Electrode assembly for electrical discharge machining

Abstract

An electrical discharge machining (EDM) assembly includes a mounting device configured to support an EDM electrode relative to a workpiece. The electrode includes an axial opening extending between opposite ends of the electrode, a first portion including one end, and a second portion including the opposite ends. The first portion is more flexible than the second portion. For example, the first portion may be a helical spring, and the second portion may be a rigid tube. The mounting device includes a back plate, an upright portion projecting from the back plate, and a curved sleeve disposed in a through-hole penetrating the back plate and the upright portion. The electrode is movably disposed within the sleeve.

Description

Background Technology

[0001] Electrical discharge machining (EDM) is a metal manufacturing process in which material is removed from a metal workpiece by a series of rapid, repeated electrical discharges between an electrode and the workpiece. EDM can also be called electrical spark machining or arc machining.

[0002] The electrode and workpiece are separated by a dielectric fluid and subjected to a voltage. The dielectric fluid can be, for example, deionized water or hydrocarbon oil. In EDM, current flows between the electrode and the workpiece. The dielectric fluid acts as an electrical insulator until a sufficient voltage is applied to bring it to its ionization point, at which point it becomes an electrical conductor. The resulting spark discharge erodes the workpiece to form the desired final shape.

[0003] EDM offers excellent surface finish, minimal heat-affected zone, and the ability to cut hardened materials and rare alloys. Furthermore, EDM provides accurate and precise holes, even in hardened or rare materials.

[0004] In some applications, EDM can employ rigid rotating conductive tubes as electrodes to form blind holes in a workpiece. In this application, a continuous flow of dielectric fluid is supplied to the workpiece surface through the interior of the tube, which serves to refresh the dielectric fluid and flush the cut area. However, due to the rigidity of the electrode, it is difficult to form directional or redirected blind holes within the workpiece without using multiple passes to provide intersecting holes. Such multiple passes result in multiple openings on the workpiece surface, which can be disadvantageous because any external openings on the workpiece surface used to form the passage must be plugged, posing a risk of leakage. Therefore, it is desirable to provide an electrode capable of providing orientation changes for the holes formed in the workpiece. Summary of the Invention

[0005] Flexible electrode EDM assemblies can be used to form complex blind holes in a workpiece. An exemplary workpiece is an integral fuel rail structure configured to provide high-pressure fuel distribution to fuel injectors, which in turn supply fuel to the cylinders of an engine. While plastic fuel rails are known, metal fuel rails can be used to deliver fuel at high pressure and include a main fluid supply conduit referred to as a “round bar.” As used herein, the term “high pressure” refers to a pressure greater than 200 bar. The round bar has a main fuel passage through which fuel is supplied from the fuel tank. The fuel rail includes distribution arms for distributing fuel to the individual cylinders of the engine. The distribution arms project from the round bar and provide a fuel passage communicating with the main fuel passage. Each distribution arm terminates in an injector cup (sometimes called a bushing). Each injector cup includes a cavity that receives and holds the inlet end of a fuel injector. The fuel injector inlet end includes a seal that mates with the cavity to define a high-pressure fuel distribution chamber within the injector cup. Fuel is supplied at high pressure to the fuel distribution chamber via the main fuel passage of the round bar and the fuel passage of the corresponding distribution arm. The relative geometries of the round rod, distribution arm, and injector cup are complex and depend on the engine geometry and the available space within the engine system.

[0006] The workpiece is formed into an integral fuel rail structure using a manufacturing process in which the round stock, distribution arms, and injector cups are integrally formed from a single metal blank. Manufacturing processes used to form the integral fuel rail structure can include, but are not limited to, extrusion, casting, forging, and injection molding. Some conventional integral fuel rail structures can be completed by machining the main fuel passage within the round stock, the fuel passage within each distribution arm, and the cavity within each injector cup using a twist drill. However, machining the distribution arm fuel passage through the injector cup cavity into the main fuel passage of the round stock without piercing the cavity and compromising the integrity of the fuel distribution chamber, particularly in geometries where the centerline of the cavity is offset relative to the centerline of the main fuel passage, is challenging. For example, to avoid compromising the integrity of the fuel distribution chamber, machining is limited to providing a fuel passage aligned with the centerline of the cavity and having a maximum offset from the centerline of the cavity corresponding to the radius of the cavity. Therefore, the range of the fuel distribution path and the ability of the fuel rail structure to fit into the available space within the engine system are limited.

[0007] The fuel passage connecting the injector cup and the fuel round feedstock delivers high-pressure fuel from the feedstock's main fuel channel to the injector cup cavity. This passage must be free of contaminants and burrs, as these will affect functionality and durability. EDM assemblies including flexible electrodes can be used to machine the fuel passage. Specifically, by using flexible rotary EDM electrodes, the fuel passage can be machined from an entry point located within the injector cup cavity and extends through the distribution arm to the feedstock's main fuel channel.

[0008] The entry position of the hole providing a fuel passage between the injector cup cavity and the main fuel passage of the round material is set in the cavity, for example, in the sidewall of the cavity. This is achieved by inserting an EDM electrode into the open end of the cavity along a path aligned with the longitudinal axis of the cavity and bending the EDM electrode so that it enters the sidewall of the cavity at a position corresponding to the distribution arm. Since it is possible to bend the EDM electrode and machine the hole in the sidewall of the cavity, the length of the distribution arm and the position of the fuel injector cup relative to the round material can be set to provide a greater offset and a non-zero angle relative to the centerline of the cavity. Therefore, the fuel passage connecting the main fuel passage of the round material to the cavity of the integrated injector cup is formed through the injector cup via an inlet formed in the sidewall of the injector cup and extending at an angle to the centerline of the cavity, thereby allowing deviation from the centerline of the round material in two orthogonal directions perpendicular to the centerline of the main fuel passage. By machining in this way, engine designers have increased the flexibility of integrating the fuel rail assembly into the engine. Furthermore, the fuel rail disclosed herein is "backward compatible". In other words, a given engine can be upgraded through limited redesign and testing of components such as fuel injectors, pressure sensors, connecting pipes, and electrical harnesses, saving construction personnel time and money while reducing the risk of untested parts. Furthermore, the fuel rail disclosed herein allows for the reuse of equipment and process measures.

[0009] EDM electrodes form clean orifices that can be deburred by electropolishing the finished fuel rail. In some embodiments, the diameter of the orifice providing the fuel passage can range from 1 mm to 3.5 mm. The length of the fuel passage, combined with its diameter, can be configured to provide a pressure damping effect that complements or replaces orifices typically found in rail inlet fittings or injector bodies. This reduces the cost of fittings and / or injectors.

[0010] EDM (Electrode Deposition) processes are ideally suited for forming fuel passages because EDM is a precise process, and the material removed by EDM is dissolved and / or removed via a dielectric fluid, resulting in clean holes that can be deburred by electropolishing the finished fuel rail assembly. Importantly, EDM processes do not leave fine debris, chips, or other contaminants in the machined parts, which can negatively impact functionality and durability. While other processing methods can be used to form fuel passages, such as torsional drilling, laser burning, plasma burning, and waterjet etching, these methods may be unsuitable in some embodiments due to potential contamination, relative inaccuracies, and / or relatively poor form control. Furthermore, EDM processes can reduce production time relative to the time required to form a given hole or passage.

[0011] In some aspects, the EDM electrode includes a first electrode end, a second electrode end opposite to the first electrode end, and a longitudinal electrode axis extending between the first electrode end and the second electrode end. The EDM electrode includes an axial opening extending between and opening therebetween the first and second electrode ends. Additionally, the EDM electrode includes a first electrode portion containing the first electrode end and a second electrode portion containing the second electrode end. The EDM electrode is conductive, the first electrode portion has a first flexibility, and the second electrode portion has a second flexibility less than the first flexibility.

[0012] In some embodiments, the first part of the electrode is a helical spring, and the second part of the electrode is a tube.

[0013] In some embodiments, the first portion of the electrode has sufficient flexibility to bend when a bending force is applied to the first portion of the electrode, and the bending corresponds to a deflection angle of at least 20 degrees relative to the longitudinal axis of the first end. Furthermore, the first portion of the electrode has sufficient elasticity to return to a linear configuration in which the deflection angle is zero when the bending force is removed.

[0014] In some embodiments, the electrode includes an inner electrode surface defining an axial opening. Additionally, the first portion of the electrode includes a channel in the electrode surface that communicates with the axial opening and extends along a helical path between the first end of the electrode and the second portion of the electrode.

[0015] In some embodiments, the channel has a rectangular outline.

[0016] In some embodiments, the first portion of the electrode includes: an axially extending fluid path corresponding to an axial opening that allows fluid communication between the axial opening and the outside of the electrode; and a second fluid path that allows fluid communication between the axial opening and the outside of the electrode, the second fluid path extending radially relative to a longitudinal axis.

[0017] In some embodiments, the second portion of the electrode does not have a second fluid path.

[0018] In some aspects, the EDM assembly includes a mounting device configured to support an EDM electrode relative to a workpiece. The mounting device includes a backplate having a first backplate surface, a second backplate surface opposite to the first backplate surface, and side surfaces extending between the first and second backplate surfaces. The mounting device includes an upright portion projecting from the first backplate surface and a tubular sleeve disposed in a through-hole penetrating the backplate and the upright portion. The through-hole is aligned with an axis perpendicular to the first backplate surface. The sleeve includes a first sleeve end, a second sleeve end, and an inner sleeve surface defining a sleeve passage extending between the first and second sleeve ends. The sleeve is disposed in the through-hole such that the first sleeve end projects from one end of the through-hole.

[0019] In some embodiments, the sleeve is disposed in the through hole such that the first end and the second end of the sleeve protrude from opposite ends of the through hole.

[0020] In some embodiments, the sleeve is fixed inside the through hole.

[0021] In some embodiments, a first end of the sleeve is disposed outside the through hole on the side of the back plate corresponding to the first surface of the back plate, and a second end of the sleeve is disposed outside the through hole on the side of the back plate corresponding to the second surface of the back plate. Additionally, the sleeve includes a bent portion disposed outside the through hole and between the first end of the sleeve and the upright portion.

[0022] In some embodiments, the sleeve includes: a curved portion, which is closer to the first end of the sleeve than the second end of the sleeve and is disposed outside the through hole; and a linear portion extending between the curved portion and the second end of the sleeve. At least a portion of the linear portion is disposed in the through hole.

[0023] In some embodiments, the curved portion is provided with a curved section having a bending angle in the range of zero to 90 degrees relative to a line parallel to the linear portion.

[0024] In some embodiments, the upright portion has a proximal end adjacent to the back plate, a distal end spaced apart from the proximal end, a side surface extending between the proximal end and the distal end, and a flat portion disposed at the intersection of the distal end and the side surface, the flat portion being angled relative to the distal end and the side surface.

[0025] In some embodiments, the upright portion has a proximal end adjacent to the back plate, a distal end spaced apart from the proximal end, a cylindrical side surface extending between the proximal and distal ends, and an upright portion centerline equidistant from all portions of the side surface. Through-holes are parallel to and offset from the upright portion centerline.

[0026] In some embodiments, the EDM component includes an EDM electrode configured to be housed within a sleeve passage.

[0027] In some embodiments, the sleeve includes a curved portion that is closer to the first end of the sleeve than to the second end of the sleeve, and the curved portion is disposed outside the through hole.

[0028] In some embodiments, the EDM electrode is disposed in the sleeve passage, and the first flexibility is greater than the flexibility of the sleeve. Additionally, a portion of the EDM electrode in the curved portion is deflected to accommodate the shape of the curved portion.

[0029] In some embodiments, the EDM electrode can rotate and move longitudinally within the sleeve passage.

[0030] In some embodiments, when released after being bent within a curved portion, the EDM electrode is able to return to its original shape.

[0031] In some embodiments, the backplate includes a fastener hole extending between a first surface and a second surface of the backplate, the fastener hole being disposed between the upright portion and the side surface of the backplate.

[0032] In some embodiments, the back panel includes a groove disposed in a second surface of the back panel.

[0033] In some embodiments, the groove has a larger radial dimension than the through hole, and the groove is concentric with the centerline of the back plate.

[0034] In some embodiments, the upright portion includes a proximal end adjacent to the backplate and a distal end opposite to and spaced apart from the backplate. The distal end has a projection with a curved profile.

[0035] In some embodiments, the back plate is a first cylinder comprising a first height dimension parallel to the centerline of the through hole and a first radial dimension perpendicular to the centerline of the through hole. The first height dimension is smaller than the first radial dimension, and the upright portion is a second cylinder comprising a second height dimension parallel to the centerline of the through hole and a second radial dimension perpendicular to the centerline of the through hole, wherein the second height dimension is larger than the second radial dimension and larger than the first height dimension. Attached Figure Description

[0036] Figure 1 This is a top perspective view of the EDM assembly, including the mounting device and EDM electrodes.

[0037] Figure 2 yes Figure 1 A bottom-view perspective of the EDM component.

[0038] Figure 3 Is it like along Figure 1 Line 3-3 Figure 1 Cross-sectional view of the EDM component.

[0039] Figure 4 yes Figure 1 Top perspective view of the mounting device for EDM components.

[0040] Figure 5 yes Figure 1 A perspective view of the EDM electrode.

[0041] Figure 6 It is along Figure 5 A magnified cross-sectional view of the EDM electrode in line 6-6.

[0042] Figure 7 It omits the EDM electrode. Figure 1A perspective view of a portion of the EDM component.

[0043] Figure 8 This is a perspective view of a portion of an EDM assembly from an alternative embodiment, omitting the EDM electrode.

[0044] Figure 9 This is a perspective view of a portion of an EDM component from an alternative embodiment that omits the EDM electrode.

[0045] Figure 10 Is it like along Figure 9 Line 10-10 seen Figure 9 Cross-sectional view of the EDM component.

[0046] Figure 11 This is a perspective view of a portion of an integral fuel rail structure, illustrating the EDM assembly partially inserted into the open end of the injector cup.

[0047] Figure 12 Is it like along Figure 11 Line 12-12 seen Figure 11 A cross-sectional view of the integral fuel rail structure.

[0048] Figure 13 yes Figure 11 A cross-sectional view of the integral fuel rail structure, illustrating the EDM assembly inserted into the cavity of the injector cup, wherein the EDM electrode is located at the position where the inlet hole begins to form in the sidewall of the injector cup.

[0049] Figure 14 yes Figure 11 A cross-sectional view of an integral fuel rail structure, illustrating an EDM assembly inserted into a cavity in the injector cup, wherein the EDM electrode forms a pathway within the integral fuel rail structure.

[0050] Figure 15 yes Figure 11 A cross-sectional view of the integral fuel rail structure, illustrating the EDM assembly inserted into the cavity of the injector cup, wherein the EDM electrode intersects with the main fuel passage of the integral fuel rail structure.

[0051] Figure 16 yes Figure 11 A cross-sectional view of the integral fuel rail structure, illustrating the EDM assembly inserted into the cavity of the injector cup, wherein the EDM electrode retracts from the sleeve after the passage is completed.

[0052] Figure 17 yes Figure 11 A cross-sectional view of the integral fuel rail structure, illustrating the EDM assembly being pulled out of the injector cup cavity, wherein the EDM electrode retracts from the sleeve after the passage is completed. Detailed Implementation

[0053] refer to Figure 1-2 As described in 11-12, EDM assembly 1 is suitable for use in EDM processes. More specifically, EDM assembly 1 is suitable for electrical discharge machining of holes in metal workpieces 2, such as integral fuel rail precursors. EDM assembly 1 includes a conductive EDM electrode 10 and a non-conductive mounting device 30 configured to support the EDM electrode 10 relative to the workpiece 2. The EDM electrode 10 is slidably received and supported by a rigid sleeve 80 of the mounting device 30, as discussed further below. The EDM electrode 10 is configured to be electrically connected to a voltage generator (not shown) as part of a circuit comprising the EDM electrode 10, the voltage generator, and the metal workpiece 2. The mounting device 30 is a rigid support structure and includes a back plate 40, an upright portion 60 projecting from a first or workpiece-facing surface 41 of the back plate 40, and the sleeve 80. The sleeve 80 extends through the back plate 40 and the upright portion 60. In some embodiments, the mounting device 30 may be connected to a worktable (not shown) that is movable relative to the workpiece 2 by a servo motor or other suitable actuator (not shown). In other embodiments, the mounting device 30 may be directly connected to the actuator. The EDM electrode 10 is elastic (e.g., flexible and resilient) and is housed and supported by a sleeve 80, which includes a bent portion 84 that deflects one end of the EDM electrode 10 as it is fed through the mounting device 30 during processing. The EDM assembly 1, including the EDM electrode 10 supported by the mounting device 30, can be used to form complex blind holes or through holes in the workpiece 2, as discussed in detail below.

[0054] refer to Figure 5-6 The EDM electrode 10 is an elongated hollow cylindrical structure comprising a first electrode end 11 and a second electrode end 12 opposite to the first electrode end 11. The EDM electrode 10 includes a longitudinal axis 13 extending between the first and second electrode ends 11 and 12, and an axial opening 14 extending between the first and second electrode ends 11 and 12 and opening at each end. The end face 11a of the first electrode end 11 is substantially perpendicular to the longitudinal axis 13 and provides a "discharge surface" for the EDM electrode. During the EDM process, the end face 11a is the surface through which material is discharged toward the workpiece 2, resulting in material removal from the workpiece 2 near the end face 11a and from the first electrode end 11. The axial opening 14 provides a longitudinal fluid path 19 through the EDM electrode 10, through which dielectric fluid is supplied to the discharge surface during the EDM process.

[0055] The EDM electrode 10 includes a first portion 16 comprising a first end 11 and a second portion 17 comprising a second end 12. The first portion 16 has a first flexibility, the second portion 17 has a second flexibility, and the first flexibility is greater than the second flexibility. For example, in some embodiments, the first portion 16 has sufficient flexibility to bend when a relatively low bending force (e.g., a force in the range of 5 N to 20 N) is applied to the first portion 16, the bending corresponding to a deflection angle of at least 20 degrees relative to the longitudinal axis 13 of the first end 11. Additionally, upon removal of the bending force, the first portion 16 has sufficient elasticity to return to a linear configuration in which the deflection angle is zero. The second portion 17 is sufficiently rigid to remain linear during the application of the bending force.

[0056] In the illustrated embodiment, the first portion 16 of the electrode is a helical spring, and the second portion 17 of the electrode is a closed-wall tube. The EDM electrode 10 can be formed by cutting a helical channel 18 in a portion of the conductive closed-wall tube. For example, in the illustrated embodiment, the channel 18 extends along a helical path between the first end 11 of the electrode and the second portion 17 of the electrode, whereby the spring or the first portion 16 corresponds to approximately half the total length of the EDM electrode 10. An EDM wire cutting process can be used to form the helical channel 18, which has a rectangular profile and communicates with the axial opening 14. The channel 18 does not extend into the second portion 17 of the electrode. With this configuration, the second portion 17 of the electrode has less flexibility than the first portion 16 of the electrode and provides an attachment area through which the EDM electrode can be electrically connected to a voltage generator and a feed mechanism (not shown) that rotates the EDM electrode 10 and advances the EDM electrode 10 through the sleeve 80 of the mounting device 30 during EDM operation.

[0057] As previously discussed, the axial opening 14 provides a first longitudinal fluid path 19 through the EDM electrode 10, through which dielectric fluid is supplied to the end face 11a of the first end 11 of the electrode during the EDM process. The first fluid path 19... Figure 6 The solid arrows indicate this. The EDM electrode 10 also provides a second fluid path 20, which allows fluid communication between the axial opening 14 and the exterior of the EDM electrode 10. The second fluid path 20 corresponds to the channel 18 (e.g., the space between the turns of the helix), which allows the dielectric fluid to flow radially relative to the longitudinal axis 13 of the electrode and allows for a substantially increased flow of the dielectric fluid near the electrode end face 11a. The second fluid path 20 is... Figure 6The dashed arrows in the diagram indicate this. Although the dashed arrows are not shown at all locations in channel 18, it should be understood that the dielectric fluid exits the axial opening 14 radially along channel 18. By increasing the volume of the dielectric fluid flow near electrode end face 11a, the risk of dielectric breakdown in this region can be reduced. The removal of corroded debris from this region is improved by generating turbulence in the dielectric fluid flow near electrode end face 11a due to the fluid flowing in both the longitudinal and radial directions.

[0058] The material used to form the EDM electrode 10 is selected based on the material of the workpiece 2. In an example where the workpiece 2 is an integral fuel rail precursor formed of stainless steel, the EDM electrode 10 can be formed of copper or graphite.

[0059] refer to Figure 1-4 The mounting device 30 is a rigid structure used to support the EDM electrode relative to the workpiece 2 during the EDM process. The mounting device 30 includes a back plate 40 configured to be mounted to a worktable or actuator, an upright portion 60 protruding from the back plate 40, and a sleeve 80 extending through a through hole 32 provided in the back plate 40 and the upright portion 60. The mounting device 30 will now be described in detail.

[0060] The back plate 40 is a thick plate and includes a first back plate surface 41 facing the workpiece 2, a second back plate surface 42 opposite to the first back plate surface 41, and a side surface 43 extending between the first back plate surface 41 and the second back plate surface 42. In the illustrated embodiment, the back plate 40 has a circular profile, thus the back plate 40 is a low-profile cylinder. The term "low-profile" means that the height dimension of the back plate 40 is much smaller than the radial dimension of the back plate 40. The through hole 32 is collinear with the centerline 46 of the back plate 40, wherein the back plate centerline 46 is equidistant from and extends parallel to the back plate side surface 43. The back plate 40 includes fastener holes 44 extending between the first and second back plate surfaces 41, 42. The fastener holes 44 are spaced apart from each other and are disposed between the back plate side surface 43 and the upright portion 60. In addition, the back plate 40 includes a groove 45 disposed in the second back plate surface 42. The groove 45 is concentric with the center line 46 of the back plate and has a larger radial dimension than the through hole 32.

[0061] The upright portion 60 is a high-profile cylinder projecting from the first surface 41 of the back plate toward the workpiece 2. The term "high profile" means that the height dimension of the upright portion 60 is significantly larger than its radial dimension. The upright portion 60 includes a proximal end 61 adjacent to the first surface 41 of the back plate and a distal end 62 opposite to and spaced apart from the back plate 40. The upright portion 60 includes a curved side surface 63 extending between the proximal end 61 and the distal end 62. The centerline 64 of the upright portion 60 coincides with the centerline 46 of the back plate, wherein the centerline 64 is equidistant from and extends parallel to the side surface 63. The radial dimension of the upright portion 60 is significantly smaller than the radial dimension of the back plate 40, thereby radially inwardly spaced the side surface 63 of the upright portion relative to the side surface 43 of the back plate.

[0062] The distal end 62 of the upright portion 60 includes a protrusion 65 disposed radially inward relative to the side surface 63 of the upright portion. The protrusion 65 may have the shape of a truncated sphere or a cone, thus having a curved profile when viewed in a direction parallel to the centerline 64 of the upright portion, and a planar end 66 when viewed in a direction perpendicular to the centerline 64 of the upright portion. The shape and size of the protrusion 65 are configured to allow partial insertion into a circular entry opening in the workpiece 2 and to center the distal end 62 of the upright portion relative to the workpiece entry opening 3, as described below.

[0063] The upright portion 60 includes a flat portion 68 disposed in the side surface 63 of the upright portion at the intersection of the side surface 63 and the proximal end 61. The flat portion 68 is parallel to the centerline 64 of the upright portion. The flat portion 68 is located between the centerline 64 and the side surface 63. In some embodiments, the height dimension of the flat portion 68 is in the range of 10% to 50% of the height dimension of the upright portion 60. In some applications, when used during EDM operation, the flat portion 68 provides a visual reference indicating the rotational orientation of the mounting device 30 and / or the sleeve 80. Additionally, since the flat portion 68 is a recessed discontinuity in the circular profile of the distal end 62, the flat portion 68 provides a path for dielectric fluid to escape from the vicinity of the electrode end face 11a during EDM operation, as described below.

[0064] The through-hole 32 extends linearly and passes through the back plate 40 and the upright portion 60. The through-hole 32 has a cross-sectional shape and dimensions that accommodate the sleeve 80. The through-hole 32 is parallel to the center lines 46, 64 of the back plate 40 and the upright portion 60. In some embodiments, the through-hole 32 coincides with the center lines 46, 64 of the back plate 40 and the upright portion 60. In other embodiments ( Figure 3The through-hole 32 is offset relative to the centerlines 46, 64 of the back plate 40 and the upright portion 60. By providing the offset of the through-hole 32, it is possible to provide an increased bending angle for the bent portion 84 of the sleeve 80 (as described below), which in turn increases the range of possible directional change angles that can be achieved by the hole cut by the EDM electrode 10.

[0065] refer to Figure 3-4 In conjunction with 7-8, sleeve 80 is an elongated tube fixed within through hole 32. Sleeve 80 includes a first sleeve end 81 and a second sleeve end 82 opposite to the first sleeve end 81. Sleeve 80 includes an inner surface 83 defining a sleeve passage 88 extending between the first sleeve end 81 and the second sleeve end 82. In use, EDM electrode 10 resides in sleeve passage 88 and is axially movable within sleeve passage 88, such that during EDM operation, EDM electrode 10 can be advanced toward and / or enter into workpiece 2.

[0066] The axial dimension of the sleeve 80 is larger than the axial dimension of the through hole 32, and the first and second ends 81 and 82 of the sleeve protrude from opposite ends of the through hole 32. Specifically, the first end 81 of the sleeve is disposed outside the through hole 32 on the side of the back plate 40 corresponding to the first surface 41 of the back plate. In addition, the second end 82 of the sleeve is disposed outside the through hole 32 on the side of the back plate 40 corresponding to the second surface 42 of the back plate.

[0067] The sleeve 80 includes a curved portion 84 and a linear portion 85. The curved portion 84 is positioned closer to the first end 81 of the sleeve than the second end 82. The linear portion 85 extends between the curved portion 84 and the second end 82. The curved portion 84 resides outside the through-hole 32 and is positioned between the first end 81 and the upright portion 60. In the illustrated embodiment, the curved portion 84 includes a single bend with a bending angle θ relative to a line parallel to the linear portion 85, ranging from zero to 90 degrees. Figure 7 In the middle, sleeve 80 has a bending angle θ1 of approximately 70 degrees. Figure 8 In one alternative embodiment, sleeve 180 has a bending angle θ2 of approximately 30 degrees. In other embodiments, the bending portion 84 may include a plurality of consecutive bends.

[0068] The mounting device 30 can be formed on any suitable non-conductive material. In some embodiments, the substrate 40, the upright portion 60, and the sleeve 80 can each be formed of the same material, while in other embodiments, the mounting device 30 is not limited to this configuration. In some embodiments, the sleeve 80 is formed of nylon, hardened plastic, or heat-resistant glass.

[0069] refer to Figure 9 and 10In another alternative embodiment, the sleeve 280 can be used with the substrate 40 and the upright portion 60 to support the EDM electrode 10. The alternative embodiment sleeve 280 is similar to the one described above. Figure 1-7 The sleeve 80 is described, and common reference numerals are used to refer to common elements. Figure 9 and 10 The sleeve 280 shown differs from the previous embodiment in that it includes an insert 90 disposed in the first end 81 of the sleeve. The insert 90 is an annular structure that provides coverage for the end face 89 of the first end 81 of the sleeve and wraps around the inner surface 83 of the sleeve adjacent to the end face 89. The insert 90 improves the wear resistance of the sleeve 80 and is formed of a wear-resistant and non-conductive material such as ceramic.

[0070] In use, the EDM electrode 10 is supported relative to the workpiece 2 by the mounting device 30, with the first end 11 of the electrode protruding from the first end 81 of the sleeve. For example, the EDM electrode 10 can be positioned near the workpiece 2 such that there is a small gap between the end face 11a of the first end 11 of the electrode and the workpiece 2. As material is removed from the workpiece 2, the EDM electrode 10 is consumed. In order to maintain an appropriate gap during the forming of the workpiece 2 and the consumption of the EDM electrode 10, the EDM electrode 10 is advanced toward the workpiece 2 through the sleeve 80 during EDM operation.

[0071] Therefore, in use, the first portion 16 of the EDM electrode 10 resides within and passes through the curved portion 84 of the sleeve 80. The sleeve 80 is much less flexible than the first portion 16 of the EDM electrode 10, and the first portion 16 of the EDM electrode 10 deflects to conform to the shape of the curved portion 48. In other words, portion 16a of the first portion 16 of the EDM electrode residing in the curved portion 84 conforms to the shape of the curved portion 84. The EDM electrode 10 is elastic, such that portion 16b of the first portion 16 of the EDM electrode protruding from the first end 81 of the sleeve returns to a linear configuration. In other words, the EDM electrode 10 returns to its original shape upon release after undergoing bending within the curved portion 84 of the sleeve.

[0072] refer to Figure 11-17In the example where workpiece 2 is an integral fuel rail precursor, the fuel rail precursor is a forged, integral metal structure machined using an EDM process to provide a finished fuel rail (not shown). The finished fuel rail is configured to supply fuel to multiple fuel injectors (not shown), which inject fuel directly into the cylinders of an internal combustion engine (not shown). The fuel rail precursor 2 includes a round bar 5 that receives high-pressure fuel from a fuel tank or fuel pump (not shown). The fuel rail precursor 2 includes integral distribution arms 6 spaced along the length of the round bar 5 and projecting from the outer surface of the round bar 5. As used herein, the term "integral" is defined as "monolithic, formed as a single unit with another part." Figure 11 and 12 The diagram shows only a portion of the fuel rail precursor 2, including a single distribution arm 6. Each distribution arm 6 is configured to distribute pressurized fuel to a corresponding individual cylinder of the engine. Each distribution arm 6 terminates in an integral injector cup 8, which is configured to receive and hold the inlet end of a fuel injector (not shown). Fuel is supplied at high pressure via the main fuel passage 9 of the round member 5 and fuel passages 100 disposed in the respective distribution arms 6. Figure 16 The fuel is supplied to each injector cup 8. Therefore, the high-pressure fuel contained in the finished fuel rail is directly distributed to each cylinder of the engine via the corresponding distribution arm 6, injector cup 8, and fuel injector. The relative geometry of the round rod 5, distribution arm 6, and injector cup 8 is complex and depends on the engine geometry and the available space within the engine system.

[0073] Fuel passage 100 can be formed in distribution arm 6 of fuel rail precursor 2 to extend between main fuel passage 9 of round material 5 and injector cup 8 via EDM process employing EDM assembly 1. EDM assembly 1 supports EDM electrode 10 relative to fuel rail precursor 2. Figure 13-17 The illustration shows an example of how EDM component 1 and EDM electrode 10 can be used to form fuel passage 100 in distribution arm 6 of fuel rail precursor 2.

[0074] like Figure 13As shown, initially, the upright portion 60 of the mounting device 30 is positioned adjacent to the injector cup 8 such that a protrusion 65 of the upright portion is inserted into the open end of the injector cup 8. The protrusion 65 positions the EDM assembly 1 relative to the injector cup 8 while providing a gap between the inner surface of the injector cup and the flat portion 69 of the upright portion 60. This gap allows the dielectric fluid pumped through the EDM electrode 10 out of the injector cup 8 along the first and second fluid paths 19, 20 during the EDM process. The first end 81 of the sleeve is positioned to be closely spaced relative to the inner surface of the injector cup 8 at an entry position corresponding to the entry position of the EDM electrode 10 into the fuel rail precursor 2. The entry position coincides with a line 90 extending between the main fuel passage 9 of the round material and the internal space of the injector cup 8, and passes through the distribution arm 6.

[0075] like Figure 14 As shown, during the EDM process, the EDM electrode 10 is advanced toward the fuel rail precursor 2 via the sleeve 80. As the EDM electrode advances, it moves longitudinally toward the first end 81 of the sleeve via the sleeve 80 and also rotates about the longitudinal axis 13 of the EDM electrode. Furthermore, a discharge is emitted from the electrode end face 11a toward the fuel rail precursor 2, resulting in the removal of material from the fuel rail precursor 2 near the end face 11a, thereby cutting a hole in the fuel rail precursor 2 having a shape and size slightly larger than the electrode end face 11a.

[0076] like Figure 15 As shown, the EDM process continues until the electrode end face 11a enters the main fuel passage 9 of the round material 5. The hole cut by the EDM electrode through the distribution arm 6 provides a fluid communication path between the main fuel passage 9 of the round material and the internal space of the injector cup 8, and corresponds to the fuel passage 100.

[0077] like Figure 16 As shown, after the fuel passage 100 is formed, the EDM electrode 10 is withdrawn from the fuel passage 100. In some embodiments, the EDM electrode 10 may also be partially or completely withdrawn from the sleeve 80.

[0078] like Figure 17 As shown, as a final step, the mounting device 30 is removed from the injector cup 8.

[0079] although Figure 13-17 The illustration shows an example of how an EDM assembly 1, including mounting device 30 and EDM electrode 10, can be used to form a fuel passage 100 in the distribution arm 6 of a fuel rail precursor. However, the EDM assembly 1 is not limited to the one shown in the figure or other configurations. Figure 13-17 The events shown are used in sequence. Furthermore, it should be understood that EDM component 1 is not limited to processing fuel rail precursor 2, but can be used to form complex holes in any metal workpiece.

[0080] Although the first or spring portion 16 of the EDM electrode 10 is described as being formed by cutting a helical channel 18 in a portion of a conductive closed-wall tube, the EDM electrode 10 is not limited to being formed during an EDM wire cutting process. It should be understood that other methods can be used to provide the EDM electrode.

[0081] Although the back plate 40 and the upright portion 60 are cylindrical in the illustrated embodiment, they are not limited to having a circular profile. For example, the back plate 40 may have a profile adapted to the attachment requirements of a worktable or actuator. Additionally, the upright portion 60 may have a profile adapted to the shape of the entry opening for the workpiece 2.

[0082] Selective illustrative embodiments of an EDM assembly, including a mounting device and EDM electrodes, have been described in detail above. It should be understood that only structures deemed necessary for illustrating the EDM assembly have been described herein. Other conventional structures and those accessory and auxiliary components of the EDM assembly are assumed to be known and understood by those skilled in the art. Furthermore, although working examples of the EDM assembly have been described above, the EDM assembly is not limited to the working examples described above, but various design changes can be made without departing from the EDM assembly, mounting device, and / or EDM electrodes set forth in the claims.

Claims

1. A discharge machining (EDM) electrode, comprising: First end of the electrode; The second end of the electrode opposite to the first end of the electrode; The longitudinal axis of the electrode extending between the first end of the electrode and the second end of the electrode; The electrode has an axial opening that extends between the first end of the electrode and the second end of the electrode and opens at the first end of the electrode and the second end of the electrode; Including the first portion of the electrode at the first end of the electrode; and Including the second portion of the electrode at the second end of the electrode, in The electrode is conductive. The first portion of the electrode has a first degree of flexibility. The first part of the electrode includes Corresponding to the axially extending fluid path of the axial opening, the axial opening allows fluid communication between the axial opening and the outside of the electrode, and A second fluid path, extending radially relative to the longitudinal axis, allows fluid communication between the axial opening and the outside of the electrode. The second portion of the electrode has a second flexibility, and The second flexibility is less than the first flexibility.

2. The electrical discharge machining (EDM) electrode according to claim 1, wherein, The first part of the electrode is a helical spring, and the second part of the electrode is a tube.

3. The electrical discharge machining (EDM) electrode according to claim 1, wherein... The first portion of the electrode has sufficient flexibility to bend when a bending force is applied to it, the bending corresponding to a deflection angle of at least 20 degrees relative to the longitudinal axis of the first end. The first portion of the electrode has sufficient elasticity to return to a linear configuration in which the deflection angle is zero when the bending force is removed.

4. The electrical discharge machining (EDM) electrode according to claim 1, wherein... The electrode includes an inner surface defining the axial opening, and The first portion of the electrode includes a channel in the electrode surface, the channel communicating with the axial opening and extending along a helical path between the first end of the electrode and the second portion of the electrode.

5. The electrical discharge machining (EDM) electrode according to claim 4, wherein, The channel has a rectangular outline.

6. The electrical discharge machining (EDM) electrode according to claim 1, wherein, The second part of the electrode does not have the second fluid path.

7. A discharge machining (EDM) assembly, comprising a mounting device configured to support an EDM electrode according to any one of claims 1-6 relative to a workpiece, the mounting device comprising: A backplate having a first backplate surface, a second backplate surface opposite to the first backplate surface, and a side surface extending between the first backplate surface and the second backplate surface; An upright portion protruding from the first surface of the back plate; and A tubular sleeve disposed in a through-hole extending through the back plate and the upright portion, the through-hole being aligned with an axis perpendicular to a first surface of the back plate, the sleeve comprising... First end of the sleeve, The second end of the sleeve, and The inner surface of the sleeve defines the sleeve passage extending between the first end and the second end of the sleeve. The sleeve is disposed in the through hole such that the first end of the sleeve protrudes from one end of the through hole.

8. The electrical discharge machining (EDM) assembly according to claim 7, wherein, The sleeve is disposed in the through hole in such a manner that the first end and the second end of the sleeve protrude from opposite ends of the through hole.

9. The electrical discharge machining (EDM) assembly according to claim 7, wherein, The sleeve is fixed inside the through hole.

10. The electrical discharge machining (EDM) assembly according to claim 7, wherein The first end of the sleeve is disposed outside the through hole on the side of the back plate corresponding to the first surface of the back plate. The second end of the sleeve is disposed outside the through hole on the side of the back plate corresponding to the second surface of the back plate, and The sleeve includes a curved portion, which is disposed outside the through hole and between the first end of the sleeve and the upright portion.

11. The electrical discharge machining (EDM) assembly according to claim 7, wherein, The sleeve includes: The curved portion, compared to the second end of the sleeve, is closer to the first end of the sleeve and is located outside the through hole; and A linear portion extending between the curved portion and the second end of the sleeve, at least a portion of which is disposed in the through hole.

12. The electrical discharge machining (EDM) assembly according to claim 11, wherein, The curved portion provides a curved section having a bending angle relative to a line parallel to the linear portion in the range of 0 to 90 degrees.

13. The electrical discharge machining (EDM) assembly according to claim 7, wherein The upright portion has Adjacent to the proximal end of the back plate, The distal end, spaced apart from the proximal end, A cylindrical side surface extending between the proximal end and the distal end, and The centerline of the upright portion equidistant from all parts of the side surface. And among them, The through hole is parallel to the center line of the upright portion and deviates from the center line of the upright portion.

14. The electrical discharge machining (EDM) assembly of claim 7, comprising an electrical discharge machining (EDM) electrode configured to be received within the sleeve passage.

15. The electrical discharge machining (EDM) assembly according to claim 7, wherein... The sleeve includes a curved portion that is closer to the first end of the sleeve than to the second end of the sleeve. The curved portion is located outside the through hole. The electrical discharge machining (EDM) electrode is disposed in the sleeve passage, and The first flexibility is greater than the flexibility of the sleeve, and A portion of the electrical discharge machining (EDM) electrode disposed in the curved section is deflected to adapt to the shape of the curved section.

16. The electrical discharge machining (EDM) assembly according to claim 7, wherein, The electrical discharge machining (EDM) electrode can move longitudinally within the sleeve passage.

17. The electrical discharge machining (EDM) assembly according to claim 10, wherein, The electrical discharge machining (EDM) electrode is able to return to its original shape when it is released after being bent within the bent portion.

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