Elasticity (automotive engineering)

The elasticity of a motor vehicle drive describes the fact that the nominal speed of a drive unit is greater than the speed at which the unit delivers the highest torque; The nominal speed is the speed at which the nominal power is delivered. The further the speed of the maximum torque is (relatively) away from the speed of the maximum power, the more elastic the drive. The more elastic an engine, the greater the economical driving range , also known as the elastic range , which lies between maximum torque and maximum power. As a rule, the greatest possible engine elasticity is sought in motor vehicles in order to make the individual transmission gears effectively usable over the largest possible speed range. In this way, for example, increases in load (in the sense of an increase in driving resistance ), for example due to a hill start or a headwind, can be managed without changing gear despite falling speed.

Calculation of the motor elasticity

When it comes to motor elasticity, a distinction is made between torque elasticity, speed elasticity and the overall elasticity of the motor (according to Wolfgang Flössel):

Torque elasticity

{\ displaystyle e_ {Md} = {\ frac {Md_ {2}} {Md_ {1}}}}

With

{\ displaystyle Md_ {1}}

= Torque at max. power

{\ displaystyle Md_ {2}}

= max. Torque

Speed elasticity

{\ displaystyle e_ {n} = {\ frac {n_ {1}} {n_ {2}}}}

With

{\ displaystyle n_ {1}}

= Speed at max. Power (nominal speed)

{\ displaystyle n_ {2}}

= Speed at max. Torque

Total elasticity of the motor

{\ displaystyle E = e_ {Md} \ cdot \; e_ {n} = {\ frac {Md_ {2}} {Md_ {1}}} \ cdot \; {\ frac {n_ {1}} {n_ { 2}}}}

Sometimes the speed elasticity is called "overall elasticity" and the torque elasticity is called "engine elasticity"; is the "elastic area". ${\ displaystyle n_ {1} -n_ {2}}$

literature

Karl-Heinz Dietsche, Thomas Jäger, Robert Bosch GmbH: Automotive pocket book. 25th edition, Friedr. Vieweg & Sohn Verlag, Wiesbaden, 2003, ISBN 3-528-23876-3
Max Bohner, Richard Fischer, Rolf Gscheidle: Expertise in automotive technology. 27th edition, Verlag Europa-Lehrmittel, Haan-Gruiten, 2001, ISBN 3-8085-2067-1
Jan Drummans: The car and its technology. 1st edition, Motorbuchverlag, Stuttgart, 1992, ISBN 3-613-01288-X