How can I linear increase to Location Value I want want to lineer increase to Location Value. 
How can i do that? 
For example i have a car and i need to go 100 meter. 
But i just know this car can go 20 meter. 
I want to go 20 meter and again 20 meter and again and agian. 
I don't want to go 100.
You only need two keyframes to animate a value with a constant linear variance.

By default an fcurve uses a constant extrapolation, that is it stays at the last animated value. You can change this in the Graph Editor or the Dopesheet in the Channel->Extrapolation Mode menu or &#8679; ShiftE.



If you want it to stop after a certain time, you can go to that frame and insert a new keyframe, then reset the extrapolation back to constant.