JP2007314824A - Masking tool for thermal spraying - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a masking tool for thermal spraying capable of preventing a spray deposit film deposited on an inner surface of an opening of the masking tool for thermal spraying from dropping during the thermal spraying, and easily removing the deposited spray deposit film. <P>SOLUTION: The masking tool 1 for thermal spraying, which is provided on an end face 9 of a cylinder block 2 when depositing a spray deposit film 4 by a thermal spraying gun 7 on a wall surface 10 of a cylinder bore 3 of the cylinder block 2, and has a cylindrical opening 6 concentric with the cylinder bore 3, and masks deposition of the spray deposit film on the end face 9 of the cylinder block 2, is characterized in that a cylindrical opening inner surface 8, where the spray deposit film 5 is deposited by the thermal spraying gun 7, is made into a rugged surface. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a masking jig for thermal spraying, and in particular, when a thermal spray coating is formed on a wall surface of a cylinder bore of a cylinder block by a thermal spray gun, masking of the thermal spray coating on the end surface of the cylinder block is masked. It relates to a jig.

  A wall surface of a cylinder bore of a cylinder block of a vehicle engine or the like is protected by forming a film on the surface because wear resistance or the like is required. In general, a sprayed coating is formed on the wall surface of the cylinder bore by a metal spraying method. This metal spraying method is a method in which a metal or metal oxide spray material is heated to a molten state, and its fine powder or the like is sprayed onto a wall surface by a spray gun to form a spray coating. Generally, plasma spraying or arc spraying is employed as a heat source for the thermal spraying.

  FIG. 4 is a sectional view showing a method for forming a thermal spray coating by metal spraying on the wall surface of a cylinder bore of a conventional cylinder block. A spray coating 4 is continuously formed on the wall surface 10 of the cylinder bore 3 of the cylinder block 2 by the spray gun 7. The spray gun 7 is inserted into the cylinder bore 3 and continuously sprays the spray frame 11 on the wall surface 10 of the cylinder bore 3 while moving up and down in FIG.

  The end surface 9 of the cylinder bore 3 is generally machined. Therefore, the thermal spraying masking jig 1 is placed in close contact with the end surface 9 of the cylinder block 2 in order to prevent the thermal spray coating from adhering to the end surface 9 during thermal spraying. The thermal spraying masking jig 1 is coaxial with the cylinder bore 3 and has a cylindrical opening 6 having an inner diameter smaller than the inner diameter of the cylinder bore 3. Further, since the masking jig 1 for thermal spraying has a certain plate thickness, the inner surface 8 of the opening is exposed to the thermal spray gun 7 similarly to the wall surface 10 of the cylinder bore 3. At the time of thermal spraying, the thermal spray coating 5 adheres to the inner surface 8 of the opening of the masking jig 1 for thermal spraying.

  As the thermal spraying masking jig 1, carbon steel for machine structure is usually used, and the inner surface 8 of the opening is a smooth surface machined as shown in FIG. The thermal spray coating 5 adheres to and deposits on the inner surface 8 of the masking jig 1 for thermal spraying along the smooth surface. When the deposited thermal spray coating 5 has a certain thickness, it is desirable that the melted coating is cooled and condensed to be peeled off as an integrated annular coating. However, when sprayed onto a smooth surface, it is difficult to peel off as a unit. Therefore, the sprayed coating 5 adhered to the smooth surface is usually removed by machining such as a lathe or discarded together with the masking jig 1 for spraying.

  On the other hand, as the material for the thermal spraying masking jig 1, a special material such as carbon to which the thermal spray coating 5 is difficult to adhere may be used. However, since the adhesion force of the thermal spray coating 5 to the wall surface 10 is not sufficient, during the thermal spraying, the spray particles partially fall off from the opening inner surface 8 of the jig and adhere to the wall surface 10 of the cylinder bore 3, and defects due to sputtering are present. May occur.

  Patent Document 1 discloses a protective mask device that is attached to an engine block during thermal coating of a cylinder bore. Here, the protective mask device is divided into an annular outer portion and a hollow cylindrical insertion member, and the insertion member is made as a part with a limited number of uses and is usually discarded after 1 to 10 uses.

JP 2002-339053 A

  In the case of a conventional masking jig for thermal spraying that uses carbon steel for mechanical structures as the material and the inner surface of the opening is a smooth surface, the thermal spray coating can be easily removed because of its high adhesion to the material. Instead, it is removed by machining after use, or the masking jig itself is discarded. For this reason, the masking jig for thermal spraying requires labor and cost for its production and machining.

  On the other hand, if a material such as carbon that can be easily peeled off is used for the masking jig for thermal spraying, the sprayed particles partially fall off from the inner surface of the opening of the masking jig and adhere to the wall surface of the cylinder bore. There is a risk that defects due to sputtering occur.

  That is, it is difficult to adjust the adhesion strength of the thermal spraying masking jig to the inner surface of the opening by using the material of the thermal spraying masking jig to achieve both the adhesion of the thermal spray coating to the inner surface of the opening and the film removal property.

  The purpose of the present application is to provide a masking jig for thermal spraying that solves such problems and prevents the sprayed coating adhering to the inner surface of the opening of the masking jig for thermal spraying from falling off during thermal spraying and can easily remove the deposited thermal sprayed coating. Is to provide.

  In order to achieve the above object, the thermal spraying masking jig according to the present invention is provided on the end surface of the cylinder block when the thermal spray coating is formed on the wall surface of the cylinder bore of the cylinder block by the thermal spray gun, and is coaxial with the cylinder bore. In a masking jig for thermal spraying that has a cylindrical opening and masks the adhesion of the thermal spray coating to the end surface of the cylinder block, the inner surface of the cylindrical aperture to which the thermal spray coating is adhered by the thermal spray gun is an uneven surface. It is characterized by that.

  Moreover, it is preferable that the masking jig for thermal spraying has a surface roughness (Rz) of the inner surface of the opening within a range of about 20 μm to about 70 μm.

  Moreover, it is preferable that the masking jig | tool for thermal spraying consists of a substantially chevron-shaped groove | channel where the cross section of the inner surface of opening has an alternating continuous recessed part and convex part. Moreover, it is preferable that the masking jig | tool for thermal spraying consists of a substantially trapezoidal groove | channel where the cross section of the inner surface of opening has an alternating continuous recessed part and convex part.

  Moreover, it is preferable that the masking jig for thermal spraying is a plurality of annular grooves along the inner surface of the opening. Moreover, it is preferable that the groove | channel of the masking jig for thermal spraying is a helical groove | channel along the inner surface of opening.

  Further, the masking jig for thermal spraying is preferably provided with a spiral groove on the inner surface of the opening.

  With the above configuration, in the masking jig for thermal spraying, the cylindrical opening inner surface to which the thermal spray coating adheres becomes an uneven surface. As will be described later, compared to the case of spraying on a surface substantially perpendicular to the spray frame of the spray gun, there is a tendency that the adhesion force decreases when spraying on a surface having an angle with respect to the spray frame. That is, when the surface is sprayed onto the inner surface of the opening having an uneven surface, each surface is a surface having an angle with respect to the sprayed frame, so that the adhesion is reduced. Therefore, although the film having the surface deposited in an uneven shape is condensed by cooling, it can be more easily peeled off because the adhesion to the inner surface of the opening is lower than in the case of a smooth surface.

  Further, when a sprayed coating is sprayed on the uneven surface, the sprayed coating itself is also formed along the shape of the uneven surface. That is, a film having an uneven surface is formed. A three-dimensional effect to be described later occurs in the sprayed coating having an uneven surface, and the out-of-plane rigidity of the coating itself increases. Therefore, it is possible to prevent the sprayed coating from partially falling off during the thermal spraying as compared with the case of a smooth surface.

  Further, the above-described three-dimensional effect is also exhibited in a sprayed coating that has been condensed from a molten state due to a decrease in internal temperature to a solid state. That is, the coating having the surface deposited in an uneven shape has increased unity due to the three-dimensional effect, and can be easily peeled off as a lump.

  As described above, according to the masking jig for thermal spraying according to the present invention, it becomes possible to prevent the sprayed coating adhered to the inner surface of the opening of the masking jig for thermal spraying from falling off during thermal spraying. The film can be easily removed.

  Embodiments according to the present invention will be described below in detail with reference to the drawings.

(Schematic configuration of thermal spraying masking jig)
FIG. 1 is a sectional view showing a schematic configuration of a thermal spraying masking jig. FIG. 1 shows a cylinder bore 3 of the cylinder block 2, a thermal spraying masking jig 1, and a thermal spray gun 7. In addition, about the structure similar to FIG. 4 which shows a prior art, it shows with the same code | symbol.

  A cylinder block 2 such as a vehicle engine is mainly made of an aluminum alloy and has a cylinder bore 3. The wall surface 10 of the cylinder bore 3 is subjected to metal spraying for spraying a ferrous material having high wear resistance. Here, thermal spraying means that the thermal spray material is heated or melted or softened by using combustion or electrical energy ("melting"), accelerated into fine particles and collided with the substrate ("fired"), and flattened. It forms a film by solidifying and depositing the particles. As a heat source for thermal spraying, plasma thermal spraying and arc thermal spraying, which are electric sprays, are used, and a thermal spray coating 4 of about several tens of microns is formed. The thermal spray coating 4 is bonded to the substrate by a physical adhesion mechanism by mechanical engagement. The thermal spray coating 4 is a sponge-like structure having pores inside the film, and is effective in relieving the stress of the attached film, and is effective in preventing the film from cracking and peeling.

  On the wall surface 10 of the cylinder bore 3 of the cylinder block 2, as shown in FIG. 1, the thermal spray frame 11 is fired from the thermal spray gun 7 to form the thermal spray coating 4. The thermal spray frame 11 is radiated slightly downward with respect to the wall surface 10.

  The end surface 9 of the cylinder bore 3 is generally machined. Therefore, the thermal spraying masking jig 1 is placed in close contact with the end surface 9 of the cylinder block 2 in order to prevent the thermal spray coating from adhering to the end surface 9 during thermal spraying. This thermal spraying masking jig 1 is coaxial with the cylinder bore 3 and has an opening 6 having an inner diameter smaller than the inner diameter of the cylinder bore 3. The opening inner surface 8 of the thermal spraying masking jig 1 usually requires a width of about 10 mm due to the rigidity of the thermal spraying masking jig 1. Thus, since the masking jig 1 for thermal spraying has a certain plate thickness, the inner surface 8 of the opening is exposed to the thermal spray gun 7 in the same manner as the wall surface 10 of the cylinder bore 3. At the time of thermal spraying, the thermal spray coating 5 is also adhered to the inner surface 8 of the masking jig 1 for thermal spraying by the thermal spray gun 7. The thermal spraying masking jig 1 is generally made of mechanical structural carbon steel (S45C).

  In the present embodiment, as shown in FIG. 1, a groove 12 is formed along the opening inner surface 8 on the opening inner surface 8 of the thermal spraying masking jig 1. The groove 12 is a lathe surface formed by cutting, and the opening inner surface 8 becomes an uneven surface by the lathe surface. The surface roughness (surface roughness) of the inner surface 8 of the opening is preferably in the range of about 20 μm to about 70 μm in terms of ten-point average height (Rz).

  2A and 2B are partial sectional views showing another embodiment of the groove 12 in the opening inner surface 8 of the thermal spraying masking jig 1. 2A shows a case where the groove 12 is spiral, and FIG. 2B shows a case where the groove 12 is a plurality of annular grooves 17. The groove 12 in FIG. 2 (a) is formed by rolling on the opening inner surface 8 of the thermal spraying masking jig 1, which is carbon steel for machine structure (S45C). In the present embodiment, the groove 12 is a normal lathe surface, but may have a general thread shape. In this case, the inner angle formed by the two sides connecting the top and bottom of the thread is an angle of approximately 60 degrees, and the thread is in the shape of a substantially equilateral triangle. In addition, when the thermal spraying masking jig 1 is manufactured by casting or the like, the shape of the annular grooves 17 in the plurality of annular grooves 17 in FIG.

  The cross-sectional shape of the groove 12 may be, for example, a substantially mountain-shaped groove 12 in which concave portions and convex portions are alternately continuous, or a substantially trapezoidal groove 12 in which concave portions and convex portions are alternately continuous. Further, the irregular surface provided on the inner surface 8 of the masking jig 1 for thermal spraying may be of any shape as long as the irregular surface is formed on the entire cylindrical inner surface 8 of the opening. For example, it may be a continuous dimple surface such as the surface of a golf ball, or may be a surface where triangular pyramidal protrusions are continuous.

(Effect of uneven surface)
Hereinafter, three characteristics when the opening inner surface 8 of the thermal spraying masking jig 1 is an uneven surface will be described based on a difference from a smooth surface which is a conventional technique.

  The first feature is that the opening inner surface 8 is an uneven surface, so that the adhesion of the thermal spray coating 5 to the substrate is reduced as compared with a smooth surface. This is based on the phenomenon that the adhesion force is highest when the ground surface is perpendicular to the thermal spray frame 11 of the thermal spray gun 7, and the adhesion force decreases as the angle increases. That is, in the case of the conventional smooth surface, the thermal spraying is performed at an angle substantially perpendicular to the thermal spraying frame 11, whereas in the case of the uneven surface, the entire thermal spraying frame 11 is almost vertical. Although sprayed at an angle, each of the uneven surface portions is sprayed at an angle with respect to the spray frame 11. Therefore, as a whole, the adhesion is reduced as compared with the case of a smooth surface. This phenomenon, as described above, the bonding with the substrate by thermal spraying is "physical adhesion mechanism by mechanical meshing with the substrate", "acceleration of the thermal spray material in the form of fine particles to collide with the substrate, It is explained from “solidifying and depositing flattened particles”. That is, when thermal spraying is performed almost vertically on the substrate, the sprayed material in the form of fine particles is crushed flat enough to be mechanically engaged. On the other hand, when thermal spraying is performed at an angle, the larger the angle, the more difficult the fine particles are crushed flat, and the degree of mechanical engagement becomes weaker. Therefore, by making the opening inner surface 8 of the masking jig 1 for thermal spraying an uneven surface, the adhesion to the substrate is reduced as compared with the case of a smooth surface. The greater the degree of inclination of the surface, the larger it becomes.

  The second feature is that the inner surface 8 of the opening is an uneven surface, so that the out-of-plane rigidity of the thermal spray coating 5 itself is increased and is less likely to fall off locally as compared to a smooth surface. This is because the sprayed coating 5 itself sprayed on the base material becomes a concavo-convex plate along the shape of the concavo-convex surface of the inner surface 8 of the opening and rests against each other. In FIG. 3, the formed thermal spray coating 5 is shown as a plan view. FIG. 3 shows a case of an uneven surface by the groove 12 according to the present embodiment. FIG. 3A is a plan view of the groove 12, and FIG. 3B is a cross-sectional view taken along the line AA in FIG. However, the sprayed coating 5 sprayed on the inner surface 8 of the opening sprayed on the substrate has a cylindrical shape as a whole, but here it will be described with a simplified and partially developed plan view. The sprayed thermal spray coating 5 forms a so-called “folded plate” on the substrate. The folded plate refers to a three-dimensional shape formed by bending a flat plate, such as a folding screen. By making the flat plate in this way, as shown in FIG. 3, for example, a plurality of inclined surfaces 13, 14, 15 are configured continuously. For example, when the peeled portion 16 is generated in a part of the thermal spray coating 5 on the inclined surface 14 by this folded plate, the strip is peeled off by a plate having a continuous waveform (shown in the section AA) in the Y direction shown in the figure. The portion 16 is held, and adjacent inclined surfaces 13 and 15 lean against each other in the X direction shown in the drawing to hold the inclined surface 14 of the peeling portion 16. That is, this folded plate has an effect that the out-of-plane rigidity of the thermal spray coating 5 itself is increased and it is difficult to fall off locally.

  When the opening inner surface 8 is a smooth surface, the sprayed coating 5 sprayed onto the opening inner surface 8 is, as described above, “the sprayed coating 5 is a sponge-like structure having pores inside the film”, and thus falls off during spraying. There is a case. However, since the opening inner surface 8 is a folded plate, a plurality of inclined surfaces (for example, 13, 14, 15) are formed, and the sprayed coating 5 can be prevented from falling off due to the effect of the folded plate described above. This three-dimensional effect is not limited to the case of this folded plate, but the same effect occurs in the arch effect by configuring the arch-shaped plate, the shell effect by configuring the spherical plate, and the like. Therefore, these effects are collectively referred to as “stereoscopic effects”. That is, by forming an uneven surface on the inner surface 8 of the opening, this “three-dimensional effect” occurs, and the sprayed sprayed coating 5 itself increases the integral strength and the out-of-plane rigidity. This effect can prevent the sprayed coating 5 from falling off. Therefore, if the uneven surface on the inner surface 8 of the opening is uneven in the surface, this “steric effect” occurs.

  A third feature is that the deposited thermal spray coating 5 can be easily removed by making the opening inner surface 8 an uneven surface as compared with a smooth surface. That is, when the thermal spray coating 5 is deposited on the inner surface 8 of the opening, the thermal spray coating 5 is reduced in adhesion to the substrate due to shrinkage due to cooling, but the entire thermal spray coating 5 is integrated from the second feature. It becomes easy to peel from the substrate as a lump. In addition, from the first feature, the fact that the adhesion to the substrate is originally lower than that in the case of a smooth surface promotes this integral peeling.

(Example)
A masking jig 1 for thermal spraying having an inner diameter of 79 mm and a thickness of 10 mm is attached to the cylinder bore 3 of the cylinder block 2, and plasma spraying and arc spraying are performed. The ease of this was confirmed. The results are summarized in Table 1 below. “Example” in the table is a case where the groove 12 is provided spirally on the opening inner surface 8 according to the present embodiment, and “Comparative Example” is a conventional technique in which the opening inner surface 8 is a smooth surface. This is the case.

  In Examples 1, 3, and 4, which are the present embodiment, carbon steel for mechanical structure (S45C) is used as the thermal spraying masking jig 1, and the surface roughness (Rz) of the inner diameter of the thermal spraying masking jig 1 is changed. It was. Generally, when the surface roughness is increased, the adhesion strength increases, and when the surface roughness is decreased, the adhesion strength tends to decrease. As a result, spatter due to coating peeling from the thermal spraying masking jig 1 does not occur regardless of the surface roughness, and the ease of peeling from the thermal spraying masking jig 1 after spraying is easy. As a result.

  On the other hand, in the case of the comparative example which is a conventional technique, when aluminum (A7075) is used as the material of the masking jig 1 for thermal spraying (Comparative Example 2) or when carbon is used (Comparative Example 6), Sputtering due to film peeling from the masking jig 1 occurred. Moreover, when the surface roughness (Rz) of the inner diameter of the thermal spraying masking jig 1 was increased too much as in Comparative Example 7, it was difficult to separate the thermal spraying masking jig 1 from the thermal spraying. Furthermore, in the case of Comparative Example 5, it was difficult to remove part of the ease of peeling from the masking jig 1 for thermal spraying after thermal spraying.

It is sectional drawing which shows the schematic structure of one Embodiment of the masking jig for thermal spraying which concerns on this invention. It is a fragmentary sectional view which shows embodiment of the opening inner surface of the masking jig for thermal spraying. It is the top view and sectional drawing which show the shape of the sprayed coating at the time of forming an uneven surface with a groove | channel. It is sectional drawing which shows an example of the conventional masking jig for thermal spraying.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Masking jig for thermal spraying, 2 Cylinder block, 3 Cylinder bore, 4, 5 Thermal spray coating, 6 opening, 7 Thermal spray gun, 8 Opening inner surface, 9 End surface, 10 Wall surface, 11 Thermal spray frame, 12 Groove, 13, 14, 15 inclined surface, 16 peeling part, 17 annular groove.

Claims (7)

When the spray coating is formed on the wall of the cylinder bore of the cylinder block by a spray gun, the spray coating is provided on the end surface of the cylinder block and has a cylindrical opening coaxial with the cylinder bore, and is applied to the end surface of the cylinder block. In the masking jig for thermal spraying that masks the adhesion of
A masking jig for thermal spraying, wherein an inner surface of a cylindrical opening to which a thermal spray coating is adhered by a thermal spray gun is an uneven surface.   2. The masking jig for thermal spraying according to claim 1, wherein the surface roughness (Rz) of the inner surface of the opening is in the range of about 20 μm to about 70 μm.   3. The masking jig for thermal spraying according to claim 1 or 2, wherein the cross section of the inner surface of the opening is formed of a substantially chevron-shaped groove in which concave portions and convex portions are alternately continued. .   3. The masking jig for thermal spraying according to claim 1 or 2, wherein the cross section of the inner surface of the opening is formed of a substantially trapezoidal groove in which concave portions and convex portions are alternately continuous. .   The thermal spraying masking jig according to any one of claims 1 to 4, wherein the groove is a plurality of annular grooves along the inner surface of the opening.   The thermal spraying masking jig according to any one of claims 1 to 4, wherein the groove is a spiral groove along the inner surface of the opening.   7. The masking jig for thermal spraying according to claim 6, wherein a groove having a thread shape is spirally provided on an inner surface of the opening.

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