AUTOMATIC TRANSAXLE SYSTEM

Clutch Pressure Control

1. The ECM monitors the signals from various types of sensors, such as the transmission revolution sensor (NT) and transmission revolution sensor (NC), allowing the linear solenoid valves SLT, SL1, SL2, SL3, SL4, SL5, SL6 and SLU to precisely control the clutch pressure in accordance with engine output and driving conditions. As a result, the transmission has smooth shift characteristics.

   

Clutch-to-Clutch Pressure Control

1. Clutch-to-Clutch pressure control is used for shift control. As a result, shift control in 2nd gear or above is possible without using a one-way clutch, making the automatic transaxle lightweight and compact.

2. Using the fluid pressure circuit, which enables the clutches and brakes (C1, C2, C3, C4, B1 and B2) to be controlled independently, and the high flow SL1, SL2, SL3, SL4, SL5, and SL6 linear solenoid valves, which directly control the clutch pressure, the ECM controls each clutch and brake accordingly with the optimum fluid pressures and timings in accordance with the information transmitted by the sensors, and then shifts the gears. As a result, the transmission has highly responsive and excellent shift characteristics.

   

Line Pressure Control

1. The line pressure is controlled using shift solenoid valve SLT.

2. Through the use of shift solenoid valve SLT, the line pressure is optimally controlled in accordance with the engine torque information, as well as with the internal operating conditions of the torque converter clutch assembly and the automatic transaxle assembly.

3. Accordingly, the line pressure can be accurately controlled in accordance with the engine output, traveling condition, and the ATF temperature, thus realizing smooth shift characteristics and optimizing the workload of the oil pump (reducing parasitic losses).

   

All Range Lock-up

1. Compared to the previous model, the UA80E performs lock-up control at lower speeds as well as at higher opening angles, enabling direct transmission of power similar to a manual transmission. Furthermore, the increased rate of engagement contributes to improved fuel efficiency.

2. By increasing the lock-up range, and suppressing engine revving, smooth driving with high responsiveness and linearity is realized.

   

   *1	UA80E L/U Range
   *2	Accelerator Pedal Angle
   *3	Conventional A/T
   *4	Vehicle Speed

   

3. Previously, lock-up was cancelled when downshifting to avoid shift shock, but with a torque converter adopting a multiple disc lock-up clutch as well as precision control taking into account transient characteristics of engine torque and hydraulic pressure, it has become possible to maintain lock-up continuously.

4. In 1st gear and the low engine speed regions of 2nd and higher gears, lock-up is not performed, and the torque converter function is employed to realize smooth driving.

   Gear Position	Shift Lever Position
   	D, M
   1st	X
   2nd	○*(During acceleration)
   3rd	○*
   4th	○*
   5th	○*
   6th	○*
   7th	○*
   8th	○*

   ○: Operates

   X: Does not operate

   *: Except at low engine speed range

Flex Lock-up Clutch Control

1. During acceleration, partial control of the power transmission between the lock-up clutch and torque converter greatly boosts transmission efficiency in accordance with the driving conditions, improving fuel economy.

2. Even when the vehicle is decelerating (the accelerator pedal is released), flex lock-up clutch control operates. As a result, the fuel-cut area is expanded and fuel economy is improved.

3. By allowing flex lock-up clutch control to continue operating during gearshifts, smooth torque transmission is obtained. As a result, fuel economy and driveability are improved.

4. For flex lock-up clutch control, H infinity (H∞) control theory is used to achieve a high level of system stability and response to various characteristic changes.

   

   Figure 1. Flex Lock-up Operating Range

   

   Flex Lock-up Clutch Control Operation

   Gear Position	Shift Range
   	D, M
   1st	X
   2nd	○
   3rd	○
   4th	○*
   5th	○*
   6th	○*
   7th	○*
   8th	○*

   ○: Operates

   X: Does not operate

   *: Flex lock-up clutch control also operates when the vehicle decelerates.

Flex Start Control

1. Flex start control suppresses unnecessary engine speed increases to achieve improved fuel economy.

2. When starting off, the lock-up clutch operates frequently to improve power transmission efficiency, making it possible to decrease the engine speed.

3. Also, since flex lock-up can be quickly performed even after upshifting to the 2nd gear due to flex lock-up being performed when starting off, driveability and improved fuel economy are achieved.

   

Deceleration Downshift Control

1. The ECM performs downshift control to help prevent the engine speed from decreasing, thus keeping fuel cut control operating for as long as possible. In this way, fuel economy is improved.

2. In this control, the transmission downshifts from 7th to 3rd before fuel cut control ends when the vehicle is decelerated in the 8th gear, so that fuel cut control continues operating.

   

Direct Connected Downshift

1. Smooth vehicle acceleration changes and linear changes in engine speed during downshifting were realized.

2. By precisely controlling hydraulic pressure, downshifting from a high gear to a low gear is accomplished with a smooth shift through the intermediate gears without any unevenness of engine speed or drive force.

   

   *1	Conventional A/T
   *2	Accelerator Pedal Angle
   *3	Engine Speed
   *4	Vehicle's Acceleration Forces

Artificial Intelligence Shift Control (AI-shift Control)

1. The automatic transaxle gear is determined by the shift pattern, which uses the vehicle speed and throttle valve opening angle.

2. Additionally, AI-shift control enables the ECM to estimate the road conditions and the driver's intention in order to automatically control the shift pattern in the optimal manner. As a result, a comfortable ride has been achieved.

3. The AI-shift control includes road condition support control and driver's intention support control.

4. The AI-shift control determines optimal transaxle control based on input signals and automatically changes the shift pattern.

   

5. Under road condition support control, the ECM determines the throttle opening angle and the vehicle speed in addition to whether the vehicle is being driven uphill or downhill. To achieve optimal drive force while driving uphill, this control prevents unnecessary upshifts. To achieve the optimal engine braking while driving downhill, this control automatically performs downshifts.

   

6. Driver's Intention Support Control

   
   

   • The driver's intention is estimated based on the accelerator pedal depression angle and vehicle condition to switch to a shift pattern that is well-suited to the driver.

     

7. Driver Intention/Driving Scene Support Control

   
   

   • Driver intention/driving scene support control selects the optimal gear position according to the driver's intentions and the driving scene at that point in time.

   • When the driver is driving in a relaxed manner, a high gear position is selected to emphasize fuel efficiency.

   • When the driver is driving in a sporty manner, a low gear position is selected to emphasize drive force and responsiveness.

   • Even if the driver has the D range selected while sporty driving is performed on winding roads and race tracks, shifting is performed using a shift pattern that makes it feel like gear positions are being selected manually, achieving a high-speed responsive drive.

     Tech Tips

     Driver intention/driving scene support control will be canceled when Eco mode is selected.

     

Multi-mode Automatic Transmission

1. When the shift lever is moved to M, the system changes from automatic shift control to M mode control, where the driver can manually change the gear position by moving the shift lever to the "+" (upshift) and "-" (downshift) sides.

2. When the vehicle is being driven at a speed that is higher than the maximum safe speed for a downshift, any attempt to shift to a lower range by operating the shift lever will not be performed. This is done in order to protect the automatic transaxle. In this case, the ECM sounds the buzzer in the combination meter assembly twice to alert the driver.

   

3. Under this control, the ECM performs optimal shift control within the usable gear range that the driver selects. As with an ordinary automatic transaxle, it shifts to 1st gear when the vehicle is stopped.

4. The shift lever position and the shift range are indicated by the shift position indicator in the combination meter assembly (The shift range is shown only when the M mode control).

5. In order to prevent excessive engine speed, a function was adopted that automatically selects a higher shift range before engine speed becomes too high.

6. In order to protect the automatic transmission, a function is adopted that automatically selects a higher shift range when the fluid temperature is high.

   Usable Gear Chart:

   Shift Range	Shift Position Indicator	Usable Gear
   M8	8	8th
   M7	7	7th
   M6	6	6th
   M5	5	5th
   M4	4	4th
   M3	3	3rd
   M2	2	2nd
   M1	1	1st

7. Gear Hold Control

   
   

   • Gear shifting will not be performed under gear hold control as long as the shift lever is not operated. This makes it possible to make efficient use of the highest engine speeds. However, in the following cases, operation of gear hold control is limited.

   
   

   1. When the vehicle speed and engine speed decrease, a downshift is performed.

   2. When the engine speed reaches the red zone, an automatic upshift is performed.

   3. When the ATF temperature is high, gear shifting will be performed automatically.

   4. When the ATF or engine coolant temperature is low, gear shifting will be performed automatically.

8. Blipping Downshift Control

   
   

   • The blipping downshift control regulates each clutch and brake using the clutch to clutch pressure control, allowing them to be engaged smoothly and disengaged quickly. In addition, fuel injection volume is increased and engine speed is boosted by the powertrain cooperative control, thus ensuring proper engine brake force. In this way, a smooth and quick downshift is achieved.

   • The blipping downshift control activates by downshifting with the shift lever in D or M.

     Figure 2. Downshift from 3rd to 2nd Gear