GB2380780A

GB2380780A - A vehicle drive-line torsional vibration damper

Info

Publication number: GB2380780A
Application number: GB0124200A
Authority: GB
Inventors: Richard David Maitland Cooke
Original assignee: AP TMF Ltd
Current assignee: AP TMF Ltd
Priority date: 2001-10-09
Filing date: 2001-10-09
Publication date: 2003-04-16
Also published as: GB0124200D0

Abstract

A vehicle drive-line torsional vibration damper (10 in Fig. 1) which includes an input mass (11) for connection with a vehicle engine and an output mass (12) for connection with a vehicle drive-line, the input and output masses being relatively rotatable against damping means (40, 34D, 34E, 60) to absorb/attenuate alternate torsional vibrations emanating from the engine. The damping means may take numerous forms such as, for example, bob-weight damping linkages (40) which connect the masses for the transmission of drive torque and which provide a speed depending torsional damping effect, springs (34D, 34E) loaded in compression, fluid damping devices and friction damping devices (60). One of the masses (11) has a vibration damping layer (61) applied to one or more parts thereof.

Description

TORSIONAL VIBRATION DAMPERS This invention relates to vehicle driveline torsional vibration dampers and in particular to a torsional vibration damper (of the type specified) in the form of twin mass flywheels which includes an input mass for connections with a vehicle engine and an output mass for connection with a vehicle drive line, the input and output masses being relatively rotatable against damping means to absorb/attenuate alternate torsional vibrations emanating from the engine. The damping means may take numerous forms and may include, for example, one or more of the following :bob-weight damping linkages which connect the masses for the transmission of drive torque and which provide a speed depending torsional damping effect, springs loaded in compression, fluid damping devices ad friction damping devices and, friction damping devices.

One of the problems associated with torsional vibration dampers of the type specified is that they can themselves be the source of vibration/noise and thus vibration/noise may be propagated from the damper into the associated vehicle transmission and hence to the vehicle occupants. This problem is more pronounced when one or both flywheel masses have portions formed from lighter sheet metal components as opposed to being of a cast construction.

It is an object of the present invention to provide a torsional vibration damper of the type specified which at least mitigates the above problem.

Thus according to a first aspect of the present invention there is provided a vibration damper of the type specified in which at least one of the masses has a vibration damping layer applied to one or more parts thereof.

At least one of the masses may be a multi-piece component with a vibration damping layer

between at least two pieces of the multi-piece component.

In one arrangement the input mass comprises an inner disc-like piece and an outer annular piece fastened to an outer peripheral zone of the inner piece with said vibration insulating layer between said pieces.

The outer piece may conveniently be formed from cast iron and may be rivetted to the inner piece at circumferentially spaced locations.

The vibration insulating layer may be formed from a plastics material or any other suitable vibration/sound deadening material such as a visco-elastic damping material.

The vibration deadening layer may only be located between overlapping portions of the inner and outer pieces or may additionally or alternatively extend across all or part of one or both sides of the inner disc-like piece.

In accordance with a further aspect of the present invention the input mass of a torsional vibration damper of the type specified may comprise an inner disc-like piece an outer annular piece and a plurality of circumferential spaced fastening means fastening the outer piece to an outer peripheral zone of the inner piece, at least one of said pieces having a series of circumferential spaced convolutions or other formations which are pulled flat when the inner and outer pieces are fastened together to load the fastening means in tension and hence reduce any tendency for the fastening means to loosen and cause noise during the operation of the damper.

The circumferentially spaced convolutions or other formations may also be used with the vibration insulating layer of the first aspect of the invention.

The input mass may also have a radially inwardly extending flange secured to the outer annular piece at an axially spaced location from the inner piece, this flange being secured to the outer piece by adhesive. This use of adhesive further assists in the reduction in the

propagation of sound/vibrations within the damper.

In accordance with a still further aspect of the invention the concept of securing a radially inwardly extending flange to the remainder of the input mass of a torsional vibration damper of the type specified by adhesive can be used when the input mass is a multi-piece component or a single piece component.

The various aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which :- Figure 1 is an axial sectional view of a twin mass flywheel taken in the direction of arrow B of Figure 2; Figure 2 is a sectional view taken along the line Z-Z of Figure 1; and Figure 3 shows a sectional view similar to Figure 2 of a modified form of twin mass flywheel.

With reference to figures 1 and 2 there is illustrated a twin mass flywheel 10 which is formed by two flywheel masses 11 and 12. One flywheel mass 11 (also known as the input flywheel mass) is fixed to a crankshaft 16 of an internal combustion engine by way of a central hub 20 using bolts (not shown) which extend through bores 15. A friction clutch (not shown) is secured to the second flywheel mass 12 (also known as the output flywheel mass) to connect the second flywheel mass with the input shaft (not shown) of an associated gearbox.

The multi-piece flywheel mass 11 comprises the central hub 20, a disc-like inner piece 21, an outer annular piece 22, a radially inwardly extending flange or cover plate 23, and a starter ring 21 a which is welded to the input plate 21. Cover plate 23 is spot welded at its outer periphery to outer piece 22.

The output flywheel mass 12 comprises an output plate 30, and a pivot plate 32 rotationally fast with each other. The output mass 12 is mounted for rotation relative to the input mass 11

by an L-shaped plain bearing member 50 supported for rotation with mass 12 by an annular bearing support 51 which is received in a bore 52 in plate 30.

The radially inner surface 53 of a plain bearing member 50 is coated with a plain bearing material such as a filled fluoro-polymer which rotates relative to the outer surface 54 of hub 20. Alternatively, bearing member 50 could be formed from PTFE impregnated with a sintered metal or could be a solid polymeric bearing member. The bearing 50 and support 51 are held in position on hub 20 against axial displacement away from input mass 11 by a retaining ring 55 held in place by the bolts which pass through bore 15. Retaining ring 55 carries a contact ring 56 also of polymeric or other suitable bearing material which contacts the radially outwardly extending portion 50a of bearing 50.

Relative rotation between two flywheel masses 11 and 12 is controlled by a damping means which primarily comprises a plurality of pivotal linkages 40. The damping means also comprises a plurality of spring units 34D, 34E, carried on the input mass 11 via pins 34G which extend between and secure together disc 21 and cover plate 23, and also includes a friction damping device 60. The relative rotation of the flywheel masses is limited by contact between stop surfaces 32C on pivot plate 32 and stops 33A mounted on the input mass 11 via pin 34G. All these components assist in controlling the relative rotation of the two flywheel masses 11 and 12 at specific relative angular positions or in specific angular ranges.

Each pivotal linkage 40 comprises a first link 41 (also known as a bobweight link) pivotally mounted between a centre hub portion 35 of the output plate 30 and pivot plate 32 by way of a first pivot 43, and a second flexible link 42 pivotally mounted on the output flywheel mass 12 by way of a second pivot 44 which extends between and secures together disc 21 and cover plate 23. The two links 41 and 42 pivotally connected to each other by means of a third pivot 45. It will be noted from Figure 1 that the first pivot 43 is positioned radially inwardly of the second and third pivots 44 and 45.

Under no-load conditions with the clutch 4 disengaged and the flywheel driven by the crankshaft in the direction of arrow E of Figure 1, centrifugal force acts on the pivotal

linkages 40 and particularly on the first bobweight link 41 and urges the linkages in a radially outward direction with pivot 45 adopting a position radially outboard of pivot 43 as shown in fig 1 (this position is regarded as the neutral position between the drive and over-run directions of relative rotation of the flywheel masses). At higher rotational speeds the centrifugal force is greater and whilst this does not affect the configuration under no-load conditions it greatly affects the force required to move the flywheel mass 12 relative to the flywheel mass 11 i. e. the flywheel torsional stiffness.

If the clutch is engaged and power is transmitted in the drive direction from flywheel mass 11 to flywheel mass 12 there is a tendency for the two masses to rotate relative to each other (flywheel mass 11 rotates clockwise relative to flywheel mass 12 when viewing figure 1). At relatively low speeds when the influence of centrifugal force is smaller the flywheel masses move readily relative to each other i. e. the flywheel torsional stiffness is relatively low.

However at relatively high speeds the influence of centrifugal force is much greater and relative rotation of the flywheel masses requires greater force i. e. the flywheel torsional stiffness is relatively high. Thus the flywheel torsional stiffness is speed sensitive.

If the clutch is engaged and power is transmitted in the over-run direction from flywheel mass 12 to flywheel mass 11 the effects are similar to the above except that the direction of relative rotation is reversed (flywheel mass 11 rotates anticlockwise relative to flywheel mass 12 when viewing figure 1) and in the embodiment shown in Figure 1 the first link 41 folds up relative to the second link 42.

Spring units 34D are only compressed when the flywheel masses rotate relative to each other in the drive direction. This compression occurs when arms 32E on the pivot plate contact the ends 34F of the springs after a given amount of relatively rotation determined by circumferential clearance P.

Similarly rubber block springs 34E come into operation towards the latter part of relative rotation between the masses in the drive direction when abutments 32D'on the pivot plate 32

contact the rubber springs and in the overrun direction when abutments 32D"on the pivot plate contact the rubber springs.

In accordance with a first aspect of the present invention a layer of vibration/sound deadening material 61 is provided on the left hand side of disc-like piece 21. This layer may comprise a plastics or any other suitable sound deadening material such as a visco-elastic damping material.

In the arrangement shown in Figure 2, layer 61 extends not only between pieces 22 and 21 but also over the entire left hand side 21b of piece 21 which is not contacted by the crankshaft 16.

In alternative arrangements layer 61 may extend only between the overlapping portions of pieces 21 and 22 or only over part of the exposed portion of piece 21.

An additional layer (not shown) could also be provided over all or part of the right hand side 21c of piece 21.

As shown in Figure 2, the vibration/sound insulating layer 61 is clamped between the pieces 21 and 22 by circumferentially spaced rivets 62. In accordance with a second aspect of the invention the inner piece 21 may be provided with a series of circumferentially spaced convolutions or other axially extending formations which are pulled flat when the rivets 62 are installed. This arrangement ensures that the rivets 62 remain under tension and this assists in reducing any tendency for the rivets to work loose during use of the flywheel thus preventing the generation of further noise.

In the arrangement shown in Figure 3, the separate pieces 21 and 22 of the flywheel input mass 11 are replaced by a single piece casting 22. In accordance with a third aspect of the invention the radially inwardly extending cover plate 23 is bonded to the axially extending portion 22a of input mass 22 by an elastomeric layer 65 of adhesive. This adhesive replaces the spot welding employed between the cover plate 23 and the input mass piece 22 in the arrangement shown in Figure 2. This use of the adhesive bonding layer 65 helps to isolate the cover plate 23 from the input mass piece 22 thus further reducing the transmission of noise

within the input flywheel. In the figure 3 arrangement plain bearing 50 is non-rotatably supported directly in a bore 52 in output plate 30 and retaining plate 55 does not have contact ring 56.

This technique of bonding the cover plates 23 to the remainder of the input mass 11 could be used in the multi-piece input mass construction shown in Figure 2.

Claims

CLAIMS 1) A vibration damper of the type specified in which at least one of the masses has a vibration damping layer applied to one or more parts thereof.
2) A vibration damper according to claim 1 in which one of the masses is a multi-piece component with a vibration damping layer between at least two pieces of the multi- piece component.
3) A vibration damper according to claim 1 or 2 in which the input mass comprises an inner disc-like piece and an outer annular piece fastened to an outer peripheral zone of the inner piece with said vibration insulating layer between said pieces.
4) A vibration damper according to claim 3 in which the outer piece is formed from cast iron and may be rivetted to the inner piece at circumferentially spaced locations.
5) A vibration damper according to any one of claims 1 to 4 in which the vibration insulating layer is formed from a plastics material or any other suitable vibration /sound deadening material such as a visco-elastic damping material.
6) A vibration damper according to any one of claims 2 to 5 in which the vibration damping layer is only be located between overlapping portions of the inner and outer pieces or may additionally or alternatively extend across all or part of one or both sides of the inner disc-like piece.
7) A vibration damper according to any one of claims 3 to 6 in which the inner disc-like piece and outer annular piece are fastened together by a plurality of circumferentially spaced fastening means, at least one of said pieces having a series of circumferential spaced convolutions or other formations which are pulled flat when the inner and outer pieces are fastened together to load the fastening means in tension and hence

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reduce any tendency for the fastening means to loosen and cause noise during the operation of the damper.
8) A vibration damper according to any one of claims 1 to 7 in which the input mass has a radially inwardly extending flange secured to an outer annular portion of the input mass by adhesive.
9) A torsional vibration damper of the type specified comprising an inner disc-like piece an outer annular piece and a plurality of circumferential spaced fastening means fastening the outer piece to an outer peripheral zone of the inner piece, at least one of said pieces having a series of circumferential spaced convolutions or other formations which are pulled flat when the inner and outer pieces are fastened together to load the fastening means in tension and hence reduce any tendency for the fastening means to loosen and cause noise during the operation of the damper.
10) A torsional vibration damper of the type specified in which the input mass has a radially inwardly extending flange secured to an outer annular portion of the input mass by adhesive.
11) A torsional vibration damper of the type specified constructed and arranged substantially as hereinbefore described with reference to and as shown in figures 1 and 2 or 3 of the accompanying drawings.