WO2015068519A1 - Spray coating forming device and spray coating forming method - Google Patents

Abstract

This spray coating forming device is provided with: a cylinder block at which a plurality of cylinder bores are formed; a spray gun that forms a spray coating by blowing droplets of molten metal at the inner surfaces of the plurality of cylinder bores; and a cooler that locally cools the inner walls of the cylinder bore that is being sprayed among the plurality of cylinder bores when spraying by means of the spray gun. By means of the spray coating forming device, it is possible to effectively prevent production defects (cracks and deformation) of the cylinder block stemming from the spraying.

Description

Thermal spray coating forming apparatus and thermal spray coating forming method

The present invention relates to a thermal spray coating apparatus [an apparatus forming aspray coating] that forms a spray coating on the inner surface of a cylinder bore and a spray coating formation method [a method for す る forming aspray coating].

An internal combustion engine such as an automobile has a cylinder block in which a cylinder bore is formed. The following Patent Document 1 discloses a sprayed bore. The thermal spray bore is a cylinder bore in which a metal or ceramic film is formed on the inner surface by thermal spraying. After thermal spraying, the coating surface is smoothed by finishing (honing), and the sliding surface of the piston ring is formed. Before spraying, in order to improve the adhesion of the coating, the inner surface of the cylinder bore is subjected to special machining or roughening treatment by shot blasting.

Demand for sprayed bores is high, and the number of models adopted tends to be expanded. Along with such a trend, there is a demand for further improvement of the film adhesion, shortening of the roughening time, reduction of tool costs for the roughening treatment, and the like. The film adhesion is improved by increasing the output of the thermal sprayer.

Japanese Unexamined Patent Publication No. 2009-155720

In order to prevent surplus particles [surplus particles], soot [soot], etc. from entering the sprayed coating, fluid around the cylinder block (for example, gas such as air, hereinafter described as air) is sucked during spraying. Dust collection is done by doing. Dust collection is performed by sucking air with an exhaust device arranged in the thermal spray equipment. The outer surface of the cylinder block is cooled by forced convection formed around the cylinder block by suction. As a result, the inside of the cylinder bore becomes high temperature due to the thermal spraying heat, while the outer surface of the cylinder block becomes low temperature, and thermal stress due to this temperature difference is generated. If the thermal stress exceeds the tensile strength of the cylinder block material, the cylinder block may crack.

An object of the present invention is to provide a thermal spray coating forming apparatus and a thermal spray coating forming method capable of preventing manufacturing defects (cracking and deformation) of a cylinder block due to thermal spraying.

A first feature of the present invention is a thermal spray coating forming apparatus, in which a thermal spray coating is formed by spraying molten metal droplets onto the inner surfaces of the cylinder block and a plurality of cylinder bores. There is provided a spray coating apparatus including a gun and a cooler that locally cools an inner wall of a sprayed cylinder bore among the plurality of cylinder bores during spraying by the spray gun.

A second feature of the present invention is that a natural metal convection is generated around the cylinder block, and molten metal droplets are sprayed from a spray gun inserted into a plurality of cylinder bores formed in the cylinder block. A sprayed coating forming method for spraying each inner surface to form a sprayed coating, wherein the inner wall of the sprayed cylinder bore is locally cooled by forced convection when sprayed by the spray gun, There is provided a method for forming a sprayed coating, wherein an internal temperature of the sprayed cylinder bore is made equal to a temperature outside the cylinder block.

It is a perspective view which shows the thermal spray coating formation apparatus which concerns on embodiment. It is explanatory drawing which shows the exhaust flow in the said thermal spray coating formation apparatus. It is a perspective view which shows insertion to the cylinder bore of a thermal spray gun. It is sectional drawing which shows formation of the thermal spray coating on the inner surface of a cylinder bore. It is sectional drawing of 1st Embodiment which attracts | sucks the air inside a cylinder bore below with a cooler, and cools the inner wall of a cylinder bore. (A) is a characteristic line diagram showing the relationship between the heat transfer coefficient and the thermal stress on the inner surface of the cylinder bore, and (B) is a characteristic line showing the relationship between the heat transfer coefficient and the thermal stress on the outer surface of the cylinder block. FIG. It is a perspective view of 2nd Embodiment which supplies air to a water jacket with a cooler and cools the inner wall of a cylinder bore. It is sectional drawing of 3rd Embodiment which supplies air to a water jacket using the masking as a cooler, and cools the inner wall of a cylinder bore. It is a perspective view of 4th Embodiment which makes the cooling metal as a cooler contact a cylinder bore upper end, and cools the inside of a cylinder bore. It is a perspective view of 5th Embodiment which supplies air to a water jacket using a cooling metal and cools the inner wall of a cylinder bore. It is a graph which shows the relationship between the temperature and 20% yield strength in an aluminum cylinder block.

Hereinafter, embodiments of a thermal spray coating forming apparatus (method) will be described with reference to the drawings. As shown in FIG. 1, the spray coating apparatus includes a spray gun 2 for forming a spray coating on the inner surface of each cylinder bore 6 (6A to 6D) of the cylinder block 1, and a cylinder block 1 for collecting dust. And a housing 3 for housing.

The housing 3 is formed in a rectangular box shape. In addition, the shape of the housing | casing 3 is not limited to the shape of FIG. An air supply duct 4 is provided on the left side surface (the left side surface in FIG. 1) 3 a of the housing 3. Further, exhaust ducts 5 are respectively provided on the right side surface 3b, the upper surface 3c, and the lower surface 3d of the housing 3.

A fluid (for example, a gas such as air, hereinafter described as air) is supplied from the air supply duct 4 to the inside of the housing 3. Air in the housing 3 is discharged from the exhaust duct 5 to the outside of the housing 3. From the exhaust duct 5, together with the discharged air, surplus particles formed from the droplets 11 for the spray coating 12, soot, and the droplets 11 scattered without being spray coating 12 are collected (dust collection). .

The air supplied from the air supply duct 4 to the inside of the housing 3 flows as indicated by arrows in FIG. In addition to flowing around the cylinder block 1, air also flows inside the cylinder bore 6 (6A to 6D). In the case of the cylinder block 1 of the in-line 4-cylinder engine, the first cylinder bore 6A, the second cylinder bore 6B, the third cylinder bore 6C, and the fourth cylinder bore 6D are sequentially arranged from one end.

The thermal spray gun 2 is an arc spray gun as shown in FIGS. In the thermal spray gun 2, the metal wire 7 as the positive electrode and the metal wire 8 as the negative electrode are continuously sent out so as to be close to each other at the tip of the nozzle to generate an arc 10, and an atomization gas 9 is generated. Supplied. The wires 7 and 8 are melted by the arc 10 to form droplets 11. The droplet 11 adheres to the inner surface 6a of the cylinder bore 6 and a sprayed coating 12 is formed.

It has been found that the adhesion of the thermal spray coating 12 formed on the inner surface 6a of the cylinder bore 6 depends on the preheating temperature for heating the cylinder block 1 before thermal spraying. When the preheating temperature of the cylinder block 1 is increased, the adhesion of the thermal spray coating 12 is also improved.

In the thermal spray coating forming apparatus of the present embodiment, the thermal spray output of the thermal spray gun 2 is also increased in order to improve the adhesion of the thermal spray coating 12. For this reason, the amount of heat input to the cylinder block 1 increases. On the other hand, as described above, dust collection is performed to prevent defects in the thermal spray coating 12 (exhaust of air in the housing 3). As a result, the inside of the cylinder bore 6 becomes high temperature due to the increase in spraying output, while the outer surface of the cylinder block 1 is cooled by exhaust. In the present embodiment, manufacturing defects (cracks and deformations) of the cylinder block 1 due to thermal stress resulting from this temperature difference are prevented.

Specifically, the thermal spray coating forming apparatus of the present embodiment includes a cooler that locally cools the inner wall of the cylinder bore 6 during thermal spraying by the thermal spray gun 2. As the cooler, for example, a local exhaust device [local ventilation device] or a cooler [local cooling device] that sucks and exhausts soot, surplus particles or splashed droplets generated during thermal spraying is used as the cooler.

The cooler shown in FIG. 5 is the local exhaust device 13 (first embodiment). The local exhaust device 13 is disposed at least at the lower end of the sprayed cylinder bore 6. The local exhaust device 13 sucks the air in the cylinder bore 6 downward. By this exhaust, the inner wall of the cylinder bore 6 is locally cooled. Exhaust by the local exhaust device 13 flows as indicated by an arrow 17 in FIG. When the local cooling device is used as a cooler, the inner wall of the cylinder bore 6 is forcibly cooled by the cold air generated by the local cooling device.

Next, the process for forming the thermal spray coating 12 will be described. First, the cylinder block 1 is disposed in the housing 3, and the cylinder block 1 is preheated with a heater or the like. Then, the inside of the housing 3 is exhausted by supplying air from the air supply duct 4 and exhausting from the exhaust duct 5. As a result, an air flow as shown in FIG. 2 is generated. At this time, the periphery of the cylinder block 1 is natural convection.

Next, the thermal spray gun 2 is inserted into the cylinder bore 6 from the cylinder head mounting surface side, and thermal spraying is started. In the thermal spraying, metal droplets 11 ejected from the thermal spray gun 2 are sprayed onto the inner surface 6 a of the cylinder bore 6. In addition, in order to improve the contact | adhesion power of the sprayed coating 12, the roughening process is performed to the inner surface 6a previously. During the thermal spraying, the local exhaust device 13 disposed at the lower end of the sprayed cylinder bore 6A is operated, and the air inside the cylinder bore 6 is flowed downward from above to cool the inner wall of the cylinder bore 6. The local exhaust device 13 performs exhaust so that the internal temperature of the cylinder bore 6 is the same as the temperature outside the cylinder block 1. In addition, when the local exhaust apparatus 13 is arrange | positioned also at the remaining cylinder bore 6 which is not sprayed, the local exhaust apparatus 13 of those remaining cylinder bores 6 which are not sprayed waits without operating.

For example, the flow rate of the exhaust flow by the local exhaust device 13 is 25.0 m / s, and the heat transfer coefficient of forced convection for cooling the inner wall of the cylinder bore 6 is 400 W / (m ² K) or more. On the other hand, the heat transfer coefficient of natural convection around the cylinder block 1 (outside) is set to 20 W / (m ² K) or less. 6A shows the relationship between the heat transfer coefficient and the thermal stress on the inner surface 6a of the cylinder bore 6, and FIG. 6B shows the relationship between the heat transfer coefficient and the thermal stress on the outside of the cylinder block 1. FIG. Yes.

If there is no temperature difference between the inner surface 6a of the cylinder bore 6 and the outer side of the cylinder block 1, no thermal stress is generated. However, the cylinder bore 6 expands due to thermal spraying, and when the temperature outside the cylinder block 1 is low, the cylinder bore 6 generates a large stress outside the cylinder block 1 due to expansion. For this reason, the internal stress 6a of the cylinder bore 6 is cooled as much as possible, and thermal stress can be suppressed by suppressing escape of heat from the outside of the cylinder block 1. For this purpose, the heat transfer coefficient of forced convection for cooling the inner wall of the cylinder bore 6 is set to 400 W / (m ² K) or more (see FIG. 6A), and the heat transfer of natural convection outside the cylinder block 1 is performed. The rate is desirably 20 W / (m ² K) or less (see FIG. 6B).

The droplets 11 ejected from the spray gun 2 adhere to the inner surface 6a of the cylinder bore 6A and deposit to form a sprayed coating 12. In this way, the spray coating 12 is sequentially formed on all the cylinder bores 6. The order of spraying may be the cylinder bores 6A to 6D in order from the end, or the next cylinder bore 6 may be sprayed by interposing at least one cylinder bore 6 from the sprayed cylinder bore 6.

According to the spray coating apparatus of this embodiment, the internal temperature of the sprayed cylinder bore 6 is increased, but the inner wall of the cylinder bore 6 is locally cooled by the local exhaust device (cooler) 13. Increase in the internal temperature of the cylinder block 1 is suppressed, and the temperature gradient with the outside of the cylinder block 1 is reduced. Therefore, the thermal stress generated inside the cylinder block 1 can be reduced. As a result, manufacturing defects (cracking and deformation) of the cylinder block 1 can be prevented.

Moreover, according to the thermal spray coating formation apparatus of this embodiment, since the local exhaust apparatus 13 is used as a cooler, not only the inner wall of the cylinder bore 6 is cooled, but also excess particles generated during thermal spraying, soot, and unnecessary droplets 11 are removed. It can be discharged from the cylinder bore 6. Accordingly, it is possible to prevent excess particles from being mixed into the sprayed coating 12.

According to the thermal spray coating forming method of the present embodiment, the inside of the sprayed cylinder bore 6 is cooled to make the internal temperature of the cylinder bore 6 the same as the temperature outside the cylinder block 1, so that the inside of the cylinder bore 6 and the cylinder The temperature gradient with the outside of the block 1 becomes small. Therefore, the thermal stress generated inside the cylinder block 1 can be reduced. As a result, manufacturing defects (cracking and deformation) of the cylinder block 1 can be prevented.

Further, according to the thermal spray coating forming method of the present embodiment, the heat transfer coefficient of natural convection around the cylinder block 1 is set to 20 W / (m ² K) or less, and forced convection for locally cooling the inner wall of the cylinder bore 6 is used. Since the heat transfer rate is set to 400 W / (m ² K) or more, the temperature gradient between the inside of the cylinder bore 6 and the outside of the cylinder block 1 becomes small. Therefore, the thermal stress generated inside the cylinder block 1 can be reduced. As a result, manufacturing defects (cracking and deformation) of the cylinder block 1 can be prevented.

In the first embodiment described above, the local exhaust device 13 is used as a cooler, but in the second embodiment shown in FIG. 7, the cooler cools the inside of the water jacket 14 formed in the cylinder block 1. As a result, the inner wall of the cylinder bore 6 is cooled. Specifically, a fluid (for example, a gas such as air, hereinafter described as air) is supplied to the inside of the water jacket 14, and the heat of the inner wall of the cylinder bore 6 is discharged from the water jacket 14 side to the outside of the cylinder block 1. To do. In FIG. 7, the shape of the water jacket 14 is schematically shown so that it can be easily understood how the supplied air flows inside the water jacket 14.

In order to cool the inside of the water jacket 14, air 15 is supplied to the water jacket 14 from a fluid supply unit such as a blower, and the heat of the inner wall of the cylinder bore 6 is taken away from the water jacket 14 side. The air 15 deprived of heat is discharged to the outside of the cylinder block 1. At this time, similarly to the first embodiment, the supply amount of the air 15 is adjusted so that the internal temperature of the sprayed cylinder bore 6 becomes the same as the temperature outside the cylinder block 1.

Also in the present embodiment, the temperature gradient between the inside of the cylinder bore 6 and the outside of the cylinder block 1 is reduced as in the first embodiment described above. Therefore, the thermal stress generated inside the cylinder block 1 can be reduced. As a result, manufacturing defects (cracking and deformation) of the cylinder block 1 can be prevented.

Also in the third embodiment shown in FIG. 8, the cooler cools the inner wall of the cylinder bore 6 by cooling the inside of the water jacket 14 formed in the cylinder block 1. However, the cylinder block 1 of this embodiment is an open deck type or a semi-closed deck type in which a water jacket 14 is opened on a cylinder head mounting surface, and a water jacket is supplied from a fluid supply unit such as a blower through the opening. A fluid (for example, a gas such as air) 15 is supplied to 14. Also in this case, the heat of the inner wall of the cylinder bore 6 is taken from the water jacket 14 side, and the air 15 that has taken the heat is discharged from the other open end of the water jacket 14 to the outside of the cylinder block 1. Also in the present embodiment, the supply amount of the air 15 is set so that the internal temperature of the sprayed cylinder bore 6 becomes the same as the temperature outside the cylinder block 1 as in the first and second embodiments described above. Adjusted.

In this embodiment, the masking member 20 disposed on the cylinder head mounting surface during spraying is used to supply the air 15 to the opening of the water jacket 14 formed with the cylinder head mounting surface. The masking member 20 is a jig necessary to prevent the droplets 11 scattered during spraying from adhering to the cylinder mounting surface. In this embodiment, the masking member 20 is used to remove the air 15 from the water jacket 14. Supply inside. A supply path 22 for air 15 is formed in the masking member 20.

Also in the present embodiment, the temperature gradient between the inside of the cylinder bore 6 and the outside of the cylinder block 1 is reduced as in the first and second embodiments described above. Therefore, the thermal stress generated inside the cylinder block 1 can be reduced. As a result, manufacturing defects (cracking and deformation) of the cylinder block 1 can be prevented.

Especially, since the cylinder head mounting surface side of the open bore type or semi-closed deck type cylinder bore 6 is an open end, thermal deformation is likely to occur and cracks are likely to occur. For this reason, the open end can be effectively cooled by supplying the air 15 from the opening of the water jacket 14 formed on the cylinder head mounting surface. As a result, manufacturing defects (cracks and deformation) of the cylinder block 1 can be reliably prevented.

Furthermore, in this embodiment, the masking member 20 is used to supply the air 15 from the opening of the water jacket 14 formed on the cylinder head mounting surface. The masking member 20 is a jig required at the time of thermal spraying, and by using such a jig, the inner wall of the cylinder bore 6 can be efficiently cooled at the time of thermal spraying.

In the fourth embodiment shown in FIG. 9, chills 16 as a cooler are provided on the cylinder head mounting surface during spraying. The chiller 16 is made of a metal having excellent thermal conductivity, and takes heat from thermal spraying from the inner wall of the cylinder bore 6. In the present embodiment, the inner wall of the cylinder bore 6 is cooled by bringing the cooling metal 16 into contact with the cylinder head mounting surface.

Further, at the time of thermal spraying, the cooling metal 16 closes the opening of the water jacket 14, and the heat input to the inner wall of the cylinder bore 6 at the time of thermal spraying is transmitted to the cylinder bore 6 through the water jacket 14, and the inside of the cylinder bore 6. The temperature can also be lowered. As a result, the temperature gradient between the internal temperature of the cylinder bore 6 and the temperature outside the cylinder block is reduced. Therefore, the thermal stress generated inside the cylinder block 1 can be reduced. As a result, manufacturing defects (cracking and deformation) of the cylinder block 1 can be prevented.

In the fifth embodiment shown in FIG. 10, the air 15 is also supplied to the water jacket 14 by using the cooling metal 16 described above. If it does in this way, the cooling effect as cooling metal 16 and the cooling effect by supply of air 15 can be acquired, and the inner wall of cylinder bore 6 can be cooled more effectively.

Next, the temperature of the cylinder bore 6 (inner wall) during spraying will be described. FIG. 11 is a graph showing the relationship between the temperature and the 0.2% yield strength [0.2% offset yield stress] in the cylinder block 1 made of aluminum alloy. The stress-strain curve of steel clearly shows the yield stress, but the stress-strain curve of aluminum alloy does not clearly show the yield stress. The permanent strain at the yield of steel is 0.2%. For this reason, in an aluminum alloy, the stress at which the permanent strain upon unloading is 0.2% is called 0.2% proof stress, and is used instead of the yield stress.

As can be seen from the temperature-0.2% proof stress curve shown in FIG. 11, when the temperature of the aluminum alloy exceeds 250 ° C., the 0.2% proof stress decreases rapidly. For this reason, in order to prevent manufacturing defects (cracking and deformation) of the cylinder block 1 made of aluminum alloy, the temperature of the cylinder block 1, that is, the inner wall of the cylinder bore 6, is preferably set to 250 ° C. or less. Further, as described above, the cylinder block 1 (inner wall of the cylinder bore 6) is preheated in order to improve the adhesion of the thermal spray coating 12. For this reason, it is preferable that the temperature of the inner wall of the cylinder bore 6 is 50 ° C. or higher. That is, in order to prevent manufacturing defects (cracking and deformation) of the cylinder bore 6, the outer surface (and the center in the thickness direction of the inner wall) of the inner wall of the cylinder bore 6 is 50 ° C. or more and 250 ° C. or less during spraying. It is preferable that

Considering that the inner surface of the inner wall of the cylinder bore 6 is heated by the droplet 11, the outer surface of the inner wall of the cylinder bore 6 on the water jacket 14 side (and the center in the thickness direction of the inner wall) is 200 ° C. or less during spraying. It is particularly preferred that Moreover, when the improvement of the adhesiveness of the sprayed coating 12 is considered, it is especially preferable that the outer surface on the water jacket 14 side (and the center in the thickness direction of the inner wall) is set to 100 ° C. or higher. That is, the outer surface of the inner wall of the cylinder bore 6 on the water jacket 14 side (and the center in the thickness direction of the inner wall) is particularly preferably set to 100 ° C. or higher and 200 ° C. or lower during thermal spraying.

Furthermore, as described above, the cylinder head mounting surface side of the cylinder bore 6 of the open deck type or the semi-closed deck type is an open end, so that thermal deformation is likely to occur, and manufacturing defects (cracks and deformation) are likely to occur. For this reason, it is preferable that the cylinder head mounting surface side of the cylinder bore 6 is controlled to the above-described temperature range during spraying.

In the above-described embodiment, the internal temperature of the cylinder bore 6 is made equal to the temperature outside the cylinder block 1 by lowering the internal temperature of the cylinder bore 6. However, it is also possible to make the internal temperature of the cylinder bore 6 the same as the temperature outside the cylinder block 1 by heating the outside of the cylinder block 1.

The entire contents of Japanese Patent Application No. 2013-229169 (filed on Nov. 5, 2013) are incorporated herein by reference. Although the present invention has been described above with reference to embodiments of the present invention, the present invention is not limited to the above-described embodiments. The scope of the invention is determined in light of the claims.

Claims (13)

A thermal spray coating forming device,
A cylinder block formed with a plurality of cylinder bores;
A spray gun that sprays molten metal droplets on each inner surface of the plurality of cylinder bores to form a spray coating;
And a cooler for locally cooling an inner wall of the sprayed cylinder bore among the plurality of cylinder bores during spraying by the spray gun. The thermal spray coating forming apparatus according to claim 1,
The thermal spray coating forming apparatus, wherein the cooler locally cools the inner wall by sucking a fluid inside the sprayed cylinder bore. The thermal spray coating forming apparatus according to claim 1,
The thermal spray coating formation apparatus which cools the said inner wall locally by the said cooler cooling the inside of the water jacket formed in the said cylinder block. The thermal spray coating forming apparatus according to claim 3,
The thermal spray coating forming apparatus, wherein the cooler supplies the fluid to the inside of the water jacket to cool the inside of the water jacket. The thermal spray coating forming apparatus according to claim 4,
The cylinder block is an open deck type or semi-closed type cylinder block,
An apparatus for forming a thermal spray coating, wherein the cooler supplies a fluid to the inside of the water jacket from the water jacket opened on a cylinder head mounting surface of the cylinder block. The thermal spray coating forming apparatus according to claim 5,
A masking member disposed on the cylinder head mounting surface of the sprayed cylinder bore;
The thermal spray coating forming apparatus, wherein the cooler supplies a fluid to the inside of the water jacket via the masking member. The thermal spray coating forming apparatus according to claim 1,
The said cooler is a thermal spray coating formation apparatus which cools the said inner wall locally by making a cooling metal contact the said inner wall. While generating natural convection around the cylinder block, sprayed molten metal droplets from the spray gun inserted into the cylinder bores formed in the cylinder block are formed on the inner surfaces of the cylinder bores to form a sprayed coating. A thermal spray coating forming method comprising:
During spraying by the spray gun, the inner wall of the sprayed cylinder bore is locally cooled by forced convection among the plurality of cylinder bores, and the internal temperature of the sprayed cylinder bore is set to the temperature outside the cylinder block. The same sprayed film forming method. The thermal spray coating forming method according to claim 8,
A method for forming a thermal spray coating, wherein the natural convection heat transfer coefficient is 20 W / (m ² K) or less, and the forced convection heat transfer coefficient is 400 W / (m ² K) or more. The thermal spray coating forming method according to claim 8,
A thermal spray coating forming method of locally cooling the inner wall by cooling the inside of a water jacket formed on the cylinder block. The thermal spray coating forming method according to claim 10,
The cylinder block is an open deck type or semi-closed type cylinder block,
A thermal spray coating forming method of supplying fluid to the inside of the water jacket from the water jacket opened on the cylinder head mounting surface of the cylinder block. The thermal spray coating forming method according to claim 11,
A thermal spray coating forming method of supplying a fluid to the inside of the water jacket via a masking member disposed on the cylinder head mounting surface of the cylinder bore being sprayed. The thermal spray coating forming method according to any one of claims 8 to 12, wherein the inner wall is cooled such that the temperature of the outer surface of the inner wall on the water jacket side is 50 ° C or higher and 250 ° C or lower. Thermal spray coating formation method.

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