WO2024180999A1 - Shock absorber - Google Patents

Abstract

This shock absorber (D) comprises a cylinder (1), a cylindrical piston rod (2) that is inserted into the cylinder (1) so as to be movable in the axial direction, a piston (3) that is connected to the piston rod (2) and that divides the interior of the cylinder (1) into an expansion-side chamber (R1) and a compression-side chamber (R2), a damping passage (P) via which the expansion-side chamber (R1) and the compression-side chamber (R2) communicate, a control rod (4) inserted into the piston rod (2) so as to be movable in the axial direction, a damping force adjustment valve (5) in which resistance to the flow of liquid passing through the damping passage (P) is changed via displacement of the control rod (4), a housing (6) that is connected to the piston rod (2) and that has a hole (6c) of circular cross section, a push nut (7) inserted into the hole (6c) of the housing (6), a motor (8) provided to the housing (6), and a threaded shaft (9) that is threaded into an eccentric screw hole (7a) provided in the push nut (7) and that is driven by the motor (8).

Description

Shock absorber

The present invention relates to a shock absorber.

Shock absorbers are used, for example, by being interposed between the body and wheels of a saddle-type vehicle, and suppress vibrations between the body and wheels by the damping force generated when the shock absorber expands and contracts.

As disclosed in JP2012-047310A, for example, such a shock absorber is configured to include a cylinder, a piston movably inserted into the cylinder to divide the cylinder into an extension side chamber and a compression side chamber filled with hydraulic oil, a piston rod movably inserted into the cylinder and connected to the piston, a tank for storing hydraulic oil, an extension side leaf valve provided on the piston to provide resistance to the flow of hydraulic oil from the extension side chamber to the compression side chamber, a compression side leaf valve provided on the piston to provide resistance to the flow of hydraulic oil from the compression side chamber to the extension side chamber, a bypass passage connecting the extension side chamber and the compression side chamber via the piston rod, and a needle valve provided in the bypass passage to provide resistance to the flow of hydraulic oil passing through the bypass passage (see, for example, Patent Document 1).

In a shock absorber constructed in this way, in order to make it possible to adjust the degree of opening of the needle valve, the piston rod is made cylindrical, a control rod is inserted into the piston rod and abuts against the needle valve, and an adjuster is provided at the end of the piston rod for mounting on the vehicle body, which displaces the control rod in the axial direction.

The adjuster is cylindrical and has a conical contact portion at its tip that contacts the tip of the control rod, a threaded portion on the outer periphery of the base end, and a groove at the base end for inserting a tool. It is screwed into a threaded hole that opens from the side of the bracket and faces the opening at the top end of the piston rod.

By using a tool to rotate the adjuster, it can be moved axially back and forth within the threaded hole. When the adjuster is displaced in a direction that inserts it into the threaded hole, the conical abutment portion pushes the control rod into the piston rod, so that the control rod moves in a direction that inserts into the piston rod and the opening area of the needle valve can be reduced. Conversely, when the adjuster is displaced in a direction that removes it from the threaded hole, the abutment portion retracts and the pressure inside the piston rod that the needle valve receives presses the control rod in a direction that moves out of the piston rod, so that the control rod moves in a direction that removes it from within the piston rod and the opening area of the needle valve increases.

JP2012-047310A

As mentioned above, in conventional shock absorbers, the user of the shock absorber can manually operate the adjuster to adjust the opening degree of the needle valve and thereby adjust the damping force generated by the shock absorber. In this way, in conventional shock absorbers, the damping force is adjusted by manually operating the adjuster, but there are cases where it is desired to motorize the damping force adjustment by rotating the adjuster using a motor.

However, conventional shock absorbers use a structure in which an adjuster with a large outer diameter is screwed into a screw hole in a bracket, which means that the adjuster is subjected to a large frictional resistance when rotated. As a result, in order to rotate the adjuster, a large motor capable of generating torque that overcomes the frictional resistance is required, which makes the entire shock absorber larger and difficult to install in a vehicle, making it difficult to motorize the damping force adjustment in conventional shock absorbers.

The present invention aims to provide a shock absorber that allows for motorized damping force adjustment.

　In order to solve the above problems, the shock absorber of the present invention includes a cylinder, a cylindrical piston rod inserted into the cylinder so as to be axially movable, a piston connected to the piston rod and inserted into the cylinder so as to be axially movable, and dividing the inside of the cylinder into an extension side chamber and a compression side chamber, a damping passage connecting the extension side chamber and the compression side chamber, a control rod inserted into the piston rod so as to be axially movable, a damping force adjustment valve provided in the damping passage and changing the resistance to the flow of liquid passing through the damping passage by the displacement of the control rod, a housing connected to the piston rod and having a hole with a circular cross section, a cylindrical push nut inserted into the hole of the housing so as to be axially slidable, abutting against the control rod and displacing it axially within the hole, thereby displacing the control rod in the axial direction, a motor provided in the housing, and a screw shaft screwed into an eccentric screw hole provided at a position radially eccentric from the axis of the push nut and driven by the motor.

In a shock absorber configured in this manner, the screw shaft driven by the motor is screwed into an eccentric screw hole in the push nut, so the outer diameter of the screw is smaller than in conventional structures, and the torque required of the motor to displace the push nut is smaller. In addition, the push nut is cylindrical and slidably inserted into a hole with a circular cross section, and a rotation stop is formed by the fit between the hole and the push nut, so the frictional force generated between the hole and the push nut can be reduced compared to rotation stop mechanisms that use keys, etc.

FIG. 1 is a cross-sectional view of a shock absorber according to one embodiment. FIG. 2 is a diagram showing a shock absorber attached to a saddle-type vehicle. FIG. 3 is a partially enlarged cross-sectional view of the shock absorber according to the embodiment. FIG. 4 is a partially enlarged cross-sectional view of a shock absorber according to a first modified example of the embodiment. FIG. 5 is a partially enlarged cross-sectional view of a shock absorber according to a second modified example of the embodiment.

The present invention will be described below based on the embodiment shown in the drawings. As shown in FIG. 1, the shock absorber D in one embodiment includes a cylinder 1, a cylindrical piston rod 2 inserted into the cylinder 1 so as to be movable in the axial direction, a piston 3 connected to the piston rod 2 and inserted into the cylinder 1 so as to be movable in the axial direction, and dividing the cylinder 1 into an extension side chamber R1 and a compression side chamber R2, a damping passage P connecting the extension side chamber R1 and the compression side chamber R2, a control rod 4 inserted into the piston rod 2 so as to be movable in the axial direction, a needle valve 5 provided in the damping passage P as a damping force adjustment valve that changes the resistance applied to the flow of liquid passing through the damping passage P by the displacement of the control rod 4, a housing 6 connected to the piston rod 2 and having a hole 6c with a circular cross section, a push nut 7 inserted into the hole 6c of the housing 6, a motor 8 provided in the housing 6, and a screw shaft 9 screwed into an eccentric screw hole 7a provided in the push nut 7 and driven by the motor 8.

As shown in FIG. 2, this shock absorber D is used by being interposed between the body F and the rear wheel W of a saddle-type vehicle M such as a motorcycle, and suppresses vibrations of the body F and the rear wheel W. Note that the shock absorber D may also be used to suppress vibrations of vehicles other than the saddle-type vehicle M.

The various components of shock absorber D will be described in detail below. As shown in FIG. 1, cylinder 1 is cylindrical, and its lower end in FIG. 1 is closed by bottom cap 11. An annular rod guide 10, through which piston rod 2 is inserted, is attached to the upper end in FIG. 1 of cylinder 1. Rod guide 10 is provided with an annular seal member 10a on its inner periphery that slides against the outer periphery of piston rod 2, and an annular bush 10b. Sealing member 10a seals the outer periphery of piston rod 2 to seal inside cylinder 1, and bush 10b guides the axial movement of piston rod 2.

The inside of the cylinder 1 is divided into an extension side chamber R1 and a compression side chamber R2, which are filled with liquid, by a piston 3 attached to the outer periphery of the tip of the piston rod 2. In this embodiment, the liquid is hydraulic oil, but other liquids such as water or an aqueous solution can also be used.

The piston rod 2 is cylindrical and hollow, with its upper end in FIG. 1 penetrating the rod guide 10 and protruding outside the cylinder 1. A housing 6 having a bracket 6b that can be connected to the vehicle body F of the saddle-type vehicle M is attached to the upper end of the piston rod 2 in FIG. 1. Furthermore, a small diameter portion 2a is provided at the lower end of the piston rod 2 to which the piston 3 is attached.

The piston 3 is annular and is attached to the outer periphery of the small diameter portion 2a of the piston rod 2, and has an extension side port 3a and a compression side port 3b that communicate in parallel with the extension side chamber R1 and the compression side chamber R2, respectively. An extension side damping valve 13 is annular and attached to the outer periphery of the small diameter portion 2a to open and close the extension side port 3a, and is stacked at the lower end of the piston 3 in FIG. 1. A compression side check valve 14 is annular and attached to the outer periphery of the small diameter portion 2a to open and close the compression side port 3b, and is stacked at the upper end of the piston 3 in FIG. 1. The piston 3, the extension side damping valve 13, and the compression side check valve 14 are fitted to the outer periphery of the small diameter portion 2a of the piston rod 2, and are fixed to the piston rod 2 by a piston nut 15 that is screwed to the lower end of the small diameter portion 2a.

In the shock absorber D of this embodiment, the extension side damping valve 13 is a laminated leaf valve that is composed of multiple annular plates stacked on the lower end of the piston 3 in FIG. 1, and is fixed on the inner circumferential side. When the outer circumferential side is deflected by the pressure of the extension side chamber R1, the extension side damping valve 13 opens and closes the extension side port 3a. When the shock absorber D is expanded, the extension side damping valve 13 opens to provide resistance to the flow of liquid passing through the extension side port 3a from the extension side chamber R1 to the compression side chamber R2, and closes to block the extension side port 3a when the shock absorber D is contracted. Note that the extension side damping valve 13 may be a damping valve other than a laminated leaf valve as long as it provides resistance to the flow of liquid from the extension side chamber R1 to the compression side chamber R2 and exerts a damping force that prevents the expansion of the shock absorber D when the shock absorber D is expanded.

In contrast, in the shock absorber D of this embodiment, the compression side check valve 14 is configured as a leaf valve with its inner circumference fixed and placed on the upper end of the piston 3 in FIG. 1, and is a valve that opens the compression side port 3b when the outer circumference is deflected by the pressure of the compression side chamber R2. The compression side check valve 14 can open and close the compression side port 3b, and when the shock absorber D expands, it closes to block the compression side port 3b, and when the shock absorber D contracts, it opens to allow the flow of liquid through the compression side port 3b from the compression side chamber R2 to the extension side chamber R1. The compression side check valve 14 is a valve that can only allow the flow of liquid from the compression side chamber R2 to the extension side chamber R1 when the shock absorber D contracts without much resistance, but it may be set to provide resistance.

In this embodiment, as shown in FIG. 1, the bottom cap 11 includes a cap portion 11a that is attached to the lower end of the cylinder 1 in FIG. 1, a tank holding portion 11b that holds the tank 16, and a connection portion 11c that extends from the side of the cap portion 11a and is connected to the tank holding portion 11b.

The cap portion 11a is cylindrical with a bottom and is attached to the lower end of the cylinder 1 in FIG. 1, closing the lower end of the cylinder 1. At the bottom, which is the lower part in FIG. 1, there is a bracket 11d that can be connected to a swing arm SA that holds the rear wheel W of a saddle-type vehicle M.

A cylindrical tank 16 is attached to the tank holding portion 11b. A free piston 17 is inserted into the tank 16 so that it can slide freely, and the inside of the tank 16 is divided by the free piston 17 into a liquid chamber L which is filled with liquid, and an air chamber G which is filled with gas. Gas is sealed in the air chamber G so that the pressure in the air chamber G is at least equal to or higher than atmospheric pressure when the shock absorber D is fully extended. The liquid chamber L and the air chamber G in the tank 16 can be divided by using a diaphragm, bladder, etc., in addition to using the free piston 17.

The fluid chamber L in the tank 16 is connected to the compression side chamber R2 in the cylinder 1 through the compression side damping passage 11e and the suction passage 11f provided in the connection portion 11c. The compression side damping passage 11e is provided with a compression side damping valve 18 that only allows fluid to flow from the compression side chamber R2 to the fluid chamber L of the tank 16 and provides resistance to the fluid flow, and the suction passage 11f is provided with an extension side check valve 19 that only allows fluid to flow from the fluid chamber L to the compression side chamber R2.

The piston rod 2 is cylindrical and has a horizontal hole 2b that opens from the side above the piston 3 in FIG. 1 and leads to the inside, forming a damping passage P that communicates between the expansion side chamber R1 and the compression side chamber R2 through the horizontal hole 2b and the inside. An annular valve seat member 51 is attached to the inner circumference of the piston rod 2 below the horizontal hole 2b in FIG. 1. A needle valve body 52 is inserted into the piston rod 2 so as to be movable in the axial direction. The needle valve body 52 has a conical needle 52a at its lower end in FIG. 1, which is its tip, and a large-diameter sliding portion 52b at its upper end in FIG. 1, which is its base, that comes into sliding contact with the inner circumference of the piston rod 2.

The needle valve body 52, together with the valve seat member 51, constitutes the needle valve 5, and by moving in the vertical direction in FIG. 1, which is the axial direction, within the piston rod 2, the needle 52a at the tip can be moved closer to or closer to the upper open end of the valve seat member 51, thereby adjusting the size of the annular gap between the needle 52a and the valve seat member 51. Thus, when the needle valve body 52 is moved axially, the needle valve 5 can adjust the flow path area and adjust the resistance to the flow of liquid passing through the damping passage P. In addition, when the needle 52a of the needle valve body 52 is seated on the open end of the valve seat member 51, the needle valve 5 closes, cutting off communication between the expansion side chamber R1 and the compression side chamber R2 through the damping passage P.

The sliding portion 52b is in sliding contact with the inner circumference of the piston rod 2, above the horizontal hole 2b in FIG. 1, and a notched groove 52c is provided on the outer circumference along the axial direction. The outer diameter of the needle valve body 52 below the sliding portion 52b in FIG. 1 is smaller than the inner diameter of the piston rod 2, and when the needle valve 5 opens, liquid can pass between the outer circumference below the sliding portion 52b of the needle valve body 52 and the inner circumference of the piston rod 2, and move back and forth within the damping passage P.

The control rod 4 is inserted into the piston rod 2 so as to be movable in the axial direction with its lower end abutting against the upper end of the sliding portion 52b of the needle valve body 52, and its upper end protrudes upward from the upper end of the piston rod 2. The control rod 4 has a head 4a which is the upper end, and a shaft portion 4b which hangs down from the head 4a, is inserted into the piston rod 2 and abuts against the needle valve body 52, and the upper end of the head 4a is conical. The outer diameter of the shaft portion 4b is smaller than the inner diameter of the piston rod 2, and the shaft portion 4b is inserted slidably into the annular bearing 22, annular packing 23, and annular cap 24 which are provided on the inner circumference of the upper end of the piston rod 2. The control rod 4 is inserted slidably into the bearing 22, and can be displaced axially inside the piston rod 2 without axial wobble. In addition, the gap between the shaft 4b and the piston rod 2 is sealed with a packing 23, preventing some of the liquid passing through the damping passage P from passing through the notched groove 52c of the sliding portion 52b and leaking out of the shock absorber D from the upper end of the piston rod 2.

The cap 24 presses the packing 23 from above, preventing it from falling off. In this way, when the shaft 4b separates from the needle valve body 52, the control rod 4 is pressed upward against the piston rod 2 by the pressure of the liquid filling the piston rod 2; however, because the outer diameter of the shaft 4b is smaller than the inner diameter of the piston rod 2 to reduce the pressure-receiving area, the force pressing the control rod 4 upward is reduced, preventing a large load from acting on the push nut 7, which will be described later. The control rod 4 is constantly urged upward against the piston rod 2 by the pressure inside the piston rod 2.

The housing 6 attached to the upper end of the piston rod 2 includes a housing body 6a that is screwed to the upper end of the piston rod 2, and a bracket 6b that is provided at the upper end of the housing body 6a and can be connected to the vehicle body F of the saddle-type vehicle M, as shown in Figures 1 and 3.

The housing body 6a has a hole 6c with a circular cross section that opens from the side, a screw hole 6d that opens from the bottom end and into which the upper end of the piston rod 2 is screwed, and a rod insertion hole 6e that is concentric with the screw hole 6d and communicates with the hole 6c and the screw hole 6d. The rod insertion hole 6e opens halfway through the hole 6c, and the hole 6c opens from the side of the housing body 6a and extends horizontally, straddling the rod insertion hole 6e and extending further. The head 4a of the control rod 4 is inserted into the rod insertion hole 6e. Therefore, when the piston rod 2 is screwed into the screw hole 6d and the piston rod 2 is screwed to the housing 6, the head 4a of the control rod 4 protrudes into the hole 6c through the rod insertion hole 6e.

As shown in FIG. 3, the push nut 7 is cylindrical and has an axial length shorter than the hole 6c, and is inserted into the hole 6c of the housing 6 so as to be slidable in the axial direction. Therefore, the push nut 7 is allowed to move in the axial direction within the hole 6c. The push nut 7 also has an eccentric screw hole 7a that opens from a position eccentric to the radially upward direction from the center of the axis of the rear end, which is the end on the inlet side of the hole 6c, and an inclined surface 7b formed by a notched groove formed from the side surface to the tip surface. The inclined surface 7b is an inclined surface that moves away from the side surface as it moves from the side surface to the tip, and the inclination angle of the inclined surface 7b is the same as the inclination angle of the conical surface of the upper end of the head 4a of the control rod 4 when viewed from the radial direction, so that the inclined surface 7b can abut against the head 4a in a line contact.

When the push nut 7 is moved along the axis of the hole 6c in a direction to push it into the hole 6c with the inclined surface 7b abutting against the head 4a, the inclined surface 7b moves toward the back of the hole 6c, and the head 4a slides along the inclined surface 7b, displacing the control rod 4 in a direction to push it into the piston rod 2. Conversely, when the push nut 7 is moved along the axis of the hole 6c in a direction to retreat from inside the hole 6c, the inclined surface 7b moves toward the entrance of the hole 6c, and the control rod 4 is biased upward by the pressure inside the piston rod 2, so that the head 4a is displaced upward from inside the piston rod 2 to a position where it abuts against the inclined surface 7b.

Thus, although the direction of movement of the push nut 7 relative to the hole 6c is different from the direction of movement of the control rod 4, the inclined surface 7b converts the horizontal movement of the push nut 7 relative to the hole 6c into vertical movement of the control rod 4. In this way, the inclined surface 7b of the push nut 7 functions as a movement direction conversion part that abuts against the control rod 4 and converts the axial movement of the push nut 7 into the axial movement of the control rod 4. The closer the angle between the plane perpendicular to the axis of the push nut 7 and the inclined surface 7b is to 90 degrees, the less force is required to drive the push nut 7 in the axial direction when moving the control rod 4 up and down. The inclined surface 7b may be an inclined surface created by cutting off the push nut 7 from the side to the tip.

As shown in FIG. 3, the motor 8 has a rotor shaft itself that is a screw shaft 9 with a screw portion on the outer periphery of the tip, and the screw shaft 9 can be rotated by passing electricity through it. The screw shaft 9 may be connected to the shaft of the motor 8 via a coupling, or may be formed by providing a screw groove on the outer periphery of the shaft as shown. When the motor 8 is attached to the side of the housing 6, the screw shaft 9 protrudes into the hole 6c and the axis of the screw shaft 9 is positioned at a position shifted upward from the center of the hole 6c in FIG. 3. The screw shaft 9 is also screwed into the eccentric screw hole 7a of the push nut 7, and when the motor 8 rotates the screw shaft 9, it applies a torque to the push nut 7 to rotate it around the axis of the eccentric screw hole 7a. Therefore, the push nut 7 tries to rotate circumferentially around the eccentric screw hole 7a, but it cannot rotate around the eccentric screw hole 7a because it is slidably fitted into the hole 6c and the eccentric screw hole 7a is located at a position radially offset from the axis of the push nut 7. In this way, the push nut 7 is prevented from rotating because the center of rotation caused by the drive of the screw shaft 9 is located at a position radially offset from the axis and is fitted into the hole 6c of the housing 6, so it is only allowed to move axially back and forth within the hole 6c.

Therefore, when the motor 8 is driven to rotate the screw shaft 9, the push nut 7 is displaced axially within the hole 6c toward the back or the entrance without rotating about its axis, depending on the direction of rotation of the screw shaft 9. When the push nut 7 is displaced, the control rod 4 is displaced vertically, which is the axial direction relative to the piston rod 2, so that the control rod 4 can be moved vertically by driving the motor 8.

The shock absorber D is constructed as described above and is mounted between the vehicle body F and the rear wheel W of the saddle-type vehicle M by the bracket 11d provided on the bottom cap 11 and the bracket 6b provided on the housing 6 attached to the tip of the piston rod 2. As shown in FIG. 2, the shock absorber D in this embodiment is mounted between the vehicle body F and the rear wheel W by connecting the piston rod 2 to the vehicle body F and the cylinder 1 to the rear wheel W, but it may also be mounted between the vehicle body F and the rear wheel W by connecting the piston rod 2 to the rear wheel W and the cylinder 1 to the vehicle body F upside down.

The operation of the shock absorber D will be described below. During the extension stroke of the shock absorber D, in which the piston 3 moves upward in FIG. 1 relative to the cylinder 1, liquid moves from the extension chamber R1, which is compressed by the piston 3, to the compression chamber R2 via the extension port 3a. During this extension stroke, the shock absorber D generates an extension damping force that hinders extension by providing resistance to the flow of liquid passing through the extension port 3a using the extension damping valve 13. Also, during the extension stroke of the shock absorber D, if the needle valve 5 in the damping passage P is open, the liquid moves from the extension chamber R1 to the compression chamber R2 through the needle valve 5 as well as the extension damping valve 13, so the needle valve 5 also contributes to the generation of the extension damping force. Then, by driving the motor 8 to move the push nut 7 in the axial direction and displacing the control rod 4 up and down within the piston rod 2, the needle valve body 52 can be moved closer to and farther from the valve seat member 51, changing the flow path area, and the extension damping force can be adjusted.

In addition, during the extension stroke of the shock absorber D, the piston rod 2 retreats from the cylinder 1, causing a shortage of liquid in the compression side chamber R2 by the volume of the piston rod 2 retreating from the cylinder 1. However, this shortage of liquid is supplied to the compression side chamber R2 from the liquid chamber L of the tank 16 via the opening of the extension side check valve 19 and the suction passage 11f as the free piston 17 moves within the tank 16 to expand the air chamber G.

In addition, during the extension stroke of shock absorber D, the compression side damping valve 18 closes and blocks the compression side damping passage 11e, so the damping force characteristics of the extension stroke of shock absorber D are determined by the extension side damping valve 13, and the needle valve 5 does not affect the damping force during the extension stroke.

On the other hand, during the contraction stroke of shock absorber D, in which piston 3 moves downward in FIG. 1 relative to cylinder 1, hydraulic oil in compression side chamber R2 compressed by piston 3 opens compression side check valve 14 and moves to expansion side chamber R1 via compression side port 3b. During the contraction stroke of shock absorber D, piston rod 2 enters cylinder 1, so that the volume of liquid in cylinder 1 that piston rod 2 has entered becomes excess. This excess liquid is discharged to liquid chamber L in tank 16 via compression side damping passage 11e by opening compression side damping valve 18. In tank 16 from which liquid is discharged, free piston 17 moves within tank 16 to reduce air chamber G.

In this way, during the contraction stroke of shock absorber D, liquid moves from the compression side chamber R2 through the compression side damping valve 18 to the tank 16 according to the contraction speed of shock absorber D. As described above, during the contraction stroke of shock absorber D, the compression side port 3b is opened and placed in communication with the expansion side chamber R1 and the compression side chamber R2 in the cylinder 1, and the compression side damping valve 18 provides resistance to the flow of liquid from the compression side chamber R2 to the tank 16.

During the contraction stroke of the shock absorber D, the expansion side chamber R1 and the contraction side chamber R2 are in communication with each other through the compression side port 3b, so the pressures in the expansion side chamber R1 and the contraction side chamber R2 both rise to approximately the same pressure. In the shock absorber D of this embodiment, the area of the piston 3 facing the expansion side chamber R1 is smaller than the area of the piston 3 facing the compression side chamber R2 by the area of the circle of the outer diameter of the piston rod 2, so the contracting shock absorber D exerts a damping force in a direction that hinders the contraction, the damping force being the pressure in the cylinder 1 multiplied by the area of the circle of the outer diameter of the piston rod 2. In other words, in the case of the shock absorber D set as a single rod type in which the piston rod 2 is present only on one side of the piston 3 described above, a damping force proportional to the area of the circle of the outer diameter of the piston rod 2 is generated during the contraction stroke.

If a damping valve is provided instead of the compression side check valve 14, a difference in pressure will occur between the expansion side chamber R1 and the compression side chamber R2 during the contraction stroke of the shock absorber D, making it possible to adjust the damping force using the needle valve 5, and thus adjusting the damping force on the compression side of the shock absorber D.

In addition, in the shock absorber D of this embodiment, the motor 8 is used to adjust the flow area of the needle valve 5. As described above, when the motor 8 is energized to rotate the screw shaft 9, the push nut 7, which is prevented from rotating in the hole 6c, moves left and right in FIG. 3 along the axial direction of the hole 6c relative to the housing 6. Depending on the moving direction of the push nut 7, the control rod 4 also moves upward or downward along the axial direction, so that the needle valve body 52 moves closer to and farther from the valve seat member 51, thereby adjusting the flow area of the needle valve 5. In addition, in the shock absorber D of this embodiment, a structure adopted in a conventional shock absorber in which a screw portion is provided on the inner circumference of the hole 6c and an adjuster is screwed, is not adopted, but the screw shaft 9 driven by the motor 8 is screwed into the eccentric screw hole 7a provided in the push nut 7, so that the outer diameter of the screw is smaller than that of the conventional structure, and the torque required of the motor 8 to displace the push nut 7 is smaller. In addition, the push nut 7 is cylindrical and slidably inserted into the hole 6c, which has a circular cross section, and the anti-rotation mechanism is formed by fitting the hole 6c into the push nut 7, so the frictional force generated between the hole 6c and the push nut 7 can be reduced compared to anti-rotation mechanisms that use keys or the like.

As described above, the shock absorber D of this embodiment comprises a cylinder 1, a cylindrical piston rod 2 inserted into the cylinder 1 so as to be axially movable, a piston 3 connected to the piston rod 2 and inserted into the cylinder 1 so as to be axially movable and dividing the inside of the cylinder 1 into an extension side chamber R1 and a compression side chamber R2, a damping passage P connecting the extension side chamber R1 and the compression side chamber R2, a control rod 4 inserted into the piston rod 2 so as to be axially movable, and a control rod 4 provided in the damping passage P and adapted to change the resistance applied to the flow of liquid passing through the damping passage P by the displacement of the control rod 4. It is equipped with a needle valve (damping force adjustment valve) 5, a housing 6 connected to the piston rod 2 and having a hole 6c with a circular cross section, a cylindrical push nut 7 that is inserted axially slidably into the hole 6c of the housing 6 and displaces the control rod 4 axially by abutting against it and displacing it axially within the hole 6c, a motor 8 provided in the housing 6, and a screw shaft 9 that is screwed into an eccentric screw hole 7a provided at a position radially eccentric from the axis of the push nut 7 and is driven by the motor 8.

In shock absorber D configured in this manner, screw shaft 9 driven by motor 8 is screwed into eccentric screw hole 7a provided in push nut 7, so the outer diameter of the screw is smaller than in conventional structures, and the torque required of motor 8 to displace push nut 7 is smaller. In addition, push nut 7 is cylindrical and slidably inserted into hole 6c with a circular cross section, and a rotation stop is formed by fitting hole 6c into push nut 7, so the frictional force generated between hole 6c and push nut 7 can be reduced compared to a rotation stop mechanism that uses a key or the like.

As described above, according to the shock absorber D of this embodiment, the frictional resistance that the motor 8 experiences when driving the control rod 4 is reduced, and the control rod 4 can be driven using a small motor 8. Even if the motor 8 is installed, the overall size of the shock absorber D does not increase, making it possible to electrically adjust the damping force.

In the shock absorber D of this embodiment, the damping force adjustment valve is a needle valve 5, but it may be any valve that can change the resistance it provides to the flow of liquid through the damping passage P by displacing the control rod 4. Thus, for example, the control rod 4 may be configured as a spool valve that is cylindrical and has a port that can be slidably inserted into the piston rod 2 and opposed to the lateral hole 2b of the piston rod 2, and that can change the degree of opposition between the lateral hole 2b and the port by axial movement relative to the piston rod 2, thereby adjusting the flow path area. In addition, the damping force adjustment valve may use the extension side port 3a (compression side port 3a) as a damping passage P, and may include a spring bearing that can move axially relative to the piston rod 2 in conjunction with the control rod 4, and a spring that is interposed between the spring bearing and the extension side damping valve 13 (compression side check valve 14) to bias the extension side damping valve 13 (compression side check valve 14). The biasing force of the spring may be adjusted by the displacement of the control rod 4, thereby adjusting the resistance that the extension side damping valve 13 (compression side check valve 14) provides to the flow of liquid passing through the extension side port 3a (compression side port 3a).

In addition, in the shock absorber D of this embodiment, the push nut 7 and the control rod 4 move in different directions, and the push nut 7 has an inclined surface (movement direction conversion part) 7b that abuts against the control rod 4 to convert the axial movement of the push nut 7 to the axial movement of the control rod 4. With the shock absorber D configured in this way, the movement directions of the push nut 7 driven by the motor 8 and the control rod 4 do not need to match, so the design freedom of the mounting attitude of the motor 8 to the shock absorber D is improved. In addition, in the shock absorber D of this embodiment, the inclined surface (movement direction conversion part) 7b of the push nut 7 is formed by a notch groove formed from the side surface to the tip surface of the push nut 7, so that the area of the circumferential surface that slides against the inner circumferential surface of the hole 6c of the push nut 7 can be made larger than when the inclined surface (movement direction conversion part) 7b is formed in a shape in which the push nut 7 is cut off from the side, and the push nut 7 can move more smoothly within the hole 6c.

In addition, in the shock absorber D described above, the motor 8 is attached to the housing 6 with its axis perpendicular to the axis of the piston rod 2, but the design of the attachment position of the motor 8 relative to the housing 6 can be changed as long as the control rod 4 can be displaced axially within the piston rod 2.

Therefore, as in the shock absorber D1 in the first modified example shown in Fig. 4, when the moving direction of the push nut 7 is made to coincide with the moving direction of the control rod 4, the hole 6c of the housing 6 may be formed along the axial direction of the piston rod 2, the push nut 7 may be inserted into the hole 6c, and the lower end surface of the push nut 7 may be abutted against the head 4a of the control rod 4 without providing an inclined surface on the push nut 7. In this case, the motor 8 may be attached to the housing 6 so that the screw shaft 9 protrudes into the hole 6c, and the screw shaft 9 may be screwed into the eccentric screw hole 7a that opens at a position eccentric from the axis of the push nut 7. In addition, if the upper end surface of the head 4a of the control rod 4 is made parallel to the lower end surface of the push nut 7, the head 4a of the control rod 4 that receives the load from the push nut 7 can be prevented from gnawing and damaging the lower end surface of the push nut 7. In this way, in the shock absorber D1 of the first modification, the motor 8, push nut 7, and control rod 4 are arranged in series, so even if the shock absorber D1 is equipped with the motor 8, it does not become larger in the radial direction. Therefore, this shock absorber D1 of the first modification has a relatively long overall length, making it easy to use as a shock absorber built into a front fork that can easily secure installation space for the motor 8 inside in the axial direction.

5, the housing 6 may be provided with a pair of annular bushings 30, 31 as support members that are mounted in the hole 6c and slidably fitted to both ends of the push nut 7 in the axial direction. In this case, the inclined surface 7b provided on the push nut 7 is provided in the center of the push nut 7 in the axial direction, avoiding both ends that slide against the bushings 30, 31, and abuts against the head 4a of the control rod 4. In this case, the push nut 7 moves axially within the hole 6c while being guided by the bushings 30, 31. The use of the bushings 30, 31 allows the push nut 7 to move axially even more smoothly within the hole 6c in the housing 6, so that the torque borne by the motor 8 can be further reduced, and a smaller motor 8 can be used to adjust the damping force. In addition, the support member may be arranged on the opposite side of the push nut 7 to the control rod, and may support the push nut 7 to allow the push nut 7 to move in the axial direction while restricting the upward movement of the push nut 7 toward the opposite side of the control rod in FIG. 5 , and may be modified in shape and structure to that extent, and may not be annular, and may be composed of a member other than the pair of bushes 30, 31. The bushes 30, 31 as support members may be attached to both ends of the push nut 7 in the axial direction. Even with this configuration, the push nut 7 can move in the hole 6c together with the bushes 30, 31, and the use of the bushes 30, 31 allows the push nut 7 to move more smoothly in the axial direction within the hole 6c in the housing 6, so that the torque borne by the motor 8 can be further reduced, and a smaller motor 8 can be used for damping force adjustment. In addition, the support member attached to the push nut 7 is arranged on the opposite side of the push nut 7 to the control rod, and it is sufficient that it supports the push nut 7, allowing the push nut 7 to move in the axial direction while restricting its movement upward in FIG. 5, which is the opposite side to the control rod, and to that extent, the design can be modified in terms of shape and structure, it does not have to be annular, and it can be composed of a member other than the pair of bushes 30, 31.

Although the preferred embodiment of the present invention has been described in detail above, modifications, variations, and changes are possible without departing from the scope of the claims.

1: Cylinder, 2: Piston rod, 3: Piston, P: Damping passage, 4: Control rod, 5: Needle valve (damping force adjustment valve), 6: Housing, 6c: Hole, 7: Push nut, 7a: Eccentric screw hole, 7b: Inclined surface (movement direction change part), 8: Motor, 9: Screw shaft, 30, 31: Bush (support member), D, D1, D2: Shock absorber, R1: Expansion side chamber, R2: Compression side chamber

Claims (4)

A shock absorber,
A cylinder;
A cylindrical piston rod is inserted into the cylinder so as to be axially movable;
a piston connected to the piston rod and inserted into the cylinder so as to be axially movably therein, the piston dividing the interior of the cylinder into an expansion-side chamber and a compression-side chamber;
a damping passage communicating the expansion-side chamber and the compression-side chamber;
a control rod inserted into the piston rod so as to be movable in the axial direction;
a damping force adjusting valve provided in the damping passage for changing the resistance applied to the flow of the fluid passing through the damping passage in response to the displacement of the control rod;
a housing connected to the piston rod and having a hole with a circular cross section;
a cylindrical push nut that is slidably inserted in the axial direction into the hole of the housing and abuts against the control rod to displace in the axial direction within the hole, thereby displacing the control rod in the axial direction;
A motor provided in the housing;
a screw shaft that is screwed into an eccentric screw hole provided at a position radially eccentric from the axis of the push nut and is driven by the motor. 2. The shock absorber according to claim 1,
The push nut and the control rod move in different directions,
the push nut has a movement direction conversion portion that abuts against the control rod to convert axial movement of the push nut into axial movement of the control rod. 3. The shock absorber according to claim 1 or 2,
the housing has a support member that is mounted in the hole and slidably supports the push nut on the side opposite to the control rod. 3. The shock absorber according to claim 1 or 2,
The push nut has a support member on an opposite side to the push rod, the support member being slidably inserted into the hole of the housing.

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