GB2233424A

GB2233424A - Torsional vibration damper

Info

Publication number: GB2233424A
Application number: GB9003173A
Authority: GB
Inventors: Terry Coldford
Original assignee: Carl Freudenberg KG
Current assignee: Carl Freudenberg KG
Priority date: 1989-06-29
Filing date: 1990-03-20
Publication date: 1991-01-09
Anticipated expiration: 2010-03-20
Also published as: GB2233424B; GB9003173D0

Abstract

A torsional vibration damper comprises a flywheel ring (3) fixed to the outside circumference of a metallic hub (1) by a rubber spring ring (4), the hub (1) being provided on its side facing the spring ring (4) with a firmly adhesive, continuous coating (5) of thermosetting plastics material. The ratio of the average radial thickness (A) of the coating (5) to the average radial thickness (B) of the spring ring (4) lies within the range 0.25 to 3. The thermal expansion of the coating (5), arising during use, effects a radially directed prestress in the spring ring (4) of corresponding size. By this means, the spring ring always has largely conforming spring characteristics independent of the operating temperature. <IMAGE>

Description

TORSIONAL VIBRATION DAMPER This invention relates to a torsional vibration damper of the kind in which a metallic flywheel ring is fixed to the outside circumference of a metallic hub via the intermediary of a rubber spring ring, the hub having, on its side facing the spring ring, a continuous coating of plastics material firmly adhered thereto. Hereinafter such a torsional vibration damper will be referred to as a tor- sional vibration damper of the kind referred to .

A torsional vibration damper of the kind referred to is known from DE-A-2,825,075. In this case, the hub is produced from thermosetting plastics material with a view to improving the weight per unit of power and is proviced in the region of its outside circumference with a metallic reinforcing insert to reduce the tendency to creep. The damping effect achieved is influenced to a great extent by the temperat7ures which arise during the intended use.

The underlying object of the invention is to develop further a torsional vibration damper of the kind referred to in such a way that the damping effect arising under the influence of alternating ambient temperatures is more constant.

According to the invention this object is achieved with a torsional vibration damper of the kind referred te in which the coating comprises a thermosetting plastics material and the ratio of the average radial thickness A of the coating to the average radial thickness of the spring ring ranges from 0.25 to 3.

By the use of thermosetting plastics material for the coating, the latter is resistant to creep. Therefore, a basic variation of the design of the coating arising through manufacture is nct to be expected even under the radial prestress of the spring ring, whjich may under certain circumstances be considerable. Therefore, the prestress in the spring ring arising through manufacture is largely retained even in long-term use.

Even with rising temperatures which can, for example, arise through use, the prestress in the spring ring does not undergo substantial variation insofar as the decrease in the rigidity of the spring ring arising in such a situation is compensated by an increasing prestress of the spring ring. This latter prestress is caused by a radial expansion of the outside diameter of the coating due to the heating. In a quantitative respect, lkike the decrease in the rigidity of the spring ring, it is dependent on the temperatures reached. By this means, the damping effect arising is largely independent of temperature and is always present in the same manner.

Advantageously the ratio of the average radial thickness A of the coating and the average radial thickness B of the spring ring may range from 1 to 2.

If epoxy or polyester resin is used to manufacture the coating, a particularly good effectiveness is achieved.

The hub undergoes a noticeable improvement of its rigidity in the region of its casing by the firmly adhesive coating made of thermosetting material. By this means it is possible to produce the hub by deep drawing from a steel sheet, which differs from the known embodiments by a greatly reduced thickness. The reduction of the total weight of the hub thus arising permits the mass of the flywheel ring to be increased to the same extent and, by this means, an essentially improved damping power to be achieved in relation to the total weight of the torsional vibration damper.

To improve the bonding of the coating, the casing of the hub can be provided with radial indentations. By this means, its surface facing the coating is enlarged, which effects an increase in the forces which can be transmitted.

The indentations can be formed by the interspaces of a sinusouidal undulation of the casing extending in a circumferential direction. In addition to an enlargement of the adhesive surface required for a secure bonding of the coating, this results in a great increase in the dimensional stability of the hub. The thickness of the starting material required for the manufacture of the hub can accordingly be further reduced.

The indentations can be composed of holes completely penetrating the casing such as are produced, for example, by punching or drilling. After penetrating the holes the coating, moulded on in fluid state, is guaranteed a secure bonding to the casing.

The casing can be reinforced on the inside by a second, directly moulded on continuous coating made of thermosetting plastics material. In this case, a sandwich structure results in the region of the jacket of the hub, which sandwich structure is distinguished by a particularly good dimensional stability. With a construction of this type, the two coatings are expediently designed to merge together in one piece, for example by projections which enclose the casing of the hub at the end face or by holes completely penetrating the casing of the hub.

The coating can be reinforced by fibres internally distributed, for example by fibres from textiles, mineral or metal material. If the fibres are short, direct merging is possible, which simplifies the achievement of an even distribution. If the fibres are of greater length, the fibres can be combined to form an inherently firm surface structure, for example a surface structure in the form of a fabric, a knitted fabric or a non-woven material. This should expediently extend in a circumferential direction.

With regard to the selection and installation of appropriate reinforcing elements, it must be considered that the impairment of the linear thermal expansion of the coating is not so lkarge that the compensation of the reduction in the rigidity of the spring ring arising at higher temperatures is inadequate. From this aspect, the quantitative proportion of appropriate reinforcing elements must also not be too greatly dimensioned.

Embodiments of the invention will now be described, by way of example only, with particular reference to the accompanying drawings, in which: Figures 1 and 2 show a first embodiment of a torsional vibration damper according to the invention in longitudinal section and in front view, respectively.

Figures 3 and 4 show a second embodiment of a tcrsional vibration damper according to the invention in longitudinal section and in front view, respectively, and Figures 5, 6 and 7 show different segment sections of modified embodiments of torsional vibration dampers according to the invention.

The torsional vibration damper shown in Figures 1 and 2 comprises a metallic hub ribng made of deep-drawn metal sheet which is designed in the shape of a pot and has a casing or jacket 2 extending substantially parallel to its axis. The jacket 2 is coated on the outside with a continuous intermediate layer 5 made of a thermosetting plastics material, typically a fibre-reinforced epoxy resin, which intermediate layer is moulded on in fluid state and subsequently reinforced. The intermediate layer is of rotationally symmetrical design. Seen in longitudinal direction it has a sinusoidally bounded profile on the side facing radially outwards.

On the insdie of the jacket 2, the intermediate layer 5 is complemented continuously in the layer 9 constructed rotationally symmetrically. On the inside, this is bounded by a cylindrical surface.

On the outside, the intermediate layer 5 is surrounded by a flywheel ring 3. On the inside, the flywheel ring 3 is bounded by a rotationally symmetrical surface which extends substantially parallel to the outside contour of the intermediate layer 5.

Pressed in the axial direction into the interspace between the flywheel ring 3 and the intermediate layer 5 is a spring ring 4 produced separately of rubber. Arising through manufacture, the spring ring 4 has a radial extension which is greater than the available width of the gap between the intermediate layer 5 and the flywheel rinbg 3.

The elastic prestress in the spring ring 4 resulting from this guarantees a torsionally elastic, but captive fixing of the flywheel ring 3 on the outside circumference of the hub ring 1.

With the exemplary embodiment shown in Figures 1 and 2, the rubber spring ring 4 has in the installed state a uniform thickness of approximately 4 mm in all partial regions.

In the intermediate zone between the jacket 2 and the spring ring 4, the intermediate ring 5 has a thickness in radial direction which varies in the different partial regions between 7 mm and 9 mm and is on average 7.6 mm.

The radial thickness of the spring ring 4 is denoted as B and that of the intermediate layer 5 in the region of the largest extension and in the region of the smallest extension is denoted as A2 and Al, respectively.

With the exemplary embodiment of a torsional vibration damper described above, the flywheel ring 3 is designed in the region of its outside circumference as a V-belt pulley.

A construction of the torsional vibration damper deviating from the latter is possible without problem. For example, a design is possible in which the coating 5 of the jacket 2 in the region not radially enclosed by the flywheel ring 3 is provided on the outside with a V-belt pulley profile.

The embodiment of a torsional vibration damper shown in Figures 3 and 4 differs from that described above essentially by the fact that the jacket 2 of the hub ring 1 is provided with a circumferential undulation, the individual undulations of which extend parallel to the axis of the hub ring 1. By this means, the jacket 5 undergoes an essential stiffening, which permits a deep-drawing sheet of comparatively reduced thickness to be used for the manufacture of the hub ring 1.

According to the above descriptions, the jacket is embedded in synthetic resin, the coatings 5 and 9 being bounded radially inwards and radially outwards by surfaces surrounding the axis of rotation concentrically.

Arising through the axially bell-shaped pattern of the bounding surface pointing radially outwards of the coating 5 and the sinusoidal pattern of the jacket 2 in circumferential direction, the coating 5 has a radial thickness which varies permanently both in axial direction and in circumferential direction. Some of the values to be considered when determining the average thickness are entered in Figures 3 and 4 and are denoted as Al to A4.

The radial thickness of the spring ring 4, made of rubber, is denoted as B.

Figure 5 shows a torsional vibration damper, in which the jacket 5 is provided on the outside with calotte-shaped indentations, which noticeably increase the adhesive surface area for the bonding of the intermediate layer 5.

The indentations 6 can be produced through stamping or punching. They can be formed particularly easily at a time when the starting material used for the manufacture of the hub ring 1 is still in a flat shape. When proceeding in this manner, the indentations present even in the area of the region of the hub ring 1 projecting radially inwards are generally not a disturbance.

With the embodiment shown in Figure 6, apart from indentations of the type mentioned above, wave troughs of the jacket 2 of the hub ring 1 are additionally present following in succession in the circumferential direction.

Apart from a particularly reliable bonding of the polymeric material forming the intermediate layer 5, this results in a noticeable reinforcement of the hub ring 1. The thickness of the startibng material forming the hub ring and, consequently, the weight can accordingly be further reduced in relation to the embodiment shown in Figure 5.

With the embodiment shown in Figure 7, the jacket 2 is radially penetrated by holes 8 and provided with waves following successively in the circumferential direction.

By this means, the intermediate latyer 5 composed of the same polymeric material and the layer 9 are joined together through the holes in the jacket 2 in a particularly intimate manner. Fibres inserted in the polymeric material increase the dimensional stability of the intermediate layer 5 and the layer 9. On the one hand, they comprise short fibres 10 which are evenly distributed in the entire block of material and, on the other hand, long fibres which are combined to form a fabric tube 11 embedded in the intermediate layer 5 and primarily effect a circumferential reinforcement of the intermediate layer 5. The crosssection of the holes is not considered when determining the average thickness of the intermediate layer in the radial direction.

The forces exerted radially by the spring ring 4 due to the subsequent pressing-in and elastic prestress can be absorbed with all the embodiments by using hub rings 1 which, in comparison with the known embodiments, have a greatly reduced wall thickness and accordingly a reduced weight. By this means, the torsional vibration dampers have an improved damping power at a given total weight.

Additionally, a reduction in the rigidity of the spring ring 4 arising through heating is compensated favourably in radial direction by the thermal expansion of the coating 5 arising simultaneously. By this means there are no further fears of the resonant frequency of the torsional vibration damper being shifted due to the heating into a deviating range. With regard to the suppression of disturbing torsional vibrations this is of great advantage.

In all the embodiments described the ratio of the average radial thickness A of the coating or layer 5 and the average radial thickness B of the spring ring 4 ranges from 0.25 to 3.

Claims

1. A torsional vibration damper, in which a metallic flywheel ring is fixed to the outside circumference of a metallic hub via the intermediary of a rubber spring ring, the hub having on its side facing the spring ring, a continuous coating of plastics material firmly adhered thereto, characterised in that the coating comprises a thermosetting plastics material and in that the ratio of the average radial thickness of the spring ring ranges from 0.25 to 3.

2. A torsional vibration damper according to claim 1, characterised in that the ratio A to B ranges from 1 to 2.

3. A torsional vibration damper according to claim 1 or 2, characterised in that the coating comprises an epoxy or polyester resin.

4. A torsional vibration damper according to any of claims 1 to 3, characterised in that the plastics material of the coating is reinforced by internally distributed fibres.

5. A torsional vibration damper according to claim 4, characterised in that the fibres are mutually combined to form an inherently firm surface structure.

6. A torsional vibration damper according to any of claims 1 to 5, characterised in that the coating is provided with circumferentially distributed projections extending radially inwards, and in that recesses are associated with the projections corresponding to the distribution, shape and size of the hub ring.

7. A torsional vibration damper according to claim 6, characterised in that the projections and recesses are formed by a sinusoidal undulation of the surfaces of the coating and of the hub ribng which face each other.

8. A torsional vibration damper constructed and arranged substantially as herein described with reference to, and as illustrated in, Figures 1 and 2, Figures 3 and 4, Figure 5, Figure 6 or Figure 7 of the accompanying drawings.

9. A pulley wheel incorporating a torsional vibration damper as claimed in any one of the preceding claims.