Patent Application
20180347617
The present disclosure relates generally to the assembly of a metal part to a workpiece comprising a different hardness material, and more specifically to tools and methods of manufacture for high fluid pressure sealing structures.
Next generation fuel systems 100, such as shown in part in
Thus, what is needed is a reliable sealing structure for high pressure connections, such as between fuel sensors and higher material hardness fuel rails.
The embodiments described herein provide assembly processes and apparatus for fixating a metal washer to a workpiece in order to form a reliable, high pressure sealing structure. By placing a portion of the metal washer between a pocketed port of the workpiece (e.g., a fuel pressure sensor, etc.) and high hardness mechanical element, such as a fuel rail, to which the pressure sensor is to be joined, a robust seal can be established. The methods and equipment described permit an integrated seal via fixation of the washer to the pressure sensor without plastic deformation of the washer that would render uncertain the reliability of the seal of the pressure sensor to the fuel rail. Integrating the washer into the pressure sensor port, such that the washer stays fixed during transportation of the pressure sensor, avoids potential disruption of the sensor port that might occur if the washer were required to be added just prior to connecting the pressure sensor to the fuel rail.
In one embodiment, an assembly process is provided, wherein a non-circular (e.g., oval, square, etc.) washer and a workpiece configured with an annular recess (e.g., a pocket or groove, etc.) having an inner diameter less than a maximum radial dimension of the washer are received. The washer is elastically deformed while being driven into the annular recess, such that the washer takes on a round shape with a diameter that is equal to or less than the inner diameter of the annular recess. Once the elastically deformed washer is pressed into the annular recess, the washer is released. Upon release, the washer will attempt to expand back into its original shape, but will be fixated against the inner wall of the annular recess by a retention force resulting from washer expansion and contact with the recess wall.
In one embodiment, the fixated expanded washer comprises an element in a sealing structure, where the height of the fixated washer is greater than a height of the annular recess inner wall. The washer may be composed of a malleable metal material that is softer than the pressure sensor annular recess inner wall. The washer may be elastically deformed by being pressed toward the annular recess through a (frusto-)conically shaped surface of an insertion tool positioned near the annular recess of the pressure sensor port. The insertion tool has a first end defining a diameter that is smaller than the diameter of the pressure sensor's annular recess, and a second end wide enough to accommodate the un-deformed washer's maximum radial dimension.
In another embodiment, the elastically deformed washer may be released while being further driven into the annular recess while the washer interacts with a chamfered region of the insertion tool extending from the first end of the conically shaped surface of the insertion tool. Mechanical interaction with the chamfer permits the released washer to slowly expand radially out to the annular recess inner wall. Through the disclosed fixating processes, the washer may be elastically deformed in the radial direction only, e.g., with no or inconsequential plastic deformation.
The deforming and driving of the elastically deformable, non-circular washer may be accomplished by pressing the washer and workpiece together with a force of less than 150N, and perhaps less than 100N, depending upon the materials and dimensions required for an application. The washer is preferably comprised of a material softer than the workpiece/pressure sensor and the fuel rail to be joined thereto. The insertion tool is also preferably formed of a material having a hardness greater than the washer, in order to reduce or avoid wear of the insertion tool.
In another aspect, a workpiece assembly system is provided for fixating the metal washer to a workpiece (e.g., pressure sensor) in order to form an integrated reliable, high pressure sealing structure. The assembly system may be configured with a mechanical press configured to push the workpiece and a lower press member (i.e., a plunger) together. The plunger has an end adapted to accommodate the non-circular elastically deformable washer. The assembly system also includes an insertion tool adaptable to the workpiece that has a port with an annular recess of a diameter less than the maximum radial dimension of the washer. A frustoconical surface of the insertion tool is positioned at a first open end positioned (when manufacturing is occurring) near the sensor port annular recess. The first open end has a diameter less than or equal to the recess inner wall diameter, but wide enough to accommodate a reciprocating tip of the plunger press member. The frustoconical surface has a second open end coaxially aligned with the first open end and dimensioned wide enough to accommodate the non-deformed maximum radial dimension of the non-circular (e.g., oval, square, etc.) washer. While pressing the washer through the insertion tool into the sensor port annular recess, the washer is elastically deformed to a round shape via radial compression by the frustoconical surface of the tool.
The insertion tool may be configured with a chamfer or a step extending from the first open end of the frustoconical surface, which permits the elastically deformed washer to expand, once it has been released by fully traversing the first open end, to mate with the inner wall of the recess of the pressure sensor. The chamfer may be configured with an angle that permits gradual expansion of the elastically deformed washer, while the step may be configured to cause a more instantaneous expansion.
In some embodiments, the tip of the plunger press member includes an annular notch for receiving the non-circular washer. The notch is dimensioned to have a width sufficient to accommodate the washer in its original non-deformed and elastically deformed shapes without imparting a retention force on the washer in either washer shape.
In alternative embodiments, the insertion tool may have an internal surface for deforming the washer that has a non-conical shape, but which radially, elastically deforms the washer from an original shape to a shape fitting into the workpiece recess. A non-annular (e.g., triangular, or four-sided shape) fixation of the washer into the workpiece recess may provide even greater retention force, i.e., wherein the washer expands partially into axial grooves in the recess inner wall.
An advantage of the disclosed embodiments is that they provide an improved, integrated sealable connector requiring few parts with effective, reliable sealing at high pressures. The washer may be composed of stainless steel, e.g., type AISI 304 stainless steel. The workpiece may comprise a fuel pressure sensor to be sealed against a fuel rail operating at high pressures (e.g., around 2700 bar).
It is to be understood that the summary, drawings, and detailed description are not restrictive of the scope of the inventive concepts described herein.
The foregoing and other objects, features and advantages will be apparent from the following, more particular description of the embodiments, as illustrated in the accompanying figures, wherein like reference characters generally refer to identical or structurally and/or functionally similar parts throughout the different views. The figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the embodiments, wherein:
The following detailed descriptions of embodiments of integrated washer fixation methods, tools and systems are merely exemplary in nature, and in no way intended to limit the scope, equivalents, applications or principles of the disclosed embodiments. Alternatives to the embodiments may be devised without departing from the scope of the disclosure. Well-known elements of technologies associated with the embodiments will not be described in detail, or will be omitted, so as not to obscure the relevant details of the novel methods and apparatus. For example, a significant discussion of the types of machine presses that might be employed is not included, as such systems are known to those of skill in the art.
The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. Likewise, the term “embodiment” and the descriptive language associated with each use of the term do not require that all embodiments include the discussed feature, limitation, advantage or mode of operation. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “having”, “configured”, “includes” and/or “including”, when used herein, specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise. In addition, the terms “conical” and “frustoconical” may be used interchangeably in the descriptions below to mean in the shape of a frustum of a cone, including two open coaxially aligned opposed ends of different diameter, with a sloping surface there between.
As described above, and with reference to
The disclosed assembly methods and tools were conceived for applications within the field of sensing high pressure liquids, such as fuel, in applications requiring reliable, pressure resistant sealing between the pressure sensor 206 and a fuel rail such as fuel rail 102 in
An assembly method that elastically stresses the washer 200 radially to secure it to the pressure sensor port 204 in a manner that is not destructive for either component will be better understood with reference to
The plunger notch 224 has a width 228 wide enough to accommodate the washer 200 in its initial noncircular, non-deformed shape and an annular diameter 229 smaller than the smallest radial dimension of the washer 200 in its radially deformed round shape (shown later.) The notch has a height 230 is less than the height 232 of the washer 200, which will likely not change because the washer 200 will not be subjected to axial compression forces sufficient to axially deform the washer 200. Washer 200 has a non-circular maximum radial dimension 234 that, in its non-deformed state, is greater than the diameter 236 of annular recess 202 in the port 204 of pressure sensor 206. The insertion tool 214 is configured with a frustoconical inner surface 238 sloping inward (toward a central axis of the tool) with a tapered draft angle 240 from a first open end 242 disposed proximate the port recess 202 to a second open end 244 for accommodating the plunger 222 and the maximum radial dimension 234 of the non-deformed washer 200. The plunger 222 has an outer diameter 223 that is less than the annular recess diameter 236 and the diameter 246 of the first open end 242. The first open end 242 has a diameter 246 slightly smaller than the annular recess diameter 236 but wide enough to accommodate the plunger 222 and the washer 200 in its elastically radially deformed shape (e.g., round). The draft angle 240 is selected to make gradual the application of radial compression forces by the conical surface 238 to the external wall 210 of washer 200.
As shown in
With reference to
The annular shape of the recess inner wall 208 may or may not allow the washer 200 to regain or maintain a little of its original oval shape, expanding from its elastically deformed shape by, for example, perhaps up to a few tens of millimeters. A radial force is exerted on the portion of the exterior wall of washer 200 contacting the recess inner wall 208. In one alternative embodiment, the inner wall 208 of the recess 202 is not necessarily a substantially smooth cylinder. Rather, discontinuities (e.g., one or more grooves, etc.) in an otherwise smooth continuous surface of the inner wall 208, or a non-annular shape to the entire recess 202, may permit the washer 200 to expand slightly more into such discontinuities in order to further fixate the washer 200 against rotation within the port 204.
The expansion of the released washer 200 may occur quickly, snapping outward to the recess inner wall 208 immediately after the washer 200 is released from the insertion tool first open end 242. The insertion tool may be configured with a stepped chamfer that permits washer 200 to quickly expand to a maximum shaped determined by the recess inner wall 208 dimensions. Alternatively, washer expansion may be designed to occur gradually, by configuring the frustoconical insertion tool 214 with a chamfer 250 that begins at the first open end 242 and radially expands down to a surface 252 of the insertion tool 214 that abuts a facing surface 254 of the sensor port 204. The chamfer 250 has an angled surface 256 that interacts with the external wall 210 of the released washer 200, permitting the released washer 200 to gradually radially expand as the released washer 200 is further pressed by plunger 222 into port recess 202. Expansion of the released washer 200 along the insertion tool chamfer 250 will halt when the released washer's outer wall 210 encounters the recess inner wall 208.
Advantageously, only radial elastic deformation is exhibited by the washer 200. The forces designed to deform the washer 200 as desired are a function of hardness and mechanical profile parameters for the washer 200, the frustoconical insertion tool 214 (including drafting angle 240 and chamfer 250), sensor port recess 202 and plunger 222. The washer 200 material and hardness may vary, depending on the design pressures, the dimensions, the application of the sealing structure, but is formed of a material softer than the fuel rail 102, pressure sensor 206 and insertion tool 214. For example, the washer 200 may be comprised of stainless steel or alloy steel and have a hardness of less than 200 HV Rockwell (B-scale), while the fuel rail 102 and port has a hardness range has a hardness on the order of about 314 HV and the port has a hardness in the range of 350 HV. It has been observed that components of these hardness ranges can achieve suitable elastic deformation with pressing forces of less than 100N. The washer may be formed by metal forming processes (e.g., fine blanking) that minimize rough edges.
Those of skill in the art will readily appreciate that numerous variations in the disclosed embodiments may be made without deviating from the inventive concepts disclosed. For example, in one embodiment, non-circular washer 200 may have a triangular, square or other shape, and be compressed to be received by a corresponding triangular, square or other shaped port recess. In another embodiment, insertion tool 214 may be comprised of multiple compression elements that cooperate to radially compress the washer.
Whereas many alterations and modifications of the disclosure will no doubt become apparent to a person of ordinary skill in the art after having read the foregoing description, it is to be understood that the particular embodiments shown and described by way of illustration are in no way intended to be considered limiting. No element, act, or instruction used herein should be construed as critical or essential unless explicitly described as such.
