WO2017142534A1

WO2017142534A1 - Stop/start accumulator design

Info

Publication number: WO2017142534A1
Application number: PCT/US2016/018306
Authority: WO
Inventors: David C. MILLS
Original assignee: Borgwarner Inc.
Priority date: 2016-02-17
Filing date: 2016-02-17
Publication date: 2017-08-24

Abstract

The hydraulic accumulator (20) may comprise a tube (22) having an open end (30), a closed end (26) and a side portion (28) which may define an internal cavity (32) within the tube (22). Furthermore, the hydraulic accumulator (20) may comprise a piston (36) disposed inside the internal cavity (32) and the piston (36) may be configured to be movable between a first piston position (38) and a second piston position (42) within the internal cavity (32). A piston sealing element (54) may be circumferentially placed around the piston (36) and disposed between the piston (36) and the side portion (28) of the tube (22). Moreover, a spring (34) may be disposed inside the internal cavity (32) positioned below the piston (36) and the spring (34) may be displaceable between a first spring position (40) and a second spring position (44). A solenoid housing (24) may be inserted into the open end (30) of the tube (22) and enclose the piston (36) and the spring (34) within the internal cavity (32) of the tube (22).

Description

STOP/START ACCUMULATOR DESIGN

Technical Field

[0001] The present disclosure relates generally a hydraulic accumulator, and more specifically to a hydraulic accumulator for an automatic stop/start system and methods of manufacturing the same.

Background

[0002] Some vehicles and machines such as, automobiles, trucks, vans, tractors or other such vehicles and machines may be equipped with hydraulic accumulators that form part of an automatic stop/start system. Furthermore, the hydraulic accumulators may be coupled with an internal combustion engine and/or a drive train that may be used to provide power and propulsion of the vehicles and machines. In general, the automatic stop/start system with the hydraulic accumulator may be used to at least partially shut down the internal combustion engine when the vehicle or machine is stopped or idle, such as at a red light or in a traffic jam, and quickly restart the engine when the vehicle or machine is instructed to move again. More specifically, the hydraulic accumulator may be configured to store energy during normal vehicle or machine operating conditions and expend the stored energy to quickly and seamlessly restart the internal combustion engine and/or drive train following an engine shut down that was initiated by the automatic stop/ start system.

[0003] In some designs, hydraulic accumulator components, such as tubes, pistons, guide rings and other components, may be fabricated using machining or other such fabrication processes. The machining process starts with a piece of bulk material and portions of the bulk material are removed to fabricate the desired size and shape of the component.

Furthermore, the machining process often times will leave behind particles and other machining debris and the machined components need to be thoroughly cleaned before they can be used. Moreover, the machining of individual components creates a more time consuming and complicated manufacturing process. As a result, the machining of components may increase the number of process steps which in turn may increase the manufacturing cost of hydraulic accumulators.

[0004] US Patent No. 8,568,262 (the '262 patent') discloses an accumulator valve assembly which includes an integrated accumulator. The accumulator includes a piston slidably disposed within a bore and a first end of the piston and the bore cooperate to define a cavity. The accumulator further includes an inlet/outlet port that allows the hydraulic fluid to communicate in and out of the accumulator. A biasing member or spring acts on an end of the valve opposite the end in contact with the accumulator. While the '262 patent discloses an accumulator valve assembly with in integrated accumulator, an improved accumulator is needed.

Summary of the Disclosure

[0005] In accordance with one aspect of the disclosure, a hydraulic accumulator is disclosed. The hydraulic accumulator may comprise a tube having an open end, a closed end and a side portion and the open end, the closed end and the side portion define an internal cavity within the tube. Furthermore, the hydraulic accumulator may comprise a piston disposed inside the internal cavity and the piston may be configured to be movable between a first piston position and a second piston position within the internal cavity. A piston sealing element may be circumferentially placed around the piston and disposed between the piston and the side portion of the tube. Moreover, a spring may be disposed inside the internal cavity positioned below the piston and the spring may be displaceable between a first spring position and a second spring position. A solenoid housing may be inserted into the open end of the tube and enclose the piston and the spring within the internal cavity of the tube.

[0006] In accordance with another aspect of the disclosure, a hydraulic accumulator is disclosed. The hydraulic accumulator may comprise a tube having an open end, a closed end and a side portion and the open end, the closed end and the side portion define an internal cavity within the tube. Furthermore, the tube may be fabricated from a single piece of material having a seamless transition between the closed end and the side portion of the tube. The hydraulic accumulator may further comprise a piston disposed inside the internal cavity and the piston may be configured to be movable between a first piston position and a second piston position within the internal cavity. A piston sealing element may be circumferentially placed around the piston and disposed between the piston and the side portion of the tube. Moreover, a spring may be disposed inside the internal cavity positioned below the piston and the spring may be displaceable between a first spring position and a second spring position. A solenoid housing may be inserted into the open end of the tube and enclose the piston and the spring within the internal cavity of the tube.

[0007] In accordance with a further aspect of the disclosure a method of manufacturing a hydraulic accumulator is disclosed. The method may comprise stamping a tube, the tube having a closed end, an open end and a side portion. The closed end, the open end and the side portion may define an internal cavity within the tube. The method may further disclose disposing a piston inside the internal cavity and the piston may be moveable between a first position and a second position within the internal cavity. Furthermore, a piston sealing element may be inserted into a piston annular groove, the piston sealing element may be disposed circumferentially around the piston and positioned between the piston and the side portion of the tube forming a fluid tight seal. Additionally, a spring may be disposed inside the internal cavity positioned between the piston and the closed end of the tube and a solenoid housing may be inserted into the open end of the tube enclosing the piston and the spring within the internal cavity. The piston housing may be coupled to the tube fixedly attaching the piston housing to the tube.

[0008] These and other aspects and features of the present disclosure will be better understood when reading the following detailed description in conjunction with the accompanying drawings.

Brief Description of the Drawings

[0009] FIG. 1 is a side view of a hydraulic accumulator consistent with an embodiment of the present disclosure;

[0010] FIG. 2 is an axial cross-sectional view of the hydraulic accumulator of FIG. 1 in the uncharged state and viewed along axis A- A;

[0011] FIG. 3 is an axial cross-sectional view of the hydraulic accumulator in a charged state consistent with an embodiment of the present disclosure and viewed along axis A-A;

[0012] FIG. 4 is an enlarged sectional view of a closed end of the accumulator tube consistent with an embodiment of the present disclosure;

[0013] FIG. 5 is a cutaway sectional view of the solenoid housing flange consistent with an embodiment of the present disclosure; [0014] FIG. 6 is a cutaway sectional view of another exemplary solenoid housing flange consistent with an embodiment of the present disclosure;

[0015] FIG. 7 is a flow chart illustrating an exemplary process or method which may be practiced in accordance with an embodiment of the present disclosure.

Detailed Description

[0016] Referring now to FIG. 1, an exemplary hydraulic accumulator for an automatic start/stop system constructed in accordance with the present disclosure is generally referred to by reference numeral 20. The hydraulic accumulator 20 may be paired with an internal combustion engine, an electric motor, a transmission or other components of vehicles or machines, such as, but not limited to, automobiles, trucks, vans, excavators, and tractors. The hydraulic accumulator 20 may be incorporated into an automatic stop/start system designed to shut down the internal combustion engine and/or other systems while the vehicle or machine is stopped and/or placed into an idle state. Furthermore, the hydraulic accumulator 20 may be configured to store energy generated during normal operation of the vehicle or machine. When the vehicle or machine stops and subsequently starts again, (e.g., in a traffic jam or at a red light) the hydraulic accumulator 20 may supply the previously stored energy to help facilitate a near-instantaneous restart of the vehicle or machine. In one non-limiting example, the hydraulic accumulator 20 may include an accumulator tube 22 and a solenoid housing 24. Moreover, the accumulator tube 22 may be configured to have a closed end 26 and a side portion 28. In some embodiments, the accumulator tube 22 may be formed out of steel, alloy, composite or any other suitable material, and the closed end 26 of the

accumulator tube 22 may be formed at the same time as the side portion 28 using a deep drawn stamping process or other known stamping process. Furthermore, the solenoid housing 24 may contain a solenoid valve (not shown) that may control the movement of fluid into and out of the hydraulic accumulator 20 during operation.

[0017] Moving on to FIGS. 2 -3, cross-sections along A-A of the hydraulic accumulator 20 of FIG. 1 are illustrated. A portion of the accumulator tube 22 and solenoid housing 24 are cut away to provide greater detail of the hydraulic accumulator tube 22 and some of the internal components. For example, the accumulator tube 22 may form an internal cavity 32 that is defined by the closed end 26, an open end 30, and the side portion 28 of the accumulator tube 22. An accumulator spring 34 and a piston 36 may be disposed to fit within the internal cavity 32. In some embodiments, the piston 36 may be completely disposed within the internal cavity 32 and the accumulator spring 34 may be positioned below the piston 36, however other configurations are possible. Additionally, the piston 36 may be configured to be displaceable within the internal cavity 32 of the accumulator tube 22. For example, when the hydraulic accumulator 20 is in an uncharged state, as illustrated in FIG. 2, the piston 36 may reside at a first position 38 adjacent to the solenoid housing 24 and the open end 30 of the accumulator tube 22. In some embodiments, when the piston 36 is at the first position 38 the accumulator spring 34 may be in a lightly compressed position 40. Moreover, when the accumulator 20 is in a charged state, as illustrated in FIG. 3, the piston 36 may be displaced within the internal cavity 32 and reside at a second position 42. When the piston 36 is at the second position the accumulator spring 34 may be at a higher compressed position 44. It should be noted that the second position 42 is one-non limiting example of positions where the piston 36 may reside within the internal cavity 32, other locations of the piston 36 are possible. [0018] As further illustrated in FIGS. 2-3, the accumulator spring 34 may reside within the internal cavity 32 of the accumulator tube 22 and positioned between the piston 36 and the closed end 26 of the accumulator tube 22. As a result, the internal cavity 32 may be subdivided into first area 46 and a second area 48. In some embodiments, the first area 46 may be defined by the area inside the accumulator tube 22 that is between the solenoid housing 24 and a first surface 50 of the piston 36 and the second area 48 is defined by the area inside the accumulator tube 22 positioned between a second surface 51 of the piston 36 and the closed end 26 of the accumulator tube 22. The size of the first area 46 and second area 48 may change depending upon a compression amount of the accumulator spring 34 and the position of the piston 36. Moreover, the accumulator spring 34 may be configured such that it resides within the second area 48 and the accumulator spring may be placed between the second surface 51 of the piston 36 and the closed end 26 of the accumulator tube 22.

[0019] During charging of the hydraulic accumulator 20 a fluid or other material may be forced into the accumulator tube 22 such that it causes a displacement of the piston 36 between the first position 38 and the second position 42. In one-non limiting example, the incoming fluid may enter the first area 46 and contact the first surface 50 of the piston, and a force generated by the incoming fluid pressure may cause the displacement of the piston 36, as well as compression of the underlying accumulator spring 34. As a result, during the charging event, a supply of energy may be created to be stored and later released by the hydraulic accumulator 20. Alternatively, in a discharging event the hydraulic accumulator 20 may release some or all of the acquired stored energy, to an uncharged or partially charged state, by forcing the fluid out of the accumulator tube and solenoid housing 24. In some embodiments, during a discharging event the piston 36 may be displaced towards the solenoid housing 24 and the piston first position 38. Furthermore, the previously compressed accumulator spring 34 may decompress and help displace the piston 36 towards the solenoid housing 24 and to push fluid out of the hydraulic accumulator 20.

[0020] The piston 36 may be configured with at least one annular groove 52 that is formed around a periphery of the piston 36. Furthermore, the annular groove 52 may be

circumferentially formed around the piston 36 and configured to mate or receive a piston sealing element 54, such as an O-ring or other known sealing element. In some

embodiments, the piston 36 may be arranged within the internal cavity 32 such that the annular groove 52 and the sealing element 54 are placed adj acent to and along an inner surface 56 of the side portion 28 of the accumulator tube 22. The sealing element 54 may compress against, and sealingly engage with, the inner surface 56 and form a substantially fluid tight seal between the piston 36 and the inner surface 56 of the accumulator tube 22. However, the formation of the substantially fluid tight seal between sealing element 54 and the inner surface 56 may not restrict the displacement of the piston 36 within the accumulator tube 22. As discussed above, during charging of the hydraulic accumulator 20 a fluid or other material may enter the accumulator tube 22. The entering fluid may contact the first surface 50 and cause a displacement of the piston 36 within the internal cavity 32. In some embodiments, the piston first surface 50 may be formed as a domed surface for added strength. Furthermore, the piston 36 may incorporate ribs or other strengthening features to improve the robustness of the piston 36. As discussed above, the piston may be molded out of plastic or other light-weight material. Forming a domed surface along the piston first surface 50 allows the piston to be fabricated out of a lighter weight material without sacrificing strength. Moreover, the entering fluid may be contained within the first area 46 due to the substantially fluid tight seal created between the piston sealing element 54 and the inner surface 56 of the accumulator tube 22. As a result, the fluid may be substantially contained within the first area 46 and will not leak from the first area 46 into the second area 48.

[0021] As illustrated in FIG. 3, the first area 46 of the internal cavity 32 may generally be defined as the area created between a first surface 50 or fluid face surface of the piston 36 and an internal surface 58 of the solenoid housing 24. In some embodiments, the solenoid housing 24 may have a flange 60 formed around the periphery of the solenoid housing 24. The flange 60 may be configured such that the solenoid housing 24 may be inserted into the open end 30 of the accumulator tube 22. Furthermore, the flange 60 may have a seal groove 62 that is circumferentially formed around the solenoid housing 24. The seal groove 62 may be configured to mate or receive an accumulator tube sealing element 64, such as an O-ring or other known sealing element. Moreover the flange 60 may have a fastening groove 66 circumferentially formed around the solenoid housing 24. The fastening groove 66 may be used to fixedly attach the solenoid housing 24 to the open end 30 of the accumulator tube 22.

[0022] In some embodiments, the accumulator tube 22 may have a crimp assembly 68 that mates with and extends into the fastening groove 66 such that the accumulator tube 22 and solenoid housing 24 are fixedly attached. The crimp assembly 68 may allow a crimping, compressing or other known attachment method where the crimp assembly 68 mates with the fastening groove 66 to fixedly attach the accumulator tube 22 to the solenoid housing 24. Moreover, prior to crimping or otherwise fastening of the accumulator tube 22 to the solenoid housing 24 the accumulator tube sealing element 64 may come into contact, compress against and sealingly engage the inner surface 56 of the accumulator tube 22 to form a substantially fluid tight seal. In one embodiment, the accumulator tube sealing element 64 may be configured such that the substantially fluid tight seal may be formed without the need to crimp or otherwise fasten the accumulator tube 22 to the solenoid housing 24. Furthermore, the substantially fluid tight seals formed between the piston housing sealing element 54, the accumulator sealing element 64 and the inner surface 56 of the accumulator side portion 28 may facilitate the forming the first area 46 into a substantially fluid tight area. The fluid may not leak past the piston sealing element 54 nor will it leak past the accumulator tube sealing element 64. As a result, the fluid that enters the first area 46 during charging of the hydraulic accumulator 20 may be held and stored within the first area 46 until its release is required.

[0023] The hydraulic accumulator 20 may store energy during the normal operation of the vehicle or machine. In some embodiments, the energy stored during the charging of the hydraulic accumulator 20 may be created by the compression of the accumulator spring 34 by a force created by hydraulic fluid or other fluid that enters the accumulator tube 22 through the solenoid housing 24. A valve or other mechanism (not shown), such as a solenoid valve, may be associated with the solenoid housing 24 and the valve may help control movement of the hydraulic fluid in and out of the accumulator tube 22. When the hydraulic fluid enters into the accumulator tube 22 the fluid may come into contact with first surface 56 of the piston and pressure created by the incoming hydraulic fluid may compress the accumulator spring 34. In some embodiments, the accumulator spring 34 may be positioned in the second area 48, which may be filled with air or other gas. During the charging of the hydraulic accumulator 20 fluid may enter the first area 46 and force a displacement of the piston 36 and a compression of the accumulator spring 34 until the piston 36 completes a full stroke 69, at which point the hydraulic accumulator may be fully charged. In some embodiments, the full stroke 69 may be the distance the piston 36 travels between the first and second piston positions 38, 42, however other stroke distances are possible. Furthermore, the piston stroke 69 may be limited by a piston stop 70 that is formed as part of a spring guide 72 or other interior structure of the accumulator tube 22. In some embodiments, the piston stop 70 may be configured such that it defines the maximum piston stroke 69 that the piston 36 may be displaced.

[0024] Moreover , the spring guide 72 may be formed along the closed end 26 of the accumulator tube 22. In some embodiments, the spring guide 72 may be annular in shape and positioned radially from a center axis C and adjacent to the side portion 28 of the accumulator tube 22 and . The spring guide 72 may be sized such that the accumulator spring 34 fits inside of the spring guide 72 and the spring guide may help to keep the accumulator spring 34 centered within the accumulator tube 22. Furthermore, the spring guide 72 may be configured to define the piston stop 70 such that a piston contact surface 73 may come into contact with the piston stop 70 when the piston 36 reaches its full stroke 69.

[0025] As discussed above, the piston 36 may be molded out of plastic or other suitable material that is capable of withstanding a temperature range between -40° C to 150° C.

Furthermore, the piston 36 may have a cylindrical portion 74 that extends away from the second surface 51 of the piston 36. In some embodiments, the cylindrical portion 74 may be positioned below piston annular groove 52 and piston sealing element 54 and as a result, the cylindrical portion 74 may reside in the second area 48 of the internal cavity 32. The cylindrical portion 74 may be formed having an open end 76 that is formed opposite to the piston second surface 51 and in one non-limiting example the open end 76 and the piston second surface 51 may be spaced apart a length 78. While one non-limiting length 78 is shown, it will be understood that a shorter or longer length may be used. Additionally, the piston contact surface 73 may be formed adjacent to the cylindrical portion open end 76. As a result, the piston stroke 69 may be changed by increasing or decreasing the cylindrical portion length 78. Furthermore, the cylindrical portion 72 and the open end 76 may be sized such that the accumulator spring 34 fits inside of the cylindrical portion 72 and the spring 34 is positioned between the piston second surface 51 and the closed end 26 of the accumulator tube 22. A piston spring guide ring 77 may be molded directed into a portion of the piston 36 and the piston spring guide ring 77 may be configured to position and secure the accumulator spring 34 along the piston second surface 51. In some embodiments, the piston spring guide ring 77 is formed along and extending away from the piston second surface 51, however other configurations are possible.

[0026] Moving on to FIG. 4, an alternative closed end 80 of an accumulator tube 82 with a plurality of steps 84 formed into the closed end 80 is illustrated. The plurality of steps 84 may be formed during part of the accumulator tube 80 fabrication process. In one example, the plurality of steps 84 may form a central spring guide 86 that extends, at least partially, into the internal cavity 92. The central spring guide 86 may be configured to be centered around a central axis C of the accumulator tube 80, however other configurations are possible. As further illustrated in FIG. 4, a plurality of springs, such as a smaller diameter spring 88 and a larger diameter spring 90 may be disposed within the internal cavity 92 of the accumulator tube 80. In some embodiments, the central spring guide 86 may partially extend into an inner diameter 94 of the smaller diameter spring 88 and center the smaller diameter spring 88, with respect to the central axis C, within the internal cavity 92 of the accumulator tube 80. Furthermore, a plurality of springs may be used in some embodiments of the hydraulic accumulator 20 and the smaller diameter spring 88 may be configured to fit inside an inner diameter 96 the larger diameter spring 90. As a result, the larger diameter spring 90 may be centered around the smaller diameter spring 88. Moreover, an outer diameter 98 of the larger diameter spring 90 may fit within the plurality of steps 84 formed in the closed end 80 and the plurality of steps 84 may help guide and center the larger diameter spring 90 within the internal cavity 92 of the accumulator tube 82.

[0027] The plurality of steps 84 formed in the closed end 80 may also define an alternative piston stop 100 which runs around a periphery of the accumulator tube 82. As described above, the piston stop 100 may help limit further movement of the piston 36 when its maximum stroke is reached during charging of the hydraulic accumulator 20. In addition to the plurality of steps 84, a vent connection 102 may be formed in the closed end 80 or other portion of the accumulator tube 82 that may be configured to allow air or other material to be vented to move in and/or out of the internal cavity 92 of the accumulator tube 82. Moreover, an external hose or other venting assembly may be connected to the vent connection 102 to facilitate the external venting of the hydraulic accumulator 20.

[0028] Moving back to FIGS. 2-3, strengthening ribs 103 may be formed along the closed end 26 during the fabrication of the accumulator tube 22. The strengthening ribs 103 may provide extra support at stress concentration points at various locations along the accumulator tube 22. Furthermore, the strengthening ribs 103 may allow for thinner walls to be used in the construction of the accumulator tube 22 without sacrificing structural integrity.

Moreover, as illustrated in FIGS. 2-4 a plurality of mounting brackets 104 may be formed during the stamping process and positioned at various locations along the accumulator tube 22 to accommodate mounting the hydraulic accumulator 20 where it is needed. Additionally or alternatively, the mounting brackets 104 may be individually formed and added to the hydraulic accumulator 20.

[0029] Moving on to FIGS. 5 a close up of an embodiment of the solenoid housing flange 60 is illustrated. As described above, FIG. 5 illustrates one non-limiting example of the solenoid housing flange 60 having a seal groove 62 and a fastening groove 66. The seal groove 62 may be configured to receive the accumulator tube sealing element 64 and the fastening groove 66 may be configured to receive the accumulator tube crimped assembly 68. The solenoid housing flange 60 may also be configured with a tapered portion 106 and a lip portion 108 to aid with positioning, inserting, and fastening the solenoid housing 24 to the accumulator tube 22. In some embodiments, the lip portion 108 may limit the amount the solenoid housing 24 may be inserted into the open end 30 of the accumulator tube 22.

[0030] FIG. 6 illustrates a non-limiting embodiment of an alternate solenoid housing flange 110 with a substantially planar portion 112 that is formed without any grooves, however the flange 110 may be configured with the tapered portion 106 and the lip portion 108. As discussed above, the tapered portion and the lip portion 108 may aid in positioning, inserting, and fastening the solenoid housing 24 to the accumulator tube 22. Moreover, the lip portion 108 may limit the amount the solenoid housing 24 may be inserted into the open end of the accumulator tube 22. The substantially planar portion 112 of the alternate solenoid housing flange 110 may be configured to be positioned adjacent to the side portion 28 of the accumulator tube 22 when the alternate solenoid housing flange 110 is inserted into the open end 30 of the accumulator tube 22. Furthermore, a magnetic pulse welding process or other fastening process compatible with the substantially planar portion 112 may be used to fixedly attach the solenoid housing 24 with the alternative solenoid housing flange 110 to the accumulator tube 22.

Industrial Applicability

[0031] Based on the forgoing, it can be seen that the hydraulic accumulator 20 of the present disclosure may find utility in various applications such as, but not limited to, automobiles, trucks, vans, construction equipment and agricultural equipment. Through the novel teachings outlined above, the hydraulic accumulator 20 may be formed using an accumulator tube 22 that has thinner walls. Additionally, the hydraulic accumulator 20 may incorporate a piston 36 which is molded out of a plastic or other light-weight material.

Furthermore, the piston 36 may be molded with a domed face and other strength improving features, such as ribs. As a result, the hydraulic accumulator 20 may take up less space, be lighter in weight, and more robust compared to other designs. Moreover, the present disclosure may reduce the number of individual parts and or eliminate the need for machining during the fabrication process, thereby realizing a reduction of overall parts in the hydraulic accumulator 20, an elimination of machining debris and in turn, a reduction in overall manufacturing costs.

[0032] Incorporating the hydraulic accumulator 20, as described in the present disclosure, may provide significant reliability improvements and a reduction in manufacturing costs. The accumulator tube 22 may be formed using a deep drawn stamping process which may allow the tube 22, including the closed end 22, side portion 28, and open end 30 to be formed out of a single piece of steel or other such material. As a result, the use of stamping to fabricate the accumulator tube 22 eliminates the need to machine individual components and subsequently assembling them. Additionally, the use of stamping may allow the tube to be formed with thinner walls and strengthening ribs 103 may be formed along the closed end 26, or other locations on the tube, to provide added strength where needed. Moreover, the piston 36 may be formed using a plastic molding process which allows for a lighter weight piston compared to pistons formed out of metal. Additionally, the plastic molding of the piston eliminates the need for machining the piston and provides other advantages, such as molding guide rings 77 and a domed piston face in one assembly step.

[0033] FIG. 7 illustrates an exemplary method or process 114 of fabricating the hydraulic accumulator 20. In a first block 116 of the method 114 a stamping process, such as deep drawing or other known process, is used to form the accumulator tube 22. In some embodiments, the accumulator tube 22 is formed having a closed end 26, an open end 30 and a side portion 28. Furthermore, the closed end 26, the open end 30 and the side portion 28 may be arranged such that an internal cavity 32 of the accumulator tube 22 is defined.

[0034] In another block 118 a piston 36 may be disposed inside the internal cavity 32 and the piston 36 may be configured to be movable between a first position 38 and a second position within the internal cavity 32. In a next block 120 a piston sealing element 54 may be circumferentially positioned around the piston 36. Furthermore, the piston sealing element 54 may be disposed between the piston 36 and the side portion 28 such that a substantially fluid tight seal may be formed between the piston sealing element 54 and the side portion 28 of the accumulator tube 22.

[0035] In a next block 122 an accumulator spring 34 may be disposed inside the internal cavity 32 and the accumulator spring 34 may be positioned between the piston 36 and the closed end 26 of the accumulator tube 22. Subsequently, in a next block 124 the solenoid housing 24 may be inserted into the open end 30 of the accumulator tube 22 and in a next block 126 the accumulator tube 22 may be coupled to the solenoid housing 24 such that the tube 22 and solenoid housing 24 are fixedly attached. In some embodiments, a crimping assembly 68 is formed to securely attach the tube 22 and the solenoid housing 24 together, however other attachment methods are possible.

[0036] In some embodiments, the present disclosure may provide a hydraulic accumulator 20 that is lighter in weight, less expensive, and free from certain manufacturing defects. For example, the hydraulic accumulator 20 may be made lighter by forming the accumulator tube 22 using a deep drawn stamping process that allows for the fabrication of thinner walls. As a result, a tube may be fabricated that is not only lighter in weight but also provides a savings in space. Additionally, the hydraulic accumulator 20 weight may be reduced through use of a molded plastic piston 36 instead of a metal piston. Furthermore, the hydraulic accumulator 20 may provide a cost savings through use of a crimp assembly 68 to couple components of the accumulator 20 together. Use of the crimp assembly 68 may be a more cost effective attachment method over the use of threaded retainer rings, bolts, rivets or other such methods. Finally, the hydraulic accumulator 20 of the present disclosure may reduce certain

manufacturing defects due to a reduction or elimination of the machining of certain accumulator components. Machining components can create particles and other debris that if not properly removed may pose performance and reliability issues. As a result, the present disclosure describes and depicts a hydraulic accumulator 20 heretofore neither depicted, nor suggested by the prior art.

[0037] While the foregoing detailed description has been given and provided with respect to certain specific embodiments, it is to be understood that the scope of the disclosure should not be limited to such embodiments, but that the same are provided simply for enablement and best mode purposes. The breadth and spirit of the present disclosure is broader than the embodiments specifically disclosed and encompassed within the claims appended hereto. Moreover, while some features are described in conjunction with certain specific

embodiments, these features are not limited to use with only the embodiment with which they are described, but instead may be used together with or separate from, other features disclosed in conjunction with alternate embodiments.

Claims

Claims What is claimed is:

1. A hydraulic accumulator (20) comprising:

a tube (22) having an open end (30), a closed end (26) and a side portion (28) defining an internal cavity (32);

a piston (36) disposed inside the internal cavity (32), and configured to be moveable between a first piston position (38) and a second piston position (42) within the internal cavity (32);

a piston sealing element (54) circumferentially placed around the piston (36) and disposed between the piston (36) and the side portion (28) of the tube (22);

a spring (34) disposed inside the internal cavity (32) below the piston (36) and displaceable between a first spring position (40) and a second spring position (44); and

a solenoid housing (24) being inserted into the open end (30) and enclosing the piston (36) and spring (34) within the internal cavity (32) of the tube (22).

2. The hydraulic accumulator (20) of claim 1, wherein the tube (22) being fabricated from a single piece of material and having a seamless transition between the closed end (26) and the side portion (28).

3. The hydraulic accumulator (20) of claim 1, wherein the tube (22) being composed of a plastically deformable material and a crimp assembly (68) being formed adjacent to and circumferentially around the open end (30) of the tube (22) and the crimp assembly (68) being configured to couple the solenoid housing (24) and the tube (22).

The hydraulic accumulator (20) of claim 3, wherein the solenoid housing (24) has a first annular groove (66) and a second annular groove (62), the solenoid housing (24) being inserted into the open end (30), the crimp assembly (68) mating with the first annular groove (66) to couple the tube (22) to the solenoid housing (24) and an annular sealing element (64) being received by the second annular groove (62) forming a fluid tight seal between solenoid housing (24) and the tube (22).

The hydraulic accumulator (20) of claim 2, wherein the tube (22) being formed with a plurality of attachment points (104) for mounting the hydraulic accumulator (20) and the closed end (26) being formed with strengthening rib (103).

The hydraulic accumulator (20) of claim 1, wherein the closed end (26) incorporates an integrated vent connection (102) and a plurality of stepped portions (84) being configured to form a spring guide (86) for the spring (34) and a stop platform (100) for the piston (36).

The hydraulic accumulator (20) of claim 1, wherein the piston (36) being formed from a molded plastic, the piston (36) having a first surface (50) a second surface (51) and a cylindrical portion (74), the first surface having a curved domed shape, the cylindrical portion (74) extending from the second surface (51) and the cylindrical portion (74) having an open end (76) configured to fit over the spring (34).

8. The hydraulic accumulator (20) of claim 7, wherein the piston (36) includes a piston spring guide structure (77) extending away from the second surface (51) the piston spring guide structure (77) being configured to position and align the spring (34) along the second surface (51) of the piston (36).

9. The hydraulic accumulator of claim 7, wherein the piston (36) being formed with an integrated piston contact surface (73) configured to contact the closed end (26) of the tube (22) and define a travel limit of the piston (36).

10. A method of manufacturing (112) a hydraulic accumulator (20), the method (112) comprising:

stamping a tube (22), the tube (22) having a closed end (26), an open end (30) and a side portion (28) defining an internal cavity (32) of the tube (22);

disposing a piston (36) inside the internal cavity (32), the piston (36) being movable between a first position (38) and a second position (42) within the internal cavity (32);

inserting a piston sealing element (54) into a piston annular groove (52), the piston sealing element (54) being disposed circumferentially around the piston (36) and positioned between the piston (36) and the side portion (28) of the tube (22) forming a fluid tight seal;

disposing a spring (34) inside the internal cavity (32) between the piston (36) and the closed end (26) of the tube (22);

inserting a solenoid housing (24) into the open end (30) of the tube 922) and enclosing the piston (36) and the spring (34) within the internal cavity (32); and coupling the solenoid housing (24) to the tube (22).

11. The method (114) of claim 10, wherein the tube (22) being formed from a single piece of material using a deep drawing stamping process, the tube (22) having a thin-walled side portion (28), a seamless transition between the closed end (26) and the thin- walled side portion (28), strengthening ribs (103) being formed on the closed end (26), and a plurality of attachment points (104) being formed for mounting the hydraulic accumulator (20).

12. The method (114) of claim 11, wherein the tube (22) being formed from a plastically deformable material, a crimp assembly (68) being formed along the thin-walled side portion (28) adjacent to the open end (30) of the tube (22), a plurality of stepped portions (84) being formed along the closed end (26) of the tube (22), the plurality of step portions (84) being configured to define a spring guide (86) and a piston stop (100), and an integrated vent connection (102) being formed through the closed end (26) of the tube (22).

13. The method (114) of claim 12, wherein the solenoid housing (24) being formed with a first annular groove (66) and a second annular groove (64), the crimp assembly (68) being aligned with the first annular groove (66) and coupling the tube (22) with the solenoid housing (24), the second annular groove (62) receiving an annular sealing element (64) and forming a fluid tight seal between the solenoid housing (24) and the tube (22).

14. The method (114) of claim 10, wherein the piston (36) being molded from plastic, the piston (36) having a first surface (50) and a second surface (51), the first surface (50) being molded with a curved and domed shape and the second surface (51) having a plurality of spring guide structures (77) extending away from the second surface (51) and configured to position and align the spring (34) along the second surface (51) of the piston (36) .

15. The method (114) of claim 14, wherein the piston (36) being formed with cylindrical portion (74) formed around a periphery of the piston and extending away from the second surface (51) of the piston (36), the cylindrical portion sized to fit around and at least partially enclose the spring (34).