JP2008095953A - Pneumatic shock absorber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic shock absorber provided with a structure in which a piston rod does not easily get long freely even if inner pressure rises. <P>SOLUTION: This pneumatic shock absorber is provided with an inner rod 4 erecting in a cylinder 3 from a bottom part of the cylinder, an annular piston 5 slidably inserted on an outer circumference surface of the inner rod and in an inner circumference surface of the cylinder, a tubular piston rod 6 passing through a head side rod guide 12 of the cylinder with sliding on the outer circumference surface of the inner rod, air passages 21, 22 provided in the piston and establishing communication between a rod side chamber 40 and an anti-rod side chamber 50, damping force generating parts 23, 25 provided in a middle of the air passages, a communication passage 9 establishing communication between a reservoir chamber R and the anti-rod side chamber, and a connection passage 19 connecting the reservoir chamber and the rod side chamber. Gas is filled in the cylinder and lubricating oil is injected in the anti-rod side chamber and the reservoir chamber. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic shock absorber, and more particularly to an improvement of a pneumatic shock absorber that can be used in a suspension device of a vehicle 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.

  This pneumatic shock absorber is a so-called single rod type, a cylinder, a piston slidably inserted into the cylinder, a piston rod movably inserted into the cylinder via the piston, And a damping force generator provided on the piston. The piston defines the inside of the cylinder into a rod side chamber and an anti-rod side chamber.

In this pneumatic shock absorber, a relief valve that opens the flow path when the frequency of the input vibration is high is provided to prevent the damping force in the high frequency region from increasing. .
JP 2000-104778 A (page 3 right column 41st line to page 4 left column 22nd line, FIGS. 2 and 3)

  Since the pneumatic shock absorber configured as described above uses a working medium as a gas, it is lighter than a hydraulic shock absorber that also uses working oil as the working medium, and does not use any working oil. Also friendly.

  In addition, since no aeration is caused because no hydraulic oil is used, a predetermined damping force can be accurately generated, and this is very effective as a shock absorber. When used in a suspension device, the following problems may occur.

  That is, since the gas has a higher coefficient of thermal expansion than hydraulic oil, the internal pressure is likely to rise when placed in a high temperature use environment or continuously used. In the above single rod type pneumatic buffer, As a result of this increase in internal pressure, the piston rod is retracted from the cylinder due to the difference in the pressure receiving area of the piston, that is, the difference between the pressure receiving area of the piston with respect to the rod side chamber and the pressure receiving area of the piston with respect to the opposite rod side chamber.

  Therefore, when the pneumatic shock absorber is used in a vehicle suspension device, the vehicle height of the vehicle rises regardless of the driver's intention due to the withdrawal operation of the piston rod from the cylinder. It may be a hindrance when getting on and off.

  Accordingly, an object of the present invention is to provide a pneumatic shock absorber having a structure in which a piston rod is difficult to withdraw from a cylinder without permission even when an internal pressure increases.

  In order to achieve the above object, one means of the present invention includes a bottomed cylindrical cylinder, an inner rod standing in the cylinder from the bottom of the cylinder, an outer peripheral surface of the inner rod, and an inner periphery of the cylinder. An annular piston slidably inserted into the surface, a rod side chamber and an anti-rod side chamber partitioned through the piston in the cylinder, and sliding from the outer peripheral surface of the inner rod extending from the piston A cylindrical piston rod that penetrates the cylinder head side rod guide, an air passage that is provided in the piston and communicates the rod side chamber and the non-rod side chamber, and a damping force generator provided in the middle of the air passage. The gas is sealed in the cylinder, and lubricating oil is injected into at least one of the anti-rod side chamber or the rod side chamber. It is.

  Similarly, the other means includes a bottomed cylindrical outer cylinder, a similarly bottomed cylindrical cylinder disposed inside the outer cylinder, a reservoir chamber formed between the cylinder and the outer cylinder, An inner rod that rises in the cylinder from the bottom of the cylinder, an annular piston that is slidably inserted into the outer peripheral surface of the inner rod and the inner peripheral surface of the cylinder, and a partition in the cylinder via the piston. A rod-side chamber and an anti-rod-side chamber, a cylindrical piston rod extending from the piston and penetrating the head-side rod guide of the cylinder while sliding on the outer peripheral surface of the inner rod, and the rod provided on the piston The same as the air passage that communicates the side chamber and the anti-rod side chamber, the damping force generator provided in the middle of the air passage, and the communication passage that communicates the reservoir chamber and the anti-rod side chamber And a connecting passage for connecting the reservoir chamber and the rod side chamber, with a gas is sealed inside the cylinder, is characterized in that the injected lubricant in the anti-rod side chamber and the reservoir chamber.

  According to the invention of each claim, the pressure receiving area of the piston with respect to the rod side chamber and the pressure receiving area of the piston with respect to the non-rod side chamber can be made substantially equal by making the cross sectional area of the inner rod close to the cross sectional area of the piston rod. Therefore, if the piston rod is formed in a thin cylindrical shape within a range in which sufficient strength is ensured, it is difficult for the piston rod to be retracted from the cylinder due to the pressure receiving area difference even if the internal pressure increases.

  For this reason, for example, in the operating state in which the pneumatic shock absorber of the present invention is used in a vehicle suspension device, even if the internal pressure rises due to being placed in a high temperature use environment or continuously used, the pressure receiving area described above Retraction operation of the piston rod from the cylinder due to the difference can be prevented as much as possible.

  Accordingly, it is possible to reliably prevent the vehicle height of the vehicle from rising due to the retreating operation of the piston rod regardless of the driver's intention, for example, hindering passengers from getting on and off.

  Hereinafter, an embodiment in which the present invention is embodied in a pneumatic shock absorber used in a suspension device for an automobile 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 similarly bottomed cylindrical cylinder 3 disposed inside the outer cylinder 2, The reservoir chamber R formed between the cylinder 3 and the outer cylinder 2, the inner rod 4 protruding from the bottom 3 a of the cylinder 3, and the outer peripheral surface of the inner rod 4 and the inner peripheral surface of the cylinder 3 are slidable. An annular piston 5 that is inserted into the cylinder 3 to define a rod-side chamber 40 and an anti-rod-side chamber 50 and extends in a cylindrical shape from the piston 5, and an inner peripheral surface thereof is an outer peripheral surface of the inner rod 4. A piston rod 6 which can project from the cylinder 3 by sliding; an air passage provided in the piston 5 for communicating the rod side chamber 40 and the anti-rod side chamber 50; and a damping force generating portion provided in the air passage; ,the above A communication path 9 that communicates the reservoir chamber R and the anti-rod side chamber 50 and a connection path that similarly connects the reservoir chamber R and the rod side chamber 40, and the gas G is sealed in the cylinder 3, and the anti-rod Lubricating oil O is injected into the side chamber 50 and the reservoir chamber R.

  More specifically, a rod guide 12 for guiding the piston rod 6 is provided at the opening end of the cylinder 3 that is the inner periphery of the upper end of the outer cylinder 2, and an oil seal 13 is mounted on the upper surface of the rod guide 12. Is placed.

  The outer cylinder 2, the oil 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 oil 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 not shown, but is a piston rod. 6 is sealed in the cylinder 3 with a dust lip that slidably contacts the outer peripheral surface of the cylinder 6 to prevent dust from entering from the atmosphere side, and a lubricating oil O that is slidably contacted with the outer peripheral surface of the piston rod 6 and from a storage recess 18 described later. And an oil lip that prevents leakage to the outside along with the gas G.

  The rod guide 12 is formed in a columnar shape having a guide hole 17 for guiding the piston rod 6 at the center, and a storage recess 18 for storing lubricating oil O is formed at the center of the upper surface. .

  The reservoir recess 18 is connected to a reservoir chamber side connection path 19 as a connection path communicating with the reservoir chamber R and a rod side chamber side connection path 20 as a connection path communicating with the rod side chamber 40. The lubricating oil O in the reservoir chamber R flows out to the rod side chamber 40 through the storage recess 18.

  In addition, lubricating oil O is stored in the storage recess 18 up to the position where the lower end of the inner peripheral lip 15 is immersed, preventing oil film breakage between the inner peripheral lip 15 and the piston rod 6, and the inner peripheral lip. The connection position of the rod side chamber side connection path 20 with respect to the storage recess 18 is determined so that excess lubricating oil O accumulated up to the upper side of the lower end of 15 flows out to the rod side chamber 40.

  The piston 5 has an outer mounting groove 5a formed on the outer peripheral surface thereof. An outer seal member 16a is mounted in the outer mounting groove 5a, and an inner mounting groove 5b is also formed on the inner peripheral surface of the piston 5. The inner seal member 16b is mounted in the inner mounting groove 5b.

  The outer seal member 16a is in sliding contact with the inner peripheral surface of the cylinder 3, so that the gas G and the lubricating oil O in the rod side chamber 40 leak into the anti-rod side chamber 50, or conversely the anti-rod side chamber 50. The internal gas G and the lubricating oil O are prevented from leaking into the rod side chamber 40, and the inner seal member 16b is in sliding contact with the outer peripheral surface of the inner rod 4, so that Gas G and lubricating oil O are prevented from leaking outside through an air chamber 60 described later.

  On the outer peripheral side of the upper surface of the piston 5, a pressure side communication path 21 and an extension side communication path 22 as the air passage communicating the rod side chamber 40 and the anti-rod side chamber 50 are respectively bored toward the lower surface.

  In the middle of the pressure side communication passage 21, only the pressure side damping valve 23 as a damping force generating portion and the flow of the gas G and the lubricating oil O from the rod side chamber 50 to the rod side chamber 40 above the pressure side damping valve 23. An allowable pressure side check valve 24 is provided, and an expansion side damping valve 25 as a damping force generation unit is provided in the middle of the expansion side communication path 22, and a rod side chamber 40 is provided below the expansion side attenuation valve 25. An extension check valve 26 that allows only the flow of the gas G and the lubricating oil O toward the non-rod-side chamber 50 is provided.

  The expansion side and compression side damping valves 25 and 23 serving as the damping force generating section can employ various damping force generating structures such as orifices and leaf valves.

  The lower end of the cylinder 3 is provided with a valve case 31 constituting the bottom 3a. The valve case 31 is formed with the communication passage 9 for communicating the reservoir chamber R and the non-rod side chamber 50. A case-side check valve 32 that permits only the flow of gas O and lubricating oil G from the non-rod-side chamber 50 toward the reservoir chamber R is provided in the middle of the communication passage 9.

  A mounting recess 37 is provided at the center of the upper surface of the valve case 31, and a mounting portion 4 a at the lower end of the inner rod 4 is fixedly attached to the mounting recess 37 via an annular elastic member 38.

  The elastic member 38 is formed of an elastic body made of natural or synthetic rubber, synthetic resin or the like, and the inner rod 4 can move in the circumferential direction of the valve case 31 within a range where the elastic member 38 is elastically deformed. It has become.

  The inner rod 4 is formed in a cylindrical shape, and a tapered portion 4b is formed on the outer periphery of the tip (referring to the upper end in FIG. 1). When the piston rod 6 slides along the inner rod. The piston rod 6 is prevented from being caught by the tip of the inner rod 4 so that a good sliding state can be secured.

  The inner rod 4 is provided with a cooling passage 33, one of which is open to the tip and the other is opened to the outside through the valve case 31 and the bottom 2a of the outer cylinder 2, and the cooling passage 33 has A cooling check valve 34 that allows only inflow of gas from the outside is provided.

  The piston rod 6 is formed in a cylindrical shape having an insertion hole 6a through which the inner rod 4 can slide, and a rod-side communication passage 29 communicating with the outside is formed at the upper end of the insertion hole 6a. The rod side communication passage 29 is provided with a communication passage side check valve 30 that allows only gas inflow from the insertion hole 6a side.

  Therefore, when the air chamber 60 defined by the inner rod 4 in the insertion hole 6 a repeats expansion and contraction in accordance with the forward / backward movement of the piston rod 6, the air chamber 60 is supplied with gas via the cooling passage 33. Enters, and then is discharged through the rod side communication passage 29 to the outside.

  The piston rod 6 is formed in a thin cylindrical shape as long as sufficient strength is ensured, and the piston rod 6 with respect to the rod side chamber 40 is made closer to the sectional area S1 of the inner rod 4 being closer to the sectional area S2 of the piston rod 6. The pressure receiving area of 5 and the pressure receiving area of the piston 5 with respect to the non-rod-side chamber 50 are made substantially equal so that the withdrawal operation of the piston rod 6 due to the pressure receiving area difference described above is difficult to occur.

  The pneumatic shock absorber 1 configured as described above attaches, for example, a rod side eye 35 provided at the tip of the piston rod 6 to the vehicle body side, and an outer cylinder side eye 36 provided at the lower end of the outer cylinder on the axle side. It is installed in the suspension device of the automobile by attaching to the.

  Next, the operation will be described. The piston rod 6 retreats from the cylinder 3, that is, in the expansion stroke of the pneumatic shock absorber 1, the gas G and the lubricating oil O enclosed in the rod side chamber 40 are transferred to the piston 5. While passing through the provided extension side communication path 22 and flowing into the anti-rod side chamber 50, an extension side damping force is generated by the extension side damping valve 25 provided in the middle of the extension side communication path 22.

  Further, when the piston rod 5 enters the cylinder 3, that is, in the contraction stroke of the pneumatic shock absorber 1, the gas G sealed in the anti-rod side chamber 50 passes through the pressure side communication passage 21 provided in the piston 5. While flowing into the rod side chamber 40, a pressure side damping force is generated by the pressure side damping valve 23 provided in the middle of the pressure side communication passage 21.

  At this time, surplus lubricating oil O accumulated in the storage recess 18 flows out to the rod side chamber 40 via the rod side chamber side connection path 20 and adheres to the sliding contact portion between the piston 5 and the cylinder 3 to provide slidability. Improve.

  Further, the lubricating oil O injected into the non-rod side chamber 50 passes through the communication passage 9 provided in the valve case 31 and flows into the reservoir chamber R, and then the reservoir chamber side connection passage 19 provided in the rod guide 12. To the storage recess 18.

  As is clear from the contraction stroke of the pneumatic shock absorber 1, the gas G sealed in the anti-rod side chamber 50 flows into the rod side chamber 40 through the pressure side communication passage 21 provided in the piston 5. At least one of the communication path 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 damping valve 23. May be provided by providing a valve 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. Specifically, for example, the case-side check valve 32 may be a leaf valve, or the flow passage areas of the communication passage 9, the reservoir chamber-side connection passage 19, and the rod-side chamber-side connection passage 20 may be reduced. Kushitari, the cross-sectional area of the annular reservoir chamber R may be very small.

  In the expansion / contraction stroke of the pneumatic shock absorber 1 described above, the air chamber 60 defined by the inner rod 4 in the piston rod 6 is subjected to the intrusion / retraction operation of the piston rod 6 and repeatedly contracts and expands. become.

  That is, in the expansion stroke of the pneumatic shock absorber 1, the air chamber 60 is in an expanded state, and the gas from the outside pushes the cooling side check valve 34 provided in the cooling passage 33 into the air chamber 60. Open and flow in.

  When the above-described pneumatic shock absorber 1 enters the contraction stroke from this state, the above-described air chamber 60 enters the contraction state, and the gas in the air chamber 60 is connected to the communication-side check valve provided in the rod-side communication passage 29. 30 is pushed open and discharged to the outside.

  Therefore, in the expansion / contraction stroke of the pneumatic shock absorber 1 described above, air is forcibly entered into the cooling passage 33, and the entered air is surely released to the outside through the air chamber 60 and the rod side communication passage 29. Therefore, it is possible to reliably prevent the inner rod 4 from being cooled by the air and the temperature in the anti-rod side chamber 50 and the rod side chamber 40 from rising.

  Further, when the pneumatic shock absorber 1 is placed in a high temperature use environment, the internal pressures of the rod side chamber 40 and the anti-rod side chamber 50 are increased without particularly operating the pneumatic shock absorber itself.

  However, in the present embodiment, by making the piston rod 6 thin, the pressure receiving area of the piston 5 with respect to the anti-rod side chamber 50 and the pressure receiving area of the piston 5 with respect to the rod side chamber 40 are set approximately equal. Therefore, the retraction operation of the piston rod 6 from the cylinder 3 due to the pressure receiving area difference as shown in the conventional example can be prevented.

  Therefore, the vehicle height of the vehicle rises regardless of the driver's intention due to the withdrawal operation of the piston rod 6 from the cylinder 3, so that it is possible to prevent, for example, an obstacle when the passenger gets on and off.

  Since the tapered portion 4 b is provided on the outer periphery of the upper end of the inner rod 4, when the piston rod 6 slides along the inner rod 4, the inner peripheral surface of the piston rod 6 is caught on the tip of the inner rod 4. It can prevent and ensure a favorable sliding state.

  Further, by attaching the inner rod 4 to the valve case 31 via the elastic member 38, the inner rod 4 can move in the circumferential direction of the valve case 31 within a range where the elastic member 38 is elastically deformed. Therefore, it becomes possible to reduce the sliding friction between the inner peripheral surface of the piston rod 6 and the tip of the inner rod 4. For example, even when the pneumatic shock absorber 1 is bent by a lateral force, the above-described sliding friction is achieved. The ride will not be damaged by the increase.

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

  1) In the present embodiment, the cooling passage 33 provided in the inner rod 4 is configured to be connected to the rod side communication passage 29 provided in the piston rod 6 so that the air that has passed through the cooling passage 33 is moved to the piston rod. However, the present invention is not limited to this, and the cooling passage 33 may be circulated only in the inner rod 6.

  2) In the present embodiment, the number of the cooling passages 33 is one. However, the present invention is not limited to this, and a plurality of cooling passages 33 may be formed, and the diameter of the cooling passages 33 is always constant. It is not necessary to increase the diameter of the portion where the cooling efficiency is desired.

  3) In the present embodiment, the lubricating oil O is not positively injected into the rod side chamber 40. However, the present invention is not limited to this, and the above lubricating oil is used to improve the slidability of the piston 5. O may be injected into the rod side chamber 40.

  4) In the present embodiment, the pneumatic shock absorber 1 having a so-called multi-cylinder structure having the outer cylinder 2 outside the cylinder 3 is embodied. However, the present invention is not limited to this. Of course, it may be embodied in a so-called single cylinder type pneumatic shock absorber 1 that does not have the cylinder 2.

It is sectional drawing which shows one embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic shock absorber 2 Outer cylinder 2a Bottom part of outer cylinder 3 Cylinder 4 Inner rod 5 Piston 6 Piston rod 6a Insertion hole 9 Communication path 19 Reservoir chamber side connection path (connection path)
20 Rod side chamber side connection path (connection path)
21 Pressure side communication path (air)
22 Extension side communication path (air)
23 Pressure-side damping valve (damping force generator)
25 Extension side damping valve (Damping force generator)
29 Rod side communication path 30 Communication path side check valve 31 Valve case (bottom of cylinder)
33 Cooling passage 34 Cooling side check valve 40 Rod side chamber 50 Anti rod side chamber O Lubricating oil G Gas R Reservoir chamber

Claims (4)

A bottomed cylindrical cylinder, an inner rod standing in the cylinder from the bottom of the cylinder, an annular piston slidably inserted into the outer peripheral surface of the inner rod and the inner peripheral surface of the cylinder, and the cylinder A rod-side chamber and an anti-rod-side chamber that are partitioned through the piston, a cylindrical piston rod that extends from the piston and passes through the head-side rod guide of the cylinder while sliding on the outer peripheral surface of the inner rod; An air passage that is provided in the piston and communicates the rod side chamber and the anti-rod side chamber; and a damping force generator provided in the middle of the air passage, encloses gas in the cylinder, and the anti-rod side chamber or A pneumatic shock absorber in which lubricating oil is injected into at least one of the rod side chambers. A bottomed cylindrical outer cylinder, a similarly bottomed cylindrical cylinder disposed inside the outer cylinder, a reservoir chamber formed between the cylinder and the outer cylinder, and the cylinder from the bottom of the cylinder An inner rod that stands up inside, an annular piston that is slidably inserted into the outer peripheral surface of the inner rod and the inner peripheral surface of the cylinder, and a rod side chamber and an anti-rod side chamber that are partitioned in the cylinder via the piston. A cylindrical piston rod that extends from the piston and slides on the outer peripheral surface of the inner rod while passing through the head side rod guide of the cylinder, and the rod side chamber and the anti-rod side chamber provided on the piston. An air passage that communicates, a damping force generator provided in the middle of the air passage, a communication passage that communicates the reservoir chamber and the non-rod side chamber, and the reservoir chamber and the And a connecting passage connecting the de-side chamber, with a gas is sealed inside the cylinder, pneumatic shock absorber, characterized in that the injection of the lubricating oil to the anti-rod side chamber and the reservoir chamber. 3. The pneumatic shock absorber according to claim 1, wherein a cooling passage communicating with the outside is provided in the inner rod. The inner rod is provided with a cooling passage, one of which is opened in the piston rod and the other is opened to the outside through the bottom of the cylinder and the bottom of the outer cylinder, and gas flows from the outside into the cooling passage. A cooling-side check valve that only allows the piston rod is provided, and a rod-side communication passage that communicates the inside of the piston rod to the outside is formed at the upper end of the piston rod. The pneumatic shock absorber according to claim 1 or 2, further comprising a communication path side check valve that allows only gas outflow.

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