Bushing member

Abstract

A bushing member (10) according to one embodiment of the present invention has: an Fe-based inner metal layer (12); and a bearing alloy layer (11) bonded to the inner metal layer (12). The bearing alloy layer (11) is a Cu-based alloy containing 25-45% by mass of Zn and has a Vickers hardness of 150-230 HV, and the inner metal layer (12) has a Vickers hardness of 160-240 HV.

Description

Technical Field

[0001] The present invention relates to a bushing member for a piston pin. Background Art

[0002] Conventionally, as a bushing member for a piston pin, there is known a Cu-based sliding member disclosed in Patent Document 1, for example. The sliding member disclosed in Patent Document 1 uses brass with a high Zn content as a bearing alloy layer. Thus, the sliding member of Patent Document 1 ensures corrosion resistance against sulfur components generated as the temperature in the combustion chamber rises.

[0003] However, as the temperature of the combustion chamber increases, the load applied to the piston pin increases, and the strength of the bushing member is required to be further improved. In addition, unlike the bimetallic material such as Patent Document 1, the bushing member is made into a single layer composed of a brass bearing alloy layer, thereby ensuring strength such as fatigue resistance. However, the single-layer bushing member has the following problem: it is easily affected by creep in an environment subjected to high loads.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent document 1: Japanese Patent Application Laid-Open No. 10-30137. Summary of the invention

[0007] Problem that the invention aims to solve

[0008] Therefore, an object of the present invention is to provide a bushing member that reduces the influence of creep and has high strength and corrosion resistance.

[0009] Solutions for solving problems

[0010] In order to solve the above-mentioned problems, a bushing member of one embodiment is used for a piston pin, and comprises: an Fe-based inner metal layer; and a bearing alloy layer bonded to the inner metal layer. The bearing alloy layer is a Cu-based alloy containing 25 to 45 mass % of Zn and having a Vickers hardness of 150 to 230 HV, and the inner metal layer has a Vickers hardness of 160 to 240 HV.

[0011] Thus, the bearing alloy layer of the bushing component of one embodiment is bonded to the Fe-based inner metal layer. Therefore, the bearing alloy layer reduces the influence of creep through the integrated inner metal layer. In addition, the bushing component of one embodiment is a Cu-based alloy containing Zn, that is, it is made of brass. Therefore, it has high resistance to the sulfur component brought by the additive contained in the lubricating oil, and reduces the corrosion caused by the sulfur component. Furthermore, the bushing component of one embodiment sets the hardness of the bearing alloy layer and the inner metal layer. Therefore, the processability for ensuring high dimensional accuracy and roundness accuracy can be maintained, and fatigue resistance is improved. Therefore, it is possible to maintain creep characteristics and improve strength and corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic cross-sectional view showing a bushing member according to one embodiment.

[0013] Figure 2 Schematic diagram showing a manufacturing process of a bushing member according to one embodiment.

[0014] Figure 3 It is a schematic diagram showing the results of examining creep characteristics in examples and comparative examples of a bushing member according to an embodiment.

[0015] Figure 4 It is a schematic diagram showing the results of testing the corrosion resistance of the bushing member in Examples and Comparative Examples according to one embodiment.

[0016] Figure 5 It is a schematic diagram showing the results of testing the fatigue resistance of the bushing member in Examples and Comparative Examples according to one embodiment.

[0017] Figure 6 It is a schematic diagram showing the test conditions of the fatigue resistance test. DETAILED DESCRIPTION

[0018] Hereinafter, one embodiment of a bushing member for a piston pin will be described in detail based on the drawings.

[0019] like Figure 1 As shown, the bushing member 10 has a bearing alloy layer 11 and an inner metal layer 12. The bushing member 10 is used for a piston pin that connects a piston and a connecting rod of an internal combustion engine (not shown). The bushing member 10 is formed in a cylindrical shape, the bearing alloy layer 11 is located on the inner peripheral side, and the inner metal layer 12 is located on the outer peripheral side. The surface of the bearing alloy layer 11, that is, the inner peripheral surface of the bushing member 10 forms a sliding surface 13 that slides with the counterpart member.

[0020] The inner metal layer 12 is formed of, for example, an Fe-based alloy such as steel. The Vickers hardness of the inner metal layer 12 is 160 to 240 HV. In addition, in this specification, the upper limit and lower limit values ​​representing the numerical range are both included in the range. If the Vickers hardness of the inner metal layer 12 is less than 160, it is difficult to ensure the fatigue resistance required of the bushing component 10 as a piston pin. On the other hand, if the Vickers hardness of the inner metal layer 12 is greater than 240 HV, it leads to a decrease in processability.

[0021] The bearing alloy layer 11 is integrally bonded to the inner metal layer 12 and is formed of a Cu-based alloy containing 25 to 45% by mass of Zn. That is, the bearing alloy layer 11 is formed of brass. In order to ensure higher corrosion resistance, the Zn contained in the bearing alloy layer 11 is preferably 35 to 45% by mass. The bearing alloy layer 11 may also contain additive elements such as Sn and P in addition to Zn. In addition, in the case of the bushing component 10 of the present embodiment, the bearing alloy layer 11 is more preferably an alloy of Zn and Cu excluding inevitable impurities.

[0022] The Vickers hardness of the bearing alloy layer 11 is 150 to 230 HV. If the Vickers hardness of the bearing alloy layer 11 is less than 150 HV, it is difficult to ensure the fatigue resistance required of the bushing member 10 as a piston pin. On the other hand, if the Vickers hardness of the bearing alloy layer 11 is greater than 230 HV, the processability is reduced and the seizure resistance is also reduced.

[0023] The Vickers hardness of the inner metal layer 12 is preferably 0.9 times or more of the Vickers hardness of the bearing alloy layer 11. In the case of the present embodiment, it is preferred that the hardness of the bearing alloy layer 11 and the inner metal layer 12 are similar, and it is more preferred that the inner metal layer 12 is slightly harder than the bearing alloy layer 11. In this way, by making the hardness of the bearing alloy layer 11 and the inner metal layer 12 similar, it is possible to facilitate the processing of the bushing component 10 to ensure the roundness during processing. In addition, if the hardness of the bearing alloy layer 11 and the inner metal layer 12 is too hard, it may be difficult to perform the process of pressing the bushing component 10 into the connecting rod, for example, and the cutting process after pressing. Therefore, the upper limit of the Vickers hardness of the bearing alloy layer 11 and the inner metal layer 12 is set to 240HV.

[0024] Next, a method for manufacturing the bushing member 10 having the above-described structure will be described.

[0025] like Figure 2 As shown, the bushing member 10 is manufactured by press-bonding a plate member 21 as the bearing metal layer 11 and a plate member 22 as the back metal layer 12. After being overlapped, the plate members 21 and 22 are pressed by a roller 23 until the total thickness thereof is 40 to 60%.

[0026] The laminated material 24 joined by pressurization is heated to 550-680°C and diffusion annealing is performed. By this heating, the bonding caused by diffusion between the plate member 21 and the plate member 22 in the laminated material 24 is promoted, and the plate member 21 and the plate member 22 are firmly joined. On the other hand, by diffusion annealing, the hardness of the plate member 21 as the bearing alloy layer 11 is reduced. As described above, if the Vickers hardness of the bearing alloy layer 11 is less than 150HV, it is difficult to ensure the fatigue resistance of the bearing alloy layer 11. Therefore, the heated laminated material 24 is pressurized by the roller 25 until the sum of its thickness is 3-30%. At this time, the process of pressurization can be one stage or more than two stages. In this case, the roller 25 can mainly pressurize the side of the plate member 21 as the bearing alloy layer 11 in the laminated material 24, or pressurize from both sides of the laminated material 24. Thus, the formed bearing alloy layer 11 is hardened to a Vickers hardness of more than 150HV.

[0027] As described above, the plate member 21 as the bearing alloy layer 11 and the plate member 22 as the inner metal layer 12 become a laminated material 24 formed by bonding. The laminated material 24 is formed into a cylindrical bushing member 10. In the manufacturing method of the bushing member 10 of the present embodiment, the plate member 21 as the bearing alloy layer 11 and the plate member 22 as the inner metal layer 12 are bonded by pressurization. Therefore, in the manufacturing process of the bushing member 10, such treatment as quenching that makes the inner metal layer 12 hard and brittle is not included. As a result, in the manufacturing method of the bushing member 10 of the present embodiment, the brittleness of the manufactured bushing member 10 can be reduced and the strength can be improved. Moreover, the Vickers hardness of the inner metal layer 12 of the bushing member 10 manufactured by the manufacturing method of the present embodiment is less than 240HV, so the processability is improved. As a result, the formed bushing member 10 can be formed into a cylindrical shape with high dimensional accuracy and shape accuracy. At the same time, the bushing member 10 can improve workability, for example, when being press-fitted into the connecting rod or when being ground or polished after being press-fitted.

[0028] Next, examples of the bushing member 10 of the above-described embodiment will be described.

[0029] (Test of creep characteristics)

[0030] like Figure 3 As shown, in Example 1 of the bushing member 10, the bearing alloy layer 11 and the back metal layer 12 are stacked as described above. On the other hand, although the comparative example 1 used for comparison has the same size as that of the embodiment 1, the portion corresponding to the back metal layer 12 is also formed in a single layer of brass as the bearing alloy layer 11. That is, the comparative example 1 is a so-called solid material formed entirely of brass.

[0031] For the bushing components 10 of Example 1 and Comparative Example 1, the creep characteristics were examined using a pull-out load. The pull-out load refers to the load required to pull the bushing component 10 out of the object component after the bushing component 10 is pressed into the object component. The bushing components 10 of Example 1 and Comparative Example 1 pressed into the object component were heated to 190°C, and after a predetermined heating time, cooled to room temperature. After cooling, the pull-out load of the bushing components 10 of Example 1 and Comparative Example 1 was measured. Figure 3 The graph shows the change rate of the pulling load after heating, when the pulling load before heating is set to "1.00".

[0032] according to Figure 3 It can be seen that although there is a tendency for the pull-out load to increase with the increase of the heating time in Example 1, the change in the pull-out load is small. On the other hand, the longer the heating time of Comparative Example 1, the significantly reduced pull-out load. Thus, it is shown that the bushing component 10 of Example 1 is less affected by creep than Comparative Example 1. This is because the bushing component 10 of Example 1 has an Fe-based inner metal layer 12 with little creep effect on the outer peripheral side of the bearing alloy layer 11. In contrast, it can be seen that the creep effect of Comparative Example 1 formed integrally of brass is large. In addition, in the bushing component 10 of the present embodiment, the bearing alloy layer 11 is bonded to the inner metal layer 12. Therefore, the Zn content in the bearing alloy layer 11 will not affect the creep of the bushing component 10. Therefore, the bearing alloy layer 11 of the bushing component 10 of the present embodiment can reduce the influence of creep, regardless of the Zn content.

[0033] (Corrosion resistance test)

[0034] like Figure 4 As shown, the corrosion resistance of the bushing member 10 was examined using Examples 2 to 4, Comparative Examples 2 and 3. In Examples 2 to 4, the content of Zn in the brass bearing alloy layer 11 was controlled. In Comparative Example 2 for comparison, the content of Zn contained in the bearing alloy layer 11 was lower than that in Examples 2 to 4. Comparative Example 3 was a bronze bearing alloy layer to which Sn was added instead of Zn.

[0035] For each sample of Examples 2 to 4, Comparative Examples 2 and 3, the corrosion resistance was tested based on the change in mass of each sample. The more severe the corrosion of each sample, the greater the change in mass. That is, the mass of each sample decreases as the corrosion becomes severe. However, since the degree of corrosion depends on the surface area of ​​each sample, it is difficult to accurately grasp the amount of corrosion of each sample by only measuring the change in mass. Therefore, for each sample, the change in mass per unit surface area is measured as the amount of corrosion.

[0036] For each sample, the corrosion resistance was tested by immersing it in a lubricating oil at 190°C, which is close to the operating conditions of the internal combustion engine, for 70 hours in a closed container. The lubricating oil used was a commercially available genuine product specified by a variety of internal combustion engine manufacturers. These lubricating oils are added with additives containing sulfur components in the molecules for the purpose of improving performance and maintaining quality. The additives sometimes decompose as the temperature rises due to the harsh operating conditions of the internal combustion engine, causing the generation of sulfur components contained in the molecules. These generated sulfur components cause corrosion of the bearing alloy layer 11 of the bushing member 10.

[0037] according to Figure 4 It can be seen that Examples 2 to 4, in which the Zn content of the bearing alloy layer 11 is 25% or more, have higher corrosion resistance than Comparative Example 2, in which the Zn content is 20%. In addition, it can be seen that Comparative Example 3, in which the bearing alloy layer is made of bronze, is prone to severe corrosion compared to Examples 2 to 4. Due to the above reasons, the bushing component 10 of the present embodiment, in which the Zn content is 25% or more, can improve the corrosion resistance. In particular, by comparing Examples 2 and 3 with Example 4, it can be seen that the bushing component 10 with a Zn content of 35% or more can further improve the corrosion resistance.

[0038] (Fatigue resistance test)

[0039] like Figure 5 As shown, the fatigue resistance of the bushing member 10 was tested using Examples 5 to 9 and Comparative Examples 4 to 6. In Examples 5 to 9 and Comparative Examples 4 to 6, the hardness of the bearing alloy layer 11 and the hardness of the back metal layer 12 were controlled in order to test the fatigue resistance. Figure 5 In addition to showing fatigue resistance, evaluation of the workability of the bushing member 10 is also shown.

[0040] In Examples 5 to 9 and Comparative Examples 4 to 6, based on Figure 6 The fatigue resistance is determined under the test conditions shown. Figure 6Under the conditions shown, the sample is lubricated with lubricating oil while repeatedly applying load, and fatigue resistance is measured based on the load that produces fatigue. The lubricating oil is the commercially available lubricating oil for the internal combustion engine exemplified above. The load applied to the sample is set to start from 100MPa, and the load is increased by 10MPa each time the fatigue resistance is confirmed, until 200MPa. For fatigue resistance, the case where the fatigue load is above 170MPa is considered qualified. The processability is evaluated based on whether the bushing component 10 formed by the bearing alloy layer 11 and the inner metal layer 12 can be processed to a degree that can ensure appropriate dimensional accuracy and roundness. Regarding processability, the case where appropriate processing can be ensured but the yield is low is regarded as "good: ○", the case where appropriate processing is ensured and the yield is high is regarded as "excellent: ◎", and the case where appropriate processing is difficult is regarded as "poor: ×".

[0041] like Figure 5 As shown, the hardness of the bearing alloy layer 11 of Examples 5 to 9 is 150 to 230 HV, and the hardness of the inner metal layer 12 is 160 to 240 HV. In addition, the hardness of the inner metal layer 12 of Examples 5 to 8 is more than 0.9 times the hardness of the bearing alloy layer 11. In contrast, the hardness of the inner metal layer 12 of Example 9 is less than 0.9 times the hardness of the bearing alloy layer 11. In addition, the hardness of the inner metal layer 12 of Comparative Example 4 is greater than 240 HV. Comparative Examples 5 and 6 are both examples in which the hardness of the bearing alloy layer 11 and the inner metal layer 12 is insufficient. For the hardness of the bearing alloy layer 11 and the inner metal layer 12 in Examples 5 to 9 and Comparative Examples 4 to 6, as described in the above-mentioned manufacturing method, when the stacked bearing alloy layer 11 and the inner metal layer 12 are pressurized, they are controlled by the change in their thickness.

[0042] according to Figure 5 It can be seen that Examples 5 to 9 all exhibit high processability and sufficient fatigue resistance. In particular, Examples 5 to 8, in which the hardness of the inner metal layer 12 is more than 0.9 times the hardness of the bearing alloy layer 11, all take into account high processability and sufficient fatigue resistance. On the contrary, although Example 9, in which the hardness of the inner metal layer 12 is less than 0.9 times the hardness of the bearing alloy layer 11, exhibits sufficient fatigue resistance, the yield rate for ensuring appropriate dimensional accuracy and roundness is reduced. This is because the hardness of the inner metal layer 12 is lower than that of the bearing alloy layer 11, and it is difficult to ensure the accuracy when it is formed into a cylindrical shape as a bushing component 10.

[0043] In addition, the hardness of the inner metal layer 12 of Comparative Example 4 is too high at 248 HV, so the processability is deteriorated, and it is difficult to ensure high dimensional accuracy and roundness as the bushing component 10. Therefore, Comparative Example 4 cannot be used as the bushing component 10, and fatigue resistance cannot be measured. The hardness of the bearing alloy layer 11 and the inner metal layer 12 of Comparative Examples 5 and 6 is insufficient. Therefore, although Comparative Examples 5 and 6 ensure processability, fatigue resistance is insufficient.

[0044] The present invention described above is not limited to the above-described embodiment, and can be applied to various embodiments without departing from the gist of the invention.

Claims

1. A bushing member for a piston pin, comprising: Fe-based back metal layer; and a bearing alloy layer bonded to the inner metal layer, The bearing alloy layer is a Cu-based alloy containing 25-45 mass % Zn and has a Vickers hardness of 150-230 HV. The Vickers hardness of the inner metal layer is 160-240 HV.

2. The bushing member according to claim 1, wherein: The Vickers hardness of the inner metal layer is greater than or equal to 0.9 times the Vickers hardness of the bearing alloy layer.

3. The bushing member according to claim 1, wherein: The bearing alloy layer is a Cu-based alloy containing 35 to 45 mass % of Zn.

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