Bearing Bush of Toggle Link Mechanism and Method for Manufacturing the Same

Abstract

To provide a sliding material having excellent fatigue resistance even in a usage environment where a strong impact load occurs. 【Solution means】 A sliding material used in a sliding environment where an impact load occurs, comprising a base made of a Cu-Zn-Al-based brass casting alloy, an intermetallic compound of Mn silicide or Cr silicide contained in the base and having a nanoindentation hardness of 15 GPa or more, and a solid lubricant embedded portion exposed on the sliding surface of the sliding material, wherein the embedding rate of the solid lubricant embedded portion on the sliding surface of the sliding material is 15.8% or less.

Description

Technical Field

[0001] The present invention relates to a sliding member and a method for manufacturing the same.

Background Art

[0002] An oil-free sliding material in which graphite is embedded as a solid lubricant has been used in severe mixed lubrication conditions where impact loads occur.

[0003] Conventionally, it has been known that a bearing in an environment that falls into a boundary lubrication state or a mixed lubrication state maintains its lubricity by including an embedded type graphite that assists lubrication. (See, for example, Patent Document 3)

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0005] Patent Document 1 discloses a graphite-embedded sliding material containing an Fe-Mn-Si-based intermetallic compound in a brass alloy. However, the composition of the Fe-Mn-Si-based intermetallic compound is not specified, and the sliding performance of this compound is not disclosed either.

[0006] Patent Document 2 discloses a sliding member having a base made of a brass alloy and a Cr-Fe-Si-based intermetallic compound contained in the base and having a nanoindentation hardness of 20 GPa or more and 28 GPa or less. However, Patent Document 2 does not describe any findings related to the embedding ratio of the graphite embedding portion.

[0007] Patent Document 3 proposes a bearing bush for a toggle provided with a plurality of circular holes in which a solid lubricant is embedded. However, Patent Document 3 does not describe any findings related to the embedding ratio of the graphite embedding portion.

[0008] Patent Document 4 discloses a sliding bearing used in a link mechanism or the like. However, Patent Document 4 does not disclose anything related to intermetallic compounds.

[0009] In recent years, in graphite-embedded sliding plates used in press die-related devices, there have been more processing requirements for hard high-tensile steel, and strong impact loads have occurred under reciprocating sliding. Also, in cylindrical bearings used in molding machines and hot rolling devices, impacts repeated more than 10 7 times occur, and the number of impact times also increases, and corresponding measures are required in sliding materials.

[0010] The present invention has been made to solve such conventional problems, and an object thereof is to obtain a sliding member having excellent fatigue resistance even in a usage environment where a strong impact load occurs.

Means for Solving the Problems

[0011] The present invention is A bearing bush of a toggle link mechanism used in a sliding environment of a toggle type clamping device where an impact load occurs, comprising a base made of a Cu-Zn-Al brass casting alloy, an intermetallic compound of Mn silicide or Cr silicide contained in the base and having a nanoindentation hardness of 15 GPa or more, and a solid lubricant embedding portion exposed on the surface of the bearing bush of the toggle link mechanism, wherein the embedding rate of the solid lubricant embedding portion on the sliding surface of the bearing bush of the toggle link mechanism is 15.8% or less, and the rigidity of the bearing bush of the toggle link mechanism is 7.5 kN / mm or more, the bearing bush of the toggle link mechanism as follows.

Effects of the Invention

[0012] The present invention can provide a sliding member having excellent fatigue resistance in a sliding environment where an impact load occurs.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Embodiments for Carrying Out the Invention

[0014] Hereinafter, the sliding material of the embodiment will be described in detail. Note that the present invention is not limited to this embodiment.

[0015] FIG. 1 is a diagram showing the configuration of a sliding material used in a sliding environment where an impact load occurs in the embodiment. A cylindrical sliding material (bearing type) having a plurality of solid lubricant embedded portions is shown.

[0016] As shown in FIG. 1, the sliding material 1 of the embodiment has a plurality of solid lubricant embedded portions 4 having a self-lubricating action at a predetermined embedding rate or less on the sliding surface 1A. When the embedding rate is 0%, it becomes a sliding material having no solid lubricant embedded portion 4. The sliding material 1 may be cylindrical or plate-shaped. For the solid lubricant embedded portion 4 of the embodiment, for example, solid lubricants such as graphite-based, PTFE-based, MoS2-based, and Pb alloy-based can be used. The embedding rate is more preferably 0% or more and 12% or less.

[0017] The impact load applied to the sliding material of the embodiment refers to, for example, a case where a load of 45 MPa or more is generated in 0.1 seconds as shown in FIG. 2. This is not limited thereto and refers to a case where the load rapidly increases in a short time. The sliding material of the embodiment is a sliding material used in such a harsh sliding environment, and includes an intermetallic compound 3A or 3B of Mn silicide or Cr silicide having a nanoindentation hardness of 15 GPa or more in a base material 2 of a Cu-Zn-Al-based brass casting alloy, and the embedding rate of the solid lubricant (graphite, etc.) 4 of the sliding material is 15.8% or less.

[0018] FIG. 3 is a diagram showing a wear curve that occurs when an impact load occurs. Generally, wear due to sliding is proportional to the sliding distance and the load (σ). However, when an impact load occurs, the wear does not progress linearly, but progresses exponentially after passing a certain stable state.

[0019] Based on the literature of "P.A. Engel Impact wear of multiplated electrical contact", the following basic formula of Engel's impact wear was obtained. W = f(N, σ) = kNσ n Where W: Wear amount N: Number of impact times k: Constant σ: Stress That is.

[0020] This basic formula shows that the wear amount due to impact is a function of the number of impact times N and the generated stress σ, indicating that very destructive wear progresses where the wear amount is proportional to the nth power of the stress and the repeated number of impact times.

[0021] The process leading to impact failure is divided into three stages.

[0022] ·initial wear stage Rapid wear with n > 1 corresponding to the so-called running-in state progresses to form a conforming surface. That is, through rapid wear, the true contact area is measured, the surface pressure is dispersed, and the substantial σ is reduced.

[0023] ·zero wear stage It enters a steady wear state in a smooth and stable state with n = 1. In this state, obvious wear does not occur, but due to the repeated impact load, the accumulation of dislocations leading to the next failure progresses under the surface.

[0024] ·measurable wear stage When the limit point N0 is eventually reached, wear failure with n > 1 is activated and the wear failure progresses exponentially. Usually, in this final process, surface collapse occurs due to the impact load, and the wear powder released onto the sliding surface adheres to the mating material and develops into the so-called seizure phenomenon. (Figure 3)

[0025] When following the sliding phenomenon accompanied by impact in this way, it can be seen that, unlike the process in which the surface destruction phenomenon seen in a simple sliding friction phenomenon progresses, it is a process in which an extremely serious destruction phenomenon that expands exponentially occurs due to the destruction of the material structure directly under the surface. Therefore, the biggest problem is how to reduce the generated stress σ, which is an impact load.

[0026] As described above, it is important to reduce the generated stress (σ) in impact wear. Fig. 4 shows the effect on the fatigue curve (S / N curve) of reducing the generated stress (σ) by decreasing the embedded portion of the solid lubricant, indicating that the fatigue limit is extended thereby.

[0027] That is, the vertical axis represents stress (σ) and the horizontal axis represents the number of repetitions (N). Generally, for those with a face-centered cubic fcc crystal structure, 6 exceeding 10 7 times, the fatigue strength decreases towards 10 6 times. From this, under usage conditions where the number of repetitions reaches 10 7 to 10

[0028] times, such as in cam slides and toggle bushes, it becomes important how to reduce the generated stress (σ). By reducing the embedding rate of the solid lubricant embedding portion, the generated stress occurring in the bearing decreases from σ1 to σ2. As a result, the fatigue limit number of times extends from N1 to N2, and the fatigue resistance is improved.

[0029] Fig. 6 shows the three-dimensional structure of the intermetallic compound as seen from a cross-section perpendicular to the sliding surface 1A of the sliding material 1 of the embodiment. The sliding material 1 has a base 2 and a Cr-Fe-Si-based intermetallic compound 3A.

[0030] The base 2 is made of a Cr-Zn-Al-based brass alloy. The base 2 gives the sliding material 1 a shape according to the application and mechanical strength.

[0031] In the embodiment, Cr silicide refers to the Cr-Fe-Si-based intermetallic compound 3A, and Mn silicide refers to the Mn-Fe-Si-based intermetallic compound 3B.

[0032] The Cr-Fe-Si-based intermetallic compound 3A is a compound having a composition consisting of Cr, Fe, and Si. The Cr-Fe-Si-based intermetallic compound 3A of the embodiment has a structure of (Cr,Fe)3Si. Each of the Cr-Fe-Si-based intermetallic compounds 3A has an outer shape with a rounded curved surface.

[0033] A large number of Cr-Fe-Si-based intermetallic compounds 3A contained in the substrate 2 are bonded to each other, thereby constituting a three-dimensional structure in which a large number of Cr-Fe-Si-based intermetallic compounds 3A are connected. The Cr-Fe-Si-based intermetallic compound 3A contained in the sliding member 1 of the present embodiment has a nanoindentation hardness of 28 GPa.

[0034] The hardness of the Cr-Fe-Si-based intermetallic compound 3A and the Mn-Fe-Si-based intermetallic compound 3B can be measured by hardness measurement using a nanoindenter.

[0035] The hardness measurement by the nanoindenter complies with "ISO 14577-1 Metallic materials - Instrumented indentation test for hardness and materials parameters-" and its annex "Annex A (normative) Materials parameters determined from the force / indentation depth data set". For the hardness measurement by the nanoindenter, a BRUKER HYSTRONT1980 device was used.

[0036] The measurement conditions for hardness were a test load of 800 μN, a loading time of 1 s, a holding time of 0.4 s, and an unloading time of 1 s. In ISO notation, the measurement conditions are HIT8x10 -4It was set to / 1 / 0.4 / 1. In the measurement of the particles of the Cr-Fe-Si-based intermetallic compound 3A crystallized in the alloy, a grid pattern was set in a lattice shape for the measurement range including the particles of the Cr-Fe-Si-based intermetallic compound 3A, and multi-point measurement was carried out by indenting the grid points of the grid pattern. The numerical value of the maximum hardness by the nanoindenter, which is characteristic of the Cr-Fe-Si-based intermetallic compound 3A, among the measurement values of the multi-point measurement was defined as the nanoindentation hardness of the intermetallic compound 3A.

[0037] Even when the Mn-Si-based binary intermetallic compound Mn5Si3 is ternarized like the Mn-Fe-Si-based intermetallic compound 3B, the basic structure remains Mn5Si3, and a part of Mn is substituted (Mn x ,Fe y )(where x + y = 1). That is, by introducing the concept of determining the chemical structure by SEM atomic ratio measurement, it became possible to know the accurate chemical structure.

[0038] Figure 7 is a schematic diagram of the three-dimensional shape of a sliding material containing the Mn-Fe-Si-based intermetallic compound 3B as seen from the cross section. The Mn-Fe-Si-based intermetallic compound 3B has a chemical structure of (Mn,Fe)3Si. The Mn-Fe-Si-based intermetallic compound 3B, like the Mn-Si-based intermetallic compound, has a preferential crystal growth direction, separates individually, and has a growth form in a granular or dendritic shape.

[0039] It was found that a part of the petal-shaped structure of the Mn-Fe-Si-based intermetallic compound 3B undergoes eutectification and changes to a granular structure. Also, the nanoindentation hardness of the Mn-Fe-Si-based intermetallic compound 3B by the said measurement method is 18.5 GPa.

[0040] In the brass-based cast alloy, wear resistance and low friction (low μ property) are evaluated according to the tribology basic formula (1). μ = τ0 / P H ···(1) However, μ: coefficient of friction, τ0: shear force of lubricant, P H : hardness (load / area).

[0041] The coefficient of friction μ is proportional to the shear force of the lubricant and inversely proportional to the substrate hardness. The hardness P H is the load divided by the contact area. To reduce the coefficient of friction μ, it is possible to increase the hardness of the intermetallic compound that becomes the load point during friction or to reduce the contact area of the intermetallic compound to reduce the coefficient of friction.

[0042] The effects of the Cr-Fe-Si-based intermetallic compound 3A and the Mn-Fe-Si-based intermetallic compound 3B of the embodiment are in accordance with the above tribology basic formula (1), and P H (hardness) increases to reduce the coefficient of friction. When a lubricant is interposed, the frictional work represented by μ × load × speed is reduced, thereby reducing the generation of frictional heat and exhibiting a low-friction effect. That is, a brass alloy containing a hard intermetallic compound such as Cr silicide or Mn silicide can be expected to improve its frictional properties.

[0043] (Examples) Hereinafter, examples will be described, but the present invention is not limited to these examples. First, the slidability according to the embedding rate of the solid lubricant embedding portion of the sliding member was confirmed.

[0044] The embedding rate of the solid lubricant embedding portion 4 is the ratio of the total surface area of the plurality of solid lubricant embedding portions 4 appearing on the sliding surface 1A divided by the area of the sliding surface 1A, expressed as a percentage. (Fig. 1)

[0045] As shown in Table 2, Example 1 contains a Cr-Fe-Si-based intermetallic compound 3A in the Cu-Zn-Al substrate 2 with a graphite 4 embedding rate of 12%; Example 2 contains a Cr-Fe-Si-based intermetallic compound 3A in the Cu-Zn-Al substrate 2 with a graphite 4 embedding rate of 0%; Example 3 contains a Mn-Fe-Si-based intermetallic compound 3B in the Cu-Zn-Al substrate 2 with a graphite 4 embedding rate of 12%; Example 4 contains a Mn-Fe-Si-based intermetallic compound 3B in the Cu-Zn-Al substrate 2 with a graphite 4 embedding rate of 0%; Comparative Example 1 does not contain a hard compound in the Cu-Zn-Al substrate and has a solid lubricant embedding rate of 12%; Comparative Example 2 does not contain a hard compound in the Cu-Zn-Al substrate and has a solid lubricant embedding rate of 0%. The wear amounts of these sliding materials were compared. The volume ratio of the intermetallic compound on the friction surface is in the range of 3% to 15%.

[0046] Figure 8 is a diagram showing a reciprocating sliding test apparatus. The reciprocating sliding test apparatus 4 applies a load N (in this test, a surface pressure of 30 N / mm 2 ) to the sample 5 and reciprocates it on the mating material 6. The test conditions are shown in Table 1. Conditions closer to the usage conditions where each sliding material is used were set under poor lubrication conditions.

[0047]

Table 1

[0048]

Table 2

[0049]

Table 3

[0050] Table 3 shows the variation state of the friction coefficient and the wear amount of the reciprocating sliding test results, and the transition of the friction coefficient is shown in Figures 9, 10, and 11.

[0051] As shown in the outline in Table 3, the maximum friction coefficients of Examples 1 and 2 containing the Cr-Fe-Si intermetallic compound 3A and Examples 3 and 4 containing the Mn-Fe-Si intermetallic compound 3B are also as low as 0.10 to 0.13, and the wear amounts are also as small as 0.7 μm to 2.6 μm. In comparison, Comparative Examples 1 and 2 that do not contain hard compounds have larger maximum friction coefficients of 0.14 to 0.15. Also, the wear amounts are as large as 6.0 μm to 6.8 μm. Thus, the sliding materials of the examples can reduce the wear amount while reducing the friction coefficient under high loads.

[0052] Fig. 9 shows the transition of the friction coefficients of Examples 1 and 2 containing the Cr-Fe-Si intermetallic compound 3A as the intermetallic compound. Comparing Example 1 with an embedding rate of 12% of the solid lubricant embedding part 4 and Example 2 with an embedding rate of 0% (without graphite) of the solid lubricant embedding part 4, there is also almost the same tendency, and a gradual decrease in the friction coefficient is observed. This is a characteristic of the material containing the Cr-Fe-Si intermetallic compound 3A, and it can be seen that the low friction is progressing due to the exposure of this compound on the friction surface.

[0053] Fig. 10 shows the transition of the friction coefficients of Examples 3 and 4 containing the Mn-Fe-Si intermetallic compound 3B as the intermetallic compound. Comparing Example 3 with an embedding rate of 12% of the solid lubricant embedding part 4 and Example 4 with an embedding rate of 0% (without graphite) of the solid lubricant embedding part 4, there is also almost the same tendency, and it is in a stable state throughout.

[0054] Fig. 11 shows the transition of the friction coefficients of Comparative Examples 1 and 2 that do not contain intermetallic compounds. The materials of Comparative Examples 1 and 2 have mixed lubrication (partial metal contact occurs and the friction coefficient increases), and the friction coefficient is unstable. Therefore, when the solid lubricant embedding part responsible for lubrication is eliminated, the fluctuation of the friction coefficient becomes larger. That is, it shows that when the solid lubricant embedding part that assists lubrication is eliminated, an extremely unstable sliding state is achieved. Thus, the sliding materials of Comparative Examples 1 and 2 that do not contain intermetallic compounds require a solid lubricant embedding part, and the materials of Examples 2 and 4 that contain intermetallic compounds can maintain a stable sliding state even without a solid lubricant embedding part.

[0055] In Examples 1 and 2, an example of a material containing 22 - 26% Zn and 4 - 6% Al in the Cu - Zn - Al - based substrate 2 was shown. However, the substrate 2 may contain 20 - 32% Zn and 3 - 8% Al. Also, in order to strengthen this substrate 2, it is possible to contain 1 - 5% Mn and 1 - 5% Ni.

[0056] On the other hand, the Cr - Fe - Si - based intermetallic compound 3A is a compound in which Cr:Fe:Si are combined at a ratio of 4.8:0.85:1 by weight ratio, and it is a very stable compound with a melting point of 1770°C and is preferentially formed in the molten metal. The silicide is rate - determining depending on the Si content. For example, if 0.8% Si is contained, 3.9% Cr and 0.7% Fe are consumed as the compound. Similarly, the Mn - Fe - Si - based compound 3B is a compound in which the ratio is 3.1:2.8:1 by weight ratio and is a stable compound with a melting point of 1270°C and is preferentially formed in the molten metal. Therefore, if the Si content is determined according to the weight ratio, for the Cr - Fe - Si - based intermetallic compound 3A, it becomes possible to produce the Cr - Fe - Si - based intermetallic compound 3A by adding the corresponding amounts of Cr and Fe. Similarly, for the Mn - Fe - Si - based intermetallic compound 3B, it becomes possible to produce the Mn - Fe - Si - based intermetallic compound 3B by adding the corresponding amounts of Mn and Fe. That is, the silicide is a compound rate - determining by Si, and an appropriate Si content is 0.2 - 1.5%. If the amount of silicide above this increases, the material becomes brittle.

[0057] To cast this component, a high - frequency melting furnace is used. After melting Cu at 1150°C, Zn and Al ingots are added, and Mn, Ni, Fe, Cr, and Si are sequentially added in predetermined amounts in the form of alloys with Cu. After melting, degassing, allowing it to settle and removing slag, it is then poured into a sand mold or a metal mold to obtain a casting material of a predetermined shape.

[0058] From the above test results, it was found that in the materials containing the intermetallic compounds 3 such as Cr silicide and Mn silicide of the examples, the friction conditions are relaxed and the lubricity is maintained even when the lubrication assistance by the solid lubricant embedding part 4 is low.

[0059] Next, for the sliding member of Example 1, the embedding rate was changed, and the limit of the embedding rate was determined when the number of cycles was set to 10 7 cycles as the fatigue limit.

[0060] The fatigue curve was obtained under the following conditions (Table 4).

[0061]

Table 4

[0062] Fig. 12 shows the fatigue curves at each embedding rate. The fatigue curve of the material with an embedding rate of 0%, i.e., no solid lubricant embedding part, is shown at the top. When the practical load is 130 MPa, it can be seen that the fatigue limit of the material with an embedding rate of 0% is more than 10 7 cycles. On the other hand, it can be seen that the material with an embedding rate of 28% has a fatigue limit between 10 6 and 10 7 cycles. Also, it can be seen that the embedding rate of the embedding material that does not cause fatigue of the material up to 10 7 cycles is 15.8%. Therefore, it was found that in order to have a fatigue limit of 10 7 cycles, it is necessary to keep the embedding rate at 15.8% or less.

[0063] From the results of the above examples, the sliding member 1 used in a sliding environment where an impact load occurs, which includes an intermetallic compound 3A or 3B of Mn silicide or Cr silicide with a nanoindentation hardness of 15 GPa or more in the base 2 of a Cu-Zn-Al-based brass casting alloy, and the embedding rate of the solid lubricant embedding part 4 of the sliding member is 15.8% or less, has excellent fatigue resistance even in a use environment where a strong impact load occurs.

[0064] 2. Sliding member structure In the embodiment, in a sliding environment where an impact load occurs, by including an intermetallic compound 3A or 3B such as Mn silicide or Cr silicide having a nanoindentation hardness of 15 GPa or more in the Cu-Zn-Al-based substrate 2 of the sliding member 1, the friction performance is improved, and the sliding characteristics are provided to complement the solid lubricant embedding portion 4 responsible for the friction performance. Further, the conventionally used solid lubricant embedding portion 4 is reduced, the rigidity is increased, the amount of deformation generated in the bearing is reduced, the generated stress is lowered, and it can withstand the large impact stress generated in the cam sliding portion and the toggle bush.

[0065] In order to examine the relationship between the embedding rate of the solid lubricant and the rigidity of the sliding member, FEM analysis was performed on the configuration 7 shown in FIG. 13. The rigid body 10 was completely constrained, the rigid body 8 was constrained so that only vertical movement was possible, and a load of 1 kN was applied vertically downward to examine the rigidity of the bush 9.

[0066] FIG. 14 shows the sliding members (bearing members) compared and studied by FEM analysis. 11 is a generally used embedded state with an embedding rate of 28%, 12 is one with two embedded in a row with an embedding rate of 20%, 13 is one with one embedded in a row with an embedding rate of 12%, 14 is one with the embedding in the embodiment removed and the embedding rate is 0%, 15 is one embedded according to the specification of Patent Document 3 with an embedding rate of 25%, and 16 is one with partial embedding removed and the embedding rate is 22%, and they were compared and studied.

[0067] Table 5 shows the relationship between the respective embedding rates and the rigidity.

[0068]

Table 5

[0069] FIG. 15 shows the relationship between the embedding rate and the rigidity in Table 5 in a graph. The vertical axis represents the rigidity and the horizontal axis represents the embedding rate. As shown in FIG. 15, an inverse proportional relationship was found between the embedding rate and the rigidity, and it was found that a large rigidity can be obtained by reducing the embedding rate.

[0070] In this way, by increasing the rigidity of the sliding material, the amount of deformation generated in the sliding material is reduced, the generated stress is lowered, and it becomes possible to withstand the large impact stress generated in the cam sliding portion and the toggle bush. That is, in order to avoid wear damage of the sliding material due to the repeatedly generated impact force, by reducing the above-described generated stress, an effect of extending the fatigue limit of the sliding material is obtained.

[0071] Therefore, the sliding material 1 used in a sliding environment where an impact load occurs includes an intermetallic compound 3A or 3B of Mn silicide or Cr silicide having a nanoindentation hardness of 15 GPa or more in a base 2 of a Cu-Zn-Al-based brass casting alloy, and the embedding rate of the solid lubricant embedding portion 4 of the sliding material is 15.8% or less. Preferably, the rigidity is 7.5 kN / mm or more is sufficient.

[0072] 3. Effect of the extruded material The sliding material of the embodiment is used in a sliding environment where an impact load occurs. By including an intermetallic compound such as Mn silicide or Cr silicide having a nanoindentation hardness of 15 GPa or more in the Cu-Zn-Al-based base 2 of the sliding material 1, the friction performance is improved, and the embedding rate of the solid lubricant embedding portion 4 is made smaller than a predetermined value and the rigidity is increased. As a result, the amount of deformation generated in the sliding material is reduced, the generated stress is lowered, it becomes possible to withstand the large impact stress generated in the cam sliding portion and the toggle bush, and the fatigue resistance is enhanced. Further, in the embodiment, after casting the sliding material, by performing extrusion molding, a sliding material with higher fatigue resistance is provided.

[0073] The manufacturing method of the sliding material of the embodiment is as follows. In the base 2 of the Cu-Zn-Al-based alloy, in terms of mass%, 25% of Zn and 5% of Al are contained. In order to strengthen this base 2, 2% of Mn and 3% of Ni are contained, and 4.8% of Cr, 0.85% of Fe, and 1.0% of Si are added to generate a Cr-Fe-Si-based compound 3A, or 3.1% of Mn, 2.8% of Fe, and 1% of Si are added to generate an Mn-Fe-Si compound 3B.

[0074] To cast this component, a high-frequency melting furnace is used. After melting Cu at 1150°C, Zn and Al ingots are added, and predetermined amounts of Mn, Ni, Fe, Cr, and Si are sequentially introduced in the form of alloys with Cu. After melting, degassing, calming, and skimming are carried out, and then the molten metal is poured into a cylindrical mold with a diameter of φ10 inches and a length of 600 mm to produce an extrusion billet. The extrusion part of the billet is cut, heated to 800°C, loaded into an extrusion device, and hot extruded into a ring shape with an extrusion ratio of 35.

[0075] The fatigue test described above was carried out on the ring-shaped material thus obtained. Fig. 16 shows the S / N curves of the material containing Cr silicide in Example 2 as a normal sand-shaped material and the extruded material. Thus, it can be seen that by extruding a material containing an intermetallic compound excellent in frictional performance, it can withstand a high load based on the principle shown in Fig. 5 and extend the fatigue limit.

[0076] 3. Effect of resin coating containing MoS2 Materials containing intermetallic compounds can reduce the embedding rate of the solid lubricant embedding part, thereby improving rigidity and reducing deformation, and can reduce the generated stress even when a high load occurs repeatedly, making it possible to extend the fatigue limit. Also, considering the case where lubricating oil cannot be used due to a temperature rise, the effect of coating the surface of the sliding material with a resin containing MoS2 was demonstrated.

[0077] First, a resin containing MoS2 was coated on the surface of a brass alloy containing Cr silicide under the following conditions. The content of the resin coating material (2) is as follows. · Resin component: Solid lubricant MoS2 57%, Gr. 17%, epoxy resin, remainder · Resin coating thickness: 20 - 30 μm · Resin coating method: Spray coating · Firing conditions: 200°C x 0.5 h in air Next, under the condition that this coating material was heated to 150°C, the surface pressure was 6.0 N / mm 2Then, the sliding distance of 190 m was reciprocally slid, and the transition of the friction coefficient was observed. Note that a bronze sintered material containing 10% graphite (trade name deva.metal) (1) was used as a comparative material.

[0078] Fig. 17 shows an overview of the rotational sliding test apparatus. 17 is the test apparatus, 18 is the housing, 19 is the bush, and 20 is the shaft. A load N is applied to the housing 18, and the shaft 20 is rotated.

[0079] Fig. 18 shows the friction coefficient of the material coated with the resin containing MoS2. (1) is a bronze sintered material containing 10% graphite, and (2) is the one coated with the resin containing the solid lubricant in Example 2 of Table 2. For (2), the transition of the friction coefficient is also stably maintained at the 0.1 level. Even when there is no oil film, the resin coating material containing solid lubrication is confirmed to have better friction characteristics than (1).

[0080] 4. Application Examples The oil-free sliding material embedded with the solid lubricant graphite has been used for use in a severe mixed lubrication state where an impact load occurs. In particular, as such severe use conditions, there are examples of being used as a sliding member of a cam device used for a mold and as a bearing of a toggle link mechanism of a molding machine.

[0081] Fig. 19 shows a cross-sectional view of the cam device of the embodiment. 21 is the cam device, 24 is the cam holder, 25 is the cam slider, 26 is the cam driver, 22 is the upper part of the mold, 23 is the bottom part of the mold, 27 is the plate material, and 28 is the sliding material. The cam device 21 is composed of a cam holder 24, a cam slider 25, and a cam driver 26. The cam device 21 is installed between the upper mold 22 that moves up and down and the fixed lower mold 23, and pierces the side surface of the plate material 27 to be molded. As shown in Fig. 12, when the up and down movement of the press mold head performs piercing under reciprocating sliding, an impact load occurs. In recent years, the steel plates to be processed have advanced in hard high-tensioning, and more significant impacts have occurred. Since high accuracy is required for the relative position adjustment between the processing tool and the workpiece, etc., it is required that the wear generated on the cam holder sliding surface and the cam driver sliding surface is small, and higher durability has been demanded.

[0082] Generally, an injection molding machine closes a mold with a mold clamping device, injects and fills high-pressure resin from an injection device into the cavity of the mold while a large mold clamping force is applied to the mold, and takes out a resin molded product from the largely opened mold after cooling and solidification, thereby producing a resin molded product of a desired shape. Such a mold clamping device is required to have a function of opening and closing the mold in a short time and applying a large mold clamping force to the mold. A toggle type mold clamping device having a toggle link mechanism as a force multiplying mechanism that draws a tan curve under reciprocating sliding and has a rapidly increasing load is widely used.

[0083] Fig. 20 shows a schematic diagram of a toggle device. In the toggle link mechanism of the toggle type mold clamping device 29, a plurality of joints are provided between a fixed platen and a movable platen 30. In the bearing bushing 31 used for this joint, equal load does not act on the entire circumference of the cylindrical inner peripheral surface. At the initial stage of mold closing of the movable platen, that is, at the initial stage from mold opening to mold closing, the speed of the movable platen is fast and the mold closing force is small, so a large load does not act on the cylindrical inner peripheral surface of the bearing bushing. However, as the mold closing is completed, the speed of the movable platen rapidly decreases, and instead, the mold closing force by the movable platen significantly increases, and a large load acts on the cylindrical inner peripheral surface of the bearing bushing 31. The range of the cylindrical inner peripheral surface where this large impact load acts is about one-eighth of the entire circumference of the inner peripheral surface of the bearing bushing 31. In recent years, injection molding machines have been required to have a high-cycle high-speed molding function, and impact loads that are repeatedly applied in a short time have occurred on the bearings.

[0084] Examples of applications where impact loads occur include sliding materials for press molds and bushings of toggle mechanisms of molding machines. In addition, bushings of side rolls of hot rolling mills, etc. have used sliding materials of the solid lubricant embedded type to reinforce conventional boundary - mixed lubrication. In the embodiment, by reducing the number of embedded holes and making the sliding material more tough, it is possible to provide a sliding material with increased fatigue resistance and excellent durability. Therefore, it is applicable not only to the examples of application but also to many impact-resistant sliding parts.

[0085] The embodiment reconsiders the very existence of the solid lubricant embedding portion and provides a technique for suppressing the fatigue failure of the sliding material due to impact load. For example, in the sliding material used for a press die, as shown in Fig. 2, an impact load of 45 MPa occurs in 0.1 seconds. The embodiment is applied to the case where such a rapid load occurs.

[0086] Even under severe sliding conditions where the sliding surface falls into boundary lubrication due to the generation of an impact load, by using a low-friction material, the fluid lubrication state is maintained, the solid lubricant embedding portion that impairs the bearing rigidity is reduced, the stress generated is reduced by reducing the deformation of the sliding material, and the fatigue load is increased by applying extrusion molding. Even under sliding conditions where reciprocating sliding is repeated in a short time and the number of repeated impact loads exceeds 10 6 times, it is possible to maintain a sound state.

[0087] The above describes the embodiment, but this embodiment is presented as an example and is not intended to limit the scope of the invention. This novel embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. This embodiment and its modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and its equivalent scope.

Description of Reference Numerals

[0088] 1. Sliding material, 1A. Sliding surface, 2. Substrate, 3A. Cr-Fe-Si-based intermetallic compound, 3B. Mn-Fe-Si-based intermetallic compound

Claims

1. A bearing bush for a toggle link mechanism used in a toggle-type clamping device in which an impact load is generated, A base material made of a Cu-Zn-Al brass casting alloy; An intermetallic compound of Mn silicide or Cr silicide having a nanoindentation hardness of 15 GPa or more contained in the base material; a solid lubricant embedded portion exposed on a surface of the bearing bush of the toggle link mechanism, a coverage rate of the solid lubricant-embedded portion on the sliding surface of the bearing bush of the toggle link mechanism is 15.8% or less; A bearing bush for a toggle link mechanism, wherein the rigidity of the bearing bush for the toggle link mechanism is 7.5 kN / mm or more.

2. A bearing bush for a toggle link mechanism used in a toggle-type clamping device in which an impact load is generated, A base material made of a Cu-Zn-Al brass casting alloy; The base material contains an intermetallic compound of Mn silicide or Cr silicide having a nanoindentation hardness of 15 GPa or more, The toggle link mechanism does not have a solid lubricant embedded portion exposed on a surface of the bearing bush, A bearing bush for a toggle link mechanism, wherein the rigidity of the bearing bush for the toggle link mechanism is 7.5 kN / mm or more.

3. 3. The toggle link mechanism bearing bush according to claim 1, wherein a surface of the toggle link mechanism bearing bush has a resin coating containing a solid lubricant.

4. A method for manufacturing a bearing bushing for a toggle link mechanism according to claim 1 or 2, comprising the steps of: The method includes the steps of casting a material, producing a billet from the cast material, and extruding the billet, In the case where the bearing bushing is provided with a solid lubricant embedded portion, the manufacturing method includes a step of forming a solid lubricant embedded portion on a surface of the bearing bushing.

Images