Actual vehicle performance of the "Smoother-E Autoshift".

An electro-magnetic solenoid type actuator is used in the gearshift unit. The advantage of this actuator is its simple construction and quick operating speed, while also having the negative characteristic where the available thrust (the power to shift gears) is different based on the actuator's travel direction and position. Figure 8 shows the various examples of the different electro-magnetic solenoid thrust characteristics. Gearshifts using this solenoid have quicker operating speeds (compared to shift speeds of ordinary drivers), with the characteristic being the shift force is maximized near the end of the shift process.

Figure 8 Electro-Magnetic Solenoid Thrust

Furthermore, the load on the synchro is smaller as the rotational inertia of the wet multiple disc clutch used on the "Smoother-E Autoshift" is much smaller (approximately 1/3) than the dry clutches used in manual vehicles. Therefore, it is possible to cause gear noise when combining with a manual transmission featuring a conventional synchro function, as the gears will engage before synchronization is complete; the synchro function can not function properly during the shifting operation using only a simple control system. Examples of this can be seen in Figure 9.
Although the load on the synchro is so small that the driver will not notice this insignificant gear noise, it will have a significant impact on the durability of the synchro function. In order to guarantee the durability of the synchro function, the "Smoother-E Autoshift" studied the shifting operation of manual vehicles, and adopted a gearshift control unit that stops once near neutral. Actual examples are shown in Figure 9. In this way, we realized the combination of a simple electro-magnetic solenoid gearshift unit with a conventional manual transmission, by stopping near neutral and suppressing shift speeds at the synchro staring-point.

Figure 9 Optimum Shift Control

From how low the vehicle speed can be to lock-up the clutch on transmissions using fluid coupling like the "Smoother-E" and conventional ATs, has a big influence on the vehicle's fuel economy. On the other hand, there is the possibility of unpleasant rattling noises being created through torsional resonance of the drivetrain when the clutch is locked-up from low vehicle speeds. We were able to lock-up the clutch from low vehicle speeds in the low 10[km/h] range, by using an expanded Vulcan to operate the lock-up clutch and damper strokes. We also adopted a control system that changes the lock-up timing signal by monitoring the vehicle's positive acceleration. Examples are shown Figure 10. We improved fuel efficiency in the practical use area by locking up at vehicle speeds exceeding the rattling noise generation area during low positive acceleration, and lowering the lock-up vehicle speed when the positive acceleration is large.

Figure 10 Lock-Up Control

As with conventional ATs, the shift schedule (shift MAP) of the "Smoother-E Autoshift" is based on the output characteristics of the engine, but differs from ATs as it is set so clutch lock-up is not released during normal driving conditions. Not only is this favorable in improving the fuel economy, it also helps avoid repetitive lock and unlock (busy) conditions on the Smoother where clutch lock up takes place at low vehicle speeds. The "Smoother-E Autoshift" controls gearshifts according to the shift schedules above, and we were able to limit to a minimum any unwarranted gearshifts or actions conflicting with the driver's intentions, by monitoring vehicle and driver actions such as vehicle speeds and changes in vehicle speeds, footbrake usage, accelerator pedal movement amount and release speeds. As a result, we were able to design an automatic transmission ideal for commercial vehicles with heavy vehicle weight properties, as the low speed lock-up and MT-like gear ratios provided outstanding engine braking performance compared with conventional ATs. Due to these features, we were able to engineer an extremely user-friendly commercial vehicle automatic transmission that simultaneously achieves fuel efficiency levels comparable with MT vehicles.