JP2006322411A - Piston for compressor and method for coating piston - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of coating a piston capable of coating only necessary section and forming high quality coating layer with improved yield of material by using coating material having ordinary viscosity of 500-1000 mPa s, and the piston coated by the method. <P>SOLUTION: In the method of coating the piston, lubricating coating is formed by applying coating material containing fluorine resin and binder on an outer circumference of a piston head part of a compressor by using a film coating means and the piston is applied with the coating. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a piston for a compressor and a coating method for the piston, and in particular, a film coating means is used to apply a coating material mainly composed of a fluororesin and a binder to the outer peripheral surface of the piston head of the compressor. The present invention relates to a method for coating a piston.

  Piston compressor pistons used in automobile air conditioning systems, etc., do not have a piston ring, and are of a type that slides with the outer peripheral surface of a cylindrical piston head in direct contact with the inner peripheral surface of the cylinder bore. Exists. In this type of compressor, the outer surface of the piston head is mainly placed on the outer surface of the piston head in order to ensure sliding characteristics, sealing properties, wear resistance, etc. between the outer surface of the piston and the inner surface of the cylinder bore. A coating layer (lubricating film) mainly composed of a fluororesin and a binder is provided.

  Examples of a coating method suitable for forming such a coating layer include a spray coating method, a screen printing method (Japanese Patent Laid-Open Nos. 10-26081 and 2000-161224), and a roll coating method (Japanese Patent Laid-Open No. 2000-161224). 2000-170657 gazette, Unexamined-Japanese-Patent No. 2002-48057), etc. are known.

  However, in the case of the spray coating method, the coating is applied to a part that is not necessary for coating, the coating material is scattered from the spray nozzle, the thickness of the coating layer is uneven, or the coating material is scattered around the periphery other than the piston. As a result, there is a problem that the yield is deteriorated.

  In the case of the spray coating method, in order to smoothly spray the coating material from the spray nozzle, it is necessary to use a coating material having a low viscosity of several hundred mPa · s. For this reason, thick coating or coating is applied. It was difficult to form a coating layer having a uniform thickness due to material sagging later.

On the other hand, in the case of the screen printing method and the roll coating method, although the drawbacks due to the spray coating method are considerably eliminated, in this case, the viscosity of the coating material used is adjusted to a high viscosity of about 5000 to 150,000 mPa · s. For this reason, thin coating is difficult, screen clogging and piping clogging are likely to occur, and cleaning during switching of coating materials is difficult. It was.
Japanese Patent Laid-Open No. 10-26081 JP 2000-161224 A JP 2000-170657 A JP 2002-48057 A

  The present invention develops a new coating method in place of the conventional spray coating method, screen printing method and roll coating method in the coating process on the piston head of the compressor, thereby providing an essential feature of these coating methods. The purpose is to solve the problem.

  That is, the object of the present invention is to enable coating only on necessary portions of the piston of the compressor from the viewpoint of improving the yield of the coating material, and from the viewpoint of homogenizing the coating layer and improving workability. Is to provide a coating method for a piston that allows a coating material having a general viscosity of 500 to 1000 mPa · s to be used.

  As a result of intensive studies to solve these problems, the present inventors have recently been used when coating small objects such as electronic substrates in place of the spray coating method, screen printing method and roll coating method. The present inventors have found that a film coating means using a small liquid discharge nozzle for an extremely small curtain coater can be applied to the coating of a piston, and completed the present invention.

  That is, according to the present invention, the coating material is not ejected into the piston as droplets, but the coating material having a viscosity of 500 to 1000 mPa · s is discharged as a liquid film using a special dedicated nozzle. The coating is applied while rotating the head portion of the piston at a predetermined speed, thereby eliminating the coating on unnecessary portions and forming a lubricating film composed of a uniform coating layer.

  The present invention utilizes a film coating means for forming a curtain flow, and the gist of the present invention is that (1) a fluororesin is formed on the outer peripheral surface of the piston head of the compressor using the film coating means. And a coating method on the piston in which a coating material mainly composed of a binder is applied and a lubricating film is formed. (2) At the end of the application, the supply of the coating material to the film coating means is instantaneously cut. (3) The coating method of (1) or (2), wherein the coating material has a viscosity of 500 to 1000 mPa · s. (4) ) The piston is in the coating method of any one of (1) to (3), which is made of metal.

  Another aspect of the present invention is that (5) a film coating means is used to apply a coating material mainly composed of a fluororesin and a binder to the outer peripheral surface of the piston head of the compressor, and a lubricating film (6) The lubricating coating is on the piston of (5) that has been polished, and (7) the piston is made of metal (5) or (6) On the piston.

  According to the present invention, by applying the film coating means using the small liquid discharge nozzle for the ultra-small curtain coater to the coating of the piston, it is possible to eliminate the coating to the part not necessary for the coating, and the coating material This prevents scattering of the coating layer from causing unevenness in the thickness of the coating layer and worsening the yield.

  According to the present invention, since a coating material having a general viscosity of 500 to 1000 mPa · s can be used, a high-quality coating layer having a uniform thickness that hardly causes material sag is formed. Is possible. Further, since the clogging of the coating material supply pipe is prevented and the cleaning property is improved, the workability in the coating process is further improved.

  In addition, according to the present invention, the film coating means can be installed in a very compact manner, and it is possible to quickly cope with a change in the shape of the piston applied by changing the nozzle arrangement or the like. The film coating process can be inlined in the assembly line, and as a result, the yield of the product can be improved.

  The present invention is a coating method for a piston in which a coating material mainly composed of a fluororesin and a binder is applied to the outer peripheral surface of a piston using a film coating means, and a lubricating film is formed. It is suitable for coating on the piston head of a compressor having a part that does not require coating. The present invention also provides a piston having a lubricating film formed using the film coating means.

  Examples according to one embodiment of the present invention will be described below, but the present invention is not limited to these examples, and various modifications can be made without departing from the technical idea of the present invention. is there.

  FIG. 1 shows a piston 1 of a compressor coated according to the invention. The piston 1 is composed of a cylindrical head portion 10 and a body portion 11 having an opening formed integrally therewith, and is generally made of an aluminum alloy which is a kind of metal material. The head 10 is provided with an annular groove 12 that functions to fit a piston ring, or to retain lubricating oil when the piston ring is not fitted.

  Further, a coating layer 13 is formed on the outer peripheral surface of the head 10, and sliding characteristics, sealing properties, and abrasion resistance between the outer peripheral surface of the head 10 and the inner peripheral surface (not shown) of the cylinder bore are provided. It works to ensure wear. The coating layer 13 in this embodiment is coated with polytetrafluoroethylene, which is a kind of fluororesin, and the use of the fluororesin is particularly in the outer peripheral surface of the head 10 of the piston 1 and the cylinder bore. It is useful for preventing seizure of metals between the peripheral surface and making the gap between the two as small as possible. The material of the piston 1 and the coating material of the coating layer 13 are not limited to those described above, and other materials may be used.

  FIG. 2 shows an intermediate product 2 which is produced when the piston 1 is manufactured, from which two pistons 1 are manufactured. Therefore, as shown in FIG. 2, the intermediate product 2 includes the head portions 10 a and 10 b of the piston 1 at the coaxial end portions, and the body portions 11 a and 11 b integrated with them are opposite to each other. It is connected to. Further, projecting portions 20a and 20b for rotating the intermediate product 2 during coating and machining are provided on the end faces of the heads 10a and 10b. The intermediate product 2 is rotated in a centered state by fixing the protruding portions 20a and 20b at both ends to a work holder (not shown) of a rotating device.

  Next, a method for forming a coating layer on the outer peripheral surfaces of the heads 10a and 10b of the intermediate product 2 will be described. 3 and 4 schematically show film coating means 3 for applying a coating material mainly composed of a fluororesin and a binder to the outer peripheral surfaces of the heads 10a and 10b of the intermediate product 2 to form a lubricating film. It is shown.

  In the coating material, for example, a binder such as polyamideimide, a solvent such as PTFE, N-methylpyrrolidone, and a filler are included, and the viscosity of the coating material is adjusted within a range of 500 to 1000 mPa · s. . This viscosity is determined by adjusting the mixing ratio of the solvent. Further, by adjusting the viscosity of the coating material within the above range, the film coating means can be coated with almost no material sagging, and the pipes and nozzles are not clogged.

  The film coating means 3 includes a rotation device (not shown) for rotating the intermediate product 2 and a film coating device 4. The rotation device includes a work holder for rotatably holding the intermediate product 2 at a predetermined position, and a drive device for rotating the work holder about its rotation axis.

  As shown in FIG. 5, the coating apparatus 4 includes a tank 40 for storing the coating material, a pump 41 for supplying the coating material sucked from the tank to the nozzle, and a heater 42 for adjusting the temperature of the coating material. , A filter 43 for removing foreign matters mixed in the coating material and lumps formed in the coating material, a nozzle 44 for applying the coating material to the piston in a liquid film form, and these components are liquid The supply pipe 45 includes an opening / closing valve 47 for instantaneously stopping or restarting the supply of the coating material. Depending on the properties of the coating material used, accessories such as the heater 42 and the filter 43 and the return pipe 46 may be omitted.

  In order to apply the coating material to the intermediate product 2 using the film coating means 3, first, the intermediate product 2 is rotated at a predetermined speed in the direction of the arrow by a driving device (see FIG. 4). Next, by starting the pump 41 and opening the opening / closing valve 47 in the coating material supply pipe 45, the coating material is spread from the nozzle 44 into a liquid film and applied to the heads 10 a and 10 b of the intermediate product 2. . The thickness of the coating layer applied at this time is adjusted by controlling the supply amount of the coating material supplied from the nozzle 44 and the rotational speed of the intermediate product 2.

  As the nozzle 44, for example, a commercially available small liquid discharge nozzle for a very small curtain coater can be used. Since such a type of nozzle is small, its appearance is similar to an air spray nozzle. Specifically, the nozzle hole has a feature that it has a slit shape or eye shape shape with a width of several millimeters.

  The nozzles 44 are arranged so as to be parallel to the rotation axis of the intermediate product 2, and when there is an unnecessary portion such as a groove on the outer peripheral surface of the head on one side, as shown in FIG. By arranging the plurality of nozzles 44 immediately above the head on one side, it is possible to accurately coat the coated portion and the non-coated portion without masking.

  As shown in FIG. 4, the nozzle 44 is disposed immediately above the intermediate product 2 so as to be substantially perpendicular to the outer peripheral surface thereof. Depending on the viscosity of the coating material, the coating material may be disposed on the outer periphery of the heads 10a and 10b. The discharge angle of the nozzle 44 can also be arranged at an angle in the rotation direction with respect to the outer peripheral surface of the intermediate product 2 so that the liquid does not return from the surface in the direction opposite to the rotation direction.

  According to the coating method using the film coating means 3 according to the present invention, even a relatively low viscosity coating material can be coated in a wide range of thickness from thin coating to thick coating such as 20 to 80 μm.

  In addition, a plurality of nozzles 44 are arranged on the top of the object to be coated, and each nozzle 44 can be translated with respect to the rotation axis of the object to be coated, and the distance between the objects to be coated can be adjusted. By using this method, line switching can be performed quickly and easily even when the coating range of the object to be coated is different, especially compared to the case of using a roll coater. Work time can be greatly reduced. As a result, the film coating process can be in-lined in the piston assembly line, and the yield of products to be coated can be further improved.

  The coating is completed by closing the opening / closing valve 47 in the supply pipe 45 when the outer peripheral surfaces of the heads 10a, 10b of the intermediate product 2 are rotated once. Of course, depending on the thickness of the coating layer required for the intermediate product 2, the rotation may be terminated by closing the opening / closing valve 47 after a plurality of rotations. Since the supply of the coating material to the nozzle using the opening / closing valve 47 is instantaneously stopped, unnecessary use of the coating material is prevented during application, and the number of times of application (the number of layers of the coating layer) is spread over the entire circumference. It is possible to achieve a uniform thickness of the applied coating layer.

  In addition, when it is desired to form a coating layer with a stricter thickness, the control of the thickness of the coating layer can be made more strict by providing a doctor knife or an air knife downstream of the coating position by the nozzle 44.

  Further, when it is desired to further improve the response of stopping the supply of the coating material to the nozzle 44, the nozzle 44 can be instantaneously opened and closed to shut off the liquid film formed between the nozzle 44 and the object to be coated. A shielding plate or the like can also be provided.

  When the coating is finished, the intermediate product 2 is taken out from the work holder, the solvent in the coating material is removed in the drying process and baked in the baking process. On the outer peripheral surface of the heads 10a and 10b of the intermediate product 2, for example, A coating layer having a thickness of 20 to 80 μm is formed.

  Further, when it is desired to further improve the accuracy of the thickness of the coating layer formed on the outer peripheral surfaces of the heads 10a and 10b of the intermediate product 2, or when slight unevenness occurs in the thickness, the thickness of the coating layer is corrected. Therefore, a polishing process is performed after the baking process.

  As described above, according to the present invention, by applying the film coating means using the small liquid discharge nozzle for the ultra-small curtain coater to the coating of the piston, the coating layer having a relatively wide thickness of 20 to 80 μm can be obtained. It is possible to form the coating layer, and it is possible to prevent the coating material from being coated to a portion that is not necessary for coating. Further, it is possible to prevent the coating layer from being scattered and the yield from being deteriorated due to scattering of the coating material.

  According to the present invention, since a coating material having a general viscosity of 500 to 1000 mPa · s can be used, a high-quality coating layer having a uniform thickness that hardly causes material sag is formed. Is possible. In addition, clogging of the coating material supply pipe and the like is prevented and the cleaning performance is improved, so that the workability in the coating process is further improved.

  In addition, according to the present invention, the film coating means can be installed in a very compact manner, and it is possible to quickly cope with the change in the coating object to be applied by changing the nozzle arrangement, etc. In addition, the film coating process can be inlined, and as a result, the yield of the product can be improved.

1 is a front view showing a piston of a compressor coated with a film according to the present invention. FIG. It is a front view which shows the intermediate product for manufacturing 2 pairs of pistons shown by FIG. It is a front view which shows typically the film coating means used for this invention. It is a side view which shows the film coating means shown by FIG. It is a conceptual diagram which shows the structure of a film coating apparatus typically.

Claims (7)

  A coating method for a piston, in which a coating material mainly composed of a fluororesin and a binder is applied to the outer peripheral surface of a piston head of a compressor using a film coating means to form a lubricating film.   2. The method of coating a piston according to claim 1, wherein at the end of application, the supply of the coating material to the film coating means is instantaneously cut.   The coating method according to claim 1, wherein the coating material has a viscosity of 500 to 1000 mPa · s.   The coating method according to claim 1, wherein the piston is made of metal.   A piston in which a lubricant film is formed by applying a coating material mainly composed of a fluororesin and a binder to the outer peripheral surface of a piston head of a compressor using film coating means.   The piston according to claim 5, wherein the lubricating film is polished.   The piston according to claim 5 or 6, wherein the piston is made of metal.

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