JP2006275216A - Piston structure of hydraulic shock absorber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To install a piston band on an outer peripheral surface of a piston of a divided structure, without relying on cutting work. <P>SOLUTION: This piston structure of a hydraulic shock absorber is formed by installing the resin piston band 21 on the outer peripheral surface of the piston 10 for forming an oil liquid passage 14 by communicating passages 12 and 13, by joining two piston half bodies 10A and 10B for penetratingly arranging a plurality of passages 12 and 13 to the periphery of an insertion hole arranged in a central part. The piston 10 has an annular groove 20 formed around a joining part of the piston half bodies 10A and 10B out of a small diameter part 22 of the respective piston half bodies 10A and 10B. The piston band 21 is arranged by fitting its whole to the annular groove 20, and is restricted in the shaft direction, and is also restricted in the rotational direction by fitting a projection integrally formed on an outer peripheral surface of the small diameter part 22 by molding of a metal mold to a recessed groove formed on its inner peripheral surface. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a piston structure of a hydraulic shock absorber, and more particularly to a piston structure of a hydraulic shock absorber having a divided piston structure.

  In general, a piston provided in a cylindrical hydraulic shock absorber has a rod insertion hole through which a piston rod is inserted and connected to a central portion thereof, and a plurality of oils around the rod insertion hole. A liquid passage is provided. A part of the plurality of oil liquid passages is used as an extension side passage, and the rest is used as a contraction side passage. The inlet opening of each passage is opened to two upper and lower chambers defined by pistons. On the other hand, the outlet opening of each passage is always closed by a disc valve (damping force generating mechanism) seated on seat portions formed at both ends of the piston. Then, according to the expansion and contraction of the piston rod, the oil liquid flows between the upper and lower two chambers through the oil liquid passage. During this time, the flow of the oil liquid is controlled by the disc valve, and a predetermined damping force is generated.

  By the way, in order to increase the operating efficiency of the disc valve, the oil liquid passage provided in the piston has an inlet opening disposed near the outer periphery of the piston and an outlet opening disposed near the inner periphery of the piston. The oil liquid passage is inclined with respect to the shaft. On the other hand, since the cost can be reduced and the accuracy can be easily secured, recently, a sintered product obtained by die molding has been frequently used as a piston. However, an oil liquid passage inclined with respect to the shaft, which attempts to change the piston of the above-described hydraulic shock absorber to a sintered product, becomes an obstacle to mold forming, and the use of a substantially sintered product has to be abandoned. In order to form a slanting oil passage, drilling was required.

  Therefore, when a sintered product is used as the piston, various studies have been made to improve the moldability by using the piston as a divided structure. FIGS. 14 to 16 show an example of a piston having such a divided structure. A piston 10 slidably fitted to the cylinder 1 is divided into two piston halves 10A and 10B which are divided into two in the axial direction. And integrated. The two piston halves 10A and 10B have the same shape, and an insertion hole 11 through which the piston rod 2 is inserted is provided at the center, and a plurality of inlet passages 12 and outlets are provided around the insertion hole 11. The passages 13 are alternately provided at equal intervals in the circumferential direction. In a state where the two piston halves 10A and 10B are coupled, the outlet passage 13 of one piston half 10A and the inlet passage 12 of the other piston half 10B, and the inlet passage 12 and the other of the one piston half 10A The piston half body 10B is in communication with the outlet passage 13 of the piston half body 10B. As a result, the piston 10 has a series of expansion side passages (oil-liquid passages) 14 and contraction-side passages (oil-liquid passages) 15. And are formed. In this case, the inlet openings 14a and 15a of the respective oil passages 14 and 15 are arranged closer to the outer periphery and the outlet openings 14b and 15b are arranged closer to the inner periphery, respectively, which is substantially the same as a conventional general (integrated structure) piston. It has a passage structure.

  The mating surfaces of the piston halves 10A and 10B are formed with arc-shaped fitting convex portions 16 and fitting concave portions 17 for positioning them in the rotational direction with respect to each other (FIG. 16). An annular seat portion 18 for seating the disk valves 3 and 4 as a damping force generating mechanism is formed on the surface of the piston halves 10A and 10B opposite to the mating surface (FIG. 15). In FIG. 14, reference numeral 6 denotes a rod stopper that regulates the extended end of the piston rod 2, and is fixed to the piston rod 2 using a retaining ring 7.

  The piston 10 having the above-described split structure is formed together with the disk valves 3 and 4 in a state where the two piston halves 10A and 10B are coupled to each other while the fitting convex portion 16 and the fitting concave portion 17 are fitted to each other. It is connected to the rod 2 using a nut 5. Similar to the hydraulic shock absorber having an integral piston, the oil liquid flows in the oil liquid passages 14 and 15 according to the expansion and contraction of the piston rod 2, and a predetermined damping force is applied by the disk valves 3 and 4. appear. A piston having a similar divided structure is described in Patent Document 1.

By the way, a resin-made piston band 19 is mounted on the outer peripheral surface of the piston 10 in advance, and the piston 10 is in sliding contact with the cylinder 1 through the piston band 19. Conventionally, the piston band 19 is attached to the piston 10 by a method in which the piston band 19 is thermocompression bonded to a large number of annular circumferential grooves 10a formed on the outer peripheral surface of the piston 10 (piston halves 10A and 10B). (For example, see Patent Document 2).
Japanese Patent Publication No. 48-21378 JP 2002-139088 A

  However, according to the method in which the piston band 19 is thermocompression-bonded to a large number of annular circumferential grooves 10a formed on the outer circumferential surface of the piston 10 as described above, the circumferential groove 10a is an obstacle to mold forming of the piston halves 10A and 10B. Therefore, the formation of the circumferential groove 10a has to rely on cutting after the piston half is completed, and there is a problem that the manufacturing cost increases accordingly.

  The present invention has been made in view of the above-mentioned problems, and the problem is that it is possible to mount a piston band on the outer peripheral surface of a piston having a divided structure without relying on cutting, and thus manufacturing costs. An object of the present invention is to provide a piston structure for a hydraulic shock absorber that greatly contributes to the reduction of the pressure.

  In order to solve the above-mentioned problem, the present invention combines two piston halves each provided with an insertion hole through which a piston rod is inserted at the center, and a plurality of passages are formed around the insertion hole. A piston structure of a hydraulic shock absorber in which a resin-made piston band is mounted on the outer periphery of a piston formed by communicating the passages of two piston halves with each other to form an oil-liquid passage. A small-diameter portion is formed around the coupling portion of the piston half, and the entire piston band is fitted and disposed in an annular groove formed by the small-diameter portion. Further, the small-diameter portion of each piston half is arranged. A convex portion that restrains the piston band in the rotation direction is molded on the outer peripheral surface integrally with the piston half body.

  In such a piston structure, the entire piston band is fitted and arranged in an annular groove provided on the outer peripheral surface of the piston, and on the outer peripheral surface of the small diameter portion of each piston half body forming the annular groove. Since the convex portion that restrains the piston band in the rotational direction is provided, the piston band is restrained in both the axial direction and the rotational direction. In addition, since the convex portion that restrains the piston band in the rotational direction is molded integrally with the piston half, a cutting process for mounting the piston band becomes unnecessary.

  In the present invention, the convex portion provided on the outer peripheral surface of the small-diameter portion of each piston half may be a plurality of protrusions extending in the axial direction. In this case, the protrusions are pressed against the inner peripheral surface of the piston band. Then, the piston band is restrained in the rotation direction. In this case, it is desirable that a part of the plurality of protrusions be arranged at a position where the passage is closest to the outer peripheral surface of the small-diameter portion of the piston half body, thereby increasing the opening area of the passage as much as possible. This is convenient for setting the flow of the oil liquid, and hence the damping force characteristics.

  As described above, when the protrusion is provided on the outer peripheral surface of the small-diameter portion of each piston half, the piston band has a concave groove that can be fitted to the protrusion of the piston half on the inner peripheral surface, As a structure arranged in the annular groove with the projections of the piston half fitted, or as a structure having a smooth inner peripheral surface and outer peripheral surface and arranged in the annular groove by thermocompression bonding Also good. In the former structure, the piston band is securely restrained in the rotational direction by fitting the protrusion and the concave groove, and in the latter structure, no extra groove processing is required in the piston band. Is easy to manufacture.

In the present invention, the convex portion provided on the outer peripheral surface of the small-diameter portion of each of the piston halves is disposed at a corner portion of the small-diameter portion, and is inclined to be inclined from the outer peripheral surface of the small-diameter portion toward the large-diameter portion. It is good also as a part. In this case, since both end portions of the piston band ride on the inclined portion and bulge outward, the sealing performance with the cylinder inner surface is improved.
to

  According to the piston structure of the hydraulic shock absorber according to the present invention, it is not necessary to perform cutting or the like for mounting the piston band on the outer periphery of the piston, so that the die half of the piston half constituting the piston can be smoothly molded. The manufacturing cost can be reduced.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

  1 to 3 show a divided piston according to a first embodiment of the present invention. The piston is mounted on the cylindrical hydraulic shock absorber, and the basic structure thereof is the same as that shown in FIGS. In addition, overlapping explanation will be omitted. In the first embodiment, the piston 10 having a split structure formed by connecting two piston halves 10A and 10B is provided with an annular groove 20 around a connecting portion between the two piston halves 10A and 10B. In addition, the entire resin-made piston band 21 is fitted in the annular groove 20.

  The annular groove 20 is formed by a small-diameter portion 22 of each of the piston halves 10A and 10B. On the outer peripheral surface of the small-diameter portion 22, as shown in FIG. ) 23 extending in the axial direction and equally spaced in the circumferential direction. On the other hand, a concave groove 24 that can be fitted to the protrusion 23 is formed on the inner peripheral surface of the piston band 21 as shown in FIG. The piston band 21 is disposed in the annular groove 20 with the protrusion 23 fitted in the concave groove 24. That is, the piston band 21 has both the axial direction and the rotational direction by fitting the concave groove 24 and the projections 23 on the piston half bodies 10 </ b> A and 10 </ b> B side into an uneven groove 20. It is restrained by. In addition, the cross-sectional shape of the protrusion 23 is arbitrary, and instead of the arc shape described above, for example, a trapezoidal shape, a triangular shape, or the like can be used. In this case, the concave groove 24 formed in the piston band 21 is also formed in a trapezoidal shape, a triangular shape or the like in accordance with the protrusion 23.

  Here, the inlet passage 12 of each of the piston halves 10A, 10B has a rectangular portion provided as the inlet opening 14a of the extension side passage (oil liquid passage) 14 and the contraction side passage (oil liquid passage) 15 described above. And formed near the outer periphery. Thus, the plurality of protrusions 23 provided on the outer peripheral surface of the small-diameter portion 22 of each of the piston halves 10A and 10B are partly the outer peripheral surface of the small-diameter portion 22 as shown in FIG. On the other hand, the inlet passage 12 (inlet opening 14a) is disposed at the closest location. By doing in this way, sufficient thickness is ensured between the entrance channel | path 12 and the outer peripheral surface of the small diameter part 22. FIG. In other words, the opening area of the inlet passage 12 can be increased by the increase in the wall thickness, which is convenient for the flow of the oil liquid and the setting of the damping force characteristic.

  In the present embodiment, the piston halves 10A and 10B are made of a sintered product, including the inlet passage 12 and the outlet passage 13 used as the oil passage, the fitting convex portion 16 for fitting, and the fitting. Portions necessary for the piston 10 such as the recess 17 and the seat portion 18 for seating the disc valves 2 and 3 are integrally formed by molding. In forming the mold, the small-diameter portion 22 having a large number of protrusions 23 on the peripheral surface is also integrally formed. In this case, since the protrusion 23 including the inlet passage 12 and the outlet passage 13 is formed to extend in the axial direction, there is no hindrance to mold forming.

  To assemble the piston 10, as shown in FIG. 6, the two piston halves 10 A and 10 B are pushed into the piston band 21 from opposite directions while matching the phases of the projection 23 and the groove 24. Like that. In this case, the two piston halves 10A and 10B may be sequentially pushed into the piston band 21 or may be pushed simultaneously. Moreover, it goes without saying that the fitting projections 16 and the fitting recesses 17 formed on the mating surfaces are engaged with each other during the pressing. The piston 10 integrated in this way is connected to the piston rod 2 together with the disk valves 3 and 4 using a nut 5 (FIG. 1). In this state, the piston 10 is connected to the cylinder 1 via the piston band 21. Slid in contact.

  The action of the hydraulic shock absorber incorporating the piston 10 of this split structure is the same as the conventional one. In the extension stroke of the piston rod 2, the oil liquid in the rod side chamber R1 passes through the extension side passage 14 and counteracts from the outlet opening 14b. The fluid flows to the rod side chamber R2, and during this time, the flow of the oil is controlled by one of the disk valves 3, and a predetermined damping force is generated. In the contraction stroke of the piston rod 2, the oil liquid in the non-rod side chamber R2 flows through the contraction side passage 15 and flows from the outlet opening 15b to the rod side chamber R1, and during this time, the oil liquid flows by the other disk valve 4. Controlled and a predetermined damping force is generated. During this time, the piston 10 slides along the inner surface of the cylinder 1 via the piston band 21, but the piston band 21 is restrained in both the axial direction and the rotational direction in the annular groove 20 as described above. Therefore, the piston 10 stably slides in the cylinder 1 while ensuring a sealing property with the inner surface of the cylinder 1, thereby obtaining a desired damping force stably over a long period of time. Be able to.

  7 and 8 show a second embodiment of the present invention. A feature of the second embodiment is that instead of the piston band 21 in the first embodiment, a cylindrical piston band 25 (FIG. 7) having a smooth inner peripheral surface and outer peripheral surface is used. 10 in that it is thermocompression-bonded and arranged in an annular groove 20 provided on the outer peripheral surface. In this case, the inner diameter of the piston band 25 is set to be equal to or slightly larger than the diameter of the pitch circle in contact with the tip of the protrusion 23 formed on the small diameter portion 22 of the piston halves 10A and 10B. Therefore, in a state where the piston halves 10A and 10B are coupled via the piston band 25 (subassembly state), as shown on the left side of FIG. 8, the piston band 25 is connected to the outer periphery of the piston halves 10A and 10B. It is arranged in the annular groove 20 in a state slightly floating from the surface 22 (freely fitted state).

  In the second embodiment, as shown in FIG. 8, the piston 10 in the sub-assembly state is press-fitted with its axis aligned in a cylindrical die 27 heated by a heater 26. Let the inside pass. Then, the piston band 25 is pressed in the direction of diameter reduction by the inner surface of the die 27, and is thermocompression bonded to the bottom surface of the annular groove 20, that is, the outer peripheral surface of the small diameter portion 22 of the piston halves 10A, 10B. As shown, the piston 10 integrated through the piston band 25 is obtained. At the time of the thermocompression bonding, since a large number of protrusions 23 exist on the outer peripheral surface of the small diameter portion 22, the inner surface of the piston band 25 is thermally deformed along the protrusion 23, whereby the piston band 25 is Similar to the embodiment, it is arranged in the annular groove 20 while being restrained in both the axial direction and the rotational direction. On the other hand, the outer peripheral surface of the piston band 25 is finished smoothly by the inner surface of the die 27 and finished to a specified outer diameter. Therefore, in a state where the piston 10 is incorporated as a hydraulic shock absorber (see FIG. 1), the piston 10 slides stably in the cylinder 1 while ensuring a sealing property with the inner surface of the cylinder 1. According to the second embodiment, in particular, it is not necessary to provide the concave groove 24 (FIGS. 3 and 4) that fits with the projection 23 on the piston half body 10A, 10B side on the inner peripheral surface of the piston band 25. The piston band 25 can be easily manufactured.

  9 to 11 show a third embodiment of the present invention. The feature of the third embodiment is that the corners of the small-diameter portion 22 of each piston half body 10A, 10B in the first embodiment are inclined from the outer peripheral surface of the small-diameter portion 22 toward the large-diameter portion. The inclined portion 30 is provided. Here, the inclined portion 30 is selectively provided between the plurality of protrusions 23 formed on the outer peripheral surface of the small diameter portion 22. The inclination angle θ of the inclined portion 30 is not particularly limited, but about several degrees to several tens of degrees is sufficient.

  In the third embodiment, the two piston halves 10A and 10B are aligned with the piston band 21 in the same procedure as shown in FIG. Push in from the opposite direction. Then, in the vicinity of the pushing end, both end portions of the piston band 21 ride on the inclined portions 30 on the piston half bodies 10A and 10B, and the piston band 21 bulges at the groove end portion of the annular groove 20 as shown in FIG. Part 31 is formed. Therefore, when such a piston 10 is assembled to a hydraulic shock absorber (see FIG. 1), the bulging portion 31 of the piston band 21 is in strong sliding contact with the inner surface of the cylinder 1, and the piston 10 and the inner surface of the cylinder 1 correspondingly. The sealing property between the two is further improved.

  FIG. 12 shows a fourth embodiment of the present invention. The feature of the fourth embodiment is that the protrusion 23 is eliminated from the outer peripheral surface of the small diameter portion 22 of each piston half body 10A, 10B in the third embodiment, and the inclined portion is formed at the corner portion of the small diameter portion 22. 30, the inclined portion 35 is provided over the entire circumference, and the smooth-shaped piston band 25 as shown in FIG. 7 is used. Here, the inner diameter of the smooth-shaped piston band 25 is set to be the same as or slightly larger than the diameter of the small diameter portion 22 of each of the piston halves 10A and 10B.

  In the fourth embodiment, when the two piston halves 10A and 10B are pushed into the piston band 25 from opposite directions (see FIG. 6), the pushing end is the same as in the third embodiment. In the vicinity, both end portions of the piston band 25 ride on the inclined portions 35 on the piston half bodies 10A and 10B, and the bulging portion (31) of the piston band 25 is formed at the groove end portion of the annular groove 20 as shown in FIG. It is formed. Therefore, when such a piston 10 is assembled to the hydraulic shock absorber (see FIG. 1), the bulging portion of the piston band 25 is in strong sliding contact with the inner surface of the cylinder 1 as in the third embodiment, and the piston The sealability between 10 and the inner surface of the cylinder 1 is further improved. In the fourth embodiment, the inclined portion 35 functions as a convex portion that restrains the movement of the piston band 25 in the rotational direction (static friction resistance function). Therefore, according to the fourth embodiment, As in the first embodiment, the fitting structure between the projections 33 on the piston halves 10A and 10B side and the concave groove 34 on the piston band 21 side becomes unnecessary, and in addition, as in the second embodiment, the piston band 25 thermocompression bonding is also unnecessary, which is advantageous in terms of manufacturing cost.

  In addition, the piston bands 21 and 25 in each of the above embodiments may of course have a seamless shape, but for example, may have a shape having a seam S as shown in FIG.

It is sectional drawing which shows the structure of the piston as a 1st Embodiment of this invention, and the principal part structure of the hydraulic shock absorber incorporating this piston. It is sectional drawing which expands and shows the structure of the piston as 1st Embodiment. It is sectional drawing which shows the coupling structure of the piston half body and piston band in 1st Embodiment. It is a top view which shows the structure of the piston half body in 1st Embodiment. It is a top view which shows the shape of the piston band used in 1st Embodiment. It is a side view which shows the assembly procedure of the piston half body and piston band in 1st Embodiment. It is a top view which shows the shape of the piston band used in the 2nd Embodiment of this invention. It is sectional drawing which shows the assembly procedure of the piston half body and piston band in 2nd Embodiment. It is sectional drawing which shows the structure of the piston half body used in the 3rd Embodiment of this invention. It is a side view which shows the structure of the piston half body used in 3rd Embodiment. It is sectional drawing which expands and shows the structure of the piston as the 3rd Embodiment of this invention. It is a side view which shows the structure of the piston half body used in the 4th Embodiment of this invention. It is a side view which shows the shape of the piston band which has a seam which can be used by this invention. It is sectional drawing which shows the principal part structure of the piston of the conventional division structure, and the hydraulic shock absorber incorporating this piston. It is a top view which shows the structure of the piston half body shown in FIG. It is a rear view which shows the structure of the piston half body shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylinder, 2 Piston rod 3, 4 Disc valve 10 Piston 10A, 10B Piston half body 11 Insertion hole, 12 Inlet passage, 13 Outlet passage 14 Elongation side oil liquid passage, 15 Shrinkage side oil liquid passage 20 Annular groove 21, 25 Piston Band 22 Small-diameter portion of piston half 23 Protrusion (convex)
24 concave groove 30, 35 inclined part (convex part)

Claims (6)

  An insertion hole through which the piston rod is inserted is provided at the center, and two piston halves each having a plurality of passages are formed around the insertion hole, and the passages of the two piston halves are communicated with each other. A piston structure of a hydraulic shock absorber in which a piston band made of resin is mounted on the outer periphery of a piston formed with an oil liquid passage, wherein the piston has a small-diameter portion around the coupling portion of the two piston halves The whole piston band is fitted and arranged in an annular groove formed by the small diameter portion, and the piston band is rotated on the outer peripheral surface of the small diameter portion of each piston half body. A piston structure of a hydraulic shock absorber, wherein a convex portion constrained to the die is molded integrally with the piston half.   2. The piston structure of a hydraulic shock absorber according to claim 1, wherein the convex portions provided on the outer peripheral surface of the small diameter portion of each piston half are a plurality of protrusions extending in the axial direction.   The piston structure of the hydraulic shock absorber according to claim 2, wherein a part of the plurality of protrusions is disposed at a position where the oil passage is closest to the outer peripheral surface of the small-diameter portion of the piston half. .   The piston band has a concave groove that can be fitted into the protrusion of the piston half on the inner peripheral surface thereof, and is disposed in the annular groove with the protrusion of the piston half fitted in the concave groove. The piston structure of the hydraulic shock absorber according to claim 2 or 3, wherein   The piston structure of the hydraulic shock absorber according to claim 2 or 3, wherein the piston band has a cylindrical shape having a smooth inner peripheral surface and an outer peripheral surface, and is disposed in the annular groove by thermocompression bonding. The convex portion provided on the outer peripheral surface of the small-diameter portion of each piston half is an inclined portion that is disposed at the corner portion of the small-diameter portion and is inclined from the outer peripheral surface of the small-diameter portion toward the large-diameter portion. The piston structure of the hydraulic shock absorber according to claim 1, characterized in that:

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