TM-9-2520-234-35 Technical Manual for M109 Transmission XTG-411-2A Download

CHAP 2, SEC I DESCRIPTION AND OPERATION OF PAR 9 INPUT TRANSFER ASSEMBLY fold-out 2) supports the turbine assembly in the converter cover assembly 68. b. Lockup Clutch Components (fig. 373, fold-out 2). The lockup clutch in- cludes converter cover assembly 68, piston 74, clutch plate 77, reaction plate 78 and related minor components. Cover assembly 68 serves jointly as the input drive for the torque converter as well as a cylinder for lockup piston 74. Clutch plate 77 is faced on both sides with a friction material. It has splines on its internal diameter which engage splines on the hub of turbine 79. Reaction plate 78 is a steel ring which includes one clutch friction surface. Its outer diameter is held between pump assembly 82 and cover assembly 68 by bolts 86 and nuts 71. c. Operation of Torque Converter — and Lockup Clutch (1) The torque converter and lockup clutch are combined in a compact subassembly which serves as the input member for the main transmission section. This combination acts as a torque multi- plier, a fluid coupling or a direct-drive coupling — depending upon the require- ment at any particular time. (2) Engine torque is delivered to converter cover 69 by transfer gear 67. Converter cover, lockup clutch piston 74, reaction plate 78 and converter pump as- sembly 82 rotate as a unit and constitute the drive members. Stator assembly 94 is located between pump assembly 82 and turbine assembly 79. The stator is the reaction member. Turbine assembly 79 and lockup clutch plate 77 rotate as a unit and with converter turbine shaft 2 (fig. 375, fold-out 4). This group constitutes the driven members. (3) The cavity within the assem- bled components is kept charged with oil which continually circulates for cooling and lubrication. Rotation of the converter pump while the vehicle engine is at idle speed will not transmit a significant amount of power hydraulically to the con- verter turbine. Thus, during engine idle, the converter acts as a disengaged clutch. The pressure of the oil in the converter cavity keeps the lockup clutch piston pushed to its released position except when a higher pressure is applied to the opposite side of the piston. This occurs only at higher speeds. (4) When the engine is accelera- ted, the vanes of the converter pump throw oil radially outward and into the blades of the turbine. The impact of this oil against the turbine blades causes the turbine to rotate. Oil leaves the vanes of the turbine at a point near the turbine hub but flowing in a direction opposite to con- verter rotation. This flow in an opposite direction is most pronounced at lower turbine speeds. At higher turbine speeds, the flow changes and is more toward the direction of rotation. (5) To return to the converter pump, the oil must pass between the stator vanes. At low turbine speeds, the oil strikes the concave sides of the stator vanes. This tends to drive the stator in a direction opposite to converter rotation. The stator locks up, however, and the sta- tor blades turn the flow of oil and direct it in the same direction as the converter pump rotates. The unexpended energy of the oil is thus added to the movement of the pump. This is the key to torque mul- tiplication. (6) When turbine speed preaches pump speed, the direction of oil flow from turbine to pump changes. The returning oil strikes the convex sides of the stator vanes, causing the stator to freewheel. Under these conditions, the torque converter acts as a fluid coupling. There is no multiplication of torque. (7) When the converter reaches sufficient speed, and there is no further need for either torque multiplication or fluid drive, automatic valves direct pres- sure to the lockup clutch piston. The pis- ton compresses the lockup clutch plate against the back plate, locking the con- verter turbine to the converter cover as- sembly. Therefore, during lockup, the converter turbine is driven directly from the engine. There is no hydraulic action within the torque converter because the pump and turbine rotate as a unit. The stator freewheels to prevent any hydraulic drag. There is no loss from slippage, which 12 Change 2