JP2012167785A - Hydraulic shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve ride comfort of a vehicle, by facilitating generation of a damping force even at a low speed, in improvement of a hydraulic shock absorber such as a front fork.SOLUTION: The hydraulic shock absorber includes: a cylinder 4 storing a working fluid; a piston 6 demarcating the inside of the cylinder 4 into two working chambers A, B; a damping force generator V generating the damping force when the working fluid passes through a communication passage 60 of the piston 6; a bypass passage L1 bypassing the communication passage 60; and a choke flow passage T formed in the middle of the bypass passage L1. The hydraulic shock absorber further includes: a choke member 7A having a choke part 70 provided with a choke groove 70a formed to an outer periphery thereof; and a case member 8B in which the choke member 7A is inserted and relatively movable in an axis direction with respect to the choke member 7A. The case member 8A has a cover part 86 brought into slide-contact with the choke part 70 to form the choke flow passage T between the cover part 86 and the choke groove 70a. Length of the choke flow passage T is determined by the overlap-amount between the choke part 70 and the cover part 86.

Description

  The present invention relates to an improvement in a fluid pressure shock absorber such as a front fork that suspends a front wheel of a motorcycle.

  Various proposals have been made for fluid pressure shock absorbers so far. For example, the fluid pressure shock absorber is used as a suspension device such as a front fork or a rear cushion unit that suspends a wheel of a two-wheeled vehicle and attenuates road surface vibration input to the wheel. The

  Patent Document 1 discloses a configuration of a conventional front fork, and the front fork includes a fork body including an outer tube and an inner tube that is slidably inserted into the outer tube. The front fork accommodates an upright damper that generates a predetermined damping force in the fork main body, forms a reservoir chamber between the fork main body and the damper, and accommodates the working fluid in the reservoir chamber. .

  As shown in FIG. 2 of Patent Document 1, the damper includes a cylinder that contains a working fluid, a rod that is movably inserted in the cylinder in the axial direction, and a rod that is held by the rod to the inner periphery of the cylinder. A piston is provided that partitions the inside of the cylinder into two working chambers while sliding the outer periphery. These working chambers are composed of an extending side working chamber formed on the rod side and a pressure side working chamber formed on the piston side.

  The piston is provided with a communicating passage that communicates the two working chambers, and a damping valve that generates a predetermined damping force when the working fluid passes through the communicating passage.

  The damper includes a bypass passage that bypasses the communication passage and communicates the working chambers, and a needle that forms an orifice in the middle of the bypass passage. This needle is driven by adjusting means provided on the back surface side, and protrudes and disappears in the bypass path to change the opening area of the orifice.

  By providing the above configuration, as shown by the one-dot chain line in FIG. 7, when the piston speed is low and the damping valve does not act (between 0 and X in FIG. 7), the working fluid passes through the orifice and the damping force. Is generated. When the piston speed increases (X or more in FIG. 7), the working fluid pushes the damping valve and generates a damping force.

JP 2010-007758 A

  The front fork as the conventional fluid pressure buffer is provided with the orifice, so that when the piston speed is low, the working fluid can move between the working chambers through the orifice to generate a damping force. Although useful in some respects, the following problems may be pointed out.

  That is, the damping force when the piston speed is low is generated when the working fluid passes through the orifice, and has a square characteristic as shown between 0 and X in FIG. Therefore, it is difficult to generate a damping force in an extremely low speed region where the piston starts to move, and the ride comfort of the vehicle is deteriorated.

  Accordingly, an object of the present invention is to provide a fluid pressure shock absorber that can easily generate a damping force even in an extremely low speed region and can improve the damping force responsiveness.

  Means for solving the above-mentioned problems include a cylinder that contains a working fluid, a rod that is inserted into the cylinder so as to be movable in the axial direction, and an outer periphery that is held by the rod and that slides on the inner periphery of the cylinder. However, a piston that divides the inside of the cylinder into two working chambers, a communication passage that is formed in the piston and communicates with both working chambers, and a damping that generates a predetermined damping force when the working fluid passes through the communication passage. A choke groove is formed on the outer periphery of a fluid pressure shock absorber comprising a force generating means, a bypass passage that bypasses the communication passage and communicates the working chambers, and a choke passage formed in the middle of the bypass passage. A choke member having a choke portion, a case member into which the choke member is inserted and movable relative to the choke member in the axial direction, the choke member and the case Adjustment means for moving the material relative to each other, and the case member has a cover portion that is in sliding contact with the choke portion and forms the choke flow passage between the choke groove, and the length of the choke flow passage. This is determined by the amount of overlap between the choke portion and the cover portion.

  According to the present invention, when the piston speed is low and the damping force generating means does not operate, the working fluid moves between the two working chambers via the choke channel to generate a damping force. The force has a substantially proportional characteristic, and it becomes easy to generate a damping force even in an extremely low speed region where the piston starts to move, thereby improving the damping force responsiveness and improving the riding comfort of the vehicle.

  Further, it is possible to adjust the damping force by changing the overlap amount of the choke portion and the cover portion by moving the choke member and the case member relative to each other by the adjusting means, and changing the length of the choke flow path.

It is a longitudinal cross-sectional view which shows partially the front fork which is a fluid pressure buffer which concerns on one embodiment of this invention. It is a partial expanded longitudinal cross-sectional view which shows the choke flow path periphery of the front fork which is a fluid pressure buffer which concerns on one embodiment of this invention. It is the example of a change of the front fork which is a fluid pressure buffer which concerns on one embodiment of this invention, and is a longitudinal cross-sectional view which shows the change part of FIG. 1 partially. It is a longitudinal cross-sectional view which shows partially the front fork which is a fluid pressure buffer which concerns on other embodiment of this invention. FIG. 6 is a partially enlarged longitudinal sectional view showing the vicinity of a choke channel of a front fork as a fluid pressure shock absorber according to another embodiment of the present invention. FIG. 5 is a longitudinal sectional view showing a modified example of a front fork as a fluid pressure shock absorber according to another embodiment of the present invention and partially showing a modified part of FIG. 4. It is a graph which shows the damping force characteristic of the front fork which is a fluid pressure buffer which concerns on this invention, and the front fork which is a conventional fluid pressure buffer.

  A fluid pressure shock absorber according to an embodiment of the present invention will be described below with reference to the drawings. The same reference numerals given throughout the several drawings indicate the same or corresponding parts.

  The fluid pressure shock absorber according to the present embodiment is a front fork that suspends a front wheel of a motorcycle and attenuates road surface vibration input to the front wheel due to unevenness of the road surface.

  Although not shown, the front fork is composed of a pair of left and right fork members whose upper end portions are connected by a bridge mechanism, and the lower ends of the fork members are connected to the axles of the front wheels and suspended so as to sandwich the front wheels.

  Further, although not shown, the bridge mechanism has a steering shaft coupled to a handle, and the front mechanism can be steered by operating the handle by including the configuration.

  As shown in FIG. 1, the fork member includes a fork main body including an outer tube 1 and an inner tube 2 that is slidably inserted into the outer tube 1, and accommodates a damper 3 therein.

  The damper 3 includes a cylinder 4 that contains a working fluid, a rod 5 that is inserted into the cylinder 4 so as to be movable in the axial direction, and is held by the rod 5 so that its outer periphery is in sliding contact with the inner periphery of the cylinder 4. However, a piston 6 that divides the inside of the cylinder 4 into two working chambers A and B, a communication passage 60 that is formed in the piston 6 and communicates with both the working chambers A and B, and a working fluid passes through the communication passage 60. Formed in the middle of the bypass passage L1, an expansion side damping valve V as a damping force generating means for generating a predetermined damping force when passing, a bypass passage L1 that bypasses the communication passage 60 and communicates the two working chambers. Choke flow path T.

  Further, as shown in FIG. 2, the damper 3 includes a choke member 7A having a choke portion 70 in which a choke groove 70a is formed on the outer periphery, and the choke member 7A is inserted into the choke member 7A in the axial direction. A relatively movable case member 8A, and adjusting means 9A (FIG. 1) for relatively moving the choke member 7A and the case member 8A are provided.

  The case member 8A has a cover lower portion 86 which is a cover portion that is in sliding contact with the choke portion 70 and forms the choke channel T between the choke groove 70a, and the length of the choke channel T. Is determined by the amount of overlap between the choke portion 70 and the cover lower portion 86.

  Hereinafter, each component of the front fork according to the present embodiment will be described in detail with reference to FIGS. FIG. 1 is a longitudinal sectional view partially showing a front fork according to the present embodiment, with a state in which a choke channel is elongated on the left side of the center line and a state in which the choke channel is shortened on the right side of the center line. Show. FIG. 2 is a partially enlarged longitudinal sectional view showing the vicinity of the choke channel T of the front fork according to the present embodiment.

  The fork main body composed of the outer tube 1 and the inner tube 2 constitutes an inverted front fork in which the outer tube 1 is disposed on the vehicle body side and the inner tube 2 is disposed on the axle side.

  Although the fork body is not shown, the upper and lower ends thereof are sealed with a cap member and a bottom member, respectively, and a seal member 11 slidably contacting the outer periphery of the inner tube 2 is provided at the inner periphery of the lower end portion of the outer tube 1 in the figure. Thus, by providing this configuration, the working fluid and gas accommodated in the fork main body do not leak out of the fork main body.

  Further, the fork main body accommodates therein a suspension spring S that absorbs road vibration and a damper 3 that generates a predetermined damping force. By providing the structure, the front fork can attenuate the expansion and contraction movement of the fork main body due to the absorption of the road surface vibration by the suspension spring S by the damper 3, and the ride comfort of the vehicle can be improved. Become.

  Further, a reservoir chamber R is formed between the fork main body and the damper 3 to store the working fluid. Although not shown, gas is sealed upward through the liquid surface to form an air chamber. The The internal pressure of the air chamber can also be adjusted with an air valve (not shown), and the air chamber expands and contracts with the expansion and contraction of the fork main body to generate a predetermined spring reaction force and functions as an air spring.

  As shown in FIG. 1, the damper 3 housed in the fork main body rises at the axial center portion of the inner tube 2 and the axial center portion of the outer tube 1 as the fork main body expands and contracts. A rod 5 that moves in the cylinder 4 in the axial direction and a piston 6 that is held at the tip of the rod 5 via a case member 8A are provided.

  The cylinder 4 is partitioned from the reservoir chamber R by an annular rod guide 40 that is attached to the upper end side in the drawing and a base member (not shown) that is mounted on the lower end side in the drawing. A working fluid chamber filled with a working fluid is formed between the base member and the base member. This working fluid chamber is divided into upper and lower parts in the figure by the piston 6, and an extension side action chamber A is formed on the upper side in the figure, and a pressure side action chamber B is formed on the lower side in the figure.

  The rod 5 appears and disappears in the working fluid chamber of the cylinder 4 while being supported on the inner periphery of the rod guide 40, and holds the piston 6 at the tip (lower end in the figure) via the case member 8A. The rod 4 is formed in a cylindrical shape, and a control rod 90 constituting the adjusting means 9A is inserted into the axial center portion of the rod 4 so as to be movable in the axial direction.

  The piston 6 is formed in an annular shape and is held on the outer periphery of the case member 8A via a nut N. The piston 6 is formed with communication passages 60 and 61 for communicating the expansion side working chamber A and the pressure side working chamber B. The expansion side damping valve V and the check valve C for opening and closing the communication passages 60 and 61 are connected to the compression side. It is provided opposite to the working chamber B and the extension side working chamber A.

  The communication passages 60 and 61 are always in communication with the extension side working chamber A and the outlet side communication passage 60 whose outlet is blocked by the extension side damping valve V on the compression side action chamber B side, and the pressure side action chamber B at all times. Then, the pressure side communication passage 61 whose outlet is closed by the check valve C on the extension side working chamber A side is provided.

  The extension side damping valve V only allows the working fluid to move from the extension side working chamber A to the pressure side working chamber B, and the check valve C allows the working fluid to move from the pressure side working chamber B to the extension side working chamber A. Only allow movement.

  Although not shown, the base member mounted on the lower end side of the cylinder 4 is formed with a communication path that connects the pressure side working chamber B and the reservoir chamber R, and a check valve that opens and closes the communication path and a pressure side damping. A valve is provided opposite to the pressure side working chamber B and the reservoir chamber R.

  Although not shown in the drawing, the communication path of the base member is always in communication with the reservoir chamber R and the outlet side communication path where the outlet is blocked by the check valve on the pressure side working chamber B side, and the pressure side working chamber B. A pressure-side communication passage whose outlet is closed by a pressure-side damping valve on the reservoir chamber R side.

  The check valve provided in the base member only allows the working fluid to move from the reservoir chamber R to the pressure side working chamber B, and the pressure side damping valve moves the working fluid from the pressure side working chamber B to the reservoir chamber R. Only allow that.

  With the above configuration, when the rod 5 is withdrawn from the cylinder 4 in the front fork extension process, the extension side working chamber A is pressurized and the working fluid pushes and opens the extension side damping valve V, so that the extension side of the piston 6 is extended. A predetermined damping force is generated through the communication path 60. At this time, the working fluid deficient in the working fluid chamber of the rod 5 withdraws opens the check valve of the base member and passes through the communicating passage on the same extension side.

  On the other hand, when the rod 5 is immersed in the cylinder 4 in the front fork contraction process, the pressure side working chamber B is pressurized and the working fluid opens the check valve C of the piston 6 and passes through the communication passage 61 on the pressure side. At this time, surplus working fluid in the working fluid chamber of the rod 5 pushes open the compression side damping valve of the base member and passes through the communication passage on the same pressure side to generate a predetermined damping force.

  That is, in the present embodiment, the extension side damping valve V and the compression side damping valve constitute a damping force generating means.

  The case member 8A that holds the piston 6 at the tip of the rod 5 is screwed into the outer periphery of an annular tip member 63 that is formed in a substantially cylindrical shape and screwed into the outer periphery of the tip portion (lower end portion in the drawing). It becomes. And case member 8A has a case member main body (not shown) which accommodates choke member 7A inside, and piston holding part 81 which has an outer diameter smaller than this case main body. A seal 61 that slides on the outer periphery of the control rod 90 is provided on the inner periphery of the tip member 63. With this seal 61, the working fluid flows from the coupling gap between the tip member 63 and the case member 8A into the shaft center portion of the rod 5. To prevent intrusion. The case member 8A is formed with a longitudinal hole 12 penetrating in the axial direction and a transverse hole 13 intersecting the longitudinal hole 12 and penetrating in the radial direction.

  The case body is formed in a cylindrical shape, and in order from the upper side in the drawing, is screwed to the outer periphery of the tip member 63, a choke insertion portion 83 into which the choke member 7 </ b> A is inserted, and the choke insertion portion 83. A large inner diameter portion 84 having an inner diameter larger than the inner diameter, and the lateral hole 13 is opened in a substantially central side surface of the choke insertion portion 83. As shown in FIG. 2, in the choke insertion portion 83, the upper side in the figure from the lateral hole 13 is the cover upper part 85 and the lower side in the figure is the cover lower part 86.

  As shown in FIG. 1, the piston holding portion 81 is formed in a cylindrical shape and has an outer diameter smaller than the large inner diameter portion 84, and a stepped portion 73 is provided on the outer peripheral portion of the lower surface of the large inner diameter portion 84 in the drawing. The piston 6 is sandwiched between the stepped portion 73 and the nut N. Further, the inside of the piston holding portion 81 communicates with the inside of the large inner diameter portion 84 to constitute a part of the vertical hole 12.

  The choke member 7A inserted into the choke insertion portion 83 has a hollow portion (not shown), and as shown in FIG. 2, an annular groove is formed at a substantially central position of the axial length on the outer periphery thereof. 71, a base portion 72 having a seal 72a on the outer periphery in the drawing is formed above the annular groove 71, and a choke portion 70 having a helical choke groove 70a on the outer periphery in the lower portion in the drawing from the annular groove 71 is formed. .

  The base 72 is disposed in the cover upper portion 85, the annular groove 71 is disposed in the lateral hole 13, and the choke portion 70 is disposed opposite to the cover lower portion 86, and the choke groove 70 a of the overlapping portion where the choke portion 70 and the cover lower portion 86 overlap each other. And a choke channel T is formed between the inner periphery of the cover lower portion 86. In other words, in the present embodiment, the cover lower portion 86 corresponds to a cover portion referred to in the claims.

  In addition, although it becomes possible to reduce weight by forming a hollow part in the said choke member 7A, you may form solidly. Further, by forming the choke groove 70a in a spiral shape, it is possible to form the choke groove 70a long while shortening the axial length of the choke portion 70, and to easily secure the length of the choke channel T. Become. However, the shape of the choke groove 70a is not limited to the above, and it is possible to select an appropriate shape as long as the choke flow path T can be formed between the cover lower portion 86 and the choke groove 70a.

  The opening on the rod 5 side in the vertical hole 12 is closed by a seal 72a (FIG. 2) provided on the choke member 7A. As a result, the working fluid can move between the expansion side working chamber A and the pressure side working chamber B through the inside of the lateral hole 13, the annular groove 71, the choke flow path T, the large inner diameter portion 84, and the piston holding portion 81. It becomes.

  That is, a bypass path L1 that bypasses the communication paths 60 and 61 of the piston 6 is configured inside the horizontal hole 13, the annular groove 71, the choke flow path T, the large inner diameter portion 84, and the piston holding portion 81.

  Further, since the choke channel T is formed in the middle of the bypass channel L1, the damping force generated when passing through the choke channel T has a substantially proportional characteristic (between 0 and Y in FIG. 7), and the piston Even in the extremely low speed range where the 6 starts to move, it becomes easy to generate a damping force, thereby improving the damping force responsiveness and improving the riding comfort of the vehicle.

  That is, as shown in FIG. 7, when the piston speed is low and the damping force generating means (extension-side damping valve V or compression-side damping valve) does not operate (between 0 and Y in FIG. 7), the working fluid is choke flow path T. Damping force is generated by passing through. When the piston speed increases (Y or higher in FIG. 7), the working fluid pushes open the damping force generating means to generate a damping force.

  The choke member 7A and the case member 8A can be moved relative to each other via the adjusting means 9A. In the present embodiment, the choke member 7A is moved in the axial direction by the adjusting means 9A to The overlap amount of the cover lower part 86 is changed, and the length of the choke channel T is adjusted.

  As shown in FIG. 1, the adjusting means 9A is opposed to the control rod 90 that is inserted into the axial center of the rod 5 and abuts against the base 72 of the choke member 7A, and the non-piston side end of the control rod 90. An adjuster (not shown) that moves the control rod 90 in the axial direction, and a biasing spring 91 that biases the choke member 7A toward the control rod 90.

  With the above configuration, when the adjuster is driven to advance the control rod 90 toward the piston 6 (right side in FIG. 1), the choke member 7A is moved downward in the figure against the urging force of the urging spring 91. Moving. As a result, the choke portion 70 protrudes from the cover lower portion 86, the amount of overlap between the choke portion 70 and the cover lower portion 86 is reduced, the choke passage T is shortened, and the damping that occurs when the working fluid passes through the bypass passage L1. The power is reduced.

  On the other hand, when the adjuster is driven to retract the control rod 90 (left side in FIG. 1), the choke member 7A moves upward in the drawing until it comes into contact with the control rod 90 according to the urging force of the urging spring 91. As a result, the choke part 70 enters the cover lower part 86, the overlap amount between the choke part 70 and the cover lower part 86 increases, the choke flow path T becomes longer, and this occurs when the working fluid passes through the bypass path L1. Damping force increases.

  That is, it is possible for the occupant to arbitrarily set the damping force by relatively moving the choke member 7A and the case member 8A with the adjusting means 9A.

  In the present embodiment, the adjuster moves the control rod 90 in the axial direction to drive the choke member 7A, which corresponds to a drive member in the scope of the claims, but is not limited thereto. Of course, the drive member may be used.

  When the amount of movement of the control rod 90 is the amount of movement of the control rod 90 toward the piston 6 as compared with the state in which the control rod 90 is most retracted, in this embodiment, the larger the amount of movement. The amount of overlap between the choke portion 70 and the cover lower portion 86 is reduced, and the amount of movement and the amount of overlap are inversely proportional. Therefore, by setting the expansion rate of the rod 5 to be larger than the expansion rate of the control rod 90, it is possible to guarantee a temperature change due to the working fluid.

  Specifically, when the front fork becomes hotter than when the damping force is set, the control rod 90 is shortened with respect to the rod 5 due to thermal expansion, and the control rod 90 is substantially retracted to reduce the amount of movement. As a result, the amount of overlap between the choke portion 70 and the cover lower portion 86 is increased to lengthen the choke flow path T, thereby preventing the viscosity of the working fluid from being lowered due to the temperature rise and the damping force from becoming lower than the setting.

  On the other hand, when the temperature of the front fork becomes lower than when the damping force is set, the control rod 90 becomes longer than the rod 5, and the control rod 90 moves substantially forward to increase the amount of movement. Thereby, the overlap amount of the choke part 70 and the cover lower part 86 is reduced, the choke flow path T is shortened, and the viscosity of the working fluid is increased due to the temperature drop and the damping force is prevented from becoming higher than the setting.

  That is, by appropriately setting the thermal expansion coefficients of the rod 5 and the control rod 90, it is possible to ensure the temperature by absorbing the influence on the damping force caused by the change in the viscosity of the working fluid due to the temperature change.

  The setting of the expansion coefficient of the rod 5 and the control rod 90 can be realized by using different materials. In the present embodiment, for example, the rod 5 is made of aluminum and the control rod 90 is made of iron. What is necessary is just to form.

  In the present embodiment, as shown in FIG. 3, an annular groove 87 is provided on the inner periphery of the choke insertion portion 83 so as to face the annular groove 71 of the choke member 7A and the lateral hole 13 is opened. The amount of movement and the amount of overlap between the case portion 70 and the choke lower portion 86 may be proportional to each other.

  FIG. 3 is a longitudinal sectional view partially showing a modification of the front fork according to the embodiment, and shows a state in which the choke channel T is elongated on the left side of the center line, and the choke channel on the right side of the center line. The state where T is shortened is shown. In this case, since the amount of movement and the amount of overlap are proportional, it is possible to ensure temperature by setting the expansion rate of the rod 5 to be lower than the expansion rate of the piston rod 90.

  Specifically, when the front fork becomes hotter than when the damping force is set, the control rod 90 becomes longer than the rod 5 due to thermal expansion, and the control rod 90 moves substantially forward to increase the amount of movement. As a result, the amount of overlap between the choke portion 70 and the cover lower portion 86 is increased to lengthen the choke flow path T, thereby preventing the viscosity of the working fluid from being lowered due to the temperature rise and the damping force from becoming lower than the setting.

  On the other hand, when the front fork becomes cooler than when the damping force is set, the control rod 90 is shortened with respect to the rod 5, and the control rod 90 is substantially retracted to reduce the movement amount. Thereby, the overlap amount of the choke part 70 and the cover lower part 86 is reduced, the choke flow path T is shortened, and the viscosity of the working fluid is increased due to the temperature drop and the damping force is prevented from becoming higher than the setting.

  In this case, the expansion rate of the rod 5 and the control rod 90 may be set by, for example, forming the rod with aluminum and the control rod 90 with iron. A pair of upper and lower sealing members that move in the axial direction while sealing the adjuster side and piston side openings are provided, the working fluid is sealed inside, and the operation from the adjuster is performed via the working fluid and the both sealing members. Then, it may be transmitted to the choke member 7A.

  Next, a fluid pressure shock absorber showing another embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a longitudinal sectional view partially showing the front fork according to the present embodiment, in which the choke channel T is elongated on the left side of the center line, and the choke channel T is shortened on the right side of the center line. Indicates the state. FIG. 5 is a partially enlarged longitudinal sectional view showing the periphery of the choke channel T of the front fork according to the present embodiment.

  The fluid pressure shock absorber according to another embodiment has the same basic structure as that of the above embodiment, and the piston 6 is held at the tip of the rod 5 via a choke member 7B. The outer periphery of the choke member 7B The case member 8 </ b> B to be mounted on is moved in the axial direction by the adjusting member 9 to change the length of the choke channel T. Therefore, only the configuration different from that of the embodiment will be described below, and the same configuration will be denoted by the same reference numerals and detailed description thereof will be omitted.

  The choke member 7B according to the present embodiment includes, in order from the top in the figure, a rod connecting portion 701 that is screwed to the tip end portion of the rod 5, a choke body 702 to which the case member 8B is mounted on the outer periphery, and a nut N. And a piston holding part 703 for holding the piston 6 on the outer periphery.

  The rod connecting portion 701 includes a screw hole 701a formed in the upper part in the figure and a diameter hole 701b formed in the lower part in the figure and penetrating in the radial direction. The diameter hole 701b is formed at the bottom of the screw hole 701a. The screw hole 701a communicates with a shaft hole 701c to be opened.

  The choke main body 702 is formed in a cylindrical shape, and in order from the top in the figure, a base portion 704 having a seal 704a on the outer periphery, a choke portion 700 having a spiral choke groove 700a (FIG. 5) on the outer periphery, 705, and an annular groove 706 is formed at the boundary between the base portion 704 and the choke portion 700. In addition, the annular groove 706 is provided with a lateral hole 23 that is opened in the radial direction toward the inside of the choke body 702. The shape of the choke groove 700a can be selected as appropriate as in the choke groove 70a of the embodiment.

  The piston holding portion 703 is formed in a cylindrical shape and has an outer diameter smaller than that of the body portion 705. A step portion 707 is formed on the outer peripheral portion of the lower surface of the body portion 705 in the figure, and the step portion 707 and the nut N are formed. The piston 6 is sandwiched between the two. Further, the inside of the piston holding part 703 communicates with the inside of the choke body 702 and forms the vertical hole 22 together with the inside of the choke body 702.

  The case member 8B mounted on the outer periphery of the choke body 702 is movable in the axial direction on the outer periphery of the choke body 702 by the adjusting means 9, and as shown in FIG. 5, the inner periphery of the upper part 801 in the drawing is the choke member 7B. The lower portion 802 in the figure overlaps with the choke portion 700 through the seal 704a, and the choke channel T is formed between the inner periphery thereof and the choke groove 700a. That is, in the present embodiment, the lower portion 802 of the case member 8B corresponds to the cover portion in the claims.

  With the above configuration, the working fluid can move between the expansion side working chamber A and the compression side working chamber B via the choke flow path T, the annular groove 706, the lateral hole 23, and the vertical hole 22, and the choke The flow path T, the annular groove 706, the horizontal hole 23, and the vertical hole 22 constitute a bypass path L2 that bypasses the communication paths 60 and 61 of the piston 6.

  Further, since the choke channel T is formed in the middle of the bypass channel L2, the damping force generated when passing through the choke channel T has a substantially proportional characteristic (between 0 and Y in FIG. 7). Similar to the embodiment, it is possible to easily generate a damping force even in an extremely low speed region where the piston 6 starts to move, thereby improving the damping force responsiveness and improving the riding comfort of the vehicle.

  The choke member 7B and the case member 8B can be moved relative to each other via the adjusting means 9B. In the present embodiment, the adjusting member 9B moves the case member 8B in the axial direction to move the choke portion 7B. The amount of overlap of the lower portion 802 of the case portion 8B material is changed, and the length of the choke channel T is adjusted.

  As shown in FIG. 4, the adjusting means 9 </ b> B moves the control rod 90 in the axial direction so as to oppose the control rod 90 inserted into the axial center portion of the rod 5 and the non-piston side end portion of the control rod 90. An adjuster (not shown), a tip rod 93 that is inserted into the axial center of the rod 5 so that the control rod 90 comes into contact with the back surface and the head protrudes into the diameter hole 701b, and the tip rod 93 and the case member 8B, and a biasing spring 95 that biases the case member 8B toward the control rod 90. Note that the outer periphery of the tip rod 93 is in sliding contact with the inner periphery of the rod 5 via a seal (not shown), and this seal allows the working fluid in the extension side working chamber A to enter the axial center of the rod 5. To prevent.

  With the above configuration, when the adjuster is driven to retract the control rod 90 away from the piston 6 (right side in FIG. 4), the tip rod 93 contacts the control rod 90 according to the urging force of the urging spring 95. The receiving plate 94 and the case member 8B move upward in the drawing until they come into contact. As a result, the amount of overlap between the choke portion 700 and the lower portion 802 of the case member 8B is reduced, the choke flow path T is shortened, and the damping force generated when the working fluid passes through the bypass path L2 is reduced.

  On the other hand, when the adjuster is driven to advance the control rod 90 (left side in FIG. 4), the case member 8B moves downward in the figure against the urging force of the urging spring 95. As a result, the amount of overlap between the choke portion 700 and the lower portion 802 of the case member 8B increases, the choke flow path T becomes longer, and the damping force generated when the working fluid passes through the bypass path L2 increases.

  That is, the driver can arbitrarily set the damping force by relatively moving the choke member 7B and the case member 8B by the adjusting means 9B.

  In the present embodiment, the adjuster moves the control rod 90 in the axial direction to drive the case member 8B, which corresponds to the drive member in the claims, but is not limited thereto. Needless to say, a solenoid, a motor, or the like may be used as a drive member in the same manner as described above.

  In the present embodiment, since the amount of movement of the control rod 90 is proportional to the amount of overlap between the choke portion 700 and the lower portion 802 of the case member 8B, the expansion rate of the rod 5 is set smaller than the expansion rate of the control rod 90. This makes it possible to guarantee the temperature.

  Specifically, when the front fork becomes hotter than when the damping force is set, the control rod 90 becomes longer than the rod 5 due to thermal expansion, and the control rod 90 moves substantially forward to increase the amount of movement. As a result, the amount of overlap between the choke portion 700 and the lower portion 802 of the case member 8B is increased, the choke flow path T is lengthened, and the viscosity of the working fluid is reduced due to the temperature rise to prevent the damping force from being lower than the setting. To do.

  On the other hand, when the front fork becomes cooler than when the damping force is set, the control rod 90 is shortened with respect to the rod 5, and the control rod 90 is substantially retracted to reduce the movement amount. As a result, the amount of overlap between the choke portion 700 and the lower portion 802 of the case member 8B is reduced, the choke flow path T is shortened, and the viscosity of the working fluid rises due to a temperature drop to prevent the damping force from becoming higher than the setting. To do.

  In the other embodiment, as shown in FIG. 6, annular grooves 708 and 800 are formed on the inner periphery of the case main body 8B and the lower outer periphery in the drawing of the choke portion 700 of the choke member 7B. The amount of movement of 90 and the overlapping amount of the choke portion 700 and the lower portion of the case member 8B may be inversely proportional.

  FIG. 6 is a longitudinal sectional view partially showing a modified example of the front fork according to another embodiment, in which the choke channel T is elongated on the left side of the center line, and the choke on the right side of the center line. The state which shortened the flow path T is shown. In this case, the temperature can be ensured by setting the expansion rate of the rod 5 higher than the expansion rate of the piston rod 90.

  Specifically, when the front fork becomes hotter than when the damping force is set, the control rod 90 is shortened with respect to the rod 5 due to thermal expansion, and the control rod 90 is substantially retracted to reduce the amount of movement. As a result, the amount of overlap between the choke portion 700 and the lower portion 802 of the case member 8B is increased, the choke flow path T is lengthened, and the viscosity of the working fluid is reduced due to the temperature rise to prevent the damping force from being lower than the setting. To do.

  On the other hand, when the front fork becomes cooler than when the damping force is set, the control rod 90 becomes longer than the rod 5, and the control rod 90 moves substantially forward, and the movement amount of the control rod 90 increases. As a result, the amount of overlap between the choke portion 700 and the lower portion 802 of the case member 8B is reduced, the choke flow path T is shortened, and the viscosity of the working fluid rises due to a temperature drop to prevent the damping force from becoming higher than the setting. To do.

  While the preferred embodiment of the present invention has been described above, it should be understood that modifications, variations and changes may be made without departing from the scope of the claims.

  For example, in the above embodiment, the present invention is embodied in the front fork. However, the present invention is not limited to this. For example, the present invention may be embodied in another fluid pressure buffer such as a rear cushion unit.

  In the above embodiment, the front fork and the damper are set upside down. However, the front fork and the damper may be set upright, and even if the present invention is embodied in a double rod type damper. good.

A Stretching side working chamber B Pressure side working chamber C Check valves L1, L2 Bypass passage R Reservoir chamber T Choke passage V Stretching side damping valve 1 Outer tube 2 Inner tube 3 Damper 4 Cylinder 5 Rod 6 Piston 7A, 7B Choke member 8A, 8B Case member 9A, 9B Adjustment means 11 Seal member 70, 700 Choke part 70a, 700a Choke groove 90 Control rod

Claims (5)

A cylinder that contains the working fluid, a rod that is inserted into the cylinder so as to be movable in the axial direction, and the inside of the cylinder is divided into two working chambers while being held by the rod and in sliding contact with the inner periphery of the cylinder. A partitioning piston, a communicating passage formed in the piston and communicating with the two working chambers, a damping force generating means for generating a predetermined damping force when the working fluid passes through the communicating passage, and bypassing the communicating passage In a fluid pressure shock absorber comprising a bypass passage communicating the two working chambers and a choke passage formed in the middle of the bypass passage,
A choke member having a choke portion formed with a choke groove on the outer periphery; a case member in which the choke member is inserted and movable relative to the choke member in the axial direction; and the choke member and the case member Adjusting means for moving,
The case member has a cover portion that is in sliding contact with the choke portion and forms the choke channel between the choke groove, and the choke channel has a length between the choke portion and the cover portion. A fluid pressure buffer characterized by being determined by the amount of overlap.   The fluid pressure shock absorber according to claim 1, wherein the choke groove is spirally formed on an outer periphery of the choke member. The piston is held by the rod via the case member, and the bypass path is formed in the case member.
The fluid pressure shock absorber according to claim 1 or 2, wherein the choke member is moved in the axial direction in the case member by the adjusting means. The piston is held by the rod via the choke member, and the bypass path is formed between the choke member and the choke member and the case member,
The fluid pressure shock absorber according to claim 1 or 2, wherein the case member is moved in an axial direction on an outer periphery of the choke member by the adjusting means. The adjusting means includes a control rod that is inserted into an axial center portion of the rod formed in a cylindrical shape, and a drive member that moves the control rod in the axial direction to drive the case member or the choke member. And
When the movement amount of the control rod is proportional to the overlap amount, the expansion rate of the rod is set smaller than the expansion rate of the control rod, and when the movement amount of the control rod is inversely proportional to the overlap amount, the expansion of the rod The fluid pressure buffer according to any one of claims 1 to 4, wherein a rate is set to be larger than an expansion rate of the control rod.

Images