Rotary shafts – gudgeons – housings – and flexible couplings for ro – Torque transmitted via flexible element – Coil spring
Reexamination Certificate
1998-12-31
2001-06-12
Browne, Lynne H. (Department: 3629)
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Torque transmitted via flexible element
Coil spring
C192S212000, C464S067100
Reexamination Certificate
active
06244962
ABSTRACT:
STATE OF THE ART
The present invention concerns torsion dampers and damping devices equipped with such torsion dampers, such as the devices which are for example 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 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.
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 400, 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, and in particular at the end of the relative angular movement, the spring
20
itself deforms so that its axis
21
, initially rectilinear, adopts a curved shape, as shown in
FIG. 3
, whose concavity is turned towards the outside; consequently the spring
20
operates under poor conditions, the mean radius on which the tangential force due to the springs
20
is manifested decreasing, and it is difficult ultimately to control this force.
It will be understood that, the longer the springs
20
, the greater this drawback. Naturally, in order to avoid this drawback, it is possible to use short springs, but this requires, in order to obtain a large movement, a large number of springs disposed in series, which results in a complex design having regard notably to the large number of components, to which there is added the difficulty of controlling the parasitic friction.
In order to avoid the curvilinear deformation of the axis
21
of the spring
20
, notably at the end of movement, it has been proposed to associate different windows with the input element and output element, the windows in one of these two elements having lateral or support edges forming, with the internal edge, an angle slightly greater than a right angle; more precisely, as shown in
FIG. 4
, the windows formed in the guide washers, for example the windows
22
,
23
in the figure, have lateral edges
35
,
36
which are not parallel but inclined, which thus form an angle
38
with the lateral edges
15
,
16
in the windows
11
of the disc
1
; the angle
38
is designed so that, when the input element and the output element have effected their maximum relative movement, which corresponds to the columns which connect the guide washers coming into abut
Bacher Michel
Kovac Josip
Lucsak Patrick
Browne Lynne H.
Liniak Berenato Longacre & White
Thompson Kenneth
Valeo
LandOfFree
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