Accumulator with a hydraulic port welded on the shell, a bellow guide and a bellow protector

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: The present invention relates to an accumulator according to the preamble of claim 1. The accumulator such as the above is known from US-A-4 010 773 and comprises a cylindrical shell including two divided shell bodies joined to each other in an axial thereof. The interior of the shell is subdivided by a partitioning member into a hydraulic chamber and a gas chamber. A 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 guide is provided at a free end of the partitioning member so that the partitioning member does not enter the hydraulic chamber. A protecting member in form of a two-partite ring is provided between a joined portion of the divided shell bodies and the partitioning member so as to screen both. An object of the present invention is to provide an accumulator in which the guiding of the partitioning member is improved. This object is achieved by the characterising part of claim 1. According to the specific feature of the protecting member, a sleeve coaxially aligned with the shell along the inner surface of the shell is 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. The Figure shows an accumulator of an embodiment according to the invention. 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 172a 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 173b 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 130a 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 130a 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 130a of the cap shell 130, the resonance box 174, and the through hole 172a 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 130a, the resonance box 174, and the through hole 172a, 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 172a, 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.

Claims: An accumulator comprising: a cylindrical shell (110) including plural divided shell bodies (120, 130) joined to each other in an axial direction thereof; a partitioning member (170) for partitioning the interior of the shell (110) into a hydraulic chamber (111) and a gas chamber (112), the partitioning member (170) expanding and contracting in the axial direction of the shell (110); and a guide (175) provided at a free end of the partitioning member (170), the guide (175) guiding the expansion and contraction of the partitioning member (170) along an axial direction thereof; wherein variation of the pressure of a hydraulic fluid flowing into the hydraulic chamber (111) is accommodated by expansion and compression of a gas in the gas chamber (112) according to expansion and contraction of the partitioning member (170); and a protecting member is provided between a joined portion (121, 131) of the divided shell bodies (120, 130) and the partitioning member (170) so as to screen both, characterised in that the protecting member is a sleeve (180) disposed in the shell (110), and the guide (175) slides on a inner surface of the sleeve (180). An accumulator according to claim 1, wherein the sleeve (180) is a ring-shaped member covering an inner surface of the joined portion (121, 131) of the divided shell bodies (120, 130). An accumulator according to claim 2, wherein the sleeve (180) is positioned outside the region where the guide (175) moves, and the guide (175) slides within a inner surface of one divided shell body (120).

Inventors: MIZUKAMI HIROSHI, NAKAMURA KOJI, UMETSU CHIHARU, YAMADA KOICHIRO, MIZUKAMI, HIROSHI, NAKAMURA, KOJI, UMETSU, CHIHARU, YAMADA, KOICHIRO, Mizukami, Hiroshi, c/o NHK Spring Co., Ltd., Nakamura, Koji, c/o NHK Spring Co., Ltd., Umetsu, Chiharu, c/o NHK Spring Co., Ltd., Yamada, Koichiro, c/o NHK Spring Co., Ltd.
Applicants: NHK SPRING CO LTD, NHK SPRING CO., LTD.
Application year: 2001
Main classification: F15B1
IPC codes: F15B1