Torque converter assembly with reverse acting bypass clutch

Abstract: A hydrokinetic torque converter assembly has a turbine (80) and an impeller (70) located in a converter housing and a lockup clutch construction (24) in the converter housing that includes a one-piece stamped clutch and piston housing (90) secured to the inner wall of the converter housing wherein the outer extremity of the stamoed housing carries friction discs (124,126). An annular piston (116) is located between the discs and the converter housing wherein the piston is stroked toward the turbine upon introduction of control pressure to a control chamber (112) defined by the piston and the cylinder, the driven discs of the clutch being connected to a turbine shaft (84) through a damper (132) and the friction elements of the clutch being continuously exposed to circulating fluid within the converter wherein piston charge pressure is established without a requirement for continuous flow when the clutch is actuated.

Description: The present invention comprises developments in a hydrokinetic torque converter and lock-up clutch assembly shown, for example, in U.S. Patent US-A-4,509,389 and depicted in Fig. 1 of the attached drawing. That patent describes a three-element torque converter including a turbine and an impeller located in a common converter housing wherein a clutch cavity is formed in the converter housing between the radial wall of the housing and the turbine, the radial wall of the housing being proximate to an engine crankshaft which is drivably connected to the impeller through the converter housing. The construction further includes a friction disc in the form of a piston plate having a friction surface on its outer margin. The friction surface on the piston plate is adapted to engage a friction surface formed on an adjacent annular wall of the converter housing. The inner margin of the plate is supported by a turbine hub to which the turbine is connected. The piston plate, together with the adjacent wall of the converter housing, define a control pressure space which is pressurized with control fluid, thereby establishing radial fluid circulation across friction surfaces. A damper assembly is used to connect drivably an outward radial portion of the piston plate to the turbine hub. Thus, when the clutch is applied, torque is distributed mechanically through the clutch from the engine crankshaft to the turbine, thus bypassing the hydrokinetic torque flow path through the torque converter. When the clutch is disengaged, all the torque is distributed from the crankshaft to the turbine shaft hydrokinetically, thus permitting hydrokinetic torque multiplication to occur when the torque converter operates in a torque multiplication mode. The clutch is disengaged by increasing the control pressure in the cavity between the clutch plate and the adjacent wall. This causes cooling oil to circulate throughout the friction discs. That fluid is added to the flow of fluid in the torus cavity and circulated through the torous circuit into an oil cooler. When the control pressure in the pressure cavity behind the piston plate decreases, the clutch is applied by controlling the control pressure. The degree of engagement may be controlled if continuous slipping is desired. The pressure may be modulated in accordance with the driving conditions to effect a continuous slip. This complements the cushioning action and the damping effect of the spring cushion and damper assembly that connects the drive plate to the turbine shaft. DE-A-2,620,937 describes a similar hydrokinetic torque converter in particular with the features in accordance with the preamble of the independent claim. With these prior art constructions a continuous flow of fluid through the control pressure space is required during clutch disengagement. If continuous slipping is desired and if the control pressure in the control pressure space is controlled accordingly, continuous flow through the pressure space is likewise required. In accordance with the present invention as noted by the characterizing portion of the independent claim, the clutch construction is arranged so that the friction discs are located adjacent the turbine where they are continuously exposed to circuit fluid, thus effecting optimum cooling as energy is dissipated when the clutch is partially applied. It is possible when using the arrangement to increase or decrease the torque capacity for given dimensions of the clutch assembly by adding additional friction discs or subtracting discs depending upon the torque requirements of a particular driveline. In the embodiment of this invention as described, a damper is used to connect a driven disc of a clutch assembly to the turbine hub, but in some applications it would be possible to eliminate the damper and to establish the cushion and damper functions by allowing the clutch to slip as pressure behind the annular piston is modulated appropriately. Brief Description of the Figures of the Drawings Figure 1 shows a prior art torque converter and lockup clutch assembly wherein a friction clutch mechanism is disposed within the converter housing; and Figure 2 is a converter and lockup clutch assembly embodying the teachings of this invention. Particular Description of the Invention Numeral 10 in Figure 1 designates an engine crankshaft. It is connected by drive plate 12 to a torque converter housing 14. The housing 14 is welded at its outer margin to an impeller housing 16 of a hydrokinetic torque converter 20. A lockup clutch cavity 22 is formed in the converter housing 14. It contains a lockup clutch assembly 24 situated between housing wall 26 and turbine 28 of the converter 20. Stator 30 is mounted by means of an overrunning brake and stator hub on stationary stator sleeveshaft 32 which is connected to the transmission housing 34. The lock-up clutch assembly 24 includes a piston plate 36 and a damper assembly 38, the latter being splined to turbine shaft 40. A drive sprocket and chain assembly 42 is driven by the turbine shaft. The driven sprocket that registers with the drive chain is mounted on an axis parallel to the axis of the converter and serves as a torque input element for multiple ratio gearing, as taught by U.S. Patent 4,509,389. While control pressure is distributed between the piston plates 36 and the wall 26, the pressurized fluid flows radially outward across the friction surfaces at the margin of the piston plate, thereby disengaging the clutch. When the control pressure is reduced relative to the static pressure is the torus circuit of the converter, the clutch becomes applied. Figure 2 shows the the present invention. It does not require the use of a piston plate of the kind shown in Figure 1, and it does not require continuous flow of fluid that is subjected to a control pressure to disengage the clutch. Further, the piston acts to engage friction discs carried within the torus circuit where heat may be dissipated. In this respect, the heat transfer characteristics are improved over a design such as that shown in the ′389 patent where the heat must be transferred into the converter housing. In Figure 2, the converter housing identified by numeral 44 includes a radial wall 46 that is bolted, as shown at 48, to a starter ring gear and drive plate assembly 50, the latter being bolted at 52 to the end of an engine crankshaft 54. The outer margin of the converter housing is welded at 56 to impeller shell or housing 58. Impeller blades 60 are provided with tabs on their outer margins as shown at 62. These tabs register with blade retaining recesses in the interior wall of the impeller shell 58. The hub 64 of the impeller is journalled on stator sleeve shaft 66 which is connected to transmission housing 68. As in the case of the Figure 1 construction, the converter includes a stator, as shown at 70. A stator hub 72 is splined to the outer race 74 of an overrunni-ng brake. The inner race of overunning brake 76, is splined to stationary sleeve shaft 66 as shown at 78. Converter turbine 80 includes an outer shroud 82 and radial inflow blades. The radially inward margin of the shroud 82 is secured to turbine hub 84, which is splined at 86 to turbine sleeve shaft 88. A one-piece cylinder identified generally by numeral 90 is made preferably by stamping operation. The cylinder 90 includes an axial extension 92 which defines an annular sealing surface 94. It is formed also with an annular surface 96. The radially outward portion of the cylinder is secured preferably by welding to the inner surface of the wall 46 as shown at 98. Cylinder 90 is provided with a central opening 100 through which hub 102 extends. The hub is splined to a hydraulic pump drive shaft 104 of the kind described in the ′389 patent, and it is sealed at 107 on an extension of the turbine hub 84. Turbine shaft 88 and the drive shaft for the pump define an annular flow passage 106 which communicates with the control pressure cavity 108 through porting formed in the hub 102. The pressure cavity 108 is defined by the inner surface of the wall 46 and the cylinder 90. A space 110 is provided between the cylinder 90 and the adjacent wall 46. It communicates with a clutch pressure chamber 112 through port 114. An annular piston 116 is formed, preferably, by a stamping operation. It is provided with an axially extending first portion 118 which is in sliding and sealing engagement with surface 94 and a second axially extending portion 120 which is in sliding and sealing engagement with surface 96. When pressure is distributed through control pressure passage 106 and into the space between the cylinder and the adjacent wall 46, a pressure buildup occurs in the chamber 112, thereby causing the piston 116 to stroke in a left-hand direction. The radially outward margin of the cylinder 90 is splined at 122 to provide a secure driving connection with reaction ring 124 and a pressure plate 126. A friction disc 128 having a friction surface on each side thereof at its outer margin is disposed between the reaction plate 124 and the pressure plate 126. The assembly of discs and plates is held axially fast by snap ring 130. The clutch disc 128 is connected to the drive plate 131 of a damper assembly generally identified by reference numeral 132. The damper assembly includes a hub 134, which is splined to the turbine hub 84. The fluid that circulates through the torus circuit comes in direct contact with the clutch disc and the clutch plate, thereby providing adequate cooling during operation. It is possible to control the magnitude of the pressure in the working chamber 112 to effect a continuous slipping of the clutch, thereby damping torsional vibrations and transient engine torque changes during operation. The heat that is generated by the slipping of the clutch or by repeated application and release of the clutch is adequately dissipated in the fluid that is circulated through the torus circuit. That circuit includes a flow passage 136 formed in the stator sleeve shaft 60. The turbine hub can be ported, as shown at 138, to provide a torus circuit feed. Fluid is returned radially inward through port 139 formed in the impeller hub and in the stator hub. It then is returned to the transmission oil cooler through another passage, not shown. The above described construction substantially reduces manufacturing costs and greatly simplifies the assembly of the converter and clutch assembly. Application and release of the clutch may be achieved without the necessity for increased converter flow as in the prior art. The extensions 120 and 118 of the piston include recesses for annular seal rings. When they are arranged as shown in the assembly view of Figure 2, the centrifugal force on the ring due to rotation of the impeller increases the sealing effort of the seal rings, thereby maintaining an adequate seal regardless of rotary speed. This is true both with the seal for extension 118 as well as for extension 120. By eliminating the continuous flow of fluid in the clutch pressure chamber by providing a so-called dead-head passage, the clutch may be controlled more effectively with less transient capacity variation.

Claims: A hydrokinetic torque converter and lockup clutch assembly for use with a power transmission mechanism adapted to deliver torque from a driving shaft (54) to a driven shaft (88) comprising: a torque converter housing (44, 46) having a closed converter cavity, said cavity enclosing a bladed impeller (60) and a bladed turbine (80) arranged in toroidal fluid flow relationship, said turbine being located within said cavity between said driving shaft (54) and said impeller (60); said turbine (80) including a turbine hub (84) connected to said driven shaft (88); a cylinder member (90) fixed to said housing (44, 46) extending radially with respect to said turbine hub (84) to a radially outward location within said converter cavity, friction discs (124, 126) of a lockup clutch secured to said cylinder member at said outward location, said cylinder member having radially spaced annular surfaces (94, 96) extending axially; an annular piston (116) having axially extending portions (118, 120) defining annular surfaces registering with said annular surfaces (94, 96) of said cylinder member (90), said cylinder member and said piston defining a pressure chamber (112); a pressure distributor passage (106, 108, 110, 114) extending from a radially inward location adjacent said turbine hub (84) and defined by said cylinder member (90) and the interior wall of said housing (44, 46) said distributor passage being in communication with said pressure chambers (112); and a driving clutch disc (128, 131) disposed adjacent said friction discs (124, 126) and connected to said driven shaft (88) whereby said impeller (60) and said turbine (80) are locked together when said pressure chamber (112) is pressurized; characterized in that said friction discs (124, 126) being secured to a portion (122) of said cylinder member (90) that is common to portions thereof that define said pressure chamber (112) and said pressure distributor passage (106, 108, 110, 114); said annular surfaces (94, 96)of said cylinder member (90) comprising surfaces facing radially inward with respect to said driven shaft (88) and said annular surfaces of said piston (116) comprising surfaces facing radially outward with respect to said driven shaft, whereby each radially outward facing surface has a seal groove, and an annular seal in each groove registering with one of said radially inward facing annular surfaces whereby certrifugal forces on each of said seals increase the sealing capacity of said annular seals. A hydrokinetic torque converter according to claim 1, wherein said friction discs (124, 126) are secured to a portion (122) of said cylinder member (90) that is formed in one piece with portions thereof that define said pressure chamber (112) and said distributor passage (106, 108, 110, 114), said cylinder member portions forming a unitary part. A hydrokinetic torque converter according to claim 1 or claim 2, wherein a portion of said cylinder member (90) located between said radially spaced annular surfaces (94, 96) being apertured (114) whereby fluid under clutch engaging pressure is distributed to the full radial extent of said pressure chamber (112).

Inventors: MARTIN DALE E, MARTIN, DALE E.
Applicants: FORD FRANCE, FORD MOTOR CO, FORD WERKE AG, FORD FRANCE SOCIETE ANONYME, FORD MOTOR COMPANY LIMITED, FORD-WERKE AKTIENGESELLSCHAFT
Application year: 1990
Main classification: F16H45
IPC codes: F16H45