192 clutches and power-stop control – Elements – Engaging surfaces
Reexamination Certificate
1999-10-12
2001-04-10
Lorence, Richard M. (Department: 3681)
192 clutches and power-stop control
Elements
Engaging surfaces
C192S003290, C192S10700R, C192S113360
Reexamination Certificate
active
06213273
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to friction liners, in particular for bridging clutches for torque converters.
More particularly, the invention relates to a friction liner of the above type which has an annular friction surface for making axial contact against a reaction surface, the liner being also of the type in which the friction surface is formed with a network of grooves to enable a liquid to flow between the liner and the reaction surface.
BACKGROUND OF THE INVENTION
Torque converters are in particular used in motor vehicles to provide a coupling between the heat engine of the vehicle and the gearbox, which may be automatic and/or of a continuously variable type. In a torque converter, the transmission of the torque is obtained by circulation of a fluid between two bladed or finned wheels or rotors, one of which is coupled to the engine and the other to the gearbox. In their construction, these two wheels are not coupled together mechanically, so that there always exists between them the possibility of relative slipping movement. In some operating modes of the vehicle, this slipping movement is of no value and can even be detrimental to the overall performance of the drive train of the vehicle.
In addition, in parallel with the torque converter, a bridging clutch is generally provided, for the purpose of making a direct mechanical coupling between the engine and the gearbox in certain operating modes, corresponding for example to quasi stabilized speed ranges. Up to the present time, such bridging clutches have been used essentially in an “all or nothing” operating mode, that is to say they are used only in a fully engaged state or a fully disengaged state.
With a view to optimizing the performance of the drive train of the vehicle considered as a whole, it is now thought desirable to use the bridging clutch in a larger number of operating modes of the drive train, and especially, for example, during gear changing operations. In addition, the bridging clutch is tending more and more to be used, no longer only in its fully engaged and fully disengaged states, but also in a mode in which it slips, in particular with a view to damping out torque variations.
Thus, there is now an increasing tendency for the bridging clutch to be operated in a way which tends to give rise to severe heating, firstly of the contact surfaces and secondly of the oil which not only controls the clutch but also cools it.
With a view to preventing this additional heating causing accelerated wear of the liners, or causing the oil to be degraded by carbonization, it has previously been proposed to arrange on the friction liners a network of grooves which give improved circulation of the oil between the friction liner and the reaction surface. Various proposals have been made as to the form of the grooves in this type of network, all of them aiming to establish communication between the outer and inner perimeters of the annular friction liner.
However, the existence of the network of grooves gives rise to a loss of oil, even when the bridging clutch is used in its fully engaged mode and when there are no longer any differences in speed between the input shaft connected to the engine and the output shaft connected to the gearbox. In addition, the presence of these grooves in the friction liner substantially reduces the effective contact surface between the friction liner and the reaction surface, to the detriment of the torque that can be transmitted without slipping by the bridging clutch.
DISCUSSION OF THE INVENTION
The object of the invention is to overcome the above mentioned problems.
According to a first embodiment of the invention, a friction liner for a bridging clutch of a torque converter, having an annular friction surface which is adapted to make axial engagement against a reaction surface, the friction liner being of the type in which the friction surface includes a network of grooves to enable a liquid to flow between the liner and the reaction surface, is characterized in that the network of grooves comprise concentric circular grooves which are connected together through radial grooves spaced apart circumferentially, in that radial grooves are open firstly into an inner circular groove and secondly at the inner edge of the liner, in that the radial grooves formed between two circular grooves are offset circumferentially with respect to the radial grooves formed between the inner circular groove and the inner edge, and in that the radial grooves are not open radially to the outside of the liner.
According to a second embodiment of the invention, a friction liner for a bridging clutch of a torque converter, having an annular friction surface which is adapted to make axial engagement against a reaction surface, the friction liner being of the type in which the friction surface includes a network of grooves to enable a liquid to flow between the liner and the reaction surface, is characterized in that the network of grooves is not open radially to the outside of the liner, and in that the liner has a spiral groove and a set of radial grooves which are open at the inner edge of the liner, the said radial grooves intersecting the spiral groove at several points.
According to a third embodiment of the invention, a friction liner, having an annular friction surface which is adapted to make axial engagement against a reaction surface, the friction liner being of the type in which the friction surface includes a network of grooves to enable a liquid to flow between the liner and the reaction surface, is characterized in that the network of grooves is not open radially to the outside of the liner, in that it has a single groove which is elliptical and centred on the axis of the liner, the major axis of the ellipse defined by the said single groove being shorter than the outer diameter of the liner, and in that radial grooves put the elliptical groove in communication with the inner edge of the liner.
The friction liner is preferably incorporated in a bridging clutch of a torque converter.
The depth of the grooves of the friction liner is preferably substantially equal to one half of the axial thickness of the liner.
The liner is preferably made of a composite material including carbon.
Further features and advantages of the invention will appear more clearly on a reading of the following detailed description of some preferred embodiments of the invention, which is given by way of non-limiting example only and with reference to the accompanying drawings.
REFERENCES:
patent: 2856050 (1958-10-01), Mathews
patent: 4878282 (1989-11-01), Bauer
patent: 5101953 (1992-04-01), Payvar
patent: 5501309 (1996-03-01), Walth et al.
patent: 43 22 231 (1995-01-01), None
patent: 0 305 582 (1989-03-01), None
patent: 0 550 961 (1992-11-01), None
patent: 669982 (1952-04-01), None
patent: 6-42606 (1994-02-01), None
Patent Abstracts of Japan vol. 010, No. 171 (M-489); Jun. 17, 1986.
Luquet Philippe
Menard Denis
Lorence Richard M.
Morgan & Finnegan , LLP
Valeo
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