WO2016043284A1

WO2016043284A1 - Slide member and method for producing same

Info

Publication number: WO2016043284A1
Application number: PCT/JP2015/076545
Authority: WO
Inventors: 容敬伊藤; 隆宏後藤; 里路　文規
Original assignee: Ntn株式会社; 容敬伊藤; 隆宏後藤; 里路　文規
Priority date: 2014-09-19
Filing date: 2015-09-17
Publication date: 2016-03-24

Abstract

　A starting material powder mainly containing a metal powder is molded to form a metal powder compact 3', which is sintered to from a metal substrate 3. Lubricating members 4 are formed from an aggregate of graphite particles 13, and the lubricating members 4 constitute at least a portion of a bearing surface 11. After the lubricating members 4 are fitted into the metal powder compact 3', the metal powder compact 3' is sintered, during which time the lubricating members 4 are secured to the metal substrate 3 by contractile force F arising in the metal powder compact 3'.

Description

Sliding member and manufacturing method thereof

The present invention relates to a sliding member and a manufacturing method thereof.

A sintered bearing, which is a kind of sliding member, is obtained by impregnating a porous metal body manufactured by powder metallurgy with a lubricating oil. Lubricating oil retained in the air holes inside the bearing oozes from the inside of the bearing to the bearing surface, which is a sliding surface, due to the pumping action and heat generated by the rotation of the shaft, and forms a lubricating oil film on the bearing surface. (For example, Patent Document 1).

JP 2010-175002 A JP 2013-14645 A Japanese Utility Model Publication No. 06-32812 JP 2000-266056 A

In recent years, it has been desired to provide sintered bearings that can be used under severe conditions such as high surface pressure and high temperature. However, in existing sintered bearings, metal contact due to breakage of the lubricating oil film is likely to occur under high surface pressure, and the lubricating oil is likely to deteriorate early at high temperatures. Therefore, there is a problem that it is difficult to obtain stable lubricity. Therefore, in Patent Document 1, a proposal has been made to improve the composition and characteristics of the lubricating oil impregnated in the sintered bearing, thereby increasing the lubricating oil film strength so that it can be used even under high surface pressure. However, as long as the lubricating function is mainly performed by the lubricating oil, use under severe conditions is limited. Further, the sintered bearing impregnated with the lubricating oil as in Patent Document 1 has a problem that it cannot be used in an environment where mixing of the lubricating oil is disliked.

On the other hand, in a sintered bearing as described in Patent Document 1, it is usual to add a solid lubricant such as graphite to the metal powder in order to supplement the lubricity of the bearing surface. However, if the blending amount of the solid lubricant powder is increased too much in order to increase the lubricity, there is a problem that the bonding between the metal particles is inhibited and the material strength is reduced. There is a limit.

Therefore, a first object of the present invention is to provide a sliding member that is low in cost and can maintain a stable lubricating performance even when used in a special environment such as a harsh environment, and a manufacturing method thereof.

Further, the above-mentioned Patent Document 2 shows a sliding member in which a lubricating member is embedded in a sliding surface of a cylindrical base. In this document, as an example of a lubricating member, a fired body mainly composed of artificial graphite is cited. A cylindrical base body of the sliding member is provided with a radial through hole, and a lubricating member is fitted into the through hole and fixed by adhesion.

However, in such a sliding member, it is necessary to fix the lubricating member to the base body with high accuracy, so that the fixing work is troublesome. Moreover, since it is necessary to process the through-hole of a base | substrate and the outer peripheral surface of the lubricating member fitted to this with high precision, processing cost becomes high. In particular, when a carbon-based fired body is used as the lubricating member, the carbon-based fired body is less likely to be plastically deformed, so that shaping by cutting or the like is required to increase the dimensional accuracy, which further increases the processing cost.

Further, Patent Document 3 described above shows an internal gear pump for supplying gasoline as shown in FIG. This gear pump includes an inner rotor 161, a main body 162 having a fixed shaft 162 a inserted in the inner periphery of the inner rotor 161, and an outer rotor 163 that meshes with the inner rotor 161 and is eccentric with respect to the inner rotor 161. The inner rotor 161 is rotated by rotating the outer rotor 163 by the drive unit, and the outer rotor 163, the inner rotor 161, and the main body 162 cooperate to exert a pumping action.

Since the inner rotor 161 provided in this gear pump rotates while sliding with the fixed shaft 162a inserted in the inner periphery, lubricity is required. However, since the inner rotor 161 is in contact with gasoline, lubricating oil that contaminates gasoline cannot be used. For this reason, the carbon ring 164 is sometimes press-fitted into the inner periphery of the inner rotor 161 base.

Even in such an inner rotor 161, it takes time to press-fit the carbon ring 164 into the inner periphery of the base body, and it is necessary to process the base body and the carbon ring 164 with high accuracy, resulting in an increase in manufacturing cost.

Therefore, a second object of the present invention is to increase the productivity of a sliding member using a carbon-based fired body and reduce the manufacturing cost.

Also, a lubricating member whose sliding surface is mainly composed of graphite is used, for example, as a rotor and vane for a vacuum pump, a bearing used in a high temperature environment exceeding 200 ° C., or a bearing for a construction machine. Such a lubricating member is manufactured by compression-molding a raw material powder mainly containing graphite particles to form a green compact, and sintering the green compact. However, since graphite particles themselves hardly undergo plastic deformation, if most of the raw material powder is composed of graphite particles, the raw material powder cannot be hardened by compression molding, and a green compact cannot be formed. For this reason, when molding a green compact mainly composed of graphite, a raw material powder in which graphite particles and a binder such as tar pitch or coal tar are mixed is used (for example, the above-mentioned patents). Reference 4).

However, in order to form a green compact by the method as described above, it is necessary to use nearly 50 wt% of the raw material powder as a binder (see paragraph 0010 of Patent Document 4). For this reason, a large amount of decomposition gas is generated due to the decomposition of the binder during sintering, resulting in problems of contamination of the sintering furnace and exhaust gas. In order to reduce such a problem, it is necessary to proceed with the sintering slowly over a long time, and the productivity is significantly lowered.

Therefore, a third object of the present invention is to increase the productivity of a lubricating member whose sliding surface is mainly made of graphite.

A first invention of the present application is a sliding member having a sliding surface that slides with a mating member, a metal base formed by sintering a raw material powder mainly composed of metal powder, and solid lubricant particles And a lubricating member made of an aggregate, wherein at least a part of the sliding surface is constituted by a lubricating member, and the lubricating member is fixed to a metal substrate by a sintering operation for sintering the raw material powder. Is.

In such a configuration, the lubricating member formed on at least a part of the sliding surface is a solid lubricant supply source. Since the solid lubricant supplied from the lubricating member spreads over the entire sliding surface by relative sliding with the counterpart member, a lubricating effect can be obtained over the entire sliding surface. Further, in the sliding member, the mating member does not necessarily slide with respect to the entire sliding surface, and a limited partial area of the sliding surface may slide with the mating member. is there. In that case, design the position and shape of the lubrication member so that the lubrication member is located in the sliding area with the mating member, or install the sliding member so that the lubrication member is located in the sliding area. By adjusting, it becomes possible to always slide the counterpart member with respect to the lubricating member. Further, if the area of the lubricating member appearing on the sliding surface is increased, the lubricating effect can be enhanced. Even in such a case, the strength of the sliding member can be avoided since the bonding force between the metal particles does not decrease unlike the conventional product.

On the other hand, in the case where the lubricating member is arranged only in a partial region of the sliding surface, there is a problem of how to fix the lubricating member to the base metal base. On the other hand, the present invention adopts a new technical means that the lubricating member is fixed to the metal substrate by a sintering operation when the metal substrate is sintered. If the lubricating member is fixed to the metal substrate by a sintering operation that is indispensable in the manufacturing process of the sliding member, it is not necessary to perform a fixing operation in a process unrelated to the original manufacturing process of the sintered metal such as press-fitting or adhesion. Therefore, near net shape molding of the sliding member is possible, and the cost of the sliding member can be reduced.

As an example of a structure for fixing the lubrication member and the metal base, it is conceivable that the lubrication member and the metal base are brought into an interference fit state by a contraction force generated in the metal base in association with the sintering operation.

In this case, the lubricating member can be formed by firing a powder containing solid lubricant powder and a binder.

The coated powder formed by coating the solid lubricant powder with metal can be sintered by the sintering operation to form a lubricating member. In this case, as another example of the structure for fixing the lubrication member and the metal base, it is conceivable that the metal of the coating powder is diffused into the metal powder constituting the metal base to bond the lubrication member and the metal base.

Sizing the sliding surface, a highly accurate sliding surface can be obtained at low cost. This sizing can be performed on only one of the metal base and the lubricating member. Sizing may be performed not only on the sliding surface but also on other surfaces as necessary. Since sizing itself is usually performed even with an existing sintered metal sliding member, even if such treatment is performed, it does not cause an increase in cost.

The sliding member described above bakes a powder containing solid lubricant powder and a binder to form a lubricating member, forms a raw material powder containing metal powder as a main component to form a molded body, and The lubricating member is brought into contact with the molded body so that a part of the lubricating member appears on the surface to be a sliding surface, and in that state, the lubricating member and the molded body are heated at a sintering temperature, and the molded body is sintered. It can be manufactured by forming a metal substrate and fixing the lubricating member to the metal substrate with a shrinkage force generated in the compact during the sintering.

In addition, the sliding surface of the first powder mainly composed of a powder coated with a solid lubricant powder with a metal and the second powder mainly composed of a metal powder in a state where both powder filling regions are separated. A molded body is formed by molding so that the first powder appears on the surface to be formed, and the molded body is heated at a sintering temperature to form a lubricating member by sintering the first powder, and the second powder. A metal base is formed by sintering, and the lubricating member is fixed to the metal base by diffusing the metal of the coating powder contained in the first powder into the metal powder of the second powder during the sintering operation. A moving member can be manufactured.

A highly accurate sliding surface can be obtained at low cost by sizing the sliding surface after fixing the lubricating member to the metal substrate.

The second invention of the present application is a sliding member having a sliding surface that slides with a counterpart material, the carbon-based fired body comprising carbon as a main component and constituting at least a part of the sliding surface, and the carbon-based material Provided is a sliding member that is a resin injection-molded product using a fired body as an insert part and has a resin base body integrated with the carbon-based fired body. This sliding member is formed by compressing a raw material powder containing carbon-based powder as a main component to form a green compact, and firing the green compact to form carbon constituting at least a part of the sliding surface. Through a fired body forming process for forming a carbon fired body and an insert molding process for forming a resin substrate integrated with the carbon fired body by injection molding with a resin using the carbon fired body as an insert part Can be manufactured.

Thus, in the sliding member according to the present invention, the carbon-based fired body and the resin base are integrated by injection-molding the resin with the carbon-based fired body as an insert part. This eliminates the need for fixing the carbon-based fired body and the resin substrate, thereby reducing the number of steps and improving productivity. In addition, it is not necessary to form a through-hole for attaching the carbon-based fired body to the resin base, and it is not necessary to form the carbon-based fired body with high precision so as to fit into the through-hole. Reduced.

In the above-described sliding member, sizing is performed on an integrated product of the carbon-based fired body and the resin base, whereby the dimensional accuracy in the state of the integrated product (particularly the surface accuracy of the sliding surface) can be increased. In particular, when the sliding member has a plurality of separately formed carbon-based fired bodies, by sizing the integrated product of the plurality of carbon-based fired bodies and the resin base, The sliding surface can be arranged at a predetermined position (for example, on the same cylindrical surface).

In the above sliding member, if oil is impregnated in the internal pores of the carbon-based fired body, the oil oozes out on the sliding surface, and the lubricity is further improved. In this case, for example, the internal pores of the carbon-based fired body can be impregnated with oil by immersing an integrated product of the carbon-based fired body and the resin base in oil.

In the above sliding member, it is preferable to use, for example, a resin mainly composed of a crystalline resin as the resin forming the resin base.

The above sliding member can be used, for example, as a bearing or gear having a sliding surface on the inner peripheral surface. Specifically, for example, the sliding member described above can be used as a gear for an oil supply pump having a sliding surface that slides on the inner peripheral surface with the outer peripheral surface of the shaft and a tooth surface on the outer peripheral surface.

The third invention of the present application is a method of manufacturing a lubricating member in which graphite particles occupy the largest area on a sliding surface, and is a pressure for obtaining a green compact by compression molding the raw material powder containing the graphite particles to which a binder metal powder is adhered. Provided is a method for producing a lubricating member, which includes a powdering step and a sintering step for bonding the binder metals by sintering the green compact at a temperature equal to or lower than the melting point of the binder metal.

A lubricating member in which graphite particles occupy the largest area on the sliding surface by the above manufacturing method, wherein a binder metal is attached to each graphite particle, and the binder metal is bonded by sintering. Obtainable.

Thus, the lubricating member of the present invention is in a state where the binder metal is interposed between the graphite particles contained in the raw material powder by using the raw material powder containing the graphite particles to which the binder metal is adhered. Thus, the binder metal is plastically deformed during compression molding, so that the raw material powder is hardened and the green compact can be molded. Moreover, the graphite particles can be bonded to each other through the binder metal by bonding the binder metals attached to the graphite particles by sintering. As described above, since the binder of the raw material powder can be omitted (or reduced), generation of decomposition gas during sintering can be suppressed, and the productivity can be improved by shortening the sintering time.

According to the first invention of the present application, it is possible to provide a sliding member having high lubrication performance while being low in cost. With this sliding member, it is possible to obtain high lubrication performance in a special environment, for example, in a severe environment such as high temperature, high surface pressure, and high speed rotation, or in an environment where it is difficult to use lubricating oil.

According to the second invention of the present application, the productivity of the sliding member using the carbon-based fired body can be increased and the manufacturing cost can be reduced.

According to the third invention of the present application, it is possible to increase the productivity of the lubricating member whose sliding surface is mainly composed of graphite.

It is a front view of the sintered bearing concerning 1st embodiment of this invention 1st invention. FIG. 2 is a cross-sectional view taken along line BB of the sintered bearing of FIG. It is a front view of a sintered body. It is a side view of a sintered body. It is sectional drawing which shows granulated powder. It is sectional drawing of the baked lubricating member. It is a front view of a metal substrate. It is sectional drawing of plating powder. It is sectional drawing which shows a compression molding process. It is sectional drawing which shows a compression molding process. It is sectional drawing which shows a compression molding process. It is sectional drawing which shows a compression molding process. It is sectional drawing which shows a compression molding process. It is sectional drawing which shows a compression molding process. It is the front view and principal part enlarged view of the sintered bearing concerning 2nd embodiment of this invention 1st invention. It is a front view which shows other embodiment of a sintered bearing. It is a front view which shows other embodiment of a sintered bearing. It is a model figure which shows the metal powder before sintering. It is a model figure which shows the metal powder after sintering. It is a disassembled perspective view of an internal gear pump. It is sectional drawing which shows the fitting part of an outer rotor and an inner rotor. It is a front view of the sliding member (bearing) which concerns on one Embodiment of this-application 2nd invention. It is sectional drawing in the BB line of the sliding member of Fig.18 (a). It is an expanded sectional view of a carbon system calcination object. It is sectional drawing which shows an insert molding process. It is the top view which looked at the insert molding process of FIG. 20 from the C direction. It is sectional drawing which shows a sizing process. It is sectional drawing which shows a sizing process. It is an expanded sectional view of the carbon-type sintered body of the sliding member which concerns on other embodiment. It is a front view which shows other embodiment of a sliding member. It is a front view which shows other embodiment of a sliding member. It is a front view which shows other embodiment of a sliding member. It is a front view which shows other embodiment of a sliding member. It is a front view which shows other embodiment (inner rotor for oil supply pumps) of a sliding member. FIG. 29 is a cross-sectional view taken along line AA of the sliding member of FIG. 28. It is a front view which shows other embodiment (planetary gear) of a sliding member. It is a disassembled perspective view of an internal gear pump. It is sectional drawing of the particle | grains of the copper adhesion graphite powder by which all the surfaces of the graphite particle were covered with copper. It is sectional drawing of the particle | grains of the copper adhesion graphite powder by which a part of surface of the graphite particle was covered with copper. It is an expanded sectional view of the sliding surface vicinity of the sliding component which concerns on embodiment of this-application 3rd invention.

Hereinafter, a sintered bearing is taken as an example of the sliding member according to the first invention of the present application, and details thereof will be described with reference to FIGS.

As shown in FIGS. 1A and 1B, the sintered bearing 1 has a cylindrical shape, and a cylindrical bearing surface 11 is formed as a sliding surface on the inner periphery thereof. By inserting a shaft 2 (indicated by a two-dot chain line) as a mating member into the inner periphery of the sintered bearing 1, the shaft 2 is rotatably supported by the bearing surface 11. When the shaft 2 is a rotating shaft, the outer peripheral surface 12 of the sintered bearing 1 is fixed to an inner peripheral surface of a housing (not shown) by means such as press fitting or adhesion. In this way, in addition to the shaft 2 being the rotating side, the shaft 2 can be the stationary side and the sintered bearing 1 can be the rotating side.

The sintered bearing 1 illustrated in FIGS. 1A and 1B includes a metal base 3 made of sintered metal and a lubricating member 4 made of an aggregate of many graphite particles. The metal substrate 3 has holding portions 3a for holding the lubricating member 4 at a plurality of locations equally arranged in the circumferential direction. Each holding portion 3 a is a recess opened in the inner peripheral surface 3 b of the metal base 3, and its cross section (cross section in a direction orthogonal to the axial direction) is formed in a shape that matches the cross sectional shape of the lubricating member 4. The holding portion 3a in the present embodiment has a shape of a partial cylindrical surface obtained by cutting out a partial region in the circumferential direction of the cylindrical surface, and the shaft of the metal substrate 3 is opened at both axial end surfaces of the metal substrate 3. It is formed in the same shape over the entire length.

The lubricating member 4 is formed in a shape (partial cylindrical shape) that matches the shape of the holding portion 3a of the metal base 3. The peripheral surface of the lubricating member 4 includes an outer surface 4 a that faces the holding portion 3 a of the metal base 3 and an inner surface 4 b that faces the outer peripheral surface of the shaft 2. The outer side surface 4a is formed in a convex cylindrical surface shape in surface contact with the holding portion 3a of the metal base 3, and the inner side surface 4b is formed in a concave cylindrical surface shape continuous with the inner peripheral surface 3b of the metal base member 3 without a step. The inner peripheral surface 3b of the metal base 3 and the inner side surface 4b of the lubricating member 4 constitute a bearing surface 11 having a perfectly circular cross section as a sliding surface.

In the sintered bearing 1, the lubricating member 4 formed on a part of the bearing surface 11 serves as a supply source of graphite particles. Since the graphite particles supplied from the lubricating member 4 are distributed over the entire bearing surface 11 by the relative movement of the bearing surface 11 and the shaft 2, a lubricating effect can be obtained over the entire bearing surface 11.

Further, in the sintered bearing 1, the shaft 2 does not necessarily slide with respect to the entire bearing surface 11, and a limited partial region of the bearing surface 11 often slides with the shaft 2. For example, when the shaft 2 is in a horizontal posture, the shaft 2 often falls due to gravity and comes into sliding contact with the bearing surface 11 in the lower region of the bearing surface 11. In that case, the position and shape of the lubricating member 4 are designed so that the lubricating member 4 is located in the sliding region with the shaft 2, or the circle of the sintered bearing 1 is arranged so that the lubricating member 4 is located in the sliding region. By adjusting the phase in the circumferential direction, the shaft 2 can always be slid with respect to the lubricating member 4. Therefore, a high lubrication effect can be obtained, and the shaft 2 can be supported even in an oilless state where no lubricating oil is interposed on the bearing surface 11. Therefore, the sintered bearing 1 that can withstand use under severe conditions such as high temperature, high surface pressure, and high speed rotation can be provided.

When graphite particles are dispersed on the bearing surface, as in existing sintered bearings, to improve lubricity, it is possible to increase the concentration of graphite particles on the bearing surface by increasing the blending ratio of graphite powder to the raw material powder. Further, the excessively blended graphite particles inhibit the bonding between the metal particles, so that the strength of the sintered bearing is reduced. Therefore, there is a limit to improving the lubricity. On the other hand, if at least a part of the sliding surface is formed of the lubricating member 4 made of an aggregate of solid lubricant particles (graphite particles or the like) as described above, the number of the lubricating members 4 can be increased or the lubricating members can be increased. By simply increasing the size of 4, the amount of graphite particles supplied to the bearing surface 11 can be increased to enhance the lubrication effect. Even in this case, since the bond strength between the metal particles in the metal substrate 3 does not decrease, a decrease in the strength of the sintered bearing 1 can be avoided.

On the other hand, when a part of the bearing surface 11 is constituted by the lubricating member 4 which is an aggregate of graphite particles, how to fix the lubricating member 4 to the metal base 3 becomes a problem. If press-fitting is employed as the fixing means, it is necessary to machine both fitting surfaces with high precision by machining or the like in order to obtain an appropriate press-fitting allowance, and the machining cost increases. In addition, if bonding is employed as the fixing means, a new bonding process is required, leading to a reduction in productivity. In any case, the greatest merit of the sintered bearing 1 of cost reduction by near net shape molding is reduced.

In view of such a problem, the present invention adopts a new configuration in which the lubricating member 4 is fixed to the metal base 3 by a sintering operation when the raw material powder is sintered to form the metal base 3. This is based on the new idea of securing the fixing force by physical change or chemical change of the metal structure by the sintering operation.

As described above, as a first method for fixing the lubricating member 4 to the metal base 3 by the sintering operation, it is conceivable to use the contraction force F of the metal base 3 generated by the sintering operation. Hereinafter, the manufacturing process of the sintered bearing 1 by this method will be described as a first embodiment.

Lubrication member 4 is formed by molding and firing raw material powder containing graphite powder as solid lubricant powder and a binder. In this case, if mixed powder of binder powder and graphite powder is used as raw material powder, the flowability of graphite powder is low, so when a large amount of graphite powder is included in graphite powder, the mixed powder is formed into a predetermined shape It becomes difficult to do. Therefore, as raw material powder, it is preferable to use granulated graphite powder 7 obtained by granulating a plurality of graphite powders 6 in the presence of a binder 5 as shown in FIG.

As the graphite powder used in the granulated graphite powder 7, either natural graphite powder or artificial graphite powder can be used. Natural graphite powder is generally scaly and has excellent lubricity. On the other hand, the artificial graphite powder is characterized by a lump shape and excellent formability. Therefore, it is preferable to use granulated graphite powder using natural graphite powder when emphasizing lubricity, and to use artificial graphite powder when emphasizing formability. As the binder, for example, a resin material such as a phenol resin can be used.

The granulated graphite powder 7 described above is uniformly mixed by adding a molding aid, a lubricant, a modifier or the like as necessary. The mixture is supplied to a molding die and subjected to pressure molding to form a molded body 4 ′ (graphite powder molded body) corresponding to the shape of the lubricating member 4, as shown in FIGS. 2 (a) and 2 (b). Thereafter, the graphite powder molded body 4 ′ is fired at, for example, a furnace temperature of 900 ° C. to 1000 ° C. to obtain a porous fired body (lubricating member 4). Firing is performed in an atmosphere without oxygen, for example, in an inert gas atmosphere such as nitrogen gas or in a vacuum atmosphere. This is because when oxygen is present in the atmosphere, graphite powder is volatilized and disappears as CO or CO ₂ during firing.

FIG. 4 schematically shows the microstructure of the fired lubricating member 4. The resin binder contained in the granulated graphite powder by firing becomes a carbide (amorphous amorphous carbon) and constitutes a binder component 14 having a network structure. In the mesh of the binder component 14, graphite particles 13 as solid lubricant particles derived from the graphite powder are retained. The graphite particles 13 are held by the surface of the binder component 14 being entangled with the surface of the graphite particles 13. Reference numeral 15 in the figure is a number of holes formed in the microstructure. On the surface of the lubricating member 4, the graphite particles 13 occupy 60% or more, preferably 80% or more in area ratio, so that high lubricity can be obtained when sliding with the shaft 2.

On the other hand, the metal substrate 3 is a normal manufacturing process adopted for sintered bearings, that is, a raw material powder mainly composed of metal powder is compression-molded with a molding die, and the molded body (metal powder molded body) is heated and sintered. Manufactured by bonding. As the metal substrate 3, any kind of sintered metal is used including copper-based copper-based, iron-based iron-based, copper and iron-based copper-iron-based. Can do. In addition, special sintered metals such as aluminum-bronze can be used.

For example, in a copper-iron based sintered bearing, a mixture of iron powder, copper powder, and low melting point metal powder is used as raw material powder. The low-melting point metal is a component for melting itself at the time of sintering to advance liquid phase sintering, and a metal having a lower melting point than copper is used. Specifically, a metal having a melting point of 700 ° C. or lower, such as tin (Sn), zinc (Zn), phosphorus (P), etc., can be used, and among these, Sn that is compatible with copper is preferably used. . The low melting point metal can be added by alloying with other metal powders in addition to adding the simple powder to the mixed powder.

In addition to the above metal powder, a sintering aid such as calcium fluoride and a lubricant such as zinc stearate are added to the raw material powder as necessary, and graphite powder as a solid lubricant powder is further added. You can also By adding the graphite powder, the graphite particles can be dispersed in the sintered structure of the metal base 3 after sintering, so that the lubricity at the portion of the bearing surface 11 formed by the metal base 3 is further increased. Can be increased.

In the molding step, the raw material powder is filled in the mold and compressed to form a molded body 3 ′ (metal powder molded body) having a shape corresponding to the metal substrate 3 as shown in FIG. 5. In the metal powder molded body 3 ′, a recess 3 a ′ corresponding to the holding portion 3 a of the metal base 3 is formed at the time of molding.

Next, the fired body (lubricant member 4) manufactured by the above-described procedure is fitted into each recess 3a 'of the metal powder molded body 3' by a clearance fit. Thereafter, the assembly of the metal powder molded body 3 ′ and the lubricating member 4 is subjected to a sintering temperature necessary to sinter the metal powder molded body 3 ′ (for example, 750 if the metal powder molded body 3 ′ is a copper iron-based material). To about 900 ° C.) to sinter the metal powder compact 3 ′. During the sintering, the fired lubricating member 4 is also heated, but the structure of the lubricating member 4 does not change during heating, and the structure and form of the lubricating member 4 are maintained before and after firing. .

Incidentally, at the stage of the metal powder molded body before sintering, as shown in FIG. 15A, the metal powders P1 and P2 are in contact with each other (the interparticle distance at this time is E). On the other hand, when the metal powder molded body is sintered, as shown in FIG. 15 (b), the partial structures of the adjacent metal powders P1 ′ and P2 ′ diffuse to the other side. The distance e is smaller than the inter-particle distance E before sintering (E> e). Since the distance between the particles is reduced as the sintering proceeds, the shrinking force F in the direction of reducing both the inner diameter surface and the outer diameter surface of the sintered metal base 3 (see FIG. 1A). The shrinkage force F causes the fitting of the metal base 3 and the lubricating member 4 to shift from the gap fitting state to the tight fitting state. Therefore, it is possible to securely fix the lubricating member 4 to the metal base 3 and prevent the lubricating member 4 from being dropped during use. In particular, as shown in FIG. 1A, if the opening width D0 of the holding portion 3a in the metal base 3 is smaller than the maximum width D (diameter dimension) of the lubricating member 4, the inner diameter side of the lubricating member 4 is increased. Can be more reliably regulated.

The shrinkage of the metal powder molded body 3 ′ during sintering can be reinforced by using irregularly shaped particles as particles constituting the metal powder, for example. In this case, the irregularly shaped particles become spherical with sintering, and the distance between the particles becomes small, so that the contraction of the molded body 3 ′ becomes more remarkable. Typical examples of iron powder and copper powder include reduced powder, atomized powder, electrolytic powder, etc., but using reduced iron powder in the form of a porous sponge as iron powder, and electrolytic copper in dendritic form as copper powder. If powder is used, since the irregularity degree is large, a high contraction force F can be obtained. Therefore, if it is desired to increase the shrinkage force F, it is preferable to use reduced iron powder or electrolytic copper powder as the iron powder or copper powder in the raw material powder. By adding other types of iron powder to the reduced iron powder or adding other types of copper powder to the electrolytic copper powder, the magnitude of the shrinkage force F generated during sintering can be adjusted.

The sintered product that has undergone the sintering process is transferred to the sizing process, and the dimensions of the surface parts (inner peripheral surface, outer peripheral surface, and both end surfaces) are corrected by recompression in the mold. At this time, by sizing at least the inner peripheral surface that becomes the bearing surface 11, it is possible to obtain the bearing surface 11 with a high roundness and to obtain stable bearing performance. Since the bearing surface 11 is finally finished by sizing as described above, there may be a step between the inner peripheral surface 3b of the metal base 3 and the inner side surface 4b of the lubricating member 4 at the end of sintering. Absent. When there is a level difference that cannot be corrected by sizing, machining such as cutting is applied to the entire inner peripheral surface of the sintered product, that is, the inner peripheral surface 3b of the metal base 3 and the entire inner surface 4b of the lubricating member 4. Then sizing.

The sintered bearing 1 shown in FIGS. 1A and 1B is completed through the sizing process. The sintered bearing 1 is basically used as a dry bearing that is not impregnated with lubricating oil or liquid grease. However, if necessary, an oil impregnation treatment for impregnating them may be performed after sizing, and the lubricating oil component may be held in the pores of one or both of the metal substrate 3 and the lubricating member 4.

As a second method for fixing the lubricating member 4 to the metal substrate 3 by a sintering operation, it is conceivable to form the lubricating member 4 from a material that can be sintered. Hereinafter, the structure of the sintered bearing 1 by this method and its manufacturing process will be described as a second embodiment.

In the second embodiment, the lubricating member 4 is formed by sintering a molded body obtained by molding a raw material powder. In this case, the raw material powder is mainly composed of a coating powder obtained by coating a solid lubricant powder with a metal. As the coating powder, as shown in FIG. 6, for example, plating powder 9 obtained by plating solid lubricant powder 6 with metal 8 (electroless plating) can be used (in the following description, metal 8 is referred to as “coating metal”). Called). The solid lubricant powder 6 is preferably graphite powder, and the coating metal 8 is preferably copper (Cu) or nickel (Ni). The plating powder 9 is most preferably one in which the entire surface of the graphite powder 6 is coated with the coating metal 8, but it is not always necessary to cover the entire surface, and a part of the surface of the graphite powder 6 is outside the single plating powder 9. It may be exposed. The ratio of the covering metal 8 in the plating powder 9 is 10 wt% or more and 80 wt% or less, preferably 15 wt% or more and 60 wt% or less, more preferably 20 wt% or more and 50 wt% or less. If the amount of the coating metal 8 is too small, the proportion of the graphite powder 6 exposed on the surface of the plating powder 9 increases, and the bonding strength between the sintered particles becomes insufficient. On the other hand, if the amount of the covering metal 8 is too large, the amount of graphite exposed on the inner surface 4b of the lubricating member 4 that becomes the bearing surface 11 decreases, and the lubricity of the lubricating member 4 decreases. In addition, since specific gravity is substantially the same with copper and nickel, even if it uses any of copper and nickel as the covering metal 8, a substantial difference does not arise in a preferable weight ratio.

As the graphite powder 6 used in the plating powder 9, artificial graphite powder is preferably used. This is because if scaly natural graphite powder is used, it is difficult to sufficiently coat the graphite powder 6 with the coating metal 8. If the coating of the graphite powder 6 with the coating metal 8 is insufficient, the coating metals 8 of the plating powder cannot be bonded together in the subsequent sintering step, and the strength cannot be ensured.

In order to firmly bond the coating metals 8 of the plating powder 9, the raw material powder contains a low melting point metal. As a method of inclusion, it is conceivable to add a single powder of a low melting point metal to the plating powder 9 or to deposit the coated metal 8 alloyed with the low melting point metal around the graphite powder 6 at the time of plating. As in the first embodiment, the low melting point metal can be a metal having a melting point of 700 ° C. or lower, such as tin (Sn), zinc (Zn), phosphorus (P), etc., among which Sn is used. It is preferable to do this.

In this case, the ratio of the low melting point metal to the coated metal 8 is set in the range of 0.3-5 wt%, preferably 0.5-3 wt%. If the proportion of the low melting point metal is too small, the liquid phase sintering does not proceed, so that the required strength cannot be obtained. Conversely, if the proportion of the low melting point metal is too large, the inner surface of the lubricating member 4 that becomes the bearing surface 11 The amount of graphite exposed to 4b is reduced, and the inner side surface 4b is unnecessarily hardened and the lubricity of the lubricating member 4 is lowered.

In addition to the above powder (plating powder and low melting point metal powder if necessary), a sintering aid and a lubricant are added to the raw material powder forming the lubricating member 4 as necessary.

In this second embodiment, the raw material powder for forming the metal substrate 3 is the same as the raw material powder for forming the metal substrate 3 of the first embodiment, so a duplicate description is omitted. Hereinafter, the manufacturing process of the sintered bearing 1 will be described with the raw material powder of the lubricating member 4 (including the plating powder 9) as the first powder Ma and the raw material powder of the metal base 3 as the second powder Mb.

In the molding process of this embodiment, a so-called two-color molding (multicolor molding) method is adopted in which the first powder Ma and the second powder Mb are supplied to the same mold and simultaneously molded. In this two-color molding, two cavities are defined in a mold, and each cavity is filled with powder and molded.

An example of a mold for two-color molding is shown in FIG. This mold includes a die 21, a core pin 22 disposed on the inner periphery of the die 21, a lower punch 23 disposed between the inner peripheral surface of the die 21 and the outer peripheral surface of the core pin 22, and a partition member 25 ( 8), a conical guide 28 (see FIG. 8), and an upper punch 29 (see FIG. 12). The guide 28 is provided for facilitating the filling of the first powder Ma into the cavity, and the guide 28 can be omitted if the filling is performed smoothly.

As shown in FIG. 8, the partition member 25 includes an inner partition 26 and an outer partition 27 arranged concentrically. Both

partitions

26 and 27 are configured to be movable up and down independently of each other. The inner partition 26 is formed in a shape corresponding to each lubricating member 4 shown in FIG.

In this compression molding step, first, as shown in FIG. 7, the core pin 22 and the lower punch 23 are raised with the partition member 25 and the guide 28 retracted from the mold, and the upper end surfaces thereof are set as the upper end surfaces of the die 21. It is arranged at the same level as 21a. The retracting direction of the partition member 25 and the guide 28 with respect to the mold may be either upward or lateral.

Next, as shown in FIG. 8, the partition member 25 and the guide 28 are arranged on the mold, the lower end surface of the inner partition 26 is brought into contact with the upper end surface of the lower punch 23, and the lower end surface of the outer partition 27 is placed on the die 21. Is brought into contact with the upper end surface 21a. Further, the lower end surface of the guide 28 is brought into contact with the upper end surface of the core pin 22. In this state, the space between the inner partition 26 and the guide 28 is filled with the first powder Ma, and the space between the inner partition 26 and the outer partition 27 is filled with the second powder Mb.

Next, as shown in FIG. 9, while maintaining the positions of the lower punch 23 and the inner partition 26, the die 21, the core pin 22, and the outer partition 27 are raised together. Thereby, the inner cavity 24a between the inner partition 26 and the core pin 22 is filled with the first powder Ma, and the outer cavity 24b between the inner partition 26 and the die 21 is filled with the second powder Mb.

Next, as shown in FIG. 10, the inner partition 26 is raised, the inner partition 26 that has partitioned the inner cavity 24a and the outer cavity 24b is removed, and both the

cavities

24a and 24b are integrated. Even if the inner partition 26 is removed in this way, the first powder Ma and the second powder Mb are not completely mixed, and the two powders Ma and Mb are maintained in a separated state (the broken line in the figure is This is a line given for convenience in order to express the boundary between Ma and Mb of both powders).

Next, as shown in FIG. 11, the partition member 25 and the guide 28 are removed, and the excess powder overflowing from the

cavities

24a and 24b is removed, and then the upper punch 29 is lowered as shown in FIG. The first powder Ma and the second powder Mb in the cavity are compressed to produce a molded body 1 ′.

Thereafter, the molded body 1 ′ is taken out from the mold and sintered at a temperature higher than the melting point of the low melting point metal and lower than the melting point of the coating metal 8 (copper or nickel) of the plating powder 9 (for example, about 750 to 900 ° C.). Thus, the sintered bearing 1 shown in FIG. 13 is completed. At this time, the lubricating member 4 is formed by sintering the first powder Ma, and the metal base 3 is formed by sintering the second powder Mb.

During this sintering, the low melting point metal contained in the inner first powder Ma is melted and wets the coating metal 8 (for example, copper) of the plating powder 9 to become an alloy with the coating metal 8. By this alloying, the surface of the coating metal 8 is melted at a temperature lower than its melting point, and the coating metal 8 of the plating powder 9 is bonded by this melt, and the first powder Ma becomes a sintered body.

The alloy melt of the coating metal 8 and the low-melting-point metal penetrates into the compact made of the second powder Mb, diffuses into the metal powder contained in the second powder Mb, and forms metal powders (for example, iron powders, copper Powders or iron powder and copper powder) are combined. When the second powder Mb contains a low melting point metal, copper, or the like, the metal powders contained in the second powder Mb are bonded together by the same action. Further, even when the second powder Mb is made of iron-based powder and does not contain low melting point metal and copper, the alloy melt generated in the first powder Ma diffuses into the iron powder of the second powder Mb, and iron Combine the powders together. Due to the above-described action, the entire molded body 1 ′ becomes a sintered body, so that a high-strength sintered bearing 1 can be obtained. Further, since the boundary portion between the metal base 3 and the lubricating member 4 also has a sintered structure without an interface, the lubricating member 4 can be reliably fixed by the metal base 3.

On the other hand, since the graphite powder 6 contained in the plating powder 9 of the first powder Ma basically remains without moving to the second powder Mb side, the lubricating member 4 has a structure containing the graphite particles richly. Become.

Thereafter, similarly to the first embodiment, at least the bearing surface 11 is sized, and further oil-impregnated as necessary, whereby the sintered bearing 1 shown in FIG. 1B and FIG. 13 is completed.

By the way, since almost the entire surface of the plating powder 9 is covered with the coating metal 8, most of the inner side surface 4b of the lubricating member 4 is covered with metal particles derived from the coating metal 8 immediately after the sintering step. It is in the state. In the subsequent sizing step of the bearing surface 11, if the metal particles on the inner side surface 4b of the lubricating member 4 are peeled or dropped by sliding with a sizing die (for example, a core rod), a large amount of graphite particles are exposed on the inner side surface 4b. The distribution amount (area ratio) of the graphite particles on the inner side surface 4b can be increased to the same extent as in the first embodiment. When sizing the bearing surface 11 in order to effectively remove or drop off the metal particles, an operation such as sizing the inner peripheral surface of the sintered product with a sizing type, for example, pressing the sintered product into a die and firing it. It is preferable to perform an operation of pressing the inner peripheral surface of the product against the sizing die and sliding the sizing die in the axial direction in this state.

Even if the amount of graphite particles exposed on the inner surface 4b of the lubricating member 4 in the initial state is insufficient, if the shaft 2 (see FIG. 1B) is rotated thereafter, the shaft 2 and Thus, the metal particles covering the inner side surface 4b are peeled off and dropped, and a necessary and sufficient amount of graphite particles appears on the inner side surface 4b.

In the sintered bearing 1 of the second embodiment, when the inner partition 26 is removed, it is inevitable that both powders are mixed in the vicinity of the boundary between the first powder Ma and the second powder Mb. Therefore, there is no clear interface between the metal base 3 and the lubricating member 4, and the concentration of each element between the metal base 3 side and the lubricating member 4 side is as shown in the enlarged view of FIG. 13. A transition layer X having a gradient is formed.

As a third embodiment, the sintered bearing 1 can be manufactured by a combination of the first embodiment and the second embodiment. The manufacturing procedure of the sintered bearing 1 in the third embodiment is as follows. That is, the lubricating member 4 is formed by molding and sintering the raw material powder containing the plating powder 9 as a main component in the same manner as in the second embodiment. Next, the lubricating member 4 is fitted into the recess 3a ′ of the metal powder molded body 3 ′ (see FIG. 5) described in the first embodiment, and in this state, the metal powder molded body 3 ′ and the lubricating member 4 are separated. The resulting assembly is heated at the sintering temperature to sinter the metal powder compact 3 ′. The lubricating member 4 is fixed to the metal base 3 by the shrinkage force F generated in the metal powder molded body 3 ′ during the sintering. Then, the sintered bearing shown in FIGS. 1A and 1B can be obtained by sizing at least the bearing surface 11.

In the above description, the bearing is illustrated as an example of the sliding member. However, the sliding member of the present invention can be widely used as a member that supports the counterpart member that performs relative motion. The relative motion here includes not only rotational motion but also linear motion. Moreover, as a form of the member of the other party, arbitrary forms, such as planar shape other than a shaft shape, are employable. Also, the form of the sliding member is arbitrary, and is not limited to the cylindrical shape as in the sintered bearing 1, but may be a flat form called a sliding pad.

In the above description, the case where the lubricating members 4 are arranged at a plurality of locations in the circumferential direction of the metal base 3 is illustrated, but the form of the lubricating members 4 is not limited to this. For example, as shown in FIG. 14 (a), the lubricating member 4 continuously arranged in the circumferential direction is arranged so as to cover the substantially half circumference of the bearing surface 11, or as shown in FIG. It can also be arranged to cover substantially the entire circumference.

Furthermore, the lubricating member 4 may be arranged in a spiral shape with the shaft center as the center, in addition to being arranged along the axial direction as shown in FIGS. As a result, it is possible to pass the lubricating member 4 through each part of the shaft 2 in the axial direction at least once during one rotation, so that good lubricity can be obtained. Further, as shown in FIGS. 1A and 1B, the lubricating member 4 may be disposed only in a partial region in the axial direction in addition to the entire length in the axial direction of the metal base 3. In any case, the effect of the present invention can be obtained if at least a part of the bearing surface 11 is formed of the lubricating member 4.

In addition, the lubricating member 4 can be extended in the radial direction, and a part of the mounting surface (for example, the outer peripheral surface 12 of the metal base 3) with respect to the other member of the sliding member can be constituted by the lubricating member 4.

In the above description, the case where graphite is used as the solid lubricant constituting the lubricating member 4 is exemplified. However, solid lubricants other than graphite, such as molybdenum disulfide, can be widely used.

The use of the sliding member described above is not limited, but it is suitable for use under severe conditions such as high temperature, high surface pressure, and high speed rotation. For example, it can be used for a bearing for a fuel pump in an automobile engine, a bearing for an EGR valve of an exhaust gas circulation device (EGR device) installed for the purpose of reducing nitrogen oxide (NOx) in exhaust gas, and the like. is there. In these applications, since the bearings are required to have corrosion resistance against gasoline and waste gas, it is preferable to use an aluminum-bronze system having excellent corrosion resistance as the metal substrate 3. In addition, it can also be used as a bearing or the like used for an arm joint part in a construction machine (bulldozer, hydraulic excavator, etc.).

The sliding member described above can also be used as a driven element (gear, pulley, etc.) that is rotatably supported by a fixed shaft in the torque transmission mechanism. Depending on the use of the driven element, it may not be preferable to interpose lubricating oil in the sliding portion between the fixed shaft, and the sliding member of the present invention is suitable for such use. For example, a fueling gear pump is disposed in a measuring machine installed in a gas station or the like, and a driven gear may be disposed in a fueling path of the fueling gear pump. In this case, it is not preferable to impregnate the driven gear with the lubricating oil in order to avoid the mixing of the lubricating oil into the fuel, kerosene or the like. Therefore, it is preferable to use the sliding member of the present invention that can obtain high lubricity without using lubricating oil as the driven gear used for such applications.

FIG. 16 shows an exploded perspective view of an internal gear pump used as the above-mentioned oil supply gear pump. As shown in the figure, this gear pump has a main body 51 on the stationary side, an outer-tooth type inner rotor 52 (driven gear), and an inner-tooth type outer rotor 53. The outer rotor 53 is provided with a drive shaft 53a that is driven by a rotational drive source such as a motor. The main body 51 is provided with a fixed shaft 51a that is eccentric with respect to the drive shaft 53a, and the shaft hole 52a of the inner rotor 52 is rotatably fitted to the outer periphery of the fixed shaft 51a. As shown in FIG. 17, the inner rotor 52 is arranged eccentrically on the inner diameter side of the outer rotor 53 with its outer teeth meshing with the inner teeth of the outer rotor 53. The number of teeth of the outer rotor 53 is one or more than the number of teeth of the inner rotor 52.

In such a configuration, when the outer rotor 53 is driven to rotate, the inner rotor 52 also receives a rotational force due to the meshing of the teeth and rotates in the same direction following the outer rotor 53. As a result, the volume of the space between the teeth is enlarged and reduced, so that gasoline and the like can be sucked and discharged.

In this oil supply gear pump, the inner rotor 52 as the driven gear has the metal base 3 and the lubricating member 4 fixed to the inner peripheral surface of the metal base 3, similarly to the sintered bearing 1 already described. The metal substrate 3 is obtained by sintering raw material powder containing metal powder as a main component, and has a gear shape having a plurality of teeth on the outer periphery and holes on the inner periphery. The lubricating member 4 is made of an aggregate of graphite particles, and is fixed to the inner peripheral surface of the metal substrate 3 by a sintering operation in which the raw material powder of the metal substrate 3 is sintered. The inner peripheral surface of the lubricating member 4 constitutes a sliding surface (shaft hole 52a) that slides with the outer peripheral surface of the fixed shaft 51a. Each configuration of the metal base 3 and the lubricating member 4 and a fixing method for both are common to the first to third embodiments of the sintered bearing 1. Since the metal substrate 3 is also required to have corrosion resistance against gasoline, it is preferable to use an aluminum-bronze system having excellent corrosion resistance as the metal substrate 3.

After the lubricating member 4 is fixed to the metal base 3, the inner rotor 52 shown in FIG. 16 is completed by performing finishing processing such as sizing and cutting on the inner peripheral surface of the lubricating member 4 as necessary. The metal base 3 and the lubricating member 4 are not impregnated with lubricating oil.

Since the inner rotor 52 having such a configuration does not contain lubricating oil, it is possible to avoid mixing the lubricating oil into the fuel and kerosene supplied by the measuring machine. On the other hand, since the sliding surface has high lubricity, the torque cross at the inner rotor 52 can be minimized.

Next, a bearing is taken as an example of the sliding member according to the second invention of the present application, and details thereof will be described with reference to FIGS.

18 (a) and 18 (b), the bearing 101 has a cylindrical shape, and a shaft 102 (shown by a chain line) as a counterpart material is inserted into the inner periphery thereof. A bearing surface 111 as a sliding surface that slides on the shaft 102 is provided on the inner peripheral surface of the bearing 101. In the present embodiment, the outer peripheral surface 112 of the bearing 101 is fixed to an inner peripheral surface of a housing (not shown) by means such as press-fitting or bonding, and the shaft 102 inserted into the inner periphery of the bearing 101 is rotatably supported. In this way, in addition to the shaft 102 being the rotation side, the shaft 102 can be the stationary side and the bearing 101 can be the rotation side.

The bearing 101 includes a carbon-based fired body 103 containing carbon as a main component (a component having the largest weight ratio) and a resin base body 104 that holds the carbon-based fired body 103. In the present embodiment, a plurality (five in the illustrated example) of carbon-based fired bodies 103 are arranged at equal intervals in the circumferential direction, and the plurality of carbon-based fired bodies 103 are collectively held on the resin substrate 104. . Each carbon-based fired body 103 is exposed on the inner peripheral surface of the bearing 101 and constitutes a part of the bearing surface 111. In the illustrated example, each carbon-based fired body 103 has an inner side surface 103 a exposed on the inner peripheral surface of the bearing 101 and an outer side surface 103 b in close contact with the resin substrate 104. The inner side surface 103 a of each carbon-based fired body 103 is formed in a concave cylindrical surface shape that is continuous with the inner peripheral surface 104 a of the resin substrate 104 without a step. In the present embodiment, the inner surface 103a of each carbon-based fired body 103 and the inner peripheral surface 104a of the resin substrate 104 constitute a bearing surface 111 having a perfect circular cross section. The outer surface 103b of each carbon-based fired body 103 is formed in a convex cylindrical surface shape, and is in close contact with the holding surface 104b of the concave cylindrical surface shape of the resin substrate 104 throughout the entire area.

In this bearing 101, the carbon-based fired body 103 constituting a part of the bearing surface 111 is a supply source of graphite particles. The graphite particles supplied from the carbon-based fired body 103 spread over the entire bearing surface 111 due to the relative movement of the bearing surface 111 and the shaft 102, so that the lubricating effect of the graphite particles can be obtained on the entire bearing surface 111.

Further, in the bearing 101, the shaft 102 does not necessarily slide with respect to the entire bearing surface 111, and a limited partial region of the bearing surface 111 often slides with the shaft 102. For example, when the shaft 102 is in a horizontal posture, the shaft 102 often falls due to gravity and slides with the bearing surface 111 in the lower region of the bearing surface 111. In that case, the position and shape of the carbon-based fired body 103 in the bearing 101 are designed so that the carbon-based fired body 103 is positioned in the sliding region with the shaft 102, or the circumferential phase of the bearing 101 is adjusted. Thus, the shaft 102 can always slide with the carbon-based fired body 103. As a result, a high lubricating effect can be obtained, so that the shaft 102 can be supported in an oilless state in which no lubricating oil is interposed between the bearing surface 111 and the like, for example. Of course, it can also be used in a state where lubricating oil is interposed between the bearing surface 111 and the shaft 102, and in this case, the lubricating effect is further enhanced. In the present embodiment, lubricating oil is interposed between the bearing surface 111 and the shaft 102, and the internal pores of the carbon-based fired body 103 are impregnated with oil. In this case, oil oozes out from the surface (inner surface 103a) of the carbon-based fired body 103 due to a temperature rise accompanying the rotation of the shaft 102, and this oil is supplied to the sliding region between the bearing surface 111 and the shaft 102. The oil film in the sliding region is surely avoided, and excellent slidability is maintained.

The bearing 101 is manufactured through a fired body forming process, an insert molding process, a sizing process, and an oil impregnation process. Hereinafter, each process will be described in detail.

[Firing body forming step]
The carbon-based fired body 103 is formed using a raw material powder containing a carbon-based powder and a resin binder powder. As the carbon-based powder, for example, graphite powder can be used, and specifically, any of natural graphite powder and artificial graphite powder can be used. Natural graphite powder has a feature of excellent lubricity because it is in the form of scales. On the other hand, artificial graphite powder has a feature that it is excellent in formability because it is in a lump shape. The carbon-based powder is not limited to the graphite powder that is a crystalline powder, and amorphous powders such as pitch powder and coke powder can also be used. For example, phenol resin powder can be used as the resin binder powder.

The graphite powder and the resin binder powder described above are mixed uniformly by adding a molding aid, a lubricant, a modifier or the like as necessary. The mixture is supplied to a mold and then compression molded to form a green compact corresponding to the shape of the carbon-based fired body 103. Thereafter, the green compact is fired at, for example, a furnace temperature of 900 to 1000 ° C. to obtain a porous carbon-based fired body 103. Firing is performed in an atmosphere without oxygen, for example, in an inert gas atmosphere such as nitrogen gas or in a vacuum atmosphere. This is because if there is oxygen in the atmosphere, the graphite powder volatilizes and disappears as CO or CO ₂ .

As a raw material powder for the carbon-based fired body 103, a mixed powder of graphite powder and resin binder powder as described above is used, and a granulated graphite powder obtained by granulating graphite powder in the presence of a resin binder is used. You can also. Since the granulated graphite powder has a larger specific gravity and higher fluidity than a single resin binder powder or graphite powder, the granulated graphite powder can be easily supplied to a mold and can be accurately molded into a predetermined shape.

FIG. 19 schematically shows the microstructure of the carbon-based fired body 103. The resin binder contained in the granulated graphite powder by firing becomes a carbide (amorphous amorphous carbon) and constitutes a binder component 114 having a network structure. In the mesh of the binder component 114, graphite particles 113 as solid lubricant particles derived from graphite powder are held. The graphite particles 113 are held by the surface of the binder component 114 entangled with the surface of the graphite particles 113. Reference numeral 115 in the figure is a number of holes formed in the microstructure. On the surface (particularly the inner side surface 103a) of the carbon-based fired body 103, the graphite particles 113 occupy 60% or more, preferably 80% or more in terms of area ratio. Therefore, high lubricity is achieved when sliding with the shaft 102. can get.

[Insert molding process]
By using the carbon-based fired body 103 as an insert part and injection-molding with a resin, an integrated product of the plurality of carbon-based fired bodies 103 and the resin substrate 104 holding the carbon-based fired body 103 is formed. As shown in FIG. 20, the molding die 120 used here includes a fixed die 121 and a movable die 122. The fixed die 121 is provided with a cylindrical portion 121a, and the inner peripheral surface 104a of the resin base body 104 is formed by the outer peripheral surface of the cylindrical portion 121a. Of the fixed mold 121, a gate 121b is provided on a molding surface 121c for molding the end surface of the resin substrate 104. In the present embodiment, a plurality (three in the illustrated example) of gates 121b are arranged on the molding surface 121c of the fixed die 121 at equal intervals in the circumferential direction (see FIG. 21). The gate type is not limited to the dotted gate as in the illustrated example, and may be, for example, an annular film gate.

In the insert molding process, first, a plurality of carbon-based fired bodies 103 are arranged at predetermined locations on the outer periphery of the cylindrical portion 121a of the fixed mold 121. In this state, the cavity 123 is formed by clamping the movable mold 122 and the fixed mold 121, and the plurality of carbon-based fired bodies 103 are disposed in the cavity 123. At this time, each carbon-based fired body 103 is sandwiched between the fixed mold 121 and the movable mold 122 from both sides in the axial direction. As a result, each carbon-based fired body 103 is fixed at a predetermined location in the cavity 123, and positional deviation at the time of injection of the molten resin is prevented.

Then, molten resin is injected into the cavity 123 from the runner 121d through the gate 121b, and the cavity 123 is filled with the molten resin. Examples of the synthetic resin that is the main component (the largest component by weight) of the molten resin include polyamide (PA), polycarbonate (PC), polybutylene terephthalate (PBT), polyacetal (POM), and liquid crystal polymer (LCP). , Wholly aromatic polyester, polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyamideimide (PAI), polyetherimide (PEI), polyimide (PI), polytetrafluoroethylene / perfluoroalkylvinylether copolymer Fluorine resins (polyfluorinated olefin resins) such as (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), and olefins such as polyethylene Such as butter, and the like. Each of these synthetic resins may be used alone or may be a polymer alloy in which two or more kinds are mixed.

As the main component of the resin that forms the resin substrate 104, it is preferable to use a crystalline resin. A crystalline resin is superior in mechanical strength and has a large molding shrinkage rate compared to an amorphous resin. By using a crystalline resin having excellent mechanical strength, the rigidity of the resin substrate 104 is improved. Further, by using a crystalline resin having a high molding shrinkage rate, the holding surface 104b of the resin substrate 104 is reduced in diameter by molding shrinkage when the molten resin is injected into the cavity and then solidified, and the resin substrate 104 is carbon-based fired. The body 103 is securely grasped (details will be described later). Examples of the crystalline resin include LCP, PEEK, PBT, PPS, PA, and POM. For example, at least one or more crystalline resins selected from the group of crystalline resins consisting of LCP, PEEK, and PPS are excellent in chemical resistance, heat resistance, and the like. Among crystalline resins, PPS is a particularly preferable material because it is excellent in chemical resistance and cost. In this embodiment, the resin substrate 104 is formed of a resin composition containing PPS as a main component and various fillers. As PPS, cross-linked PPS, semi-cross-linked PPS, linear PPS and the like can be used. For example, linear PPS excellent in toughness is preferably used.

充填 Filler is added for the purpose of improving friction and wear characteristics and reducing the linear expansion coefficient. Specific examples of the filler include, for example, fibers such as glass fibers, carbon fibers, aramid fibers, alumina fibers, polyester fibers, boron fibers, silicon carbide fibers, boron nitride fibers, silicon nitride fibers, metal fibers, and cloths thereof. Knitted in shape, minerals such as calcium carbonate, talc, silica, clay, mica, inorganic whiskers such as aluminum borate whisker and potassium titanate whisker, various heat resistant resins such as polyimide resin and polybenzimidazole, etc. It is done. In addition, additives such as antistatic agents (carbon nanofibers, carbon black, graphite, etc.), mold release agents, flame retardants, weather resistance improvers, antioxidants, and pigments may be added as appropriate.

In this embodiment, carbon fiber that is a fibrous reinforcing material and PTFE that is a solid lubricant are added as fillers. By blending carbon fibers, mechanical strength such as flexural modulus is improved, and by blending PTFE, sliding characteristics with respect to the shaft 102, the cylindrical portion 121a of the molding die 120, and the like are improved. Carbon fibers are roughly classified into pitch systems and PAN systems, and any of them can be used. For example, carbon fibers having an average fiber diameter of 20 μm or less and an average fiber length of 0.02 to 0.2 mm are used. The blending ratio of the carbon fibers is, for example, 10% by mass or more and 40% by mass or less, preferably 20% by mass or more and 30% by mass or less with respect to the entire resin base 104. The blending ratio of PTFE is, for example, 1% by mass or more and 40% by mass or less, and preferably 2% by mass or more and 30% by mass or less with respect to the entire resin substrate 104.

Thereafter, the resin filled in the cavity 123 is cooled and solidified to form the resin substrate 104. At this time, due to resin molding shrinkage, the holding surface 104b of the resin base 104 is reduced in diameter, and the outer surface 103b of the carbon-based fired body 103 is pressed {see arrow F in FIG. 18 (a)}. As a result, the holding surface 104b of the resin substrate 104 and the outer surface 103b of the carbon-based fired body 103 are brought into close contact with each other, so that both are firmly fixed. At this time, the opening width D0 in the circumferential direction of the holding surface 104b of the resin base 104 (that is, the circumferential width of the inner side surface 103a of the carbon-based fired body 103) is set to the maximum width D (in the circumferential direction of the holding surface 104b). If it is smaller than (approximately the diameter of the carbon-based fired body 103), the falling of the carbon-based fired body 103 toward the inner diameter side can be more reliably regulated. In addition, although the inner peripheral surface 104a of the resin substrate 104 is reduced in diameter by the resin substrate 104 being molded and contracted as described above, the carbon-based fired body 103 is moved to the inner diameter side as the resin substrate 104 is reduced in diameter. Thus, the inner side surface 103a of the carbon-based fired body 103 and the inner peripheral surface 104a of the resin substrate 104 are maintained in a continuous state.

[Sizing process]
Next, sizing by molding is performed on the integrated product 101 ′ of the carbon-based fired body 103 and the resin base body 104. Specifically, first, as shown in FIG. 22A, the core pin 131 is inserted into the inner periphery of the integrated product 101 ′. At this time, the inner peripheral surface 111 ′ (the inner surface 103 a of the carbon-based fired body 103 and the inner peripheral surface 104 a of the resin base body 104) of the integrated product 101 ′ and the outer peripheral surface of the core pin 131 are interposed through a slight radial gap. It is mated. Then, in a state where the axial width of the integrated product 101 ′ is defined by the upper punch 132 and the lower punch 133, the integrated product 101 ′, the core pin 131, and the upper and

lower punches

132, 133 are integrated as shown in FIG. The integrated product 101 ′ is pressed into the inner periphery of the die 134. As a result, the outer peripheral surface 112 ′ of the integrated product 101 ′ is formed on the inner peripheral surface of the die 134, and at the same time, the integrated product 101 ′ is pressed from the outer periphery, and the inner peripheral surface 111 ′ of the integrated product 101 ′ is Pressed against the outer peripheral surface. Thereby, the inner peripheral surface 104a of the resin base 104 is plastically deformed following the outer peripheral surface of the core pin 131, and the radial position of each carbon-based fired body 103 is corrected. Specifically, by pressing a plurality of carbon-based fired bodies 103 against a common core pin 131, each carbon-based fired body 103 is arranged at a predetermined radial position, and the inner side surface 103a of each carbon-based fired body 103 is the same. Arranged on a cylindrical surface.

In this way, by performing sizing on the integrated product 101 ′ composed of the carbon-based fired body 103 and the resin base 104, the carbon-based fired body 103 and the resin base 104 can be processed without performing high-precision processing. The surface accuracy (cylindricity and roundness, coaxiality with respect to the outer peripheral surface 112 ′, etc.) of the peripheral surface 111 ′ (bearing surface 111) can be increased. In the present embodiment, the carbon-based fired body 103 is mainly composed of carbon (graphite particles 113 and a binder component 114 made of a carbide of a resin binder), and therefore hardly undergoes plastic deformation. Therefore, each carbon-based fired body 103 itself is hardly sized, and the surface of the inner side surface 103 a pressed against the core pin 131 is only slightly adjusted.

[Oil impregnation process]
Thereafter, oil is impregnated in the internal pores of the carbon-based fired body 103 of the integrated product 101 ′ (bearing 101) that has undergone the sizing process. Specifically, after the integrated product 101 ′ is immersed in the lubricating oil under a reduced pressure environment, the internal pores of the carbon-based fired body 103 are impregnated with oil by returning to the atmospheric pressure. Thus, the bearing 101 is completed.

The present invention is not limited to the above embodiment. Hereinafter, although other embodiment of this invention is described, description is abbreviate | omitted about the point which overlaps with said embodiment.

In the above-described embodiment, the case where a resin is used as the binder for holding the graphite particles as the carbon-based fired body 103 is shown. However, the carbon-based fired body 103 may be formed using a metal binder. it can. Specifically, for example, a raw material powder containing, as a main component, a coating powder obtained by coating a part or all of the surface of a carbon-based powder with a metal is used. As the coating powder, for example, a plating powder obtained by plating graphite particles with a metal (electroless plating) can be used. For example, copper or nickel is preferably used as the metal that coats the graphite particles (hereinafter referred to as the coating metal). In the present embodiment, copper-coated graphite powder in which the surface of graphite particles is coated with copper is used as the plating powder.

The ratio of the coating metal in the plating powder is 10% by mass to 80% by mass, preferably 15% by mass to 60% by mass, and more preferably about 20% by mass to 50% by mass. If the amount of the coating metal is too small, the proportion of the graphite powder exposed on the surface of the plating powder increases and the bond strength between the particles after firing becomes insufficient. On the other hand, if the amount of the coated metal is too large, the amount of graphite exposed on the inner surface 103a of the carbon-based fired body 103 constituting the bearing surface 111 is reduced, and the lubricity of the carbon-based fired body 103 is lowered. In addition, since specific gravity is substantially the same with copper and nickel, even if it uses any of copper and nickel as a covering metal, a substantial difference does not arise in a preferable weight ratio.

It is preferable to use artificial graphite powder as the graphite powder used for the plating powder. This is because if scaly natural graphite powder is used, it is difficult to sufficiently coat the graphite powder with a coating metal. If the coating of the graphite powder with the coating metal is insufficient, the coating metals of the plating powder cannot be bonded together in the subsequent firing step, and the strength cannot be ensured. Further, it is preferable to use non-granulated graphite particles in order to increase the ratio of graphite in each particle.

Thus, by covering the graphite particles having a small specific gravity with metal, the apparent density is increased and the fluidity of the graphite particles is increased, so that the filling property to the molding die is improved, and the raw material powder is added to the molding die. It becomes possible to fill uniformly. In addition, when compression molding the raw material powder, the graphite particles are not plastically deformed, but the metal covering each graphite particle meshes with each other while being plastically deformed, and can be molded into a predetermined shape without using a resin binder. Become.

In order to firmly bond the coating metal of the plating powder, the raw powder contains a low melting point metal. As a method of inclusion, it is conceivable to add a single powder of a low melting point metal to the plating powder, or to deposit a coated metal alloyed with the low melting point metal around the graphite particles during plating. The low melting point metal is a component for allowing liquid phase sintering to proceed by melting itself during sintering. As the low melting point metal, a metal having a melting point lower than the sintering temperature is used. Specifically, a metal having a melting point of 700 ° C. or lower, such as tin (Sn), zinc (Zn), phosphorus (P), etc. Is used. If a general sintered metal such as copper-based, iron-based, or copper-iron-based is used, it is preferable to use Sn that is compatible with copper.

In this case, the ratio of the low melting point metal to the coated metal is set in the range of 0.3 to 5% by mass, preferably 0.5 to 3% by mass. If the proportion of the low-melting point metal is too small, the required strength cannot be obtained because the liquid phase sintering does not proceed. Conversely, if the proportion of the low-melting point metal is too large, the carbon-based fired body 103 constituting the bearing surface is not obtained. The amount of graphite exposed on the inner side surface 103a is reduced, and the inner side surface 103a is unnecessarily hardened, so that the lubricity of the carbon-based fired body 103 is lowered.

In addition to the above powder (plating powder and low melting point metal powder if necessary), a sintering aid and a lubricant are added to the raw material powder forming the carbon-based fired body 103 as necessary. To do.

The raw material powder having the above composition is compression-molded to form a green compact, which is sintered by heating at a sintering temperature lower than the melting point of the coated metal and higher than the melting point of the low-melting metal. A body (carbon-based fired body 103) is obtained. Specifically, a low-melting-point metal (for example, tin) in the raw material powder is melted, and a part thereof diffuses into the coated metal to form an alloy layer on the surface of the coated metal. The plating powders are bonded together by diffusion bonding these alloy layers in a solid state. Further, among the molten low melting point metals, those that have not diffused into the coating metal play a role like glue by solidifying between the plating powders, and contribute to an improvement in the bonding force between the plating powders.

By the way, if the raw material powder of the green compact contains a resin binder, the resin binder is decomposed during firing to generate decomposition gas, and the dimensional change due to disappearance of the resin binder due to firing increases. In order to suppress such generation of cracked gas and dimensional change, it is necessary to heat the green compact for a long time and to proceed with firing slowly. On the other hand, in this embodiment, since the green compact does not contain a resin binder as described above, sintering can be performed in a relatively short time, and productivity is increased.

As shown in FIG. 23, the carbon-based fired body 103 formed as described above has a structure in which the graphite particles 13 are held in a network formed by joining copper 116 as a covering metal together by sintering. Make it. In FIG. 23, the low melting point metal is not shown.

In the subsequent insert molding process, an integrated product in which the carbon-based fired body 103 is held by the resin substrate 104 is formed, and a sizing process is performed on the integrated product. As shown in FIG. 23, the carbon-based fired body 103 of the present embodiment can be sized by molding because copper 116 that easily undergoes plastic deformation is interposed between the graphite particles 113. Therefore, in the sizing process, not only the inner peripheral surface 104a of the resin base 104 but also the inner surface 103a of the carbon-based fired body 103 is sized, so that the surface accuracy of the bearing surface 111 can be further improved.

In the above embodiment, the case where the carbon-based fired body 103 is exposed only on the inner peripheral surface (bearing surface 111) of the bearing 101 is shown, but the present invention is not limited thereto. For example, in the embodiment shown in FIG. 24, the carbon-based fired body 103 is exposed not only on the inner peripheral surface of the bearing 101 but also on the outer peripheral surface 112. In this case, in the sizing step, each carbon-based fired body 103 can be pressed from both sides in the radial direction, so that sizing is facilitated. In this embodiment, it is preferable to use a carbon-based fired body 103 using a metal binder shown in FIG.

In the above embodiment, the case where the plurality of carbon-based fired bodies 103 are arranged at equal intervals in the circumferential direction has been described, but the present invention is not limited thereto. For example, as shown in FIG. 25, a semi-cylindrical carbon-based fired body 103 that is continuous in the circumferential direction may be disposed so as to cover the substantially half circumference of the bearing surface 111. Alternatively, as shown in FIG. 26, the entire circumference of the bearing surface 111 may be covered with a cylindrical carbon-based fired body 103.

In the above embodiment, the case where the inner surface 103a of the carbon-based fired body 103 and the inner peripheral surface 104a of the resin substrate 104 are arranged in the same cylindrical surface, and the bearing surface 111 is constituted by these is shown. It is not limited to this. For example, as shown in FIG. 27, the inner surface 103a of the carbon-based fired body 103 is arranged on the inner diameter side of the inner peripheral surface 104a of the resin substrate 104, and the bearing surface 111 is configured only by the inner surface 103a of the carbon-based fired body 103. May be. In this case, the inner side surfaces 103a of the plurality of carbon-based fired bodies 103 are arranged on the same cylindrical surface.

Further, the carbon-based fired body 103 may be disposed only in a partial region in the axial direction in addition to being disposed over the entire axial length of the bearing 101 as shown in FIG. 18B, for example, separated in the axial direction. You may arrange | position in multiple places.

Further, the present invention is not limited to a bearing that supports the relative rotation of the shaft, but can also be applied to a bearing that supports the axial movement of the shaft. Further, the present invention is not limited to a cylindrical sliding member, and can be applied to a sliding member having another shape (for example, a semi-cylindrical shape or a rectangular parallelepiped shape).

The sliding member according to the present invention can be used as a gear having a sliding surface on the inner peripheral surface.

For example, the sliding member according to the present invention can be used as an inner rotor 141 incorporated in an oil pump gear, in particular, a positive displacement rotary gear pump as shown in FIG. As shown in FIGS. 28 and 29, the inner rotor 141 includes a carbon-based fired body 103 mainly composed of carbon, and a resin substrate 104 that holds the carbon-based fired body 103. In the present embodiment, the carbon-based fired body 103 is formed in a cylindrical shape, and the entire outer peripheral surface 103 b of the carbon-based fired body 103 is held by the resin substrate 104. The inner peripheral surface 103a of the carbon-based fired body 103 is exposed on the inner peripheral surface of the inner rotor 141, and functions as a sliding surface 111 that slides with the outer peripheral surface of the fixed shaft 162a (see FIG. 31). A tooth surface 141 a that meshes with the outer rotor 163 (see FIG. 31) is formed on the outer peripheral surface of the resin base 104. The inner rotor 141 is manufactured through a fired body forming process and an insert molding process. In addition, a sizing process is performed on the integrated product of the carbon-based fired body 103 and the resin substrate 104 obtained in the insert molding process as necessary. Since each process is the same as that of said embodiment, duplication description is abbreviate | omitted.

Further, the sliding member according to the present invention can be used as the planetary gear 151 (see FIG. 30) constituting the planetary gear reducer. The planetary gears 151 are arranged at a plurality of positions in the circumferential direction between the sun gear and the internal gear (not shown) arranged coaxially, and each planetary gear 151 meshes with both the sun gear and the internal gear.

As shown in FIG. 30, the planetary gear 151 includes a carbon-based fired body 103 containing carbon as a main component and a resin base body 104 that holds the carbon-based fired body 103. In the illustrated example, the carbon-based fired body 103 is formed in a cylindrical shape, and the entire outer peripheral surface 103 b of the carbon-based fired body 103 is held by the resin substrate 104. The inner peripheral surface 103 a of the carbon-based fired body 103 is exposed on the inner peripheral surface of the planetary gear 151 and functions as a sliding surface 111 that slides with the outer peripheral surface of the shaft 102. A tooth surface 151 a that meshes with the sun gear and the internal gear is formed on the outer peripheral surface of the resin substrate 104. The planetary gear 151 is manufactured through a fired body forming process and an insert molding process. Moreover, one or both of a sizing process and an oil impregnation process are performed to the integrated product of the carbon-based fired body 103 and the resin base body 104 obtained in the insert molding process as necessary. Since each process is the same as that of said embodiment, duplication description is abbreviate | omitted.

Next, an embodiment of a lubricating member according to the third invention of the present application will be described with reference to FIGS.

Lubricating members include a compacting process for compressing raw powder to obtain a compact, a sintering process for obtaining a sintered compact by sintering the compact, and a sizing for recompressing and sizing the sintered compact It is manufactured through processes. Hereinafter, details of each process will be described.

(1) Compacting process First, various powders containing graphite particles, a binder metal, and a low melting point metal are mixed to prepare a raw material powder.

As the graphite particles, artificial graphite or natural graphite can be used. The graphite particles are preferably granular (not scale-like or earthy), and granular artificial graphite is used in this embodiment. Further, the graphite particles can be used either non-granulated or granulated. However, in order to granulate the graphite particles, a binder for bonding the graphite particles is required, and the ratio of graphite in each particle is reduced. Therefore, it is preferable to use non-granulated graphite particles.

The binder metal is attached to the surface of each graphite particle. As the binder metal, a metal having a melting point higher than a sintering temperature described later is used. As the binder metal, a material having a hardness lower than that of the graphite particles and easily plastically deformed is used. Specifically, for example, copper or nickel can be used as the binder metal, and copper is used in the present embodiment.

As the low melting point metal, a metal having a melting point lower than the sintering temperature described later is used. As the low melting point metal, for example, tin or zinc can be used, and tin is used in the present embodiment.

The raw material powder is prepared, for example, by mixing copper-adhered graphite powder in which copper as a binder metal adheres to the surface of graphite particles and tin powder that becomes a low melting point metal. In the present embodiment, a copper-plated graphite powder obtained by performing copper plating on the surface of graphite particles is used as the copper-attached graphite powder. Further, as the copper-attached graphite powder, for example, as shown in FIG. 32A, the surface of the graphite particles (Gr) is entirely covered with copper (Cu), or as the copper-attached graphite powder, FIG. As shown in FIG. 4, it is possible to use a material in which copper (Cu) is dispersed and adhered to the surface of graphite particles (Gr) in an island shape. The copper-attached graphite powder shown in FIG. 32 (a) and the copper-attached graphite powder shown in FIG. 32 (b) can be used alone or in combination. In this embodiment, the copper-attached graphite powder shown in FIG. 32 (b) is used alone.

成形 Fill the above-mentioned raw material powder into a molding die. Usually, graphite particles are very fine, so that the fluidity is poor and the filling property into a molding die is poor. In this embodiment, by attaching copper to the graphite particles, the apparent density is increased and the fluidity of the graphite particles is increased, so that the filling property to the molding die is improved, and the raw material powder is uniformly distributed in the molding die. Filling becomes possible.

Thus, the green compact is formed by compression molding the raw material powder filled in the molding die. At this time, the graphite particles are not plastically deformed, but the copper adhering to each graphite particle meshes with each other while being plastically deformed, so that it can be formed into a predetermined shape. This makes it possible to form a green compact composed mainly of graphite particles without using a binder such as tar pitch or coal tar.

(2) Sintering process Next, by heating the green compact obtained in the above compacting process in a sintering furnace, the copper adhering to each graphite powder is bonded by sintering, and the sintered body becomes It is formed. Specifically, when the green compact is heated, the tin powder contained in the green compact is melted, and a part of the tin powder diffuses into the surface layer of copper adhering to each graphite particle, and the copper surface A tin alloy layer is formed. The copper-tin alloy layers are diffusion bonded in a solid state, thereby bonding the copper-plated graphite powders to form a sintered body. The sintering temperature at this time is lower than the melting point of copper and higher than the melting point of tin.

By the way, if the green compact contains a binder such as tar pitch or coal tar as in the case of a conventional lubricating member, a decomposition gas of the binder is generated during sintering, and the binder is almost lost by sintering. Therefore, the dimensional change due to sintering (the dimensional difference between the green compact and the sintered body) increases. In this case, sudden sintering in a short time may cause cracks in the sintered body due to a sudden dimensional change. Therefore, it is necessary to heat the green compact for a long time and proceed with the sintering slowly. there were. On the other hand, in the present embodiment, since the green compact does not contain a binder such as tar pitch or coal tar as described above, no decomposition gas of the binder is generated during sintering, and sintering is performed. Dimensional change due to is suppressed. Accordingly, there is little concern about cracking of the sintered body, and the sintering time can be made relatively short.

(3) Sizing Step As the green compact is sintered as described above, shrinkage occurs. Therefore, it is desirable to size the sintered body by sizing after sintering. For example, a conventional lubricating member formed by firing a green compact including graphite particles and a binder is in a state in which the graphite particles are bound together by a binder carbonized by firing. When sizing such a lubricating member, the graphite particles themselves hardly undergo plastic deformation as described above, and therefore there is a high risk of the lubricating member being damaged. For this reason, it is necessary to perform sizing of the conventional lubricating member by machining, which causes a problem of increasing costs and reducing productivity.

In the sintered body of the present embodiment, since the binder metal is interposed between the graphite particles, the binder metal can be plastically deformed and sized by applying sizing. Specifically, the sintered body is sized to a desired size by compressing the sintered body with a sizing die (die, core, upper punch, and lower punch). This eliminates the need for shaping by machining as in a conventional lubricating member, thereby reducing costs and improving productivity. Thus, the lubricating member is completed.

In this sizing process, the sintered body and the die and core of the sizing mold slide in a pressure contact state. Thereby, copper of the copper plating graphite powder exposed on the surface of the sintered body is peeled off from the graphite particles, and the ratio of the graphite particles exposed on the surface of the sintered body can be increased. Therefore, by sliding the portion that becomes the sliding surface of the sintered body in a pressure contact state with the sizing die, the ratio of the graphite particles exposed to the sliding surface can be increased, and the slidability can be improved. . Of course, if it is not necessary to peel the copper of the copper-plated graphite powder on the sliding surface by sizing in this way, the portion that will become the sliding surface of the sintered body is a surface that does not slide with the sizing die (for example, the upper and lower punches). You may make it contact | abut with an end surface.

The lubricating member 201 formed as described above has graphite particles (Gr), copper (Cu) as a binder metal, and tin (Sn) as a low melting point metal, as shown in an enlarged view in FIG. . In FIG. 33, graphite particles (Gr) are indicated by dots, copper (Cu) is indicated by hatching, and illustration of tin (Sn) is omitted.

The copper adhering to each graphite particle is bonded by sintering. Copper does not melt at the sintering temperature, and is bonded to the copper adhering to other graphite particles in a solid state. Specifically, a part or all of tin melted by sintering diffuses into the copper to form a copper-tin alloy layer on the surface layer, and the copper-tin alloy (bronze) regions are diffusion-bonded to each other. Also, among the tin melted by sintering, the one that has not diffused into the copper solidifies between the copper adhering to each graphite particle, so that this tin plays a role like glue, Contributes to improving power.

The surface of the lubricating member 201, particularly the sliding surface 201a that slides with other parts, occupies the maximum area of graphite particles. For example, the area ratio of the graphite particles on the sliding surface is 50% or more, preferably 80% or more. Preferably, it is 90% or more. In the present embodiment, the lubricating member 201 includes graphite particles having a maximum volume ratio of graphite particles, for example, 50% or more by volume ratio.

As described above, by exposing many graphite particles to the sliding surface, the sliding property between the lubricating member 201 and the counterpart material is enhanced by the self-lubricating property of graphite. For this reason, the lubrication member 201 is suitably used as a lubrication member that slides with the counterpart material in a non-lubricated environment (that is, without interposing a lubricant such as oil). Specifically, the lubricating member 201 can be used as, for example, a rotor and vane for a vacuum pump, a bearing used in a high temperature environment exceeding 200 ° C., or a bearing for construction equipment. The lubrication member 201 is not limited to a use in an unlubricated environment, but can also be used in a use in a lubrication environment in which a lubricant such as oil is interposed to slide with a counterpart material.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the raw material powder is composed of the copper-adhered graphite powder and the tin powder. However, the present invention is not limited to this. For example, a low melting point metal is further added to the surface of the binder metal adhered to the graphite powder. An attached powder may be used. For example, a powder obtained by further tin-plating a copper-plated graphite powder and attaching tin to the copper surface can be used.

In the above embodiment, the lubricating member is made of graphite particles, a binder metal, and a low melting point metal. However, the lubricating member may further contain other metals such as iron.

In the above embodiment, the sintered part has a low melting point metal, but the low melting point metal may be omitted if not particularly necessary. In this case, copper adhering to each graphite particle does not form an alloy layer, and pure copper is diffusion bonded by sintering.

In the above embodiment, the case where the sizing process is performed on the sintered body has been shown. However, when the sizing process is not particularly necessary, the sizing process may be omitted.

The configurations of the embodiments of the first invention of the present application, the second invention of the present application, and the third invention of the present application described above may be combined as appropriate. For example, the lubricating member according to the embodiment of the third invention of the present application may be used for the sliding member (bearing or the like) according to the embodiment of the first invention of the present application or the second invention of the present application.

1 Sintered bearing (sliding member)
2 axis (part on the other side)
3 Metal base 4 Lubricating member 5 Resin binder 6 Graphite powder (solid lubricant powder)
8 Coated metal (metal)
9 Plating powder (coating powder)
11 Bearing surface (sliding surface)
13 Graphite particles (solid lubricant particles)
52 Inner rotor (sliding member)
F contraction force

Claims

A sliding member having a sliding surface that slides with a counterpart member,
A metal base formed by sintering a raw material powder containing metal powder as a main component, and a lubricating member made of an aggregate of solid lubricant particles, wherein at least a part of the sliding surface is constituted by a lubricating member, and A sliding member, wherein a lubricating member is fixed to a metal substrate by a sintering operation for sintering the raw material powder.
The sliding member according to claim 1, wherein the lubricating member and the metal substrate are brought into an interference fit state by a contraction force generated in the metal substrate in association with the sintering operation.
The sliding member according to claim 2, wherein the lubricating member is formed by firing a powder containing solid lubricant powder and a resin binder.
The sliding member according to claim 1, wherein a lubricating member is formed by sintering a coating powder obtained by coating a solid lubricant powder with a metal by the sintering operation.
The sliding member according to claim 4, wherein the metal of the coating powder is diffused in the metal powder constituting the metal base to bond the lubricating member and the metal base.
The sliding member according to any one of claims 1 to 5, wherein the sliding surface is sized.
A manufacturing method of a sliding member having a sliding surface that slides with a counterpart member,
A lubricating member is formed by firing a powder containing solid lubricant powder and a binder,
The raw material powder containing metal powder as a main component is formed to form a metal powder molded body, and the lubricating member is brought into contact with the metal powder molded body so that a part of the lubricating member appears on a surface to be a sliding surface. Let
In this state, the lubricating member and the metal powder molded body are heated at the sintering temperature to form a metal base by sintering the metal powder molded body, and the lubricating member is formed by the shrinkage force generated in the metal powder molded body during the sintering. A method for producing a sliding member, wherein the sliding member is fixed to a metal substrate.
A manufacturing method of a sliding member having a sliding surface that slides with a counterpart member,
The first powder mainly composed of a powder coated with a solid lubricant powder and a second powder mainly composed of a metal powder and a sliding surface in a state where both powder filling regions are separated. Form the molded body so that the first powder appears on the power surface,
The molded body is heated at a sintering temperature to form a lubricating member by sintering the first powder, and to form a metal substrate by sintering the second powder,
A method for manufacturing a sliding member, wherein the lubricating member is fixed to a metal substrate by diffusing the metal of the coating powder contained in the first powder into the metal powder of the second powder during the sintering.
The manufacturing method of the sliding member of Claim 8 which uses the plating powder which gave metal plating to solid lubricant powder as coating powder.
The method for manufacturing a sliding member according to any one of claims 7 to 9, wherein the sliding surface is sized after the lubricating member is fixed to the metal substrate.