Front fork

Abstract

A front fork (F) is provided with: a fork body (1) having a vehicle body-side tube (2), an axle-side tube (3), and an axle bracket (4) having a bottomed cylindrical tube section (4a) attached to the outer periphery of the lower end of the axle-side tube; a damper box (D); a collar (30) housed in the cylindrical section (4a), having a ring-shaped seal ring (30e) that is in close contact with the axle-side tube (3), and sandwiched between the axle-side tube (3) and the axle bracket (4); and a connecting bolt (40) which has a head inserted into a bolt through-hole (4c) of the axle bracket (4), and a threaded shaft (40b) which is in threaded engagement with a cap (13) inserted through the inner circumference of the collar (30) and fixed to the lower end of the damper box (D), and which connects the cap (13) to the collar (30).

Description

Technical Field

[0001] The invention relates to a front fork. Background Art

[0002] Conventionally, for example, a front fork is used as a suspension device that accommodates a damper box that generates a damping force when extending or retracting, and is installed between a vehicle body and a front wheel of a straddle-type vehicle to suppress vibration of the vehicle.

[0003] More specifically, for example, the front fork includes a fork body and a damper box housed in the fork body, wherein the fork body includes a vehicle body side tube, an axle side tube that can move axially relative to the vehicle body side tube, and an axle bracket that includes a bottomed cylindrical portion that is engaged with the outer periphery of the lower end of the axle side tube and closes the lower end of the axle side tube and holds the front wheel axle.

[0004] In addition, the damper box has a cylinder, a piston rod inserted into the cylinder in an axially movable manner, a piston connected to the piston rod and inserted into the cylinder in an axially movable manner to divide the interior of the cylinder into an extension side chamber and a compression side chamber, and a bottom component that closes the lower end of the cylinder and has a threaded hole opened at the lower end.

[0005] The damper box having the structure as described above is housed in a fork body, for example, as shown in JP2016-070313A, and one end of the piston rod is connected to the vehicle body side tube via a head cover, and the threaded hole of the bottom component is threadedly engaged with the connecting bolt that passes through the bottom of the axle bracket tube, and is installed between the vehicle body side tube and the axle side tube.

[0006] Therefore, when the front fork expands and contracts as the front wheel vibrates during travel of the suspension straddle type vehicle, the damper box built into the fork body also expands and contracts to generate a damping force, thereby suppressing the vibration of the front wheel and the vehicle body and improving the ride comfort of the suspension straddle type vehicle. Prior art literature Patent Literature

[0007] Patent Document 1: JP2016-070313A Summary of the invention Problems to be solved by the invention

[0008] In previous front forks, the axle bracket that closes the lower end of the axle side tube also acts as a part of the pressure vessel for storing liquid in the fork body, and the inner periphery of the axle bracket tube portion embedded in the outer periphery of the axle side tube has an annular groove for accommodating a sealing ring that fits tightly with the outer periphery of the axle side tube.

[0009] Furthermore, a threaded portion for screwing the outer periphery of the axle side tube is provided closer to the opening end side than the annular groove for accommodating the sealing ring on the cylindrical portion of the axle bracket. The axle bracket having the above structure is manufactured by cutting the casting after obtaining a roughly formed casting by casting.

[0010] The inner circumference of the axle bracket tube is machined to form a threaded portion and an annular groove, but if the chips generated by the cutting process remain in the annular groove, the chips will contaminate the hydraulic oil in the front fork and may have an adverse effect on the operation of the damping valve, etc. Therefore, in the past, when manufacturing front forks, operators had to perform a very tedious task, that is, using a mirror or the like to check whether there were any chips remaining in the deepest annular groove of the axle bracket tube.

[0011] In addition, there is a problem with conventional front forks. The axle bracket is a casting and is also part of a pressure vessel. If there are air holes on the axle bracket, hydraulic oil will leak. Therefore, all axle brackets manufactured must be X-rayed to confirm whether there are air holes that may cause hydraulic oil leakage, which increases manufacturing costs.

[0012] There is another problem that since an annular groove for accommodating the sealing ring is provided on the inner periphery of the axle bracket tube, the wall thickness of the tube needs to be increased accordingly, and the outer diameter of the tube will also increase, so the weight of the front fork will increase.

[0013] Therefore, an object of the present invention is to provide a front fork which can reduce the workload of manufacturing workers and can reduce manufacturing costs and weight. Solutions to Solve Problems

[0014] In order to solve the above-mentioned problems, the front fork of the present invention has the following structure: a telescopic fork body, which has a body side tube, an axle side tube that can move axially relative to the body side tube, and an axle bracket having a bottomed cylindrical barrel portion installed on the outer periphery of the lower end of the axle side tube; a damper box accommodated in the fork body, which has a cylinder, a piston rod that is inserted into the cylinder in an axially movable manner and one end of which is connected to the body side tube, a piston that is connected to the piston rod and inserted into the cylinder in an axially movable manner to divide the inside of the cylinder into an extension side chamber and a compression side chamber, and a convex cover that is fixed to the lower end of the cylinder and closes the lower end of the cylinder; a collar accommodated in the barrel portion, which has a ring-shaped sealing ring that tightly fits the axle side tube and is clamped between the axle side tube and the axle bracket; a connecting bolt, which has a head inserted into a bolt through hole that passes through the bottom of the barrel portion of the axle bracket, a threaded shaft that is inserted through the inner periphery of the collar and is threadedly engaged with the convex cover, and connects the convex cover to the collar.

[0015] In a front fork having the structure as described above, since the axle bracket does not come into contact with the liquid in the front fork, there is no need to provide an annular groove on the inner circumference of the axle bracket tube. This not only makes it very convenient to confirm whether there are any chips remaining from the cutting process, but also reduces the wall thickness of the tube and the outer diameter of the tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a cross-sectional view of a front fork according to an embodiment of the present invention. Figure 2 This is a partially enlarged cross-sectional view of a front fork according to an embodiment of the present invention. Figure 3 This is a partially enlarged cross-sectional view of a front fork according to a first modified example of one embodiment of the present invention. DETAILED DESCRIPTION

[0017] The present invention will be described based on the embodiments shown in the drawings. Figure 1 As shown, the front fork F in one embodiment functions as a part of a suspension device mounted between a body and a front wheel of a suspended straddle-type vehicle such as a motorcycle or a three-wheeled motorcycle (not shown).

[0018] The following is a detailed description of the various components constituting the front fork F. Figure 1 and Figure 2 As shown, the front fork F includes a fork body 1 , a damper box D, a collar 30 , and a connecting bolt 40 .

[0019] The fork body 1 includes an outer tube 2 as a vehicle body side tube, an inner tube 3 as an axle side tube that can axially move relative to the outer tube 2, and an axle bracket 4 having a bottomed cylindrical tube portion 4a installed on the outer periphery of the lower end of the inner tube 3. Since the inner tube 3 can move axially relative to the outer tube 2, it is telescopic.

[0020] The inner tube 3 is inserted into the outer tube 2, and has an annular sleeve 3a on the outer periphery of the upper end that is in sliding contact with the inner periphery of the outer tube 2, and a threaded portion 3b on the outer periphery of the lower end.

[0021] The open end of the upper end of the outer tube 2 is installed with a head cover 5, and the inner periphery of the lower end is provided with an annular sleeve 2a, a sealing ring 2b and a dust ring 2c that are in sliding contact with the outer periphery of the inner tube 3. The open end of the upper end of the outer tube 2 is sealed by the head cover 5. When the inner tube 3 is inserted into the outer tube 2, the sleeve 2a is in sliding contact with the outer periphery of the inner tube 3, and the sleeve 3a is in sliding contact with the inner periphery of the outer tube 2, so that the inner tube 3 can achieve axial relative movement relative to the outer tube 2 without radial axial deviation.

[0022] Furthermore, the sealing ring 2b prevents the liquid in the fork body 1 from leaking from between the outer tube 2 and the inner tube 3, and the dust seal 2c prevents dust and water from entering the fork body 1 from outside the fork body 1 through between the outer tube 2 and the inner tube 3.

[0023] The axle bracket 4 includes a bottomed cylindrical portion 4a, a C-shaped gripping portion 4b disposed below the bottom of the cylindrical portion 4a and holding the front wheel axle of the suspension straddle type vehicle (not shown) in a rotatable manner, and a bolt through hole 4c that penetrates the bottom of the cylindrical portion 4a and passes through the inner periphery of the gripping portion 4b. A threaded portion 4d for threaded engagement with a threaded portion 3b disposed on the outer periphery of the lower end of the inner tube 3 is provided on the bottom side of the inner periphery of the cylindrical portion 4a. In addition, although not shown, the axle bracket 4 has a fender support arm on the side of the cylindrical portion 4a, which is used to support a bracket that holds the brake caliper of the front wheel and a fender covering the upper portion of the front wheel. In addition, the axle bracket 4 is mounted on the inner tube 3 by threading the cylindrical portion 4a with the outer periphery of the lower end of the inner tube 3, but it can also be mounted on the outer tube 3 by other joining methods such as welding in addition to threading.

[0024] The structure of the shaft ring 30 includes a fitting portion 30a which is annular and fitted on the inner periphery of the lower end of the inner tube 3, an annular flange portion 30b which radially protrudes from the outer periphery of the lower end of the fitting portion 30a, an annular recess 30c arranged on the inner periphery of the lower end of the fitting portion 30a, an annular groove 30d formed along the circumferential direction on the outer periphery of the fitting portion 30a, and a sealing ring 30e installed in the annular groove 30d.

[0025] The outer diameter of the fitting portion 30a is a diameter that can be fitted into the inner circumference of the inner tube 3, so that the fitting portion 30a can be fitted into the lower end of the inner tube 3. When the fitting portion 30a is fitted into the inner tube 3, the sealing ring 30e in the annular groove 30d is radially compressed by the inner circumference of the inner tube 3, elastically deformed, and tightly fitted with the inner circumference of the inner tube 3 and the bottom of the annular groove 30d, thereby sealing the space between the collar 30 and the inner tube 3.

[0026] The outer diameter of the flange portion 30b of the collar 30 is larger than the inner diameter of the inner tube 3 and can be fitted into the inner circumference of the cylinder portion 4a of the axle bracket 4. When the collar 30 is inserted into the cylinder portion 4a of the axle bracket 4, the lower end of the collar 30 abuts against the bottom of the cylinder portion 4a, and the inner circumference of the collar 30 communicates with the bolt through hole 4c of the axle bracket 4.

[0027] The connecting bolt 40 has a head 40a that can be inserted into the bolt through hole 4c and cannot pass through the inner periphery of the collar 30, and a threaded shaft 40b extending from the head 40a. Figure 2The hexagonal hole 40c is open at the middle and lower end and can be fitted with a tool, so that the tool can be used to rotate the connecting bolt 40. An annular washer 41 is installed on the outer periphery of the base end of the threaded shaft 40b. When the connecting bolt 40 is inserted into the bolt through hole 4c from the inner periphery of the gripping portion 4b of the axle bracket 4, the front end of the threaded shaft 40b of the connecting bolt 40 can be made to protrude to the upper side of the collar 30 through the inner periphery of the collar 30. In addition, the outer diameter of the head 40a is slightly smaller than the outer diameter of the annular recess 30c formed on the inner periphery of the lower end of the collar 30. The outer diameter of the washer 41 is smaller than the outer diameter of the annular recess 30c, and the axial length of the washer 41 is shorter than the depth (axial length) of the annular recess 30c.

[0028] As described above, when the lower end of the inner tube 3 is inserted into the tube 4a and the threaded portion 3b is threadedly engaged with the threaded portion 4d in a state where the collar 30 is inserted into the tube 4a and the collar 30 is pressed against the bottom of the tube 4a, the lower end surface of the inner tube 3 will eventually press against the upper end surface of the flange 30b of the collar 30, and the flange 30b is clamped by the inner tube 3 and the axle bracket 4. The inner tube 3 and the axle bracket 4 apply a load to the flange 30b of the collar 30 in the axial direction and clamp it, and the load applied to the flange 30b can be adjusted by adjusting the tightening torque of the inner tube 3 to the axle bracket 4. Therefore, an appropriate load can be applied to the flange 30b, and the collar 30 can be firmly fixed to the inner tube 3 and the axle bracket 4.

[0029] The damper box D is accommodated in the fork body 1. The damper box D has the following structure: a cylinder 10, a piston rod 11 inserted into the cylinder 10 in an axially movable manner and one end of which is connected to the outer tube 2 as the vehicle body side tube through the head cover 5, a piston 12 connected to the piston rod 11 and inserted into the cylinder 10 in an axially movable manner to divide the inside of the cylinder 10 into an extension side chamber R1 and a compression side chamber R2, a convex cover 13 fixed to the lower end of the cylinder 10 and closing the lower end of the cylinder 10 and having a threaded hole 13e opened from the lower end, and a base valve 14 held on the convex cover 13 and dividing the inside of the cylinder 10 into the compression side chamber R2 and a chamber r located below the compression side chamber R2. The extension side chamber R1 and the compression side chamber R2 are filled with liquid such as hydraulic oil, and a liquid reservoir R for storing the liquid is formed between the damper box D and the fork body 1.

[0030] Cylinder 10 Figure 1 As shown, the cylinder 10 is cylindrical and has a threaded portion 10a provided on the inner periphery of the lower end and a through hole 10b provided above the threaded portion 10a and connecting the inside and outside of the cylinder 10. The through hole 10b opens below the liquid level O of the liquid filled in the liquid storage chamber R.

[0031] In addition, an annular rod guide 15 is mounted at the open end of the upper end of the cylinder 10, into which the piston rod 11 can be slidably inserted. The rod guide 15 has an annular guide portion 15a that is threadedly engaged with the inner circumference of the upper end of the cylinder 10 and is in sliding contact with the outer circumference of the piston rod 11 inserted into the inner circumference, and a cylindrical housing portion 15b that protrudes upward from the upper end of the guide portion 15a. The upper end of the housing portion 15b is always located below the liquid level O of the liquid in the liquid storage chamber R, and the housing portion 15b is always filled with liquid.

[0032] exist Figure 1 In the embodiment, one end of the piston rod 11 as the upper end is connected to the head cover 5 by threaded engagement, and the other end as the lower end is inserted into the cylinder 10 through the rod guide 15. An annular locking piece 16 is provided on the outer periphery of the middle part of the piston rod 11, and when it intrudes into the housing part 15b of the rod guide 15, a blocking gap is formed between the outer periphery and the housing part 15b to apply resistance to the flow of liquid from the inside of the housing part 15b to the outside of the housing part 15b.

[0033] The locking plate 16 and the housing portion 15b form a hydraulic buffer, and the piston rod 11 is relative to the cylinder 10. Figure 1 When the piston rod 11 moves downward during the stroke and moves to the vicinity of the stroke end, the lock piece 16 intrudes into the housing portion 15 b, increases the pressure in the housing portion 15 b, and inhibits the piston rod 11 from moving downward relative to the cylinder 10.

[0034] The piston 12 has an extension-side damping passage 12a and a compression-side passage 12b that communicate the extension-side chamber R1 and the compression-side chamber R2, an extension-side damping valve 12c that is provided on the extension-side damping passage 12a and applies resistance to the liquid flow from the extension-side chamber R1 to the compression-side chamber R2, and a compression-side check valve 12d that is provided on the compression-side passage 12b and does not apply resistance to the liquid flow from the compression-side chamber R2 to the extension-side chamber R1 and allows the liquid flow to pass. Furthermore, the extension-side damping passage 12a is set as a one-way passage that allows only the liquid flow from the extension-side chamber R1 to the compression-side chamber R2 by the extension-side damping valve 12c, and the compression-side passage 12b is set as a one-way passage that allows only the liquid flow from the compression-side chamber R2 to the extension-side chamber R1 by the compression-side check valve 12d.

[0035] A convex cover 13 is fixed to the inner periphery of the lower end of the cylinder 10. Specifically, the convex cover 13 is as follows Figure 2 As shown in the figure, the disc-shaped cover 13a has a threaded portion 13b inserted into the inner periphery of the lower end of the cylinder 10 and threadedly engaged with the threaded portion 10a of the cylinder 10 at the outer periphery to close the lower end of the cylinder 10, and a cover 13a extending from the cover 13a to the inner periphery of the cylinder 10. Figure 2 The shaft portion 13c protruding from the middle and upper part into the cylinder 10, the threaded portion 13d provided on the outer periphery of the upper end of the shaft portion 13c, and the cover portion 13a extending from the cover portion 13a are provided. Figure 2The axial center portion of the middle and lower end opens to a threaded hole 13e extending axially. In addition, although not shown in the figure, a plurality of grooves are provided at regular intervals on the outer periphery of the lower end of the cover portion 13a, into which a tool used to thread the convex cover 13 to the threaded portion 10a of the cylinder 10 can be inserted. The diameter of the shaft portion 13c decreases from the middle to the front end, and a step portion 13c1 is provided in the middle. In the front fork F of this embodiment, the convex cover 13 is threadedly engaged with the cylinder 10 and fixed to the lower end of the cylinder 10, but in addition to threaded engagement, the cylinder 10 can also be locked from the outer peripheral side and the convex cover 13 can also be fixed to the cylinder 10 by other joining methods such as welding.

[0036] A basic valve 14 is provided on the outer periphery of the front end side of the shaft portion 13c of the convex cap 13. The basic valve 14 includes a ring-shaped partition body 17 mounted on the outer periphery of the convex cap 13, a compression side damping valve 18 stacked on the lower end of the partition body 17, and an extension side check valve 19 stacked on the upper end of the partition body 17.

[0037] The partition body 17 is fitted into Figure 2 On the upper side of the through hole 10b of the middle cylinder 10, the cylinder 10 is divided into a compression side chamber R2 and a chamber r connected to the liquid storage chamber R, and has a compression side damping channel 17a and a suction channel 17b connecting the compression side chamber R2 and the liquid storage chamber R.

[0038] The compression side damping valve 18 is a laminated leaf valve formed by laminating annular leaf valves below the partition body 17. The inner periphery is fixed to the shaft portion 13c and the outer periphery is allowed to bend, opening and closing the outlet end of the lower end of the compression side damping passage 17a. In addition, the compression side damping valve 18 bends the outer periphery to open the compression side damping passage 17a for the liquid flow from the compression side chamber R2 to the liquid storage chamber R, and at the same time applies resistance to the liquid flow passing through the compression side damping passage 17a. In this way, the compression side damping passage 17a is set as a one-way passage that only allows the liquid flow from the compression side chamber R2 to the liquid storage chamber R through the compression side damping valve 18.

[0039] On the other hand, the extension side check valve 19 includes an annular valve body 19a that can be separated from the upper end of the partition body 17 to open or close the suction passage 17b, a valve stopper 19b with an edge opposite to the anti-partition body side of the valve body 19a, and a spring 19c installed between the valve body 19a and the valve stopper 19b to push the valve body 19a toward the partition body 17. The extension side check valve 19 compresses the spring 19c for the liquid flow flowing from the liquid storage chamber R to the compression side chamber R2, so that the valve body 19a is separated from the partition body 17 and the suction passage 17b is opened. The extension side check valve 19 applies almost no resistance to the liquid flow passing through the suction passage 17b. In this way, the suction passage 17b is set as a one-way passage that allows only the liquid flow from the liquid storage chamber R to the compression side chamber R2 by the extension side check valve 19.

[0040] In addition, the compression side damping valve 18, the partition body 17 and the extension side check valve 19 constituting the basic valve 14 are assembled onto the outer periphery of the small diameter portion on the front end side of the shaft portion 13c of the convex cover 13, and then clamped at the front end of the shaft portion 13c by the nut 20 and the step portion 13c1 installed on the threaded portion 13d, and retained on the convex cover 13.

[0041] The convex cover 13 assembled with the basic valve 14 is inserted into the inner circumference of the lower end of the cylinder 10, and the threaded portion 10a is threadedly engaged with the threaded portion 13b on the outer circumference of the cover portion 13a, and is fixed to the cylinder 10. A gap is formed between the cover portion 13a and the basic valve 14 by providing a step portion 13c1, and when the convex cover 13 is mounted on the cylinder 10, a chamber r is formed that communicates with the through hole 10b through the gap.

[0042] The damper box D having the above-mentioned structure is obtained by assembling the components, and then inserted into the inner tube 3 from the convex cover 13 side as described above, and the collar 30 thereof is mounted on the inner tube 3 and the axle bracket 4. Then, the connecting bolt 40 is inserted into the bolt through hole 4c and the inner periphery of the collar 30 against the lower end of the convex cover 13 and the upper end of the collar 30 fixed in the axle bracket 4, and then the connecting bolt 40 is rotated to screw the threaded shaft 40b into the threaded hole 13e of the convex cover 13. When the threaded shaft 40b of the connecting bolt 40 is screwed into the threaded hole 13e of the convex cover 13, the head 40a of the connecting bolt 40 and the cover 13a of the convex cover 13 clamp the collar 30, and the collar 30 is connected to the damper box D.

[0043] The collar 30 is sandwiched between the inner tube 3 as the axle side tube and the axle bracket 4 and fixed to the inner tube 3 and the axle bracket 4, so that the cylinder 10 in the damper box D is connected to the inner tube 3 by screwing the connecting bolt 40 into the convex cover 13. When the convex cover 13 that closes the lower end of the cylinder 10 of the damper box D is fixed to the collar 30 by the connecting bolt 40, the damper box D is connected to the inner tube 3, and then, as long as the upper end of the piston rod 11 of the damper box D is connected to the outer tube 2 via the head cover 5, the damper box D can be accommodated in the fork body 1 and installed between the outer tube 2 as the vehicle body side tube and the inner tube 3 as the axle side tube, and can be extended and retracted together with the fork body 1.

[0044] When the connecting bolt 40 is screwed to the convex cap 13 as described above, the washer 41 mounted on the outer periphery of the threaded shaft 40b is accommodated in the annular recess 30c formed on the inner periphery of the lower end of the convex cap 13, and is sandwiched between the head 40a of the connecting bolt 40 and the axially opposing surfaces of the head 40a of the annular recess 30c of the collar 30 in a state of bearing a load, and the washer 41 seals between the connecting bolt 40 and the collar 30. In the front fork F of the present embodiment, the inner periphery of the lower end of the collar 30 has the annular recess 30c for accommodating the annular washer 41 fitted on the outer periphery of the threaded shaft 40b of the connecting bolt 40, so that even if the washer 41 is compressed and deformed between the head 40a and the bottom of the annular recess 30c, it is deformed while being accommodated in the annular recess 30c. Therefore, even when the connecting bolt 40 is screwed into the male cover 13, the washer 41 does not protrude to the outside from the annular recessed portion 30c.

[0045] If the collar 30 is not provided with the annular recess 30c for accommodating the washer 41, there is nothing to prevent the outer diameter of the washer 41 from expanding. Therefore, the washer 41 may be compressed between the head 40a and the lower end surface of the collar 30 by screwing the connecting bolt 40 into the convex cover 13, and the outer diameter of the washer 41 may expand and enter the chamfer 4e formed on the inner edge of the side end of the tube portion 4a of the bolt through hole 4c of the axle bracket 4. If such a situation occurs, even if the connecting bolt 40 is loosened and removed from the convex cover 13, the washer 41 has entered between the collar 30 and the chamfer 4e of the axle bracket 4, so it is difficult to pull the washer 41 out of the front fork F through the bolt through hole 4c, and the washer 41 may not be replaced. Therefore, by providing the annular recess 30c for accommodating the washer 41 on the collar 30, not only can the appropriate sealing performance be obtained by the washer 41, but also the washer 41 can be easily replaced when the front fork F is maintained.

[0046] Next, the operation of the front fork F having the above structure will be described. First, when the front fork F is extended, the outer tube 2 and the inner tube 3 are separated in the axial direction, so that the piston rod 11 moves upward relative to the cylinder 10, and the damper box D also extends. When the damper box D extends, the piston 12 moves upward in the cylinder 10. Figure 1 The expansion side chamber R1 moves upward in the expansion side chamber R2, shrinking the expansion side chamber R1 and expanding the compression side chamber R2. In this way, the liquid moves from the expansion side chamber R1 to the compression side chamber R2 through the expansion side damping passage 12a and the expansion side damping valve 12c. The expansion side damping valve 12c applies resistance to the liquid flow passing through the expansion side damping passage 12a, so the pressure in the expansion side chamber R1 rises.

[0047] In addition, the piston rod 11 withdraws from the cylinder 10, so the expanded compression side chamber R2 lacks liquid equivalent to the volume of the piston rod 11 withdrawing from the cylinder 10, and the extension side check valve 19 opens to supply this insufficient liquid from the liquid storage chamber R to the compression side chamber R2 through the suction passage 17b. Therefore, the pressure in the compression side chamber R2 is substantially equal to the pressure in the liquid storage chamber R.

[0048] As described above, when the front fork F extends, the pressure in the extension chamber R1 increases and becomes higher than the pressure in the compression chamber R2, and acts on the piston 12, so that the damper cartridge D generates an extension damping force that prevents the front fork F from extending.

[0049] Next, when the front fork F is contracted, the outer tube 2 and the inner tube 3 are axially close to each other, so the piston rod 11 moves downward relative to the cylinder 10, and the damper box D is also contracted. When the damper box D is contracted, the piston 12 moves downward in the cylinder 10. Figure 1 The piston 12 moves downward in the cylinder 10, shrinking the compression side chamber R2 and expanding the extension side chamber R1. In this way, the liquid moves from the compression side chamber R2 to the extension side chamber R1 through the compression side passage 12b and the compression side check valve 12d of the piston 12. In addition, the piston rod 11 enters the cylinder 10, so there is a liquid remaining in the cylinder 10 that is equivalent to the volume of the piston rod 11 entering the cylinder 10. This excess liquid squeezes and opens the compression side damping valve 18, and moves from the compression side chamber R2 to the liquid storage chamber R through the compression side damping passage 17a. The compression side check valve 12d applies almost no resistance to the liquid flow, making the pressure in the extension side chamber R1 and the pressure in the compression side chamber R2 approximately equal. On the other hand, the compression side damping valve 18 applies resistance to the liquid flow passing through the compression side damping passage 17a, so the pressure in the cylinder 10 rises.

[0050] As described above, when the front fork F contracts, the pressure in the extension side chamber R1 and the pressure in the compression side chamber R2 rise approximately equally, the pressure in the extension side chamber R1 acts on the top surface of the piston 12, and the pressure in the compression side chamber R2 acts on the bottom surface of the piston 12, but the piston 12 is connected to the piston rod 11, so the pressure area of ​​the bottom surface of the piston 12 is larger than the pressure area of ​​the top surface, so the damper box D generates a compression side damping force that hinders the contraction of the front fork F.

[0051] As described above, the front fork F of the present embodiment has the following structure: a telescopic fork body 1, which has an outer tube (body side tube) 2, an inner tube (axle side tube) 3 that can move axially relative to the outer tube (body side tube) 2, and an axle bracket 4 having a bottomed cylindrical tube portion 4a installed on the outer periphery of the lower end of the inner tube (axle side tube) 3; a damper box D accommodated in the fork body 1, which has a cylinder 10, a piston rod 11 that is inserted into the cylinder 10 in an axially movable manner and one end of which is connected to the outer tube (body side tube) 2, and a piston rod 11 that is connected to the piston rod 11 and inserted into the cylinder 10 in an axially movable manner to move the cylinder 10. 0 is divided into an extension side chamber R1 and a compression side chamber R2 inside, a convex cover 13 fixed to the lower end of the cylinder 10 and closing the lower end of the cylinder 10; a collar 30 accommodated in the cylindrical portion 4a, which has a ring-shaped sealing ring 30e that fits tightly on the inner tube (axle side tube) 3 and is clamped between the inner tube (axle side tube) 3 and the axle bracket 4; a connecting bolt 40, which has a head 40a inserted into a bolt through hole 4c at the bottom of the cylindrical portion 4a of the axle bracket 4, and a threaded shaft 40b inserted through the inner periphery of the collar 30 and threadedly engaged with the convex cover 13, and connects the convex cover 13 to the collar 30.

[0052] In the front fork F having the above-described structure, the connecting bolt 40 is inserted through the collar 30 clamped between the inner tube (axle side tube) 3 and the axle bracket 4, and is threadedly engaged with the convex cap 13 that closes the lower end of the cylinder 10, and the cylinder 10 is fixed to the axle bracket 4 by the connecting bolt 40. In the front fork F of the present embodiment as described above, the collar 30 has the sealing ring 30e that closely fits the inner tube (axle side tube) 3 and seals the inner tube (axle side tube) 3 and the collar 30, and the convex cap 13 in the damper box D is connected to the collar 30 by the connecting bolt 40, so that the axle bracket 4 does not come into contact with the liquid stored in the front fork F. In other words, in the front fork F of the present embodiment, the lower end of the inner tube (axle side tube) is directly sealed by the shaft ring 30, the convex cover 13 fixed on the shaft ring 30, and the connecting bolt 40. Although the cylindrical portion 4a of the axle bracket 4 has the same function of retaining the shaft ring 30 as the inner tube (axle side tube), it is not a component that directly seals the lower end of the inner tube (axle side tube).

[0053] As described above, when the front fork F of this embodiment is used, the axle bracket 4 does not come into contact with the liquid in the front fork F due to the structure. Therefore, it is not necessary to form an annular groove for arranging a seal ring on the inner periphery of the tube portion 4a of the axle bracket 4 by cutting.

[0054] Therefore, if the front fork F of the present embodiment is used, since it is not necessary to provide an annular groove on the inner periphery of the tube portion 4a of the axle bracket 4, it is possible to easily check whether the chips generated during the cutting process remain, and the work burden of the manufacturing operator of the front fork F can be reduced. In addition, if the front fork F of the present embodiment is used, since it is not necessary to provide an annular groove on the inner periphery of the tube portion 4a of the axle bracket 4, the wall thickness of the tube portion 4a of the axle bracket 4 can be reduced, and the outer diameter of the tube portion 4a can be reduced, thereby reducing the weight of the front fork F.

[0055] Furthermore, when the front fork F of this embodiment is used, since the axle bracket 4 does not come into contact with the liquid in the front fork F due to the structure, even if the axle bracket 4 is a casting, it is no longer necessary to check for pores by X-ray inspection, which can reduce manufacturing costs.

[0056] As described above, if the front fork F of the present embodiment is used, not only the burden on the manufacturing workers can be reduced, but also the manufacturing cost and weight can be reduced. In addition, in the front fork F of the present embodiment, the damper box D and the collar 30 can be separated and the damper box D can be easily removed from the axle bracket 4 and the inner tube (axle side tube) 3 by simply loosening and removing the connecting bolt 40 from the convex cover 13, which makes maintenance more convenient. In addition, in the front fork F of the present embodiment, the vehicle body side tube is used as the outer tube and the axle side tube is used as the inner tube, but the fork body 1 can also be constructed by inserting the vehicle body side tube into the axle side tube in a manner that allows axial movement.

[0057] In the front fork F of the present embodiment, the axle bracket 4 has a threaded portion 4d screwed to the outer periphery of the lower end of the inner tube (axle side tube) 2 on the inner periphery of the tube portion 4a, and the collar 30 has a fitting portion 30a which is annular and fitted to the inner periphery of the lower end of the inner tube (axle side tube) 3, a flange portion 30b which is provided on the outer periphery of the lower end of the fitting portion 30a and is clamped between the inner tube (axle side tube) 3 and the bottom of the tube portion 4a of the axle bracket 4, and a seal ring 30e which is received in an annular groove 30d provided on the fitting portion 30a and is closely attached to the inner periphery of the inner tube (axle side tube) 3. When the front fork F having the above-mentioned structure is used, the collar 30 can be easily fixed to the inner tube (axle side tube) 3 and the axle bracket 4 by simply receiving the collar 30 in the tube portion 4a and screwing the tube portion 4a to the lower end of the inner tube (axle side tube) 3.

[0058] Furthermore, in the front fork F of the present embodiment, the reservoir chamber R is formed in the space between the fork body 1 and the damper box D, and the basic valve 14 is held on the convex cover 13 and fitted in the cylinder 10 to partition the inside of the cylinder 10 into the compression side chamber R2 and the chamber r communicating with the reservoir chamber R. If the front fork F having the above-described structure is used, the convex cover 13 for connecting the cylinder 10 to the collar 30 holds the basic valve 14, so that no other component is required to set the basic valve 14 in the cylinder 10, and the number of components can be reduced.

[0059] Furthermore, in the front fork F of the present embodiment, an annular washer 41 is provided which is fitted on the outer periphery of the threaded shaft 40b of the connecting bolt 40, and an annular recess 30c which accommodates the washer 41 is provided on the inner periphery of the lower end of the collar 30. If the front fork F having the above-described structure is used, even if the washer 41 is compressed and deformed by being sandwiched between the head 40a and the collar 30, the washer 41 will not protrude from the annular recess 30c, so that not only can appropriate sealing performance be obtained by the washer 41, but also the washer 41 can be easily replaced when the front fork F is maintained.

[0060] In addition, you can Figure 3 As shown in the front fork F1 of the first modified example, the outer periphery of the lower end of the convex cap 13 has a tapered surface 13f with a reduced diameter on the lower end side, and the inner periphery of the upper end of the collar 30 has a recessed portion 30f that fits with the tapered surface 13f of the convex cap 13 and aligns the convex cap 13. In the front fork F1 having the above structure, when the damper box D is fixed to the collar 30 fixed to the axle bracket 4 using the connecting bolt 40, if the tapered surface 13f of the convex cap 13 is pressed against the recessed portion 30f of the collar 30, the tapered surface 13f of the lower end of the convex cap 13 slides on the tapered inclined surface 30f1 of the recessed portion 30f, and the convex cap 13 is automatically aligned with respect to the collar 30 until the axis of the threaded hole 13e coincides with the axis of the collar 30. Therefore, when the threaded shaft 40b of the connecting bolt 40 is inserted into the inner circumference of the collar 30 from below, the front end of the threaded shaft 40b faces the opening of the threaded hole 13e in the axial direction, so that the operation of assembling the connecting bolt 40 to the male cap 13 can be easily performed. In addition, the collar 30 has the recessed portion 30f, so the weight of the collar 30 can be reduced. In addition, in the above, the tapered surface 13f is provided on the outer circumference of the lower end of the male cap 13, and the recessed portion 30f having the tapered inclined surface 30f1 that fits with the tapered surface 13f is provided on the collar 30, but a curved surface may be provided on the outer circumference of the lower end of the male cap 13, and a recessed portion having a curved surface that fits with the curved surface may be provided on the collar 30. In addition, in the front fork F1 of the first modified example, the collar 30 has the recessed portion 30f, and a longer stroke length of the front fork F1 can be ensured, so that the degree of freedom in designing the front fork F1 can be increased, for example, the total length of the front fork F1 can be shortened.

[0061] Although the preferred embodiments of the present invention have been described in detail above, modifications, variations and changes may be made without departing from the scope of the claims.

[0062] This application claims priority based on Japanese Patent Application No. 2022-169880 filed with the Japan Patent Office on October 24, 2022, the entire contents of which are incorporated herein by reference. Explanation of symbols

[0063] 1 fork body 2. Outer tube (body side tube) 3 Inner tube (body side tube) 4 Axle bracket 4a Cylinder 10 Cylinders 11 Piston rod 12 Piston 13 Raised cover 13g Cone 14 Basic valve 30 Collar 30a chimeric part 30b Flange 30c Annular concave portion 30e Seal 30f recess 40 Connecting bolts 40a Head 40b threaded shaft 41 Washer D Damper Box F, F1 front fork R reservoir R1 elongation side chamber R2 Compression side chamber

Claims

1. A front fork, wherein: It has the following structure: A telescopic fork body having a vehicle body side tube, an axle side tube capable of axial movement relative to the vehicle body side tube, and an axle bracket having a bottomed cylindrical portion mounted on the outer periphery of the lower end of the axle side tube; a damper box accommodated in the fork body, comprising a cylinder, a piston rod inserted into the cylinder in an axially movable manner and connected to the vehicle body side tube at one end, a piston connected to the piston rod and inserted into the cylinder in an axially movable manner to divide the interior of the cylinder into an extension side chamber and a compression side chamber, and a convex cover fixed to the lower end of the cylinder and closing the lower end of the cylinder; A shaft ring housed in the cylinder portion, which has a sealing ring in an annular shape and closely fits the axle side tube, and is clamped between the axle side tube and the axle bracket; A connecting bolt has a head inserted into a bolt through hole penetrating the bottom of the cylindrical portion of the axle bracket, a threaded shaft inserted through the inner periphery of the collar and threadedly engaged with the convex cap, and connects the convex cap to the collar.

2. The front fork according to claim 1, wherein: The outer periphery of the lower end of the convex cover has a conical surface or a curved surface with a reduced diameter at the lower end side. The inner periphery of the upper end of the collar has a recessed portion that fits into the tapered surface or the curved surface and aligns the convex cover.

3. The front fork according to claim 1, wherein: An annular washer is provided which is fitted on the outer periphery of the threaded shaft of the connecting bolt, The inner circumference of the lower end of the collar is provided with an annular recess for accommodating the washer.

4. The front fork according to claim 1, wherein: A liquid storage chamber is formed in the space between the fork body and the damper box. A base valve is provided which is held on the convex cover, is fitted in the cylinder, and partitions the cylinder into the compression side chamber and a chamber communicating with the liquid storage chamber.

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