TORSIONAL VIBRATION DAMPERS

Abstract: A torsional vibration damper for use in vehicles having an input member (11) for connection with an associated engine and an output member (12) for connection with an associated vehicle driveline. The input and output members are relatively rotatable via a support bearing acting therebetween against the action of a torsional damping means to damp torsional vibrations in the associated vehicle driveline. The support bearing is a plain bearing (80) moulded in situ between the input and output members (11, 12) or between bearing carriers (60, 61) to be connected with a respective input or output member. A method of manufacturing the plain bearing (80) by moulding in situ is also disclosed.

Description: TORSIONAL VIBRATION DAMPERS This invention relates to torsional vibration dampers for use in vehicles, hereinafter referred to as of the kind specified, comprising an input member for connection with an associated engine and an output member for connection with an associated vehicle driveline, said members being relatively rotatable via a support bearing acting therebetween against the action of a torsional damping means to damp torsional vibrations in the associated vehicle driveline Such torsional vibration dampers may be in the form of twin mass flywheels in which the input and output members are each of significant mass or may have relatively light input and output members which possess relatively little flywheel mass Such dampers may be positioned at any convenient point in the drive line The support bearing for such torsional dampers conventionally comprises a ball or roller bearing and, although the use of a plain bearing has been suggested in the patent literature for many years, plain bearings have not had any significant usage in practice due mainly to the high level of accuracy required in their manufacture in order to achieve satisfactory operation It is an object of the present invention to provide a torsional vibration damper of the kind specified with an improved plain support bearing Thus according to the present invention there is provided a torsional vibration damper of the kind specified in which the support bearing comprises a plain bearing formed in situ between the input and output members The plain bearing may be formed in situ directly on the input and output members or between a first bearing carrier connected with one member and a second bearing carrier connected with the other member The carriers may be made from sheet metal by any suitable technique or can be made by casting, forging or sintering. In a preferred arrangement the plain bearing is moulded in situ from a polymer such as PEEK (polyetheretherketone) with fillers such as glass fibre, carbon fibre and/or friction modifiers such as molybdenum disulphide Alternatively PES (polyethersulphone) with similar fillers and modifiers may be used Other forms of modified or unmodified thermoplastic or thermosetting polymers may be used The carriers preferably have generally axially extending regions between which the low friction plain bearing means is located to support the members radially and may also include generally radially extending regions which are used to secure each of the carriers to its respective member An axially acting spring means, such as a belleville spring, may act between confronting generally radially extending regions of the carriers to generate friction damping on said relative rotation This axially acting spring may also bias other surfaces which rotate with the respective masses into frictional contact to generate further friction damping One of the members may include circumferential spaced axially facing support pads which contact a co-operating support surface on the other member to control relative axial movement of the members These pads may also help to control relative tipping of the members during use of the damper Alternatively, the plain bearing may be moulded with a generally axially extending portion and a generally radially extending portion, the generally radially extending portion controlling axial movement and tipping of the members The invention also provides a method of manufacturing a support bearing for a torsional vibration damper the kind specified, said method comprising the steps of - placing a pair of concentric annular members into a mould, closing the mould to define a void between said members, injecting bearing material into said void to form a bearing sleeve between said members, opening said mould to release the members and sleeve The method may include the additional step of moving said members relative to each other to crack the sleeve from one or both members to provide a functioning support bearing in which said members are relatively rotatable via the sleeve In a twin mass flywheel the concentric annular members may be the flywheel masses themselves or may be separate first and second bearing carriers for subsequent connection with the input and output masses respectively Similarly in a non-flywheel torsional damper the concentric annular members may also be the input and output members themselves or may be separate first and second bearing carriers for subsequent connection with the input and output members respectively Portions of the mould adjacent one or both members may be cooled or heated to discourage bonding of the bearing sleeve to the cooler mould portion(s) This differential cooling or heating may be controlled to cause slight shrinkage of the moulded bearing sleeve away from the cooler mould portion to provide a working clearance between the sleeve and members In a further alternative arrangement one or both members may be coated in a release agent prior to injection of the bearing material to remove the need for, or at least facilitate, cracking of the members from the moulded bearing sleeve Where separate bearing carriers are used the mould may be designed to support the carriers against the moulding pressure Alternatively more rigid carriers may be used Portions of the members may be held in direct contact to partially define the void during the moulding process For example, when carriers are used, each carrier may comprise a generally axially extending region between which the void is defined and a generally radially extending portion, these radially extending portions being held in contact with each other during the moulding process to close-off one end of the void, the other end of the void being closed by the mould In such an arrangement the carriers can be displaced axially and/or rotated relative to each other to crack the moulded sleeve from one or both carriers The present invention will now be described, by way of example only, with reference to the accompanying drawings in which - Figure 1 is a side view of a twin mass flywheel embodying the present invention, Figures 2 and 3 show sections on lines B-Bl and B2-B3 of figure 1 respectively, Figures 4 shows part of figure 2 on a larger scale, Figure 5 shows a further part of figure 1 on a larger scale, Figure 6 shows part of a casting mould for an in situ moulded plain bearing, Figure 7 shows an alternative in situ moulded plain bearing, and Figure 8 shows an alternative tapering form of in situ moulded plain bearing Referring to figures 1 to 5 a twin mass flywheel 10 comprises an input flywheel mass 1 1 [carrying a starter ring 11a] and an output flywheel mass 12 which are mounted for limited relative rotation about a common axis A-A via a plain bearing arrangement 13 described in detail below carried on a bearing support block 1 Id Relative rotation of the input and output flywheel members is opposed by a damping means in the form of bob-weight linkages 14, compression spring assemblies 15, elastomeric springs 16, and a radially inner multi-plate friction damper 17 All these damping means act in parallel between the input and output flywheel masses Input flywheel mass 1 1 is of a composite construction having pressed metal central disc portion 1 lb and a forged outer annular portion 1 lc which are welded together by a weld bead 1 If and are centred relative to each other by contact between the outer periphery of disc portion 1 lb and annular surface 1 le on outer portion l ie The output flywheel mass 12 is of a cast metal construction The two flywheel masses are held in an assembled state, prior to attachment to the associated engine crankshaft by screws 18 see Figure 1 , on the same pitch circle diameter as bolt holes 1 As is conventional the twin mass flywheel is bolted to the crankshaft by attachment bolts 19a which extend through circumferentially spaced bolt holes 1 in bearing support block 1 Id and input flywheel mass disc portion 1 lb Compression spring assemblies 15 each act between a first abutment 20 (see figure 1 ) which is forged out of input flywheel 11 and a second abutment 21 which is cast into output flywheel 12 By forming both of the abutments integrally with the respective flywheel masses the number of separate components in the flywheel is significantly reduced and the axial space required is also reduced since separate spring abutment members are eliminated Each compression spring assembly may comprise an outer compression spring 15a and an inner compression spring 15b with the operation of the inner compression spring 15b being timed to be delayed by several degrees from the commencement of the operation of the outer compression spring 15a Alternatively, one pair of diametrically opposite compression springs 15 may be arranged to operate before the other pair of diametrically opposite compression springs during the relative rotation of the two flywheel masses The springs 15a and 15b have a natural shape in which their longitudinal axes are straight When mounted between abutments 20 and 21 the springs are deflected to an acute shape by a sheet metal support member 40 which will be described further below Figure 1 shows the flywheel in its central or neutral position and, with the flywheel rotating in the direction of arrow D, in the normal drive condition a relative rotation of P (see Figure 5) occurs before abutments 21 are contacted by spring chairs 15c which fit around the end of the springs 15 Springs 15 are non-operational in the overrun condition when abutments 21 tend to move away from springs 15 The elastomeric compression springs or blocks 16 (see figure 5) are each supported on the input mass 11 between end plates 16a in a window 22 pressed out of input flywheel mass 1 1 by a sheet metal casing member 41 Member 41 has end portions 41a and 41b which are respectively curved around a radially outer abutment 24 which is pressed out of input flywheel mass 1 1 and around the bottom edge 22a of window 22 The end plates 16a are acted upon by abutments 23 on a ring 23a which is secured to output flywheel mass 12 by rivets 23b The end plates 16a have wings 16b which extend between abutments 23 and output mass 12 and tabs 16c which hook under the radially inner edge of block 16 Each elastomeric spring block 16 is also located against radially outwards movement to mass 1 1 by radially outer abutment 24 The elastomeric spπngs 16 are therefore confined within windows 22 between the two flywheel masses 1 1 and 12 As will be appreciated the blocks 16 operate to damp relative rotation of the flywheel masses in the end zones of the relative rotation both in the drive and overrun conditions Blocks 16 operate in the drive condition after a relative rotation of Q and in the overrun condition after a relative rotation of R Further details of blocks 16 are set out in the Applicant's co-pending UK patent application No 98 28399 7 Each bob-weight linkage 14 comprises a bob-weight 25 which is pivotally mounted on output flywheel mass 12 via a cantilevered pivot pin 26 and a bush 27 which is press fit into the bob- weight The linkage is completed by a flexible link 28 which is connected at one end with the input flywheel mass 11 via a rivet 29 and at its other end with a bob- weight 25 via a rivet 30 Each rivet 29 extends through a mounting tab 40a of support member 40 The other end 40b of spring support member 40 rests on outer radially abutment 24. The details of pivotal connections 28 and 29 are again described in greater detail in the previously referred to co-pending application no. 98 28399.7. As can be seen from figure 1 , pivots 29 are located radially within compression spring assemblies 15 This allows a longer length for links 28 so that the total permitted relative rotation between the input and output flywheel masses can be increased Bob-weights 25 are also shaped having a cut-out portions 25a, to concentrate their mass as radially far outwards as possible Output mass 12 is provided with radially outwardly projecting lugs 45 which move in circumferentially extending slots 46 between radially inwardly extending lugs 47 on input mass 1 1 Relative rotation between mass 1 1 and 12 in the drive condition is limited by contact between surfaces 47a and 45a on lugs 47 and 45 and in the overrun condition by contact between surfaces 47b and 45b The multi-plate friction damper 17 is best seen in Figure 4 This damper comprises discs 50 and 51 which are splined onto output mass 12 at 50a and 51 a respectively, the disc 52 which is splined at 52a onto a first bearing carrier 60 which has a radially inwardly extending portion 60d which is bolted to input flywheel mass disc portion 1 lb by bolts 19a and further discs 53 and 54 which are splined at 53a and 54a to an annular band 55 which is itself splined at 55a onto spines 52a of disc 52 The friction damper is completed by a pair of belleville springs 56 which act between disc 50 and a second bearing carrier 61 which is secured via rivets 23b to output flywheel mass 12 This basic form of friction damping device is described in the Applicant's co-pending patent application No WO96/29525 and includes co-operating ramps formed on discs 50 and 54 which are indicated diagramatically at 57 in figure 4 As described in co-pending application No WO96/29525, after the two flywheel masses have rotated relative to each other through a given angle from the neutral or central position, the ramps come into operation and force the discs 50 and 54 apart against the action of belleville springs 56 to generate increasing friction from damping device 17 The device can be arranged to generate no friction in the central region before the ramps become operative or can have its axial loading adjusted to ensure that friction is generated at all times The precise set-up of the friction damper depends on the desired operating characteristics of the flywheel In accordance with the present invention the above referred to bearing carriers 60 and 61 have concentric generally axially extending portions 61a and 60a respectively between which a plain bearing sleeve 80 which is formed in situ is located The bearing is completed by a belleville spring 62 which acts between radially extending regions 60c and 61c of the bearing carriers to bias the regions 60c and 61c apart and hence axially load the output flywheel mass 12 to the left, as viewed in figure 4, relative to the input mass 11 In effect disc 52 which is sandwiched between the input and output flywheel masses acts as an axial thrust bearing/support member To provide further support for the relative rotation of the flywheel masses 1 1 and 12 axially facing support pads 66 are provided at circumferentially spaced locations around the input mass 1 1 These pads contact the confronting surface 12a of the output mass 12 to control any tendency of the two flywheel masses to move axially or tilt relative to each other during relative rotation Pads 66 could replace disc 52 to take axial loading or could supplement disc 52 to control tilt to a given level In accordance with the Applicant's co-pending UK patent application No (Applicant's reference A2622) of even date the input flywheel mass 1 1 is provided with additional mass 70 at circumferentially spaced positions around the input mass to increase the inertia of the flywheel This additional mass is located generally in the annular zone within which the bob weight linkages 14 operate but is located to the side of the linkages in a non swept volume of this annular zone This extra mass is forged into the outer annular portion 1 lc of the input mass and includes the spring abutments 20 The bearing support block 1 Id is preferably manufactured from cast metal and, in order to avoid problems due to local radial distortion of the support block when attachment bolts 19a are fully tightened the radially outer surface 1 lg of block l id may be sized to be positioned with a slight clearance from the bearing carrier 60 and the carrier 60 may be supported against radially inward movements by annular washer 65 through which the attachment bolts 19a extend This washer is also provided to prevent the attachment bolts digging into the cast support 1 Id Alternatively earner 60 may be supported on support 1 Id The plain bearing sleeve 80, as indicated above, is formed in situ between the carriers 60 and 61 using a mould arrangement part of which is shown diagrammatically in Figure 6 Essentially the mould comprises two platens 81 and 82 which support the bearing carriers 60 and 61 with their radially extending portions 60c and 61c in contact with each other to seal off one end of a void between the bearing supports within which the bearing sleeve 80 will be moulded The other end of the void is sealed by the platen 82 Platen 82 includes injection nossles 83 through which polymeric bearing material is injected When the bearing material is solidified the supports 60 and 61 together with the in situ moulded sleeve 80 are removed from the mould and the supports 60 and 61 are moved axially and/or rotated relative to each other to crack the bond between the sleeve 80 and one or both of the supports 60 and 61 to provide a functioning bearing The bearing is then subsequently mounted in its operational position in the flywheel with the two radially extending portions 60c and 61c spaced apart as shown, for example, in figure 4 To improve the adhesion of the bearing sleeve 80 to one of the carriers 60,61, carrier 60 may, for example, be formed with a series of holes, cut-outs, grooves or other recesses into which the sleeve 80 may flow during the moulding process to provide a positive key If no carriers 60,61 are used and the sleeve is directly moulded onto the flywheel masses 1 1 and 12 one of these masses may be provided with the above keying recesses The moulding process may be modified by providing differential temperature control to the platens This can be achieved by providing one or both of the platens with a cooling water gallery which cools one or both carriers 60 or 61 so that the in situ moulded bearing sleeve does not attach itself to the or each cooled carrier This obviates the need to crack the carriers from the moulded sleeve 80. If the or each platen is cooled sufficiently the bearing sleeve may shrink back slightly from the cooled carrier(s) to give a working clearance Alternatively differential temperature of the platens can be achieved by applying heat rather than cooling In a further alternative arrangement in place of platen cooling one or both of the carriers may be coated in a release agent prior to insertion into the mould to remove the need to, or at least facilitate, cracking of the carriers from sleeve 80 Clearly one big advantage of forming the bearing sleeve by in situ moulding is that absolute accuracy of the internal and external diameters of the bearing sleeve is guaranteed without the need for any expensive machining or any particularly high manufacturing accuracies The material from which the bearing sleeve is moulded may, for example, comprise modified or unmodified thermoplastic or thermosetting polymers For example, PEEK (polyetherether ketone) with fillers such as glass fibre, carbon fibre and/or friction modifiers such as molybdenum disulphide may be used Alternatively PES (polyethersulphone) with similar fillers and modifiers may be used The bearing construction shown in Figure 4 may be modified, for example, by moving belleville spring 62 to the position occupied by disc 52 and forming bearing sleeve 80 with an integral radially extending portion 80a (see Figure 7) which replaces disc 52 and acts as an axial thrust bearing Bearing sleeve 80 with the radially extending portion 80a may be cast in situ by a suitable modification of the mould platens shown in Figure 6 If desired the bearing sleeve 80, with or without radially extending portion 80a, may be directly moulded or otherwise formed into portions of flywheel mass 12 and support 1 Id or an axially extended portion of flywheel mass 11 This arrangement requires appropriate modification of the mould platens shown in Figure 6 To counteract problems due to shrinkage of sleeve 80 when in use, causing the sleeve to grip support 60 and hence prevent relative rotation between sleeve 80 and support 60, the supports 60 and 61 and the sleeve 80 may be of a slightly tapering form, as shown in Figure 8, so that any slight shrinkage can be counteracted by slight migration of the sleeve 80 down the taper as indicated by arrow M in Figure 8 Also if sleeve 80 is cracked away from support 61 and not from support 60 any shrinkage of sleeve 80 will have no effect on the ability of sleeve 80 to rotate relative to support 61 As indicated above, the invention is not only applicable to twin mass flywheels but can also be used in relation to torsional vibration dampers of the kind specified in general and is not limited to dampers which use bob-weight torsional damping but can be used with any type of torsional damping between the input and output members

Claims: CLAIMS 1 A torsional vibration damper of the kind specified characterised in that the support bearing comprises a plain bearing formed in situ between the input and output members or between bearing carriers to be connected with a respective input or output member 2 A damper according to claim 1 charactensed in that the beanng earners are made from sheet metal or are made from cast, forged or sintered metal 3 A damper according to claim 2 characterised in that the bearing earners have generally axially extending regions between which the low friction plain beanng means is located to support the members radially and also include generally radially extending regions which are used to secure each of the earners to its respective input or output member 4 A damper according to claim 3 characterised in that an axially acting spring means acts between confronting generally radially extending regions of the carriers to generate friction damping on said relative rotation 5 A damper according to claim 4 characterised in that the axially acting spring also biases other surfaces which rotate with the input and output members into frictional contact to generate further fπctton damping 6 A damper according to any one of claims 1 to 5 charactensed in that one of the input or output members includes circumferential spaced axially facing support pads which contact a co-operating support surface on the other member to control relative axial movement of the members 7 A damper according to any one of claims 1 to 5 charactensed in that the plain bearing is moulded with a generally axially extending portion and a generally radially extending portion A damper according to any one of claims 1 to 7 characterised in that the plain bearing is of a tapering form A damper according to any one of claims 1 to 8 charactensed in that one of the input and output members or one of the beanng earners is provided with recesses into which the plain beanng is moulded A damper according to any one of claims 1 to 9 characterised in that the plain bearing is moulded in situ from a modified or unmodified thermoplastic or thermosetting polymer A damper according to claim 10 characterised in that the polymer is polyetheretherketone with suitable fillers or modifiers A damper according to claim 10 characterised in that the polymer is polyethersulphane with suitable fillers or modifiers A method of manufacturing a support beanng for a torsional vibration damper of the kind specified, said method comprising the steps of - placing a pair of concentric annular members into a mould, closing the mould to define a void between said members, injecting beanng material into said void to form a bearing sleeve between said members, opening said mould to release the members and sleeve A method according to claim 13 comprising the additional step of moving said members relative to each other to crack the sleeve from one or both members to provide a functioning support beanng in which said members are relatively rotatable via the sleeve A method according to claim 13 or 14 in which one or more portions of the mould adjacent one or both members are cooled or heated to discourage bonding of the bearing sleeve to the cooler mould portιon(s) A method accordmg to claim 15 in which the differential cooling or heating of said one or more portions of the mould is controlled to cause slight shrinkage of the moulded bearing sleeve away from the cooler mould portion to provide a working clearance between the sleeve and members A method according to claim 13 or 14 in which one or both members are coated with a release agent prior to injection of the bearing material to remove the need for, or at least facilitate, cracking of the members from the moulded bearing sleeve A method accordmg to any one of claims 13 to 16 in which separate bearing carriers are used and the mould is designed to support the earners against moulding pressure A method according to any one of claims 13 to 17 in which portions of the members are held in direct contact to partially define the void during the moulding process A method accordmg to claim 19 in which carriers are used and each carrier has a generally axially extending region between which the void is defined and a generally radially extending portion, these radially extending portions being held in contact with each other during the moulding process to close-off one end of the void, the other end of the void being closed by the mould A method according to claim 18 m which the bearing carriers have a generally axially extending portion and a generally radially extending portion which are held in a spaced relation to each other in the mould to form a plain beanng therebetween having a generally axially extending portion and a generally radially extending portion A method according to any one of claims 18 to 21 in which the carriers are displaced axially and/or rotated relative to each other to crack the moulded sleeve from one or both carriers A plam beanng for a torsional vibraton damper of the kmd specified formed by a method according to any one of claims 13 to 22 A torsional vibration damper of the land specified having a plain bearmg in accordance with claim 23 A torsional vibration damper of the kmd specified constructed and arranged substantially as hereinbefore described with reference to an ad shown in the accompanying drawings

Inventors: SOOD BHARAT BUSHAN, YOUNG ALASTAIR JOHN, SOOD, BHARAT, BUSHAN, YOUNG, ALASTAIR, JOHN
Applicants: AP TMF LTD, SOOD BHARAT BUSHAN, YOUNG ALASTAIR JOHN, AP TMF LIMITED, SOOD, BHARAT, BUSHAN, YOUNG, ALASTAIR, JOHN
Application year: 2000
Main classification: F16F15
IPC codes: F16F15