192 clutches and power-stop control – Clutches – Axially engaging
Reexamination Certificate
1999-08-18
2001-04-17
Marmor, Charles A (Department: 3681)
192 clutches and power-stop control
Clutches
Axially engaging
C192S213120
Reexamination Certificate
active
06216838
ABSTRACT:
STATE OF THE ART
The present invention concerns torsion dampers and damping devices equipped with such torsion dampers, such as for example the devices which are incorporated in clutch friction members for motor vehicles.
Clutch friction members are known, equipped with a torsion damping device comprising two torsion dampers: a main damper and a predamper.
The main damper has an input element fixed to two guide washers disposed on each side of a disc. The guide washers are connected together by struts, which fix them to each other. The input element consists, in the case of an application to a clutch friction member, of a support disc on each face of which friction linings are fixed, intended to be clamped between the thrust and reaction plates of the clutch.
As a variant, the input element can consist of a disc fixed directly to the vehicle engine flywheel; this can also be one of the guide washers which is extended radially and fixed directly to the engine flywheel.
The input element, when it is a case of a friction lining support disc, is pressed against one of the guide washers of the main damper whilst being fixed thereto by the struts or, as a variant, by specific rivets.
The struts pass through scallops formed at the external periphery of the disc; in this case, the angular movement between the disc and guide washers is limited through the cooperation of the struts with the edge of the scallops.
As a variant, this limitation is achieved by the fact that the helical springs constituting circumferentially acting elastic members, here with high stiffness, elastically coupling the guidance washers and the disc, come to have contiguous turns.
The guide washers surround the output element of the damper device consisting in general of an internally fluted hub; the same applies to the disc of the main damper, which for its part meshes with clearance with the hub. The main damper is therefore kinematically driven directly by the input element.
The predamper is located between the disc and one of the guide washers of the main damper, and this radially below the springs of the main damper.
The predamper is placed kinematically directly upstream of the output element and also has two guide washers disposed on each side of a disc fixed with respect to rotation to the hub by means of teeth. Elastic members, such as helical springs, elastically couple the disc of the predamper to its associated guide washers. This predamper disc is crimped to the hub, whose flutes have a different height in order to form a shoulder serving to fix the said disc axially.
In such a device with two dampers, the guide washers of the predamper are connected with respect to rotation to the disc of the main damper. The circumferentially acting springs of the predamper are less stiff than the circumferentially acting springs of the main damper.
The predamper is adapted to filter the vibrations in the idling range of the engine, whilst the main damper is adapted to filter the vibrations in the normal operating range of the vehicle, referred to as the running range, as from the idling range of the engine; the predamper can also be adapted to filter the vibrations in the running range at low engine torque.
The efficacy of a torsion damping device with regard to the low-frequency torsional vibrations in the vehicle running range, as from idling of the engine up to 2500 revolutions per minute, for example, requires a large angular movement between the driving element and the driven element, for example around 40°, this movement taking place counter to circumferentially acting elastic members elastically coupling the guide washers and the disc of the main damper.
Generally, the elastic members are helical springs disposed in windows formed in the guide washers and the disc, respectively. The three windows receiving one and the same spring, namely the two windows in the guide washers and the window in the disc, are in line with each other; each of these windows has an internal edge, two lateral or support edges, and an external edge; as shown schematically in
FIGS. 1 and 2
, the windows
11
in the disc
1
and the windows
12
and
13
in the guide washers
2
and
3
respectively have an internal edge
14
and
114
and lateral edges
15
,
16
and
115
,
116
disposed along the three sides of a rectangle, the internal edge
14
or
114
extending along the length of the said rectangle; the external edge
17
,
117
which faces the internal edge
14
,
114
is curvilinear in shape with its concavity directed towards the internal edge
14
,
114
, in other words towards the axis
90
about which the disc
1
and guide washers
2
and
3
rotate in operation. In
FIG. 1
, the contours of these three windows have been superimposed in plan view for convenience of the drawing; in practice, where it is a case notably of the windows
12
and
13
in the guide washers
2
and
3
, the lateral edges
115
and
116
are offset axially with respect to the internal
114
and external
117
edges, which form part of a flap
18
,
19
, as shown in
FIG. 2
; in
FIG. 1
, the external edge
117
and the internal edge
114
of the windows in the guide washers have been illustrated by a line representing the projection along the axis
90
, in the plane of the figure, of the generator which guides the helical spring
20
radially; in order to facilitate reading of the drawing, the window in the disc
11
is in solid lines, the dotted lines designating a window formed in the guide washers.
The helical spring
20
is a conventional spring whose axis
21
is rectilinear; when the spring
20
is placed in the windows
11
,
12
and
13
, its axis
21
is parallel to the internal edge
14
,
114
of the said windows and its end turns are in abutment on the lateral edges
15
,
115
and
16
,
116
of the said windows. The seating of the said end turns is perfect, and when there is a relative angular movement of the input element and output element, that is to way of the disc
1
and the guide washers
2
and
3
, these end turns remain in contact with the said lateral edges, without any relative movement of the said turns with respect to the said lateral edges; there is therefore no parasitic friction, at the lateral edges
15
,
115
and
16
,
116
, which might interfere with the calculated internal friction of the main damper for adjusting its hysteresis. Unfortunately, the above arrangement has the drawback that, in operation, whilst the torque transmitted by the springs
20
is still weak or nil, the spring
20
subjected to the action of the centrifugal force has a tendency to be progressively, with the speed, pressed against the external edge of the windows in the guide washers and/or in the disc whilst at the same time it deforms so that its axis
21
, initially rectilinear, adopts a curved shape whose concavity is turned towards the inside.
The consequences of this are that, on the one hand, parasitic friction is introduced into the damper and, on the other hand, the ends of the elastic members leave the support edges of the windows. More precisely,
FIGS. 1 and 2
show the most usual embodiment in which the guidance role of the springs
20
is entrusted entirely to the guide washers
2
and
3
; this is because, as can be seen in the figures, the end turns of the springs
20
in abutment on the lateral edges
115
,
116
are centred by the internal
114
and external
117
edges at their junction with the lateral edges
115
,
116
respectively; the flaps
18
,
19
, and therefore the external edge
117
, are semi-circular: the external edge
117
is an arc of a circle centred at
91
which is further towards the outside with respect to the axis
90
; consequently, the external edge
17
of the window
11
in the disc
1
is an arc of a circle centred at
92
, further towards the outside compared with the point
91
; the external edge
17
is consequently an edge with a clearance with respect to the spring
20
; however, the ends of the said external edge
17
are practically tangent to the end turn of the spring
20
in the
Bacher Michel
Kovac Josip
Lucsak Patrick
Liniak Berenato Longacre & White
Marmor Charles A
Rodriguez Saul
Valeo
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