JP2005298884A - Method for adjusting porosity in thermal-sprayed film, and cylinder block of engine having porosity in inner face of cylinder bore adjusted with the method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily change a porosity in the surface of a thermal-sprayed film. <P>SOLUTION: This porosity-adjusting method includes sprouting a high-pressure fluid 9 onto the surface 1 of the thermal-sprayed film formed by thermal-spraying the droplets 3 of a metallic material for thermal spraying, thereby blowing a part of the droplets 3 which form the thermal-sprayed film, and forming fine pores in the surface 1 of the thermal-sprayed film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for adjusting the porosity of a sprayed coating surface on which a coating is formed by spraying droplets of a thermal spraying material, and a cylinder block of an engine in which the porosity of an inner surface of a cylinder bore is adjusted by this method.

  The thermal spray coating is obtained by melting the thermal spraying metal material and spraying it on the processing surface as droplets. One of the important aspects of the surface properties of such a thermal spray coating is porosity. The porosity is the area ratio occupied by the recesses (pores) due to the gaps between the droplets peculiar to the thermal spray coating on the surface of the thermal spray coating, and tends to be determined by the thermal spraying method, the thermal spray material, and the pre-processing method of the thermal spray coating surface. .

For example, Patent Document 1 below discloses a technique for cleaning a surface on which a thermal spray coating is formed using a high-pressure water spray nozzle as a pretreatment for forming the thermal spray coating.
JP 2003-117502 A

  If the three items of spraying method, spraying material, and pre-processing method that determine the porosity of the above-mentioned sprayed coating surface are determined by design requirements, equipment costs, etc., change the porosity, for example, There is a problem that it is not easy to achieve oil retention and lubricity.

  Accordingly, an object of the present invention is to make it easy to change the porosity of the surface of the sprayed coating.

  The present invention is directed to spraying a high pressure fluid onto the surface of a thermal spray coating formed by spraying a droplet of a thermal spray material, and blowing off a part of the droplet forming the thermal spray coating, thereby forming a microscopic surface on the surface of the thermal spray coating. The most important feature is the formation of open pores.

  According to the present invention, the area ratio (porosity) occupied by the pores corresponding to the gaps between the droplets can be easily changed by blowing off a part of the droplets after forming the sprayed coating.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a thermal spray coating porosity adjusting method according to an embodiment of the present invention. The sprayed coating surface 1 of the workpiece W shown in FIG. 1A has a sprayed coating formed by a spraying device (not shown). As shown in FIG. 1B, the spray coating surface 1 is sprayed with a spray gun (not shown) by melting a metal material for spraying so that the spray droplets 3 are flattened and overlapped. Is attached to the workpiece surface.

  Here, there is a porosity as an index representing the surface property of the sprayed coating surface 1, but the porosity is a recess formed by the gap 5 between the droplets 3 or a recess formed by dropping of the droplet 3 during spraying. It is shown by the ratio of the area which occupies in the thermal spray coating surface 1. That is, each above-mentioned recessed part is equivalent to a pore, and the area ratio which the pore of the thermal spray coating surface 1 occupies becomes a porosity.

  By appropriately setting such a porosity, for example, when a sliding surface such as the inner surface of a cylinder bore of an engine is used as a thermal spray coating, the effect on oil retention is great, while ensuring a pressure resistance, the area By increasing the rate, the slidability increases.

  And in this embodiment, the liquid which consists of water or oil, for example as a high-pressure fluid 9 is sprayed on the sprayed coating surface 1 with the high-pressure liquid injection gun 7, and a part of the droplet 3 is blown off and forcibly dropped. Adjust the porosity.

  Here, before performing the injection of the high-pressure fluid described above, processing as shown in FIG. 2 is performed. In other words, after processing the processed surface of the workpiece W into a predetermined shape in the previous process, in order to facilitate the adhesion of droplets to the processed surface, the surface is roughened by a shot blasting method, etc. To form the above-mentioned sprayed coating surface 1.

  Then, the sprayed coating surface 1 is machined and smoothed, and then the high-pressure fluid 9 is sprayed onto the sprayed coating surface 1 by the high-pressure liquid spray gun 7, and then the workpiece W is conveyed to the next step. The injection of the high-pressure fluid 9 here also serves to clean the sprayed coating surface 1 after machining.

  Further, it is desirable that the spray angle of the high-pressure fluid 9 with respect to the sprayed coating surface 1 is vertical. This is because if the spray is performed while being inclined with respect to the sprayed coating surface 1, a stable inertia force of the high-pressure fluid 9 cannot be obtained, and the droplet 3 is difficult to drop off.

  In this way, by spraying the high pressure fluid 9 on the sprayed coating surface 1, a part of the droplet 3 is dropped off by forcibly blowing off a small droplet 3 or a part of the large droplet 3 on the sprayed coating surface 1. And adjust the porosity. In this case, the porosity is adjusted by spraying the high-pressure fluid 9 as appropriate after spraying, even if the spraying method, spraying material, and pre-processing method are determined by design requirements and equipment costs. It can be done easily.

  FIG. 3 is a graph showing the relationship between the discharge pressure of the high-pressure fluid 9 and the porosity (%). This shows that the porosity increases as the discharge pressure increases to 20 MPa, 30 MPa, and 40 MPa. 4 (a), (b), and (c) show the state of the sprayed coating surface 1 after the high pressure fluid 9 is jetted by each discharge pressure. It can be seen that the higher the pressure, the more pores and the higher the porosity.

  Further, in particular, when the high-pressure fluid 9 is sprayed after the sprayed coating surface 1 is machined and smoothed as described above, a phenomenon occurs in which part of the periphery of the pores of the sprayed coating swells. Therefore, by finishing the sprayed coating surface 1 after the high-pressure fluid injection, it is possible to remove the swelled portion and make the sprayed coating surface 1 smooth.

  FIG. 5 is a schematic diagram in which the porosity is adjusted by spraying high-pressure fluid using the cylinder bore inner surface 9 of the cylinder block of the engine as the spray coating surface. In FIG. 5, the upper part is near the top dead center of the piston, and the lower part is near the bottom dead center. In this case, increase the porosity by increasing the discharge pressure of the high-pressure fluid near the top dead center, and increase the porosity by reducing the discharge pressure of the high-pressure fluid to the lowest part near the top dead center and the vicinity of the bottom dead center. , And the vicinity of the bottom dead center is set to an intermediate discharge pressure so that the porosity is intermediate between the vicinity of the top dead center and the vicinity of the bottom dead center.

  By increasing the porosity near the top dead center and near the bottom dead center from the middle part, the oil retaining property of the cylinder bore inner surface 9 is enhanced, and in particular, the highest porosity near the top dead center where high oil retaining property is required. Thus, the lubricity of the cylinder bore inner surface 9 is improved, and problems such as seizure can be prevented.

  According to the present invention, after spraying a part of the droplets forming the sprayed coating, the surface of the sprayed coating is finished, so that the area around the pores of the sprayed coating is removed to smooth the surface of the sprayed coating. can do.

  After machining the surface of the thermal spray coating, high pressure liquid is sprayed onto the surface of the thermal spray coating to blow off some of the droplets, and then the surface of the thermal spray coating is finished, so cleaning after machining can be performed with the high pressure liquid. At the same time, the surface of the thermal spray coating can be smoothed by removing the swelled portion around the pores of the thermal spray coating.

  Since the area ratio occupied by the pores on the surface of the thermal spray coating is changed depending on the site on the surface of the thermal spray coating, the area ratio occupied by the pores can be appropriately obtained as necessary.

  The surface of the sprayed coating is the inner surface of the cylinder bore of the engine, and the area ratio occupied by the pores near the top dead center on the inner surface of the cylinder bore is higher than that of other parts. be able to.

  By changing the discharge pressure of the high-pressure fluid, the area ratio occupied by the pores on the surface of the thermal spray coating is changed. Therefore, the area ratio occupied by the pores can be easily changed with respect to the same thermal spray coating surface. .

1 shows a method for adjusting the porosity of a sprayed coating surface according to an embodiment of the present invention, wherein (a) is an operation explanatory diagram showing a state in which a high-pressure fluid is sprayed on the surface of the sprayed coating, and (b) is a droplet on the surface of the sprayed coating. It is a schematic diagram which expands and shows. It is a processing-process figure concerning one Embodiment of this invention. It is a graph which shows the relationship between the discharge pressure of a high pressure fluid, and a porosity. It is a shape figure of the thermal spray coating surface after injecting a high pressure fluid by each discharge pressure. It is the schematic diagram which adjusted the porosity by spraying a high pressure fluid by making the cylinder bore inner surface of an engine into the sprayed coating surface.

Explanation of symbols

1 Sprayed coating surface 3 Droplet 5 Gap between droplets (pores)
9 Cylinder bore inner surface

Claims (7)

  By spraying a high-pressure fluid onto the surface of the sprayed coating formed by spraying the droplets of the thermal spraying material, a small pore is formed on the surface of the sprayed coating by blowing off a part of the droplet forming the sprayed coating. A method for adjusting the porosity of a sprayed coating, characterized by:   The method for adjusting the porosity of a sprayed coating according to claim 1, wherein the surface of the sprayed coating is finished after a part of the droplet forming the sprayed coating is blown off.   3. The thermal spraying according to claim 2, wherein after machining the surface of the thermal spray coating, a high-pressure liquid is sprayed onto the surface of the thermal spray coating to blow off a part of the droplets, and then the surface of the thermal spray coating is finished. Method for adjusting the film porosity.   The method for adjusting the porosity of a sprayed coating according to any one of claims 1 to 3, wherein an area ratio occupied by pores on the surface of the sprayed coating is changed depending on a portion of the surface of the sprayed coating.   5. The thermal spray coating porosity adjusting method according to claim 4, wherein the thermal spray coating surface is an inner surface of a cylinder bore of an engine, and the area ratio occupied by the pores in the vicinity of the top dead center on the inner surface of the cylinder bore is made higher than other portions. .   6. The thermal spray coating porosity adjusting method according to claim 4, wherein the area ratio occupied by pores on the surface of the thermal spray coating is changed by changing a discharge pressure of the high-pressure fluid.   A cylinder block for an engine, wherein the area ratio occupied by pores on the surface of the sprayed coating is changed by the method for adjusting the porosity of the sprayed coating according to claim 5.

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