Accumulator

Abstract
Disclosed is an accumulator comprising a cylindrical shell including a cylindrical portion, a partitioning member for partitioning the interior of the shell into a hydraulic chamber and a gas chamber, and a port including a hydraulic fluid flow path for communicating the exterior of the shell and the hydraulic chamber. The variation of the pressure of a hydraulic fluid flowing into the hydraulic chamber is accommodated by expansion and compression of a gas in the gas chamber according to expansion and contraction of the partitioning member. The port is approximately airtightly inserted into the cylindrical portion of the shell, and is welded to an outer circumference of the cylindrical portion by means of welding.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates to an accumulator used for, for example, hydraulic circuits in hydraulic control apparatuses, specifically relates to a securing structure for hydraulic ports with respect to sealed vessels (shells) for hydraulic fluids and gases, and relates to a protecting structure for a partitioning member installed therein.




2. Background Art




The accumulator such as the above generally comprises a cylindrical shell partitioned into a gas chamber and a hydraulic chamber by a bellows. The pressure variation of the hydraulic fluid flowing into the hydraulic vessel is accommodated by the expansion and compression of the gas in the gas chamber according to the elastic motion of the bellows. The accumulator is widely used in devices such as a hydraulic circuit in automobiles for effectively inhibiting pulsation in the hydraulic fluid flowing therein.




In

FIG. 5

, an example of a conventional accumulator is shown, and reference numeral


80


is a cylindrical shell which forms a sealed vessel by joining a bottom shell


81


and a cap shell


82


. Reference numeral


83


is a metallic bellows assembly partitioning the interior of the shell


80


into a hydraulic chamber


91


and a gas chamber


92


. Reference numeral


93


is a port comprising a flow path


93




a


for communicating a hydraulic circuit (not shown) and the hydraulic chamber


91


. The bellows assembly


83


forms the hydraulic chamber


91


therein, and comprises bellows


84


elastically moving in the axial direction of the shell


80


, and a bottom seal


85


and a bellows cap


86


joined to both ends of the bellows


84


. The bottom seal


85


is joined to the cap shell


82


.




The bellows cap


86


is a free end of the bellows assembly


83


. The circumference of the bellows cap


86


is mounted with a circular bellows guide


87


which slides with the inner surface of the shell


80


so as to guide the elastic movement of the bellows


84


in the axial direction.




The axial length of the bottom shell


81


is longer than that of the cap shell


82


. The joining portion of the shells


81


and


82


approximately faces the bellows


84


even if the bellows


84


is in the most contracted condition.




In such an accumulator, when the hydraulic fluid flows into the hydraulic chamber


91


via the flow path


93


a and the pressure of the hydraulic fluid exceeds the gas pressure in the gas chamber


92


, the bellows


84


expands, and the gas in the gas chamber


92


is compressed. In contrast, when the hydraulic fluid pressure in the hydraulic chamber


91


is below the gas pressure in the gas chamber


92


, the bellows


84


is contracted and the gas in the gas chamber


92


is expanded. Due to the expansion and compression of the gas in the gas chamber


92


, the variation of the pressure of the hydraulic fluid in the hydraulic circuit is accommodated and pulsation thereof is inhibited. The two-dot chain line in

FIG. 5

shows the position of the bellows cap


73


when the bellows assembly


70


is in the most expanded condition.




The port


93


in the conventional accumulator is joined to the cap shell


82


by projection welding, or the like, which is one type of resistance welding. Welding produces sparks in some cases, and splashed material adheres to the inner surface of the port


93


and the cap shell


82


, thereby contaminating therein. When the accumulator is assembled with the contamination, the hydraulic fluid is contaminated and results in malfunctioning of the accumulator. Although cleaning is performed to remove the contamination, it is difficult to completely remove the contamination since there are portions where the cleaning is not easily performed. Furthermore, the cleaning is labor intensive, and the production efficiency is decreased.




In assembly of the conventional accumulator, the bottom shell


81


is welded to the cap shell


82


after joining the bellows assembly


83


to cap shell


82


by welding. Similarly in this case, when the shells


81


and


82


are welded by projection welding, sparks are emitted to the interior of the shell


80


, and the bellows


84


may be damaged. Although the service life of the bellows is shortened when the bellows


84


is damaged, it cannot be ascertained whether the bellows


84


is damaged since it is contained in the shell


80


, and the normal operation of the accumulator cannot be ensured.




SUMMARY OF THE INVENTION




An object of the present invention is to provide an accumulator in which contamination of the interior thereof due to sparks emitted in welding a port can be inhibited and the production efficiency can be improved.




Another object of the invention is to provide an accumulator in which damage to a bellows due to sparks emitted in welding shells can be inhibited and the normal operation of the accumulator in over the long term can be ensured.




The present invention provides an accumulator comprising: a cylindrical shell including a cylindrical portion; a partitioning member for partitioning the interior of the shell into a hydraulic chamber and a gas chamber; and a port including a hydraulic fluid flow path for communicating the exterior of the shell and the hydraulic chamber. Variation of pressure of a hydraulic fluid flowing into the hydraulic chamber is accommodated by expansion and compression of a gas in the gas chamber according to expansion and contraction of the partitioning member. The port is approximately airtightly inserted into the cylindrical portion of the shell, and is welded to an outer circumference of the cylindrical portion by means of welding.




According to the invention, the port is approximately airtightly press fitted into the cylindrical portion of the shell, and the inner surface of the cylindrical portion and the outer surface of the port are closely contacted to each other. Therefore, the outer ridge portion of the cylindrical portion is isolated from the interior of the shell. As a result, when sparks occur during welding, the sparks are not emitted into the interior of the shell, and the interior of the shell is not contaminated by splashing of the sparks. Therefore, the contamination in the shell can be easily controlled and the production efficiency can be improved. Furthermore, even if sparks are emitted in the shell the sparks remain in the gas chamber and do not enter into the hydraulic chamber, so that the system including the hydraulic circuit to which the accumulator is connected is not contaminated by splashing of the sparks.




According to the preferable feature of the invention, in which the overall length of the accumulator can be shortened, the cylindrical portion is projected into the interior of the shell. Several kinds of forming method can be applied to the feature, but burring in which a through hole is formed in the shell and a punch having larger diameter than that of the through hole is press fitted thereinto is preferable.




The partitioning member may comprise a fixed portion and a movable portion mounted to the fixed portion via an elastic member, which corresponds to the bellows assembly


83


in the conventional accumulator in FIG.


5


. The fixed portion, the elastic member, and the movable portion correspond to the bottom seal, the bellows, and the bellows cap respectively. It is preferable feature that the fixed portion is integrally formed with the port. Heretofore, the fixed portion (bottom seal) has been joined to the inner surface of the cap shell, so that sparks occurring in welding results in problems of contamination similarly in the port. However, by integrating the fixed portion with the port, the fixed portion needs not to be welded to the cap shell, and the problems due to the sparks can be solved.




According to another preferable feature of the invention, the shell comprises plural divided shell bodies joined to each other. The partitioning member includes a guide for sliding on an inner surface of the shell so as to guide the expansion and contraction of the partitioning member along an axial direction thereof. The joined portion between the divided shell bodies is positioned outside the region where the bellows guide moves. The guide slides within an inner surface of one divided shell body. According to the feature, even if a step is formed at the joined portion of the divided shell bodies (boundary between both), the guide can slide smoothly with no influence from the step, and is not damaged by the joined portion, so that durability thereof can be improved.




According to another aspect of the invention, the invention provides an accumulator comprising: a cylindrical shell including plural divided shell bodies joined to each other in an axial direction thereof; a partitioning member for partitioning the interior of the shell into a hydraulic chamber and a gas chamber, the partitioning member expanding and contracting in the axial direction of the shell; and a guide provided at a free end of the partitioning member, the guide guiding the expansion and contraction of the partitioning member along an axial direction thereof is provided. Variation of the pressure of a hydraulic fluid flowing into the hydraulic chamber is accommodated by expansion and compression of a gas in the gas chamber according to expansion and contraction of the partitioning member. A protecting member is provided between a joined portion of the divided shell bodies and the partitioning member so as to screen both.




The divided shell bodies correspond to the bottom shell and the cap shell respectively, and the partitioning member corresponds to the bellows assembly in the conventional accumulator in FIG.


5


. According to the invention, the divided shell bodies are joined to each other by joining means such as projection welding. Sparks occurring in the welding are blocked by the protecting member and cannot strike the partitioning member. Therefore, damage to the partitioning member is prevented and a long service life thereof is ensured, and normal operation of the accumulator can be ensured.




According to the specific feature of the protecting member, a sleeve coaxially aligned with the shell along the inner surface of the shell can be applied. The sleeve extends overall region where the guide moves according to the expansion and contraction of the partitioning member, and the guide slides on a inner surface of the sleeve. According to the feature, the guide moves smoothly sliding on the sleeve, and the partitioning member usually operates in normal manner.




According to another specific feature of the protecting member, it may be a ring-shaped member covering an inner surface of the joined portion of the divided shell bodies. In this case, the ring-shaped member is preferably positioned outside the region where the guide moves, and the guide slides within an inner surface of one divided shell body. According to the feature, even if a step is formed between the divided shell bodies and the ring-shaped member (boundary between both), the guide can slide smoothly with no influence from the step, and the partitioning member can usually operates in normal manner.











BRIEF EXPLANATION OF THE DRAWINGS





FIG. 1

is a vertical cross section of an accumulator of a first embodiment according to the invention.





FIG. 2

is a vertical cross section of an accumulator of a second embodiment according to the invention.





FIG. 3

is a vertical cross section of an accumulator of a third embodiment according to the invention.





FIG. 4

is a vertical cross section of an accumulator of a fourth embodiment according to the invention.





FIG. 5

is a vertical cross section of a conventional accumulator.











DETAILED EXPLANATION OF THE INVENTION




Preferred embodiments of the invention will be explained in detail hereinafter.





FIG. 1

is a cross section showing an accumulator of a first embodiment according to the invention. In

FIG. 1

, reference numeral


10


is a cylindrical shell forming a sealed vessel.




The shell


10


consists of a bottom shell (divided shell body)


20


as a main body and a cap shell (divided shell body)


30


which are joined to each other by welding and are divided in the axial direction. The length in the axial direction of the bottom shell


20


is longer than that of the cap shell


30


. axial direction of the bottom shell


20


is longer than that of the cap shell


30


. The shells


20


and


30


are made from a metal such as steel and are formed by a press to an approximately uniform thickness. The axially extending body portions of the shells


20


and


30


are joined to each other by projection welding.




A circular circumferential portion


21


or


31


projecting outward is formed at the joining end of the shells


20


and


30


around the entire circumference thereof. The end surfaces of these circular circumferential portions


21


and


31


are joined to each other, and a circular recess having a trapezoidal cross section is formed therebetween. A bellows protector


40


is fitted into the circular recess. The bellows protector


40


is made from an insulating resin. The inner diameter of the bellows protector


40


is identical to that of the shell


10


, and the outer surface thereof is formed with a groove


41


around the entire circumference.




A cylindrical portion


32


is formed at the center end portion of the cap shell


30


by inwardly (upward in

FIG. 1

) projecting the portion by means of burring. A port


50


is press fitted with an airtight seal into the through hole


33


of the cylindrical portion


32


from the inner side thereof. The port


50


has a flow path


51


for hydraulic fluid and projects outside from the through hole


33


of the cylindrical portion


32


. The outer surface of the projected portion of the port


50


is formed with a screw portion


52


to which a hydraulic circuit (not shown) is connected.




The port


50


is fixed to the cap shell


30


by fillet welding the outer surface of the port


50


to the outer circumference


32




a


of the cylindrical portion


32


. Reference numeral


60


is a bead formed by the welding, and is formed around the entire circumference of the port


50


. The fillet welding is performed by arc welding or the like. A bottom seal


72


of a bellows assembly (partitioning member)


70


, mentioned below, is integrally formed at the inner end of the port


50


. The bottom seal


72


is brought into contact with the inner end surface of the cylindrical portion


32


.




The metallic bellows assembly


70


is contained in the shell


10


so as to partition the interior of the shell


10


into a hydraulic chamber


11


and a gas chamber


12


. The bellows assembly


70


comprises an approximately cylindrical bellows (elastic member)


71


which can elastically move in the axial direction; the bottom seal (securing portion)


72


connected to an end of the bellows


71


; a bellows cap (fixed portion)


73


connected to the other end of the bellows


71


; and a resonance box


74


which is connected to the bottom seal


72


in the hydraulic chamber


11


. The inner space of the bellows assembly


70


forms the hydraulic chamber


11


. The space formed between the bellows assembly


70


and the shell


10


is the gas chamber


12


. Welding method such as TIG welding and plasma arc welding is applied to connect the bottom seal


72


and the bellows cap


73


to the bellows


71


, and to connect the resonance box


74


to the bottom seal


72


.




The bellows cap


73


comprises a recess


73




a


projecting into the hydraulic chamber


11


, of which the flanged circumference is mounted with a ring-shaped bellows guide


75


. The bellows guide


75


is fitted into the inner surface of the bottom shell


20


in a sliding condition, and guides the bellows cap


73


so as not to vibrate when the bellows


71


moves elastically. The bellows guide


75


comprises plural grooves (not shown) which communicate both portions of the gas chamber


12


partitioned thereby, and the grooves make the gas pressure in the gas chamber


12


uniform.




The joining portion between the shells


20


and


30


in which the bellows guide


75


is supported faces the bellows


71


when the bellows


71


is in the most contracted condition. That is, the joining portion of the shells


20


and


30


is positioned outside the region where the bellows guide


75


moves. Two-dot chain line shows the position of the bellows cap


73


when the bellows assembly


70


is in the most expanded condition.




A through hole


74




a


is provided for communicating the interior and the exterior of the resonance box


74


. A self seal


76


made from a rubber is secured to the inner surface of the bellows cap


73


in the hydraulic chamber


11


. The self seal


76


can close the through hole


74




a


of the resonance box, and can prevent excess compression of the bellows


71


and damage to the bellows cap


73


due to this.




A hydraulic fluid is flowed into the hydraulic chamber


11


from the hydraulic circuit via flow path


51


of the port


50


. An inert gas such as nitrogen gas is charged in the gas chamber


12


at a predetermined pressure. The inert gas is charged into the gas chamber


12


through a gas feeding through hole


22


formed at the center end of the bottom shell


20


. The gas feeding through hole


22


is sealed by a plug


23


secured to the bottom shell


20


. A head


24


which has a hexagonal cross section and covers the plug


23


is secured to the center end of the bottom shell


20


. The plug


23


and the head


24


are secured to the bottom shell


20


by means of welding such as projection welding.




According to the above-constructed first embodiment of the accumulator, when the hydraulic fluid flows into the hydraulic chamber


11


via the flow path


51


and the pressure of the hydraulic fluid exceeds the gas pressure in the gas chamber


12


, the bellows


71


expands and the gas in the gas chamber


12


is compressed. In contrast, when the hydraulic fluid pressure in the hydraulic chamber


11


is below the gas pressure in the gas chamber


12


, the bellows


71


is contracted and the gas in the gas chamber


12


is expanded. Due to the expansion and compression of the gas in the gas chamber


12


, the variation of the pressure of the hydraulic fluid in the hydraulic circuit is accommodated and pulsation thereof is inhibited. When the pressure of the hydraulic fluid is below the operating pressure of the accumulator, pulsation is absorbed by the hydraulic fluid in the resonance box


74


.




When the hydraulic pressure in the resonance box


74


is reduced, the bellows


71


is contracted to maintain the hydraulic pressure in the resonance box


74


. When the hydraulic pressure in the resonance box


74


is below the gas pressure in the gas chamber


12


, the self seal


76


closely contacts the resonance box


74


so as to close the through hole


74




a


, and the hydraulic chamber


11


is self-sealed so that the pressure therein is higher than that of the gas chamber


12


.




When the bellows


71


is in the most contracted condition, the bellows guide


75


is positioned at the bottom shell


20


side rather than the joining portion of the bottom shell


20


and the cap shell


30


, and the joining portion of the shells


20


and


30


covered by the bellows protector


40


faces the bellows


71


. Therefore, the bellows guide


75


slides only on the inner surface of the bottom shell


20


in the elastic movement of the bellows


71


.




Next, the process for assembling the above accumulator will be explained.




First, the resonance box


74


is welded to the bottom seal


72


integral with the port


50


, and the bellows


71


is welded to the bottom seal


72


, then the bellows cap


73


is welded to the bellows


71


. TIG welding or plasma welding is applied to the above welding. Next, the port


50


is press fitted into the through hole


33


of the cylindrical portion


32


of the cap shell


30


from the inside thereof, and the outer circumference


32




a


of the cylindrical portion


32


and the port


50


are arc welded. Then, the bellows guide


75


is mounted to the bellows cap


73


.




Next, the bottom shell


20


is abutted to the cap shell


30


in a condition in which the bellows protector


40


is fitted into the inner portions of the circular circumferential portions


21


and


31


. Then, projection welding is performed to the abutted portion of the shells


20


and


30


. In the welding, sparks are often emitted from the welded portion, and the sparks are blocked by the bellows protector


40


. Therefore, damage to the bellows


71


is prevented and a long service life of the bellows


71


is ensured. Beads projecting from the inner and outer surfaces are formed according to the welding. The bead projecting from the inner surface is received in the groove


41


of the bellows protector


40


. The bead projecting from the outer surface is preferably removed by machining or the like. In an alternative manner, the port


50


may be press fitted into the through hole


33


of the cylindrical portion


32


and the bellows assembly


70


may be assembled in the cap shell


30


, the shells


20


and


30


may then be welded, and then the port


50


and the cap shell


30


may be welded.




A hydraulic fluid is charged into the hydraulic chamber


11


via flow path


51


for backup so as to exchange the air in the hydraulic chamber


11


with the hydraulic fluid. Then, a liquid is charged into the gas chamber


12


for adjusting the volume of gas, and an inert gas is charged into the gas chamber


12


through the gas feeding through hole


22


. The plug


23


is inserted into the gas feeding through hole


22


, and is welded to the bottom shell


20


, and finally, the head


24


is welded to the bottom shell


20


.




According to the accumulator in the first embodiment, the port


50


is airtightly press fitted into the cylindrical portion


32


formed in the cap shell


30


, and the inner surface of the cylindrical portion


32


and the outer surface of the port


50


are closely contacted to each other. Therefore, the outer ridge portion of the cylindrical portion


32


is isolated from the interior of the cap shell


30


. As a result, when sparks occur during welding the port


50


to the cap shell


50


, the sparks are not emitted into the interior of the cap shell


30


, and the interior of the cap shell is not contaminated by splashing of the sparks. Therefore, the contamination in the shell


10


can be easily controlled and the production efficiency can be improved.




Since the cylindrical portion


32


is projected into the interior of the cap shell


30


, the overall length of the accumulator can be shorter and can be compact rather than the case in which the cylindrical portion


32


is projected outwardly. In order to form the cylindrical portion


32


, several methods can be applied. Burring is preferably applied as in the embodiment since high precision can be easily obtained.




The bottom seal


72


forming the bellows assembly


70


is integrally formed with the port


50


, so that the bottom seal


72


need not be welded to the cap shell


30


, and contamination due to sparks can be prevented.




Furthermore, even if a step is formed between the bellows protector


40


and the shells


20


and


30


(boundary between both), the bellows guide


75


can slide smoothly with no influence from the step since the bellows guide


75


slides on the inner surface of the bottom shell


20


. Therefore, the bellows


71


can usually operate in normal manner, and the bellows guide


75


is not damaged and durability thereof can be improved.




(2) Second Embodiment




A second embodiment will be explained with reference to

FIG. 2

hereinafter. In

FIG. 2

, numerals corresponding to those in the first embodiment are attached to the same elements as in the first embodiment, and explanation thereof are omitted.




The accumulator in the embodiment has the same essential structure as the first embodiment except that the resonance box


74


in the first embodiment is not used to, and the depth of the recess


73




b


of the bellows cap


73


is larger than that of the recess


73




a


in the first embodiment. Therefore, when the bellows


71


is in the most contracted condition, a self seal


76


adhered to the inner surface of the bellows cap


73


directly closes the flow path


51


of the port


50


. The two-dot chain line in

FIG. 2

shows the position of the bellows cap


73


when the bellows assembly


70


is in the most expanded condition.




Similarly in the accumulator in the embodiment, the port


50


is airtightly press fitted into the cylindrical portion


32


formed in the cap shell


30


, and the outer circumference of the cylindrical portion


32


and the outer surface of the port


50


is fillet welded by arc welding or the like. Therefore, contamination in the shell due to sparks occurring in the welding can be prevented. Moreover, the advantages in the first embodiment can be obtained. That is, the structure can be compact since the cylindrical portion


32


is projected into the interior of the cap shell


30


, and contamination can be prevented since the bottom seal


72


is integrally formed with the port


50


.




(3) Third Embodiment





FIG. 3

shows an accumulator of a third embodiment according to the invention. In

FIG. 3

, numerals corresponding to those in

FIG. 5

are attached to the same elements as in the first embodiment, and explanations thereof are simplified or omitted.




The shell


110


consists of a bottom shell (divided shell body)


120


and a cap shell (divided shell body)


130


which are joined to each other by welding. A circular circumferential portion


121


or


131


projecting outward is formed at the joining end of the shells


120


and


130


around the entire circumference thereof. The circular circumferential portions


121


and


131


are formed for reinforcement and so as not to project a bead formed in welding both by projection welding, which is a kind of resistance welding, from the inner surface of the shell


110


.




The bellows assembly (partitioning member)


170


is contained in the shell


110


so as to partition the interior of the shell


110


into a hydraulic chamber


111


and a gas chamber


112


. The bellows assembly


170


comprises a bellows


171


, a bottom seal


172


and a bellows cap


173


respectively connected to both ends of the bellows


71


. The bottom seal


172


is joined to the cap shell


130


so as to form a resonance box


174


, so that the bellows assembly


170


is secured to the interior of the shell


110


. A through hole


172




a


for communicating the resonance box


174


and the hydraulic chamber


111


is formed at the center of the bottom seal


172


. Welding method such as TIG welding and plasma arc welding is applied to connect the bottom seal


172


and the bellows cap


173


to the bellows


171


. Projection welding is applied to connect the bottom seal


172


to the cap shell


130


.




The bellows cap


173


comprises a recess


173




b


projecting into the hydraulic chamber


111


, of which a flanged circumference is mounted with a ring-shaped bellows guide


175


. The bellows guide


175


guides the bellows cap


173


so as not to vibrate when the bellows


171


moves elastically. The bellows guide


175


comprises plural grooves (not shown) which communicate both portions of the gas chamber


112


partitioned thereby, and the grooves make the gas pressure in the gas chamber


112


uniform. A self seal


176


made from a rubber is adhered to the inner surface of the bellows cap


173


in the hydraulic chamber


111


. The self seal


176


can prevent excess compression of the bellows


171


and damage to the bellows cap


173


due to this.




A through hole


130




a


communicated to the resonance box


174


is formed at the center end of the cap shell


130


. A port


150


having a hydraulic fluid flow path


151


linearly aligned and connected to the through hole


130




a


is connected to the outer surface of the cap shell


130


by projection welding. The port


150


comprises a screw portion


152


to which a hydraulic circuit (not shown) is connected. A hydraulic fluid is flowed into the hydraulic chamber


111


from the hydraulic circuit via flow path


151


of the port


150


, the through hole


130




a


of the cap shell


130


, the resonance box


174


, and the through hole


172




a


of the bottom seal


172


.




An inert gas such as nitrogen gas is charged at a predetermined pressure in the gas chamber


112


. A gas feeding through hole


122


is formed at the center end of the bottom shell


120


for charging the inert gas into the gas chamber


112


. The gas feeding through hole


122


is sealed by a plug


123


secured to the bottom shell


120


. A head


124


which has a hexagonal cross section and covers the plug


123


is secured to the center end of the bottom shell


120


. The plug


123


and the head


124


are secured to the bottom shell


120


by means of welding such as projection welding.




In this embodiment, a sleeve


180


with a uniform diameter is disposed in the shell


110


. The sleeve


180


extends over the overall length of the body portion of the shell


110


, and is coaxially aligned with the shell


110


maintaining a slight clearance with the inner surface of the shell


110


. The sleeve


180


is located between joined portion of the bottom shell


120


and the cap shell


130


, and the bellows


171


so as to screen both. The bellows guide


175


slides on the inner surface of the sleeve


180


. The sleeve


180


is preferably made from an insulating resin, and the inner surface thereof is preferably treated with Teflon (trademark) so that the bellows guide


175


can slide smoothly and high durability can be obtained. The sleeve is not secured to other parts since the movement thereof is restricted by abutting to the each shell


120


and


130


, but may be adhered to the shells


120


and


130


if necessary.




According to the embodiment of the accumulator, when the hydraulic fluid flows into the hydraulic chamber


111


via the flow path


151


, through hole


130




a


, the resonance box


174


, and the through hole


172




a


, and the pressure of the hydraulic fluid exceeds the gas pressure in the gas chamber


112


, the bellows


171


expands and the gas in the gas chamber


112


is compressed. In contrast, when the hydraulic fluid pressure in the hydraulic chamber


111


is below the gas pressure in the gas chamber


112


, the bellows


171


is contracted and the gas in the gas chamber


112


is expanded. Due to the expansion and compression of the gas in the gas chamber


112


, the variation of the pressure of the hydraulic fluid in the hydraulic circuit is accommodated and pulsation thereof is inhibited. The expansion and contraction of the bellows


171


is guided in the axial direction of the shell


110


by sliding and moving the bellows guide


175


along the inner surface of the sleeve


180


. The two-dot chain line in

FIG. 3

shows the position of the bellows cap


173


when the bellows assembly


170


is in the most expanded condition.




When the hydraulic pressure in the resonance box


174


is reduced, the bellows


171


is contracted to maintain the hydraulic pressure in the resonance box


174


. When the hydraulic pressure in the resonance box


174


is below the gas pressure in the gas chamber


112


, the self seal


176


closely contacts the resonance box


174


so as to close the through hole


172




a


, the hydraulic chamber


111


is self-sealed so that the pressure therein is higher than that of the gas chamber


112


.




Next, the process for assembling the above accumulator will be explained.




First, the bottom seal


172


and the bellows cap


173


are welded to the bellows


171


to assemble the bellows assembly


170


. The port


150


and the bottom seal


172


is welded to the cap shell


130


, and the bellows guide


175


is mounted to the bellows cap


173


. Then, the sleeve


180


is inserted into the bottom shell


120


. The cap shell


130


is abutted to the bottom shell


120


during insertion of the bellows assembly


170


into the sleeve


180


, and the shells


120


and


130


are welded. A hydraulic fluid is charged into the hydraulic chamber


111


via flow path


151


for backup so as to exchange the air in the hydraulic chamber


111


with the hydraulic fluid. Then, a liquid is charged into the gas chamber


112


for adjusting the volume of a gas, and an inert gas is charged into the gas chamber


112


through the gas feeding through hole


122


. The plug


123


is inserted into the gas feeding through hole


122


, and is welded to the bottom shell


120


, and finally, the head


124


is welded to the bottom shell


120


.




According to the accumulator in the embodiment, in the welding, sparks are often emitted from the welded portion, the sparks are blocked by the sleeve


180


and cannot strike the bellows


171


. Therefore, damage to the bellows


171


due to the sparks is prevented and a long service life of the bellows


171


is ensured. As a result, the normal operation of the accumulator can be ensured. Furthermore, even if sparks are emitted in the shell


110


, the sparks remain in the gas chamber


112


and do not enter into the hydraulic chamber


111


, so that the system including the hydraulic circuit to which the accumulator is connected is not contaminated by splashing of the sparks. Moreover, since the bellows guide


175


slides on the inner surface of the sleeve


180


, the bellows guide


175


can slide smoothly with no influence from the joined portion of the shells


120


and


130


, and the bellows


171


can usually operate in normal manner.




(4) Fourth Embodiment




A fourth embodiment will be explained with reference to

FIG. 4

hereinafter. In

FIG. 4

, numerals corresponding to those in the third embodiment are attached to the same elements as in the third embodiment, and explanations of these elements are omitted.




The difference features in the fourth embodiment from the third embodiment will be described.




A cylindrical portion


132


is formed at the center end portion of the cap shell


130


by inwardly (upward in

FIG. 4

) projecting the portion by means of burring. A port


150


is press fitted with an airtight seal into the through hole


133


of the cylindrical portion


132


from the inner side thereof. The port


150


projects outward from the through hole


133


of the cylindrical portion


132


.




The port


150


is fixed to the cap shell


130


by fillet welding the outer surface of the port


150


to the outer circumference


132




a


of the cylindrical portion


132


. Reference numeral


160


in

FIG. 4

is a bead formed by the welding, and is formed around the entire circumference of the port


150


. A bottom seal


172


of a bellows assembly


170


is integrally formed at the inner end of the port


150


. The bottom seal


172


is brought into contact with the inner end surface of the cylindrical portion


132


.




A circular recess having a trapezoidal cross section is formed at the inside of the circular circumferential portions


121


and


31


. A bellows protector (ring member, protecting member)


140


is provided in the recess instead of the sleeve


180


in the third embodiment. The bellows protector


140


is made from an insulating resin. The inner diameter of the bellows protector


140


is identical to that of the shell


110


, and the outer surface thereof is formed with a groove


141


around the entire circumference.




This embodiment does not include the resonance box


174


as in the third embodiment. A self seal


176


is adhered to the inner surface of the bellows cap


173


, and directly closes the flow path


151


of the port


150


when the bellows


171


is in the most contracted condition. The bellows guide


175


moves according to expansion and contraction of the bellows


171


sliding on the inner surface of the bottom shell


120


. The bellows protector


140


is positioned outside the region where the bellows guide


175


moves. Two-dot chain line shows the position of the bellows cap


173


when the bellows assembly


170


is in the most expanded condition.




The operation of the accumulator in the embodiment is approximately same as the third embodiment except that the bellows guide slides on the inner surface of the bottom shell


120


.




Next, the process for assembling the above accumulator will be explained.




First, the bellows


171


is welded to the bottom seal


172


integrally formed with the port


150


, and the bellows cap


173


is welded to the bellows


171


, thereby assembling the bellows assembly


170


, and the bellows guide


175


is then mounted to the bellows cap


173


. Then, the port


150


is press fitted into the through hole


133


of the cylindrical portion


132


of the cap shell


130


from the inside thereof, and the outer circumferential


132




a


of the cylindrical portion


132


and the port


150


are welded.




Then, the bottom shell


120


is abutted to the cap shell


130


in a condition in which the bellows protector


140


is fitted into the inner portions of the circular circumferential portions


121


and


131


. Then, welding is performed to the abutted portion of the shells


120


and


130


. In the welding, a bead often projects from the inner surfaces, the bead is received in the groove


141


of the bellows protector


140


. In an alternative manner, the port


150


may be press fitted into the through hole


133


of the cylindrical portion


132


and the bellows assembly


170


may be assembled in the cap shell


130


, the shells


120


and


130


may be then welded, and then the port


150


and the cap shell


130


may be welded. Next, a hydraulic fluid is charged into the hydraulic chamber


111


for backup, a liquid is charged into the gas chamber


112


for adjusting the volume of gas, and an inert gas is charged into the gas chamber


112


through the gas feeding through hole


122


. The plug


23


is inserted into the gas feeding through hole


122


, and is welded to the bottom shell


120


, and finally, the head


124


is welded to the bottom shell


120


.




According to the accumulator in the embodiment, the shells


120


and


130


are joined by means of projection welding or the like. In the welding, sparks emitted from the welded portion are blocked by the bellows protector


140


and do not strike the bellows


171


. Therefore, damage to the bellows


171


due to the sparks can be prevented and a long service life is ensured. As a result, normal operation of the accumulator can be ensured in a long term. Furthermore, even if a step is formed between the bellows protector


140


and the shells


120


and


130


(boundary between both), the bellows guide


175


can slide smoothly with no influence from the step since the bellows guide


175


slides on the inner surface of the bottom shell


120


. Therefore, the bellows


171


can usually operates in normal manner. Moreover, the advantage in which the emitted sparks in the shell


110


remains in the gas chamber


112


as in the third embodiment can obtained.




It should be noted that the metallic bellows assembly is used as a partitioning member for partitioning the interior of the shell into the hydraulic chamber and the gas chamber in the embodiments. The bellows assembly can be formed from materials other than metals. Furthermore, the partitioning member is not limited to bellows assemblies, but pistons, diaphragms, and balloons can be used. In this case, these partitioning members may be accompanied with an airtight seal with respect to shells according to the kind thereof.



Claims
  • 1. An accumulator comprising:a cylindrical shell including a cylindrical portion; a partitioning member for partitioning an interior of the shell into a hydraulic chamber and a gas chamber; and a port including a hydraulic fluid flow path for communicating an exterior of the shell and the hydraulic chamber; wherein variation of pressure of a hydraulic fluid flowing into the hydraulic chamber is accommodated by expansion and compression of a gas in the gas chamber according to expansion and contraction of the partitioning member; the port is approximately airtightly inserted into the cylindrical portion of the shell, and is welded to an outer circumference of the cylindrical portion by means of welding; wherein the shell comprises plural divided shell bodies joined to each other; the partitioning member includes a guide for sliding on an inner surface of the shell so as to guide the expansion and contraction of the partitioning member along an axial direction thereof; and a joined portion between the divided shell bodies is positioned outside the region where the guide moves, and the guide slides within an inner surface of one divided shell body.
  • 2. An accumulator according to claim 1, wherein the partitioning member comprises a fixed portion and a movable portion mounted to the fixed portion via an elastic member, and the fixed portion is integrally formed with the port.
  • 3. An accumulator comprising:a cylindrical shell including plural divided shell bodies joined to each other in an axial direction thereof; a partitioning member for partitioning the interior of the shell into a hydraulic chamber and a gas chamber, the partitioning member expanding and contracting in the axial direction of the shell; and a guide provided at a free end of the partitioning member, the guide guiding the expansion and contraction of the partitioning member along an axial direction thereof; wherein variation of the pressure of a hydraulic fluid flowing into the hydraulic chamber is accommodated by expansion and compression of a gas in the gas chamber according to expansion and contraction of the partitioning member; a protecting member is provided between a joined portion of the divided shell bodies and the partitioning member so as to screen both; and the protecting member is a sleeve disposed in the shell, and the guide slides on an inner surface of the sleeve.
  • 4. An accumulator according to claim 3, wherein the protecting member is a ring-shaped member covering an inner surface of the joined portion of the divided shell bodies.
  • 5. An accumulator according to claim 4, wherein the ring-shaped member is positioned outside the region where the guide moves, and the guide slides within an inner surface of one divided shell body.
  • 6. An accumulator according to claim 1, wherein the cylindrical portion is projected into the interior of the shell and formed by burring the shell.
Priority Claims (2)
Number Date Country Kind
2000-160223 May 2000 JP
2000-160224 May 2000 JP
US Referenced Citations (8)
Number Name Date Kind
3918497 Schon Nov 1975 A
3963053 Mercier Jun 1976 A
4010773 Bihlmaier Mar 1977 A
4055067 Kozima Oct 1977 A
4299254 Zahid Nov 1981 A
4348792 Zahid Sep 1982 A
4881725 Shioda et al. Nov 1989 A
6286552 Shimbori et al. Sep 2001 B1
Foreign Referenced Citations (10)
Number Date Country
1232418 Jan 1967 DE
2029457 Dec 1971 DE
1373342 Jan 1965 FR
61222642 Oct 1986 JP
63260631 Oct 1988 JP
01104421 Apr 1989 JP
04083902 Mar 1992 JP
11000724 Jan 1999 JP
2002346682 Dec 2002 JP
WO 9917029 Aug 1999 WO
Non-Patent Literature Citations (1)
Entry
Partial European Search Report, Application No. EP 01 11 3085; Sep. 4, 2001.