General Operation
General OperationThe automatic transmission is a combination of a 3-element torque converter and four-shaft electronically controlled unit which provides 5 speeds and 1 reverse. The entire unit is positioned in line with the engine.
Torque Converter, Shafts, Gears, and Clutches
The torque converter consists of a pump, turbine, and stator assembly in a single unit. The converter housing (pump) is connected to the IMA motor rotor through the drive plate and torque converter supporting hub. The IMA motor rotor is connected to the end of the engine crankshaft. Around the outside of the torque converter is a ring gear. When an IMA motor control system malfunction occurs, the engine doesn't crank with the IMA motor, the ring gear meshes with the starter pinion and the engine cranks with the starter. The entire torque converter assembly serves as a flywheel, transmitting power to the transmission mainshaft. The transmission has four parallel shafts: the mainshaft, the countershaft, the secondary shaft, and the intermediary shaft. The mainshaft includes the 4th and 5th clutches, and gears for 3rd, 4th, 5th, and reverse (reverse gear is integral with the 5th gear). The countershaft includes gears for the final drive, 2nd, idler, 1st, 4th, 5th, and reverse (the final drive gear is integral with the countershaft). The secondary shaft includes the 1st, 1st-hold, and 2nd clutches, and gears for park, 2nd, idler, and 1st. The intermediary shaft includes the 3rd clutch, and gears for 3rd and 4th. The countershaft 5th gear and the countershaft reverse gear can be locked to the countershaft at its left end, providing 5th gear or reverse, depending with which way the selector is moved. The gears on the mainshaft, secondary shaft and intermediary shaft are in constant mesh with those on the countershaft. When certain conditions of gears in the transmission are engaged by the clutches, power is transmitted through the mainshaft, and/or to the secondary shaft, intermediary shaft, then to the countershaft to provide drive.
Electronic Control
The electronic control system consists of the powertrain control module (PCM), sensors, and seven solenoid valves. Shifting and lock-up are electronically controlled for comfortable driving under all conditions. The PCM is located below the dashboard, under the front lower panel behind the center console.
Hydraulic Control
The valve bodies include the main valve body, the regulator valve body, the secondary valve body, and the accumulator body. The main valve body contains the manual valve, the modulator valve, the shift valve A, the shift valve B, the shift valve E, the CPC valve A, the servo control valve, the lubrication check valve, the lubrication control valve, the torque converter check valve, the lock-up timing valve, the relief valve, the cooler check valve, the lock-up shift valve, and the ATF pump gears. The regulator valve body contains the regulator valve, the lock-up control valve, the servo valve, and the 3rd accumulator. The secondary valve body contains the shift valve C, the shift valve D, the CPC valve B, the CPC valve C, the reverse control valve, and the reverse CPC valve. The accumulator body contains the 1st, 1st-hold, 2nd, 4th, and 5th accumulators, shift solenoid valves A, B, C, and D. The auxiliary transmission fluid pump (ATFP) is mounted on the outside of the torque converter housing. When the vehicle comes to a stop in auto idle stop, the auxiliary transmission fluid pump starts to operate, and supply hydraulic pressure to the regulator valve. Fluid from the regulator passes through the manual valve to the various control valves. All the clutches receive fluid from the internal hydraulic circuit.
Shift Control Mechanism
To shift gears, the PCM controls shift solenoid valves A, B, and C, and automatic transmission (A/T) clutch pressure control solenoid valves A and B, while receiving input signals from various sensors and switches located throughout the vehicle. The shift solenoid valves shift the positions of the shift valves to switch the port to send hydraulic pressure to the clutches. The A/T clutch pressure control solenoid valves A and B control the CPC valves A and B to shift smoothly between lower and higher gear. This pressurizes a line to one of the clutches, engaging the clutch and its corresponding gear.
Lock-up Mechanism
The lock-up mechanism operates in the D position (2nd, 3rd, 4th, and 5th), and D3 position (2nd and 3rd). The pressurized fluid is drained from the back of the torque converter through a fluid passage, causing the torque converter clutch piston to be held against the torque converter cover. As this takes place, the mainshaft rotates at the same speed as the engine crankshaft (and the IMA motor rotor). Together with hydraulic control, the PCM optimizes the timing and volume of the lock-up mechanism. When the shift solenoid valve D is turned on by the PCM, shift solenoid valve D pressure switches the lock-up shift valve lock-up on and off. The A/T clutch pressure control solenoid valve C, the lock-up control valve, and the lock-up timing valve control the amount of the lockup conditions. The shift solenoid valve D is located on the accumulator body in the transmission, and A/T clutch pressure control solenoid valve C is mounted on the transmission housing.
Gear Selection
The shift lever has seven positions; P: PARK, R: REVERSE, N: NEUTRAL, D: DRIVE (1st through 5th gear ranges), D3: DRIVE (1st through 3rd ranges), 2: SECOND (2nd gear), and 1: FIRST (1st gear).
Starting is possible only in the P and N positions because of a slide-type neutral-safety switch.
Automatic Transmission (A/T) Gear Position Indicator
The A/T gear position indicator in the instrument panel shows which shift lever position has been selected without having look down at the shift lever.