JP2016080028A - Bearing portion for chain, pin, and chain using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem on increase of early abrasion of a bearing portion such as a pin under severe environment of poor lubrication in a chain composed of the pin having a coating film of hard metal carbonitride such as vanadium.SOLUTION: At least one of members configuring a bearing portion for a chain, for example, a pin 2 includes a surface layer 21 composed of a coating film of hard metal carbonitride (for example, VCN) such as V, Ti, Nb, Cr and the like, on a surface of a base material 20. An oxide coating film 22 of a prescribed thickness is formed on a surface of the surface layer. The oxide coating film is softer than the surface layer and mirror-finished so that it has low counterpart aggressiveness. As antioxidation characteristic is improved by nitrogen in the surface layer, excessive formation of the oxide coating film can be suppressed even under a high temperature environment.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a chain pin, a bearing portion, and a chain such as a silent chain using the same, and is particularly suitable for a chain disposed in an internal combustion engine, and more specifically, an oxide film is formed on the surface. Relates to the surface layer.

  In general, a silent chain causes relative rotational sliding between a pin and a link plate, and a roller chain causes wear between the pin and the bush, and the pin and the fitting member (link plate or bush) wear, resulting in wear elongation of the chain. In particular, a silent chain such as a timing chain disposed in an internal combustion engine is required to have high durability even under conditions close to a boundary lubrication state in which sliding heat generation is a concern.

  Conventionally, particles made of a hard inorganic material different from the hard inorganic material such as aluminum oxide are dispersed in a base coating of a hard inorganic material such as titanium carbide (TiC), vanadium carbide (VC), or chromium carbide (CrC). A wear-resistant coating has been devised in which some of the dispersed particles are exposed on the coating surface (see Patent Document 1).

  The wear-resistant coating is applied to the pin surface of the silent chain, and the coated surface becomes in a boundary lubrication state and the temperature rises. As a result, the coated surface is oxidized, and a sufficient wear-resistant effect cannot be obtained. In order to solve the problem, a minute gap is formed at the interface between the base coating material and the dispersed dispersed hard inorganic material particles, and the lubricating oil penetrates into the minute gap to keep it. It is characterized by improved liquidity and contributing to lower wear of the coating surface.

JP 2003-139199 A

  Due to the recent increase in environmental and energy problems, there is an increasing demand for sustainable development even for internal combustion engines, etc., while there is an urgent need to improve the fuel efficiency of engine vehicles. Ensuring reliability is an important issue. In such next-generation engines, the viscosity of the lubricating oil may decrease, or the amount of lubricating oil may dilute due to changes in the engine mechanism. In such a chain drive mode, it has been discovered that a pin (hereinafter referred to as a VC pin) having vanadium carbide as a surface layer as the hard metal carbide may cause abnormal wear. .

  In the above-described abrasion-resistant coating of Patent Document 1, since the hard inorganic material particles dispersed in the base coating material are in sliding contact with the mating member in a small area, such an abrasion-resistant coating is manufactured. Even if it can, the opponent's aggression will become high and chain growth may occur at an early stage.

As a result of earnest research on the abnormal wear of the VC pin, the present inventors have first made other MCs such as vanadium carbide (VC) film such as chromium carbide (CrC), niobium carbide (NbC) in a conventional engine chain. (M: Metal of Cr, Nb, Ti, etc.) type hard carbide film has a higher wear resistance than the mechanism,
(I) Since a very thin and soft oxide film is continuously formed on the surface of the VC film, the pin sliding surface is easily mirror-finished, so that the partner (link plate hole surface) is less aggressive.
(Ii) It has higher toughness than other MC type carbide coatings, and it is difficult for the coating to break down (surface failure due to micro-peeling) even under high surface pressure, and the mirrored sliding surface can be maintained for a long time.
Analyzed that there was.

  In the chain drive test assuming the next-generation engine, the cause of abnormal wear of the VC pin is that the lubrication of the sliding part (pin surface and link plate hole surface) is in the boundary lubrication state in a severe lubrication environment. As the surface of the pin heats up and heats up, an oxide film that promotes a decrease in the partner's aggression is formed thickly, and the wear of the soft oxide film wears up, increasing the wear of the pin itself I guessed it.

  That is, the present inventors have found that the oxide film formed on the surface of the hard metal carbide film increases the wear of the pin itself due to the enlargement of the oxide film at a high temperature as shown in the problem of Patent Document 1. As shown in (i) above, the thin and soft oxide film is continuously formed, and the pin sliding surface is mirrored to reduce the partner's aggression performance. I inferred that there is a positive side to do.

  In the future, with the evolution of internal combustion engines, such as further reduction in fuel consumption of vehicles, it is predicted that the demands on chains will become more severe. There is a demand for a durable chain that can be operated for a long period of time even in a situation where the lubrication environment is deteriorated due to an increase in chain load tension or the like as well as the above-described reduction in the viscosity of the lubricating oil.

  Therefore, the present invention is excellent in reducing both the partner's aggressiveness due to the thin and soft oxide film and preventing the increase in wear of the surface layer by suppressing the enlargement of the oxide film even in a high temperature environment. An object of the present invention is to provide a chain bearing portion, a pin having durability, and a chain using the same.

The present invention consists of two members (2) (3, 7) that are slidably fitted to each other, and a chain bearing portion (9) for flexibly connecting a large number of links (5) (8). ,
At least one member (for example, 2) constituting the chain bearing portion includes a surface layer (21) formed of a hard metal carbonitride (MCN) film formed on the surface of the base material (20),
An oxide film (22) having a predetermined thickness that is softer than the surface layer is formed on the surface of the surface layer with the other member (for example, 7) constituting the chain bearing portion. Features.

In the chain pin (2) for flexibly connecting a number of links (5) (8),
A surface layer (21) formed of a hard metal carbonitride (MCN) film formed on the surface of the base material (20);
An oxide film (22) having a predetermined thickness that is softer than the surface layer is formed on the surface of the surface layer.

  The hard metal is at least one of vanadium (V), titanium (Ti), niobium (Nb), and chromium (Cr).

  The hard metal carbonitride film has a crystal structure of NaCl structure and a hardness of 1600 [Hv] or more.

A first link (8) having a pin (2) constituting one of the chain bearing portions;
A second link (5) having a fitting member (for example, 3) constituting the other of the chain bearing portion,
The chain is characterized in that the first link (8) and the second link (5) are connected endlessly by the chain bearing portion (9).

A first link (8) and a second link (5) that are flexibly connected by a chain pin (2);
The chain is characterized in that the first link (8) and the second link (5) are connected endlessly.

The first link (8) has a guide link plate (6) connected by a pair of pins (2);
The second link (5) is provided with pin holes (7) for fitting the pins (2) at both ends thereof, and constitutes the fitting member and has a pair of teeth (10, 10). Having a link plate (3),
The chain is a silent chain (1).

The first link (8) has a guide link plate (6) connected by a pair of pins (2);
The second link (5) has a pin hole (7) for fitting the pin (2) at both ends and an inner link plate (3) having a pair of teeth (10, 10);
The chain is a silent chain (1).

The first link has an outer link plate fixed by a pair of the pins;
The second link has a bush which is the fitting member, and an inner link plate connected by the pair of bushes,
The chain is a roller chain.

  The chain is a chain disposed in an internal combustion engine.

  In addition, although the code | symbol in the said parenthesis is for contrast with drawing, it does not have any influence on the structure as described in a claim by this.

  According to the first or seventh aspect of the present invention, at least one member constituting the bearing portion for the chain or the pin for the chain (including the rocker pin) has the surface layer made of the hard metal carbonitride film, and thus has high toughness. In addition to reducing the occurrence of cracks and resulting film defects, and forming an oxide film that mirrors the sliding surface, it is possible to keep the opponent's aggressiveness low, and in severe environments such as dilute lubrication. In addition, the excessive formation of the oxide film is suppressed, the wear of the pin and the other side that is in sliding contact with the pin is suppressed, and the chain length is maintained even under severe use conditions such as a next-generation engine. Life can be extended.

  According to the second or eighth aspect of the present invention, vanadium is preferable as the hard metal, but titanium, niobium, or chromium is also applicable, and any of the hard metals should be a carbonitride film in the same manner as vanadium. Therefore, it is possible to provide an oxidation resistance property that suppresses the excessive formation of an oxide film in a high temperature environment, and the degree of freedom in material design can be improved.

  According to the third or ninth aspect of the present invention, the hard metal carbonitride film has a crystal structure composed of a NaCl structure, and the interstitial distance is shortened by the inclusion of nitrogen in the metal carbide, so that oxygen diffuses and penetrates. By suppressing this, the oxidation resistance, particularly the oxidation resistance in a high temperature environment is improved. The higher the nitrogen content, the better the oxidation resistance, but the higher the nitrogen content, the lower the hardness. When the hardness is 1600 [Hv] or higher, which is higher than the hardness of the soot into which the engine oil flows, the amount of nitrogen is 45 [atom%] or lower, for example. Wear performance can be obtained.

  According to the fourth or tenth aspect of the present invention, it is possible to provide a chain having excellent durability even in a harsh environment by being used for a chain such as a silent chain or a roller chain.

  According to the present invention of claim 5 or 11, the silent chain has a small contact area on the pin hole or rocker pin of the inner link plate that is the other side of the pin, and is severe with respect to the opponent attack by the pin. One member of the bearing part is less attacked by the soft oxide film, and the increase in wear of one member of the bearing part such as a pin due to excessive formation of the oxide film is low, so that it is silent in a harsh environment. With respect to the chain, the wear of both the pin and the other side can be reduced in a well-balanced manner, and the life can be extended with high reliability.

  According to the sixth or twelfth aspect of the present invention, a roller chain with high durability and reliability can be obtained by applying to a roller chain composed of pins and bushes.

  According to the thirteenth aspect of the present invention, the present invention is applied to a chain in a next-generation internal combustion engine that becomes a harsh use environment, and can have a long life with high reliability. It can contribute to environmental protection.

The front view which shows the silent chain which can apply this invention. (A) is a figure which shows the component ratio by the distance from the pin surface which has a surface layer which consists of vanadium carbonitride (VCN) based on this invention, (b) is a vanadium carbide (VC) film | membrane and vanadium carbonitride The figure which shows the change of the amount of nitrogen (N) from the surface of a (VCN) film | membrane, (c) is a schematic diagram of a pin surface part. The figure which shows the thickness of the oxide film by temperature. The enlarged photograph which shows the oxide film of the VC film | membrane and the VCN film | membrane surface in the A point and B point of FIG. The figure which shows the lattice constant of carbide | carbonized_material and nitride of a hard metal. The figure which shows the toughness and hardness of various hard films. The figure which shows the change by the test time of the sliding surface roughness of various hard films. The figure which shows the elongation of the chain using the pin which consists of a VC film (VC chain), and the chain which used the pin which consists of a VCN film (VCN chain). The figure which shows the abrasion of the bearing part component of a VC chain and a VCN chain. (A) shows the chain elongation performance by the change of the nitrogen (N) amount of the pin having the VCN film, (b) shows the pin wear performance by the N amount change, and (c) shows the N amount change. The figure which shows the hardness of a pin surface. (A) shows the hardness and toughness by the difference in N amount of a surface layer, (b) is a figure which shows the sliding surface roughness by N amount. The figure which compared the VCN- (Ti, Si) film | membrane which added another element, and the said VCN film | membrane, (a) shows the hardness by N amount change, (b) is pin wear performance by N amount change. Indicates. (A) shows the film toughness evaluation of the surface layer of various elements, (b) is a diagram comparing the chain elongation performance with respect to the N amount change of the VCN-Mo and VCN film surface layer, (c) is the sliding The figure which compared the surface roughness.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the silent chain 1 to which the present invention can be applied is configured such that inner link plates 3 are alternately endlessly formed by pins 2, and the inner link plates 3 are (second). A guide link plate 6 is disposed on the outermost side in the width direction of the link 5. The pin 2 is fixed and connected to the left and right guide link plates 6 by caulking, interference fitting, etc., and the pins 2 are slidable in pin holes 7 and 7 formed at both ends in the longitudinal direction of the inner link plate 3. Is fitted. The guide link plate 6 and the pin 2 constitute a (first) link 8.

  Accordingly, the chain bearing portion 9 in which the pin 2 and the pin hole 7 of the link plate 3 can slide relative to each other is formed. The guide link row G aligned with the guide link plate 6 in the width direction does not rotate relative to the pin 2 including the inner link plate 3, and the inner link plate of the non-guide row N adjacent to the guide row. 3 rotates relative to the pin 2, and the silent chain 1 can be bent freely. However, the inner link plates 3 of the guide link row G and the non-guide row N are usually the same, and the inner link plate The above-mentioned chain bearing portion 9 is formed between the pin 2 and 3 as a fitting member.

  The inner link plate 3 has a pair of left and right pin holes 7 and 7 and a pair of teeth 10 and 10 on the inner diameter side of a line (pitch line) connecting the centers of the pin holes. The teeth 10 have inner flank surfaces 12 and 12 formed on the side of the crotch 11 therebetween, and outer flank surfaces 13 and 13 formed on the outer sides of the teeth. The tooth 10 is a meshing mechanism in which the inner flank surface 12 and the outer flank surface 13 are joined to the sprocket teeth. For example, after the outer flank surface 13 is joined to the sprocket teeth and the meshing proceeds, the inner flank surface 12 becomes the sprocket teeth. Sit down (per thigh outer thigh, inner thigh sitting).

  In this embodiment, one member constituting the chain bearing portion 9, the pin 2 is made of a vanadium carbonitride (hereinafter referred to as VCN) film having a predetermined thickness (for example, approximately 6 to 12 μm). A surface layer is formed. The surface layer includes a step of forming a vanadium carbide (VC) film on the surface of the pin base material (vanadium permeation diffusion treatment) and a step of permeating nitrogen (N) into the surface of the pin base material (nitriding treatment). The VCN film is formed. In addition, the said VCN film | membrane is shown as a representative of the hard metal carbonitride film | membrane (MCN) of vanadium (V), titanium (Ti), niobium (Nb), and chromium (Cr).

Specifically, the pin base material is a steel material such as a high carbon chrome bearing steel (SUJ2) or chrome molybdenum steel (SCM), and the wire is cut to a predetermined length. The pin base material is first subjected to vanadium permeation diffusion treatment (VC composite diffusion permeation treatment) by a powder pack method. That is, a powder composed of FV (ferrovanadium) as a permeation material, Al ₂ O ₃ (alumina, aluminum oxide) as a sintering prevention material, and NH ₄ Cl (ammonium chloride) as a reaction aid (promoter) is pinned. It is put in a furnace together with the base material, heated to 900 ° C. to 1100 ° C., held for a predetermined time, and then cooled. Thereby, a vanadium carbide (VC) film having a predetermined thickness is formed on the surface of the pin base material.

Next, nitriding treatment is performed in which the pin material on which the VC film is formed is heated in a nitrogen atmosphere for several hours. That is, N ₂ gas is sent into the furnace and heated at a high temperature of 1000 ° C. or higher for several hours, and then cooled. As a result, as shown in FIG. 2 (c), vanadium charcoal composed of VCxNy is combined by diffusion of nitrogen (N) into the VC coating on the surface of the pin base material 20 mainly composed of iron (Fe). The surface layer 21 of the nitride (VCN) film is formed, and the content (ratio) of nitrogen (N) is inclined and changed so as to gradually decrease from the surface toward the interface of the base material. A very thin vanadium oxide (VO) film 22 is formed on the extreme surface of the surface layer 21 made of the VCN film.

  As shown in FIG. 2 (a), the pin base material 20 is mainly composed of iron (Fe), and a VCN film is formed on the surface of the pin base material. Vanadium (V) having substantially the same content, carbon (C) that gradually increases from the surface toward the base material interface, and nitrogen (N) that gradually decreases from the surface toward the base material interface . As shown in FIG. 2B, the VCN film contains a large amount of nitrogen (N) on the surface, but gradually decreases toward the pin base material interface. In addition, the pin which consists of a vanadium carbide (VC) film | membrane has the amount of nitrogen (N) substantially zero.

  The chain pin (one member) 2 repeats relative sliding with respect to the pin hole 7 of the inner link plate 3 which is a mating member (the other member) constituting the bearing portion 9, and the chain pin (one member) 2 The oxide (VO) film 22 is slidingly worn. The oxide (VO) film 22 is softer than the VCN film of the surface layer 21, and therefore has less aggressiveness against the pin hole (the counterpart member) and becomes a mirror surface when slidably contacted, and wears the pin itself and the pin hole. Suppress.

  FIG. 3 is a diagram showing the thickness of the oxide film with respect to the temperature of a chain bearing portion such as a timing chain. In the oxide film, the surface layer is formed even by a VC film, and the present inventors have found that the oxide (VO) film greatly affects the durability of the chain. In the conventional VC film, it has been found that the oxide film is excessively formed, which leads to an increase in wear of the VC pin. The internal combustion engine is required to further improve fuel efficiency, and a low-viscosity lubricating oil has been developed to reduce the shear resistance of the lubricating oil for the purpose of reducing friction of the sliding member. In this case, the environment of the lubrication itself in the engine deteriorates and the temperature of the chain bearing portion tends to increase.

  FIG. 4 shows a conventional type VC pin and a VCN according to this reference example at point A in FIG. 3, that is, at a low temperature (conventional engine environment) and at point B, that is, at a high temperature (next-generation engine environment). It is the photograph (transmission electron microscope TEM image) which image | photographed the oxide (VO) film | membrane of the pin surface. In FIG. 4, the original image is adjusted to have the same magnification. At the point A where the temperature of the chain bearing portion is low, the oxide film of the conventional type VC pin and the oxide film of the VCN pin according to the present embodiment have substantially the same thickness (about 2 nm). At the point B where the lubrication environment is worsened and the temperature of the bearing portion is locally increased, the VC pin has a significantly thick oxide film (for example, a thickness exceeding 10 times), but the VCN pin has an oxide film. There is little change in thickness (for example, it does not exceed twice). FIG. 3 is derived from the results of measuring the layer thickness of the oxide film at a plurality of temperatures of the VC pin and the VCN pin shown in FIG. 4, and the thickness of the oxide film in the VC pin is high. The thickness of the oxide film in the VCN pin changes significantly with respect to the temperature as compared with the VC pin. This is presumed that the binding (oxidation) with oxygen is suppressed in VCN compared to VC, and the excessive formation of oxide is suppressed because VCN has higher oxidation resistance.

  As shown in FIG. 5, vanadium carbide (VC) and vanadium nitride (VN) have the same crystal structure of NaCl structure, and their lattice constants are VC of 4.182 (Å) and VN of 4.128. (Ii) and VN is smaller than VC. The lattice constant of vanadium carbonitride VCN was measured, and 4.164 was obtained for VCN (N10%) with an N amount of 10 [atom%], and 4.147 was obtained with VCN (N30%) for an N amount of 30 [atom%]. It was. That is, it is presumed that both the VC and VN have the same NaCl structure crystal structure, and the interstitial distance is shortened, thereby suppressing the diffusion and penetration of oxygen (O). As a result, the VCN film suppresses the generation of oxide as compared with the VC film, suppresses an increase in the oxidation rate particularly at high temperatures, and suppresses the enlargement of the oxide film in a high temperature environment. Moreover, the inhibitory function of the oxide film increases as the amount of nitrogen (N) increases.

  FIG. 6 shows the relationship between the toughness and hardness of the film made of each hard material. Note that the toughness is defined by a creep calculated by the nanoindentation method as a parameter, and the unit is percent [%]. For example, when considering a fracture model of a film accompanying a diamond indenter load by the Vickers test, the larger the creep, the fewer the cracks, which means that the higher the film toughness, the higher the bearing strength even if the bearing load increases. . In FIG. 6, the hardness is high for TiC, low for CrC, VCN and VC are in the middle, and the toughness is high. In particular, VCN indicates that the toughness is higher than that of VC. Therefore, the VCN pin is not only tougher than other materials such as CrC and TiC, but also tougher than conventional VC pins, and the microscopic breakage of the film, that is, the sliding surface is less likely to progress. Low aggression against sliding material and excellent wear performance.

  FIG. 7 shows changes in the sliding surface roughness with respect to the test time in a state where a predetermined load is applied to the pins of each hard coating (TiC, CrC, VC, VCN). The tenth average roughness Rzjis is used as the roughness, and the unit is [μm]. From FIG. 7, the VC and VCN films have lower sliding surface roughness due to the formation of the above-described oxide film as compared to other hard films (TiC, CrC). However, it can be seen that the roughness of the sliding surface is kept low for a long time. As shown in FIGS. 6 and 7, it can be seen that the VCN pin has excellent sliding characteristics and improved wear performance in addition to other hard coatings (TiC, CrC) as well as the VC pin. .

  FIG. 8 is a diagram showing the results of a chain wear elongation test in a poor lubricating environment assuming a next-generation engine. In this environment, local heat generation occurs in the bearing due to poor lubrication, and the surface pressure increases. As a result, the chain wear elongation rate of a chain using a conventional VC pin rapidly increases in a predetermined driving time. To do. The chain using the VCN pin maintains a substantially constant chain wear elongation over the entire test drive time.

  Fig. 9 shows parts wear due to a chain using a VC pin and a chain using a VCN pin. The white part is the wear amount of the pin hole of the inner side link plate, and the hatched part is the wear amount of the pin itself. Indicates the wear ratio between the pin hole and the pin. As shown in FIGS. 3 and 4, the VC film grows excessively in a high temperature environment due to dilute lubrication, and the soft and thick oxide film peels off from the surface. The VCN film does not grow excessively due to excessive growth of the oxide (VO) film even if it becomes a high temperature state due to local heat generation. The oxide film that is maintained in this state has a soft and mirror-sliding contact surface between the pin hole on the other side and has little peeling or chipping, so that the pin itself does not wear early. As a result, as shown in pin wear in FIG. 9, the VCN pin has a smaller amount of wear than the VC pin.

  The VCN film has higher toughness as shown in FIG. 6 and lower sliding surface roughness as shown in FIG. 7 than the VC film. As a result, even if a relatively high surface pressure acts on the bearing sliding surface, the pin surface layer 21 is held on the mirror surface having a low surface roughness, coupled with the interposition of the relatively thin oxide film 22. The aggressiveness with respect to the pin hole which is the bearing counterpart member is low, and the wear amount of the pin hole of the inner link plate is lower than that of the chain using the VC pin. Therefore, the amount of pin wear and pin hole wear that cause chain wear elongation is lower for both VCCN pins using VCN pins compared to VC pins using VC pins. Chain wear elongation is small.

  As described above, the thickness of the oxide film on the pin surface is significantly lower for the VCN pin than the VC pin, so even if the pin wear amount and the pin hole wear amount of the plate are both reduced, Since the amount of pin wear is remarkably reduced under the environment, the pin wear ratio is lower in the VCN chain than in the VC chain.

  Next, the nitrogen (N) ratio on the surface of the pin surface layer 21 made of the VCN film will be described. Since N permeates from the pin surface by nitriding treatment, the surface of the pin surface layer 21 has the highest content (ratio) and gradually decreases toward the base material interface as shown in FIG. As shown in FIG. 10 (a), the elongation performance of the chain increases as the ratio increases and the amount of N increases to 30 [atom%]. It saturates in the vicinity and exceeds 45 [atom%] and decreases. As shown in FIG. 10B, the pin wear performance (the wear on the upper side of the graph is small) increases as the ratio increases when the N amount is 10 [atom%] or more, and exceeds 30 [atom%]. It is saturated at 45 [atom%] and lowers. As shown in FIG. 10C, the surface hardness (Vickers hardness Hv0.1) of the pin surface layer 21 decreases as the N amount ratio increases. The hardness of the soot mixed in the engine oil is 800 to 1500 Hv, and the hardness on the pin surface is preferably 1600 [Hv 0.1] or more in consideration of the abrasive wear scratches on the coating surface due to soot. Considering the above, if the ratio of nitrogen (N) on the surface of the pin surface layer is 10 [atom%] or less, the pin wear suppression effect is not sufficient, and if it is 45 [atom%] or more, it should be generated in the internal combustion engine. Since there is a possibility that the hardness becomes lower and an increase in pin wear due to the wrinkles is concerned, the range of 10 to 45 [atom%] is preferable.

  FIG. 11 shows the influence of the N amount on the sliding surface. The film toughness of the surface layer is higher as the N content is larger, as shown in FIG. Further, as shown in FIG. 11B, the sliding surface roughness is smaller as the N amount is larger. Therefore, when the wear on the pin surface is taken into consideration, it is preferable that the N amount ratio is larger in the range of the predetermined amount or less.

  The pin made of the VCN film has a smaller wear amount than the VC pin, but gradually wears with use. Since the amount of N in the pin surface layer 21 gradually decreases from the surface toward the base material interface, the effect of suppressing the excessive formation of the oxide film also gradually decreases. However, since the decrease changes slowly, Since the mirror surface of the moving surface can be maintained over a long period of time, and there is no sudden change point of the N amount, it is possible to prevent the VCN film from being lost and peeled off.

  Next, a partially modified embodiment will be described with reference to FIGS. In this embodiment, functional elements such as titanium (Ti), silicon (Si), and molybdenum (Mo) are added to the above-described VCN film, and these functional elements are fixed to the VCN film. Melt. The highly functional element means an element that improves the characteristics of the VCN film by adding an element that increases the hardness of the V-based hard film such as Ti or Si or an element that has high creep (toughness) characteristics such as Mo. means. In addition, since the film to which the highly functionalizing element is added is based on the VCN film, the above-described oxide film is formed in the same manner, and acid resistance is suppressed to prevent the oxide film from being excessively formed in a high temperature environment. The same characteristic is provided. In addition, the highly functional elements such as Ti, Si, and Mo have a significantly lower content than the main components of V, C, and N.

  FIG. 12 shows an embodiment [denoted as VCN- (Ti, Si)] in which Ti or Si, which is a hardening element, is added to a VCN film to form a solid solution. As shown in FIG. 12A, the VCN- (Ti, Si) film has a high hardness in all N amounts as compared with the VCN film. When the amount of N in the film increases, the hardness decreases. In the above VCN film, there is a possibility that it may be lowered depending on the hardness of the wrinkles. Therefore, it was necessary to make it 45% or less, but in this VCN- (Ti, Si) film, it is high for each N amount. Since the hardness is increased, it is possible to use a larger amount of N.

  FIG. 12B is a diagram showing the pin wear performance with respect to the N amount change. In the VCN film, when the N amount is 45 atom% or more, the wear performance is reduced, but this VCN- (Ti , Si) film, even if the N content exceeds 45 [atom%], the wear performance does not decrease immediately.

  FIG. 13 shows an embodiment (denoted as VCN-Mo) in which Mo, which is a toughening element, is added to the VCN film to form a solid solution. As shown in FIG. 13 (a), the VCN-Mo film has substantially the same hardness as the VC film, 10 [atm%] VCN (N10%) film, but the film toughness parameter (characteristic). Is higher than VC film and VCN (N10%) film, and has excellent characteristics. Therefore, as shown in FIG. 13B, the chain elongation performance with respect to the change in the N amount is superior to that of the VCN film, particularly in a state where the N amount is low, and the N amount is 10 [atom%]. It can also be applied to the following.

  The sliding surface roughness of the pin surface is lower in the VCN (N10%) film than the VC film as described above, but the VCN (N10%)-Mo film having the same N amount [10 atom%] is the same as the VCN. Even lower than (N10%). Therefore, the pin having the surface layer made of the present VCN-Mo film can prevent the film from being broken and peeled off due to high toughness, and has low wear resistance against the pin hole due to low sliding surface roughness. .

The VCN-Mo film is composed of FV (ferrovanadium) added with Mo as an additive element as a permeation material, Al ₂ O ₃ (alumina, aluminum oxide) as a sintering preventing material, and NH ₄ as a reaction aid (promoter). In the vanadium permeation diffusion treatment by the so-called powder pack method in which Cl (ammonium chloride) is put into a furnace together with a pin base material, nitrogen (N) decomposed and generated from NH ₄ Cl as the reaction aid serves as a reaction medium. As a result, the VCN-Mo film is formed. That is, the VCN-Mo film is formed without performing the above nitriding treatment. In addition to V and C as main components, the film contains nitrogen (N) close to 10 [atom%] and a trace amount of Mo.

  The VCN- (Ti, Si, Mo) film in which the highly functional elements are dissolved is the powder pack described above using ferrovanadium (FV) to which a highly functional element such as Ti, Si, Mo or the like is added as a penetrating material. After forming a VC- (Ti, Si, Mo) film by the method, nitriding is performed to form a VCN- (Ti, Si, Mo) film. The powder pack method can be applied not only to Ti and Si, but also to Mo. The content of Mo can be adjusted as compared with VCN-Mo using Mo as a reaction medium, and nitrogen ( N) The amount can also be adjusted.

  It should be noted that only one of the highly functional elements such as Ti, Si, and Mo may be added, or a plurality of elements may be added. The highly functional elements are not limited to Ti, Si, and Mo, but may be other elements such as tungsten (W), cobalt (Co), tantalum (Ta), and manganese (Mn).

  The hard metal is preferably vanadium (V) as described above, but other hard metals of titanium (Ti), niobium (Nb), and chromium (Cr) can be similarly carbonitrided and applied. . As shown in FIG. 5, in Ti, the lattice constants are 4.3186 (Å) for TiC, 4.235 (Å) for TiN, and TiCN takes an intermediate value according to the N amount. Also in Nb, the lattice constant is 4.4691 (Å) for NbC, 4.439 (Å) for NbN, and NbCN takes an intermediate value corresponding to the N amount. Therefore, similarly to the description in the VCN, TiCN and NbCN have a shorter interstitial distance than TiC and NbC, thereby suppressing diffusion and permeation of oxygen (O), and oxidation resistance characteristics, particularly in a high temperature environment. Oxidation resistance at

  Although the crystal structure of CrC is not the NaCl structure and the growth of the oxide film is difficult to proceed, the oxide is thicker at about 20 nm than the V, Ti, Nb-based oxide film is about 2 nm at room temperature. Form a film. Considering that the thick oxide film is used for chain pins, etc., and is recovered and recovered immediately after being scraped or peeled off by wear, it is equivalent to the above-described oxide film that is excessively generated in the high temperature environment described above. And since CrN consists of the said NaCl structure and a lattice constant is 4.12, CrCN is provided with the oxidation-resistant characteristic similarly to the above-mentioned description.

  In addition, the surface layer made of hard metal carbonitride may include not only one kind of V, Ti, Nb, and Cr, but also a plurality of kinds, and not only the hard metal, carbon, and nitrogen, Not only highly functional elements but also elements other than highly functional elements may be added.

  In the above embodiment, the surface layer made of the hard metal carbonitride film is formed on the pin of the silent chain. However, the surface layer is not limited to this, and the surface layer is formed on at least one of the two members constituting the bearing portion for the chain. May be formed. For example, a surface layer may be formed in the inner link plate, particularly in the pin hole, instead of or in addition to the pin of the silent chain. Moreover, not only a silent chain but the 1st link which has a pin which comprises one member of a bearing part, and the 2nd link which has a fitting member which comprises the other member of a bearing part are the said bearing parts. It can be applied to chains connected endlessly. For example, in the case of a silent chain, the first link has a guide link plate and the second link has an inner link plate. In the case of a roller chain, the bearing portion includes a pin that is one member and a bush that is the other member that constitutes a fitting member that fits the pin, and the first link has an outer link plate. The second link has an inner link plate. The hard metal carbonitride film can also be applied to a rocker pin when the pins connecting the chains are a pair of rocker pins having arcuate contact surfaces that contact each other.

  The present invention is suitable for use in a timing chain for transmitting rotation of a crankshaft to a camshaft in an internal combustion engine, but is not limited to this, and is applicable to an internal combustion engine chain including driving of a cam, a balancer, and an oil pump. It is also possible to apply to a chain other than in the engine.

  In the above embodiment, as a method for forming the VCN film, the nitriding treatment is performed at 1000 ° C. or higher after the VC film is formed. However, the present invention is not limited to this, and the VCN film can be formed even in a low temperature condition or in an ammonia atmosphere. Further, the permeation diffusion treatment and the nitriding treatment may be performed simultaneously.

1 (Silent) chain 2 One member (pin)
3,7 The other member (fitting member, inner link plate, pin hole)
5 Second Link 6 Guide Link Plate 8 First Link 9 Chain Bearing 10 Teeth 20 (Pin) Base Material 21 Surface Layer 22 Oxide Film M (V, Ti, Nb, Cr) Hard Metal

Claims (13)

In the chain bearing part that consists of two members that are slidably fitted to each other and that flexibly connects a large number of links,
At least one member constituting the chain bearing portion includes a surface layer formed of a hard metal carbonitride film formed on the surface of the base material,
Between the other member constituting the chain bearing portion, an oxide film having a predetermined film thickness softer than the surface layer is formed on the surface of the surface layer.
A bearing portion for a chain characterized by that. The hard metal is at least one of vanadium, titanium, niobium and chromium;
The bearing portion for a chain according to claim 1. The hard metal carbonitride film has a crystal structure of NaCl structure and a hardness of 1600 [Hv] or more.
The chain bearing part according to claim 1 or 2. A bearing portion for a chain according to any one of claims 1 to 3,
A first link having a pin constituting one of the chain bearing portions;
A second link having a fitting member constituting the other of the chain bearing portion,
The first link and the second link are connected endlessly by the chain bearing portion,
A chain characterized by that. The first link has a guide link plate connected by a pair of the pins;
The second link has pin holes for fitting the pins at both ends, and has an inner link plate that constitutes the fitting member and has a pair of teeth,
The chain is a silent chain;
The chain according to claim 4. The first link has an outer link plate fixed by a pair of the pins;
The second link has a bush which is the fitting member, and an inner link plate connected by the pair of bushes,
The chain is a roller chain;
The chain according to claim 4. In chain pins that flexibly connect multiple links,
Provided with a surface layer made of a hard metal carbonitride film formed on the surface of the base material,
On the surface of the surface layer, an oxide film having a predetermined thickness that is softer than the surface layer is formed.
A pin for a chain characterized by that. The hard metal is at least one of vanadium, titanium, niobium and chromium;
The chain pin according to claim 7. The hard metal carbonitride film has a crystal structure of NaCl structure and a hardness of 1600 [Hv] or more.
The chain pin according to claim 7 or 8. A first link and a second link that are flexibly connected by the chain pin according to any one of claims 7 to 9,
The first link and the second link are connected endlessly,
A chain characterized by that. The first link has a guide link plate connected by a pair of the pins;
The second link has an inner link plate having a pin hole and a pair of teeth for fitting the pin at both ends,
The chain is a silent chain;
The chain according to claim 10. The first link has an outer link plate fixed by a pair of the pins;
The second link includes a bushing and an inner link plate connected by the pair of bushings;
The chain is a roller chain;
The chain according to claim 10. The chain is a chain disposed in an internal combustion engine;
The chain according to any one of claims 4 to 6 or claims 10 to 12.