CN108662084B

CN108662084B - Chain

Info

Publication number: CN108662084B
Application number: CN201810241109.2A
Authority: CN
Inventors: 海老沼和幸; 朝田美沙; 川田尚史; 中安友明; 吉本幸太; 内田修弘; 宫永正太
Original assignee: Tsubaki Chain Co ltd
Current assignee: Tsubaki Chain Co ltd
Priority date: 2015-08-28
Filing date: 2018-03-22
Publication date: 2020-09-01
Anticipated expiration: 2038-03-22
Also published as: CN108662083B; CN108662083A; CN108662084A

Abstract

The invention provides a chain component which has a simple surface treatment structure and can maintain good wear resistance for a long time, and a chain which is provided with the chain component and can maintain good wear resistance and elongation. A chain component of an industrial power transmission chain (1) is characterized in that a chromium nitride layer containing more than 0 mass% and 55 mass% or less of iron is formed on the outer side of a steel base material, and at least the surface of the chromium nitride layer sliding with other components is a rough surface having irregularities.

Description

Chain

Technical Field

The present invention relates to chain components such as pins, bushes, link plates, and rollers, which are components of industrial power transmission chains such as roller chains and silent chains used as timing chains of automobiles, for example, and to a chain provided with the chain components.

Background

It is known that wear resistance and corrosion resistance of a metal are improved by forming a chromium nitride film on a surface of the metal, and the film formation of the chromium nitride film is widely performed to increase the life of machine members, molds, tools, and the like.

The chromium nitride film is generally formed by a physical vapor deposition method (PVD method) such as an ion plating method in which Cr is evaporated and ionized in a vacuum combustion chamber, and irradiated onto a base material, and nitrogen gas is introduced, and a sputtering method in which a high voltage is applied between a target and a substrate to generate a glow discharge, Ar ions made into a plasma collide with the target surface, and Cr atoms are collided and deposited on the substrate.

However, when the chromium nitride film formed by the PVD method is used as a surface treatment layer of a highly loaded sliding member such as a chain, it is likely to peel off from a metal base material such as steel, and it is difficult to integrate the chromium nitride film with the base material so as to adhere to the surface of the base material and to peel off.

In addition, there is a problem that metal droplets (droplets) may be generated on the surface by the PVD method, and when the metal droplets are generated, the surface roughness increases, cracks are generated from the metal droplets as starting points, and the wear resistance is deteriorated. Even when the metal droplets are peeled off by polishing, holes are formed in the portion where the metal droplets are peeled off, and the holes are enlarged by a load and connected to each other, which causes a problem that it is difficult to improve the wear resistance.

In addition, the PVD method has a problem that the life cannot be prolonged by increasing the film thickness because cracks are generated and the wear resistance is lowered.

Further, when the material to be processed has, for example, a hole, there is a problem that it is difficult to form a film also on the inner surface of the hole.

Examples of the mechanical member include pins provided in a timing chain for an automobile engine. The timing chain may be a roller chain, a bush chain, or a silent chain.

The roller chain is formed such that both end portions of a cylindrical bush are press-fitted into bush holes of a pair of inner flat plates in a state where rollers are fitted to the bush, and both end portions of a pin fitted into the bush are press-fitted into pin holes of a pair of outer flat plates disposed on both outer sides of a pair of inner flat plates. The bush chain does not have rollers.

In a conventional timing chain, a steel base material of a pin is subjected to chromizing treatment in order to improve wear resistance of a bush and the pin.

However, when the timing chain is used together with engine oil that has been greatly aged in an engine room of an automobile, there is a problem that the pin and the bush are easily worn and the service life may be shortened.

Further, when soot (soot) generated during combustion of the engine is mixed into the engine oil, the soot is hard, and therefore the lubricating oil containing soot intrudes between the pin and the bush which are parts of the timing chain moving at a high speed and a high load, and although a film is formed between the pin and the bush, the film may be damaged to increase the friction coefficient between the pin and the bush or promote wear.

Thus, it is required to perform surface treatment in order to further improve the wear resistance of the chain.

In order to solve the problem that when a chromium nitride film is formed on a metal surface, peeling of the metal due to thermal history is likely to occur and adhesion to a base material is deteriorated, patent document 1 discloses a method in which Cr plating is performed on the surface of the metal material, then the metal material is heated in a halogen compound or a reactive gas containing halogen to purify and activate the surface of the Cr plating layer, and then the Cr plating layer is heated in a nitrogen atmosphere to nitride the surface of the Cr plating layer to form a chromium nitride film.

Further, there is also known a method of forming fine recesses on the surface and allowing soot of the soot-containing lubricating oil to fall into the recesses to suppress the increase in the friction coefficient and the wear due to the soot.

Patent document 1: japanese unexamined patent publication No. Hei 11-29848

Disclosure of Invention

The method of forming a chromium nitride film of patent document 1 is very complicated in process because a substrate material such as steel is subjected to special Cr plating such as industrial Cr plating, crack-free Cr plating with high corrosion resistance, macro-porous Cr plating, and amorphous Cr plating containing 2 to 4% carbon (amophorus), and further subjected to a halogen pretreatment and then to a nitriding treatment. Further, as in examples 1 to 3 of patent document 1, the vickers hardness of the obtained chromium nitride film is 1700 to 2000HV, and the hardness variation between the chromium nitride film and the softer base material is large, so that sufficient adhesion cannot be obtained, and there is a possibility that the wear resistance cannot be maintained for a long period of time.

Therefore, when the surface treatment method of patent document 1 is applied to a chain component such as a pin of a timing chain, the manufacturing process is complicated, the manufacturing cost is high, and a problem that good wear resistance cannot be maintained for a long period of time is conceivable.

In addition, when fine recesses are provided on the surface, if only the rough surface is formed, only the top of the projection comes into contact with the counter surface, and therefore, the surface pressure may increase and damage the counter surface.

Therefore, although it is necessary to flatten the convex portions as much as possible, the more the convex portions are flattened, the more the concave portions for discharging the soot are not sufficiently secured, and when the amount of soot is large or the operation is performed for a long time, there is a possibility that a sufficient effect cannot be obtained, and conversely, when the soot is accumulated in the concave portions and is projected while being kept staying, there is a possibility that the opposing surface is adversely affected.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a chain component having a simple surface treatment structure and capable of maintaining excellent wear resistance for a long period of time, and a chain having the chain component and capable of maintaining excellent wear resistance elongation.

The present invention relates to a chain component of an industrial power transmission chain, comprising: a steel-based base material; and a chromium nitride layer formed on the outer side of the steel base material and containing more than 8 mass% and not more than 32 mass% of iron, wherein at least a surface of the chromium nitride layer sliding with other parts is a rough surface having concave and convex portions.

A chain according to the present invention is a chain in which a plurality of pairs of outer plates connected by 2 pins and a plurality of pairs of inner plates connected by 2 bushings are alternately connected in a state in which the pins are movably fitted in the bushings, wherein at least 1 of the pins, the bushings, the inner plates, and the outer plates is the chain component.

The chain according to the present invention is a chain in which a plurality of pairs of outer plates connected by 2 pins and a plurality of pairs of inner plates connected by 2 bushings each externally fitted with a roller are alternately connected in a state where the pins are movably fitted in the bushings, wherein at least 1 of the pins, the bushings, the inner plates, the outer plates, and the rollers is the chain component.

A chain according to the present invention is a chain in which a plurality of inner plates each having a pair of connecting teeth formed in a W shape at one end in a width direction and a pair of pin holes in front and rear are connected to be bendable by a pin inserted into the pin hole in a state where one connecting tooth of one inner plate adjacent to another inner plate in the width direction of the chain overlaps with another connecting tooth of another inner plate, and guide plates each having the pin inserted and fixed therein are disposed on both outer sides in the width direction, wherein at least 1 of the pin, the inner plates, and the guide plates is the chain component.

According to the chain component of the present invention, the chromium nitride layer is formed on the outer side of the steel base material, the surface treatment structure is simple, and the chain component can be easily and inexpensively manufactured through a small number of steps.

Since chromium nitride has a low friction coefficient and high toughness, the chain component on which the chromium nitride layer is formed has low destruction to the counter member and is less damaged by fine and high-hardness soot or the like.

The chromium nitride layer having a low friction coefficient causes less sliding heat, has a high oxidation initiation temperature of chromium nitride, and does not oxidize even at high temperatures, thereby maintaining the wear resistance of the chain component satisfactorily.

Further, since the chromium nitride layer contains iron, the adhesion to the steel base material is good, and since the iron content is more than 0 mass% and not more than 55 mass%, the wear resistance of the chain component is maintained for a long period of time.

Further, since the chromium nitride layer is less destructive to the counterpart member, damage due to fine and highly hard soot or the like is also less, and thus the degree of freedom in setting the gap distance of the sliding portion is improved.

Further, since at least the surface of the chromium nitride layer which slides against other parts is a rough surface having concave and convex portions, soot can be dropped into the concave portions of the rough surface and discharged from the gaps, and the destruction of the counter surface is reduced.

Further, since the chromium nitride layer has high toughness, even if the surface pressure is increased by only the top of the convex portion of the rough surface coming into contact with the counterface, the counterface is not damaged.

According to the chain of the present invention, since the chain component exhibiting the above-described effects is provided, the wear resistance and elongation properties are excellent.

Drawings

Fig. 1 is a partial perspective view showing an example of a roller chain.

Fig. 2 is a partial perspective view showing an example of a silent chain.

FIG. 3 is a graph showing the cross-sectional composition distributions of Fe, Cr and N of the pin of example 1, which were obtained by line analysis using an EPMA (Electron Probe Micro Analyzer).

Fig. 4 is a graph showing results of checking wear amounts of a pin and a bush in which the pin is embedded after running the chain for a predetermined time, with respect to a roller chain using the pin of example 1 and a roller chain using the pin of comparative example 1.

FIG. 5 is an optical microscope photograph showing the pin surface of example 1.

FIG. 6 is an optical microscope photograph showing the pin surface of comparative example 2.

FIG. 7 is a graph showing the relationship between the Fe content of the chromium nitride layer and the wear elongation ratio.

FIG. 8 is a graph showing the relationship between the layer thickness of a chromium nitride layer and the wear elongation ratio.

Fig. 9 is a sectional view showing a gap between a pin and a bush of a bush chain.

FIG. 10 is a graph of the amount of age-related wear due to differences in pin-to-bushing clearance and surface layers.

FIG. 11 is an optical microscope photograph showing the surfaces (b) and (d) of conventional examples (a) and (c) and the present invention when an aged engine oil is used.

Fig. 12 is a graph showing the amount of aged wear when the surface is made rough.

Description of the symbols

1-a roller chain; 2-inner flat plate; 2 a-bushing hole; 3-a bushing; 4-a roller; 5-outer plate; 5 a-pin hole; 6. 12-a pin; 10-silent chain; 11-inner plate; 13-a guide plate; 20-bush chain.

Detailed Description

The chain component of the present invention includes a steel base material and a chromium nitride layer formed on the outer side of the steel base material.

The chromium nitride layer contains more than 0 mass% and 55 mass% or less of Fe. The lower limit of the Fe content is preferably 1 mass%, more preferably 5 mass%, and still more preferably 8 mass%. The upper limit is preferably 45 mass%, more preferably 32 mass%.

It is preferable that Fe has a concentration distribution gradually decreasing from the surface of the steel-based base material toward the outside.

The content of Cr and N is preferably gradually decreased from the outside toward the surface side of the steel base material.

The chromium nitride layer preferably contains more than 8 mass% and 32 mass% or less of Fe, 45 mass% or more and 90 mass% or less of Cr, and 5 mass% or more and 25 mass% or less of N, when the total amount is 100 mass%.

The lower limit of the Cr content is preferably 48 mass%, more preferably 51 mass%. The upper limit is preferably 77% by mass, more preferably 67% by mass.

The lower limit of the N content is preferably 9% by mass, more preferably 13% by mass.

The Fe content is a value obtained by qualitative and quantitative analysis of EPMA. The contents of Cr and N are corrected in consideration of the analysis value of the standard sample of chromium nitride, relative to the value obtained by qualitative/quantitative analysis of EPMA.

The chromium nitride layer preferably has a thickness of 2 μm or more and 30 μm or less. In this case, the surface roughness is small, cracks are less likely to occur, the wear resistance is good, and the wear resistance elongation of the chain obtained by assembling the chain components is good.

An intermediate layer for improving the adhesion of the chromium nitride layer to the steel base material can be arranged between the chromium nitride layer and the steel base material.

Examples of the intermediate layer may include Cr, CrB and CrB₂、CrC、Cr₂N、Cr₂O₃、CrSi₂、CrNi、CrB-O、CrB₂-O、(V、Cr)C、(Cr、Zr)N、CrBN、CrB₂+ Ni, (Cr, Mn) C, (Cr, Mo) N, (V, Cr) B, (Cr, Fe) C, (Cr, W) N, (Cr, Mn) B, (Cr, Co) C, (Cr, Cu) N, (Cr, Fe) B, (Cr, Ni) C, (Cr, V) N, (Cr, Co) B, (Cr, Cu) C, (Cr, Ni) B, (Cr, Zn) C, (Cr, Cu) B, (Cr, Zr) C, (Cr, Zn) B, (Cr, Nb) C, (Cr, Zr) B, (Cr, Mo) C, (Cr, Nb) B, (Cr, Hf) C, (Cr, Mo) B, (Cr, Ta) C, (Cr, Hf) B, (Cr, W) C, (Cr, Ta) B, (Cr, W) B and the like.

The chromium nitride layer of the chain component according to the present invention is formed on the outer side of the steel base material by a method in which the steel base material and a treatment agent containing Cr powder, alumina, and ammonium halide are stored in a heating furnace, the heating furnace is heated to a target temperature, and the heating furnace is slowly cooled after being maintained for a predetermined time. The treatment agent may contain a compound that is a source of an element contained in the intermediate layer.

Hereinafter, a case will be described in which the chain component according to the present invention is applied to a pin of a roller chain used as a timing chain of an automobile engine or the like.

Fig. 1 is a partial perspective view showing an example of a roller chain 1.

The roller chain 1 is configured such that both ends of a bush 3 are press-fitted into

bush holes

2a, 2a of a pair of inner flat plates 2, respectively, and both ends of a pin 6 fitted into the bush 3 are press-fitted into

pin holes

5a, 5a of a pair of outer

flat plates

5, 5 arranged on both outer sides of the pair of inner

flat plates

2, 2. The bush 3 is externally embedded with a roller 4.

The outer side of the pin 6 is provided with said chromium nitride layer.

Hereinafter, a method for manufacturing a chain component according to the present invention will be described by taking the pin 6 as an example.

As a steel base material of the pin 6, for example, a wire rod such as carbon steel, chromium molybdenum Steel (SCM), high carbon chromium bearing Steel (SUJ), or the like is used.

Cr is diffused and impregnated into the surface of the steel base material of the pin 6, and N is diffused and impregnated to form a chromium nitride layer on the front side.

As the diffusion permeation treatment of Cr, a known method called "powder packing (pack) method" can be used.

Specifically, the pin 6 and the treatment agent containing Cr powder, alumina, and ammonium halide are first filled in, for example, an alumina crucible, and the alumina crucible is stored in, for example, a heating furnace such as an electric furnace. The treating agent preferably contains 60 to 67 mass% of Cr powder, 30 to 37 mass% of alumina, and 0.2 to 3 mass% of ammonium halide, wherein the total amount is 100 mass%.

Examples of the ammonium halide include ammonium chloride, ammonium bromide, ammonium iodide, and ammonium fluoride. 1 or 2 or more ammonium halides are selected depending on the layer constitution of the object.

Before heating, passing through Ar and N₂And replacing with inert gas.

Thereafter, the mixture was heated to a predetermined temperature.

In this case, NH may be supplied at a predetermined flow rate according to the thickness of the chromium nitride layer, the film structure, the thickness of the entire film, and the like₃And/or N₂And (4) circulating.

Cooling is performed after a prescribed time.

When the desired film is not formed, NH is again caused to form₃And/or N₂The mixture is circulated, heated to a predetermined temperature, and cooled after being held for a predetermined time.

The composition ratio of the treating agent, the treatment temperature and the holding time are determined in consideration of the composition of the steel base material, the thickness of the intended chromium nitride layer, the film structure, the thickness of the entire film, and the like.

Specific examples of the method for forming the chromium nitride layer include a method of nitriding the surface of the steel base material or the CrC layer.

According to the method for forming a chromium nitride layer, the chromium nitride layer can be easily and inexpensively formed on the outer side of the steel base material by a small number of steps. Moreover, Cr, C and Fe have concentration gradient, and the chromium nitride layer has good adhesion with the steel base material.

The chromium nitride layer, which has a high oxidation start temperature and does not oxidize even at high temperatures, is formed on the outer side of the chain component obtained by the above-described manufacturing method, and therefore, the wear resistance is excellent.

Further, although the case where the chromium nitride layer is formed on the pin 6 has been described, the chromium nitride layer may be formed on the surface of at least 1 of the chain components of the inner plate 2, the bushing 3, the roller 4, and the outer plate 5, without being limited thereto.

According to the chain 1 including the chain component according to the present invention, good elongation resistance against wear can be maintained for a long period of time.

The chain to which the invention relates may also be a bush chain without rollers.

The chain to which the invention relates may also be a silent chain.

Fig. 2 is a partial perspective view showing an example of the silent chain 10.

The silent chain 10 is configured such that, in a state where one connecting tooth 11a of one inner plate 11 adjacent to another inner plate 11 in the width direction of the silent chain 10 overlaps another connecting tooth 11a of another inner plate 11, a plurality of inner plates 11 each having a pair of connecting

teeth

11a, 11a formed in a W shape at one end in the width direction are connected to each other so as to be bendable by a pin 12 inserted into a pin hole, and guide plates 13 each having a fixing pin inserted therein are disposed on both outer sides in the width direction.

The silent chain 10 has a chromium nitride layer on the surface of at least 1 of the chain parts of the inner plate 11, the pins 12, and the guide plate 13.

Examples

The present invention will be specifically described below with reference to examples.

Example 1

As a material to be processed in example 1, a wire rod of SUJ2 was cut into a predetermined length and subjected to grinding treatment to obtain a base material of a pin 6 as a steel base material.

Cr powder, alumina, NH to be blended in the numerical range₄The treating agent of Cl and the pin 6 were contained in an alumina crucible, and the alumina crucible was placed in a heating furnace.

Replacing with inert gas, and flowing additive gas (NH) at appropriate flow rate₃And N₂) And heated to said temperature, and maintained at this temperature to form a chromium nitride layer on the outside of the pin 6. Thereafter, the heater is turned off to perform slow cooling.

As described above, the pin 6 having the chromium nitride layer formed on the outer side of the steel base material was obtained.

The chromium nitride layer had an Fe content of 13 mass%, a Cr content of 74 mass%, and an N content of 13 mass%, and a thickness of 13 μm.

FIG. 3 is a graph showing the cross-sectional composition distributions of Fe, Cr and N of the pin 6 of example 1, which were obtained by line analysis using EPMA. The horizontal axis represents the length in the thickness direction, and the vertical axis represents the detection intensity of the component.

The measurement conditions were as follows.

Acceleration voltage: 15kV

Sample current: 50nA

Electron beam diameter: 1 μm

As can be seen from fig. 3, the Fe content gradually increases from the outside toward the base surface side of the pin 6, and the Cr and N contents gradually decrease. This confirmed that Cr and N diffused and penetrated into the surface side portion of the base material of the pin 6, and a chromium nitride layer was formed on the outer side of the steel base material. Since Cr and N diffuse and permeate, they have a concentration gradient. Fe also has a concentration distribution in which the content gradually decreases from the surface side portion of the steel base material toward the outside. Since Fe, Cr and N have concentration gradients, the adhesion between the base material of the pin 6 and the chromium nitride layer is good.

Comparative example 1

The pin of comparative example 1 in which a CrC layer having a thickness of 15 μm was formed on a steel base material was obtained by a conventional powder packaging method.

Comparative example 2

The pin of comparative example 2 in which a 6 μm chromium nitride layer was formed on a steel base material by a conventional PVD method was obtained.

A roller chain was assembled using the pin 6 of example 1, the pin of comparative example 1, and the pin of comparative example 2.

The abrasion resistance and elongation of each roller chain were evaluated.

First, aged engine oil was recovered from automobiles which used engine oil of SAE standard "5W-30" and actually traveled 5000km, 10000km, and 15000km on the road, respectively.

Further, a severe test was performed by rotating the roller chain provided with the pins of example 1, comparative example 1, and comparative example 2 at a high speed for 100 hours using each engine oil. The results are shown in table 1. Table 1 shows the ratio of the wear elongation (wear elongation ratio) of example 1 and comparative example 2 when the wear elongation of the roller chain of comparative example 1 is 100 with respect to the engine oil for each running distance.

TABLE 1

TABLE 1 (%)

Distance traveled (km)	Example 1	Comparative example 1	Comparative example 2
				5000	80	100	118
10000	70	100	146
				15000	63	100	182

As is clear from table 1, the abrasion resistance and elongation properties were good in the order of example 1, comparative example 1, and comparative example 2. That is, it is found that the roller chain 1 of example 1 in which the chromium nitride layer containing more than 0 mass% and 55 mass% or less of Fe was formed on the outer side of the steel base material had good wear resistance elongation. Further, the effect of improving the wear resistance elongation of the chromium nitride layer is greater with the use of engine oil for a longer running distance (aging progress).

Fig. 4 is a graph showing results of checking wear amounts of a pin and a bush in which the pin is embedded after running the chain for a predetermined time, with respect to the roller chain using the pin 6 of example 1 and the roller chain using the pin of comparative example 1.

As can be seen from fig. 4, when the roller chain having the pin 6 of example 1 was used, the wear amounts of the pin and the bush were reduced as compared with when the roller chain having the pin of comparative example 1 was used. In particular, the wear amount of the bush is greatly reduced, because the chromium nitride layer of the pin 6 of example 1 is less destructive to the counterpart member (bush) which slides.

FIG. 5 is an optical microscope photograph showing the surface of the pin 6 of example 1, and FIG. 6 is an optical microscope photograph showing the surface of the pin of comparative example 2.

As will be seen, in the case of the pin 6 of example 1 in fig. 5, no metal droplets were present on the surface, whereas in the case of the pin of comparative example 2, many metal droplets were generated. It is understood that in the case of the pin of comparative example 2, the surface roughness increased, cracks were generated starting from the metal droplets, and the wear resistance was deteriorated.

Next, the results of the wear resistance elongation evaluation test using aged engine oil with the Fe content of the chromium nitride layer of the roller chain changed will be described.

The pins 6 of examples 4 and 5 and the pins of comparative examples 3 to 6 having the elemental compositions shown in Table 2 below were produced in the same manner as in example 1. Table 2 also shows example 1 and comparative example 1.

The Fe content in the elements in table 2 is a value obtained by qualitative and quantitative analysis of EPMA. The contents of Cr and N are values which are corrected in consideration of the analytical value of the standard sample of chromium nitride, relative to the value obtained by the qualitative/quantitative analysis of EPMA.

TABLE 2

As the aged engine oil, an engine oil of SAE standard "0W-20" was used, and an oil recovered from an automobile actually running on a road for 10000km was used.

The roller chains including the pins of examples 1 to 6, comparative example 1, and comparative example 3 were rotated at high speed for 150 hours using the engine oil, and a severe test was performed. The results are shown in table 2. Table 2 shows the ratio of the wear elongation (wear elongation ratio) of each of the examples and comparative example 3 when the wear elongation of the roller chain of comparative example 1 is 100.

Fig. 7 is a graph showing the relationship between the Fe content of the chromium nitride layer and the wear elongation ratio, with the horizontal axis representing the Fe content (mass%) and the vertical axis representing the wear elongation ratio (%).

As is clear from table 2 and fig. 7, the roller chain 1 of each example in which the chromium nitride layer containing more than 8 mass% and 32 mass% or less of Fe was formed had good wear-resistant elongation.

The results of the wear resistance elongation evaluation test using aged engine oil with the layer thickness of the chromium nitride layer of the roller chain changed will be described.

As the aged engine oil, an engine oil of SAE standard "0W-30" was used, and an oil recovered from an automobile actually running on a road for 10000km was used.

The roller chain having the pin of each example in which the layer thickness of the chromium nitride layer was changed was rotated at a high speed for 180 hours using the engine oil, and a severe test was performed.

Fig. 8 is a graph showing the relationship between the layer thickness of the chromium nitride layer and the wear elongation ratio, and the horizontal axis represents the layer thickness (μm) and the vertical axis represents the ratio (%) of the wear elongation when the wear elongation of the roller chain of comparative example 1 is 100.

It is understood from FIG. 8 that the wear resistance elongation is good when the layer thickness of the chromium nitride layer is 2 μm or more and 30 μm or less. When the layer thickness is more than 30 μm, the abrasion-resistant elongation is deteriorated.

Accordingly, since the chromium nitride layer of the pin 6 according to the example of the present invention does not have metal droplets, peeling is less likely to occur, and since the opposite member is less destructive and the layer thickness can be made 2 μm or more and 30 μm or less, the roller chain 1 has good wear resistance elongation, and it is confirmed that the wear resistance elongation can be maintained well for a long period of time.

Next, the test results when aged engine oil is used in the bush chain 20 shown in fig. 9 will be described.

Generally, the clearance distance CL between the pin 6 and the inner periphery of the bush 3 is designed to be small for improving wear resistance as follows, and the bearing surface pressure is reduced when tension is applied.

However, if the clearance distance CL is reduced, the twisting and flexing properties of the entire chain are deteriorated, and the strength is reduced due to the deterioration of the engine assembling property and the application of the load to the chain itself.

Further, if the clearance distance CL is reduced, soot and the like mixed in the engine oil are likely to accumulate, and the inner peripheral surfaces of the pin and the bush are damaged by the soot and the like, so that the friction coefficient increases, and heat generation, resistance, and wear increase.

Therefore, the clearance distance CL is strictly designed within a very narrow range in consideration of the relationship between the reduction of the bearing surface pressure when the tension is applied and other influences, depending on the application and the use environment.

In the present invention, by applying a chromium nitride layer having a low friction coefficient and high toughness to the surface, it is possible to suppress the wear resistance from being lowered even if the clearance distance CL is increased to increase the bearing surface pressure.

Further, since the chromium nitride layer has low destructiveness to the counterpart member and causes little damage due to fine and high-hardness soot or the like, even if the clearance distance CL is reduced and soot or the like is likely to accumulate, it is possible to suppress generation of damage due to soot or the like to the inner peripheral surface of the pin or bush, and to suppress increase in heat generation, resistance, and wear associated with increase in the friction coefficient.

This allows the clearance distance CL to be set with a high degree of freedom, and can flexibly cope with changes in various applications and use environments.

Specifically, it was confirmed that the clearance distance CL between the pin 6 and the bush 3 was usable within a range of 30 μm to 120 μm without any problem.

In addition, it was confirmed that, when the thickness of the chromium nitride layer is N, it can be used without any problem in the case of 60. gtoreq.CL/N. gtoreq.2.8, and that the clearance distance CL can be sufficiently increased even if the thickness of the layer is reduced.

Fig. 10 shows changes in the aged wear elongation of a chain in which a conventional chromizing treatment was applied to the surface of the pin 6 and a chain provided with a chromium nitride layer according to the present invention when aged engine oil was used.

The elongation of the chain provided with the chromium nitride layer of the present invention is surely suppressed regardless of the size of the clearance distance CL.

Even when the clearance distance CL is increased in the chain provided with the chromium nitride layer according to the present invention, it can be confirmed that only substantially the same elongation as that when the clearance distance CL of the chain subjected to the conventional chromizing treatment is decreased occurs, and the degree of freedom in setting the clearance distance CL can be improved.

Fig. 11 is a photograph showing the surface state of a pin subjected to a conventional chromizing treatment and a pin provided with a chromium nitride layer according to the present invention.

Fig. 11a and 11b show the state of scratches on the surface of a conventional chromizing-treated pin and a pin having a chromium nitride layer according to the present invention when aged engine oil is used, and fig. 11c and 11d show the states of indentations on the surface of a conventional chromizing-treated pin and a pin having a chromium nitride layer according to the present invention when subjected to a vickers hardness test.

As is clear from the scratch states in fig. 11a and 11b, the surface of the pin subjected to the conventional chromizing treatment was scratched in a large amount, whereas the pin provided with the chromium nitride layer according to the present invention had a low friction coefficient and high toughness, and therefore hardly scratched.

As is clear from fig. 11c and 11d, cracks occurred around the indentation in the conventional pin subjected to the chromizing treatment, whereas cracks did not occur in the pin provided with the chromium nitride layer according to the present invention because of high toughness.

FIG. 12 is a graph showing the results of the wear amount of the sliding surface when the sliding surface of the chromium nitride layer is roughened in the present invention.

The graph on the left of FIG. 12 is a graph showing the amount of wear when the silent chain pins were surface treated and run for 100 hours using aged oil containing soot from 0W to 16.

Compared with the existing pin with the vanadium carbide layer, the wear loss of the pin and the connecting flat plate is extremely small on the pin with the chromium nitride layer.

In addition, the graph on the right side of fig. 12 is a graph showing the amount of wear when the pins of the bush chain are surface-treated and run for 100 hours using aged oil containing soot of 0W to 16.

In the pin having a chromium nitride layer of the present invention, the wear amount of the pin is substantially the same as that of the conventional pin having a chromium carbide layer, but the wear amount of the counter surface, i.e., the bush, is small regardless of the surface roughness.

In addition, even if the surface of the pin having the chromium nitride layer of the present invention is roughened to 0.32 μm, the amount of wear of the countersurface, i.e., the bush, is smaller than that of the conventional pin having the chromium nitride layer and having a surface roughness of 0.15 μm, and a sufficient soot removal effect can be obtained even in an environment containing more soot.

As described above, the chain component according to the present invention is a chain component of an industrial power transmission chain, comprising: a steel-based base material; and a chromium nitride layer formed on the outer side of the steel base material and containing more than 8 mass% and 32 mass% or less of iron, wherein at least the surface of the chromium nitride layer sliding with other parts is a rough surface having concave and convex portions.

In the present invention, since the surface roughness is rk0.05 μm to 0.5 μm, soot in aged engine oil having a particle size of not more than the particle size of the surface irregularities can be sufficiently removed from the sliding surface, and the damage to the counter surface can be reduced.

Further, if the parameter of the surface roughness includes a numerical range substantially corresponding to Rk0.05 μm to 0.5 μm, other parameters may be substituted.

In the present invention, the chromium nitride layer is formed on the outer side of the steel base material, the surface treatment structure is simple, and the steel base material can be easily and inexpensively manufactured by a small number of steps.

Chromium nitride has a low coefficient of friction, and the chain component on which the chromium nitride layer is formed has low damage to the counter member. The sliding heat on the chromium nitride layer is less. Further, since the oxidation start temperature of chromium nitride is high, oxidation does not occur even at high temperatures, and therefore, the wear resistance of the chain component is favorably maintained.

The chromium nitride layer has good adhesion to the steel base material because it contains iron, and the wear resistance of the chain component is maintained for a long period of time because the iron content is greater than 8 mass% and not greater than 32 mass%.

In the chain component according to the present invention, the iron has a concentration distribution that gradually decreases from the surface of the steel base material toward the outside.

In the invention, the adhesion with the steel base material is better.

In the chain component according to the present invention, the chromium and nitrogen in the chromium nitride layer have a concentration distribution in which the concentration decreases gradually from the outside toward the surface of the steel base material.

In the invention, the adhesion with the steel base material is better.

The chain component according to the present invention is characterized in that the content of the iron in the chain component is 1 mass% or more and 45 mass% or less.

In the invention, the wear resistance is better.

The chain component according to the present invention is characterized by containing more than 8 mass% and 32 mass% or less of iron, 45 mass% or more and 90 mass% or less of chromium, and 5 mass% or more and 25 mass% or less of nitrogen, when the total amount is 100 mass%.

In the present invention, the adhesion to the steel base material is further improved while the wear resistance is further improved.

The chain component according to the present invention is characterized in that the chromium nitride layer has a thickness of 2 μm or more and 30 μm or less.

In the invention, the surface roughness is small, cracks are difficult to occur, and the wear resistance is good.

In the chain according to the present invention, a plurality of pairs of outer flat plates connected by 2 pins and a plurality of pairs of inner flat plates connected by 2 bushings are alternately connected in a state where the pins are movably fitted in the bushings, and at least 1 of the pins, the bushings, the inner flat plates, and the outer flat plates is the arbitrary one of the chain components.

The bush chain of the present invention has good elongation against abrasion.

In the chain according to the present invention, a plurality of pairs of outer flat plates connected by 2 pins and a plurality of pairs of inner flat plates connected by 2 bushings each having a roller fitted therein are alternately connected in a state where the pins are movably fitted in the bushings, and at least 1 of the pins, the bushings, the inner flat plates, the outer flat plates, and the rollers is one of the chain components.

The roller chain of the present invention has good wear resistance and elongation.

In the chain according to the present invention, at least one of the pin and the bush is the one chain component, and a clearance distance between the pin and the bush is 30 μm to 120 μm.

The chain of the present invention has good elongation against abrasion and is flexible in response to various uses and changes in the use environment.

In the chain according to the present invention, a plurality of inner plates having a pair of coupling teeth formed in a W shape at one end portion in a width direction are coupled to be bendable by a pin inserted into the pin hole in a state where one coupling tooth of one inner plate adjacent to another inner plate in the width direction of the chain overlaps another coupling tooth of another inner plate, and guide plates into which the pin is inserted and fixed are disposed on both outer sides in the width direction, wherein at least 1 of the pin, the inner plates, and the guide plates is the arbitrary one chain component.

In the silent chain of the present invention, the wear-resistant elongation is good.

In the chain according to the present invention, at least one of the pin and the inner plate is the one chain component, and a clearance distance between the pin hole of the inner plate in sliding contact with the pin and the pin is 30 μm to 120 μm.

The presently disclosed embodiments are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is not limited to the above description, but includes all modifications within the scope of the claims equivalent to the claims.

For example, the chain components of the present invention are not limited to the components of roller chains, bush chains, and silent chains. Further, the present invention can be applied to parts of industrial power transmission chains other than timing chains.

Claims

1. A chain, which is an industrial power transmission bush chain, is characterized in that,

the pin has: a steel-based base material;

and a chromium nitride layer formed on the outer side of the steel base material and containing more than 8 mass% and 32 mass% or less of iron,

at least the surface of the chromium nitride layer sliding with other parts is a rough surface having concave and convex parts,

the chromium nitride layer has a thickness of 2 [ mu ] m or more and 30 [ mu ] m or less,

when the clearance distance between the pin and the bush is CL and the thickness of the chromium nitride layer is N, 60/N is more than or equal to CL/N and more than or equal to 2.8.

2. The chain according to claim 1, wherein the rough surface has a surface roughness of rk0.05 μm to 0.5 μm.

3. The chain according to claim 1, wherein the iron has a concentration distribution gradually decreasing from the surface of the steel-based base material toward the outside.

4. The chain as claimed in claim 1, wherein the chromium and nitrogen of the chromium nitride layer have a concentration distribution gradually decreasing from an outer side toward a surface of the steel-based base material.

5. The chain according to claim 1, wherein the pin contains more than 8 mass% and 32 mass% or less of iron, 45 mass% or more and 90 mass% or less of chromium, and 5 mass% or more and 25 mass% or less of nitrogen, based on the total amount of the pin taken as 100 mass%.

6. The chain of claim 1,

the clearance distance between the pin and the bush is 30-120 mu m.