JP2006220128A - Valve device of engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a valve device of an engine provided in an intake path of the engine and capable of reducing friction greatly by adopting a hard carbon material and grease in a sliding contact part of a valve shaft and a valve bearing part in the valve device. <P>SOLUTION: In this valve device provided in the intake path of the engine, the valve shaft 5 provided with a valve 4 and the valve bearing part 6 for holding the valve shaft 5 turnably come into sliding-contact mutually through grease formed by using ester oil and/or ether oil as base oil. A hard carbon thin film having hydrogen content of 20 atom% or less is formed on a sliding-contact face of at least either of the valve shaft 5 and the valve bearing part 6. By using the hard carbon thin film and grease in the sliding-contact part of the valve shaft 5 and the valve bearing part 6 in this way, friction in the sliding-contact part can be greatly reduced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a butterfly-type valve device used for, for example, a variable intake control valve, a swirl control valve, a throttle valve and the like in an automobile engine.

  Valve devices such as engine variable intake control valves and swirl control valves use butterfly valves that open and close the intake path. In these valve devices, a plate-like valve is attached to a valve shaft, the valve shaft is rotatably held by a valve bearing portion, and the valve is rotated together with the valve shaft using a negative pressure type or motor type actuator as a drive source. It has a structure. Even in the throttle valve, the basic structure is the same as that of the valve device.

  Here, in the above valve device, the valve shaft and the valve bearing portion are in sliding contact. Particularly, in the variable intake control valve and the swirl control valve, the air moment due to the intake air, the vibration of the engine, and the low temperature environment. Since the friction at the sliding contact portion increases due to the influence of the above, etc., an actuator that can sufficiently cope with the load has been used.

By the way, in recent years, environmental problems on a global scale such as global warming and destruction of the ozone layer have been greatly highlighted, and in particular, CO ₂ reduction, which is said to have a major impact on global warming, has been There is great interest in how to determine the regulation value. Regarding this CO ₂ reduction, it is one of the major issues to reduce the fuel consumption of automobiles, and in automobiles having various sliding mechanisms, a sliding mechanism with a low friction coefficient is realized to reduce fuel consumption. In addition, the sliding material and the lubricating oil play a large role.

  In automobiles, the role of sliding materials is to exhibit excellent wear resistance and low coefficient of friction for parts with severe frictional wear environment. Recently, various hard thin film materials have been applied. Yes. In general, hard carbon materials, particularly DLC (diamond-like carbon) materials, have a friction coefficient in the air or in the absence of lubricating oil, and wear-resistant hard coating materials such as titanium oxide (TiN) and chromium nitride (CrN). Therefore, it is expected as a low friction sliding material.

  In addition, as a fuel-saving measure for lubricating oils, 1) reduction of viscosity resistance in the fluid lubrication area by lowering the viscosity, 2) mixing and mixing under the boundary lubrication area by combining optimum friction modifiers and various additives Reduction of friction loss has been proposed, and as a friction modifier, many studies have been conducted focusing on organic molybdenum compounds such as molybdenum dithiocarbamate (MoDTC) and molybdenum dithiophosphate (MoDTP). On the sliding surface made of the material, a lubricating oil blended with an organomolybdenum compound exhibiting an excellent low friction coefficient at the beginning of use was applied, and the effect was improved.

For example, Non-Patent Documents 1 and 2 have been reported on the friction characteristics of such DLC materials and the performance of organic molybdenum compounds as friction modifiers.
Kano et al., Proceedings of Japan Society of Tribology, May 1999, p. 11-12 Kano et al., World Tribology Congress 2001.9, Vienna, Proceeding p. 342

  However, in the valve device as described above, when a variable intake control valve or a swirl control valve uses a large actuator so as to be able to cope with friction generated in the sliding contact portion between the valve shaft and the valve bearing portion, As a result, there is a problem in that it is disadvantageous in terms of response speed, power consumption, manufacturing cost, layout in the engine room, and the like.

  The reason why a large actuator is required as described above is due to the friction generated in the sliding contact portion between the valve shaft and the valve bearing portion. Improvement was desired.

  Further, Non-Patent Document 1 reports that a general DLC material that is excellent in low friction in air does not necessarily have a large friction reducing effect in the presence of lubricating oil. According to No. 2, it has been found that even if a lubricating oil composition containing an organomolybdenum compound is applied to such a sliding material, the friction reducing effect may not be sufficiently exhibited.

  Further, in engine valve devices that are exposed to relatively high temperatures and high pressures, grease is used as a lubricant instead of lubricating oil. However, the use of such grease with a hard carbon material such as DLC is still not available. Not considered.

  The present invention has been made in view of the above-described conventional situation, and in a valve device provided in an intake passage of an engine, a hard carbon material and grease are employed in a sliding contact portion between a valve shaft and a valve bearing portion. Therefore, an object of the present invention is to provide an engine valve device capable of realizing a significant reduction in friction.

  An engine valve device according to the present invention is a valve device provided in an intake passage of an engine, and the like, and a valve shaft provided with a valve and a valve bearing portion that rotatably holds the valve shaft include ester oil and / or It is in sliding contact with grease based on ether oil, and a hard carbon thin film is formed on at least one sliding contact surface of the valve shaft and valve bearing part, and the hydrogen content of the hard carbon thin film Is 20 atomic% or less, which realizes a significant reduction in friction at the sliding contact portion between the valve shaft and the valve bearing portion.

  Moreover, the suitable form of the valve apparatus of the engine which concerns on this invention is characterized by the said grease using the metal soap or the urea type compound containing calcium or lithium as a thickener.

  The engine valve device of the present invention employs a hard carbon material such as DLC and a specific grease for the sliding contact portion between the valve shaft and the valve bearing portion, thereby greatly reducing the friction of the sliding contact portion. Can do.

  As a result, in valve devices such as variable intake control valves and swirl control valves, it is possible to reduce the size of the drive actuator and simplify the structure along with the reduction of friction. As the speed increases, it is possible to realize an improvement in response speed, power saving, improvement in fuel efficiency and cost reduction accompanying power saving, and further contribute to improvement in engine performance.

  In particular, in a valve device such as a throttle valve, as the friction at the sliding contact portion is reduced, the clearance between the valve shaft and the valve bearing portion is reduced, and the sealing performance at the sliding contact portion is increased to improve the sealing performance. The amount of air leakage can be significantly reduced, which can contribute to improving engine performance and eliminate the application of molybdenum, which has been done to reduce clearance, improving workability and reducing costs. , Improvement in quality and durability can be realized.

  Hereinafter, the present invention will be described in more detail. In this specification, “%” represents a mass percentage unless otherwise specified.

  FIG. 1 is a diagram illustrating a variable intake control valve (tumble control valve) as an engine valve device. This valve is a butterfly type valve, and is provided in each intake passage corresponding to each cylinder in the intake manifold 1 to increase the length of the effective intake port by closing at low and medium speeds. By opening at high speed, the length of the effective intake port is reduced to improve the torque in each rotation region.

  The variable intake control valve includes a plate-like valve 4 that opens and closes a port 3 formed on the flange 2 of the intake manifold 1 and a valve shaft 5 that passes through the intake manifold 1 so as to pass through each port 3. Each valve 4 is screwed to the valve shaft 5. The valve shaft 5 is rotatably held in the intake manifold 1 by valve bearing portions 6 provided on both sides of each valve 4, and both ends are rotatably held by lip seals 7 made of a rubber material. It is. Note that grease is applied to the lip seal 7.

  The valve shaft 5 is made of various metal materials typified by iron-based alloys such as steel and non-ferrous metal alloys such as aluminum alloys, or a synthetic resin having desired mechanical strength and heat resistance. Further, the valve bearing portion 6 may be integrated with the intake manifold 1 as in this embodiment, or may be attached to the intake manifold 1 as a separate part. Depending on these cases, iron such as steel may be used. It is selected from various metal materials typified by non-ferrous metal alloys such as base alloys and aluminum alloys, or synthetic resins having desired mechanical strength and heat resistance.

  A rotation lever 8 is connected to one end of the valve shaft 5, and a connecting pin 9 is provided at a position offset from the valve shaft 5. Is connected to the output rod 10a of the negative pressure actuator 10. Thus, when the variable intake control valve drives the output rod 10a of the negative pressure actuator 10 to advance and retreat, the valve shaft 5 reciprocates through the rotation lever 8, and at the same time, the valve 4 reciprocates to rotate the port. 3 is opened and closed.

  At this time, in the variable intake control valve, the valve shaft 5 including the valve 4 and the valve bearing portion 6 that rotatably holds the valve shaft 5 are in sliding contact at a plurality of locations. Therefore, the variable intake control valve particularly has a hard carbon thin film having a hydrogen content of 20 atomic% or less formed on at least one sliding contact surface between the valve shaft 5 and the valve bearing portion 6, and the valve shaft. 5 and the valve bearing 6 are made to interpose grease based on ester oil and / or ether oil as a base oil, thereby greatly reducing friction at the sliding contact portion while ensuring sealing performance. ing.

  In terms of ease of film formation, it is more desirable to form a hard carbon thin film on the valve shaft 5, and when one is a metal and the other is a resin, it is at least made of a metal. It is more desirable to form a hard carbon thin film.

  In this way, if the friction at the sliding contact portion between the valve shaft 5 and the valve bearing portion 6 is reduced, even if it is affected by air moment due to intake air, vibration of the engine, low temperature environment, etc., a small negative pressure type The actuator 10 can sufficiently drive the valve 4 and does not require an amplification mechanism such as a crank mechanism for increasing torque, for example, thereby increasing the degree of freedom in layout of equipment in the engine room and response speed. Improvement of power consumption, power saving, improvement in fuel consumption and cost reduction associated with power saving can be realized.

  FIG. 2 is a diagram illustrating a swirl control valve as an engine valve device. This valve is a butterfly valve, and is provided in each intake passage corresponding to each cylinder in the intake manifold 11, and in particular, the intake passages 13a and 13b branched into two for each cylinder. One of the intake passages 13a is opened and closed.

  The swirl control valve is configured to pass through each intake passage 3a with respect to the intake manifold 11 and a plate-like valve 14 that opens and closes the intake passage 3a in the intake manifold 11 in the same manner as the variable intake control valve. A valve shaft 15 is provided, and each valve 14 is screwed to the valve shaft 15. The valve shaft 15 is rotatably held by the valve bearing portions 16 on both sides of each valve 14 in the intake manifold 11, and both ends thereof are rotatably held by lip seals 17 made of rubber material. is there.

  A rotating lever 18 is connected to one end of the valve shaft 15, and a connecting pin 19 is provided at a position offset from the valve shaft 15. The output rod 20a of the electronic control motor type actuator 20 is connected to this. Thereby, when the output rod 20a of the electronic control motor type actuator 20 is driven forward and backward, the swirl control valve reciprocates the valve shaft 15 via the rotation lever 18, and simultaneously the valve 14 reciprocates. The intake passage 3a is opened and closed.

  At this time, in the swirl control valve, the valve shaft 13 including the valve 14 and the valve bearing portion 16 that rotatably holds the valve shaft 13 are in sliding contact with each other at a plurality of locations. Accordingly, the swirl control valve forms a hard carbon thin film having a hydrogen content of 20 atomic% or less on at least one sliding contact surface between the valve shaft 15 and the valve bearing portion 16, and the valve shaft 15 and the valve shaft. Grease using ester oil and / or ether oil as a base oil is interposed between the bearing portion 16 and the friction at the sliding contact portion is greatly reduced while ensuring sealing performance.

  In this way, if the friction at the sliding contact portion is reduced, the valve 14 can be sufficiently connected even with the small electronically controlled motor type actuator 20 even if it is affected by the air moment due to the intake air, the vibration of the engine and the low temperature environment. As a result, the degree of freedom of the layout of the equipment in the engine room can be increased. In addition, the response speed can be improved, the power can be saved, the fuel consumption can be improved, and the cost can be reduced.

  FIG. 3 is a diagram for explaining a throttle valve in an engine as an engine valve device. As is well known, this valve is a butterfly valve that opens and closes the intake path in conjunction with the operation of the accelerator pedal.

  The throttle valve includes a plate-like valve 23 for opening and closing the intake passage 22 and a valve shaft 24 provided across the intake passage 22 in the valve housing 21 constituting a part of the air duct. Valve 23 is screwed. The valve shaft 24 is made of, for example, an iron-based material, and both ends are rotatably held by the valve bearing portion 25.

  Here, in the throttle valve shown in FIG. 3A, the valve bearing portion 25 that holds one end portion of the valve shaft 24 is configured by a bearing 25 </ b> A and a through hole 25 </ b> B formed in the valve housing 21. And the inner peripheral surface of the through hole 25B are in sliding contact. Therefore, in this throttle valve, a hard carbon film is formed on at least one sliding contact surface of the valve shaft 24 and the through hole 25B, thereby greatly reducing friction at the sliding contact portion.

  In the throttle valve shown in FIG. 3B, the valve bearing portion 25 that holds one end of the valve shaft 24 is a holding hole (25) formed in the valve housing 21, and the valve shaft 24 and the holding hole (25 ) In sliding contact. Therefore, in this throttle valve, a hard carbon film is formed on at least one sliding contact surface of the valve shaft 24 and the holding hole (25), thereby greatly reducing friction at the sliding contact portion.

  Further, in the throttle valve shown in FIG. 3C, the valve bearing portion 25 that holds one end portion of the valve shaft 24 includes a bearing 25 </ b> A and a through hole 25 </ b> B formed in the valve housing 21, and the valve shaft 24. The valve shaft 24 and the inner peripheral surface of the through hole 25B are in sliding contact with each other, and the end surface of the flange portion 24a and the inner wall of the intake passage 22 substantially included in the valve bearing portion 25 are formed in the flange portion 24a. And sliding contact. Therefore, in this throttle valve, a hard carbon film is formed on at least one sliding contact surface between the valve shaft 24 including the flange portion 24a and the valve bearing portion 25 including the through hole 25B and the inner wall of the intake path, thereby sliding the valve shaft 24. Friction at the moving contact part is greatly reduced.

  In each of the valve devices shown in FIGS. 3 (a) to 3 (c), as the friction in the sliding contact portion is reduced, the clearance of the sliding contact portion can be set small. The amount of air leakage when fully closed can be reduced, which can contribute to improvement in engine performance. In addition, the application of molybdenum, which has been done to reduce the clearance in the past, can be abolished, improving workability, reducing costs, improving quality (stability of flow control values), and durability (flow after deterioration) Improvement of characteristics). In each valve device shown in FIG. 3, it is desirable to form a hard carbon coating on the valve shaft 24 in terms of ease of film formation.

  Here, in the valve device of the engine shown in FIGS. 1 to 3, the valve shaft and the valve bearing portion are in an environment that receives high-frequency vibration and pressure pulsation (low pressure side and high pressure side). It is necessary to reduce friction in consideration of the environment. Table 1 shows examples of engine types, high-frequency vibrations, and pressure pulsations.

  Therefore, in the present invention, the valve shaft and the valve bearing portion are in sliding contact with each other via grease using ester oil and / or ether oil as a base oil, and at least one of the valve shaft and the valve bearing portion is slid. By forming a hard carbon thin film with a hydrogen content of 20 atomic% or less on the contact surface, it is possible to reduce friction at the sliding contact portion between the valve shaft and the valve bearing portion even in the above environment. Yes.

  Examples of the hard carbon thin film include a crystalline or amorphous thin film containing carbon, in particular, a diamond thin film and a DLC thin film, such as various PVD methods, specifically, arc ion plating. A DLC thin film (diamond-like carbon thin film) formed by a method is desirable.

The DLC thin film is composed of a so-called DLC material, and this DLC material is an amorphous material mainly composed of carbon atoms, and the bonding form of the carbon atoms is a diamond structure (SP ³ Bond) and graphite bond (SP ² bond).

  Specifically, aC (amorphous carbon) consisting only of carbon atoms, aC: H (hydrogen amorphous carbon) containing hydrogen, and some metal atoms such as titanium (Ti) and molybdenum (Mo). In the present invention, the lower the hydrogen content, the more preferable. The hydrogen content is 20 atomic% or less, preferably 10 atomic% or less, particularly 0.5 atomic% or less, An aC-based (amorphous carbon-based) material that does not contain hydrogen can be preferably used.

  The film thickness of the hard carbon thin film depends on the type and required performance of the target valve shaft and valve bearing part, the type of each material constituting the valve shaft and valve bearing part, the surface roughness of the sliding part, etc. Although it is affected, in the case of the DLC thin film, it is preferable to set the thickness to about 0.3 to 2.0 μm, for example.

  In addition, the surface roughness of the base material before the formation of the hard carbon thin film is also determined depending on the type and required performance of the target valve shaft and valve bearing part, the type of base material constituting the valve shaft and valve bearing part, Although affected by the surface roughness of the moving part, when the DLC thin film is applied to the valve device of the engine, when the base material is steel, the surface roughness before coating of the hard carbon thin film is 0. It is preferable to be 1 μm or less.

  Further, when the base material is an aluminum alloy, Ra is preferably 0.02 μm or less, and when the base material is plastic, Ra is preferably 0.1 μm or less.

  Furthermore, the hard carbon thin film is usually coated on the entire sliding surface of at least one of the valve shaft and the valve bearing portion, but may be coated on a part of at least one sliding surface.

  Next, as described above, the grease used is based on ester oil and / or ether oil, but this base oil is not limited to those containing only ester oil or ether oil. However, other natural oils and synthetic oils may be included. Examples of other base oil components include mineral oil, silicone oil, fluorocarbon oil, and the like.

  The ester oil is not particularly limited as long as it can be used as a component of a lubricant, but it is not limited whether it is a natural oil or a synthetic oil. Specific examples include ditridecyl glutarate, dioctyl adipate, diisodecyl adipate, ditrile. Examples include decyl adipate, dioctyl sebacate, trimethylolpropane caprylate, trimethylolpropane pelargonate, trimethylolpropane isostearinate, pentaerythritol 2-ethylhexanoate, pentaerythritol pelargonate, and the like. Rate is preferably used.

  It does not matter whether the ether oil is a natural oil or a synthetic oil as long as it can be used as a component of a lubricant. Specific examples include polyoxyalkylene glycol, dialkyl diphenyl ether and polyphenyl ether, and dialkyl diphenyl ether is preferred.

The base oil containing the above components typically has a base oil viscosity at 100 ° C. of about ^{2 to} 100 mm ² / s, preferably about ² to 40 mm ² / s, more preferably about 10 to 20 mm ² / s. It becomes.

In addition, when kinematic viscosity is less than 2 mm < ² > / s, since sufficient abrasion resistance is not acquired and an evaporation characteristic may be inferior, it is unpreferable. On the other hand, if the kinematic viscosity exceeds 100 mm ² / s, it is difficult to exhibit low friction performance, and low temperature performance may be deteriorated, which is not preferable.

  The viscosity index of such base oil is typically 100 or more, preferably 120 or more, and more preferably 140 or more. By selecting a base oil having a high viscosity index, it is possible to obtain a composition that not only has excellent low-temperature viscosity characteristics, but also has low oil consumption and excellent low-temperature viscosity characteristics, fuel saving performance, and friction reduction effect.

  On the other hand, examples of the thickener contained in the grease include various metal soap-based materials and non-metal soap-based materials. Examples of the metal soap material include sodium, calcium, aluminum, lithium, barium, copper and lead salts of higher fatty acids, and complex salts of higher fatty acids with lower fatty acids or dibasic acids. As these metal soap materials, calcium stearate, lithium hydroxystearate, lithium stearate, sodium stearate and aluminum stearate are suitable.

  Non-metallic soap materials include inorganic materials (organic thickeners) such as silica gel and bentonite, and organic materials (inorganic thickeners) such as copper phthalocyanine, allylurea, imide derivatives and indanthrene blue. be able to. As these non-metallic soap thickeners, urea compounds such as diurea, sodium terephthalamate and PTFE are suitable.

  In the above-described grease, it is possible to add an antioxidant, a detergent, an antiwear agent, a solid lubricant and the like to the base oil and the thickener.

  The antioxidant is not particularly limited, and examples thereof include those conventionally used in greases. Examples thereof include amine compounds, phenols, sulfur compounds, and carbamates.

  In addition, the detergent is not particularly limited, and examples thereof include those conventionally used in greases. Examples thereof include sulfonates, phenates, sacylates, and amine compounds.

  The antiwear agent is not particularly limited, and examples thereof include those conventionally used in grease. Examples thereof include phosphate esters, zinc dialkyldithiophosphates, sulfur compounds, and chlorides.

  Furthermore, the solid lubricant is not particularly limited, and examples thereof include those conventionally used in grease.

  The properties of the above grease itself are affected by the purpose and operating conditions of the sliding mechanism used, but typically the consistency is about 265 to 295 and the dropping point is about 100 to 300 ° C. Is preferred.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to these Examples.

(Examples 1-4)
As shown in FIG. 4, a cylinder-shaped test piece 100 and a disk-shaped test piece 200 were made of SUJ2 steel in order to measure the friction coefficient using a cylinder-on-disk single-piece reciprocating friction tester. These cylindrical test piece 100 and disc-shaped test piece 200 correspond to the valve shaft and the valve bearing portion.

Next, the surface of the upper sliding surface of the disk-shaped test piece 200 is subjected to a PVD arc ion ion plating method with a hydrogen atom amount of 0.5 atomic% or less, a Knoop hardness Hk = 2170 kg / mm ² , and a surface roughness Ry = 0. A DLC thin film having a thickness of 03 μm and a thickness of 0.5 μm was formed, and the sliding mechanism of this example using the cylindrical test piece 100 and the disk-shaped test piece 200 as sliding members was manufactured.

  Next, about 0.3 g of the grease shown in Table 2 was applied between the cylindrical specimen 100 and the disk specimen 200, and a friction test was performed under the following conditions to measure the friction coefficient. Table 2 shows the components of the specimen material and grease. Further, the coefficient of friction of the sliding mechanism of each example after 10 minutes of the test was graphed and shown in FIG.

[Friction test conditions]
・ Test equipment: Cylinder-on-disk single-piece reciprocating friction tester ・ Sliding side test piece; φ15 × 22 mm cylindrical test piece ・ Math side test piece; φ24 × 7.9 mm disc-like test piece ・ Load; (Pressing load of one piece)
・ Amplitude: 1.5mm
・ Frequency: 50Hz
Test temperature: 80 ° C
・ Measurement time: 10 min

(Comparative Examples 1-6)
Except that no DLC thin film was formed on the disk-shaped test piece 200, the same operation as in Examples 1 to 4 was repeated, and the friction coefficient was measured. The obtained results are shown in FIG.

As an embodiment of an engine valve device according to the present invention, an exploded perspective view (a) illustrating a variable intake control valve, a sectional view (b) of a lip seal portion, a side view (c) of a negative pressure actuator portion, and It is a front view (d) of the flange part of an intake manifold. As other embodiments of the valve device of the engine according to the present invention, a sectional view for explaining a swirl control valve (a), a valve front view in an open state (b), a valve front view in a closed state (c), and It is side part sectional drawing (d). FIG. 6 is a view for explaining a throttle valve as still another embodiment of the valve device for an engine according to the present invention, and is a front view (a) to (c) of each valve showing different forms of a valve shaft and a valve bearing portion. . FIG. 2 is a perspective view schematically illustrating a cylinder-on-disk single-piece reciprocating friction tester. It is a graph which shows a friction coefficient.

Explanation of symbols

5 15 24 Valve shaft 6 16 25 Valve bearing

Claims (7)

  A valve device provided in an intake passage or the like of an engine, wherein a valve shaft provided with a valve and a valve bearing portion that rotatably holds the valve shaft are greases based on ester oil and / or ether oil. The hard carbon thin film is formed on at least one sliding contact surface of the valve shaft and the valve bearing portion, and the hydrogen content of the hard carbon thin film is 20 atomic% or less. An engine valve device.   2. The valve device for an engine according to claim 1, wherein the hydrogen content of the hard carbon thin film is 10 atomic% or less.   2. The valve device for an engine according to claim 1, wherein the hydrogen content of the hard carbon thin film is 0.5 atomic% or less.   The engine according to any one of claims 1 to 3, wherein the surface roughness of the substrate of the member on which the hard carbon film is formed is 0.1 µm or less in Ra before coating with the hard carbon thin film. Valve device.   The engine valve device according to any one of claims 1 to 4, wherein the grease comprises a metal soap containing calcium or lithium or a urea compound as a thickener.   6. The engine valve device according to claim 1, wherein the hard carbon thin film has a thickness of 0.3 to 2.0 [mu] m.   7. The valve device for an engine according to claim 1, wherein the hard carbon thin film is a DLC thin film formed by a PVD method.

Images