KR20190030632A - Injector for reductant delivery unit having fluid volume reduction assembly - Google Patents

Abstract

The present invention relates to an injector for a reductant delivery unit (RDU) having a fluid volume reduction assembly, which is improved for a non-purge selective catalyst reduction (SCR) system. According to the present invention, the injector for an RDU for a fluid volume reduction assembly comprises 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 adjacent to the fluid inlet, and a correction filter tube disposed on a downstream of the filter. The correction filter unit comprises a first end part portion adjacent to the filter and an axial through-bore. The through-bore defines at least a part of the fluid path through the fluid injector. An actuator unit is disposed in the fluid injector and is engaged with a second end part of the correction filter tube. A valve assembly is coupled to the actuator unit to be able to operate. The position of the correction filter tube in the tube sets an opening force of the valve assembly. A cap member has a sidewall to define an inner space for storing the filter and the sidewall is attached by coming in contact with a first end part of the correction filter tube.

Description

≪ Desc / Clms Page number 1 > INJECTOR FOR REDUCTANT DELIVERY UNIT HAVING FLUID VOLUME REDUCTION ASSEMBLY < RTI ID = 0.0 >

Cross-reference to related application

This application is a continuation-in-part of U.S. patent application __________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ United States Patent Application ___ (Attorney Docket No. 2017P03660US), filed in the name of "SEAL MEMBER FOR REDUCTANT DELIVERY UNIT"; (Attorney Docket No. 2017P03659US), filed in the name of the inventor of the present invention and entitled " INJECTOR FOR REDUCTANT DELIVERY UNIT HAVING FLUID VOLUME REDUCTION ASSEMBLY. &Quot; The entire contents of which are incorporated herein by reference.

Technical field

The present invention generally relates to a fluid ejector of a reductant delivery unit (RDU), and more particularly to a robust RDU fluid ejector for non-purge applications.

In Europe and North America, emissions regulations are particularly favored for lean burn technologies such as stratified-charge spark ignition engines (usually direct injection) and compression ignition (diesel) engines operating in lean and very lean conditions, Processing system. Lean combustion engines exhibit high levels of NOx emissions (NOx), which is difficult to handle in an oxygen-rich exhaust gas environment, which is characteristic of lean burns. An exhaust gas aftertreatment technology for treating NOx in this state is currently being developed.

One of these techniques involves a catalyst that catalyzes the reaction of ammonia (NH ₃ ) with exhaust gas nitrogen oxides (NO x) to produce nitrogen (N ₂ ) and water (H ₂ O). This technique is referred to as Selective Catalytic Reduction (SCR). Because ammonia is difficult to handle in an automotive environment in its pure form, this system uses diesel exhaust gas fluid (DEF) and / or is generally liquid aquatic (CO (NH ₂ ) ₂ ) at a concentration of 32% Urea solution is generally used. This solution is called AUS-32 and is also known by the commercial name AdBlue. The reducing agent solution is typically delivered to the hot exhaust gas stream using an injector and converted to ammonia before entering the catalyst. More specifically, the solution is delivered to the hot exhaust stream and is converted to ammonia in the exhaust gas after pyrolysis with ammonia and isocyanic acid (HNCO) or after pyrolysis. The isocyanic acid is hydrolyzed into water present in the exhaust gas and converted into ammonia and carbon dioxide (CO ₂ ), and the ammonia produced by pyrolysis and hydrolysis catalyzes the nitrogen oxide as described above.

AUS-32 or AdBlue has a freezing point of -11 ° C, which is expected to freeze in the system in cold climates. Since this fluid is aqueous, the volume expansion occurs after transition to solid state during icing. The expanding solids can exert considerable force on any closed volume, such as an injector. There is another SCR strategy to overcome the expansion of the reducing agent, since such expansion can damage the injection unit.

There are two known SCR system strategies in the market: fuzzy systems and non-fuzzy systems. In a fuzzy SCR system, the reducing agent urea and / or DEF solution is purged from the RDU when the vehicle engine is turned off. In a non-purge SCR system, the reducing agent remains in the RDU throughout the lifetime of the vehicle. During normal operation of the non-purge SCR system, the RDU injector operates at a temperature higher than the freezing point of the reducing agent so that the reducing agent in the RDU is maintained in a liquid state. However, when the vehicle engine is turned off in the non-fuzzy SCR system, the RDU injector is filled with the reducing agent as it is, and the RDU injector may be damaged due to the expansion of the reducing agent in the freezing condition.

The exemplary embodiment overcomes the disadvantages found in conventional RDU fluid injectors and provides an improved fluid ejector for a non-fuzzy SCR system in which adverse effects are reduced by the RDU being at a temperature below the freezing point of the reducing agent. According to an exemplary embodiment, the RDU includes a fluid injector having a fluid inlet disposed at a first end of the fluid injector to receive a reducing agent and a fluid outlet disposed at a second end of the fluid injector for discharging the reducing agent . The fluid injector forms a fluid path for the reducing agent from the fluid inlet to the fluid outlet. The fluid ejector having a tube member having an end disposed at or near the fluid inlet of the fluid ejector and configured to pass a reducing agent along the fluid path; A filter disposed within the tube member proximate to the fluid inlet of the fluid injector; And a calibration filter tube disposed in the tube member downstream of the filter with respect to a flow direction of the reducing agent along the fluid path from the fluid inlet to the fluid outlet of the fluid injector, Further comprising a bore having a first end portion and a second end adjacent the filter and axially formed through the calibration filter tube, the bore forming at least a portion of the fluid path through the fluid ejector. An actuator unit is disposed in the fluid injector downstream of the calibration filter tube and the actuator unit engages the second end of the calibration filter tube. A valve assembly is operably coupled to the actuator unit, the position of the calibration filter tube in the tubular member at least partially establishing an opening force against the valve assembly. The volume reduction member has a bore through 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. In one exemplary embodiment, the filter, the calibration filter tube, and the volume reducing member form a unitary subassembly component of the fluid injector.

In one exemplary embodiment, the volume reducing member is formed of a compressible material, and the compressible material is one of a rubber composition and a closed cell foam.

In one exemplary embodiment, the volume reducing member includes a sidewall, and the sidewall of the volume reducing member forms an undulating in a direction along the longitudinal axis of the fluid ejector.

The fluid ejector may further comprise a cap member including a sidewall defining an interior space in which the filter is disposed, the sidewall contacting the first end of the calibration filter tube. The first end portion of the calibration filter tube is disposed in the internal space of the cap member. 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 reducing member, and the filter form an integral subassembly component of the fluid injector .

The actuator unit may include a pole piece having a bore disposed in a fixed position in the fluid ejector and formed axially through the bore, and an armature positioned movably within the fluid ejector and having a pocket. The actuator unit may further comprise a coil disposed proximate the pole piece and the armature, and a spring at least partially disposed within the pocket of the armature. In one exemplary embodiment, the calibration filter tube is disposed within the bore of the pole piece such that the second end of the calibration filter tube is in contact with the spring, and the spring is configured such that when there is no current passing through the coil, Is deflected away from the extreme so that the valve assembly is placed in the closed position to prevent the reducing agent from passing through the fluid outlet.

The calibration filter tube includes a second portion extending axially from the first end portion of the calibration filter tube and a third portion disposed between the second end portion and the second portion of the calibration filter tube do. Wherein the volume reducing member is disposed about the second portion and the third portion is disposed within the bore of the pole piece and the downstream end of the volume reducing member is positioned adjacent the flow path of the reducing agent along the fluid path, Adjacent the upstream end.

The outer diameter of the second portion of the calibration filter tube may be greater than the outer diameter of the third portion of the calibration filter tube.

In another exemplary embodiment, the RDU fluid ejector has 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 ejector for discharging the fluid, A fluid ejector forms a fluid path of the fluid from the fluid inlet to the fluid outlet. The tube member has an end disposed at or near the fluid inlet of the fluid injector, wherein the tube member is configured to pass fluid along the fluid path. A filter is disposed within the tubular member proximate the fluid inlet of the fluid injector. A calibration filter tube is disposed within the tube member downstream of the filter with respect to a flow direction of the 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 proximate to the filter, a second end, and a bore axially formed through the calibration filter tube, the bore having at least a portion of the fluid path through the fluid injector . An actuator unit is disposed in the fluid injector downstream of the calibration filter tube and the actuator unit engages the second end of the calibration filter tube. A valve assembly is operably coupled to the actuator unit, the position of the calibration filter tube in the tube member establishing an opposed opening force of the valve assembly. The fluid ejector further comprises a cap member having a sidewall defining an interior space in which the filter is disposed. In one exemplary embodiment, the sidewall is attached in contact with 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.

Embodiments of the present invention will be described in detail below with reference to exemplary embodiments with reference to the drawings.
1 is a side cross-sectional view of an RDU for a non-purge SCR system according to an exemplary embodiment;
Figure 2 is a side cross-sectional view of the fluid injector of the RDU of Figure 1;
3 is an enlarged cross-sectional view of an inlet portion of the fluid injector of the RDU of FIG. 1 according to an exemplary embodiment;
4 is an exploded perspective view of components of a fluid ejector of the RDU of FIG. 1 according to an exemplary embodiment;
5 is an enlarged cross-sectional view of an outlet portion of the fluid injector of the RDU of FIG. 1 according to an exemplary embodiment;
Figure 6 is an enlarged cross-sectional view of an inlet portion of the fluid injector of the RDU of Figure 1 according to another exemplary embodiment;
Figure 7 is an exploded perspective view of the components of the fluid ejector of Figure 6;
Figure 8 is a cross-sectional view of the components of Figure 6;
Figure 9 is an enlarged cross-sectional view of an inlet portion of a fluid injector of the RDU of Figure 1 according to yet another exemplary embodiment;
Figure 10 is a cross-sectional view of the components of the fluid injector of Figure 9;
Figure 11 is a perspective view of the components of the fluid ejector of Figure 9;
12 is a cross-sectional view of the inlet portion of the fluid injector of the RDU of FIG. 1 according to another exemplary embodiment;
Figure 13 is a cross-sectional view of the integrated component of the fluid ejector of Figure 12;
Figure 14 is an exploded perspective view of the components of the fluid ejector of Figure 13;
15 is a cross-sectional view of an inlet portion of a fluid injector of the RDU of FIG. 1 according to another exemplary embodiment;
Figure 16 is a cross-sectional view of the integrated component of the fluid ejector of Figure 15;
Figure 17 is an exploded perspective view of the components of the fluid ejector of Figure 15;

The following description of exemplary embodiment (s) is merely exemplary in nature and is not intended to limit the invention, its application, or uses.

An exemplary embodiment relates to an RDU for a non-purge SCR system in which damage is generally reduced by the icing of the reducing agent, DEF and / or urea solution in the RDU injector.

1 illustrates an RDU 10 of a non-purge SCR system according to an exemplary embodiment. The RDU 10 includes a solenoid fluid injector, generally designated 12, which provides a metering function of the fluid and provides for spraying fluid into the vehicle's exhaust path during injection applications. Thus, the fluid injector 12 is constructed and arranged to be associated with an exhaust gas flow path upstream of a selective catalytic reduction (SCR) catalytic converter (not shown). The fluid injector 12 may be an electrically operated solenoid fuel injector. 1 and 2, the fluid injector 12 includes an actuator unit having a coil 14 and a moving armature 16. The components of the injector 12 form a fluid path for the reducing agent, DEF, and / or urea solution passing through the injector 12. The reducing agent, DEF, and / or urea solution that the RDU 10 is configured to inject into the exhaust path of the vehicle engine will hereinafter be referred to as "reducing agent" for simplicity.

The fluid injector 20 is disposed in the inner carrier 18 of the RDU 10 as shown in FIG. The injector shield generally designated 20 is formed of an upper shield 20A and a lower shield 20B which surround the injector 12 and are connected to a carrier 18 and an upper shield 20A to the carrier 18 by folding the tangs of the flanges 22 of the lower shield 20B over the shelf features. As a result, the shield 20 and the carrier 18 are secured with respect to the injector 12.

The inlet cup structure of the RDU 10, generally indicated at 24 in FIG. 1, includes a cup 26 and a fluid supply tube 28 formed integrally with the cup 26. The fluid supply tube 28 is communicatively connected to a source of a reducing agent (not shown) which is injected from the fluid outlet 32 of the injector into the exhaust stream of a vehicle engine (not shown) To the fluid inlet (30). The fluid outlet (32) of the injector (12) is in fluid communication with the fluid supply tube (28). The fluid outlet 32 is in fluid communication with the flange outlet 34 of the exhaust flange 36 which is directly coupled to the end of the lower shield 20B of the RDU 10.

The injector 12 includes an injector body structure in which the components of the injector 12 are disposed. The injector body structure includes a first injector body portion 38 in which a coil 14 and an armature 16 are disposed and a valve body portion 40 in which a valve assembly of the injector 12 is at least partially disposed. The first injector body portion 38 and the valve body portion 40 are directly or indirectly fixedly connected to each other.

Referring to Figures 1 and 3, the fluid injector 12 includes a tube member 42 that is at least partially disposed within the first injector body portion 38. The outer surface of the tube member 42 contacts the inner surface of the first injector body portion 38. The open end of the tube member 42 is disposed within the cup 26 and is in fluid communication with the fluid supply tube 28. The O-ring 44 is disposed within the cup 26 proximate the open end of the tube member 42 between the inner surface of the cup and the outer surface of the tube member 42. The O-ring 44 serves to ensure that the reducing agent exiting the fluid supply tube 28 passes into the open end of the tube member 42 of the injector 12.

The actuator unit of the fluid injector 12 further comprises a pole piece 46 fixedly disposed within the first injector body portion 38. The coil 14 at least partially surrounds the pole piece 46 and the armature 16. The pole piece 46 is disposed upstream of the armature 16 in the injector 12. The piece 46 includes a central bore formed axially therethrough.

The armature 16 includes a U-shaped cross section defining a pocket in which at least a portion of the spring 50 is disposed. The spring 50 which is part of the actuator unit deflects the moving armature 16 such that the armature 16 is spaced from the pole piece 46 when no current passes through the coil 14. [ The spring 50 partially extends in the central bore of the pole piece 46. One end of a spring (50) extending within the piece (46) contacts the spring control tube (52). The spring regulating tube 52 is at least partially disposed within the central bore of the piece 46 upstream of the spring 50 (with respect to the flow direction of the reducing agent through the injector 12). The spring control tube 52 includes a bore formed axially therethrough. The through bore of the spring regulating tube 52 partially forms a fluid path for the reducing agent in the fluid injector 12 and forms a unique fluid path for the reducing agent through the piece 46. By engaging the spring 50, the spring regulating tube 52 is used to calibrate the dynamic flow of the reducing agent through the fluid injector 12.

The armature 16 further includes one or more channels 60 (Figs. 1 and 2) formed through the armature 16 from the interior of the pocket to the upstream end portion of the pin member 58. The channels 60 may be evenly spaced around the armature 16. [ In one exemplary embodiment, the armature 16 includes a single channel formed entirely around the base of the pocket formed by the pocket wall 16A. The channel (s) 60 allow the reducing agent to flow from the pocket of the armature 16 into the space around the upstream end of the pin member 58. The pocket and channel (s) 60 of the armature 16 together form a reductant fluid path of the fluid injector 12 and form a unique portion of the fluid path through or around the armature 16 .

Referring to Figures 1, 2 and 5, the valve assembly of the injector 12 includes a sealing member 54 and a seat 56. [ The sealing member 54 is connected to the armature 16 via a pin member 58 disposed between the downstream end of the armature 16 and the sealing member 54. [ The sealing member 54, the pin member 58 and the armature 16 may be combined to form an armature assembly. When the coil 14 is energized the coil 14 generates an electromagnetic force acting on the armature 16 which overcomes the deflection force from the spring 50 and moves the armature 16 towards the pole piece 46 Correspondingly, the pin member 58 is moved to lift the sealing member 54 up from the seat 56 and move the armature assembly to the open position so that the reducing agent flows through the fluid outlet 32 to the flange outlet 34 Pass through the exhaust path of the vehicle engine. When the coil 14 is non-energized, the electromagnetic force is dissipated and the spring 50 deflects the armature 16 to move the armature 16 away from the pole piece 46, So as to change the armature assembly back to its closed position. When the armature assembly is in the closed position, the reducing agent is prevented from flowing through the seat 56 and the flange outlet 34 to the exhaust path of the vehicle engine.

As discussed above, the RDU 10 forms part of a non-purge SCR exhaust after treatment system. As a result, a reducing agent remains in the fluid injector 12 after the vehicle engine is turned off. In an exemplary embodiment, the fluid injector 12 is configured to reduce the amount of reducing agent in the fluid injector 12. In other words, the total volume in which the reducing agent is present in the fluid path in the fluid injector 12 is reduced. By reducing the space in which the reducing agent is present in the injector 12, the amount of reducing agent in the RDU 10 that can potentially freeze is reduced, causing the reducing agent to freeze and damage the injector 12 by the expanding force The risk of this happening is reduced.

In order to reduce the volume of the reducing agent fluid path in the fluid injector 12, the thickness of the valve body portion 40 is increased. In addition, the pin member 58 is configured as a solid element so that the reducing agent flows around the outer surface of the pin member 58, not through the pin member. The gap between the inner surface of the valve body portion 40 that partially defines the fluid path for the reducing agent passing through the injector 12 and the outer surface of the fin 58 becomes narrower. This narrow portion of the fluid path is the only fluid path where there is a reducing agent between the armature 16 and the sheet 56 in the fluid injector 12. The narrow fluid path between the pin 58 and the valve body portion 40 provides a sufficient reductant flow rate through the fluid injector 12 to perform the atomizing of the reducing agent during normal operation of the RDU 10, By keeping the volume of the reducing agent in the nozzle 12 relatively small, the risk of damage to the injector 12 at the time of freezing of the reducing agent can be reduced.

The thickness of the pocket wall 16A of the armature 16 can also be increased by reducing the diameter of the pocket of the armature 16 in which the spring 50 is at least partly disposed. In an exemplary embodiment, the thickness of the pocket wall 16A is 45% to 75%, for example, about 60% of the diameter of the pocket. Not only the thickness of the pocket wall 16A increases but also the thickness of the valve body portion 40 is increased and the pin member 50 is a solid pin so that the components of the injector 12 are reinforced, You can resist more than that.

Further, the bore of the spring regulating tube 52 has a size that reduces the volume of the reducing agent fluid path in the injector 12. In an exemplary embodiment, the diameter of the bore of the spring regulating tube 52 is 12% to 22%, particularly 16% to 19%, of the outer diameter of the pole piece 46.

Figure 3 shows the upstream portion of the injector 12. The tube member 42 extends at least partially through the injector 12. The reducing agent fluid path through the injector 12 passes through the tube member 42. The injector 12 includes a filter 204 disposed within the tube member 42 proximate the open end of the tube member. The filter 204 is a structurally rigid and sintered metal filter, such as a stainless steel material, to better withstand the expanding force that occurs when the reducing agent is frozen. The filter 204 may have a supporting outer structure for additional strength. As best seen in FIG. 3, the filter 204 is disposed within the cap member 206. The cap member 206 is a generally cylindrical shape having a sidewall 206A that extends in the circumferential direction and defines an interior volume having a size therein for receiving the filter 204 therein. The cap member 206 has a dimension that fits within the tubular member 42 and in particular has a dimension such that the outer surface of the side wall 206A of the cap member 206 is in contact with the inner surface of the tubular member 42. [ The cap member 206 further includes an annular member 206B disposed along the axial end of the cap member 206 and extends radially inward from the side wall 206A. The annular member 206B serves to keep the filter 204 in the fixed position within the cap member 206. [ The cap member 206 is comprised of a metal or similar composition.

The injector 12 further includes a retaining ring 207 disposed in the tube member 42 in contact with the cap member upstream of the cap member 206 as shown in Figures 1-3. . The retainer ring 207 is secured to the tube member 42 along the inner surface of the tube member. The retaining ring 207 secured in place along the tube member 42 serves to retain the downstream components of the injector 12 in a fixed position within the first injector body portion 38. In an exemplary embodiment, the retainer ring 207 is welded along the inner surface of the tube member 42. This weld connection is formed along the entire circumference of the upper edge of the retainer ring 207. However, it is understood that it is also possible to use other connection mechanisms for fixing the retainer ring 207 to the tube member 42. [

Referring to Figures 1-4, the injector 12 further includes a volume reducing member 208 that serves to further reduce the volume of the reducing agent fluid path in the injector 12. [ The volume reducing member 208 is a generally cylindrical shape having an upper (upstream) end and a lower (downstream) end, as shown in FIG. In one embodiment, the volume reducing member 208 is constructed of a metal such as stainless steel. It is understood, however, that the volume reducing member 208 may be formed from other metal or metal compositions. The outer surface of the volume reducing member 208 has a size such that it contacts the inner surface of the tube member 42.

The volume reducing member 208 further includes a bore 208A (Figs. 2 and 3) formed axially through the volume reducing member 208 from one axial (upper) end to the other axial (lower) . The bore 208A is located along the longitudinal axis of the volume reducing member 208 and the bore itself forms part of the fluid path through the injector 12 with the reducing agent. The bore 208A forms a unique fluid path for the reducing agent to pass through or around the volume reducing member 208. In an exemplary embodiment, the diameter of the bore 208A is between 12% and 20%, for example, about 16%, of the outer diameter of the volume reducing member 208. Because volume reduction member 208 extends radially to the inner surface of tube member 42 and the diameter of bore 208A is smaller than the outer diameter of volume reduction member 208, Reducing the space or volume in which the reducing agent may be present in the injector 12 reduces the volume of the fluid path in which the reducing agent is present. The volume reducing member 208 is configured to maintain the spring regulating tube 52 in place in the injector 12 so that the pin regulating tube 52 maintains the desired force on the spring 50 to prevent the calibration from being lost Help me further. Specifically, the retainer ring 207 maintains the position of the filter 204 and the corresponding cap member 206, maintaining the position of the volume reducing member 208 maintaining the position of the spring regulating member 52.

1 to 4, the fluid injector 12 further includes a volume compensating member 210 disposed between the lower (downstream) end of the volume reducing member 208 and the upper end of the pole piece 46. The volume compensating member 210 is made of an elastic material and has the function of occupying a space between the volume reducing member 208 and the pole piece 46 to further reduce the volume of the fluid path in which the reducing agent is present in the injector 12 do. The volume compensating member 210 may be compressed within the injector 12 when assembled and the volume reducing member 208, the piece 46, the inner surface of the tube member 42, and the spring adjusting member 52 As shown in FIG.

Figure 5 shows the downstream end portion of the fluid injector 12. As can be seen, the sheet 56 includes a bore formed axially through the sheet 56. In an exemplary embodiment, by reducing the length of the through bore of the sheet 56, the volume of the fluid path in which the reducing agent is passing through the sheet 56, and particularly the volume of the sheet 56 engaged with the sealing member 54 It is possible to further reduce the sac volume below the sealing band.

According to one exemplary embodiment, the fluid injector 12 includes a plurality of orifice discs 212 disposed in a stacked arrangement. An orifice disk stack is disposed at the downstream end of the sheet 56. In the exemplary embodiment shown in FIG. 5, the disk stack includes a first disk 212A having one or more orifices configured to provide a desired spray pattern of a reducing agent exiting the sprayer. It is understood that the dimensions and location of the orifice of the first disk 212A may vary and may vary depending on the reductant injection requirements of a particular vehicle engine. The disc stack further includes a second disc 212B disposed downstream of the first disc 212A and having an orifice through which the reducing agent spray passes. The second disk 212B is thicker than the thickness of the first disk 212A and is disposed in contact with the first disk 212A and is more susceptible to being deflected by the expansion force generated by freezing of the reducing agent upstream of the first disk 212A And supports the first disk 212A to prevent the thin first disk 212A from being deformed.

As described above, the fluid injector 12, and particularly its components, is configured to reduce the volume of the fluid path in which the reducing agent is present in the injector 12. In the exemplary embodiment, the components (coil 14, armature 16, pole piece 46, spring control tube 52, volume reduction member 208, volume compensation member 210, The filter 204, the retaining ring 207, the spring 50, the pin member 58, the sealing member 54, the seat 56, the first injector body portion 20A and the valve body portion 40 The ratio of the volume of the fluid path in the fluid injector 12 to the volume of the fluid (not limited thereto) is 0.08 to 0.30, in particular 0.12 to 0.20, for example about 0.15. This volume is defined by a first surface along the open end of the tube member 42 (i.e., fluid inlet 30) and a second surface along the lowest surface (i.e., the fluid outlet 32) 2 plane, between the orthogonal planes with respect to the longitudinal axis of the fluid injector 12. It is understood that the specific ratio of the volume of the reducing agent path to the volume of the injector components in the fluid injector 12 can vary depending on the number of cost and performance related factors and can be any value from about 0.08 to about 0.30. Reducing the ratio of the volume of the reductant fluid path volume to the volume of the ejector component in the fluid injector to fall within this range advantageously reduces the amount of reducing agent present in the injector 12 and even if the reducing agent in the injector 12 is freezing The risk of damaging the RDU 10 can be reduced.

6-8, the fluid injector 12 includes a volume reducing member 308 having many of the characteristics of the volume reducing member 208 described above with reference to Figures 1-5. do. Similar to the volume reducing member 208, the volume reducing member 308 is made of stainless steel or a similar composition and disposed within the tube member 42 of the fluid injector 12 between the volume compensating member 210 and the filter 204 do. However, the volume reducing member 308 includes a first portion 308A and a second portion 308B. 7, each of the first portion 308A and the second portion 308B has a cylindrical shape and the outer diameter of the first portion 308A is smaller than the outer diameter of the second portion 308B . The outer diameter of the first portion 308A is smaller than the diameter of the second portion 308B by the thickness of the side wall 306A of the cap member 306 as will be described in more detail below. The volume reducing member 308 includes a top (upstream) and a bottom (downstream) end portion, respectively, forming the axial ends of the first portion 308A and the second portion 308B. The outer surface of the second portion 308B is sized to contact the inner surface of the tube member 42. [

As described above, the outer diameter of the first portion 308A of the volume reducing member 308 is smaller than the outer diameter of the second portion 308B of the volume reducing member. 6 through 8, the volume reducing member 308 extends axially between the outer surface of the first portion 308A and the outer surface of the second portion 308B and has a physical interface therebetween, And an angled annular surface or skirt 308D that serves as a cross-section. The angle of the volume reduction member 308 and / or the angled surface 308D relative to the longitudinal axis of the injector 12 is acute. Alternatively, the angle of the angled surface 308D is perpendicular to the longitudinal axis of the volume reducing member 308 and / or the injector 12.

The volume reducing member 308 further includes a bore 308C formed axially through the volume reducing member 308 from one axial (upper) end to the other axial (lower) end. The bore 308C is located along the longitudinal axis of the volume reducing member 308 and the bore itself forms part of the reducing agent fluid path through which the reducing agent passes through the injector 12 and passes through the volume reducing member 308, Forming the only reductant fluid path through the perimeter. In an exemplary embodiment, the diameter of the bore 308C is between 12% and 20%, for example, about 16%, of the outer diameter of the volume reducing member 308. The volume reducing member 308 is located in the vicinity of the ejector 308 because the volume reducing member 308 extends to the inner surface of the tube member 42 and the diameter of the bore 308C is relatively small relative to the outer diameter of the volume reducing member 308 12 to reduce the volume or volume of the reducing agent fluid path through the injector 12 to reduce the amount of reducing agent that can damage the injector 12 when it freezes in the injector 12. [

The cap member 306 includes a number of identical characteristics of the cap member 206 described above with respect to FIGS. 1-5. 7, cap member 306 is a generally cylindrical shape having a sidewall 306A that extends circumferentially and defines an interior volume having a size to receive filter 204 therein. The cap member 306 has a dimension to fit within the tubular member 42 and in particular has a dimension such that the outer surface of the side wall 306A of the cap member 306 is in contact with the inner surface of the tubular member 42. [ The cap member 306 further includes an annular member 306B disposed along the axial (upstream) end of the cap member 306 and extending radially inwardly from the side wall 306A. The annular member 306B serves to hold the filter 204 in the cap member 306 in a fixed position. Like the cap member 206, the cap member 306 is comprised of a metal or similar composition and provides a structural support to the filter 204. [

In an exemplary embodiment, the cap member 306 is engaged and secured with the volume reducing member 308. In this manner, the filter 204, the cap member 306, and the volume reducing member 308 form a single integral integrated component as shown in Fig. Having a single integral component formed from the filter 204, the cap member 306 and the volume reducing member 308 advantageously allows for a simpler and less complex process for assembling the injector 12 during manufacture have.

In an exemplary embodiment, the cap member 306 is configured to fit or engage on at least a portion of the first portion 308A of the volume reducing member 308, as shown in Figures 6 and 8, Respectively. In one exemplary embodiment, the cap member 306 forms an engagement with the first portion 308A in a press fit. In another exemplary embodiment, the cap member 306 includes a first portion 308A such as a fillet weld between the lower end surface 306C of the cap member 306 and the radially outer surface of the first portion 308A. 308A. In each of these embodiments, the angled surface 308D provides sufficient spacing to secure the cap member 306 to the first portion 308A. It is understood that the cap member 306 may be secured to the first portion 308A of the volume reducing member 308 through another mechanism.

By fitting the cap member 306 onto the first portion 308A of the volume reducing member 308, the outer diameter of the side wall 306A is equal to or substantially equal to the outer diameter of the second portion 308A. 6 and 8.

As discussed above, the volume reducing member 308 is constructed of a metal, such as stainless steel, according to an exemplary embodiment. In another exemplary embodiment, a portion of the second portion 308B is comprised of a plastic or similar composition. Specifically, as shown in Figs. 9-11, the first part 308A and the first part 308B-1 of the second part 308B are formed as a single metal member, and the second part 308B- The second part 308B-2 of the portion 308B is plastic overmolded around the first part. 11 shows the first part 308B-1 of the first metal part 308A and the second part 308B. The first part 308B-1 of the second part 308B is formed with an intermediate section 308B-3 extending in a direction away from the first section 308A in the axial (downstream) direction, And a distal section 308B-4 attached to the intermediate section 308B-3 and extending axially (in a downstream direction). The distal section 308B-4 is configured to extend radially from the longitudinal axis of the volume reducing member 308 (and / or the injector 12) to a radially extending portion of the intermediate section 308B-3 to form a ledge As shown in Fig. The second part 308B-2 of the second part 308B made of overmolded plastic or other similar composition is formed around the protrusion formed of the intermediate section 308B-3 and the distal section 308B-4, Member 308 as a single integral integrated component. As described above, the volume reducing member 308 is connected to the cap member 306 and includes a volume reducing member 308 that forms a single assembly component for use in assembling the injector 12, a filter 204 And the cap member 306. [

During assembly of the injector 12, a single assembly component (filter 204, cap member 306 and volume reduction member 308) is inserted into the tube member 42 under pressure while contacting the volume compensator 212 do. After insertion and still under pressure, the cap member 306 is welded to the tube member 42 along all intersections along the upper portion of the tube member 42. In one embodiment, the weld connection is fillet welding.

12 shows a fluid injector 12 according to another exemplary embodiment. In this embodiment, the fluid injector 12 includes a filter 204 as described above, and a cap member 306 in which the filter 204 is disposed. The fluid injector 12 also includes a calibration filter tube 402 and a volume reduction member 408. The calibration filter tube 402 includes a bore 402A formed axially through the calibration filter tube 402. At one (upstream) end of the calibration filter tube 402, the bore 402A is in fluid communication with the filter 204 to receive the reducing agent from the filter. At the other (downstream) end of the calibration filter tube 402, the bore 402A provides a reducing agent to the armature 16. In this way, the calibration filter tube 402 forms part of the fluid path for the reducing agent passing through the fluid injector 12 and forms a unique fluid path from the filter 204 to the armature 16. If the diameter of the bore 402A of the calibration filter tube 402 is smaller than the inner diameter of the tube member 42 then the volume of the fluid path for the reducing agent passing through the injector 12 is reduced, It is possible to reduce the adverse effects that may occur.

The calibration filter tube 402 further includes a first end portion 402B that is at least partially disposed within the cap member 306 and contacts the filter 204, as shown in Figs. 12-14. The first end 402B is generally disk shaped having a side wall 402C that contacts the inner surface of the side wall 306A of the cap member 306. [ In one exemplary embodiment, the first end portion 402B of the calibration fluid member 402 is configured such that the cap member 306, the filter 204, and the calibrating filter tube 402 form a single integral integrated subassembly component To the cap member 306 so as to simplify assembly of the fluid injector 12. In one exemplary embodiment, the cap member 306 engages the first end portion 402B and particularly engages the first end portion with a press fit. In another exemplary embodiment, the cap member 306 may be formed as a fillet weld connection between the axial end of the side wall 306A of the cap member 306 and the outer surface of the side wall 402C of the first portion 402A, Is welded to the first end portion 402B. Alternatively or additionally, it is understood that the cap member 306 may be secured to the first end portion 402B of the calibration filter tube 402 using other techniques.

The calibration filter tube 402 further includes a elongated second portion 402D extending axially from the first portion 402A as shown in Figs. 12-14. The second portion 402D has a size that extends into the pole piece 46 such that the second end portion 402E opposite the first end portion 402B engages the spring 50 (FIG. 12). The second portion 402D is a generally cylindrical shape having a bore 402A disposed therein. The calibration filter tube 402 further includes an annular tab 402F that extends radially outward from the outer surface of the second portion 402D. The tab 402F extends slightly outwardly from the outer surface of the second portion 402D of the calibration filter tube 402 to be in contact with the inner surface of the pole piece 46 forming the central bore and is located along the second portion . This contact between the center bore of the piece 46 and the tab 402F causes the calibration filter tube 402 to form an attachment with the piece 46 with press fit.

As described above, the second end 402E of the calibration filter tube 402 is in contact with the spring 50 and is engaged. Due to the engagement between the calibration filter tube 402 and the spring 50 and the engagement between the armature 16 and the spring 50, the calibration filter tube 402 will calibrate the dynamic flow of the reducing agent passing through the fluid injector 12 . Specifically, if the cap member 306, the filter 204, and the calibration filter tube 402 are formed as a single, integral, subassembly component, the spring 50 may be removed before the cap member 306 is welded to the tube member. It is simpler to position the calibration filter tube 402 at the desired location within the tube member 42 to provide the desired calibrated force.

The calibration filter tube 402 is formed of a metal composition such as stainless steel.

12-14, the injector 12 further includes a volume reduction member 408 disposed around the second portion 402D of the calibration filter tube 402. The volume reduction member 408 is disposed around the second portion 402D of the calibration filter tube 402. As shown in FIG. The volume reducing member 408 has a cylindrical shape with a central bore formed axially through the volume reducing member 408. The central bore of the volume reducing member 408 has a size for receiving the calibration filter tube 402 therein. As shown in FIG. 12, the outer radial surface of the volume reducing member 408 is in contact with the inner surface of the tube member 42. One axial (upstream) end of the volume reduction member 408 is disposed adjacent to and in contact with the first end portion 402B of the calibration filter tube 42 and the other axial direction of the volume reduction member 408 Are disposed adjacent to and in contact with the upstream end of the pole piece 46. [ In this manner, the volume reducing member 408 is positioned upstream of the cathode piece 46 and downstream of the first end portion 402B of the calibrating filter tube 402 to remove the tube member 42 and the calibration filter tube 402 And occupies a space between the two portions 402D. In one exemplary embodiment, the volume reducing member 408 is configured such that the volume reducing member 408 forms a single, integrated component with the cap member 306, the filter 204 and the calibrating filter tube 402 Is attached to the calibration filter tube (402).

In one exemplary embodiment, the volume reducing member 408 is constructed of an elastic and compressible material and is compressible along the fluid injector 12 at least axially. The axially compressible volume reduction member 408 is configured to provide a single assembly component (cap member 306, filter 204, and calibration filter 408) so that the opening and closing forces of the valve assembly of the fluid injector 12 can be easily calibrated as desired. Tube 402) is positionable within the tube member 42 relative to the pole piece 46. In one embodiment, the volume reducing member 408 is comprised of a closed cell foam. It is understood, however, that the volume reducing member 408 may be constructed of other compressible materials. When constructed with a closed cell foam, the volume reducing member 408 is compressible in the axial direction (longitudinal direction) and the radial direction (lateral direction). In one exemplary embodiment, the volume reducing member 408 is in a compressed state in the fluid injector 12.

Figures 15-17 illustrate a fluid injector 12 according to another exemplary embodiment. In this embodiment, the fluid injector 12 includes a filter 204 as described above, and a cap member 306 in which the filter 204 is disposed. The fluid injector 12 also includes a calibration filter tube 502. The calibration filter tube 502 has many of the features of the calibration filter tube 402 described above with respect to Figures 12-14.

The calibration filter tube 502 includes a bore 502A formed through the calibration filter tube 502 in an axial direction. At one (upstream) end of the calibration filter tube 502, the bore 502A is in fluid communication with the filter 204 to receive the reducing agent from the filter. At the other (downstream) end of the calibration filter tube 502, the bore 502A provides a reducing agent to the armature 16. In this way, the calibration filter tube 502 forms part of the fluid path for the reducing agent passing through the fluid injector 12 and forms a unique fluid path from the filter 204 to the armature 16. If the diameter of the bore 502A of the calibration filter tube 502 is small relative to the inner diameter of the tube member 42 then the volume of the fluid path for the reducing agent passing through the injector 12 is reduced, It can reduce the adverse effects that may occur.

As shown in FIGS. 15-17, the calibration filter tube 502 further includes a first end portion 502B that is at least partially disposed within the cap member 306 to contact the filter 204. As shown in FIG. The first end portion 502B is generally disk shaped with a side wall 502C that contacts the inner surface of the side wall 306A of the cap member 306. [ In one exemplary embodiment, the first end portion 502B of the calibration fluid member 502 is configured such that the cap member 306, the filter 204, and the calibrating filter tube 502 form a single, To the cap member 306 so as to simplify assembly of the fluid injector 12. In one exemplary embodiment, the cap member 306 engages the first end portion 502B and, in particular, forms a meshing engagement with the first end portion. In another exemplary embodiment, the cap member 306 may be formed as a fillet weld connection between the axial end of the side wall 306A of the cap member 306 and the outer surface of the side wall 502C of the first portion 502B, And welded to the first end portion 502B. Additionally or alternatively, it is understood that the cap member 306 may be secured to the first end portion 502B of the calibration filter tube 502 using other techniques.

The calibration filter tube 502 comprises a elongated second portion 502D extending axially from the first portion 502A as shown in Figures 15-17 and a second elongated second portion 502C extending axially from the second portion 502D, And a third elongated third portion 502E extending therefrom. The third portion 502E has a size that allows the second end 502F of the calibration filter tube 502 opposite the first end portion 502B to extend into the pole piece 46 to engage the spring 50 . The second portion 502D and the third portion 502E are generally cylindrical in shape with a bore 502A disposed therein.

In one exemplary embodiment, the outer diameter of the second portion 502D is greater than the outer diameter of the third portion 502E. The outer diameter of the third portion 502E is sized to be received within the central bore of the pole piece 46.

The calibration filter tube 502 further includes an annular tab 502G (FIG. 17) extending radially outward from the outer surface of the third portion 502E. The tab 502G extends slightly outward from the outer surface of the third portion 502E of the calibration filter tube 502 to contact the inner surface of the pole piece 46 forming the central bore, . This contact between the center bore of the piece 46 and the tab 502G causes the calibrating filter tube 502 to engage the piece 46 with a press fit.

The calibration filter tube 502 is formed of a metal composition such as stainless steel.

As described above, the second end 502F of the calibration filter tube 502 is in contact with the spring 50 and is engaged. Due to the engagement between the calibration filter tube 502 and the spring 50 and the engagement between the spring 50 and the armature 16, the calibration filter tube 502 provides a dynamic flow of the reducing agent through the fluid injector 12 It is used for calibration. Specifically, if the cap member 306, the filter 204 and the calibrating filter tube 502 are formed as a single, integral, subassembly component, fluid may be injected into the fluid injector 12 It is simpler to position the calibration filter tube 502 at the desired location in the tube member 42 to provide the desired calibrated force to the spring 50 that sets the opening and closing force against the valve assembly of the valve assembly.

15-17, the injector 12 further includes a volume reduction member 508 disposed around the second portion 502D of the calibration filter tube 502. The volume reduction member 508 is disposed around the second portion 502D of the calibration filter tube 502. As shown in FIG. The volume reducing member 508 has a generally cylindrical shape with a central bore formed axially through the volume reducing member 508. The central bore of the volume reducing member 508 has a size for receiving the second portion 502D of the calibration filter tube 502 therein. As shown in FIG. 12, the outer radial surface of the volume reducing member 508 contacts the inner surface of the tube member 42. One axial (upstream) end of the volume reducing member 508 is disposed adjacent and contacting the first end portion 502B of the calibrating filter tube 42 and the other axial (downstream) Are disposed adjacent to and in contact with the upstream end of the pole piece 46. [ In this manner, the volume reducing member 508 is positioned upstream of the piece 46 and downstream of the first end portion 502B of the calibrating filter tube 502 to remove the tube member 42 and the calibration filter tube 502 And occupies a space between the two portions 502D.

In one exemplary embodiment, the volume reducing member 508 is comprised of a compressible material such as at least axially compressible along the fluid injector 12. At least the axially compressible volume reducing member 508 includes a single assembly component (cap member 306, filter 204, and calibration filter tube 502) so that the valve assembly of the fluid injector 12 can be calibrated as desired. To be positionally adjustable within the tube member 42 relative to the piece 46. [ In one exemplary embodiment, the volume reducing member 508 is in a compressed state in the fluid injector 12.

As shown in Figures 15-17, the volume reducing member 508 includes side walls 508A that extend between two axial ends. The downstream axial end wall 508B of the volume reducing member 508 extends radially inward from the side wall 508A and contacts the outer surface of the third portion 502E of the calibration filter tube 502. [ The upstream axial end of the volume reducing member 508 may be open and may contact the downstream surface of the first portion 502B of the calibration filter tube 502.

The sidewall 508A of the volume reduction member 508 may have a peak in the sidewall and a peak in the sidewall 508A in a wavy pattern with respect to the longitudinal axis of the volume reduction member 508 and / Thereby forming a waveform in the alternate axial direction. Having a corrugated sidewall 508A allows sidewall 508A to be compressible in the axial direction (longitudinal direction) and radially (sideways) or partially folded in another manner. In one exemplary embodiment, the volume reducing member 508 is comprised of a compressible, resilient material, such as a rubber composition or other similar material. The volume reducing member 508 may be in a compressed state in the fluid injector 12. [

Although exemplary embodiments are described herein in an illustrative manner, it is to be understood that the terminology which has been used is intended to be in the nature of describing the invention rather than of limitation. Obviously, many modifications and variations of the present invention are possible in light of the above description. The foregoing description is merely exemplary in nature and, thus, modifications may be made to the invention without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (20)

As the reducing agent delivery unit,
A fluid injector having a fluid inlet disposed at a first end of the fluid injector to receive a reducing agent and a fluid outlet disposed at a second end of the fluid injector for discharging the reducing agent, Forming a fluid path for the reducing agent 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 a reducing agent along the fluid path;
A filter disposed within the tube member proximate to the fluid inlet of the fluid injector;
A calibration filter tube disposed in the tube member downstream of the filter with respect to a flow direction of the reducing agent along the fluid path from the fluid inlet to the fluid outlet of the fluid injector, Further comprising: a bore formed at a first end portion and a second end, the bore being formed axially through the calibration filter tube, the bore defining at least a portion of the fluid path through the fluid ejector, tube;
An actuator unit disposed in 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, the position of the calibration filter tube within the tubular member at least partially setting an opening force against the valve assembly; And
A volume reducing member having a bore extending from said calibration filter tube and occupying a space between an outer surface of said calibration filter tube and an inner surface of said tube member;
Wherein the filter, the calibration filter tube and the volume reducing member form a single subassembly component of the fluid injector. 2. The reducing agent delivery unit of claim 1, wherein the volume reducing member is formed of a compressible material. The reductant delivery unit of claim 2, wherein the compressible material comprises one of a rubber composition and a closed cell foam. 3. The reductant delivery unit of claim 2, wherein the volume reducing member includes a sidewall, the sidewall of the volume reducing member forming a corrugation in a direction along the longitudinal axis of the fluid ejector. 2. The apparatus of claim 1, wherein the fluid injector further comprises a cap member having a sidewall defining an interior space in which the filter is disposed, the sidewall contacting the first end of the calibration filter tube, . 6. The reducing agent delivery unit of claim 5, wherein the first end portion of the calibration filter tube is disposed in the interior space of the cap member. 6. The apparatus of claim 5, wherein the first end portion of the calibrating filter tube is adapted to receive the calibration filter tube, the cap member, the volume reducing member, and the filter to form a single subassembly component of the fluid injector. And attached to the side wall. The fluid ejector of claim 1, wherein the actuator unit comprises: a pole piece having a bore disposed in a fixed position within the fluid ejector and formed axially through, an armature movably positioned within the fluid ejector and having a pocket, And a spring disposed at least partially within the pocket of the armature, wherein the calibrating filter tube is configured to allow the second end of the calibrating filter tube to contact the spring Wherein the spring biases the armature away from the pole piece when there is no current passing through the coil and places the valve assembly in a closed position to prevent the reducing agent from passing through the fluid outlet A reducing agent delivery unit. 9. The calibration filter tube of claim 8 wherein the calibration filter tube comprises a second portion extending axially from the first end portion of the calibration filter tube and a second portion extending between the second end portion and the second portion of the calibration filter tube Wherein the volume reducing member is disposed about the second portion, the third portion is disposed within the bore of the pole piece, and the downstream end of the volume reducing member is located along the fluid path, Adjacent the upstream end of said pole piece with respect to the direction of flow of said reductant. 10. The reducing agent delivery unit of claim 9, wherein an outer diameter of the second portion of the calibration filter tube is greater than an outer diameter of the third portion of the calibration filter tube. As fluid injectors,
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, wherein the fluid injector is operable to move the fluid from the fluid inlet to the fluid outlet The fluid inlet and the fluid outlet;
A tube member having an end disposed at or near the fluid inlet of the fluid injector and configured to pass fluid along the fluid path;
A filter disposed within the tube member proximate to the fluid inlet of the fluid injector;
A calibration filter tube disposed within the tube member downstream of the filter with respect to a flow direction of the fluid along the fluid path from the fluid inlet to the fluid outlet of the fluid injector, Further comprising a bore having a first end portion and a second end formed axially through the calibration filter tube and wherein the bore defines at least a portion of the fluid path through the fluid injector, tube;
An actuator unit disposed in 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, the position of the calibration filter tube within the tubular member establishing an opening force against the valve assembly; And
And a sidewall defining a sidewall defining an interior space in which the filter is disposed, the sidewall being adapted to receive a portion of the calibrated filter tube to form a single subassembly component of the fluid injector, Said first end being in contact with said first end of said fluid ejector. 12. The apparatus of claim 11, further comprising a volume reducing member having a bore through which the calibration filter tube extends, the volume reducing member occupying a space between an outer surface of the calibration filter tube and an inner surface of the tube member, Wherein the volume reducing member, the cap member, the filter, and the calibration filter tube form a single subassembly component of the fluid ejector. 13. The fluid ejector of claim 12, wherein the volume reducing member is compressible. 14. The fluid ejector of claim 13, wherein the volume reducing member comprises one of a rubber composition and a closed cell foam. 13. The fluid ejector of claim 12, wherein the volume reducing member includes a sidewall, the sidewall of the volume reducing member forming a corrugation along the longitudinal axis of the fluid ejector. 13. The fluid ejector of claim 12, wherein the actuator unit comprises: a pole piece including a bore disposed in a fixed position in the fluid ejector and formed axially through, an armature movably positioned within the fluid ejector and including a pocket, And a spring disposed at least partially within the pocket of the armature, wherein the calibrating filter tube is configured to allow the second end of the calibrating filter tube to contact the spring Wherein the spring biases the armature away from the extreme when there is no current passing through the coil to place the valve assembly in a closed position to prevent fluid from passing through the fluid outlet The fluid injector. 16. The calibration filter tube of claim 15, wherein the calibration filter tube includes a second portion extending axially from the first end portion of the calibration filter tube, and a second portion disposed between the second end portion and the second portion of the calibration filter tube Wherein the volume reducing member is disposed about the second portion and the third portion is disposed within the bore of the pole piece and the downstream end of the volume reducing member is located within the bore of the fluid along the fluid path Adjacent the upstream end of the pole piece with respect to the flow direction. 18. The fluid ejector of claim 17, wherein an outer diameter of the second portion of the calibration filter tube is greater than an outer diameter of the third portion of the calibration filter tube. 18. The apparatus of claim 17, wherein the calibration filter tube further comprises an annular tab extending from the third portion of the calibration filter tube, wherein the annular tab is disposed within the bore of the pole piece to engage the pole piece with a press fit Of the fluid injector. 12. The fluid ejector of claim 11, wherein the first end portion of the calibration filter tube is disposed in the interior space of the cap member.

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