Main Components and Functions
Main Components and Functions
This transmission system has been divided into 6 sub-systems that relate to specific functional areas. These sub-systems are:
- a clutch/actuator system which transfers engine crankshaft speed and torque.
- an active input system which includes applied clutch disc, bearings, speed gears and output shaft.
- a passive input system which includes disengaged clutch disc, bearings, speed gears and an output shaft system.
- a synchronizer/engagement system which includes a torque carrying interface between speed gear and output shaft.
- a differential system that is the final drive output system which includes drive pinions, ring gear, support bearings and side gears.
- an electrical control system which includes control system logic, Transmission Control Module (TCM), speed sensors, electric motors and a wire harness.
Sub-System Overview
Clutch/Actuator System
The clutch and actuator sub - system consists of engine crankshaft mounted rotating components. These include, a center flywheel, odd and even clutch pressure plates, clutch actuating mechanisms and engagement components. The clutch actuators are independent systems within the clutch housing that apply an axial force to the clutch diaphragm springs causing their respective clutch to apply. This apply force is reacted back into the transaxle through the input shaft unlike a manual transaxle dry clutch system, no thrust is applied to the engine crankshaft. Normally the clutch capacity commands are mutually exclusive (to prevent tie-up) with minor overlaps to allow synchronous shifting. A clutch "touch point" position must be established by a learning algorithm within the system software. Establishing the touch point is the system's method for ensuring that the displacement-based clutch actuation system is properly calibrated. This is necessary so that the clutch capacity can be controlled correctly by the TCM (Transmission Control Module) and be engaged and released to the required torque capacity and within the required time.
Active Input System
The active input system of the transaxle can be viewed as two transaxles within a common housing (one for 1st, 3rd & 5th and another for Reverse, 2nd, 4th & 6th). For any driving gear there is one transaxle actively engaged in the power flow between the engine and the wheels and one that is disconnected or passive. This system will discuss considerations for the driving input shaft system whether it be the ODD or EVEN transaxle. The driving or active input shaft system consists of the input shaft and clutch disc, support bearings and the meshed speed gears with their needle roller bearings.
Passive Input System
The passive input system can be viewed as two transaxles within a common housing (one for 1st, 3rd & 5th and another for Reverse, 2nd, 4th & 6th). For any driving gear there is one transaxle actively engaged in the power flow between the engine and the wheels and one that is disconnected or passive. The non-driving, or passive input shaft system consists of the input shaft and clutch disc, support bearings and the meshed speed gears with their needle roller bearings.
Synchronizer Systems
The synchronizer systems are comprised of single and dual cone synchronizer systems. The synchronizers are designed to act as the torque carrying interfaces between each speed gear and corresponding output shaft. The synchronizer design and function are similar to manual transaxle operations.
Basic Synchronizer Hardware Operation
As in manual transaxle operation, gear pre-selection is made by sliding the synchronizer sleeve towards a speed gear. This causes the internal splines of the synchronizer sleeve to bridge a gap between the output hub and the external spline feature of the speed gear, thus transmitting speed and torque between the gear and output shaft. Synchronizers are small cone wet friction clutches mounted to the transaxle output shaft. They are used to bring the rotation speed of the engaging speed gear in sync with the output shaft speed. After synchronous speed has been attained the final power flow connection is made possible and the synchronizer sleeve is permitted to pass by and engage the external spline teeth on the speed gear.
Shift Fork Mechanical System Overview
The shift system consists of two independent sub-systems for controlling the transaxle synchronizer pre - selections and engagements. Using this arrangement provides an independent control of the two transaxles and a mechanical interlock that prevents two gears within the same transaxle from being engaged simultaneously. The TCM (Transmission Control Module) houses two electric motors that mesh with and drive the first double gear wheel, which drives the second double gear which finally drives the shift drum. Gearing between the shift motors and the drums reduce speed and multiply torque. Position sensors in the TCM (Transmission Control Module) detect feedback of the motor angular position. Shift drum position is learned by the TCM (Transmission Control Module) during a teach-in process that involves rotating each drum against hard stops located on the shift drum and the transaxle housing.
Differential System
The output shaft system consists of the output shaft gears, differential ring (final drive) gear and the differential assembly. Typically when a vehicle is traveling down the road both wheels are rotating at the same speed; however, when a vehicle is turning, the outside wheel must travel a greater distance than the inside wheel. To do this, in the same time, the outside wheel must rotate faster than the inside wheel. The differential is designed to provide speed compensation for the wheels to allow the vehicle to negotiate turns smoothly.
Electrical Control System
Electrical components function:
- Input shaft speed sensor 1 measures the speed and the rotating direction of the input shaft 1. The input shaft can be stationary.
- Input shaft speed sensor 2 measures the speed of the input shaft 2. The rotation direction is not measured.
- OSS (Output Shaft Speed) sensor measures the speed of the output shaft. The rotation direction is not measured.
- Two electrical clutch motors are used to actuate the dual clutch in the transmission- one motor for each clutch. The motors work independently of each other. When the clutch is fully closed, the clutch motor provides the holding torque in addition with spring force. The clutch motors work against a clutch spring and self disengage with no electrical power.
- TR (Transmission Range) sensor detects the angular position of the shift lever shaft.
- TCM (Transmission Control Module) is an assembly of an electronic module, sensors, and electrical motors.
- The TCM (Transmission Control Module) 's electrical motors (2) control the mechanical shift fork system. The shift drums are the link from electrical to mechanical operation. The TCM (Transmission Control Module) collects incoming vehicle, transmission and driver demand signals and uses these signals to select the next required gear ratio. The TCM (Transmission Control Module) receives transmission sensor signals and transmits clutch motor current through externally mounted wire harness. The TCM (Transmission Control Module) uses these signals to control shift feel.