JP6063312B2 - Shock absorber - Google Patents

Description

  The present invention relates to an improved shock absorber.

  Conventionally, in this type of shock absorber, a cylinder, a piston that is slidably inserted into the cylinder and divides the cylinder into an extension side chamber and a pressure side chamber, a piston rod connected to the piston, A damping passage communicating the extension side chamber and the pressure side chamber; a bypass passage provided in the piston rod to bypass the damping passage and communicating the extension side chamber and the pressure side chamber; and provided in the bypass passage. Some include a relief valve that opens under the pressure of the extension side chamber (see, for example, Patent Document 1).

  In such a shock absorber, during the extension stroke, until the relief valve opens, resistance is given to the flow of liquid passing through the damping passage. Therefore, until the relief valve is opened, the damping force with respect to the piston speed is reduced. The characteristic shows that the damping force gradient becomes relatively large, and the flow path area increases after the relief valve is opened, so that the damping force gradient becomes small.

  The shock absorber that exhibits the damping force characteristics as described above has a damping force because the relief valve opens and releases the pressure from the expansion side chamber to the compression side chamber when the piston speed is extended to reach the high speed region. It is possible to suppress the excessive damping force and to improve the riding comfort in the vehicle.

JP 2010-007817 A

  As described above, the conventional shock absorber is very useful in that the ride comfort in the vehicle can be improved. However, the vibration amplitude input to the shock absorber is large and the extension speed is high. In this case, the shock absorber is fully extended when the relief valve is opened and the damping force reaches a peak, so that the cushion provided on the piston rod of the shock absorber and the rod guide that supports the piston rod vigorously. There is a possibility that the shock and the hitting sound when the shock absorber is extended will increase and the ride comfort in the vehicle will be deteriorated due to frequent collisions.

  Accordingly, the present invention has been developed to improve the above-described problems, and the object of the present invention is to reduce the shock and hitting sound at the time of drawing and improve the riding comfort in the vehicle. It is to provide a shock absorber that can.

  In order to solve the above-described object, the problem solving means in the present invention includes a cylinder, a piston that is slidably inserted into the cylinder, and divides the cylinder into an extension side chamber and a pressure side chamber, and is connected to the piston. A piston rod, a damping passage communicating the extension side chamber and the pressure side chamber, a bypass path provided in the piston rod, bypassing the damping passage and communicating the extension side chamber and the pressure side chamber, and the bypass A shock absorber provided with a relief valve that is provided in a passage and opens upon receiving the pressure of the extension side chamber, and includes a telescopic shutter member that is formed of a plurality of cylindrical members having different diameters and can be expanded and contracted, and the shutter An outermost cylinder member disposed on the outermost periphery of the member is fixed to the cylinder, and an innermost cylinder member disposed on the innermost periphery of the shutter member is fixed to the piston rod. When the piston rod is displaced by a predetermined amount in the compression direction with respect to the cylinder from a neutral position, the flow passage area of the bypass passage is reduced by the innermost cylindrical member. To do.

  Even when the shock absorber is extended and the relief valve is open and the damping force is prevented from becoming excessive, in the situation where the shutter member reduces the flow area of the bypass passage, The damping force can be increased, and the piston speed can be decreased.

  Therefore, according to the shock absorber of the present invention, it is possible to improve the ride comfort in the vehicle by reducing the shock and sound of stroking.

It is a longitudinal cross-sectional view of the shock absorber in one embodiment. It is a longitudinal cross-sectional view of the shock absorber in one embodiment in the extended state. It is a figure which shows the characteristic of the damping force with respect to the piston speed of the buffer in one Embodiment. It is a longitudinal cross-sectional view of the shock absorber in one modification of one embodiment.

  Hereinafter, the present invention will be described with reference to the drawings. As shown in FIG. 1, the shock absorber D <b> 1 in the embodiment of the present invention is slidably inserted into the cylinder 1 and is divided into two extension side chambers R <b> 1 and a pressure side chamber R <b> 2. A piston 2, a piston rod 3 connected to the piston 2, damping passages 4, 5 communicating with the extension side chamber R 1 and the pressure side chamber R 2, and provided in the piston rod 3 to bypass the damping passages 4, 5. A bypass passage B communicating the extension side chamber R1 and the pressure side chamber R2, a relief valve 6 provided in the bypass passage B and opened by receiving the pressure of the extension side chamber R1, and a shutter member S; It is interposed between the vehicle body and the axle of the vehicle to generate a damping force and suppress the vibration of the vehicle body.

  A base valve (not shown) is provided below the cylinder 1 in the figure, and a reservoir R is provided between the cylinder 1 and the outer cylinder 19 that covers the outer periphery of the cylinder 1. The cylinder 1 is filled with a liquid such as hydraulic oil, and the reservoir R is filled with a liquid and a gas. In addition to the hydraulic oil, for example, a liquid such as water or an aqueous solution can be used as the liquid.

  Hereinafter, each part will be described in detail. First, the piston rod 3 has a small diameter portion 3a formed on the lower end side in FIG. 1, and a screw portion 3b formed on the distal end side of the small diameter portion 3a. Further, the upper end side in FIG. 1 of the piston rod 3 is projected outward through an annular rod guide 7 mounted on the inner periphery of the upper end in FIG. 1 of the cylinder 1. The rod guide 7 is provided with a cylindrical bush 8 on the inner periphery, and supports the piston rod 3 inserted into the bush 8 so that the piston rod 3 moves in the axial direction which is the vertical direction in FIG. To guide you. Further, a seal member U that seals between the cylinder 1 and the piston rod 3 is laminated above the rod guide 7 in FIG. 1, and the inside of the cylinder 1 is kept liquid-tight.

  A flange-like rebound stopper 9 is mounted on the outer periphery of the piston rod 3 above the small diameter portion 3a. The upper end of the rebound stopper 9 in FIG. 1 is mounted on the outer periphery of the piston rod 3. An annular rebound cushion 10 is laminated. Further, the piston rod 3 has a vertical hole 3c extending in the axial direction from the tip, which is the lower end in FIG. 1, and an extension side chamber opening from the upper vicinity of the rebound cushion 10 in FIG. 1 to communicate the extension side chamber R1 with the vertical hole 3c. A side hole 3d and a small-diameter portion 3a and a horizontal hole 3e that opens from the upper side in FIG. 1 to the screw hole 3b and communicates with the vertical hole 3c are provided. In addition, the ball F is driven into the opening end of the longitudinal hole 3c on the tip end side of the piston rod 3 and is closed.

  The extension side chamber side hole 3d constitutes an opening on the extension side chamber side of the bypass passage B, and when the piston rod 3 is displaced from the neutral position by a predetermined amount in the direction of compressing the extension side chamber R1 with respect to the cylinder 1, the shutter member. S blocks the extension side chamber side hole 3d to reduce the flow passage area of the bypass passage B.

  The piston 2 is formed in an annular shape, and the small diameter portion 3a of the piston rod 3 is inserted on the inner peripheral side thereof. Specifically, the piston 2 includes a disk portion 2a having an expansion side port 2b and a pressure side port 2c communicating with the expansion side chamber R1 and the pressure side chamber R2, and a cylinder 1 that rises from the outer periphery of the disk portion 2a downward in FIG. And a cylindrical skirt 2d that is in sliding contact with the inner peripheral surface.

  Further, a leaf valve V1 is stacked on the lower end of the disk portion 2a of the piston 2 in FIG. 1, and the leaf valve V1 is fixed to the piston rod 3 on the inner peripheral side, and the extension port 2b of FIG. It opens and closes the openings at the middle and lower ends.

  The leaf valve V1 is a laminated leaf valve formed by laminating a plurality of annular plates. When the leaf valve V1 is bent by the pressure of the extension side chamber R1, only the flow of liquid from the extension side chamber R1 to the pressure side chamber R2 is opened by opening the extension side port 2b. The flow is resisted while allowing the flow to flow in the opposite direction, but the extension side port 2b is blocked against the flow of the liquid in the opposite direction, and the extension side port 2b is one-way. Is set. The extension side port 2b and the leaf valve V1 constitute an attenuation passage 4. The number of annular plates forming the leaf valve V1 can be arbitrarily set according to the damping force characteristics required for the shock absorber D1.

  On the other hand, a leaf valve V2 is stacked on the upper end of the disk portion 2a of the piston 2 in FIG. 1, and the leaf valve V2 is fixed to the piston rod 3 on the inner peripheral side, and the pressure side port 2c in FIG. The upper end opening is opened and closed.

  The leaf valve V2 is a laminated leaf valve formed by laminating a plurality of annular plates. When the leaf valve V2 is bent by the pressure of the pressure side chamber R2, the pressure side port 2c is opened, and only the flow of liquid from the pressure side chamber R2 toward the extension side chamber R1 is allowed. Although resistance is given to the flow while allowing, the pressure side port 2c is blocked by blocking the pressure side port 2c against the liquid flow in the opposite direction, and the pressure side port 2c is set to be one-way. ing. The pressure side port 2c and the leaf valve V2 constitute a damping passage 5. The number of annular plates forming the leaf valve V2 can be arbitrarily set according to the damping force characteristic required for the shock absorber D1.

  The leaf valve V1 is a damping valve that generates an expansion-side damping force when the shock absorber D1 is extended, and the other leaf valve V2 is a damping valve that generates a compression-side damping force when the shock absorber D1 is contracted. Even when the expansion side port 2b and the compression side port 2c are closed by the leaf valves V1, V2, the expansion side chamber R1 and the compression side chamber R2 are communicated with each other by a known orifice (not shown). The orifice is formed, for example, by providing a notch on the outer periphery of the leaf valves V1, V2, or by providing a recess in the valve seat on which the leaf valves V1, V2 are seated. In addition to the configuration in which the orifice and the leaf valves V1, V2 coexist, the damping valve can adopt a configuration in which the choke is coexisted in the leaf valves V1, V2, a configuration of only the choke and the orifice, or only the leaf valve. A poppet valve can also be employed.

  From the above, the shock absorber D1 is set to a so-called single rod type in which the piston 2 is connected to the tip of the piston rod 3. Therefore, as the buffer D1 expands and contracts, the total volume of the expansion side chamber R1 and the compression side chamber R2 changes depending on the volume of the piston rod 3 that moves forward and backward in the cylinder 1. By supplying to the cylinder 1 or discharging from the cylinder 1 to the reservoir R, the change in the total volume is compensated. As described above, since the shock absorber D1 is set to a double cylinder type, the volume change is compensated for by installing the reservoir R. However, when the single cylinder type is set, the shock absorber D1 is disposed below the cylinder 1. A sliding partition may be provided and an air chamber may be installed to compensate for the volume change. In this case, the shock absorber D1 may be set to a double rod type instead of a single rod type.

  A valve stopper 12, a leaf valve V2, a piston 2, and a leaf valve V1 that limit the amount of bending of the leaf valve V2 are assembled to the small diameter portion 3a of the piston rod 3 from above in FIG. Fixed.

  Further, below the leaf valve V1 in FIG. 1, an annular spacer 11, a pressure side valve disk 16, and a pressure side relief valve 15 formed by laminating an annular plate, an annular spacer 14, a valve disk 13, and an annular plate are sequentially formed. Relief valves 6 formed by laminating are laminated, and these members are assembled to the outer periphery of the small diameter portion 3 a of the piston rod 3. Each member assembled to the small diameter portion 3a of the piston rod 3 including the valve stopper 12, the leaf valve V2, the piston 2, and the leaf valve V1 is attached to the piston rod 3 by a piston nut 17 screwed to the screw portion 3b. It is fixed. Instead of closing the opening end of the longitudinal hole 3c on the tip end side of the piston rod 3 with the ball F, the piston nut 17 may be used as a cap nut to close the opening of the longitudinal hole 3c.

  The valve disk 13 is annular and is assembled at the outer periphery of the small-diameter portion 3a of the piston rod 3 and stacked below the spacer 14 in FIG. 1, and is formed at the opposite end of the piston, which is the lower end in FIG. An annular window 13a that faces the pressure side chamber R2, a passage 13b that opens from the piston side end that is the upper end in FIG. 1 and communicates with the annular window 13a, an annular groove 13c that is provided on the inner periphery, and an annular groove 13 c and a communication groove 13 d that communicates with the passage 13 b. When the valve disc 13 is assembled to the small diameter portion 3a of the piston rod 3 as described above, the annular groove 13c is opposed to the lateral hole 3e formed in the piston rod 3, and the annular window 13a is connected to the passage 13b and the communication groove 13d. The annular groove 13c, the lateral hole 3e, the vertical hole 3c, and the extension side chamber side hole 3d are communicated with the extension side chamber R1.

  The annular window 13a is opened and closed by a relief valve 6 stacked on the opposite end of the valve disk 13 from the piston side. The relief valve 6 is configured by laminating a plurality of annular plates. The inner peripheral side is fixed to the piston rod 3 and the outer peripheral side is allowed to bend. The relief valve 6 is given an initial deflection, and a valve opening pressure is set when the annular window 13a is opened by the initial deflection. When the pressure of the expansion side chamber R1 is received from the annular window 13a side and the differential pressure between the expansion side chamber R1 and the pressure side chamber R2 reaches the valve opening pressure, the relief valve 6 bends and opens the passage 13b, thereby allowing the expansion side chamber R1 to be compressed. It communicates with the chamber R2 and allows the flow of liquid from the extension side chamber R1 toward the compression side chamber R2. On the other hand, the relief valve 6 closes the annular window 13a to block the flow of liquid from the pressure side chamber R2 to the extension side chamber R1. From the above description, in this embodiment, the bypass passage B includes the annular window 13a formed in the valve disk 13, the passage 13b, the communication groove 13d and the annular groove 13c, and the lateral hole 3e formed in the piston rod 3. The vertical hole 3c and the extension side chamber side hole 3d are configured. The number of annular plates constituting the relief valve 6 and the initial deflection applied to the relief valve 6 can be arbitrarily set according to the characteristics desired for the relief valve 6 and the valve opening pressure.

  Subsequently, an annular spacer 14 is laminated on the upper end in FIG. 1 which is the piston side end of the valve disk 13, and a pressure side relief valve 15 is laminated on the upper side of the spacer 14 in FIG. 1, a pressure side valve disk 16 is laminated on the upper side.

  The compression side valve disc 16 is annular and is the outer periphery of the small diameter portion 3a of the piston rod 3, and is formed on the annular window 16a formed at the non-piston side end which is the lower end in FIG. 1, and the piston which is the upper end in FIG. A passage 16b that opens from the side end and communicates the pressure side chamber R2 with the annular window 16a and a partition cylinder 16c that rises from the outer periphery of the non-piston side end are configured.

  As described above, when the valve disk 13 is stacked on the pressure side valve disk 16 via the spacer 14 and the pressure side relief valve 15, the valve disk 13 is fitted to the inner periphery of the partition cylinder 16c provided on the outer periphery of the pressure side valve disk 16. Thus, in cooperation with the pressure side valve disk 16, a chamber 18 partitioned from the pressure side chamber R2 is formed. The room 18 faces the communication groove 13d and communicates with the extension side chamber R1. An annular window 16 a provided on the pressure side valve disk 16 faces the room 18. Therefore, the passage 16b provided in the pressure side valve disk 16 is communicated with the expansion side chamber R1 via the annular window 16a communicating with the chamber 18. A seal ring may be interposed between the pressure side valve disk 16 and the partition cylinder 16c in order to make the sealing performance perfect. The partition wall cylinder 16c may be integrated with the valve disk 13 instead of the pressure side valve disk 16, or may be mounted on the outer periphery of both as a separate body from the valve disk 13 and the pressure side valve disk 16.

  The annular window 16 a in the pressure side valve disc 16 is opened and closed by a pressure side relief valve 15 stacked on the opposite side end of the pressure side valve disc 16.

  The pressure side relief valve 15 is configured by laminating a plurality of annular plates, and the inner peripheral side is fixed to the piston rod 3 and the outer peripheral side is allowed to bend. Further, the pressure-side relief valve 15 is given an initial deflection, and a valve opening pressure when the annular window 16a is opened by the initial deflection is set. When the pressure side relief valve 15 receives the pressure of the pressure side chamber R2 from the annular window 16a side and the pressure difference between the pressure side chamber R2 and the expansion side chamber R1 reaches the valve opening pressure, the pressure side relief valve 15 bends and opens the passage 16b. The pressure side chamber R2 is communicated with the expansion side chamber R1 via the pressure to allow the flow of liquid from the pressure side chamber R2 toward the expansion side chamber R1. In contrast, the pressure side relief valve 15 closes the annular window 16a to block the flow of liquid from the expansion side chamber R1 to the pressure side chamber R2. From the above, in this embodiment, the pressure relief valve 15 is provided in the bypass passage B in parallel with the relief valve 6. The pressure side relief valve 15 can be abolished if unnecessary. Further, the number of the annular plates constituting the pressure side relief valve 15 and the initial deflection applied to the pressure side relief valve 15 can be arbitrarily set according to the characteristics desired for the pressure side relief valve 15 and the valve opening pressure.

  In this case, the spacer 14 may be integrated with the valve disk 13, and the bent pressure side relief valve 15 is prevented from interfering with the valve disk 13 while suppressing the inner periphery of the pressure side relief valve 15.

  In this embodiment, the shutter member S is formed of four cylindrical members 20, 21, 22 and 23 having different diameters, is formed into a telescopic type, and can be expanded and contracted. Specifically, among the cylindrical members 20, 21, 22, and 23, the outermost cylindrical member 20 disposed on the outermost periphery is cylindrical and has a tapered portion 20b in the middle of the diameter, and the upper side in FIG. 1 is provided on the outer periphery of the body 20a having a large-diameter portion 20c and a small-diameter portion 20d on the lower side, and the non-piston side end that is the upper end in FIG. 1 of the large-diameter portion 20c, and projects outward. A flange 20e, an inner flange 20f provided on the inner periphery of the piston side end which is the lower end in FIG. 1 of the small diameter portion 20d, and an orifice hole 20g provided in the taper portion 20b so as to penetrate the trunk portion 20a. And is configured. The outermost peripheral cylinder member 20 is fixed to the cylinder 1 by sandwiching the outer flange 20 e between the upper end of the cylinder 1 in FIG. 1 and the rod guide 7. In this embodiment, the outer diameter of the body portion 20a is set smaller than the inner diameter of the cylinder 1 so that the orifice hole 20g is not closed and communicated with the extension side chamber R1. An annular gap is formed between the body 20 a of the outer cylinder member 20 and the cylinder 1. Since the orifice hole 20g and the extension side chamber R1 only need to communicate with each other, the shape of the body portion 20a of the outermost peripheral cylinder member 20 can be appropriately changed in design, and the cross-sectional shape of the body portion is not limited to a circle.

  In this case, the outermost cylindrical member 20 is directly fixed to the cylinder 1, but may be fixed to the cylinder 1 indirectly by being fixed to the rod guide 7.

  The cylindrical members 21 and 22 are both cylindrical barrel portions 21a and 22a, and outer flanges 21b and 22b that are provided on the outer periphery of the non-piston side end that is the upper end in FIG. 1 and project outward. 1 is provided with inner flanges 21c and 22c provided on the inner periphery of the piston side end, which is the lower end in FIG. 1, and projecting inward.

  Further, among the cylindrical members 20, 21, 22, and 23, the innermost circumferential side cylindrical member 23 arranged on the innermost circumferential side is formed of a cylindrical body portion 23a and an anti-piston side end that is an upper end in FIG. The outer flange 23b is provided on the outer periphery and protrudes outward. The body 23a is slidably contacted with the outer periphery of the piston rod 3. Therefore, the innermost peripheral cylinder member 23 is slidably mounted on the outer periphery of the piston rod 3 and can move in the axial direction with respect to the piston rod 3. Then, the inner circumference of the innermost circumferential side cylinder member 23 can be opposed to the opening facing the extension side chamber R1 of the extension side chamber side hole 3d so that a part or all of the extension side chamber side hole 3d can be closed. Yes.

  Further, among the cylindrical members 20, 21, 22, and 23, the outermost peripheral side cylindrical member 20 disposed on the outermost peripheral side is formed on the outer periphery of the cylindrical body portion 20a and the opposite end of the piston opposite to the upper end in FIG. An outer flange 20e that is provided and protrudes outward, an inner flange 20f that is provided on the inner periphery of the piston side end, which is the lower end in FIG. 1, and protrudes inward, and an orifice hole 20g that penetrates the body portion 20a. It is configured with. The outermost peripheral cylinder member 20 is fixed to the cylinder 1 by sandwiching the outer flange 20 e between the upper end of the cylinder 1 in FIG. 1 and the rod guide 7. In this case, the outermost cylindrical member 20 is directly fixed to the cylinder 1, but may be fixed to the cylinder 1 indirectly by being fixed to the rod guide 7.

  The cylindrical member 21 is inserted into the outermost cylindrical member 20 configured as described above, the cylindrical member 22 is inserted into the cylindrical member 21, and the innermost cylindrical member 23 is inserted into the cylindrical member 22. is there. The inner periphery of the inner flange 20f of the outermost cylindrical member 20 is in sliding contact with the outer periphery of the barrel portion 21a of the cylindrical member 21, and the outer periphery of the outer flange 21b of the cylindrical member 21 is the small diameter portion 20d of the outermost cylindrical member 20. The cylindrical member 21 can come into and out of the outermost cylindrical member 20 without any play. Further, when the cylindrical member 21 moves downward in FIG. 1 with respect to the outermost cylindrical member 20 and the inner flange 20f of the outermost cylindrical member 20 and the outer flange 21b of the cylindrical member 21 collide, The further downward movement of the cylindrical member 21 relative to the side cylindrical member 20 in FIG. 1 is restricted.

  The inner periphery of the inner flange 21 c of the cylindrical member 21 is in sliding contact with the outer periphery of the barrel portion 22 a of the cylindrical member 22, and the outer periphery of the outer flange 22 b of the cylindrical member 22 is in sliding contact with the inner periphery of the barrel portion 21 a of the cylindrical member 21. Thus, the cylindrical member 22 can enter and leave the cylindrical member 21 without play. Further, when the cylindrical member 22 moves downward in FIG. 1 with respect to the cylindrical member 21 and the inner flange 21c of the cylindrical member 21 and the outer flange 22b of the cylindrical member 22 collide, Further downward movement in FIG. 1 is restricted.

  The inner periphery of the inner flange 22 c of the cylindrical member 22 is in sliding contact with the outer periphery of the barrel portion 23 a of the innermost peripheral side cylindrical member 23, and the outer periphery of the outer flange 23 b of the innermost peripheral side cylindrical member 23 is the barrel of the cylindrical member 22. The inner peripheral side cylindrical member 23 is in sliding contact with the inner periphery of the portion 22a so that the innermost peripheral side cylindrical member 23 can enter and exit without any play. Further, when the innermost cylinder member 23 moves downward in FIG. 1 with respect to the cylinder member 22 and the inner flange 22c of the cylinder member 22 and the outer flange 23b of the innermost cylinder member 23 collide with each other, The further downward movement of the innermost cylinder member 23 relative to the cylinder member 22 in FIG. 1 is restricted.

  Therefore, in the shutter member S, the cylindrical member 21 can move in the axial direction with respect to the outermost peripheral cylindrical member 20 fixed to the cylinder 1, and the cylindrical member 22 can move in the axial direction with respect to the cylindrical member 21. Since the innermost circumferential cylinder member 23 is movable in the axial direction with respect to the cylinder member 22, it can be expanded and contracted.

  In this case, among the cylindrical members 20, 21, 22, and 23 constituting the shutter member S, the cylindrical members 21 that face the rebound cushion 10 and abut against the rebound cushion 10 when the shutter member S contracts most. 22 and the innermost peripheral cylinder member 23 have the same axial length, and the anti-pistons that are the upper ends of the cylindrical members 21 and 22 and the innermost peripheral cylinder member 23 in FIG. The side end contacts the lower surface of the rod guide 7 in FIG. In this state, the piston side end surfaces which are the lower end surfaces in FIG. 1 of the cylindrical members 21 and 22 and the innermost peripheral side cylindrical member 23 are flush with each other. In this embodiment, the lower end surface in FIG. 1 of the outermost cylindrical member 20 is also flush with the piston side end surfaces of the cylindrical members 21, 22 and the innermost cylindrical member 23 in FIG. Is set to

  Further, the shutter member S has the innermost cylinder member 23 slidably in contact with the outer periphery of the piston rod 3 and the outermost cylinder member 20 is fixed to the cylinder 1, so that the shutter member S extends inward of the shutter member S. A space 24 communicating with the side chamber R1 via the orifice hole 20g is defined. Therefore, when the shutter member S contracts, the liquid is discharged from the space 24 to the expansion side chamber R1 through the orifice hole 20g, and the orifice hole 20g gives resistance to the flow of the liquid at that time. When this is contracted by an external force, a reaction force that prevents the expansion and contraction occurs.

  Then, when the shutter member S is in the most extended state, when the piston rod 3 is displaced from the neutral position by a predetermined amount in the direction in which the extension side chamber R1 is compressed with respect to the cylinder 1, the innermost peripheral cylinder member 23 of the shutter member S. 1 starts to close against the extension side chamber side hole 3d, and when the piston rod 3 moves further upward in FIG. 1, the innermost peripheral cylinder member 23 opens the opening of the extension side chamber side hole 3d. The degree of blockage increases, and the flow path area of the bypass path B is reduced by the shutter member S. The predetermined amount of displacement can be set arbitrarily. Further, the neutral position of the piston rod 3 with respect to the cylinder 1 is the position of the stroke center when the shock absorber D1 is attached to the vehicle, and the position where the piston 2 attached to the tip of the piston rod 3 comes to the center of the cylinder 1 is not necessarily the position. The neutral position may not be set.

  As described above, the shock absorber D1 is configured, and the operation thereof will be described below. First, when the shock absorber D1 expands and contracts within a range in which the shutter member S does not reduce the flow passage area of the bypass passage B, that is, in this embodiment, the extension side chamber side hole 3d is formed on the inner periphery of the innermost peripheral side cylinder member 23. A case where the shock absorber D1 expands and contracts within a range where the two do not face each other will be described.

  When the shock absorber D1 exhibits an extension operation, the piston 2 moves upward in FIG. 1 with respect to the cylinder 1 and the extension side chamber R1 is compressed, so that the liquid passes through the leaf valve V1 in the attenuation passage 4 from the extension side chamber R1. It moves to the compression side chamber R2 which opens and passes through the expansion side port 2b and is enlarged. Since the leaf valve V1 provides resistance to the flow of the liquid, the pressure in the expansion side chamber R1 rises, a differential pressure is generated between the expansion side chamber R1 and the pressure side chamber R2, acting on the piston 2, and the shock absorber D1 performs the expansion operation. Depresses the extension side damping force. When the piston speed increases and the pressure difference between the extension side chamber R1 and the pressure side chamber R2 reaches the valve opening pressure of the relief valve 6, the relief valve 6 is opened and the pressure in the extension side chamber R1 via the bypass passage B is opened. To the pressure side chamber R2, the damping force of the shock absorber D1 reaches a peak with respect to the increase of the piston speed, and the damping coefficient after the relief valve 6 is opened becomes small. During this extension operation, the piston rod 3 is retracted from the inside of the cylinder 1, so that a shortage of liquid in the cylinder 1 is supplied from the reservoir R due to a decrease in the total volume of the expansion side chamber R 1 and the pressure side chamber R 2, and there is insufficient liquid in the cylinder 1. Compensation not to cause

  When the shock absorber D1 exhibits a contraction operation, the piston 2 moves downward in FIG. 1 with respect to the cylinder 1 and the pressure side chamber R2 is compressed, so that the liquid passes through the leaf valve V2 in the attenuation passage 5 from the pressure side chamber R2. It opens and moves to the expansion side chamber R1 that is enlarged through the compression side port 2c. Since the leaf valve V2 gives resistance to the flow of the liquid, the pressure in the pressure side chamber R2 rises, a differential pressure is generated between the pressure side chamber R2 and the expansion side chamber R1, and acts on the piston 2, and the shock absorber D1 is contracted. Demonstrate the pressure side damping force to suppress. When the piston speed increases and the pressure difference between the pressure side chamber R2 and the extension side chamber R1 reaches the valve opening pressure of the pressure side relief valve 15, the pressure side relief valve 15 opens and the pressure side chamber R2 is opened via the bypass passage B. Is released to the expansion side chamber R1, the damping force of the shock absorber D1 reaches a peak with respect to the increase of the piston speed, and the damping coefficient after opening the compression side relief valve 15 becomes small.

  Therefore, the damping force characteristics (both the characteristics of the damping force with respect to the piston speed) of the buffer D1 have a large damping coefficient until the relief valve 6 and the pressure side relief valve 15 are opened as shown in FIG. However, after opening the valve, the damping coefficient becomes smaller. In FIG. 3, the damping force is greatly increased when the piston speed is low. This is a characteristic due to an orifice (not shown) arranged in parallel with the leaf valves V <b> 1 and V <b> 2, and the leaf valves V <b> 1 and V <b> 2. Since the valve passes through the orifice until the valve is opened, the characteristic of the orifice appears.

  Thus, in the shock absorber D1, when the extension side piston speed is increased and the relief valve 6 is opened, the rate of increase of the extension side damping force is reduced with respect to further increase of the piston speed. Further, it is possible to suppress excessive damping force during the extension stroke, and to improve the riding comfort in the vehicle. In this embodiment, the shock absorber D1 is provided with the pressure-side relief valve 15 in parallel with the relief valve 6 in the middle of the bypass passage B. Therefore, the contraction-side piston speed increases and the pressure-side relief valve 15 When the valve is opened, the rate of increase of the damping force on the compression side is reduced with respect to further increase in the piston speed, so excessive damping force can be suppressed even during the contraction stroke, and the ride comfort in the vehicle is reduced. Can be improved.

  Subsequently, when the shock absorber D1 extends and the shutter member S reduces the flow path area of the bypass passage B, that is, in this embodiment, the inner side of the innermost cylindrical member 23 has an extension side chamber side hole 3d. Will be described in the case where the two are closed facing each other.

  The shock absorber D1 is extended, and the piston rod 3 is displaced from the neutral position by a predetermined amount in the direction of compressing the expansion side chamber R1 with respect to the cylinder 1, so that the expansion side chamber side hole 3d is formed in the innermost peripheral cylinder member 23 of the shutter member S. Are opposite to each other, the extension side chamber side hole 3d begins to be closed on the inner peripheral surface of the innermost peripheral cylinder member 23, and the extension side chamber side hole 3d is opposed to the inner peripheral surface of the innermost peripheral cylinder member 23. Then, the bypass path B is completely blocked. Then, even when the relief valve 6 is in the open state and the damping force is suppressed from becoming excessive, in the situation where the shutter member S reduces the flow area of the bypass path B, The damping force can be increased. Then, in a situation where the shock absorber D1 is extended to the maximum, even if the damping force is reduced by opening the relief valve 6, the flow area of the bypass passage B is reduced to increase the extension side damping force. Since it can be increased, the damping force can be increased before the rod guide 7 and the rebound cushion 10 collide to decrease the piston speed, and the rod guide 7 when the shock absorber D1 is fully extended (at the maximum extension). It is possible to improve the riding comfort in the vehicle by reducing the shock and sound caused by the collision of the rebound cushion 10. Furthermore, when the innermost circumferential cylinder member 23 of the shutter member S abuts on the rebound cushion 10 and the piston rod 3 moves further in the direction of compressing the expansion side chamber R1 relative to the cylinder 1, the piston rod 3 in FIG. As the shutter moves up, the shutter member S is pressed from below by the rebound cushion 10 and contracts. In such a situation, since the shutter member S contracts, a reaction force that suppresses the contraction of the shutter member S is generated, and this reaction force is loaded as a damping force that suppresses the rise of the piston rod 3 in FIG. It will be. Therefore, this shock absorber D1 can exhibit a damping force depending on the position of the piston rod 3, and in addition to increasing the damping force by reducing the flow passage area of the bypass passage B, the shutter When the member S starts to contract, a damping force due to the reaction force can be applied, and the speed of the piston rod 3 can be sufficiently increased before reaching the stroke end on the extension side of the piston rod 3 by exerting a larger damping force. Can be reduced.

  Finally, when the piston rod 3 is displaced with respect to the cylinder 1 to the end of the stroke to the extension side, the rebound cushion 10 causes the shutter member S to contract most, as shown in FIG. Of the members 20, 21, 22, and 23, the piston-side end surfaces of the cylindrical members 21, 22, and 23 that abut against the rebound cushion 10 are flush with each other, so that the contact area of the rebound cushion 10 with the shutter member S increases. Further, wear can be reduced without applying an unbalanced load to the rebound cushion 10, and the durability of the rebound cushion 10 is not deteriorated. Moreover, the axial lengths of the cylindrical members 21 and 22 where the rebound cushion 10 abuts on the shutter member S and the innermost peripheral cylinder member 23 are the same, and the pressing force from the rebound cushion 10 is applied to each cylindrical member 21, 22 and 23, the shutter member S can withstand a large axial load and is not deformed. The number of cylindrical members constituting the shutter member S can be arbitrarily set. However, if at least the axial lengths of the cylindrical members facing the rebound cushion 10 are made equal, the durability of the rebound cushion 10 is improved. Does not worsen sex. Further, like the shock absorber D2 in one modification of the embodiment shown in FIG. 4, the body portion 23a of the innermost circumferential side cylinder member 23 is extended to the piston side which is the lower side in FIG. An annular rebound plate 25 that can collide with the rebound cushion 10 may be provided. By doing in this way, the rebound plate 25 with a smooth surface facing the rebound cushion 10 can be brought into contact with the rebound cushion 10, and even in this case, deterioration of the durability of the rebound cushion 10 can be prevented. Can do.

  If a coil spring is interposed between the innermost circumferential side cylinder member 23 and the rod guide 7, the shutter member S will not be pressed from the piston rod 3 even when the shutter member S is contracted. S can be quickly extended, and the bypass passage B can be closed when the piston rod 3 is always displaced by a predetermined amount from the neutral position when the piston rod 3 moves to the extension side.

  Further, when the relief valve 6 is provided, it is not necessary to provide the extension side chamber side hole 3d between the piston 2 and the rebound stopper 9 that determines the stroke length of the shock absorber D1, that is, the extension side chamber side hole 3d is not provided. 1, the distance between the rebound stopper 9 and the piston 2 can be reduced, and the stroke length of the shock absorber D1 is not sacrificed.

  In this case, the shutter member S closes the expansion side chamber side hole 3d with the innermost circumferential side cylinder member 23, and the expansion side chamber side is moved in accordance with the upward movement of the piston rod 3 with respect to the cylinder 1 in FIG. Since the hole 3d is gradually closed, even when the relief valve 6 is opened to reduce the damping force on the extension side, the shock absorber is provided along with the gradually closing of the extension side chamber side hole 3d. The extension-side damping force generated by D1 can be gradually increased, the sudden change of the damping force can be reduced, and a shock due to the sudden change of the damping force can be prevented from being applied to the vehicle body of the vehicle.

  The shutter member S starts to decrease the flow passage area of the bypass passage B when the piston rod 3 is displaced from the neutral position by a predetermined amount in the direction of compressing the expansion side chamber R1 with respect to the cylinder 1. The displacement can be arbitrarily set, but at least when the shock absorber D1 is most extended, it is set so that a part or all of the extension side chamber side hole 3d is closed.

  Further, if the edge of the opening facing the outer periphery of the piston rod 3 in the extension side chamber side hole 3d is chamfered, the inner circumference of the innermost circumferential cylinder member 23 will enter when the innermost circumferential cylinder member 23 enters. Surface curling can be prevented. Further, in this embodiment, only one extension side chamber side hole 3d is provided. However, a plurality of extension side chamber side holes 3d may be provided. For example, one extension side chamber side hole 3d may be provided at a position shifted in the axial direction with respect to the piston rod 3. It is possible to tune the degree by which the flow path area of the bypass passage B decreases as the piston rod 3 moves upward in FIG. When two or more extension side chamber side holes 3d are provided in the piston rod 3 while being shifted in the axial direction, the extension side chamber side holes 3d may be provided by being completely shifted in the axial direction, or may be provided so as to overlap. Furthermore, the shape of the opening when the extension side chamber side hole 3d is viewed from the outer peripheral side of the piston rod 3 may be a shape other than a circle, a long hole along the axial direction or the circumferential direction, or a rhombus For example, the pressure loss due to the reduction of the flow passage area of the bypass passage B with respect to the movement of the piston rod 3 may be set to be proportional.

  This is the end of the description of the embodiment of the present invention, but the scope of the present invention is of course not limited to the details shown or described.

  The shock absorber of the present invention can be used for vibration control of vehicles.

DESCRIPTION OF SYMBOLS 1 Cylinder 2 Piston 3 as a partition member Piston rod 3d Expansion side chamber side holes 4, 5 Damping passage 6 Relief valve 7 Rod guide 10 Rebound cushion 20 Outermost circumference side cylinder members 21, 22 Cylinder member 23 Innermost circumference side cylinder member 25 Rebound Plate B Bypass D1, D2 Buffer R1 Extension side chamber R2 Pressure side chamber S Shutter member

Claims (3)

  A cylinder, a piston that is slidably inserted into the cylinder and divides the cylinder into an extension side chamber and a pressure side chamber, a piston rod connected to the piston, and an attenuation that communicates the extension side chamber and the pressure side chamber A passage, a bypass passage provided in the piston rod, bypassing the damping passage and communicating the extension side chamber and the pressure side chamber, and a relief provided in the bypass passage for receiving the pressure of the extension side chamber and opening the valve A shock absorber provided with a valve includes a telescopic shutter member that is formed of a plurality of cylindrical members having different diameters and can be expanded and contracted, and an outermost cylindrical member disposed on an outermost periphery of the shutter member is disposed on the cylinder. The innermost cylinder member fixed to the innermost periphery of the shutter member is brought into sliding contact with the outer periphery of the piston rod, and the piston rod is moved from the neutral position to the cylinder. Shock absorber and wherein the subtracting the above innermost tubular member flow area of the bypass passage when a predetermined amount displace said expansion side chamber to the compression direction for. Of the cylindrical members constituting the shutter member, the cylindrical member that abuts on the rebound cushion mounted on the outer periphery of the piston rod when the shutter member is contracted is flush with the piston-side end surface when the shutter member is contracted. 2. The buffer according to claim 1, wherein the end face on the side opposite to the piston is flush and is attached to the inner circumference of the end on the extension side chamber side of the cylinder and abuts on a rod guide that pivotally supports the piston rod. vessel.   2. The shock absorber according to claim 1, wherein an annular rebound plate that abuts a rebound cushion mounted on an outer periphery of the piston rod is provided at a piston side end of the innermost circumferential cylinder member.

Images