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Transmission Hydraulic Systems

Transmission Hydraulic Systems. Chapter 4. Introduction. How the transmission develops hydraulic pressure How transmission generates, regulates and modifies pressures Control of up shifts and downshifts Lubrication and cooling of transmission How apply devices are applied. Pump Types.

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Transmission Hydraulic Systems

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  1. Transmission Hydraulic Systems Chapter 4

  2. Introduction • How the transmission develops hydraulic pressure • How transmission generates, regulates and modifies pressures • Control of up shifts and downshifts • Lubrication and cooling of transmission • How apply devices are applied

  3. Pump Types • Three Types • Gear Pump • Rotor Pump • Vane Pump • Driven by Torque Converter Page 56C

  4. Gear Type Pump • Continually operating whenever engine is running • Two meshing gears • Inner gear powered by torque converter • Fluid is carried between gear teeth • Positive Displacement • Requires pressure regulation Page 56C

  5. Rotor Pump • Inner Drive Rotor • Driven Outer rotors • Operates and delivers fluid whenever the engine is operating Page 57C

  6. Vane Pump • Vanes are operated by centrifugal force • Can be positive displacement or Variable displacement pump • Are self regulating • Variable Displacement • Moving Slide controlled by regulated pressure See Page 58C

  7. Pressure Regulation • Regulator Valve • Variable Regulated Pressure • Electronic Regulation • Uses solenoid to modify system pressure by pulse width modulation Page 61C Building to Max Pressure

  8. Pressure Regulator Valve • Bleeds off pressure when maximum pressure is reached. • Exhausts back to sump • If left unregulated can damage components Page 61C

  9. Transmission Hydraulic Pressures Mainline Pressure Throttle Pressure Governor Pressure Page 59C

  10. Mainline Pressure(“line pressure”) • Regulated Mainline Pressure • Is source for all flow • Controlled by pressure regulator • Applies bands and clutches • Feeds Valve Body valves • Applies pressure to one end of pressure regulator valve Page 60C

  11. BOOST PRESSURE • Boosted Mainline Pressure • Boost Valve to raise pressure at low rpm and high engine load • Other pressures are used to modify regulated pressure Page 61C

  12. Throttle Pressure(“modulated pressure”) • Engine Load Sensing • Mechanical • Vacuum • Electronic • Works against governor pressure • Primary Shift Control signal • Can be Electronic Controlled • Always less or equal to mainline pressure Page 62C

  13. Mechanical Throttle Valve Operation Page 67C

  14. Throttle Valve OperationLow Pressure

  15. TV Valve PressureHigher Pressure PAGE 68c

  16. Vacuum Operated Throttle Valve(vacuum modulated) Page 68c

  17. Road Speed signal Opposes TV pressure to control shift points Driven by output shaft Higher speeds = Higher pressure Electronic transmission use a PWM solenoid Governor Types Gear Driven Spool Valve Type Check-ball Type Shaft Mounted Valves allow fluid to not bleed off the higher speed you go. Governors stick sometimes and can be cleaned Governor Pressure

  18. Governor Types: Gear Driven, Shaft mounted and Electronic Solenoid Centrifugal Governor Operation Spool Valve operated Page 71c

  19. Torque Converter Pressure • Fluid coupling • Fills torque converter during start up • Regulated by fill valve • Torque Converter Clutch Apply Pressure

  20. Shifting and Shift Operations • Manual Valve • Throttle Valve • Downshift Valves • Governor Valve • Spool Valve design • Check-ball design • Shaft Mounted governors Page 73c

  21. Manual Valve Operation • Positioned manually by gear selector lever • Lever moves valve to one of several detent positions • Directs mainline pressure to correct shift valves and apply devices • Electronic transmission have a MLPS Page 66C

  22. Shift Valve Operation • Shift Valves are: • Flow directing • Switching valves • Spool Type valves • Governor Pressure on one end • Throttle Pressure on other end with spring assist • Blocks or allows fluid flow • Valves must move instantly Page 73C

  23. Shift Valve Operation When speed is high, governor Pressure is higher than throttle Pressure. Allows mainline pressure to pass Through and cause a upshift When Vehicle speed low Throttle pressure and spring Pressure are higher than Governor pressure Page 73c

  24. Valve Body(The Brain)

  25. Lubrication Flow and Pressure

  26. Hydraulic CircuitLow Gear • 1 – 2 Shift valve controls upshifts and downshifts between • first and second gears • 2 –3 shift valve controls upshifts and downshifts between second and third gears

  27. Hydraulic CircuitSecond Gear

  28. Hydraulic CircuitThird Gear

  29. Electronic Shift Control

  30. ACCUMULATORS • Serves as a “shock absorber” for the system • Cushions application of servos and clutches • Allows a gradual application of apply device • Independent Piston –Type Accumulator • Plumbed in parallel with servo • Integral Piston _ Type Accumulator • Built into the servo assembly • Valve Type Accumulator • Contains a small valve to restrict fluid flow Page 111C

  31. ORIFICES FIG. 4-43 Page 75C • Small restriction in a fluid passage • Functions like a pressure regulating valve • Delay pressure build up on one side • Eventually equalizes on other opposite side

  32. The End

  33. Oil Cooler Flow and Pressure • Fluid must be cooled • Transmission must be cooled

  34. Band and Clutch Apply Pressure

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