GB2078332A

GB2078332A - A spur gear transmission system

Info

Publication number: GB2078332A
Application number: GB8117800A
Authority: GB
Original assignee: Voith Getriebe KG
Current assignee: Voith Getriebe KG
Priority date: 1980-06-12
Filing date: 1981-06-10
Publication date: 1982-01-06
Also published as: DE3022020C2; FR2484585B1; GB2078332B; FR2484585A1; CH653754A5; DE3022020A1

Abstract

In a spur gear transmission system of the type having two intermeshing gear-wheels (10, 20) and a thrust ring (13) which is attached to one gear-wheel (10) and rotates with it, the thrust ring bracing one gear-wheel against the other gear-wheel for transmitting an axial torce, for the purpose of accommodating the thrust ring (13) in the central region of its teeth, one gear-wheel (10) has a circumferential groove (15), in the vicinity of which tooth stumps (16) are provided. The thrust ring 13) has inner teeth (17) formed in such a way that they can be introduced across the teeth of one gear-wheel (10) into the circumferential groove (15) and rest on the tooth stumps (16) after rotation through half an interval between the inner teeth. <IMAGE>

Description

SPECIFICATION A spur gear transmission system The invention relates to spur gear transmission systems of the type comprising two intermeshing gear-wheels and a thrust ring which is fitted on one of the gear-wheels and rotates with it, the thrust ring bracing one of the gear-wheels against the other gear-wheel for transmitting an axial force, and one gear-wheel having a circumferential groove in the central region of the teeth for accommodating the thrust ring, the depth of this groove being less than the height of the teeth so as to provide so-called tooth stumps in the vicinity of the circumferential groove remain. This type of transmission system is known from the following literature sources: 1. Dubbel, "Taschenbuch für den Machinenbau", ("Pocket Book of Machine Construction",) 1 sot Edition, 1953, page 681, illustration 239.

2. "KEM" (Construction, Elements, Methods), 1977, June SI, page 66, bottom of left-hand column.

The known transmission systems have a thrust ring or two thrust rings (also calied "thrust cogs") which are fitted on the gear-wheel shaft next to the smaller gear-wheel. The gear-wheel can have straight teeth or single-helical teeth. By means of the thrust ring or rings an axial force can be transmitted from one gear-wheel to the other gear-wheel. In particular, the axial force which arises in singlehelical teeth can be compensated.

Generally, it has to be borne in mind that axial forces can arise in both directions. For this reason, it is usually necessary to provide two thrust rings. The securing of the thrust rings against axial displacement under the axial force also presents problems.

For this purpose, supplementary securing rings are normally required. Overall, this means the thrust rings require a considerable amount of space. As a result, there is a considerable distance between the bearings of the gear-wheel shaft which bears the thrust rings. This gives rise to the danger that this gear-wheel shaft will be subject to unacceptable bowing and/or that the rotary critical bending speed will come too close to the rotary drive speed.

Sometimes, for certain applications, larger gearing has to be provided purely to avoid the said disadvantages.

An object of the invention is to provide an improvement in the known transmission systems whereby the distance between the bearings on the gear-wheel shaft fitted with a thrust ring can be as short as possible, while still ensuring that the thrust ring is adequately secured against axial displacement.

According to this invention, a spur gear transmission system of the type discussed above is characterised in that the thrust ring has inner teeth formed in such a way that they can be introduced into the circumferential groove across the teeth of one gear-wheel and, after rotation has been carried out relative to the gear-wheel, the thrust ring is shrinkfitted with its inner teeth on the tooth stumps, the other gear-wheel has a circumferential groove in which the thrust ring can engage, and the thrust ring is arranged at least approximately centrally between the bearings of the shaft of one of the gear-wheels.

Thus, with the invention, only one single thrust ring is required, even when the axial forces arise in both directions. The thrust ring is in fact arranged in a circumferential groove in the central region of one of the gear-wheels. This means that under the axial force the thrust ring is braced laterally on the circumferential groove, which is bounded by the teeth which remain whole. The axial force can be transmitted completely form-locked. Supplementary securing rings can be omitted. However, the thrust ring can be made narrower than in known gearing.

Overall, therefore, the distance between the bearings can be reduced considerably, compared with hitherto.

The arrangement of the thrust ring in the central region of one of the gear-wheels is possible due to the fact that the other gear wheel has a circumferential groove in which the thrust ring can engage, even when said one gear-wheel is made in one piece. That is, it is not necessary to shrink-fit an initially separate gear-ring onto the gear-wheel body. The invention can therefore also be used for pin ions with very small numbers of teeth, which often have a dedendum diameter which is only slightly greater than the diameter of the shaft.

Preferably, the thrust ring will be arranged centrally between the bearings. In this way the advantage is obtained that the thrust ring does not tilt at an angle if the gear-wheel shaft should bow. By this means, unlike in the case of the known solutions, the meshing geometry between the thrust ring and the other gear-wheel remains unchanged. Edgepressure is thereby avoided, and the risk of wear is reduced.

Compared to that known transmission systems, the design according to the invention is also less affected by manufacturing inaccuracies or by variations in the axial forces.

A further advantage is afforded by cutting into the flanks of the teeth with the circumferential grooves; this means that the thermal loading of the lubricating oil in the teeth mesh is reduced.

An advantageous feature of the invention is claimed in Claim 2. This concerns the construction of the circumferential groove with bevelled transitional surfaces between the sides of the groove and the base of the groove. Thus, if the thrust ring is pushed over the teeth in the heated state and rotated into the groove, upon cooling the said bevelled transitional surfaces come up against corresponding bevelled surfaces on the thrust ring. The thrust ring thus centres itself into a position in which displacement is not possible within the width-tolerance of the circumferential groove under considerable axial foce.

This makes the gearing particularly suitable for transmitting high axial forces through the transmission system.

A further important concept concerns a process for producing the gear-wheel which bears the thrust ring as claimed in Claim 3.

In order that the invention can be readily understood andfurtherfeatures made apparent two embodiment examples of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 shows the two gear-wheels of a spur gear transmission system, according to one embodiment, partially in elevation and partially in section.

Figure2a is a cross-section along the line II in Figure 1, as the thrust ring is being inserted.

Figure2b is a cross-section along the line II in Figure 1, with the thrust ring fully mounted.

Figure 3 is a partial section through another embodiment of the invention.

Figures 2a and 2b are on a larger scale than Figure 1.

In Figure 1 two inermeshing gear-wheels 10 and 20 of a spur gear transmission system can be seen.

The gear-wheel 10, which is the so-called pinion, is made in one piece and has a smaller pitch circle diameter than the other gear-wheel, which is the so-called greater wheel 20. The shaft 11 of the pinion 10 is mounted in bearings 12, and the shaft 21 of the greater wheel 20 is likewise mounted in bearings 22 and 23.

In the centre of the pinion 10 a thrust ring 13 is arranged. This engages in a corresponding circumferential groove 24 in the greater wheel 20. The side surfaces of the thrust ring 13, the so-called butting faces 14, are bevelled sufaces with a very large bevel angle which is only slightly less than 180 degrees.

The pinion 10 can brace itself in the axial direction via one of these butting surfaces 14 against the greater wheel 20. For this purpose its circumferential groove 24 has corresponding bevelled side surfaces (butting surfaces 25).

To accommodate the thrust ring 13 in the teeth of the pinion 10, the latter has a circumferential groove 15. The depth thereof is less than the height h of the teeth. Preferably, the depth t is approximately equal to half the tooth height h. The width of the circumferential groove iSis only slightly greater than the thickness of the thrust ring 13. In the vicinity of the circumferential groove 15 the so-called tooth stumps 16 of the teeth on the pinion 10 remain.

The thrust ring 13 has teeth 17 on its inner face.

The addendum circle diameter of these is the same as the addendum circle diameter of the tooth stumps 16. As shown in Figure 2a, to insert the thrust ring 13 in the circumferential groove 15 the teeth 17 on the thrust ring are guided through the interstices be tween the teeth on the pinion 10. When the thrust ring 13 has been brought into the annular groove 15, it is rotated relative to the pinion 10 through half an interval between the teeth, so that the teeth 17 finally rest on the tooth stumps 16 (Figure 2b).

The thrust ring 13 is fixed in this position, prefer ably by shrinking. As can be seen in the Drawing, the pinion 10 and the thrust ring 13 preferably have the same number of teeth. Furthermore, the width of the top surfaces of the tooth stumps 16 and the teeth 17 is at least approximately the same. However, it is not necessary to adherto these characteristics. The teeth 17 preferably have smooth flanks. However, the toothflanks may also be in the shape of an evolute as is indicated at 18 (Figure 2a) in dashed lines.

To secure the thrust ring 13 against rotation a bolt 30 may be provided (Figure 2b), projecting into one of the interstices between two tooth stumps 16.

Alternatively, a hollow space located between the tooth stumps 16 and the teeth 17 is filled with a curable synthetic substance, as has been indicated at; 40 (Figure 2b) in dashed lines.

The gear-wheels 10 and 20 can have straight teeth (with the teeth extending parallel to the axis of rotation) or single-helical teeth (as indicated at 19 and 29 with lines at an angle to the axial direction).

Accordingly, the inner teeth 17 on the thrust ring 13 are also straight teeth or helical teeth.

While the circumferential groove 15 in Figure 1 has a rectangular cross-section and the thrust ring 13 therefore rests on the base of the groove or (to put it better) on the tops of the tooth stumps 16, Figure 3 shows an embodiment example which differs from this: Between the base of the circumferential groove 15a in the gear-wheel 10a and its side walls 32 (lying approximately in radial planes) there are transitions formed by bevelled sufaces 31. The thrust ring 13a rests on these bevelled surfaces 31, having corresponding bevelled surfaces 33 on its teeth 17 for this purpose.

Claims

1. A spur gear transmission system of the type having two intermeshing gear-wheels and a thrust ring which is fitted on one of the gear-wheels and rotates with it, the thrust ring bracing one of the gear-wheels against the other gear-wheel for transmitting an axial force, and one gear-wheel having a circumferential groove in the central region of the teeth for accommodating the thrust ring, the depth of this groove being less than the height of the teeth so as to provide so-called tooth stumps in the vicinity of the circumferential groove, characterised in that a) the thrust ring has inner teeth formed in such a way that they can be introduced into the circumferential groove across the teeth of one gear-wheel and, after rotation has been carried out relative to the gear-wheel, the thrust ring is shrink-fitted with its inner teeth on the tooth stumps, b) the other gear-wheel has a circumferential groove in which the thrust can engage, and, c) the thrust ring is arranged at least approxi mately centrally between the bearings of the shaft of one of the gear-wheels.

2. A transmission system accoding to Claim 1, characterised in that the circumferential groove has a bevelled transition into at least one of its two side surfaces, and that the teeth of the thrust ring have corresponding bevelled sufaces so that the thrust ring rests on the bevelled transition(s).

3. A transmission system according to one of Claims 1 or 2, characterised in that the gear-wheel which bears the thrust ring is produced by a process in which a) on the blank for the gear-wheel the circumferential groove is machined in a known way, and then the teeth are produced (or vice versa); b) the thrust ring equipped with the inner teeth is heated and pushed over the teeth of the gear-wheel in the axial direction, and then rotated in the circumferential groove until it rests with its teeth on the tooth stumps, and upon cooling forms a firm connection by shrinking; and c) the thrust ring is finished off by machining.

4. A transmission system constructed, arranged and adapted for use substantially as hereinbefore described with reference to Figures 1,2a and 2b, on Figure 3 of the accompanying drawings.