JP2010185571A - Front fork - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a front fork having a damper free of generation of any excessive reaction force even when it is energized in the elongating direction, capable of decreasing the number of component parts contributing to reduction of the weight. <P>SOLUTION: The front fork is structured so that an intra-reserver air chamber A bounded by the liquid surface O is provided in the fork body able to make expansion and contraction with a vehicle body side tube 1 and a wheel side tube 2, and also in the fork body, the damper able to make expansion and contraction with a cylinder 3 and a rod 4 is arranged, wherein an air pressure at or over the atmospheric is encapsulated in the intra-reserver air chamber A when the fork body is in the maximally elongated condition so as to generate a reaction force, and a suppressing means S suppresses the reaction force in the prescribed stroke region in which the fork body contracts from the maximally elongated condition, so that it is possible to lessen the reaction force in the contracting motion in the prescribed stroke region from the maximally elongated condition. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a front fork, and more particularly, to an improvement in a front fork that is a shock absorber that absorbs road vibration input to a front wheel that is mounted on a front wheel side of a two-wheeled vehicle and is suspended at a lower end portion.

  There have been various proposals for a front fork as a shock absorber that absorbs road surface vibration that is input to a front wheel that is mounted on a front wheel side of a motorcycle and is suspended at a lower end portion. As shown, many front forks have a suspension spring consisting of a coil spring that urges the fork body in the extension direction within the fork body that can be expanded and contracted by the vehicle body side tube and the wheel side tube. ing.

  On the other hand, the front fork disclosed in Patent Document 1 has an inverted type damper having a cylinder body as an upper end side member in the fork body, and this damper is on the pressure side in the bottom end portion of the cylinder body. In addition to having a damping means, there is a free piston which is slidably disposed downstream of the pressure side damping means and defines a pressure receiving surface side oil chamber and a back side air chamber in the bottom end portion.

  In this damper, the back side air chamber defined by the free piston communicates with a reservoir in the fork main body outside the damper through a communication hole opened at the bottom end of the cylinder body. And a biasing spring comprising a coil spring that biases the free piston from the back side against the pressure in the damper.

  In addition, in this damper, the free piston is caused by the expansion of the working fluid due to the temperature rise of the working fluid in the damper, the working fluid outside the damper flowing into the damper during the operation of the damper, etc. When the working fluid in the damper exceeds a predetermined amount, the working fluid moves backward so as to rise above a predetermined stroke, and the surplus working fluid is returned to the reservoir through the open communication hole at the bottom end of the cylinder body. To release.

  Therefore, in the front fork disclosed in Patent Document 1, the fork main body is urged in the extending direction by the suspension spring, the amount of working fluid in the damper is stabilized, and the damper generates an excessive reaction force. Disappear.

Japanese Patent Laid-Open No. 6-109054 (see paragraphs 0022, 0024, 0044 to 0046, FIGS. 1 and 8 in the specification)

  However, in the proposal disclosed in Patent Document 1 described above, there is basically no problem in that the damper does not generate an excessive reaction force while the fork body is biased in the extension direction by the suspension spring. However, there is a possibility that it is pointed out that there is a slight defect in the implementation.

  That is, in many front forks proposed so far, including the proposal disclosed in Patent Document 1, the fork body has a suspension spring and is biased in the extending direction.

  Therefore, in the conventional front forks, there is a problem that it is difficult to reduce the number of parts and the preferable weight reduction effect cannot be obtained because of the suspension spring.

  The present invention was devised in view of such a current situation, and the object of the present invention is that the damper does not generate an excessive reaction force while being urged in the extending direction. It is possible to reduce the number of parts that contribute to reduction, and to provide a front fork that is optimal for expecting an improvement in versatility.

  In order to achieve the above-described object, the structure of the front fork according to the present invention is basically configured as a reservoir internal air chamber with a liquid level as a boundary in a fork body that can be expanded and contracted by a vehicle body side tube and a wheel side tube. And a fork body having a damper that can be expanded and contracted by a cylinder body and a rod body, when the fork body is in a fully extended state, the reservoir interior air chamber is large. It is assumed that the fork main body has a reaction force by enclosing a pressure higher than the atmospheric pressure, and has a suppression means for suppressing the reaction force in a predetermined stroke region in which the fork main body contracts from the maximum extension state.

  Therefore, in the present invention, when the fork main body is in the most extended state, the air pressure in the reservoir is filled with a pressure higher than atmospheric pressure so as to have a reaction force, so that the inside of the fork main body can be maintained in a pressurized state. Therefore, the cylinder body in the damper can be maintained in a pressurized state. As a result, when the damper in the most extended state starts the contraction operation, a stable damping operation from the beginning by the compression side damping means is enabled.

  In the present invention, when the fork main body is in the most extended state, the air pressure in the reservoir is filled with atmospheric pressure equal to or higher than the atmospheric pressure to provide a reaction force, so the fork main body is always urged in the extending direction. Therefore, the fork main body can be urged in the extending direction without having a suspension spring. As a result, the weight can be reduced and the number of parts can be reduced by the absence of the suspension spring. .

  Further, in the present invention, when the fork main body is in the maximum extension state, a pressure higher than the atmospheric pressure is sealed in the air chamber in the reservoir to provide a reaction force, while the fork main body contracts from the maximum extension state. Therefore, the reaction force during the contraction operation in the predetermined stroke region can be reduced from the maximum extension state.

  Further, in the present invention, since the suppressing means is disposed in the cylinder body of the damper, the balance spring is disposed compared to the case where the suppressing means is disposed outside the cylinder body. The number of related parts can be reduced.

It is a front view which fractures | ruptures the front fork by one Embodiment of this invention, and shows it partially in a cross section. FIG. 2 is a partial semi-longitudinal longitudinal sectional view showing an enlarged upper end side portion of the front fork of FIG. 1. It is a figure which shows the lower side of the intermediate part in the front fork of FIG. 1 similarly to FIG. FIG. 3 is a view showing an upper side of an intermediate portion in the front fork of FIG. 1 in the same manner as FIG. 2. It is a figure which shows the downward side of the intermediate part in the front fork by other embodiment similarly to FIG.

  Hereinafter, the present invention will be described based on the illustrated embodiment. A front fork according to the present invention is mounted on the front wheel side of a two-wheeled vehicle and absorbs road surface vibrations inputted to the front wheel of the two-wheeled vehicle that is traveling. Functions as a shock absorber.

  By the way, the front fork of the present invention is said to be mounted on the front wheel side of the two-wheeled vehicle, but the two-wheeled vehicle is a problem in terms of expression, and may be mounted on the front wheel side of the three-wheeled vehicle. Of course, it may be mounted on the front wheel side of a four-wheeled vehicle such as a car.

  The front fork includes a fork main body that has a top end coupled to a handle (not shown) in a two-wheeled vehicle and suspends a front wheel (not shown) in the two-wheeled vehicle at a lower end, and is housed in the fork main body. And a damper that expands and contracts in synchronism with the expansion and contraction of the fork main body and has a predetermined damping action.

  As shown in FIG. 1, the fork main body has a vehicle body side tube 1 composed of a large-diameter outer tube whose upper end side is coupled to the handle side, and a lower end while the upper end side is inserted into the lower end side of the vehicle body side tube 1 so as to be able to protrude and retract. The wheel-side tube 2 formed of a small-diameter inner tube that suspends the front wheel at the portion is an inverted type, and is formed into a telescopic type that can be expanded and contracted.

  Incidentally, in the figure, the fork main body is set to be an inverted type in which the large-diameter outer tube is the vehicle body side tube 1, but from the viewpoint of realizing the present invention, the fork main body has a large-diameter outer tube. The wheel side tube 2 may be set upright.

  The fork main body has a reservoir R that is inside and outside the damper, as shown in the figure, and this reservoir R is a reservoir that is bordered by an oil surface O that is a liquid surface in the working oil that is a working fluid. It has an inside air chamber A.

  Incidentally, in the present invention, the air pressure A which is equal to or higher than the atmospheric pressure when the fork main body is in the fully extended state is sealed in the air chamber A in the reservoir. This will be described in detail later.

  As for the height position of the oil level O in the reservoir R, as shown in the figure, when the fork main body is in the most extended state, the wheel side tube 2 is pierced and between the vehicle body side tube 1. It is positioned so as to have a communication hole 2a in the lower oil that allows the hydraulic oil to flow into the emerging lubricating gap (not shown).

  And the height position of the oil level O in this reservoir R is preferably held at the upper end of the wheel side tube 2 so that the bearing member 21 slidably contacting the outer periphery of the cylinder body 3 in the damper described later is placed in the lower oil. In place of this, although not shown, it may be positioned below the head end which is the lower end in the drawing of the cylinder body 3 in the damper to be described later.

  At this time, the bearing member 21 is formed in an annular shape, and has a plurality of communication holes 21a formed at appropriate intervals in the circumferential direction, so that the bearing member 21 can communicate vertically.

  As shown in the figure, the damper is set upside down with the cylinder body 3 as an upper end side member and the rod body 4 as a lower end side member. The rod body 4 is suspended from the shaft core portion of the tube 1, and is coupled to the wheel side tube 2 and is erected on the shaft core portion of the wheel side tube 2.

  Incidentally, in the damper shown in the figure, the cylinder body 3 is formed into a cylindrical shape with the cylinder body 3 being screwed into the upper end opening of the vehicle body side tube 1 while the cylinder body 3 is formed in a cylindrical shape. A cap member 11 is screwed to the connecting portion 3a to seal the upper end opening of the vehicle body side tube 1.

  Further, the base end portion which is the lower end portion in the figure of the rod body 4 is coupled to the shaft core portion of the bottom member 22 which is screwed to the lower end portion of the wheel side tube 2 under the use of the tightening bolt 41 and the wheel. It stands up in the side tube 2.

  On the other hand, this damper has a piston body 5 which is also slidably received in the cylinder body 3 while being held at the tip portion which is the upper end portion of the rod body 4 in the drawing, as shown in FIG. The piston body 5 includes a damping means that defines a rod side chamber R1 and a piston side chamber R2 in the cylinder body 3 and allows mutual communication between the rod side chamber R1 and the piston side chamber R2. An extension side damping valve 51 and an extension side check valve 52 are provided, and a predetermined extension side damping action is realized when hydraulic fluid passes through the extension side damping valve 51.

  Note that any configuration may be employed for the above-described damping means. For example, the above-described extension side check valve 52 may be replaced with a suction valve or a pressure side damping valve. May be.

  And, as with many dampers of almost all kinds, even in this damper, the extension spring 53 for absorbing the acting force at the time of the maximum extension operation of the fork body, that is, the maximum extension operation of the damper is provided. Have.

  The front fork shown in the drawing has an oil lock mechanism that absorbs the acting force at the time of the most contraction operation, and this oil lock mechanism is, as shown in FIG. 1, the head end portion of the cylinder body 3 in the damper. The oil lock piece 31 held on the outer periphery of the cylinder and the oil lock case 23 disposed in the bottom end portion of the wheel side tube 2, and the rod body 4 retracts into the cylinder body 3 with a large stroke. During operation, the oil lock piece 31 is inserted into the oil lock case 23, and absorbs the acting force during the most contraction operation.

  On the other hand, in this damper, during the contraction operation in which the rod body 4 is immersed in the cylinder body 3, an amount of hydraulic oil corresponding to the rod intrusion integral that becomes redundant in the piston side chamber R <b> 2 passes through the compression side damping means 6. Allow to flow out to the free piston 7 side.

  In this damper, contrary to the above, when the rod body 4 projects from the cylinder body 3 during the extension operation, the amount of hydraulic oil corresponding to the rod withdrawal volume integral which is insufficient in the piston side chamber R2 is supplied to the free piston 7. Replenishment from the side through the compression side damping means 6.

  By the way, in this damper, as shown in FIG. 2, the cylinder body 3 includes a compression side damping means 6 corresponding to a damping means provided in a base valve portion of a so-called hydraulic shock absorber in the bottom end portion, and this pressure side damping. And a free piston 7 positioned downstream of the means 6.

  At this time, the cylinder body 3 has the same outer diameter in the entire length from the head end to the bottom end, while the body portion 3b, ie, the compression side damping means 6 is the other portion of the inner diameter in the vicinity of the connecting portion 3a. And a diameter-enlarged portion 3d having a communication hole 3c that allows communication between the inside and the outside while being larger than the body portion 3b that slidably accommodates the free piston 7 and expands the diameter of the body portion 3b. A taper portion 3e is provided between the portion 3d and the portion 3d.

  When the cylinder body 3 is formed as described above, the compression side damping means 6 defines the inside of the main body 3b on the piston side chamber R2 side and the reservoir R side, that is, the free piston 7 side, Mutual communication between the piston side chamber R2 side and the free piston 7 side is allowed.

  The pressure side damping means 6 includes, for example, a pressure side damping valve 61 and a pressure side check valve 62 in parallel therewith. When the piston side chamber R2 side is communicated with the free piston 7 side, the pressure side damping valve 61 is provided. To realize a predetermined compression-side damping action.

  Incidentally, the compression side attenuating means 6 is, as shown in the figure, a front end portion facing the piston side chamber R2 in the cylinder body 3 which is the lower end portion in the figure in the center rod 8 suspended from the shaft core portion of the vehicle body side tube 1. Retained.

  The center rod 8 is basically suspended from the shaft core portion of the cap member 11 that closes the upper end opening of the vehicle body side tube 1, and is present on the shaft core portion of the cylinder body 3. 11 has an air valve V that enables gas supply and discharge so that the air pressure in the above-described reservoir air chamber A can be optimized.

  On the other hand, the damper has a slidable free piston 7 that is housed in the main body 3b of the cylinder body 3 so as to be in series with the downstream side of the compression side damping means 6 described above.

  The free piston 7 defines the inside of the main body portion 3b of the cylinder body 3 into a pressure receiving surface side oil chamber R3 which is the pressure side damping means 6 side and a back side air chamber A1 having air spring force.

  In this damper, the back side air chamber A1 can be communicated with the reservoir internal air chamber A in the fork main body outside the damper via the communication hole 3c, and enclosed in the reservoir internal air chamber A. It becomes the same pressure as the atmospheric pressure.

  The free piston 7 is in sliding contact with the inner periphery of the main body 3b in the cylinder body 3 while having the seal 72 and the bush 73 on the outer periphery of the main body 71, and the center rod described above while having the check seal 74 on the inner periphery. 8 is slidably arranged on the outer periphery of the outer periphery, that is, slidable.

  In addition, the free piston 7 moves backward in the main body 3b so as to rise in the drawing, and particularly when the lower end of the main body 71 reaches the inside of the tapered portion 3e, A gap appears between the taper portion 3e and the inner periphery of the taper portion 3e, and the passage to the reservoir R through the communication hole 3c inside the main body portion 3b is allowed through the gap.

  Therefore, in this free piston 7, when the amount of hydraulic oil in the damper is at a predetermined amount, the cylinder body 3 is driven by the air spring force as a reaction force in the back side air chamber A1 defined behind the free piston 7. Maintain the pressure-increasing tendency of the inside.

  In the free piston 7, for example, the hydraulic oil expands due to an oil temperature rise in the damper or the hydraulic oil from the reservoir R outside the cylinder body 3 flows into the damper during the operation of the damper. For example, when the hydraulic oil in the damper exceeds a predetermined amount, the hydraulic oil moves backward so as to rise more than a predetermined stroke, so that surplus hydraulic oil is stored in the cylinder body 3 through the open communication hole 3c. Release back to R.

  As described above, when the compression side damping means 6 is held at the distal end portion of the center rod 8 connected to the cap member 11 that closes the upper end opening of the vehicle body side tube 1, the center rod 8 interposes the free piston 7. Therefore, the compression side damping means 6 and the free piston 7 can be assembled together with the cap member 11 so as to be advantageous in improving the assembly of the front fork.

  By the way, in the present invention, the fork main body in the most extended state is filled with a pressure higher than the atmospheric pressure so as to have a reaction force. Therefore, the rear side air defined in the cylinder body 3 by the free piston 7 is provided. The chamber A1 does not have this booster spring as compared with the front fork disclosed in Patent Document 1 and the booster spring formed of a coil spring.

  That is, in the front fork according to the present invention, the reaction chamber is filled with a pressure higher than the atmospheric pressure in the reservoir air chamber A defined by the oil level O in the most extended fork body. To have.

  The applicant confirmed that when the fork main body having the inner diameter of the cylinder body 3 of approximately 35 mm and the length of 300 mm is in the most extended state, the reservoir air chamber A has an atmospheric pressure of about 0.3 MPa. When the gas is sealed, the internal pressure of the fork main body in the most contracted state is approximately 1.5 MPa.

  Therefore, in this front fork, when the fork main body is in the maximum extension state, the inside of the fork main body can be maintained at a high pressure tendency, and therefore, when the fork main body starts the contraction operation, that is, the contraction operation of the fork main body. Enables stable contraction operation from the beginning.

  In this front fork, since the fork body is filled with atmospheric pressure higher than atmospheric pressure and has a reaction force, the fork body is always urged in the extending direction, and there is no suspension spring. As long as the main body can be urged in the extending direction, the weight can be reduced and the number of parts can be reduced as long as there is no suspension spring.

  Moreover, in this front fork, since the atmospheric pressure higher than the atmospheric pressure is enclosed in the fork main body, as a result, the fork main body can be urged in the extending direction without having a suspension spring. Since there is no spring, the volume for distributing the suspension spring can be reduced.

  Therefore, the diameter of the cylinder body 3 when the suspension spring is not provided in the fork body can be set larger than when the suspension spring is provided in the fork body, and the piston body 5 accommodated in the cylinder body 3 can be set. It is easy to give a degree of freedom to the damping action of the damping means and the compression side damping means 6 included in.

  In addition, since the cylinder body 3 can be formed in a so-called straight shape in the present invention, as disclosed in Patent Document 1 described above, a portion in which the free piston is accommodated in the cylinder body is a so-called main body of the cylinder body. There is an advantage that the number of parts is reduced as compared with the case where another part for forming a larger diameter than the part is required.

  Further, when the damper is in the most extended state, the free piston 7 is moved down to the lowest level in the cylinder body 3, that is, moved forward to maintain the pressure increasing tendency in the cylinder body 3, that is, in the damper. This makes it possible to realize a stable compression-side damping action from the beginning when the damper in the most extended state starts the contraction operation.

  Since the air pressure in the reservoir internal air chamber A that has a reaction force in the front fork reaches the back side air chamber A1 defined by the free piston 7 through the communication hole 3c opened in the cylinder body 3, This backside air chamber A1 does not need to be provided with a mechanical spring consisting of a coil spring other than an air spring, that is, a booster spring, and can reduce the weight and the number of parts by not having this booster spring. To do.

  As disclosed in the above-mentioned Patent Document 1 and as disclosed in Japanese Patent Application Laid-Open No. 2005-30534, this type of free piston has a coil spring as a biasing means behind. It is normal to have a booster spring (39 or 4).

  However, when a booster spring comprising a coil spring is provided behind the free piston, in the case of the coil spring, the urging force is applied to the free piston, which is the urged member adjacent to the tip, in the circumferential direction that is the winding direction of the coil spring. It is difficult to act evenly on the free piston, and this free piston is liable to cause the phenomenon.

  Thus, when the free piston 7 is energized from the back and the air spring force is used without using the boost spring as in the present invention, at least the free piston by using the boost spring is used. There is no need to worry about the occurrence of the swaying phenomenon in FIG.

  In addition, when the free piston 7 is urged by an air spring force, the occurrence of a sag phenomenon in the free piston 7 can be prevented. Therefore, although not shown, in order to stabilize the slidability of the free piston 7, the free piston 7 As shown in the drawing, the size of the free piston 7 in the sliding direction of the main body 71 is reduced to prevent an unnecessarily large increase in weight. .

  In the front fork formed as described above, the fork main body in the most extended state is filled with an atmospheric pressure that is equal to or higher than the atmospheric pressure to have a reaction force, thereby making the fork main body have a high pressure tendency. A stable contraction operation is realized from the beginning when the fork body in the most extended state starts the contraction operation.

  On the other hand, although no literature is shown, there has been a proposal of a front fork that urges the fork main body in the extending direction only at the air pressure enclosed without a suspension spring, that is, only with an air spring.

  It is also well known that when assembling the front fork, it becomes more difficult to assemble the front fork unless the atmospheric pressure enclosed in the fork main body is higher than atmospheric pressure.

  Therefore, in the present invention, for example, an atmospheric pressure equal to or higher than 0.3 MPa is enclosed in the fork main body, and further, an atmospheric pressure equal to or higher than atmospheric pressure is enclosed in the fork main body as described later. While having a reaction force, the suppression means, that is, the fork main body has specificity in that it has a suppression means for suppressing a reaction force in a predetermined stroke region where the fork main body contracts from the maximum extension state. Yes.

  That is, the front fork according to the present invention has a reaction force caused by the atmospheric pressure at which the fork main body in the most extended state is enclosed. Therefore, when starting the contraction operation from the most extended state, the enclosed atmospheric pressure Compared to the case where there is no reaction force due to, for example, there is a risk that the rider in a motorcycle will give the impression that the front fork is hard, but the reaction force due to the atmospheric pressure enclosed in this maximum extension state is suppressed By doing so, it is possible to avoid giving the rider in the motorcycle the impression that the front fork is hard.

  The predetermined stroke region is a region of a contraction stroke that starts from the most extended state, and is preferably a stroke region that is approximately 1/3 of the entire stroke from the most extended state to the most contracted state. This is not an absolute one, and even if there are some differences, the intention of the suppression means in the present invention is not different.

  In addition, this suppression means has a balance spring S made of a coil spring, as shown in the figure, and this balance spring S is housed in the cylinder body 3 and the rod body 4 is immersed in the cylinder body 3. The fork body is urged in the contracting direction.

  From the viewpoint of energizing the fork body in the extending direction, the balance spring S is a spring similar to the extension spring 53 (see FIGS. 1 and 3) of the housing, that is, the next extension. There is room to call it a cutting spring.

  However, from the viewpoint of canceling out the so-called initial reaction force of the fork body in the most extended state, the balance spring S functions differently from the extension spring 53 that absorbs the acting force during the maximum extension operation of the damper. To do.

  By the way, the balance spring S is disposed in the cylinder body 3 of the damper as shown in the figure, and the balance spring S is disposed outside the cylinder body 3 in addition to preventing the damper from being made into a cartridge. Compared to the case where the balance spring S is provided, the number of related parts required for disposing the balance spring S can be reduced.

  Incidentally, the balance spring S has a base end, which is the lower end in the figure, supported by a head end part, which is the lower end part in the figure, of the cylinder body 3 under the intervention of the spring sheet S1 and a tip which is the upper end in the figure. The cylinder body 3 is slidably accommodated and is locked to a seat portion 4a adjacent to the piston body 5 which is held at the tip portion which is the upper end portion of the rod body 4 in the drawing.

  The extension spring 53 is provided inside the balance spring S. A stopper whose upper end is held by the rod body 4 while the base end, which is the lower end of the extension spring 53, is supported on the spring sheet S1. It is locked to 53a.

  The balance spring S basically urges the fork main body in the contracting direction. The balance spring S is in the stroke region starting from the front before the fork main body is extended and fully extended. The balance spring S contracts and tends to suppress the movement of the fork main body in the extension direction. In particular, the reaction force of the fork main body in the maximum extension state is reduced to zero, and the rider in the motorcycle is contracted from the maximum extension state. Avoid giving the impression that the front fork is stiff when starting.

  In addition, since the restraining means having the balance spring S is disposed in the cylinder body 3 of the damper, the balance spring S is not compared with the case where the restraining means is disposed outside the cylinder body 3. This makes it possible to reduce the number of related parts for installation.

  FIG. 5 shows a front fork according to another embodiment of the present invention, that is, when an upright damper is housed in an inverted fork main body, and the reservoir is when the fork main body is in the most extended state. The inside air chamber A is filled with a pressure higher than the atmospheric pressure to have a reaction force, and has a suppression means for suppressing the reaction force in a predetermined stroke region where the fork main body contracts from the most extended state.

  In other words, the above description has been made assuming that the damper is set upside down. However, when the present invention is intended, that is, considering the arrangement of the balance spring S, the damper is set upright. Even if it is done, there is no problem, and the realization of the same effect can be expected.

  In the following, the explanation will be made a little, but in the place shown in FIG. 5, where the configuration is the same as described above, only the same reference numerals are given in the figure, and the detailed description thereof is provided unless necessary. Description is omitted.

  First, the damper is set upright in the figure so that the cylinder body 3 is a lower end side member and the rod body 4 is an upper end side member. Although not shown in detail, the cylinder body 3 is on the wheel side. The rod body 4 is coupled to the tube 2 and is erected on the shaft core portion of the wheel side tube 2, and the rod body 4 is coupled to the vehicle body side tube 1 and suspended from the shaft core portion of the vehicle body side tube 1.

  Incidentally, in the illustrated damper, a rod guide (not shown) that closes the upper end opening of the cylinder body 3 and passes the rod body 4 through the shaft core portion also serves as the oil lock case 23. Of course, you don't have to.

  On the other hand, this damper also has a piston body 5 that is slidably accommodated in the cylinder body 3 while being held at the tip portion which is the lower end portion of the rod body 4 in the figure. Has an extension side damping means which defines a rod side chamber R1 and a piston side chamber R2 in the cylinder body 3 and allows mutual communication between the rod side chamber R1 and the piston side chamber R2. An extension side damping valve 51 and an extension side check valve 52 are provided, and a predetermined extension side damping action is realized when hydraulic fluid passes through the extension side damping valve 51.

  By the way, even in the fork main body shown in FIG. 5, the atmospheric pressure that is equal to or higher than the atmospheric pressure in the maximum extension state is sealed, and the negative effect caused by sealing the atmospheric pressure that is equal to or higher than the atmospheric pressure in the maximum extension state. It has the suppression means for removing.

  The suppressing means has a balance spring S made of a coil spring, and this balance spring S is housed in a damper. This point is the same as in the case of the above-described embodiment.

  However, since the damper is an upright type, the lower end of the balance spring S is supported by the seat portion 4a of the rod body 4, and the upper end of the balance spring S closes the upper end opening of the cylinder body 3 described above. It is latched by the spring seat S1 provided next to.

  An extension spring 53 is provided inside the balance spring S. The extension spring 53 is supported by a stopper 53 a whose upper end is locked to the spring sheet S 1 and whose lower end is held by the rod body 4. The

  Therefore, even in the front fork shown in FIG. 5, only the damper is made upright, and the suppressing means exhibits a predetermined function as in the case where the damper is turned upside down.

  That is, even in this front fork, when the fork main body is in the most extended state, since the atmospheric pressure that is equal to or higher than the atmospheric pressure is enclosed in the fork main body, the inside of the fork main body can be maintained in a pressurized state. The cylinder inside the damper can be maintained in a pressurized state. As a result, when the damper in the most extended state starts contracting operation, stable damping operation from the beginning by the compression side damping means is possible.

  And, from the above, the fork main body is always urged in the extending direction, and therefore the fork main body can be urged in the extending direction without having the suspension spring, and as a result, there is no suspension spring. This makes it possible to reduce the weight and the number of parts.

  In addition, when the fork main body is in the maximum extension state, a pressure higher than atmospheric pressure is sealed in the reservoir air chamber A to provide a reaction force, while the fork main body has a reaction in a predetermined stroke region where the fork main body contracts from the maximum extension state. Since the suppression means for suppressing the force is provided, it is possible to reduce the reaction force during the contraction operation in the predetermined stroke region from the maximum extension state.

  Further, since the restraining means is disposed in the cylinder body 3 of the damper, the related parts for disposing the balance spring S are compared with the case where the restraining means is disposed outside the cylinder body 3. Allows a reduction in the number.

  Furthermore, when this damper is set upright, the liquid-tightness of the damper is no longer an absolute condition compared to the case where the damper is set upside down. As a result, it is easy to ensure the slidability, which is advantageous in ensuring the operability of the damper.

  In the above description, the fork main body does not have the suspension spring. However, in view of the function of the balance spring S as the restraining means in the present invention, the embodiment of the present invention is realized even if the fork main body has the suspension spring. Of course, there is no difference in the operational effects in that case.

  In the above description, the balance spring S that constitutes the suppression means is disposed in the damper. However, when importance is placed on the function of the balance spring S, the balance spring S is the cylinder body 3. In this case, the setting of the spring force in the balance spring S can be easily changed, and so-called maintainability is improved.

  It is suitable for use as a shock absorber that absorbs road surface vibration that is input to the front wheel that is mounted on the front wheel side of the motorcycle and is suspended at the lower end.

DESCRIPTION OF SYMBOLS 1 Car body side tube 2 Wheel side tube 3 Cylinder body 3c Communication hole 4 Rod body 5 Piston body 6 Pressure side damping means 7 Free piston 21 Bearing member A Reservoir inside air chamber A1 Back side air chamber O Oil surface R3 pressure side oil Chamber S Balance spring constituting suppression means

Claims (4)

  A fork body that can be expanded and contracted by a vehicle body side tube and a wheel side tube has a reservoir air chamber with a liquid level as a boundary, and a damper that can be expanded and contracted by a cylinder body and a rod body in the fork body. In the front fork having the fork main body, when the fork main body is in the maximum extension state, the air pressure in the reservoir is filled with an atmospheric pressure higher than atmospheric pressure and has a reaction force, and the fork main body is in the maximum extension state. A front fork comprising suppression means for suppressing a reaction force in a predetermined stroke area contracting from the front fork.   The above damper is set to an inverted type in which the cylinder body is the upper end side member and the rod body is the lower end side member, or in the upright type in which the cylinder body is the lower end side member and the rod body is the upper end side member. The front fork according to claim 1, which is set.   When the suppression means has a balance spring made up of a coil spring, the balance spring is used when the damper contracts a stroke of approximately 1/3 or more of the entire stroke from the maximum extension state to the maximum contraction state. The front fork according to claim 1, further comprising a spring force that suppresses a reaction force in the fork main body.   The cylinder body has a pressure side damping means and a free piston disposed downstream of the pressure side damping means. The free piston defines a pressure receiving surface side oil chamber and a back side air chamber in the cylinder body. The back side air chamber is communicated with the cylinder air chamber through the open communication hole to the cylinder body, and the pressure receiving pressure is applied when the free piston moves back a predetermined stroke. The front fork according to claim 1, wherein the surface side oil chamber is communicated with the reservoir internal air chamber via the communication hole.

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