It meant the Magpies became only the fourth side to win promotion to the top flight with 100 points or more - a feat first achieved by arch rivals Sunderland 11 years ago.
Chris Hughton's men were helped by the sending off of former Newcastle defender Peter Ramage just 40 seconds into the second half.
Geordie Ramage, a lifelong Newcastle fan who played for the club for five years, was shown a straight red card after bringing down Shola Ameobi.
Ramage was distraught and his dismissal was a blow for Rangers, who were the better side before the break,
Alejandro Faurlin, Dusko Tosic and Jay Simpson had early efforts saved by Newcastle keeper Tim Krul, while Akos Buzsaky volleyed over and Tamas Priskin shot wide as QPR continued to have the upper hand.
Newcastle's best moment of the first half came when former R's winger Wayne Routledge, back at Loftus Road for the first time since his January move to Tyneside, had a shot saved by keeper Radek Cerny.
Even after the loss of Ramage, QPR kept up the pressure and thought they had gone ahead when Priskin netted after being put through by Simpson, but the Hungarian striker was offside.
Lovenkrands, on the other hand, managed to stay onside and break the deadlock in the 71st minute.
The Dane perfectly timed his run to latch onto Joey Barton's pass before dinking the ball over Cerny and into the net.
Simpson missed Rangers' best chance to equalise when he fired straight at Krul after being picked out by the impressive Faurlin.