Lock-up piston plate for recirculating flow torque converter

Abstract: A piston plate (38) for providing a lock-up of a hydrodynamic torque transmitting unit (10) has a friction lining (50) bonded to a flat area (54A) thereon near the outer diameter which is arranged to slip with respect to the front cover (14) of a rotating housing of the torque converter (10). The friction lining (50) has an annular sealing segment (55) to seal fluid leakage across the lining (50); and a plurality of grooves (60) is formed from the outside diameter (58) of the lining (50) to an intermediate point on the width to communicate through an axial hole (72) in the piston plate (38) to provide a path for flow of cooling fluid through the lining (50) for removing heat build up therefrom; the source of the cooling fluid also is the fluid source for applying pressure to the plate (38) for providing lock-up in the torque transmitting unit (10).

Description: The present invention relates to hydrodynamic torque transmitting units. Various proposals have been suggested for including a selectively engageable friction clutch within a hydrodynamic torque converter to split torque or for producing an all mechanical drive. Such clutch or lock-up constructions are particularly advantageous in change speed torque converter transmissions for vehicles to increase the transmissions' operating efficiency. In some clutch devices, split torque usage is limited to small diameter clutches where oil pressure effects are small or on lock-up clutches where differential speeds are low. For example, if there is a shift from an open converter to a split torque drive for cruise operation in a torque converter transmission, the centrifugal pressures on opposite sides of the clutch plate mounted in the hydraulic unit can be unequal and thereby can make the clutch application and release difficult to calibrate. A variety of proposals are known in the art for engaging the friction element of the lock-up in such torque converters. One such proposal is featured in US-A-2404657 which discloses an arrangement wherein valves for directing fluid pressure onto the friction plate are activated by centrifugal force. In the arrangement there is no cooling flow once the friction plate is engaged. US-A-3972400 discloses the use of friction plates run in a fluid. Various groove patterns are suggested for directing flow from the I.D. (inner diameter) of the friction plates to the O.D. (outer diameter) thereof. The provision of grooves across the entire width of the facing would leak in a torque converter application where it is desirable to seal the activating fluid from the outboard face of a piston plate for carrying friction material that is engageable with the front cover of a rotatable housing of a torque converter for producing a desired lock-up therein. There is further disclosed in US-A-4445599 a torque converter lock-up system which provides cooling flow once the lock-up is engaged. In this arrangement, passages are provided through a metal piston plate to cool the locked up clutch rather than providing for flow through grooves in the friction material. The fluid flow in the -599 arrangement, again, will provide a leakage path for flow of the pressurizing fluid from the unit during lock-up. Similarly, US-A-4,462,492 discloses a torque converter lock-up system in which the coolant arrangement is, again, through a piston plate material, rather than the friction material and the path again constitutes a leakage path for the energizing fluid. Yet another such proposal is featured in US-A-4,638,897 which generally discloses a hydrodynamic torque transmitting unit comprising input and output rotors in a rotating housing with a front cover engageable with a piston plate energizable by fluid pressure to lock up the torque transmitting unit, a pressure space on one side of the piston plate and a void space on the other side of the piston plate between the piston plate and the front cover having a pressure differential thereacross which will cause the piston plate continuously to slip with respect to the front cover, and an annular friction facing means on the other side of the piston plate including seal means engageable with the front cover to seal the void space against the ingress of circulating fluid. In accordance with one aspect of the present invention as claimed, the aforesaid generally disclosed hydrodynamic torque transmitting unit is characterized in that passage means are provided in the annular friction facing means for circulating fluid from the pressure space across the annular friction facing means between the seal means and the outside diameter of the annular friction facing means to remove heat from the annular friction facing means as the annular friction facing means is continuously slipped with respect to the front cover. A further such proposal is featured in US-A-4,469,206 which generally discloses a piston plate for use in a hydrodynamic torque transmitting unit having a rotatable housing with a cover, the piston plate having an annular friction lining with seal means bonded thereto for producing a lock-up force on the cover under the influence of pressure fluid from a pressure space located on a side of the piston plate remote from the cover. In accordance with another aspect of the invention as claimed, the aforesaid generally disclosed piston plate is characterized in that the piston plate has an inlet therethrough for supplying such pressure fluid to a coolant passage in the annular friction lining for flow of such pressure fluid across the annular friction lining in a radially outward direction so that the pressure fluid will also act as coolant fluid to remove heat therefrom, and in that the seal means of the annular friction lining includes a continuously uninterrupted annular seal segment radially inwardly of the coolant passage and adapted to engage the cover for sealing against the radial inward flow of such fluid past the inside diameter of the annular friction lining. In a preferred embodiment of the present invention, the hydrodynamic torque transmitting unit includes pump means for directing the actuating fluid through the friction facing means or the friction lining to remove heat therefrom as the facing means or lining is continuously slipped with respect to the cover of the hydrodynamic torque transmitting unit, and the passage means or coolant passage comprising a plurality of grooves or annularseal formed in the friction facing means of friction lining radially outwardly of the seal means for promoting oil circulation through the friction facing means or friction lining for removing heat therefrom during a continuously slipping torque converter lock-up mode of operation. In order that the invention may be well understood, there will now be described an embodiment thereof, given by way of example, reference being made to the accompanying drawings, in which: FIG. 1 is a cross-sectional view of an upper portion of a hydrodynamic torque converter embodying the present invention; FIG. 2 is a fragmentary cross-sectional view taken along the line 2-2 of FIG. 1, looking in the direction of the arrows; and FIG. 3 is an enlarged fragmentary sectional view of a circled region 3 in FIG. 1. Detailed Description of the Preferred Embodiment Referring firstly to FIG. 1, a hydrodynamic torque transmitting unit 10 is illustrated of the recirculating flow type, hereinafter referred to as a torque converter. The torque converter 10 includes an input lug 12 connected to a rotatable annular front cover 14. The front cover 14 is connected by suitable fastener means such as lugs 16 to a rear cover 18. Located within the rotatable front cover and rear cover 18 is located a pump 20 having a plurality of blades 22 forming a torus operatively connected to the rear cover 18. A turbine 24 with a plurality of blades 26 is drivingly connected to a hub 28 splined to a torque transmitting sleeve shaft 30. The sleeve shaft 30 is of the type adapted to be connected to a transmission and, in particular, can be connected to a sun gear of a planetary gear unit by suitable clutch means, as is well known in the art. The sleeve shaft surrounds a rotatable torque transmitting shaft 32 that extends concentrically within the sleeve shaft 30 in a rearward direction where it can be drivingly connected to a ring gear of a transmission, as is known in the prior art. The forward end of the torque transmitting shaft 32 is spline connected to a front annular hub 34. The front annular hub 34 has an annular shoulder 36 which connects to a piston plate 38 of a torque converter lock-up clutch 40 constructed in accordance with the present invention. More specifically, the piston plate 38 has an axially directed flange 42 thereon that is secured to the annual hub 34 for rotation therewith. The torque converter lock-up clutch 40 is adapted to be energized by hydraulic pressure produced in the torque converter 10 as the pump 20 and turbine 24 are rotated with respect to a bladed stator 44 which is connected through a one way brake 46 to a ground sleeve 48 located radially outwardly of and coaxially along the torque transmitting shaft 32. The lock-up clutch 40 includes a friction lining 50 having a surface 50a thereon bonded to a flat surface portion 54a of the outboard face 54 of the piston plate 38. The friction lining 50 further includes an annular seal segment 55 formed continuously circumferentially around the inside diameter surface 56 of the friction lining 50. The friction lining 50 further includes a radially outwardly located O.D. surface 58 thereon which is located radially inwardly of an axially directed flange portion 14a of the front cover 14. The friction lining 50 further includes a plurality of coolant passages 60 each including a radially angled segment 60a that is located at an inclination with respect to radial lines through the friction lining 50. The radially angled segments 60a only extend across part of the width of the friction lining 50 and start at a point located radially outwardly of the I.D. surface 56 and the annular seal segment 55 so that the seal segment 55 will seal a void space 62 located between the outboard surface 38a of the piston plate 38 and the inboard surface 14b of the front cover 14. The void space 62 may be relieved of pressure or pressurized through a passage 64 in the hub 34 and a transmission passage 66. The annular seal segment 55 will prevent leakage of the actuating fluid back into the void space 62 during energization of the lock-up clutch 40. The piston plate 38 is actuated when fluid is exhausted from the space 62 through a converter clutch control valve 65. The piston plate 38 is released (disengaged) when the space 62 is pressurized by feeding transmission fluid to the converter from the converter clutch control valve 65 through the passage 66, the passage 64 and into the void space 62. The piston plate 38 can be operated to apply a continuously slipping torque between the front face 50b of the friction lining 50 and the inboard surface 14b of the front cover 14. The radially angled segments 60a of the coolant passages 60 will receive pressure fluid from a pressure space 70 through inlet openings 72 in the piston plate 38 that are directed axially therethrough at a point radially outwardly of the annular seal segment 55. The inlet openings 72 align with axial inlet openings 60b of the coolant passages 60. The piston plate 38 will be rotated by the rotatable housing of the torque converter 10 to cause fluid flow through the radially angled segment 60a by a combination of centrifugal force action thereon and a shear force produced by the angle of the groove 60a on fluid forced therein from the pressure space 70. Additionally, there is a pressure differential between the space 70 and the outlet of the passage 60 at the O.D. of the lining 50. The groove arrangement thus continuously flows fluid through the friction lining 50. The fluid flow removes heat build-up from the friction lining 50 thereby enabling it to be continuously slipped on the cover 14 and run at higher energy levels as compared to conventional continuous slip lock-up clutch devices. The afore described configuration of the friction lining enables the fluid that produces the application pressure on the piston plate 38 also to be used as cooling flow without leakage back into the void space 62 between the outboard surface of the piston plate 38 and the rotating front cover 14. The piston plate 38 and the friction lining 50 of the present invention are shown in association with a torque converter having high capacity large diameter pump and turbine components, but are equally suitable for use in any hydrodynamic torque converter having a rotatable housing and including an actuatable piston plate for locking up a clutch component of a torque converter. By virtue of the construction, the piston plate 38 has an engagement force to the left as illustrated, which is primarily dependent on pressure within a single pressure space 70, thereby to avoid the need for controls to balance and modulate pressures on either side of the piston plate 38. Such a single biasing pressure provides for excellent control of the clutch in a continuous slip mode of operation regardless of pump turbine or clutch plate speed. The hydrodynamic torque transmitting unit described above has the advantage that the response time to apply a lock-up force between the piston plate 38 and the rotating front cover 14, either to produce a split torque drive or to produce an all mechanical drive, is minimised. It also has the advantage that heat is continuously removed from the friction lining 50 of the piston plate 38 while providing for a seal across the friction facing means during the slip operation.

Claims: A hydrodynamic torque transmitting unit (10) comprising input and output rotors in a rotating housing with a front cover (14) engageable with a piston plate (38) energizable by fluid pressure to lock up the torque transmitting unit (10), a pressure space (70) on one side of the piston plate (38) and a void space (62) on the other side of the piston plate (38) between the piston plate (38) and the front cover (14) having a pressure differential thereacross which will cause the piston plate (38) continuously to slip with respect to the front cover (14), and an annular friction facing means (50) on the other side of the piston plate (38), the annular friction facing means (50) including seal means (55) engageable with the front cover (14) to seal the void space (62) against the ingress of circulating fluid, characterised in that passage means (60) are provided in the annular friction facing means (50) for circulating fluid from the pressure space (70) across the annular friction facing means (50) between the seal means (55) and the outside diameter of the annular friction facing means (50) to remove heat from the annular friction facing means (50) as the annular friction facing means (50) is continuously slipped with respect to the front cover (14). A hydrodynamic torque transmitting unit as claimed in claim 1, wherein the passage means (60) includes means (60a) for circulating coolant flow by centrifugal force produced by rotation of the piston plate (38). A hydrodynamic torque transmitting unit as claimed in claim 1 or claim 2, wherein the passage means (60) includes radially angled segments (60a) for applying a shear force on the pressure fluid during during rotation of the piston plate (38). A hydrodynamic torque transmitting unit as claimed in any of the preceding claims, further including means (72) for directing fluid from the pressure space (70) to the passage means (60) for flow through the annular friction facing means (50) for removing heat therefrom. A piston plate (38) for use in a hydrodynamic torque transmitting unit (10) having a rotatable housing with a cover (14), the piston plate (38) having an annular friction lining (50) with seal means (55) bonded thereto for producing a lock-up force on the cover (14) under the influence of pressure fluid from a pressure space (70) located on a side of the piston plate (38) remote from the cover (14), characterized in that the piston plate (38) has an inlet (72) therethrough for supplying such pressure fluid to a coolant passage (60) in the annular friction lining (50) for flow of such pressure fluid across the annular friction lining (50) in a radially outward direction so that the pressure fluid will also act as coolant fluid to remove heat therefrom, and in that the seal means (55) of the annular friction lining (50) includes a continuously uninterrupted annular seal segment radially inwardly of the coolant passage (60) and adapted to engage the cover (14) for sealing against the radial inward flow of such fluid past the inside diameter of the annular friction lining (50). A piston plate as claimed in claim 5, wherein the coolant passage (60) includes a plurality of grooves (60a) in the annular friction lining (50) each having an inlet (60b) located radially outwardly of the annular seal segment (55) and an outlet opening located in the outer diameter of the annular friction lining (50). A piston plate as claimed in claim 5, wherein the coolant passage (60) includes a groove (60a) radially inclined through the annular friction lining (50) having an inlet (60b) located radially outwardly of the annular seal segment (55) and an outlet located at the radially outermost surface (58) of the annular friction lining (50). A piston plate as claimed in claim 6 or claim 7, further including an axial hole (72) through the piston plate (38) for forming the inlet (72) to the inlet (60b) of the coolant passage (60).

Inventors: VIERK DAVID T, VIERK, DAVID T.
Applicants: BORG WARNER AUTOMOTIVE, BORG-WARNER AUTOMOTIVE, INC.
Application year: 1990
Main classification: F16H45
IPC codes: F16H45, F16D13