JP2023036234A - Sintered sliding component and manufacturing method thereof - Google Patents

Abstract

To provide a sintered sliding component capable of improving sliding performance and maintaining the sliding performance for a long period, and a manufacturing method thereof.SOLUTION: A sintered sliding component has a porous sintered component body formed with a sliding surface for slidably supporting a sliding object, and made of a sintered metal. On the sliding surface, a solid lubrication phase containing a solid lubricant and a ground surface on which a large number of pores of the sintered component body are opened are dispersedly formed, where an area ratio of the solid lubrication phase on the sliding surface is 10% or more and 60% or less, and a part of the solid lubrication phase penetrates into the sintered component body.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a sintered sliding part such as an oil-impregnated sintered bearing that can be lubricated smoothly by impregnating the inside with lubricating oil, and a method for manufacturing the same.

As sintered sliding parts, relatively soft bronze-based or brass-based copper-based bearings, iron-based bearings containing high-strength iron, and iron-copper-based bearings, which are intermediate bearings of these, are known. It is used properly depending on the speed and the size of the load. For example, copper-based bearings are mainly used for high-speed sliding and low-load specifications, iron-based bearings are used for low-speed sliding and high-load specifications, and iron-copper-based bearings are used in between.

In order to minimize the frictional resistance of such various bearings, an iron-copper-based sintered sliding component described in Patent Document 1 is known, which contains a solid lubricant as necessary.
In order to improve the slidability of these iron-copper-based sintered sliding parts, solid lubricant powders such as graphite and molybdenum disulfide (MoS ₂ ) are mixed with the base metal powder and sintered. In addition to dispersing free graphite, the copper component in the surface layer is increased, and the surface layer is supported by a back metal layer containing a reaction phase such as a pearlite phase in which graphite and iron react. We provide sintered sliding parts with enhanced durability.

However, in the iron-copper-based sintered sliding part described in Patent Document 1, when graphite is used as a solid lubricant, cementite and the like is produced by a reaction between iron and graphite during sintering of the metal powder and the solid lubricant powder. When a high-strength structure is generated and provided on the surface layer, the high-strength structure may damage the sliding object. Moreover, when MoS ₂ is used as a solid lubricant, it is difficult to cause MoS ₂ to exist in the sintered body in the state of MoS 2 because the MoS ₂ is decomposed by the high temperature during sintering.
In addition, if a solid lubricant is blended and sintered, the sinterability will be hindered, and the strength and hardness of the bearing will decrease. Furthermore, since iron-based materials are generally used for shafts and the like to slide, if the sintered sliding parts contain iron-based powder, sliding between similar metals (so-called togane) will occur. Adhesive wear or seizure may occur due to

In order to solve the above-described problems, a method for forming a solid lubricant-containing metal layer by impregnating a sintered body of metal powder with a solid lubricant has been proposed, for example, manufacturing a sintered oil-impregnated bearing described in Patent Document 2. method is known.
In the method for manufacturing a sintered oil-impregnated bearing described in Patent Document 2, a bearing body (sintered body) obtained by sintering is sized, and oil is added to obtain a desired average pore diameter to be exposed on the sliding receiving surface. An oil hole having an average diameter larger than that of the hole is formed in the slide receiving surface, a solid lubricant-containing metal layer is provided on the slide receiving surface, and the edge of the oil hole is covered by the solid lubricant-containing metal layer. , an oil hole having a desired average hole diameter is formed in the sliding receiving surface.

As a method for forming a low-friction layer made of a fluororesin such as PTFE on a sintered body of metal powder, for example, a method for manufacturing a sintered oil-impregnated bearing described in Patent Document 3 is known.
In the method for manufacturing a sintered oil-impregnated bearing described in Patent Document 3, after the surface of the sintered metal is pressed and molded, a resin film is formed on the molded surface to form a low-friction layer, and the low-friction layer leaving at least a portion of the surface pores on the surface.

JP 2011-94167 A JP-A-2005-147201 JP 2010-249242 A

By the way, since both the solid lubricant-containing metal layer and the low-friction layer formed on the surface have a layer structure, when the sliding object slides for a long period of time, the solid lubricant-containing metal layer or the low-friction layer There is concern that the layer will wear and durability will decrease. Therefore, it is difficult to maintain slidability over a long period of time.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a sintered sliding part that can improve slidability and maintain the slidability over a long period of time, and a method of manufacturing the same. and

The sintered sliding part of the present invention is a sintered sliding part having a porous sintered part body made of a sintered metal and having a sliding surface for slidably supporting a sliding object, On the sliding surface, a solid lubricating phase containing a solid lubricant and a ground surface in which a large number of pores of the sintered part body are opened are dispersedly formed, and the area of the solid lubricating phase on the sliding surface The ratio is 10% or more and 60% or less, and part of the solid lubricating phase penetrates into the sintered component body.

In the present invention, since the bare surface remains on the sliding surface, the lubricating action is enhanced by the solid lubricating phase, and the base portion (skin surface) having higher strength than the solid lubricating phase absorbs the load from the sliding object. By supporting, slidability can be greatly improved. In addition, since a part of the solid lubricating phase penetrates into the main body of the sintered part, even if the surface of the sliding surface wears due to the sliding object, it is possible to suppress the deterioration of the slidability. You can stay mobile.
When the area ratio of the solid lubricating phase on the sliding surface is less than 10%, the coefficient of friction becomes large. As a result, the coefficient of friction increases, and the load bearing performance (load bearing action) decreases.

As a preferred embodiment of the sintered sliding part of the present invention, the sliding surface roughness Rz (JIS B 0601 2001) is preferably 5 μm or less.
In the above embodiment, even if the sliding surface is slightly rough, the solid lubricating phase attached to the surface is the main unevenness, so the presence of the solid lubricating phase does not significantly reduce the sliding characteristics. On the contrary, it is possible to improve conformability, form a good sliding surface, and expect an improvement in anti-seizure effect and a low-friction effect.
If the roughness Rz (JIS B 0601 2001) of the sliding surface exceeds 5 μm, there is a possibility that the friction of the sliding surface will increase due to the generation of excessive abrasion powder during running-in at the initial stage of sliding.

As a preferred embodiment of the sintered sliding part of the present invention, the penetration depth of the solid lubricating phase into the sintered part body is preferably 50 μm or more.
If the penetration depth of the solid lubricating phase into the sintered part body is less than 50 μm, it is difficult to improve the slidability over a long period of time.

As a preferred aspect of the sintered sliding part of the present invention, the solid lubricating phase may contain a resin.
In the above aspect, since the solid lubricating phase contains a resin softer than the sintered part main body and the sliding object, even if the solid lubricating phase wears due to the sliding of the sliding object, the wear powder will generate the sintered part. It is possible to suppress damage to the main body and sliding objects.

As a preferred embodiment of the sintered sliding component of the present invention, the main component of the sintered component body is preferably an iron-based metal.
In the above aspect, since the sintered sliding part is mainly composed of an iron-based metal, the strength of the sintered sliding part can be increased and the manufacturing cost can be reduced.

As a preferred aspect of the sintered sliding part of the present invention, the solid lubricant may contain a substance having cleavability or a substance softer than the sliding object.
Examples of the substance having cleavability and the substance softer than the sliding object include graphite, molybdenum disulfide, calcium fluoride, talc, boron nitride, and graphite fluoride.

As a preferred embodiment of the sintered sliding part of the present invention, at least part of the pores are impregnated with lubricating oil.
In the above-described aspect, since the sliding surface has a bare surface with a large number of open pores, the lubricating oil is discharged from these pores as the sliding object slides. Sliding property can be further improved. In addition, the solid lubricant in the pores and the lubricating oil impregnated in the pores become turbid and are gradually supplied to the sliding surface, so that the slidability of the sintered sliding part can be further improved.

As a preferred aspect of the sintered sliding part of the present invention, the solid lubricating phase preferably has lipophilicity.
In the above aspect, the solid lubricating phase formed in the sintered part main body can suppress the lubricant impregnated in the pores from being discharged to the outside.

A method for manufacturing a sintered sliding part according to the present invention is a method for manufacturing the above-described sintered sliding part, comprising a molding step of filling a molding die with raw material powder and applying pressure to form a green compact; A sintering step of sintering a compact to form a sintered body, an impregnating step of impregnating the sintered body with a diluted liquid mixed with a solid lubricant, and the sintered body after the impregnating step A heating step of heating to volatilize the liquid content of the diluent, and a sizing step of sizing the sintered body after the heating step to form a sintered component body.

In the present invention, since the solid lubricating phase is formed after the sintering process, the solid lubricant reacts with the metal components constituting the sintered body during sintering to generate a high-strength structure, and the high-temperature can suppress the decomposition of the solid lubricant. Therefore, it is possible to expand the range of solid lubricants to be selected.
Here, if the solid lubricating phase is formed after sizing the sintered body, it becomes difficult to maintain the dimensional accuracy and surface roughness due to the uneven thickness of the solid lubricating phase adhering to the surface. Since the opening diameter of the pores formed on the surface of is small, the solid lubricant is less likely to enter the pores.
On the other hand, in the present invention, since the sizing step is performed after the impregnation step and the heating step, the solid lubricant can easily enter the pores in the impregnation step. can also be formed.

In a preferred embodiment of the method for producing a sintered sliding component according to the present invention, the diluent is mixed with the solid lubricant and the resin binder.
In the above aspect, the solid lubricating phase can be formed from a solid lubricant and a resin. Since this resin is softer than the sintered part body and the sliding object, even if the solid lubricating phase wears due to the sliding of the sliding object, the wear powder will not damage the sintered part body and the sliding object. can.

As a preferred embodiment of the method for producing a sintered sliding component according to the present invention, it is preferable to further include a lubricating oil impregnation step of impregnating with a lubricating oil after the sizing step.
In the above aspect, a sintered oil-impregnated sliding component (for example, a sintered oil-impregnated bearing) can be provided by impregnating the sintered sliding component with lubricating oil.

In a preferred embodiment of the method for producing a sintered sliding part of the present invention, in the impregnation step, the diluted liquid mixed with the solid lubricant having a particle size smaller than the opening diameter of the pores on the sliding surface is used. It is preferable to impregnate the sintered body.
In the above aspect, since the solid lubricant contains particles having a particle diameter smaller than the opening diameter of the pores, the solid lubricant can easily enter the pores. Therefore, the solid lubricating phase can be easily formed in the pores. Furthermore, when the pores are impregnated with lubricating oil, the lubricating oil becomes turbid with the solid lubricating phase in the pores and is discharged onto the sliding surface, so that the slidability can be further enhanced.

In a preferred embodiment of the method for producing a sintered sliding component according to the present invention, before the impregnation step, a region of the sintered body other than the region to be the sliding surface is processed to close at least part of the pores. It is preferable to provide a blinding step.
In the above aspect, when the impregnation step is performed by an immersion method, etc., it is possible to suppress the intrusion of the solid lubricant, which becomes the solid lubricating phase, into the region other than the region that becomes the sliding surface, thereby reducing the manufacturing cost.

ADVANTAGE OF THE INVENTION According to this invention, the slidability of a sintered sliding component can be improved, and the slidability can be maintained for a long period of time.

1 is a cross-sectional view of a sintered sliding component (sintered oil-impregnated bearing) according to an embodiment of the present invention; FIG. FIG. 2 is a view showing a cross-sectional SEM image of the sintered oil-impregnated bearing shown in FIG. 1; 3 is a partially enlarged view of the cross-sectional SEM image shown in FIG. 2; FIG. 4 is a flow chart showing a method for manufacturing the sintered sliding component of the embodiment; It is the image which carried out the elemental analysis of the sliding surface surface of the sintered oil-impregnated bearing in an Example.

An embodiment of the present invention will be described below with reference to the drawings.

[Schematic configuration of sintered oil-impregnated bearing]
The sintered oil-impregnated bearing 1 of this embodiment corresponds to the sintered sliding component of the present invention, and is a cylinder formed by impregnating a porous bearing body 10 (sintered component body) made of sintered metal with lubricating oil. It is a shaped bearing. The sintered oil-impregnated bearing 1 is formed with a bearing hole 11 having a sliding surface 12 for supporting the outer peripheral surface of the shaft (not shown) through which a sliding object is inserted. This bearing hole 11 slidably supports the inserted shaft.

Since this sintered oil-impregnated bearing 1 is formed of a sintered body of metal powder (for example, metal powder containing iron-based metal powder as a main component), it is a porous body having a large number of pores formed therein. formed by The open porosity (JIS Z 2501 2000) of this sintered oil-impregnated bearing 1 (bearing body 10) is set to 14 vol % to 25 vol %, and the pores of the bearing body 10 are impregnated with lubricating oil.
The open porosity is the volume ratio of pores that can impregnate fluid such as lubricating oil with respect to the bearing body 10 . This open porosity is expressed as a percentage of the volume of the bearing main body 10, and is obtained by dividing the volume of the oil after complete impregnation by the volume of the bearing main body 10 and multiplying by 100. That is, the open porosity is substantially the same as the oil content with respect to the volume of the bearing main body 10 .

The lubricating oil impregnated in the pores expands as the shaft slides and the temperature of the bearing body 10 rises, and the sliding of the shaft absorbs the lubricating oil in the pores of the bearing body. Due to the pumping action, the leaked lubricating oil is drawn into the bearing body 10 when the shaft stops sliding and the temperature of the sintered oil-impregnated bearing 1 drops. and collected.

[Configuration of sliding surface]
Such a sliding surface 12 is formed by a mixture of a ground surface in which numerous pores of the bearing body 10 are opened and a solid lubricating phase containing a solid lubricant. This solid lubricating phase is composed of a substance having cleavability, a substance softer than the shaft to be slid, and a resin. Specifically, examples of such substances include graphite, molybdenum disulfide, calcium fluoride, talc, boron nitride, and graphite fluoride. Consists of
The solid lubricating phase preferably has lipophilicity. If the solid lubricating phase has lipophilicity, it becomes possible to impregnate the lubricating oil appropriately in the pores, and it is possible to suppress the discharging of the lubricating oil impregnated in the pores to the outside. It's for. Therefore, even if the solid lubricant has oil repellency, it is sufficient that the solid lubricating phase itself has lipophilicity by containing the resin. In this specification, oleophilicity means that the lubricating oil can be retained in the pores of the bearing body 10 provided with the solid lubricating phase. This oleophilicity is judged, for example, by whether or not oil is sucked into the bearing when the oil is dripped in a non-impregnated state of lubricating oil. If it absorbs, it is judged to be lipophilic, and if it forms a ball on the surface and does not absorb, it is judged to be non-lipophilic.

The reason why the solid lubricating phase contains a resin is that the resin is softer than the bearing body 10 and the shaft, and it is possible to suppress damage to the main body and the shaft by abrasion powder generated when the solid lubricating phase containing resin wears. The resin does not necessarily have to be included in the solid lubricating phase, and the solid lubricating phase may consist of only the solid lubricant.

Moreover, the particle size of the solid lubricant may be smaller than the opening diameter of the pores in the sliding surface 12 . For example, when the opening diameter of the pores in the sliding surface 12 is set to 5 μm to 100 μm, the solid lubricant containing particles smaller than that is used. In other words, the particle size of the solid lubricant is sufficient as long as it contains particles smaller than the pore opening diameter, and may partially contain particles larger than the pore opening diameter. It may be smaller than the opening diameter. Therefore, a solid lubricating phase made of solid lubricant is formed not only on the surface (sliding surface 12) of the bearing body 10 but also in the pores.

Such a solid lubricating phase contributes to the improvement of the slidability of the sliding surface 12, and is formed in part of the surface of the sliding surface 12 and in the bearing body 10, as shown in FIG. Specifically, the area ratio of the solid lubricating phase in the sliding surface 12 is 10% or more and 60% or less, and the area other than the solid lubricating phase is the ground surface. For example, in the example shown in FIG. 5, the solid lubricating phase on the surface of the sliding surface 12 is a portion displayed in black, which is mixed with the ground surface displayed in white and gray.
When the area ratio of the solid lubricating phase on the sliding surface 12 is less than 10%, the friction coefficient of the sliding surface 12 increases, and when it exceeds 60%, the surface area of the sliding surface 12 decreases. , the load-bearing action of the ground surface is reduced.

Further, the penetration depth of the solid lubricating phase into the bearing body 10 is preferably 50 μm or more. Specifically, as shown in FIG. 2, the solid lubricating phase is arranged in the bearing body 10 in a dispersed state. FIG. 3 is an enlarged view of the SEM image of the portion surrounded by the frame in FIG. 2, and the portion indicated by the arrow in FIG. 3 is the solid lubricating phase. 2 and 3, it can be seen that the solid lubricating phase penetrates into the bearing body 10 within the range described above, and as a result, when the sliding surface 12 wears due to sliding of the shaft, the slidability deteriorates. is suppressed.
If the penetration depth of the solid lubricating phase into the bearing body 10 is less than 50 μm, it is difficult to maintain the slidability for a long period of time.

On the other hand, the open porosity of the bearing body 10 after the formation of the solid lubricating phase is preferably 14 vol % or more and 25 vol % or less. As a result, the sintered oil-impregnated bearing 1 can be sufficiently impregnated with lubricating oil, and the slidability can be improved. Moreover, by suppressing excessive impregnation of the solid lubricating phase into the bearing body 10, the manufacturing cost can be reduced.
If the solid lubricating phase impregnates too much into the sintered body and the open porosity of the bearing body 10 drops below 14 vol%, the amount of lubricating oil to be impregnated will decrease. The function of the oil-impregnated bearing 1 may be deteriorated. In addition, excessive impregnation of the solid lubricating phase may increase manufacturing costs.

The roughness Rz (JIS B 0601 2001) of the sliding surface 12 on which such a solid lubricating phase is formed is preferably 5 μm or less, preferably 2 μm or less. As a sliding member, the roughness should be small, but in this structure, the solid lubricating phase adhering to the surface may cause slight unevenness. does not drop significantly.
Note that if the roughness Rz (JIS B 0601 2001) of the sliding surface 12 exceeds 5 μm, the coefficient of friction of the sliding surface 12 may increase due to the generation of excessive abrasion powder during running-in at the initial stage of sliding. be.

[Manufacturing method of sintered oil-impregnated bearing]
The sintered oil-impregnated bearing 1 is produced by a molding step (step S11) in which raw material powder is filled in a molding die and pressurized to form a cylindrical compact, and the compact is sintered to form a sintered compact. A sintering step of forming (step S12), an impregnating step (step S13) of impregnating the sintered body with a diluent mixed with a solid lubricant, and heating the sintered body after the impregnating step to dilute the liquid A heating step (step S14) for volatilizing the components, a sizing step (step S15) for sizing the sintered body after the heating step to form the bearing body 10, and a lubricant for impregnating the bearing body 10 with the lubricant after the sizing step and an impregnation step (step S16). Hereinafter, each process will be described along the flowchart shown in FIG.

(Molding process)
Although the metal used as the material for the sintered oil-impregnated bearing 1 is not particularly limited, it is preferable to use an iron-based powder or an iron-copper-based powder as the raw material powder.
The iron-based powder is iron powder whose main component is iron or an iron alloy, and may contain low-melting-point metal powder whose melting point is equal to or lower than the sintering temperature. In this case, a combination of 0.5% to 70% by mass of copper-based powder, 0.5% to 10% by mass of low-melting-point metal powder, and the balance of iron-based powder. Incidentally, in iron alloy materials, copper may be used as a low-melting-point metal.

In the molding process, a molding die (not shown) is used. Raw material powder is put into the space formed by the molding die, and a cylindrical upper punch is inserted from above to form a lower molding die. A green compact is formed by compressing the raw material powder at 100 MPa to 800 MPa by narrowing the distance between the punch and the upper punch for molding.

(Sintering process)
Next, in the sintering step, this compact is sintered at a temperature of 600.degree. C. to 1150.degree. As a result, the green compact is sintered into a sintered body. The maximum temperature holding time is preferably 5 to 30 minutes.
The open porosity of the sintered body at this point is 15 vol % to 30 vol %. The open porosity is the volume ratio of pores that can be impregnated with a fluid such as lubricating oil to the sintered body, and is expressed as a percentage of the volume of the sintered body. divided by and multiplied by 100.

(Impregnation process)
In the impregnation step, for example, the sintered compact is impregnated with a diluted solution obtained by diluting at least one solid lubricant such as graphite, molybdenum disulfide, calcium fluoride, talc, boron nitride, and graphite fluoride, and a resin binder with a solvent. Let These solid lubricants preferably have lipophilic properties, and their average particle diameter is preferably smaller than the average opening diameter of the pores on the surface of the sliding surface 12 of the sintered body. It should be noted that the solid lubricant is not limited to the respective substances exemplified above, and any solid lubricant may be used as long as it is a substance having cleavability or a substance softer than the sliding object.
In the present embodiment, for example, 10% by mass of molybdenum disulfide and 10% by mass of an epoxy-based resin binder are put into an organic solvent and stirred to produce a diluted solution. Then, the sintered body is impregnated with the diluent by immersing the sintered body in the diluent for a predetermined time (for example, 5 minutes to 30 minutes). At this time, since the particle size of the solid lubricant contains particles smaller than the opening diameter of the pores formed on the surface of the sintered body, part of the solid lubricant enters the pores.
In addition, the area ratio of the solid lubricating phase on the sliding surface 12 is 10% or more and 60% or less, the roughness Rz (JIS B 0601 2001) of the sliding surface 12 is 5 μm or less, and the penetration depth of the solid lubricating phase into the bearing body 10 In order to obtain a thickness of 50 μm or more, it is preferable to set the dilution concentration of the solid lubricant and the resin binder in the diluent to 20 mass % to 30 mass % and immerse the sintered body in this diluent for 3 seconds to 30 minutes.

In the above embodiment, the sintered body is impregnated with the diluent by immersing it in the diluent, but the present invention is not limited to this. You may let

(Heating process)
In the heating step, the sintered body impregnated with the diluent is heated. The heating temperature in this heating step is preferably a temperature at which the solid lubricant does not decompose during heating and a temperature at which the liquid portion of the diluent can be volatilized. For example, the heating condition of the heating step is to keep the sintered body at 150° C. to 250° C. for 30 minutes to 120 minutes.

(Sizing process)
In the sizing step, the bearing body 10 is formed by clamping the inner peripheral surface, the outer peripheral surface and both end surfaces of the sintered body with a correcting mold (not shown) to correct the size of the sintered body.

(Lubricating oil impregnation process)
Then, the pores of the bearing body 10 are impregnated with lubricating oil. Thus, the sintered oil-impregnated bearing 1 is manufactured.

In this embodiment, since the sliding surface 12 has a surface with many pores open, the lubricating action of the solid lubricating phase and the load bearing action of the surface are combined to greatly improve the slidability. can be made In addition, since the solid lubricating phase permeates the bearing body 10, even if the surface of the sliding surface 12 is worn by the sliding object (shaft), it is possible to suppress the deterioration of the slidability, The solid lubricant and the lubricating oil impregnated in the pores become turbid and are supplied to the sliding surface 12 little by little, so the slidability can be maintained for a long period of time. Furthermore, since the sliding surface 12 has a small roughness Rz and is formed flat without protruding unevenness, it is possible to suppress the generation of excessive abrasion powder on the sliding surface 12, thereby Friction on moving surfaces can be reduced.

Further, the solid lubricating phase contains a resin that is softer than the bearing body 10 and the sliding object, and the solid lubricant that forms the solid lubricating phase together with the resin has a cleavable substance or a substance that is softer than the sliding object ( For example, graphite, molybdenum disulfide, calcium fluoride, talc, boron nitride, graphite fluoride, etc.), even if the solid lubricating phase wears due to the sliding of the sliding object, the wear powder will It is possible to suppress damage to the main body 10 and sliding objects.
Furthermore, since the sintered oil-impregnated bearing 1 is mainly composed of iron-based metal, the strength of the sintered oil-impregnated bearing 1 can be increased and the manufacturing cost can be reduced.
In addition, since the sliding surface 12 has a bare surface with a large number of open pores, the lubricating oil is discharged from these pores as the sliding object slides. You can improve your mobility. In this case, since the solid lubricating phase is oleophilic, the solid lubricating phase formed in the bearing body 10 can suppress the discharge of the lubricating oil impregnated in the pores to the outside.

In the method for manufacturing the sintered oil-impregnated bearing 1 of the present embodiment, since the solid lubricating phase is formed after the sintering process, the solid lubricant reacts with the metal components constituting the sintered body during sintering to form a high-strength structure. It is possible to suppress the occurrence of sintering and the decomposition of the solid lubricant due to the high temperature during sintering. Therefore, it is possible to expand the range of solid lubricants to be selected.
Here, if the solid lubricating phase is formed after sizing the sintered body, it becomes difficult to maintain the dimensional accuracy and surface roughness due to the uneven thickness of the solid lubricating phase adhering to the surface. Since the opening diameter of the pores formed on the surface of is small, the solid lubricant is less likely to enter the pores.
In contrast, in the present embodiment, the sizing step is performed after the impregnation step and the heating step, so that the solid lubricant can easily enter the pores in the impregnation step. can also be formed.

In addition, since the solid lubricant contains particles having a particle diameter smaller than the opening diameter of the pores, the solid lubricant can easily enter the pores. Therefore, the solid lubricating phase can be easily formed in the pores. Furthermore, since the pores are impregnated with lubricating oil, the lubricating oil becomes turbid with the solid lubricating phase in the pores and discharged to the sliding surface 12 as the shaft, which is the object to slide, slides. The slidability of the oil-impregnated bearing 1 can be further enhanced.

It should be noted that the present invention is not limited to the configurations of the above-described embodiments, and various modifications can be made to the detailed configurations without departing from the gist of the present invention.
For example, in the above embodiment, the impregnation step is performed immediately after the sintering step, but the present invention is not limited to this. For example, before the impregnation step, a filling step may be provided for filling at least part of the pores by processing the regions (both end surfaces and the outer peripheral surface of the bearing body 10) other than the region that will become the sliding surface 12 in the sintered body. good. By this filling step, when the impregnation step is performed by an immersion method, etc., it is possible to suppress the intrusion of the solid lubricant that becomes the solid lubricating phase into regions other than the region that becomes the sliding surface 12, thereby reducing the manufacturing cost.

In the above embodiment, the metal powder used as the base of the sintered oil-impregnated bearing was exemplified by an iron-based metal powder, but the present invention is not limited to this, and various sintered metals may be used.

In the above embodiment, in order to form the solid lubricating phase, a diluent made of an organic solvent in which molybdenum disulfide and a resin binder are mixed is used. An organic solvent in which two or more solid lubricants such as calcium, talc, boron nitride, and graphite fluoride are mixed with a resin binder may be used as the diluent. Moreover, the solid lubricant is not limited to the above-mentioned substances exemplified as solid lubricants, and any solid lubricant may be used as long as it is a substance having cleavability or a substance softer than the object to be slid.

In the above-described embodiment, the sintered sliding part is exemplified by a sintered oil-impregnated bearing impregnated with lubricating oil, but the invention is not limited to this and includes a dry sintered bearing. In this case, the lubricating oil impregnation step may be omitted.
In addition, in order to provide a sintered oil-impregnated bearing having properties suitable for use conditions, the metal materials used (mixture of metal powder) and various conditions in the manufacturing process may be changed as appropriate.
Moreover, the shape of the sintered sliding part is not limited to the shape of the bearing, and any shape can be used as long as it has a sliding surface capable of supporting the object to be slid.

The results of tests conducted to demonstrate the effects of the present invention will be described.
In Examples 1 to 7 and Comparative Examples 1 and 2, an iron-copper powder obtained by mixing iron, copper, tin and the like was used as the raw material powder. The raw material powder composed of iron-copper-based powder was adjusted to contain 48% by mass of iron powder, 2% by mass of tin powder, and the balance of copper powder. In the molding step, the raw material powder was compression-molded at 300 MPa to form a compact, and in the sintering step, the green compact was sintered at a temperature of 900° C. to form a sintered compact. Regarding the area ratio, penetration depth, and sliding surface roughness of the solid lubricating phase, the dilution concentration of the diluent used in the solid lubricating phase imparting step is 20 mass% to 30 mass%, and the immersion time is 3 seconds to 30 seconds. minutes. In Examples 1, 3 and 5, 10% by mass of molybdenum disulfide and 10% by mass of an epoxy resin binder are added to an organic solvent and stirred to prepare a diluted solution, and the sintered body is immersed in the diluted solution for 30 minutes. After impregnating the sintered body with the diluent, the sintered body is heated at 200° C. for 60 minutes to volatilize the liquid content of the diluent and form a solid lubricating phase on the sliding surface and inside of the sample. , to form a sintered bearing having a bearing body diameter of 16 mm and a bearing hole diameter of 8 mm. Then, the sintered bearing was impregnated with mineral oil of ISO grade VG68 (kinematic viscosity at 40° C. of 68 cst) to form a sintered oil-impregnated bearing (hereinafter referred to as a sample).
In Example 2, a sample was formed in the same manner as in Example 1 except that the sintered body in Example 1 was immersed in the diluent for 15 minutes. Furthermore, in Examples 4 and 7, 15 mass% of molybdenum disulfide and 15 mass% of an epoxy resin binder were added to an organic solvent and stirred to prepare the diluent, and the other steps were the same as in Example 1. to form the sample. In Example 6, a sample was prepared in the same manner as in Example 1, except that the time for immersion in the diluent was set to 3 seconds.

On the other hand, in Comparative Example 1, the sintered bearing having the shape described above was formed by sizing immediately after the sintering process. In Comparative Example 2, the same diluent as in Example 4 was used, and the sintered body was immersed in the diluent for 30 minutes. After that, the sample was again immersed in the diluent for 30 minutes and then heated at 200° C. for 60 minutes.
The surface thickness of the solid lubricating phase of each sample, the penetration depth, the area ratio of the solid lubricating phase on the sliding surface, roughness Rz (JIS B 0601 2001), oil content (open porosity), friction coefficient and Evaluation of durability is as shown in Table 1.

(Measurement of surface thickness)
The surface thickness of the solid lubricating phase was obtained by subtracting the inner diameter of the sintered body before forming the solid lubricating phase from the inner diameter of each sample on which the solid lubricating phase was formed. Specifically, (inner diameter of each sample with solid lubricating phase formed−inner diameter of solid lubricating phase)/2 was calculated.

(Measurement of penetration depth)
The penetration depth of the solid lubricating phase was determined by cutting each sample along the axial direction and observing the cross section on the inner peripheral surface side with an electron microscope (SEM: Scanning Electron Microscope). Since the solid lubricating phase uses molybdenum disulfide (MoS ₂ ) as a solid lubricant, the penetration depth was confirmed by performing mapping using Mo and S as extraction elements.

(Measurement of area ratio)
Each sample (oil-impregnated sintered bearing) is divided into two in the axial direction, elemental analysis of the sliding surface surface of the sample is performed by SEM at any one point, Mo and S are mapped as extracted elements, and an image is obtained. The image was binarized using processing software (see FIG. 5), and the area in which Mo and S elements were detected was expressed as a ratio to the area of the entire image, and was defined as an area ratio.

(Measurement of roughness Rz (JIS B 0601 2001))
Roughness Rz (JIS B 0601 2001) was measured using a roughness meter (SE700 manufactured by Kosaka Laboratory Co., Ltd.). Palpation was performed using a chisel-type stylus with an R of 1 mm to eliminate as much as possible the effect of stoma on measurements.

(Measurement of oil content)
The oil content was measured according to JIS Z 2501.

(Measurement of friction coefficient)
A shaft (shaft) made of S45C as a sliding object is inserted into the bearing hole of each sample arranged in a direction perpendicular to the direction of gravity, and the shaft is rotated to rotate the shaft. The coefficient of friction of the samples was evaluated. A break-in operation and measurement were performed at room temperature under the conditions of a load on the shaft of 3 MPa and a rotational speed of 100 m/min. The coefficient of friction was measured when the friction coefficient stabilized after running in. The friction coefficient was obtained by measuring the torque generated in the bearing as a load using a load cell (UT-1K manufactured by MinebeaMitsumi Co., Ltd.) and then converting the distance from the measurement position.

(Evaluation of durability)
Durability evaluation was carried out for each sample having the oil content shown in Table 1 under the conditions of room temperature, surface pressure against the shaft of 3 MPa, and sliding speed (rotational speed) of 100 m/min for 150 hours of continuous operation. evaluated. In this evaluation, it was judged as "stopped" when it stopped due to seizure or abrasion powder, and it was judged as "no abnormality" when it was able to operate continuously for 150 hours. The evaluation results are as shown in Table 1.

As shown in Table 1, in Examples 1 to 7 in which the lubricating phase is dispersed on the sliding surface and part of the lubricating phase penetrates inside, the coefficient of friction is as low as 0.125 or less. It was found that the slidability can be improved. Moreover, the samples of Examples 1 to 7 did not show any abnormalities even after continuous operation for 150 hours, and thus maintained high slidability. Among these, in Examples 1, 3 and 5, the area ratio of the solid lubricating phase on the sliding surface is 10% or more and 60% or less, and the penetration depth of the solid lubricating phase into the sintered component body (bearing body) was 50 µm or more and the roughness Rz (JIS B 0601 2001) of the sliding surface was 5 µm or less, the coefficient of friction was particularly small, 0.089 or less, and it was found that the slidability could be further improved.

On the other hand, in Comparative Example 1, since no solid lubricating phase was formed, the coefficient of friction was as high as 0.153, and the slidability could not be improved. In Comparative Example 1, since no solid lubricating phase was formed, the surface was seized after 3 hours of operation, and the operation was stopped. In addition, in Comparative Example 2, since the solid lubricating phase was formed on the entire sliding surface, the lubricating oil supply to the sliding surface was insufficient, and the shaft was supported only by the solid lubricating phase with low strength. Therefore, the coefficient of friction was as high as 0.193 due to the generation of excessive abrasion powder, and the slidability could not be improved. In addition, the progress of wear on the sliding surface was rapid, and after 25 hours of operation, abrasion powder was deposited, and the operation was stopped.

1 sintered oil-impregnated bearing 10 bearing body (sintered body, sintered part body)
11 bearing hole 12 sliding surface

Claims (13)

A sintered sliding part having a porous sintered part body made of a sintered metal and having a sliding surface for slidably supporting a sliding object,
On the sliding surface, a solid lubricating phase containing a solid lubricant and a ground surface in which a large number of pores of the sintered part body are opened are dispersedly formed, and the area of the solid lubricating phase on the sliding surface A sintered sliding part, wherein the ratio is 10% or more and 60% or less, and part of the solid lubricating phase permeates into the body of the sintered part. 2. A sintered sliding component according to claim 1, wherein said sliding surface has a roughness Rz (JIS B 0601 2001) of 5 μm or less. 3. The sintered sliding part according to claim 2, wherein the penetration depth of said solid lubricating phase into said sintered part body is 50 [mu]m or more. The sintered sliding part according to any one of claims 1 to 3, wherein the solid lubricating phase contains a resin. The sintered sliding part according to any one of claims 1 to 4, wherein the main component of the sintered part main body is an iron-based metal. The sintered sliding part according to any one of claims 1 to 5, wherein the solid lubricant contains a substance having cleavability or a substance softer than the object to be slid. 7. The sintered sliding part according to claim 1, wherein at least part of said pores are impregnated with lubricating oil. The sintered sliding part according to claim 7, wherein the solid lubricating phase has lipophilicity. A method for manufacturing a sintered sliding component according to any one of claims 1 to 8,
A molding step of filling the raw material powder into a molding die and pressing to form a green compact, a sintering step of sintering the green compact to form a sintered body, and solid lubrication to the sintered body. an impregnation step of impregnating a diluent mixed with an agent, a heating step of heating the sintered body after the impregnation step to volatilize the liquid content of the diluent, and the sintered body after the heating step A method of manufacturing a sintered sliding component, comprising: a sizing step of sizing to obtain a sintered component body. 10. The method of manufacturing a sintered sliding part according to claim 9, wherein the diluted liquid is mixed with the solid lubricant and the resin binder. 11. The method of manufacturing a sintered sliding part according to claim 9, further comprising a lubricating oil impregnation step of impregnating the lubricating oil after the sizing step. 12. In the impregnation step, the sintered body is impregnated with the diluent mixed with the solid lubricant having a particle size smaller than the opening diameter of the pores in the sliding surface. A method for manufacturing a sintered sliding component according to any one of Claims 1 to 3. 13. The method according to any one of claims 9 to 12, further comprising a filling step for filling at least part of the pores by processing a region other than the sliding surface region of the sintered body before the impregnation step. A method for manufacturing a sintered sliding part according to claim 1.

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