JP5669375B2 - Hydraulic shock absorber - Google Patents

Description

  The present invention relates to a hydraulic shock absorber.

  As a hydraulic shock absorber that is mounted on a motorcycle or the like and absorbs road surface vibration, as described in Patent Document 1, a piston provided on a piston rod is provided in an oil chamber formed inside a cylinder tube of a damper. A free piston that slidably inserts from the lower end side and that divides the oil chamber above the oil chamber that houses the piston inside the cylinder tube is movably provided, and the free piston is urged toward the piston. Some have a pressure spring. The free piston urged by the pressurizing spring constantly pressurizes the pressure side oil chamber to improve the rising response of the compression side damping force in the compression stroke in which the piston rod enters the oil chamber.

  In the hydraulic shock absorber described in Patent Document 1, when the spring load of the pressurizing spring is increased, the spring reaction force of the initial compression stroke becomes excessive and the piston rod is prevented from entering the oil chamber, so that the riding comfort of a two-wheeled vehicle or the like is increased. Make it worse. On the other hand, if the spring load of the pressure spring is softened, the spring reaction force in the latter half of the compression stroke will be insufficient, and the strut will not work and the riding comfort will be impaired.

  On the other hand, as a hydraulic shock absorber that improves the ride comfort of the initial compression stroke while using a pressure spring that can secure a predetermined spring reaction force in the latter half of the compression stroke, An arrangement in which an air spring mechanism is arranged in series on the oil chamber side or the downstream side has been proposed. The air spring mechanism is configured by one in which the air cushion chamber is hermetically formed by a bladder provided in the cylinder tube, or one in which the air cushion chamber is hermetically formed by a free piston that is slidable in the cylinder tube. The air cushion chamber formed by the bladder or the free piston is closed by the oil chamber pressure in the initial compression stroke to allow the piston rod to enter the oil chamber and improve the riding comfort. In the latter half of the compression stroke, the contraction of the air cushion chamber stops and the riding comfort is maintained by a predetermined spring reaction force of the pressure spring.

JP2005-30534 JP2004-286137

  However, the hydraulic shock absorber described in Patent Document 2 has the following problems. In the case where the air cushion chamber is hermetically formed by the bladder, the air cushion chamber does not start to contract until the oil chamber pressure in the initial compression stroke reaches the magnitude of the load that crushes (shrinks and deforms) the bladder (resists). The piston rod cannot enter the oil chamber, and the riding comfort cannot be improved. Even if the air cushion chamber is hermetically formed by the free piston, the air cushion chamber does not start to contract until the oil chamber pressure in the initial compression stroke exceeds the friction (resisting) generated at the seal portion of the free piston. Cannot enter the oil chamber and cannot improve riding comfort.

  SUMMARY OF THE INVENTION An object of the present invention is to reliably improve the riding comfort of an initial compression stroke from the beginning of compression while using a pressure spring that can ensure a predetermined spring reaction force in the latter half of the compression stroke in the hydraulic shock absorber.

The invention according to claim 1, by inserting an axle-side tube slidably on the vehicle body side tube, inside the cylinder tube of the damper which is connected to該車side tube of the vehicle body-side tube, the inside of the axle side tube the main piston mounted on a piston rod which is connected to the axle side tube is slidably inserted, partitions the inside of the cylinder tube in the piston side oil chamber and the rod side oil chamber by the main piston, said piston of said main piston the extension side damping valve installed in a flow path communicating the side oil chamber and the rod side oil chamber, the main piston that faces the sub-piston is provided from the top inside the main piston of the cylinder tube, wherein this sub piston the sub oil chamber partitioned upwardly relative to the piston side oil chamber of the cylinder tube, the peak of the sub-piston The compression side damping valve provided tons side oil chamber and the sub-oil chamber in the flow path to allow communication, provided movably inside the sub piston that faces the free piston from the top the sub piston of the cylinder tube, wherein in a hydraulic shock absorber comprising a pressure spring for biasing the free piston to the side of the sub-piston, which is held on the support shaft, wherein the sub-piston is attached to the upper end of the cylinder tube, the free piston is provided movably in the annular space between the support shaft and the cylinder tube, the free setting of the air cushion chamber to the side facing the sub-oil chamber of the piston only, the error a cushion chamber the sub oil chamber opening to the oil in the oil chamber is freely and out, and an outer peripheral skirt projecting the oil facing the sub-oil chamber of the free piston, the The air cushion chamber that forms an annular shape between the outer peripheral skirt portion and the inner peripheral skirt portion by an inner peripheral skirt portion that protrudes toward the side facing the sub oil chamber around the support shaft of the sub piston in the piston. An inner peripheral seal member is formed on the lower end side of the inner peripheral skirt portion so as to be in sliding contact with the support shaft of the sub-piston. The inner peripheral seal member can be immersed in the oil in the oil chamber, in standing Shin switching state of the vessel, the oil of the sub-oil chamber intrudes to a certain level within said air cushion chamber, in which air constant volume on top of the air cushion chamber was set to be is ensured .

According to a second aspect of the present invention, in the first aspect of the present invention, when the outer peripheral sealing member provided on the outer periphery of the free piston rises up to a predetermined position in the cylinder tube, the free piston and the sub-piston In the meantime, the sub oil chamber is provided with a surplus oil discharge passage communicating with a reservoir outside the cylinder tube .

(Claim 1)
(a) An air cushion chamber is provided on the side of the free piston facing the oil chamber, and the air cushion chamber opens into the oil chamber so that oil in the oil chamber can freely enter and exit. Therefore, in the initial compression stroke, the oil in the compression side oil chamber starts to directly compress the air in the air cushion chamber, reliably generates an air spring, allows the piston rod to enter without raising the free piston, and compresses Improving ride comfort from the beginning. After the predetermined compression stroke, the compression side oil chamber further compresses the air in the air cushion chamber, and the free piston is also raised to start the compression of the pressure spring. Ensure strength and maintain ride comfort.

(b) The air cushion chamber is surrounded by the outer skirt that protrudes into the oil chamber of the free piston, and the oil in the oil chamber is constant inside the air cushion chamber when the hydraulic shock absorber is upright and extended. It penetrates to the level and a certain volume of air is secured in the upper part of the air cushion chamber. Therefore, when the oil in the compression side oil chamber compresses the air in the air cushion chamber in the above (a), the air pressurized in the ceiling of the air cushion chamber is surrounded by the outer peripheral skirt portion and is not released to the outside. A stable generation of the spring is aimed at.
(c) The free piston has an inner peripheral skirt portion that protrudes toward the oil chamber around the support shaft of the sub-piston, and surrounds and forms an annular air cushion chamber between the outer peripheral skirt portion and the inner peripheral skirt portion. To do. As a result, when the oil in the compression side oil chamber compresses the air in the air cushion chamber in the above (a), the air pressurized in the ceiling of the air cushion chamber is enclosed by the outer peripheral skirt portion and the inner peripheral skirt portion. Stable generation of air springs without escaping outside. At this time, an inner peripheral seal member that is in sliding contact with the support shaft of the sub piston is provided on the lower end side of the inner peripheral skirt portion, and the inner peripheral seal member is lubricated by immersing the inner peripheral seal member in the oil in the oil chamber. The sealing performance for enclosing and forming the air cushion chamber is maintained.

(Claim 2 )
(d) When the outer peripheral seal member provided on the outer periphery of the free piston rises up to a predetermined position inside the cylinder tube, the sub oil chamber between the free piston and the sub piston communicates with the reservoir outside the cylinder tube. Provide an oil drain. As a result, the surplus oil and high pressure adhering to the outer peripheral surface of the piston rod and brought into the cylinder tube from the reservoir at the uppermost end, which is a predetermined position further above the normal upper end of the compression stroke, It can be discharged to the reservoir via the via and released. At this time, the air pressurized in the ceiling of the air cushion chamber of the free piston is surrounded by the outer skirt of the free piston described in (b) above, and the surplus oil is accompanied by the surplus oil. There is no discharge from the discharge channel.

1 is an overall cross-sectional view showing a hydraulic shock absorber according to a first embodiment. FIG. 2 is a lower cross-sectional view of FIG. FIG. 3 is a top sectional view of FIG. FIG. 4 is a sectional view showing the compression stroke end of the free piston.

Example 1 (FIGS. 1 to 4)
As shown in FIGS. 1 to 3, the front fork 10 (hydraulic shock absorber) has an axle side tube (inner tube) 12 slidably inserted into a vehicle body side tube (outer tube) 11. A suspension spring 13 is interposed therebetween, and the single cylinder damper 14 is inverted and is internally provided.

The vehicle body side tube 11 is supported on the vehicle body side, and the axle side tube 12 is coupled to the axle.
The upper end portion of the cylinder tube 16 (upper cylinder tube 16A) of the damper 14 is screwed to the upper end portion of the vehicle body side tube 11 via an O-ring, and the upper open end of the cylinder tube 16 is closed by a fork bolt 15. The fork bolt 15 is inserted and screwed into the inner periphery of the upper cylinder tube 16A via an O-ring.

  An axle bracket 19 is screwed to the lower end portion of the axle side tube 12, and the base end portion of the oil lock collar 17 is sandwiched between the axle side tube 12 and the axle bracket 19. The oil lock collar 17 is liquid-tightly fitted to the inner periphery of the lower end portion of the axle tube 12 via an O-ring, and seated liquid-tightly on the bottom surface inside the axle bracket 19 via the O-ring. . Further, a bottom bolt 18 is screwed to the axle bracket 19 from the outside via an O-ring. A base end portion of a piston rod (hollow rod) 20 of the damper 14 is screwed to the bottom bolt 18 and is locked by a lock nut 18 </ b> A, and a tip end portion of the piston rod 20 is inserted into the cylinder tube 16. The piston rod 20 is supported by a bush 21A of a rod guide 21 screwed into an opening on the lower end side of the cylinder tube 16 (lower cylinder tube 16B), and is inserted into the cylinder tube 16 through the seal member 21B. Yes. The seal member 21 </ b> B has a unidirectional sealing function that seals an oil chamber 43 </ b> B (described later) of the cylinder tube 16 and prevents oil in the oil chamber 43 </ b> B from escaping out of the cylinder tube 16. An oil lock collar 22 is provided on the outer periphery of the rod guide 21. A rebound spring 23 is supported on the inner end face of the rod guide 21. The cylinder tubes 16A and 16B are connected and locked by a pipe nut 16C.

  The suspension spring 13 includes an outer peripheral step surface of the base end portion of the oil lock collar 17 and a perforated spring collar 25 (a large number of communication holes 25A) that are externally attached to the cylinder tube 16 (lower cylinder tube 16B) and locked in the axial direction. ) Is interposed between the spring receiver 26 fixed to the tip end portion. Also, an oil chamber 31 and a gas chamber 32 constituting a reservoir 30 are provided inside the vehicle body side tube 11 and the axle side tube 12 and outside the damper 14, and the oil chamber 31 and the gas chamber 32 form a free interface. The gas that is in contact with each other and trapped in the gas chamber 32 constitutes a gas spring. The elastic force of the suspension spring 13 and the gas spring absorbs the impact force that the vehicle receives from the road surface.

  The damper 14 has a main valve device (extension side damping valve device) 40 and a sub valve device (pressure side damping valve device) 50. The damper 14 suppresses the expansion and contraction vibration of the vehicle body side tube 11 and the axle side tube 12 due to the absorption of the impact force by the suspension spring 13 and the gas spring by the damping force generated by the main valve device 40 and the sub valve device 50.

(Main valve device 40)
The main valve device 40 has a piston holder 41 attached to the tip of the piston rod 20 and a main piston 42 attached to the piston holder 41. The main piston 42 partitions the inside of the cylinder tube 16 into a piston-side oil chamber 43A in which the piston rod 20 is not accommodated and a rod-side oil chamber 43B in which the piston rod 20 is accommodated, and slides in the cylinder tube 16. . The main piston 42 is provided with an extension side damping valve 44A and is provided with an extension side flow path 44 capable of connecting the piston side oil chamber 43A and the rod side oil chamber 43B, and a pressure side damping valve (check valve) 45A. The pressure side flow path 45 which enables communication between the oil chamber 43A and the rod side oil chamber 43B is provided.

  Further, the main valve device 40 is provided with an adjuster 46 that can be rotated from the outside to the aforementioned bottom bolt 18 that is screwed to the axle bracket 19. The main valve device 40 passes a damping force adjusting rod 47 coupled to an adjuster 46 through a hollow portion of the piston rod 20 and is moved by a needle 47A at the tip of the damping force adjusting rod 47 that advances and retreats in the axial direction when the adjuster 46 rotates. The flow passage area of the bypass passage 48 between the piston-side oil chamber 43A and the rod-side oil chamber 43B provided in the piston holder 41 can be adjusted.

(Sub-valve device 50)
The sub-valve device 50 has a guide pipe 51 (support shaft) screwed to the fork bolt 15 screwed to the upper end of the upper cylinder tube 16A, and a piston holder 51A screwed to the tip of the guide pipe 51. The sub-piston 52 is held on the piston holder 51A by a nut 51B or the like. The sub-piston 52 is disposed inside the cylinder tube 16 relative to the main piston 42, in liquid-tight contact with the small inner diameter portion 71 of the upper cylinder tube 16A, and the sub-oil chamber 53 is defined above the piston-side oil chamber 43A. To do. The sub-piston 52 is provided with a pressure-side damping valve 54A so that the piston-side oil chamber 43A and the sub-oil chamber 53 can communicate with each other, and an extension-side damping valve 55A is provided with the piston-side oil chamber 43A and the sub-oil. An extension-side flow channel 55 that enables communication with the chamber 53 is provided. The piston holder 51 </ b> A includes a bypass path 56 that bypasses the pressure side flow path 54 and the extension side flow path 55 to allow the piston side oil chamber 43 </ b> A and the sub oil chamber 53 to communicate with each other.

  The damping force adjustment rod 58 screwed into the fork bolt 15 includes an adjuster 59 and is inserted into the guide pipe 51 and is flown through the bypass flow path 56 by a needle 58A at the tip which is advanced and retracted in the axial direction by the rotation operation of the adjuster 59. The road area can be adjusted. The fork bolt 15 has an adjuster 59 and its holder 59A embedded in the center of the end face of the head.

  The sub-valve device 50 is provided inside the upper cylinder tube 16A so as to be movable in an annular space between the upper cylinder tube 16A and the guide pipe 51, and between the free piston 60 and the fork bolt 15. There is a pressure spring 70 interposed therebetween. The pressure spring 70 is a compression coil spring and biases the free piston 60 toward the sub-piston 52 side. When the piston rod 20 enters the cylinder tube 16 and compresses, the pressure spring 70 contracts, and the oil chamber in the cylinder tube 16 is pressurized by the amount of the spring load of the pressure spring 70 at this time, thereby compressing the pressure side. While improving the rising response of force, the occurrence of cavitation of oil in the cylinder tube 16 during extension is prevented.

  At this time, the free piston 60 forms a bottomed cylindrical body having a bottom portion 61 and a cylindrical portion 62, and includes an outer peripheral skirt portion 63 protruding from the outer peripheral portion of the bottom portion 61 toward the side facing the sub oil chamber 53. The free piston 60 includes an inner peripheral skirt portion 64 that protrudes to the side facing the sub oil chamber 53 around the guide pipe 51 of the sub piston 52 in the bottom portion 61.

  In the free piston 60, an upper piston ring 65U is provided in an annular groove on the outer periphery of the intermediate portion of the cylindrical portion 62, a lower piston ring 65L is provided in an annular groove on the lower outer periphery of the outer peripheral skirt portion 63, and an annular groove on the upper outer periphery of the cylindrical portion 62 An outer peripheral sealing member 66 such as an oil seal is provided on the outer side. The outer peripheral sealing member 66 is loaded on the outer side of the O-ring 66A loaded in the annular groove on the upper outer periphery of the cylindrical portion 62, and is pressed against the inner circumference of the upper cylinder tube 16A by the O-ring 66A. In addition, the free piston 60 is provided with an inner peripheral seal member 67 such as an oil seal in an annular groove in the lower inner periphery of the inner peripheral skirt portion 64.

  In a normal moving range in which the free piston 60 moves in the annular space between the upper cylinder tube 16A and the guide pipe 51 in order to compensate for the volume of the piston rod 20 that enters and exits the cylinder tube 16 as the damper 14 expands and contracts. The upper piston ring 65U, the lower piston ring 65L, and the outer peripheral seal member 66 slide on the middle inner diameter portion 72 above the small inner diameter portion 71 of the upper cylinder tube 16A, and the inner peripheral seal member 67 is the straight outer periphery of the guide pipe 51. Slide. In the above-described normal movement range, the free piston 60 is configured such that the outer peripheral seal member 66 slides liquid-tightly on the inner diameter portion 72 of the upper cylinder tube 16A, and the inner peripheral seal member 67 slides liquid-tightly on the outer periphery of the guide pipe 51. By moving, the sub oil chamber 53 communicating with the piston side oil chamber 43A on the sub piston 52 side and the gas chamber (volume compensation chamber) 68 behind the free piston 60 are partitioned.

  In the free piston 60, when the free piston 60 moves abnormally large downward in the upper cylinder tube 16A, the piston whose front end surface of the inner peripheral skirt portion 64 is screwed to the guide pipe 51. The front end face of the outer peripheral skirt part 63 is set so as not to fit into the boundary taper part of the small inner diameter part 71 and the inner inner diameter part 72 so as to abut against the shoulder part of the holder 51A first.

  The sub valve device 50 communicates the gas chamber 32 of the reservoir 30 and the gas chamber 68 behind the free piston 60 through a through hole 69 provided on the upper end side of the upper cylinder tube 16A. Fork an exhaust plug 34 for discharging air that has entered the gas chamber 32 of the reservoir 30 and the gas chamber 68 behind the free piston 60 from the sliding portion of the vehicle body side tube 11 and the axle side tube 12 by the expansion and contraction of the front fork 10. It is provided on the bolt 15.

  Each time the piston rod 20 of the front fork 10 strokes, the sub-valve device 50 brings the oil in the oil chamber 31 attached to the outer peripheral surface of the piston rod 20 from the seal member 21B of the rod guide portion 21 into the cylinder tube 16. . As a result, the hydraulic oil in the oil chambers 43A, 43B, 53 inside the cylinder tube 16 is gradually increased, the hydraulic pressure in these oil chambers 43A, 43B, 53 is increased, and the free piston 60 is moved in the normal movement range described above. When the upper end of the cylinder (the normal rising end of the compression stroke of the damper 14) moves to the uppermost end (FIG. 4) which is a predetermined position, the sub oil chamber 53 between the free piston 60 and the sub piston 52 becomes a cylinder tube. 16 is provided with a surplus oil discharge passage 74 communicating with the external reservoir 30. In the present embodiment, when the free piston 60 moves to the above-described highest end, the outer peripheral seal member 66 of the free piston 60 moves from the middle inner diameter portion 72 of the upper cylinder tube 16A to the larger inner diameter portion above the middle inner diameter portion 72. A blow passage is formed between the inner diameter portion 73 and the large inner diameter portion 73, and the sub oil chamber 53 is opened to the aforementioned through hole 69 opening to the large inner diameter portion 73. In the present embodiment, the through hole 69 constitutes the surplus oil discharge path 74 described above. As a result, surplus oil and high pressure in the damper 14 are discharged from the sub oil chamber 53 to the reservoir 30 outside the cylinder tube 16 via the outer periphery of the free piston 60 and the through hole 69 of the upper cylinder tube 16A, and released.

  However, in the front fork 10, in order to improve the riding comfort of the initial compression stroke from the beginning of the compression stroke while using the pressurizing spring 70 that can ensure a predetermined spring reaction force in the latter half of the compression stroke, It has a configuration.

  That is, the front fork 10 is provided with an air cushion chamber 80 on the side of the free piston 60 facing the sub oil chamber 53, and the air cushion chamber 80 opens into the sub oil chamber 53 so that oil in the sub oil chamber 53 can freely enter and exit. Is done. In the front fork 10 of the present embodiment, an air cushion chamber 80 having an annular shape is surrounded and formed between the outer peripheral skirt portion 63 and the inner peripheral skirt portion 64 of the free piston 60. Air A is accommodated in the ceiling side of air cushion chamber 80 (bottom 61 of free piston 60), and oil B in sub oil chamber 53 is injected into the lower part thereof, and air A and oil B are in contact with each other through a free interface. is there. With the front fork 10 assembled, the oil B in the sub oil chamber 53 enters the air cushion chamber 80 to a certain level, and a certain volume of air A is secured above the air cushion chamber 80. At this time, the inner peripheral sealing member 67 provided on the lower end side of the inner peripheral skirt portion 64 is set so as to be immersed in the oil in the sub oil chamber 53.

Therefore, according to the present embodiment, the following operational effects can be obtained.
(a) An air cushion chamber 80 is provided on the side of the free piston 60 facing the sub oil chamber 53, and the air cushion chamber 80 opens into the sub oil chamber 53 so that the oil B in the sub oil chamber 53 can enter and exit. Therefore, in the initial compression stroke, the oil B in the compression side oil chamber 53 starts to directly compress the air A in the air cushion chamber 80 to surely generate an air spring, and without raising the free piston 60, the piston rod 20 Allow entry and improve riding comfort from the beginning of compression. After the predetermined compression stroke, the oil B in the pressure side oil chamber 53 further compresses the air A in the air cushion chamber 80, and the free piston 60 is also raised to start the compression of the pressure spring 70. A predetermined spring reaction force by the spring 70 is ensured and riding comfort is maintained.

  (b) The air cushion chamber 80 is surrounded and formed by the outer peripheral skirt portion 63 protruding to the side of the free piston 60 facing the sub oil chamber 53. Therefore, when the oil B in the pressure side oil chamber 53 compresses the air A in the air cushion chamber 80 in the above (a), the air A pressurized in the ceiling of the air cushion chamber 80 is surrounded by the outer peripheral skirt portion 63. In order to prevent the air from escaping outside, the air spring is stably generated.

  (c) When the outer peripheral sealing member provided on the outer periphery of the free piston 60 rises up to a predetermined position inside the cylinder tube 16, the sub oil chamber 53 between the free piston 60 and the sub piston 52 is moved to the outside of the cylinder tube 16. A surplus oil discharge passage 74 communicating with the reservoir 30 is provided. As a result, surplus oil and high pressure adhering to the outer peripheral surface of the piston rod 20 and brought into the cylinder tube 16 from the reservoir 30 are transferred to the surplus end at a predetermined position further above the normal ascent end of the compression stroke. It can be discharged to the reservoir 30 via the oil discharge path 74 and released. At this time, the air A pressurized in the ceiling of the air cushion chamber 80 of the free piston 60 is enclosed by the outer peripheral skirt portion 63 of the free piston 60 described above (b) and is accompanied by the excess oil. Thus, it is not discharged from the surplus oil discharge path 74.

  (d) The free piston 60 is provided with an inner peripheral skirt portion 64 projecting to the side facing the sub oil chamber 53 around the guide pipe 51 of the sub piston 52, and an annular shape is formed between the outer peripheral skirt portion 63 and the inner peripheral skirt portion 64. The air cushion chamber 80 is formed so as to surround it. Thereby, when the oil B in the pressure side oil chamber 53 compresses the air A in the air cushion chamber 80 in the above-described (a), the air A pressurized in the ceiling of the air cushion chamber 80 is changed into the outer peripheral skirt portion 63 and the inner skirt 63. The air spring is stably generated without being surrounded by the peripheral skirt portion 64 to escape to the outside. At this time, by providing an inner peripheral seal member 67 slidably contacting the guide pipe 51 of the sub-piston 52 on the lower end side of the inner peripheral skirt portion 64 and immersing the inner peripheral seal member 67 in the oil in the sub oil chamber 53, The inner periphery sealing member 67 is lubricated to maintain the sealing performance for enclosing and forming the air cushion chamber 80.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration of the present invention is not limited to this embodiment, and even if there is a design change or the like without departing from the gist of the present invention. It is included in the present invention.

  According to the present invention, in a hydraulic shock absorber that is mounted on a two-wheeled vehicle or the like and absorbs road surface vibrations, the comfort of the initial compression stroke is compressed while using a pressure spring that can secure a predetermined spring reaction force in the latter half of the compression stroke. Can be improved from the beginning.

10 Front fork (hydraulic shock absorber)
11 Body side tube 12 Axle side tube 14 Damper 16, 16A, 16B Cylinder tube 20 Piston rod 30 Reservoir 42 Main piston 43A Piston side oil chamber 43B Rod side oil chamber 44 Stretch side flow path 44A Stretch side damping valve 51 Guide pipe (support) axis)
52 sub piston 53 sub oil chamber 54 pressure side flow path 54A pressure side damping valve 60 free piston 63 outer peripheral skirt portion 64 inner peripheral skirt portion 66 outer peripheral seal member 67 inner peripheral seal member 68 gas chamber 69 through hole 70 pressure spring 74 excess oil discharge Road 80 Air cushion room

Claims (2)

Insert the axle side tube slidably into the body side tube,
A cylinder tube of the damper which is connected to該車side tube inside of the vehicle body-side tube, the main piston provided inside with a piston rod which is connected to the axle-side tube of the axle side tube is slidably inserted, the the interior of the cylinder tube is divided into a piston side oil chamber and the rod side oil chamber by a main piston, an extension side damping valve installed in a flow path that communicates the rod side oil chamber and the piston side oil chamber of said main piston,
Said cylinder inside the said main piston that faces the sub-piston to above the main piston of the tube is provided, defines a sub-oil chamber upwardly relative to the interior of the piston side oil chamber of the cylinder tube by the sub-piston, said sub the compression side damping valve provided the piston side oil chamber of the piston and the flow path which allows communication the sub oil chamber,
A free piston facing the sub-piston is movably provided above the sub-piston inside the cylinder tube,
In a hydraulic shock absorber comprising a pressure spring for biasing the free piston to the side of the sub-piston,
The sub piston is held by a support shaft attached to the upper end of the cylinder tube, and the free piston is provided movably in an annular space between the cylinder tube and the support shaft,
The set air cushion chamber to the side facing the sub-oil chamber of the free piston only, the error A cushion chamber is freely oil of the oil chamber open to the sub-oil chamber and out,
And an outer peripheral skirt projecting the oil facing the sub-oil chamber of the free piston, the inner peripheral skirt projecting side facing the sub-oil chamber at about the support shaft of the sub-piston in the free piston, An inner peripheral seal member that surrounds and forms the air cushion chamber that forms an annular shape between the outer peripheral skirt portion and the inner peripheral skirt portion, and that is in sliding contact with the support shaft of the sub-piston on the lower end side of the inner peripheral skirt portion the provided the inner sealing member to enable immersed in the oil of the oil chamber, in a standing Shin switching state of the hydraulic shock absorber, the oil of the sub-oil chamber intrudes to a certain level within said air cushion chamber, A hydraulic shock absorber, wherein a fixed volume of air is secured in an upper portion of the air cushion chamber. Wherein when said outer peripheral sealing member provided on the outer periphery of the free piston rises the inside of the cylinder tube to a predetermined position, the sub-oil chamber between the said free piston sub piston, of the cylinder tube outside the reservoir The hydraulic shock absorber according to claim 1 , wherein a surplus oil discharge passage communicating with the hydraulic shock absorber is provided.

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