JP5485061B2 - Hydraulic shock absorber - Google Patents

Description

  The present invention relates to a hydraulic shock absorber used for a motorcycle front fork or the like.

  As a hydraulic shock absorber, a damper cylinder is provided inside the outer tube and the inner tube, and in order to reduce the number of parts compared to the case where a piston is slidably contacted with the inner periphery of the damper cylinder, the number of components is described in Patent Document 1. As described above, there is one in which a piston is slidably contacted with an inner periphery of an inner tube without providing a damper cylinder.

  In this conventional hydraulic shock absorber, the inner tube is slidably inserted into the outer tube through bushes fixed to the inner circumferential opening of the outer tube and the outer circumferential tip of the inner tube. An annular oil chamber surrounded by the inner periphery of the outer tube, the outer periphery of the inner tube, and the two bushes is partitioned, a partition member is provided on the inner periphery of the inner tube, and an oil chamber is partitioned in the lower portion, An oil reservoir chamber is defined in the upper part, a piston rod attached to the outer tube is slidably inserted into the partition member, and is slidably contacted with the inner periphery of the inner tube at the tip of the piston rod inserted into the inner tube. A piston is provided, and the oil chamber is partitioned into a piston rod side oil chamber in which the piston rod is accommodated and a piston side oil chamber in which the piston rod is not accommodated. It communicates with the piston rod side oil chamber of the oil chamber through the oil hole provided in the inner tube.

  And a check valve for forming a cross-sectional area S1 of the annular oil chamber to be equal to or larger than a cross-sectional area S2 of the piston rod and preventing flow from the oil chamber to the oil reservoir chamber during the extension side stroke of the partition member. And the oil discharged from the annular oil chamber and the piston rod side oil chamber in the extension side stroke passes only through the communication path provided in the piston rod.

  Furthermore, the communication path is provided in the piston rod and opens to the piston-side oil chamber; a small hole provided in the piston rod that communicates the hollow portion with the piston rod-side oil chamber; Provided on the piston rod, the hollow portion is composed of a small hole communicating with the oil reservoir chamber.

  As a result, when the piston rod enters the inner tube in the pressure side stroke, the oil in the piston side oil chamber compressed by the piston flows out into the oil reservoir chamber through the hollow portion and small hole of the communication path. The compression side damping force is generated by the aperture resistance of the small hole. At the same time, the oil in the oil reservoir is supplied to the piston rod side oil chamber expanded by the piston via the check valve.

  In this pressure side stroke, the oil corresponding to the volume of the piston rod entering the inner tube is transferred from the piston rod side oil chamber of the inner tube to the annular oil chamber through the oil hole of the inner tube. At this time, since the volume increase ΔS1 (replenishment amount) of the annular oil chamber becomes equal to or greater than the volume increase ΔS2 of the piston rod, the shortage of (ΔS1−ΔS2) of the required oil replenishment amount to the annular oil chamber is oil. The piston rod side oil chamber, and thus the annular oil chamber, is replenished from the reservoir chamber via a check valve.

  In addition, when the piston rod retracts from the inner tube during the extension side stroke, the oil in the piston rod side oil chamber compressed by the piston does not flow into the oil reservoir chamber due to the presence of the check valve, and the small hole ( And the hollow portion) and flows into the piston side oil chamber, and the expansion side damping force is generated by the restriction resistance of the small hole.

  In this extension side stroke, the oil corresponding to the retracted volume of the piston rod that retreats from the inner tube is transferred from the annular oil chamber to the piston rod side oil chamber of the inner tube and eventually to the piston side oil chamber through the oil hole of the inner tube. . At this time, since the volume decrease ΔS1 (discharge amount) of the annular oil chamber becomes equal to or greater than the volume decrease ΔS2 of the piston rod, the excess amount (ΔS1−ΔS2) of the oil discharge amount from the annular oil chamber is the piston. The oil is discharged from the rod side oil chamber to the oil reservoir chamber through a small hole, a hollow portion and a small hole in the communication path.

JP2010-38172

  In the hydraulic shock absorber described in Patent Document 1, the inner tube has an annular oil chamber sandwiched between a bush fixed to the inner peripheral opening of the outer tube and a bush fixed to the outer peripheral tip of the inner tube. The piston rod side oil chamber communicates with the oil hole.

  For this reason, during the extension side stroke, a large oil pressure in the piston rod side oil chamber compressed by the piston acts on the annular oil chamber, reaches the bush of the opening of the outer tube, and eventually the oil seal, and the tip of the inner tube. Extends to the bush of the department.

  The oil pressure exerted on the oil seal at the opening of the outer tube increases the tension of the seal lip of the oil seal that is in close contact with the outer periphery of the inner tube and increases the friction. At the same time, the life of the oil seal is shortened, and oil leaks easily due to minute scratches on the seal lip.

  The oil pressure on the bush at the tip of the inner tube requires a high sealing performance for the bush, which again increases the friction.

  An object of the present invention is to provide a hydraulic shock absorber in which a piston is slidably contacted with an inner periphery of an inner tube, generating a damping force while expanding and contracting the piston rod, and having a large oil chamber in an outer tube, an inner tube bush and an oil seal. It is to improve the oil leakage toughness by preventing the oil pressure from reaching and to improve the seal life.

  According to the first aspect of the present invention, an inner tube is slidably inserted into the outer tube, an oil chamber is defined inside the inner tube by a partition member provided on the inner tube, and an oil reservoir chamber is provided above the inner chamber. The partition member is always disposed in the oil, the piston rod attached to the outer tube is slidably inserted into the partition member, and the inner tube is inserted at the tip of the piston rod inserted into the inner tube. The oil chamber is partitioned into a piston rod side oil chamber in which the piston rod is accommodated and a piston side oil chamber in which the piston rod is not accommodated. A check valve for preventing flow from the oil chamber to the oil reservoir and allowing flow from the oil reservoir to the oil chamber in a compression stroke; A flow path that connects the piston rod side oil chamber and the piston side oil chamber is provided on the lower end side, and a small hole that connects the oil chamber to the oil reservoir chamber is provided on the upper end side of the piston rod. A hydraulic shock absorber, wherein an upper and lower spring and a free piston sandwiched between the upper and lower springs are arranged inside the inner tube between the piston of the piston rod and the inner tube, and the free piston Is in sliding contact with the inner circumference of the inner tube, partitions the piston-side oil chamber with respect to the air chamber below it, and determines the spring strength of the upper spring and the lower spring, and the movement volume of the free piston The piston rod is set to be larger than the volume of entry / exit into the oil chamber.

  According to a second aspect of the present invention, in the first aspect of the present invention, the flow path connecting the piston rod side oil chamber and the piston side oil chamber is a hole-shaped flow path and / or the piston rod side oil chamber. From the piston side oil chamber to the piston rod side oil chamber, and a flow path with a check valve that allows the flow from the piston side oil chamber to the piston rod side oil chamber.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the piston rod further includes a hollow communication path, and a lower end of the hollow communication path is opened to the piston-side oil chamber. A small hole communicating with the oil reservoir chamber is opened at the upper end of the shape communication path.

  The invention according to claim 4 is the portion of the invention according to claim 3, which is a part of the piston rod that is constantly immersed in oil inside the hollow communication path, and is provided on the piston rod. A throttle channel is provided above the hole-shaped channel communicating with the piston rod side oil chamber.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, further comprising an outer periphery of the piston rod, around the small hole that is provided on the piston rod and communicates with the oil reservoir chamber. In addition, a check valve is provided for preventing the flow from the oil reservoir to the small hole and allowing the flow from the small hole to the oil reservoir.

(Claim 1)
(a) When the piston rod enters the inner tube in the pressure side stroke, the oil in the piston side oil chamber compressed by the piston flows through the small hole on the upper end side of the piston rod and flows into the oil reservoir chamber. The compression side damping force is generated by the diaphragm resistance.

  The oil in the piston side oil chamber passes through the flow path on the lower end side of the piston rod and is replenished to the piston rod side oil chamber expanded by the piston, and the compression side damping force is also generated by the throttle resistance of this flow path.

  At this time, the hydraulic pressure in the piston-side oil chamber defined by the free piston is increased according to the generation of the compression-side damping force due to the piston rod entering the inner tube. It moves downward to balance the air pressure of the side air chamber and the spring force of the lower spring. And by setting the spring strength of the upper and lower springs, the free piston movement volume ΔV1 (increase in the piston-side oil chamber) is larger than the piston rod oil chamber (piston-side oil chamber) entering volume. (ΔV1> ΔV2). Accordingly, the required replenishment amount of oil to the piston side oil chamber is (ΔV1−ΔV2), and this required replenishment amount is supplied from the oil reservoir chamber to the oil chamber (piston rod side oil chamber) via the check valve provided on the partition wall member. Will be replenished.

  (b) In the extension side stroke, when the piston rod retracts from the inner tube, the oil in the piston rod side oil chamber compressed by the piston does not flow into the oil reservoir chamber due to the presence of the check valve provided in the partition member, It flows into the piston-side oil chamber through the flow path on the lower end side of the piston rod, and the expansion-side damping force is generated by the throttle resistance of this flow path.

  At this time, the piston-side oil chamber defined by the free piston is expanded due to the above-mentioned withdrawal of the piston rod from the inner tube, and the oil pressure is reduced. It moves upward to balance the air pressure in the chamber and the spring force of the lower spring. And by setting the spring strength of the upper and lower springs, the free piston movement volume ΔV1 (decrease in the piston side oil chamber) is compared with the retraction volume ΔV2 from the piston rod oil chamber (piston side oil chamber). (ΔV1> ΔV2). Accordingly, the required amount of oil discharged from the piston side oil chamber is (ΔV1−ΔV2), and this required amount of discharge is discharged from the small hole on the upper end side of the piston rod to the oil reservoir chamber. The expansion side damping force is generated by the drawing resistance of the small hole.

  (c) High oil pressure in the oil chamber (piston side oil chamber or piston rod side oil chamber) in the inner tube compressed by expansion and contraction of the piston rod in both the pressure side stroke of (a) and the extension side stroke of (b) Stops inside the inner tube (and the hollow communication path of the piston rod) and does not reach the outside of the inner tube (such as an annular gap between the inner tube and the outer tube). This means that the large oil pressure in the oil chamber in the inner tube does not reach the outer tube and the upper and lower bushes of the inner tube and the oil seal at the opening of the outer tube. means. Therefore, high sealing performance is not required for the upper and lower bushes of the outer tube and the inner tube, and friction is not increased. Further, the tightening force of the seal lip of the oil seal that is in close contact with the outer periphery of the inner tube is not increased, the friction is not increased, the oil leakage toughness is improved, and the life of the oil seal can be extended.

  (d) In the present invention, by setting the spring strength of the upper and lower springs, the free piston moving volume ΔV1 is larger than the piston rod oil chamber (piston side oil chamber) entry / exit volume ΔV2. The reason for setting it to be large is as follows.

  If the free piston movement volume ΔV1 is smaller than the piston rod oil chamber (piston side oil chamber) entry / exit volume ΔV2 (ΔV1 <ΔV2), the oil stroke chamber is moved from the oil reservoir to the oil chamber. It becomes necessary to supply (ΔV2−ΔV1) of oil to the (piston side oil chamber). However, in the extension stroke, oil cannot be supplied from the oil reservoir chamber to the piston rod side oil chamber, and hence to the piston side oil chamber, due to the presence of the check valve provided on the partition wall member. Even if the hole can suck the upper air of the oil reservoir chamber, the lower oil of the oil reservoir chamber cannot be sucked, and oil cannot be supplied to the piston side oil chamber. That is, setting the free piston moving volume ΔV1 to be smaller than the piston rod oil chamber (piston rod side oil chamber) entry / exit volume ΔV2 can be achieved from the oil reservoir chamber required for the extension stroke to the oil chamber. Oil cannot be supplied to the (piston side oil chamber) and cannot be used.

(Claim 2)
(e) The flow path connecting the piston rod side oil chamber and the piston side oil chamber of the above (a) and (b) is a hole-shaped flow path and / or a flow from the piston rod side oil chamber to the piston side oil chamber. And a flow path with a check valve that allows the flow from the piston side oil chamber to the piston rod side oil chamber.

  If the flow path with a check valve is slightly conductive even in the extension side stroke (allows a slight flow from the piston rod side oil chamber to the piston side oil chamber), It becomes unnecessary.

(Claim 3)
(f) The piston rod has a hollow communication path, a lower end of the hollow communication path is opened in the piston-side oil chamber, and a small hole communicating with the oil reservoir chamber is formed at the upper end of the hollow communication path. By making it open, the communication path from the oil chamber inside the inner tube to the small hole on the upper end side of the piston rod can be easily formed by the hollow portion of the piston rod.

(Claim 4)
(g) A portion of the piston rod that is constantly immersed in the oil inside the hollow portion, and is provided above the small hole that is provided in the piston rod and communicates with the oil chamber on the piston rod side. A flow path was provided. Therefore, since the sealing performance of the partition member sealing the oil chamber inside the inner tube with respect to the oil reservoir chamber is not perfect, the oil reservoir via the small hole communicating with the oil reservoir chamber of the piston rod is used. The air in the chamber enters the hollow portion of the piston rod, the head pressure of the oil in the hollow portion of the piston rod leaks the oil in the oil chamber to the oil reservoir chamber, and the oil level in the hollow portion of the piston rod is the oil reservoir chamber Even in a state where it is lowered lower than the small hole communicating with the cylinder, the throttle channel is provided between the oil surface where the hollow portion of the piston rod is lowered and the hole-shaped channel communicating with the piston rod side oil chamber.

  Thus, even if the oil level of the hollow portion of the piston rod is lowered, the oil in the piston side oil chamber compressed by the piston flows upward in the hollow portion of the piston rod in the compression side stroke, It passes through the throttle channel immersed in oil, and generates a compression side damping force due to the throttle resistance of the throttle channel without a response delay.

(Claim 5)
(h) An outer periphery of the piston rod, the flow from the oil reservoir chamber to the small hole is prevented around the small hole provided on the piston rod and communicating with the oil reservoir chamber, A check valve was provided to allow flow from the hole to the oil reservoir. Therefore, even when the sealing performance of the partition member sealing the oil chamber inside the inner tube with respect to the oil reservoir chamber is not perfect, the oil is passed through the small hole communicating with the oil reservoir chamber of the piston rod. The air in the reservoir does not enter the hollow portion of the piston rod, and as a result, the head pressure of the oil in the hollow portion of the piston rod does not cause the oil in the oil chamber to leak into the oil reservoir.

  As a result, the hollow portion of the piston rod and the small hole are surrounded by the check valve and are always filled with oil, and the oil in the piston side oil chamber compressed by the piston in the pressure side stroke passes through the small hole in the oil. It flows into the reservoir and generates a compression side damping force due to the throttle resistance of the small hole without a response delay.

FIG. 1 is a sectional view showing the entire hydraulic shock absorber. FIG. 2 is a lower cross-sectional view of FIG. FIG. 3 is a top sectional view of FIG. FIG. 4 is an enlarged cross-sectional view of the main part of FIG. FIG. 5 is a sectional view showing a fastening structure of the fork bolt, the piston rod, and the mounting bolt.

  As shown in FIGS. 1 to 4, the hydraulic shock absorber (front fork for a motorcycle) 10 is fixed to the outer periphery of the inner end of the lower end opening of the outer tube 11 and the outer periphery of the upper end opening of the inner tube 12. The inner tube 12 is slidably inserted into the outer tube 11 through the bush 12A. An oil seal 11C and a dust seal 11D are stored in a seal case 11B connected to the lower end opening of the outer tube 11. A fork bolt 13 is screwed into the upper end opening of the outer tube 11 in a sealed state. A bottom piece 15 is inserted in a sealed state at the lower end opening of the inner tube 12 and is prevented from coming off by a retaining ring 16 attached to the inner periphery of the inner tube 12, and a bottom bracket 17 is provided at the outer periphery of the lower end of the inner tube 12. The bolt 18 inserted and inserted into the through hole in the bottom portion of the bottom bracket 17 from the outside is screwed to the bottom piece 15 to draw the bottom piece 15, and the bottom bracket 17 is provided at the lower end portion of the inner tube 12.

  The hydraulic shock absorber 10 defines an annular oil chamber 20 surrounded by the inner circumference of the outer tube 11, the outer circumference of the inner tube 12, and the two bushes 11A and 12A. The annular oil chamber 20 communicates with an oil chamber 22 </ b> A of an oil reservoir chamber 22, which will be described later, through an oil hole 20 </ b> A provided in the inner tube 12, and the volume change of the annular oil chamber 20 accompanying the expansion / contraction stroke of the outer tube 11 and the inner tube 12. In addition, the bushes 11A and 12A and the oil seal 11C are lubricated. However, in the hydraulic shock absorber 10, bushes are fixed to each of the inner periphery of the lower end opening of the outer tube 11 and the inner periphery of the intermediate portion of the outer tube 11, and the two bushes forming a fixed interval therebetween. The volume of the annular oil chamber sandwiched between the two can be kept unchanged.

  The hydraulic shock absorber 10 has a collar 31 with a lower annular plate (provided with a lower annular plate 32), an upper annular plate 33, a long collar 34, a washer on the inner periphery of the inner tube 12 whose inner diameter is increased stepwise. 35 are inserted in order, and these are caulked and held by the upper caulking portion 12B of the inner tube 12. The collar 31 with the lower annular plate and the upper annular plate 33 constitute a partition member 30 provided on the inner periphery of the inner tube 12. The oil chamber 21 is partitioned below the partition member 30 and the oil reservoir 22 is partitioned above. To do. In the oil reservoir chamber 22, the lower region is an oil chamber 22A, and the upper region is an air chamber 22B. The aforementioned oil hole 20 </ b> A provided in the inner tube 12 passes through the long collar 34 of the partition wall member 30, and always opens below the oil level of the oil chamber 22 </ b> A of the oil reservoir chamber 22.

  In the hydraulic shock absorber 10, the fork bolt 13 is sealed and screwed into the screw hole 37 of the upper end opening of the outer tube 11 via an O-ring 37 </ b> A, and the outer peripheral flange 13 </ b> A of the fork bolt 13 is connected to the upper end surface of the outer tube 11. Lock it against. The upper end portion of the piston rod 40 is screwed into the screw hole 38 provided on the central axis of the fork bolt 13 from one side of the fork bolt 13 (inside the shock absorber), and the upper end surface of the piston rod 40 is connected to the screw hole 38. Lock against the top surface. The tip screw portion of the mounting bolt 19 that is inserted from the stepped bolt hole 39 provided on the other side of the fork bolt 13 (outside of the shock absorber) and engages in the axial direction is the top screw portion of the hollow portion 61 of the piston rod 40. Screwed to 61A. The mounting bolt 19 locks the head 19 </ b> A against the stepped surfaces of the large diameter hole and the small diameter hole of the stepped bolt hole 39, and an O-ring 39 </ b> A between the small diameter hole of the bolt hole 39 and the upper end surface of the piston rod 40. It is sealed through. Thereby, the piston rod 40 is attached to the fork bolt 13.

  The fastening structure of the fork bolt 13, the mounting bolt 19 and the piston rod 40 is as follows. That is, in the hydraulic shock absorber 10, as described above, the fork bolt 13 is sealed to the upper end portion of the outer tube 11, and the piston rod 40 is screwed to the fork bolt 13 from one side of the fork bolt 13 (the inside of the shock absorber). The mounting bolt 19 engaged from the other side of the fork bolt 13 (outside the shock absorber) was screwed to the piston rod 40. At this time, the screw A (see FIG. 5) for screwing the piston rod 40 to the fork bolt 13 and the screw B (see FIG. 5) for screwing the mounting bolt 19 to the piston rod 40 were reversed to each other. That is, A is a left-hand thread and B is a right-hand thread. Or, A is a right-hand thread and B is a left-hand thread.

  The hydraulic shock absorber 10 slidably inserts a piston rod 40 attached to the fork bolt 13 of the outer tube 11 from the partition member 30 into the inner tube 12. A piston 41 that slides on the inner periphery of the inner tube 12 is provided at the tip of the piston rod 40 inserted into the inner tube 12. A piston ring 41 </ b> A is provided on the outer periphery of the piston 41. The piston 41 of the piston rod 40 divides the oil chamber 21 inside the inner tube 12 into a piston rod side oil chamber 21A in which the piston rod 40 is accommodated and a piston side oil chamber 21B in which the piston rod 40 is not accommodated.

  The hydraulic shock absorber 10 includes upper and lower suspension springs 42A and 42B between the lower end surface of the piston 41 facing the piston-side oil chamber 21B and the upper end surface of the bottom piece 15 facing the piston-side oil chamber 21B. And a later-described free piston 43 sandwiched between the upper and lower suspension springs 42A and 42B. The hydraulic shock absorber 10 absorbs the impact force received from the road surface when the vehicle travels by the expansion and contraction of the suspension springs 42A and 42B.

  In the hydraulic shock absorber 10, a stopper rubber 44 that contacts the lower surface of the fork bolt 13 is disposed around the outer periphery of the upper end of the piston rod 40, and a washer 46 that is backed up by a retaining ring 45 that is engaged with the outer periphery of the upper end of the piston rod 40 is stopped. Press against the lower surface of the rubber 44. When the hydraulic shock absorber 10 is most compressed, the upper end crimped portion 12B of the inner tube 12 abuts against the stopper rubber 44 via the washer 46, thereby restricting the maximum compression stroke.

  The hydraulic shock absorber 10 carries a rebound spring 47 disposed around the outer periphery of the lower end of the piston rod 40 on the upper surface of the piston 41. When the hydraulic shock absorber 10 is fully extended, the partition member 30 abuts on the rebound spring 47 to restrict the maximum extension stroke.

  However, in the hydraulic shock absorber 10, the free piston 43 strokes in contact with the inner periphery of the inner tube 12 and partitions the piston-side oil chamber 21 </ b> B with respect to the lower air chamber 23. The free piston 43 moves in accordance with the balance between the spring strength of the upper and lower suspension springs 42A and 42B, the oil pressure of the piston-side oil chamber 21B, and the air pressure of the air chamber 23 over the entire stroke. Compensate the volume of entry / exit into (piston rod side oil chamber 21A, piston side oil chamber 21B). In the pressure side stroke from the arbitrary stroke position of the hydraulic shock absorber 10, the oil pressure in the piston side oil chamber 21 </ b> B defined by the free piston 43 is increased as described later, and therefore the free piston 43 is moved from the arbitrary stroke position. Move downward. In the extension side stroke from the arbitrary stroke position of the hydraulic shock absorber 10, the oil pressure in the piston side oil chamber 21B defined by the free piston 43 is reduced as will be described later. Move upward from.

  In the present invention, the spring strength of the upper suspension spring 42A and the lower suspension spring 42B is set such that the movement volume ΔV1 of the free piston 43 (volume change amount of the air chamber 23) is the oil chamber 21 of the piston rod 40 (piston rod side oil chamber 21A). The volume is set to be larger (ΔV1> ΔV2) than the volume ΔV2 entering / exiting the piston-side oil chamber 21B). Thereby, in the pressure side stroke of the hydraulic shock absorber 10, it is necessary to replenish the amount of oil (ΔV1−ΔV2) from the oil chamber 22A of the oil reservoir chamber 22 to the piston side oil chamber 21B. In the extension side stroke, the piston side The amount of oil (ΔV1−ΔV2) is discharged from the oil chamber 21B to the oil reservoir chamber 22.

  Therefore, in the hydraulic shock absorber 10, the partition wall member 30 is prevented from flowing oil from the piston rod side oil chamber 21A to the oil reservoir chamber 22 in the extension stroke, and from the oil reservoir chamber 22 to the piston rod in the compression stroke. A partition wall check valve 50 is provided that allows the flow of oil to the side oil chamber 21A by the required replenishment amount (ΔV1−ΔV2). The partition check valve 50 is housed between the lower annular plate 32 and the upper annular plate 33 of the partition member 30, is shorter than the interval between the lower annular plate 32 and the upper annular plate 33, and is smaller in outer diameter than the inner diameter of the short collar 31. A cylindrical shape that slides up and down in contact with the outer periphery of the piston rod 40 is formed, and a lateral groove 51 is formed on the lower end surface. The partition check valve 50 is interposed between the lower annular plate 32 and a valve spring 52 made of a compression coil spring, and is biased toward the upper annular plate 33. In the pressure side stroke, the partition check valve 50 moves along with the piston rod 40 entering the inner tube 12 and moves downward, abuts on the lower annular plate 32, and forms a gap with the upper annular plate 33. The oil in the oil reservoir chamber 22 can be introduced from the lateral groove 51 into the piston rod side oil chamber 21A via its outer periphery. In the extension stroke, the partition check valve 50 moves along with the piston rod 40 that retreats from the inner tube 12, moves upward, abuts the upper annular plate 33, and closes the gap between the upper annular plate 33, The oil in the piston rod side oil chamber 21 </ b> A is prevented from being discharged into the oil reservoir chamber 22.

  The hydraulic shock absorber 10 is configured such that oil discharged from the piston rod side oil chamber 21 </ b> A to the oil reservoir chamber 22 through the extension side stroke passes only through the communication path 60 provided in the piston rod 40. The oil discharged from the piston side oil chamber 21 </ b> B to the oil reservoir 22 in the pressure side stroke is also configured to pass only the communication path 60.

  The communication path 60 of the present embodiment is provided in the piston rod 40 (including the piston 41) and provided in the hollow portion 61 that opens to the piston-side oil chamber 21B, and the lower end side of the piston rod 40 (including the piston 41). The piston rod side oil chamber 21A is connected to the hollow portion 61 and the piston side oil chamber 21B, and the flow path 62 is provided on the upper end side of the piston rod 40 to provide the hollow portion 61 and the oil chamber 21 (piston rod side oil chamber 21A. And a small hole 63 that directly communicates the piston side oil chamber 21 </ b> B) with the air chamber 22 </ b> B of the oil reservoir 22. The lower end of the hollow portion 61 opens directly to the piston-side oil chamber 21 </ b> B, and the small hole 63 opens directly to the upper end of the hollow portion 61.

  The flow path 62 provided on the lower end side of the piston rod 40 is provided on the lower end side of the piston rod 40, and the hole-like flow path 62A and / or the piston that directly communicates the hollow portion 61 with the piston rod side oil chamber 21A. 41 can be constituted by a flow path 62B with a check valve provided on the outer periphery of 41. The flow passage 62B with a check valve blocks the flow from the piston rod side oil chamber 21A to the piston side oil chamber 21B in the extension stroke, and the flow from the piston side oil chamber 21B to the piston rod side oil chamber 21A in the pressure side stroke. Allow. The valve body provided in the flow path 62B with the check valve is shared with the piston ring 41A of the piston 41.

  The hydraulic shock absorber 10 is a portion that is constantly immersed in the oil inside the hollow portion 61 that constitutes the communication path 60 of the piston rod 40, and is provided on the piston rod 40 and is provided on the piston rod side oil chamber 21 </ b> A. A throttle channel 71 is provided above the hole-shaped channel 62 </ b> A communicating with the channel. In the present embodiment, a hole-shaped throttle channel 71 is formed in the center of the throttle piece 70, and the throttle piece 70 is press-fitted into the hollow portion 61 of the piston rod 40 to be inserted and fixed.

  In the hydraulic shock absorber 10 of the present embodiment, the hollow portion 61, the hole-shaped flow path 62A, the flow path with check valve 62B, the small hole 63, and the throttle flow path 71 become a throttle that generates a damping force in the compression side stroke. The path 62A, the small hole 63, and the throttle channel 71 serve as a throttle that generates a damping force in the extension side stroke.

  The hydraulic shock absorber 10 is arranged on the outer periphery of the piston rod 40 around the small hole 63 provided on the piston rod 40 and communicating with the air chamber 22B of the oil reservoir 22 from the air chamber 22B of the oil reservoir 22 to the piston. A check valve 80 for preventing the flow of the rod 40 to the hollow portion 61 is provided.

  The check valve 80 can be made of an elastic body such as rubber, or can be made of another material or mechanism. In this embodiment, the check valve 80 is shared with the stopper rubber 44 that regulates the maximum compression stroke of the inner tube 12, and is sandwiched between the inner surface of the fork bolt 13 and the washer 46 around the piston rod 40. It is set.

The check valve 80 according to the present embodiment is formed of an annular body that surrounds the outer periphery around the small hole 63 of the piston rod 40. An annular space 80A (FIG. 5) defined between the lower portion of the main body 81 of the check valve 80 and the outer periphery around the small hole 63 of the piston rod 40 is defined by an annular lip 82 provided on the upper inner periphery of the main body 81. The oil communicates with the hollow portion 61 and the oil chamber 21 of the piston rod 40 through the hole 63 and is always filled with the oil in the oil chamber 21 and the hollow portion 61. The oil flowing out from the annular space 80 </ b> A to the oil reservoir 22 pushes and opens the lip 82 of the check valve 80, rotates around the outer periphery of the lateral groove 83 provided at the upper portion of the main body 81 and the main body 81, and the oil chamber of the oil reservoir 22. Drop to 22A.
The check valve 80 also constitutes a damping valve that generates a damping force in the compression side stroke.

The hydraulic shock absorber 10 operates as follows.
(Pressure side stroke)
In the compression side stroke, an oil flow indicated by a solid arrow in FIG. 4 is generated.
That is, when the piston rod 40 enters the inner tube 12 in the pressure side stroke, the oil in the piston-side oil chamber 21B compressed by the piston 41 is the hollow portion 61 of the connecting passage 60 of the piston rod 40, the throttle passage 71, the upper end. Passing through the small hole 63 on the side, the check valve 80 is pushed open and flows out into the oil reservoir chamber 22, and the compression side damping force is generated by the restriction of the hollow portion 61, the throttle channel 71 and the small hole 63.

  The oil in the piston-side oil chamber 21B passes through the flow path 62 (hole-shaped flow path 62A, check valve-equipped flow path 62B) on the lower end side of the piston rod 40, and is expanded by the piston 41. The pressure side damping force is also generated by the throttle resistance of the flow path 62 (hole flow path 62A, check valve-equipped flow path 62B).

  At this time, the hydraulic pressure in the piston-side oil chamber 21B defined by the free piston 43 is increased according to the generation of the compression-side damping force due to the entry of the piston rod 40 into the inner tube 12, and free The piston 43 moves downward so as to balance the air pressure of the lower air chamber 23 and the spring force of the lower suspension spring 42B. Then, by setting the spring strength of the upper and lower suspension springs 42A and 42B, the movement volume ΔV1 of the free piston 43 (the increase in the piston-side oil chamber 21B) is changed to the oil chamber 21 (piston-side oil chamber 21B) of the piston rod 40. It is set so as to be larger than the volume of entry into (ΔV1> ΔV2). Therefore, the required replenishment amount of oil to the piston side oil chamber 21B is (ΔV1−ΔV2), and this required replenishment amount is transferred from the oil reservoir chamber 22 to the oil chamber 21 ( The piston rod side oil chamber 21A) is replenished.

(Extension process)
In the extension side stroke, an oil flow indicated by a one-dot chain line arrow in FIG. 4 is generated.
That is, in the extension stroke, when the piston rod 40 retreats from the inner tube 12, the oil in the piston rod side oil chamber 21 </ b> A compressed by the piston 41 is stored in the oil reservoir due to the presence of the partition check valve 50 provided in the partition member 30. It does not flow into the chamber 22 but flows into the piston-side oil chamber 21B through the flow path 62 (hole-shaped flow path 62A) on the lower end side of the piston rod 40, and the throttle resistance of this flow path 62 (hole-shaped flow path 62A). To generate the extensional damping force.

  At this time, the piston-side oil chamber 21B defined by the free piston 43 is expanded due to the withdrawal of the piston rod 40 from the inner tube 12, and the oil pressure is reduced. It moves upward so as to balance the air pressure of the lower air chamber 23 and the spring force of the lower suspension spring 42B. Then, by setting the spring strength of the upper and lower suspension springs 42A and 42B, the moving volume ΔV1 of the free piston 43 (reduced amount of the piston side oil chamber 21B) is changed to the oil chamber 21 (piston side oil chamber 21B) of the piston rod 40. It is set to be larger than the withdrawal volume ΔV2 from (ΔV1> ΔV2). Accordingly, the required amount of oil discharged from the piston-side oil chamber 21B is (ΔV1−ΔV2), and this required amount of discharge is the hollow portion 61 of the connecting passage 60 of the piston rod 40, the throttle passage 71, and the small hole 63 on the upper end side. To the oil reservoir 22. The expansion side damping force is generated by the throttle resistance of the hollow portion 61, the throttle channel 71, and the small hole 63.

Therefore, according to the present embodiment, the following operational effects can be obtained.
(a) Large oil in the oil chamber 21 (piston side oil chamber 21B or piston rod side oil chamber 21A) in the inner tube 12 compressed by expansion and contraction of the piston rod 40 in both the compression side stroke and the extension side stroke of the hydraulic shock absorber 10 The pressure stops inside the inner tube 12 (and the hollow communication path 60 of the piston rod 40) and does not reach the outside of the inner tube 12 (such as the annular oil chamber 20 of the inner tube 12 and the outer tube 11). This is because the outer tube 11 and the bushes 11A and 12A above and below the inner tube 12 and the oil seal 11C at the opening of the outer tube 11 are disposed outside the inner tube 12 and the oil chamber in the inner tube 12. It means that the big oil pressure of 21 does not reach. Therefore, the upper and lower bushes 11A and 12A of the outer tube 11 and the inner tube 12 do not require high sealing performance, and the friction is not increased. Further, the tightening force of the seal lip of the oil seal 11C that is in close contact with the outer periphery of the inner tube 12 does not increase, the friction is not increased, the oil leakage toughness is improved, and the life of the oil seal 11C is extended. it can.

  (b) The flow path 62 provided on the lower end side of the piston rod 40 and communicating the piston rod side oil chamber 21A and the piston side oil chamber 21B is formed from the hole-shaped flow path 62A and / or the piston rod side oil chamber 21A. It can be constituted by a flow path 62B with a check valve that prevents the flow to the side oil chamber 21B and allows the flow from the piston side oil chamber 21B to the piston rod side oil chamber 21A.

  In addition, if the flow path 62B with the check valve is slightly conductive even in the extension side stroke (allows a slight flow from the piston rod side oil chamber 21A to the piston side oil chamber 21B), the above-described hole flow path is provided. The combined use of 62A becomes unnecessary.

  (c) The piston rod 40 has a hollow communication path 60, the lower end of the hollow communication path 60 opens into the piston-side oil chamber 21 </ b> B, and the oil reservoir chamber 22 is formed at the upper end of the hollow communication path 60. By opening the small hole 63 communicating with the inner tube 12, the communication path 60 of the oil chamber 21 inside the inner tube 12 to the small hole 63 on the upper end side of the piston rod 40 is formed by the hollow portion 61 of the piston rod 40. Easy to form.

  (d) The portion of the piston rod 40 that is constantly immersed in the oil inside the hollow portion 61 and is provided in the piston rod 40 and communicates with the piston rod side oil chamber 21A. A throttle channel 71 is provided at a higher level. Therefore, since the sealing performance of the partition member 30 that seals the oil chamber 21 in the inner tube 12 with respect to the oil reservoir chamber 22 is not perfect, the small size communicating with the oil reservoir chamber 22 of the piston rod 40 is small. The air in the oil reservoir 22 enters the hollow portion 61 of the piston rod 40 via the hole 63, and the head pressure of the oil in the hollow portion 61 of the piston rod 40 leaks the oil in the oil chamber 21 to the oil reservoir 22. Even when the oil surface of the hollow portion 61 of the piston rod 40 is lowered below the small hole 63 communicating with the oil reservoir chamber 22, the oil surface and the piston rod side oil of the hollow portion 61 of the piston rod 40 are lowered. A throttle channel 71 is provided between the hole-shaped channel 62A communicating with the chamber 21A.

  Thus, even if the oil level of the hollow portion 61 of the piston rod 40 is lowered, the oil in the piston-side oil chamber 21B compressed by the piston 41 flows upward in the hollow portion 61 of the piston rod 40 in the compression stroke. It is sure to pass through the throttle channel 71 immersed in the oil of the hollow portion 61, and the compression side damping force due to the throttle resistance of the throttle channel 71 is generated without a response delay.

  (e) The flow from the oil reservoir chamber 22 to the small hole 63 around the small hole 63 provided on the piston rod 40 and communicating with the oil reservoir chamber 22 on the outer periphery of the piston rod 40 Is provided, and a check valve 80 is provided to allow the flow from the small hole 63 to the oil reservoir 22. Therefore, even when the sealing performance of the partition member 30 that seals the oil chamber 21 in the inner tube 12 with respect to the oil reservoir chamber 22 is not perfect, it communicates with the oil reservoir chamber 22 of the piston rod 40. The air in the oil reservoir chamber 22 does not enter the hollow portion 61 of the piston rod 40 via the small hole 63, and as a result, the head pressure of the oil in the hollow portion 61 of the piston rod 40 increases the oil in the oil chamber 21. Will not leak into the oil reservoir 22.

  Thereby, the hollow portion 61 of the piston rod 40 and the small hole 63 are surrounded by the check valve 80 and are always filled with oil, and the oil in the piston-side oil chamber 21B compressed by the piston 41 in the pressure side stroke is contained in the oil. It flows into the oil reservoir chamber 22 through the small hole 63, and the compression side damping force due to the throttle resistance of the small hole 63 is generated without a response delay.

  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.

  The present invention slidably inserts an inner tube into an outer tube, partitions an oil chamber inside the inner tube by a partition member provided on the inner tube, partitions an oil reservoir chamber on the top thereof, The partition member is always placed in oil, a piston rod attached to the outer tube is slidably inserted into the partition member, and the inner end of the inner tube is placed at the tip of the piston rod inserted into the inner tube. A piston in sliding contact, and the oil chamber is partitioned into a piston rod side oil chamber in which the piston rod is accommodated and a piston side oil chamber in which the piston rod is not accommodated. A check valve that prevents the flow to the oil reservoir and allows the flow from the oil reservoir to the oil chamber in the pressure side stroke is provided on the lower end side of the piston rod, A hydraulic shock absorber provided with a flow path communicating the piston rod side oil chamber and the piston side oil chamber, and having a small hole communicating the oil chamber with the oil reservoir chamber on the upper end side of the piston rod. In the inner tube, an upper and lower spring and a free piston sandwiched between the upper and lower springs are arranged between the piston included in the piston rod and the inner tube, and the free piston is the inner tube. The piston-side oil chamber is partitioned from the lower air chamber, the spring strength of the upper spring and the lower spring is determined, and the movement volume of the free piston is the volume of the piston rod. It set so that it might become large compared with the approach / exit volume to an oil chamber. As a result, in the hydraulic shock absorber in which the piston is slidably contacted with the inner periphery of the inner tube, a damping force is generated while the piston rod is expanded and contracted. The oil leakage toughness can be improved and the seal life can be improved.

DESCRIPTION OF SYMBOLS 10 Hydraulic buffer 11 Outer tube 12 Inner tube 21 Oil chamber 21A Piston rod side oil chamber 21B Piston side oil chamber 22 Oil reservoir chamber 23 Air chamber 30 Partition member 40 Piston rod 41 Piston 42A Upper suspension spring (upper spring)
42B Lower suspension spring (lower spring)
43 Free piston 50 Check valve 60 Communication path 61 Hollow part 62 Flow path 62A Hole-shaped flow path 62B Flow path with check valve 63 Small hole 71 Restriction flow path 80 Check valve

Claims (5)

Insert the inner tube slidably into the outer tube,
An oil chamber is defined inside the inner tube by a partition member provided in the inner tube, an oil reservoir chamber is defined on the upper portion thereof, and the partition member is always disposed in the oil.
A piston rod attached to the outer tube is slidably inserted into the partition member,
The piston rod inserted into the inner tube is provided with a piston slidably in contact with the inner periphery of the inner tube, and the oil chamber includes a piston rod side oil chamber in which the piston rod is accommodated and a piston side in which the piston rod is not accommodated. Partition into an oil chamber,
The partition member is provided with a check valve that prevents the flow from the oil chamber to the oil reservoir in the extension stroke, and allows the flow from the oil reservoir to the oil chamber in the compression stroke,
Provided on the lower end side of the piston rod is a flow path that connects the piston rod side oil chamber and the piston side oil chamber;
A hydraulic shock absorber provided with a small hole communicating the oil chamber with the oil reservoir chamber on the upper end side of the piston rod,
Inside the inner tube, an upper and lower spring and a free piston sandwiched between the upper and lower springs are arranged between the piston provided in the piston rod and the inner tube,
The free piston is in sliding contact with the inner periphery of the inner tube, and the piston-side oil chamber is partitioned from the air chamber below it,
A hydraulic shock absorber in which the spring strength of the upper spring and the lower spring is set so that the moving volume of the free piston is larger than the volume of the piston rod entering / exiting the oil chamber.   A flow path communicating the piston rod side oil chamber and the piston side oil chamber prevents a flow from the hole-shaped flow path and / or the piston rod side oil chamber to the piston side oil chamber. 2. The hydraulic shock absorber according to claim 1, comprising a flow passage with a check valve that allows a flow from a chamber to the piston rod side oil chamber.   The piston rod has a hollow communication path, the lower end of the hollow communication path is opened to the piston-side oil chamber, and a small hole communicating with the oil reservoir chamber is opened to the upper end of the hollow communication path. The hydraulic shock absorber according to claim 1 or 2.   The part of the piston rod that is constantly immersed in the oil inside the hollow communication path, above the hole-shaped flow path that is provided on the piston rod and communicates with the oil chamber on the piston rod side, The hydraulic shock absorber according to claim 3, wherein a throttle channel is provided.   The outer periphery of the piston rod is provided around the small hole provided on the piston rod and communicated with the oil reservoir chamber, and the flow from the oil reservoir chamber to the small hole is prevented, and the small hole The hydraulic shock absorber according to any one of claims 1 to 4, further comprising a check valve that allows flow to the oil reservoir chamber.

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