JP6530671B2 - Double cylinder type shock absorber - Google Patents

Description

  The present invention relates to a double cylinder type shock absorber.

  In Patent Document 1, a rod guide which is fitted at an end of a cylinder and which supports a piston rod via a bush provided on an inner periphery, and provided on the opposite side of a liquid chamber of the rod guide There is disclosed a double cylinder type shock absorber provided with an oil seal in close contact with an outer peripheral surface.

  In the shock absorber described in Patent Document 1, a housing portion in which the seal lip of the oil seal is provided is provided on the surface of the rod guide on the oil seal side.

Japanese Patent Application Laid-Open No. 9-112619

  In the shock absorber described in Patent Document 1, the end face on the oil seal side of the bush is provided at a position lower than the bottom surface of the housing portion of the rod guide. That is, an annular groove is formed around the piston rod by the rod guide and the bush.

  In such a configuration, contamination and wear powder in the housing portion easily accumulate around the piston rod. Here, at the time of extension of the shock absorber when the piston rod exits from the cylinder, the hydraulic oil is dragged by the piston rod by the viscous resistance and enters into the seal lip of the oil seal. For this reason, contamination and the like accumulated around the piston rod may enter the seal lip of the oil seal together with the hydraulic oil, which may reduce the durability of the oil seal.

  The present invention has been made in view of such technical problems, and it is an object of the present invention to suppress accumulation of contamination and the like around the piston rod and to improve the durability of the oil seal.

  According to a first aspect of the present invention, in the double-tube type shock absorber, the rod guide is provided with a recess formed outward in the radial direction starting from a position separated by a predetermined distance from the outer peripheral surface of the piston rod. .

  In the first aspect of the present invention, the rod guide has a recess provided at a position where contamination that moves in the housing by eddy current tends to accumulate. For this reason, the contamination in the accommodation portion is accumulated in the recess, and the accumulation of contamination around the piston rod is suppressed.

  A second invention is characterized in that the bush is provided flush with the bottom surface of the housing portion or protruding from the bottom surface.

  In the second aspect of the invention, the end face of the bush is provided flush with or below the bottom surface of the housing portion, so that a space in which contamination is likely to be accumulated is not formed around the piston rod. As a result, it is possible to suppress the accumulation of contamination around the piston rod.

  A third invention is characterized in that corner portions of a radially inner bottom surface and a recess are chamfered.

  In the third invention, the corner between the bottom and the recess is chamfered. For this reason, the contamination which exists around a corner becomes easy to fall to a crevice. As a result, it is possible to suppress the accumulation of contamination around the piston rod.

A fourth invention is characterized in that, in the double cylinder type shock absorber, a bush is provided so as to protrude from the bottom surface of the housing portion. Further, the fifth invention is characterized in that the bottom surface of the housing portion is provided to be inclined so as to be away from the oil seal as it goes radially outward.

In the fourth and fifth inventions, the bush and the rod guide define a recess where the contamination is accumulated. As described above, the concave portion is provided at a position where the contamination moving in the housing portion by the vortex flow is easily accumulated. For this reason, the contamination in the accommodation portion is accumulated in the recess, and the accumulation of contamination around the piston rod is suppressed.

  According to the present invention, the accumulation of contamination and the like around the piston rod is suppressed, and the durability of the oil seal can be improved.

It is a sectional view of a shock absorber concerning a 1st embodiment of the present invention. It is an enlarged view of the rod guide periphery of FIG. It is an enlarged view of rod guide circumference of a shock absorber concerning a 2nd embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the attached drawings.

First Embodiment
A shock absorber 100 according to a first embodiment of the present invention will be described with reference to FIGS. 1 and 2. The shock absorber 100 shown in FIG. 1 is a double-tube type shock absorber used for a strut type suspension of a vehicle such as a car.

  As shown in FIGS. 1 and 2, the shock absorber 100 is disposed so as to cover the inner case 1 and the inner case 1 as a cylinder filled with hydraulic fluid as the hydraulic fluid, and between the inner case 1 and the inner case 1. An outer case 2 as an outer cylinder forming a reservoir chamber 70 for storing hydraulic oil, and a piston 3 slidably inserted in the inner case 1 and dividing the inner case 1 into an expansion side chamber 50 and a pressure side chamber 60 And a piston rod 4 which is inserted into the inner case 1 so as to be able to move back and forth, and one end of which is connected to the piston 3. The shock absorber 100 is connected to the vehicle body via an upper mount (not shown) at the other end of the piston rod 4 and is connected to a knuckle or the like for supporting the wheel via a connecting member (not shown) formed on the outer case 2 .

  The inner case 1 is fitted to the cylindrical inner tube 6 and the end of the inner tube 6 on the extension side chamber 50 side, and supports the piston rod 4 slidably, and the pressure side chamber of the inner tube 6 And a base valve 8 as a partition member fitted to the end on the 60 side.

  The rod guide 7 is formed so as to axially penetrate the small diameter portion 7a fitted to the inner circumferential surface of the inner tube 6, the large diameter portion 7b having a diameter larger than the small diameter portion 7a, and the piston rod 4 is inserted And the rod insertion hole 7c. The detailed shape of the rod guide 7 will be described later.

  The base valve 8 has passages 8 a and 8 b communicating the pressure side chamber 60 and the reservoir chamber 70. The passage 8a is provided with a check valve 16 that opens when the shock absorber 100 extends and opens the passage 8a. A passage 8b is opened when the shock absorber 100 is contracted to open the passage 8b, and a damping valve 17 that resists the flow of hydraulic fluid moving from the pressure side chamber 60 to the reservoir chamber 70 through the passage 8b. Provided.

  The piston 3 slidably inserted into the inner case 1 has passages 3 a and 3 b for communicating the expansion side chamber 50 with the pressure side chamber 60. In the passage 3a, the damping valve 18 opens to open the passage 3a when the shock absorber 100 is extended, and also provides resistance to the flow of hydraulic fluid moving from the expansion chamber 50 to the pressure chamber 60 through the passage 3a. Provided. The passage 3 b is provided with a check valve 19 that opens when the shock absorber 100 contracts and opens the passage 3 b.

  The outer case 2 is, as shown in FIGS. 1 and 2, an outer tube 2a formed coaxially with the inner tube 6 and a crimped portion bent radially inward at the end of the outer tube 2a on the extension side chamber 50 side. 2b and a closed portion 2c that closes the end of the outer tube 2a on the pressure side chamber 60 side. An oil seal 11 is sandwiched and fixed between the caulking portion 2 b of the outer case 2 and the rod guide 7.

  As shown in FIG. 2, the oil seal 11 includes an annular base metal 11a, a seal lip 11b and a dust lip 11c attached to the inner periphery of the base metal 11a and in sliding contact with the outer periphery of the piston rod 4, and the base metal 11a. An annular check lip 11 d extending toward the rod guide 7 and an outer peripheral seal 11 e attached to the outer peripheral side of the base metal 11 a and in contact with the inner periphery of the outer case 2 and the upper surface of the rod guide 7.

  The seal lip 11 b is provided toward the rod guide 7 to prevent the hydraulic oil from leaking to the outside. The dust lip 11 c is provided on the side opposite to the rod guide 7 to prevent foreign matter from entering the inner tube 6.

  Subsequently, the detailed shape of the rod guide 7 will be described with reference to FIG.

  The rod guide 7 is provided on the inner peripheral side of the large diameter portion 7b, and a communication hole communicating the housing portion 7d and the reservoir chamber 70 with the housing portion 7d in which the seal lip 11b and the check lip 11d of the oil seal 11 are housed. 7e and a recess 7h provided on the bottom 7f of the housing 7d. A plurality of recesses 7 h are provided at intervals in the circumferential direction. The number of recesses 7 h is not limited to a plurality, and may be one. In addition, the recess 7 h may be formed as an annular groove.

  The check lip 11d is in sealing contact with the inner peripheral side of the communication hole 7e of the rod guide 7, and the communication between the housing portion 7d and the reservoir chamber 70 is restricted by the check lip 11d. Specifically, when the pressure in the storage portion 7 d becomes higher than the pressure of the reservoir chamber 70 by a predetermined value or more, the check lip 11 d separates from the rod guide 7 and allows communication between the storage portion 7 d and the reservoir chamber 70. . That is, the check lip 11d functions as a check valve that allows only the flow of hydraulic oil from the storage portion 7d to the reservoir chamber 70.

  The side surface 7j on the piston rod 4 side of the recess 7h is provided to be inclined away from the piston rod 4 as it goes to the bottom 7i of the recess 7h. The side 7k opposite to the piston rod 4 of the recess 7h is provided to be inclined so as to approach the piston rod 4 as it goes to the bottom 7i. Further, the bottom portion 7i is provided to be inclined such that the depth from the bottom surface 7f becomes deeper as it goes radially outward. An R-chamfering process (not shown) is applied to the corner 7m between the side surface 7j and the bottom surface 7f.

  The recess 7 h is formed radially outward with a position separated from the outer peripheral surface of the piston rod 4 by the starting distance L 2 as a starting point 7 g. The starting point 7g is a virtual intersection of the side surface 7j and the bottom surface 7f. The starting point distance L2 is 1/1 of the separation distance L1, which is the distance between the bottom surface 7f radially inward of the recess 7h and the flat portion 11f of the seal lip 11b of the oil seal 11 axially opposed to the bottom surface 7f. It is set within the range of 4 or more and the separation distance L1 or less.

  The bush 9 is attached to the rod insertion hole 7c. The end face 9a on the oil seal 11 side of the bush 9 is provided flush with the bottom face 7f. The piston rod 4 inserted through the rod insertion hole 7 c is slidably supported by the rod guide 7 via the bush 9.

  Next, the operation and effect of the shock absorber 100 by providing the rod guide 7 of the above configuration will be described.

  Contamination exists in the shock absorber 100. Here, for example, when the end face 9 a on the oil seal 11 side of the bush 9 is provided at a position lower than the bottom face 7 f of the housing 7 d of the rod guide 7, an annular groove is formed around the piston rod 4. . In such a configuration, contamination in the accommodation portion 7 d is likely to be accumulated around the piston rod 4.

  At the time of extension of the shock absorber 100 in which the piston rod 4 withdraws from the inner case 1, the hydraulic oil is dragged by the piston rod 4 by viscous resistance and enters the seal lip 11 b of the oil seal 11. For this reason, as described above, in the state where the contamination is accumulated around the piston rod 4, the contamination may enter the seal lip 11b together with the hydraulic oil, and the durability of the seal lip 11b may be deteriorated.

  On the other hand, in the present embodiment, the recess 7h is provided on the bottom surface 7f of the housing 7d, so that the contamination in the housing 7d is positively stored in the recess 7h.

  At the time of extension of the shock absorber 100 in which the piston rod 4 withdraws from the inner case 1, a vortex flow in the direction indicated by the arrow in FIG. The eddy current is generated in a range of a circle (two-dot chain line) in contact with the piston rod 4 with a separation distance L1 being a distance between the bottom surface 7f of the rod guide 7 and the flat portion 11f of the oil seal 11 as a diameter.

  The hydraulic fluid flows from the rod guide 7 toward the oil seal 11 on the piston rod 4 side of the center of the vortex flow. In addition, hydraulic oil flows from the oil seal 11 toward the rod guide 7 radially outward of the center of the vortex.

  For this reason, when the starting point 7g of the recess 7h is set in a range from a position separated by 1⁄4 from the piston rod 4 to a position separated by the same distance as the separation distance L1, the hydraulic oil flows toward the recess 7h. It will be. At this time, gravity and centrifugal force act on the contamination mixed in the working oil and flowing toward the recess 7 h, so that the contamination in the working oil tends to fall into the recess 7 h. In addition, contamination collides with the side surface 7j, so that the contamination is likely to be led to the recess 7h. Therefore, the contamination can be positively stored in the recess 7 h, and the contamination in the housing portion 7 d can be reliably isolated from the piston rod 4 and the oil seal 11.

  Here, when the starting point distance L2, which is the distance from the piston rod 4 to the starting point 7g of the recess 7h, is set shorter than 1⁄4 of the separation distance L1, the working oil flows so as to roll up the contamination from the recess 7h. Therefore, it is difficult to accumulate contamination in the recess 7 h.

  In addition, when the starting point distance L2 is set longer than the separation distance L1, the eddy current can not be used, and it becomes difficult to efficiently collect the contamination in the concave portion 7h. Even in this case, since the contamination dropped in the recess 7 h is prevented from being wound up by the eddy current, it is possible to isolate the contamination in the accommodation portion 7 d from the piston rod 4 and the oil seal 11.

  Thus, the starting point distance L2 is set according to the ease of accumulation of contamination in the recess 7h. In particular, the starting point distance L2 is around 1/2 of the separation distance L1, for example, so that the starting point 7g is provided around the position where the flow direction of the vortex flows from the flow toward the rod guide 7 to the flow away from the rod guide 7. Preferably, the distance is set in the range of 1⁄4 to 3⁄4 of the separation distance L1.

  According to the first embodiment described above, the following effects can be obtained.

  In the present embodiment, the starting point 7g of the recess 7h provided in the housing portion 7d is set in a range from a position separated by 1⁄4 of the separated distance L1 from the piston rod 4 to a position separated by the same distance as the separated distance L1. As described above, the recess 7 h is provided at a position where contamination that moves in the housing 7 d due to the vortex flow is likely to be accumulated. For this reason, the contamination in the accommodation portion 7d is accumulated in the recess 7h, and the accumulation of the contamination around the piston rod 4 is suppressed. As a result, entry of contamination into the seal lip 11b at the time of extension of the shock absorber 100 can be prevented, and the durability of the oil seal 11 can be improved.

  Further, in the present embodiment, since the end face 9a of the bush 9 is provided flush with the bottom face 7f of the housing 7d, a space in which the contamination is easily accumulated around the piston rod 4 is not formed. Contamination can be suppressed. As a result, entry of contamination into the seal lip 11b at the time of extension of the shock absorber 100 can be prevented, and the durability of the oil seal 11 can be improved. The end face 9a of the bush 9 may protrude from the bottom surface 7f of the housing 7d to the oil seal 11 side. Also in this case, accumulation of contamination around the piston rod 4 can be suppressed.

  Further, in the present embodiment, since the corner 7m of the bottom surface 7f and the recess 7h has an R-chamfered shape, contamination present around the starting point 7g is likely to fall into the recess 7h. As a result, the accumulation of contamination around the piston rod 4 can be suppressed. The chamfering shape formed in the corner 7m is not limited to the R-chamfering, and may be a C-chamfering.

  Further, the side surface 7 j on the side of the piston rod 4 of the recess 7 h is provided to be inclined away from the piston rod 4 as it goes to the bottom 7 i, so that the contamination dropped to the recess 7 h is the bottom 7 i Move to As a result, the accumulation of contamination around the piston rod 4 can be suppressed.

  Further, the side surface 7 k opposite to the piston rod 4 of the recess 7 h is provided to be inclined so as to approach the piston rod 4 as it goes to the bottom 7 i. For this reason, the contamination moved by the vortex flow is easily led to the recess 7 h along the side surface 7 k. Also, the contamination that has collided with the side surface 7k falls along the side surface 7k into the recess 7h. As a result, the accumulation of contamination around the piston rod 4 can be suppressed.

  Further, the bottom 7i of the recess 7h is provided to be inclined so that the depth from the bottom surface 7f becomes deeper as going radially outward, so that the contamination dropped to the recess 7h is at a position further away from the piston rod 4. It becomes easy to accumulate. As a result, the accumulation of contamination around the piston rod 4 can be suppressed.

Second Embodiment
Subsequently, a shock absorber 200 according to a second embodiment of the present invention will be described with reference to FIG. Hereinafter, differences from the shock absorber 100 according to the first embodiment will be mainly described, and the same configuration as that of the first embodiment is denoted by the same reference numeral, and the description will be omitted.

  The shock absorber 200 is different from the first embodiment in that the concave portion is not provided on the bottom surface 7f of the housing portion 7d, and the end surface 9a of the bush 9 is provided to protrude from the bottom surface 7f to the oil seal 11 side. Do.

  The end face 9a of the bush 9 is provided so as to protrude from the bottom face 7f, thereby forming an annular recess 7p defined by the outer peripheral surface 9b of the bush 9, the bottom face 7f and the side face 7n of the housing 7d. The bottom surface 7f which is the bottom of the annular recess 7p is provided to be inclined away from the oil seal 11 as it goes radially outward. Further, the side surface 7 n of the annular recess 7 p is provided to be inclined so as to approach the piston rod 4 as it goes to the bottom surface 7 f.

  Next, the operation and effect of the shock absorber 200 by providing the annular recess 7p will be described.

  In the second embodiment, by providing the annular recess 7p defined by the outer peripheral surface 9b, the bottom surface 7f, and the side surface 7n of the bush 9, contamination in the accommodation portion 7d is positively stored in the annular recess 7p. There is.

  At the time of extension of the shock absorber 200 in which the piston rod 4 withdraws from the inner case 1, eddy current in the direction indicated by the arrow in FIG. 3 is generated in the accommodation portion 7 d. The hydraulic fluid flows from the rod guide 7 toward the oil seal 11 on the piston rod 4 side of the center of the vortex flow. In addition, hydraulic oil flows from the oil seal 11 toward the rod guide 7 radially outward of the center of the vortex.

  Therefore, the hydraulic oil flows along the side surface 7n toward the annular recess 7p. The gravity and the centrifugal force act on the contamination mixed in the working oil and flowing toward the annular recess 7p, so that the contamination in the working oil tends to fall into the annular recess 7p. Therefore, the contamination can be positively stored in the annular recess 7p, and the contamination in the housing portion 7d can be reliably isolated from the piston rod 4 and the oil seal 11.

  According to the above second embodiment, the following effects can be obtained.

  In the shock absorber 200, an annular recess 7p in which the contamination is accumulated is defined by the outer peripheral surface 9b of the bush 9, the bottom surface 7f and the side surface 7n of the housing portion 7d. As described above, the annular recess 7p is provided at a position where contamination that moves in the accommodation portion 7d is easily accumulated by the vortex flow. For this reason, the contamination in the accommodation portion 7d is accumulated in the annular recess 7p, and the accumulation of the contamination around the piston rod 4 is suppressed. As a result, entry of contamination into the seal lip 11b at the time of extension of the shock absorber 200 can be prevented, and the durability of the oil seal 11 can be improved.

  Further, since the bottom surface 7 f is provided to be inclined so as to be away from the oil seal 11 as it goes radially outward, the contamination that has fallen into the annular recess 7 p tends to accumulate at a position further away from the piston rod 4. As a result, the accumulation of contamination around the piston rod 4 can be suppressed.

  Hereinafter, the configuration, operation, and effects of the embodiment of the present invention will be collectively described.

  The double cylinder type shock absorber 100 includes an inner case 1 in which hydraulic oil is enclosed, a piston 3 slidably inserted into the inner case 1 and defining a liquid chamber into an expansion side chamber 50 and a pressure side chamber 60, and an inner The piston rod 4 is inserted into the case 1 so as to be able to move back and forth, and is connected to the piston 3, and the piston rod 4 fitted to the end of the inner case 1 on the expansion side chamber 50 side and provided on the inner periphery Oil seal which is held between the rod guide 7 slidably supporting the outer case 2 forming the reservoir chamber 70 between the inner case 1 and the rod guide 7 and the outer case 2 and is in sliding contact with the piston rod 4 11 and a base valve 8 having a passage communicating the pressure side chamber 60 with the reservoir chamber 70 and separating the pressure side chamber 60 from the reservoir chamber 70; The guide 7 has a housing portion 7d formed on the surface on the oil seal 11 side, in which the seal lip 11b of the oil seal 11 is housed, and a concave portion 7h concaved on the bottom surface 7f of the housing portion 7d. Is formed radially outward with a position separated from the outer peripheral surface of the piston rod 4 by the starting distance L2 as the starting point 7g, and the starting distance L2 is an axis on the bottom surface 7f radially inward of the recess 7h and the bottom surface 7f It is characterized in that it is set within a range of 1⁄4 or more of the separation distance L1 which is the distance between the flat portion 11f of the oil seal 11 opposed in the direction and the separation distance L1.

  In this configuration, the starting point 7g of the recess 7h provided in the housing portion 7d is set in a range from a position separated by 1⁄4 of the distance L1 from the piston rod 4 to a position separated by the same distance as the distance L1. As described above, the recess 7 h is provided at a position where contamination that moves in the housing 7 d due to the vortex flow is likely to be accumulated. For this reason, the contamination in the accommodation portion 7d is accumulated in the recess 7h, and the accumulation of the contamination around the piston rod 4 is suppressed. As a result, entry of contamination into the seal lip 11b at the time of extension of the shock absorber 100 can be prevented, and the durability of the oil seal 11 can be improved.

  Further, the bush 9 is characterized in that it is provided flush with the bottom surface 7 f or protruding from the bottom surface 7 f.

  In this configuration, the end face 9a of the bush 9 is provided flush with the bottom surface 7f of the housing 7d or protruding from the bottom surface 7f, so that a space in which contamination tends to stay around the piston rod 4 is not formed. It is possible to suppress the accumulation of contamination around 4. As a result, entry of contamination into the seal lip 11b at the time of extension of the shock absorber 100 can be prevented, and the durability of the oil seal 11 can be improved. The end face 9a of the bush 9 may protrude from the bottom surface 7f of the housing 7d to the oil seal 11 side. Also in this case, accumulation of contamination around the piston rod 4 can be suppressed.

  Further, the corner 7m of the radially inner bottom surface 7f and the recess 7h is chamfered.

  In this configuration, the corner 7m of the bottom 7f and the recess 7h has an R-chamfered or C-chamfered shape. For this reason, the contamination around the starting point 7g is likely to fall into the recess 7h. As a result, the accumulation of contamination around the piston rod 4 can be suppressed.

  The double cylinder type shock absorber 200 includes an inner case 1 in which hydraulic oil is sealed, a piston 3 slidably inserted in the inner case 1 and defining a liquid chamber into an expansion side chamber 50 and a pressure side chamber 60, and an inner The piston rod 4 is inserted into the case 1 so as to be able to move back and forth, and is connected to the piston 3, and the piston rod 4 fitted to the end of the inner case 1 on the expansion side chamber 50 side and provided on the inner periphery Oil seal which is held between the rod guide 7 slidably supporting the outer case 2 forming the reservoir chamber 70 between the inner case 1 and the rod guide 7 and the outer case 2 and is in sliding contact with the piston rod 4 11 and a base valve 8 having a passage communicating the pressure side chamber 60 with the reservoir chamber 70 and separating the pressure side chamber 60 from the reservoir chamber 70; The guide 7 has a housing 7d formed on the surface on the side of the oil seal 11 and in which the seal lip 11b of the oil seal 11 is housed, and the bush 9 is provided protruding from the bottom surface 7f of the housing 7d. Do.

  In this configuration, the annular recess 7p in which the contamination is accumulated is defined by the outer peripheral surface 9b of the bush 9, the bottom surface 7f and the side surface 7n of the housing portion 7d. As described above, the annular recess 7p is provided at a position where contamination that moves in the accommodation portion 7d is easily accumulated by the vortex flow. For this reason, the contamination in the accommodation portion 7d is accumulated in the annular recess 7p, and the accumulation of the contamination around the piston rod 4 is suppressed. As a result, entry of contamination into the seal lip 11b at the time of extension of the shock absorber 200 can be prevented, and the durability of the oil seal 11 can be improved.

  As mentioned above, although the embodiment of the present invention was described, the above-mentioned embodiment showed only a part of application example of the present invention, and in the meaning of limiting the technical scope of the present invention to the concrete composition of the above-mentioned embodiment. Absent.

  For example, in each of the above embodiments, hydraulic oil is used as the hydraulic fluid, but other liquids such as water may be used.

100, 200 ... shock absorber (double cylinder type shock absorber), 1 ... inner case (cylinder), 2 ... outer case (outer cylinder), 3 ... piston, 4 ... piston rod, 7 rod guide 7 a small diameter portion 7 b large diameter portion 7 c rod insertion hole 7 d housing portion 7 e communication hole 7 f bottom surface 7g: starting point, 7h: recess, 7i: bottom, 7j: side surface, 7k: side surface, 7m: corner, 7n: side surface, 7p: annular recess, 8: base valve, 9: bush, 9a: end face, 9b: outer peripheral surface, 11: oil seal, 11a: base metal, 11b: seal lip, 11c.・ Dust lip, 11d ・ ・ ・ Check lip, 11e ・ ・ ・ Outer rim Le, 11f ... flat portion 50 ... expansion side chamber, 60 ... compression side chamber, 70 ... reservoir chamber, L1 ... distance, L2 ... origin distance

Claims (5)

A cylinder in which the working fluid is sealed;
A piston slidably inserted into the cylinder to divide the fluid chamber into an expansion chamber and a compression chamber;
A piston rod inserted in the cylinder so as to be movable back and forth and coupled to the piston;
A rod guide which is fitted at an end of the cylinder on the expansion side and supports the piston rod slidably via a bush provided on an inner periphery thereof;
An outer cylinder forming a reservoir chamber between the cylinder and the cylinder;
An oil seal held by the rod guide and the outer cylinder and in sliding contact with the piston rod;
It has a passage which connects the pressure side chamber and the reservoir chamber, and has a partition member which divides the pressure side chamber and the reservoir chamber,
The rod guide has a housing portion which is formed on the surface on the oil seal side and in which the seal lip of the oil seal is housed, and a concave portion which is recessed on the bottom surface of the housing portion.
The recess is formed radially outward from a position separated by a predetermined distance from the outer circumferential surface of the piston rod.
The predetermined distance is not less than 1/4 of the separation distance which is the distance between the bottom surface radially inward of the recess and the flat portion of the oil seal axially opposed to the bottom surface A double cylinder type shock absorber characterized by being set within the following range.   The double-tube type shock absorber according to claim 1, wherein the bush is provided flush with the bottom surface or protruding from the bottom surface.   The double cylindrical shock absorber according to claim 1 or 2, wherein a corner between the radially inner bottom surface and the recess is chamfered. A cylinder in which the working fluid is sealed;
A piston slidably inserted into the cylinder to divide the fluid chamber into an expansion chamber and a compression chamber;
A piston rod inserted in the cylinder so as to be movable back and forth and coupled to the piston;
A rod guide which is fitted at an end of the cylinder on the expansion side and supports the piston rod slidably via a bush provided on an inner periphery thereof;
An outer cylinder forming a reservoir chamber between the cylinder and the cylinder;
An oil seal held by the rod guide and the outer cylinder and in sliding contact with the piston rod;
It has a passage which connects the pressure side chamber and the reservoir chamber, and has a partition member which divides the pressure side chamber and the reservoir chamber,
The rod guide has an accommodating portion which is formed on the surface on the oil seal side and accommodates at least a part of the seal lip of the oil seal radially inward .
A double cylinder type shock absorber characterized in that the bush is provided so as to protrude from the bottom surface of the housing portion. The double cylinder type shock absorber according to claim 4, wherein the bottom surface is inclined to be away from the oil seal as it goes radially outward.

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