GB2170295A

GB2170295A - Flywheel unit

Info

Publication number: GB2170295A
Application number: GB08601155A
Authority: GB
Inventors: Manfred Caspar; Peter Anders; Bernhard Schierling
Original assignee: Fichtel and Sachs AG
Current assignee: ZF Sachs AG
Priority date: 1985-01-24
Filing date: 1986-01-17
Publication date: 1986-07-30
Also published as: FR2576357A1; GB8601155D0; JPS61248938A; DE3502229A1

Abstract

The flywheel unit comprises a first flywheel (13) adapted to be separably fixed on the crankshaft (3) of an internal combustion engine, and a second flywheel (15, 17) mounted to be rotatable in relation to the first flywheel (13). A torsional vibration damper (39) couples the two flywheels together in torsionally elastic fashion. The second flywheel consists of, disposed on axially opposite sides of the first flywheel (13), two annular flywheel discs of which the first flywheel disc (15) which is axially adjacent the internal combustion engine has its inner periphery rotatably mounted on the crankshaft (3) via a bearing ring (25) connected thereto and in which the second flywheel disc (17) which is axially remote from the internal combustion engine is rigidly connected to the first flywheel disc (15) by spacers (19). The comparatively long heat transfer path disengages the bearing (25) thermally from the second flywheel disc (17) which forms the bearing face of the motor vehicle friction clutch. <IMAGE>

Description

SPECIFICATION Flywheel unit The invention relates to a flywheel unit for mounting on a crankshaft of an internal combustion engine and in particular a flywheel unit which consists of two flywheels coupled together in torsionally elastic manner through a torsional vibration damper.

Flywheel units are known from German Patent No. 28 26 274 and German Published Specification No. 29 31 423, in which, through a bearing ring, there is mounted on a bearing projection of a first flywheel which is bolted on the crankshaft a second flywheel.

This second flywheel is coupled to the first flywheel in torsionally elastic manner through a torsional vibration damper and in the case of motor vehicles forms the mating surface of the starting-up and gear changing clutch. The second flywheel is constructed as a one-piece flywheel which, in the region of its inner periphery, is mounted on the bearing projection through a plain bearing. The heat generated by the starting-up and gear changing clutch is dispersed directly into the bearing by the second flywheel.The thermal loading reduces the effective life of the bearing and necessitates a greater bearing clearance since the bearing clearance must on the one hand and under maximal thermal loading remain within predetermined limits while it must on the other hand be guaranteed that the flywheel unit remain capable of functioning even at very low ambient temperatures, for example in conditions of frost.

The object of the invention is to point a way whereby in a structurally simple manner, the two flywheels of the flywheel unit can be mounted on each other in mechanically stable fashion and whereby at the same time the thermal loading on the bearing can be reduced in order to increase its effective life.

According to the invention, the second flywheel which is rotatably mounted in relation to the first flywheel and in relation to the crankshaft consists of two flywheels connected to each other through spacers and rigidly to form one rigid unit and disposed on axially opposite sides of the first flywheel. The driven first flywheel which is axially adjacent the internal combustion engine is. through a bearing, mounted for rotation either directly on the crankshaft or on a bearing projection mounted on the crankshaft. The second flywheel which is on the output side and which is remote from the internal combustion engine constitutes the mating surface of the clutch plate of the starting-up and gear shifting clutch of the motor vehicle.The spacers which are preferably spacing rivets diminish the heat conducting cross-section between the first and second flywheels and are expediently provided in the region of the outer periphery of the flywheels so that there is a relatively long heat path from the second flywheel through the spacing rivets and the first flywheel to the bearing. The bearing is thus thermally disengaged from the thermally loaded second flywheel end is only subjected to comparatively minimal thermal loading.

The first flywheel is expediently utilised as a structural element of the torsional vibration damper. In a preferred embodiment, the torsional vibration damper comprises, mounted on axially opposite sides, two side plates which are mounted on the two flywheel discs of the second flywheel by which they are supported. The first flywheel is of disc-shaped construction in the region of the torsional vibration damper. For torsionally elastic coupling of the two flywheels, the torsional vibration damper comprises a plurality of thrust springs which are seated in axially aligned recesses in the disc-shaped part of the first flywheel on the one hand and the two side plates on the other and which during relative rotation of the two flywheels are subjected to a resilient loading.The disc-shaped part of the first flywheel and the two side plates can be manufactured comparatively inexpensively by being stamped out as sheet metal parts. The first flywheel is, in order to increase its flywheel effect, connected in the region of its outer periphery to a flywheel ring, being for example rivetted thereto. Like the two flywheel discs of the second flywheel, the flywheel ring may be constructed as a casting. Since the springs of the torsional vibration damper do not engage the castings but stamped-out metal parts, metal-removing secondary machining operations on the castings of the flywheels are reduced to a minimum.

Further preferred measures relate to friction devices within the torsional vibration damper which preferably comprises a plurality of friction devices which are used with varying magnitudes of friction torque in different ranges of relative rotation angles of the two flywheels.

The fact that the disc-shaped part of the first flywheel is in the region of a hub projection which extends axially away from the first flywheel disc concave and curves in dish-like fashion away from the first flywheel disc, forms sn annular space to accommodate friction devices. The hub projection mounts the first flywheel disc axially on the crankshaft and further, more carries the friction devices which surround it. The friction rings and the thrust rings of two friction devices can be mounted axially beside one another on the hub projection so that the friction force can be generated by a common axially effective spring.An idling device in the path of torque of one of the two friction devices ensures that this friction device only comes into operation at relatively high sngles of relative rotation, whereas the other friction device is expediently effective in the entire range of relative rotation of the torsional vibration damper.

A third friction device may be provided outside of the dishshaped portion of the first flywheel between the latter and the two flywheel discs. The third friction device can be dimensioned for a high frictional torque in the region of maximum angle of relative rotation so that also the pronounced torsional vibrations which occur during starting and shuttingdown the internal combustion engine can be damped.

Since the two side plates of the torsional vibration damper are preferably supported over their surface on the flywheel discs, they do not have to be annularly closed, but may be constructed as segments which are individually connected to the flywheel discs through a plurality of fixing rivets which may also be the spacing rivets. The segmental construction of the side discs reduces the amount of sheet metal waste resulting from the stsmping-out process.

The invention will be explained in greater detail hereinafter with reference to the accompanying drawings, in which: Fig. 1 is an axial longitudinal section through the upper half of a flywheel unit of the internal combustion engine of a motor vehicle; Fig. 2 is an axial longitudinal section through the lower haif of an alternative form of flywheel unit; Fig. 3 is a sectional view of a plain bearing which can be used in the flywheel units shown in Figs. 1 and 2; Fig. 4 is a sectional view through an alternative form of plain bearing, and Fig; 5 is a partial view of a side plate which can be used in a torsional vibration damper for the flywheel units shown in Figs. 1 and 2.

Fig. 1 shows the clutch end of a crankshaft 3 of the internal combustion engine of a motor vehicle which rotates about a rotary axis 1. Reference numeral 5 denotes a gearbox input shaft which in conventional manner and through a pilot bearing 7 is equiaxially mounted in an end aperture 9 of the crankshaft 3. By means of screws 11, a first flywheel 13 is bolted on an end face of the crankshaft 3. Disposed axially on either side of the flywheel 3 are annular flywheel discs 15, 17 which are connected rigidly to each other through peripherally spaced apart spacing rivets 19 in order to form a rigid unit. The flywheel discs 15, 17 form a second flywheel which is rotatable in relation to the flywheel 13, the spacing rivets 19 which pass through peripheral siots 21 in the flywheel 13 defining the angle of relative rotation.The flywheel disc 15 on the drive side and axially adjacent the internal combustion engine carries on its inner periphery and projecting axially towards the flywheel disc 17 a hub projection 23 which is mounted on the crankshaft 3 through a bearing 25, preferably a plain bearing or a rolling-type bearing which supports the flywheel 15 in rotatable but axislly fixed manner. The flywheel 17 which is axially remote from the internal combustion engine forms a bearing surface 26 for a clutch plate 27 of a conventional motor vehicle friction clutch which is not shown in greater detail but of which the clutch housing 29 is mounted on the flywheel disc 17 in conventional manner.

The friction clutch is not shown in detail. Likewise not shown is the rotationally rigid but sxialiy movable coupling of the clutch plate 27 to the gearbox input shaft 5. A torsional vibration damper 31 couples the flywheel 13 in torsionally elastic fashion to the flywheel discs 15, 17 and damps the torsional vibrations which in operation arise in the drive train of the motor vehicle.

The frictional heat which in operation is generated by friction between the flywheel disc 17 and the clutch plate 27 leads only to a relatively minimal thermal loading on the bearing 25 since the heat conductive cross-section of the spacing rivets 19 is relatively small and the heat bridge formed by the spacing rivets 19 is at a comparatively great distance from the bearing 25.

The torsional vibration damper 31 comprises, disposed on axially opposite sides of a disc part 33 of the flywheel 13, two side plates 35, 37 and a plurality of coil thrust springs 39 distributed in a peripheral direction and seated in recesses 31 in the disc part 33 at one end and recesses 43, 45 in the side plates 35, 37 on the other and which, during relative rotation of the flywheel discs 15, 17 are subjected to a compression loading in relation to the flywheel 13. To this end, the side plates 35, 37 are rigidly connected by spacing rivets 19 to whichever are the adjacent flywheel discs 15. 17.

In the region of the hub projection 23, the disc part 33 of the flywheel 13 is inwardly conically shaped away from the flywheel disc 15. The hub projection 23 engages into this concave portion shown at 47 and at the same time constitutes s bearing for two axially disposed friction devices which are accommodated in the annular space formed by the concave shape 47. A first friction device comprises a thrust ring 49 which is rotatably but not axially displaceably mounted on the hub projection 23. A friction ring 51 is provided axially between the thrust ring 49 and the flywheel disc 15. Protruding axially from the inner periphery of the thrust ring 49 are projections 53 which engage apertures 55 in the disc part 33 and couple the thrust ring 49 in rotationally rigid but axially displaceable fashion to the disc part 33. Axially between the thrust ring 49 and the disc part 33, a second thrust ring 57 encloses the hub projection 23.

The thrust ring 57 is rotatable in relation to the thrust ring 49 end is also axially movable and carries on its outer periphery axially bentover lugs 59 which engage in axially movable fashion into apertures 61 on the flywheel disc 15. The projections 59 couple the thrust ring 57 in rotationally rigid fashion to the flywheel disc 15, although with a predetermined rotational clearance. A friction ring 63 is located axially between the thrust rings 49, 57. A further friction ring 65 is seated axially between the thrust ring 57 and a third thrust ring 67 which is in turn located between the thrust ring 67 and the disc part 33. The thrust ring 67 is rotationally rigidly but axially displaceably guided on the projections 53.Between the thrust ring 67 and the disc part 33 there is clamped an axially operative spring, for example a plate spring 68 which clamps the thrust ring-friction ring package securely against the flywheel disc 15.

In the case of torsional vibrations comprising an angle of rotation smaller than the rotary clearance of the projections 59 in the apertures 61, the friction moment is determined by the friction effect between the thrust ring 49, the friction ring 51 and the flywheel disc 15. In the case of greater angles of rotation, the projections 59 abut the extreme limits of the apertures 61 so that in addition to the aforedescribed friction effect, the friction effect between the thrust ring 57 and the friction rings 63, 65 or the thrust rings 49, 67 comes into consideration. There is increased friction damping in this operating condition.

The torsional vibration damper 31 comprises a third friction device which is substantially only effective in the region of maximum angle of rotation and which generates a comparatively very high frictional torque in order to damp the more extensive torsional vibrations which occur during start-up end shut-down of the internal combustion engine. The third friction device is located substantially radially outside of the concave curvature 47 and comprises annularly the two previously explained friction devices. It comprises axially on either side of the side plate 33 two annular control plates 69, 71 which are rotatable on axially -opposite sides of the side plate 33 between the disc part 33 and the side plates 35, 37 and relative to the side plates 35, 37.The control plates 69, 71 have control arms 73, 75 through which they are coupled to the end faces of the springs 39. Projecting axially from the control plate 69 are projections 77 which engage through apertures 79 in the disc part 33 and which connect the control plate 69 in rotationally rigid but axially movable manner to the control plate 71. A friction ring 81 is located axially between the control plate 69 and the flywheel disc 15. A further friction ring 83 is disposed between the control plate 71 and the flywheel disc 17. The projections 77 have axial shoulders 85 on which the outer periphery of a plate spring 87 is braced. The inner periphery of the plate spring 87 is clamped against the control disc 71 so that the plate spring 87 clamps the control plates 69, 71 axially away from each other and against the flywheel discs 15, 17 through the friction rings 81, 83.The projections 77 couple the control discs 69, 71 in rotationally rigid fashion, but with rotary clearance, to the disc part 33. The magnitude of the rotational clearance is sufficient to allow a relative rotation of the control discs 69, 71 only in the region of the angle of maximum rotation of the torsional vibration damper 31 in relation to the flywheel discs 15, 17, so that the friction device is effective only in the region of the maximum angle of rotation. The plate spring 87 generates comparatively high axial forces which can without problem be absorbed, however, by the stable flywheel discs 15, 17.

The bearing 27 which may be a plain bearing or a rolling type bearing is axially fixed in the hub projection 23 on axially one side by an annular collar 89 projecting radially inwardly from the flywheel disc 15 and on the axially other side by a retaining ring 91. The mounting 25 is axially fixed on the crankshaft 3 by an annular shoulder 93 on the one hand and by projections 95, which are pressed out of the disc part 33 in a peripheral direction and at intervals from one another.

The disc part 33 is a sheet metal stamping and carries on its outer periphery an axiallyprojecting flywheel ring 97 which engages axially around the flywheel 17. The flywheel ring 97 is fixed for example rivetted onto the outer periphery of the disc part 33. The flywheel discs 15, 17 and also the flywheel ring 97 are castings into which any apertures and recesses which may be required are already integrally cast, as shown in the case of pockets 99 in the flywheel discs 15, 1 7 which accommodate the springs 39. Thus there is no need for any metal removing secondary working on the castings. The control edges and the like required for the operation of the torsional vibration damper 31, on the other hand, can be formed with accuracy on the sheet metal stampings of the side plates 35, 37 or disc part 33 by a stamping operation.The flywheel unit can therefore be manufactured at a relatively favourable cost.

Fig. 2 shows an alternative flywheel unit which differs from the flywheel unit in Fig. 1 substantially only by the manner in which the flywheel is mounted on the crankshaft. Parts which form the same function are identified by the reference numerals shown in Fig. 1 plus the letter a to ensure differentiation. For explanation, reference is made to the description of Fig. 1. For the rest, Figs. 1 and 2 show the upper and lower halves of the same construction of flywheel unit but from different angles of intersection. The parts 19, 21, 31, 39 to 45, 55, 59, 61, 77, 79, 85 and 99 are present but not shown in Fig. 2. On the other hand, Fig. 2 shows a rivet 101 not shown in the section in Fig. 1 but used for fixing the flywheel ring 97a on the disc part 33a.

In contrast to the embodiment shown in Fig.

1, the bearing 25 is not mounted directly on the crankshaft 3a but on an annular projection 103 fixed on the crankshaft 3a together with the flywheel 13a by means of bolts 1 1a. The annular projection 103 carries in an aperture 105 the pilot bearing 7a which guides the gearbox input shaft 5a. The bearing 25a is axially fixed between (at the crankshaft end) an annular shoulder 107 on the annular projection 103 on the one hand and a spacing ring 109 fitted between the disc part 33a and the bearing 25a.

Figs. 3 and 4 show details of the bearing portion of the flywheel unit in Fig. 2 when a plain bearing is used. The plain bearing 25a in Fig. 3 comprises an outer ring 111 which is axially fixed between the radially inwardly projecting annular shoulder 89a and the locking washer 91a. The outer ring 111 has, inclined towards each other, two sliding faces 113, 115 in the form of two equiaxial conical faces which widen axially outwardly away from each other. In cross-section, the outer ring 111 is substantially V-shaped. Enclosing the annular projection 103 are two axially adjacently disposed inner rings 117, 119 which have complementary sliding faces bearing on the sliding faces 113, 115 and axially fixed between the annular shoulder 107 and the disc part 33a.

By appropriate dimensioning of the axial thickness of the spacing ring 109, it is possible to compensate for axial and radial clearance of the outer ring 111. Fig. 4 shows an alternative plain bearing 25c. The plain bearing 25c comprises, axially fixed in the hub projection 23a, an outer ring 121 of which the cylindrical inner shell 123 is radially guided on an inner ring 125. The inner ring 125 has a radially outwardly projecting annular flange 127 which guides the outer ring 121 on axially one side and on a plane end face. On the side of the outer ring 121 which is opposite the annular flange 127, the outer ring 121 is guided by a flat annular disc 129. The inner ring 125 and the annular disc 129 are axially fixed between the annular shoulder 107 of the annular projection 103 and the disc part 33a.By a suitable choice of axial thickness of the spacing ring 109, it is possible to compensate for axial clearance of the outer ring 121. The outer ring 121 is of substantially T-shaped crosssection so that the bearing flange 127 and the annular disc 129 are axially flush with the outer ring 121. The plain bearings in Figs. 3 and 4 can also be used with the flywheel unit shown in Fig. 1.

Fig. 5 shows a partial view of the side plate 35 in Fig. 1. The side plate 37 is built up in the same way, as is also the side plate 35a and 37a shown in Fig. 2. The side plate 35 comprises a plurality of segments 131, for example two or three segments 131, which combine to form a complete ring. Each of the segments 131 is connected by at least two peripherally adjacent spacer rivets 19 to whichever is the adjacent flywheel disc, in this case the flywheel disc 15. Fig. 5 shows only apertures 133 through which the spacer rivets 19 can pass. Fig. 5 also shows an alternative with regard to Fig. 1, whereby the windows provided to accommodate the springs 39 are radially in hardly open, as shown at 135. Subdivision of the side plates into segments offers advantages where manufacture is concerned since far less waste occurs compared with the production of a closed ring. The reduced rigidity of the side plates presents no problem since they are strengthened by the flywheel discs.

Claims

1. A flywheel unit for mounting on a crankshaft of an internal combustion engine and comprising a) a first flywheel (13) which is to be mounted separably on the crank shaft (3), b) a bearing (25) adapted for separable but axially fixed mounting on the crankshaft (3), c) a second flywheel (15, 17) mounted on the bearing (25) to be rotatable relative to the first flywheel (13) but axially fixed, d) a torsional vibration damper (31) coupling the two flywheels (13, 15, 17) together in torsionally elastic fashion through a plurality of springs (39), characterized in that the second flywheel consists of, disposed on axially opposite sides of the first flywheel (13), two annular flywheel discs (15, 17) of which the first flywheel disc (15) which is axially adjacent the internal combustion engine has its inner periphery seated on the bearing (25), the second flywheel disc (17) which is axially remote from the internal combustion engine being connected rigidly to the first flywheel disc (15) by means of spacers (19).

2. Flywheel unit according to Claim 1, characterized in that the bearing (25a) is seated on an annular projection (103) connected to the crankshaft (3a) and is axially fixed between the first flywheel (13a) and an annular shoulder (107) on the annular projection (103).

3. Flywheel unit according to Claim 2, characterized in that the annular projection is an integral component of the crankshaft.

4. Flywheel unit according to one of Claims 1 to 3, characterized in that the first flywheel (13) includes, constructed as an annular discshaped sheet metal stamping, a disc part (33) which in the region of its inner periphery is intended to be bolted onto the crankshaft (3), and a flywheel ring (97) adapted, in the region of the outer periphery of the disc part (33), to be disposed rigidly on this latter and in that the flywheel ring (97) radially outwardly encloses the second flywheel discs (17) of the second flywheel.

5. Flywheel unit according to one of Claims 1 to 4, characterized in that the first flywheel disc (15) of the second flywheel has on its inner periphery and enclosing the bearing (25) an annular hub projection (23) projecting axially towards the second flywheel disc (17).

6. Flywheel unit according to Claim 5, characterized in that the torsional vibration damper (31) comprises between the first flywheel disc (15) and the first flywheel (13) and mounted radially on the hub projection (23) a friction device (49 to 68) which comes into effect upon a relative rotation of the first (13) and second (15, 17) flywheel.

7. Flywheel unit according to Claim 6, characterized in that the friction device (49 to 68) comprises, enclosing the hub projection (23), three thrust rings (49, 57, 67) of which the first thrust ring (49) is rotationally rigidly but axially movably connected to the first flywheel (13) and of which the second thrust ring (57) is located axially between the first thrust ring (49) and the first flywheel (13) and is coupled to the first flywheel disc (15) to as to be axially movable and, except for a predetermined amount of rotary clearance, rotationally rigid, and of which the third thrust ring (67) is located axially between the second thrust ring (57) and the first flywheel (13) end is rotationally rigidly but axially movably connected to the first flywheel (13) and in that axially between the first flywheel (13) and the third thrust ring (67) there is clamped an axially operative spring (68) and in that the first thrust ring (49) bears through a first friction ring (51) on the first flywheel disc (15), the second thrust ring (57) bears through a second friction ring (63) on the first thrust ring (49) and the third thrust ring (67) bears through a third friction ring (65) on the second thrust ring (57).

8. Flywheel unit according to Claim 6 or 7, characterized in that the first flywheel (13) has in the region of the hub projection of the first flywheel disc the form of a concave disc, the disc shape of which tends to diverge from the first flywheel disc (15), the hub projection (23) extending axially into the concave shape (55), and in that in the region of the outer periphery of the concave shape (55), axially between the first flywheel (13) and the second flywheel disc (17) there is a further friction device (69 to 87).

9. Flywheel unit according to Claim 8, characterized in that the further friction device (69 to 87) comprises, located on axially opposite sides of the first flywheel (13), two control discs (69, 71) and axially between each of the control discs (69, 71) and the adjacent flywheel disc (15, 17) a friction ring (81, 83) and in that a first of the control discs (69) has axially bent-over lugs (77) which engage through apertures (79) in the first flywheel (13) and connect the first control disc (69) in axially movable manner to the first flywheel (13) so that the said first control disc (69) is rotationally rigid except for a predetermined amount of rotary clearance, and also couple the first control disc (69) in rotationally rigid but axially movable manner to the second control disc (71) and in that between the lugs (77) and the second control disc (71) there is clamped an axially operative spring (87).

10. Flywheel unit according to one of Claims 1 to 9, characterized in that the torsional vibration damper (31) has, disposed axially on both sides of the first flywheel (13), between the first flywheel (13) and the flywheel discs (15, 17) of the second flywheel, and connected to the flywheel discs (15, 17) to form one unit and axially supported on the flywheel discs (15, 17), two side plates (35, 37), the springs (39) of the torsional vibration damper (31) being seated in recessrs (41, 43, 45) of the first flywheel (13) on the one hand and the two side plates (35, 37) on the other.

11. Flywheel unit according to Claim 10, characterized in that the two flywheel discs (15, 17) are castings and have in the region of the recesses (43, 45) in the side plates (35, 37) integrally cast pockets (99) for the springs (39).

12. Flywheel unit according to Claim 10 or 11, characterized in that the spacers are constructed as spacing rivets (19) and at the same time hold the side plates (35, 37) on the flywheel discs (15, 17) and in that the side plates (35, 37) consist of a plurality of segments (131) each of which is mounted on the adjacent flywheel disc (15, 17) by at least two of the spacing rivets (19).

13. A flywheel unit as claimed in claim 1, substantially as described herein with reference to and as illustrated by any one of the examples shown in the accompanying drawings.