Abstract: A viscous coupling (29) is disclosed for use as a by-pass element in a torque converter (15). The viscous coupling (29) includes a body member (31) and a cover member (33), with an annular clutch member (35) being disposed in a viscous shear area defined by the body and the cover. When the coupling is filled with viscous fluid, it has a nominal drive factor. The body member (31) defines a fill-hole (63) and an evacuation (discharge) passage (65). A pump element (71) is disposed adjacent the evacuation passage. A valve member (79) moves in response to changes in fluid pressure in an apply chamber (A), and in a low-gain mode, permits flow through the evacuation passage (65) filling the shear space radially outward of the pump element (71). In a high-gain mode, the valve member (79) blocks flow through the evacuation passage (65), and the entire shear area is filled.

Abstract: A bypass assembly (27) is disclosed for use in a torque converter (15) of an automatic transmission. The assembly includes a fluid coupling (29) and a driveplate assembly (31) which cooperate with the torque converter and its housing (22) to define a release pressure chamber (R), a first apply chamber (A1), and a second apply chamber (A2). At relatively low vehicle speeds, and relatively high levels of driveline vibration, the assembly operates in a release mode. At medium vehicle speeds, and medium levels of vibration, the pressures in the apply chambers (A1) and (A2) are approximately the same, and only the fluid coupling (29) is in operable engagement. At relatively higher vehicle speeds, and at relatively lower levels of vibration, the pressure in the apply chamber (A1) increases, moving a valve member (115) in opposition to a spring (123) to an open position, draining pressure from the second apply chamber (A2) to the release chamber (R).

Abstract: A viscous coupling (11) is disclosed of the type used as a by-pass element in a torque converter assembly (T) including a torque converter housing (H) and an output shaft (S). The coupling includes a body member (13), a cover member (15), and an annular clutch assembly (19). The clutch assembly includes a pair of clutch plates (53 and 57), riveted to a mounting portion (37), and the coupling housing includes a housing plate (59), disposed between the clutch plates. The housing plate (59) has an outer portion (61) which is fixed between the body and cover members, by means of tabs (65) engaging the body member (13) and tabs (69) engaging the cover member (15). Preferably, the tabs (65) are received in recesses (67) to prevent relative rotation of the housing plate (59) and body member (13). Also disclosed is an assembly and fluid fill method which eliminates the need for fill holes and plugs or balls being pressed into the fill holes.

Abstract: A viscous coupling (11) is provided for use as a by-pass element in a torque converter (T). The coupling includes a body member (13) having a body hub portion (25) and a cover member (15) having a cover hub portion (35). The body and cover hub portions are journalled on the outer surfaces (53,57) of a clutch hub portion (41) by means of a pair of identical bushing (59). Each bushing defines on its outer surface a fluid passage (79) including a restricted flow orifice (81). The restricted orifice results in a substantial pressure drop from a high pressure chamber (73) to a seal chamber (70). The cover hub portion (35) defines a counterbore (85) which communicates with the fluid passage (79) to by-pass the restricted orifice (81), such that the seal chamber (70) is maintained at substantially the pressure of a downstream, low pressure chamber (71).

Abstract: A bypass element (27) for a torque converter (15) is provided in which the bypass element comprises a viscous coupling (29). The viscous coupling includes a housing assembly comprising a body member (35) and a cover member (37), defining a viscous chamber (39) therebetween. Disposed within the viscous chamber is a clutch assembly (41) including a clutch portion (61) and a hub portion (65). The body member includes a hub portion (47) on which are disposed bushings (85 and 87). The cover member includes a hub portion (59) on which is disposed a bushing (89). The hub portion defines annular seal chambers (101 and 103) which include O-ring seals (105 and 107) respectively. Disposed upstream of the upstream O-ring, the hub portion defines an annular leakage groove (113) and an axial passage (115), communicating from the leakage groove to a downstream chamber (109) adjacent the coupling.

Abstract: A vibration reducing shoe for biasing a cam ring of a variable displacement ball pump into engagement with a surface of the pump housing. In a hydrostatic transmission having a variable displacement pump and a fixed displacement motor a pair of shoes are located within bores in the pintle. The shoes are slidably received in the bores and exert a force against the cam ring which is proportional to the pressure of the fluid used to rotate the motor. Since the pump is reversible, one shoe is in fluid communication with one of the passages directing fluid to the motor and the other shoe is in fluid communication with the other passage. Accordingly, the force exerted on the cam ring by the shoes increases and decreases with increases and decreases in the pressure of the fluid from the pump to the motor.

Abstract: An improved drive system includes a pair of hydrostatic transmissions which are driven by a common engine or prime mover and are drivingly connected with different tracks of a vehicle. The input to output speed ratios of the hydrostatic transmissions are simultaneously varied by operating a single speed control valve to port control fluid pressure to pressure responsive secondary or control motors in pump and motor actuators of the hydrostatic transmissions. A pair of charge pumps are provided to charge the hydrostatic transmissions and provide control fluid. If the fluid pressure output of either of the charge pumps falls below a predetermined level, a control arrangement reduces the control fluid pressure transmitted to the pump and motor actuators by the speed control valve to deswash or destroke both of the transmissions. The control arrangement also short circuits the hydrostatic loops interconnecting the pump and motor units. In addition, the brakes of the vehicle are engaged to stop the vehicle.