JP2010230068A - Hydraulic shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the volume of an air chamber behind a free piston from being reduced due to the infiltration of oil or the like and the pressure of the air chamber to rise abnormally.
In a hydraulic shock absorber (10), a pressure in an air chamber (73) behind a free piston (60) is fixed to a communication path (90) connecting the air chamber (73) behind the free piston (60) inside the cylinder tube (16) to a reservoir (30). A valve provided with a check valve 100 that opens when it becomes higher than the above and allows the release of pressure from the air chamber 73 behind the free piston 60 to the reservoir 30.
[Selection] Figure 3

Description

  The present invention relates to a hydraulic shock absorber such as a front fork for a motorcycle.

  As a hydraulic shock absorber used for a front fork for a motorcycle, as disclosed in Patent Document 1, an axle side tube is slidably inserted into a vehicle body side tube, and a damper connected to the vehicle body side tube inside the vehicle body side tube is used. A main piston provided on a piston rod connected to the axle side tube inside the axle side tube is slidably inserted into the cylinder tube, and the inside of the cylinder tube is inserted into the piston side oil chamber and the rod side oil chamber by the main piston. A sub-piston facing the main piston is provided above the main piston inside the cylinder tube, and the sub-piston chamber is defined above the piston-side oil chamber inside the cylinder tube by the sub-piston. A pressure-side damping valve is installed in the flow path that enables communication between the piston-side oil chamber and the sub-tank chamber. In the cylinder tube, a free piston opposed to the sub piston is slidably provided above the sub piston, and has a pressure spring that biases the free piston toward the sub piston. is there.

  In this hydraulic shock absorber, the air chamber behind the free piston is blocked from the air chamber of the reservoir. As a result, the free piston provided inside the cylinder tube of the damper has a spring force that increases in proportion to the stroke amount of the pressure spring and an air spring that increases in proportion to the volume change of the air chamber behind the free piston. Energized by force. Therefore, the inside of the cylinder tube of the damper is always pressurized by the free piston, and a predetermined damping force is generated by the compression side damping valve from the beginning when the damper starts the compression operation from the maximum extension state.

  In addition, in this hydraulic shock absorber, even when the air spring force of the reservoir needs to be increased on the most compression side of the damper according to the vehicle weight or running condition of the vehicle, the air pressure of the reservoir is reduced by the cylinder tube of the damper. There is no influence behind the free piston inside. Therefore, the increase in the internal pressure of the cylinder tube of the damper is suppressed by that amount, the entry resistance force acting on the piston rod trying to enter the cylinder tube in the compression stroke is reduced by that amount, and the piston rod can be easily entered to improve the riding comfort. It can be improved.

JP2005-30534

  In the hydraulic shock absorber described in Patent Document 1, a sub piston is provided on a guide shaft in which a damper is connected to a cylinder tube, and a free piston facing the sub piston is provided slidably on the inner periphery of the cylinder tube and the outer periphery of the guide shaft. ing. At this time, the seal member provided on each of the outer periphery and the inner periphery of the free piston partitions the sub tank chamber and the air chamber behind the free piston, but has a structure that maintains a seal by forming an oil film. Infiltration of oil from the sub tank chamber to the air chamber behind the free piston cannot be prevented.

  Further, in the hydraulic shock absorber described in Patent Document 1, the damper closes the open end of the cylinder tube with a fork bolt, and the fork bolt includes a plug bolt for the reservoir air chamber and an air chamber behind the free piston. Plug bolts are provided. It is also possible to open the plug bolt for the reservoir air chamber, adjust the air pressure of the air chamber, and optionally refill the reservoir with oil to increase the reservoir air spring force. The plug bolt for the air chamber behind the free piston can be opened to adjust the air pressure of the air chamber. However, the plug bolt for the air chamber behind the free piston may be inadvertently mistakenly opened as the plug bolt for the air chamber of the reservoir, resulting in a mistake in injecting oil into the air chamber behind the free piston. There is.

  Oil that has entered the free piston from the seal member of the free piston and misused plug bolt for the air chamber behind the free piston accumulates in the air chamber behind the free piston without being discharged anywhere. As a result, the volume is reduced, and the air spring characteristic (air spring force) depending on the compression rate of the air chamber is deviated from the initial setting. In addition, the pressure of the air chamber behind the free piston becomes a value that exceeds expectations at the time of maximum compression, and there is a risk of causing puncture (damage of component parts).

  An object of the present invention is to provide a hydraulic shock absorber that blocks an air chamber behind a free piston from an air chamber of a reservoir, and the volume of the air chamber behind the free piston is reduced by oil infiltration or the like. The purpose is to avoid an abnormal rise in pressure.

  In the first aspect of the present invention, the axle side tube is slidably inserted into the vehicle body side tube, and the cylinder tube of the damper connected to the vehicle body side tube inside the vehicle body side tube is connected to the axle side inside the axle side tube. A main piston provided on a piston rod connected to the tube is slidably inserted, and the inside of the cylinder tube is partitioned into a piston-side oil chamber and a rod-side oil chamber by this main piston, and the interior of the cylinder tube is above the main piston. A sub-piston opposite to the main piston is provided in the cylinder, and the sub-piston defines a sub-tank chamber above the piston-side oil chamber inside the cylinder tube so that the piston-side oil chamber of the sub-piston can communicate with the sub-tank chamber. A pressure-side damping valve is provided in the passage, and the sub-pipes are arranged above the sub-piston inside the cylinder tube. A free piston facing the ton is slidably provided, a pressure spring is provided to urge the free piston toward the sub-piston side, and the air chamber behind the free piston in the cylinder tube In a hydraulic shock absorber that is blocked from the chamber, the pressure of the air chamber behind the free piston becomes higher than a certain value in the communication path that connects the air chamber behind the free piston inside the cylinder tube to the reservoir. And a check valve that opens when the free piston is allowed to release pressure from the air chamber behind the free piston to the reservoir.

  According to a second aspect of the present invention, in the first aspect of the present invention, further, a communication hole communicating with the reservoir is provided in the tube wall of the cylinder tube, and a lower inner periphery below the communication hole of the cylinder tube is provided on a lower outer periphery of the free piston. A lower seal member that is slidably contacted is provided, and an upper seal member that is slidably contacted to the upper inner periphery above the communication hole of the cylinder tube is provided on the upper outer periphery of the free piston, and from the bottom of the free piston facing the air chamber behind the free piston. The free piston is provided with a communication passage extending on the outer periphery between the upper seal member and the lower seal member, and the check valve is provided in the communication passage.

  According to a third aspect of the present invention, in the second aspect of the present invention, when the free piston is in a normal movement range caused by an expansion / contraction stroke of the damper, the communication hole is formed between the free piston and the sub piston by a lower seal member of the free piston. When the free piston exceeds the normal moving range and rises to the highest end due to the high pressure surplus of hydraulic oil that has entered the cylinder tube from the reservoir, the lower seal member of the free piston Thus, the communication hole is opened to a sub tank chamber between the free piston and the sub piston, and the sub tank chamber communicates with a reservoir outside the cylinder tube.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, a sub-piston is provided on a guide shaft in which the damper is connected to the cylinder tube, and the free piston facing the sub-piston is defined as the inner periphery of the cylinder tube. The guide shaft is slidably provided on the outer periphery of the guide shaft.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the damper closes the opening end of the cylinder tube with a fork bolt, and the fork bolt includes a plug bolt for the air chamber of the reservoir. The plug bolt for the air chamber behind the free piston is provided.

(Claim 1)
(a) In a hydraulic shock absorber that shuts off the air chamber behind the free piston from the air chamber of the reservoir, the pressure of the air chamber behind the free piston is connected to the communication path that connects the air chamber behind the free piston to the reservoir. A check valve is provided that opens when the pressure becomes higher than a certain value and allows discharge of pressure from the air chamber behind the free piston to the reservoir. As a result, oil that has permeated into the air chamber behind the free piston is discharged to the reservoir via the communication path and the check valve, and the volume reduction of the air chamber and the abnormal increase in pressure can be avoided. Therefore, the air spring characteristic depending on the compression ratio of the air chamber behind the free piston can be maintained at the initial setting, and the puncture at the time of the most compression of the air chamber can be prevented.

(Claim 2)
(b) A communication hole communicating with the reservoir is provided in the tube wall of the cylinder tube, and a lower seal member is provided on the lower outer periphery of the free piston so as to be in sliding contact with the lower inner periphery below the communication hole of the cylinder tube. An upper seal member that slides on the upper inner circumference above the communication hole of the cylinder tube is provided on the outer circumference, and is sandwiched between the upper and lower seal members of the free piston from the bottom of the free piston facing the air chamber behind the free piston. A communication passage extending on the outer periphery is provided, and the check valve (a) described above is provided in this communication passage. As a result, a communication path for communicating the air chamber behind the free piston to the reservoir is formed in the free piston and the cylinder tube, and the oil accumulated in the bottom of the air chamber behind the free piston is accumulated in the communication path (continuous). It can be discharged to the reservoir via a passage and a communication hole) and a check valve.

(Claim 3)
(c) When the free piston is in the normal movement range due to the expansion / contraction stroke of the damper, the communication hole is closed to the sub tank chamber between the free piston and the sub piston by the lower seal member of the free piston, When the upper end of the hydraulic oil that has entered the cylinder tube from the reservoir and rises to the highest end due to the high pressure surplus oil, the communication hole is formed between the free piston and the sub piston by the lower seal member of the free piston. The sub tank chamber is opened, and the sub tank chamber communicates with a reservoir outside the cylinder tube. While maintaining the air chamber behind the free piston against the air chamber of the reservoir, the high-pressure surplus oil that has entered the cylinder tube from the reservoir is released directly from the sub tank chamber to the reservoir, High pressure can be avoided.

(Claim 4)
(d) A free piston is slidably provided not only on the inner periphery of the cylinder tube but also on the outer periphery of the guide shaft. Therefore, the oil that has entered the air chamber behind the free piston through the seal members provided on the outer periphery and the inner periphery of the free piston is stored in the reservoir via the communication path and the check valve described in (a) and (b) above. Can be discharged.

(Claim 5)
(e) Fork bolts were provided with a plug bolt for the air chamber of the reservoir and a plug bolt for the air chamber behind the free piston. Therefore, the plug bolt for the air chamber behind the free piston was inadvertently mistakenly opened as the plug bolt for the air chamber of the reservoir and mistakenly injected oil into the air chamber behind the free piston. However, the injected oil can be discharged to the reservoir via the communication paths (a) and (b) and the check valve.

FIG. 1 is an overall cross-sectional view showing a hydraulic shock absorber. 2 is an enlarged cross-sectional view of the lower part of FIG. FIG. 3 is a cross-sectional view showing a lowered end state of the free piston. FIG. 4 is a cross-sectional view showing a normal rising end state of the free piston. FIG. 5 is a cross-sectional view showing the most elevated end state of the free piston.

  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 a fork integrated with the cylinder tube 16 It is blocked by the 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. Further, an oil chamber 31 and an air 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 air chamber 32 form a free interface. The air that is in contact with each other and trapped in the air chamber 32 constitutes an air spring. The elastic force of the suspension spring 13 and the air 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 air 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)
In the sub-valve device 50, a pipe-shaped guide shaft 51 (support shaft) is screwed to the fork bolt 15 screwed to the upper end of the upper cylinder tube 16A, and a piston holder 51A is attached to the tip of the guide shaft 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 relative to the main piston 42 inside the cylinder tube 16, is in fluid-tight contact with the inner peripheral portion of the upper cylinder tube 16A, and defines a sub-tank chamber 53 above the piston-side oil chamber 43A. The sub-piston 52 is provided with a pressure-side damping valve 54A to allow the piston-side oil chamber 43A and the sub-tank chamber 53 to communicate with each other, and the extension-side damping valve 55A is provided with a piston-side oil chamber 43A and the sub-tank chamber 53. And an extension-side flow channel 55 that can communicate with each other. 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 tank chamber 53 to communicate with each other.

  The damping force adjusting rod 58 screwed into the fork bolt 15 includes an adjuster 59 and is inserted into the guide shaft 51 and is flown through the bypass flow channel 56 by a needle 58A at the tip which is advanced and retracted in the axial direction by the rotating 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 16 </ b> A so that the free piston 60 can be moved in an annular space between the upper cylinder tube 16 </ b> A and the guide shaft 51, and between the free piston 60 and the fork bolt 15. There is a pressure spring 70 interposed therebetween. The free piston 60 is above the sub piston 52 inside the upper cylinder tube 16 </ b> A and faces the sub piston 52. The pressure spring 70 is a compression coil spring and biases the free piston 60 toward the sub-piston 52 side.

  At this time, the free piston 60 has a bottomed cylindrical body, and the bottom 61 of the free piston 60 is disposed near the sub-piston 52, and the outer periphery of the small outer diameter portion below the bottom 61 to the cylindrical portion 62 of the free piston 60. Are provided with a lower piston ring 63L and a lower seal member 64L such as an oil seal, and an upper piston ring 63U and an upper seal member 64U such as an oil seal are provided on the outer periphery of the large outer diameter portion of the upper portion of the cylindrical portion 62 of the free piston 60. Further, the free piston 60 is provided with an inner peripheral seal member 65 such as an oil seal in an inner peripheral concave portion of the bottom 61 of the free piston 60. The annular space between the upper cylinder tube 16A and the guide shaft 51 is lowered as shown in FIG. 3 in order to compensate for the volume of the piston rod 20 that the free piston 60 enters and leaves the cylinder tube 16 as the damper 14 extends and retracts. The lower piston ring 63L and the lower seal member 64L slide on the lower inner diameter portion 71 on the lower side of the upper cylinder tube 16A in the normal movement region that moves between the end and the normal rising end shown in FIG. 4, and the upper piston ring 63U. The upper seal member 64U slides on the large inner diameter portion 72 (expanded diameter portion) on the upper side of the upper cylinder tube 16A, and the inner peripheral seal member 65 slides on the straight outer periphery of the guide shaft 51. In the free piston 60, the seal members 64L and 64U slide in a liquid-tight manner on the small inner diameter portion 71 and the large inner diameter portion 72 of the upper cylinder tube 16A, and the inner peripheral seal member 65 is the guide shaft 51. By sliding the outer periphery in a liquid-tight manner, a sub tank chamber 53 communicating with the piston side oil chamber 43A on the sub piston 52 side and an air chamber (volume compensation chamber) 73 behind the free piston 60 are partitioned. .

  However, in the sub valve device 50, the air chamber 73 behind the free piston 60 inside the cylinder tube 16 is blocked from the air chamber 32 of the reservoir 30. Thereby, the air spring force of the air chamber 32 of the reservoir 30 is not introduced into the air chamber 73 behind the free piston 60 by the compression stroke of the damper 14. The increase in the pressure of the air chamber 73 behind the free piston 60 of the damper 14 is suppressed by that amount, and the entry resistance force acting on the piston rod 20 trying to enter the cylinder tube 16 in the compression stroke is reduced accordingly, and the piston rod 20 It is possible to improve the riding comfort by making the entry easier.

  The sub-valve device 50 removes the oil in the oil chamber 31 adhering to the outer peripheral surface of the piston rod 20 from the seal member 21B of the rod guide portion 21 to the inside of the cylinder tube 16 every time the piston rod 20 of the front fork 10 strokes. Bring it in. As a result, the hydraulic oil in the oil chambers 43A, 43B, 53 inside the cylinder tube 16 gradually increases to become high-pressure surplus oil, the hydraulic pressure in these oil chambers 43A, 43B, 53 is increased, and the free piston 60 5 exceeds the above-mentioned normal rising end of the normal movement range and further rises to the highest rising end shown in FIG. 5 which is a predetermined position above the sub-tank chamber 53 between the free piston 60 and the sub-piston 52. It communicates with an external reservoir 30. As a result, surplus oil and high pressure in the damper 14 are discharged from the sub tank chamber 53 to the reservoir 30 outside the cylinder tube 16 and released.

  That is, the communication hole 80 which allows the sub tank chamber 53 between the free piston 60 and the sub piston 52 to communicate with the reservoir 30 outside the cylinder tube 16 is provided in the cylinder tube 16, and in this embodiment, the tube wall of the upper cylinder tube 16A is connected to the inside and outside And is drilled in the vicinity of the lower end of the large inner diameter portion 72 (a tapered portion connected to the small inner diameter portion 71 within the range of the large inner diameter portion 72). The lower seal member 64L is in sliding contact with the lower inner periphery below the communication hole 80 of the cylinder tube 16, and the upper seal member 64U is in sliding contact with the upper inner periphery above the communication hole 80 of the cylinder tube 16. When the free piston 60 is in the normal movement range, the communication hole 80 of the cylinder tube 16 is positioned between the upper and lower seal members 64U and 64L provided on the outer periphery of the free piston 60 as shown in FIGS. The communication hole 80 is closed with respect to the sub tank chamber 53 by the lower seal member 64L. When the free piston 60 further rises from the normal movement range to the highest end, the lower seal member 64L provided on the outer periphery of the free piston 60 is connected to the large inner diameter portion 72 on the inner periphery of the cylinder tube 16 as shown in FIG. When the lower seal member 64L reaches the lower end of the large inner diameter portion 72, the lower seal member 64L moves away from the inner periphery of the large inner diameter portion 72. Is opened to the sub tank chamber 53 through the sliding gap 81, and the sub tank chamber 53 communicates with the reservoir 30 outside the cylinder tube 16. The high-pressure surplus oil in the sub tank chamber 53 is discharged to the reservoir 30 through the sliding gap 81 and the communication hole 80 along the path indicated by the arrow in FIG. Further, the upper seal member 64U and the inner seal member 65 on the outer periphery of the free piston 60 always cause the air chamber 73 behind the free piston 60 to move against the sub tank chamber 53 and the air chamber 32 of the reservoir 30. Even cut off.

  In the front fork 10, the air chamber 32 of the reservoir 30 is adjusted to atmospheric pressure using the cylinder tube 16, the plug bolt 33 provided in the fork bolt 15 in this embodiment. Further, the air chamber 73 behind the free piston 60 is adjusted to atmospheric pressure by using the cylinder tube 16, the plug bolt 34 provided in the fork bolt 15 in this embodiment. Air that has entered the air chamber 32 of the reservoir 30 and the air chamber 73 behind the free piston 60 from the sliding portions of the vehicle body side tube 11 and the axle side tube 12 due to the expansion and contraction of the front fork 10 is externally supplied from the plug bolts 33 and 34. Can be exhausted. Further, the oil for increasing the air spring force by the air chamber 32 of the reservoir 30 can be supplied to the oil chamber 31 of the reservoir 30 by opening the plug bolt 33.

  However, in the sub-valve device 50, the volume of the air chamber 73 behind the free piston 60 is reduced by oil that has infiltrated from the seal members 64L, 64U, 65, or oil that has been injected due to misuse of the plug bolt 34, In order to avoid an abnormal increase in the pressure of the air chamber 73, the following configuration is provided.

  That is, the sub valve device 50 has a constant pressure in the air chamber 73 behind the free piston 60 in the communication path 90 that communicates the air chamber 73 behind the free piston 60 inside the cylinder tube 16 with the air chamber 32 of the reservoir 30. A check valve 100 is provided that opens when the pressure becomes higher than the value, and allows discharge of pressure from the air chamber 73 behind the free piston 60 to the air chamber 32 of the reservoir 30. That is, when the volume of the air chamber 73 behind the free piston 60 is reduced by the oil that has infiltrated from the seal members 64L, 64U, 65 or the oil that has been injected by misuse of the plug bolt 34, the pressure of the air chamber 73 is reduced. When the free piston 60 rises by a rise of the free piston 60 due to the compression stroke of the damper 14, the check valve 100 is opened by this high pressure and the pressure of the air chamber 73 is released to the air chamber 32 of the reservoir 30 via the communication path 90. To do. As a result, the oil and the oil injected into the air chamber 73 are discharged to the reservoir 30.

  At this time, an oil reservoir 66 having an annular interval surrounding the guide shaft 51 is provided at the bottom of the free piston 60 facing the air chamber 73 behind the free piston 60. A communication passage 91 extending from the oil reservoir 66 at the bottom of the free piston 60 to the outer periphery sandwiched between the upper seal member 64U and the lower seal member 64L of the free piston 60 is provided, and the check valve 100 is provided in the communication passage 91. . The communication path 90 is formed by a communication path 91 of the free piston 60, an area between the cylinder tube 16 and the free piston 60, which is sandwiched between the upper and lower seal members 64U and 64L, and a communication hole 80 of the cylinder tube 16. To be composed.

  As shown in FIG. 3B, the check valve 100 has a ball valve 102 seated on a valve seat of the valve chamber 101 that is a part of the communication passage 91 provided in the free piston 60, and is opened to the outer periphery of the free piston 60. A perforated plug 103 is screwed into a screw hole of the valve chamber 101 to be compressed, and a compression coil spring 104 is interposed between the ball valve 102 and the plug 103. The perforated plug 103 includes a tool engaging hexagonal hole 103A and a hole passage 103B that are also part of the communication passage 91. The high pressure in the air chamber 73 behind the free piston 60 allows the ball valve 102 of the check valve 100 to be pushed open.

According to the present embodiment, the following operational effects can be obtained.
(a) In the front fork 10 that blocks the air chamber 73 behind the free piston 60 from the air chamber 32 of the reservoir 30, a free passage is provided in the communication path 90 that connects the air chamber 73 behind the free piston 60 to the reservoir 30. A check valve 100 is provided that opens when the pressure of the air chamber 73 behind the piston 60 becomes higher than a certain value and allows the pressure release from the air chamber 73 behind the free piston 60 to the reservoir 30. As a result, oil that has permeated into the air chamber 73 behind the free piston 60 is discharged to the reservoir 30 via the communication path 90 and the check valve 100, and reduction of the volume of the air chamber 73 and an abnormal increase in pressure can be avoided. . Therefore, the air spring characteristic depending on the compression rate of the air chamber 73 behind the free piston 60 can be maintained at the initial setting, and the air chamber 73 can be prevented from being punctured at the maximum compression.

  (b) A communication hole 80 that communicates with the reservoir 30 is provided in the tube wall of the cylinder tube 16, and a lower seal member 64 </ b> L that slides on the lower outer periphery of the free piston 60 on the lower inner periphery below the communication hole 80 of the cylinder tube 16. And an upper seal member 64U that is in sliding contact with the upper inner periphery above the communication hole 80 of the cylinder tube 16 is provided on the upper outer periphery of the free piston 60, and the bottom of the free piston 60 that faces the air chamber 73 behind the free piston 60 A communication passage 91 extending from the oil reservoir 66 to the outer periphery sandwiched between the upper seal member 64U and the lower seal member 64L of the free piston 60 is provided, and the check valve 100 of the above-described (a) is provided in the communication passage 91. As a result, a communication path 90 that connects the air chamber 73 behind the free piston 60 to the reservoir 30 is formed in the free piston 60 and the cylinder tube 16, and the air chamber 73 behind the free piston 60 is infiltrated into the air chamber 73. Oil accumulated in the oil reservoir 66 can be discharged to the reservoir 30 via the communication path 90 (communication path 91 and communication hole 80) and the check valve 100.

  (c) When the free piston 60 is in a normal movement range due to the expansion / contraction stroke of the damper 14, the communication hole 80 is connected to the sub tank chamber 53 between the free piston 60 and the sub piston 52 by the lower seal member 64 </ b> L of the free piston 60. On the other hand, when the free piston 60 exceeds the normal moving range and rises to the highest rise end due to the high pressure surplus oil of the hydraulic oil that has entered the cylinder tube 16 from the reservoir 30, the lower seal member 64L of the free piston 60 Thus, the communication hole 80 is opened to the sub tank chamber 53 between the free piston 60 and the sub piston 52, and the sub tank chamber 53 communicates with the reservoir 30 outside the cylinder tube 16. While maintaining the air chamber 73 behind the free piston 60 against the air chamber 32 of the reservoir 30, the high-pressure surplus oil that has entered the cylinder tube 16 from the reservoir 30 directly from the sub-tank chamber 53. Therefore, the high pressure in the cylinder tube 16 can be avoided.

  (d) The free piston 60 is slidably provided not only on the inner periphery of the cylinder tube 16 but also on the outer periphery of the guide shaft 51. Accordingly, the oil that has penetrated into the air chamber 73 behind the free piston 60 through the seal members 64L, 64U, 65 provided on the outer periphery and the inner periphery of the free piston 60 is communicated as described above in (a) and (b). It can be discharged to the reservoir 30 via the path 90 and the check valve 100.

  (e) The fork bolt 15 is provided with a plug bolt 33 for the air chamber 32 of the reservoir 30 and a plug bolt 34 for the air chamber 73 behind the free piston 60. Therefore, the plug bolt 34 for the air chamber 73 behind the free piston 60 is inadvertently mistakenly opened as the plug bolt 33 for the air chamber 32 of the reservoir 30 and opens to the air chamber 73 behind the free piston 60. Even if the oil is misinjected, the injected oil can be discharged to the reservoir 30 via the communication path 90 and the check valve 100 described above (a) and (b).

  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.

  In the hydraulic shock absorber, the hydraulic shock absorber opens in a communication path that connects the air chamber behind the free piston inside the cylinder tube to the reservoir when the pressure of the air chamber behind the free piston becomes higher than a certain value. A check valve is provided that allows the pressure to be released from the air chamber behind the free piston to the reservoir. Therefore, it is possible to avoid the volume of the air chamber behind the free piston from being reduced due to the infiltration of oil or the like, and the pressure in the air chamber rising abnormally.

10 Front fork (hydraulic shock absorber)
11 Car body side tube 12 Axle side tube 14 Damper 15 Fork bolt 16, 16A, 16B Cylinder tube 20 Piston rod 30 Reservoir 32 Air chamber 33, 34 Plug bolt 42 Main piston 43A Piston side oil chamber 43B Rod side oil chamber 51 Guide shaft 52 Sub piston 53 Sub tank chamber 54 Pressure side flow path 54A Pressure side damping valve 60 Free piston 64L, 64U, 65 Seal member 70 Pressurizing spring 73 Air chamber 80 Communication hole 90 Communication path 91 Communication path 100 Check valve

Claims (5)

Insert the axle side tube slidably into the body side tube,
A main piston provided on a piston rod connected to the axle side tube inside the axle side tube is slidably inserted into a cylinder tube of a damper connected to the body side tube inside the body side tube. To divide the inside of the cylinder tube into a piston side oil chamber and a rod side oil chamber,
A sub-piston facing the main piston is provided above the main piston inside the cylinder tube, and the sub-piston chamber is defined above the piston-side oil chamber inside the cylinder tube by the sub-piston. A pressure-side damping valve is provided in the flow path that enables communication between the sub tank chamber and
A free piston facing the sub piston is slidably provided above the sub piston inside the cylinder tube.
A pressure spring that biases the free piston toward the sub-piston,
In the hydraulic shock absorber in which the air chamber behind the free piston inside the cylinder tube is blocked from the air chamber of the reservoir,
Opened when the pressure of the air chamber behind the free piston rises above a certain value in the communication path that connects the air chamber behind the free piston to the reservoir inside the cylinder tube, from the air chamber behind the free piston A hydraulic shock absorber provided with a check valve that allows release of pressure to a reservoir. A communication hole communicating with the reservoir is provided in the tube wall of the cylinder tube,
A lower seal member is provided on the lower outer periphery of the free piston to be in sliding contact with the lower inner periphery below the communication hole of the cylinder tube.
An upper seal member that is in sliding contact with the upper inner periphery above the communication hole of the cylinder tube is provided on the upper outer periphery of the free piston,
A communication passage extending from the bottom of the free piston facing the air chamber behind the free piston to an outer periphery sandwiched between the upper seal member and the lower seal member of the free piston is provided, and the check valve is provided in the communication passage. The hydraulic shock absorber according to 1. When the free piston is in a normal moving range due to the expansion / contraction stroke of the damper, the communication hole is closed with respect to the sub tank chamber between the free piston and the sub piston by the lower seal member of the free piston,
When the free piston exceeds the normal travel range and ascends to the highest end due to the high pressure surplus of hydraulic oil that has entered the cylinder tube from the reservoir, the free piston and the sub piston are connected to the communication hole by the lower seal member of the free piston. The hydraulic shock absorber according to claim 2, wherein the hydraulic tank is opened to a sub tank chamber between the two and the sub tank chamber communicated with a reservoir outside the cylinder tube.   The sub-piston is provided on a guide shaft connected to the cylinder tube by the damper, and a free piston facing the sub-piston is slidably provided on the inner periphery of the cylinder tube and the outer periphery of the guide shaft. Hydraulic shock absorber.   2. The damper has a cylinder tube with an open end closed by a fork bolt, and the fork bolt is provided with a plug bolt for a reservoir air chamber and a plug bolt for an air chamber behind a free piston. The hydraulic shock absorber in any one of -4.

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