Patent Application
20100078504
The present disclosure relates generally to nozzle assemblies in fuel injectors, and in particular, to nozzle assemblies including a pressure containment system.
Manufacturers of fuel injectors are continuously trying to raise the injection pressure of fuel to reduce undesirable emissions as well as improve fuel efficiency in engines. However, due to geometrical limitations and spatial constraints in smaller fuel injectors, structural problems may prevent the fuel injectors from sustaining pressures above 200 MPa. Currently, the nozzle assembly of fuel injectors defines a heart shaped cavity formed in a metallic tip to contain the pressure inside the nozzle assembly.
U.S. Pat. No. 7,331,329 ('329 patent) discusses improving fuel efficiency by reducing static leakage by connecting a spring chamber to a common rail instead of to a low pressure vent. FIG. 4 of the '329 patent illustrates an embodiment of a nozzle assembly without the type of heart shaped cavity inside the fuel injector that is typical in the art.
The present disclosure is directed to overcoming one or more of the problems set forth above.
In one aspect a nozzle assembly includes a tip component defining a nozzle outlet. A high-pressure containment sleeve is disposed within an injector body casing. The high-pressure containment sleeve and the tip component partially define a nozzle chamber. A needle valve member is movable between a first position that closes the nozzle outlet and a second position that opens the nozzle outlet. The needle valve member includes an opening hydraulic surface exposed to fluid pressure in the nozzle chamber. The needle valve member is out of contact with the high-pressure containment sleeve.
In another aspect, a fuel injector includes an injector body, which includes a tip component that defines a nozzle outlet and a high-pressure containment sleeve disposed within an injector body casing. The high-pressure containment sleeve and the tip component partially define a nozzle chamber. The fuel injector also includes a needle valve member that is disposed within the injector body and movable between a first position that closes the nozzle outlet and a second position that opens the nozzle outlet. The needle valve member includes an opening hydraulic surface exposed to fluid pressure in the nozzle chamber. The needle valve member also includes a closing hydraulic surface that is exposed to fluid pressure in a needle control chamber. The needle valve member is out of contact with the high-pressure containment sleeve, and a control valve assembly is fluidly connected to the needle control chamber.
In yet another aspect, a method of operating a fuel injector includes a step of forming a nozzle chamber within a high-pressure containment sleeve. The method also includes the step of containing pressure inside the nozzle chamber with a wall thickness of the high-pressure containment sleeve. The method also includes sealing the nozzle chamber by sizing annular sealing lands between the high-pressure containment sleeve and a tip component and an injector stack component, respectively, to have radial widths smaller than the wall thickness of the high-pressure containment sleeve. The method also includes exposing an opening hydraulic surface of a needle valve member to fluid pressure inside the nozzle chamber, and maintaining the high-pressure containment sleeve out of contact with the needle valve member.
The present disclosure relates to a nozzle assembly of any fuel injector that incorporates a high-pressure containment sleeve that partially defines a nozzle chamber. In the past, nozzle assemblies included a heart shaped cavity, which was surrounded by a metallic wall of a tip component. As the pressures inside fuel injectors are increased to achieve better emissions and fuel efficiency, the metallic wall of the heart shaped cavity of the nozzle assemblies may form cracks and stress fractures. The heart shaped cavity may only become problematic in small injectors with inadequate wall thickness at higher pressures. Larger fuel injectors may not experience the formation of cracks and stress fractures in the walls of the heart shaped cavity because there is ample space inside the fuel injector to increase the wall thickness of the metallic wall that defines the heart shaped cavity. The present disclosure replaces the heart shaped cavity by introducing a high-pressure containment sleeve, which will allow smaller fuel injectors to sustain fuel pressures over 200 MPa without experiencing stress fractures. Further, the present disclosure is pertinent to all types of fuel injectors including common rail, hydraulic and cam actuated fuel injectors as well as fuel injectors of varying sizes. For the sake of simplicity, a common rail fuel injector is described. However, various types of fuel injectors incorporating the nozzle assembly described herein all fall within the scope of this disclosure. The present disclosure describes a nozzle assembly, which replaces a heart-shaped cavity design with a high-pressure containment sleeve.
Referring to
The high-pressure containment sleeve 70 has an outer wall surface 71, an inner wall surface 69, a top surface 92 and a bottom surface 94. The high-pressure containment sleeve 70 has a hollow, cylindrical shape, which means the high-pressure containment sleeve 70 is cylindrical in shape and has a hollow interior bore through the top and bottom surfaces 92 and 94 of the high-pressure containment sleeve 70. The high-pressure containment sleeve has a wall thickness defined by the difference between the radius of the outer wall surface 71 and the radius of the inner wall surface 69 of the high-pressure containment sleeve 70. The wall thickness of the high-pressure containment sleeve 70 is designed to accommodate expected hoop stresses from expected pressure levels in the high-pressure containment sleeve 70. Those skilled in the art appreciate that hoop stress may be the greatest towards the mid-section of the high-pressure containment sleeve 70, therefore, the thickness of the high-pressure containment sleeve 70 is determined from the thickness at the mid-section of the high-pressure containment sleeve 70. Although the thickness of the high-pressure containment sleeve 70 may vary throughout its length, it may be easier to manufacture a high-pressure containment sleeve 70 with a uniform thickness. In one embodiment, the high-pressure containment sleeve 70 has a uniform wall thickness along a majority of the length of the high-pressure containment sleeve 70, which means that the wall thickness remains the same for more than half of the length of the high-pressure containment sleeve 70.
The high-pressure containment sleeve 70 includes an upper sealing land 72 located on the top surface 92 of the high-pressure containment sleeve 70 and a lower sealing land 73 located on the bottom surface 94 of the high-pressure containment sleeve 70. The upper and lower sealing lands 72 and 73 may be annular, and have a radial surface width smaller than the thickness of the wall of the high-pressure containment sleeve 70. The term radial surface width is defined as the difference between the radius of an outer edge of the sealing land and the radius of an inner edge of the sealing land. Those skilled in the art may appreciate that by having the radial surface width of the sealing lands 72 and 73 smaller than the wall thickness of the high-pressure containment sleeve 70, the clamping pressure acting on the sealing lands 72 and 73 will be greater, therefore, producing better sealing. The top surface 92 and the bottom surface 94 of the high-pressure containment sleeve 70 may have chamfers 74, or some other surface contour, which also result in the sealing lands 72 and 73 having a smaller radial surface width compared to the wall thickness at the mid-section of the high-pressure containment sleeve 70. The bottom surface 94 of the high-pressure containment sleeve 70 and a top surface 68 of the tip component 65 are in contact and form a seal to prevent fluid from leaking out of the nozzle chamber 61.
The outer wall surface 71 of the high-pressure containment sleeve 70 is separated from the inner wall 53 of the injector body casing 52 by a space, which may be referred to as a leakage path 88. The leakage path 88 runs along the inner wall 53 of the injector body casing 52 into a drain outlet port (not shown) of the fuel injector 10.
In addition to the high-pressure containment sleeve 70, the nozzle assembly 60 includes the tip component 65 that includes an outer wall 66, a top surface 68, a bottom end 67, which defines a nozzle outlet 64. A bore 62 is defined within the tip component 65 and runs from the top surface 68 of the tip component 65 towards the bottom end 67 of the tip component 65, where it opens up into the nozzle outlet 64. The tip component 65 is partially disposed within the injector body casing 52, and the outer wall 66 of the tip component 65 may form a sealing contact 56 with the injector body casing 52, preventing any fuel that enters into the leakage path 88 to escape from between the inner wall surface 53 of the injector body casing 52 and the outer surface 66 of the tip component 65.
In the embodiment shown in
The nozzle chamber 61 is fluidly connected to a rail inlet port 14 of the fuel injector 10 via a fuel supply passage 41. The nozzle chamber 61 allows high-pressure fuel entering into the rail inlet port 14 to enter through the fuel supply passage 41 into the nozzle chamber 61. A pressure communication passage 42 fluidly connects the nozzle chamber 61 to the control valve assembly 30. The pressure communication passage 42 is also fluidly connected to the needle control chamber 80 via a first flow restrictor 46 that extends between the pressure communication passage 42 and the needle control chamber 80.
The control valve assembly 30 includes a control valve member 31 that moves between a lower valve seat 37 and an upper valve seat 36. The control valve assembly 30 may be electrically actuated by a solenoid coil 25, which controls the movement of an armature assembly 20 between a first armature position and a second armature position. The control valve assembly 30 is fluidly connected to the needle control chamber 80 via a valve supply passage 43 and a second flow restrictor 47. The second flow restrictor 47 is fluidly connected to the needle control chamber 80, and the flow area of the second flow restrictor 47 may be greater than the flow area of the first flow restrictor 46.
The control valve assembly 30 may fluidly connect the valve supply passage 43 to a low pressure drain or to the pressure communication passage 42, depending on whether the control valve member 31 is seated at the upper valve seat 36 or lower valve seat 37, respectively.
Typically, the nozzle chamber 61 and the pressure communication passage 42 are always at high-pressure as there is an unobstructed fluid connection with the common rail (not shown) through the rail inlet port 14. However, the pressure inside the needle control chamber 80 varies between high-pressure and low-pressure. When the solenoid coil 25 is de-energized, the armature assembly 20 is in the first armature position and the control valve member 32 is seated at the lower valve seat 37. The pressure communication passage 42 is fluidly connected to the valve supply passage 43, which in turn is connected to the needle control chamber 80 via the second flow restrictor 47. The pressure communication passage 42 is continuously supplying high-pressure fuel to the needle control chamber 80 via the first flow restrictor 46 and therefore, the needle control chamber 80 is exposed to high-pressure fuel when the solenoid coil 25 is de-energized. When the solenoid coil 25 is energized, the armature assembly 20 moves to the second armature position and the control valve member 32 is seated at the upper valve seat 36. The fluid connection between the pressure communication passage 42 and the valve supply passage is now blocked. Instead, the valve supply passage 43 is now fluidly connected to a low-pressure drain (not shown), allowing fuel from the needle control chamber 80 to flow to the low-pressure drain. As the second flow restrictor 47 has a larger flow area than the first flow restrictor 46, more fuel leaves the needle control chamber 80 than the amount of fuel entering, hence reducing the pressure inside the needle control chamber 80.
Referring to
Referring generally to
The check lift sleeve 170 has an outer wall surface 171, an inner wall surface 169, a top surface 192 and a bottom surface 194. The check lift sleeve 170 has a hollow, cylindrical shape, which means the check lift sleeve 170 is cylindrical in shape and has a hollow interior bore through the top and bottom surfaces 192 and 94 of the check lift sleeve 170. The check lift sleeve 170 has a wall thickness defined by the difference between the radius of the outer wall surface 171 and the radius of the inner wall surface 169 of the check lift sleeve 170. The wall thickness of the check lift sleeve 170 is designed to accommodate expected hoop stresses from expected pressure levels in the check lift sleeve 170. Those skilled in the art appreciate that hoop stress may be the greatest towards the mid-section of the check lift sleeve 170, therefore, the thickness of the check lift sleeve 170 is determined from the thickness at the mid-section of the check lift sleeve 170. Although the thickness of the check lift sleeve 170 may vary throughout its length, it may be easier to manufacture a check lift sleeve 170 with a uniform thickness. In one embodiment, the check lift sleeve 170 has a uniform wall thickness along a majority of the length of the check lift sleeve 170, which means that the wall thickness remains the same for more than half of the length of the check lift sleeve 170.
In one embodiment, the check lift sleeve 170 includes an upper sealing land 172 located on the top surface 192 of the check lift sleeve 170 and a lower sealing land 173 located on the bottom surface 194 of the check lift sleeve 170. The upper and lower sealing lands 172 and 173 may be annular, and have a radial surface width smaller than the thickness of the wall of the check lift sleeve 170. The term radial surface width is defined as the difference between the radius of an outer edge of the sealing land and the radius of an inner edge of the sealing land. Those skilled in the art may appreciate that by having the radial surface width of the sealing lands 172 and 173 smaller than the wall thickness of the check lift sleeve 170, the clamping pressure acting on the sealing lands 172 and 173 will be greater, therefore, producing better sealing. In one embodiment of the disclosure, the top surface 192 and the bottom surface 194 of the check lift sleeve 170 may have chamfers 174, which also result in the sealing lands 172 and 173 having a smaller radial surface width compared to the wall thickness of the check lift sleeve 170 at the mid-section of the check lift sleeve 70. The bottom surface 194 of the check lift sleeve 170 and a top surface 168 of the tip component 165 are in contact and form a seal to prevent fluid from leaking out of the nozzle chamber 161.
The outer wall surface 171 of the check lift sleeve 170 is separated from the inner wall 153 of the injector body casing 152 by a space. The space between the outer wall surface 171 of the check lift sleeve 170 and the inner wall 153 of the injector body casing 152 defines a leakage path 188. The leakage path 188 runs along the inner wall 153 of the injector body casing 152 into a drain outlet port (not shown) of the fuel injector 100.
In addition to the check lift sleeve 170, the nozzle assembly 160 includes the tip component 165 that includes an outer wall 166, a top surface 168, a bottom end 167, which defines a nozzle outlet 164. A bore 162 is defined within the tip component 165 and runs from the top surface 168 of the tip component 165 towards the bottom end 167 of the tip component 165, where it opens up into the nozzle outlet 164. The tip component 165 is partially disposed within the injector body casing 152, and the outer wall 166 of the tip component 165 may form a sealing contact 156 with the injector body casing 152, preventing any fuel that enters into the leakage path 188 to escape from between the inner wall surface 153 of the injector body casing 152 and the outer surface 166 of the tip component 165.
In the embodiment shown in
This nozzle assembly 160 is a part of a fuel injector 100 (partially shown in
It may further be appreciated by those skilled in the art that this disclosure relates to a nozzle assembly 60 that may be implemented into a wide variety of fuel injectors. The disclosure herein may pertain to certain types of fuel injectors, such as, common rail fuel injectors. However, the scope of the disclosure is not intended to be limited to the embodiments described herein, but rather to all embodiments that fall within the spirit of this disclosure.
The present disclosure finds potential application in fuel injectors and fuel systems in any engine or machine. The present disclosure has a general applicability in fuel injectors used in smaller engines and a particular applicability in smaller sized fuel injectors operating at higher pressures, such as above 200 MPa.
The nozzle assemblies 60 and 160 described in this disclosure may be used to operate any fuel injector. The nozzle assemblies 60 and 160 described in this disclosure may be suitable for common rail fuel injectors that want to achieve higher fuel injection pressures. Those skilled in the art may appreciate the various ways of controlling the flow of fuel through the nozzle outlet via a solenoid actuated valve assembly. The present disclosure describes the sequence of an injection event inside an electrically actuated common rail fuel injector 10, 100 including the nozzle assembly 60, 160 shown in
An injection event begins from the time the electrical actuator 25 is energized, and ends when the electrical actuator 25 is de-energized. Prior to an injection event, the electrical actuator 25 is de-energized, and the armature assembly 20 is in the first armature position. The control valve member 31 is seated at the lower valve seat 37, thereby allowing the valve supply passage 43, 143 to be fluidly connected to the pressure communication passage 42, 142. The control valve assembly 30 has a first configuration when the needle control chamber 80, 180 is connected to a low-pressure passage and has a second configuration when the needle control chamber 80, 180 is blocked from the low-pressure passage. During this period, fuel enters the fuel injector 10 through the rail inlet port 14 and enters the nozzle chamber 61, 161 through the fuel supply passage 41, 141. The nozzle chamber 61, 161 contains high-pressure fuel, which is exerted on the opening hydraulic surface 79. 179 of the needle valve member 78, 178. In the embodiment shown in
As the electrical actuator 25 is energized, the armature assembly 20 moves from the first armature position to the second armature position. The control valve member 31 also moves from the lower valve seat 37 to the upper valve seat 36, where it remains until the actuator 25 is de-energized. Fuel from the valve supply passage 43, 143 may flow through the lower valve seat 37 into a low-pressure drain (not shown) instead of through the upper valve seat 36 to the pressure communication passage 42, 142. Fuel may continue to move into the needle control chamber 80, 180 from the first flow restrictor 46, 146, but because the valve supply passage 43 is now connected to the low pressure drain, high-pressure fuel moves from the needle control chamber 80, 180 to the drain via the second flow restrictor 47, 147 and the valve supply passage 43, 143 because the second flow restrictor 47, 147 has a larger flow area than the first flow restrictor 46. The needle control chamber 80, 180 now may have a lower pressure and subsequently, lower pressure is acting on the closing hydraulic surface 82, 182 of the needle valve member 78, 178.
When the actuator 25 is energized and the needle control chamber 80, 180 has lower pressure, the force acting upon the opening hydraulic surface 79, 179 of the needle valve member 78, 178 exceeds the preload of the nozzle spring 59, 159 and the force acting upon the closing hydraulic surface 82, 182. Relieving the pressure acting on the closing hydraulic surface 82, 182 of the needle valve member 78, 178 inside the needle control chamber 80, 180 allows the needle valve member 78, 178 to move to the open position, allowing the nozzle outlet 64, 64 to open. In one embodiment, the closing hydraulic surface 82, 182 of the needle valve member 78, 178 does not touch the injector stack component 85, 185 because the interaction between the first and second flow restrictors 46, 146 and 47, 147 hydraulically stops the needle valve member 78, 178 before it hits the injector stack component 85, 185. In the nozzle assembly 60 shown in
The needle valve member 78, 178 is guided via an interaction between the needle valve member 78, 178 and the tip component 65, 165. In one embodiment, the guide segment 84, 184 of the needle valve member 78, 178 guides the needle valve member 78, 178 along the bore 62, 162 of the tip component 65, 165, and the guide segment 84, 184 may prevent the needle valve member 78, 178 from being misaligned with the bore 62, 162 of the tip component 65, 165. Those skilled in the art will understand the importance of maintaining the alignment of the needle valve member 78, 178 with respect to the bore 62, 162 of the tip component 65, 165 and the nozzle assembly 60, 160 because maintaining alignment between the bore 62, 162 and the needle valve member 78, 178 will reduce wear and tear caused by rubbing the needle valve member 78, 178 against the bore 62, 162 as well as improve the accuracy at which the nozzle outlet 64, 164 is opened and closed.
In order to end the injection event, the nozzle outlet 64, 164 is closed by de-energizing the actuator 25. When the actuator 25 is de-energized, the armature assembly 20 moves from the second armature position to the first armature position, consequently moving the control valve member 31 from the upper valve seat 36 back to the lower valve seat 37. Once the control valve member 32 is at the lower valve seat 37, the fluid connection between valve supply passage 43, 143 and the low pressure drain is now disconnected. Instead, the valve supply passage 43, 143 is once again fluidly connected to the pressure communication passage 42, 142 allowing high-pressure fuel from the pressure communication passage 42, 142 to flow to the valve supply passage 43, 143. In the nozzle assembly 60 shown in
Those skilled in the art will also appreciate that the pressure inside the nozzle chamber 61, 161 is dependent upon the rail pressure. Further, because there is an unobstructed fluid connection between the rail inlet port 14 and the nozzle chamber 61, 161 and the nozzle outlet's 64, 164 flow area is smaller than the flow area of the fuel supply passage 41, 141, the nozzle chamber 61, 161 maintains high-pressure both during and between injection events.
Also, the sealing lands 72, 172 and 73, 173 of the high-pressure containment sleeve 70, 170 may be annular and may be smaller in width than the wall thickness of the high-pressure containment sleeve 70, 170. The sealing lands 72, 172 and 73, 173 prevent the high-pressure fuel from leaking into the leakage path 88, 188. Because the components of the fuel injector 10, 100 are clamped together to contain the fuel pressure, the forces are exerted on the respective components of the fuel injector 10, 100. By reducing the surface area of the sealing lands of the components, the pressure is increased on the surface of the sealing land allowing for better sealing capabilities.
Referring to
The floating check guide 175 defines the first flow restrictor 146, which extends between the nozzle chamber 161 and the needle control chamber 180 and thereby maintains an unobstructed fluid connection between the nozzle chamber 61 and the needle control chamber 80 during and between injection events. The second flow restrictor 182 is defined within the control orifice component 186 and extends between the needle control chamber 186 and the valve supply passage 143. Similar to the embodiment shown in
The nozzle assembly 160 also differs from the nozzle assembly 60 shown in
The present disclosure improves a fuel injector's ability to withstand higher injection pressures. By using a high-pressure containment sleeve, with adequate wall thickness and free from stress concentrating surface features, such as those associated with the heart shaped cavity of the prior art, smaller fuel injectors may withstand higher pressures without forming stress fractures. The ease in manufacturing the high-pressure containment sleeve also reduces the manufacturing costs of producing these fuel injectors, as machining a heart shaped cavity surrounded by metal may be more costly. Further, designing the high-pressure containment sleeves with annular sealing lands may provide for a better seal capable of withstanding these higher pressures for a longer injector life.
It should be understood that the above description is intended for illustrative purposes only, and is not intended to limit the scope of the present disclosure in any way. Thus, those skilled in the art will appreciate that other aspects of the disclosure can be obtained from a study of the drawings, the disclosure, and the appended claims.
