JPS6134499B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a bearing for an internal combustion engine equipped with a bearing made of an aluminum (Al) bearing alloy that exhibits less growth of Sn (tin) particles and less decrease in hardness in high-temperature conditions, has excellent fatigue resistance, and has excellent wear resistance. It is related to the device. Conventional aluminum bearing alloys are mainly Al-Sn alloys, such as Al-Sn (20%)-Cu.
(Copper) 1%, Al-Sn (20%) - Pb (Lead) 3% -
Cu (1%) - Si (silicon) 3%, etc. are used, but when this alloy is used in bearings for automobile internal combustion engines, fatigue failure occurs in a short period of time when the internal combustion engine continues to operate under high load. Sometimes something happened. This is because the oil in an internal combustion engine becomes particularly hot during continuous high-load operation, for example, the temperature of the oil in the oil pan reaches 130℃ to 150℃, so it is expected that the bearing will reach a considerably high temperature on its sliding surface. As a result, in conventional Al-Sn alloys, the hardness rapidly decreases at high temperatures, causing melting and movement of Sn, which is thought to be the cause of the decrease in fatigue strength. The inventors of the present invention fabricated an alloy with high hardness or an alloy in which Sn does not easily move under high temperatures into the shape of an internal combustion engine bearing, and conducted a dynamic load fatigue test under high temperature oil. As a result, the fatigue strength was improved. This recognition supports the above consideration. Furthermore, in addition to the above-mentioned decrease in fatigue strength due to the decrease in high-temperature hardness, in conventional Al-Sn alloys, coarsening of Sn particles in the alloy structure is also a cause of decrease in fatigue strength. In other words, aluminum bearing alloys are formed by press-welding an Al-Sn alloy to a backing steel plate, but in order to increase the adhesive strength of both metals, it is essential to anneal the alloy after press-welding.
Generally, this annealing is performed at a temperature below the temperature at which Al--Fe intermetallic compounds precipitate (approximately 475°C), and the higher the temperature and the longer the time, the greater the adhesive strength. However, when conventional Al-Sn alloys are subjected to high temperatures during annealing, Al grain boundaries and Sn particles move within the alloy structure, and as a result, the Sn particles become coarser over time. There was a drawback that it was difficult to use.
In other words, when conventional aluminum bearing alloys are annealed to increase the adhesive strength with the backing steel plate, the Sn particles become coarser, and this coarsening is the cause of lowering the fatigue strength of Al-Sn alloys. . The inventors of the present invention have added various additive elements to Al-Sn alloys to improve their high-temperature hardness and fatigue strength. We have developed an alloy containing Zr (zirconium), Cu, etc., and have filed a patent application (Japanese Patent Application No. 52-2690). Furthermore, Sn, Cr and
In addition to Cu, Pb or In (indium) is added,
We developed an alloy with particularly improved conformability while maintaining the same fatigue resistance, and applied for a patent (patent application 1972-
18255). As a result of further research, the present invention has revealed that Al-Sn
This was achieved by discovering a material whose wear resistance can be significantly improved regardless of the mating material by increasing the Cr content in the alloy. Al of the bearing constituting the bearing device according to the present invention
Sn-based alloys basically have a content of 3.5% to 35% by weight.
Based on Al-Sn alloy made of Sn and more than 1.0% and 7.0% Cr, Cu and/or Mg (magnesium) up to 3.0% (not including 0) and up to 9% (not including 0). ) and at least one of Pb, In, and Bi (bismuth), and the amount of Sn is the largest among the added elements, and compared to conventional Al-Sn alloys. Cr, Pb, Bi,
By adding In, Sn became finer and its conformability improved, and in addition, the hardness increased, and it was observed that there was almost no movement or growth of Sn, especially at high temperatures. Also, there is little decrease in high temperature hardness. Furthermore, when we conducted a dynamic load fatigue test,
Improvement in fatigue strength under high oil temperature was confirmed. It has also been confirmed that the bearing material has sufficient wear resistance regardless of the material of the bearing, that is, the material of the shaft, which has a particularly large effect on the sliding performance of the bearing, such as spheroidal graphite cast iron. The reason for limiting the Sn content to 3.5 to 35% by weight is that Sn is an element added primarily for the purpose of lubrication, but adding more than 35% of Sn increases compatibility.
Lubricity improves but hardness decreases, which is 3.5%
This is because, on the contrary, the conformability and the like as a bearing alloy are inferior. The amount of Sn added is 15% in conventional Al-Sn alloys in order to isolate and disperse Sn.
The upper limit is set at around 15%.
It was believed that if more than % is added, the Sn particles in the alloy become isolated in Al and cannot be dispersed and begin to exist in a continuous state, resulting in a decrease in hardness. However, in the present invention, the effect of adding other elements as described later Even when these were added up to 35%, the Sn particles were isolated and dispersed, and there was no practical problem. In addition, the amount of Sn added
How to set it within the range of 3.5 to 35% should be determined appropriately depending on the application, but in general, when the load applied to the bearing is large,
It is better to reduce the amount of Sn, and increase the amount of Sn when the load is small. From another point of view, it is better to increase the amount of Sn when used in a state where there is a concern about seizure, and to decrease the amount of Sn when there is no concern.
However, recently, bearings have become hot due to high oil temperatures, and this has caused problems such as deformation, seizure, and fatigue of bearings, so it is also necessary to determine the amount of Sn from the point of view of minimizing deformation at high temperatures. Cr is particularly effective in that it prevents increases in hardness and softening at high temperatures, does not cause coarsening of Sn particles even during annealing, and has sufficient wear resistance regardless of the material used. Additive effect is high.
First, speaking of increasing hardness and preventing softening at high temperatures, if the amount of Cr added is less than 1.0% by weight, improvement in high temperature hardness can be expected, but no improvement in wear resistance can be expected. When 7.0% or more is added, Al-Cr such as Cr and Al
Too much intermetallic compound precipitates, making it too hard as a bearing alloy, and even if the wear resistance is improved, the conformability is too low, so the amount added is limited to more than 1.0% and 7.0%. To explain this improvement in high-temperature hardness in more detail, Cr increases the recrystallization temperature of Al by forming a solid solution in Al, and the solid solution itself increases the hardness of the Al base. At the same time, rolling several times also increases the hardness compared to when casting. Increasing the recrystallization temperature is effective in maintaining stable mechanical properties even in the high temperature range to which internal combustion engine bearings are exposed.
In particular, with regard to hardness, it is possible to reduce the decrease in hardness at high temperatures, thereby preventing the bearing from softening in the high temperature range, which in turn leads to an improvement in fatigue strength. In addition, the Al-Cr intermetallic compound that precipitates past the solid solubility limit has a Witzkars hardness of approximately 370. Therefore, the dispersed precipitation of this compound helps maintain high-temperature hardness, and dispersion of this compound in an appropriate amount is essential. produces good effects. Next, we will discuss the effect of Cr addition on inhibiting the coarsening of Sn particles. The coarsening of Sn particles is a phenomenon that occurs due to the movement of Al grain boundaries and Sn particles when Al-Sn alloys are exposed to high temperatures. Precipitates of compounds are formed, and these precipitates are finely dispersed in the Al base metal, so these intermetallic compounds are not directly linked to Al.
This is thought to be because it prevents the movement of grain boundaries and at the same time prevents the growth of Al crystal grains, thereby preventing the movement of Sn particles, that is, the coarsening of Sn particles. This means that rolling,
This leads to keeping the Sn particles that have been made fine by annealing, etc., and has the various effects mentioned above. This phenomenon occurs when the amount of Sn is relatively large (approximately 10% or more), and a more significant effect occurs when Sn begins to exist continuously at approximately 15% or more. However, the amount of Sn is 10%
It goes without saying that even if it is below, the above-mentioned effect of adding Cr may be required depending on the usage conditions and applications. In addition, the fact that Sn particles remain fine and exist in the Al base metal means that
At the same time, it is thought to be effective in preventing the elution phenomenon of Sn particles, which have a low melting point of 232°C, at high temperatures, and from this point of view, the effect of preventing a decrease in hardness is significant. The above is a description of the effect of inhibiting the coarsening of Sn particles in relation to annealing, but the above effect is also valid even when the usage environment of this device is at a high temperature comparable to that of annealing. By preventing this, fatigue strength can be improved. Next, the effect of improving wear resistance by adding Cr will be described. As mentioned above, Cr is present in Al ingots.
This precipitate is an intermetallic compound of Al-Cr, which has a Witzkars hardness of about 370, and is a very hard precipitate, so this precipitate significantly reduces the wear of the bearing due to friction with the shaft. Dispersion of this in an appropriate amount produces good effects. Here, the appropriate amount range is Cr as mentioned above.
This means 7.0% or less, and within this range, the above-mentioned precipitates are uniformly dispersed, and the effect of improving wear resistance can be obtained without affecting other properties such as conformability. In addition, Al-Cr precipitates have the following effects. In other words, the mating material of a bearing greatly influences the bearing performance. For example, if a conventional Al-Sn bearing is used in combination with a spheroidal graphite cast iron shaft, the bearing performance in terms of seizure resistance, wear resistance, etc. will be significantly impaired.
Recently, spheroidal graphite cast iron shafts, which are cheaper to process, have been increasingly used in place of steel shafts. However, in spheroidal graphite cast iron, soft graphite is scattered within the iron base, and for this reason, when this shaft is ground, grinding burrs with sharp edges are generated around the graphite. When a bearing is slid against a shaft with such abrasive burrs under such a high load that the oil film thickness is the same as the surface roughness of the shaft and bearing, the burrs will cut the bearing surface that is softer than the shaft. As this situation progresses, the bearing surface accuracy becomes rougher, the clearance between the shaft and the bearing increases, and oil film pressure is no longer formed.
When the oil film breaks, the oil film is no longer formed, and as a result, more direct contact, that is, metal contact, occurs between the shaft and the bearing, leading to seizure. However, the bearing alloy constituting the bearing device according to the present invention has Al-Cr precipitates that are harder than the burrs of the spheroidal graphite cast iron shaft dispersed in the Al ground, and these Al-Cr precipitates cause the grinding of the spheroidal graphite cast iron shaft. Effect of removing burr and Al-
It also has the effect of making it difficult for Cr precipitates to migrate and stick together, thereby suppressing the progress of wear on the bearing surface in a relatively short period of time and creating a stable oil film. As a result, wear resistance and seizure resistance are particularly improved for spheroidal graphite cast iron shafts. Next, in the present invention, Cu or (and) Mg is added in an amount of 3% or less by weight in addition to the above composition. Among these, when Cu is used, the amount added is 3% or less. This is because adding 3% or more of Cu improves hardness, but as Cu increases, rollability and corrosion resistance decrease, which is not preferable. Here, a more preferable addition ratio is 2.0 or less. As for Mg, if it is added in an amount of 3% or more, the hardness will improve, but the increase in hardness due to rolling will be too large and sufficient rolling will not be possible, making it difficult to obtain a fine Sn structure. Furthermore, Mg that was dissolved in Al during annealing is likely to precipitate, and the excess amount added will precipitate, so it cannot be expected that the solid solution will strengthen the Al base. Here, a more preferable addition ratio is 2.0 or less. The above-mentioned effects of Cu and Mg occur when Cr is added at the same time, and Cu or Mg alone cannot be expected to have the effect of increasing hardness at high temperatures. In other words, when Cu or Mg is added to Al, the hardness increases significantly during rolling. Even at the same rolling rate, the increase in hardness is remarkable compared to Al materials with other elements added, but at temperatures near 200℃ When heated to a high temperature, it easily softens and cannot be expected to maintain its hardness at high temperatures. On the other hand, Cr
When Cu or Mg is added at the same time, Cu or
The hardness increased during rolling due to the effect of Mg,
Even after annealing, the effect of adding Cr, that is, the increase in the recrystallization temperature, does not cause much decrease. This hardness is maintained even at high temperatures, resulting in an alloy with higher high-temperature strength than conventional alloys, which in turn leads to improved fatigue strength. If Cu and Mg are added at the same time, the total amount should be within 3%, of which Cu is 2%.
It is preferable to set it within %. Next, Pb, Bi, In
The purpose of adding at least one of these is to improve the properties of Sn as a lubricating metal, and the effect is observed when it is added together with Cr. Conventional
It is possible to add these elements to Al-Sn alloys, and some have done so, but if these elements are added alone, they will be alloyed into Al-Sn alloys. Therefore, the disadvantage that the melting point of Sn becomes low cannot be avoided. For this reason, in conventional Al-Sn alloys, Sn easily melts and moves at low temperatures, and as a result, it tends to grow into coarse Sn grains, and when used as a bearing, it partially melts during continuous high-load operation. However, it may peel off. On the other hand, if the Sn grains are made finer by adding Cr as in the present invention, and the structure is maintained even at high temperatures,
Adding at least one of Pb, Bi, and In can improve the lubricity of Sn without causing the above-mentioned adverse effects, and it can also be used in bearings that require high fatigue strength. Furthermore, in addition to fatigue resistance, conformability can also be improved. In addition, a thin film of Sn-based low melting point metal, whose lubricating performance has been improved by adding Pb, Bi, and In, is formed on the surface layer of the precipitated Al-Cr intermetallic compound exposed on the bearing surface, which reduces friction. Characteristics are improved. Pb, Bi, and
The amount of at least one type of In added is 9% or less (0
), and preferably about 15% or less based on the amount of Sn contained. Note that the total amount of Pb, Bi, and In may be 9% or less. Furthermore, Sn and Pb,
The total amount of addition of at least one of Bi and In is 35
It is better to be within %. Note that the amount of Sn must be the largest among the additive elements in order to allow the lubricating metal to exist finely in Al. When an Al bearing alloy with the above structure is used as a bearing constituting a bearing device for an internal combustion engine, it is normally used by being pressure-bonded to a backing steel plate, and after this pressure-bonding, it is annealed to increase the adhesive strength. However, as mentioned above, in conventional Al-Sn alloys, the Al grain boundaries and Sn particles in the alloy structure move due to several rounds of annealing after rolling, causing the Sn particles to become coarser, resulting in a decrease in hardness. There were drawbacks such as a decrease in the amount of water and elution of Sn particles. In contrast, in the present invention, the precipitates of Al-Cr intermetallic compounds generated from the rolling and annealing processes impede the movement of Al grain boundaries and inhibit the growth of Al crystal grains, so the above-mentioned adverse effects due to annealing are avoided. Therefore, the annealing temperature was increased to
The adhesive strength between the Sn-based alloy and the backing steel plate can be increased. This also means that this alloy remains valid even when it is placed under high temperatures comparable to annealing, so it can contribute to improving fatigue strength by preventing softening. Next, the present invention will be explained with reference to Examples. The following table shows alloys 1 to 17 as shaft materials of the bearing constituting the bearing device for an internal combustion engine according to the present invention, and alloy 1 as a comparative material.
It shows chemical component values from 8 to 21.

【table】

[Table] For Alloys 1 to 17, Al base metal is melted in a gas furnace, and then Al-Cr mother alloy or Al-Cu mother alloy Al
- Mg master alloy is melted according to the target components, and finally Sn
After adding Pb, etc., degassing treatment was performed, and casting was performed in a mold at a hot water temperature of 720℃.Then, the sample was made by repeating rolling and annealing (350℃), and high-temperature hardness measurement was performed. Ta. Next, this sample was further rolled, and then these alloys and a backing steel plate were pressure-welded to form a bimetallic material, which was annealed (380°C) and then processed into a flat bearing and subjected to a dynamic load fatigue test. For convenience of comparison, Alloys 18 to 21 were prepared using conventional compositions using the same manufacturing method as the above-mentioned alloys, and were subjected to the same tests. The table shown on the previous page shows the results of measuring the hardness of Alloys 1 to 21 at high temperatures using Witzkers hardness. As is clear from these results, bearing alloys 1 to 1 of the bearing device according to the present invention
7 has higher hardness in almost all temperature ranges than conventional alloys 18 to 20, and has higher hardness than conventional alloys 21 to 20.
In comparison with Alloy 21, there are cases where the hardness is higher in the low temperature range, but the hardness of Alloy 21 decreases rapidly as the temperature rises.
Alloys 1 to 17 of the device of the present invention have a gradual decrease in hardness as the temperature rises, and therefore have the effect of reducing changes in the bearing condition due to changes in temperature. This means that while Comparative Alloy 21 significantly decreases its Witzkars hardness as the temperature rises, Alloys 1 to 17 according to the present invention are relatively stable against temperature rises, and are stable at high temperatures of 200°C. It is also clear from the table listed on page 18 that the hardness of these materials is maintained high. In addition, from the alloy structure, Alloys 1 to 17 of the bearing device according to the present invention have
No coarsening of Sn particles was observed. FIG. 1 shows the results of a power load bearing fatigue test on alloys 9 and 16 of the device of the present invention and conventional alloys 18 and 19. This test is based on the shaft rotation speed
3000r.pm, using hardened spheroidal graphite cast iron as the shaft material, and under forced lubrication at a constant oil temperature, to understand the fatigue status of steel materials.10 ⁷ stress repetition conditions with different oil temperatures to improve fatigue resistance surface pressure. This is what was measured. As is clear from this graph, alloy 9,1
Alloys 9, 18 and 19 of the bearing device according to the present invention have lower fatigue resistance surface pressure as the temperature increases.
The degree of decrease in fatigue resistance surface pressure is lower than that of conventional alloy 18,1.
Not as large as 9, and alloy 9, 16 and alloy 18,
Although the difference in fatigue resistance surface pressure on the low temperature side of No. 19 is not so large, it is clearly recognized that Alloys 9 and 16 exceed Alloys 18 and 19 in the fatigue resistance surface pressure on the high temperature side. Note that although FIG. 1 shows alloys 9 and 19 as representative alloys used in the bearing device according to the present invention, and alloys 18 and 19 as representative conventional alloys, other alloys also show similar trends. The results shown are obtained. Further, FIG. 4 shows the seizure load when a seizure test was conducted on Alloys 14 and 15 as bearing materials constituting the bearing device according to the present invention and conventional Alloys 18 and 19.

[Table] In this experiment, the shaft rotation speed was 1000 r.pm, and the shaft material was
The load (static load) up to seizure was measured using S55C hardened material under forced lubrication at a constant oil temperature (140°C). It shows superior seizure load resistance compared to Alloys 18 and 19, and it is recognized that this is due to the effect of Pb, an additive that improves conformability. Further, FIG. 2 is a graph showing the results of measuring changes in friction torque when the load is increased for bearing alloy 9 of the bearing device according to the present invention and conventional alloy 18. In this experiment, the situation during the load increase during the seizure test was measured using an oscillograph. According to this graph, in the conventional alloy 18, the friction torque increases while greatly fluctuating with a peak occurring each time the load is increased. On the other hand, in Alloy 9 of the device of the present invention, the friction torque increases extremely smoothly following the increase in load, and no harmful friction torque fluctuations occur. This shows that the alloy of the device of the present invention has excellent conformability and is less prone to seizure. In other words, the peak waveform with large fluctuations seen in conventional Alloy 18 means that the oil film on the sliding surface is partially destroyed, solid contact occurs, and if this is repeated, total destruction (seizure) will occur. Alloy 9 of the device of the present invention, which does not produce such waveforms, has high conformability and seizure load resistance. In addition, in the alloy composition of the bearing device according to the present invention, it goes without saying that Al contains impurities that cannot be avoided by ordinary scouring techniques. Next, FIG. 3 shows the experimental results regarding the wear resistance of alloy 1 of the bearing device according to the present invention.
4 and 15 have a large difference in wear amount from the conventional alloy 18. However, the results shown in FIG. 3 show that alloys 14 and 15, which are the bearing materials of the device of the present invention, and conventional alloy 19 have almost the same effect in terms of anti-seizure load; 1
It is clear from FIG. 1 that alloy No. 9 has disadvantages that are inferior to alloys 9 and 16 of the present invention. Therefore, it can be said that Alloys 14 and 15 have the effect of compensating for the deficiencies in fatigue resistance and surface pressure properties of conventional alloys. Next, FIG. 4 shows alloy 1 of the bearing device according to the present invention.
3 is a graph showing the surface pressure at the time of seizure when a seizure test was conducted for Alloys 4 and 15 and conventional alloys 18 and 19 using a spheroidal graphite cast iron shaft as the mating material. According to this graph, conventional alloy 18
It is observed that Alloys 14 and 15 with Cr added have higher seizure surface pressures. Furthermore, even in alloys containing Cr, differences in seizure load are observed depending on the Cr content. In other words, alloy 1 with a large amount of Cr added
No. 5 has better seizure resistance than No. 14. Furthermore, conventional Alloy 19 has improved seizure resistance, which is thought to be due to Si in its chemical components. However, as mentioned above, these conventional materials do not exhibit the prevention of reduction in high temperature hardness, improvement in fatigue resistance, etc., which are one of the characteristics of the alloy of the present invention device. As described above, the bearing device for an internal combustion engine according to the present invention improves hardness by adding Cr to an aluminum-tin bearing alloy as a bearing material, prevents a decrease in high-temperature hardness, and prevents coarsening of Sn particles. In addition to improving fatigue resistance and wear resistance through these, it also improves wear resistance and seizure resistance when using a spheroidal graphite cast iron shaft as a mating shaft, and is also effective when added with Cr. Pb,
Bi and In can improve conformability and seizure resistance, and addition of Cu and Mg further improves high-temperature strength.

[Brief explanation of the drawing]

Figure 1 is a graph plotting changes in the aluminum bearing alloy constituting the bearing device for an internal combustion engine according to the present invention and a conventional bearing alloy with respect to temperature changes, and Figure 2 is a graph plotting the change in temperature when the load is increased. A graph showing the state of change in friction torque, Figure 3 is a graph showing the amount of wear on the spheroidal graphite cast iron shaft,
FIG. 4 is a graph showing the seizure pressure against the spheroidal graphite cast iron shaft.

Claims (1)

[Claims] 1 In a bearing device for an internal combustion engine, the shaft material is spheroidal graphite cast iron, and the bearing material is tin 3.5 to 3.5% by weight.
35%, over 1.0 chromium 7.0%, copper and/or magnesium 3.0% or less (not including 0), Pb,
A bearing device for an internal combustion engine, comprising a bearing made of an aluminum-tin bearing alloy containing at least 9.0% (excluding 0) of at least one of Bi and In, and the remainder being essentially aluminum.