (28). <IMAGE>

Description

SPECIFICATION Tensioning wheel This invention relates to a tensioning wheel for a belt drive or the like.

According to the present invention there is provided a tensioning wheel for a belt drive or the like, comprising a hub and an outer element which is supported for rotation relatively to the hub about a wheel axis, mounting means being provided for mounting the hub for pivotal movement about an adjustment axis which is spaced from the wheel axis, the mounting means having a part which is operable to release the hub, to allow such pivotal movement, and to engage the hub, to secure the hub in a selected position, this operable part being disposed within a recess in the hub.

With such a construction, the operable part of the mounting means lies between the ends of the hub, and consequently the tensioning wheel need not project to a significant extent beyond the belt which runs over it.

In a preferred embodiment, the recess comprises a cylindrical cavity extending from one end of the hub and terminating short of the other end to leave an end wall. A hole is provided in the end wall for receiving the mounting means, which may, for example, be in the form of a bolt, the head of the bolt constituting the operable part and being disposed within the cavity. The hub is also provided with a formation for engagement by a suitable tool in order to pivot the hub about the adjustment axis. This formation may take the form of a non-circular (for example hexagonal) hole in the end wall.

The tensioning wheel may be constructed in the form of a rolling element bearing, the hub constituting the inner race and the outer element constituting the outer race. The outer element may be provided with a tyre, which may take the form of a moulded-on plastics element.

For a better understanding of the present invention, and to show how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a partly cut-away perspective view of an internal combustion engine provided with a known form of tensioning pulley; Figure 2 is a sectional view through the tensioning pulley of Figure 1; Figure 3 is a view taken in the direction of the arrow Ill in Figure 2; Figure 4 is a sectional view of another form of tensioning pulley; Figure 5 is a view taken in the direction of the arrow V in Figure 4; Figure 6 is a sectional view of a tensioning pulley in accordance with the present invention; Figure 7 is a view taken in the direction of the arrow VII in Figure 6; Figure 8 is a sectional view of another form of tensioning pulley in accordance with the present invention;; Figure 9 is a view taken in the direction of the arrow IX in Figure 8.

The engine shown in Figure 1 has an overhead camshaft 2 which is provided at one end with a toothed wheel 4. The crankshaft 6 is provided with another toothed wheel 8, and a further toothed wheel 10 provided on an auxiliary shaft 1 2. A toothed belt 1 4 runs over the wheels 4, 8 and 10, the teeth of the belt engaging the teeth of the wheels to prevent slip. The rear (i.e. untoothed) face of the belt 14 runs over a tensioning pulley 16, which is shown in greater detail in Figures 2 and 3.

The tensioning pulley comprises an outer element 1 8 which comprises two pressed steel parts which are riveted together. The outer element 1 8 is supported by rolling elements 20 on a hub 22, for rotation about an axis 24. The hub 22 is provided at one end with a hexagonal boss 26, and the entire pulley wheel is secured to the engine block B by a bolt 28 which extends through a hole 30 in the hub 22. It will be appreciated that the centreline 34 of the bolt 28 is spaced from the axis 24.

To adjust the tension in the belt 14, the hub is pivoted about the centreline 34 of the bolt 28. This is done by unscrewing the bolt 28, by means of an Allen key, and then rotating the hub by means of a spanner 36 engaging the hexagonal boss 26, as shown in Figure 3. When the tension in the belt 1 4 is correct, the bolt 28 is re-tightened, while holding the hub 22 in its adjusted position with the spanner 36.

It will be appreciated from Figures 1 and 2 that the boss 26 and the head of the bolt 28 project for some distance from the plane of the adjacent edge of the belt 14. Figure 1 shows a timing belt cover 38, which is provided with pressed-out portions 40 to accommodate the boss 22 and the head of the bolt 28. This increases the overall length of the engine. Another disadvantage of the tensioning pulley shown in Figures 1 to 3 is that the hub 22 needs to have a relatively large diameter in order that the distance between the axis 24 and the centreline 34 is large enough to provide a range of adjustment between the required limits. Because the hub 22 is solid, it is uneconomical in the use of material and also is heavy.

Figures 4 and 5 show a tensioning pulley which avoids some of the disadvantages of that shown in Figures 1 to 3. The embodiment of Figures 4 and 5 is known to us but is not yet available to the public.

In the embodiment of Figures 4 and 5, the outer element 1 8 is again formed from two parts which are riveted together. However, the hub, instead of being a solid component, comprises a hollow cup 42 provided with an end cover 44. The cup 42 is provided with a hexagonal hole 46 for receiving an Allen key to rotate the hub 22 about the centreline 34 of the bolt 28.

While the embodiment of Figures 4 to 5 reduces the weight and axial length of the assembly compared to the embodiment of Figures 1 to 3, it has further disadvantages in that the cup 42 and end cover 44 have to be fitted together, which requires an extra step in the assembly of the pulley as a whole. Furthermore, the cup 42 and the end cover 44 have to be manufactured to close tolerances, because they have a decisive influence on the alignment and orientation of the outer element 18.

Figures 6 and 7 show a tensioning pulley in accordance with the present invention. In this embodiment, the outer element 18 comprises an outer race of a bearing, the inner race of which comprises the hub 22. The hub 22 is in the form of a cup, having a cavity 48 which extends from one end of the hub 22 and terminates short of the other end to leave an end wall 50. The end wall 50 has the hole 30 for the bolt 28, and the hexagonal hole 46 for turning the hub 22 about the centreline of the bolt 28. It will be appreciated that the head of the bolt 28 is situated entirely within the cavity 48, with the result that no part of the pulley 1 6 needs to project, in the direction away from the engine block B, beyond the edge of the belt 14.

The hub 22 can conveniently be manufactured as a cold extrusion. This technique enables the hub 22 to be formed with a relatively thin-walled cylindrical portion and a relatively thick-walled.end wall 50. By way of example, the wall thickness of the cylindrical portion may be not more than 60% of the wall thickness of the end wall 50. The wall thickness of the end wall 50 is preferably not less than 50% (typically about 60%) of the width across the flats of the hexagonal hole 46, in order that the required torque can be applied to the hub 22 without plastically deforming the hole 46.

The pulley of Figures 6 and 7 has a double row of balls 20 to provide enough strength for heavy duty applications. The belt 14 runs directly on the outer surface of the outer element 1 8. Figures 8 and 9 show an alternative construction, using substantially the same form of hub 22, but with the outer element 1 8 supported by only a single row of balls 20. The outer element 20 is provided with a plastis tyre which is moulded onto it in order to provide a larger outside diameter and axial extent.

Claims

1. A tensioning wheel for a belt drive or the like, comprising an inner bearing element and an outer bearing element which is supported on the inner bearing element by rolling elements for rotation relatively to the inner bearing element about a wheel axis, the inner bearing element comprising a cylindrical portion, which is engaged by the rolling elements, and an end wall which is integral with the cylindrical portion, the end wall having a hole which receives mounting means for mounting the inner bearing element for pivotal movement about an adjustment axis which is spaced from the wheel axis, the mounting means having a part which is operable to release the inner bearing element, to allow such pivotal movement, and to engage the inner bearing element, to secure the inner bearing element in a selected position, this operable part being disposed within the cylindrical portion of the inner bearing element.

2. A tensioning wheel as claimed in claim 1, in which the mounting means comprises a bolt which extends through the hole, the operable part comprising a head of the bolt.

3. A tensioning wheel as claimed in claim 1 or 2, in which the end wall is provided with a formation for engagement by a suitable tool in order to pivot the inner bearing element about the adjustment axis.

4. A tensioning wheel as claimed in claim 3, in which the formation comprises a noncircular aperture in the end wall.

5. A tensioning wheel as claimed in any one of the preceding claims, in which the end wall comprises a single thickness of material which is clamped, in use, between the operable part of the mounting means and a surface to which the inner bearing element is secured.

6. A tensioning wheel as claimed in any one of the preceding claims, in which the end wall has a face which constitutes an extreme axial end face of the inner bearing element.

7. A tensioning wheel as claimed in any one of the preceding claims, in which the inner bearing element is formed by cold extrusion.

8. A tensioning pulley as claimed in any one of the preceding claims, in which the wall thickness of the cylindrical portion of the inner bearing elements is less than the thickness of the end wall.

9. A tensioning pulley as claimed in claim 8, in which the wall thickness of the cylindrical portion is not more than 60% of the thickness of the end wall.

1 0. A tensioning wheel as claimed in any one of the preceding claims, in which there are two rows of the rolling elements between the inner bearing element and the outer bearing element.

11. A belt drive including a tensioning wheel in accordance with any one of the preceding claims.

1 2. An internal combustion engine comprising a crankshaft and a camshaft which is driven from the crankshaft by a belt drive in accordance with Claim 11.

11. A tensioning wheel as claimed in any one of the preceding claims, in which the outer bearing element is provided with a tyre.

12. A tensioning wheel substantially as described herein with reference to, and as shown in, Figures 6 and 7 or Figures 8 and 9 of the accompanying drawings.

1 3. A belt drive including a tensioning wheel in accordance with any one of the preceding claims.

1 4. An internal combustion engine comprising a crankshaft and a camshaft which is driven from the crankshaft by a belt drive in accordance with claim 1 3.

CLAIMS Amendments to the claims have been filed, and have the following effect: Claims 1-14 above have been deleted or textually amended.

New or textually amended claims have been filed as follows:

1. A tensioning wheel for a belt drive or the like, comprising an inner bearing element and an outer bearing element which is supported on the inner bearing element by rolling elements for rotation relatively to the inner bearing element about a wheel axis, the inner bearing element comprising a cylindrical portion, which is engaged by the rolling elements, and an end wall which is integral with the cylindrical portion, the wall thickness of the cylindrical portion being not more than 60% of the thickness of the end wall, the end wall having a hole receiving mounting means for mounting the inner bearing element on a support body for pivotal movement about an adjustment axis which is spaced from the wheel axis, the mounting means having a part which is operable to release the inner bearing element, to allow such pivotal movement, and to clamp the end wall against a surface of the support body, to secure the inner bearing element in a selected position, this operable part being disposed within the cylindrical portion of the inner bearing element.

5. A tensioning wheel as claimed in any one of the preceding claims, in which the end wall comprises a single thickness of material which is clamped, in use, between the operable part of the mounting means and the surface of the support body.

8. A tensioning wheel as claimed in any one of the preceding claims, in which there are two rows of the rolling elements between the inner bearing element and the outer bearing element.

9. A tensioning wheel as claimed in any one of the preceding claims, in which the outer bearing element is provided with a tyre.

1 0. A tensioning wheel substantially as described herein with reference to, and as shown in, Figures 6 and 7 or Figures 8 and 9 of the accompanying drawings.