Injector for reductant delivery unit having fluid volume reduction assembly

A reductant delivery unit, comprising:

• a fluid injector having a fluid inlet disposed at a first end of the fluid injector for receiving a reductant, and a fluid outlet disposed at a second end of the fluid injector for discharging the reductant, the fluid injector defining a fluid path for the reductant from the fluid inlet to the fluid outlet, the fluid injector comprising:
• a tube member having an end disposed at the fluid inlet of the fluid injector, the tube member configured to pass reductant along the fluid path;
• a filter disposed in the tube member proximal to the fluid inlet of the fluid injector;
• a volume reduction member disposed in the tube member downstream of the filter, relative to a direction of reductant flow along the fluid path from the fluid inlet to the fluid outlet of the fluid injector, the volume reduction member contacting an inner surface of the tube member and including a bore defined through the volume reduction member, the bore defining at least a portion of the fluid path through the fluid injector, the bore having a smaller diameter than an outer diameter of the volume reduction member and the volume reduction member occupying a volume in the tube member such that the volume reduction member reduces a volume of the fluid path for reductant to occupy in the fluid injector;
• a cap member in which the filter is disposed, the cap member engaged with and secured to the volume reduction member such that the filter, the volume reduction member and the cap form a single member;
• a movable armature disposed within the fluid injector;
• a spring disposed within the fluid injector and having a first longitudinal end which contacts the movable armature and a second longitudinal end;
• a spring adjustment tube disposed upstream, relative to the direction of reductant flow along the fluid path, of the movable armature and the spring, and having a first longitudinal end which contacts the second longitudinal end of the spring, and a second longitudinal end which is adjacent to and contacts the volume reduction member without being disposed within the volume reduction member;
• a stationary pole piece disposed within the fluid injector and having a first longitudinal end which is engaged or spaced apart from the movable armature and a second longitudinal end, the stationary pole piece including a through-bore in which the spring adjustment tube is partly disposed;
• and
• a volume compensation member constructed from a compressible material and disposed in a compressed state between and contacting the second longitudinal end of the pole piece and a downstream end, relative to the direction of reductant flow along the fluid path, of the volume reduction member.