JP7510655B1 - Front fork built-in hydraulic shock absorber - Google Patents

Abstract

[Problem] To provide a hydraulic shock absorber built into a front fork that is built into the front fork of a motorcycle or the like, suppresses cavitation that occurs inside, and generates the required damping force according to the extension and contraction action. [Solution] A hydraulic shock absorber 100 is built into the front fork of a motorcycle, closed with an inner tube 80 connected to the vehicle body side and an outer tube 90 connected to the wheel side, and has a piston rod 10 suspended from the inner tube 80, a working cylinder 20 vertically fixed to the outer tube 90, a main piston portion 70 penetrating the piston rod 10 and generating a damping force, and a pressurizing piston portion 71 penetrating the tip of the piston rod 10, and is a through-rod type hydraulic shock absorber in which both ends of the piston rod 10 protrude from a main cylinder area 20A. [Selected drawing] Figure 1

Description

The present invention relates to a hydraulic shock absorber that is built into the front fork of a motorcycle or the like, and more specifically, to a hydraulic shock absorber that is built into the front fork and that suppresses cavitation that occurs in the cylinder or reservoir tank and generates the required damping force according to the extension and retraction operation.

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 into the lower end of the inner tube, a damper cylinder (working cylinder) is erected from the bottom piece into the inner tube, and an oil hole (communication hole) is formed in the lower end of the damper cylinder (working cylinder) to connect the inside and outside.

As shown in FIG. 2, in the conventional hydraulic shock absorber described in Patent Document 1, 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 and 3B of the working cylinder 2 increases in volume due to the entry of the piston rod 1. Then, the hydraulic oil, whose hydraulic oil pressure has increased and reached the required pressure, 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.

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 retreats from the working cylinder 2, and hydraulic oil in the oil chamber 3A above the piston 7 passes through the piston extension side flow passage 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 retreated 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 to allow it to flow in.

Japanese Utility Model Application Publication No. 3-35337

However, in the conventional hydraulic shock absorber 200, the compression side damping force is generated only by the bottom valve 4B during the compression process shown in Figure 2, so the oil chambers 3A and 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 reduced in pressure from high pressure to atmospheric pressure, which can cause cavitation, which generates air bubbles 6 in the hydraulic oil in the reservoir tank.

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, there is a problem in that the air bubbles 6 also flow into the oil chamber 3B at the same time that the hydraulic oil flows from the oil chamber 3C into the oil chamber 3B.

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 flowing into oil chamber 3B. Furthermore, if the compression stroke is started while air bubbles 6 have flowed into oil chamber 3B, even if the piston rod 1 enters the working cylinder 2, 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 damping force is generated on the compression side.

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, when 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, and a play stroke area occurs where no damping force is generated on the extension side. 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 an even greater shortage of hydraulic oil, and the degree of the shortage increases.

As mentioned 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, the movement of the hydraulic oil is delayed, making it difficult to properly replenish the hydraulic oil. Furthermore, there is also the problem that the air bubbles 6 generated by cavitation create a play stroke range in which the required damping force corresponding to the extension and contraction of the piston rod 1 is not generated.

The present invention has been devised to achieve the above object. More specifically, it is a hydraulic shock absorber that is installed in the radial center of a motorcycle front fork that defines an inner chamber closed by a substantially cylindrical inner tube connected to the vehicle body side and a substantially cylindrical outer tube connected to the wheel side, and generates a required damping force in conjunction with the extension and contraction of the front fork. The hydraulic shock absorber includes a piston rod suspended in the radial center of the inner tube, a substantially cylindrical working cylinder vertically fixed to the radial center of the outer tube, a main piston portion that penetrates the piston rod at a required position near the middle part and generates a damping force, and a pressurizing piston portion that penetrates the piston rod near the tip part and pressurizes the hydraulic oil to be supplied, and includes a through-rod type hydraulic shock absorber configuration in which both ends of the piston rod are defined within the working cylinder and each protrude from the main cylinder area, which is the operating area of the main piston.

The front fork -integrated hydraulic shock absorber of the present invention is a so-called through-rod type hydraulic shock absorber, which reduces the amount of hydraulic oil that leaks out from the main cylinder area that generates the damping force to the outside. In addition, the pressurized piston portion 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 supply hydraulic oil, eliminating any delay in supply and ensuring that the required amount of hydraulic oil is always available in the main cylinder area.

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 that extends below the main cylinder area and is the operating area of the pressurized piston section, and has a communication hole that allows hydraulic oil to flow between the working cylinder and the reservoir tank section at a required position below the pressurized cylinder area, 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, 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 it from flowing back, and a pressurized valve below the pressurized piston for pressurizing the hydraulic oil.

The hydraulic shock absorber built into the front fork of the present invention is a through-rod type hydraulic shock absorber. In conventional hydraulic shock absorbers, the large pressure difference that occurs when the hydraulic oil flows out 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, the hydraulic shock absorber built into the front fork of the present invention has the effect of suppressing the occurrence of cavitation by suppressing the amount of hydraulic oil that flows out.

The present invention includes a top cap that is fitted to the 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 allows the piston rod to pass through. The top cap has a bearing member for allowing 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 for allowing the piston rod to slide freely, a seal member for 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.

Since the front fork built-in hydraulic shock absorber of the present invention has the above-mentioned configuration, the hydraulic oil flows from the reservoir tank to the pressurized cylinder area, and then into the main cylinder area, passes through the sliding gap of the top cap, and flows out from the top into the reservoir tank in a continuous flow, except for the part where it is supplied by the pressurizing piston and overflows. Therefore, the air bleeding work during assembly can be easily completed by simply supplying hydraulic oil to the reservoir tank and performing the extension/retraction operation, and even if cavitation occurs due to special operating conditions, air bubbles will naturally flow out to the reservoir tank together with the hydraulic oil by simply extending and retracting the front fork, which has the effect of generating a stable and required damping force.

In conventional hydraulic shock absorbers, in addition to the large amount of hydraulic oil moving between the working cylinder and the reservoir tank, the movement between the working cylinder and the reservoir tank was carried out by opening a valve due to the pressure difference between the working cylinder and the reservoir tank to replenish the hydraulic oil, which posed the problem of not being able to keep up with the replenishment. However, the front fork -integrated hydraulic shock absorber of the present invention requires less movement of hydraulic oil between the main cylinder area and the reservoir tank compared to conventional hydraulic shock absorbers, and further, a pressurized piston is installed through the piston rod so that hydraulic oil can be forcibly replenished in conjunction with the extension and contraction movement, which has the effect of preventing the condition of a shortage of hydraulic oil in the main cylinder area that occurred in conventional hydraulic shock absorbers.

In addition, by not providing a seal 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 hydraulic oil is expanded or contracted, so the air bubbles naturally flow out of the sliding gap into the reservoir tank section and can be transferred to the air chamber.

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, resulting in high pressure inside the working cylinder.In contrast, the front fork -integrated hydraulic shock absorber of the present invention generates a compression damping force by relying on the movement of hydraulic oil between the upper and lower oil chambers of the main piston.By 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.

1 is a cross-sectional view illustrating an embodiment of a front fork -mounted hydraulic shock absorber according to the present invention. FIG. 11 is a cross-sectional view illustrating a compression process in a conventional hydraulic shock absorber. FIG. 11 is a cross-sectional view illustrating an extension process in a conventional hydraulic shock absorber.

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. In addition, the drawings may include parts in which the dimensional relationships and ratios differ from one another. In addition, in the present embodiment, when describing the front fork- integrated hydraulic shock absorber, the vehicle body side will be expressed 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, based on the state in which the front fork -integrated hydraulic shock absorber is attached to the vehicle body.

As shown in FIG. 1, the front-fork -integrated hydraulic shock absorber 100 is integrated into the approximate radial center of the front fork, which defines an inner chamber closed off 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.

The front fork -integrated hydraulic shock absorber 100 is formed 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 vertically fixed at approximately the radial center of the outer tube 90, a main piston portion 70 that is provided through the piston rod 10 at a required position approximately in the middle in the up-down direction and generates a damping force, and a pressurizing piston portion 71 that is similarly provided through the piston rod 10 near its lower end and applies pressure to replenish hydraulic oil.

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

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

Furthermore, in this embodiment, the top cap 21 is fitted to the upper end of the working cylinder 20 and allows the piston rod 10 to slide through it, and the bottom cap 22 is arranged at a required position of the working cylinder 20, partitioning the main cylinder area 20A and the pressurized cylinder area 20B and allowing the piston rod 10 to pass through it. The top cap 21 has a bearing member 23 for allowing the piston rod 10 to slide freely and a sliding gap 24 that allows the hydraulic oil and air bubbles to flow out. The bottom cap 22 is formed of the bearing member 23 for allowing the piston rod 10 to slide freely, a seal member 25 for liquid tightness, and a bottom cap check valve 26 that allows the hydraulic oil to flow from the oil chamber 30D of the pressurized cylinder area 20B to the oil chamber 30B of the main cylinder area 20A and prevents backflow. The bottom cap check valve 26 is formed of a hydraulic oil flow path, a ball-shaped opening and closing valve, a coil spring that presses the opening and closing valve, and a stopper that fixes the coil spring.

The main piston section 70 is formed of a main piston 70A, a compression side damping valve 70B consisting of an annular leaf valve extending through the upper side of the main piston 70A, an extension side damping valve 70C consisting of an annular leaf valve extending through the lower side of the main piston 70A, a main piston section extension side flow passage 70D which serves as a passage through which hydraulic oil moves, and a main piston section compression side flow passage 70E.

The pressurizing piston part 71 is formed of a pressurizing piston 71A, a pressurizing piston part check valve 71B that is provided above the pressurizing piston 71A to allow hydraulic oil to flow from the oil chamber 30F of the pressurizing cylinder area 20B to the oil chamber 30D and prevent its backflow, and a pressurizing valve 71C that is provided below the pressurizing piston 71A and consists of an annular leaf valve to pressurize the hydraulic oil. The pressurizing piston 71A is formed of a pressurizing piston part supply flow path 71D that serves as a passage through which the hydraulic oil moves, and an overflow flow path 71E. The pressurizing piston part check valve 71B is formed of a circular leaf valve, a coil spring that presses the leaf valve, and a stopper that fixes the coil spring.

The front-fork -integrated hydraulic shock absorber 100 of this embodiment shown in Figure 1 differs from the conventional hydraulic shock absorber 200 shown in Figures 2 and 3 in that both ends of the piston rod 10 are defined within the working cylinder 20 and are formed as a so-called through-rod type that each protrudes outside in the vertical direction of the main cylinder area 20A, which is the operating area of the main piston portion 70.

Next, the flow of hydraulic oil in this embodiment will be described. First, when assembling, hydraulic oil is injected into the oil chamber 30C of the reservoir tank section, and the front fork built-in hydraulic shock absorber 100 of this embodiment is slowly expanded and contracted. Then, hydraulic oil flows from the oil chamber 30C of the reservoir tank section to the oil chamber 30F via the communication hole 20C. Furthermore, the hydraulic oil stored in the oil chamber 30F flows into the oil chamber 30D via the pressurized piston section supply flow passage 71D, opening the pressurized piston section check valve 71B. The hydraulic oil stored in the oil chamber 30D is pressurized by the pressurized piston 71A, opens the bottom cap section check valve 26, and flows into the oil chamber 30B. The hydraulic oil stored in the oil chamber 30B flows into the oil chamber 30A through the main piston section compression side flow passage 70E, expanding the compression side damping valve 70B, and the oil chamber 30A is filled with hydraulic oil, and the injection of hydraulic oil is completed. During this operation, the air present inside the front-fork built-in hydraulic shock absorber 100 is first released through the sliding gap 24 into the oil chamber 30C of the reservoir tank portion, thereby completing the air bleeding operation.

When the hydraulic shock absorber 100 with built-in front forks is expanded or contracted after the hydraulic oil injection operation, the required damping force is generated by the expansion and contraction of the main piston 70, and a small amount of hydraulic oil, the volume of which expands due to the temperature rise caused by the operation, is released into the oil chamber 30C of the reservoir tank through the sliding gap 24. Meanwhile, the pressurizing piston 71, which operates in conjunction with the expansion and contraction operation, opens the bottom cap check valve 26 and supplies the required amount of hydraulic oil from the oil chamber 30D to the oil chamber 30B, and causes the 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 by the pressurizing valve 71C.

As described above, the front fork -integrated hydraulic shock absorber of this embodiment is a so-called through-rod type hydraulic shock absorber in which both ends of the piston rod protrude from the main cylinder area which generates the damping force. The amount of hydraulic oil flowing out from the main cylinder area is very small, and further, since there is a pressurized piston at the tip of the piston rod, the 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.

As described above, the best configurations, methods, and the like 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 is 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, a so-called poppet-type damping force generating mechanism consisting of a coil spring and a hemispherical valve may also be used.

REFERENCE SIGNS LIST 1, 10 piston rod 2, 20 working cylinder 20A main cylinder area 20B pressurized cylinder area 20C communicating hole 21 top cap 22 bottom cap 23 bearing member 24 sliding gap 25 seal member 26 bottom cap check valve 3A, 3B, 3C, 30A, 30B, 30C, 30D, 30F oil chamber 30E air chamber 4A bottom compression side flow passage 4B bottom valve 4C bottom check valve 4D supply passage 6 air bubble 7 piston 7A piston extension side flow passage 7B piston valve 7C piston check valve 7D piston compression side flow passage 70 main piston 70A main piston 70B compression side damping valve 70C extension side damping valve 70D main piston extension side flow passage 70E main piston compression side flow passage 71 Pressurizing piston section 71A Pressurizing piston 71B Pressurizing piston section check valve 71C Pressurizing valve 71D Pressurizing piston section supply flow path 71E Overflow flow path 8, 80 Inner tube 9, 90 Outer tube 100 Front fork built-in hydraulic shock absorber 200 Conventional hydraulic shock absorber O Liquid level

Claims (3)

A hydraulic shock absorber installed inside a front fork of a motorcycle, the front fork being closed off with 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 of the inner tube, a working cylinder vertically fixed at the center of the outer tube, a main piston portion extending through the piston rod and generating a damping force, and a pressurizing piston portion similarly extending through the piston rod near the tip end thereof and pressurizing 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 region defined within the working cylinder, which is the operating region of the main piston portion. 2. The hydraulic shock absorber built into the front fork according to claim 1, characterized in that the inside of the front fork has an oil chamber of a reservoir tank section filled with hydraulic oil to a required height and an air chamber filled with air at atmospheric pressure, the working cylinder has 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 section, the main piston section has a main piston, a compression side damping valve, and an extension side damping valve, and the pressurized piston section has a pressurized piston, a check valve that allows hydraulic oil to flow from the reservoir tank section to the pressurized cylinder area and prevents the backflow, and a pressurization valve for pressurizing the hydraulic oil. 3. The hydraulic shock absorber with built-in front forks according to claim 2, further comprising: a top cap that is fitted onto an upper end of the working cylinder and through which the piston rod passes slidably; 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 passes through the piston rod, wherein the top cap has a bearing member for allowing the piston rod to slide slidably and a sliding gap that allows hydraulic oil and air bubbles to flow out, and the bottom cap has a bearing member for allowing the piston rod to slide slidably, a seal member for obtaining 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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