Auxiliary lift axle suspension

Abstract

A lift axle suspension adapted to be mounted to a vehicle frame for selectively supporting a vehicle frame on an axle with ground engaging wheels includes a pair of trailing arm assemblies each of which includes a hanger bracket adapted to be mounted to the vehicle frame, a trailing arm pivotally mounted to the hanger bracket for pivotal movement relative to the frame about a pivot axis, a spring operably connecting the trailing arm to the vehicle frame for resisting the pivotal movement of the trailing arm about the pivotal axis toward the frame, an inflatable lift bag operably connecting the trailing arm to the hanger bracket and for selectively raising the trailing arm relative to the frame when the lift bag is inflated and an axle rigidly mounted to the trailing arm. The iift bag is positioned inboard of the hanger bracket and the trailing arm. The hanger bracket is adapted to be mounted to the outboard side of the frame rail. Preferably, the lift bag is laterally spaced from a plane in which the trailing aim pivots. The hanger bracket is U-shaped in horizontal cross section and the hanger bracket has a stiffening element mounted vertically within sidewalls of the U-shaped cross section. The pivot axis between the trailing arm and the hanger bracket is between forward and rearward ends of the trailing arm. The axle is mounted rearwardly of the pivot axis and the lift bag is mounted forwardly of the pivot axis. Substantially the entire lift bag is located forwardly of the pivot axis and above the forward end of the trailing arm.