Torque transmitting apparatus

A hydrokinetic torque converter with a built-in bypass clutch is provided with an arrangement which regulates the cooling of the clutch at a rate dependent upon the slip between the coaxial driving and driven parts of the clutch, and hence upon the quantity of generated friction heat. The cooling unit for the driving and/or driven part of the clutch can employ, for example, one or more pumps; a supply of a substance which changes its aggregate state from liquid to gaseous or from solid to flowable in response to heating, and vice versa in response to cooling; one or more porous washers in the path for the flow of hydraulic fluid between the customary plenum chambers provided in the housing of the torque converter to move a piston of the driven part of the clutch into and from frictional engagement with the housing; and/or a system of recesses, grooves, channels and/or other passages serving to convey fluid between the chambers at a rate which is higher or highest when the clutch operates with maximum slip. Such rate can decrease to zero when the torque converter is idle or the clutch is fully engaged to operate without slip.

BACKGROUND OF THE INVENTION

The present invention relates to improvements in torque transmitting apparatus, and more particularly to improvements in hydrokinetic torque converters of the type often utilized in the power trains of motor vehicles, e.g., to transit torque between the output element of a prime mover (such as a crankshaft or a camshaft of a combustion engine) and the input shaft of a change-speed transmission.

A torque converter of the character to which the present invention pertains normally comprises a rotary housing which is driven by the prime mover and drives a vaned pump, a vaned turbine which can be rotated by the body of fluid filling the housing and being circulated by the pump when the prime mover is on, an optional stator between the pump and the turbine, and a so-called bypass clutch or lockup clutch (hereinafter called bypass clutch) which can be engaged to transmit torque from the housing directly to the turbine or to a hub which rotates with the turbine and serves to transmit torque to the input shaft of the transmission.

The bypass clutch can operate with or without slip and is engageable and disengageable by moving a piston into or from full or partial frictional engagement with a portion of the housing or with a part which rotates with the housing. The housing contains two fluid-filled plenum chambers and the piston is moved axially to partly or fully engage or disengage the clutch in response to changes of pressure differential between the bodies of fluid filling the two plenum chambers. The torque converter often further comprises one or more torsional vibration dampers operating between the housing and the turbine and/or between the turbine and the hub.

A torque converter of the above outlined character is disclosed, for example, in German patent No. 36 14 158. The patented apparatus employs a bypass clutch which operates between the housing and an axially movable piston which rotates with the hub. Such apparatus are known as twin-channel torque converters wherein the piston of or for the bypass clutch separates the plenum chambers from each other when the bypass clutch is at least partially engaged so that a friction lining on the piston engages and receives torque from a portion (e.g., a radial wall) of the housing or from a friction lining on the housing. Partial engagement of the bypass clutch involves a slip of the piston relative to the housing and/or vice versa, and such slip results in the generation of heat in such quantities that the fluid medium in the housing of the torque converter is not always capable of absorbing excess heat. Excessive heating of friction linings forming part of the bypass clutch can entail damage to and frequently rapid destruction of the friction linings; in addition, overheating can adversely influence the hydraulic fluid in the housing of the torque converter.

Abrupt full engagement of the bypass clutch, i.e., without slip, is likely to be even more damaging to the torque converter and can also adversely affect the comfort to the occupant(s) of the motor vehicle. Thus, an abrupt transition from disengagement to full engagement of the bypass clutch can be a cause of discomfort to the occupant(s). In other words, the ride is much more comfortable if the bypass clutch of the torque converter is engaged gradually with an initially pronounced and thereupon gradually decreasing slip, i.e., with the generation of large quantities of undesirable friction heat. Thus, it is desirable to devise a torque converter wherein the bypass clutch is fully engaged upon a gradual reduction of slip but the thus developing large quantities of friction heat can be dissipated and/or otherwise disposed of without affecting the comfort to the occupant(s) of the motor vehicle (if the torque converter is installed in the power train of a motor vehicle) and without damage to the friction linings and/or other heat-sensitive parts of the torque converter and of its bypass clutch. Such requirements cannot be met, or cannot be adequately satisfied, by presently known torque converters. It is also desirable and important to ensure that the withdrawal of requisite quantities of heat be effected without unduly increasing the space requirements of the torque converter, especially in the power train of a motor vehicle.

OBJECTS OF THE INVENTION

An object of the instant invention is to provide a novel and improved arrangement which renders it possible to withdraw heat from and/or to dissipate heat in a torque converter at a rate which is required to avoid damage to various heated heat-sensitive parts and/or substances, such as friction linings, oil, transmission fluid and the like.

Another object of the invention is to provide a simple, compact and relatively inexpensive heat exchange system which can be incorporated in existing types of hydrokinetic torque converters and which can be readily set up or designed to ensure adequate withdrawal of excess heat at a rate which varies or which can vary proportionally with variations of the quantities of surplus heat.

A further object of our invention is to provide a novel and improved method of removing heat from the bypass clutch of a hydrokinetic torque converter in such a way that the presently preferred construction and/or mode of operation of the bypass clutch can remain at least substantially unchanged.

An additional object of the invention is to provide a novel and improved bypass clutch for use in hydrokinetic torque converters.

Still another object of the invention is to provide a torque converter wherein the parts of the bypass clutch and the hydraulic fluid can be shielded from overheating even though the connections to the source(s) of hydraulic fluid and the paths for the flow of fluid into, within and from the housing of the torque converter remain at least substantially unchanged.

A further object of the instant invention is to provide the hydrokinetic torque converter with a cooling system which is or which can be set up to be effective only when a withdrawal of heat from the bypass clutch and/or from hydraulic fluid is advisable or actually necessary.

Another object of the invention is to provide a cooling system which can be installed in or incorporated into existing torque converters in such a way that it adds little, if anything, to the space requirements as seen in the radial and/or in the axial direction of the torque converters.

An additional object of the invention is to provide novel and improved friction linings for use in the bypass clutches of hydrokinetic torque converters, e.g., for utilization in the power trains of motor vehicles.

Still another object of the invention is to provide novel and improved fluid agitating devices for use in a torque converter wherein the bypass clutch is designed to operate with slip.

A further object of the invention is to provide a novel and improved fluid flow regulating arrangement which embodies or forms part of the aforementioned cooling system and can be incorporated into existing types of hydrokinetic torque converters using bypass clutches which operate in a manner necessarily involving the generation of substantial quantities of friction heat.

SUMMARY OF THE INVENTION

One feature of the present invention resides in the provision of a hydrokinetic torque converter which comprises a housing rotatable about a predetermined axis, a pump which is rotatable by the housing about the predetermined axis and can be of one piece with the housing, a turbine which is rotatable in the housing about the predetermined axis by the pump (actually by the supply of fluid which is circulated in the housing by the pump when the torque converter is in use), means for rotating the housing (such means can include a camshaft or a crankshaft receiving torque from a prime mover such as a combustion engine, an electric motor, a gas turbine, or a hybrid prime mover in the power train of a motor vehicle), an output element (such as the input shaft of the change-speed transmission in the power train of a motor vehicle) which is rotatable about the predetermined axis and is arranged to receive torque from the turbine, and a fluid-operated bypass clutch which is disposed in the housing and is arranged to transmit variable torque between the housing and the output element. The clutch includes a driving component rotatable with the housing and a driven component rotatable with the output element and movable axially of the housing into and from frictional engagement—with and without slip—with the aforesaid driving component. The improved torque converter further comprises means for moving the driven component relative to the driving component in the axial direction of the housing (such moving means comprises first and second plenum chambers containing bodies of hydraulic fluid at variable pressure with the provision for fluid flow between the chambers through the clutch), and means for regulating the fluid flow between the chambers in dependency upon the magnitude of torque being transmitted by the clutch when the latter is at least partially engaged.

The regulating means preferably comprises means for automatically altering the rate of fluid flow between the plenum chambers in response to variations of the slip between the driving and driven components.

The regulating means can also comprise at least one channel (such as a recess or groove or the like) which is provided in at least one of the driving and driven components and is arranged to establish a path for the flow of fluid between the plenum chambers when the clutch is operated with slip.

The regulating means is designed to increase the rate of fluid flow between the chambers in response to increasing slip of the driving and driven components relative to each other.

The regulating means can include means for regulating the rate of fluid flow between the plenum chambers in dependency upon changes of RPM between the means for rotating the housing and the output element.

The torque converter can further comprise means for varying the pressure of fluid in at least one of the plenum chambers independently of the regulating means. Such varying means is or can be operative to vary the pressure of fluid in the at least one chamber as a function of changes of the RPM of the means for rotating the housing.

The viscosity of fluid in the flow between the plenum chambers varies in response to the changes of the extent of slip between the driving and driven components, and the rate of fluid flow between the plenum chambers can be regulated in response to variations of the viscosity of fluid.

As a rule, the temperature of fluid in the flow between the plenum chambers varies in response to changes of the extent of slip between the driving and driven components, and the regulating means can change the rate of fluid flow in dependency on such temperature changes.

The regulating means can be provided with at least one channel which is machined or otherwise provided in at least one of the driving and driven components to establish a path for the flow of fluid between the chambers when the clutch is operated with slip, and such regulating means can comprise an adjustable barrier which determines the rate of fluid flow in the at least one channel.

The driven component can comprise a piston and at least one of the driving and driven components can comprise a friction lining which contacts the other component in the engaged condition of the clutch. The driving component can form part of or can be affixed to the housing and the piston can be non-rotatably but axially movably mounted on the turbine or on the output element of the torque converter. Such piston can be arranged to at least partially seal the plenum chambers from each other, at least while the driven component frictionally engages the driving component.

It is also possible to provide each of the driving and driven components with a friction lining, and such friction linings can be and normally are mounted in such a way that they contact each other in the partly or fully engaged condition of the bypass clutch.

The bypass clutch can be constructed in such a way that the driving component forms part of the torque converter housing and that the driven component comprises a piston which at least partially seals the plenum chambers from each other in the engaged condition of the bypass clutch.

The bypass clutch can further comprise a preferably resilient friction lamella which is disposed between the driving and driven components and is movable axially of the torque converter housing, in response to axial movement of the driven component, to a position of frictional engagement with the two components in the partly or fully engaged condition of the bypass clutch. The driven component can comprise a piston which is rotatable with the housing, and such clutch preferably further comprises at least one friction lining which is or can be provided on the lamella and frictionally engages one of the driving and driven components in the engaged condition of the bypass clutch. The arrangement can be such that the clutch further comprises a first friction lining which is carried by the lamella or by the driving component and engages the driving component or the lamella in the engaged condition of the clutch, and a second friction lining which is carried by the lamella or the driven component and engages the driven component or the lamella in the engaged condition of the clutch. Alternatively the just described embodiment of the clutch can comprise at least one friction lining which is provided on the driving or driven component and frictionally engages the lamella in the fully or partly engaged condition of the clutch.

The torque converter or the regulating means can comprise one or more cooling units for the bypass clutch; such cooling unit(s) can be set up to exchange heat with the driving and/or with the driven component.

In accordance with another presently preferred embodiment, the bypass clutch further comprises at least one friction lining which is borne by one of the driving and driven components and frictionally engages the other component in the partly or fully engaged condition of the clutch. The driving and driven components and the at least one friction lining are provided with friction surfaces each of which engages another of the surfaces at least in the engaged condition of the clutch, and the regulating means of the torque converter embodying the just described bypass clutch can be provided with recesses which extend at least substantially radially of the housing axis and are machined, impressed or otherwise provided in at least one of the surfaces to establish at least a portion of the fluid flow in the engaged condition of the bypass clutch. For example, the recesses can be provided in the surface of the driving and/or driven component and can be embossed into the respective friction surface. Alternatively, the recesses can be formed by displacing some material of the driving and/or driven component and/or friction lining, e.g., by impressing grooves into one side of the friction lining to thus develop raised portions at the other side of the friction lining; the grooves at the one side of the friction lining can constitute a set of recesses, and the depressions between the raised portions can serve as another set of recesses.

The friction lining can resemble a washer and, if the recesses are provided in the surface of at least one of the driving and driven components, such recesses can extend radially of the axis of the torque converter housing and the lengths of at least some of such radially extending recesses can exceed the radial width of the friction lining; the latter overlies only portions of such recesses in the engaged condition of the bypass clutch.

The recessed surface (or each recessed surface) can be provided with an annular array of between about 8 or 10 and 400 recesses, preferably between about 100 and 300 recesses. The lengths of such radially extending recesses can be in the range of between 10 and 50 mm, preferably between 10 and 30 mm, and their depths can be less than 0.3 mm, preferably less than 0.15 mm. The widths of at least some of the recesses can be in the range of between 0.2 and 20 mm, preferably between 0.1 and 1 mm.

The ratio of the area taken up by the recesses to the area of the non-recessed portion of the at least one surface can be within the range of between about 2:1 and 1:200, preferably between about 1:1 and 1:10. Otherwise stated, if the recessed surface is to engage a flat surface, between 33% and 95% (preferably between 50% and 91%) of the flat surface are in actual contact with the recessed surface. At least some of the edges of the recessed surface bounding the recesses can be chamfered or bevelled (e.g., rounded).

If the bypass clutch employs a friction lamella which is disposed between the driving and driven components, the recesses can be provided in one or both surfaces of the lamella, i.e., i.e., in the surface confronting the driving component and/or in the surface confronting the driven component. Such recesses form part of the regulating means in that they establish paths for the flow of fluid between the plenum chambers in the partly or fully engaged condition of the clutch. Each component, or at least that component which faces a single recessed surface of the lamella, can be provided with a friction lining which engages the recessed surface in the engaged or partly engaged condition of the bypass clutch. The recesses in one or both surfaces of the lamella can include first recesses which are open inwardly toward the axis of the torque converter housing and second recesses which are open outwardly away from such axis. Individual second recesses or groups of second recesses can alternate with individual first recesses or groups of first recesses, as seen in the circumferential direction of the preferably annular recessed surface or surfaces. At least some of the recesses extend or can extend at least substantially radially of the axis of the torque converter housing.

The torque converter can further comprise a damper which is set up to damp torsional vibrations between the housing of the torque converter and the output element in the engaged condition of the bypass clutch. The damper can be designed to comprise an input having a lamella disposed between and frictionally engaging the driving and driven components in the engaged condition of the clutch, an output arranged to rotate with the output element of the torque converter, and at least one energy storing device (e.g., at least one coil spring or a suitably configurated and dimensioned block of rubber or the like) which is interposed between the input and the output to offer a desired resistance to turning of the input and output relative to each other.

The clutch or the regulating means can further comprise at least one porous (i.e., foraminous or permeable) layer which is disposed between the driving and driven components and establishes a plurality of paths for the flow of hydraulic fluid between the plenum chambers in the engaged condition of the bypass clutch. The porous layer can include or constitute an annular disc which contains a sintered material and/or another material that exhibits adequate porosity and can stand mechanical and/or thermal stresses developing in a hydrokinetic torque converter. For example, the porous layer can consist of sintered metal, plastic, glass, a suitable ceramic substance or a mixture or compound of the above enumerated materials. The clutch utilizing the porous layer can further employ a friction lining which is interposed between the driving and driven components; the porous layer can be force-lockingly connected with the driving component, driven component or friction lining.

If the bypass clutch or the regulating means comprises a friction lamella which is disposed between the driving and driven components and is movable axially of the torque converter housing, the housing can be provided with an internal abutment (such as a washer-like structure) which limits the movability of the lamella in one direction and the bypass clutch or the regulating means can be provided with a piston which is movable axially of the housing, which forms part of the driven component and which limits the movability of the lamella in the other direction (as seen axially of the housing of the torque converter). The internal abutment can be axially movably mounted on a portion of the torque converter housing which surrounds the bypass clutch.

At least one of the driving and driven components can consist, at least in part, of a porous material which is employed to establish a plurality of paths for the flow of fluid between the plenum chambers in the engaged condition of the bypass clutch. The other component of such clutch can include a friction lining which abuts the one component in the partially or fully engaged condition of the bypass clutch. For example, a porous member can be riveted to the driving or to the driven component to provide a plurality of paths for the flow of fluid between the plenum chambers in the engaged condition of the clutch.

The regulating means can comprise at least one array of recesses provided in the driving and/or driven component and communicating with one of the plenum chambers, and ports provided in the recessed component and communicating (a) with the recesses and (b) with the other plenum chamber. The recessed component can include at least one friction lining which confronts the other component and is actually provided with the recesses; such recessed component can further comprise a piston which carries the friction lining and is provided with the aforementioned ports.

The recesses can be provided with open ends which communicate with the one plenum chamber, and the ports are or can be located radially outwardly of the open ends of the recesses (it is assumed here that the recesses extend radially outwardly from their respective open ends). The component which is provided with recesses is or can be the driving component and can include a friction lining which is actually provided with recesses; the driven component of such bypass clutch can include a piston actually provided with the ports which are distributed in such a way that they repeatedly communicate with the recesses during operation of the clutch with slip. The arrangement can be such that the ports repeatedly communicate with the recesses only when the clutch is operated with slip. The number of the ports can be different from the number of the recesses, and the regulating means can further comprise open-and-shut valves for the ports.

In accordance with a presently preferred embodiment, each valve comprises a tongue or flap which is movably carried by the at least one component. It is preferred to employ resilient tongues which tend to assume positions in which they permit hydraulic fluid to flow between the respective recesses and the other plenum chamber. The tongues can be arranged to seal the respective recesses from the other chamber in response to changes of fluid pressure in the other plenum chamber relative to the fluid pressure in the one chamber. The arrangement is preferably such that the valves open in response to rotation of the driving and driven components relative to each other The recesses of the at least one array have open ends which communicate with the one chamber and the regulating means can further comprise an annular second array of recesses which are provided in the at least one component to alternate with the recesses of the at least one array. The recesses of the second array have open ends communicating with the other chamber and such recesses repeatedly communicate with the ports while the bypass clutch operates with slip.

The regulating means can include at least one annular array of recesses which are provided in one of the driving and driven components and communicate with one of the plenum chambers, an annular array of ports provided in the other component and repeatedly communicating with successive recesses of the at least one array during operation of the bypass clutch with slip, and bellows which are borne by the other component and each of which communicates with one of the ports. The bellows are contacted by fluid in the other plenum chamber and are deformable in response to the establishment of a sufficient differential between the pressures of fluid bodies in the two plenum chambers. The bellows are or can be resilient and are arranged to receive fluid from the other plenum chamber when the pressures of fluid in the two plenum chambers differ to a predetermined extent. One of the driving and driven components, preferably only the other component, can be provided with a friction lining. The preferably elastic bellows can consist, at least in part, of thin sheet metal or rubber, and the fluid receiving capacities of such bellows are preferably limited. It is often advisable to arrange a relatively large number of bellows in a circle; such circle can comprise between about 3 and 36 bellows, preferably between about 9 and 24 bellows. The other component of the bypass clutch can comprise a piston and the bellows can include sheet metal blanks which are at least substantially sealingly affixed to the piston. It is also possible to employ a plurality of bellows all of which form part of a single piece of sheet-like material affixed to the other component of the bypass clutch. The bellows can be designed in such a way that they normally offer resistance to the inflow of fluid; the arrangement is or can be such that the bellows are inflatable against the resistance of fluid in the other plenum chamber. At least one of such bellows can include a sheet metal member which is affixed to the other component and is arranged to move by snap action between first and second positions in which the fluid receiving capacity of the at least one bellows respectively assumes a relatively large and a relatively small value. The regulating means employing such bellows can further comprise at least one stop which is arranged to limit the extent of movement of the sheet metal member by snap action to at least one of the first and second positions. Such at least one stop can be arranged to prevent a movement of the sheet metal member beyond the second position. The other component of the bypass clutch in a torque converter having regulating means operating with bellows can include a piston and the at least one stop can form part of such piston.

Each of the aforementioned ports is preferably arranged to admit fluid into and to provide a path for expulsion of fluid from a discrete bellows; the ports can be arranged to establish communication between the interiors of the respective bellows and the other plenum chamber; the one component of the bypass clutch can include a friction lining and the recesses can be provided in the friction lining. The recesses can be provided with enlarged portions communicating with successive ports of the annular array of ports when the clutch is operated with slip. For example, the recesses having enlarged portions can constitute substantially T-shaped recesses.

In accordance with a further embodiment, the regulating means can comprise an annular undulate surface which is provided on one of the driving and driven components, and a sealing member having a second surface adjacent the undulate surface and provided on the other component. These surfaces establish a plurality of paths for the flow of fluid only when the bypass clutch is operated with slip. The undulate surface can be provided on a deformable ring-shaped member of a piston forming part of the one component. The ring-shaped member can be provided on a radially outermost portion of the piston, i.e., on a portion which is remote from the axis of the torque converter housing. The second surface can be provided on such housing.

As already mentioned before, the regulating means can include means for pumping hydraulic fluid between the plenum chambers.

The driven component of the bypass clutch can include a first piston and the regulating means can comprise an auxiliary (second) piston defining with the first piston a third chamber which communicates with the plenum chambers by way of passages provided in at least one of the driving and driven components.

The regulating means can comprise a cooling unit which is provided at that side of one of the driving and driven components which faces away from the other component; the cooling unit can employ a third chamber for a supply of coolant. The two components can frictionally engage each other at a first radial distance from the axis of the torque converter housing in the at least partly engaged condition of the clutch, and the third chamber can be dimensioned and configurated in such a way that it includes a first portion at the first radial distance from the axis and a second portion at a lesser second radial distance from the axis. Such third chamber can be outwardly adjacent the housing of the torque converter; alternatively, the driven component can include a piston located in the housing of the torque converter, and the third chamber is adjacent that side of such piston which faces away from the driving component.

It is also possible to employ a cooling unit which comprises a substantially cup-shaped enclosure for the third chamber; such enclosure is sealingly affixed to one of the driving and driven components. The enclosure can be secured to the one component by at least one of the undertakings including welding, caulking and snap action.

The coolant can be selected from the group consisting of water and a liquefied gaseous fluid. Such coolant can be arranged to exchange heat with at least one of the driving and driven components in accordance with evaporation enthalpy. If the coolant is a liquid at lower temperature, it changes its aggregate state by convection to a gaseous state in response to heating as a result of contact with at least one of the driving and driven components. The change of aggregate state can be effected under the action of centrifugal force when the driving and driven components rotate and the clutch operates with slip.

In accordance with a presently preferred embodiment, the cooling unit is constructed in the following way: The driving and driven components of the bypass clutch frictionally engage each other at a first radial distance from the axis of the torque converter housing in at least partly engaged condition of the clutch. The third chamber (i.e., the chamber for the supply of coolant) includes a first portion at the first radial distance from the axis and a second portion at a lesser second radial distance from the axis. The coolant is a liquid which at least partially fills the first portion of the third chamber and assumes a gaseous aggregate sate in the second portion of the third chamber with a tendency to become a liquid and to flow back to the first portion of the third chamber under the action of centrifugal force in response to cooling of the gaseous phase in the second portion of the third chamber.

In addition to or in lieu of the already described undertakings involving the enhancement of exchange of heat between the fluid filling the plenum chambers and the fluid flowing between such chambers on the one hand, and the adjacent structural elements of the torque converter and its bypass clutch on the other hand, it is possible to simply agitate the fluid within the housing of the torque converter. To this end, the regulating means can comprise at least one blade or vane (hereinafter called blade) which is provided on the turbine and is preferably adjacent one of the driving and driven components of the bypass clutch (particularly the driven component) to agitate some of the fluid in the housing of the torque converter. The at least one blade is or can be affixed (such as welded, glued or riveted) to or can be of one piece with the turbine. It is also possible to make the at least one blade of one piece with one of the customary vanes provided at that side of the turbine which confronts the vanes of the pump forming part of the torque converter. For example, each vane of the turbine can be of one piece with one of the blades. If the bypass clutch comprises one or more friction linings, the blade or blades of the turbine can be adjacent the single friction lining or one of several friction linings.

It is often advisable to provide the turbine with an anular array of preferably equidistant blades. Such array of blades can be mounted on or can form part of an annular carrier which is affixed to the turbine.

If the regulating means of the improved torque converter comprises at least one pumping device, such device can be arranged to convey fluid from one of the plenum chambers into the other plenum chamber and/or to convey fresh fluid from a source into one or both plenum chambers and/or to enhance the flow of fluid from one or both plenum chambers when the bypass clutch is operated with slip. In accordance with one presently preferred embodiment, the at least one pumping device comprises a pump body having first and second openings which respectively communicate with a source of fresh or recycled fluid and with one of the plenum chambers, and a spherical or otherwise configurated pumping element which is reciprocable in the pump body to effect a transfer of fluid from the source to the one chamber. The at least one pumping device can be installed in or on a hub which surrounds the output element (such as the input shaft of the change-speed transmission) of the torque converter. The pumping element seals one of the two openings in the pump body when the bypass crutch is operated without slip. At least one of the driving and driven components can include a friction lining which is remote from the axis of the torque converter housing, and the at least one pumping device can be installed in the housing in such a way hat it is adjacent the friction lining. Furthermore, the at least one pumping device can be arranged to communicate with at least one of the plenum chambers by way of recesses provided in one of the driving and driven components. These recesses can have open ends which communicate with the one plenum chamber of the torque converter, and such regulating means can include additional recesses which are sealed from the one plenum chamber. The recesses can be provided in the one or in the only friction lining of the bypass clutch.

The regulating means can comprise an annular array of pumping devices which are or which can be equidistant from each other and which are or can be identical.

Another feature of the present invention resides in the provision of a hydrokinetic torque converter which comprises a housing rotatable about a predetermined axis, a pump which is rotatable by the housing about such axis, a turbine which is rotatable in the housing about the latter's axis by as well as relative to the pump, means for rotating the housing, an output element which is rotatable about the axis of the housing and is arranged to receive torque from the turbine, and a fluid-operated bypass clutch which is arranged to transmit variable torque between the housing and the output element independently of the turbine. The clutch includes a first part which is rotatable with the housing, a second part which is rotatable with the output element, and friction generating means operable to transmit torque between the first and second parts with and without slip with attendant generation of friction heat during operation with slip. The torque converter further comprises first and second plenum chambers which contain bodies of hydraulic fluid at variable pressure with the provision for fluid flow between the plenum chambers past the friction generating means, and means for regulating the fluid flow in dependency upon the magnitude of torque being transmitted by the clutch.

The just discussed torque converter can further comprise torsional vibration damping means operating between the first part of the bypass clutch and at least one of the second part of the friction clutch, the turbine and the output element. Such torque converter can further comprise a stator which is provided in the housing intermediate the Dump and the turbine.

A further feature of our invention resides in the provision of a hydrokinetic torque converter which comprises a housing rotatable about a predetermined axis, a pump rotatable by the housing about such axis, a turbine rotatable in the housing by and relative to the pump, means for rotating the housing, an output element which is rotatable about the axis of the torque converter housing and is arranged to receive torque from the turbine, and a fluid-operated bypass clutch which is arranged to transmit variable torque between the housing and the output element. The pump comprises a driving component rotatable with the housing and a driven component including a piston rotatable with the output element and movable in the housing axially into and from frictional engagement—with and without slip—with the driving component, and the torque converter further comprises means for moving the piston including first and second plenum chambers in the housing, means for supplying to the plenum chambers hydraulic fluid at variable pressure with the provision for fluid flow between the chambers through the clutch, and adjustable means for regulating the fluid flow between the chambers in dependency upon the magnitude of torque being transmitted by the clutch. Such adjustable regulating means is or can be adjacent at least one of the driving and driven components of the bypass clutch.

Still another feature of the present invention resides in the provision of a method of cooling an engageable and disengageable bypass clutch which is installed in the rotary housing of a hydrokinetic torque converter and has coaxial rotary driving and driven components which frictionally engage each other when the clutch is at least partly engaged. The partial engagement involves (i.e., results in) a slip of the components of the bypass clutch relative to each other. The method comprises the steps of providing in the housing first and second plenum chambers and maintaining in the plenum chambers bodies of hydraulic fluid arranged to at least partly engage the clutch in response to the establishment of adequate pressure differential between the two bodies of fluid, establishing at least one path for the flow of fluid between the plenum chambers by way of the clutch, at least in the part y engaged condition of the clutch, and regulating the flow of fluid along the at least one path in dependency upon (i.e., as a function of) the extent of slip between the driving and driven components.

The regulating step can include increasing the rate of fluid flow along the at least one path when the clutch operates with slip and reducing such rate when the clutch operates without slip.

The regulating step can also include interrupting the flow of fluid along the at least one path when the clutch is operated without slip, i.e., when the generation of friction heat is reduced to zero.

The regulating step can include installing an adjustable valve in the at least one path.

The step of establishing the aforementioned at least one path can include providing the driving and driven components of the clutch with pluralities of first and second passages (such as channels, recesses, grooves or the like) for the flow of fluid to and from the first and second plenum chambers, and the regulating step of such method can include establishing communication between the first and second passages at a frequency which increases in response to increasing slip of the driving and driven components of the bypass clutch relative to each other.

The regulating step can include pumping the fluid along the at least one path at a rate which increases in response to increasing slip of the driving and driven components of the bypass clutch relative to each other.

Still further, the regulating step can include continuously contacting at least one of the driving and driven components of the bypass clutch with a confined supply of coolant which changes its aggregate state in response to changes of temperature of the at least one component of the bypass clutch.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved hydrokinetic torque converter itself, however, both as to its construction and modes of assembling, installing and operating the same, together with numerous additional important and advantageous features and attributes thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawings.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring first toFIG. 1, there is shown a hydrokinetic torque converter1having a housing4arotatable about a predetermined axis (see the axis X—X shown inFIG. 2) by a prime mover2. The latter can constitute an internal combustion engine of the type employed in motor vehicles, an electric motor, a gas turbine or a hybrid drive means. The output shaft3of the prime mover2can be fixedly of force-lockingly connected with a portion4of the housing4ain any one of a number of different ways. The portion4which is shown inFIG. 1is a flexible annular metallic washer-like wall which drives the other part or parts of the housing4aand also a rotary pump5of the torque converter1. A turbine6of the torque converter is coaxial with and is normally rotated or can be rotated by the pump5by way of a body of hydraulic fluid in the housing4a.FIG. 1further shows a stator10which constitutes an optional part of the torque converter1.

The output element7of the torque converter1shown inFIG. 1is the input shaft of a change-speed transmission8which can transmit torque to one or more wheels9of a motor vehicle by way of a differential and one or more wheel axles in a manner well known in the art and not forming part of the present invention. Reference may be had, for example, to commonly owned U.S. Pat. No. 5,501,309 granted Mar. 26, 1996 to Walth et al. for “HYDROKINETIC TORQUE CONVERTER WITH LOCKUP CLUTCH”, U.S. Pat. No. 5,674,155 granted Oct. 7, 1997 to Otto et al. for “METHOD OF AND APPARATUS FOR TRANSMITTING TORQUE IN THE POWER TRAINS OF MOTOR VEHICLES”, U.S. Pat. No. 5,738,198 granted Apr. 14, 1998 to Walth et al. for “FRICTION ELEMENT FOR USE IN CLUTCHES”, and U.S. Pat. No. 5,782,327 granted Jul. 21, 1998 to Otto et al. for “HYDROKINETIC TORQUE CONVERTER AND LOCKUP CLUTCH THEREFOR”.

The transmission8can constitute a manual or automatic transmission or a continuously variable transmission (CVT) with an endless link chain and adjustable pulleys.

Though the stator10is optional, it is often desirable and necessary, e.g., to vary the torque within certain RPM ranges. In the embodiment ofFIG. 1, the stator is mounted on a fixed part12(such as an axially expanded tubular part of the housing or case of the transmission8) by way of a freewheel11.

A so-called bypass or lockup clutch13is provided to bypass the pump5and to establish a driving connection between the output element3of the prime mover2(and more specifically the wall4) and the turbine6. The illustrated clutch13comprises an axially reciprocable member16here shown as a piston which can be moved toward and away from the wall4. The wall4carries an annular driving component14, and the piston16carries an annular driven component15of an adjustable friction generating device21of the clutch13. At least one of the components14,15can be provided with a friction lining of the type customarily employed in the friction clutches of the power trains in motor vehicles; such friction lining can be moved into sliding or non-sliding frictional engagement with a friction lining or a metallic cr other suitable member on the other of the components14and15. Such member can be provided with a smooth, roughened and/or otherwise treated surface which can engage the friction lining when the device21is to transmit torque between the wall4and the piston16; this piston can transmit torque directly to the input shaft7of the transmission8or indirectly by way of the turbine6. That torque which is actually transmitted by the clutch13can be a mere fraction of the torque which the wall4can transmit to the piston16when the frictional engagement between the components14,15is at least substantially free of slip.

The piston16is mounted on a hub (corresponding to the hub106ashown inFIG. 2) which is non-rotatably mounted on the shaft7and can also support the turbine6. The connection between the piston16and the shaft7includes a first torsional vibration damper23, and the connection between the turbine6and the shaft7includes a second torsional vibration damper24.

The magnitude of torque which is being or which is to be transmitted by the bypass clutch13can be regulated by selecting the pressures of bodies of hydraulic fluid confined in or flowing through two chambers17,18defined by the housing4aof the torque converter1. The pressure of fluid entering the chamber18by way of a conduit19ais determined by a fluid conveying pump19having an intake arranged to draw fluid (such as oil or transmission fluid) from a sump20aor another suitable source. A pressure limiting relief valve19cis or can be installed in the conduit19a. A further conduit19bserves to convey fluid from the chamber17into a reservoir20, e.g., a sump20.

When the fluid pressure in the chamber18exceeds that in the chamber17, the piston16is moved or urged to the left, as viewed inFIG. 1, so that the component15bears upon the component14with a force which is proportional to the pressure differential and the wall4drives the piston16(and hence the turbine6and the input shaft7) with or without slip.

When the pressure differential between the bodies of fluid filling the chambers17,18decreases to a predetermined value, one or more springs or other biasing means (not shown) are free to disengage the component15from the component14, i.e., to disengage the bypass clutch13. It is also possible to employ a throttle19dor any other suitable flow restrictor (shown schematically inFIG. 1) in the conduit19bto predetermine the circumstances under which the bypass clutch13is permitted or caused to open so that, from there on, the input shaft7can be driven by the wall4through the medium of the pump5, the body of fluid which orbits the vanes of the turbine6in response to orbiting of vanes forming part of the pump5, and the torsional vibration damper24.

The sumps20,20acan form parts of a single sump, they can constitute two discrete identical or different sumps, or they can be connected to each other by one or more conduits20bwhich preferably contain one or more fluid cooling units20cserving to ensure that the inlet of the pump19receives a flow of fluid having a temperature not exceeding a preselected maximum permissible value.

The structure which is shown schematically inFIG. 1can be modified in a number of ways without departing from the spirit of this invention. For example, the pump19can be installed in the conduit19bto draw fluid from the sump20and to convey such fluid into the chamber17whence the fluid flows (when necessary or desired) into the chamber18, conduit19aand sump20a.

The chambers17,18are sealed from each other in such a way that, when desired or necessary, they can communicate only by way of the bypass clutch13(and more specifically by way of the friction generating device21including the components14and15).

In accordance with a feature of the present invention, the friction generating device21is constructed and assembled and operates in such a way that the components14,15can regulate the flow of fluid between the chambers17,18, i.e., that there exists a fluid flow regulating or limiting arrangement22which conforms the rate of fluid flow to the momentary requirements, i.e., to the desired or required extent of frictional engagement between the components14and15. The arrangement22conforms the extent of fluid flow into and from the chambers17,18to the required or desired or necessary extent of frictional engagement between the components14and15.

The requirements can be such that there normally exists an at least small (such as negligible) rate of flow of pressurized fluid involving a negligible angular displacement of the driving means (including the wall4) and the driven means (including the input shaft7) relative to each other, and/or a rate of flow which varies in dependency upon a slip parameter; the operation of the flow regulating arrangement22can be controlled in dependency upon (a) the RPMs of the wall4and shaft7, (b) the differential between the pressures of fluid bodies in the chambers17,18, (c) the viscosity of the fluid, and/or (d) an evaluation of the just enumerated parameters (a) to (c). It is important and highly desirable, as well as practical for normal use of the torque converter1, that the operation of the regulating arrangemet22take place automatically within the torque converter. The means for effecting such automatic operation of the arrangement22can include or resemble the driving and driven components14,15and/or means for metering the flow of fluid through these components.

The slip-dependent regulation or control of the flow of hydraulic fluid exhibits the important advantage that, when the rate of fluid flow increases in response to an increasing difference between the RPMs of the wall4and the shaft7, the components14,15(which generate a larger quantity of heat if the aforementioned difference between the RPMs increases while the components are in frictional engagement with each other) undergo a more pronounced cooling action because the rate of fluid flow from one of the chambers17,18, through the device21including the components14,15, and into the other chamber is more pronounced. Otherwise stated, the temperature of fluid flowing between the chambers17,18via flow regulating arrangement22is lower if the speed of fluid flow is higher.

A less pronounced heating of the components14,15is desirable and advantageous because it involves a lesser wear upon the device21and also because the composition of the fluid remains unchanged (i.e., acceptable) for a longer interval or period of time. Furthermore, a damming of the fluid by the regulating arrangement22in response to a reduced slip exhibits the advantage that the operation of the pump19is more economical because the output of the pump must be increased due to higher losses resulting from the flow of fluid into the lower-pressure chamber (i.e., into the chamber17within the housing4ashown inFIG. 1) when the bypass clutch13is engaged, namely when the pump output is higher because the pressure of fluid in the chamber18(this entails an engagement of the bypass clutch) is raised by the pump.

The dampers23,24counteract torsional vibrations; each of these dampers can be a single-stage or a multistage damper. If the damper23and/or24is a multistage damper, the individual stages can be set up to operate in series or in parallel. The individual stops of a multistage damper can serve to protect the elastic means between the input and output parts of the damper23and/or24. In addition, one can provide delayed or non-delayed friction generating devices each of which is superimposed upon a single stage or each of which acts upon several stages.

The first damper23is installed in the power flow between the bypass clutch13and the input shaft7of the transmission8, i.e., it bypasses the turbine6. The input of this damper is the piston16, and its output is the aforementioned hub which is non-rotatably but axially movably mounted on the shaft7(or which non-rotatably but axially movably supports the piston6).

The damper24is installed between the turbine6and the shaft7. For example, the turbine6can be mounted (with limited freedom of angular movement) on a hub which is borne by the shaft7; the output of the damper24is then non-rotatably mounted on such hub. The range of the damper24(which is mounted in the just described manner) is determined by the extent to which the turbine6can turn relative to the hub on the shaft7.

It is also possible to replace the dampers23,24with a single damper. For example, the input of such single damper receives torque from the piston16and/or from the turbine6, and its output is operatively connected with the input shaft7or with the hub which is non-rotatably mounted on the shaft7.

The flow regulating or limiting arrangement22(or an equivalent thereof) does not constitute the only novel feature of the improved torque converter1. Thus, this torque converter can be provided with auxiliary masses25a,25b,25c, and25dwhich serve to meet (satisfy) specific requirements regarding the damping and/or absorption (elimination) of torsional vibrations. For example, one can rely on the so-called dual mass flywheel effect by installing the auxiliary masses25b,25aupstream and downstream of the torsional vibration damper23and/or by instaling the auxiliary masses25c,25dup-stream and downstream of the damper24. The auxiliary masses (or one or more such masses) need not constitute separately produced parts, i.e., at least one thereof can constitute a standard component or a group of two or more standard components of a torque converter wherein, in addition to their well known functions, they also serve as auxiliary masses associated with the torque converter23or24. By way of example only, one of the auxiliary masses25ato25dcan constitute or form part of the turbine6, of the housing4a, of one or more portions of the housing4aand/or others, as long as the moment of inertia and/or the bulk or weight of such multiple-purpose auxiliary mass is satisfactory for utilization in conjunction with the damper23or24.

Still further, it is within the purview of the invention to omit the auxiliary mass25aand/or25d, i.e., to utilize only the auxiliary mass(es)25b, and/or25cwhich is or which are installed in the power flow(s) upstream of the respective damper(s)23and/or24. The single auxiliary mass (25b, or25b) is preferably that mass which is more distant from the axis of the shaft7, i.e., which is located radially outwardly of the respective torsional vibration damper23and/or24. Stated otherwise, the single auxiliary mass (25b, and/or25c) is installed in the power flow upstream of the respective damper (23and/or24); this enhances the moment of inertia.

It is advisable (and actually highly desirable and advantageous) to install the auxiliary mass(es) in such space or spaces which is or which are available in a hydrokinetic torque consorter; such spaces include, for example, that or those at the radially outer and/or inner torus of the turbine, and in a corner or region of the housing4aradially outwardly of the piston16.

The auxiliary mass25aand/or25dcan be directly or indirectly mounted on the input(s) of the respective damper(s)23and/or24, and the mass25band/or25ccan be directly or indirectly mounted on the input(s) of the respective damper23and/or24. For example, and as actually shown inFIG. 1, the auxiliary mass25bis provided on or forms part of the piston16upstream of the damper23(as seen in the direction of power flow from the bypass clutch13(i.e., from the wall4) to the input shaft7. Furthermore, and as also shown inFIG. 1, the auxiliary mass25cis mounted on or forms part of the turbine6, i.e., such mass is located in the flow of power toward the input of the damper24.

FIG. 2is an axial sectional view of a torque converter101which is driven by the output shaft (such as a crankshaft)103of a prime mover, e,g, the engine of a motor vehicle. The shaft103has an axially extending centering projection103aengaging a flexible torque transmitting member126which is or which can be made of a metallic sheet material and can be said to form a detachable part of a housing104aof the torque converter101. The means for fixedly but separably securing the radially innermost annular portion of the member126to the shaft103includes an annulus of threaded fasteners103b. Other types of fasteners can be utilized with equal advantage.

The annular radially outermost portion of the member126is non-rotatably connected with an annular starter gear126ain such a way that the latter cannot move axially of the housing104a. The rotation-preventing connection between the starter gear126aand the housing104acan include mating gear teeth, a caulking, a welded joint or the like. It is also possible to employ a starter gear which is shrunk onto the member126or onto another part of the housing104a.

The member126and/or another part of the housing104acan also serve to carry a set of markers or other suitable indicia which rotate with the housing and form Apart of a means for regulating the operation of the prime mover. An annulus of receptacles104bis separably connected with the member126between the annulus of fasteners103band the starter gear126a; the connection can include threaded fasteners126b, a self-locking device, a bayonet mount (not shown) or the like.

The receptacles104bcan constitute circular or arcuate bodies and are affixed to the radially outermost portions of the housing104a, e.g., by welding, by rivets or the like; for example, the housing104aand/or the member126can be provided with projections which are riveted to the receptacles104b.

The housing104acan be axially offset at the receptacles104bso that the receptacles are axially spaced apart and provided room for the fastening of the member126on the crankshaft103. To this end, the radially outer portion of the member126(namely the portion adjacent the receptacles104b) can be configurated to extend axially of the torque converter101and away from the crankshaft103.

The receptacles104bare provided with circumferentially spaced-apart axially extending lobes104cwhich are affixed to the housing104a. In addition to or in lieu of such lobes104c, the connection between the receptacles104band the housing104acan be constructed and designed in such a way that, in accordance with a desirable aspect of the invention, it need not employ discrete fasteners (such as the lobes104c); instead, the housing104acan be provided with separately produced embossed portions104dwhich together constitute a cam ring affixed to the housing and such cam ring can be provided with teeth, profiled portions, Hirth gears or serrations and/or pins. This renders it possible to dispense with the fastener means126b. Moreover, such design (which can be employed with advantage in all or nearly al types of torque converters) renders it possible to simplify the mounting of the torque converter101on the flexible torque transmitting member126during the final stage of assembly of the power train of a motor vehicle.

The member126can be mounted on the housing104ain such a way that it stores energy and the axial torque of the torque converter is preferably applied in a direction toward the transmission case (not shown) or toward the transmission input shaft107by way of an abutment which is or which can be mounted in a bearing. The form-locking connection between the member126and the housing104acan be designed in such a way that it automatically orients itself during the assembly while the connection is being established.

It is clear that the lobes104ccan be made of one piece with the member126, e.g., by folding partially separated lugs of the member126over themselves. In addition, the fasteners126band/or the receptacles104band/or the starter gear126acan serve as auxiliary masses which positively influence the torsional vibration behavior of the power train by resorting to the so-called dual masses effect.

It is also possible to omit the member126and to establish a direct form-locking connection between the housing104aand the crankshaft103. For example, the crankshaft103can be made of one piece with or can carry a hardened extension having a diameter less than that of the member126and being located at the same radial distance from the axis X—X as the fasteners103b. Such hardened extension can be affixed direztly to a complementary portion of the housing104a(e.g., to a stamped portion of the housing) to thus establish a form-locking connection. The form-locking connection can be configurated in such a way that it can simultaneously compensate for an offset between the crankshaft103and the transmission input shaft107. The housing104acan be axially flexible between its periphery and the form-locking connection, e.g., by employing a sheet metal having varying thicknesss in the region of such connection.

An important advantage of the form-locking connection is to serve as a noise reducing or noise damping arrangement, and such noise-reducing effect can be enhanced by providing the relevant parts with suitable coatings made of one or more metals, alloys, plastics or ceramics. Still further, it is possible to employ between the parts of the form-locking connection one or more energy storing elements in the form of springs, inserts made of rubber and the like.

The housing104aand the pump105of the torque converter101are form-lockingly connected to each other, as at105a, to constitute the input element of the torque converter101. As can be seen inFIG. 2, the form-locking connection105acan comprise several equidistant parts (FIG. 2shows three parts) disposed at the periphery of the pump105and each including a male part provided on the pump105and extending into a complementary female part of the housing104a.

That end portion (104e) of the housing104awhich is remote from the member126(as seen in the direction of the axis X—X ) constitutes a sleeve surrounding an axially projecting tubular extension108aof the transmission. The extension108ais sealingly surrounded by the sleeve104eand is also surrounded by the freewheel111for the stator110.

The pump105and the turbine106are provided with customary vanes or blades (not shown) which cooperate to ensure that the body of hydraulic fluid in the housing104arotates the turbine106in response to rotation of the pump105by the crankshaft103. The (optional) stator110is disposed between the pump105and the turbine106(as seen in the direction of the axis X—X) and is radially outwardly adjacent the freewheel111.

The turbine106is non-rotatably connected with a hub106a, e.g., by an annular array of rivets, and this hub is non-rotatably but axially movably affixed to the transmission input shaft107. An annular seal107ais interposed between the shaft107and the hub106a, and the latter abuts a thrust bearing110bwhich, in turn, abuts the stator110.

The hub106ahas an axial extension surrounded by the radially innermost portion of the axially movable piston116which forms part of the torque converter bypass clutch113. An annular seal106cis inserted between the piston116and the hub106a; the latter has a disc-shaped extension106bwhich extends radially outwardly and is riveted to the turbine106. The extension106bfurther serves as a stop which determines the extent of rightward axial movement of the piston116of the bypass clutch113.

The piston116cooperates with the radial wall104of the housing104ato transmit torque from the crankshaft103(via wall104) directly to the hub106a(i.e., to the transmission input shaft107), namely to bypass the pump105and the turbine106, when the bypass clutch113is engaged (with or without slip). More specifically, the piston116carries a friction lining115(or has a properly finished friction surface) which engages a complementary friction lining or friction surface114of the wall104when the clutch113is at least partly engaged. If used, the friction lining or linings (such as115and/or114) can be glued, riveted and/or otherwise affixed to the piston116and/or to the wall104. Certain presently preferred embodiments of the fluid flow regulating or limiting arrangement122of the bypass clutch113or an analogous bypass or lockup clutch will be described in greater detail with reference toFIGS. 9to13.

The piston116divides a part of the interior of the housing104ainto plenum chambers117,118which are sealed from each other (when the bypass clutch113is engaged, either entirely or with slip) to the extent determined by the flow regulating arrangement122. Hydraulic fluid is admitted into the plenum chamber118by way of a conduit119awhich is defined by an annular clearance between the sleeves104eand108a. A conduit107bwhich serves to permit hydraulic fluid to issue from the chamber117is a bore in the transmission input shaft107which discharges into an annular passage119bof the shaft107. The sleeve108aand the shaft107are sealingly engaged by a friction bearing108bwhich serves as a means for sealing the passage119bfrom the surrounding atmosphere; in addition, the combined bearing element and seal108bprevents the flow of hydraulic fluid from the conduit119ainto the chamber118.

When the fluid pressure in the plenum chamber118rises above that in the plenum chamber117, the piston116is moved axially and the friction generating device121including the frictionally engageable members114,115having friction surfaces114′,115′ establishes a frictional engagement to transmit torque from the wall104of the housing104ato the piston116.

If the fluid pressure in the chamber117thereupon rises above that in the chamber118, the surfaces114′,115′ become separated from each other so that the bypass clutch113ceases to transmit torque; the transmission of torque from the crankshaft103to the transmission input shaft107then takes place by way of the housing104a, pump105, fluid between the pump105and the turbine106, and the turbine hub106a.

When the bypass clutch113is fully or partly, engaged (i.e., when it operates without slip or with some slip), the piston116continues to transmit at least some torque to the hub106a. Vibrations of such torque can be damped by a damper123which operates between the piston116and the hub106a. The damper123includes an input member123awhich is non-rotatably affixed to the piston116, and an output member123bnon-rotatably affixed to the hub106a. The input member123acomprises two discs which flank the disc-shaped output member123b. The discs of the input member123aare shown as being riveted to the piston116. The disc of the output member123bis non-rotatably but axially movably mounted on the hub106a; to this end, the member123bhas one or more axially parallel internal teeth mating with external teeth of the hub106a. One or more energy storing elements123c(one shownFIG. 2) yieldably oppose angular movements of the input and output members123a,123brelative to each other; to this end, the energy storing element(s)123creacts or react against one or more abutments provided on the input member123aand bear upon one or more abutments on the output member123b. Reference may be had, for example, to commonly owned U.S. Pat. No. 5,860,863 granted Jan. 19, 1999 to Friedmann et al. for “APPARATUS FOR DAMPING VIBRATIONS”. The torsional vibration damper123is further provided with suitable means for limiting the extent of angular movability of the input and output members123a,123brelative to each other; such limiting means can provide first and second stops which are respectively mounted on or made of one piece with the members123a,123b.

It is further possible and often advisable to provide a slip clutch123dwhich operates between the input and output members123a,123band permits such members to turn relative to each other only when the torque being transmitted by the input member123arises to a predetermined value. The illustrated slip clutch123dacts axially between the members123a,123band can comprise one or more energy storing devices.

The wall104of the housing104aof the torque converter101carries a centering stub104fwhich extends into a recess103cof the crankshaft103. The stub104fis welded to the wall104and is centered thereon by a projection104gwhich is a stamped out part of the wall104; however, it is also possible to make the stub104fof one piece with the wall104. The just described combined centering and torque transmitting means can serve to compensate for eventual angular and/or axial misalignments of the shaft103and the transmission input shaft107relative to each other.

The aforementioned axial projections103aof the crankshaft103are preferably profiled and dimensioned in such a way that they facilitate the insertion of the stud104finto the opening or recess103cduring mounting of the torque converter101on the output shaft103of the prime mover.

The projection104gcan further serve to facilitate accurate mounting (e.g., welding) of the stub104fon the wal104, particularly to accurately center the stud. The latter need not be a solid body but can be replaced with a tube or sleeve. Moreover, welding of the stub104fto the wall104(as actually shown inFIG. 2) is optional, i.e., it can be replaced by riveting or the like.

It can be said that the stub104fforms part of a pilot bearing which ensures simple, predictable and accurate mounting of the torque converter101on the output shaft103of the prime mover; such pilot bearing can be utilized with advantage in many other types of torque converters, clutches and the like. Furthermore, a similar or analogous or at least substantially identical pilot bearing can be utilized for accurate and reliable mounting of the transmission input shaft107in the torque converter101and/or in the crankshaft103. For example, the front end portion of the shaft107can be received in a sleeve-like central part of the housing104aof the torque converter101. The housing104acan be provided with a projection similar to or analogous to the projection104gand extending into a sleeve-like member which, in turn, receives the front end portion of the transmission input shaft107.

FIG. 3is an axial sectional view of a torque converter201which differs from the torque converter101ofFIG. 2primarily in the design of the bypass clutch or lockup clutch213. Thus, the radially outermost portion of the piston216of the clutch213is non-rotatably but axially movably secured to the radial wall204of the housing204a. A feature of the piston216(this feature can be embodied in the pistons of all or nearly all bypass clutches for torque converters) is that the radially outermost portion of the piston carries leaf springs216awhich are affixed to the housing204a. The leaf springs216aare spaced apart from each other (as seen in the circumferential direction of the piston216), one end portion of each leaf spring216ais affixed to the housing204a, and the other end portion of each such leaf spring is secured to the piston216of the bypass clutch213. The leaf springs216aare preferably riveted to the wall204; to this end, the wall204is provided with wart-like projections or protuberances204h. However, it is also possible to provide such or similar protuberances on the piston216.

The piston216is turnable on a hub206awhich surrounds the input shaft207of the transmission. A thrust bearing206dis interposed between the hub206aand the piston216; the illustrated bearing206dis a disc which is installed between a radially outwardly extending portion of the hub206aand the adjacent radially extending annular portion of the piston216.

When the bypass clutch213transmits torque (i.e., when the piston216rotates with the wall204with or without slip), the transmission input shaft207receives torque by way of the input member223aof the torsional vibration damper223which frictionally engages the output member223b. The latter is non-rotatably but axially movably mounted on the hub206a. The input member223ais riveted or otherwise affixed to a friction lamella223dthe radially outermost portion of which carries two friction linings having friction surfaces214a′,214b′ disposed radially inwardly of the projections204h. The linings having the surfaces214a′,214b′ are respectively adjacent to complementary friction linings having friction surfaces215a′,215b′.

The output member223bof the damper223is non-rotatably secured to the hub206aby annuli of mating teeth223e. The reliability of such connection is enhanced by providing the radially innermost portion of the output member223bwith a sleeve having axially parallel internal teeth in mesh with complementary teeth of the hub206a.

The torsional vibration damper223is similar to (or can be identical with) the damper123shown in FIG.2.

The bypass clutch213is designed to transmit torque by way of two friction linings, i.e., it provides a larger composite friction surface than the bypass clutch113of FIG.2. This can be of advantage in that the clutch213is capable of transmitting larger torques or of transmitting torques similar to those transmittable by the clutch113but with smaller friction surfaces; the latter feature is important when it is desirable or necessary to reduce the dimensions of the bypass clutch.

The fluid flow regulator222can be provided on (or can utilize) the friction linings having the surfaces214′,215′ and/or214b′,215b′. Presently preferred embodiments of such regulator are depicted inFIGS. 22to25.

FIG. 4shows certain features of a hydrokinetic torque converter301which is similar to the torque converter201of FIG.3. The prime mover and the transmission are not shown in FIG.4. The main difference between the torque converters201and301is that the latter employs a different bypass clutch313and a different torsional vibration damper323. In accordance with a feature of the invention which is embodied in the torque converter301, the torsional vibration damper323serves as a turbine damper as well as a means for damping vibrations being transmitted by the by pass clutch313. To this end, the input323aof the damper313is non-rotatably secured to the hub306afor the turbine306(this turbine is non-rotatably secured to the hub306a) as well as to the friction lamella (energy storing device)323d. Thus, the input323aof the damper323can receive torque from the turbine306as well as from the bypass clutch313.

The input323aof the damper323is form-lockingly secured to the hub306aby annuli of mating teeth323e, and the lamella323dis fixedly secured (e.g., by rivets) to the input323aradially outwardly of the energy storing elements323c. The hub306ais free to rotate relative to the input shaft (not shown) of the transmission; to this end, a discrete hub portion306fis provided with internal teeth307bmating with complementary teeth of the transmission input shaft. The hub306ais rotatable on the discrete hub portion306f, preferably in a friction bearing306gor on an anti-friction bearing (not shown) which surrounds the discrete hub portion306f.

The output323bof the damper323is fixedly secured to the discrete hub portion306f, e.g., by welding (such as laser, impulse or spot welding) or by caulking.

In order to facilitate broaching of the teeth307c, there is provided a discrete hub portion or member306hwhich can be received in the hub306a; e.g., the hub306acan be a press fit on the discrete member306hand is also mounted on the transmission input shaft. The latter can be provided with bearings rotatably mounting the member306h.

Damping of torsional vibrations is effected by causing the input323aof the damper323to turn relative to the output323band/or vice versa against the opposition of the energy storing element(s)323cas well as by overcoming (a) the resistance of a friction generating device323dbetween an axially effective energy storing element323b′ sand the input323aand/or (b) the friction torque of the friction bearing306gand/or preferably a slip clutch323b″. The lateral part323b′ is connected with the output323bby an annulus of rivets323f′ and cooperates with the output323bto confine the input323a; the radially outer portion of the input323ais secured to the lamella323dby rivets323f. The input323ais disposed between the output323band the lamella323d; these parts are provided with at least partially registering windows for the energy storing element(s)323ceach of which can include a single coil spring or two or more suitably interfitted coil springs. The output323band the lamella323dare or can be provided with suitable stops (not referenced) which determine the maximum compression of the coil spring(s) and the maximum extent of angular movability of the input323aand the output323bof the torsional vibration damper323relative to each other.

FIGS. 5 and 6respectively illustrate parts of torque converters401and401awhich are similar to but not identical with each other. All such parts of these torque converters which are plainly identical with each other are denoted by identical reference characters. The housing404aof each torque converter is driven by a prime mover (e.g., a combustion engine, not shown) and transmits torque to the respective pump405. The latter can drive the turbine406which cooperates with the pump to flank an optional stator410. The bypass clutch413can be engaged to transmit torque (with or without slip) from the washer-like annular part404iof the housing404adirectly to the hub406anon-rotatably surrounding the input shaft (not shown) of the change-speed transmission in the power train of a motor vehicle. An entraining disc416bis riveted to the piston416of the bypass clutch413and is axially movably but non-rotatably mounted on the hub406a. The disc416bis provided with an annulus of axially parallel internal teeth416cmating with complementary external teeth of the hub406a. The connection between the piston416and the disc416bcomprises an annular array of rivets416d(only one shown in each of FIGS.4and5).

In accordance with a modification, the disc416bin each of the torque converters401and401acan be replaced with a torsional vibration damper having an input and an output which can be turned relative to each other against the resistance of one or more coil springs or other suitable energy storing elements and/or against the opposition of one or more slip clutches. The input and/or the output of the device which replaces the disc416bof the torque converter401or401acan consist of several laminations, and the input can be further affixed to the turbine406(in addition to or instead of the connection to the disc416b) or to a part which shares the angular movements of the turbine.

Frictional engagement between the piston416(driven part) and the housing404a(driving part) can be established by the cooperating friction generating members414and415, and more specifically by the friction surfaces414′,415′ of the respective members. The driving member414receives torque from the aforementioned washer-like portion404iof the housing404a. The portion404ihas an annular part which is welded to the major part of the housing404a(namely to the part which carries or is of one piece with the pump405) and extends toward the prime mover (not shown), and a radially inwardly extending part which bears the member415. The member414is affixed to the radially outermost portion of the piston416. At least one of the members414,415can constitute or comprise at least one friction lining having the respective one of the friction surfaces414′,415′.

The reference character422denotes the fluid flow regulator which, in certain parts of this specification, is denoted by the character x22wherein x denotes the respective Figure of the drawings. This regulator corresponds to the previously described regulators (such as the regulator222shown in FIG.3). The washer-like member404ireplaces the walls4,104,204,304respectively shown inFIGS. 1,2,3and4.

The mode of operation of the torque converter401or401adeparts from that of the torque converters1,101,201and301in the following respects: In the torque converters401and401a, the pressurized fluid first flows into the plenum chamber417and the bypass clutch413is engaged when the pressure of fluid in the plenum chamber417exceeds that of fluid in the plenum chamber418, i.e., when the fluid begins to flow through the fluid flow regulator422. The bypass clutch413begins to transmit torque (with or without slip) when the pressure of fluid in the plenum chamber417reaches a level at which the bypass clutch413is at least partially engaged, i.e., when the piston416has moved axially toward the turbine406to a position in which the friction surfaces414′,415′ of the members414,415frictionally engage each other so that the washer-like member404iof the housing404a(which is driven by the prime mover) begins to transmit torque to the hub406a(and hence to the input shaft of the transmission) by way of the members414,415and the piston416.

The bypass clutch413remains at least partly engaged as long as the pressure of fluid in the chamber417at least slightly exceeds the pressure in the chamber418. It is often desirable to employ at least one energy storing device which automatically disengages the bypass clutch413as soon as the pressure of fluid in the chamber417begins to decrease; for example, such device can include one or more coil springs or other suitable springs which react against the hub406aand bear upon the piston416in a direction to move the piston axially to the left, as viewed inFIGS. 5 and 6. An advantage of such energy storing device or devices is that they reduce the likelihood of overheating of the fluid (such as oil or a transission fluid) which fills the chambers417,418and is likely to be heated during prolonged operation of the bypass clutch413with slip, i.e., during that stage of operation of the clutch413when the fluid is caused to flow gradually through the fluid flow regulator422from the chamber417into the chamber418. It is to be borne in mind that, in many instances, the fluid which fills the chambers417,418is circulated through the transmission and is likely to adversely affect the heat-sensitive part(s) of the transmission if it is permitted to reach an elevated temperature during flow through the regulator422at a rate which is customary during operation of the clutch413with slip. The situation is different if the fluid leaving the chamber418is caused to enter an evacuating conduit which causes the heated fluid to flow through one or more fluid cooling units (hea exchangers). Such cooling unit(s) can be dispensed with if the fluid leaving the chamber417is caused to mix with the body of cooler fluid in the chamber418prior to entering the transmission.

It is equally within the purview of the invention to convey the fluid through one or more cooling units prior to entry into the chamber417, i.e., to ensure that the parts414,415of the regulator422are invariably contacted by a relatively cool fluid which passes through the regulator422in small or relatively small quantities.

The torque converters401,401arespectively comprise fluid cooling units427a,427bof the type adapted to be utilized with advantage in the previously described torque converters1,101,201and301as well as in many other types of torque converters. The purpose of the cooling units is to agitate the fluid in the plenum chamber418adjacent the washer-like member404iof the housing404a. Such agitation takes place as soon as or as long as the parts406and404iturn relative to each other. Analogous results can be obtained by installing one or more cooling units in positions in which they become active as soon as the piston and the turbine begin to perform angular movements relative to one another.

The cooling unit427aofFIG. 5comprises an annular array of blades or vanes428awhich are mounted on or form part of the turbine406and are arranged to orbit adjacent the member404iof the housing404a. For example, the blades428aof the cooling unit427acan constitute separately produced parts which are riveted, welded and/or otherwise reliably affixed to the turbine406. The blades428aof the cooling unit427acan also perform one or more additional functions, such as of securing the customary turbine vanes406′ to the turbine406; the blades428acan form suitably deformed integral lugs or analogous parts of the turbine406.

When the cooling unit427ais in actual use, the blades428acause the fluid which is heated in the region of the fluid flow regulator422to flow away from the parts414,415and to intensively mix with cooler fluid in those portions of the chamber417which are remote from the parts414,415. Moreover, the blades428acause the fluid (which has been heated by the parts414,415) to exchange heat with the portion404iof the housing404a. All such modes of preventing excessive localized heating of fluid at the regulator422contribute to prevention of overheating of the fluid in the chamber417as well as of fluid which issues from the chamber417to flow, for example, into the transmission of the power train employing the torque converter401.

The cooling action of the cooling unit427bin the torque converter401aofFIG. 6is analogous to that of the cooling unit427ain the torque converter401of FIG.5. The difference is that the blades428bof the cooling unit427bform part of a separately produced disc-shaped member428cwhich is welded to the turbine406and is located in the plenum chamber418. It is clear that the blades428bcan constitute separately produced parts which are welded, riveted or otherwise affixed to the member428c. Again, the blades428bare adjacent the portion404iof the housing404a, i.e., next to the members414,415which are a cause of heating of fluid in the chamber418or on its way from the chamber417into the chamber418.

FIG. 7shows a torque converter501wherein the rotary housing504acomprises a hollow pin504fhaving teeth meshing with the teeth of a hollow transmission input shaft507. The latter receives torque from the prime mover (not shown) by way of the torque converter501. The pin504fhas an axial extension which non-rotatably but axially movably supports an auxiliary piston516ehaving a radially outermost portion in sealing engagement with the adjacent axially extending tubular part of the housing504a. The thus obtained annular compartment518abetween the leftmost portion of the housing504aand the auxiliary piston516ecan receive fluid to effect an axial movement of the auxiliary piston in a direction to the right, as viewed in FIG.7.

The auxiliary piston516aabuts the axially movable piston516of the bypass clutch513. The piston516is mounted on an extension or projection506iof a hub506awhich is movable axially of but cannot rotate relative to the transmission input shaft507. The piston516constitutes or is connected with a discrete output member of the torque converter501; for example, the discrete output member can be welded (such as spot welded), riveted and/or otherwise non-rotatably affixed to the piston516so that it shares all axial movements of the latter.

The driving part is constituted by a washer-like member504iwhich is non-rotatably (such as form-lockingly) connected with the housing504aand is held against axial movement by an abutment or stop504k. The member504iextends radially inwardly from the radially outer or outermost portion of the housing504a. The form-locking connection is or can be established by a profiled (such as toothed) external surface which is provided on the member504iand mates with a complementary (e.g., put through) internal surface of the adjacent portion of the housing504a. Frictional engagement involves a lamella523dby way of friction surfaces514a,514b,515a,515b. The friction surfaces514a,514bcan be provided on the friction linings which are preferably affixed to the lamella523dand, in order to establish a connection, are provided with a channel530, e.g., a pattern or array of grooves. The lamella523dis non-rotatably but axially movably mounted on the hub506aradially outwardly of the piston516, and preferably coaxially with the latter, by way of a torsional vibration damper523analogous to the damper223shown in and already described with reference to FIG.3.

When the bypass clutch513is at least partially engaged, the piston516cooperates with the friction surfaces514a,514b,515a,515bto establish a fluid flow limiting or regulating arrangement522which determines the rate of fluid flow between the plenum chambers517and518. In order to engage the bypass clutch513, the compartment518areceives hydraulic fluid at a pressure higher than that in the chamber518; on the other hand, the pressure of fluid in the compartment518ais reduced below that in the chamber518if the clutch513is to be disengaged. The compartment518areceives fluid from a source (not shown) by way of a bore or channel504pprovided in a pipe504eof the stator. The channel504pcommunicates with a radial bore504nwhich, in turn, communicates with bores507e,507frespectively provided in the transmission input shaft507and the additional shaft507c. The latter has an axial passage or bore or channel507dwhich communicates with one or more radial bores5041discharging into the compartment518a.

In the embodiment ofFIG. 7, the admission of pressurized fluid into the compartment518ais preferably independent of the fluid flow through the fluid flow regulating arrangement522, i.e., the flow of fluid through the plenum chambers517,518can take place independently of the pressure of fluid in the compartment518a. The direction of fluid flow in and the sequence in which the chambers517,518receive fluid depends upon the intended use and/or mode of operation of the torque converter501shown in FIG.7.

In the embodiment which is shown inFIG. 7, the plenum chamber517is first to receive pressurized fluid; the admission of fluid into the chamber517takes place by way of a second conduit504p′ in the stator, an axial bore504oin the non-rotatable stator pipe504e, and at least one axially parallel bore504qin the hub506a. The fluid which leaves the chamber517enters the chamber518by way of the array of grooves530at the fluid flow regulating arrangement522. The fluid which leaves the chamber518enters an evacuating conduit (not shown) provided in the stator pipe504by way of the chamber517, grooves530, compartment518aand an opening504r.

The stator pipe504eand the transmission input shaft507are respectively provided with openings504m,507dwhich supply hydraulic fluid to the transmission, e.g., to the torque sensor of a continuously variable transmission (CVT), by way of at least one of additional conduits504p,504p′,519abetween the shaft507cand the input shaft507. It will be appreciated that certain bores, openings, channels and like fluid path establishing passages which are referred to hereinabove and at least some of which are shown inFIG. 7must be temporarily, intermittently or permanently sealed from each other in order to establish paths for the flow of fluid to and from selected chambers and/or compartments during different stages of operation of the torque converter501. The aforementioned CVT can be of the type disclosed in any one of a number of US and foreign patents owned by the assignee of the present application, for example, in U.S. Pat. No. 5,711,730 granted Jan. 27, 1998 to Friedmann et al. for “TORQUE MONITORING APPARATUS” and in the U.S. patents referred to in this patent to Friedmann et al.

It is further clear that the additional or auxiliary piston516eand the compartment518acan be utilized with advantage in numerous torque converters other than those specifically described and shown in the present case, i.e., in torque converters not employing a fluid flow regulating arrangement522(or an equivalent thereof) and/or an auxiliary drive. The required arrangements of conduits, channels, bores, holes and/or analogous paths for the flow of fluid will be selected in dependency upon the specific requirements of the modified torque converters. Furthermore, the flow of fluid from the various embodiments of the improved torque converter can be limited and/or otherwise regulated by specially designed and/or mounted valves. For example, a fluid flow regulating arrangement (such as the one shown at522inFIG. 7) can employ a valve which regulates the flow of pressurized fluid in dependency upon the temperature of such fluid, e.g., in such a way that, when the temperature of fluid rises while and/or because the bypass clutch operates with slip, the rate of fluid flow is increased. To this end, the valve need not or should not be disposed in immediate or close proximity to the regulator522; for example, it often suffices to install a thermometer next to the regulator522and to utilize the thermometer as a means for transmitting signals to a fluid flow regulating valve which can be installed at a location close to or remote from the bypass clutch and from the fluid flow regulator.

FIG. 8illustrates certain details of a torque converter601which constitutes a modification of the torque converter101shown in FIG.2. The piston616of the bypass clutch613in the torque converter601differs from the piston116in order to establish a modified fluid flow regulating arrangement622. Furthermore, the torque converter622employs modified friction generating members614,615respectively having friction surfaces614′,615′. Such constituents of the arrangement622will be described in full detail with reference toFIGS. 16aand16b. The piston616has a circumferentially distributed annulus of resilient pressure transmitting components629; these parts will be fully described and their function explained with reference toFIGS. 14 and 15.

FIGS. 9to13aillustrate four presently preferred embodiments x(9), x(10), x(11) and x(12) of the improved fluid flow regulating arrangement, and more specifically four embodiments of the arrangement122shown in FIG.2. InFIG. 9, the piston116of the bypass clutch113cooperates with the radial wall104of the torque converter housing to regulate the flow of hydraulic fluid between the plenum cambers117,118(refer toFIG. 2) when the bypass clutch113is engaged. The wall104has a cooling surface104kwhich confronts the piston116and is provided with radially extending grooves or channels130; such grooves can be impressed into the surface104kof the wall104. The non-depressed portions of the cooling surface104k(i.e., the radially extending surfaces alternating with the grooves130constitute one friction surface114′ of the arrangement122, and an annular friction lining115on the radially outermost portion of the piston116defines a second friction surface115′ which bears upon the friction surface114′ when the clutch113is at least partly engaged. At such time, hydraulic fluid can flow only through the grooves130when the pressure of such fluid in the chamber117exceeds that of fluid in the chamber118.

The quantity of fluid flowing from the chamber117into the chamber118depends upon the pressure differential between the fluid bodies in these chambers as well as upon the combined cross-sectional area of unobstructed portions of the grooves130. In other words, such rate of fluid flow is dependent upon several parameters including the pressure differential between the fluid bodies filling the chambers117,118, the total number of grooves130, the extent to which the flow of fluid through these grooves is permitted by the friction surfaces114′,115′, and the depths, widths and lengths of the grooves (these grooves are assumed to have but need not have identical dimensions).

Another factor which influences or determines the rate of fluid flow through the grooves130is the temperature (and hence the viscosity) of fluid leaving that one of the chambers117,118wherein the fluid pressure is higher. The temperature of fluid rises as a result of friction moment developing at the surfaces114′,115′, i.e., the temperature of fluid being forced through the grooves130increases while the wall104and the piston116slip relative to each other because, at such time, the fluid exchanges heat with the surfaces surrounding the grooves, Such heating of the fluid entails a drop of viscosity, and the rate of flow of such fluid through the grooves130increases if the pressure in the chambers117,118remain unchanged.

It will be seen that, by properly selecting the parameters of the grooves130, one can achieve an optimal cooling of the surface.114′,115′ as well as an optimum rate of fluid flow between the chambers117and118. It will also be seen that, in the embodiment which is shown inFIG. 9, the fluid flow regulating arrangement operates in dependency upon the extent of slip between the surfaces114′ and115′. If necessary or desired, the parameters of the grooves130can be selected in such a way that one can achieve a desired cooling effect with a very high degree of accuracy. In other words, one can ensure that the operation of the bypass clutch113is at least substantially independent of changes of viscosity of the fluid.

In accordance with a presently preferred embodiment, the length l of the grooves130(as measured radially of the wall104, i.e., at right angles to the plane ofFIG. 13aand as shown in FIG.13), is between 10 and 50 mm, most preferably between 10 and 30 mm. As shown inFIG. 9, the length of the grooves130can exceed the width of the friction lining115; this is desirable and advantageous because such dimensioning of the lengths l of the grooves130and of the radial width of the friction lining115ensures a practically unimpeded inflow of fluid into and a practically unimpeded outflow of fluid from the grooves130.

As concerns the hydrodynamic aspects, the important parameters include the length l (FIG.13), the width b (FIG. 13a) and the depth t (FIG. 13a) of the grooves130, especially the ratio of t to b. The edges130′ (seeFIG. 13) of the surfaces bounding the grooves130may but need not be rounded. The width b of a groove130can be within the range of between about 0.2 and 20 mm, and the depth t can be less than 0.3 mm, preferably less than 0.15 mm. Still further, a groove130need not have an exactly rectangular cross-sectional outline; for example, the cross-sectional outlines of those end portions of the grooves130which are adjacent their radially outermost portions (at130ainFIG. 13) can have a trapeziform cross-sectional outline with each groove becoming wider as seen in a direction from the bottom toward the surface114′ of the wall104. The cross-sectional area of each groove130can increase radially outwardly toward the radially outermost portion130ashown in FIG.13.

Still further, each of the grooves130need not extend exactly radially of the wall104; for example, at least some of these grooves can include portions extending exactly or substantially circumferentially of the wall104. It is also possible to replace equidistant grooves130with grooves disposed at different distances from each other, as seen in the circumferential direction of the wall104.

An advantage of grooves130which include portions extending radially and portions extending circumferentially of the wall104is that the rate of fluid flow through such grooves increases with increasing RPM of the wall104.

The number of grooves130can vary within a wide range, e.g., between 8 and 400. It is presently preferred to provide the wall104with a substantial number of grooves, particularly between 100 and 300.

The making of grooves130in the surface114′ of the wall104can involve a pressing, erosion, milling or any other suitable material removing or material displacing technique. The groove130shown inFIG. 9is assumed to have been impressed into the surface114′ of the wall104.

FIG. 10illustrates a portion of a modified fluid flow regulating arrangement x(10) wherein the grooves130bare obtained by providing the wall104with radially extending rib-shaped projections130cat that side which faces away from the piston116of the bypass clutch. Thus, the grooves130bofFIG. 10are obtained by displacing portions of the material of the wall104away from the piston116, i.e., into the surface114′.

FIG. 11shows a portion of a fluid flow regulating arrangement x(11) which is the opposite of that shown in FIG.10. Thus, the left-hand side of the wall104is provided with elongated grooves or recesses130dwhich are obtained by depressing the material of the wall104toward the piston116. Consequently, the grooves (not shown) at the surface114are flanked by ribs which project beyond the surface114. In other words, the grooves in the wall104ofFIG. 11are obtained as a result of raising elongated radially extending rib-shaped portions of the material of the wall104toward the adjacent left-hand surface of the piston116.

The making of the projections shown at the right-hand side of the wall104depicted inFIG. 11can involve the use of a suitable tool or implement (not shown) having raised portions which impress the grooves or recesses130dto thus provide the surface114′ with raised portions which, in turn, flank grooves having open sides facing the surface115′ of the friction lining115on the piston116.

The fluid flow regulating arrangement x(12) ofFIG. 12does not employ any grooves in the surface114′ and/or115′. Instead, that side of the wall104which confronts the piston116carries a continuous or composite annular layer131of a material which is permeable to the fluid filling the chambers117,118. The layer131can be made of or can contain a sintered substance, a porous ceramic material (e.g., porous glass), a temperature-resistant porous organic plastic material or the like. The surface114′ of such layer131acooperates with the surface115′ of the friction lining115on the adjacent surface of the piston116.

FIG. 12shows the bypass clutch which employs the permeable layer131in disengaged condition, i.e., the layer131is out of contact or not in sufficient contact with the surface115′ of the friction lining115on the piston116. If the piston116is moved to the left so that the bypass clutch including the structure shown inFIG. 12is engaged to operate with or without slip, the hydraulic fluid is forced to penetrate through the permeable layer131as soon as the pressure of fluid in one of the chambers117,118exceeds the fluid pressure in the other chamber. Heat which develops as a result of frictional engagement between the exposed surface114′ of the layer131and the surface115′ of the friction lining115(while the bypass clutch operates with slip) is withdrawn by the flowing fluid. The rate of flow of fluid through the porous layer131depends upon the porosity of the material of such layer and the viscosity (temperature) of the fluid.

The layer131is secured to the wall104by rivets131a(one shown in FIG.12). Alternatively, the layer131can be secured to the wall104by a suitable adhesive, by projections provided on the wall104and extending into complementary recesses in the left-hand side of the layer131, and/or in any other suitable manner. Furthermore, the layer131can be formed by applying to the wall104one or more films of a material which, when hardened or set, constitutes the layer131.

It is clear that the porous layer131can be applied to the piston116and that the wall104can carry a friction lining115or bears directly upon the permeable layer on the piston116. Still further, it is possible to provide two porous layers131, one on the wall104and the other on the piston116. It is also possible to provide the exposed side of the porous layer131with a friction lining which bears directly upon the adjacent surface of the piston116or upon a friction lining on the piston116when the bypass clutch embodying the structure ofFIG. 12or an analogous structure is at least partially engaged.

FIGS. 14 and 15illustrate the distribution of and the manner of mounting the resilient pressure transmitting members or components629one of which is shown in the upper part of FIG.8. For the sake of simplicity, such components will be referred to as bellows since each thereof defines at least one internal space which can receive and discharge a quantity of fluid. As can be seen inFIG. 14, the piston616of the bypass clutch613carries an annular array of equidistant and rather closely adjacent oval bellows629each of which has its marginal portion affixed to the radially outermost portion of the piston616(as at629a). The connections629acan be established by an adhesive, by welding or in any other suitable manner.

For example, the bellows629can be made of a metal (such as a thin layer of sheet metal), of rubber or of any other suitable material which can perform the functions to be described hereinafter. The oval bellows629can be replaced with circular or otherwise configurated components.

The central portion of each bellows629registers with a discrete port629aof piston616; each such port permits hydraulic fluid to enter into or to issue from the respective bellows. The ports629btogether form a circular array. The bellows629change their volumes in dependency upon the pressure differentials between their interior and the surrounding atmosphere. Such volumetric changes are possible due to the deformability of the material of the bellows. The bellows629shown inFIGS. 8,14and15are assumed to consist of thin metallic sheet material.

FIG. 16ashows an empty (deflated) bellows629and shows that this bellows is located at the side of the piston616facing away from the fluid flow regulator622.FIG. 16bshows an at least partially inflated bellows629. Each ofFIGS. 16a,16bshows the bypass clutch including the wall604and the piston616in disengaged condition in order to facilitate the interpretation of the manner in which various constituents of the bypass clutch and of its fluid flow regulator622are affixed to each other. However, it is to be borne in mind that the regulator622is activated and that the bellows629can perform their intended functions only or primarily when the bypass clutch613is at least partly engaged.

FIG. 16ashows that the friction lining614at the right-hand side of the wall604has a friction surface614′ provided with a recess630a portion of which registers with the port629bof the piston616. Each recess630has an open radially inner end and a closed radially outer end. When the piston616turns relative to the wall604and/or vice versa, each port629bcommunicates with each of the recesses630once during each complete revolution of the parts604,615relative to each other.

It is now assumed that the pressure in the plenum chamber618shown inFIG. 16arises above that in the chamber617(reference should be had again to the description of the mode of operation of the torque converter101shown in FIG.2). Therefore, the fluid in the chamber18deforms the bellows629whenever the respective ports629bcommunicate with the adjacent recesses630so that a certain amount of fluid can flow in the recesses630radially inwardly and into the chamber617. An inflated bellows629is shown inFIG. 16b, and a deflated bellows is shown inFIG. 16a. The flow of fluid from the bellows629, through the ports629b, through the recesses630and into the chamber617causes a cooling of the surfaces614′,615′ which slide relative to each other while the wall604and the piston616turn relative to each other when the bypass clutch operates with slip.

The bellows629are refilled, again and again, during successive stages of angular movements of the parts604,616relative to each other when the ports629bcommunicate with radially outwardly extending recesses630a(seeFIG. 16b) which alternate with the recesses630and are also provided in the friction surface614′ of the friction lining614on the wall604. Each recess630ahas a closed radially inner end (disposed radially inwardly of the ports629b) and a radially outer end communicating with the chamber618. Each bellows629receives fluid from the chamber618when the respective port629bcommunicates with one of the radially outwardly open recesses630a.

The just described repeated and at least partial emptying and at least partial refilling of the bellows629takes place as long as the wall604and the piston616turn relative to each other, i.e., as long as the bypass clutch operates with slip. Such repeated refilling and emptying of the bellows629is interrupted whenever the bypass clutch operates without slip and whenever the bypass clutch is disengaged (i.e., when the friction surfaces614′,615′ are out of frictional engagement with each other).

It will be seen that the bellows629can be said to cooperate with or to form part of the fluid flow regulating arrangement622. A feature common to the regulating arrangement622and to the bellows629is that each thereof operates in dependency upon the presence or absence and/or extent of slip of the surfaces614′,615′ relative to each other.

The number of ports629band the numbers of recesses630,630acan be readily selected in such a way that the likelihood of vibrations and/or noise generation, as a result of repeated (rhythmical) overlapping of the recesses630,630awith the ports629bto bring about repeated filling and emptying of the bellows629, is very remote or nil. This not only applies to the parts613,616but also to all component parts of the improved torque converter as well as to other component parts in the power train and/or in other units of a motor vehicle.

The number of ports629bis preferably different from that of the recesses630,630a, and such numbers preferably have a large common denominator.

FIGS. 17aand17bshow a modified assembly of parts in and at the fluid flow regulator of a bypass clutch613a. The bellows629(only one shown) are mounted on the radially outermost portion of the piston616, the same as the friction lining615; this friction lining is not provided with recesses630,630aof the type shown inFIGS. 16aand16b; instead, such recesses are provided in the friction surface614's of the wall604and the friction lining615is provided with ports629′ registering with the ports629bin the radially outermost portion of the piston616. The grooves or recesses630,630aare impressed or milled or eroded into the right-hand side of the wall604.

FIGS. 18aand18billustrate a portion of a bypass clutch613cwherein the bellows629are borne by the outer side of the wall604and the piston616carries a friction lining614with recesses630,630aof the type shown inFIGS. 16aand16b. The recesses630a,630bare provided in the surface614′ of the friction lining614, and the ports629bare provided in the wall604.

FIGS. 19aand19billustrate, drawn to a larger scale, certain details of a bypass clutch213aconstituting a modification of the bypass clutch213shown in FIG.3. The leaf springs216aof the torque converter213are omitted, and the piston216of the bypass clutch213ais non-rotatably but axially movably affixed to the inner side of the tubular radially outermost portion of the torque converter housing204aby two sets of mating gear teeth216a′.

FIGS. 19aand19bshow the bypass clutch213ain disengaged condition in order to facilitate the understanding of the relationships between various interconnected and relatively movable parts; however it will be appreciated that the illustrated parts cooperate only when the clutch213ais at least partly engaged. The same applies for the friction clutch213bwhich is shown inFIGS. 20aand20b.

The friction lamella223dwhich is shown inFIGS. 19aand20acarries a first friction lining214ahaving a friction surface214a′ confronting a friction surface215b′ at the inner side of the wall204, and a second friction lining214bhaving an exposed friction surface214b′ confronting a friction surface215a′ of the piston216. A set of inflatable receptacles (called bellows)229is provided at the right-hand side of the piston216, and the latter has openings229b(hereinafter called ports) communicating with successive opening or ports229cin the lamella223d.

The lamella223dfurther carries a second friction lining214bhaving an exposed friction surface214b′ confronting a friction surface215b′on the piston216. InFIG. 19a, the illustrated bellows229can receive fluid from the chamber217via recesses230aprovided in the friction surface214a′ of the friction lining214a, ports229cof the lamella223dand ports229bin the piston216.

InFIG. 19b, the reference character230denotes one of those recesses which alternate with the recesses230a(one shown inFIG. 19b) but are open toward the chamber217. Fluid can enter the bellows229via recesses230a, ports229cand ports229b. InFIG. 19a, fluid can enter the bellows229from the chamber218via form-locking connection216a′ and/or through one or more openings (not shown inFIG. 19a) in the pisron216between the connection216a′ and the friction surface215b′ and thereupon through the ports229b.

The grooves230are provided in the surface214′ of the friction lining214awhich engages the friction surface215a′ of the wall204in the engaged condition of the friction clutch213a. In order to establish communication between the ports229b, the friction linings214a,214band the lamella223dare provided with the ports229c.

The emptying of the bellows229is shown inFIG. 19b. The recesses230a(FIG. 19a) alternate with the recesses230(FIG. 19b). The exact manner in which the fluid is caused or permitted to leave the bellows229is the same as or analogous to that already described with reference toFIG. 16a.

FIGS. 20aand20brespectively illustrate the emptying and refilling of bellows229in a manner analogous to that already described with reference toFIGS. 19aand19b., The difference between the bypass clutches213aand213bofFIGS. 19a-19band20a-20bis that, in the clutch213a, recesses are provided in the friction surface215b′ of the friction lining215. Consequently, the ports229cofFIGS. 19a-19bare not necessary in the friction clutch213bofFIGS. 20a-20bbecause the fluid flowing between the ports229band the recesses230or230ashown inFIGS. 20a-20bneed not flow through part223d.

The features of the friction clutches213a,213brespectively shown inFIGS. 19a-19band20a-20bcan be combined in a single torque converter, i.e., each of the friction linings614a,614bcan be provided with recesses230,230a. In such embodiment of the present invention, alternating bellows229are or can be arranged to respectively receive and/or discharge fluid by way of channels230,230aprovided in the friction linings214aand214b.

FIG. 21illustrates a portion of a torque converter having a bypass clutch213dwhich constitutes a further modification of the clutch213shown in FIG.3. The friction lamella223d′ is flanked by two friction linings214′,214″ which are affixed to the wall204and to the piston216, respectively. The piston216is axially movably but non-rotatably affixed to the housing including the wall204by leaf springs216a. The friction linings214′,214″ frictionally engage the respective sides of the lamella223d′ when the bypass clutch213dis at least partially engaged.

The left-hand side of the lamella223d′ is provided with a profile230bwhich varies in the circumferential direction and the details of which are shown in FIG.22. The left-hand (233b) and right-hand (233a) sides of the lamella223d′ (as seen inFIG. 22) constitute friction surfaces which respectively engage the adjacent friction linings214′ and214″. The surfaces233band233aare respectively provided with recesses232a,232b; these recesses form part of the fluid flow regulating arrangement222, i.e., of the arrangement which regulates the flow of fluid between the plenum chambers217,218(seeFIG. 3) when the structure shown inFIGS. 21 and 22is incorporated into the torque converter201of FIG.3. The arrangement222then serves to determine the rate of fluid flow between the chambers217,218in dependency upon the temperature (and hence the viscosity) of the fluid. As concerns the parameters (such as the depth, the width, the length, the number and the orientation) of the grooves232a,232b, reference should be had to the descriptions of the bypass clutches shown inFIGS. 16a-16b,17a-17band18a-18b, especially inFIGS. 17a-17band by bearing in mind that the structure actually shown inFIGS. 21 and 22does not employ bellows (such as those shown at629inFIGS.16a-18b).

FIGS. 23 and 24illustrate a structure which constitutes a modification of that shown in FIG.12. In the bypass clutch213aofFIG. 23, a friction lamella223d″ carries two porous layers231a,231bwhich are respectively adjacent a friction lining214″ on the wall204and a friction lining214′ on the piston216. The friction lining214′ can be affixed to the porous layer231ainstead of to the piston216, and the friction lining214″ can be affixed to the porous layer213b(instead of to the wall204). Furthermore, the bypass clutch213acan utilize all of the parts shown inFIG. 23plus at least one additional friction lining (affixed to the porous layer231aor231b).

InFIG. 24, the bypass clutch213bcomprises a single porous layer231(e.g., a layer made of sintered metal) which is riveted to the friction lamella223d″. The layer231has friction surfaces215,215awhich (when the clutch213bis at least partly engaged) respectively bear upon friction linings214′ (provided on the piston216) and214″ (provided on the wall204). The radially outermost portion of the friction lamella223d″ is located radially inwardly of the friction linings214′.214″.

FIG. 25shows certain details of a bypass clutch613dhaving a friction generating device621composed of parts614,615. A piston616dreplaces the piston116or616ofFIG. 2orFIG. 8to allow for an advantageous further modification of the fluid flow regulating arrangement122ofFIG. 2or622of FIG.8. The fluid flow regulator embodying certain parts of the structure shown inFIG. 25serves to regulate the flow of hydraulic fluid between the plenum chambers617and618.

The wall604ofFIG. 25carries a friction lining614′ which is provided with circumferentially distributed recesses or grooves630dextending radially outwardly to register with ports629bin the radially outer portion of the piston616d. The radially outer ends of the recesses630dare closed from the chamber618(when the bypass clutch613dofFIG. 25is at least partly engaged) but the radially inner ends of such recesses are open toward the chamber617.

The bellows629are not used in the bypass clutch613d; instead, the ports629bof the piston616dcommunicate directly with the chamber618. When the piston616dand the housing (including the wall604) are caused to turn relative to each other, the ports629bmove into and beyond positions of register with the recesses630dof the friction lining614′ on the wall604to thus respectively establish paths for the flow of fluid between the chambers617and618. Such repeated flow of fluid between the chambers617,618ensures that at least the friction lining614′ is adequately cooled as soon and as long as the bypass clutch613doperates with slip.

If the pressure of fluid in the chamber618rises above that in the chamber617, i.e., if the piston616dis moved axially toward the wall604, the extent of relative angular movement of the piston616dand the housing (including the wall604) of the torque converter decreases and comes to a halt when the clutch616dis fully engaged. The number of ports629band/or the number of recesses630dcan be selected in such a way that the likelihood of unsatisfactory or unacceptable overlap is remote or nil; this can be readily accomplished by proper selection of the numbers and/or proper distribution of the ports629band recesses630d.

Furthermore, and as actually shown inFIG. 25, one can provide a closing device or lid635which, when the bypass clutch613dis engaged, seals the ports629bfrom the plenum chamber618so that there can be no flow of fluid from the chamber618, via ports629band recesses630d, and into the chamber617(wherein the fluid pressure is assumed to be lower than in the chamber618when the bypass clutch613dis fully engaged, i.e., when such bypass clutch operates without slip). The reason for the provision of the closing device635is that there is no need to cool the friction lining614′ when the bypass clutch613dis fully engaged so that the wall604and the piston616dcannot slip relative to each other.

It is clear that the closing device635can be designed to close and actually seal only some of the ports629bfrom the plenum chamber618.

FIG. 26shows, drawn to a larger scale, the structure within the phantom-line circle Y in FIG.25.FIG. 27is a view as seen in the direction of arrow X inFIG. 26, andFIG. 28is a view as seen in the direction of arrow W in FIG.25. The closing device635comprises a series of tongues or flaps635awhich are pivotable to move substantially axially of the bypass clutch613d. The tongues635aform integral parts of or are pivotably mounted on a ring-shaped carrier635which is welded, riveted or adhesively or otherwise affixed to the piston616d. It is preferred to make the carrier635bof a resilient material and to ensure that the tongues635atend to assume their inoperative or idle positions (shown inFIGS. 25to27) in which they permit fluid to flow from the chamber618into the ports629b. For example, the carrier635band its tongues635acan be made of thin layers of spring steel. The thickness and/or the resiliency of the material of the carrier635bare selected in such a way that the tongues635aare compelled to yield and to pivot to their operative or closed positions (to seal the respective ports629bfrom the chamber618) as soon as the pressure of fluid in the chamber618ries to a value indicating that the clutch613dofFIGS. 25-28is engaged, i.e., that the wall604and the piston616ddo not turn relative to each other. When the pressure differential between the bodies of fluid in the chambers617,618decreases, the innate resiliency of the tongues635asuffices to initiate a movement of the tongues to the open positions shown inFIGS. 25to27.

In order to even more reliably ensure pivotal movements of the tongues635ato their open or inoperative positions as soon as the piston616dand the wall604are free to turn relative to each other, the friction lining614′ ofFIG. 25is provided with at least one groove which is open radially outwardly; such groove or grooves permits or permit entry of fluid which exerts pressure upon the tongues635aand ensures or ensure that the tongues reassume the open positions ofFIGS. 25-27as soon as the wall604and the piston616begin to turn relative to each other. Otherwise stated, the just mentioned groove or grooves in the friction lining614′ ensures or ensure that the pressure of fluid at the inner sides of the tongues635ais the same as at their outer sides (i.e., in the plenum chamber618) as soon as the wall604and the piston616dbegin to turn relative to each other so that the innate tendency of the tongues635asuffices to maintain them in open positions when the clutch613dis partially engaged so that it operates with slip.

By embodying the structure ofFIGS. 25-28in the bypass clutch of FIG.2and/or8, one ensures that the respective fluid flow regulating assembly (122or622) even more reliably ensures adequate cooling of the hydraulic fluid by exchange of heat as long as the respective bypass clutch operates with slip, and that the extent of cooling is commensurate with (a) the speed of relative angular movement between the torque converter housing (wall104or604) and the piston (116or616), and (b) the extent of pressure differential between the bodies of fluid in the plenum chambers (117and118or617and618). On the other hand, the tongues635ain the structure ofFIGS. 25-28also ensure that the circulation of fluid through the fluid flow regulating arrangement122or622is interrupted when a cooling of fluid is not necessary, i.e., when the bypass clutch embodying the structure ofFIGS. 25-28is disengaged or fully engaged.

The structure which is shown inFIGS. 25-28(or one or more structural and functional equivalents thereof) can be utilized with equal or similar advantage in torque converters which are different from those shown inFIGS. 2 and 8, i.e., with differently configurated, mounted and assembled friction linings, friction lamellae and/or other constituents of the fluid flow regulating arrangements. By way of example only, the structure shown inFIGS. 25-28can be incorporated into torque converters embodying the features of the structures shown inFIGS. 16ato20b.

FIGS. 29ato29krespectively illustrate portions of friction linings636ato636kwhich can be utilized in lieu of previously described friction linings (such as those shown inFIGS. 16ato20b) to ensure even more predictable flow of fluid between the two plenum chambers (not shown inFIGS. 29ato29k).

For example, if one utilizes a fluid flow regulating arrangement622(FIG. 8) or622a(FIG.25), it is advisable to employ radially inwardly opening grooves or recesses636a″-636k″ (seeFIGS. 29a-29k) as well as radially outwardly open recesses636a′-636k′ in such numbers that the overall number of radially outwardly opening recesses (e.g.,636a′) matches or approximates the overall number of radially inwardly opening recesses (e.g.,636a″). Moreover, individual radially inwardly opening recesses (such as636a″) or groups of such recesses can alternate with individual radially outwardly opening recesses (such as636a′) or groups of such recesses, as seen in the circumferential direction of the respective friction ring (such as636a). The recesses or grooves of each set can be equidistant from each other and can be straight, arcuate, undulate, zigzag shaped, comb-shaped, T-shaped, V-shaped and/or otherwise configurated.

It is also possible to alternate groups of two or more inwardly opening recesses (such as636a″) with individual outwardly opening recesses (such as636a′); such arrangement can be resorted to in the embodiment of FIG.25).

FIG. 29ashows that the radially inner ends of the recesses636a′,636a″ extend circumferentially of the friction lining636a. If such arrangement is used in the embodiment ofFIGS. 16-16b, it ensures longer-lasting communication of successive alternating recesses636a′ and636a″ with successive ports629bshown inFIGS. 16aand16b.

The recesses or grooves636band636cofFIGS. 29band29cextend radially of the respective friction linings636b,636c; therefore, the intervals of communication with the ports629bofFIGS. 16a-16b(if the friction lining shown inFIGS. 16aand16bis replaced with the friction lining636bor636c) are relatively short if and when the wall604and the piston616ofFIGS. 16aand16bare caused to turn relative to each other. The depths of the recesses636b′,636b″ are such that their closed inner ends communicate with successive ports629bif the friction lining636breplaces the friction lining shown inFIGS. 16aand16b.

The recesses636c′,636c41of the friction lining636cshown inFIG. 29care much longer than those shown inFIG. 29b.

The inclination of the straight recesses636d′,636d″ in the friction lining636ofFIG. 29dis dependent upon the desired duration of communication with successive ports629bif the friction lining636dreplaces the one shown inFIGS. 16aand16b. The illustrated recesses636d′,636d″ are inclined in the same direction, i.e., clockwise, as seen inFIG. 29d; however, they can be inclined in opposite directions if so required or desirable or advantageous for a specific mode of fluid flow regulation.

Each of the recesses636e′,636e″ (in the friction lining636eofFIG. 29e),636f′,636f″ (in the friction lining636fofFIG. 29f) and636g′,636g″ (in the friction lining636gofFIG. 29g) has two open ends which extend inwardly from the outer and inner edge faces of the respective friction lining. The recesses of the friction linings shown inFIGS. 29eto29gcan have identical (FIGS. 29e,29g) or different (FIG. 29f) shapes and/or sizes, such as part circular, U-shaped, trapeziform or U-shaped outlines.

FIGS. 29hand29irespectively show recesses636h′,636h″ and636i′,636i″ having widths (as seen circumferentially of the respective friction rings636h,636i) greatly exceeding their depths. Furthermore, the depths of the recesses636i′,636i″ vary continuously, as seen in the circumferential direction of the friction ring636i.

It is to be noted that theFIGS. 29a-29killustrate merely a relatively small number of different recesses636a′-636k′ and636a″-636k″. Thus, it is possible to combine the shapes actually shown in these Figures to arrive at a host of additional configurations having constant or varying depths and/or widths and/or lengths, depending upon the desired nature, duration and other characteristics of fluid flow between the two plenum chambers.

FIG. 29jshows a friction lining636jwherein the zig-zag shaped recesses636j′,636j″ are dimensioned, configurated and oriented to ensure extensive (pronounced) cooling of the friction lining because such recesses can come into frequent and long-lasting contact with successive ports629b(if the friction lining636jis utilized in the structure shown inFIGS. 16aand16b).

The comb-shaped grooves636k′,636k″ in the friction lining636kofFIG. 29kalso ensure long-lasting communication of their ridges with successive ports629bif the friction lining636kis utilized in lieu of the friction lining shown inFIGS. 16aand16b.

At least some of the grooves or recesses shown inFIGS. 29a-29kcan be utilized in parts other than friction linings, e.g., in lieu of the recesses630a,630respectively shown inFIGS. 17aand17b; the recesses630a,630are provided in the inner side of the wall604, i.e., in a portion of the housing of the torque converter including the structure shown inFIGS. 17aand17b.

Still further, it is possible to provide recesses or grooves of the type shown inFIGS. 29ato29kin the piston of the bypass clutch or in a friction lamells (see the part223d′ shown in FIGS.21and22).

FIG. 30shows a hydrokinetic torque converter701having a fluid flow regulating arrangement722which is effective to influence the operation of the bypass clutch713, namely to regulate the rate of fluid flow between the wall704of the housing704aof the torque converter and the axially movable piston716. The controlling factor is the difference between the RPM of the wall704and that of the piston716.

The reference character737denotes a metering pump which is installed in the hub706aof the turbine706in the housing704a. The piston716and the turbine constitute the output members of the bypass clutch713. A torsional vibration damper723is employed to prevent the transmission of vibrations from the piston716and/or from the turbine706to the hub706aand hence to the transmission when the bypass clutch713is engaged to operate with or without slip.

The pump737is rotatable relative to and is confined in the hub706a. A safety ring737ais provided to prevent axial movements of the pump737relative to the hub706a. The housing737bof the pump737is non-rotatably connected with the wall704but is rotatable relative to the hub706a. The non-rotatable connection between the pump housing737band the wall704comprises at least one projection or stud737cprovided on the pump housing and extending into a socket704f′ of a plug or stud704fwhich is welded to the wall704. The pump housing737bconfines a pumping element738here shown as a sphere which is movable back and forth in a preferably cylindrical internal chamber or space741to seal the opening or outlet739or740of the pump737. The openings739,740are or can be surrounded by suitable sealing elements (such as elastic washers, O-rings or the like). The openings739,740respectively confront conduits742,743which are provided in the hub706aand respectively communicate with an inlet719aand an outlet719bfor hydraulic fluid.

When the housing704aand the plug704fturn relative to the hub706aand/or vice versa, the openings739,740alternately but simultaneously communicate with the conduits742,743in response to successive 180° turns of the pump housing737b. Thus, when the wall704turns relative to the hub706aand the pressure of fluid in the conduit743exceeds that in the conduit742, successive quantities of fluid entering chamber741are transferred from the conduit743into the conduit742. The spherical pumping element738is caused to move in the chamber741back and forth first into sealing position relative to the opening739, thereupon (as a result of rotation of the pump housing737bthrough 180° with the wall704relative to the hub706a) to the position in which it seals the opening740, again into a position in which it seals the opening739, and so forth. This causes the transfer of metered quantities of fluid from the conduit743into the conduit742. Such pumping of successive metered quantities of fluid continues as long as the wall704and the hub706aturn relative to each other (this also involves rotation of one of these parts relative to the other part).

When the clutch713is disengaged, the pressure in the conduit742matches that in the conduit743so that the rate of fluid flow between these conduits is practically nil even if the wall704turns relative to the hub706aand/or vice versa (due to slip of the turbine706and the pump705relative to each other).

The means for conveying metered quantities of fluid from the conduit742into the region of the bypass clutch713, namely to the locus of direct or indirect frictional engagement of the piston716with the wall704, i.e., for removing heat from the friction surfaces714′,715′, includes a disc-shaped member744which cooperates with the piston716to define a chamber745which communicates with the conduit742and is sealed from the plenum chamber718. The member744can constitute an injection molded plastic part or an embossed sheet metal part; this member is sealed outwardly against the piston716and inwardly against the hub706a.

The reference character723gdenotes a rivet constituting one of the fasteners which secure the the torsional vibration damper723to the piston716; the member744can have a cutout for each of the fasteners723g, and each such cutout is surrounded by a seal (not shown) which ensures that fluid entering the chamber745is compelled to flow from the openings739,740to the bypass clutch713.

The radially outermost portion of the piston716has an annulus of ports729bwhich direct pressurized fluid from the chamber745against the friction lining714′, and such fluid ultimately enters the plenum chamber717or718to exchange heat with the friction lining714′ and to transfer such heat to the body of fluid in the chamber717or718. The reference character715denotes a friction surface provided on the friction lining714′ and having grooves of the type shown, for example, inFIG. 19bto direct the fluid into the plenum chamber717. The chamber717communicates with the outlet719b.

The aforementioned grooves (e.g., in the surface715) can be of the type shown inFIGS. 29ato29k, except that all such grooves are laid out to convey hydraulic fluid from the ports729b(i.e., from the chamber745) into the chamber717(reference should be had to the grooves636a″ to636k″ shown inFIGS. 29ato29k.

The plenum chamber718of the torque converter701receives fluid from the inlet719afor pressurized fluid in a manner not specifically shown inFIG. 30; the path for the flow of fluid from the inlet719aof the torque converer701to the chamber718is defined by parts not visible in the sectional view of FIG.30.

FIGS. 31,32aand32billustrate the details of a further fluid flow regulating arrangement822which constitutes a modification of the arrangement shown in FIG.30. The piston816of the bypass clutch in the torque converter which embodies the structure ofFIGS. 31,32aand32bis provided with an annular array of circumferentially spaced-apart metering pumps837(two shown inFIG. 31) which, in contrast to the centrally mounted pump737of the torque converter701shown inFIG. 30, are mounted in the region of frictional engagement between the parts of the fluid flow regulating arrangement822when the clutch including the piston816is at least partly engaged, i.e., when the wall804of the housing of the torque converter and the piston816turn relative to each other.

The character814′ denotes a friction lining which can be affixed (e.g., bonded) to the piston816or to the wall804(preferably to the wall). The pumps837are adjacent the radially outermost portion of the piston816; an advantage of such mounting of the pumps is that the delivery of fluid to their inlets or intakes and the flow of fluid from their outlets are simpler and hence the entire torque converter is less expensive than that embodying the structure shown in FIG.30.

The ends of the elongated pumps837are provided with outlets839,840constituted by pipes839a,840a(seeFIG. 32a) which are recessed in the piston816to the extent determined by the stops839c,840c, respectively. The pipes839a,840aand a length of a pipe837cbetween them together constitute the housing837bof the respective pump837. The pumping element838is a sphere which is movable back and forth in the pipe837aall the way between the pipes839a,840a.

The pipes839a,840acan constitute composite (such as two-part) components made, e.g., in an injection molding machine, of a suitable plastic material. The same applies for several or all other parts of each pump837.

The friction lining814′ of the torque converter shown in part inFIGS. 32aand32bis assumed to be affixed to the wall804of the housing of the torque converter. This friction lining has radially outwardly extending recesses or cutouts830which alternate with radially inwardly extending recesses or cutouts830a. These recesses extend inwardly to an extent such that they communicate with the openings839,840(these are used as inlets or outlets) of successive pumps837when the wall804and the piston816turn relative to each other. The spacing of the recesses830,830ain the circumferential direction of the friction lining814′ is such that one thereof registers with the opening839of a pump817while the other thereof registers with the opening840. The illustrated recesses830,830aconstitute but one of numerous embodiments which can be provided in the friction lining814′; reference may be had, for example, toFIGS. 29ato29k.

If a friction lining (replacing the friction lining814′on the wall804) is replaced with a friction lining on the piston816, the recesses830,830aor their equivalents are machined into or otherwise provided in that surface of the wall804which confronts the piston816.

The mode of operation of the bypass clutch embodying the structure shown inFIGS. 31,32aand32bis such that, when the fluid flows from one of the two plenum chambers (e.g., from the plenum chamber118shown in FIG.2), such fluid is caused to enter the recesses830ain the direction of arrows shown inFIG. 32ato cause the spherical pumping element838to roll or to otherwise move in the pump chamber toward the opening840and to expel a metered quantity of fluid into the chamber817. Such movement of the pumping element838results in entry of a stream of hydraulic fluid from the chamber818into the portion841of the pump chamber via opening839and in simultaneous expulsion (by the pumping element838) of a stream of fluid from the portion841aof the pump chamber, via opening840and into the plenum chamber117. The rate of fluid flow from the chamber118into the the chamber117is dependent upon the extent of angular movement of the piston816and the wall804relative to each other. When the pumping element838reaches the right-hand end of the pump chamber (841+841a), it seals the opening840from the pump chamber and the latter is filled with fluid via opening839.

As the angular displacement of the parts804,816relative to each other continues, the openings839,840respectively communicate with the recesses830,830a(seeFIG. 32b). The recess830aadmits pressurized fluid which causes the pumping element838to expel the contents of the pump housing837bvia opening839and recess830into the chamber817. At the same time, the chamber841+841ais filled with fluid entering via opening840. This stage of operation of the pump837shown inFIGS. 32aand32bis completed when the pumping element838seals the opening839. The above described alternating stages of operation are repeated, again and again, as long as the bypass clutch including the piston816and the wall804operates with slip. When the bypass clutch is fully engaged, a cooling of the friction lining814′ and/or of the neighboring parts of the torque converter is no longer necessary; at such time, the pumping element838of each pump837at least substantially seals one of the openings839,840in the respective pump to thus interrupt the flow of fluid between the plenum chambers117and118.

FIG. 33illustrates a portion of a torque converter901having a bypass clutch913and constituting a further modification of the torque converter101shown in FIG.2. The parts914′,915′ correspond to the parts114′,115′ of the torque converter101. The bypass clutch913comprises a piston916the radially outermost portion of which carries a ring-shaped resilient sealing element950having a lip951arranged to sealingly engage the inner side of the wall904. The characteristics (such as the Shore hardness and/or the modulus of elasticity) of the material of the sealing element950in the region of the lip951can be influenced by one or more reinforcing inserts (such as a wire ring or the like) in such a way that the lip951sealingly engages the wall904only when the pressure of fluid in the plenum chamber918exceeds the pressure of fluid in the plenum chamber917to a predetermined extent.

The axial profile (at952) of the right-hand side of the wall904is impressed (such as by embossing or by extruding) or otherwise formed to impart to such side an undulate outline which varies as seen in the circumferential direction of the bypass clutch. This profile952is engaged by the lip951when the pressure of fluid in the chamber918rises to a predetermined level.

FIG. 34billustrates the lip of the sealing element950in full sealing engagement with the profiled inner side of the wall904. The arrows indicate the directions of rotary movement of the parts904and916(the sealing element950rotates with the piston916). If the piston916and the wall904begin to turn relative to each other, the stiffness of the reinforced lip951and/or the undulate shape of the profiled side952of the wall904and/or the drop of pressure in the chamber918(as compared with that of the chamber917) causes the lip951to move away from the profile952and to establish pathways953for the flow of fluid between the chambers917and918, e.g., from the chamber918into the chamber917. This is shown inFIG. 34a. The friction lining914′ can be provided with recesses, channels, cutouts or like configurations which extend radially of such friction lining and permit the flow of fluid between the chambers917,918at a desired optimum rate when the parts904,916are caused or permitted to turn relative to each other. The structure shown inFIGS. 33,34aand34balso permits for an accurate regulation of fluid flow between the chambers917,918to ensure adequate cooling of surfaces which are heated while the parts904,916are caused or permitted to turn relative to each other.

FIG. 35shows a portion of a torque converter1001which embodies or can embody a fluid flow regulating arrangement corresponding to that shown at22in the torque converter101ofFIG. 2, and which further comprises a cooling unit or cooling assembly1060serving to cool the surfaces1015,1014of the friction linings1014′,1015′ in the bypass clutch1013. The cooling unit1060is installed at that side (1061) of the wall1004which faces away from the piston1016. It is also possible to install the cooling unit1060or a second cooling unit at that side of the piston1016which faces away from the wall1004.

The reference character1062denotes a cooling chamber which extends radially inwardly beyond the friction surfaces1014,1015and, in the embodiment ofFIG. 35, is defined by the wall1004and a sheet metal shroud1063which is sealingly secured (such as welded) to the outer side1061of the wall1004. The cooling chamber1062has a sealable opening1064for admission or evacuation of a coolant1065partly filling the chamber1062and having a density which varies in response to heating by friction heat developing when the parts1004,1016of he bypass clutch1013are caused or permitted to slip relative to each other. Such change of phase causes the body of coolant1065to store energy and to be accelerated radially inwardly due to a reduction of density and the lesser action of centrifugal force whenever the housing wall1004and the piston1016turn relative to each other. This enables the coolant1065to exchange heat with relatively cool (cooler) housing wall portions1004hand shroud portions1063a. Such cooling of the coolant1065entails a rise of density and an increased action of centrifugal force, i.e., the coolant flows radially outwardly and removes heat from the surface1061of the wall1004which is heated due to slippage relative to the piston1016.

The coolant1065in the chamber1062can be water, ammonia, sulfur hexafluoride, one of Freon substitutes and others with a phase change between liquid and gaseous. It is also possible to employ solid substances, such as sodium, which can undergo a pronounced phase change between gaseous and solid in response to temperature changes.

In order to ensure the establishment of optimum relationship between the phase changes and the development of friction heat while the bypass clutch1013operates with slip, the chamber1062can be maintained at subatmospheric or superatmospheric pressure.

The cooling unit1060can be utilized with particular advantage in torque converters which employ conical bypass clutches because this renders it possible to install the cooling chamber1062in the conical regions at the friction surfaces of such bypass clutches. This can result in a substantial reduction of the space requirements (especially as seen in the axial direction) of torque converters embodying cooling units of the type shown in FIG.35.

The features of the numerous embodiments shown inFIGS. 1to35can be utilized interchangeably and/or cumulatively without departing from the spirit and scope of the invention. Furthermore, the novel fluid flow regulating arrangements, bypass clutches, cooling units, fluid circulating pumps, friction linings and other constituents stintuents afore described torque converters can be utilized, with equal or similar advantage, in many other types of torque converters for use in the power trains of motor vehicles or elsewhere.

Numerous modes of assembling and operating the improved torque converter and/or its bypass clutch and/or the regulating means therefore are disclosed on pages 31 to 60 in the aforementioned commonly owned copending German patent application Ser. No. 100 20 907.6 filed Apr. 28, 2000. It is emphasized, again, that the German priority application, including the pages 31 to 60 thereof, is incorporated herein by reference, i.e., that it forms part of the present application.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic and specific aspects of the above outlined contribution to the art of hydrokinetic torque converters and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the appended claims.