JP2020008128A - Shock absorber - Google Patents

Abstract

To provide a shock absorber which suppresses sudden change of a damping force to improve riding comfort of a vehicle.SOLUTION: Axial lengths of a plurality of grooves 3a,3b,3c,3d provided along an axial direction on an inner circumference of a cylinder 1 are longer than an axial length of a piston 2, one of other grooves overlaps at least one groove over a length of the axial length of the piston 2 or more in a circumferential direction, at least one groove is formed so as to be protruded to one end side of axial direction of the cylinder 1 with respect to the other grooves at least one groove is formed so as to be protruded to the other end side in axial direction of the cylinder 1 with respect to the other grooves, when the piston 2 exists in a prescribed range with respect to the cylinder 1, at least one of respective grooves 3a,3b,3c,3d functions as a bypass passage BP and, when the piston 2 enters to the inside from the outside of the prescribed range and when the piston gets out to the outside from the inside of the prescribed range, a channel cross-section area of the bypass passage BP is gradually changed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a shock absorber.

  The shock absorber is interposed between the vehicle body and the axle, for example, and suppresses the vehicle body vibration by a damping force exerted during expansion and contraction, thereby improving the riding comfort of the vehicle.

  However, if the damping force exerted by the shock absorber is too large, the riding comfort of the vehicle may be rather deteriorated. Therefore, there is a shock absorber that reduces the damping force with respect to the operation of the piston in a specific range to improve riding comfort.

  Specifically, in such a shock absorber, a plurality of grooves longer than the axial length of the piston are provided in the inner circumference of the cylinder along the axial direction. While the piston is opposed to the groove, the groove functions as a bypass that bypasses the damping passage provided in the piston and that communicates between the expansion-side chamber and the compression-side chamber defined by the piston and defined in the cylinder. . As a result, while the piston is opposed to the groove, a part of the liquid in the cylinder bypasses the damping passage and moves back and forth between the extension side chamber and the compression side chamber through the groove.

  Therefore, during the expansion and contraction operation of the shock absorber, while the piston is at the stroke position facing the groove, the flow rate of the liquid passing through the damping passage relatively decreases by the flow rate of the liquid passing through the groove. Reduces the damping force exerted by.

JP 2009-293664 A

  However, in the conventional shock absorber, the same groove is provided in the same circumferential direction of the cylinder. Therefore, when the piston strokes to the end of the groove, all the grooves are simultaneously communicated or blocked, so that the damping force rapidly changes before and after opening and closing the groove.

  As described above, in the conventional shock absorber, when the piston strokes to the end of the groove, the damping force changes abruptly, and there is a possibility that the riding comfort of the vehicle may be deteriorated.

  Therefore, an object of the present invention is to provide a shock absorber that suppresses a sudden change in damping force and improves the riding comfort of a vehicle.

  Means for solving the above problems are a piston which is slidably inserted into a cylinder having a plurality of grooves provided in the inner periphery along the axial direction to partition the inside of the cylinder into an extension side chamber and a compression side chamber. A damping passage communicating the extension side chamber and the compression side chamber, wherein the axial length of each of the grooves is longer than the axial length of the piston, and at least one of the grooves is one of other grooves. One is overlapped in the circumferential direction with a length equal to or longer than the axial length of the piston, and at least one groove is formed so as to protrude from the other groove toward one end in the axial direction of the cylinder, and at least one groove is formed. Grooves are formed so as to protrude toward the other axial end of the cylinder with respect to other grooves, and when the piston is within a predetermined range with respect to the cylinder, at least one or more of the grooves has the damping. Bypass the passage and with the extension side chamber The bypass passage communicates with the pressure storage side chamber to function as a bypass, and when the piston enters from outside the predetermined range and exits from within the predetermined range, the flow passage cross-sectional area of the bypass gradually increases. It is characterized by changing to.

  Further, a buffer may be provided in which at least one of the grooves has a different axial length. According to this configuration, since the relatively short groove and the relatively long groove in the axial direction are arranged in the circumferential direction, a portion that does not overlap with the other short grooves in the longest groove in the circumferential direction is different from the other grooves. It becomes a protruding part. Therefore, when the piston enters from inside the predetermined range and goes out of the predetermined range, the cross-sectional area of the bypass passage gradually changes.

  Further, the buffer may be configured such that the grooves are shifted from each other in the axial direction of the cylinder. According to this configuration, one end of the groove arranged on one side in the axial direction of each groove and the other end of the groove arranged on the other side in the axial direction of each groove are respectively different from each other. It becomes a part projecting from the groove. Therefore, when the piston enters from inside the predetermined range and goes out of the predetermined range, the cross-sectional area of the bypass passage gradually changes.

  Further, each of the grooves may be a shock absorber arranged at equal intervals in a circumferential direction of the cylinder. According to this configuration, since the grooves are uniformly arranged in the circumferential direction of the cylinder, the strength of the cylinder is not deviated and the durability is excellent.

  Further, the buffer may be such that the cross-sectional area of the one end and the other end of at least one of the grooves gradually decreases toward the end. According to this configuration, a sudden change in the damping force can be further suppressed.

  ADVANTAGE OF THE INVENTION According to the shock absorber of this invention, the rapid change of damping force is suppressed and the riding comfort of a vehicle can be made favorable.

It is front sectional drawing of the shock absorber which concerns on this Embodiment. FIG. 3 is a view showing a state where the cylinder according to the present embodiment is expanded. 4 is a graph showing a relationship between a stroke position of a piston and a flow path cross-sectional area of a bypass according to the present embodiment. It is a modification of the cylinder concerning this embodiment, and is a figure showing an expanded state. (A) is a partial enlarged sectional view showing a first modified example of the groove according to the present embodiment, and (b) is a partially enlarged sectional view showing a second modified example of the groove according to the present embodiment. It is a front view.

  The present embodiment will be described below with reference to the drawings. The same reference numbers throughout the several figures indicate the same or corresponding parts.

  The shock absorber D according to the present embodiment includes a cylinder 1 having a plurality of grooves 3a, 3b, 3c, and 3d provided on an inner periphery along an axial direction, and a cylinder 1 slidably inserted into the cylinder 1 1 is provided with a piston 2 that divides the inside of the chamber 1 into an extension chamber R1 and a compression chamber R2.

  Hereinafter, each part of the shock absorber D will be described in detail. As shown in FIG. 1, an outer shell 10 that covers the cylinder 1 is arranged on the outer periphery of the cylinder 1, and a reservoir R <b> 3 is formed in an annular gap between the outer shell 10 and the cylinder 1.

  A rod 4 connected to a piston 2 and movable in the axial direction is inserted into the cylinder 1. Further, an annular rod guide 11 that closes the upper ends of the cylinder 1 and the outer shell 10 in the drawing and that supports the rod 4 is provided at the upper end of the cylinder 1 and the outer shell 10 in the drawing. Further, an annular seal member 12 whose inner periphery is in sliding contact with the outer periphery of the rod to seal the outer periphery of the rod is stacked on the upper end of the rod guide 11 in the drawing. Further, a valve case 13 for partitioning the pressure side chamber R2 and the reservoir R3 is attached to a lower end of the cylinder 1 in the drawing.

  Then, by caulking the upper end of the outer shell 10 in the drawing, the cylinder 1 is sandwiched between the valve case 13 and the rod guide 11, and the cylinder 1 is fixed in the outer shell 10.

  The expansion side chamber R1 and the compression side chamber R2 are filled with liquid, and the reservoir R3 is filled with gas and liquid. In the present embodiment, the liquid is hydraulic oil, but the liquid may be another liquid such as water, an aqueous solution, an electrorheological fluid, or a magnetic viscous fluid.

  The piston 2 is provided with an expansion-side passage 5 and a compression-side passage 6 as damping passages that connect the expansion-side chamber R1 and the compression-side chamber R2. The expansion side passage 5 is provided with a damping valve 7 that allows only the passage of the liquid from the expansion side chamber R1 to the compression side chamber R2 and gives resistance to the flow of the liquid. On the other hand, the pressure side passage 6 is provided with a check valve 8 that allows only the passage of the liquid from the pressure side chamber R2 to the expansion side chamber R1.

  Further, the valve case 13 permits only the passage of the liquid from the pressure side chamber R2 to the reservoir R3 and also allows the passage of the liquid from the reservoir R3 to the pressure side chamber R2, which gives resistance to the flow of the liquid. And a check valve 15.

  As shown in FIG. 2, grooves 3a, 3b, 3c, 3d extending in the axial direction and having an axial length longer than the axial length of the piston 2 are formed in the inner circumference of the cylinder 1 in the circumferential direction. Are provided side by side. The number of grooves is not particularly limited as long as it is two or more, and may be arbitrarily determined. Further, each of the grooves 3a, 3b, 3c, 3d always overlaps with one of the other grooves in the circumferential direction. In other words, each of the grooves 3a, 3b, 3c, 3d overlaps at least one of the other grooves by a length equal to or greater than the axial length of the piston 2 in the circumferential direction. These grooves 3a, 3b, 3c, 3d are provided near the axial center of the cylinder 1 where the piston 2 is located when the piston 2 is at the neutral position. Here, the neutral position is an axial position of the piston 2 in the shock absorber D to which no vibration is input when the shock absorber D is attached to the vehicle.

  When such a groove is provided on the inner periphery of the piston 2, for example, when the piston 2 is displaced downward from the upper position of the groove in FIG. 1, until the upper end of the piston 2 gets over the upper end of the groove, The groove communicates only with the compression-side chamber R2 and cuts off communication with the extension-side chamber R1. Further, the groove communicates with the expansion chamber R1 and the compression chamber R2 until the upper end of the piston 2 rides over the upper end of the groove and the lower end of the piston 2 reaches the lower end of the groove, bypasses the attenuation passage, and extends the expansion chamber R1. And functions as a bypass BP that communicates with the pressure side chamber R2. Then, when the lower end of the piston 2 gets over the lower end of the groove, the groove communicates only with the extension side chamber R1, and the communication with the pressure side chamber R2 is cut off.

  Therefore, when the piston 2 is in a range where at least one groove communicates with the extension-side chamber R1 and the compression-side chamber R2 (hereinafter, referred to as a “predetermined range”), at least one of the grooves functions as a bypass path BP, When it is out of the predetermined range, each groove 3a, 3b, 3c, 3d does not function as the bypass BP.

  The grooves 3a, 3b, 3c, and 3d are formed such that at least one groove is formed so as to protrude toward one end in the axial direction of the cylinder 1 with respect to the other groove, and at least one groove is formed in another groove. On the other hand, it is formed to protrude toward the other axial end of the cylinder 1.

  Therefore, when the piston 2 is displaced, all the grooves 3a, 3b, 3c, 3d are not shut off or communicated at the same time. Therefore, as shown in FIG. , The cross-sectional area of the bypass passage BP determined by the total cross-sectional area of the grooves 3a, 3b, 3c, 3d in the same circumferential direction gradually changes.

  As shown in FIG. 3, when the piston 2 enters from outside the predetermined range and exits from within the predetermined range, the flow path cross-sectional area of the bypass passage BP should be gradually changed. The grooves 3a, 3b, 3c, 3d may be provided in the cylinder 1 as follows. A specific example of the plurality of grooves 3a, 3b, 3c, 3d provided on the inner circumference of the cylinder 1 will be described. For example, as shown in FIG. 2, grooves 3a, 3b, 3c, and 3d having different axial lengths are provided on the inner periphery of the cylinder 1, and these grooves 3a, 3b, 3c, and 3d are arranged such that the center in the axial direction is the cylinder. They are arranged at equal intervals in the circumferential direction so as to be at the same position in one axial direction.

  In this manner, as shown in FIG. 2, one end, which is the upper end in the drawing, of the longest groove 3a in the axial direction is one end of the cylinder 1 from the other grooves 3b, 3c, 3d. The other end, which is the lower end in the drawing of the groove 3a, protrudes upward and projects downward from the other grooves 3b, 3c, 3d, which is the other end of the cylinder 1, in the drawing.

  When the piston 2 is displaced upward or downward in FIG. 1 from the neutral position, as the piston 2 moves, the piston 2 is cut off in order from the groove having the shorter axial length, and the cross-sectional area of the bypass passage BP gradually decreases. Become smaller. Further, when the end of the piston 2 is displaced beyond the end of the groove 3a, the piston 2 is disposed outside the predetermined range, so that the grooves 3a, 3b, 3c, 3d do not function as the bypass BP.

  Conversely, when the piston 2 is displaced from the outside of the predetermined range toward the neutral position, the piston 2 communicates in order from the groove having the longer axial length, and the cross-sectional area of the bypass passage BP gradually increases. Then, when the groove 3d having the shortest axial length communicates, the flow path cross-sectional area of the bypass BP becomes maximum.

  Accordingly, as shown in FIG. 3, the flow passage cross-sectional area of the bypass passage BP gradually increases with the displacement of the piston 2 from the upper end to the lower end with respect to the cylinder 1, reaches a maximum at the center, and gradually moves to the lower end side. Changes to decrease.

  Therefore, if a groove is provided on the inner periphery of the cylinder 1 as shown in FIG. 2, all the grooves 3a, 3b, 3c, 3d are not shut off or communicated at the same time during the stroke of the piston 2, so that the piston 2 When entering the inside from outside and inside the predetermined range, the cross-sectional area of the bypass passage BP gradually changes.

  As another example of the plurality of grooves 3a, 3b, 3c, 3d provided on the inner circumference of the cylinder 1, as shown in FIG. 4, they are provided side by side in the circumferential direction of the cylinder 1 and have the same axial length. A plurality of grooves 3a, 3b, 3c, 3d that overlap with each other in the circumferential direction may be arranged so as to be shifted from each other in the axial direction.

  In this way, as shown in FIG. 4, the groove 3a, which is arranged at the upper end in the drawing, which is the one end side of the cylinder 1 among the grooves 3a, 3b, 3c, 3d, becomes the other grooves 3b, 3c, 3d. 3d, which protrudes upward in the drawing, and among the grooves 3a, 3b, 3c, 3d, the groove 3d disposed at the lower end in the drawing, which is the other end of the cylinder 1, is the other groove 3a, 3b, 3c. Project downward from the figure.

  When the piston 2 is displaced upward in FIG. 1 from the neutral position, the piston 3 blocks the groove 3d, which is disposed at the lowest position in the figure, in the order of the groove 3c, the groove 3b, and the groove 3a. The road cross section gradually decreases. When the piston 2 is displaced downward from the neutral position in FIG. 1, the piston 3 blocks the groove 3a, which is disposed at the uppermost position, in the order of the groove 3b, the groove 3c, and the groove 3d, and gradually bypasses the bypass passage BP. Channel cross-sectional area becomes smaller. Further, when the piston 2 is displaced beyond the end of the groove 3a or the groove 3d, the piston 2 is disposed outside the predetermined range, so that the grooves 3a, 3b, 3c, 3d do not function as the bypass BP.

  Conversely, when the piston 2 is displaced toward the neutral position from a state in which the piston 2 is located above the predetermined range in the figure, the grooves 3a, 3c, and 3d are communicated in this order from the groove 3a, which is the uppermost part in the figure. , The cross-sectional area of the bypass passage BP gradually increases. Further, when the piston 2 is displaced from a state where it is arranged below the predetermined range in the figure toward the neutral position, the piston 3 communicates in the order of the groove 3d, the groove 3c, the groove 3b, and the groove 3a from the lowest groove in the figure. The cross-sectional area of the bypass passage BP gradually increases. When all the grooves 3a, 3b, 3c, 3d communicate with each other, the cross-sectional area of the bypass BP becomes maximum.

  Therefore, as shown in FIG. 3, the flow path cross-sectional area of the bypass passage BP gradually increases with the displacement of the piston 2 from the upper end to the lower end with respect to the cylinder 1, reaches a maximum at the center, and gradually moves to the lower end side. Changes to decrease.

  Therefore, if a groove is provided on the inner periphery of the cylinder 1 as shown in FIG. 4, all the grooves 3a, 3b, 3c, 3d are not cut off or communicated at the same time during the stroke of the piston 2, so that the piston 2 has a predetermined range. In the case of entering from the outside and the case of exiting from within the predetermined range, the cross-sectional area of the bypass passage BP changes gradually.

  The configuration of the plurality of grooves 3a, 3b, 3c, 3d provided on the inner periphery of the cylinder 1 shown in FIGS. 2 and 4 is an example, and these grooves 3a, 3b, 3c, 3d are pistons. All grooves 3a, 3b, 3c, 3d are designed so that the cross-sectional area of the bypass passage BP changes gradually when 2 enters the outside of the predetermined range and goes out of the predetermined range. What is necessary is just to be provided so that it may not be interrupted or communicated simultaneously.

  Specifically, at least one of the grooves 3a, 3b, 3c, 3d is formed so as to protrude toward one end of the cylinder 2 with respect to the other grooves, and at least one of the grooves 3a, 3b, 3c, 3d is formed as another groove. On the other hand, it may be formed so as to protrude toward the other end of the cylinder 2.

  Next, the operation of the shock absorber D will be described. First, the liquid in the compression side chamber R2, which is compressed when the shock absorber D contracts, moves via the compression side passage 6 into the expansion side chamber R1 which expands, and the rod 4 enters the cylinder 1; The liquid of the intrusion volume becomes excessive in the cylinder 1. Therefore, the excess liquid is discharged from the pressure side chamber R2 to the reservoir R3 via the base valve 14. Thus, the compression damping force based on the resistance of the base valve 14 is exerted, and the reservoir R3 performs volume compensation.

  Conversely, when the shock absorber D extends, the liquid in the expansion side chamber R1 to be compressed moves to the expanding compression side chamber R2 via the expansion side passage 5 and the rod 4 withdraws from the inside of the cylinder 1. The liquid corresponding to the exit volume of 4 is insufficient in the cylinder 1. Therefore, the insufficient liquid is supplied from the reservoir R3 into the cylinder 1 via the check valve 15. Thus, the extension side damping force based on the resistance of the damping valve 7 is exerted, and the volume is compensated by the reservoir R3.

  In addition, during the expansion and contraction operation of the shock absorber D, at least one of the plurality of grooves 3a, 3b, 3c, 3d provided on the inner periphery of the cylinder 1 while the piston 2 is within a predetermined range with respect to the cylinder 1. Functions as a bypass passage BP, so that the expansion-side chamber R1 and the compression-side chamber R2 communicate with each other via the bypass passage BP.

  Therefore, during the extension operation of the shock absorber D, part of the liquid that moves from the extension side chamber R1 to the compression side chamber R2 via the extension side passage 5 moves from the extension side chamber R1 to the compression side chamber R2 via the bypass path BP.

  Accordingly, while the piston 2 is within the predetermined range, the flow rate of the liquid passing through the damping valve 7 provided in the middle of the extension side passage 5 is reduced by the flow rate of the liquid flowing through the bypass passage BP. Decrease. Thereby, the damping force in the specific range of the operation of the piston 2 is reduced, and the riding comfort of the vehicle can be improved.

  Further, the plurality of grooves 3a, 3b, 3c, 3d constituting the bypass passage BP are formed such that all the grooves 3a, 3b, 3c, 3d are not simultaneously cut off or communicated during the stroke of the piston 2. . Therefore, when the piston 2 enters from outside the predetermined range and goes out of the predetermined range, the flow path cross-sectional area of the bypass passage BP gradually changes, so that the extension damping force of the shock absorber D decreases. Sudden changes are suppressed, and the riding comfort of the vehicle is improved.

  In the present embodiment, the shock absorber D is of a double-cylinder type including the cylinder 1 and the outer shell 10. However, the outer shell 10 and the valve case 13 are eliminated, and a free piston is provided below the cylinder 1. A single-cylinder type shock absorber may be provided to form an air chamber in the cylinder 1. In the case of the single cylinder type as described above, the free piston moves in the axial direction to expand and contract the air chamber, thereby compensating for the volume change in the cylinder corresponding to the rod projecting and retracting volume due to the expansion and contraction operation of the shock absorber D. .

  When the shock absorber D is of a single cylinder type and a damping valve is provided in the middle of the pressure side passage 6 of the piston 2, even when the shock absorber D is contracted, the pressure on the pressure side is equal to the flow rate of the liquid flowing through the bypass passage BP. The flow rate of the liquid passing through the damping valve provided in the middle of the passage 6 decreases. Therefore, not only the extension damping force but also the compression damping force while the piston 2 is within the predetermined range can be reduced.

  As described above, the shock absorber D according to the present embodiment has a plurality of grooves provided in the inner circumference of the cylinder 1 along the axial direction, and the shafts of the grooves 3a, 3b, 3c, 3d are provided. The axial length is longer than the axial length of the piston 2, and at least one groove overlaps at least one groove in the circumferential direction with a length equal to or greater than the axial length of the piston 2. Is formed so as to protrude toward one axial end of the cylinder 1 with respect to another groove, and at least one groove is formed so as to protrude toward the other axial end of the cylinder 1 with respect to the other groove. When the piston 2 is within a predetermined range with respect to the cylinder 1, at least one or more of the grooves 3a, 3b, 3c, 3d bypasses the extension side passage 5 as a damping passage and connects to the extension side chamber R1 and the compression side. And communicates with the chamber R2 to function as a bypass passage BP. When going out from among the case and the predetermined range enters from the outside to the inside of the predetermined range, the flow path cross-sectional area of the bypass passage BP is made to vary gradually.

  According to this configuration, all the grooves 3a, 3b, 3c, and 3d are not blocked or communicated at the same time during the stroke of the piston 2, so that the piston 2 enters from outside the predetermined range and into the predetermined range. , The cross-sectional area of the bypass passage BP gradually changes. Therefore, a sudden change in the damping force of the shock absorber D is suppressed, and the riding comfort of the vehicle is improved.

  In addition, the length of at least one of the grooves 3a, 3b, 3c, 3d is made different in the axial direction so that all the grooves 3a, 3b, 3c, 3d are simultaneously cut off or actuated during the stroke of the piston 2. Communication may not be required.

  In this way, if the axial length of at least one of the grooves 3a, 3b, 3c, 3d is different, the end of the groove having the longer axial length is shifted from the other groove in the axial direction. Since the flow passage cross-sectional area of the bypass passage BP gradually changes by the amount of the protrusion, a sudden change in the damping force of the shock absorber D can be suppressed as compared with the related art. However, as shown in FIG. 2, when the axial lengths of the grooves 3a, 3b, 3c, 3d are different from each other, the change in the damping force can be made more gentle.

  In the example of FIG. 2, the width of each groove 3a, 3b, 3c, 3d is set to be equal, but the width of each groove 3a, 3b, 3c, 3d is not particularly limited.

  Further, as shown in FIG. 4, the grooves 3a, 3b, 3c, 3d are arranged so as to be shifted from each other in the axial direction of the cylinder 1, so that all the grooves 3a, 3b, 3c, 3d May not be simultaneously blocked or communicated.

  As described above, if the grooves 3a, 3b, 3c, 3d are arranged so as to be displaced from each other in the axial direction of the cylinder 1, the bypass passage BP is displaced in the axial direction from the other grooves by the amount of the groove protruding. Since the cross-sectional area of the flow path gradually changes, a sudden change in the damping force of the shock absorber D can be suppressed as compared with the related art.

  In FIG. 4, the axial lengths of the grooves 3a, 3b, 3c, 3d are all set to be equal, but the axial lengths of the grooves 3a, 3b, 3c, 3d are different from each other. You may. Further, the width of each groove 3a, 3b, 3c, 3d shown in FIG. 4 is set equal, but the width of each groove 3a, 3b, 3c, 3d is not particularly limited.

  In the example of FIG. 4, the grooves 3a, 3b, 3c, and 3d are arranged so as to be shifted from each other in the axial direction of the cylinder 1. However, at least one of the grooves 3a, 3b, 3c, and 3d is formed. The end may be arranged so as to be shifted from the remaining other groove to one side in the axial direction, and the end of at least one groove may be arranged so as to be shifted from the remaining other groove to the other side. Even in this case, all the grooves 3a, 3b, 3c, 3d are not simultaneously cut off or communicated during the stroke of the piston 2, so that a sudden change in the damping force of the shock absorber D can be suppressed as compared with the conventional case.

  As described above, the configuration of the plurality of grooves 3a, 3b, 3c, 3d provided on the inner periphery of the cylinder 1 shown in FIGS. 2 and 4 is an example, and these grooves 3a, 3b, 3c are examples. , 3d are all grooves 3a, 3b such that the cross-sectional area of the bypass passage BP changes gradually when the piston 2 enters from outside the predetermined range and when the piston 2 exits from the predetermined range. , 3c, 3d may be provided so as not to be cut off or communicated all at once.

  Further, in the present embodiment, as shown in the graph of FIG. 3, the cross-sectional area of the bypass passage BP gradually decreases from the axial center of the cylinder 1 toward both ends. However, the flow path cross-sectional area of the bypass path BP only needs to be gradually changed at least when the piston 2 enters from outside the predetermined range and when the piston 2 exits from within the predetermined range. Accordingly, the flow path cross-sectional area of the bypass passage BP other than when the piston 2 enters from outside the predetermined range and when the piston 2 exits from within the predetermined range can be arbitrarily set.

  Also, in the present embodiment, the grooves 3a, 3b, 3c, 3d are arranged at equal intervals in the circumferential direction of the cylinder 1, but these grooves 3a, 3b, 3c, 3d are arranged at arbitrary intervals. May be arranged. However, if the grooves 3a, 3b, 3c, 3d are arranged uniformly in the circumferential direction of the cylinder 1, the strength of the cylinder 1 will not be uneven, and the durability will be excellent.

  Further, as shown in FIG. 5A, the ends of the grooves 3a, 3b, 3c, 3d are tapered, or as shown in FIG. 5B, the ends of the grooves 3a, 3b, 3c, 3d are formed. The section may be narrowed down, for example, by tapering, so that the cross-sectional area of one end and the other end of each of the grooves 3a, 3b, 3c, 3d gradually decreases toward the end.

  According to this configuration, when the piston 2 enters from outside the predetermined range and goes out of the predetermined range, the cross-sectional area of the bypass passage BP changes more gently. Abrupt changes in force are further suppressed.

  Means for gradually reducing the cross-sectional area of one end and the other end of each of the grooves 3a, 3b, 3c, 3d shown in FIGS. 5 (a) and 5 (b) is an example. However, the present invention is not limited to the examples shown in FIGS.

  As described above, the preferred embodiments of the present invention have been described in detail. However, it is obvious that modifications, variations, and changes can be made without departing from the scope of the claims.

DESCRIPTION OF SYMBOLS 1 ... Cylinder, 2 ... Piston, 3a, 3b, 3c, 3d ... Groove, 5 ... Damping path (extension side path), D ... Shock absorber, R1 ... Extension side chamber, R2: Pressure side chamber, BP: Bypass path

Claims (5)

A cylinder having a plurality of grooves provided in the inner periphery along the axial direction,
A piston which is slidably inserted into the cylinder and partitions the inside of the cylinder into an extension side chamber and a compression side chamber,
A damping passage communicating the extension side chamber and the compression side chamber,
The axial length of each groove is longer than the axial length of the piston, and at least one of the other grooves overlaps in the circumferential direction with a length equal to or greater than the axial length of the piston. ,
At least one groove is formed so as to protrude toward one axial end of the cylinder with respect to another groove, and at least one groove protrudes toward the other axial end of the cylinder with respect to another groove. Is formed,
When the piston is in a predetermined range with respect to the cylinder, at least one or more of each groove bypasses the attenuation passage and communicates with the extension side chamber and the compression side chamber to function as a bypass path,
A shock absorber wherein the cross-sectional area of the bypass passage changes gradually when the piston enters from outside the predetermined range and when the piston exits from within the predetermined range. The shock absorber according to claim 1, wherein at least one of the grooves has a different axial length. The shock absorber according to claim 1, wherein the grooves are shifted from each other in an axial direction of the cylinder. The shock absorber according to any one of claims 1 to 3, wherein the grooves are arranged at regular intervals in a circumferential direction of the cylinder. The buffer according to any one of claims 1 to 4, wherein a cross-sectional area of one end and the other end of at least one of the grooves gradually decreases toward the end. vessel.

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