AUTOMATIC TRANSAXLE SYSTEM

Powertrain Cooperative Control

1. Integrated control of the powertrain (engine and transaxle) has created a new vehicle appeal. Powertrain cooperative control calculates the driver target motive force and target shift position in response to driver operations, the vehicle status and the road environment and performs precise control according to the engine control and ECT control conditions. As a result, driveability is improved.

2. The driver target motive force is set to achieve a long pleasant acceleration when an accelerator pedal operation performed to accelerate the vehicle is detected. Also, SPORT mode is used to provide an even sportier target motive force and target gear position according to driver accelerator pedal operation, enhancing the pleasant acceleration of the turbo engine and ensuring driving appeal.

   

   Figure 1. Acceleration when Accelerator Pedal Opening Angle is Maintained at Certain Amount

   

   *a	With control
   *b	Without control
   *c	Acceleration [G]
   *d	Vehicle Speed [km/h]

3. Previous motive force characteristics depended on the torque characteristics according to the electronic throttle opening angle of the engine and the gear ratios of each shift position. Powertrain control provides a degree of freedom to the requested torque setting for each shift position and maximizes the engine torque to achieve the driver target motive force setting. In the case of depressing the accelerator pedal to accelerate during constant-speed cruising, the frequency of downshift operations is reduced to make acceleration possible in higher gears. Also, the difference in motive force before and after a downshift operation has been reduced to achieve a linear motive force characteristic and improve control performance according to accelerator pedal operation.

   Figure 2. Motive Force Characteristics

   

Line Pressure Optimal 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 and the transaxle.

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

   

Clutch Pressure Optimal Control

1. The ECM monitors the signals from various types of sensors, such as the transmission revolution sensor (NT), allowing shift solenoid valves to minutely control the clutch pressure in accordance with engine output and driving conditions. As a result, smooth shift characteristics are achieved.

   

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 can be performed without using a 1-way clutch, making the automatic transaxle lightweight and compact.

2. Based on the information about transaxle input and output speed, engine torque and other items, the ECM controls each clutch and brake in accordance with the optimum fluid pressure and timing, in order to shift the gears. The ECM changes gears using fluid pressure circuits which enable the No. 1 clutch (C1), No. 2 clutch (C2), No. 1 brake (B1) and No. 3 brake (B3) to be controlled independently, and using the high flow SL1, SL2, SL3 and SL4 shift solenoid valves which directly control the line pressure. As a result, highly responsive and excellent shift characteristics have been achieved.

   

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 4. Flex Lock-up Operating Range

   

   Flex Lock-up Clutch Control Operation

   Gear Position	Shift Range
   	D	D5	D4	D3	D2
   1st	○	X	X	X	X
   2nd	○	○	○	○	○
   3rd	○*	○*	○*	○*	-
   4th	○*	○*	○*	-	-
   5th	○*	○*	-	-	-
   6th	○*	-	-	-	-

   Tech Tips

   ○: Available

   X: Not available

   -: Not applicable

   *: Flex lock-up clutch control also operates during deceleration.

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. When the vehicle is in 6th gear and starts decelerating, the transaxle downshifts from 6th to 5th, 5th to 4th and 4th to 3rd* before fuel cut control ends so that the fuel cut control can continue operating.

   Tech Tips

   *: The operation of 4th to 3rd downshift control is prohibited when the air conditioning is off.

   

Direct Downshift Control

1. For conventional downshift control, when shifting from 6th to 3rd or 5th to 2nd, downshifts use an intermediate gear in order to achieve smooth acceleration response. In addition to conventional control, direct downshift control is used for this model. This control skips unnecessary shifts, enabling the vehicle to downshift directly from 6th to 3rd or from 5th to 2nd.

2. When the accelerator pedal is depressed quickly, direct downshift control enables direct downshifts with a quick shift response, skipping unnecessary shifts. Direct downshift control places the emphasis on reducing the time required to achieve the target gear. Conventional downshift control is used when the accelerator pedal is depressed slowly, providing smooth acceleration response. As a result, this logic achieves downshift responsiveness in accordance with the driver's intentions.

   Figure 5. Downshift from 5th to 2nd Gear

   

Artificial Intelligence Shift Control (AI-shift Control)

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

• 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 an optimal manner. As a result, a comfortable ride has been achieved.

• Also, when SPORT mode*1 or SPORT S/S mode*2 is selected, the system switches to a shift pattern which frequently uses a low shift position selected according to the vehicle acceleration and unnecessary shift changes are suppressed. Therefore, vehicle stability is achieved and vehicle acceleration is improved.

• Furthermore, AI-shift control performs control when the shift lever is in D (including during D-range paddle active control*3) based on accelerator pedal operation and brake pedal operation. When the shift lever is moved to M (M mode control), AI-shift control cancels.




• *1: Models without AVS

• *2: Models with AVS

• *3: Models with shift paddle

1. Road Condition Support Control

   
   

   • Under road condition support control, the ECM determines from the accelerator pedal depressing angle and the vehicle speed whether the vehicle is being driven uphill or downhill. To achieve the optimal drive force while driving uphill, this control prevents unnecessary upshifts. To achieve the optimal engine brake effect while driving downhill, this control automatically performs downshifts. However, when a shift paddle operation is performed during AI-shift control, AI-shift control cancels and priority is given to D-range paddle active control.*

   
   

   • *: Models with shift paddle

     

2. 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.

     

3. Quick Brake Downshift Control

   
   

   • When sudden braking is applied, the quick brake downshift control improves re-acceleration response and engine brake force by downshifting.

     

4. G AI-shift Control

   
   

   • When the shift lever is in D, and the drive mode switches to SPORT mode*1 or SPORT S/S+ mode*2, the vehicle condition when entering a corner is comprehensively determined according to the acceleration rate in the vehicle's longitudinal and lateral directions and driver operations. As a result, downshift to the optimal shift position is performed. Furthermore, the gear position is held during turning to provide powerful acceleration when leaving the corner, making smooth acceleration control possible.

   
   

   • *1: Models without AVS

   • *2: Models with AVS

   

Multi-mode Automatic Transmission

1. On models with a shift paddle, when automatic shift control is performed with the shift lever in D, D-range paddle active control is performed by shift paddle operation. The driver can select the desired shift range by operating the shift paddle to the "+" (upshift) and "-" (downshift) sides.

2. 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 or operating the shift paddle to the "+" (upshift) and "-" (downshift) sides.

   

   *A	Models with Shift Paddle	-	-
   *1	Combination Meter Assembly Shift Position Indicator Multi Buzzer	*2	ECM
   *3	Engine	*4	Transaxle
   *5	Transmission Control Switch	*6	Shift Paddle Switch (Transmission Shift Switch Assembly)
   *a	Engine Output Control Signal	*b	Fluid Pressure Control
   *c	Shift Solenoid Valve Control Signal	*d	M Mode Position Signal
   *e	Shift-down Signal	*f	Shift-up Signal
   *g	Shift Pattern	-	-

Gear Shift Indicator

1. Gear Shift Indicator is a system to promote upshifting to the fuel-efficient and optimal gear position in accordance with the driving conditions such as the accelerator pedal opening amount and the vehicle speed, etc. when the vehicle is being driven while the shift lever is in M.

2. By driving in accordance with the upshifting recommendations indicated by the Gear Shift Indicator in the combination meter assembly, the driver can enhance environmental performance, improve fuel economy and reduce exhaust gas output within the limits of engine performance.