JP4078270B2 - Piston part structure - Google Patents

Description

  The present invention relates to an improvement of a piston portion structure in a hydraulic cylinder called a ram type cylinder.

  When hydraulic oil is supplied into the cylinder body, a hydraulic cylinder called a ram-type cylinder projects a rod body that can be inserted and retracted into the cylinder body, while the hydraulic oil in the cylinder body At the time of the maximum contraction in which the rod body is largely discharged into the cylinder body by being discharged to the outside, for example, the bottom impact that the piston collides with the bottom portion of the cylinder body is prevented by the cushion effect by the cushion structure.

  At this time, as disclosed in Patent Document 1, it is assumed that the piston is held by a fixed means such as a screw on the tip of the rod body, and that the piston is a component constituting the cushion structure. Yes.

  Therefore, in the piston part structure in the hydraulic cylinder disclosed in Patent Document 1, the hydraulic cylinder can be expanded and contracted without unnecessarily increasing the number of parts, and a predetermined cushion effect can be exhibited. Will be possible.

Incidentally, in the piston part structure disclosed in Patent Document 1 above, the piston seals the opening end of the cylinder body and penetrates the rod body when the rod body protrudes from the cylinder body with a large stroke. The rod seal member is abutted and locked to prevent the rod body from coming out of the cylinder body.
Japanese Utility Model Publication No. 5-42245 (claim of utility model registration, column of conventional technology, lines 17 to 22, lines 2 and 5)

  However, in the hydraulic cylinder disclosed in Patent Document 1 described above, since the piston is fixed to the tip of the rod body, there is a concern that this piston may cause a sag phenomenon with the inner periphery of the cylinder body. is there.

  That is, in the above hydraulic cylinder, in particular, if the piston constitutes a cushion structure, it is essential that the piston is fixed to the tip of the rod body.

  Therefore, in the above hydraulic cylinder, the piston is fixed to the tip of the rod body. Therefore, when the rod body is bent due to a load or the like, the piston moves up and down with the axis of the cylinder inclined. In other words, there is a concern that the piston may hit the inner periphery of the cylinder body, and at this time, the cushion effect may not be exhibited as set.

  The present invention was devised in view of such a current situation, and the object of the present invention is that even if the rod body appears and disappears with the axis line inclined with respect to the cylinder body, the piston is the cylinder. It is to provide a piston structure that is optimal for expecting an improvement in versatility by allowing the cushion effect to be exhibited as set, without fear of wandering the inner circumference of the body.

In order to achieve the above-described object, according to the first aspect of the present invention, the piston portion structure is defined such that the rod side chamber and the piston side chamber are partitioned in the cylinder body via the piston, and the piston is inserted into the cylinder body so as to be able to protrude and retract. In the piston part structure in the ram type cylinder held at the tip part of the rod body , the piston is formed in a cylindrical shape, and between the inner circumference of the piston and the outer circumference of the rod part facing the inner circumference. A gap communicating the rod side chamber and the piston side chamber is formed along the axial direction, and a plurality of hard balls arranged in a row at appropriate intervals are held in the gap .

  And in Claim 2, while forming the recessed part which accept | permits the collection | recovery of a hard ball in either one of the inner periphery of a piston or the outer periphery of the front-end | tip part in a rod body, the side facing this recessed part side, It is assumed that the outer periphery of the tip of the rod body or the inner periphery of the piston is formed with a recessed groove or recessed portion that allows the hard balls to be collected.

  According to a third aspect of the present invention, a hole is formed in the piston to allow the passage of the hard sphere through the wall thickness, and the hole is closed with a sealing plug or a piston ring interposed on the outer periphery of the piston. Suppose that

  By the way, in order to obtain a cushioning effect, an oil hole erects from the bottom part at the shaft part of the inner bottom part in the cylinder body, and the cushion pipe is held in the hollow part formed at the shaft part at the tip part of the rod body. Thus, it is preferable to provide a cushion structure in which when the rod body is immersed in the cylinder body with a large stroke, an oil hole is inserted into the cushion pipe to obtain a cushion effect.

  Therefore, in the invention of claim 1, since the piston is held at the tip of the rod body under the spherical bearing structure, the piston is maintained in a state subordinate to the inner periphery of the cylinder body. Therefore, even if the rod body repeatedly moves in and out with respect to the cylinder body with the axis inclined with respect to the axis of the cylinder body, there is no fear that the piston may hit the inner periphery of the cylinder body.

  At this time, since the piston does not constitute a cushion structure, there is no problem even if the piston oscillates with respect to the rod body, and the piston is held at the tip of the rod body. Since the movement of the rod body in the axial direction is restricted, the piston is brought into contact with and locked by the shaft seal member that seals the opening end of the cylinder body when the hydraulic cylinder is fully extended. It functions as a stopper and prevents the rod body from coming out of the cylinder body.

  And since the hard sphere distributed between the piston and the tip of the rod body is distributed with an appropriate interval, it is in a state where it is divided vertically in terms of a hard sphere in the longitudinal sectional view. A gap, that is, a gap between the piston and the tip of the rod body is secured as a flow path for the hydraulic oil.

  In the invention of claim 2, since the hard spheres are accommodated in the recesses, it is possible to avoid the inconvenience of the so-called dropping of the hard spheres from a predetermined position, and the interval between the hard spheres is maintained, so It is possible to eliminate the unevenness of the flow path, and it is easy to form the concave groove as compared to forming an independent concave portion.

  In the invention of claim 3, when using a sealing plug, the piston can be fixedly connected to the tip of the rod body, and so-called escape of the hard sphere can be prevented, When directly sealing with a piston ring without using a sealing plug, it is possible to reduce the number of components.

  By the way, when the cushion structure is provided in a mode separated from the piston, the impact of the piston colliding with the bottom portion of the cylinder body can be alleviated by a predetermined cushion effect regardless of the movement of the piston.

  As a result, according to the present invention, there is no fear that the piston may hit the inner periphery of the cylinder body, and it is optimal for expecting improvement in versatility.

  Hereinafter, the present invention will be described based on the illustrated embodiment. The piston structure according to the present invention is embodied in a hydraulic cylinder called a ram type cylinder as shown in FIG. At this time, the hydraulic cylinder defines a rod-side chamber R1 and a piston-side chamber R2 in the cylinder body 1 by a piston 3 held by a tip portion 2a of a rod body 2 that is inserted into the cylinder body 1 so as to be able to protrude and retract.

  When the hydraulic oil from the hydraulic supply / discharge source P disposed outside is supplied to the piston side chamber R2, the piston side chamber R2 expands and the rod body 2 projects from the cylinder body 1.

  Incidentally, when the hydraulic cylinder in which the rod body 2 protrudes from the cylinder body 1 with a large stroke by supplying hydraulic oil to the piston side chamber R2, the piston 3 seals the opening end of the cylinder body 1 when not fully shown. The rod body 2 is brought into contact with and locked by a shaft sealing member that passes through the rod body 2, and the rod body 2 is prevented from coming out of the cylinder body 1.

  In addition, a piston ring 3 a that is in sliding contact with the inner periphery of the cylinder body 1 is interposed on the outer periphery of the piston 3, thereby avoiding contact between the cylinder body 1 and the piston 3.

On the other hand, in the piston part structure according to the present invention, as shown in FIGS. 1 and 2, the piston 3 is formed in a cylindrical shape, and the inner periphery of the piston 3 and the tip of the rod body 2 facing the inner periphery. A gap S that communicates the rod-side chamber R1 and the piston-side chamber R2 is formed along the axial direction between the outer periphery of the part, and a plurality of hard balls 4 arranged in a row at appropriate intervals are held in the gap S. ing.

  That is, the piston 3 is formed in a cylindrical shape having an appropriate gap S between the distal end portion 2a of the rod body 2 and has recesses 3b (see FIG. 2) formed on the inner periphery at appropriate intervals in the circumferential direction. In addition, the distal end portion 2a of the rod body 2 has a recess 2b (see FIG. 2) formed on the outer periphery so as to face the recess 3a on the piston 3 side in the circumferential direction.

  At this time, the number of the recesses 3b on the piston 3 side and the recesses 2b on the rod body 2 side is, of course, set to be the same, and the hard balls 4 are accommodated in the opposing recesses 3b and 2b, respectively. Has been.

  Incidentally, the hard ball 4 is made of, for example, a steel ball, has a predetermined mechanical strength, and guarantees a relative rotation between the piston 3 and the tip 2a of the rod body 2 permanently.

  By the way, in order to make the hard ball 4 function as a bearing, in the illustrated case, the recesses 3b and 2b are formed on the inner periphery of the piston 3 and the outer periphery of the tip 2a of the rod body 2, respectively. Thus, it can be said that either one may be a concave groove.

  That is, although not shown, for example, while the recess 3b is formed on the inner periphery of the piston 3, a recess is formed on the outer periphery of the tip 2a of the rod body 2, and in this case, the rod body Compared with the formation of the independent recess 2b on the outer periphery of the tip 2a in FIG. 2, a single groove is formed, which is advantageous in terms of machining work.

  Therefore, in the illustrated hydraulic cylinder, the piston 3 is held at the tip 2a of the rod body 2 under the spherical bearing structure, so that it is always maintained in a state subordinate to the inner periphery of the cylinder body 1, and accordingly. Even if the rod body 2 is repeatedly projected and retracted with the cylinder body 1 tilted with respect to the cylinder body 1, there is no fear that the piston 3 hits the inner periphery of the cylinder body 1.

  Not only that, the piston 3 does not constitute a cushion structure, which will be described later, so that there is no problem even if the piston 3 swings with respect to the rod body 2. Since the movement of the rod body 2 in the axial direction is restricted while being held by the tip 2a of the rod body 2, the piston 3 is not opened, but the piston 3 is opened at the open end of the cylinder body 1 when the hydraulic cylinder is fully extended. Therefore, the rod member 2 functions as a stretch stopper and effectively prevents the rod body 2 from coming out of the cylinder body 1.

  Since the hard spheres 4 arranged between the piston 3 and the tip 2a of the rod body 2 are arranged at an appropriate interval, in terms of the vertical section of FIG. A gap S that is divided into two, that is, a gap S between the piston 3 and the tip 2a of the rod body 2 is secured as a flow path for the hydraulic oil.

  From this, the illustrated hydraulic cylinder is a single-acting hydraulic cylinder, but instead of this, for example, a plurality of hydraulic cylinders having different pressure receiving areas may be used by a forklift. However, the hydraulic cylinder shown in the figure is a sub-cylinder that supplies hydraulic oil to the master cylinder that increases the pressure receiving area by comparison, i.e., the hydraulic cylinder that decreases the pressure receiving area and allows hydraulic oil to pass through. When used, it can be said that it is advantageous in that it is easy to ensure the flowability of the hydraulic oil between the rod side chamber R1 and the piston side chamber R2.

  By the way, any method may be selected for placing the hard sphere 4 between the piston 3 and the tip 2a of the rod body 2, that is, in the recesses 3b, 3b formed on both. However, in order to prevent the hard ball 4 accommodated in the recesses 3b and 3b from dropping out of the recess 3b, the sealing plug 5 penetrates the thickness of the piston 3 as shown in FIG. It may be press-fitted into a hole 3c (see FIG. 1) that allows the passage of the hard ball 4, and in this case, the piston 3 can be prevented from freely rotating with respect to the tip 2a of the rod body 2. This is advantageous.

  Further, instead of using the sealing plug 5, the piston ring 3a is interposed on the outer periphery of the piston 3 to close the hole 3c, thereby preventing the hard ball 4 from coming out from a predetermined position. In this case, it is advantageous in that the number of parts can be reduced.

  Incidentally, in the illustrated hydraulic cylinder, a cushion structure is provided. In the illustrated cushion structure, an oil hole rod 1b is provided from the bottom portion 1a to the shaft core portion of the inner bottom portion in the cylinder body 1. In addition to standing, a cushion pipe 6 is held in a hollow portion (not shown) formed in the axial center portion of the tip end portion 2a of the rod body 2 with the snap ring 6a interposed therebetween. When the oil hole 1b is inserted into the cushion pipe 6 when immersing with a large stroke, a predetermined cushion effect is obtained.

  Therefore, in the illustrated embodiment, since the cushion structure is provided in a manner separated from the piston 3, a predetermined cushioning effect is obtained regardless of the movement of the piston 3, and the piston 3 is connected to the cylinder body 1. It is possible to avoid a bottom butt that collides with the bottom portion 1a.

It is a fragmentary longitudinal cross-section which shows the hydraulic cylinder which actualized the piston part structure by this invention. It is a cross-sectional view which shows the piston part structure by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylinder body 1a Bottom part 1b Oil hole rod 2 Rod body 2a Tip part 2b, 3b Recess 3 Piston 3a Piston ring 4 Hard ball 5 Sealing plug 6 Cushion pipe 6a Snap ring P Hydraulic supply / discharge source R1 Rod side chamber R2 Piston side chamber S Crevice

Claims (3)

In a piston part structure in a ram type cylinder in which a rod side chamber and a piston side chamber are partitioned via a piston in the cylinder body, and the piston is held at the tip of a rod body that can be inserted into and retracted from the cylinder body , the piston is cylindrical. A gap is formed along the axial direction between the inner periphery of the piston and the outer periphery of the tip of the rod body facing the inner periphery along the axial direction. A piston part structure characterized by holding a plurality of hard balls arranged in a row at an appropriate interval in a gap . While forming a recess that allows the hard balls to be accommodated on either the inner periphery of the piston or the outer periphery of the tip of the rod body, the tip of the rod that is the side facing the side having the recess The piston part structure according to claim 1, wherein a concave groove or a concave part that allows the collection of hard balls is formed on the outer periphery or the inner periphery of the piston. A hole is formed in the inner periphery of the piston so as to allow the passage of the hard sphere through the wall thickness, and the hole is closed by a sealing plug or a piston ring interposed on the outer periphery of the piston. 1. The piston part structure according to 1.

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