JP2008157416A - Hydraulic shock absorber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic shock absorber which generates sufficiently great damping force when the piston speed of a piston of the shock absorber is high or medium, and which sufficiently lowers the damping force when the piston speed is low. <P>SOLUTION: The shock absorber 1 comprises the piston 18 fitted into a cylinder tube 2 for partitioning the cylinder tube 2 into first and second oil chambers 19, 20, a piston rod 21 extending from the piston 18 through the first oil chamber 19 to the outside of the cylinder tube 2, and damping force generating parts 26, 30 for generating damping force with operating oil 14 flowing between the first and second oil chambers 19, 20. On an axial center 3 of the cylinder tube 2, an elastic circular disc 38 to be moved together with the piston 18 is arranged in at least one of the first and second oil chambers 19, 20. An annular clearance 46 is formed between the inner peripheral face of the cylinder tube 2 and the outer peripheral edge of the circular disc 38. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hydraulic shock absorber in which a damping force is generated based on the flow of hydraulic oil between first and second oil chambers in a cylinder tube partitioned by a piston.

  Conventionally, the hydraulic shock absorber is disclosed in Patent Document 1 below. According to this publication, the shock absorber is applied to a vehicle suspension system. The shock absorber includes a cylinder tube, a piston that is fitted in the cylinder tube so as to be slidable in the axial direction, and partitions the cylinder tube into first and second oil chambers, and the first oil chamber from the piston. And a piston rod that extends to the outside of the cylinder tube, and a damping force generator that can generate a damping force by flowing hydraulic oil between the first and second oil chambers. Further, the damping force generator includes a leaf valve that elastically closes an oil passage penetrating the piston in the axial direction so as to be opened and closed.

When an impact force is applied to the shock absorber from the axial direction during traveling of the vehicle, the shock absorber performs an expansion operation or a compression operation. Then, the hydraulic oil in one of the first oil chamber or the second oil chamber pressurized by the piston opens the leaf valve against the elastic force of the leaf valve of the damping force generating section. Let me speak. Then, the hydraulic oil flows toward the other oil chamber through the oil passage while resisting the elastic resistance of the leaf valve. Thereby, a damping force is generated and the impact force is alleviated.
JP 2004-232845 A

  By the way, when the vehicle is traveling at high and medium speeds, and the piston speed of the piston is high and medium when the shock absorber is extended or compressed, the vehicle is better than its ride comfort. Navigability is uniquely required. Therefore, in order to improve the operability, it is conceivable to increase the damping force during high and medium speed running by increasing (hardening) the elastic coefficient of the leaf valve.

  On the other hand, when the vehicle is traveling at a low speed and the piston speed is low, good maneuverability is usually relatively easy to obtain. In this case, particularly good ride comfort is required. However, if the damping force during high and medium speed running is increased as described above, it is usually difficult to sufficiently reduce the damping force to a desired value during the low speed running. As a result, the ride comfort on the vehicle becomes hard, that is, there is a tendency that a favorable ride comfort cannot be obtained.

  The present invention has been made paying attention to the above situation, and the object of the present invention is to reduce the damping force generated by the shock absorber when the piston speed of the piston in the shock absorber is high and medium. On the other hand, when the piston speed is low, the damping force can be sufficiently reduced while increasing sufficiently.

  And, for example, by applying this shock absorber to a vehicle suspension system, it is possible to improve the maneuverability when the vehicle is traveling at high and medium speeds, while obtaining a good ride comfort to the vehicle when traveling at low speeds. That is.

The invention of claim 1 includes a cylinder tube 2 and a piston 18 that is fitted into the cylinder tube 2 so as to be slidable in the axial direction and partitions the inside of the cylinder tube 2 into first and second oil chambers 19 and 20. The hydraulic oil 14 is caused to flow between the piston rod 21 extending from the piston 18 to the outside of the cylinder tube 2 through the first oil chamber 19 and the first and second oil chambers 19 and 20. In the hydraulic shock absorber including the damping force generation units 26 and 30 that can generate the damping force,
An elastic circular plate 38 that is disposed in at least one of the first and second oil chambers 19 and 20 and moves with the piston 18 is provided on the axis 3 of the cylinder tube 2, and the cylinder tube An annular gap 46 is formed between the inner peripheral surface of 2 and the outer peripheral edge of the circular plate 38.

  In the invention of claim 2, in addition to the invention of claim 1, when the inner diameter of the cylinder tube 2 is D and the maximum outer diameter of the circular plate 38 is d1, 0.99D> d1> 0.93D. It is what I did.

  The invention of claim 3 is the one in which the circular plate 38 is arranged in the second oil chamber 20 in addition to the invention of claim 1 as exemplified in FIGS.

  In addition to the invention of claim 1, the invention of claim 4 is particularly the one in which the circular plate 38 is arranged in the first oil chamber 19 as illustrated in FIG. 6.

  In addition to the invention of claim 1, the invention of claim 5 includes the first and second circular plates 40, 41, in which the circular plate 38 is juxtaposed in close proximity to each other on the axis 3. A through hole 44 penetrating in the axial direction is formed on the radially outer end side of the first circular plate 40, and when viewed from the line of sight along the axial direction (FIG. 3), the at least part of the through hole 44 has the The two circular plates 41 are overlapped.

  In addition to the invention of claim 5, the invention of claim 6 is such that the outer diameter d2 of the second circular plate 41 is smaller than the outer diameter d1 of the first circular plate 40.

  According to a seventh aspect of the present invention, in addition to the fifth or sixth aspect of the present invention, the first and second circular plates 40 and 41 have a gap 42 between the first and second circular plates 40 and 41. A spacer 25 is provided between the radially inner ends.

  In this section, the reference numerals appended to the above terms are not to be construed as limiting the technical scope of the present invention to the section “Example” described later or the contents of the drawings.

  The effects of the present invention are as follows.

According to the first aspect of the present invention, a cylinder tube, a piston that is fitted into the cylinder tube so as to be slidable in the axial direction and partitions the inside of the cylinder tube into first and second oil chambers, and the first piston from the piston are provided. A piston rod that extends through the oil chamber to the outside of the cylinder tube, and a damping force generator that can generate a damping force by flowing hydraulic oil between the first and second oil chambers are provided. In hydraulic shock absorber,
An elastic circular plate that is disposed in at least one of the first and second oil chambers and moves together with the piston is provided on the axial center of the cylinder tube, and the inner peripheral surface of the cylinder tube and the circular plate An annular gap is formed between the outer periphery of each of the two.

  For this reason, when the shock absorber is extended or compressed due to an impact force applied to the shock absorber, a main damping force is generated by the hydraulic fluid flowing through the damping force generator. Further, a secondary damping force is generated by the hydraulic fluid flowing through the gap associated with the circular plate. And the said impact force is relieved by these main and sub damping forces.

  Here, the “damping force characteristic” in the case where hydraulic oil flows through the annular gap of the circular plate and a secondary damping force is generated is generally as follows. That is, when the piston speed of the piston during the extension operation or compression operation of the shock absorber is high, a secondary damping force proportional to the 2/3 power of the piston speed is generated. Further, when the piston speed is medium, a secondary damping force proportional to the piston speed is generated. Further, when the piston speed is low, a sub damping force proportional to the square of the piston speed is generated.

  When the piston speed is high and medium, since the flow rate per unit time of the hydraulic oil flowing through the damping force generation part and the gap related to the circular plate is large, a large damping force is generated as a whole. It tends to be.

  However, the secondary damping force generated at this time is proportional to the 2/3 power of the piston speed or simply proportional to the piston speed, depending on the "damping force characteristics" when the piston speed is high and medium as described above. It is. For this reason, the piston speed is high and medium speed as described above, compared to generating a secondary damping force proportional to the square of the piston speed as in the “damping force characteristic” when the piston speed is low. Even if it tends to generate a large sub-damping force, the sub-damping force generated at this time is restrained from increasing greatly. Accordingly, an excessively large damping force generated by the shock absorber is suppressed, that is, a moderately large damping force is obtained.

  Therefore, if the shock absorber is applied to a vehicle suspension system, the impact force applied to the shock absorber is moderate when the vehicle is driven at high, medium speed, or rough ground, where the piston speed tends to be high and medium. It is sufficiently relaxed by the large damping force, and the operability is improved. In addition, since the generation of an excessive damping force is suppressed as described above, the reaction force applied to the vehicle body side of the vehicle due to the generation of the damping force is also suppressed. It is beneficial in nature.

  On the other hand, when the piston speed is low, the flow rate of the working oil flowing as described above is smaller than that when the piston speed is high and medium, and the damping force tends to decrease as a whole.

  Here, the secondary damping force generated at this time tends to increase in proportion to the square of the piston speed due to the “damping force characteristic” when the piston speed is low as described above. However, the “damping force characteristics” at the high and medium speeds of the piston speed are lower than those at the time of the lower speed than when the secondary damping force is generated that is proportional to the piston speed 2/3 or simply proportional. Since the piston speed is greatly reduced, the sub damping force is largely and sufficiently reduced as the piston speed is reduced, that is, the piston is hardly generated.

  Therefore, if the shock absorber is applied to a vehicle suspension device, when the vehicle is traveling at a low speed where the piston speed tends to be low, the damping force as a whole decreases so as to hardly occur. For this reason, the ride comfort on this vehicle becomes soft, that is, a good ride comfort is obtained.

  The various functions and effects described above are achieved by using a circular plate with a simple configuration. Therefore, for example, the configuration of the shock absorber is simple and compact as compared with the case where a damping force generator such as a piston / piston valve is provided separately, and the forming operation can be facilitated.

  According to a second aspect of the present invention, when the inner diameter of the cylinder tube is D and the maximum outer diameter of the circular plate is d1, 0.99D> d1> 0.93D.

  Here, if the outer diameter of the circular plate is set to 0.99D or more, the secondary damping force generated by providing the circular plate may be excessive, and the circular shape is formed on the inner peripheral surface of the cylinder tube. There is a risk that the plate may come into contact when the plate is elastically deformed.

  On the other hand, if the outer diameter of the circular plate is 0.93 D or less, the area of the gap becomes excessive, and the sub damping force cannot be sufficiently generated.

  Therefore, the configuration is as described above, and according to this, a desired sub-damping force can be generated.

  According to a third aspect of the present invention, the circular plate is disposed in the second oil chamber.

  Here, it is difficult to ensure a sufficient dimension between the end of the cylinder tube, which is the extended end side of the piston rod, and the piston. For example, when a vehicle to which a shock absorber is applied rebounds, When the shock absorber is extended, the circular plate may be disposed in the second oil chamber as described above when it is not possible to sufficiently perform the extending operation.

  In this way, the shock absorber can be fully extended until the end of the cylinder tube and the piston are closer to each other without being obstructed by the circular plate.

  According to a fourth aspect of the present invention, the circular plate is disposed in the first oil chamber.

  Here, it is difficult to ensure a sufficient dimension between the piston tube and the other end of the cylinder tube opposite to the extending end of the piston rod. When the shock absorber performs a compression operation by bouncing, when the compression operation cannot be sufficiently performed, the circular plate may be disposed in the first oil chamber as described above.

  In this way, the shock absorber can be sufficiently compressed until the other end of the cylinder tube and the piston come closer to each other without being obstructed by the circular plate.

  According to a fifth aspect of the present invention, the circular plate includes first and second circular plates arranged side by side in close proximity to each other on the axis, and the shaft is disposed on a radially outer end side of the first circular plate. A through-hole penetrating in the direction is formed, and the second circular plate overlaps at least a part of the through-hole as viewed from the line of sight along the axial direction.

  For this reason, when the shock absorber performs an expansion operation or a compression operation, among the hydraulic oil partitioned by the circular plate, when the hydraulic oil on the second circular plate side tries to flow to the first circular plate side Due to the hydraulic pressure of the hydraulic oil, the second circular plate is elastically deformed toward the first circular plate and tends to close the through holes.

  Thereby, the hydraulic fluid flows mainly in the gap at a higher flow rate. Therefore, the hydraulic oil receives a greater resistance force from the circular plate and increases the sub damping force.

  On the other hand, among the hydraulic oil divided by the circular plate, when the hydraulic oil on the first circular plate side tries to flow toward the second circular plate side, the hydraulic oil passes through the through hole and the gap. It tries to flow toward the second circular plate. In this case, since the hydraulic oil after passing through the through hole flows so as to collide with the second circular plate, the second circular plate is elastically deformed away from the first circular plate.

  For this reason, the hydraulic fluid flows at a slower flow rate by flowing through the through hole and the gap, respectively. Therefore, the resistance force that the hydraulic oil receives from the circular plate is further reduced, and the sub damping force is reduced.

  That is, according to the shock absorber, a different damping force can be obtained between the extension operation and the compression operation, and the applicable range of the shock absorber can be expanded.

  In the invention of claim 6, the outer diameter of the second circular plate is made smaller than the outer diameter of the first circular plate.

  For this reason, among the hydraulic oil partitioned by the circular plate, when the hydraulic oil on the first circular plate side tries to flow to the second circular plate side through the through hole, the second circular plate side After passing through each of the through holes, the hydraulic oil heading toward is smoothly passed through the radially outer area of the second circular plate whose outer diameter is reduced, and is directed toward the second circular plate. Therefore, generation | occurrence | production of an excessive sub damping force can be suppressed by the flow of the hydraulic fluid from the said 1st circular board side to the 2nd circular board side being made smooth.

  According to a seventh aspect of the present invention, a spacer is provided between radially inner ends of the first and second circular plates so that a gap is formed between the first and second circular plates.

  For this reason, the presence of a gap between the first circular plate and the second circular plate of the circular plate causes the first circular plate and the second circular plate to come into surface contact with each other and stick to each other. Is prevented. Therefore, it is more reliably achieved that different damping forces can be obtained during the above-described extension operation and compression operation.

  Regarding the hydraulic shock absorber of the present invention, when the piston speed of the piston in the shock absorber is high and medium speed, the damping force generated by the shock absorber is sufficiently increased, while when the piston speed is low, In order to realize the object of sufficiently reducing the damping force, the best mode for carrying out the present invention is as follows.

  That is, the hydraulic shock absorber includes a cylinder tube, a piston that is fitted into the cylinder tube so as to be slidable in the axial direction, and partitions the inside of the cylinder tube into first and second oil chambers. A piston rod that extends through the oil chamber to the outside of the cylinder tube, and a damping force generator that can generate a damping force by flowing hydraulic oil between the first and second oil chambers. Yes.

  On the axis of the cylinder tube, there is provided an elastic circular plate that is disposed in at least one of the first and second oil chambers and moves together with the piston. An annular gap is formed between the inner peripheral surface of the cylinder tube and the outer peripheral edge of the circular plate.

  In order to describe the present invention in more detail, Example 1 will be described with reference to FIGS.

  In FIG. 1-4, the code | symbol 1 is a hydraulic pressure buffer. The shock absorber 1 is applied to a suspension device or a steering damper of a vehicle such as an automobile or a motorcycle.

  The shock absorber 1 includes a cylinder tube 2 extending in the longitudinal direction. The cylinder tube 2 is positioned on the axis 3 of the cylinder tube 2 and closes the opening of the tube main body 4 extending in the axial direction and one end (lower end) 5 of the tube main body 4 in the axial direction. The head cover 6 fixed to the one end portion 5 and the other end portion (upper end portion) 7 of the tube body 4 are fixed to the other end portion 7 so as to close the opening, and a through hole 8 is formed on the shaft center 3. The fixed rod guide 9 and the bump stopper 10 which is attached to the fixed rod guide 9 and protrudes toward the inside of the tube body 4 are provided.

  A free piston 13 is provided in the cylinder tube 2 so as to be freely slidable in the axial direction. The free piston 13 partitions the cylinder tube 2 into an oil chamber 15 filled with hydraulic oil 14 and a gas chamber 16 filled with high-pressure nitrogen gas. A piston 18 is provided so as to be slidable in the axial direction with respect to the oil chamber 15 of the cylinder tube 2. The piston 18 includes a pair of piston members 18 a that are arranged close to each other on the shaft 3, and partitions the oil chamber 15 into a first oil chamber 19 and a second oil chamber 20.

  A piston rod 21 located on the shaft 3 and extending from the piston 18 through the first oil chamber 19 and through the through hole 8 of the fixed rod guide 9 to the outside of the cylinder tube 2 is provided. Is provided. The proximal end portion 22 of the piston rod 21 has a smaller diameter than the other portion (general portion) of the piston rod 21, and a step surface 21 a is formed between the other portion of the piston rod 21 and the proximal end portion 22. Is formed. The base end portion 22 penetrates both piston members 18 a of the piston 18, and the piston 18 and the base end portion 22 are fixed to each other by a fastener 23. The fastener 23 includes a male screw 23a formed at a protruding end portion of the base end portion 22 of the piston rod 21 that passes through the piston 18, and a nut 23b that is screwed into the male screw 23a.

  On the shaft 3, a large disk-shaped spacer 24 is interposed between each piston member 18 a of the piston 18, the stepped surface 21 a of the piston rod 21, and the nut 23 b of the fastener 23. ing. Further, a plurality of (five) other spacers 25 having a small-diameter disk shape and different thicknesses are interposed between the spacer 24 on the fastener 23 side and the nut 23b on the shaft 3. It is installed.

  There is provided an extension side damping force generator 26 for generating a main damping force by causing the hydraulic oil 14 to flow from the first oil chamber 19 to the second oil chamber 20 when the shock absorber 1 is extended. The extension-side damping force generator 26 includes extension-side oil passages 27 formed in the piston members 18a of the piston 18 so that the first oil chamber 19 and the second oil chamber 20 communicate with each other. An extension side damping valve 28 is provided that closes the extension side oil passage 27 from the side of the second oil chamber 20 so as to be elastically openable and closable. Each of the expansion side damping valves 28 is a disc-shaped leaf valve. These extension side damping valves 28 are attached to the piston 18 with the center part sandwiched between the piston members 18a and the spacer 24 on the shaft 3, and the radially outer end side is the extension side. The oil passage 27 is closed.

  On the other hand, when the shock absorber 1 performs the compression operation B, there is provided a compression side damping force generating unit 30 that generates the main damping force by causing the hydraulic oil 14 to flow from the second oil chamber 20 to the first oil chamber 19. . The compression-side damping force generating unit 30 includes a compression-side oil passage 31 formed in each piston member 18a of the piston 18 so that the first oil chamber 19 and the second oil chamber 20 communicate with each other, and the pressure-side oil passages. A pressure-side damping valve 32 that closes the passage 31 from the first oil chamber 19 side so as to be elastically openable and closable is provided. Each of the compression side damping valves 32 is a leaf valve having the same shape and the same size as the extension side damping valve 28 and is attached to the piston 18 in the same manner as the extension side damping valve 28.

  The spacers 24 are opened when the expansion side damping valve 28 of the expansion side damping force generation unit 26 and the compression side damping valve 32 of the compression side damping force generation unit 30 are excessively opened. Also serves as a valve stopper that prevents valve operation. Thus, the maximum valve opening degree of each of the expansion side damping valve 28 and each pressure side damping valve 32 is determined, and at least a predetermined main damping force is generated.

  A male screw 35 is formed on the outer peripheral surface of the extending end portion of the piston rod 21 of the cylinder tube 2, and the extending end portion of the piston rod 21 is supported on the vehicle body side. On the other hand, the head cover 6 of the cylinder tube 2 is connected to the wheel side. A suspension spring 34 is provided to urge the cylinder tube 2 so that the shock absorber 1 is extended.

  In the shock absorber 1 having the above-described configuration, a circular plate 38 that is disposed in the second oil chamber 20 and moves together with the piston 18 is provided on the shaft 3. The circular plate 38 is formed of a metal spring plate material and extends flat in a direction perpendicular to the axis 3 in its free state. A shaft hole 39 is formed on the shaft 3 of the circular plate 38, and the base end portion 22 of the piston rod 21 is inserted through the shaft hole 39. The radially inner end of the circular plate 38 is sandwiched between the other spacers 25, and the circular plate 38 is attached to the piston rod 21.

  The circular plate 38 includes first and second circular plates 40 and 41 that are arranged close to each other on the axis 3. Among the other spacers 25, one other spacer 25 having a particularly small thickness is interposed between the radially inner ends of the first and second circular plates 40 and 41. As a result, a narrow gap 42 is formed between the first and second circular plates 40 and 41 as a whole.

  Of the first and second circular plates 40 and 41, the radially outer end side of the first circular plate 40 located on the one end 5 side of the tube body 4 of the cylinder tube 2 penetrates in the axial direction. A plurality (eight) of circular through holes 44 are formed. These through holes 44 have the same diameter, and are formed at equal pitch positions in the circumferential direction on a virtual circle 45 centered on the axis 3.

  The outer diameter d2 of the second circular plate 41 is smaller than the outer diameter d1 of the first circular plate 40. The outer diameter d1 of the first circular plate 40, which is the maximum outer diameter of the circular plate 38, is smaller than the inner diameter D of the cylinder tube 2 than the inner diameter D of the cylinder tube 2. In this case, it is preferable that 0.99D> d1> 0.93D. An annular gap 46 is formed between the inner peripheral surface of the cylinder tube 2 and the outer peripheral edge of the first circular plate 40 of the circular plate 38.

  As seen from the line of sight along the axis 3 (FIG. 3), the other spacer 25 is formed such that its outer peripheral edge is located inside the through hole 44 group. Further, when viewed from the line of sight, the second circular plate 41 is formed so that at least a part thereof overlaps the through holes 44. Specifically, the second circular plate 41 is formed such that an outer peripheral edge thereof is located outside the group of through holes 44, that is, each through hole 44 is entirely closed by the second circular plate 41. ing.

  Assume that when the vehicle travels, an impact force is applied to the shock absorber 1 from the outside in the axial direction, and the shock absorber 1 extends in the biasing direction of the suspension spring 34. Then, the hydraulic oil 14 in the first oil chamber 19 tends to flow toward the second oil chamber 20 through the extension side oil passage 27 of the extension side damping force generation unit 26. At this time, the extension side damping valve 28 is elastically deformed and opened by the hydraulic pressure of the hydraulic oil 14 in the first oil chamber 19 which exceeds the elastic biasing force of the extension side damping valve 28. Then, the hydraulic oil 14 flows while receiving the elastic resistance force from the extension side damping valve 28 through the extension side oil passage 27 thus opened. This flow further generates a main damping force and alleviates the impact force.

  On the other hand, it is assumed that the shock absorber 1 performs a compression operation B against the urging force of the suspension spring 34 by the impact force. Then, the hydraulic oil 14 in the second oil chamber 20 tends to flow toward the first oil chamber 19 through the pressure-side oil passage 31 of the pressure-side damping force generating unit 30. At this time, the pressure-side damping valve 32 is elastically deformed and opened by the hydraulic pressure of the hydraulic oil 14 in the second oil chamber 20 which exceeds the elastic biasing force of the pressure-side damping valve 32. Then, the hydraulic oil 14 flows through the pressure-side oil passage 31 thus opened while receiving the elastic resistance force from the pressure-side damping valve 32. And by this flow, the main damping force is generated and the impact force is alleviated.

  Hereinafter, the impact force is alleviated by the main damping force generated by repeating the expansion operation A and the compression operation B of the shock absorber 1. When the piston rod 21 enters and exits the oil chamber 15 along with the expansion and compression operations A and B of the shock absorber 1, the volume of the incompressible hydraulic oil 14 in the oil chamber 15 is constant. The free piston 13 slides in the axial direction by the volume of the piston rod 21 that enters and exits the oil chamber 15 as described above, so that the gas in the gas chamber 16 is expanded and compressed. The piston rod 21 can enter and exit the chamber 15.

  Further, as described above, when the shock absorber 1 performs the expansion operation A or the compression operation B, the hydraulic oil 14 divided by the circular plate 38 moves from one side of the circular plate 38 in the axial direction to the other side. The fluid flows through the through holes 44 and the gap 46 while receiving a resistance force from the circular plate 38. Then, a sub damping force is generated by this flow, and this also reduces the impact force.

  As described above, since the circular plate 38 is provided to generate the secondary damping force, the extension and compression side damping force generating units 26 and 30 are set so that the main damping force generated from these becomes small. Yes. That is, it is intended that the overall damping force of these main and secondary damping forces is not excessive.

  In FIG. 5, when the hydraulic oil 14 flows through the annular gap 46 related to the circular plate 38 and a secondary damping force is generated, the piston 18 in the expansion operation A and the compression operation B of the shock absorber 1 is generated. The “damping force characteristic” related to the piston speed (m / s) in the axial direction is generally as follows.

  That is, when the piston speed is high, a sub damping force proportional to the 2/3 power of the piston speed is generated as the “first characteristic” of the “damping force characteristic”. Further, when the piston speed is medium speed M, a secondary damping force proportional to the piston speed is generated as the “second characteristic” of the “damping force characteristic”. When the piston speed is low L, a secondary damping force proportional to the square of the piston speed is generated as the “third characteristic” of the “damping force characteristic”.

  When the piston speed (m / s) of the piston 18 when the shock absorber 1 performs the expansion operation A or the compression operation B is high and the medium speed H or M, such as when the vehicle is traveling at a high speed or at a medium speed, The flow rate per unit time of the working oil 14 flowing through the stretching and compression side damping force generating portions 26 and 30, the through holes 44 associated with the circular plate 38, and the gap 46 increases. For this reason, a larger damping force tends to be generated in the main and sub damping forces.

  However, the secondary damping force generated at this time is 2/3 of the piston speed due to the “first and second characteristics” which are the “damping force characteristics” when the piston speed is high and medium as described above. It is proportional or simply proportional. Therefore, as described above, the secondary damping force proportional to the square of the piston speed is generated as in the “third characteristic” which is the “damping force characteristic” when the piston speed is low. Even if the piston speed is high and the medium speeds H and M tend to generate a large sub-damping force, the sub-damping force generated at this time is restrained from increasing greatly. Therefore, an excessively large damping force generated by the shock absorber 1 is suppressed, that is, a moderately large damping force is obtained.

  Therefore, the impact force applied to the shock absorber 1 is sufficiently mitigated by the moderately large damping force described above when the piston speed is high and the vehicle tends to become medium speeds H and M at high and medium speeds or on rough terrain. As a result, the operability is improved. In addition, since the generation of an excessive damping force is suppressed as described above, the reaction force applied to the vehicle body side of the vehicle due to the generation of the damping force is also suppressed. It is beneficial in nature.

  On the other hand, when the piston speed is low L, such as when the vehicle is running at low speed, the flow rate of the hydraulic fluid 14 that flows as described above is smaller than that when the piston speed is high, medium speed H, M, and as a whole. Damping force decreases.

  Here, the secondary damping force generated at this time is the square of the piston speed due to the “third characteristic” which is the “damping force characteristic” when the piston speed is low as described above. Try to grow proportionally. However, the “damping force characteristics” at the high and medium speeds H and M are the “first and second characteristics”, which are proportional to the 2/3 power of the piston speed or simply proportional to the piston speed. Since the piston speed at the low speed L is significantly lower than when the secondary damping force is generated, the secondary damping force is largely and sufficiently reduced as the piston speed decreases, that is, almost It does not occur.

  Therefore, when the vehicle travels at a low speed, the overall damping force decreases so that almost no damping force is generated. For this reason, the ride comfort on this vehicle becomes soft, that is, a good ride comfort is obtained. When the vehicle travels at a low speed, the vehicle is given to the shock absorber 1 mainly by the suspension spring 34 and the small main damping force generated by the extension side damping force generator 26 and the compression side damping force generator 30. The impact force is alleviated and the vehicle travels without hindrance.

  The various functions and effects described above are achieved by using a circular plate with a simple configuration. For this reason, for example, the configuration of the shock absorber 1 is simple and compact as compared with the case where a damping force generator such as a piston / piston valve is provided separately, and the forming operation thereof can be facilitated.

  Referring to the right half of FIG. 4, among the hydraulic oils 14 divided by the circular plate 38 when the shock absorber 1 performs the expansion operation A as described above, the hydraulic oil 14 on the second circular plate 41 side is The liquid tends to flow toward the first circular plate 40 through the through holes 44 and the gaps 46. In this case, the second circular plate 41 tends to be elastically deformed toward the first circular plate 40 by the hydraulic pressure of the hydraulic oil 14, and the through holes 44 tend to be closed almost entirely (in FIG. 4). Dash-dot line).

  As a result, the hydraulic oil 14 mainly flows through the gap 46 at a higher flow rate in a concentrated manner. Therefore, the hydraulic oil 14 receives a greater resistance force from the circular plate 38, and the sub damping force increases. That is, during the extension operation A of the shock absorber 1 when the vehicle rebounds, a large sub damping force is generated (the upper half of FIG. 5).

  On the other hand, referring to the left half of FIG. 4, as described above, when the shock absorber 1 performs the compression operation B, the hydraulic oil 14 divided by the circular plate 38 operates on the first circular plate 40 side. When the oil 14 is about to flow toward the second circular plate 41, the hydraulic oil 14 tends to flow toward the second circular plate 41 through the through holes 44 and the gaps 46. In this case, since the hydraulic oil 14 after passing through the through hole 44 flows so as to collide with the second circular plate 41, the second circular plate 41 is elastically deformed away from the first circular plate 40. (Dash-dot line in FIG. 4).

  For this reason, the hydraulic fluid 14 flows at a slower flow rate by flowing through the through holes 44 and the gaps 46, respectively. Therefore, the resistance force that the hydraulic oil 14 receives from the circular plate 38 is further reduced, and the sub damping force is reduced. That is, when the vehicle bounces, the secondary damping force becomes small during the compression operation B of the shock absorber 1 when the vehicle receives a large impact force from the steering road surface (lower half of FIG. 5).

  Therefore, when the vehicle is traveling, the value of the sub damping force is made different according to the operations A and B of the shock absorber 1, and the impact force is moderated. As a result, good maneuverability in the vehicle and good ride comfort on the vehicle can be obtained more reliably.

  As described above, when the inner diameter of the cylinder tube 2 is D and the maximum outer diameter of the circular plate 38 is d1, 0.99D> d1> 0.93D.

  Here, if the outer diameter d1 of the circular plate 38 is 0.99D or more, the secondary damping force generated by providing the circular plate 38 may be excessive, and the inner peripheral surface of the cylinder tube 2 may be increased. In addition, the circular plate 38 may come into contact during elastic deformation.

  On the other hand, when the outer diameter d1 of the circular plate 38 is set to 0.93D or less, the area of the gap 46 becomes excessive, and the sub damping force cannot be sufficiently generated.

  Therefore, the configuration is as described above, and according to this, a desired sub-damping force can be generated.

  Further, as described above, the circular plate 38 is disposed in the second oil chamber 20.

  Here, it is difficult to ensure a sufficient dimension between the piston 18 and the other end 7 of the cylinder tube 2 on the extending end side of the piston rod 21, and the vehicle rebounds. When the shock absorber 1 performs the expansion operation A, the circular plate 38 may be disposed in the second oil chamber 20 as described above when the expansion operation A cannot be performed sufficiently.

  In this manner, until the other end 7 of the cylinder tube 2 and the piston 18 approach each other without being obstructed by the circular plate 38, specifically, the piston 18 side is in contact with the bump stopper 10. The shock absorber 1 can be fully extended A until it abuts (the chain line in FIG. 2).

  Further, as described above, the outer diameter d2 of the second circular plate 41 is made smaller than the outer diameter d1 of the first circular plate 40.

  Therefore, when the hydraulic oil 14 on the first circular plate 40 side of the hydraulic oil 14 partitioned by the circular plate 38 tries to flow to the second circular plate 41 side through the through holes 44. The hydraulic oil 14 toward the second circular plate 41 side passes smoothly through the radially outer region of the second circular plate 41 whose outer diameter d2 is reduced after passing through each through hole 44. It is directed toward the second circular plate 41 side. Therefore, the flow of the hydraulic oil 14 from the first circular plate 40 side to the second circular plate 41 side is smoothly performed, so that generation of an excessive auxiliary damping force can be suppressed.

  Further, as described above, the spacer 25 is provided between the radially inner ends of the first and second circular plates 40 and 41 so that a gap 42 is formed between the first and second circular plates 40 and 41. Yes.

  For this reason, due to the presence of the gap 42 between the first circular plate 40 and the second circular plate 41 of the circular plate 38, the first circular plate 40 and the second circular plate 41 are brought into surface contact with each other and adhered to each other. It is prevented that it sticks. Therefore, it is more reliably achieved that different damping forces can be obtained in the above-described extension operation A and compression operation B.

  In addition, although the above is based on the example of illustration, the piston member 18a of the said piston 18 may be single. Further, the damping force generator may be a fixed orifice provided on the outside of the cylinder tube 2. The circular plate 38 may be a single plate or three or more plates. Further, the circular plate 38 may not be geometrically completely circular. Further, the second circular plate 41 of the circular plate 38 may be configured such that only a part of the through hole 44 is closed as viewed from the line of sight along the axial direction. The arrangement of the first and second circular plates 40 and 41 may be reversed.

  The following FIGS. 6 and 7 show Examples 2 and 3. FIG. Each of these embodiments is common in many respects to the configuration and operational effects of the first embodiment. Therefore, regarding these common items, common reference numerals are attached to the drawings, and redundant description thereof is omitted, and different points are mainly described. In addition, the configurations of the respective parts in each of these embodiments may be variously combined in light of the object and the effect of the present invention.

  In order to describe the present invention in more detail, Example 2 will be described with reference to FIG.

  In FIG. 6, the circular plate 38 is disposed in the first oil chamber 19 on the shaft 3 and is attached to the piston rod 21. Further, a stopper 47 is provided which is disposed in the first oil chamber 19 on the protruding end side of the piston rod 21 with respect to the circular plate 38 and is fixed to the midway portion of the piston rod 21 in the axial direction.

  Here, it is difficult to ensure a sufficient dimension between the piston 18 and the one end portion 5 of the cylinder tube 2 opposite to the extending end of the piston rod 21, and the vehicle bounces. When the shock absorber 1 performs the compression operation B, when the compression operation B cannot be sufficiently performed, the circular plate 38 may be disposed in the first oil chamber 19 as described above.

  In this way, specifically, the piston 18 is connected to the free piston 13 until the one end portion 5 of the cylinder tube 2 and the piston 18 come closer to each other without being obstructed by the circular plate 38. The shock absorber 1 can be sufficiently compressed B until it approaches (see a solid line in FIG. 6).

  In FIG. 6, the alternate long and short dash line indicates a state where the shock absorber 1 is extended A and the stopper 47 is in contact with the bump stopper 10. This prevents the circular plate 38 from coming into contact with the bump stopper 10 and being damaged.

  In order to describe the present invention in more detail, Example 3 will be described with reference to FIG.

  In FIG. 7, the shock absorber 1 of the second embodiment is a so-called through rod (double rod) type. The piston 18 of the shock absorber 1 has substantially the same pressure receiving area of hydraulic pressure by the hydraulic oil 14 on each axial surface.

  Specifically, in place of the free piston 13 of the first embodiment, a movable rod guide 49 having a through hole 48 formed on the shaft center 3 is provided. The movable rod guide 49 is fitted to the tube body 4 of the cylinder tube 2 so as to be freely slidable in the axial direction. Further, in place of the gas chamber 16 of the first embodiment, a storage chamber 53 that communicates with the atmosphere side through a communication hole 52 formed in the head cover 6 is formed. The storage chamber 53 is formed by the one end portion 5 of the tube body 4 and the head cover 6. The accommodation chamber 53 accommodates a spring 54 that elastically pushes the movable rod guide 49 toward the oil chamber 15. A predetermined pressure is constantly applied to the hydraulic oil 14 in the oil chamber 15 by the biasing force of the spring 54.

  Between the movable rod guide 49 and the spring 54, a cylindrical sliding body 55 having a through hole formed on the shaft 3 is interposed. The sliding body 55 is fitted into the tube body 4 so as to be slidable in the axial direction without rattling. One end face (upper end face) in the axial direction of the sliding body 55 is formed so as to be orthogonal to the shaft center 3 and is in surface contact with one end face (lower end face) in the axial direction of the movable rod guide 49.

  For this reason, one end surface (upper end surface) in the axial direction of the spring 54 pressed against the other end surface (lower end surface) of the sliding body 55 is slightly inclined from a plane orthogonal to the axis in the free state of the spring 54. Even if this is the case, the sliding body 55 is prevented from being inclined with respect to the shaft center 3 due to the biasing force of the spring 54. Therefore, the movable rod guide 49 that is in surface contact with the one end surface of the sliding body 55 is also prevented from being inclined with respect to the shaft center 3 due to the biasing force of the spring 54. As a result, smooth sliding of the movable rod guide 49 with respect to the tube body 4 is ensured.

  Another piston rod 56 that is located on the axis 3 and extends from the piston 18 through the through hole 48 to the accommodation chamber 53 is provided. The other piston rod 56 is fastened to a base end portion 22 of the piston rod 21 fixed to the piston 18 and a protruding end portion of the base end portion 22 protruding from the piston 18 into the second oil chamber 20. Rod body 58 fixed by 57. That is, the base end portion 22 is also used as both the piston rods 21 and 56. The two piston rods 21 and 56 have substantially the same diameter.

  As described above, the piston rods 21 and 56 having substantially the same diameter extend from the respective axial surfaces of the piston 18, and as described above, the pressure receiving area of the hydraulic pressure on each axial surface of the piston 18. Are almost the same. Thereby, it is suppressed that the piston 18 receives a pressure reaction force from the spring 54.

FIG. 3 is a partially enlarged detail cross-sectional view of FIG. 2 showing the first embodiment. Example 1 is shown and is a longitudinal sectional view of a shock absorber. FIG. 3 is a cross-sectional view taken along the line III-III in FIG. FIG. 2 is a diagram illustrating a partial enlargement operation of FIG. 1 according to the first embodiment. It is a graph which shows Example 1 and shows the relationship between piston speed and the sub damping force by having provided the circular plate. FIG. 3 shows a second embodiment and corresponds to FIG. FIG. 9 is a diagram illustrating Example 3 and corresponding to FIG. 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Buffer 2 Cylinder tube 3 Shaft center 4 Tube main body 5 One end part 7 Other end part 13 Free piston 14 Hydraulic oil 15 Oil chamber 16 Gas chamber 18 Piston 19 1st oil chamber 20 2nd oil chamber 21 Piston rod 22 Base end 25 Spacer 26 Extension side damping force generation part 30 Compression side damping force generation part 38 Circular plate 39 Axle hole 40 First circular plate 41 Second circular plate 42 Gap 44 Through hole 45 Virtual circle 46 Gap 48 Through hole 49 Movable rod guide 56 Piston rod A Extension operation B Compression operation D Inner diameter d1 Outer diameter d2 Outer diameter H High, medium speed M Low speed L Low speed

Claims (7)

A cylinder tube, a piston that is fitted into the cylinder tube so as to be slidable in the axial direction, and divides the inside of the cylinder tube into first and second oil chambers; and from the piston through the first oil chamber, the cylinder tube In a hydraulic shock absorber provided with a piston rod extending to the outside and a damping force generation unit capable of generating a damping force by flowing hydraulic oil between the first and second oil chambers,
An elastic circular plate that is disposed in at least one of the first and second oil chambers and moves together with the piston is provided on the axial center of the cylinder tube, and the inner peripheral surface of the cylinder tube and the circular plate A hydraulic shock absorber in which an annular gap is formed between the outer periphery of the hydraulic shock absorber.   2. The hydraulic shock absorber according to claim 1, wherein 0.99D> d1> 0.93D is established, where D is an inner diameter of the cylinder tube and d1 is a maximum outer diameter of the circular plate.   The hydraulic shock absorber according to claim 1, wherein the circular plate is disposed in the second oil chamber.   The hydraulic shock absorber according to claim 1, wherein the circular plate is disposed in the first oil chamber.   The circular plate includes first and second circular plates juxtaposed in close proximity to each other on the axial center, and a through-hole penetrating in the axial direction is formed on a radially outer end side of the first circular plate. 2. The hydraulic shock absorber according to claim 1, wherein the second circular plate is formed and overlapped with at least a part of the through-hole as viewed in a line of sight along the axial direction.   6. The hydraulic shock absorber according to claim 5, wherein an outer diameter of the second circular plate is smaller than an outer diameter of the first circular plate.   The hydraulic shock absorber according to claim 5 or 6, wherein a spacer is provided between radially inner ends of the first and second circular plates so that a gap is formed between the first and second circular plates. vessel.

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