Transmission Hydraulic Systems

ارائه خدمات مهندسی هیدرولیک تعمیرات تخصصی جرثقیلهای سبک و سنگین بیلهای مکانیکی ماشین آلات صنعتی منصور ابوالقاسمی تلگرام ادمین پاسخگوی سئوالات فنی شما کانال جدید هیدرولیک تخصصی

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

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

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

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

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

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

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

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

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

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

Mechanical Throttle Valve Operation Page 67C

Throttle Valve Operation Low Pressure

TV Valve Pressure Higher Pressure PAGE 68c

Vacuum Operated Throttle Valve (vacuum modulated) Page 68c

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

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

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

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

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

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

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

Valve Body (The Brain)

Lubrication Flow and Pressure

Hydraulic Circuit Low 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

Hydraulic Circuit Second Gear

Hydraulic Circuit Third Gear

Electronic Shift Control

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

ORIFICES 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 FIG Page 75C

The End

Oil Cooler Flow and Pressure Fluid must be cooled Transmission must be cooled

Band and Clutch Apply Pressure