Sprocket

Abstract

A sprocket for a chain drive, in particular a timing chain drive for an internal combustion engine, is provided. The sprocket includes a radially outer toothed ring and a damping ring. The damping ring is axially spaced apart from, and radially inside of, the toothed ring. The damping ring has a radially outer surface that is shaped to be complementary to link plates of the timing chain. The design of the sprocket results in the damping ring being subject to practically no wear, being producible from a conventional material, and being economical to produce.

Claims

1. A sprocket for a chain mechanism, comprising: a center section; a toothed rim configured radially on an outside circumference of the center section, the toothed rim having a plurality of tooth recesses configured to receive rollers of a chain; and a damping ring axially adjacent to the toothed rim, wherein the damping ring includes a plurality of chain link plate support surfaces, each of the plurality of chain link plate support surfaces is located axially adjacent to a corresponding tooth of the toothed rim, each of the plurality of chain link plate support surfaces has a support surface shape configured to be complementary with respect to chain link plates of a chain when the chain is engaged with the toothed rim, and the plurality of chain link plate support surfaces has a radial height below a radial height of a radially smallest portion of the tooth recesses such that a gap is formed between each of the plurality of chain link plate support surfaces and a respective chain link plate of the chain, the gap being sized to accommodate an oil film between and in contact with the plurality of chain link plate support surfaces and the respective chain link plates.

2. The sprocket as claimed in claim 1, wherein the damping ring is made from the same material as the toothed rim.

3. The sprocket as claimed in claim 2, wherein the center section, the toothed rim and the damping ring are made in one piece and from the same material.

4. The sprocket as claimed in claim 3, wherein the center section, the toothed rim and the damping ring are sintered, forged or machined.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a sprocket section according to an embodiment of the invention.

(2) FIG. 2 shows a sprocket section according to an embodiment of the invention with a chain wrapped around it.

(3) FIG. 3 shows a side view of a sprocket section according to an embodiment of the invention with a chain wrapped around it.

(4) FIG. 4 shows a magnified view of a gap between a chain link and plate and a chain link plate support in accordance with the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

(5) In the following text, the same designations apply to identical structural elements in FIGS. 1 to 3.

(6) FIG. 1 shows a plan view of an embodiment of a sprocket section of a sprocket 1 according to the invention in a three-dimensional illustration. Centrally, the sprocket 1 has a toothed rim 2 which consists of a multiplicity of teeth. In this exemplary embodiment, a damping ring 3 is arranged on both sides in an axially adjacent manner with respect to the toothed rim 2. The damping ring 3 serves to bear chain link plates 4 of a control chain 5 of a chain drive.

(7) FIG. 2 once again shows the sprocket section of the sprocket 1 from FIG. 1, but with a control chain 5 wrapped partially around it. The control chain 5 is a commercially available control chain 5 with chain link plates 4, for which reason the control chain 5 is not described in greater detail, since it is generally known from the prior art to a person skilled in the art.

(8) According to the invention, the damping ring 3 has, radially on the outside, a surface which is complementary with respect to the chain link plates 4 which are in engagement with the sprocket 1. Since a small gap in the range of tenths of millimeters is configured between the chain link plates 4 and the damping ring 3 (see FIG. 4), a lubricant film is formed between the damping ring 3 and the chain link plates 4 during the operation of the chain drive, which lubricant film minimizes what is known as chain whine.

(9) The damping ring 3 is preferably made from the same material as the sprocket 1, as a result of which wear is counteracted effectively. Furthermore, the sprocket 1 and the damping ring 3 are preferably made in one piece and from the same material, and are manufactured jointly, for example, by way of sintering or forging or the removal of material.

(10) Functional principle: in the region of the sprocket which is not in engagement with the chain, an oil film is formed on the surface of the damping ring on account of, for example, airborne oil particles or splash oil which has to be displaced by the chain link plates during the entry of the chain into the sprocket. Active lubrication is not absolutely necessary in contrast to the known prior art. On account of the oil film which is formed automatically, the jolt during the entry of the sleeve or roller into the tooth root as a cause of the noise (chain whine) is damped. Here, the gap between the link plate and the damping ring is to be selected to be very small, and should lie in the range of a few tenths of millimeters.

(11) In an advantageous way, the damping ring is not subject to any wear on account of the gap, and can be produced from a conventional (non-elastomeric) material (for example, steel). It ideally consists of an identical material to the sprocket itself, and is also formed in a virtually cost-neutral manner along with the production of said sprocket, for example by way of sintering, forging or machining with the removal of material.

(12) FIG. 3 also shows a side view of the sprocket section according to the invention of the sprocket 1 with a chain wrapped around it. As can be seen in FIG. 3, the chain link plates 4 have planar bearing faces in said exemplary embodiment, that is to say the complementary surfaces of the damping ring 3 are also planar in the bearing region. The bearing region of the damping ring 3 is therefore a regular polygon. The number of planar surfaces is, for example, dependent on the transmission ratio which is aimed for or else on the diameter of the damping ring 3.

(13) The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.

LIST OF DESIGNATIONS

(14) 1 Sprocket 2 Toothed rim 3 Damping ring 4 Chain link plate 5 Control chain