Patent Application
20110315111
The present invention relates to a piston of internal combustion engine, on which a multiple-layer coating is formed.
U.S. Patent Application Publication No. 2008/0060603 corresponding to Japanese Patent Application Publication No. 2008-56750 (hereinafter referred to as, patent document 1) discloses a previously-proposed piston of internal combustion engine for an automobile, as one method of improving an abrasion resistance or a seizing resistance of the piston.
In this technique, a surface of piston base material 1a coated by a lower-layer coating composite, and a surface of the lower-layer coating composite is coated by an upper-layer coating composite. The lower-layer coating composite includes an epoxy resin and a polyamide-imide resin as binding resins, and a polytetrafluoroethylene and a molybdenum disulfide as solid lubricants. The upper-layer coating composite includes the epoxy resin and the polyamide-imide resin as the binding resins, a boron nitride as the solid lubricant, and a silicon nitride and an alumina as hard particles. That is, a double-layer coating composite is formed in order to attain a superior abrasion resistance and to improve the seizing resistance and an initial fitting property.
However, in the technique disclosed by the patent document 1, the upper and lower layers of the double-layer coating composite are simply in an overcoated state. Hence, it cannot be recognized whether or not the upper and lower layers of the double-layer coating composite have been properly formed, from an outward appearance of the piston. Therefore, there is a risk that a piston including only single layer of coating is distributed as a piston product by mistake, so that a reliability of piston product becomes low.
It is an object of the present invention to provide a piston of an internal combustion engine, devised to enable to determine whether or not a predetermined multiple-layer coating has been formed on an outer surface of the piston, from an outer appearance of the piston.
According to one aspect of the present invention, there is provided a piston for an internal combustion engine, comprising: a piston base material including a pair of skirt portions opposed to each other in a radial direction of the piston base material; a multiple-layer coating formed on at least one of surfaces of the pair of skirt portions; and marks provided to respective layers of the multiple-layer coating at locations different from each other.
According to another aspect of the present invention, there is provided a piston for an internal combustion engine, comprising: a piston base material including a pair of skirt portions opposed to each other in a radial direction of the piston base material; and a multiple-layer coating formed on at least one of surfaces of the pair of skirt portions, wherein an upper layer of the multiple-layer coating is formed with a window portion, and a surface of the piston base material or a lower layer of the multiple-layer coating is exposed through the window portion.
According to still another aspect of the present invention, there is provided a piston for an internal combustion engine, comprising: a piston base material including a pair of skirt portions opposed to each other in a radial direction of the piston base material; a multiple-layer coating formed on at least one of surfaces of the pair of skirt portions, the multiple-layer coating containing a solid lubricant; and single-layer mark coatings provided at locations which are different from each other and which are away from the multiple-layer coating through a non-coated portion between the multiple-layer coating and each of the single-layer mark coatings.
The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.
Hereinafter, embodiments of a piston of internal combustion engine according to the present invention will be explained in detail referring to the drawings. In the following embodiments, the piston is applied to a four-cycle gasoline engine.
As shown in
Whole of the piston 1 is integrally molded by an Al—Si-series aluminum alloy in AC8A (JIS: Japanese Industrial Standards). As shown in
The crown portion 7 is formed to be relatively thick and formed in a disc shape. Valve recesses 7e and 7f are formed in the crown surface 7a of the crown portion 7. Each of the valve recesses 7e and 7f functions to prevent an interference with an intake or exhaust valve. Three ring grooves 7b, 7c and 7d are formed in an outer circumferential portion of the crown portion 7. The three ring grooves 7b, 7c and 7d hold three piston rings such as a pressure ring and an oil ring.
The both skirt portions 8 and 9 are located symmetrically with respect to an axis (a center line parallel to a piston moving direction) of the piston 1, and are shaped like arc in cross section. In other words, the both skirt portions 8 and 9 are formed to be opposed to each other in a radial direction of the piston 1. Almost whole of the both skirt portions 8 and 9 is formed to be relatively thin. When the piston 1 moves toward its bottom dead center at the time of expansion stroke and the like, the thrust-side skirt portion 8 is inclined to the cylinder wall-surface 3 to become in press-contact with the cylinder wall-surface 3 in relation to an angle of the con-rod 6. On the other hand, when the piston 1 rises at the time of compression stroke and the like, the counter-thrust-side skirt portion 9 is inclined to the cylinder wall-surface 3 to become in press-contact with the cylinder wall-surface 3 in a counter direction. A load of this press contact of the thrust-side skirt portion 8 against the cylinder wall-surface 3 is larger than that of the counter-thrust-side skirt portion 9 against the cylinder wall-surface 3 because the thrust-side skirt portion 8 presses the cylinder wall-surface 3 by receiving a combustion pressure.
As shown in
That is, the multiple-layer coating composite 20 includes an upper-layer coating composite 21 and a lower-layer coating composite 22. The multiple-layer coating composite 20 is formed by using one or two selected from an epoxy resin, a polyimide resin and a polyamide-imide resin (PAI) which are superior in heat resistance, abrasion resistance (wear resistance) and adhesion property, as binding resins.
Specifically, the upper-layer coating composite 21 is set to include any one of the epoxy resin, the polyimide resin and the polyamide-imide resin (which are the binding resins) in a range from 5 to 50 wt %. Moreover, the upper-layer coating composite 21 is set to include a molybdenum disulfide (MoS2) in a range from 50 to 95 wt %, as a solid lubricant.
If the binding resin(s) accounts for a rate lower than 5 wt %, an adhesion between the upper-layer coating composite 21 and the lower-layer coating composite 22 is reduced due to a reduction of binding force. On the contrary, if the binding resin(s) accounts for a rate higher than 50 wt %, the solid lubricant is relatively decreased so that an initial fitting property (initial compatibility) is reduced.
The lower-layer coating composite 22 is set to include any one of the epoxy resin, the polyimide resin and the polyamide-imide resin (which are the binding resins) same as the upper-layer coating composite 21, in a range higher than or equal to 50 wt %. Moreover, the lower-layer coating composite 22 is set to basically include one or more of a polytetrafluoroethylene (PTFE), the molybdenum disulfide (MoS2) and a graphite (GF), in a range lower than or equal to 50 wt % as the solid lubricant. The lower-layer coating composite 22 does not necessarily need to include the solid lubricant.
If the binding resin(s) accounts for a rate lower than 50 wt % in the lower-layer coating composite 22, an adhesion between the lower-layer coating composite 22 and a piston base material (base member) 1a is reduced. In a case that each of the solid lubricants is increasingly added to the binding resin PAI as shown in
That is, the lower-layer coating composite 22 functions to secure the adhesion between the lower-layer coating composite 22 and the piston base material 1a, and to secure the adhesion between the upper-layer coating composite 21 and the lower-layer coating composite 22.
Accordingly, although the lower-layer coating composite 22 does not need to contain the solid lubricant, the solid lubricant(s) may be added to the lower-layer coating composite 22 within a rate capable of securing these adhesions, in order to improve a characteristic of the coating. If the polytetrafluoroethylene is lower than 15 wt % in the lower-layer coating composite 22, a lubricity is reduced. On the other hand, if the polytetrafluoroethylene is higher than 30 wt %, an abrasion amount is increased.
Moreover, if the molybdenum disulfide as the solid lubricant accounts for a rate lower than 5 wt % in the lower-layer coating composite 22, a seizing resistance is reduced. On the other hand, if the molybdenum disulfide accounts for a rate higher than 20 wt % in the lower-layer coating composite 22, the abrasion amount is increased due to a reduction of strength of the coating.
Moreover, an improvement of the seizing resistance can be achieved by a synergistic effect of combination between the molybdenum disulfide and the graphite given as the solid lubricants.
That is, the lower-layer coating composite 22 can be formed by using the molybdenum disulfide and the graphite in addition to the polytetrafluoroethylene as the solid lubricants. In this case, it is preferable that a total rate of the molybdenum disulfide and the graphite ranges from 5 to 20 wt %, and a rate of the molybdenum disulfide ranges from 1 to 10 wt %.
This is because the above-mentioned improvement effect of seizing resistance by the synergistic effect cannot be obtained if the molybdenum disulfide is lower than 1 wt %, and the abrasion resistance is reduced if the molybdenum disulfide is higher than 10 wt %.
Moreover, a reason to set a content (contained amount) of the molybdenum disulfide and the like functioning as the solid lubricants of the upper-layer coating composite 21 in the range from 50 to 95 wt % is as follows. That is, from an experimental result as shown in
A method of adjusting the upper-layer coating composite 21 and the lower-layer coating composite 22 which constitute the multiple-layer coating composite 20 is as follows, for example. An organic solvent is mixed with the epoxy resin, the polyimide resin and the polyamide-imide resin which are the biding resins. Then, the solid lubricant(s) is added to this resin solution. Further, as needed basis, hard particles are added to this resin solution. Then, this solution is mixed and dispersed by use of a beads-mill or the like.
A total mixture amount of the hard particles, the binding resin and the solid lubricant(s) such as PTFE, MoS2 and GF is equal to 100 wt % of the upper-layer coating composite 21 or the lower-layer coating composite 22.
The upper-layer coating composite 21 and the lower-layer coating composite 22 which constitute the multiple-layer coating composite 20 according to the present invention are diluted by organic solvent, as needed basis. Then, the upper-layer coating composite 21 and the lower-layer coating composite 22 are applied to the piston base material 1a, as a coating material.
That is, the lower-layer coating composite 22 and the upper-layer coating composite 21 are applied to an outer circumferential surface of (the thrust-side skirt portion 8 and the counter-thrust-side skirt portion 9 of) the piston base material 1a, in this order. Then, the applied lower-layer coating composite 22 and upper-layer coating composite 21 are burned and cured to obtain the multiple-layer coating composite 20.
The organic solvent which is used for the above-mentioned dilution has only to be able to dissolve the binding resin. That is, the organic solvent which is used in this embodiment is not limited to specified solvents.
A burning condition such as a burning temperature and a burning time is appropriately set. The lower-layer coating composite 22 and the upper-layer coating composite 21 can be properly burned even at a temperature lower than 200° C., and therefore, is applicable also to an aluminum-alloy base material of the piston 1.
A film thickness (coating thickness) of the multiple-layer coating composite 20 can be appropriately selected. However, it is preferable that the film thickness of the multiple-layer coating composite 20 falls within a range from 5 to 40 μm, in consideration of an applying workability of the coating composite 20 and a cost for the coating composite 20 and the like.
A concrete method for applying the multiple-layer coating composite 20 on the surface of the piston base material 1a will now be explained.
At first, oil and dirt of the surface of the piston base material 1a are removed by a pretreatment such as a solvent degreasing and an alkaline degreasing.
Next, the lower-layer coating composite 22 is applied to (putted on) the surface of the piston base material 1a by a known method such as an air spray and a screen printing. Subsequently, the upper-layer coating composite 21 is applied to (putted on) an upper surface of the lower-layer coating composite 22.
Subsequently, the organic solvent is removed by drying. Then, the applied upper-layer coating composite 21 and lower-layer coating composite 22 are burned under a known condition, for example, for thirty minutes at 180° C. or for twenty minutes at 200° C. Thereby, the multiple-layer coating composite 20 constituted by the upper-layer coating composite 21 and the lower-layer coating composite 22 is formed.
Another surface-treatment method is as follows. At first, oil and dirt are removed from the surface of the piston base material 1a on which the multiple-layer coating composite 20 should be formed, by a pretreatment such as the solvent degreasing and the alkaline degreasing.
Then, the lower-layer coating composite 22 is applied to the surface of the piston base material 1a by a known method such as the air spray and the screen printing. Then, the applied lower-layer coating composite 22 is burned under a known condition, for example, for thirty minutes at 180° C. or for twenty minutes at 200° C.
Subsequently, the piston base material 1a is drawn (pulled) out from a burning furnace. Then, the upper-layer coating composite 21 is applied to an upper surface of the lower-layer coating composite 22 of the piston base material 1a under a condition where the piston base material 1a has a temperature ranging from 50 to 120° C. Subsequently, the piston base material 1a is dried without burning, so that the multiple-layer coating composite 20 constituted by the upper-layer coating composite 21 and the lower-layer coating composite 22 is formed.
The multiple-layer coating composite according to the present invention is widely applicable to various sliding members for various intended uses under an environment of oil lubrication and an environment of dry lubrication. The epoxy resin, the polyimide resin and the polyamide-imide resin which are the biding resins for the multiple-layer coating composite are superior in adhesion property. Hence, these epoxy resin, polyimide resin and polyamide-imide resin are applicable to various materials (each constituting the base material) such as cast iron, steel and copper alloy in addition to various kinds of aluminum alloy materials, without being limited to specified kinds of base materials. In particular, it is favorable that the epoxy resin, the polyimide resin and the polyamide-imide resin are used for the piston 1 of internal combustion engine, especially, for the thrust-side skirt portion 8 and the counter-thrust-side skirt portion 9 of the piston 1 as in this embodiment.
The following formulas are satisfied as to the piston 1 having a notch shape (track recess) in an outer circumferential surface of the piston 1.
t2≧a−5 (μm)
t1≧2 (μm)
Wherein a denotes a height (depth) of the notch, t1 denotes a film thickness of the lower-layer coating composite 22, and t2 denotes a film thickness of the upper-layer coating composite 21. As the binding resins, the polyamide-imide resin (PAI) was used. The content (contained amount) of each of the graphite (GF), the molybdenum disulfide (MoS2) and the polytetrafluoroethylene (PTFE) given as the solid lubricants was varied from 0 wt % to 95 wt %.
The upper-layer coating composite and the lower-layer coating composite were adjusted as shown in the following table 1.
The organic solvent was added to and mixed with the upper-layer and lower-layer coating composites for so each of the samples No. 1 to No. 59 except the sample No. 21. Then, each of the mixed upper-layer and lower-layer coating composites of the samples No. 1 to No. 59 was dispersed by the beads-mill for thirty minutes, so that upper-layer coating paint and lower-layer coating paint for each of the samples No. 1 to No. 59 were obtained.
The lower-layer coating paint for each sample was applied on a test piece 1a having a surface shape shown in
Subsequently, the upper-layer coating paint for each sample was applied on (the lower-layer coating of) the test piece 1a so as to cause the entire upper-layer coating to have a film thickness ranging from 5 to 11 μm. Then, the upper-layer coating paint applied on the test piece 1a was dried by air drying without the burning.
Alternatively, the lower-layer coating paint applied on the test piece 1a may be dried by forced drying. In this case, the upper-layer coating paint applied on (the lower-layer coating of) the test piece 1a is burned for 30 minutes at 190° C.
As to the obtained samples No. 1 to 20 which had undergone the double-layer surface treatment and as to the sample No. 21 which had undergone no surface treatment, friction coefficients were measured by a chip-on-ring-type friction and abrasion tester under a lubricating environment where a slip speed is equal to 2 m/sec (meters per second), a contact material 1a FC250 (JIS), a slip distance is equal to 600 m, a surface pressure is equal to 1.3 MPa, and a drip amount of engine oil is equal to 5 mg/min (milligrams per minute).
That is, in order to obtain a low friction coefficient, it is effective to quickly abrade (wear) the upper-layer coating. Therefore, as is clear from
Accordingly, the low friction can be obtained in this embodiment.
For example, in the case of
Moreover, as understood by
If the lower-layer coating is set to contain the solid lubricant(s) accounting for 50 wt % or more of the lower-layer coating (see examples No. 22 to No. 40), the adhesion property between the lower-layer coating and the piston base material 1a is reduced as shown in
Therefore, the lower-layer coating in this embodiment according to the present invention is set to ensure the adhesion to the piston base material 1a and also to ensure the adhesion to the upper-layer coating containing the solid lubrication of 50 wt % or more.
As the solid lubricant for the lower-layer coating containing the binding resin of PAI, each content of the molybdenum disulfide (MoS2), the graphite (GF) and the polytetrafluoroethylene (PTFE) was varied from 15 wt % through 30 wt %, 50 wt %, 60 wt % and 75 wt % to 95 wt % under a condition that the upper-layer coating was constituted by the binding resin of 5 wt % and the molybdenum disulfide of 95 wt % which does not secure the adhesion to the aluminum-alloy base material. The adhesive forces of these various samples (see samples No. 41 to No. 59) were measured. As a result, it is found that the adhesive force can be ensured by causing the lower-layer coating to contain the solid lubricant at a rate lower than or equal to 50 wt %, even if the upper-layer coating so composite which does not ensure the adhesion property is used.
As explained above, the adhesion property of the lower-layer coating composite 22 to the piston base material 1a superior in this embodiment. Moreover, is since the content (contained amount) of the molybdenum disulfide (MoS2) is set at the range from 50 wt % to 95 wt % as the solid lubricant of the upper-layer coating composite 21, the initial fitting property (initial compatibility) is superior when the outer circumferential surfaces of the thrust-side skirt portion 8 and the counter-thrust-side skirt portion 9 of the piston 1 slide on the cylinder wall-surface 3. That is, a surface of the upper-layer coating composite 21 is abraded in a short time to quickly form a smooth sliding surface of the upper-layer coating composite 21, so that a superior initial fitting property can be obtained instantly.
In this embodiment, the single lower-layer coating composite 22 and the single upper-layer coating composite 21 are applied to both the skirt portions 8 and 9 of piston 1 in a double-layered state, as explained above. The piston 1 in this embodiment according to the present invention includes a means for checking (judging) whether or not these lower-layer coating composite 22 and upper-layer coating composite 21 have been applied without mistake. Both of the lower-layer coating composite 22 and the upper-layer coating composite 21 have a color close to black.
In more specifically, as shown in
On the other hand, as shown in
Accordingly, for example, if the upper-layer coating composite 21 has not been applied by mistake after the lower-layer coating composite 22 was applied to the piston base material 1a, the surface of the piston base material 1a is exposed through the first window portion 30 as shown by
For example, if the lower-layer coating composite 22 has not been applied by mistake although the upper-layer coating composite 21 has been applied to the piston base material 1a, the surface of the piston base material 1a is exposed through the second window portion 31 as shown by
Moreover, if both of the lower-layer coating composite 22 and upper-layer coating composite 21 have been properly applied; the first window portion 30 is coated by the upper-layer coating composite 21, and the lower-layer coating composite 22 is exposed through the second window portion 31 as a background of the second window portion 31, as shown in
Therefore, a piston including only single layer of coating can be prevented from being distributed as a piston product by error. Hence, a reliability of product can be enhanced.
The first and second window portions 30 and 31 are provided in a region of each skirt portion 8 or 9 which has a relatively less-frequent or weak slide contact with the cylinder wall-surface 3. Hence, the first and second window portions 30 and 31 are little influenced by friction so that a generation of abrasion can be suppressed. Moreover, a freedom degree of design of each skirt portion 8 or 9 in an axial direction of the piston 1 becomes high.
Moreover, the lower-layer coating composite 22 and the upper-layer coating composite 21 have filled the first and second window portions 30 and 31 in the case that both of the upper-layer coating composite 21 and the lower-layer coating composite 22 have been properly applied. Hence, the generation of abrasion and the like can be suppressed even if a slight influence of friction is caused at the first and second window portions 30 and 31.
Moreover, the first and second window portions 30 and 31 are formed together when the lower-layer coating composite 22 and the upper-layer coating composite 21 are applied and formed. Hence, a forming operation of the first and second window portions 30 and 31 is very easy without requiring any special equipment. Therefore, a rise in cost can also be suppressed.
Although the error recognition and determination using the first and second window portions 30 and 31 are done by the visual check of working person in the above explanation, the structure according to this embodiment is not limited to this. For example, the error recognition and determination using the first and second window portions 30 and 31 can be mechanically done by means of a camera or the like. Therefore, the first and second window portions 30 and 31 according to this embodiment are applicable also to an operation of automated production line.
Accordingly, if only one of the upper-layer coating composite 21 and the lower-layer coating composite 22 has been applied to the piston base material 1a, only one of the first window portion 32 and the second window portion 33 has been formed. In this case, the surface of the piston base material 1a is exposed through the first window portion 32 or the second window portion 33 as shown in
Therefore, a piston including only single layer of coating can be prevented from being distributed as a piston product by mistake. Hence, the reliability of product can be enhanced.
Moreover, if both of the lower-layer coating composite 22 and upper-layer coating composite 21 have been applied; the first window portion 32 is coated by the upper-layer coating composite 21, and the lower-layer coating composite 22 is exposed through the second window portion 33, as shown in
The other operations and effects in the second embodiment are similar as those in the first embodiment.
Accordingly, if only one of the upper-layer coating composite 21 and the lower-layer coating composite 22 has been applied to the piston base material 1a, only one of the first window portion 34 and the second window portion 35 has been formed. In this case, the surface of the piston base material 1a exposed through the first window portion 34 or the second window portion 35 as shown in
As a result, a piston including only single layer of coating can be prevented from being distributed as a piston product by mistake. Hence, the reliability of product can be improved.
Moreover, if both of the lower-layer coating composite 22 and upper-layer coating composite 21 have been applied; the first window portion 34 is covered by the upper-layer coating composite 21, and the lower-layer coating composite 22 is exposed through the second window portion 35, as shown in
In the third embodiment, the first and second window portions 34 and 35 are provided in a region of each skirt portion 8 or 9 which conducts a less-frequent or weak slide contact with the cylinder wall-surface 3. Moreover, sizes of the first and second window portions 34 and 35 are sufficiently small as compared with those of the second embodiment. Hence, the first and second window portions 34 and 35 are little influenced by friction so that the generation of abrasion can be further suppressed. Moreover, the freedom degree of design of each skirt portion 8 or 9 in the axial direction is high.
That is, as shown in
Since the first and second window portions 36 and 37 are formed respectively in the lower-layer coating composite 22 and upper-layer coating composite 21 as mentioned above, a piston including only single layer of coating can be prevented from being distributed as a piston product by mistake. Hence, a reliability of product can be enhanced, in the same manner as the above respective embodiments. Moreover, there is little influence of friction when the thrust-side skirt portion 8 and the counter-thrust-side skirt portion 9 slide in contact with the cylinder wall-surface 3, so that the generation of abrasion can be suppressed.
Moreover, after the lower-layer coating composite 22 and upper-layer coating composite 21 were applied, a radial size (diameter) between the thrust-side skirt portion 8 and the counter-thrust-side skirt portion 9 can be accurately measured by a micrometer or the like by using the radially-opposed pair of third window portions 38 and 38 of both the skirt portions 8 and 9, i.e., by using both the exposed surfaces of the piston base material 1a.
Forming locations of both of the first and second window portions 36 and 37 do not necessarily need to be set with high precision relative to the circumferential and axial directions. That is, the first and second window portions 36 and 37 have only to function as the marks of the lower-layer coating composite 22 and upper-layer coating composite 21 and also to form the third window portion 38 securing its size necessary to measure the length between the both skirt portions 8 and 9 even if the shape of third window portion 38 is somewhat deformed.
That is, as shown in
Since the first and second window portions 39 and 40 are formed respectively in the lower-layer coating composite 22 and the upper-layer coating composite 21 as mentioned above, a piston including only single layer of coating can be prevented from being distributed as a piston product by mistake. Hence, a reliability of product can be enhanced, in the same manner as the above respective embodiments. Moreover, there is little influence of friction when the thrust-side skirt portion 8 and the counter-thrust-side skirt portion 9 slide in contact with the cylinder wall-surface 3, so that the generation of abrasion can be suppressed.
Moreover, after the lower-layer coating composite 22 and upper-layer coating composite 21 were applied, the radial size (diameter) between the thrust-side skirt portion 8 and the counter-thrust-side skirt portion 9 can be accurately measured by the micrometer or the like by using the radially-opposed pair of third window portions 41 and 41 of the skirt portions 8 and 9, i.e., by using both the exposed surfaces of the piston base material 1a.
As shown in
As shown in
Therefore, in this embodiment, if the upper-layer coating composite 21 has not been applied by mistake after the lower-layer coating composite 22 was applied to the piston base material 1a, only the first mark 42 has been formed as shown in
If the lower-layer coating composite 22 has not been applied by mistake although the upper-layer coating composite 21 has been applied to the piston base material 1a, only the second mark 43 has been formed as shown by
Moreover, if both of the lower-layer coating composite 22 and the upper-layer coating composite 21 have been applied, the first mark 42 and the second mark 43 have been formed in upper-and-lower alignment (axial alignment) as shown in
Therefore, a piston including only single layer of coating can be prevented from being distributed as a piston product by mistake. Hence, the reliability of product can be enhanced, in the same manner as the above respective embodiments.
The first mark 42 and the second mark 43 are provided in a region which has a relatively less-frequent or weak slide contact with the cylinder wall-surface 3. Hence, the first mark 42 and the second mark 43 are little influenced by friction so that a generation of abrasion can be suppressed. Moreover, since the first mark 42 and the second mark 43 are formed in the region which does not directly correspond to the skirt portions 8 and 9, a freedom degree of design of the skirt portions 8 and 9 and the marks 42 and 43 is high in the axial direction.
Moreover, the first mark 42 is formed concurrently together with the lower-layer coating composite 22, and the second mark 43 is formed concurrently together with the upper-layer coating composite 21, as mentioned above. Hence, a forming operation for the first mark 42 and the second mark 43 is very easy without requiring any special equipment. Therefore, the rise in cost can also be suppressed.
Accordingly, operations and effects similar as the fifth embodiment can be obtained. In addition, since the mutually-combined first and second marks 42 and 43 form the elongated rectangular shape, a visibility for the working person becomes more favorable to enable a quick recognition or determination.
Also in the seventh embodiment, the first and second marks 42 and 43 are apart from the lower-layer coating composite 22 and the upper-layer coating composite 21 by the clearance C. Hence, also from this point of view, the recognition by vision is easy in the same manner as the fifth embodiment.
In the eighth embodiment, operations and effects similar as the above respective embodiments can be obtained. In addition, since the first and second marks 42 and 43 are continuous with the lower-layer coating composite 22 and the upper-layer coating composite 21, the forming operation for the first and second marks 42 and 43 is easy. Moreover, the visibility for the working person is favorable because of the existence of the clearance S.
Therefore, also in this ninth embodiment, operations and effects similar as the eighth embodiment can be obtained. In addition, since the first and second marks 42 and 43 are connected with each other in the axial direction so that an axially-elongated rectangular mark is formed, the visibility for the working person is favorable.
The first mark 44 is located substantially at a circumferentially-center portion of the upper edge of the lower-layer coating composite 22. On the other hand, the second mark 45 is located on a right side (of
Therefore, operations and effects similar as the ninth embodiment and the like can be obtained.
The first mark 44 is located substantially at a circumferentially-center portion of the lower edge of the lower-layer coating composite 22. On the other hand, the second mark 45 is located on the right side (of
Therefore, operations and effects similar as the ninth embodiment and the like can be obtained.
According to the tenth and eleventh embodiments, the forming locations of the first and second marks 44 and 45 may be set to cause the first and second marks 44 and 45 to be combined with each other in the circumferential direction when both of the lower-layer coating composite 22 and the upper-layer coating composite 21 are applied.
In this twelfth embodiment, as shown in
These window portions 47a to 47f are located in the circumferentially end side (right side) of each of the first-layer to sixth-layer coating composites 46a to 46f, and arranged axially in a row at even intervals. Each layer of the first-layer to sixth-layer coating composites 46a to 46f has five windows (6-1) selected from the window portions 47a to 47f. Each of the first-layer to sixth-layer coating composites 46a to 46f is exposed to the outside of the piston 1 through the corresponding window portion given from the window portions 47a to 47f.
That is, as shown in
Accordingly, for example, if the application of the fourth-layer coating composite 46d was forgotten, the fourth window portion 47d has been formed in all of the other coating composites 46a-46c, 46e and 46f. Hence, as shown in
Therefore, the working person can recognize and determine that the fourth-layer coating composite 46d has not been applied, by visibly recognizing the aluminum-alloy surface exposed from the fourth window portion 47d. As a result, a piston product having its coating failure can be sufficiently prevented from being distributed, in the same manner as the above embodiments. Hence, the reliability of product is enhanced.
If all of the first-layer to sixth-layer coating composites 46a to 46f have been applied without mistake, all of the window portions 47a to 47f have been closed or filled by the first-layer to sixth-layer coating composites 46a to 46f so that no window portion (having the color near silver) is left as shown in
The first to fourth marks 49a to 49d are respectively formed integrally with the circumferential (right) edges of the first-layer to fourth-layer coating composites 48a to 48d. The first to fourth marks 49a to 49d are arranged in a row in the axial direction (up-down direction). There is no space between adjacent two of the first to fourth marks 49a to 49d in the axial direction. That is, forming locations of the first to fourth marks 49a to 49d are set to combine the first to fourth marks 49a to 49d integrally with one another (from upper and lower directions) as axially-extending one mark when all of the first-layer to fourth-layer coating composites 48a to 48d are properly applied, as shown in
In detail, as shown in
Accordingly, for example, if only the third-layer coating composite 48c has not been applied by mistake, the first and second marks 49a and 49b and the fourth mark 49d have been formed except the third mark 49c. Hence, the combined shape of the marks 49a, 49b and 49d is in a state cut (chipped) by the location S of the third mark 49c, as shown in
Therefore, the working person can recognize and determine that the third-layer coating composite 48c has not been applied, by visibly recognizing the aluminum-alloy surface exposed from the cutout location S of the third mark 49c. As a result, a piston product having its failure can be sufficiently prevented from being distributed, in the same manner as the above embodiments. Hence, the reliability of product is enhanced.
As shown in
Accordingly, for example, if only the third-layer coating composite 50c has not been applied by mistake, the first and second marks 51a and 51b and the fourth to nth marks 51d to 51n have been formed except the third mark 51c. Hence, the combined shape of the marks 51a, 51b and 51d-51n is in a state cut (chipped) by the location S of the third mark 51c, as shown in
Therefore, the working person can recognize and determine that the third-layer coating composite 50c has not been applied, by visibly recognizing the aluminum-alloy surface exposed from the cutout location S of the third mark 51c. As a result, a piston product having its failure can be sufficiently prevented from being distributed, in the same manner as the above embodiments. Hence, the reliability of product is enhanced.
As explained above, even in the case that the multiple-layer coating includes three or more layers as in the twelfth to fourteenth embodiments, it can be judged whether or not the multiple-layer coating has been properly formed, by use of the marks (window portions).
That is, at first, the lower-layer coating composite 22 and the first mark 42 are applied to the surfaces of both skirt portions 8 and 9 of the piston 1 by the above-mentioned method. At the same time, the plurality of black-dot coating portions 52 constituting a part of the lower-layer coating composite 22 are applied to a location to which the second mark 43 of the upper-layer coating composite 21 will be applied in a next process. Thereby, whole (aggregate) of the black-dot coating portions 52 defines a partly-coating-portion forming region 53 as shown in
As shown in
A total overlapping area between the black-dot coating portions 52 and the second mark 43 can be set within a range from 10% to 85% of an area of the second mark 43. That is, the black-dot coating portions 52 can be formed to cause parts of the second mark 43 which completely overlap with (i.e., cover) the black-dot coating portions 52 in a thickness direction of the multiple-layer coating composite 20, to have its area falling within a range between 10% and 85% of the area of the second mark 43. In this example according to the fifteenth embodiment, the total overlapping area is set approximately at 50% of the area of the second mark 43.
Therefore, in the fifteenth embodiment, a piston product including only single layer of coating can be prevented from being distributed by mistake, because of the existence of the marks 42 and 43, in the same manner as the above embodiments. Moreover, when the upper-layer coating composite 21 is applied to the upper surface of the lower-layer coating composite 22, the second mark 43 is concurrently bound to the black-dot coating portions 52 in addition to the surface of the piston base material 1a exposed through the spaces between the black-dot coating portions 52 in the partly-coating-portion forming region 53. Hence, the second mark 43 can be strongly bound to the piston 1 in the partly-coating-portion forming region 53.
That is, the second mark 43 is bound with (adheres to) the surface of the piston base material 1a and is also bound with the scattered black-dot coating portions 52, in the partly-coating-portion forming region 53. The second mark 43 is strongly bound to the respective black-dot coating portions 52 on the principle that the upper-layer coating composite 21 is strongly bound to the lower-layer coating composite 22. Accordingly, the second mark 43 is prevented from being carelessly detached from the surface of the piston 1 after the upper-layer coating composite 21 was formed on the lower-layer coating composite 22. As a result, by using the above-mentioned marks 42 and 43, it can be determined whether or not the multiple-layer coating composite 20 includes only a single layer, always with certainty.
Moreover, since the partly-coating-portion forming region 53 is formed more largely than the area (dimensions) of the second mark 43, the second mark 43 is not formed outside the partly-coating-portion forming region 53.
Although the black-dot coating portions 52 each shaped like a small circle have been explained as shown in
The various kinds of partly coating portions 52 are applicable to all of the embodiments explained above. In the first to fifth embodiments shown in
Moreover, in the sixth to eleventh embodiments as shown in
Moreover, in the twelfth embodiment as shown in
Moreover, in the thirteenth embodiment as shown in
Moreover, in the fourteenth embodiment as shown in
Therefore, in the case that the partly coating portion(s) 52 is formed in the window portion 30, 32, . . . or in the partly-coating-portion forming region 53 in the above respective embodiments, operations and effects similar as the fifteenth embodiment can be obtained.
Although the invention has been described above with reference to certain embodiments of the invention, the invention is not limited to the embodiments described above. Modifications and variations of the embodiments described above will occur to those skilled in the art in light of the above teachings. For example, the above-mentioned materials (components) constituting each of the upper-layer coating composite 21 and the lower-layer coating composite 22 in the first embodiment can be changed to the other material(s).
Some technical structures obtainable from the above embodiments according to the present invention will now be listed with their advantageous effects.
[a] A piston for an internal combustion engine, comprising: a piston base material (1a) including a pair of skirt portions (8, 9) opposed to each other in a radial direction of the piston base material (1a); a multiple-layer coating (20) formed on at least one of surfaces of the pair of skirt portions (8, 9); and marks (30-37, 39, 40, 42-45, 47a-47f, 49a-49d, 51a-51n) provided to respective layers (21, 22, 46a-46f, 48a-48d, 50a-50n) of the multiple-layer coating (20) at locations different from each other.
[b] A piston for an internal combustion engine, comprising: a piston base material (1a) including a pair of skirt portions (8, 9) opposed to each other in a radial direction of the piston base material (1a); and a multiple-layer coating (20) formed on at least one of surfaces of the pair of skirt portions (8, 9), wherein an upper layer (21, 46b-46f) of the multiple-layer coating (20) is formed with a window portion (33, 35, 37, 40, 47a-47f), and a surface of the piston base material (1a) or a lower layer (22, 46a-46e) of the multiple-layer coating (20) is exposed through the window portion (33, 35, 37, 40, 47a-47f).
[c] A piston for an internal combustion engine, comprising: a piston base material (1a) including a pair of skirt portions (8, 9) opposed to each other in a radial direction of the piston base material (1a); a multiple-layer coating (20) formed on at least one of surfaces of the pair of skirt portions (8, 9), the multiple-layer coating (20) containing a solid lubricant; and single-layer mark coatings (42-43) provided at locations which are different from each other and which are away from the multiple-layer coating (20) through a non-coated portion (C) between the multiple-layer coating (20) and each of the single-layer mark coatings (42-43).
Accordingly, as an advantageous effect, for example, it can be determined whether or not the predetermined multiple-layer coating has been formed, by a visual check of the appearance of the piston by use of the marks (window portions).
[d] The piston as described in the above item [a], wherein the marks (34, 35, 42, 43, 47a-47f, 49a-49d, 51a-51n) corresponding to the respective layers (21, 22, 46a-46f, 48a-48d, 50a-50n) of the multiple-layer coating (20) are located at least on one circumferential side of the skirt portion (8, 9).
According to this structure, since the marks are provided at a skirt portion's part at which the skirt portion less-frequently or weakly slides in contact with the cylinder wall-surface, the marks are little influenced by friction so that the generation of abrasion can be suppressed. Moreover, the freedom degree of design of the skirt portion in the axial direction of piston is high.
[e] The piston as described in the above item [a], wherein each of the marks has the same composition as the corresponding layer of the multiple-layer coating (20), and the marks (44, 45) are located on an upper or lower side of the skirt portion (8, 9) relative to an axial direction of the piston.
According to this structure, since the marks are provided at a skirt portion's part at which the skirt portion less-frequently or weakly slides in contact with the cylinder wall-surface, the marks are little influenced by friction so that the generation of abrasion can be suppressed. Moreover, the freedom degree of design of the skirt portion in the axial direction of piston is high.
[f] The piston as described in the above item [a], wherein each of the marks has the same composition as the corresponding layer of the multiple-layer coating (20), and each of the marks (42-45, 49a-49d, 51a-51n) is formed to be continuous with the corresponding layer of the multiple-layer coating (20).
According to this structure, since the respective marks are continuous with the corresponding layers, the forming operation of the marks becomes easy. Moreover, the marks can be formed even if there is only a small space for forming the marks.
[g] The piston as described in the above item [a], wherein the multiple-layer coating (20) includes a lower-layer coating composite (22) coating a surface of the piston base material (1a) and an upper-layer coating composite (21) coating an upper surface of the lower-layer coating composite (22), each of the lower-layer coating composite (22) and the upper-layer coating composite (21) contains at least one of a polyamide-imide resin, a polyimide resin and an epoxy resin which are binding resins, the lower-layer coating composite (22) contains a solid lubricant including at least one of a graphite and a molybdenum disulfide, a content of the solid lubricant of the lower-layer coating composite (22) is lower than or equal to 50 wt % of the lower-layer coating composite (22), the upper-layer coating composite (21) contains a solid lubricant including one or both of the graphite and the molybdenum disulfide, and a content of the solid lubricant of the upper-layer coating composite (21) falls within a range from 50 to 95 wt % of the upper-layer coating composite (21).
According to this structure, a high adhesion property between the piston base material and the lower-layer coating composite is secured, and the upper-layer coating composite contains the solid lubricant including one or both of the graphite and the molybdenum disulfide. Moreover, the content of the solid lubricant of the upper-layer coating composite falls within a range from 50 to 95 wt % of the upper-layer coating composite. Therefore, the initial fitting property is superior when the outer circumferential surface of the piston slides on the cylinder wall-surface. That is, the surface of the upper-layer coating composite is abraded in a short time so that a smooth sliding surface of the piston is quickly formed. Hence, a superior initial fitting property can be obtained.
[h] The piston as described in the above item [b], wherein the lower layer (22, 46a-46e) of the multiple-layer coating (20) is exposed from an entire region of the window portion (33, 35, 37, 40, 47a-47e).
According to this structure, since the lower layer of the multiple-layer coating is exposed to the outside of piston from the entire window portion, the reduction of abrasion resistance due to friction can be inhibited when sliding in contact with the cylinder wall-surface.
[i] The piston as described in the above item [b], wherein the lower layer (22) of the multiple-layer coating (20) is exposed from one part of the window portion (37, 40), the surface of the piston base material (1a) is exposed from another part of the window portion (37, 40), and the another part of the window portion (37, 40) is located substantially at a circumferential center of the skirt portion (8, 9).
According to this structure, after the multiple-layer coating was applied, the radial size (diameter) between the both skirt portions can be measured by a micrometer or the like by using both the exposed surfaces of the piston base material.
[j] The piston as described in the above item [b], wherein one layer (46f) of the multiple-layer coating (20) includes at least the window portions (47a-47e) having a number obtained by subtracting 1 from a number of layers of the multiple-layer coating (20), and different layers of the multiple-layer coating (20) are exposed respectively from the window portions (47a-47e) of the one of the multiple-layer coating (20).
According to this structure, it can be judged whether or not the respective layers have been formed, by checking the corresponding window portions, even if the multiple-layer coating is constituted by two or more layers.
[k] The piston as described in the above item [j], wherein each layer of the multiple-layer coating (20) includes the window portions (47a-47f) having the number obtained by subtracting 1 from the number of layers of the multiple-layer coating (20), and each of a plurality of upper layers (46b-46f) of the multiple-layer coating (20) which are applied on an outer surface of a lowest layer (46a) of the multiple-layer coating (20) locates its window portions (47a-47f) so as to cover only one of the window portions (47b-47f) of the lowest layer (46a).
This application is based on prior Japanese Patent Applications No. 2010-145981 filed on Jun. 28, 2010 and No. 2011-63502 filed on Mar. 23, 2011. The entire contents of these Japanese Patent Applications are hereby incorporated by reference.
The scope of the invention is defined with reference to the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-145981 | Jun 2010 | JP | national |
| 2011-063502 | Mar 2011 | JP | national |
