JP2011017277A - Metallic material sliding surface structure, cylinder for internal combustion engine, and metallic material sliding surface forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metallic material sliding surface structure in which a cured layer is formed on a surface of a metallic material without forming a sprayed coating, and lubricant is sufficiently maintained without requiring waste liquid treatment, and provide a cylinder for an internal combustion engine and a metallic material sliding surface forming method.SOLUTION: A concave-convex shape is formed on a surface of a cylinder bore 6 of an aluminum alloy cylinder block 4 by carrying out a plasma melting and roughening process by a plasma melting device 2. Thereby a rough concave-convex shape is formed. In addition, a very hard concave-convex surface is formed by instantaneous solidification even when the sprayed coating is not formed. Then, a plateau surface forming process is carried out on a convex part by elastic honing processing on the concave-convex surface. A piston ring sliding surface formed by the above processes can obtain a sufficient scuffing property over a long period of time with not only a high Si aluminum alloy but also an aluminum alloy for die casting, and the liquid waste treatment or the like such as ECM is not required.

Description

  The present invention relates to a metal material sliding surface structure in which a plateau surface is formed at the tip of a convex portion formed on a surface, a cylinder for an internal combustion engine, and a metal material sliding surface forming method.

Conventionally, there exists a technique for improving the wear resistance of a metal material (see, for example, Patent Documents 1 to 3).
In Patent Document 1, a hardened layer is formed on the surface of an aluminum alloy material by vacuum arc discharge, and the top of the undulating curve generated at the time of forming the hardened layer is made smooth by rolling. In addition, this patent document 1 also discloses an example in which a smooth surface is formed by cutting the top of a wavy curve as a prior art.

  In Patent Document 2, the surface of the cam sliding portion of the camshaft is irradiated with high-density energy such as plasma arc to remelt the surface, and the surface hardened layer thus formed is pressed by a roller or a plate to The unevenness is suppressed and then polished.

  In Patent Document 3, a spray coating is formed by plasma spraying a spray powder with a spray gun in a cylinder bore of an aluminum cylinder block, and then a spray coating having minute pores on the surface is formed by honing.

JP 2000-328167 A (page 4-6, FIG. 2-7) JP 61-270340 A (page 4-5, FIG. 5) Japanese Patent Laying-Open No. 2005-171274 (page 6-7, FIG. 6-7)

  In the work by vacuum arc discharge as in Patent Document 1, it is necessary to arrange a metal material in the vacuum chamber, and the work efficiency is low and it is difficult to adopt it in the production line. Furthermore, it is not realistic to process a large metal material such as a cylinder block or a large number of cylinder liners at the same time because the apparatus becomes huge. However, in the undulating curve, the depth and number of the concave portions as a whole cannot sufficiently hold the lubricating oil, and the sliding characteristics with other members such as scuffing properties are low, and the wear resistance is insufficient.

  Also in Patent Document 2, the only purpose is to improve the surface hardness, and since the surface irregularities are suppressed, there is almost no retention of lubricating oil, low sliding characteristics with other members such as scuffing, and wear resistance. Is insufficient.

  In Patent Document 3, a metal material is used as a base material, and a thermal spray coating is formed on the surface of the thermal spray powder of another material. When such a thermal spray coating is formed on the cylinder bore, the thermal spray coating may be peeled off from the base material due to the difference in material, especially due to the difference in thermal expansion due to the high temperature of the internal combustion engine and the sliding of the piston ring. Cause problems.

In addition, there is a method of forming a recess by ECM (electrolytic machining), but since an electrolytic machining liquid is used, an environmental problem arises due to waste liquid treatment.
The present invention relates to a metal material sliding surface structure, a cylinder for an internal combustion engine, and a metal which can form a hardened layer on the surface of the metal material without forming a sprayed coating and can sufficiently retain lubricating oil without causing waste liquid treatment or the like. The object is a material sliding surface forming method.

In the following, means for achieving the above-mentioned purpose, and its operation and effect are described.
The metal material sliding surface structure according to claim 1 is a plateau that is aligned on one surface parallel to the surface of the metal material by removing the tip of the convex portion among the irregularities formed on the surface of the metal material. In the sliding surface structure forming a surface, the unevenness before the tip of the convex portion is removed is formed by melting the surface of the metal material by plasma irradiation. It is characterized by being.

  The unevenness formed on the surface of the metal material by the plasma irradiation as described above is formed by instantaneously cooling and solidifying after the surface that has melted in a moment is vigorously shaken by the collision of the plasma. is there. For this reason, not a wavy curve as in the vacuum arc discharge, but a surface uneven shape is formed in which the unevenness change is more severe, and in some cases a bag-like recess exists. In addition, due to instantaneous solidification, the surface has a very high roughness.

  By removing the tip of the convex portion with respect to the unevenness to form a plateau surface, other members can slide on the plateau surface. Since the concave portions existing between the plateau surfaces have an indented shape that can sufficiently hold the lubricating oil, sufficient lubricating oil is supplied from the concave portions to the plateau surface when other members slide on the plateau surface. As a result, the sliding characteristics with other members such as scuffing properties become high.

Moreover, since the hardened layer is formed on the surface of the metal material without forming a sprayed coating, there is no fear of peeling due to thermal expansion differences or sliding of other members.
Furthermore, there is no environmental problem since no waste liquid such as electrolytic processing liquid is generated when the metal material sliding surface structure is formed.

  In the metal material sliding surface structure according to claim 2, in the metal material sliding surface structure according to claim 1, removal of the tip of the convex portion is performed by grinding after plasma irradiation. And

Thus, the tip of the convex portion can be removed by grinding, and a metal material sliding surface structure in which a plateau surface aligned with one surface parallel to the surface of the metal material is formed can be easily realized.
The metal material sliding surface structure according to claim 3 is characterized in that, in the metal material sliding surface structure according to claim 2, the removal of the tip of the convex portion is formed by a honing process. To do.

  That is, the plateau surface can be formed by grinding with a honing grindstone, and the plateau surface itself can be formed into a smooth surface by such honing. Accordingly, the sliding of the other member can be made smoother by the lubricating oil from the concave portion between the plateau surfaces, and a metal material sliding surface structure having high sliding characteristics with the other member is obtained.

  The metal material sliding surface structure according to claim 4 is characterized in that, in the metal material sliding surface structure according to claim 3, the honing is performed by an elastic honing grindstone.

As the honing process, an elastic honing grindstone can be used, and for this, a metal material sliding surface structure with better sliding characteristics on the plateau surface can be obtained.
The metal material sliding surface structure according to claim 5, wherein in the metal material sliding surface structure according to any one of claims 1 to 4, an average depth of the concave portion of the irregularities is the plateau. It exists in the range of 1.0-20 micrometers from a surface.

  If the average depth of the concave portion is less than 1.0 μm, the retaining property of the lubricating oil is lowered and the wear resistance of the metal material surface tends to be lowered. When the average depth of the concave portion is deeper than 20 μm, the lubricating oil tends to be consumed more than necessary.

Therefore, by setting the average depth of the concave portion within the above range, it is possible to obtain a metal material sliding surface structure that can improve the retention of the lubricating oil and suppress the consumption of the lubricating oil.
In the metal material sliding surface structure according to claim 6, in the metal material sliding surface structure according to any one of claims 1 to 5, the plateau surface in the entire area of the region where the irregularities are formed. The occupied area ratio is 5 to 70%.

  When the area ratio occupied by the plateau surface is lower than 5%, it is sufficient to hold the lubricating oil, but the amount of lubricating oil consumption increases, the surface pressure on the plateau surface when other members slide is excessive, and the convex portion There is a tendency for strength reduction and sliding properties to deteriorate. When the area ratio occupied by the plateau surface is higher than 70%, the retaining property of the lubricating oil is lowered and the sliding characteristics tend to be deteriorated.

Therefore, by forming the plateau surface with the area ratio, a metal material sliding surface structure with good lubricating oil retention, lubricating oil consumption and sliding characteristics can be obtained.
In the metal material sliding surface structure according to claim 7, in the metal material sliding surface structure according to any one of claims 1 to 6, an average area per surface of the plateau surface is 5 μm 2 or more. It is characterized by that.

Thus, by setting the area of the plateau surface to an average of 5 μm 2 or more, a metal material sliding surface structure having particularly good sliding characteristics can be obtained.
In the metal material sliding surface structure according to claim 8, the metal material sliding surface structure according to any one of claims 1 to 7, wherein the metal material is an aluminum alloy.

  In applications such as automobile engines, cylinder blocks and cylinder liners are formed using an aluminum alloy as a metal material in order to reduce engine weight and improve thermal conductivity. Even in such an aluminum alloy, by adopting the above-described sliding surface structure, it is possible to sufficiently hold the lubricating oil without causing waste liquid treatment and the like, and the sliding of the metal material with improved durability such as wear resistance. It can be a plane structure.

The metal material sliding surface structure according to claim 9 is characterized in that, in the metal material sliding surface structure according to claim 8, the aluminum alloy contains silicon.
Thus, when the aluminum alloy is an alloy containing silicon, the primary crystal of silicon in the aluminum alloy is refined by plasma irradiation and dispersed in the uneven surface layer. As a result, the hardness of the aluminum alloy itself is increased and the hardness of the surface layer is further increased by the refined silicon, so that the hardness and smoothness of the plateau surface can be further increased. Therefore, the wear resistance is improved, and a metal material sliding surface structure having particularly high sliding characteristics with other members such as scuffing properties can be obtained.

  In the metal material sliding surface structure according to claim 10, in the metal material sliding surface structure according to claim 8 or 9, the unevenness is formed in a state where the hardness is 140HV or more by plasma irradiation. It is characterized by that.

  As described above, unevenness on the surface of the aluminum alloy can be formed in a high hardness state by instantaneous solidification after plasma irradiation. Even in the aluminum alloy, even if the original hardness (Vickers hardness: HV) is of a low type (100 to 110 HV), it is possible to easily form unevenness of 140 HV or higher. By forming the surface irregularities in a state of 140 HV or higher as described above, a metal material sliding surface structure with particularly improved sliding characteristics such as wear resistance can be obtained.

  The metal material sliding surface structure according to claim 11, wherein, in the metal material sliding surface structure according to claim 10, the irregularities are formed in a hardness range of 140 to 190 HV by plasma irradiation. It is characterized by.

  As described above, when the uneven portion of the aluminum alloy is formed in the range of 140 to 190 HV, a metal material sliding surface structure with sufficiently improved sliding characteristics such as wear resistance can be obtained.

  In the metal material sliding surface structure according to claim 12, in the metal material sliding surface structure according to any one of claims 1 to 11, the melting by the plasma irradiation makes the inert gas into a plasma state. It was performed by irradiating the surface of the metal material.

  Irradiation with plasma using an inert gas such as argon gas or nitrogen gas can cause melting and violent shaking on the surface of the metal material, thereby forming irregularities with high hardness.

  In such an unevenness forming process, since the thermal spray powder is not used, a metal material sliding surface structure can be obtained in which there is no fear of peeling due to a difference in thermal expansion between the hardened layer on the surface and the metal material or sliding of other members. . Furthermore, since no waste liquid such as electrolytic processing liquid is generated, a metal material sliding surface structure that does not cause environmental problems in the processing process can be obtained.

  In the metal material sliding surface structure according to claim 13, in the metal material sliding surface structure according to any one of claims 1 to 11, the melting by the plasma irradiation causes the atmosphere to be in a plasma state and the metal material. It was carried out by irradiating the surface of

  In this manner, plasma irradiation may be performed using the atmosphere, and a metal material sliding surface structure having high hardness unevenness as in the case of an inert gas can be obtained. Since it is the atmosphere, there is no need for a storage cylinder in the plasma irradiation apparatus, and it is only necessary to suck the atmosphere and use it, so that the processing cost at the time of forming the metal material sliding surface structure becomes advantageous.

An internal combustion engine cylinder according to a fourteenth aspect is characterized in that the inner peripheral surface has the metal material sliding surface structure according to any one of the first to thirteenth aspects.
Thus, by using a metal material whose inner peripheral surface has the sliding surface structure as a cylinder for an internal combustion engine, even if the piston ring slides on the inner peripheral surface, a recess formed on the inner peripheral surface Sufficient lubricating oil is supplied between the piston ring and the plateau surface, so that a cylinder for an internal combustion engine having high sliding characteristics with the piston ring such as scuffing can be obtained.

  In addition, since the hardened layer is formed on the inner peripheral surface of the cylinder for the internal combustion engine without forming a sprayed coating, there is no fear of peeling due to a difference in thermal expansion or sliding of the piston ring. Furthermore, there is no environmental problem because no waste liquid such as electrolytic processing liquid is produced during the processing of the inner peripheral surface of the cylinder for an internal combustion engine.

An internal combustion engine cylinder according to a fifteenth aspect is characterized in that the internal combustion engine cylinder according to the fourteenth aspect is formed as a cylinder liner.
Thus, in the cylinder for an internal combustion engine, a cylinder liner having an inner peripheral surface having the sliding surface structure can be used, and the operation and effect described in the fourteenth aspect are produced.

According to a sixteenth aspect of the present invention, in the internal combustion engine cylinder according to the fourteenth aspect, the internal combustion engine cylinder is formed integrally with a cylinder block.
Thus, the present invention can be applied to a cylinder formed integrally with a cylinder block instead of a cylinder liner. That is, even if the cylinder is integrally formed of the same metal material as that of the cylinder block, by forming the unevenness and the plateau surface by the plasma irradiation as described above, the operation and effect described in the above-mentioned claim 14 can be achieved. Arise.

  The method for forming a metal material sliding surface according to claim 17 includes a plasma melting and roughening step in which irregularities are formed on the surface and solidified by melting and shaking the surface of the metal material by plasma irradiation, and the plasma melting After the roughening step, a plateau surface that forms a plateau surface at the front end of the convex portion by removing the front end of the convex portion up to one surface that is parallel to the surface of the metal material and is set at an intermediate position in the thickness direction of the unevenness The forming step is performed.

  In the plasma melting and roughening step, the surface of the metal material is instantaneously melted by plasma irradiation, and at the same time, the liquefied surface portion is vigorously shaken. When the plasma irradiation is completed, heat is immediately absorbed by the metal material portion below the surface, and the surface is rapidly cooled to solidify while maintaining the uneven state at the time of shaking, and the roughening is completed.

  For this reason, after the plasma melting and roughening step, a surface shape with more rugged changes is formed instead of the undulating curve as in the conventional vacuum arc discharge. In addition, due to instantaneous solidification, it has a very high unevenness state.

In the plateau surface forming step, the plateau surface is formed by removing the protrusions so that the tips of the convex portions are aligned on one surface.
In the metal material sliding surface formed in this way, the concave portion existing between the plateau surfaces has an indented shape that can sufficiently hold the lubricating oil. Therefore, when the other member slides on the plateau surface, sufficient lubricating oil is supplied from the concave portion, and a metal material sliding surface having high sliding characteristics with the other member such as scuffing property can be formed.

  In addition, since the surface of the metal material is processed into a highly hard uneven shape, a hardened layer can be formed on the surface of the metal material without forming a sprayed coating. Therefore, it is possible to form a metal material sliding surface that does not have a fear of peeling due to a difference in thermal expansion or sliding of another member.

Further, since no waste liquid such as an electrolytic processing liquid is generated, no environmental problem occurs even if such a method for forming a sliding surface of a metal material is executed.
The metal material sliding surface forming method according to claim 18, wherein in the metal material sliding surface forming method according to claim 17, the plateau surface forming step removes a tip of the convex portion by grinding. And

  As described above, in the plateau surface forming process, by removing the tip of the convex portion by grinding, a plateau surface that is aligned with one surface parallel to the surface of the metal material can be easily formed at the intermediate position in the thickness direction of the unevenness. it can.

  In the metal material sliding surface forming method according to claim 19, in the metal material sliding surface forming method according to claim 18, the plateau surface forming step is characterized in that the grinding is performed by honing.

  In the plateau surface forming step, the plateau surface can be formed by grinding with a honing grindstone. As a result, a smooth plateau surface can be formed. By being able to form such a plateau surface on the sliding surface, it is possible to make the sliding of other members smoother together with the lubricating oil from the concave portion, and a metal material sliding surface structure with high sliding characteristics with other members. Become.

  The metal material sliding surface forming method according to claim 20 is characterized in that, in the metal material sliding surface forming method according to claim 19, the honing is performed by an elastic honing grindstone.

  The honing process performed in the plateau surface forming step can be performed using an elastic honing grindstone. As a result, a metal material sliding surface having a smooth plateau surface can be formed.

  The metal material sliding surface forming method according to claim 21, wherein in the metal material sliding surface forming method according to any one of claims 17 to 20, the plateau surface forming step includes forming the plateau surface into a concave shape. The average height from the bottom of the portion is formed in the range of 1.0 to 20 μm.

  If the average depth of the concave portion is shallower than 1.0 μm with respect to the plateau surface formed in the plateau surface forming step, the retention of the lubricating oil tends to be lowered and the wear resistance tends to be lowered. When the average depth of the concave portion is deeper than 20 μm, the lubricating oil tends to be consumed more than necessary.

  Therefore, by forming the average height of the plateau surface from the bottom of the concave portion in the above range, it is possible to form a metal material sliding surface that can improve the retention of the lubricating oil and suppress the consumption of the lubricating oil.

  In the metal material sliding surface forming method according to claim 22, in the metal material sliding surface forming method according to any one of claims 17 to 21, the plateau surface forming step includes: It is characterized in that the area ratio occupying in the entire area of the region where the unevenness is formed is 5 to 70%.

  When the area ratio occupied by the formed plateau surface is lower than 5%, it is sufficient for holding the lubricating oil, but the amount of lubricating oil consumption increases, and the surface pressure on the plateau surface when other members slide is excessive. There is a tendency for the strength of the convex portion to decrease and the sliding characteristics to deteriorate. When the area ratio occupied by the plateau surface is higher than 70%, the retaining property of the lubricating oil is lowered and the sliding characteristics tend to be deteriorated.

  Therefore, in the plateau surface forming step, by forming the plateau surface with the area ratio, it is possible to form a metal material sliding surface with good lubricating oil retention, lubricating oil consumption and sliding characteristics.

  In the metal material sliding surface forming method according to claim 23, in the metal material sliding surface forming method according to any one of claims 17 to 22, the plateau surface forming step includes: The average area per surface is 5 μm 2 or more.

By executing the plateau surface forming step so that the area of the plateau surface becomes 5 μm 2 or more on average in this way, a metal material sliding surface with particularly good sliding characteristics can be formed.
25. The method of forming a metal material sliding surface according to claim 24, wherein the metal material is an aluminum alloy as the metal material sliding surface forming method according to any one of claims 17 to 23. And

  In applications such as automobile engines, cylinder blocks and cylinder liners are formed using aluminum alloy as a metal material in order to reduce engine weight and improve thermal conductivity. Even in such an aluminum alloy, by forming the above-described sliding surface of the metal material, it is possible to sufficiently retain the lubricating oil without causing waste liquid treatment and the like, and to improve the durability such as wear resistance. A moving surface can be formed.

The metal material sliding surface forming method according to claim 25 is characterized in that, in the metal material sliding surface forming method according to claim 24, the aluminum alloy contains silicon.
As described above, since the aluminum alloy is an alloy containing silicon, in the plasma melting and roughening step, the primary crystals of silicon in the aluminum alloy are refined by plasma irradiation and dispersed in the uneven surface layer. As a result, the hardness of the aluminum alloy itself is increased, and the hardness of the surface layer is further increased by the refined silicon. For this reason, the hardness and smoothness of the plateau surface formed by the plateau surface formation step can be further increased. For this reason, wear resistance is improved, and a metal material sliding surface having particularly high sliding characteristics with other members such as scuffing properties can be formed.

  In the metal material sliding surface forming method according to claim 26, in the metal material sliding surface forming method according to any one of claims 17 to 25, the plasma melting and roughening step is performed after the solidification. The unevenness is formed with a hardness of 140 HV or higher.

  As described above, the unevenness on the surface of the aluminum alloy can be formed in a high hardness state by instantaneous solidification after the plasma irradiation in the plasma melting and roughening step. Even in the aluminum alloy, even if the original hardness (Vickers hardness: HV) is of a low type (100 to 110 HV), it is possible to easily form unevenness of 140 HV or higher. In this way, by forming the uneven portion with a hardness of 140 HV or higher in the plasma melting and roughening step, the metal material sliding surface that has improved the sliding characteristics such as wear resistance after the plateau surface forming step. Can be formed.

  In the metal material sliding surface forming method according to claim 27, in the metal material sliding surface forming method according to claim 26, in the plasma melting and roughening step, the unevenness after solidification has a hardness of 140 ~. It is formed in the range of 190 HV.

  Thus, by forming the hardness of the uneven portion of the aluminum alloy in the range of 140 to 190 HV in the plasma melting and roughening step, a metal material sliding surface with sufficiently improved sliding characteristics such as wear resistance can be obtained. Can be formed.

  In the metal material sliding surface forming method according to claim 28, in the metal material sliding surface forming method according to any one of claims 17 to 27, the plasma melting and roughening step includes inert gas. It is characterized by irradiating the surface of the metal material in the form of plasma.

  In the plasma melting and roughening process, the surface of the metal material is melted and vigorously shaken by plasma irradiation using an inert gas such as argon gas or nitrogen gas to form high hardness irregularities. Can do.

  In such an unevenness forming process, since the thermal spray powder is not used, it is possible to form a metal material sliding surface that is free from a difference in thermal expansion between the hardened layer on the surface and the metal material or from being peeled off due to sliding of other members. . Further, in the plasma melting and roughening step, no waste liquid such as electrolytic processing liquid is generated, so that no environmental problem occurs in forming the metal material sliding surface.

  30. The metal material sliding surface forming method according to claim 29, wherein the plasma melting and roughening step comprises converting the atmosphere into a plasma state. And irradiating the surface of the metal material.

  In the plasma melting and roughening step, plasma irradiation may be performed using air, and a metal material sliding surface having high hardness unevenness can be formed as in the case of an inert gas. Since it is the atmosphere, there is no need for a storage cylinder in the plasma irradiation apparatus, and it is only necessary to suck the atmosphere and use it.

1 is a schematic block diagram of a plasma melting apparatus according to a first embodiment. The photograph instead of drawing which shows the measurement shape of the cylinder bore surface after a plasma-melting roughening process with the halftone image which displayed on the display. The graph showing the uneven | corrugated state in one cross section in FIG. The photograph instead of drawing which shows the measurement shape of the cylinder bore surface after a plateau surface formation process with the halftone image which displayed on the display. The graph showing the uneven | corrugated state in one cross section in FIG. The graph which shows the measurement result of the scuff property of the cylinder liner of Example 1 with a comparative example. (A), (b) The micrograph for the drawing which shows the surface state of the aluminum alloy of Example 2, and the unevenness | corrugation state measurement graph in the one cross section. (A), (b) As a comparative example, the micrograph for the drawing which shows the surface state of the aluminum alloy which performed only the elastic honing process, and the unevenness | corrugation state measurement graph in the one cross section. (A), (b) The microphotograph for the drawing substitute which shows the surface state of the aluminum alloy which performed ECM process as a comparative example, and the unevenness | corrugation state measurement graph in the one cross section. 10 is a graph showing the relationship between the depth of the concave portion and the scuffing property in Example 3. 10 is a graph showing the relationship between the area ratio of the plateau surface and scuffing property in Example 4. FIG. 5 is a schematic block diagram of a work robot that executes a plasma melting and roughening process in the second embodiment.

[Embodiment 1]
A metal material sliding surface forming method will be described. FIG. 1 is a block diagram showing a schematic configuration of a surface melting apparatus (hereinafter referred to as a plasma melting apparatus) 2 by plasma irradiation for performing a plasma melting and roughening step in the metal material sliding surface forming method.

  The plasma melting apparatus 2 performs plasma irradiation on a cylinder bore 6 which is an inner surface of a cylinder 5 formed integrally with a cylinder block 4 of an in-line four-cylinder internal combustion engine to melt and shake the surface to roughen the surface. It is a device to realize. Here, the cylinder block 4 (including the cylinder 5), which is a metal material, is made of an aluminum alloy. For example, high Si aluminum alloy containing 23% Si, ADC12 containing 10% Si suitable for die casting, or high strength and high wear resistant aluminum alloy containing 17% Si of intermediate properties (commodity) Various aluminum alloys such as name: A390) can be used.

  In FIG. 1, the cylinder 5 is formed integrally with the cylinder block 4. However, a cylinder liner made of an aluminum alloy formed separately may be cast into the cylinder block 4.

  The plasma melting apparatus 2 includes a plasma oscillator 8, a gas supply device 10, a plasma generator 12, a plasma nozzle 14, and a plasma head 16. The gas supply device 10 includes a compression pump therein, compresses the atmosphere to increase the pressure (0.5 to 0.7 MPa), and supplies each plasma generator 12 provided for each cylinder 5 via the gas pipe 10a. Distributes compressed air. For example, compressed air is distributed to each of the four plasma generators 12 at 20 to 60 L (liter) / min.

  Each plasma generator 12 is supplied with a high frequency high voltage from a high frequency high voltage device 8 a provided in the plasma oscillator 8. The plasma frequency is adjusted to 18 to 25 kHz, and the current amount is adjusted to 6 to 20 amperes. The compressed air is turned into plasma by the discharge in each plasma generator 12 and is irradiated toward the cylinder bore 6 from the irradiation port 14 a at the tip of the plasma nozzle 14.

  The plasma head 16 supports each plasma generator 12 and the plasma nozzle 14, and moves the position where the irradiation port 14 a faces by moving and rotating the plasma nozzle 14. Here, the plasma nozzle 14 is arranged at the axial center position of the cylinder bore 6 and is moved in the axial direction while rotating around the axis at the time of plasma irradiation. Here, the irradiation port 14a is disposed at a distance of 3 to 10 mm (for example, 5 mm) with respect to the cylinder bore 6 having a diameter of 75 to 90 mm, and the axial direction of the cylinder bore 6 is rotated while the plasma nozzle 14 is rotated at several tens of rpm (for example, 50 rpm). 1 mm to about several mm / second (for example, 0.85 mm / second). As a result, a plasma melting surface roughening step is performed by irradiating plasma to a region slid by the piston ring in the cylinder bore 6.

  In this plasma melting and roughening step, the plasma collides with the surface of the cylinder bore 6 due to the plasma irradiation, and this causes the molten surface to vibrate rapidly. As the irradiation position moves, the melted portion is instantaneously cooled by the heat conduction of the cylinder block 4 itself. By this rapid cooling, the surface of the cylinder bore 6 is solidified while maintaining the uneven state, the uneven shape is fixed, and the roughening is completed. In particular, this rapid cooling results in a roughened surface with a very high hardness (140 to 190 HV in Vickers hardness).

  Thus, the surface of the cylinder bore 6 is melted, shaken and solidified by the plasma melting apparatus 2 to complete the plasma melting and roughening step. The result of measuring the surface shape of the cylinder bore 6 at the completion of the plasma melting and roughening process is shown in the three-dimensional graph of FIG. FIG. 3 is a graph showing an uneven state in one section in FIG. 2 and 3 are surface shapes measured by a confocal optical microscope after performing a plasma melting and roughening process on the ADC 12.

  As shown in FIGS. 2 and 3, it can be seen that the severe uneven state caused by the plasma irradiation is solidified and fixed. The hardness of the unevenness is 180 HV, which indicates a high rise compared to the original ADC 12 having a hardness of 100 to 110 HV.

  Next, with respect to the cylinder bore 6 thus roughened, the tip of the convex portion V (FIG. 3) is removed by grinding as a plateau surface forming step to form a sliding surface. That is, the tip of the convex portion V is removed up to one surface which is parallel to the cylinder bore 6 and set at an intermediate position in the thickness direction of the unevenness. Here, for example, grinding is performed so as to remove the tip of the convex portion V at a position of about 1/3 (from above) of the thickness of the concave and convex portion.

  As the honing process, either a finishing process using a normal honing grindstone or a finishing process using an elastic honing grindstone may be used. Here, an elastic honing process using an elastic honing grindstone is particularly performed.

  As a result, as shown in the three-dimensional graph shown in FIG. 4 and the concavo-convex state graph in one section shown in FIG. 5, the tip of the convex portion V becomes flat and is aligned with one surface parallel to the cylinder bore 6 which is the surface of the metal material. The plateau surface P thus formed is formed. 4 and 5 are measured in the same manner as in FIGS.

  Here, the plateau surface P is formed in the range whose average height from the bottom part of the recessed part C is 1.0-20 micrometers. That is, the average depth of the concave portion C exists in the range of 1.0 to 20 μm from the plateau surface P. The plateau surface P is formed by a honing process, particularly an elastic honing process in FIGS.

  Further, the ratio of the total area of the plateau surface P to the total area of the region where the irregularities are formed (hereinafter referred to as the area ratio of the plateau surface P) is practically used in Example 4 described later as a sliding surface. As described, it is 5 to 70%. That is, the relationship between the total area Σsp of the plateau surface P formed on the convex portion V and the total area Σsc of the concave portion area Sc as shown in FIG.

[Formula 1] 5 ≦ 100 · Σsp / (Σsp + Σsc) ≦ 70
Example 1
For an aluminum alloy cylinder liner (continuous casting, ADC12 may be die-cast), the cylinder bore is subjected to the plasma melting roughening step and the plateau surface forming step as described above, and the piston ring sliding surface FIG. 6 shows the result of measuring the scuffing property (hour: minute) for the film formed with the film. In the embodiment, the plasma melting and roughening step is performed by using Ar (argon gas), N2 (nitrogen gas), or air as a gas for converting into plasma at a flow rate of 20 L / min. As a comparative example, an example in which a sliding surface is formed only by elastic honing processing, a combination of elastic honing and normal plasma surface treatment, and ECM treatment alone is shown.

The scuffing property was measured as follows.
First, a part of the cylinder liner having the sliding surface as described above is cut out as a test piece to a height of 50 mm and a width of 30 mm, and lubricating oil (0.13 mg / cm 2) is applied to the sliding surface. A nitride ring piece having a height of 20 mm and a width of 10 mm is pressed against the sliding surface at a surface pressure of 330 MPa. In this state, the nitride ring piece is vibrated at 500 cycles / min with a vertical stroke of 40 mm. Then, the vibration duration time until the nitrided ring piece stops due to an increase in frictional force with the test piece is measured.

  It shows that the longer the measurement time is, the longer the state in which the sliding surface of the cylinder liner is not damaged and a sufficient lubricating oil film is formed and the low friction state is maintained. That is, the longer the measurement time, the higher the scuffing property.

  In the examples according to the present embodiment, sufficient scuffing properties for a long time are obtained with any aluminum alloy. Overall, higher scuffing is obtained than in the case of ECM. As shown in the comparative example, only the elastic honing process or the combination of the normal plasma surface process and the elastic honing process is not practical because of insufficient scuffing.

(Example 2)
As an embodiment of the present invention, FIG. 7A shows an aluminum alloy (here, ADC12) subjected to a plasma melting and roughening step and a plateau surface forming step by elastic honing as described above with nitrogen gas. The micrograph which shows the surface state in a case, (b) is the unevenness | corrugation state measurement graph in the one cross section.

  As a comparative example, FIG. 8A is a micrograph showing a surface state when only elastic honing is performed on the same metal material, and FIG. Similarly, (a) of FIG. 9 shown as a comparative example is a micrograph showing the surface state when ECM processing is performed on the same metal material, and (b) is an uneven state measurement graph in one section thereof.

  In the embodiment shown in FIG. 7, the concave portion is sufficiently deep and the function as an oil pit is high. At the same time, the individual plateau surfaces P (white islands in the photograph) are sufficiently wide, and the surface area is more than 10 times that of the comparative example by ECM processing in FIG. What has been made ultrafine in the plasma melting and roughening step is present under the plateau surface P. Moreover, the hardness rises from the original hardness (100 to 110 HV) after processing and reaches 140 to 190 HV. It is 180HV in actual measurement. As a result, generation of wear powder due to friction with the piston ring can be suppressed. Furthermore, since the plateau surface P is wide, the surface pressure at the time of piston ring friction is reduced, and the oil film of lubricating oil supplied from a sufficiently deep recess is also thickened. Therefore, the wear resistance is sufficiently high. In fact, in the test piece of FIG. 7, the actual scuffing value exceeds 40 minutes.

  Only the elastic honing process shown in FIG. 8 cannot form the recesses sufficiently deep, and there is almost no lubricating oil retention capability. In addition, the hardness has not increased, and Si crystals protrude from the surface. For this reason, abrasion resistance is low. Actually, in the test piece of FIG. 8, the measured value of scuffing is 0.75 minutes, which is very low.

  When the ECM processing shown in FIG. 9 is executed, the concave portion can be formed at a certain depth, but the hardness does not increase, the plateau surface at the tip of the convex portion becomes very small, and the wear resistance is It is insufficient. Si crystal protrudes on the surface. In addition, it is a process that generates waste liquid, which causes environmental problems. Actually, in the test piece of FIG. 9, the measured value of scuffing is 5.75 minutes, which is considerably shorter than the test piece of FIG.

  Thus, the metal material sliding surface structure according to the present embodiment can form a hardened layer on the surface of the metal material (here, the cylinder bore) without forming a sprayed coating, and the concave portion can be made sufficiently deep so that lubricating oil can be applied. It can be retained sufficiently. Moreover, environmental problems such as waste liquid treatment do not occur.

  Therefore, even if an aluminum alloy material is used as the metal material, a cylinder bore having very high wear resistance can be formed, and even if it is used for a cylinder block or a cylinder liner of an internal combustion engine, it is sufficiently practical. This makes it possible to further reduce the weight of the internal combustion engine and contribute to improving fuel consumption.

(Example 3)
The plasma melting and roughening step and the plateau surface forming step are executed by changing the conditions (here, the pressure and flow rate of nitrogen gas to be converted into plasma), and the depth of the concave portion (the same as the height of the plateau surface P). ) Were made of test pieces of various aluminum alloys (ADC12). However, the average area of the plateau surface was 5 μm 2 (square micrometer), and the area ratio of the plateau surface was 15%. The result of measuring the scuffing property of this test piece is shown in FIG.

  If the depth of the concave portion is less than 1.0 μm, the scuffing property tends to rapidly decrease, and if it exceeds 20 μm, the amount of consumption of lubricating oil tends to increase. Therefore, practically, the depth of the concave portion is desirably in the range of 1.0 to 20 μm.

Example 4
An aluminum alloy (ADC12) in which the plasma melting roughening step and the plateau surface forming step are executed by changing various conditions (here, the pressure and flow rate of nitrogen gas to be converted into plasma) and the plateau surface area ratios are different. A test piece was created. However, the average depth of the concave portion (the same as the height of the plateau surface P) is 10 μm, and the average area of the plateau surface is 5 μm 2. The result of measuring the scuffing property of this test piece is shown in FIG.

  If the area ratio of the plateau surface is less than 5%, the contact stress increases due to an increase in the surface pressure with the piston ring and the scuffing property tends to decrease. Lubricating oil does not rotate sufficiently and the scuffing property tends to decrease. Therefore, practically, as shown in the formula 1, the area ratio of the plateau surface is preferably in the range of 5 to 70%.

[Embodiment 2]
FIG. 12 shows an example of a work robot 52 that executes the metal material sliding surface forming method and forms the sliding surface by processing the surface of the workpiece 50 as the metal material as in the above-described embodiments. The workpiece 50 may be a cylinder block or a cylinder liner of an internal combustion engine, or may be a metal material used for other sliding portions, for example, a bearing such as a connecting rod, a crank bearing, or a cam bearing. Further, the metal material itself is not limited to an aluminum alloy, but can be applied to alloys of other metals such as cast iron.

The work robot 52 has a plasma nozzle 56 attached to the tip of an arm 54.
Plasma irradiation is performed from the irradiation port 56a to the processing target surface 50a of the workpiece 50 disposed on the work table 58, whereby a plasma melting and roughening step is executed, as shown in FIGS. An uneven surface with high hardness is formed.

  Here, a high voltage current is supplied to the plasma nozzle 56 from a high frequency high voltage device 60 attached to the arm 54 at a plasma frequency of 18 kHz, and a compressed nitrogen gas having a pressure of 0.52 to 0.53 MPa flows from the nitrogen cylinder 62. It is supplied at 20 liters / minute. As a result, the nitrogen gas is turned into plasma by the plasma generator provided in the plasma nozzle 56 and irradiated from the irradiation port 56a. The plasma frequency, voltage, and current amount supplied from the high-frequency and high-voltage device 60 are controlled by the plasma melting device main body 64. At the same time, the work operation of the work robot 52 and the movement of the work table 58 are also controlled by the plasma melting apparatus main body 64.

  For example, when the workpiece 50 is a cylinder liner of an internal combustion engine, the distance to the irradiation port 56a is 5 mm with respect to the cylinder bore which is the inner peripheral surface, the relative rotational speed with respect to the plasma nozzle 56 is 50 rpm, plasma The plasma melting and roughening step is performed by moving the cylinder liner in the axial direction relative to the nozzle 56 at a speed of 0.85 mm / sec.

  Note that the irregular shape and hardness are adjusted to the desired range by adjusting the plasma frequency, voltage, current, gas pressure, flow rate, etc., but it is not necessary to adjust all the adjustment elements, especially depending on the gas pressure and flow rate. Full adjustment is possible within a certain range.

  After completion of the plasma melting and roughening process by the work robot 52, the cylinder bore is formed with a hardened surface having irregularities as shown in FIGS. The work table 58 is moved to the work position of the robot that executes the above, and mirror finish processing by elastic honing is executed as a plateau surface forming step.

As a result, a cylinder bore with a plateau surface P can be formed as shown in FIGS. As a result, the effect as shown in the first embodiment can be obtained.
[Other embodiments]
In Examples 2 to 4 of the first embodiment, ADC 12 was used as the aluminum alloy, but a high Si aluminum alloy containing 23% Si, a high strength high wear resistant aluminum alloy containing 17% Si, etc. Various aluminum alloys may be used, and the high wear resistance becomes even more remarkable.

  DESCRIPTION OF SYMBOLS 2 ... Plasma melting apparatus (surface melting apparatus), 4 ... Cylinder block, 5 ... Cylinder, 6 ... Cylinder bore, 8 ... Plasma oscillator, 8a ... High frequency high voltage apparatus, 10 ... Gas supply apparatus, 10a ... Gas piping, 12 ... Plasma generator, 14 ... Plasma nozzle, 14a ... Irradiation port, 16 ... Plasma head, 50 ... Workpiece, 50a ... Surface to be processed, 52 ... Working robot, 54 ... Arm, 56 ... Plasma nozzle, 56a ... Irradiation port, 58 ... Work table, 60 ... high frequency high voltage device, 62 ... nitrogen cylinder, 64 ... plasma melting apparatus main body, C ... concave portion, P ... plateau surface, V ... convex portion.

Claims (29)

A sliding surface structure that forms a plateau surface that is aligned with one surface parallel to the surface of the metal material by removing the tip of the convex portion among the irregularities formed on the surface of the metal material,
The metal material sliding surface structure, wherein the unevenness before the tip of the convex portion is removed is formed by melting the surface of the metal material by plasma irradiation. The metal material sliding surface structure according to claim 1, wherein the removal of the tip of the convex portion is performed by grinding after plasma irradiation. The metal material sliding surface structure according to claim 2, wherein the removal of the tip of the convex portion is formed by a honing process. The metal material sliding surface structure according to claim 3, wherein the honing is performed by an elastic honing grindstone. 5. The metal material sliding surface structure according to claim 1, wherein an average depth of the concave portion in the concave and convex portions is in a range of 1.0 to 20 μm from the plateau surface. Characteristic metal material sliding surface structure. The metal material sliding surface structure according to any one of claims 1 to 5, wherein an area ratio occupied by the plateau surface in a total area of a region where the unevenness is formed is 5 to 70%. Metal material sliding surface structure. The metal material sliding surface structure according to any one of claims 1 to 6, wherein an average area per surface of the plateau surface is 5 µm 2 or more. The metal material sliding surface structure according to any one of claims 1 to 7, wherein the metal material is an aluminum alloy. 9. The metal material sliding surface structure according to claim 8, wherein the aluminum alloy contains silicon. The metal material sliding surface structure according to claim 8 or 9, wherein the unevenness is formed in a state where the hardness is 140 HV or more by plasma irradiation. 11. The metal material sliding surface structure according to claim 10, wherein the irregularities are formed by plasma irradiation in a hardness range of 140 to 190 HV. The metal material sliding surface structure according to any one of claims 1 to 11, wherein the melting by the plasma irradiation is performed by irradiating the surface of the metal material with an inert gas in a plasma state. Characteristic metal material sliding surface structure. The metal material sliding surface structure according to any one of claims 1 to 11, wherein the melting by the plasma irradiation is performed by irradiating the surface of the metal material in a plasma state. Metal material sliding surface structure. A cylinder for an internal combustion engine, wherein the inner peripheral surface has the metal material sliding surface structure according to any one of claims 1 to 13. The internal combustion engine cylinder according to claim 14, wherein the internal combustion engine cylinder is formed as a cylinder liner. The internal combustion engine cylinder according to claim 14, wherein the internal combustion engine cylinder is formed integrally with a cylinder block. A plasma melting and roughening step in which the surface of the metal material is melted and shaken by plasma irradiation to form solidities on the surface and solidify;
After the plasma melting and roughening step, the tip of the convex portion is removed to one surface that is parallel to the surface of the metal material and set at the intermediate position in the thickness direction of the concave and convex, and a plateau surface is formed at the tip of the convex portion A plateau surface forming step,
The metal material sliding surface forming method characterized by performing. The metal material sliding surface forming method according to claim 17, wherein the plateau surface forming step includes removing a tip of the convex portion by grinding. The method for forming a metal material sliding surface according to claim 18, wherein the plateau surface forming step includes performing the grinding by honing. 20. The method for forming a metal material sliding surface according to claim 19, wherein the honing is performed by an elastic honing grindstone. The metal material sliding surface forming method according to any one of claims 17 to 20, wherein in the plateau surface forming step, the plateau surface has an average height from a bottom portion of a concave portion of 1.0 to 20 µm. A method for forming a sliding surface of a metal material, characterized in that it is formed in a range. The metal material sliding surface forming method according to any one of claims 17 to 21, wherein in the plateau surface forming step, an area ratio that occupies the plateau surface in a total area of the region where the unevenness is formed is 5. A method for forming a sliding surface of a metal material, characterized in that it is formed as ˜70%. The metal material sliding surface forming method according to any one of claims 17 to 22, wherein the plateau surface forming step forms the plateau surface with an average area per surface being 5 µm2 or more. Metal material sliding surface forming method. 24. The method of forming a metal material sliding surface according to claim 17, wherein an aluminum alloy is used as the metal material. 25. The method for forming a metal material sliding surface according to claim 24, wherein the aluminum alloy contains silicon. 26. The metal material sliding surface forming method according to any one of claims 17 to 25, wherein in the plasma melting and roughening step, the unevenness after solidification is formed with a hardness of 140 HV or more. A metal material sliding surface forming method. 27. The method of forming a metal material sliding surface according to claim 26, wherein the plasma melting and roughening step forms the unevenness after solidification within a hardness range of 140 to 190 HV. Surface forming method. The metal material sliding surface forming method according to any one of claims 17 to 27, wherein the plasma melting and roughening step irradiates a surface of the metal material with an inert gas in a plasma state. Metal material sliding surface forming method. The metal material sliding surface forming method according to any one of claims 17 to 28, wherein the plasma melting and roughening step irradiates a surface of the metal material with plasma in the atmosphere. Material sliding surface forming method.