acceleration - How does dark energy allow the universes expansion to accelerate?

I was wondering how dark energy is effecting the rate at which the universes expansion occurs.

Answer

How does dark energy allow the universes expansion to accelerate?

I hope that it is clear to the questioner and the readers that the horse pulling dark energy is the experimental observation that the expansion of the universe is accelerating. Dark energy is proposed as the reason why the expansion is accelerating. It is called "dark" because it is not interacting with normal matter, but only with the space time structure.

Take a three dimensional explosion in space. The fragments will fly off and steadily expand from each other. If one observed that their expansion was accelerating, it would mean that extra energy was appearing in the system ( explosives in the fragments? ). The same reasoning applies. The geodesics in space were supposed to follow the Big Bang (after the inflationary period) expanding at a steady rate imposed by the initial impetus, but in an accurate model decelerating slowly because of the weak effect of gravity which is attractive. The observation that the expansion is accelerating introduced the simple concept of extra energy entering the local four dimensional space , and called "dark energy". It is still a matter for research.