Pressurizing method of floating piston energy accumulator

Abstract

A method of pressurizing an accumulator including an end cap and a floating piston includes positioning the floating piston outside an interior volume of the end cap. Pressurized gas is supplied to the interior volume through the open end of the end cap. The floating piston is inserted through the open end and sealingly engaged with the end cap to define a pressurized plenum within the end cap. The method further includes mechanically deforming the end cap to define a radially inwardly extending protrusion that restricts removal of the floating piston from the end cap. The pressurizing method provided by the invention can pressurize the floating piston energy accumulator under the condition that an inflation port is not used.

Description

Technical Field

[0001] The present disclosure generally relates to techniques for assembling gas-charged accumulators. More specifically, a method for pressurizing a floating piston accumulator without using a charge port is described. Background Art

[0002] The background description provided herein is intended to generally introduce the background of the present disclosure. The work of the inventors described in this background section, as well as the description of aspects that may not qualify as prior art at the time of application, are neither explicitly nor implicitly admitted to be prior art for the present disclosure.

[0003] Various machines are equipped with energy storage devices that can be selectively charged and decharged during operation. In one example, an automobile includes a shock absorber connected to a wheel end. A pressurized gas accumulator is connected to the shock absorber's fluid-holding chamber. The accumulator includes a floating piston that separates the pressurized gas chamber from a fluid chamber, which is in fluid communication with the shock absorber's fluid.

[0004] Existing gas-over-liquid accumulators are typically pre-charged before vehicle operation. This pre-charging process involves providing a charging port that extends through the accumulator housing, which contains a floating piston. After the accumulator is assembled, pressurized gas is introduced through the charging port. A plug or expander is secured to the accumulator housing to seal the charging port and contain the pressurized gas within the accumulator. While this arrangement has been effective in the past, there are opportunities for improvement. For example, accumulator housings are typically reinforced or cast, with the wall thickness at the charging port being significantly greater than elsewhere in the housing. This additional thickness increases the cost and weight of the housing. If the plug or expander is damaged, leakage may occur, allowing pressurized gas to escape from the charging port. Before the plug or expander is inserted into the accumulator, the accumulator housing is typically not subjected to surface treatments such as anodizing to improve its sealing properties after the accumulator is charged with pressurized gas. It is best to surface treat the accumulator housing before assembly. Therefore, there is a need in the art for an improved method of pressurizing a floating piston accumulator. Summary of the Invention

[0005] A method for pressurizing an accumulator including an end cap and a floating piston includes positioning the floating piston outside an interior volume of the end cap. Pressurized gas is supplied to the interior volume through an open end of the end cap. The floating piston is inserted through the open end and sealingly engaged with the end cap to define a pressurized gas chamber within the end cap. The method also includes mechanically deforming the end cap to form a radially inwardly extending protrusion that restricts removal of the floating piston from the end cap.

[0006] An alternative method for pressurizing a shock absorber accumulator includes positioning the shock absorber housing, end cap, and floating piston within a chamber. The floating piston is positioned outside the interior volume of the end cap. Pressurized gas is supplied to the chamber, allowing the pressurized gas to enter the interior volume of the end cap through an open end of the end cap. The end cap and floating piston are moved relative to each other to insert the floating piston through the open end and sealably engage the end cap, thereby forming a pressurized gas chamber within the end cap. The end cap is coupled to the housing such that the open end of the end cap is in fluid communication with the interior volume of the housing. The supply of pressurized gas to the chamber is terminated. An inner tube is coupled to the housing.

[0007] Further areas of applicability of the present disclosure will become apparent from the detailed description, claims, and drawings.The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The present disclosure can be more fully understood from the detailed description and accompanying drawings, in which:

[0009] Figure 1 is a schematic diagram of an example vehicle equipped with a shock absorber constructed according to the disclosed method;

[0010] Figure 2 is a partial cross-sectional view of a shock absorber equipped with an accumulator constructed according to the pressurization method disclosed herein;

[0011] Figure 3A-3G The steps of a floating piston accumulator pressurization method are described;

[0012] Figures 4A-4F The steps of another method of pressurizing a floating piston accumulator are described; and

[0013] Figures 5A-5C An alternative method of pressurizing a floating piston accumulator is described.

[0014] Among the drawings, reference numerals may be repeated to identify similar and / or identical elements. DETAILED DESCRIPTION

[0015] Figure 1 An example vehicle 10 is shown including a suspension system 12 and a vehicle body 14. The suspension system 12 includes shock absorbers 20 and coil springs 22. The shock absorbers 20 may be semi-active, with the damping level controlled by an electronic control unit 25. The electronic control unit 25 receives information from sensors (not shown), such as acceleration, displacement, steering angle, brake applications, and vehicle speed.

[0016] Figure 2An exemplary shock absorber 20 is shown that utilizes a single tube arrangement for gas and oil separation. The shock absorber 20 may be any shock absorber 20 of the vehicle 10. The shock absorber 20 may optionally be configured as a continuously variable semi-active suspension system shock absorber. The shock absorber 20 contains a fluid, which may be, by way of example and not limitation, a hydraulic fluid or oil. The shock absorber 20 includes an inner tube 30 that extends longitudinally between a first inner tube end 32 and a second inner tube end 34. A piston 36 is slidably disposed in the inner tube 30. The piston 36 defines a first working chamber 38 and a second working chamber 40 in the inner tube 30. The first working chamber 38 and the second working chamber 40 are each filled with a fluid.

[0017] The first working chamber 38 is positioned longitudinally between the piston 36 and the first inner tube end 32 and serves as a rebound chamber during the movement of the piston 36. The second working chamber 40 is positioned longitudinally between the piston 36 and the second inner tube end 34 and serves as a compression chamber. The volumes of the first and second working chambers 38, 40 change with the movement of the piston 36. The piston 36 is sealed against the inner side of the inner tube 30. Figure 2 In the example shown, the piston 36 has no orifices or passages, so no fluid flows through the piston 36. Fluid in the first working chamber 38 cannot pass through the piston 36 into the second working chamber 40, and vice versa. However, other configurations are also contemplated in which the piston 36 includes valving (not shown) to limit high internal pressures within the first and second working chambers 38, 40.

[0018] Shock absorber 20 includes a piston rod 42. Piston rod 42 is coaxially aligned with longitudinal axis 44. One end of piston rod 42 is connected to piston 36 and reciprocates with piston 36. The other end of piston rod 42 includes a connecting fitting 46 that can be connected to a component of vehicle 10.

[0019] Shock absorber 20 includes an outer tube 50 disposed about inner tube 30 and including an inner cylindrical surface 52 facing and spaced apart from inner tube 30. Outer tube 50 is coaxially aligned with inner tube 30 along longitudinal axis 44. Outer tube 50 extends longitudinally between a first outer tube end 54 and a second outer tube end 56. Piston rod 42 extends longitudinally outwardly through first outer tube end 54.

[0020] A rod guide 60 is positioned at the first outer tube end 54 of the outer tube 50. The rod 42 extends through the rod guide 60. A seal 62 is provided within the rod guide 60 to prevent fluid from flowing out of the first working chamber 38 through the rod guide 60. It should be understood that the inner tube 30, the piston 36, the rod 42, the outer tube 50, and the rod guide 60 can be configured as a tube and piston subassembly 66.

[0021] The housing 70 receives and is secured to the tube and piston subassembly 66. More specifically, the housing 70 includes a bore 72 that receives the second end 34 of the inner tube 30. The housing 70 includes another bore 74 coaxially aligned with the bore 72 and that receives the second end 56 of the outer tube 50. Both the inner tube 30 and the outer tube 50 are sealingly coupled to the housing 70. The housing 70 includes a first valve bore 80 and a second valve bore 82 extending substantially perpendicular to the longitudinal axis 44. The housing 70 also includes an accumulator port 84 fluidly coupled to and receiving an accumulator 86. The first valve bore 80 receives a first valve 88. The second valve bore 82 receives a second valve 90.

[0022] A fluid transfer chamber 94 is located between the inner tube 30 and the outer tube 50. The fluid transfer chamber 94 is in fluid communication with the first working chamber 38. The fluid communication between the fluid transfer chamber 94 and the first working chamber 38 may be achieved through a passage in the rod guide 60 or a hole extending through the inner tube 30. Figure 2 The geometry of the channels or pores is not described.

[0023] The fluid transfer chamber 94 is in fluid communication with the first valve orifice 80. The second working chamber 40 is in fluid communication with the orifice 72 and the second valve orifice 82. The accumulator port 84 is in fluid communication with both the first valve orifice 80 and the second valve orifice 82. The first valve 88 can be selectively fully opened, fully closed, or partially opened to control the flow of fluid from the first working chamber 38 and the fluid transfer chamber 94 to the accumulator 86 and the second valve orifice 82. Similarly, the second valve 90 can be selectively opened, closed, or partially opened to fluidly connect the second working chamber 40 to the accumulator 86 and the first valve orifice 80.

[0024] The accumulator 86 includes an end cap 100 having a closed first end 102 and an opposite, open second end 104 defining an interior volume 106. The second end 104 is sealingly secured to the housing 70. A floating piston 108 is slidably mounted within the end cap 100. The floating piston 108 defines an air chamber 110 and a fluid chamber 112 on opposite sides of the floating piston 108.

[0025] Figure 3A – Figure 3G A method for pressurizing the accumulator 86, including the floating piston 108, is illustrated schematically without requiring a charge port extending through the end cap 100. The pressurization process begins by placing the end cap 100 and the floating piston 108 into the work cell 120. The work cell 120 includes a fixture 124, a movable ram 126, a first translatable jaw 128, and a second translatable jaw 130. A first seal 132 and a second seal 134 are positioned within a recess in the fixture 124. A pressurized gas inlet port 136 extends through the wall of the fixture 124 to allow gas to be selectively exhausted from or entered into a cavity 140 of the fixture 124.

[0026] like Figure 3B As shown, the method of pressurizing the accumulator 86 includes axially translating the end cap 100 into the cavity 140 and engaging the first seal 132 with the outer surface 144 of the end cap 100. The outer surface 146 of the plunger 126 is sealingly engaged with the second seal 134. Once the end cap 100 is positioned as shown in FIG. Figure 3B As shown, the cavity 140 is sealed from the atmosphere. An optional vacuum application step can be performed to evacuate the air from the end cap 100 and the cavity 140. This step ensures that a specific concentration of gas, such as nitrogen, is stored in the accumulator 86 when the process is completed.

[0027] After inserting the end cap 100 into the fixture 124 and completing the optional step of evacuating the cavity 140, pressurized gas is supplied to the port 136 through the external pipe 148 to inject a gas such as nitrogen into the end cap 100 and the cavity 140 to reach a predetermined pressure.

[0028] exist Figure 3C The process continues with the plunger 126 moving axially in the direction of the arrow, inserting the floating piston 108 and its associated seal 150 into the end cap 100. At this point, the seal 150 is in sealing engagement with the inner surface 152 of the end cap 100. In this step, the pressurized air chamber 110 is defined. Figure 3B As shown, the final target gas pressure within the pressurized gas chamber 110 is set by initially pressurizing the cavity 140 to a first pressure level and then driving the piston 108 to a known distance in the end cover 100 via the plunger 126, thereby compressing the gas within the pressurized gas chamber 110 to the final target gas pressure.

[0029] The pressurization method of the accumulator 86 is as follows: Figure 3D When the relative axial positions of the floating piston 108, the end cap 100 and the clamp 124 are maintained as shown Figure 3C As shown, the first and second translatable jaws 128, 130 are driven laterally toward the end cap 100. The first jaw 128 engages the end cap 100 and forms a first radially inwardly extending notch 154. The second jaw 130 simultaneously forms a second radially inwardly extending notch 156. These mechanical deformation processes may be considered swaging or crimping processes. Any number of tools, such as the first and second translatable jaws 128, 130, may be circumferentially spaced apart around the perimeter of the end cap 100. The number of tools or notches required may correspond to the desired ultimate gas pressure within the pressurized gas chamber 110 and the goal of retaining the floating piston 108 within the end cap 100 during the service life of the shock absorber 20. The jaws 128, 130, or other suitable swaging tools, may include any number of end shapes, such as flat surfaces or semi-circular surfaces.

[0030] like Figure 3E As shown, once the notches are permanently formed, the first and second translatable jaws 128, 130 translate radially outwardly, thereby disengaging from the end cap 100. It should be understood that the pressurized gas may be discontinued at any time now or after the floating piston 108 enters the end cap 100 to define the pressurized gas chamber 110.

[0031] like Figure 3F As shown, the plunger 126 is now axially retracted and disengaged from the floating piston 108. Figure 3G As shown, the pressurized accumulator 86 may be removed from the fixture 124 and processed as a pressurized assembly that may be moved to another workstation within the facility where it was manufactured, or shipped to another facility where the accumulator will be used as a subassembly of the shock absorber 20 .

[0032] Figures 4A-4F An alternative method of pressurizing the accumulator is described. Figures 4A-4F The alternative method described in Figure 3A-3G The methods described in [1] are essentially similar. Therefore, only the essential differences will be discussed in detail. Some elements of the tools or hardware used to perform the alternate process are similar to those previously described. Figure 3A-3G The accumulator completed using the alternate pressurization process is substantially similar to accumulator 86. Therefore, similar elements will retain their previously introduced reference numerals, including the primary suffix.

[0033] For example, Figure 4A and Figure 4B As shown, the steps of pressurizing the accumulator 86' are similar to those of Figure 3A and Figure 3B The steps performed and described are essentially the same. The floating piston 108 is placed on the end face of the movable plunger 126'. The inlet port 136' is open to the atmosphere. Figure 4B In the embodiment of the present invention, end cap 100 is axially translated into cavity 140' to a predetermined distance, at which point second end 104 is spaced apart from clamp 124'. After outer surface 144 of end cap 100 is sealingly engaged with first seal 132', pressurized gas enters cavity 140' and the interior volume of end cap 100 through port 136'.

[0034] Figure 4C Steps and Figure 3C The plunger 126 ′ is axially displaced to position the floating piston 108 and its associated piston seal 150 a predetermined distance within the end cap 100 to set the final target gas pressure within the pressurized gas chamber 110 .

[0035] Clamp 124' differs from clamp 124 in that a tapered guide surface 166 extends radially inwardly toward plunger 126'. Clamp 124' also includes a reduction land 168 adjacent to tapered guide surface 166. Reduction land 168 tapers radially inwardly and exhibits an inner diameter, designated D2, that is less than the outer diameter D1 of end cap 100 at second end 104. Reduction land 168 may be conical or concavely curved. Reduction land 168 may be formed continuously around the entire circumference of cavity 140' or may include circumferentially spaced portions having a reduced diameter D2.

[0036] like Figure 4D As shown, the process continues by driving the end cap 100 further axially into the fixture 124', causing the second end 104 of the end cap 100 to mechanically deform inward when the end cap 100 is inserted a predetermined distance into the fixture 124'. The second end 104 now presents a radially inwardly curved end 172. The inner diameter of the curved end 172 is smaller than the outer diameter of the floating piston 108. As a result, the floating piston 108 is now trapped and cannot be removed from the end cap 100.

[0037] Figure 4E Plunger 126' is shown subsequently retracted from engagement with floating piston 108. Figure 4F As shown, the backup accumulator 86' having the bent end 172 can be removed from the fixture 124'.

[0038] Figures 5A-5C Another floating piston accumulator pressurization method is described. In this case, the end cap 100 is separated from the floating piston 108 and the subassembly of the assembly including the housing 70, the first valve 88 and the second valve 90. The tube and piston subassembly 66 are also separated from these components. Figure 5A As shown, to perform the method, the end cap 100, the floating piston 108, and the subassembly consisting of the housing 70, the first valve 88, and the second valve 90 are positioned within a pressurizable container 200. The tube and piston subassembly 66 need not be positioned within the container 200, but may also be positioned within the container 200. When the components within the container 200 are spaced apart from one another as previously described, pressurized gas is provided to the container 200.

[0039] Then, if Figure 5BAs shown, the end cap 100 is aligned with the housing 70 and moved toward the housing 70, securing the floating piston 108 within the interior volume 106 of the end cap 100. The end cap 100 is sealingly secured to the housing 70. In the example shown, the seal 84 engages the second end 104 of the end cap 100. The retaining ring 204 is positioned within a groove 206 in the housing 70 and a corresponding groove 208 formed in the outer surface of the end cap 100. Once the end cap 100 contains pressurized gas, contains the floating piston 108, and is sealingly connected to the housing 70, the supply of gas to the vessel 200 can be stopped.

[0040] like Figure 5C As shown, the subassembly of accumulator 86, housing 70, first valve 88, and second valve 90 can be removed from container 200. As previously described, tube and piston subassembly 66 can now be secured to housing 70. The longitudinal axis 44 of subassembly 66 is aligned parallel to the longitudinal axis of end cap 100. Working fluid (typically liquid oil) can now be pumped into first working chamber 38, second working chamber 40, fluid transfer chamber 94, first valve orifice 80, second valve orifice 82, accumulator port 84, first valve 88, and second valve 90. At this point, the working fluid of shock absorber 20 contacts one side of floating piston 108, while pressurized gas within pressurized gas chamber 110 acts on the other side of floating piston 108.

[0041] Example embodiments are provided to make the present disclosure more comprehensive and to fully convey the scope of the present disclosure to those skilled in the art. In order to allow people to thoroughly understand the embodiments of the present disclosure, many specific details are listed, such as examples of specific components, devices, and methods. It is obvious to those skilled in the art that the example embodiments can be embodied in a variety of different forms without adopting specific details, and neither form should be construed as limiting the scope of the present disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

[0042] The terms used herein are intended only to describe specific example embodiments and are not intended to be limiting. As used herein, the singular forms "a," "an," and "the" also include the plural forms, unless the context clearly indicates otherwise. The terms "comprise," "include," "contain," and "have" are inclusive and therefore specify the presence of the features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or their components. The method steps, processes, and operations described herein should not be understood to necessarily be performed in the specific order discussed or described, unless the order of execution is specifically indicated. It should also be understood that other steps or alternative steps may also be used.

[0043] When an element or layer is referred to as being "on," "engaged to," "connected to," or "coupled to" another element or layer, it can be directly on, engaged, connected, or coupled to the other element or layer, or there may be intervening elements or layers. Conversely, when an element is referred to as being "directly on," "directly engaged to," "directly connected to," or "directly coupled to" another element or layer, there may be no intervening elements or layers. Other words used to describe the relationship between elements should be interpreted in a similar manner (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.). As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0044] Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms may only be used to distinguish one element, component, region, layer or part from another region, layer or part. Unless the context clearly indicates otherwise, the "first", "second" and other numerical terms used herein do not imply an order or sequence. Therefore, the first element, component, region, layer or part discussed below may be referred to as the second element, component, region, layer or part without departing from the teachings of the exemplary embodiments.

[0045] For ease of description, spatially relative terms such as "inside," "outside," "below," "beneath," "lower," "above," "upper," etc., may be used herein to describe the relationship of one element or feature to another element or feature shown in the figures. In addition to the orientations depicted in the figures, spatially relative terms may also include different orientations of the device during use or operation. For example, if the device in the figure is turned over, other elements or features described as "below" or "beneath" would be placed "above" the other elements or features. Thus, the example term "below" may include both "above" and "below" orientations. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatially relative descriptors used herein may be interpreted accordingly.

[0046] In light of the above teachings, many modifications and variations of the present invention are possible and can be implemented in ways other than those specifically described within the scope of the appended claims. These foregoing should be interpreted as including any combination in which the novel features of the present invention are utilized.

Claims

1. A method for pressurizing an accumulator including an end cover and a floating piston, the method comprising: positioning the floating piston outside the interior volume of the end cap; supplying pressurized gas to the interior volume of the end cap through the open end of the end cap; inserting the floating piston through the open end into sealing engagement with the end cap to define a pressurized air chamber within the end cap; mechanically deforming the end cap to define a radially inwardly extending protrusion; as well as Removal of the floating piston from the end cap is restricted by the radially inwardly extending projection.

2. The method of claim 1, further comprising evacuating the interior volume of the end cap prior to the supplying of the pressurized gas.

3. The method of claim 1 , further comprising providing a fixture comprising a cavity, and coupling the end cap to the fixture and placing the cavity in fluid communication with the interior volume of the end cap, wherein the step of supplying the pressurized gas comprises providing the pressurized gas to the cavity. 4 . The method of claim 3 , further comprising positioning the floating piston within the cavity prior to the supplying of the pressurized gas.

5. The method of claim 4, further comprising engaging the floating piston with an axially movable plunger, wherein the plunger is translated to perform the inserting the floating piston step.

6. The method of claim 1 further comprising translating the floating piston within the end cap a predetermined amount to reduce the volume of the pressurized air chamber.

7. The method of claim 6, wherein said translating said floating piston a predetermined amount produces a target gas pressure within said end cap.

8. The method of claim 1, wherein the mechanical deformation comprises moving a jaw into contact with a surface of the end cap.

9. The method of claim 8, wherein the mechanical deformation further comprises moving opposing jaws into contact with a surface of the end cap to define another radially inwardly extending protrusion.

10. The method of claim 1, wherein the mechanical deformation comprises axially driving the open end of the end cap into a reduction band. 11 . The method of claim 10 , wherein the mechanical deformation comprises defining an additional radially inwardly extending protrusion circumferentially spaced from the radially inwardly extending protrusion.

12. The method of claim 1, wherein the method is performed without providing a port extending through the end cap and communicating with the pressurized plenum.

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