JP4667331B2 - Pneumatic shock absorber - Google Patents

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 can be exemplified. it can.

  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.

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.

  Further, 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 pressure receiving area difference.

  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 the piston rod does not withdraw from the cylinder without permission even when the internal pressure increases.

  In order to achieve the above object, the present invention provides a bottomed cylindrical cylinder tube, an inner rod standing in the cylinder tube from the bottom of the cylinder tube, an inner peripheral surface of the cylinder tube, and an outer periphery of the inner rod. An annular piston slidably inserted into the surface, a rod side chamber and an anti-rod side chamber defined by the piston in the cylinder tube, and an outer member extending from the piston and protruding from the head side rod guide of the cylinder tube A rod, an inner chamber defined in the outer rod, an air passage provided in the piston for communicating the inner chamber and the rod side chamber, a damping force generator provided in the middle of the air passage, and the reaction chamber A communication passage provided in the cylinder tube for communicating the rod side chamber to the atmosphere side, the inner chamber and the rod side chamber With a gas is sealed and is characterized a pressure receiving area of the piston relative to the rod side chamber, that has been set equal to the pressure receiving area of the inner rod with respect to the inner chamber.

  According to the present invention, the pressure receiving area of the piston with respect to the rod side chamber defined on the outer side of the outer rod and the pressure receiving area of the inner rod with respect to the inner chamber similarly defined on the inner side of the outer rod are set equal. Even if the pressure rises, the withdrawal operation of the piston rod from the cylinder tube due to the pressure receiving area difference is not performed.

  Therefore, for example, in an operating state where 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 The outer rod is not retracted from the cylinder tube due to the difference.

  Therefore, it is possible to reliably prevent the vehicle height of the vehicle from being raised regardless of the driver's intention due to the withdrawal operation of the outer rod, 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 according to the present invention includes a bottomed cylindrical cylinder tube 2, an inner rod 3 standing in the cylinder tube 2 from the bottom 2a of the cylinder tube 2, and the cylinder tube. An annular piston 4 slidably inserted into the inner peripheral surface of 2 and the outer peripheral surface of the inner rod 3, a rod side chamber 8 and an anti-rod side chamber 9 defined by the piston 4 in the cylinder tube 2, and To communicate the outer rod 5 extending from the piston 4 and projecting from the head side rod guide 14 of the cylinder tube 2, the inner chamber 7 defined in the outer rod 5, the inner chamber 7 and the rod side chamber 8. The air passages 21 and 22 provided in the piston 4, the damping force generators 23 and 25 provided in the middle of the air passages 21 and 22, and the anti-rod side chamber 9 are connected to the atmosphere side. And a communication passage 11 provided in the cylinder tube.

  More specifically, a rod guide portion 14 for guiding the outer rod 5 is provided on the inner periphery of the upper end portion of the cylinder tube 2.

The rod guide portion 14 is formed by bending the tip of the cylinder tube 2 and the like, and an attachment groove 14a is formed on the inner peripheral surface thereof, and a seal member 15 is formed in the attachment groove. It is installed.

  The seal member 15 is in sliding contact with the outer peripheral surface of the outer rod 5 to prevent the gas G enclosed in the rod side chamber 8 from leaking to the atmosphere side, and the rod side chamber 8 is filled with lubricating oil. In this case, the lubricating oil is prevented from leaking to the atmosphere side.

  The piston 4 has an outer mounting groove 4a formed on the outer peripheral surface thereof, and an outer seal member 16 is mounted in the outer mounting groove 4a. A mounting groove 4b is formed, and an inner seal member 17 is mounted in the inner mounting groove 4b.

  The outer seal member 16 is in sliding contact with the inner peripheral surface of the cylinder tube 2 to prevent the gas G in the rod side chamber 8 from leaking to the anti-rod side chamber 9 side. When the lubricating oil is filled, the lubricating oil is prevented from leaking to the anti-rod side chamber 9 side.

  The inner seal member 17 is in sliding contact with the outer peripheral surface of the inner rod 3 to prevent the gas G in the inner chamber 7 from leaking to the anti-rod side chamber 9 side. When lubricating oil is filled in, the lubricating oil is prevented from leaking to the anti-rod side chamber 9 side.

  The piston 4 is formed with a pressure side communication passage 21 and an extension side communication passage 22 as air passages for communicating the inner chamber 7 and the rod side chamber 8 respectively.

  In the middle of the pressure side communication passage 21, a pressure side damping valve 23 as a damping force generating portion, and a gas G and lubricating oil (filled) from the inner chamber 7 to the rod side chamber 8 above the pressure side damping valve 23. Is provided with a pressure check valve 24 that allows only the flow of

  Further, in the middle of the extension side communication passage 22, the extension side damping valve 25 as a damping force generation unit, and the gas G and the lubricating oil that go from the rod side chamber 8 to the inner chamber 7 below the extension side damping valve 25. An extension check valve 26 that allows only the flow (if filled) is provided.

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

  One of the cooling passages 12 provided in the inner rod 3 is connected to the anti-rod side chamber 9 and the other is opened to the atmosphere side through the bottom portion 2a. A cooling check valve 28 that allows only the inflow of the gas is provided.

  The communication passage 11 is formed in the bottom 2a of the cylinder tube 2, and the communication passage 11 is provided with a communication passage-side check valve 29 that allows only gas inflow from the atmosphere side.

  Therefore, when the anti-rod side chamber 9 repeats expansion and contraction in conjunction with the forward / backward movement of the outer rod 5, the gas in the anti-rod side chamber 9 is released to the atmosphere side through the cooling passage 12. Yes.

  For example, the pneumatic shock absorber configured as described above attaches a rod-side eye 35 provided at the tip of the outer rod 5 to the vehicle body side, and a cylinder-side eye 36 provided at the lower end of the cylinder tube 2 on the axle side. By installing it, it is built into the suspension system of a car.

  Next, the operation will be described. The outer rod 5 is retracted from the cylinder tube 2, that is, in the expansion stroke of the pneumatic shock absorber, the gas G enclosed in the rod side chamber 8 is provided on the piston 4. While passing through the communication path 22 and flowing into the inner chamber 7, the expansion side damping force is generated by the expansion side damping valve 25 provided in the middle of the expansion side communication path 22.

  Further, when the outer rod 5 enters the cylinder tube 2, that is, when the pneumatic shock absorber is in the contraction stroke, the gas G sealed in the inner chamber 7 passes through the pressure side communication passage 21 provided in the piston 4 and the rod. While flowing into the side chamber 8, a pressure side damping force is generated by a pressure side damping valve 23 provided in the middle of the pressure side communication passage 21.

  At this time, the anti-rod side chamber 9 defined between the piston 4 and the bottom 2a of the cylinder tube 2 is repeatedly contracted and expanded as the outer rod 5 enters and retracts.

  That is, in the expansion stroke of the pneumatic shock absorber, the anti-rod side chamber 9 is in an expanded state, and gas from the atmosphere side is provided in the communication passage 11 in the anti-rod side chamber 9. Push to open.

  From this state, when the pneumatic shock absorber is in a contraction stroke, the anti-rod side chamber 9 is contracted, and the gas in the anti-rod side chamber 9 pushes open the cooling path check valve 28 provided in the cooling passage 12. Released to the outside.

  Accordingly, in the expansion / contraction stroke of the pneumatic shock absorber, the gas is sucked into the cooling passage 12 via the anti-rod side chamber 9, so that the inner rod 3 is cooled by this gas, and the inner chamber 7 is cooled by the cooled inner rod 3. It is possible to reliably prevent the temperature of the inner chamber 7 from rising due to the cooling of the gas.

  Further, when the pneumatic shock absorber is placed in a high temperature use environment, the internal pressure of the rod side chamber 8 and the inner chamber 7 rises without particularly operating the pneumatic shock absorber itself.

  However, in the present embodiment, the pressure receiving area S1 of the piston 4 with respect to the rod side chamber 8 and the pressure receiving area S2 of the inner rod 3 with respect to the inner chamber 7 are set equal to each other. It is possible to reliably prevent the piston rod (referred to as the outer rod 5 in the present embodiment) from leaving the cylinder (referred to as the cylinder tube 2 in the present embodiment) due to a difference in pressure receiving area.

  Therefore, the vehicle height of the vehicle rises regardless of the driver's intention due to the retraction operation of the outer rod 5 from the cylinder tube 2. It can be surely prevented that the safety is lowered.

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

  1) In the present embodiment, the gas in the anti-rod side chamber 9 is released to the atmosphere side through the cooling passage 12 provided in the inner rod 3, but the present invention is not limited to this. Alternatively, the communication path side check valve 29 provided in the communication path 11 may be eliminated, and the gas in the anti-rod side chamber 9 may be discharged to the atmosphere side by going back and forth through the communication path 11.

  2) In the present embodiment, the atmosphere side gas enters the anti-rod side chamber 9 and then passes through the cooling passage 12 to be released to the atmosphere side. However, the present invention is not limited to this. After entering the cooling passage 12, the settings of the cooling side check valve 28 and the communication passage side check valve 29 may be changed so as to be discharged to the atmosphere side through the anti-rod side chamber 9.

  3) In the present embodiment, the communication path 11 is provided in the bottom 2a of the cylinder tube 2. However, the present invention is not limited to this and may be provided on the side surface of the cylinder tube 2. Further, the number of communication passages 11 and the hole diameter can be arbitrarily set.

  4) In the present embodiment, the inner chamber 7 and the rod side chamber 8 are not actively filled with lubricating oil or grease. However, the present invention is not limited to this, and the slidability of the piston 4 is improved. In order to achieve this, the lubricating oil or grease may be filled.

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

Explanation of symbols

2 cylinder tube 2a bottom 3 inner rod 4 piston 5 outer rod 7 inner chamber 8 rod side chamber 9 anti-rod side chamber 11 communication path 12 cooling path 21 pressure side communication path (air path)
22 Extension side communication path (air)
23 Pressure-side damping valve (damping force generator)
25 Extension side damping valve (Damping force generator)
28 Cooling path side check valve 29 Insertion path side check valve S1 Pressure receiving area of inner rod against inner chamber S2 Pressure receiving area of piston against rod side chamber G Gas

Claims (3)

A bottomed cylindrical cylinder tube, an inner rod standing in the cylinder tube from the bottom of the cylinder tube, and an annular piston slidably inserted into the inner peripheral surface of the cylinder tube and the outer peripheral surface of the inner rod A rod side chamber and an anti-rod side chamber defined by the piston in the cylinder tube, an outer rod extending from the piston and protruding from a head side rod guide of the cylinder tube, and defined in the outer rod. An inner chamber, an air passage provided in the piston for communicating the inner chamber and the rod side chamber, a damping force generating portion provided in the middle of the air passage, and a cylinder tube for communicating the anti-rod side chamber to the atmosphere side A communication passage provided on the inner chamber and the rod-side chamber, and gas is sealed in the rod and the rod A pressure receiving area of the piston relative to the chamber, pneumatic shock absorber, characterized in that set equal to the pressure receiving area of the inner rod with respect to the inner chamber. 2. The pneumatic shock absorber according to claim 1, wherein a cooling passage communicating with the atmosphere side is provided in the inner rod. One of the cooling passages is connected to the anti-rod side chamber, the other is opened to the atmosphere side through the bottom, and a cooling side check valve that allows only gas inflow from the anti-rod side chamber to the cooling passage The communication passage side check valve that allows only the inflow of gas from the atmosphere side is provided in the communication passage, and the gas in the non-rod side chamber is supplied to the atmosphere through the cooling passage in accordance with the forward and backward movement of the outer rod. The pneumatic shock absorber according to claim 2, wherein the pneumatic shock absorber is discharged to the side or sucks the gas on the atmosphere side through the communication passage.

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