Abstract:
A heated tip fuel injector includes a housing having a bore formed therein for receiving fuel under pressure; a valve seat mounted at one end of the housing, the valve seat including an orifice; a needle valve having one end mounted to an armature and another end which contacts the valve seat to close off fuel outflow from the bore and which is lifted from the valve seat to inject fuel; a heater disposed in the housing upstream of the valve seat and extending around the needle valve; and at least one flow disturbing element disposed upstream of the heater. The flow-disturbing element enhances heat transfer from the heater to the fuel.

Description:
This application is a continuation-in-part of co-pending application Ser. No. 09/088,127 entitled &#34;Fuel Injector With Internal Heater,&#34; filed on Jun. 1, 1998, which is expressly incorporated by reference herein. Related copending application Ser. No. 09/088,126 entitled &#34;Method of Preheating Fuel With an Internal Heater,&#34; filed on Jun. 1, 1998, which is also expressly incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates in general to heated tip fuel injectors with internal heaters and, in particular, to heated tip fuel injectors with enhanced heat transfer from the internal heater to the fuel. 
     It has been recognized that preheating of the fuel during cold starting will reduce hydrocarbon emissions caused by incomplete fuel vaporization during cold starts. Heated tip fuel injectors are known and described in, for example, copending application Ser. No. 09/088,127, referenced above. While that patent application generally describes enhancing the heat transfer from the heater to the fuel, more efficient heat transfer mechanisms and methods are needed to further reduce emissions. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a heated tip fuel injector with enhanced heat transfer from the internal heater to the fuel. 
     This and other objects of the invention are achieved by a fuel injector comprising a housing having a bore formed therein for receiving fuel under pressure; a valve seat mounted at one end of the housing, the valve seat including an orifice; a needle valve having one end mounted to an armature and another end which contacts the valve seat to close off fuel outflow from the bore and which is lifted from the valve seat to inject fuel; a heater disposed in the housing upstream of the valve seat and extending around the needle valve; and at least one flow disturbing element disposed upstream of the heater. 
     Preferably, the flow-disturbing element comprises a plurality of disks each having at least one opening wherein the at least one opening in one disk is offset from the at least one opening in another disk. 
     In one embodiment, the flow disturbing element comprises first, second and third disks; the second disk having an opening substantially across an entire diameter of the second disk; the first and third disks each having a central opening with a size substantially the same as a cross-section of the needle valve; the needle valve being inserted through the opening in the second disk and the central openings in the first and third disks. 
     The flow-disturbing element may be attached to the needle valve such that the flow-disturbing element reciprocates with the needle valve or, alternatively, the flow-disturbing element may be stationary with respect to the needle valve. 
     In a second embodiment, the flow-disturbing element comprises first, second and third disks each having a central opening with a size substantially the same as a cross-section of the needle valve for receiving the needle valve. 
     In a preferred embodiment, when the needle valve is in a closed position, the at least one flow disturbing element is separated from the internal heater by a gap. 
     Further objects, features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a longitudinal sectional view of a fuel injector. 
     FIGS. 2A-2C are top views of heat transfer enhancing disks according to the present invention. 
     FIG. 3 is a schematic side view of the disks of FIGS. 2A-2C. 
     FIGS. 4A-4C are top views of heat transfer enhancing disks according to the present invention. 
     FIG. 5 is a schematic side view of the disks of FIGS. 4A-4C. 
     FIG. 6 is a longitudinal sectional view of a fuel injector according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows an exemplary fuel injector 156 to which the present invention may be applied. It should be understood that the present invention is applicable to fuel injectors having constructions other than the construction of the fuel injector 156 shown in FIG. 1. 
     Referring to FIG. 1, the fuel injector 156 includes a valve body or housing 112 for insertion into an injector seat of an intake manifold or cylinder head of an engine (not shown). An O-ring 114 seals the housing 112 in the intake manifold or cylinder head. An inlet tube 16 at the upper end of the injector seats in a fuel rail (not shown) and an O-ring 18 seals the inlet tube 16 in the fuel rail. Fuel under pressure enters the inlet tube 16 and flows through the spring force adjusting tube 20, the bore 22 in the armature 24 and into a space 28 surrounding a needle valve 30 attached to the armature 24. The lower tip end of the needle valve is moved on and off a valve seat 34 to control outflow of fuel through an orifice in the valve seat 34. When energized, an electromagnetic coil 38 lifts the armature 24 off the valve seat 34. An internal heater 50 is disposed in the bottom portion of the injector 156 above the seat 34. The internal heater 50 may be, for example, in the form of a hollow cylinder. 
     A flow-disturbing element 192 induces swirl and/or turbulence in the fuel prior to the fuel passing over the inner and outer surfaces of the heater 50. The swirl and/or turbulence induced in the fuel enhances heat transfer from the heater to the fuel. The flow-disturbing element may comprise stacked disks 194. 
     FIGS. 1 and 6 show flow disturbing elements 192, 192A, respectively. It should be understood that the flow disturbing elements 192, 192A represent generic flow disturbing elements and the flow disturbing elements 200 and 240 described in detail below may be substituted for the elements 192, 192A. 
     FIGS. 2A-2C and 3 show a first embodiment 200 of the flow disturbing element 192. The flow-disturbing element 200 is primarily designed to introduce turbulence into the fuel flow upstream of the heater 50. In its broadest aspect, the flow-disturbing element 200 comprises a plurality of disks each having at least one opening. The openings in the plurality of disks are offset from one another thereby providing a tortuous passageway through which the fuel must flow and, consequently, inducing turbulence into the fuel flow pattern. 
     The flow-disturbing element 200 shown in FIGS. 2A-2C and 3 comprises first, second and third disks 202, 204, 206. The second disk 204 has an opening 208, which extends substantially across the entire diameter of the disk 204. The opening 208 is preferably circular. The first and third disks 202, 206 each have a central opening 210, 212, respectively. The central openings 210, 212 are substantially the same size as a cross-section of the needle valve 30. The needle valve 30 is inserted through the central openings 210, 212 in the disks 202, 206 and through the opening 208 in the second disk 204. The disks 202, 206 may be attached to the needle valve 30 by, for example, welding. When so attached, the flow-disturbing element 200 reciprocates with the needle valve 30. Alternatively, the flow disturbing element 200 is not attached to the needle valve 30 and the flow disturbing element 200 remains stationary while the needle valve 30 reciprocates. 
     FIG. 3 is a schematic side view of the disks 202, 204, 206 shown in FIGS. 2A-2C. The arrow labeled g indicates the direction of flow of fuel. The fuel first encounters the first disk 202, then the second disk 204 and then the third disk 206. The three disks are stacked one on top the other and may be connected together by, for example, welding. The disks may be made of a metal such as stainless steel or a plastic material, which does not interact, with fuel. The flow-disturbing element 200 may also be made as a single piece. In that case, the flow-disturbing element would be either molded or machined. 
     The first disk 202 includes a pair of opposed openings 214. The third disk includes two pairs of opposed openings 216, 218. In FIG. 2A, the arrow f indicates the distance from the central opening of the first disk 202 to the opposed openings 214. In FIG. 2C, the arrow d indicates the distance from the central opening 212 to the opposed openings 216. The arrow e indicates the distance from the central opening 212 to the opposed openings 218. The distance d from the central opening 212 of the disk 206 to the opposed openings 216 is less than the distance f from the central opening 210 of the disk 202 to the opposed openings 214. Also, the distance e from the center of the disk 206 to the opposed openings 218 is greater than the distance f from the center of the disk 202 to the opposed openings 214. 
     In a preferred embodiment, the opposed openings 214, 216, 218 of the disks 202, 206 are spaced such that, when viewed in a longitudinal direction of the fuel injector, the openings 214 in the first disk 202 do not substantially overlap either the openings 216 or the openings 218 in the third disk 206. When there is no substantial overlap of the openings 214, 216, 218, a very tortuous pathway for the fuel is created thereby increasing the flow turbulence. Preferably, the openings 214, 216, 218 are semicircular in shape. 
     Referring now to FIG. 1, as the fuel enters the space 28 above the first embodiment 200 of the flow-disturbing element 192, the fuel contacts the first disk 202. The fuel flows through the openings 214 in the first disk 202, the opening 208 in the second disk 204 and then through the openings 216, 218 in the third disk 206. The disturbed flow which exits the third disk 206 then flows around the heater 50. Because of the increased turbulence in the fuel, the heat transfer from the heater 50 to the fuel is increased. 
     FIGS. 4A-4C and 5 show a second embodiment 240 of the flow-disturbing element 192. The flow-disturbing element 240 is designed to create swirl in the fuel flow. The flow-disturbing element 240 comprises three disks 242, 244, 246 stacked one on top the other as shown in FIG. 5. The arrow h in FIG. 5 indicates the direction of fuel flow through the flow-disturbing element 240. Each of the disks 242, 244, 246 has a central opening 248, 250, 252 for receiving the needle valve 30. The disks 242, 244, 246 may be attached to the needle valve 30 by, for example, welding. In that case, the flow-disturbing element 240 reciprocates with the needle valve 30. Alternatively, the flow-disturbing element 240 may not be attached to the needle valve in which case it would remain stationary when the needle valve reciprocates. 
     The disks 242, 244, 246 may be made of metal, for example, stainless steel or a plastic, which does not interact, with the fuel. The three disks may be attached to each other by, for example, welding. Alternatively, the flow-disturbing element 240 may be formed as a single piece. The disks may be molded or machined. 
     The first disk 242 includes a first plurality of openings 256 and a second plurality of openings 254. The first plurality of openings 256 are located further from the central opening 248 than the second plurality of openings 254. Preferably, each of the plurality of openings 256 is located substantially the same distance from the central opening 248. Likewise, each of the openings 254 is preferably located the same distance from the central opening 248. Most preferably, the openings 256 are about 120 degrees apart and the openings 254 are about 120 degrees apart. 
     The second disk 244 includes a first plurality of arc-shaped openings 258 and a second plurality of arc-shaped openings 260. The openings 258 are located further from the central opening 250 than the openings 260. Preferably, each of the openings 258 is located the same distance from the central opening 250 and each of the openings 260 is located the same distance from the central opening 250. Most preferably, the openings 258 are substantially identical in size and spaced equally about the disk 244. Likewise, the openings 260 are preferably of the same size and spaced equally about the disk 244. 
     The third disk 246 includes a first plurality of openings 262 and a second plurality of openings 264. The openings 262 are located further from the central opening 252 than the openings 264. Preferably, each of the openings 262 is located the same distance from the central opening 252 and, likewise, each of the openings 264 is preferably located the same distance from the central opening 252. Most preferably, the openings 262 are about 120 degrees apart and the openings 264 are about 120 □ apart. 
     When the disks 242, 244, 246 are stacked as shown in FIG. 5, each of the openings 256 is substantially located above one end of one of the arc-shaped openings 258. Likewise, each of the openings 254 is located substantially above one of the ends of one of the openings 260. The openings 262 in the disk 246 are located at opposite ends of the arc-shaped openings 258 than the openings 256 of the disk 242. Likewise, the openings 264 in the disk 246 are located substantially below opposite ends of the arc-shaped openings 260 than the openings 254 in the disks 242. 
     With the above-described alignment of the disks, six fuel flow channels are created. For example, fuel will enter an opening 256 in the disk 242, then flow through an arc-shaped opening 258 and exit through an opening 262 in the disk 246. Likewise, fuel will enter an opening 254 in the disk 242 and then flow through an arc-shaped opening 260 and exit through an opening 264 in disk 246. The flow, which exits the openings 262 and 264, includes a swirl component. The fuel will swirl around the heater 50, thereby enhancing heat transfer from the heater 50 to the fuel. 
     Preferably, the flow directions through the arc-shaped openings 258 and 260 are opposite. For example, as shown in FIG. 4B, if the flow through the arc-shaped openings 258 is in the direction shown by the letter i, then the flow in the arc-shaped openings 260 would be in a direction opposite the arrow i. Alternatively, the flow in the openings 260 could be in the direction i and the flow in the openings 258 could be in a direction opposite the arrow i. Most preferably, the openings 256, 254 in disk 242 and the openings 262, 264 in disk 246 are substantially circular in shape. FIGS. 4A-4C show three openings 256, three openings 254, three arch-shaped openings 258, three arc-shaped openings 260, three openings 262 and three openings 264. However, the number of each of the openings could be more or less than three. 
     Referring back to the exemplary fuel injector 156 of FIG. 1, the flow disturbing element 192 is located between the heater 50 and a spacer sleeve 186 which is held in place by a spring washer 190. In the injector 156, the flow-disturbing element 192 (or 200 or 240) is not attached to the needle valve 30. That is, as the needle valve 30 reciprocates, the flow-disturbing element 192 remains stationary. 
     FIG. 6 is a longitudinal sectional view of a fuel injector 156A according to the present invention. In FIGS. 1 and 6, like reference numerals refer to like features. In the fuel injector 156A of FIG. 6, the spacer sleeve 186A extends from the spring washer 190 to the heater 50. The flow disturbing element 192A (or 200 or 240) is attached to the needle valve 30. Therefore, when the needle valve 30 reciprocates, the flow-disturbing element 192A likewise reciprocates. In FIG. 1, when the needle valve 30 is in the closed position, the flow-disturbing element 192 rests substantially on top of the heater 50. However, as shown by the arrow h in FIG. 6, the flow disturbing element 192A may be attached to any part of the needle valve 30 along the arrow h. Therefore, when the needle valve 30 is closed, a gap may exist between the bottom of the flow disturbing element 192A and the top of the heater 50. By mounting the flow disturbing element 192A higher on the needle valve 30 and creating a gap between the flow disturbing element 192A and the heater 50, the turbulence or swirl created in the fuel develops more fully before the fuel contacts the heater 50. Thus, a gap between the flow disturbing element 192A and the heater 50 is advantageous because the increased turbulence or swirl additionally enhances the heat transfer between the heater 50 and the fuel. 
     While the invention has been described with reference to certain preferred embodiments, numerous changes, modifications and alterations to the described embodiments are possible without departing from the spirit and scope of the invention, as described in the appended claims and equivalents thereof.