Mitsubishi Colt 6-speed AMT Brake Shift Transmission Module PDF Manual Reference

In cooperation with Eindhoven University of Technology, Drivetrain Innovations BV (DTI) develops a Brake Shift Transmission-module (BST-module) which can eliminate the driving torque interruptions during gearshifts of an automated manual transmission (AMT). A Mitsubishi Colt with a 6-speed AMT is in use to test this new module. The gearshift programme of this vehicle is called “Allshift”. In order to compare the performance of the BST in the future with a reference this test vehicle needs to run a test programme. Aspects like driveability, acceleration and fuel economy are very important in such a test programme. The assignment was to make and perform a test programme, which can map the most important driving characteristics of the Mitsubishi. Because of time shortage, fuel economy and emissions could not be measured within this project

In the literature many examples of problems concerning AMTs can be found. There are many developers and manufacturers of gearboxes working on solutions to overcome these problems. In this section such problems are described in order to show that there is a great market for solutions that make the AMT more driveable and popular. 2.1 AMT as “bolt on” system Motorsports and automotive technology consultant Prodrive and Italian transmission manufacturer Graziano in “Automotive Engineering International”: The problem is that current AMT systems are just as the name suggests—automated versions of existing manual gearboxes. The addition of hydraulic or electric actuators merely replicates the action of the driver-operated manual gear lever. It means that this type of AMT system is limited by the mechanical gearbox and clutch hardware and as such exhibits manual gearshift characteristics, such as slow up shifts with long torque interruptions and unpleasant torque reversal effects. The result is that unlike conventional automatics, such systems do not provide smooth shifting with carefree throttle operation, and unsatisfactory AMT clutch control leads to poor creep and park functions. 2.2 Fuel economy and costs Hitachi Group: In order to achieve widespread acceptance as a replacement for conventional transmissions, the next generation transmission must provide the good fuel economy of an MT, the effortless shifting of an AT, and must also be compact and affordable. Unfortunately, the conventional AMT fails to achieve the seamless shifting of an AT and the twin-clutch AMT is difficult to implement compactly and cost effectively.

In this section the working principle of the AMT is explained. The AMT in our test vehicle -a 1.5 litre Mitsubishi Colt- is a 6-speed gearbox with a shift programme which is called “Allshift”. The gearbox consists of speed gear sets with a special layout with two individual drums, which control the shift forks of the different gears. The so-called twin drum shift system is the hart of quicker shifting. Each drum moves a set of two forks, which are connected, to the synchromeshes. As can be seen in figure 1 drum one is connected to the shift fork controlling 1st and 3rd gear and the shift fork controlling 5th and 6th gear and drum 2 is connected to the shift fork controlling 2nd and 4th gear and reverse. By controlling both drums we are able to move the synchromesh towards the 2nd gear at the same time as we release the synchromesh from the 1st gear when shifting from 1st to 2nd gear

Brake Shift Technology (BST) The main design objectives of the BST are to eliminate the driving torque interruption during gearshifts and design the BST module as a plug-in module for the AMT. Therefore, a planetary gear and brake are added to the AMT. In Figure 4 the schematic layout of a BST power train is depicted. The annulus gear is connected to the brake, the carrier gear is connected via a reduction to the secondary transmission shaft and the sun gear is connected to the engine flywheel. In this configuration, the BST system acts as a parallel path over the AMT through which torque transmittal to the wheels can be continued when the clutch is open. The geometric parameter z and the reduction are chosen such that the sun gear’s speed is zero between 3rd and 4th gear. For that reason the BST can only eliminate drive torque interruption in the first four gears

In order to compare the performance of the BST in the future with a reference, the test vehicle needs to run a test programme. Table 1 is a representation of the tests performed with the vehicle. One can see that there is a distinction between 3 test-categories. The tests are performed in order to map the driveability and the acceleration performance of the car. It was not possible to do a fuel economy test in this stage of development. All these tests where firstly done on a roller bench. The acceleration-tests from zero to the maximum speed are done with different acceleration pedal percentages. This is done in order to check if there is a difference in time for opening the clutch and synchronising the gears and to measure the difference in torque at the driveshaft. The 100% throttle measurement is also important to compare the acceleration from 0 to 100 km/h, which is an important value when comparing car performances. These tests are done twice, with cold and hot engine, so the engine heat wouldn’t influence different measurements

Furthermore acceleration-tests have been performed at starting speed of 40, 60 and 80 km/h. The downshift situation occurs during a so-called “kick-down” when for a relatively short period extra toque is needed at the wheels, for example, to overtake another vehicle in critical situations. Because our test vehicle has apart from the 100% throttle position a special kick-down button under the acceleration pedal we did this test for both situations. At 60 km/h the tests were done starting both in 4th and 5th gear. The test vehicle in auto mode shifts to 5th gear at this speed. This is probably done in order to save fuel. To inhibit the 4th gear at 60 km/h we drive in manual mode, which is overruled when pushing a kick-down. A practical experience with the AMT gearbox is the reason for doing some special cornering tests. The AMT will shift back when one is driving at a certain low speed in 2nd or 3rd gear and one kicks down the accelerator pedal. This is very annoying because the gearshift will take a large amount of time just when the driver regrets for extra torque to the wheels. This can even lead to dangerous situations in daily traffic. Therefore we want to know what BST can improve on this aspect. This will become clearer in the simulations and animations of these events. (Chapter