Title of Invention

AN OIL LOCK APPARATUS OF A FRONT FORK IN A TWO-WHEELED VEHICLE.

Abstract

There is disclosed an oil lock apparatus of a front fork (10) in a two-wheeled vehicle, a piston valve (20) is provided in an inner periphery of a leading end portion of the inner tube (12), an annular inner peripheral side flow passage (33) is formed between an inner periphery of the piston valve (20) and an outer periphery of the hollow rod (16), an outer peripheral side flow passage (34) is formed between an outer periphery of the piston (20) and an inner periphery of the inner tube (12), annular valve seats (31, 32) which upper and lower end surfaces of the piston valve (20) are in contact with and apart from are provided in the inner periphery of the leading end of the inner tube (12), the upper and lower valve seats (31, 32) are provided with a flow passage communicating the outer peripheral side flow passage (34) with the oil chambers (21, 22) between the valve seats (31, 32) and the outer periphery of the rod (16), and notch portions (20A, 20B) penetrating in a diametrical direction are formed in upper and lower end surfaces of the piston valve (20).

Full Text

-2-BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an oil lock apparatus of a front fork in a two-wheeled vehicle. Description of the Related Art As an oil lock apparatus of a front fork in a two-wheeled vehicle as described in Japanese Utility Model Application Laid-Open No.56-119789 (patent document 1), there is disclosed a technique in which an oil chamber in a lower portion of a piston body is oil locked and a buffering at the time of most compression is achieved by abolishing a tapered oil hole limiting rod (an oil lock piece), arranging a lot of small holes 2 having different hole diameters in an axial direction on a side wall of a hollow shaft 1 close to a base portion of the hollow shaft 1, and sequentially closing the small holes 2 by a piston body provided in a lower end of an inner tube. In the oil lock apparatus of the patent document 1, at the time of changing from a most compression stroke to an expansion stroke, a working fluid is not sufficiently resupplied to the oil lock oil chamber in the lower portion of the piston body until the piston body reaches the small hole 2 at the lowermost position, the oil lock oil chamber is in a negative pressure state, and a so-called extract sound (a pop sound generated at the time of drawing a cork stopper of wine) at a time when the piston body reaches the small hole 2 at the lowermost position and the small hole is opened. -2A-SUMMARY OF THE INVENTION An object of the present invention is to prevent an extract sound from being generated at the time of changing from a most compression state to an expansion stroke as well as making it possible to abolish an oil lock piece, in an oil lock apparatus of a front fork in a two-wheeled vehicle. The present invention provides an oil lock apparatus of a front fork in a two-wheeled vehicle comprising : an inner tube in a side of a vehicle body, the inner tube being slidably fitted to an inner side of an outer tube in a side of a wheel; a hollow rod having a partition wall portion slidably in contact with an inner periphery of the inner tube, the hollow rod being provided in a standing manner in a bottom portion within the outer tube ; an oil chamber along which a piston valve provided in an inner periphery of a leading end portion of the inner tube moves forward and backward, the oil chamber being sectioned in an outer periphery of the hollow rod ; an oil reservoir chamber having an air chamber in an upper portion, the oil reservoir chamber being sectioned in an inner periphery of the hollow rod ; and an oil hole communicating the oil chamber with the oil reservoir chamber, the oil hole being provided in a lower portion of the hollow rod, wherein the piston valve is provided in an inner periphery of a leading end portion of the inner tube, an annular inner peripheral side flow passage is formed between an inner periphery of the piston valve and an outer periphery of the hollow rod, and an annular outer peripheral side flow passage is formed between an outer periphery of the piston valve and -3- an inner periphery of the inner tube, upper and lower annular valve seats are provided in the inner periphery of the leading end portion of the inner tube, such that the upper and lower end surfaces of the piston valve are capable of being in contact with, and remaining spaced apart from the said upper and lower valve seats, in the event of upward and downward movements of the piston valve, said upper and lower valve seats being each provided with a flow passage communicating the outer peripheral side flow passage with the oil chamber, between the upper and lower valve seats and the outer periphery of the hollow rod, and notch portions penetrating in a radial direction are formed in the upper and lower end surfaces of the piston valve. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS The present invention will be more fully understood from the detailed description given below and from the accompanying drawings which should not be taken to be a limitation on the invention, but are for explanation and understanding only. In the drawings: FIG. 1 is a general cross sectional view showing a front fork ; FIG. 2 shows a structure of a lower portion of the front fork, in which FIG. 2(A) is an enlarged cross sectional view of the lower portion, FIG. 2(B) is a cross sectional view showing a portion around a check valve, and FIG. 2(C) is a cross sectional view showing a portion around a piston valve ; FIG. 3 is a cross sectional view showing a final stage of a compression stroke of the front fork ; -3A- FIG. 4 is a cross sectional view showing a starting stage of an expansion stroke of the front fork; FIG. 5 shows the piston valve, in which FIG. 5(A) is a cross sectional view, FIG. 5(B) is a top elevational view and FIG. 5(C) is a bottom elevational view ; and FIG. 6 shows the check valve, in which FIG. 6{A) is a cross sectional view, FIG. 6(B) is a top elevational view and FIG. 6{C) is a bottom elevational view. -4-DESCBIPTION OF THE PREFERRED EMBODIMENTS A front fork 10 in a two-wheeled vehicle or the tike is structured, as shown in FIGS. 1 to 4, such that an inner tube 12 in a side of a vehicle body is slidably fitted into an outer tube 11 in a side of a wheel.. A dust seal 13 and an oil seal 14 are provided in an opening end of the outer tube 11 to which the inner tube 12 is inserted. A bolt 15 is inserted to a bottom portion of the outer tube 11, and a hollow rod 16 is provided in a standing manner by the bolt 15. An upper end portion of the hollow rod 16 is expanded so as to form a partition wall portion 17 which is slidably in contact with an inner periphery of the inner tube 12. In the present embodiment, a check valve 40 mentioned below constituted by a piston ring is provided in a ring groove 17A arranged in an outer periphery of the partition wall portion 17, and the check valve 40 is brought into slidable contact with the inner periphery of the inner tube 12. A suspension spring 19 is interposed between an upper end surface of the partition wall portion 17 in the hollow rod 16 and a spring seat 18 provided in an upper end portion of the inner tube 12. The spring seat 18 is sealed in an inner diameter portion of the upper end in the inner tube 12 via an O-ring 18A, and is held by a stopper ring 18B. The front fork 10 is structured such that a piston valve 20 is provided in an inner periphery of a leading end portion in the inner tube 12, upper and lower oil chambers 21 and 22 along which the piston valve 20 moves forward and backward are sectioned in an outer periphery of the hollow rod 16, an oil reservoir chamber 23 having an air chamber 24 in an upper portion is sectioned in an inner periphery of the hollow rod 16, and an oil hole 25 communicating the oil chambers 21 and 22 with the oil reservoir chamber 23 is provided in a lower portion of the hollow rod 16. The oil reservoir chamber 23 extends to the interior of the inner tube 12, and the air chamber 24 is sealed by the spring seat 18 in an upper end portion of the inner tube 12. The oil hole 25 is pierced at a plurality of positions in an axial direction and a peripheral direction of the hollow rod 16. In the inner periphery of the leading end portion of the inner tube 12, a valve housing 30 and upper and lower annular valves seats 31 and 32 are fixed to the inner tube 12 in accordance with a caulking, and there is housed the piston valve 20 which can move upward and downward in a state of being slidably in contact with the hollow rod 16 in the inner portion of the valve housing 30. In this case, the piston valve 20 may be fixed in such a manner that the piston valve 20 can not move in a vertical direction. Further, an annular inner peripheral side flew passage 33 is formed between an inner periphery of the piston valve 20 and an outer periphery of the hollow rod 16, and an. annular outer peripheral side flow passage 34 is formed between an outer periphery of the piston valve 20 and an inner periphery of the inner tube 12 (an inner periphery of the valve housing 30 in the present embodiment). The upper and lower valve seate 31 and 32 are provided in the inner periphery of the leading end side of the inner tube 12, and upper and lower end surfaces of the piston valve 20 are in contact with each other and apart from each other. The upper valve seat 31 forms as upper flow passage 31A communicating the inner peripheral side, flow passage 33 and the outer peripheral side flow passage 34 with the upper oil chamber 21 between the upper valve seat 31 and the outer periphery of the hollow rod 16. The lower valve seat 32 forms a lower flow passage 32A communicating the inner peripheral side flow passage 33 and the outer peripheral side flow passage 34 with the lower oil chamber 22, between the lower valve seat 32 and the outer periphery of the hollow rod 16. 6 The piston valve 20 is provided with upper and lower notch portions 20A and 20B penetrating in a diametrical direction formed in upper and lower end surfaces which are in contact with and apart from the upper and lower valve seats 31 and 32, as shown in FIG. 5, A check valve 40 is constituted by a C-shaped piston ring which is attached to a ring groove 17A provided in an outer periphery of the partition wall portion 17 of the hollow rod 16 so as to freely move upward and downward. The check valve 40 is slidably in contact with the inner periphery of the inner tube 12, and forms an annular flow passage 41 between the check valve 40 and a groove bottom portion of the ring groove 17A The check valve 40 is provided with a notch portion 40A penetrating in a diametrical direction formed on a lower end surface which is in contact with a side wall portion of a lower groove close to the tapper oil chamber 21, in the ring groove 17A of the partition wall portion 17, as shown in FIG. 6. The cheek valve 40 (a) moves downward (moves downward in accordance with a relative downward movement of the inner tube 12 with respect to the hollow rod 16) at the time of the compression stroke, forms a gap between an upper end surface of the check valve 40 and an upper groove side wall of the ring groove 17A in the partition wall portion 17 so as to be opened, and allows the working fluid in the oil reservoir chamber 23 in the upper portion of the partition wall portion 17 to flow toward the upper oil chamber 21 ia the outer periphery of the hollow rod 16 through the annular flow passage 41 and the notch portion 40A, and (b) moves upward (moves upward in accordance with a high pressure of the oil in the upper oil chamber 21, and a relative upward movement of the inner tube 12 with respect to the hollow rod 16) at the time of the expansion stroke, closely attaches the upper end surface of the check valve 40 to the upper groove side wall of the ring groove 17A in the partition wall portion 17 -7-so as to be dosed, and inhibits the working fluid in the upper oil chamber 21 in the outer periphery of the hollow rod 16 from flowing toward the oil reservoir chamber 23 in the partition wall portion 17. The front fork 10 is provided with an oil hole (a small hole) 26 communicating the upper oil chamber 21 with the oil reservoir chamber 23 in the hollow rod 16, and generates an expansion side damping force on a passage resistance of the oil flowing out to the oil reservoir chamber 23 from the upper oil chamber 23 by using the oil hole (the small hole), at the time of the expansion stroke. In this case, in the front fork 10, a rebound spring 27 at the time of the maximum expansion is provided between the upper valve seat arranged in the inner tube 12 and the partition wall portion 17 of the hollow rod 16. In the front fork 10, an impact applied to a wheel is absorbed and damped by the suspension spring 19 and an air spring in an air chamber 24, and an expanding and contracting vibration of the suspension spring 19 generated together with the absorption of the impact is inhibited by a damping force generated in the oil chambers 21 and 22. In other words, the front fork 10 carries out a damping effect as follows. (Compression Stroke) When the inner tube 12 moves into the oil chambers 21 and 22 in the outer periphery of the hollow rod 16, a pressure in the lower oil chamber 22 in the lower portion of the piston valve 20 in which a volumetric capacity is reduced becomes high. The piston valve 20 moves upward so as to be brought into contact with the upper valve seat 31. The working fluid in the lower oil chamber 22 in the lower portion of the piston valve 20 flows into the upper oil chamber 21 through the outer peripheral side flow passage 34 of the piston valve 20, and the flow passage foemed between the notch portion 20A of the upper end surface of the piston valve 20 and the upper valve seat 31, in addition to flowing into the upper oil chamber 21 through the inner peripheral side How passage 33 of the piston valve 20, thereby generating a compression side damping force. In this case, since the volumetric capacity of the upper oil chamber 21 in the upper portion of the piston valve 20 is expanded and the pressure becomes low, the check valve 40 provided in the partition wall portion 17 of the hollow rod 16 is opened, and the working fluid in the oil reservoir chamber 23 of the partition wall portion 17 flows into the tipper oil chamber 21 through the annular passage 41 of the check valve 40 and the notch portion 40A. Further, the working fluid at an amount corresponding to a volume by which the inner tube 12 moves into the oil chambers 21 and 22 flows toward the oil reservoir chamber 23 in the inner periphery of the hollow rod 16 through a plurality of oil holes 25 formed in the lower portion of the hollow rod 16 from the lower oil chamber 22. The compression side damping force is generated by a plurality of oil holes 25. When the piston valve 20 sequentially closes a plurality of oil holes 25 in the lower portion of the hollow rod 16 and enters into a final stage of the compression stroke, the working fluid in the lower oil chamber 22 (the oil lock oil chamber 22A) in the lower portion of the piston valve 20 flows toward the upper oil chamber 21 through only the inner peripheral side flow passage 33 and the outer peripheral side flow passage 34 of the piston valve 20, and the flow passage formed between the notch portion 20A of the upper end surface of the piston valve 20 and the upper valve seat 31, as shown in FIG. 3. As a result, an area of a flow passage for the working fluid from the oil lock oil chamber 22A to the upper oil chamber 21 is reduced so as to generate an oil -9- lock state, and the compression side damping force is increased so as to damp a bottom tough of the outer tube 11 and the inner tube 12. (Expansion Stroke) When the stroke is changed from the bottom tough state of the outer tube 11 and the inner tube 12 to the expansion stroke, the piston valve 20 moves downward and is brought into contact with the lower valve seat 32, as shown in FIG. 4. The working fluid in the upper oil chamber 21 in the upper portion of the piston valve 20 flows toward the oil lock oil chamber 22A in the lower portion of the piston valve 20 through the inner peripheral side flow passage 33 and the outer peripheral side flow passage 34 of the piston valve 20, and the passage formed between the notch portion 20B of the lower end surface of the piston valve 20 and the lower valve seat 32, smoothly cancels the negative pressure in the oil lock oil chamber 22A, and prevents an extract sound at the time of being changed to the expansion stroke. Further, when the piston valve 20 moves upward, the working fluid in the upper oil chamber 21 in the upper portion of the piston valve 20 flows in an exchanging manner toward the lower oil chamber 22 in the lower portion of the piston valve 20 through the inner peripheral side flow passage 33 and the outer peripheral side flow passage 34 of the piston valve 20, and the flow passage formed between the notch portion 20B of the lower end surface of the piston valve 20 and the lower valve seat 32, and reaches the oil reservoir chamber 23 in the inner periphery of the hollow rod 16 through the oil hole (the small hole) 26 pierced in the upper portion of the hollow rod 16. The expansion side damping force is generated in the inner peripheral side flow passage 33 of the piston valve 20, the outer peripheral side flow passage 34 and the oil hole (the small hole) 26. In this case, the oil. hole (the small hole) 26 may be omitted. In accordance with the present embodiment, the following operations and effects can be obtained. (l) In the front fork 10, it is possible to abolish the oil lock piece in the oil lock apparatus for damping at the time of the most compression time, and it is possible to smoothly cancel the negative pressure of the oil lock oil chamber 22A so as to prevent the extract sound on the basis of existence of the inner peripheral side flow passage 33, the outer peripheral side flow passage 34 and the notch portion 20B of the piston valve 20, at the time of being changed from ihe most compression state to the expansion stroke. (2) In the oil lock state at the most compression stage of the front fork 10, the working fluid in the oil lock oil chamber 22A flows toward the upper oil chamber 21 in the upper portion of the piston valve 20 through the inner peripheral side flow passages 33 and 34 of the piston valve 20, and the flow passage constituted by the notch portion 20A in the upper end surface of the piston valve 20. Accordingly, it is necessary to set the flow passage formed by the notch portion 20A in the tapper end surface of the piston valve 20 to a sufficiently small cross sectional area due to the oil lock; however, in the case where the notch portion 20A is made small, the notch portion 20A acts as an orifice at a time when the working fluid in the lower oil chamber 22 in the lower portion of the piston valve 20 flows in an exchanging manner toward the upper oil chamber 21 in the upper portion at the normal compression stroke, and the upper oil chamber 21 tends to become negative pressure. Accordingly, in the present invention, the check valve 40 opening at the time of the compression stroke is provided in the partition wall portion 17 of the hollow rod 16, whereby it is possible to prevent the upper oil chamber 21 in the upper portion of the piston valve 20 from being in the negative pressure at the time of the compression stroke. However, the check valve 40 is not necessarily provided, and a piston ring may he provided in place of the check valve 40. la this case, the oil reservoir chamher 23 in the upper portion of the partition wall portion 17 and the oil chamber 21 in the lower portion thereof are not communicated with each other at both the times of the compression stroke and the expansion stroke. In this case, in the piston valve 20, the flow passage area of the inner peripheral side flow passage 33 formed hy the piston valve 20 is smaller than the flow passage area formed by each of the notch portions 20A and 20B. As heretofore explained, embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configurations of the present invention are not limited to the illustrated embodiments but those having a modification of the design within the range of the present claimed invention are also included in the present invention. In accordance with the present invention, in the oil lock apparatus of the 6ont fork in the two-wheeled vehicle or the like, it is possible to abolish the oil lock piece, and it is possible to prevent the extract sound form being generated at the time of being changed from the most compression state to the expansion stroke. Although the invention has been illustrated and described with respect to several exemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions and additions may be made to the present invention without departing from the spirit and scope thereof. Therefore, the present invention should not be understood as limited to the specific embodiment set out above, but should be understood to -12- include all possible embodiments which can be encompassed within a scope of equivalents thereof with respect to the features set out in the appended claims. -13-WE CLAIM : 1. An oil lock apparatus of a front fork in a two-wheeled vehicle comprising : an inner tube in a side of a vehicle body, the inner tube being slidably fitted to an inner side of an outer tube in a side of a wheel ; a hollow rod having a partition wall portion slidably in contact with an inner periphery of the inner tube, the hollow rod being provided in a standing manner in a bottom portion within the outer tube ; an oil chamber along which a piston valve provided in an inner periphery of a leading end portion of the inner tube moves forward and backward, the oil chamber being sectioned in an outer periphery of the hollow rod ; an oil reservoir chamber having an air chamber in an upper portjon, the oil reservoir chamber being sectioned in an inner periphery of the hollow rod ; and an oil hole communicating the oil chamber with the oil reservoir chamber, the oil hole being provided in a lower portion of the hollow rod, wherein the piston valve is provided in an inner periphery of a leading end portion of the inner tube, an annular inner peripheral side flow passage is formed between an inner periphery of the piston valve and an outer periphery of the hollow rod, and an annular outer peripheral side flow passage is formed between an outer periphery of the piston valve and an inner periphery of the inner tube, upper and lower annular valve seats are provided in the inner periphery of the leading end portion of the inner tube, such that the upper and lower end surfaces of the piston valve are capable of being in contact with, and remaining spaced apart from the said upper and lower valve seats, in the event of upward and downward movements of the piston valve, said upper and lower valve seats being each provided with a flow passage communicating the outer peripheral side flow -14- passage with the oil chamber, between the upper and lower valve seats and the outer periphery of the hollow rod, and notch portions penetrating in a radial direction are formed in the upper and lower end surfaces of the piston valve. 2. An oil lock apparatus of a front fork in a two-wheeled vehicle as claimed in claim 1, wherein an outer periphery of the partition wall portion arranged in the hollow rod is provided with a check valve which is opened at the time of the compression stroke so as to allow the working fluid to ffow from the oil reservoir chamber in the upper portion of the partition wall portion to the oil chamber in the outer periphery of the hollow rod, and is closed at the time of the expansion stroke so as to inhibit the working fluid from flowing from the oil chamber in the outer periphery of the rod toward the oil reservoir chamber in the upper portion of the partition wall portion. 3. An oil lock apparatus of a front fork in a two-wheeled vehicle as claimed in claim 1, wherein the oil hole is pierced at a plurality of positions in an axial direction and a peripheral direction in the lower portion of the hollow rod. 4. An oi! lock apparatus of a front fork in a two-wheeled vehicle as claimed in claim 1, wherein the upper and lower valve seats are fixed in accordance with caulking to the inner tube with the valve housing held therebetween. -15- 5. An oil lock apparatus of a front fork in a two-wheeled vehicle as claimed in claim I, wherein the hollow rod is provided with an oil hole communicating an oil chamber in a side of the partition wall portion in the oil chamber sectioned by the forward and backward movement of the piston valve, with the oil reservoir chamber. 6. An oil lock apparatus of a front fork in a two-wheeled vehicle as claimed in claim 1, wherein a rebound spring is provided between the upper valve seat arranged in the inner tube, and the partition wall portion of the hollow rod. 7. . An oil lock apparatus of a front fork in a two-wheeled vehicle as claimed in claim 2, wherein the check valve is constituted by a C-shaped piston ring attached to a ring groove arranged in an outer periphery of the partition wall portion in the hollow rod in such a manner as to freely move upward and downward. 8. An oil lock apparatus of a front fork in a two wheeled vehicle, substantially as herein described, particularly with reference to the accompanying drawings. There is disclosed an oil lock apparatus of a front fork (10) in a two-wheeled vehicle, a piston valve (20) is provided in an inner periphery of a leading end portion of the inner tube (12), an annular inner peripheral side flow passage (33) is formed between an inner periphery of the piston valve (20) and an outer periphery of the hollow rod (16), an outer peripheral side flow passage (34) is formed between an outer periphery of the piston (20) and an inner periphery of the inner tube (12), annular valve seats (31, 32) which upper and lower end surfaces of the piston valve (20) are in contact with and apart from are provided in the inner periphery of the leading end of the inner tube (12), the upper and lower valve seats (31, 32) are provided with a flow passage communicating the outer peripheral side flow passage (34) with the oil chambers (21, 22) between the valve seats (31, 32) and the outer periphery of the rod (16), and notch portions (20A, 20B) penetrating in a diametrical direction are formed in upper and lower end surfaces of the piston valve (20).

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00611-kol-2003 abstract.pdf

00611-kol-2003 claims.pdf

00611-kol-2003 correspondence.pdf

00611-kol-2003 description(complete).pdf

00611-kol-2003 drawings.pdf

00611-kol-2003 form-1.pdf

00611-kol-2003 form-18.pdf

00611-kol-2003 form-2.pdf

00611-kol-2003 form-3.pdf

00611-kol-2003 form-5.pdf

00611-kol-2003 g.p.a.pdf

00611-kol-2003 letters patent.pdf

00611-kol-2003 priority document others.pdf

00611-kol-2003 priority document.pdf

611-KOL-2003-FORM-27.pdf

611-kol-2003-granted-abstract.pdf

611-kol-2003-granted-claims.pdf

611-kol-2003-granted-description (complete).pdf

611-kol-2003-granted-drawings.pdf

611-kol-2003-granted-form 2.pdf

611-kol-2003-granted-specification.pdf

611-kol-2003-priority document.pdf

611-kol-2003-translated copy of priority document.pdf