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014 shift feel devices
- 2. Transmission Shift Terminology Nonsynchronous shift Shifts that typically use a Oneway clutch as a reaction member When shift occurs OWC over-runs Does not provide engine breaking therefore can be called “freewheeling” shift Synchronous Shift Apply device must be timed with shift Can provide engine breaking because band or clutch is “locked”
- 3. Transmission Shift Terminology Shift Quality Refers to how shift feels Firm Soft Spirited Shift duration Refers to how long shift takes Early Late
- 4. Transmission Shift Terminology Shift Flair Refers to engine flair during upshift Missed shift Refers to missed gear 1-2-4 shift Do not confuse with 4-1 coasting down shift
- 5. Linear EPC Solenoids Sleev e Spool Valve High Pressure = Low Voltage High Pressure = High Voltage Hydrauli c Pressur e Current Current Hydrauli c Pressur e - or - • Linear EPC used to control shift feel, timing, and apply pressure • Acts directly on individual clutch circuit
- 6. Non Linear EPC Solenoids EPC Solenoid used to affect Main Line Pressure Affects all clutches Most “bleed off” pressure to lower Main Line Pressure
- 7. Shift Feel Devices Wave Plates Spring plate located under 1st steel Used to “cushion” application of clutch Belville Plate Convex plate located on piston As plate flattens out application is cushioned
- 8. Accumulators and Orifices Line Pressure 8 Throttle Pressure Line Pressure Accumulator Pressure
- 9. End Shift “Feel” Device Questions?? Ok… What has EPC solenoids done for the longevity and consistency of shifts over the life of the transmission? Adaptive Strategy/Shifting
Editor's Notes
- Linear solenoids are identified by an “SL” designation. They are typically connected to the electronic control circuit by two wires, because their ground is controlled through the ECU. The solenoid regulates hydraulic pressure based on current flow from the ECU (duty cycle). The relationship between current flow and hydraulic pressure is proportional, and can be either low current = high pressure or low current = low pressure.
- Accumulators act to cushion shift shock by controlling holding device application pressure. An accumulator is basically a large diameter piston located in a bore and held in position by a heavy, calibrated spring that acts against hydraulic pressure. Accumulators are placed in the hydraulic circuit between the shift valve and the holding device. When the shift valve moves, fluid is directed to the circuit of the holding device. As hydraulic pressure works to compress the holding device return springs, pressure in the circuit builds. The increasing pressure must also work against the spring in the accumulator. Pressure in the circuit cannot reach its highest level until the accumulator spring is compressed and the accumulator piston is seated. Therefore, pressure in the holding device circuit builds slowly and the holding device application is softened. Holding device application can be tailored even more closely by routing hydraulic pressure to the spring side of the accumulator. Line pressure to apply the holding device must then overcome both spring tension and additional hydraulic pressure. Hydraulic pressure to the spring side of the accumulator is controlled by an accumulator control valve, a type of pressure modulating valve.