Claims:We claim:

1. Torsional Vibration Damper (TVD) with a mode separation device for crankshaft vibrations in motor vehicles, wherein the device shifts the critical frequency mode into two separate frequency modes, i.e. a higher frequency mode and a lower frequency mode respectively, which has substantially reduced amplitude of excitations and thereby facilitates to avoid NVH related issues of Torsional Vibration Damper.

2. Torsional Vibration Damper as claimed in claim 1, wherein the mode separation device comprises a metallic inner cup and an outer metallic ring separated by an elastomer insert structure of predetermined size, shape and profile and a metallic tuner ring mass suspended therefrom radially outwards of the outer ring, thereby separating the torsional frequency from the twisting (out of plane) frequency of the TVD.

3. Torsional Vibration Damper as claimed in claim 2, wherein the elastomer insert structure of the mode separation device comprises a plurality of elastomer inserts disposed uniformly circumferentially spaced apart between the metallic inner cup and the outer metallic ring thereof.

4. Torsional Vibration Damper as claimed in claim 3, wherein each elastomer insert of the plurality of the elastomer inserts are configured in similar size and with the same shape of rectangular cuboid.

5. Torsional Vibration Damper as claimed in claim 1, wherein the mode separation device comprises a metallic inner cup and an outer metallic ring separated by an elastomer insert structure of predetermined size, shape and profile; a metallic tuner ring mass suspended therefrom radially outside the outer ring, and a thin elastomer layer completely covering the outer circumferential surface of the metallic inner cup and inner circumferential surface of the metallic outer ring for substantially separating the torsional frequency from the twisting (out of plane) frequency of the TVD.

6. Torsional Vibration Damper as claimed in claim 5, wherein the
elastomer insert structure of the mode separation device comprises a plurality of elastomer inserts disposed uniformly circumferentially spaced apart between the metallic inner cup and the outer metallic ring, the elastomer inserts are embedded within a circular elastomer ring of predetermined size, the dimension of the circular ring and the elastomer inserts adapted to be made equal in the radial direction of the TVD.

7. Torsional Vibration Damper as claimed in anyone of the claim 1 to 7, wherein the inner cup, outer ring and the tuner ring are made of steel and the elastomer of the circular ring and the plurality of inserts is rubber.

8. Torsional Vibration Damper as claimed in anyone of the claim 1 to 8, wherein the first natural frequency mode is torsional mode and the second natural frequency mode is approximately 28Hz and the difference between the first natural frequency mode is out of plane) twisting mode and wherein a mode separation of approximately 3Hz is obtained between the first (torsional mode) and the second (out of plane twisting mode) of vibration.

9. Torsional Vibration Damper as claimed in anyone of the claim 1 to 8, wherein the elastomer insert structure comprises twenty-four rubber-spokes of 3 to 5 mm thickness, 5 to 7 mm radial height and 25 to 30 mm length.

10. Torsional Vibration Damper as claimed in claim 6 to 7, wherein the elastomer insert structure comprises twenty-four rubber-spokes of about 1.5 to 2 mm thickness, radial height of about 5 to 7 mm and a length of about 25 to 30 mm and wherein the rubber-spokes are circumferentially embedded uniformly spaced apart on the circular ring with a thickness of 3 to 4 mm and a radial height of 5 to 7 mm.

Dated: this 31st day of August, 2015. SANJAY KESHARWANI
APPLICANT’S PATENT AGENT , Description:FIELD OF INVENTION

The present invention relates to torsional vibration dampers, particularly torsional vibration dampers for vehicle drivelines with internal combustion engines used in automobiles, more particularly torsional vibration dampers mounted between the differential casing and the propeller shaft of an automobile for reducing undesirable vibrations from the dynamic torque oscillations of the powertrain.

BACKGROUND OF THE INVENTION

Torsional vibration is angular vibration of a rotating object, such as a shaft, along the rotational-axis thereof. The torsional vibration is an important criterion to be considered for smooth functioning of any power transmission systems using rotating shafts or couplings, e.g. internal combustion engines. It may lead to sudden structural failures, if not checked in good time.

In particular, torsional vibrations may lead to seat vibrations or noise at certain speeds in automobiles, thereby reducing comfort to the occupants thereof.

Ideally, in any transmission system employing rotating parts, torques applied or reacted should be "smooth" for constant speed operation, and the rotating plane in which the power is generated (or input) as well as the plane from which the power is taken-off (output) has to be the same. However, in normal situations, this is practically not possible. Often, torque produced is not smooth, especially in internal combustion engines in automobiles. This is for the simple reason that the plane in which the power is generated is normally at some distance from the power take-off plane. Moreover, the torque transmitting components may generate non-smooth or alternating torques (e.g., elastic drive belts, worn gears, misaligned shafts). Such alternating torques, when applied at some distance on the rotating shafts; generate twisting vibration about the rotational axis of the shaft, since every material has a predefined inherent stiffness.

Some of the patents on torsional vibration dampers are discussed below:-

US7834090 discloses a torsional vibration damper or other vibration damping device with a rubber vibration absorbing element. The rubber element is a peroxide-cured composition based on 100 parts of ethylene-alpha-olefin elastomer, and 5 to 100 parts of polyvinyl butyral polymer which may have a molecular weight from about 40,000 to about 250,000. The composition may also include a compatibilizer or homogenizer, such as chlorinated polyethylene. The polyvinyl butyral increases the damping of the composition, and the compatibilizer improves the temperature stability of the damping.

US5573461 discloses a torsional vibration damper with an outside ring and an inside ring which surround each other and are connected to each other with rotational elasticity by way of spokes which can be deflected in the circumferential direction. The spokes are non-deformable and are connected with the inside ring and with the outside ring by way of intermediate layers made of rubber.

US5352157 discloses a speed-adaptive torsional vibration damper, with a flywheel which encircles a hub ring, and in which the hub ring and flywheel are at least temporarily connected to one another by first and second spring elements made of a rubber-like material. The second spring elements are distributed uniformly around the circumference of the hub ring. The second spring elements are capable of expanding in the radial direction under the action of centrifugal forces that result at high rotational speeds, and thereby are forced into engagement with the flywheel. When viewed in the circumferential direction, the second spring elements are delimited by a stop face which projects in the direction of the flywheel and which mates with a congruently shaped cavity of a third spring element also of a rubber-like material. The third spring elements are affixed to the flywheel. The stop face and the cavity have a radial clearance between each other in the non-rotating state of the torsional vibration damper.

US2013/0210533 discloses a torsional vibration damper for damping torsional vibrations of a shaft for industrial applications, including a damper hub having a rotational axis, a damper mass coaxial with the damper hub, and at least one elastomeric damping layer arranged between the damper hub and the damper mass. According to the disclosure, the damper hub and the damper mass are designed in such a way that an outer circumferential surface of the damper hub engages with an inner circumferential surface of the damper mass in a star-shaped manner in the radial direction with respect to the rotational axis, wherein the damper hub and the damper mass are supported against each other in the direction of the rotational axis of the torsional vibration damper by the elastomeric damping layer.

US8091450B2 discloses a torsional vibration damper includes a one-piece integral hub and annular inertia mass assembly. Between the hub and the inertia mass are intermediate rings connected integrally with the mass and the hub connected integral spokes. Elastomeric members are compression fitted within spaces formed between the hub and the mass. With this design, the damper can be formed from a polymeric material with an embedded annular weight.

DISADVANTAGES WITH THE PRIOR ART

However, none of these prior-art documents as well as several currently used tools propose any solution to the problem of the torsional vibration damper (TVD), when two modes torsional and twisting (out of plane movement) frequencies are almost the same, which results in higher strains in the rubber parts. This might lead to separation of the tuner mass from the main assembly and rubber joinery much before the stipulated life (before warranty period) of the TVD.

Therefore, there is an existing need for a device capable of separating these two modes of vibrations, i.e to distinctly separate the torsional vibration frequency from the twisting vibration frequency in order to eliminate any failure of the torsional vibration dampers (TVDs) due to such almost similar frequencies of vibrations. There also a need for avoiding or eliminating the NVH related issues of the prior art arrangements.

OBJECTS OF THE INVENTION

Some of the objects of the present invention - satisfied by at least one embodiment of the present invention - are as follows:

An object of the present invention is to provide an improved torsional vibration damper.

Another object of the present invention is to provide a torsional vibration damper which reduces strains in the rubber components used therein.

Still another object of the present invention is to provide a torsional vibration damper which sufficiently separates and decouples the torsional and twisting modes of vibrations.

Yet another object of the present invention is to provide a torsional vibration damper which reduces the effects of the shear deformations per unit area.

A further object of the present invention is to provide a torsional vibration damper of configuration with improved NVH characteristics.

Still further object of the present invention is to provide a torsional vibration damper which has a substantially higher service life.

Yet further object of the present invention is to provide a torsional vibration damper which is very simple to manufacture and implement.

Still another object of the present invention is to provide a torsional vibration damper which requires substantially reduced costs of development.

These and other objects and advantages of the present invention will become more apparent from the following description when read with the accompanying figures of drawing, which are, however, not intended to limit the scope of the present invention in any way.

DESCRIPTION OF THE INVENTION

In accordance with the present invention, the Torsional Vibration Dampers (TVDs) are usually mounted between the differential casing and the propeller shaft to reduce undesirable vibrations being transmitted to the vehicle from the powertrain dynamic torque oscillations. Additional tuner ring mass suspended on the rubber, shifts the critical frequency mode into two separate modes (higher and lower) with reduced amplitude of excitations and thereby avoids the NVH related issues. This TVD configuration is developed in-house, thus the dependency on any outside TVD supplier (Full Service Supplier or FSS) is avoided for the development thereof. This reduces the cost as well as the time for the development of TVD.

In a first embodiment of the present invention, in all 24 rubber spokes are placed distributed equally spaced apart on the circumference between the outer ring and inner cup. Each of these rubber spokes have a circumferential thickness of e.g. about 4 mm, radial height of about 6 mm and width of about 28 mm along the TVD axis (see Figures 1 and 2). The target value achieved with this first embodiment of the torsional vibration dampers is approximately 28Hz. In a second embodiment of the present invention also, 24 rubber spokes are distributed equally spaced apart on the circumference between the outer steel ring and inner steel cup. Each rubber spoke has a thickness of about 2 mm and width of about 28 mm along the TVD axis. A ring of about 3.75 mm thickness and radial height of about 6 mm is added in the center to join all rubber spokes (see Figures 4 and 5). The target value achieved with this second embodiment of the torsional vibration dampers is about 28Hz. Accordingly, two modes of vibrations, i.e. Torsional vibrations and out of plane Twisting vibrations were successfully separated by configuring different contact surface areas of the rubber components disposed between the tuning mass and the fixation cup of steel. Several iterations were carried out to achieve a sufficient mode separation between the torsion and twisting modes of vibrations. By increasing the number of rubber spokes with desired thickness and adding circumferential rib, mode separation of almost 3 Hz is obtained for providing good stiffness in torsion as well in bending independently in different modes.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a torsional vibration damper (TVD) with a mode separation device for crankshaft vibrations in motor vehicles, wherein the device shifts the critical frequency mode into two separate frequency modes, i.e. a higher frequency mode and a lower frequency mode respectively, which has substantially reduced amplitude of excitations and thereby facilitates to avoid NVH related issues of Torsional Vibration Damper.

Typically, the mode separation device comprises a metallic inner cup and an outer metallic ring separated by an elastomer insert structure of predetermined size, shape and profile and a metallic tuner ring mass suspended therefrom radially outwards of the outer ring, thereby separating the torsional frequency from the twisting (out of plane) frequency of the TVD.

Typically, the elastomer insert structure of the mode separation device comprises a plurality of elastomer inserts disposed uniformly circumferentially spaced apart between the metallic inner cup and the outer metallic ring thereof.

Typically, each elastomer insert of the plurality of the elastomer inserts are configured in similar size and with the same shape of rectangular cuboid.

Typically, the mode separation device comprises a metallic inner cup and an outer metallic ring separated by an elastomer insert structure of predetermined size, shape and profile; a metallic tuner ring mass suspended therefrom radially outside the outer ring, and a thin elastomer layer completely covering the outer circumferential surface of the metallic inner cup and inner circumferential surface of the metallic outer ring for substantially separating the torsional frequency from the twisting (out of plane) frequency of the TVD.

Typically, the elastomer insert structure of the mode separation device comprises a plurality of elastomer inserts disposed uniformly circumferentially spaced apart between the metallic inner cup and the outer metallic ring, the elastomer inserts are embedded within a circular elastomer ring of predetermined size, the dimension of the circular ring and the elastomer inserts adapted to be made equal in the radial direction of the TVD.

Typically, the inner cup, outer ring and the tuner ring are made of steel and the elastomer material of the circular ring and the plurality of inserts is rubber.

Typically, the first natural frequency mode is torsional mode and the second natural frequency mode is approximately 28Hz and the difference between the first natural frequency mode is out of plane) twisting mode and wherein a mode separation of approximately 3Hz is obtained between the first (torsional mode) and the second (out of plane twisting mode) of vibration.

Typically, the elastomer insert structure comprises twenty-four rubber-spokes of 3 to 5 mm thickness, 5 to 7 mm radial height and 25 to 30 mm length.

Typically, the elastomer insert structure comprises twenty-four rubber-spokes of about 1.5 to 2 mm thickness, radial height of about 5 to 7 mm and a length of about 25 to 30 mm and wherein the rubber-spokes are circumferentially embedded uniformly spaced apart on the circular ring with a thickness of 3 to 4 mm and a radial height of 5 to 7 mm.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The present invention will be briefly described with reference to the accompanying drawings, which include:

Figure 1 shows a first embodiment of the Torsional Vibration Damper (TVD) in accordance with the present invention.

Figure 2 shows the rubber-ring structure of the first embodiment of the Torsional Vibration Damper (TVD) of Figure 1.

Figure 3 shows a cross-sectional view along the section line A-A of the first embodiment of Torsional Vibration Damper (TVD) shown in Figure 1.

Figure 4 shows a second embodiment of the Torsional Vibration Damper (TVD) in accordance with the present invention.

Figure 5 shows the rubber-ring structure of the second embodiment of the Torsional Vibration Damper (TVD) of Figure 4.

Figure 6 shows a cross-sectional view along the section line B-B of the second embodiment of Torsional Vibration Damper (TVD) shown in Figure 4.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS

In the following, different embodiments of the present invention will be described in more details with reference to the accompanying drawings without limiting the scope and ambit of the present invention in any way.

Figure 1 shows a first embodiment of the Torsional Vibration Damper (TVD) in accordance with the present invention, which includes an inner steel cup 10, an outer steel ring 20 and twenty-four rubber-spokes 30 disposed between the inner steel cup 10 and outer steel ring 20. An additional tuner ring mass 40 of steel is radially suspended from rubber spokes 30 (see Fig. 1 for Section A-A). This configuration shifts the critical frequency mode into two separate modes, e.g. into a higher mode and a lower mode respectively, which has substantially reduced amplitude of excitations and thereby facilitates in avoiding the NVH related issues of the prior art arrangements discussed earlier. In this embodiment, the modes of vibrations frequencies are sufficiently (about 3Hz difference) separated to prevent TVD failure. This configuration is accurately validated through simulations. Rubber shear area on the inner cup is about 2700-2900 mm2 and the outer ring has an area of about 3000-3100 mm2. In conceptual TVD configuration, the shear areas for both and inner and outer cup were 2200-2400mm2 and 2500-2600mm2 respectively. Therefore, the surface area undergoing shear deformation due to torsion, axial, and twisting motion is been increased by about 16% for reducing the strains in elastomer part thereof and thus the fatigue life of the rubber component is increased.

Figure 2 shows the rubber-ring structure of the first embodiment of the Torsional Vibration Damper (TVD) of Figure 1. This structure includes twenty-four rubber spokes 30 of length about 28 mm, about 4 mm thickness and having radial height of about 6 mm. These rubber spokes 30 are disposed spaced apart uniformly on the circumference of this TVD.

Figure 3 shows a cross-sectional view along the section line A-A of the first embodiment of Torsional Vibration Damper (TVD) shown in Figure 1. This figure clearly illustrates the inner steel cup 10 and the outer steel ring 20 joined together by means of a plurality of rubber spokes 30 having 4 mm thickness, 6 mm height and 28 mm length. An additional tuner ring mass 40 made of steel is radially suspended from the rubber spokes 30 to complete the TVD assembly. However, there are uniform gaps between two successive rubber spokes 30.

Figure 4 shows a second embodiment of the Torsional Vibration Damper (TVD) in accordance with the present invention, which includes an inner steel cup 110, an outer steel ring 120 and a tuner ring mass 140 also of steel. There are two rubber layers 150 disposed on the outer circumference of the inner steel cup 110 and inside the inner circumference of the outer steel rings 120. A rubber ring structure 130 is disposed between rubber layers 150. The additional tuner ring mass 140 is disposed suspended outside the rubber ring structure 130 by means of rubber ring structure 130 (see Fig. 5 for Section B-B). This configuration also enables to sufficiently separate the torsional and out of plane motion modes with the difference in excitation frequency of 3 Hz between these two modes.

Figure 5 shows the rubber-ring structure 130 of the second embodiment of the Torsional Vibration Damper (TVD) of Figure 4. It also includes twenty-four rubber-spokes 132. Each rubber spoke 132 has a thickness (x) of 2.0 mm, radial height of 6.0 mm and length of 28.0 mm and these rubber spokes 132 are circumferentially spaced apart uniformly. The ring structure 134 connecting these spokes 132 has a thickness of 3.75 mm (~2x) and a radial Height of 6 mm (2x). Therefore, the outer edges of the rubber spoke 132 and ring structure 134 are flush or in the same plane. However, these rubber spokes 132 are configured embedded on a circular strip 134 of 3.75 mm thickness, thereby forming an integral rubber ring structure 130.

Figure 6 shows a cross-sectional view along the section line B-B of the second embodiment of Torsional Vibration Damper (TVD) shown in Figure 4. This figure also clearly illustrates the inner steel cup 110 and outer steel ring 120 joined together by means of a plurality of rubber-ring structure 130. An additional tuner ring mass 140 also of steel is radially suspended from the rubber-ring structure 130 to complete this TVD assembly. In contrast to the presence of uniform gaps between two successive rubber spokes 30 of Figure 1 (first embodiment), this second embodiment is configured to omit the gaps between the successive rubber-spokes by placing a circular ring 134.

Technical advantages and economic significance

1. Innovative approach for suitably orienting and spacing the rubber ribs to achieve the desired target frequency required for modal separation and increase in shear area of rubber placed between inner and outer rings.

2. Equally spaced 24 spokes exhibit first natural frequency mode as torsional mode of 28Hz as per functional requirement of the component.

3. Mode separation close to 3Hz is achieved between the First (torsional mode) and the second (out of plane Twisting mode) mode of vibration.

4. A 16% increase in the shear surface area from the existing design, thereby reducing the shear strains in rubber and thereby increasing the service life of the component.

5. Reduction in the part development cost due to in-house concept evaluation.

Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, shall be understood to implies including a described element, integer or method step, or group of elements, integers or method steps, however, does not imply excluding any other element, integer or step, or group of elements, integers or method steps.

The use of the expression “a”, “at least” or “at least one” shall imply using one or more elements or ingredients or quantities, as used in the embodiment of the disclosure in order to achieve one or more of the intended objects or results of the present invention.

The exemplary embodiments described in this specification are intended merely to provide an understanding of various manners in which this embodiment may be used and to further enable the skilled person in the relevant art to practice this invention.

Although, only the preferred embodiments have been described herein, the skilled person in the art would readily recognize to apply these embodiments with any modification possible within the spirit and scope of the present invention as described in this specification.

Therefore, innumerable changes, variations, modifications, alterations may be made and/or integrations in terms of materials and method used may be devised to configure, manufacture and assemble various constituents, components, subassemblies and assemblies according to their size, shapes, orientations and interrelationships.

The description provided herein is purely by way of example and illustration. The various features and advantageous details are explained with reference to this non-limiting embodiment in the above description in accordance with the present invention. The descriptions of well-known components and manufacturing and processing techniques are consciously omitted in this specification, so as not to unnecessarily obscure the specification.

While considerable emphasis has been placed on the specific features of the preferred embodiment described here, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiments without departing from the principles of the invention. These and other changes in the preferred embodiment of the invention will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.