JP2002122239A - Mounting method for resin piston ring and device thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the durability of a jig for mounting a piston ring on a piston and securely mount the piston ring in a small number of processes by increasing a mounting speed so as to improve the productivity. SOLUTION: In the mounting method for the resin piston ring 2, an outer peripheral end of the piston ring 2 is nipped between a lower retainer 14 and an upper retainer 16, the piston ring 2 is pressed down along outer periphery of the piston 1 while elastically expanding an inside diameter of the piston ring 2 nipped by the lower and upper retainers 14, 16, an inner peripheral end of the piston ring 2 is fitted in a ring groove 1A of the piston 1 by shrinking its diameter elastically to mount the piston ring 2 at outer periphery of the piston 1 in a cylindrical manner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for mounting a resin piston ring used in a hydraulic shock absorber or the like.

[0002]

2. Description of the Related Art Conventionally, as a method of attaching a resin piston ring to the outer periphery of a piston, as described in Japanese Patent Publication No. 4-81074, a preparation step of positioning a piston on a base and mounting a cone guide on the piston, The piston ring is attached to the guide, the pressing means consisting of an elastic plate is pushed down from above the piston ring along the conical guide, and the piston ring is formed into a cylindrical shape while gradually expanding its diameter. The first step of mounting, the second step of fitting the piston ring mounted on the piston into the ring groove on the upper end side of the piston by a roller jig, and passing the piston mounted with the piston ring through the heating chamber, and then into the cooling chamber And a third step of fixing the piston ring in all the ring grooves of the piston by passing the piston ring.

[0003]

The prior art has the following problems. In the first step, when the piston ring is mounted on the outer periphery of the piston, the elastic plate-like body constituting the pressing means has poor durability (short life), and it is necessary to frequently replace the elastic plate-like body. If the mounting speed is increased when the piston ring is pressed by the elastic plate-like body, the piston ring may not be fully pressed and cannot be mounted, resulting in poor productivity.

[0004] After the piston ring is mounted on the piston in the first step, a step of fitting the piston ring into the ring groove of the piston using a roller jig is required, and the productivity is poor.

SUMMARY OF THE INVENTION An object of the present invention is to improve the durability of a jig for mounting a piston ring on a piston, and to increase the mounting speed with a small number of steps and to reliably mount the piston ring, thereby improving productivity. It is in.

[0006]

According to a first aspect of the present invention, in a method of mounting a resin piston ring on the outer periphery of a piston, an outer peripheral end of the piston ring is sandwiched between a lower retainer and an upper retainer. The piston ring is pressed down along the outer periphery of the piston while the inner diameter of the piston ring held by the upper and lower retainers is elastically expanded by a conical guide, and the inner peripheral end of the piston ring is inserted into the ring groove of the piston. On the other hand, it is elastically reduced in diameter and fitted.
Fixing the piston ring in a ring groove of the piston by attaching the piston ring to the outer periphery of the piston in a cylindrical shape and passing the piston equipped with the piston ring through a heating chamber and then through a cooling chamber. And a process.

According to a second aspect of the present invention, when the piston ring is mounted on the outer periphery of the piston, the piston ring is attached to the outer periphery of the piston by a conical guide having a cylindrical portion placed on the piston. The outer periphery is guided.

According to a third aspect of the present invention, in a resin piston ring mounting device for mounting a resin piston ring on an outer periphery of a piston, a base for positioning and fixing the piston, a lower retainer and an upper retainer for clamping an outer peripheral end of the piston ring, Each of the upper and lower retainers is moved, and while the inner diameter of the piston ring sandwiched by the upper and lower retainers is elastically expanded by a conical guide, the piston ring is pushed down along the outer periphery of the piston, and A lower press moving device and an upper press moving device for fitting the peripheral end of the piston into a ring groove of the piston by elastically reducing the diameter thereof and mounting the piston ring on the outer periphery of the piston; and a piston mounted on the piston. A heating chamber for heating the ring and a cooling chamber for cooling the piston ring heated in the heating chamber are provided. Is obtained in such a manner that Te.

According to a fourth aspect of the present invention, there is further provided a conical guide having a cylindrical portion mounted on a piston positioned and fixed to the base and guiding the piston ring to the outer periphery of the piston. It is made to be.

The invention according to claim 5 is the apparatus according to claim 3 or 4, wherein the upper retainer is provided with an upper retainer capable of accommodating and holding the conical guide.

According to a sixth aspect of the present invention, in addition to the third or fourth aspect, the lower holding moving device and the upper holding moving device are constituted by air cylinders, and the cylinder receiving pressure area of the upper holding moving device is reduced by the lower holding moving device. Is larger than the cylinder pressure receiving area.

[0012]

According to the first and third aspects of the present invention, the following effects are obtained. When attaching the piston ring to the piston, hold the outer peripheral end of the piston ring by pressing it up and down and press it down.The inner diameter of this piston ring is expanded elastically by a conical guide and attached to the outer periphery of the piston At the same time, the inner peripheral end of the piston ring is elastically reduced in diameter and fitted into the ring groove of the piston. Therefore, a conical guide and upper and lower retainers are used as a jig for mounting the piston ring on the piston, and these are used to clamp the outer peripheral end of the piston ring and push down the piston ring via the conical guide. The durability of the jig can be improved.

The upper and lower retainers, which are used jigs, can improve the durability, so that they do not need to be replaced frequently, and even if the mounting speed by the upper and lower retainers is increased, the mountability is not impaired and the productivity can be improved.

The piston ring is mounted on the outer periphery of the piston, and at the same time, the inner peripheral end thereof is elastically reduced in diameter with respect to the ring groove of the piston and can be fitted into the ring groove. Apart from the steps, no extra step of fitting the piston ring into the ring groove of the piston is required, so that the total number of steps can be reduced and the productivity can be improved.

According to the second and fourth aspects of the present invention, the following effects are obtained. When attaching the piston ring to the outer circumference of the piston,
Since the piston ring is guided to the outer circumference of the piston by a conical guide having a cylindrical portion mounted on the piston, the piston ring is supplied horizontally by suppressing the inclination of the piston ring, and the piston ring is clamped by pressing up and down. In addition to ensuring that the piston ring is mounted on the piston smoothly, the mounting speed by pressing the upper and lower parts can be further increased, and the productivity can be further improved.

According to the fifth aspect of the invention, the following effects are obtained. Since the conical guide can be accommodated and held in the upper retainer, no separate attaching / detaching device is required for attaching / detaching the conical guide. Therefore, the device can be realized with a simple configuration and the size can be reduced.

According to the sixth aspect of the invention, the following operations are provided. Since the pressure receiving area of the cylinder of the upper holding device was made larger than the pressure receiving area of the cylinder of the lower holding device, the thrust of the upper cylinder was set to be larger than that of the lower cylinder simply by operating the upper and lower cylinders with the same fluid pressure. ,
The upper and lower retainers can be synchronously moved downward while sandwiching the piston ring. Thereby, the up and down holding can realize the holding operation and the pressing operation of the piston ring with a simple configuration.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a front view showing a piston ring mounting apparatus, FIG. 2 is a schematic view showing a preparation step of a piston ring mounting method, FIG. 3 is a schematic view showing a first step of a piston ring mounting method, FIG. 4 shows the second method of attaching the piston ring.
FIG. 5 is a schematic diagram showing a process, and FIG. 5 is a schematic diagram showing a process of attaching a piston ring to a piston.

As shown in FIG. 5, a piston ring mounting device 10 mounts a resin piston ring 2 on the outer periphery of a piston 1 used for a hydraulic shock absorber or the like. The piston 1 has a plurality of ring grooves on the outer circumference, and the ring groove 1 at the upper end.
A is a deep groove, and a ring groove 1B below the groove is a shallow groove. Piston ring 2 is made of tetrafluoroethylene resin (PT
FE) or the like, and is formed in a sheet shape at the material stage supplied to the piston ring mounting device 10, and after being mounted on the piston 1, is formed into a cylindrical shape and is fixed by being fitted into and engaged with the ring grooves 1 </ b> A and 1 </ b> B. .

As shown in FIG. 1, the piston ring mounting device 10 includes a gantry 11, a base 12, and a conical guide 13
A lower presser 14 and a lower presser moving device 15; an upper presser 16 and an upper presser moving device 17;
And a finish forming apparatus 20 having a cooling chamber 19.

The gantry 11 includes a lower support 11A and a middle support 1
1B and an upper support portion 11C, and a base 12 is provided on the middle support portion 11B. The base 12 is provided with a positioning pin 12A having the same outer diameter as the piston rod into which the piston 1 is incorporated, protruding from the upper end face, and by fitting the piston rod mounting hole 1C of the piston 1 to the pin 12A, the piston 1 is moved. It can be positioned and fixed at the upper end surface.

The conical guide 13 is mounted coaxially on the upper end surface of the piston 1 positioned and fixed on the base 12, and guides the piston ring 2 to the outer periphery of the piston 1. The conical guide 13 has a guide portion 13A having a cylindrical portion 101 having substantially the same diameter as the inner diameter of the piston ring and a conical portion 102 continuous from the cylindrical portion 101.
The lower end outer diameter of 3A is slightly larger than the outer diameter of piston 1,
Positioning hole 13 that fits into positioning pin 12A of base 12 that passes through piston rod mounting hole 1C of piston 1
B is provided at the center of the lower end surface. The conical guide 13
Also has a positioning projection 13D that fits into the end recess 1D of the piston 1. Also, the conical portion 102 of the guide portion 13A
A cylindrical portion 101 having a diameter slightly smaller than the inner diameter of the piston ring (within a range of substantially the same diameter) for supplying the piston ring 2 horizontally without tilting the lower presser.
The upper end face of the piston 01 is provided with a small-diameter attracted portion 13C, which is sucked by a vacuum chuck 16C of the upper retainer 16 and is detachable from the upper end face of the piston 1.

The lower retainer 14 is coaxially arranged at the center of the base 12 (positioning pin 12A), and can be moved up and down around the base 12 and the conical guide 13.
And a ring-shaped concave portion 14B for supporting the outer peripheral end of the piston ring 2 supplied from the lower side to the guide portion 13A of the conical guide 13 is provided on the inner peripheral upper edge of the hole portion 14A. Upper retainer 1
6 is a shaft portion 16 coaxial with the hole 14A of the lower retainer 14.
A, which has an outer peripheral end of the piston ring 2 supplied to the guide portion 13A of the conical guide 13 from above and is cylindrically formed on the outer periphery of the piston 1 positioned and fixed to the base 12 as described later. A ring-shaped protrusion 16B that can be attached via the ring 2 is provided on the outer peripheral lower edge of the shaft 16A. That is, the upper and lower retainers 14 and 16 hold the outer peripheral end of the piston ring 2 from above and below.

The lower holding moving device 15 connects the lifting rod 22 to a lower air cylinder 21 (two air cylinders 21 in this embodiment) supported by the lower support portion 11A of the gantry 11, and connects the lifting rod 22 to the middle. The lower guide 14 is fixedly provided at the upper end of the lifting rod 22 while being guided by a lifting guide 23 provided on the support portion 11B. Accordingly, the lower holding device 15 moves the lower holding 14 to a standby level lower than the upper end surface of the base 12 (FIG. 2A) and a lower portion of the cylindrical portion 101 of the conical guide 13 placed on the base 12. Between the receiving piston ring receiving levels (FIG. 3A).

The upper holder moving device 17 suspends and supports the upper holder 16 on an upper air cylinder 31 supported by the upper support 11C of the gantry 11, and holds the upper holder 16 of the conical guide 13 mounted on the base 12. Upper standby level (Fig. 2
(C)) and a piston ring mounting level (FIG. 3 (C)) for pressing down the lower end of a cylindrically formed piston ring 2 on the outer periphery of the piston 1 positioned and fixed to the base 12 as described later. Move between.

As a result, the lower holding movement device 15 and the upper holding movement device 17 are connected to the guide portion 13 of the conical guide 13.
The lower retainer 14 and the upper retainer 16 cooperate with each other so as to clamp the outer peripheral end of the piston ring 2 supplied to A from above and below, and the inner diameter of the piston ring 2 clamped by the upper and lower retainers 14 and 16 is conical guide 13 By pressing down along the guide portion 13A, the entire piston ring 2 is formed into a substantially cylindrical shape while elastically expanding the diameter thereof.
The piston ring 2 is further pushed down along the outer periphery of the piston 1, and the inner peripheral end of the piston ring 2 is elastically reduced in diameter with respect to the ring groove 1 </ b> A at the upper end of the piston 1 so as to be engaged. A piston ring 2 is mounted on the outer periphery of the piston 1 in a cylindrical shape.

At this time, the lower press moving device 15 and the upper press moving device 17 are connected to the cylinder 3 of the upper press moving device 17.
The pressure receiving area of No. 1 is larger than the pressure receiving area of the cylinder 21 of the lower holding device 15 (the total pressure receiving area of the two cylinders 21 in the present embodiment). The cylinder 31 of the upper holding device 17 and the cylinder 21 of the lower holding device 15
When the thrust of the upper air cylinder 31 is larger than the thrust of the lower air cylinder 21 when operated by the same air pressure,
The upper and lower retainers 14 and 16 move downward synchronously with the piston ring 2 interposed therebetween.

The upper retainer 16 is provided with a vacuum chuck 16C capable of accommodating the entire conical guide 13 at its lower end surface surrounded by the ring-shaped projection 16B of the shaft 16A and adsorbing and holding the adsorbed portion 13C. The upper retainer 16 inserts the conical guide 13 sucked by the vacuum chuck 16C into the positioning pin 12A passing through the piston rod mounting hole 1C of the piston 1 on the base 12 so that the positioning hole 13 is formed.
B. As a result, the conical guide 13 is disengaged from the piston 1
Can be attached to and detached from the upper end surface of the At this time, upper holding 1
6 can move horizontally between the supply position of the conical guide 13 and the center position of the base 12 and the lower presser 14.

The conical guide holding mechanism may be a mechanical holding mechanism, for example, a mechanical chuck mechanism or the like.

In the finish forming apparatus 20, the heating chamber 18 and the cooling chamber 19 are connected vertically and coaxially via a heat insulating portion 41. The heating chamber 18 includes an electric heater 18A.
The piston 1 with the piston ring 2 mounted thereon can be pushed in from the upper end opening 18B by the press shaft 42 in a vertically inverted state, and can be put in a stacked state, and the upper end opening 18B
Has an enlarged diameter tapered shape, and an intermediate portion is finished to an inner diameter slightly smaller than a finished large diameter of the piston ring 2 by honing or the like. The cooling chamber 19 is provided with a cooling medium 19A, is capable of receiving the piston 1 discharged from the heating chamber 18 in a laminated state, and is finished to an inner diameter slightly smaller than the finished large diameter of the re-piston ring 2 by honing or the like. . As a result, the finish forming apparatus 20 allows the piston 1 on which the piston ring 2 is mounted to pass through the heating chamber 18 and then through the cooling chamber 19 so that the piston ring 2 is engaged with all the ring grooves 1A and 1B of the piston 1. And fixed to the lower end outlet 1 of the cooling chamber 19.
It is possible to discharge from 9B.

The upper end opening 18B of the heating chamber 18
The upper end of the piston 1 is turned upside down because the upper end of the piston ring 2 is
A at the lower end side, the holding portion of the lower end portion of the piston ring 2 by the pressers 14 and 16 is protruding outward, so that the upper end side of the piston 1 extends from the upper end opening 18
B prevents separation of the piston ring 2 from the piston 1 and smoothly moves the piston 1 and the piston ring 2 to the heating chamber 18 and the cooling chamber 19.
This is to enable finish molding.

The procedure for mounting the piston ring 2 by the piston ring mounting device 10 will be described below.

(A) Preparation Step (1) The piston 1 (FIG. 5A) is mounted on the base 12 (FIG. 2A). The piston 1 is positioned and fixed by fitting its piston rod mounting hole 1C into a positioning pin 12A of the base 12.

(2) Place the conical guide 13 on the piston 1 (FIGS. 2B and 2C). The conical guide 13 is adsorbed by the vacuum chuck 16C of the upper retainer 16 and is carried in. The positioning hole 13B is fitted to the positioning pin 12A passing through the piston rod mounting hole 1C of the piston 1 on the base 12, and the piston It is positioned and fixed coaxially with 1.

(B) First Step (1) The lower presser 14 is raised by the lower presser moving device 15 from the standby level to the piston ring receiving level corresponding to the upper end of the guide portion 13A of the conical guide 13, and the sheet-like piston is moved. The ring 2 is supplied to the conical guide 13, and the lower surface of the outer peripheral end of the piston ring 2 is arranged in the ring-shaped recess 14 </ b> B of the lower retainer 14 (FIG. 3A).

(2) The upper retainer 16 is lowered from the standby level by the upper retainer moving device 17, and the upper surface of the outer peripheral end of the piston ring 2 is pressed by the ring-shaped projection 16B of the upper retainer 16. As a result, the outer peripheral end of the piston ring 2 (a portion of about 1 mm in the diameter direction) is held down by the lower presser 14 and the upper presser 1.
6 (FIG. 3B).

(3) The lower holding device 15 and the upper holding device 17 are further operated, and the piston ring 2 is pushed downward while holding the outer peripheral end of the piston ring 2 by the upper and lower holding devices 14 and 16 to move the piston ring 2 downward. By pressing down the inner diameter of the piston ring 2 along the guide portion 13A of the conical guide 13, the entirety of the piston ring 2 is formed into a substantially cylindrical shape while elastically expanding the diameter. From the side to the side of the piston 1 and further pressed down along the outer periphery of the piston 1. When the position of the inner peripheral end of the piston ring 2 is aligned with the ring groove 1A at the upper end of the piston 1 in the process of pushing down the cylindrical piston ring 2 along the outer periphery of the piston 1, the inner peripheral end of the piston ring 2 is elastic. Then, the diameter of the cylindrical piston ring 2 is fitted to and engaged with the ring groove 1A, and the mounting of the cylindrical piston ring 2 on the outer periphery of the piston 1 is completed (FIG. 3C).

The mounting state of the piston ring 2 in the first step is as shown in FIG. 5B, and only the upper end of the piston ring 2 is engaged with the ring groove 1A at the upper end of the piston 1.
It is not engaged with the other ring groove 1B, and the lower end of the piston ring 2 has a portion sandwiched by the retainers 14 and 16 projecting outward. At this time, the ring groove 1A of the piston 1 is deeper than the other ring grooves 1B, and the upper end of the piston ring 2 is firmly engaged with the ring groove 1A of the deep groove. When the ring 2 is inverted and thrown into the upper end opening 18B of the heating chamber 18 and pushed into the inside diameter of the heating chamber 18, the piston ring 2 does not peel off from the piston 1 when it is pressed.

(C) Second Step The piston 1 on which the piston ring 2 is mounted is placed in the heating chamber 18 of the finish forming apparatus 20 in an upside-down state at the upper end opening 1.
8B, the piston ring 2 is heated and pressed against the outer periphery of the piston 1 while heating.
A and 1B are engaged (FIG. 3). Subsequently, the piston 1 and the piston ring 2 are cooled and solidified in the cooling chamber 19 to complete the installation of the piston ring 2 (FIG. 3).

Since the inner diameter of both the heating chamber 18 and the cooling chamber 19 is set slightly smaller than the finished large diameter of the piston ring 2, the piston ring 2 is It is crimped to the ring grooves 1A and 1B.

FIG. 5C shows the completed state of the attachment of the piston ring 2 after the second step.

Therefore, according to the present embodiment, the following operations are provided. When the piston ring 2 is mounted on the piston 1, the outer peripheral end of the piston ring 2 is sandwiched between upper and lower retainers 14 and 16 and pressed down, and the inner diameter of the piston ring 2 is elastically expanded. At the same time as being mounted on the outer periphery of the piston 1, the inner peripheral end of the piston ring 2 is fitted to the T-ring groove 1 </ b> A of the piston 1 while elastically reducing its diameter. Accordingly, a conical guide 13 and upper and lower retainers 14 and 16 are used as jigs for mounting the piston ring 2 on the piston 1, and these pinch the outer peripheral end of the piston ring 2 and connect the piston ring 2 via the conical guide 13. The jig can be used only for pushing down, so that the durability of the jig used can be improved.

Since the upper and lower retainers 14 and 16 used as jigs can improve the durability, they do not need to be replaced frequently, and even if the mounting speed by the upper and lower retainers 14 and 16 is increased, the mountability is not impaired and the production is not affected. Performance can be improved.

The piston ring 2 is mounted on the outer periphery of the piston 1 and, at the same time, its inner peripheral end is elastically reduced in diameter with respect to the ring groove 1A of the piston 1 and can be fitted into the ring groove 1A. In addition to the mounting process of the piston ring 2, the piston ring 2 is
Since no extra step of fitting into is required, productivity can be improved by reducing the total number of steps.

When the piston ring 2 is mounted on the outer circumference of the piston 1, the conical guide 13 having the cylindrical portion 101 mounted on the piston 1 guides the piston ring 2 to the outer circumference of the piston 1. Of the piston ring 2 is supplied horizontally, and the piston ring 2 is securely held by the upper and lower retainers 14 and 16, and the attachment of the piston ring 2 to the piston 1 is smoothly performed. 16, the mounting speed can be further increased, and the productivity can be further improved.

Since the conical guide 13 is accommodated in the upper retainer 16 and can be held, a separate attaching / detaching device is not required for attaching / detaching the conical guide 13, so that the device can be realized with a simple configuration and the size can be reduced. .

Since the pressure receiving area of the cylinder 31 of the upper holding moving device 17 is made larger than the pressure receiving area of the cylinder 21 of the lower holding moving device 15, the upper and lower cylinders 21 and 31 are operated only by the same fluid pressure. The thrust of the lower cylinder 21 is made larger than the thrust of the lower cylinder 21, and the upper and lower pressers 14 and 16 can move downward synchronously with the piston ring 2 interposed therebetween. Thereby, the upper and lower pressers 14 and 16 can realize the holding operation and the pressing operation of the piston ring 2 with a simple configuration.

The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration of the present invention is not limited to this embodiment, and the design may be changed without departing from the scope of the present invention. The present invention is also included in the present invention.

[0049]

As described above, according to the present invention, the durability of a jig for mounting a piston ring on a piston is improved, and the piston ring can be securely mounted with a small number of steps and at a high mounting speed. , And productivity can be improved. Therefore, the life of the jig used can be prolonged, and the occurrence of defects in the piston to which the piston ring is attached and the stop of the production line can be reduced.

[Brief description of the drawings]

FIG. 1 is a front view showing a piston ring mounting device.

FIG. 2 is a schematic view showing a preparation step of a piston ring mounting method.

FIG. 3 is a schematic view showing a first step of a piston ring mounting method.

FIG. 4 is a schematic view showing a second step of the piston ring mounting method.

FIG. 5 is a schematic view showing a process of attaching a piston ring to a piston.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piston 1A, 1B Ring groove 2 Piston ring 10 Piston ring attaching device 12 Base 13 Conical guide 14 Lower press 15 Lower press moving device 16 Upper press 17 Upper press moving device 18 Heating chamber 19 Cooling chamber 21 Lower air cylinder 31 Upper air cylinder 101 Cylinder 102 Conical

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Yoshio Kikuchi, Inventor 1-14-1, Fujiwara-cho, Gyoda-shi, Saitama Prefecture Showa-Saitama Head Office Plant (72) Inventor Toshio Wakui 379-3 Shimohorigagawa, Kazo City, Saitama Prefecture F term in Enomoto Seiki Co., Ltd. (reference) 3J044 AA18 BA06 BC06 EA05

Claims (6)

[Claims] 1. A method of attaching a resin piston ring to an outer periphery of a piston, wherein the outer peripheral end of the piston ring is sandwiched between a lower retainer and an upper retainer, and the piston ring clamped by the upper and lower retainers is provided. Guided by a conical guide placed on the piston, the piston ring is pushed down along the outer periphery of the piston while the inner diameter is elastically expanded, and the inner peripheral end of the piston ring is elastically moved with respect to the ring groove of the piston. Fitting the piston ring to the outer periphery of the piston in a cylindrical shape, passing the piston with the piston ring through a heating chamber, and then passing the piston ring through a cooling chamber. Fixing the resin piston ring to a ring groove of the piston. 2. When the piston ring is mounted on the outer periphery of the piston, the conical guide mounted on the piston is a guide having a cylindrical portion having substantially the same diameter as the inner diameter of the piston ring and a conical portion continuous from the cylindrical portion. 2. The method according to claim 1, wherein the piston ring is guided around the outer periphery of the piston. 3. A resin piston ring mounting device for mounting a resin piston ring on an outer periphery of a piston, comprising: a base for positioning and fixing a piston; a lower retainer and an upper retainer for clamping an outer peripheral end of the piston ring; The piston ring is guided by a conical guide that places the piston ring, which is sandwiched between upper and lower retainers, on the piston, and the piston ring is pushed down along the outer periphery of the piston while elastically expanding the inner diameter. A lower press moving device and an upper press moving device for fitting the inner peripheral end of the piston ring to the ring groove of the piston by elastically reducing the diameter thereof and mounting the piston ring on the outer periphery of the piston in a cylindrical shape. A heating chamber for heating a piston ring mounted on the piston, and a piston ring heated in the heating chamber Mounting device of a resin piston ring characterized by comprising a cooling chamber for cooling the. 4. A conical guide which is mounted on a piston positioned and fixed to the base and guides the piston ring to the outer periphery of the piston, has a cylindrical portion having substantially the same diameter as the inner diameter of the piston ring, and a cone extending from the cylindrical portion. The mounting device for a resin piston ring according to claim 3, wherein the mounting device has a shape including a portion. 5. The resin piston ring mounting device according to claim 3, wherein said upper retainer has a housing portion for housing said conical guide, and said housing portion is provided with holding means for holding said guide. 6. The lower press moving device and the upper press moving device are constituted by air cylinders, and the cylinder pressure receiving area of the upper press moving device is larger than the cylinder pressure receiving area of the lower press moving device. Plastic piston ring mounting device.