JP4898608B2 - Pneumatic shock absorber - Google Patents

Description

  The present invention relates to a pneumatic shock absorber, and more particularly to an improvement in a valve structure of a pneumatic shock absorber that can be used in a vehicle suspension device such as an automobile or an industrial vehicle.

  Conventionally, as this kind of pneumatic shock absorber, those of various structures can be exemplified, but as the pneumatic shock absorber used in a vehicle suspension device, the one shown in Patent Document 1 is exemplified. Can do.

  That is, as shown in FIG. 2, the upper and lower ends of the cylinder 42 formed in a cylindrical shape are respectively closed by a head member (corresponding to a rod guide of the present invention) 43 and a bottom member 44 and slid into the cylinder 42. The cylinder 42 is partitioned into a rod side chamber 40 and a piston side chamber 50 by a piston 45 that is movably inserted.

  The head member 43 is formed in an annular shape, and has a bearing 46 that pivotally supports the piston rod 51 and an accumulation recess 47 that opens from the upper end side.

  The cylinder 42 is covered with a bottomed cylindrical outer cylinder 41 disposed outside the cylinder 42, and an annular seal is formed on the inner peripheral side at the opening end which is the upper end of the outer cylinder 41 in the figure. A sealing member 49 (corresponding to the main seal of the present invention) 49 for holding 48 (corresponding to the inner peripheral lip of the present invention) is fixed in a state of being laminated on the head member 43.

  The lower end of the annular seal 48 protruding from the sealing member 49 is disposed in the storage recess 47 of the head member 43, and the oil storage chamber S is formed by the storage recess 47, the sealing member 49, and the piston rod 51. Is defined.

  The piston rod 51 protruding from the cylinder 42 is slidably inserted into the bearing 46 of the head member 43 on the inner peripheral side of the annular seal 48, and the annular seal 48 is slid by a predetermined compression force. It is press-contacted to the outer peripheral surface.

  Therefore, the piston rod 51 passes through the oil storage chamber S, and this oil storage chamber S faces the sliding portion between the piston rod 51 and the annular seal 48.

  Further, the oil storage chamber S is communicated with the rod side chamber 40 by a rod side passage 52 provided in the head member 43, and is communicated with the inside of the reservoir chamber R by another reservoir side passage 53.

  The bottom member 44 is provided with a passage 54 that allows the piston side chamber 50 and the reservoir chamber R to communicate with each other. A check valve 55 that allows only the flow from the piston side chamber 50 to the reservoir chamber R is provided in the middle of the passage 54. Is provided.

  The cylinder 42 is filled with a gas G as a working gas, and the oil storage chamber S and the reservoir chamber R are filled with lubricating oil O. The oil level in the oil storage chamber S is the oil storage chamber. In consideration of the fact that the gas G pressure in S and the gas G pressure in the reservoir chamber R do not fall below the lowermost end of the annular seal 48, a sufficient amount of lubricating oil O is contained in the reservoir chamber R. Is filled.

A small amount of lubricating oil O is also injected into the rod-side chamber 40 and the piston-side chamber 50. The lubricating oil O injected into the rod-side chamber 40 is a cylinder when the pneumatic shock absorber starts to expand and contract. The lubricating oil O in the piston side chamber 50 is supplied before the gas G into the reservoir chamber R when the pneumatic shock absorber is contracted, so that the oil storage chamber is provided. This is to prevent the oil level in S from descending.
JP 2007-16880 (FIG. 2 and paragraph numbers 0032 to 0043)

  In the pneumatic shock absorber configured as described above, the oil level in the oil storage chamber S is lower than the lowermost end of the annular seal 48 due to the balance between the gas G pressure in the oil storage chamber S and the gas G pressure in the reservoir chamber R. The reservoir chamber R is filled with a sufficient amount of lubricating oil O so that the annular seal 48 is in direct contact with the gas G, so that the pressure-contact portion between the annular seal 48 and the piston rod 51 is reduced. The gas G is prevented from leaking to the atmosphere side.

  However, when the machining accuracy of the bearing 46 that supports the piston rod 51 is poor or when there is a component machining error such as when the surface roughness of the piston rod 51 is rough, the pneumatic pressure using these components is used. If the shock absorber is left unused for a long time in a non-operating state, the lubricating oil O passes through a slight gap between the inner peripheral surface of the bearing 46 and the outer peripheral surface of the piston rod 51, and the rod side chamber 40. It is thought that it leaks.

  In this case, the oil level is lowered below the lowermost end of the annular seal 48, the annular seal 48 is in direct contact with the gas G, and the gas G is discharged from the pressure contact portion between the annular seal 48 and the piston rod 51 to the atmosphere. It is possible to leak to the side.

  Therefore, it is conceivable to arrange a seal member such as an O-ring on the bearing 46 to prevent the lubricating oil O from leaking into the rod side chamber 40. It is difficult to dispose a seal member on a certain bearing 46, and even if it is disposed, it is necessary to have a considerably complicated configuration, which may increase the cost.

  An object of the present invention is to provide a pneumatic shock absorber having a bearing structure that can prevent the lubricating oil O in the oil storage chamber S from leaking from the sliding portion between the bearing and the piston rod to the rod side chamber at a low cost. That is.

In order to achieve the above object, the means of the present invention is provided with a rod guide for guiding a piston rod at the opening end of the cylinder which is the inner periphery of the upper end of the outer cylinder, and the piston guide is slid on the upper surface of the rod guide. A main seal having an inner peripheral lip that contacts and seals between them is placed, and an oil storage chamber is defined by the storage recess provided in the rod guide, the main seal, and the piston rod. Is a pneumatic pressure that connects a reservoir chamber side connection path to which lubricating oil from a reservoir chamber formed between the outer cylinder and the cylinder is supplied and a rod chamber side connection path that supplies oil in the oil storage chamber to the rod side chamber. In the shock absorber, the oil in the oil storage chamber leaks into the rod side chamber through a gap between the rod guide and the piston rod by contacting the inner peripheral lip with the rod guide. It provided an oil leakage blocking member stop, constitute the oil leakage blocking member and the peripheral lip integrally formed base portion above, the lip portion the base portion and is integrally formed extending toward said piston rod, in the An oil reservoir chamber is defined by the circumferential lip, the base portion, the lip portion, and the piston rod, and the oil reservoir chamber and the oil storage chamber communicate with each other through a communication hole provided in the base portion. When the pressure difference between the upper and lower sides of the lip portion becomes larger than the set value, the lip portion is elastically deformed so that the lubricating oil in the oil sump chamber flows into the rod side chamber through the gap between the rod guide and the piston rod. It is characterized by that.

According to the pneumatic shock absorber according to each of the means of the present invention, the lubricant in the oil storage chamber is brought into contact with the rod guide with respect to the inner peripheral lip through the gap between the rod guide and the piston rod. An oil leakage blocking member for preventing leakage to the side chamber is provided, and the oil leakage blocking member is formed from a base portion integrally formed with the inner peripheral lip, and a lip portion which is also integrally formed with the base portion and extends toward the piston rod. since the formed, for example, a rod guide and having an inner peripheral surface is poor machining accuracy, pneumatic shock absorber of using the resulting part of the working error surface roughness said rough surface of the piston rod, nonuse Even when left for a long period of time in a non-operating state, the lubricating oil in the storage recess is surely prevented from leaking into the rod side chamber from the gap between the inner peripheral surface of the rod guide and the outer peripheral surface of the piston rod. Kill.

Therefore, as shown in the conventional example, the oil level of the lubricating oil falls below the lowermost end of the main seal, and the working fluid comes into direct contact with the main seal, so that the pressure contact portion between the main seal and the piston rod described above It can be surely prevented from leaking to the atmosphere side.
In addition, since the oil reservoir chamber is communicated with the oil storage chamber via the communication hole, it is possible to reliably supply the lubricating oil to the oil lip constituting the inner peripheral lip to ensure the sealing performance, and the oil lip directly Since contact with the gas can also be prevented, leakage of the gas to the atmosphere can be reliably prevented.
Furthermore, the lip portion is elastically deformed when the pressure difference between the upper and lower sides, that is, the oil storage chamber and the oil reservoir chamber, and the rod side chamber exceeds a set value, and the lubricating oil from the oil storage chamber and the oil reservoir chamber is removed. Since it is designed to flow to the rod side chamber through the gap between the rod guide and the piston rod, the durability of the lip portion itself can be ensured.

  Hereinafter, an embodiment in which the valve structure of the present invention is embodied in a pneumatic shock absorber used in an automobile suspension device will be described with reference to the drawings.

  As shown in FIG. 1, the pneumatic shock absorber 1 of the present embodiment includes a bottomed cylindrical outer cylinder 2, a cylinder 3 disposed concentrically inside the outer cylinder 2, A reservoir chamber R formed between the outer cylinders 2, a piston 5 that divides the inside of the cylinder 3 into a rod side chamber 40 and a piston side chamber 50, and a piston rod 6 that is movably inserted into the cylinder 3 via the piston 5. And a communication passage 9 for communicating the reservoir chamber R and the piston side chamber 50 and a connection path for connecting the reservoir chamber R and the rod side chamber 40, and injecting lubricating oil O into the piston side chamber 50 and the reservoir chamber R. In addition, a gas G as a working gas is enclosed in the cylinder 3.

  More specifically, a rod guide 12 for guiding the piston rod 6 is provided at the opening end of the cylinder 3 which is the inner periphery of the upper end portion of the outer cylinder 2. A main seal 13 is provided on the upper surface of the rod guide 12. Is placed.

  The outer cylinder 2, the main seal 13, the rod guide 12 and the cylinder 3 are integrally crimped and fixed by bending the upper end of the outer cylinder 2 inward.

  The rod guide 12 is formed in a columnar shape having a guide hole 17 to which a bearing 12a as a bearing is attached at the center, and the inner peripheral surface of the bearing 12a is in sliding contact with the outer peripheral surface of the piston rod. A piston rod 6 is slidably supported by a bearing, and a storage recess 18 for storing lubricating oil O is formed at the center of the upper surface.

  The storage recess 18 defines an oil storage chamber S with the storage recess 18 and the main seal 13, and the storage recess 18 is connected to the reservoir chamber side connection path 19 communicating with the reservoir chamber R and the rod side chamber 40. The rod chamber side connection path 20 with the check valve 20 a that communicates is connected, and the lubricating oil O of the reservoir chamber R is temporarily stored in the oil storage chamber S, and then the rod side chamber 40 via the rod chamber side connection path 20. To come out.

  The main seal 13 includes an annular insert metal 14 and an annular inner peripheral lip 15 integrally formed on the inner peripheral side of the insert metal 14.

  The inner peripheral lip 15 is formed in a so-called triple lip structure, and in the same order as the dust lip 15a that slides in contact with the outer peripheral surface of the piston rod 6 in order from the atmosphere side to prevent dust from entering from the atmosphere side. An oil lip 15b that slides on the outer peripheral surface of the piston rod 6 and prevents the lubricating oil O from the oil storage chamber S from leaking to the atmosphere together with the gas G enclosed in the cylinder 3, and the outer peripheral surface of the piston rod 6 as well. A shutoff lip 16 is integrally formed as an oil leak shutoff member that prevents the lubricant O from the oil storage chamber S from leaking to the rod side chamber 40 side together with the gas G.

  The blocking lip 16 is formed of a base portion 16b formed integrally with the inner peripheral lip 15 and a lip portion 16a as a blocking member which is also formed integrally with the base portion 16b and extends toward the piston rod 6, The lower surface of the lip portion 16a is in pressure contact with the peripheral edge portion of the guide hole 17 of the rod guide 6 so that the lubricating oil O in the oil storage chamber S does not leak into the rod side chamber 40 through the pressure contact portion.

  An oil reservoir chamber 28 having a substantially isosceles trapezoidal cross section is formed between the shutoff lip 16 and the oil lip 15b between the outer peripheral surface of the piston rod 6 and the oil reservoir is formed in the base portion 16b. A plurality of communication holes 16c for communicating the chamber 28 and the oil storage chamber S are provided.

  The lip portion 16a is formed in a lip shape so that the lubricating oil adhering to the piston rod 6 is scraped into the oil reservoir chamber 28 when the piston rod 6 is operated, and the lip portion 16a is When the pressure difference between both sides, that is, in the oil storage chamber S and in the oil reservoir chamber 28, and the rod side chamber 40 becomes larger than a predetermined value, the lubricating oil O from the oil storage chamber S and the oil reservoir chamber 28 is elastically deformed. The rod guide 12 and the piston rod 6 are designed to flow to the rod side chamber 40 through a gap.

  Further, the lubricating oil O is stored in the oil storage chamber S up to a position where the base portion 16b of the shut-off lip 16 is immersed, and the lubricating oil O is guided to the oil reservoir chamber 28 through the communication hole 16c. When the lubricating oil O stored in the chamber 28 prevents the oil film from being cut between the inner peripheral lip 15 and the piston rod 6, and when the internal pressure in the oil storage chamber S increases due to the pressure stroke of the pneumatic shock absorber 1. The lower surface of the lip portion 16a of the blocking lip 16 is brought into pressure contact with the peripheral edge portion of the guide hole 17 of the rod guide 12 by the internal pressure to further improve the sealing performance of the pressure contact portion.

  And the connection position with respect to the storage recessed part 18 of the rod chamber side connection path 20 is rather than the said communication hole 16c so that the excess lubricating oil O collected from the communication hole 16c of the interruption | blocking lip 16 may flow out into the rod side chamber 40. The upper position is set.

  The piston 5 is mounted by inserting a mounting hole 5a provided in the center portion thereof into a mounting portion 6a formed at the lower end of the piston rod 6 and tightening and fixing with a nut 4. A piston ring 4a that is slidably in contact with the inner peripheral surface of 3 is inserted.

  The rod-side chamber 40 and the piston-side chamber 50 communicate with the back surface of the piston 5 (referred to as the upper surface in FIG. 1), and a plurality of pressure-side communication passages 21 arranged on the same circumference, and the pressure-side communication passage 21 and the same circle. A plurality of extended side communication passages 22 arranged alternately on the circumference are formed toward the lower surface.

  A pressure side seat portion 24b having a pressure side seat surface 24a on which a pressure side leaf valve 23 (described later) is placed is bulged and formed at the outlet end of the pressure side communication passage 21 on the back surface of the piston 5. At the outlet end of the extension side communication passage 22, an extension side seat portion 26 b having an extension side seat surface 26 a on which an extension side leaf valve 25 described later is placed is bulged.

  A plurality of annular pressure-side leaf valves 23 for closing the pressure-side communication passage 21 so as to be openable and closable are stacked on the pressure-side seat surface 24a, and placed on the upper surface of the pressure-side leaf valve 23 via a spacer 27. The bending amount on the outer peripheral side is regulated by the pressure side valve stopper 37 thus made.

  In addition, a plurality of annular extension side leaf valves 25 for closing the extension side communication passage 22 so as to be openable and closable are stacked on the extension side seat surface 26a, and a spacer is placed on the lower surface of the extension side leaf valve 25. The amount of deflection on the outer peripheral side is regulated by the extension side valve stopper 38 placed via the terminal 27.

  A pressure side groove portion 29 having a groove bottom portion 29a lower than the sheet surface 24a is provided on the outer peripheral side of the pressure side sheet surface 24a.

  The pressure side groove portion 29 includes a planar groove bottom portion 29a and a planar wall portion 29b whose diameter increases upward from the groove bottom portion 29a, and forms the piston 5 by sintering. It is formed integrally.

  Further, on the outer peripheral side of the extension side sheet surface 26a, an extension side groove portion 30 having a groove bottom portion 30a lower than the sheet surface 26a is provided.

  The extended-side groove portion 30 is composed of the planar groove bottom portion 30a and a planar wall portion 30b that expands downward from the groove bottom portion 30a. Similarly, the piston 5 is formed by sintering. It is integrally formed when doing.

  Then, due to the presence of the pressure side and extension side groove portions 29 and 30, the gas G as the working fluid which is ejected by deflecting the outer peripheral side of the pressure side and extension side valves 23 and 25 enters the pressure side and extension side groove portions 29 and 30. Once guided and decompressed, it flows into the rod-side chamber 40 or the piston-side chamber 50, whereby the pressure change of the gas G is moderated and the generation of the gas G ejection noise is suppressed.

  In the present embodiment, the pressure-side and extension-side leaf valves 23 and 25 are set to have an outer diameter so as to cover the upper part of the pressure-side groove portion 29 and the extension-side groove portion 30 about half. , 25 is surely guided to the compression side and extension side groove portions 29 and 30 so as to surely exert the above-described action of suppressing the ejection noise.

  A valve case 31 is provided at the lower end of the cylinder 3, and the valve case 31 is formed with the communication passage 9 that connects the reservoir chamber R and the piston side chamber 50. Is provided with a case-side check valve 32 that allows only the flow of gas G and lubricating oil O from the piston-side chamber 50 toward the reservoir chamber R.

  The rod side chamber 40, the piston side chamber 50 and the reservoir chamber R are filled with a gas G as a working fluid, and lubricating oil O is injected into the piston side chamber 50 and the reservoir chamber R.

  For example, the pneumatic shock absorber configured as described above attaches a rod-side eye (not shown) provided at the tip of the piston rod 6 to the vehicle body side, and a cylinder-side eye 36 provided at the lower end of the cylinder 3 on the axle side. By installing it, it is built into the suspension system of a car.

  Next, the operation will be described. The piston rod 6 retracts from the inside of the cylinder 3, that is, in the expansion stroke of the pneumatic shock absorber 1, the gas G sealed in the rod side chamber 40 is expanded on the piston 5. While passing through the communication path 22 and flowing into the piston side chamber 50, the expansion side is bent by bending the outer peripheral side of the expansion side leaf valve 25 placed on the expansion side seat surface 26a at the outlet end of the expansion side communication path 22. Damping force is generated.

  Further, when the piston rod 6 enters the cylinder 3, that is, in the compression stroke of the pneumatic buffer 1, the gas G sealed in the piston side chamber 50 passes through the pressure side communication passage 21 provided in the piston 5 and the rod. While flowing into the side chamber 40, a compression side damping force is generated by bending the outer peripheral side of the compression side leaf valve 23 placed on the compression side seat surface 24a at the outlet end of the compression side communication passage 21.

  At this time, the gas G which is blown out by deflecting the outer periphery of the pressure-side leaf valve 23 is once guided to the pressure-side groove portion 29 formed on the outer peripheral side of the pressure-side seat surface 24a, and after depressurizing, flows into the rod-side chamber 40, Thereby, the pressure change of the ejected gas G becomes gentle, and the generation of the ejected sound of the gas G is suppressed.

  Then, the excess lubricating oil O accumulated in the oil storage chamber S flows out to the rod side chamber 40 through the rod chamber side connection path 20 and adheres to the sliding contact portion between the piston 5 and the cylinder 3 to provide slidability. Improve.

  Also, the lubricating oil O injected into the piston side chamber 50 passes through the communication passage 9 provided in the valve case 31 and flows into the reservoir chamber R, and then passes through the reservoir chamber side connection passage 19 provided in the rod guide 12. Through the oil storage chamber S.

  In the compression stroke of the pneumatic shock absorber 1, the gas G sealed in the piston side chamber 50 passes through the pressure side communication passage 21 provided in the piston 5 and flows into the rod side chamber 40, as will be apparent. At least one of the passage 9, the reservoir chamber R, the reservoir chamber side connection path 19, and the rod side chamber side connection path 20 gives a greater resistance to the flow of the gas G and the lubricating oil O than the compression side leaf valve 23. A valve may be provided between the piston side chamber 50 and the rod side chamber 40 via the reservoir chamber R, or a pipe resistance between the piston side chamber 50 and the rod side chamber 40 via the reservoir chamber R may be provided. Specifically, for example, the check valve 20a and / or the case side check valve 32 or both of them may be leaf valves, or the communication path 9 and the reservoir chamber side connection path 19 Or by reducing the flow passage area of the rod-side chamber side connecting path 20 and the cross-sectional area of the annular reservoir chamber R may be very small.

  As described above in detail, in the pneumatic shock absorber 1 of the present embodiment, the inner peripheral lip 15 is integrally formed with the base 16b formed integrally with the inner peripheral lip 15 and the base 16b. In the oil storage chamber S, a shutoff lip 16 comprising a lip portion 16a extending toward the piston rod 6 is integrally formed, and the lower surface of the lip portion 16a is brought into pressure contact with the peripheral edge of the guide hole 17 of the rod guide 6. The lubricating oil O passes through the pressure contact portion and does not leak into the rod side chamber 40. For example, a bearing 12a with poor processing accuracy or a piston rod 6 with a rough surface causes a processing error. Even when the pneumatic shock absorber 1 using parts is left unused for a long time in a non-operating state, the clearance between the inner peripheral surface of the bearing 12a and the outer peripheral surface of the piston rod 6 is not reduced. Lubricating oil O in the oil storage chamber S is reliably prevented from leaking to the rod side chamber 40.

  Therefore, as shown in the conventional example, the oil level of the lubricating oil O falls below the lowermost end of the main seal 13, and the gas G comes into direct contact with the main seal 13, whereby the main seal 13 and the piston rod 6 described above. It is possible to reliably prevent leakage from the pressure contact portion to the atmosphere side.

  Further, since the blocking lip 16 is integrally formed when the inner peripheral lip 15 is formed, it can be manufactured at a low cost, and the inner lip 15 can be used even when used in a general pneumatic shock absorber. Since only the replacement is required, the present invention can be embodied easily and inexpensively as compared with the case where the same operation as described above is performed by adding processing to the bearing portion as shown in the conventional example.

Further, an oil reservoir chamber 28 is formed between the oil lip 16 b serving as an oil leakage blocking member and an oil lip 15 b constituting a part of the inner peripheral lip 15, and the oil reservoir chamber 28 is communicated with the oil storage chamber S. Therefore, the lubricating oil O can be reliably supplied to the oil lip 15b to ensure the sealing performance, and the oil lip 15b can also be prevented from coming into direct contact with the gas G. Can be surely prevented.

  Furthermore, when the internal pressure in the oil storage chamber S increases during the compression stroke of the pneumatic shock absorber 1, the internal pressure is transmitted to the lip portion 16a of the shutoff lip 16 via the oil reservoir chamber 28, and this lip portion 16a. Therefore, the lower surface of the lip portion 16a comes into pressure contact with the peripheral edge portion of the guide hole 17 of the rod guide 12, and the sealing performance of the pressure contact portion is further improved.

  Further, the shape of the lip portion 16a of the blocking lip 16 is such that the lubricating oil O adhering to the piston rod 6 is scraped into the oil reservoir chamber 28 when the piston rod 6 is operated. The hydraulic oil O can be reliably stored in the storage chamber 28.

  Furthermore, when the pressure difference between the upper and lower sides of the lip portion 16a, that is, the oil storage chamber S and the oil reservoir chamber 28, and the rod side chamber 40 becomes larger than a set value, the oil storage chamber S and the oil reservoir are elastically deformed. Since the lubricating oil O from the chamber 28 is designed to flow to the rod side chamber 40 through the gap between the rod guide 12 and the piston rod 6, the durability of the lip portion 16a itself can be ensured.

  Further, since the rod side chamber contact side passage 20 is disposed so as to be positioned above the communication hole 16c provided in the base portion 16b of the blocking lip 16, the lubricating oil O in the oil storage chamber S is surely contained in the oil reservoir chamber 28. Can lead to.

  In addition, this invention is not limited to the said embodiment, For example, it can also be changed as follows.

(1) In this embodiment, the blocking lip 16 is used as the oil leakage blocking member. However, the shape is not limited to this lip shape, and may be a shape other than the lip.

(2) In the present embodiment, the blocking lip 16 is formed integrally with the inner peripheral lip 15, but the present invention is not limited to this. Optionally, it may be joined to the inner peripheral lip 15 by a method.

(3) In the present embodiment, the case where the outer cylinder 2, the reservoir chamber R, and the connection path 19 are provided has been described. However, the present invention can also be applied to a single cylinder type pneumatic shock absorber without these members.

It is sectional drawing of the pneumatic shock absorber which shows one embodiment of this invention. It is sectional drawing of the pneumatic shock absorber which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic shock absorber 2 Outer cylinder 3 Cylinder 6 Piston rod 12 Rod guide 13 Main seal 15 Inner lip 16 Shut off lip (oil leakage shut off member)
16a Lip part (blocking member)
16b Base 16c Communication hole 18 Storage recess 19 Reservoir chamber side connection path 20 Rod chamber side connection path 40 Rod side chamber O Lubricating oil R Reservoir chamber S Oil storage chamber

Claims (3)

A rod guide that guides the piston rod is provided at the opening end of the cylinder that is the inner periphery of the upper end of the outer cylinder, and an inner peripheral lip that slides on the piston rod and seals between them is provided on the upper surface of the rod guide. The main seal is placed, and an oil storage chamber is defined by a storage recess provided in the rod guide, the main seal, and the piston rod. The oil storage chamber is formed from a reservoir chamber formed between the outer cylinder and the cylinder. In the pneumatic shock absorber in which the reservoir chamber side connection path to which the lubricating oil is supplied and the rod chamber side connection path for supplying the oil in the oil storage chamber to the rod side chamber are connected, the rod guide contacts the inner peripheral lip. Thus, an oil leakage blocking member is provided to prevent the lubricating oil in the oil storage chamber from leaking into the rod side chamber through the gap between the rod guide and the piston rod. A member formed integrally with the inner peripheral lip base, the base and formed integrally constituted by a lip portion extending toward the piston rod, the inner peripheral lip and said base and said lip portion and the piston rod And the oil reservoir chamber and the oil storage chamber are communicated through a communication hole provided in the base, and the pressure difference between the upper and lower sides of the lip portion is larger than a set value. Pneumatic shock absorber characterized by being designed so that when it becomes larger, it is elastically deformed so that the lubricating oil in the oil reservoir chamber flows into the rod side chamber through the gap between the rod guide and the piston rod. vessel. 2. The pneumatic shock absorber according to claim 1 , wherein the communication hole is disposed so as to be positioned below the rod chamber side connection path . 3. The pneumatic shock absorber according to claim 1, wherein the lip portion is formed in a lip shape so that lubricating oil attached to the piston rod is scraped into the oil reservoir chamber .

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