Front fork built-in hydraulic shock absorber

Abstract

To provide a front fork built-in hydraulic shock absorber that is built in a front fork of a motorcycle, etc., suppresses cavitation generated therein and generates required damping force in accordance with extension / contraction operation.SOLUTION: A hydraulic shock absorber 100 is built in a front fork of a motorcycle closed by an inner tube 80 coupled to a motorcycle body side and an outer tube 90 coupled on a wheel side. The through-rod type hydraulic shock absorber includes: a piston rod 10 suspended in the inner tube 80; a working cylinder 20 vertically fixed to the outer tube 90; a main piston part 70 provided to penetrate through the piston rod 10 and generating damping force; and a pressurized piston part 71 provided to penetrate through a tip part of the piston rod 10. Each of both ends of the piston rod 10 projects from a main cylinder region 20A.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hydraulic shock absorber that is built into the front fork of a motorcycle or the like, and more particularly to a hydraulic shock absorber that is built into the front fork and that suppresses cavitation that occurs inside the cylinder or reservoir tank and generates the required damping force in response to extension and retraction operation. [Background technology]

[0002] Patent Document 1 discloses a hydraulic shock absorber that is built into the front fork of a motorcycle or the like, in which an inner tube is slidably inserted into an outer tube, a bottom piece is fitted to the lower end of the inner tube, a damper cylinder (working cylinder) is erected from this bottom piece into the inner tube, and an oil hole (communication hole) is formed in the lower end of this damper cylinder (working cylinder) to connect the inside and outside.

[0003] In the conventional hydraulic shock absorber described in Patent Document 1, as shown in Fig. 2, when the piston rod 1 enters the working cylinder 2 during the compression stroke, part of the hydraulic oil in the oil chamber 3B passes through the piston pressure-side flow passage 7D, opens the piston check valve 7C, and moves to the oil chamber 3A. Furthermore, the hydraulic oil in the oil chambers 3A, 3B of the working cylinder 2 increases in volume due to the entry of the piston rod 1. Then, when the hydraulic oil pressure increases and reaches a required pressure, it passes through the bottom pressure-side flow passage 4A, pushes open the bottom valve 4B, and flows out into the oil chamber 3C outside the working cylinder 2, generating a compression-side damping force.

[0004] In addition, in the conventional hydraulic shock absorber described in Patent Document 1, during the extension stroke shown in FIG. 3, the piston rod 1 retracts from the working cylinder 2, and hydraulic oil in the oil chamber 3A above the piston 7 passes through the piston extension-side flow path 7A, pushes open the piston valve 7B, and flows into the oil chamber 3B below the piston 7, generating an extension-side damping force. Hydraulic oil to replenish the volumetric loss of the retracted piston rod 1 flows from the oil chamber 3C of the reservoir tank to the oil chamber 3B in the working cylinder 2 via the supply passage 4D and opens the bottom check valve 4C. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Utility Model Application Publication No. 3-35337 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the conventional hydraulic shock absorber 200, the compression side damping force is generated only by the bottom valve 4B during the compression stroke shown in Fig. 2, so the oil chambers 3A, 3B of the working cylinder 2 become high pressure. On the other hand, the oil chamber 3C of the reservoir tank is at approximately atmospheric pressure, so the hydraulic oil that passes through the bottom pressure side flow path 4A and pushes open the bottom valve 4B and flows out is suddenly depressurized from high pressure to atmospheric pressure, which can cause cavitation, in which air bubbles 6 are generated in the hydraulic oil in the reservoir tank.

[0007] Furthermore, in the conventional hydraulic shock absorber 200, in which air bubbles 6 are generated in the hydraulic oil in the reservoir tank due to cavitation, when the hydraulic oil moves to the extension stroke shown in Figure 3, the air bubbles 6 also flow into the oil chamber 3B at the same time as the hydraulic oil flows from the oil chamber 3C into the oil chamber 3B.

[0008] Furthermore, when cavitation occurs, the amount of hydraulic oil supplied to oil chamber 3B during the extension stroke falls short by the volume of the air bubbles 6 that flow into oil chamber 3B. Furthermore, if the piston rod 1 moves into the working cylinder 2 while air bubbles 6 have flowed into oil chamber 3B, and the compression stroke begins, the air bubbles 6 are simply compressed, and hydraulic oil does not flow into oil chamber 3C in the reservoir tank, creating a problem of a play stroke area where no compression damping force is generated.

[0009] At the end of this compression stroke, the amount of hydraulic oil in oil chamber 3B below piston 7 is insufficient, and so the amount of hydraulic oil in oil chamber 3A above piston 7 is also insufficient. Next, as the extension stroke begins and piston rod 1 retreats from working cylinder 2 and the hydraulic oil in oil chamber 3A is compressed by piston 7, the pressure of the hydraulic oil in oil chamber 3A does not rise immediately, creating a play stroke area where no extension damping force is generated. At the same time, air bubbles 6 expand in oil chamber 3B below piston 7, delaying the timing at which bottom check valve 4C opens, causing a further shortage of hydraulic oil supply and amplifying the shortage.

[0010] As described above, the conventional hydraulic shock absorber 200 uses the pressure difference of the hydraulic oil to open and close the bottom check valve 4C, so once cavitation occurs, there is a problem that the movement of the hydraulic oil is delayed and the hydraulic oil cannot be replenished properly.Furthermore, there is a problem that the influence of the bubbles 6 generated by the cavitation creates a play stroke range in which the required damping force corresponding to the extension and contraction operation of the piston rod 1 is not generated. [Means for solving the problem]

[0011] The present invention has been devised to achieve the above-mentioned object. More specifically, it provides a hydraulic shock absorber that is installed in the radial center of a front fork of a motorcycle, the front fork having an inner chamber closed by a substantially cylindrical inner tube connected to the vehicle body and a substantially cylindrical outer tube connected to the wheel, and that generates a required damping force in conjunction with the extension and retraction of the front fork, the hydraulic shock absorber including a piston rod suspended at the radial center of the inner tube, a substantially cylindrical working cylinder fixed to and suspended at the radial center of the outer tube, a main piston that penetrates the piston rod at a required position near an intermediate portion thereof and generates a damping force, and a pressurizing piston that penetrates the piston rod near a tip end thereof and pressurizes replenished hydraulic oil, both ends of the piston rod being defined within the working cylinder and protruding from a main cylinder region that is the operating region of the main piston, being a through-rod type hydraulic shock absorber.

[0012] Inside the front fork of this invention storehouse The hydraulic shock absorber is a so-called through-rod type hydraulic shock absorber, which minimizes the amount of hydraulic oil that leaks out from the main cylinder area that generates the damping force. In addition, the pressurizing piston section that is installed near the tip of the piston rod that protrudes from the main cylinder area works in conjunction with the extension and contraction of the piston rod to forcibly replenish hydraulic oil, eliminating any delay in replenishment and ensuring that the required amount of hydraulic oil is always available in the main cylinder area.

[0013] The present invention includes a configuration in which the inner chamber has an oil chamber of the reservoir tank section filled with hydraulic oil to a required height, and an air chamber above the oil chamber filled with air at atmospheric pressure, the working cylinder has the main cylinder area and a pressurized cylinder area extending below the main cylinder area and serving as the operating area of the pressurized piston section, and has a communication hole at a required position below the pressurized cylinder area that allows hydraulic oil to flow between the working cylinder and the reservoir tank section, the main piston section has a main piston and a compression side damping valve above the main piston, and an extension side damping valve below the main piston, and the pressurized piston section has a pressurized piston, and a check valve above the pressurized piston that allows hydraulic oil to flow from the reservoir tank section to the pressurized cylinder area and prevents backflow, and a pressurization valve below the pressurized piston for pressurizing the hydraulic oil.

[0014] In the front fork of this invention storehouse The hydraulic shock absorber is a through-rod type hydraulic shock absorber, and in conventional hydraulic shock absorbers, the large pressure difference when hydraulic oil flows from the main cylinder area to the reservoir tank section makes it easy for cavitation to occur in the hydraulic oil in the reservoir tank section. However, in the front fork of the present invention, storehouse In hydraulic shock absorbers, the amount of hydraulic oil that flows out is suppressed, which has the effect of preventing the occurrence of cavitation.

[0015] The present invention includes a configuration having a top cap that is fitted onto the upper end of the working cylinder and allows the piston rod to slidably pass through, and a bottom cap that is disposed at a required position of the working cylinder, separates the main cylinder area from the pressure cylinder area, and allows the piston rod to pass through, the top cap having a bearing member that allows the piston rod to slidably move, and a sliding gap that allows hydraulic oil and air bubbles to flow out, and the bottom cap having a bearing member that allows the piston rod to slidably move, a sealing member for liquid-tightness, and a check valve that allows hydraulic oil to flow from the pressure cylinder area to the main cylinder area and prevents backflow.

[0016] In the front fork of this invention storehouse Because the hydraulic shock absorber is configured as described above, the flow of hydraulic oil, except for the part supplied by the pressurizing piston and where it overflows, follows a continuous path: from the reservoir tank to the pressurized cylinder area, then into the main cylinder area, passes through the sliding gap in the top cap, and flows out from the top to the reservoir tank. Therefore, air bleeding during assembly can be easily completed by simply supplying hydraulic oil to the reservoir tank and operating the front fork to extend or retract. Furthermore, even if cavitation occurs due to special operating conditions, air bubbles will naturally flow out into the reservoir tank along with the hydraulic oil just by operating the front fork to extend or retract, which has the effect of generating a stable, required damping force. [Effects of the Invention]

[0017] In conventional hydraulic shock absorbers, the amount of hydraulic oil moving between the working cylinder and the reservoir tank is large, and the movement between the working cylinder and the reservoir tank is replenished by opening a valve due to the pressure difference between the working cylinder and the reservoir tank, so there is a problem that the replenishment cannot be kept up. storehouseCompared to conventional hydraulic shock absorbers, hydraulic shock absorbers require less movement of hydraulic oil between the main cylinder area and the reservoir tank section, and furthermore, since a pressurized piston is installed through the piston rod, hydraulic oil can be forcibly replenished in conjunction with the extension and contraction movement, which has the effect of preventing the condition of insufficient hydraulic oil in the main cylinder area that occurred in conventional hydraulic shock absorbers.

[0018] Furthermore, by not providing a sealing member in the top cap section, frictional resistance with the piston rod can be reduced, and at the same time, a sliding gap is provided, making it easy to bleed air when assembling the hydraulic shock absorber. Even if air bubbles are generated in the hydraulic oil due to cavitation, the hydraulic oil flows upward when the expansion / contraction operation is performed, and the air bubbles naturally flow out of the sliding gap into the reservoir tank section, allowing the bubbles to migrate to the air chamber.

[0019] In conventional hydraulic shock absorbers, the piston rod enters the working cylinder, increasing the volume of the piston rod inside the working cylinder, causing a small amount of hydraulic oil to flow out and generating a large compression damping force, which results in high pressure inside the working cylinder. storehouse Hydraulic shock absorbers generate a compression damping force by relying on the movement of hydraulic oil between the upper and lower oil chambers of the main piston. Therefore, when comparing the cross-sectional areas of the piston rod and the main piston when generating the same damping force, the pressure rise inside the main cylinder can be suppressed to a fraction of that of conventional hydraulic shock absorbers, which also has the effect of suppressing the occurrence of cavitation in the hydraulic oil. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a cross-sectional view illustrating an embodiment of a front fork-mounted hydraulic shock absorber according to the present invention. [Figure 2] FIG. 10 is a cross-sectional view illustrating a compression process in a conventional hydraulic shock absorber. [Figure 3] FIG. 10 is a cross-sectional view illustrating the extension process of a conventional hydraulic shock absorber. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. However, the drawings are schematic illustrations and do not necessarily correspond to actual dimensions, ratios, etc. Furthermore, the drawings may include portions where the dimensional relationships and ratios differ from one another. In this embodiment, the inside of the front fork storehouse When describing a hydraulic shock absorber, storehouse With the hydraulic shock absorber attached to the vehicle body as a reference, the vehicle body side will be referred to as the upper side, the wheel side as the lower side, and the direction along the width direction of the front fork as the radial direction.

[0022] As shown in Figure 1, inside the front fork storehouse The hydraulic shock absorber 100 is built into the approximate radial center of the front fork, which defines an inner chamber closed by an approximately cylindrical inner tube 80 connected to the vehicle body side and an approximately cylindrical outer tube 90 connected to the wheel side, and generates the required damping force in conjunction with the extension and retraction of the front fork.

[0023] Inside the front fork storehouse The hydraulic shock absorber 100 is composed of a piston rod 10 whose upper end is connected and suspended at approximately the radial center of the inner tube 80, a roughly cylindrical working cylinder 20 that is fixed in a vertical position at approximately the radial center of the outer tube 90, a main piston portion 70 that is inserted through the piston rod 10 at a required position in the vertical middle part and generates a damping force, and a pressure piston portion 71 that is similarly inserted through the piston rod 10 near its lower end and applies pressure to replenish hydraulic oil.

[0024] Furthermore, the inner chamber is formed by an oil chamber 30C in the reservoir tank section filled with hydraulic oil to the required height, and an air chamber 30E located above the oil chamber 30C, adjacent to the liquid level O, and filled with air at atmospheric pressure.

[0025] The working cylinder 20 is divided into a main cylinder area 20A in which the main piston portion 70 operates slidably, and a pressurized cylinder area 20B which is an operating area extending below the main cylinder area 20A and in which the pressurized piston portion 71 operates slidably. The main cylinder area 20A is formed by an oil chamber 30A which is the upper chamber of the main piston portion 70, and an oil chamber 30B which is the lower chamber of the main piston portion 70. The pressurized cylinder area 20B is formed by an oil chamber 30D which is the upper chamber of the pressurized piston portion 71, and an oil chamber 30F which is the lower chamber of the pressurized piston portion 71. A communication hole 20C is formed between the oil chamber 30F and the oil chamber 30C of the reservoir tank portion, allowing the flow of hydraulic oil.

[0026] Furthermore, this embodiment includes a top cap 21 that fits onto the upper end of the working cylinder 20 and allows the piston rod 10 to slidably pass therethrough, and a bottom cap 22 that is disposed at a required position on the working cylinder 20, separating the main cylinder region 20A from the pressure cylinder region 20B, and allowing the piston rod 10 to pass therethrough. The top cap 21 includes a bearing member 23 that allows the piston rod 10 to slide freely, and a sliding gap 24 that allows the hydraulic oil and air bubbles to escape. The bottom cap 22 includes the bearing member 23 that allows the piston rod 10 to slide freely, a seal member 25 for liquid-tightness, and a bottom cap check valve 26 that allows hydraulic oil to flow from the oil chamber 30D of the pressure cylinder region 20B to the oil chamber 30B of the main cylinder region 20A, but prevents backflow. The bottom cap check valve 26 includes a hydraulic oil flow path, a ball-shaped on-off valve, a coil spring that presses the on-off valve, and a stopper that secures the coil spring.

[0027] The main piston portion 70 is formed by a main piston 70A, a compression side damping valve 70B consisting of an annular leaf valve provided in an upward direction of the main piston 70A, an extension side damping valve 70C consisting of an annular leaf valve provided in an downward direction of the main piston 70A, a main piston portion extension side flow path 70D which serves as a passage through which hydraulic oil moves, and a main piston portion compression side flow path 70E.

[0028] The pressurizing piston 71 is made up of a pressurizing piston 71A, a pressurizing piston check valve 71B that is provided above the pressurizing piston 71A and allows hydraulic oil to flow from oil chamber 30F of the pressurizing cylinder region 20B to oil chamber 30D while preventing reverse flow, and a pressurizing valve 71C that is provided below the pressurizing piston 71A and consists of an annular leaf valve for pressurizing the hydraulic oil. The pressurizing piston 71A is provided with a pressurizing piston supply flow path 71D, which serves as a passage through which the hydraulic oil moves, and an overflow flow path 71E. The pressurizing piston check valve 71B is made up of an annular leaf valve, a coil spring that presses the leaf valve, and a stopper that secures the coil spring.

[0029] The inside of the front fork of this embodiment shown in FIG. storehouse Unlike the conventional hydraulic shock absorber 200 shown in Figures 2 and 3, the hydraulic shock absorber 100 is formed in a so-called through-rod format in which both ends of the piston rod 10 are defined within the working cylinder 20 and each protrude outside in the vertical direction of the main cylinder area 20A, which is the operating area of the main piston section 70.

[0030] Next, the flow of hydraulic oil in this embodiment will be described. First, during assembly, hydraulic oil is poured into the oil chamber 30C of the reservoir tank while the hydraulic oil is being poured into the oil chamber 30C of the front fork. storehouse When the hydraulic shock absorber 100 is slowly extended or retracted, hydraulic oil flows from the reservoir tank oil chamber 30C through the communication hole 20C into the oil chamber 30F. Furthermore, the hydraulic oil accumulated in the oil chamber 30F flows through the pressurized piston supply passage 71D, opens the pressurized piston check valve 71B, and flows into the oil chamber 30D. The hydraulic oil accumulated in the oil chamber 30D is pressurized by the pressurized piston 71A, opens the bottom cap check valve 26, and flows into the oil chamber 30B. The hydraulic oil accumulated in the oil chamber 30B flows through the main piston compression side passage 70E, pushes open the compression side damping valve 70B, and flows into the oil chamber 30A. The oil chamber 30A is filled with hydraulic oil, and the hydraulic oil injection operation is completed. During this operation, first, storehouseThe air present inside the hydraulic shock absorber 100 is released into the oil chamber 30C of the reservoir tank portion through the sliding gap 24, thereby completing the air bleeding operation.

[0031] Inside the front fork after hydraulic oil injection storehouse When the hydraulic shock absorber 100 is operated to expand or contract, the required damping force is generated by the expansion or contraction of the main piston portion 70, and a small amount of hydraulic oil, equivalent to the volume expanded due to the temperature rise caused by the operation, is released into the oil chamber 30C of the reservoir tank portion through the sliding gap 24. Meanwhile, the pressurizing piston portion 71, which operates in conjunction with the expansion or contraction operation, opens the bottom cap portion check valve 26 and supplies the required amount of hydraulic oil from the oil chamber 30D to the oil chamber 30B, and causes excess hydraulic oil to flow back into the oil chamber 30F through the overflow passage 71E. The pressure at this time can be set appropriately with the pressurizing valve 71C.

[0032] As described above, in the front fork of this embodiment, storehouse The hydraulic shock absorber is a so-called through-rod type hydraulic shock absorber in which both ends of the piston rod protrude from the main cylinder area that generates the damping force.The amount of hydraulic oil that flows out of the main cylinder area is very small, and since there is a pressurized piston at the tip of the piston rod, hydraulic oil can be reliably replenished, which has the effect of enabling the required damping force to be stably generated in response to the extension and retraction operation of the front fork.

[0033] As described above, the best configurations, methods, etc. for carrying out the present invention have been disclosed in the above description, but the present invention is not limited to these. For example, in the above embodiment, the valve that generates the damping force was described as a damping valve consisting of an annular leaf valve, but this does not limit the shape or type, and as long as it can effectively generate a damping force, it is also possible to adopt a so-called poppet-type damping force generating mechanism consisting of a coil spring and a hemispherical valve. [Explanation of symbols]

[0034] 1,10 Piston rod 2,20 Working cylinder 20A Main cylinder area 20B Pressurized cylinder area 20C communication hole 21 Top Cap 22 Bottom cap 23 Bearing materials 24 Sliding clearance 25 Sealing material 26 Bottom cap check valve 3A,3B,3C,30A,30B,30C,30D,30F Oil chamber 30E air chamber 4A Bottom pressure side flow path 4B Bottom valve 4C Bottom check valve 4D Supply Corridor 6. Bubbles 7 Pistons 7A Piston extension side flow passage 7B Piston valve 7C Piston check valve 7D Piston pressure side flow passage 70 Main piston section 70A main piston 70B compression damping valve 70C Rebound damping valve 70D Main piston extension side passage 70E Main piston pressure side passage 71 Pressure piston part 71A Pressurized Piston 71B Pressure piston check valve 71C Pressure Valve 71D Pressure piston supply flow path 71E Overflow channel 8,80 inner tube 9,90 outer tube 100 Inside the front fork storehouse Hydraulic shock absorber 200 Conventional hydraulic shock absorber O liquid level

Claims

1. A hydraulic shock absorber installed inside the front fork of a motorcycle, closed by an inner tube connected to the vehicle body side and an outer tube connected to the wheel side, the hydraulic shock absorber having a piston rod suspended at the center position of the inner tube, a working cylinder fixed to a vertical position at the center position of the outer tube, a main piston portion that passes through the piston rod and generates a damping force, and a pressurizing piston portion that also passes through the piston rod near the tip end and pressurizes hydraulic oil, the hydraulic shock absorber being a through-rod type hydraulic shock absorber in which both ends of the piston rod protrude from a main cylinder area that is defined within the working cylinder and is the operating area of the main piston portion.

2. 2. The front-fork-integrated hydraulic shock absorber according to claim 1, wherein the interior of the front fork includes an oil chamber in a reservoir tank portion filled with hydraulic oil to a required height, and an air chamber filled with air at atmospheric pressure; the working cylinder includes a pressurized cylinder area extended below the main cylinder area, and a communication hole that allows hydraulic oil to flow between the pressurized cylinder area and the reservoir tank portion; the main piston portion includes a main piston, a compression side damping valve, and an extension side damping valve; and the pressurized piston portion includes a pressurized piston, a check valve that allows hydraulic oil to flow from the reservoir tank portion to the pressurized cylinder area and prevents its reverse flow, and a pressurization valve for pressurizing the hydraulic oil.

3. 3. The front fork-integrated hydraulic shock absorber according to claim 1 or 2, further comprising: a top cap that is fitted onto an upper end of the working cylinder and through which the piston rod slidably passes; and a bottom cap that is disposed at a required position of the working cylinder, which separates the main cylinder area from the pressurized cylinder area and the bottom cap that allows the piston rod to pass through, wherein the top cap has a bearing member that allows the piston rod to slide freely and a sliding gap that allows hydraulic oil and air bubbles to flow out, and the bottom cap has a bearing member that allows the piston rod to slide freely, a seal member that achieves liquid-tightness, and a check valve that allows hydraulic oil to flow from the pressurized cylinder area to the main cylinder area and prevents backflow.

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