Press Kit: Axor with Mercedes Power-Shift
Aksaray
Jun 13, 2007
Glossary of terms in transmission technology
Transmission
The term "transmission" usually refers to a manual or range-change transmission. Its role in the powertrain is to transfer power, and therefore to adapt the varying output P (kW) and torque M (Nm) of the (internal combustion) engine to the chang­ing parameters of weight, gradient/acceleration resistance, roll resistance and aerodynamic drag. Manual transmissions are usually of the gear-only type.
Manual transmission types
  • Manual gear shifting (with interruption of tractive power)
  • Semi/fully automated manual gear shifting
  • Power-Shift
Constant mesh transmission
In a constant mesh transmission, there are no synchronising components (synchronising rings or packages) installed between the gear wheels and the shift sleeves. A force-locked connection (= engaged gear) between the meshing gear wheels and shift sleeves is only possible if both components are moving at the same speed or are at standstill. Ensuring that they move at the same speed was once the task of the driver (double-declutching, blipping the throttle). Nowadays this is done by engine and trans­mission control systems.
Synchromesh transmission
As in a constant mesh transmission, a force-locked connection between the meshing gear wheels and shift sleeves is only possible if both components are moving at the same speed or are at standstill. Ensuring that this is the case is the task of the synchromesh.
Planetary gear set
Gear set with equal input and output axes which distributes the torque and can be shifted under load. Power is distributed via at least three planetary gears. All the ratios are achieved by selective activation of the individual moving components. Major components: centre gear, planetary gears (with planetary carrier), ring gear (internal teeth).
Transmission principle
  • Single-stage: all the ratios are produced within the main gearbox, with 6-speed transmissions typical in trucks
  • Two-stage: the "main gears" of the main gearbox (usually 3 or 4) are doubled by a downstream set of gear wheels (range- change box) or an upstream set of gear wheels (splitter box)
  • Three-stage: the "main gears" of the main gearbox (usually 3 or 4) are quadrupled by a downstream set of gear wheels (range-change box) and an upstream set of gear wheels (splitter box)
Gear-ratio steps
  • Geometrical: uniform ratio steps from gear to gear
  • Progressive: ratio steps become smaller from higher gear to higher gear
Direct drive transmission
The ratio of the highest gear is 1 to 1. The input torque is transferred to the drive axle differential without conversion, and therefore without losses.
Overdrive transmission
The input torque is reduced and the rpm is increased in one (or more) stage(s).
Ratio range
Describes the ratio between the highest and lowest gear.
Layshaft brake
Braking mechanism on the layshaft of the main gearbox. Function: the flywheel mass of the clutch is braked as it enters the transmission, so as to achieve faster synchronicity between the input and output.
Clutch brake
Acts on the clutch shaft. Action: see Layshaft brake.
Gearshift systems
Direct shift: shift lever is directly on the transmission cover, with purely manual transfer of gear shifting force (muscle power).
Remote-control shift: the transmission and shift lever are spatially separated; transfer of gear shifting force is manual (muscle power via linkages/cables), hydraulic/pneumatic (usually muscle power with servo assistance) or by external means (shift by wire).
Search
Press kit contents
Glossary of terms in transmission technology
Your Media Contact
Uta
Leitner
Product Communications Trucks / Unimog / Buses & Coaches
Phone: +49 711 17-53058
Fax: +49 711 17-91595
Download complete text
Actions
ALL press kit contents
© 2014 Daimler AG. All rights reserved. Provider | Legal Notices and Terms | CookiesPrivacy Statement, | Terms of Use