JP2006083960A - Seal ring and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent change in the shape and dimension of a seal ring made of PTFE in a heating (burning) process etc. and eliminate the necessity of finishing turning processing of the inner/outer diameter face, when manufacturing the seal ring. <P>SOLUTION: The seal ring A comprises a cylindrical compressed molded body 1 of which main component is tetrafluoroethylene resin powder. A columnar die 2 of a finished size is fitted into the inner peripheral face of the cylindrical compressed molded body 1. Then, the entire compressed molded object is heated over the melting point of tetrafluoroethylene resin and burned. On the inner peripheral face 1a of the cylindrical compressed molded body 1, a melting molded layer is formed by the die 2, and the cylindrical compressed molded body 1 is cut in the axial direction into a predetermined width and manufactured. Inner and outer dimensions as expected before the burning can be obtained, and the seal ring A capable of being used as a finished face without correcting the inner/outer diameter by turning can be manufactured. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a seal ring made of a tetrafluoroethylene resin and a manufacturing method thereof, and more particularly to an oil seal ring suitable for sealing oil such as hydraulic oil and a manufacturing method thereof.

  Generally, automatic transmissions such as torque converters and hydraulic clutches and continuously variable transmissions are provided with seal rings for sealing (oil seals) that prevent leakage of hydraulic oil.

  As shown in FIGS. 3 and 4, the sealing device using the seal ring has a ring groove 5 formed on the outer periphery of the shaft 4 incorporated in the casing 3, and the seal ring A is incorporated in the ring groove 5. When the hydraulic pressure is applied to one side surface 6 of the seal ring A, the other side surface 7 of the seal ring A is brought into close contact with the side surface of the ring groove 5 and is acted on the inner peripheral surface A1 of the seal ring A together. The seal ring A is expanded by hydraulic pressure to bring the outer peripheral surface A2 into close contact with the inner peripheral surface 3a of the casing 3, and the contact between the sliding surface of the casing 3 and the shaft 4 is required to be liquid-tightly sealed.

  The synthetic resin seal ring has been improved to meet all of the requirements for oil sealability, wear resistance and manufacturing efficiency, and one of them is polyether ether ketone resin (PEEK) that can be injection molded. There was a known seal ring.

  However, since the current material price of a seal ring made of PEEK is relatively high, a seal ring made of tetrafluoroethylene resin (PTFE) is more practical in terms of sliding conditions at low pressure and low speed. It is advantageous.

  By the way, PTFE seal ring is a material that cannot be injection-molded like PEEK. For example, a tube material manufactured by ram extrusion molding is used, its inner and outer diameters are turned, and the seal ring has a predetermined dimension in the width direction. It was manufactured into a seal ring shape by cutting (Patent Document 1).

  As a technique for increasing the production efficiency of the PTFE seal ring, automatic compression molding (auto molding) is known. Automolding is a method in which PTFE powder is weighed and then automatically filled into a mold, preliminarily molded by applying a compression force by a ram, taken out from the mold, and fired at a temperature equal to or higher than the melting point of PTFE. (Non-Patent Document 1).

  When molding PTFE seal rings, the cylindrical material that is compression-molded to the size of the inner and outer diameters of the seal ring is fired and the axial length is cut to the required width as the width of the ring. Therefore, the number of manufacturing steps is reduced accordingly, and the loss of material is also reduced.

Japanese Patent Laid-Open No. 10-225999 (refer to claim 1, FIG. 1)

Nikkan Kogyo Shimbun, published on September 15, 1988, “Industrial Materials”, Vol. 36, No. 13, pages 109 to 110

  However, in the molding of a PTFE seal ring, when a compression-molded cylindrical material is fired, a shape change or a dimensional change due to heat occurs, so that the dimensional accuracy cannot be increased until the turning process can be omitted.

  Furthermore, if the firing environment (equipment conditions, etc.) is different, the rate of dimensional change is also different, so it is not easy to predict or modify the dimensional change, and substantially finish the inner and outer diameter surfaces. Turning can no longer be necessary.

  Therefore, the object of the present invention is to solve the above-mentioned problems and improve the inner and outer diameters so that there is no shape change or dimensional change in a heating (firing) step or the like when producing a PTFE seal ring. It is to make a seal ring that does not require surface finishing turning, or to make it easy to predict or correct a dimensional change, or to make a seal ring having such advantages.

  In order to solve the above-described problem, in the present invention, in a seal ring made of a compression molded body mainly composed of tetrafluoroethylene resin powder, at least an inner peripheral surface of the inner peripheral surface and the outer peripheral surface of the seal ring is The seal ring is characterized by comprising a melt-molded layer formed of a mold having a finished dimension.

  In the seal ring of the present invention configured as described above, the inner peripheral surface of the compression molded body is formed of a melt-molded layer, and this inner peripheral surface is a finished surface with a dimensional accuracy as high as that obtained by injection molding. Yes, and this surface is formed with a finished-size mold, so that it has an inner diameter of the desired dimension, and it is not necessary to perform a turning process to ensure finishability, or a dimensional change after firing Becomes constant, and the correction width can be predicted and easily corrected to the finished dimension.

  That is, the seal ring made of tetrafluoroethylene resin does not require finishing turning of the inner and outer diameter surfaces, or becomes a seal ring that can be easily corrected to a constant product size.

  Further, in the invention relating to the manufacturing method of the seal ring, a molded body material made of tetrafluoroethylene resin is compression-molded into a cylindrical shape, and the inner peripheral surface of the cylindrical compression-molded body or the outer peripheral surface is finished together with the inner peripheral surface. A mold having a size is fitted, and then the mold is heated to a temperature higher than the melting point of the tetrafluoroethylene resin to form a melt-molded layer by the mold on the inner peripheral surface or inner / outer peripheral surface of the cylindrical compression molded body. This is a manufacturing method of the seal ring.

  In the manufacturing method of the seal ring of the present invention comprising the steps described above, a mold having a finished dimension is fitted on the inner peripheral surface or inner / outer peripheral surface of the cylindrical compression molded body, and the mold is tetrafluorinated in this state. By heating above the melting point of the ethylene resin, the inner and outer diameters of the cylindrical compression-molded body shrink when heated, and their surfaces melt, and the inner peripheral surface comes into contact with a mold of a predetermined dimension. Alternatively, the outer peripheral surface is injection-molded together with the inner peripheral surface, and is formed on a melt-molded surface with high dimensional accuracy.

  In order to manufacture a seal ring having a predetermined width, it is only necessary to cut a cylindrical compression molded body having a melt-molded layer on the outer peripheral surface together with the inner peripheral surface or the inner peripheral surface with a required width in the axial direction. Even if the peripheral surface and the outer peripheral surface are not turned, a seal ring having the finished surface can be efficiently manufactured.

  As described above, according to the present invention, in a seal ring made of a compression molded body mainly composed of tetrafluoroethylene resin powder, at least the inner peripheral surface of the inner peripheral surface and the outer peripheral surface is a mold having a finished size. Therefore, the surface of the compression-molded body is formed smoothly as if it was injection-molded, and is formed to a predetermined dimension with a mold having a finished dimension. Therefore, there is an advantage that a shape change and a dimensional change in a firing step necessary in a step of manufacturing a PTFE seal ring are eliminated, and a seal ring that does not require finishing turning of inner and outer diameter surfaces can be obtained.

  Further, in the manufacturing method of the seal ring of the present invention, by fitting a mold having a finished dimension on the inner peripheral surface of the cylindrical compression molded body, or on the inner and outer peripheral surfaces, and heating it above the melting point of the tetrafluoroethylene resin, The inner and outer surfaces of the cylindrical compression-molded body shrink when heated, so that the inner and outer diameters become smaller and melt, and the melted tetrafluoroethylene resin comes into contact with a mold of a predetermined dimension and is smooth with a predetermined dimension. The inner peripheral surface, or the inner / outer peripheral surface is formed as a melt-molded surface obtained by injection molding. Therefore, there is an advantage that there is no shape change or dimensional change in the heating (firing) step, and there is an advantage of a seal ring manufacturing method that does not require finish turning of the inner and outer diameter surfaces.

  As shown in FIG. 1 and FIG. 2, the seal ring A of the embodiment is composed of a cylindrical compression molded body 1 mainly composed of tetrafluoroethylene resin powder, and a cylindrical gold having a finished dimension on the inner peripheral surface thereof. The mold 2 is fitted, and then the entire compression molded product is heated to the melting point or higher of the tetrafluoroethylene resin and fired to form a melt molded layer by the mold 2 on the inner peripheral surface 1a of the cylindrical compression molded body 1. The cylindrical compression molded body 1 is cut in the axial direction with a required width.

  The composition of the seal ring of the present invention is mainly composed of tetrafluoroethylene resin powder, but the tetrafluoroethylene resin powder used in the present invention, that is, polytetrafluoroethylene (CAS 9002-84-0) powder, A commercially available molding powder or fine powder that has a very high melt viscosity even when heated to a melting point (327 ° C.) or higher, remains in a rubber-like elastic body, does not exhibit fluidity, and has the same particle size as possible by sizing. Can be used.

  The compression molded body mainly composed of tetrafluoroethylene resin powder is obtained by filling a PTFE powder in a cylindrical body molding die and performing compression molding as a preliminary molding by a conventional method.

The PTFE may be a PTFE composition in which a reinforcing material such as glass fiber, carbon fiber or whisker, or a solid lubricant such as graphite is blended. Incidentally, the molding cycle may be about 10 to 15 seconds as usual, and when the pressure holding time is within several seconds, the preforming pressure is increased to 1000 to 2000 kgf / cm ² . Further, it is preferable that the pressure holding time is increased corresponding to the thickness of the molded product, and the actual optimum molding pressure and cycle are determined by experimental means according to the size of the target seal ring.

  Further, the mold having a finished size used in the present invention is for molding at least the inner peripheral surface of the inner peripheral surface and the outer peripheral surface, and the inner peripheral surface molding die is a heat generated when the compression molded body is fired. It is a cylindrical (mandrel) -shaped mold or a cylindrical mold designed to have a diameter that allows close contact when contracted by contraction.

  In addition, the outer peripheral surface molding die need not be in particular in close contact with the compression molded body, and may be any housing having good thermal conductivity that enables uniform heating of the outer peripheral surface during firing. That is, the mold is preferably made of a material having good thermal conductivity and a low coefficient of thermal expansion. For example, a mold made of stainless steel is appropriate in consideration of rust prevention.

  When a seal ring is fired using such a mold, the inner and outer diameters as expected before firing can be obtained, and a seal ring that can be used as a finished surface without having to modify the inner and outer diameters by turning. Can be manufactured.

After about 70% by weight of tetrafluoroethylene resin [PTFE] and about 25% by weight of glass fiber are dry-mixed, this is put into a cylindrical seal ring compression mold and preformed at a pressure of 2000 kg / cm ^2. As shown in FIGS. 1 and 2, a stainless steel mold 2 is fitted to the inner peripheral surface of a cylindrical compression molded body 1 having an outer diameter of about 32 mm and a thickness of about 1.7 mm as a cylindrical mold having a finished size. Subsequently, the entire compression molded product was fired at 370 ° C., and a melt-molded layer by the mold 2 was formed on the surface layer portion of the inner peripheral surface 1 a of the cylindrical compression molded body 1.

  The maximum and minimum dimensions of the outer diameter, thickness, and height before and after firing of the seal ring (5 pieces, No. 1 to 5 in Table 1) of Example 1 were measured, and these results are shown in Table 1. Indicated.

  Further, a seal ring of Comparative Example 1 was manufactured in the same manner as in Example 1 except that the cylindrical mold 2 having a finished dimension was not fitted to the inner peripheral surface 1a, and this seal ring (5 pieces, Table 2) was manufactured. The maximum and minimum dimensions of outer diameter, thickness, and height before and after firing of No. 6 to 10) were measured, and the results are shown in Table 2.

As is clear from the results of Tables 1 and 2, Comparative Example 1 was deformed into an ellipse after firing, and could not be used as a seal ring.
On the other hand, in Example 1, the difference between the maximum part and the minimum part (change amount) in the outer diameter, the wall thickness, and the height is larger after baking than before baking. Since the change amount of 1 is substantially constant for Nos. 1 to 5, it can be said that the change amount after firing has become constant, so that dimensional adjustment (correction after molding) is facilitated, that is, matched to the product dimensions. Adjustments are now possible.

The perspective view which shows the cylindrical compression molding body which cuts a seal ring with the manufacturing method of embodiment. The perspective view which shows the state which fitted the metal mold | die to the internal peripheral surface of the cylindrical compression molding by the manufacturing method of embodiment. The perspective view which shows the use condition of a seal ring Enlarged sectional view of the main part showing the usage state of the seal ring

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylindrical compression molding 1a Inner peripheral surface 2 Mold 3 Casing 4 Shaft 5 Ring groove 6 One side surface 7 Other side surface A Seal ring A1 Inner peripheral surface A2 Outer peripheral surface

Claims (5)

In a seal ring composed of a compression molded body mainly composed of tetrafluoroethylene resin powder,
A seal ring characterized in that at least an inner peripheral surface of the inner peripheral surface and the outer peripheral surface of the seal ring is formed of a melt-molded layer formed of a mold having a finished size.   A molded body material made of tetrafluoroethylene resin is compression-molded into a cylindrical shape, a mold having a finished dimension is fitted to the inner peripheral surface of the cylindrical compression-molded body, and then the mold is made to have a melting point higher than that of the tetrafluoroethylene resin. A method for producing a seal ring, comprising: forming a melt-molded layer with a mold on the inner peripheral surface of the cylindrical compression-molded body by heating.   A method for manufacturing a seal ring, comprising: cutting a cylindrical compression-molded body having a melt-molded layer formed on an inner peripheral surface thereof according to claim 2 in a required width in an axial direction.   A molded body material made of tetrafluoroethylene resin is compression-molded into a cylindrical shape, and a mold having a finished dimension is fitted to the inner and outer peripheral surfaces of the cylindrical compression-molded body, and then the mold is tetrafluoroethylene resin. A method for producing a seal ring comprising heating to a melting point of or higher and forming a melt-molded layer with a mold on the inner and outer peripheral surfaces of the cylindrical compression molded body.   A method for manufacturing a seal ring, comprising: cutting a cylindrical compression-molded body having a melt-molded layer formed on the inner and outer peripheral surfaces thereof according to claim 4 in a required width in an axial direction.

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