Injector for reductant delivery unit having fluid volume reduction assembly

Abstract

A fluid injector includes a fluid inlet, a fluid outlet, a fluid path from the fluid inlet to the fluid outlet; a tube; a filter disposed in the tube proximal to the fluid inlet; and a calibration filter tube disposed downstream of the filter. The calibration filter tube includes a first end portion adjacent the filter and an axial throughbore, the throughbore defining at least a portion of the fluid path through the fluid injector. An actuator unit is disposed within the fluid injector and engages a second end of the calibration filter tube. A valve assembly operatively couples to the actuator unit. A position of the calibration filter tube within the tube sets an opening force of the valve assembly. A cap member has a sidewall defining an inner space receiving the filter, and the sidewall contacts and attaches to the first end of the calibration filter tube.

What is claimed is: 
     
         1 . 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 or near 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 calibration filter tube disposed in the tube member downstream of the filter, relative to a direction of flow of reductant along the fluid path from the fluid inlet to the fluid outlet of the fluid injector, the calibration filter tube having a first end portion adjacent the filter and a second end, and further including a bore defined in an axial direction through the calibration filter tube, the bore defining at least a portion of the fluid path through the fluid injector; 
 an actuator unit disposed within the fluid injector downstream of the calibration filter tube, the actuator unit engaging the second end of the calibration filter tube; 
 a valve assembly operatively coupled to the actuator unit, wherein a position of the calibration filter tube within the tube member at least partly sets an opposing opening force for the valve assembly; and 
 a volume reduction member having a bore though which the calibration filter tube extends, the volume reduction member occupying a space between an outer surface of the calibration filter tube and an inner surface of the tube member, 
   wherein the filter, calibration filter tube and the volume reduction member form a unitary subassembly component of the fluid injector.   
     
     
         2 . The reductant delivery unit of  claim 1 , wherein the volume reduction member is formed from compressible material. 
     
     
         3 . The reductant delivery unit of  claim 2 , wherein the compressible material comprises one of a rubber composition and closed cell foam. 
     
     
         4 . The reductant delivery unit of  claim 2 , wherein the volume reduction member comprises a sidewall, the sidewall of the volume reduction member undulating in a direction along a longitudinal axis of the fluid injector. 
     
     
         5 . The reductant delivery unit of  claim 1 , wherein the fluid injector further comprises a cap member including a sidewall defining an inner space into which the filter is disposed, the sidewall contacting the first end of the calibration filter tube. 
     
     
         6 . The reductant delivery unit of  claim 5 , wherein the first end portion of the calibration filter tube is disposed in the inner space of the cap member. 
     
     
         7 . The reductant delivery unit of  claim 5 , wherein the first end portion of the calibration filter tube is attached to the sidewall of the cap member such that the calibration filter tube, the cap member, the volume reduction member and the filter form the unitary subassembly component of the fluid injector. 
     
     
         8 . The reductant delivery unit of  claim 1 , wherein the actuator unit comprises a pole piece disposed in a fixed position within the fluid injector and including a bore defined axially through the pole piece, an armature movably positioned within the fluid injector and including a pocket, a coil disposed in proximity to the pole piece and the armature, and a spring disposed at least partly in the pocket of the armature, the calibration filter tube is disposed in the bore of the pole piece such that the second end of the calibration filter tube contacts the spring, and the spring biases the armature away from the pole piece in an absence of current passing through the coil so that the valve assembly is placed in a closed position to prevent reductant from passing through the fluid outlet. 
     
     
         9 . The reductant delivery unit of  claim 8 , wherein the calibration filter tube comprises a second portion which axially extends from the first end portion of calibration filter tube, and a third portion disposed between the second portion and the second end of the calibration filter tube, the volume reduction member is disposed around the second portion, the third portion is disposed in the bore of the pole piece, and a downstream end of the volume reduction member is adjacent an upstream end of the pole piece, relative to the direction of flow of reductant along the fluid path. 
     
     
         10 . The reductant delivery unit of  claim 9 , wherein an outside diameter of the second portion of the calibration filter tube is greater than an outside diameter of the third portion thereof. 
     
     
         11 . A fluid injector, comprising:
 a fluid inlet disposed at a first end and configured to receive a fluid, and a fluid outlet disposed at a second end of the fluid injector for discharging the fluid, the fluid injector defining a fluid path for the fluid from the fluid inlet to the fluid outlet;   a tube member having an end disposed at or near the fluid inlet of the fluid injector, the tube member configured to pass fluid along the fluid path;   a filter disposed in the tube member proximal to the fluid inlet of the fluid injector;   a calibration filter tube disposed in the tube member downstream of the filter, relative to a direction of flow of fluid along the fluid path from the fluid inlet to the fluid outlet of the fluid injector, the calibration filter tube having a first end portion adjacent the filter and a second end, and further including a bore defined in an axial direction through the calibration filter tube, the bore defining at least a portion of the fluid path through the fluid injector;   an actuator unit disposed within the fluid injector downstream of the calibration filter tube, the actuator unit engaging the second end of the calibration filter tube;   a valve assembly operatively coupled to the actuator unit, wherein a position of the calibration filter tube within the tube member sets an opposing opening force of the valve assembly; and   a cap member having a sidewall defining an inner space into which the filter is disposed, the sidewall contacts and is attached to the first end of the calibration filter tube such that the cap member, the filter and the calibration filter tube form a single subassembly component of the fluid injector.   
     
     
         12 . The fluid injector of  claim 11 , further comprising a volume reduction member having a bore though which the calibration filter tube extends, the volume reduction member occupying a space between an outer surface of the calibration filter tube and an inner surface of the tube member, the volume reduction member, the cap member, the filter and the calibration filter tube form the single subassembly component of the fluid injector. 
     
     
         13 . The fluid injector of  claim 12 , wherein the volume reduction member is compressible. 
     
     
         14 . The fluid injector of  claim 13 , wherein volume reduction member is constructed from one of a rubber composition and a closed cell foam. 
     
     
         15 . The fluid injector of  claim 12 , wherein the volume reduction member comprises a sidewall, the sidewall of the volume reduction member undulating along a longitudinal axis of the fluid injector. 
     
     
         16 . The fluid injector of  claim 12 , wherein the actuator unit comprises a pole piece disposed in a fixed position within the fluid injector and including a bore defined axially through the pole piece, an armature movably positioned within the fluid injector and including a pocket, a coil disposed in proximity to the pole piece and the armature, and a spring disposed at least partly in the pocket of the armature, wherein the calibration filter tube is disposed in the bore of the pole piece such that the second end of the calibration filter tube contacts the spring, the spring biases the armature away from the pole piece in an absence of current passing through the coil so that the valve assembly is placed in a closed position to prevent fluid from passing through the fluid outlet. 
     
     
         17 . The fluid injector of  claim 15 , wherein the calibration filter tube comprises a second portion which axially extends from the first end portion of the calibration filter tube, and a third portion disposed between the second portion and the second end of the calibration filter tube, the volume reduction member is disposed around the second portion, the third portion is disposed in the bore of the pole piece, and a downstream end of the volume reduction member is adjacent an upstream end of the pole piece, relative to the direction of flow of fluid along the fluid path. 
     
     
         18 . The fluid injector of  claim 17 , wherein an outside diameter of the second portion of the calibration filter tube is greater than an outside diameter of the third portion thereof. 
     
     
         19 . The fluid injector of  claim 17 , wherein the calibration filter tube further comprises an annular tab which extends from the third portion of the calibration filter tube, is disposed within the bore of the pole piece and forms a press fit engagement therewith. 
     
     
         20 . The fluid injector of  claim 11 , wherein the first end portion of the calibration filter tube is disposed in the inner space of the cap member.