JP2019112719A - Sintered shaft bearing for egr valve - Google Patents

Abstract

To provide an aluminum bronze-based sintered shaft bearing for EGR valve enhancing abrasion resistance, corrosion resistance and slidability under high temperature dry environment, and achieving compactification and cost saving, and a manufacturing method of the aluminum bronze-based sintered shaft bearing for EGR valve having good productivity and low cost, and suitable for mass production.SOLUTION: There is provided a sintered shaft bearing for EGR valve 1 containing 9 to 12 wt.% of aluminum, 0.1 to 0.6 wt.% of phosphorus, and 3 to 10 wt.% of graphite, and the balance copper with inevitable impurities, having a structure by sintering an aluminum-copper alloy, and free graphite distributed in a pore dispersively formed.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a sintered bearing for an EGR valve which is excellent in abrasion resistance, corrosion resistance and slidability in a high temperature dry environment, and a method of manufacturing the same.

  Generally, as part of exhaust gas countermeasures for internal combustion engines such as automobile engines, these internal combustion engines again mix the gas once discharged with intake air to reduce the oxygen concentration of the air in the combustion chamber and lower the combustion temperature. An exhaust gas recirculation device (hereinafter, also referred to as an EGR device) for reducing nitrogen oxides (NOx) is widely adopted. EGR is an abbreviation of "Exhaust Gas Recirculation" and means exhaust gas recirculation. In this EGR device, part of the exhaust gas discharged is recirculated to the intake side as recirculated exhaust gas (hereinafter also referred to as EGR gas), but in order to adjust the flow rate of the EGR gas, the recirculation exhaust gas flow rate control A valve (hereinafter also referred to as an EGR valve) is used.

  In recent years, high output and low fuel consumption of internal combustion engines have been remarkable, and demands for weight reduction and downsizing have also been strong, and EGR valves also have to meet these demands. Furthermore, as the EGR valve has come to be placed near the combustion chamber of the engine, it is exposed to a high temperature environment that reaches 300 ° C. or more, combined with the increase in the amount of heat generated by the engine as the output increases. May be Under these conditions of use and environment, the bearings that slidably support the reciprocating shaft that operates the valve of the EGR valve are not resistant to abrasion, corrosion and high temperature dry (oil-free) environments. Mobility is required.

  As a sintered bearing used for such an application, for example, Patent Document 1 discloses a Cu-Ni-Sn-C-P-based sintered bearing.

  On the other hand, an aluminum bronze-based sintered bearing is known as a sintered bearing excellent in mechanical properties and corrosion resistance. In this sintered bearing, it is said that an aluminum oxide film is formed on the surface in the process of raising the temperature during sintering, and a sintered body having sufficient corrosion resistance and strength to inhibit the diffusion of aluminum can not be easily obtained. There's a problem. Patent Document 2 discloses a technology relating to a mixed powder of a sintered aluminum-containing copper alloy and a method for producing the same in order to ameliorate the above problems.

JP, 2006-63398, A JP, 2009-7650, A

  In the sintered bearing of the Cu-Ni-Sn-C-P system described in Patent Document 1, although the strength and the wear resistance are improved, it can not be said that it is sufficient in terms of corrosion resistance. Moreover, since it contains Ni which is a rare metal, there is also a problem in terms of cost.

  Although the aluminum-containing copper alloy powder described in Patent Document 2 is excellent in formability and sinterability, stable corrosion resistance as an aluminum bronze-based sintered bearing using the aluminum-containing copper alloy powder, Further studies are needed to obtain a product suitable for mass production that meets mechanical characteristics, compactness, and cost reduction.

  In view of the conventional problems, the present invention improves the wear resistance, the corrosion resistance, and the slidability in a high-temperature dry environment, as well as the aluminum bronze-based sintered bearing for an EGR valve, which achieves downsizing and cost reduction. It is an object of the present invention to provide a method for producing an aluminum bronze-based sintered bearing for an EGR valve which is good in productivity, low in cost and suitable for mass production.

The present inventors are a new aluminum bronze-based sintered bearing and a method of manufacturing the same, in which expansion due to sintering is effectively used in order to achieve compactness, cost reduction, and improvement in productivity while improving the bearing function. In order to secure performances such as wear resistance, corrosion resistance and slidability under high temperature dry environment in sintered bearings for EGR valve in high temperature dry environment as described above, assuming that the idea is a precondition In the present invention, various studies and test evaluations were conducted, and the following findings were obtained.
(1) As for the slidability in a high temperature dry environment of a sintered bearing for an EGR valve, attention was paid to the fact that the usual aluminum blending amount as an aluminum bronze sintered bearing can be applied since there is no problem of initial conformity.
(2) It was found that the coefficient of friction is lower and the slidability is excellent as the addition amount of graphite is increased in a dry environment. On the other hand, if the amount of addition of graphite is increased, the diffusion of aluminum into copper is inhibited, so it is necessary to consider.
(3) With respect to wear resistance, although the wear resistance is improved by increasing the addition amount of graphite, the wear amount is slightly increased from the addition amount of graphite of 10% by weight, which is considered to be a decrease in material strength.
(4) When the added amount of graphite is increased, the weight change rate due to organic acid corrosion is small, and the weight change rate hardly changes even after being left for a long time.
(5) In the relation between the compounding amount of aluminum and the aluminum bronze structure, as the compounding amount of aluminum increases, the proportion of the β phase increases. The β phase undergoes eutectoid transformation at 565 ° C. to become an α phase and a γ phase, and the proportion of the γ phase increases as the aluminum content increases. The γ phase lowers the resistance to organic acid corrosion in a sintered bearing for an EGR valve. Therefore, when aluminum-copper alloy powder is used as a copper source and the powder of copper alone is not added, the γ phase and the α phase are used. The ratio of
(6) In relation to the sintering temperature and the corrosion resistance, when the sintering temperature is increased, the diffusion of aluminum is enhanced and the corrosion resistance is improved.
(7) Phosphorus, which is an additive, is considered to promote the diffusion of aluminum in the sintering process to reduce the amount of aluminum and to reduce the precipitation of the γ phase of the aluminum structure which deteriorates the corrosion resistance.

  As technical means for achieving the above objects, the present invention comprises 9 to 12% by weight of aluminum, 0.1 to 0.6% by weight of phosphorus and 3 to 10% by weight of graphite, with the balance being A sintered bearing for an EGR valve containing copper as the main component and containing inevitable impurities, the sintered bearing has a structure in which an aluminum-copper alloy is sintered, and is formed in dispersed pores Is characterized by the distribution of free graphite. As a result, it is possible to realize an aluminum bronze-based sintered bearing for an EGR valve which is excellent in wear resistance, corrosion resistance, and slidability in a high-temperature dry environment, and is made compact and cost-reduced.

  Further, the present invention as a method for producing a sintered bearing for an EGR valve contains 9 to 12% by weight of aluminum, 0.1 to 0.6% by weight of phosphorus and 3 to 10% by weight of graphite, A method for producing a sintered bearing for an EGR valve, the main component of which is copper and which contains unavoidable impurities, which comprises aluminum-copper alloy powder, electrolytic copper powder, phosphorus-copper alloy powder and graphite as raw material powders. A forming step of forming a green compact in which a sintering aid is added to the raw material powder using at least a powder, a sintering step of obtaining a sintered body having an aluminum-copper alloy structure from the green compact, and And a sizing step of dimensioning the sintered body. As a result, it is possible to realize a method for producing an aluminum bronze-based sintered bearing for an EGR valve which is excellent in productivity, low in cost, and suitable for mass production. The sintered bearing for an EGR valve manufactured based on this is excellent in abrasion resistance, corrosion resistance and slidability in a high temperature dry environment, and can be made compact and cost reduction.

  The structure of the above-described aluminum-copper alloy preferably has an α phase. The α phase is effective for organic acid corrosion resistance.

  The structure of the above-mentioned aluminum-copper alloy (hereinafter also referred to as aluminum bronze structure) uses aluminum-copper alloy powder as a copper source, and does not add powder of copper alone, the ratio γ of γ phase to α phase It is preferable to set the phase / α phase to 0 ≦ γ phase / α phase ≦ 0.10. If it is the range of 0 <= (gamma) phase / (alpha) phase <= 0.10, it is excellent in organic acid-proof corrosion resistance.

  It is preferable not to add tin as a sintering aid to the above-described sintered bearing for an EGR valve. Tin is not preferable because it interferes with the diffusion of aluminum.

  In the above-described method for manufacturing a sintered bearing for an EGR valve, a total of 100% by weight of the raw material powder comprising the aluminum-copper alloy powder, electrolytic copper powder, phosphorus-copper alloy powder and graphite powder as a sintering aid Preferably, aluminum fluoride and calcium fluoride are added in a total amount of 0.05 to 0.2% by weight. When the amount is less than 0.05% by weight, the effect as a sintering aid is insufficient, and a compact sintered body having appropriate strength can not be obtained. On the other hand, if it exceeds 0.2% by weight, the effect as a sintering aid will be plateaued even if it is added more than 0.2% by weight from the viewpoint of cost.

  It is preferable to set ratio d2 / d1 of the average particle diameter d1 of said aluminum-copper alloy powder and the average particle diameter d2 of electrolytic copper powder to 2-3. When the ratio d2 / d1 is in this range, aluminum can be sufficiently diffused in copper, and the corrosion resistance is excellent.

  The above-mentioned electrolytic copper powder is composed of different powder shapes, and the ratio W2 / W1 of the ratio W1 of electrolytic copper powder having an aspect ratio of 2 or more to the ratio W2 of electrolytic copper powder less than 2 is 3 to 9 Is preferred. Electrolytic copper powder having an aspect ratio of 2 or more is effective for the diffusion of aluminum, but has poor formability. If the ratio W2 / W1 is less than 3, it is not preferable from the viewpoint of formability. On the other hand, if it exceeds 9, the diffusion of aluminum becomes insufficient, which is not preferable. Here, the aspect ratio means the ratio of the major axis length of the powder divided by the thickness of the powder.

  The above-mentioned graphite powder is preferably prepared by granulating fine powder of natural graphite or artificial graphite with a resin binder and then grinding it into a graphite powder having a particle size of 145 mesh or less. Generally, when 4% by weight or more of graphite is added, it can not be molded, but by using granulated graphite, molding was made possible.

  The second invention as a method for producing a sintered bearing for an EGR valve contains 9 to 12% by weight of aluminum, 0.1 to 0.6% by weight of phosphorus and 3 to 10% by weight of graphite, with the remainder being A method for producing a sintered bearing for an EGR valve, the main component of which is copper and which contains unavoidable impurities, wherein the method does not add powder of copper alone as a raw material powder, aluminum-copper alloy powder, phosphorus -Obtaining a sintered body having an aluminum-copper alloy structure from the green compact by using a copper alloy powder and a graphite powder and molding at least a green compact having a sintering aid added to the raw material powder The method is characterized by including a sintering step and a sizing step of dimensioning the sintered body. Here, not adding the powder of copper alone as the raw material powder means that the powder of copper alone which is inevitably contained in the manufacturing site is acceptable.

  The second invention described above as the manufacturing method can also realize the manufacturing method of the aluminum bronze-based sintered bearing for an EGR valve, which has high productivity, is low cost, and is suitable for mass production. Moreover, the sintered bearing for an EGR valve manufactured by this is excellent in abrasion resistance, corrosion resistance, and slidability in a high-temperature dry environment, and can achieve downsizing and cost reduction. Furthermore, since the powder of copper alone is not added, the portion where copper alone is biased is almost eliminated, the occurrence of corrosion due to this portion is avoided, and the corrosion resistance of each grain of the aluminum-copper alloy powder is By the improvement, it is possible to secure corrosion resistance even in a more severe use environment.

  It is preferable that it is 7-11 weight% aluminum-copper alloy powder as said aluminum-copper alloy powder as a raw material powder, for example, it is more preferable that it is 8-10 weight% aluminum-copper alloy powder. In these cases, the corrosion resistance of each grain of the aluminum-copper alloy powder is improved, and the corrosion resistance of the entire sintered bearing for an EGR valve is improved.

  The sintered bearing for an EGR valve according to the present invention is excellent in wear resistance, corrosion resistance, and slidability in a high temperature dry environment, and can be made compact and cost reduction. Further, the method for manufacturing a sintered bearing for an EGR valve according to the present invention can realize a method for manufacturing an aluminum bronze-based sintered bearing for an EGR valve suitable for mass production with good productivity and at low cost.

  Furthermore, according to the second invention as a manufacturing method using aluminum-copper alloy powder without adding powder of copper alone, a portion where copper alone is biased is substantially eliminated, and occurrence of corrosion due to this portion is avoided. By improving the corrosion resistance of each grain of the aluminum-copper alloy powder, it is possible to secure the corrosion resistance to even more severe use environments.

BRIEF DESCRIPTION OF THE DRAWINGS It is a longitudinal cross-sectional view which shows the outline | summary of the EGR valve in which the sintered bearing for EGR valves which concerns on the 1st Embodiment of this invention is used. 1 is a longitudinal sectional view of a sintered bearing for an EGR valve according to a first embodiment of the present invention and a sintered bearing for an EGR valve based on a manufacturing method according to the first embodiment of the present invention. It is a graph which shows the result of a torque test. It is a graph which shows the result of a torque test. It is a graph which shows the test result of abrasion resistance. It is a graph which shows the test result of corrosion resistance. It is a graph which shows the test result of corrosion resistance. It is a figure explaining the manufacturing process of the sintering bearing for EGR valves of FIG. It is a schematic diagram of a mixer of raw material powder. It is a schematic diagram of a mesh belt type continuous furnace. It is a figure explaining a sizing process, (a) shows a state where a sintered compact was set to a mold for sizing, (b) shows a state where the core is lowered, and (c) shows that sizing is completed. Indicates the status.

  Hereinafter, a first embodiment of a sintered bearing for an EGR valve of the present invention and a first embodiment of a method of manufacturing the same will be described based on the attached drawings. A first embodiment of a sintered bearing for an EGR valve is shown in FIGS. 1-7, and a first embodiment of a manufacturing method is shown in FIGS.

  FIG. 1 is a longitudinal sectional view showing an outline of an EGR valve in which a sintered bearing according to the present embodiment is used. In the EGR device (not shown), a part of the exhaust gas to be discharged is recirculated to the intake system as the EGR gas, but the EGR valve 31 is used to adjust the flow rate of the EGR gas.

  The EGR valve 31 includes a housing 43, an EGR gas passage 44 formed in the housing 43, a valve seat 50 provided in the middle of the EGR gas passage 44, and a valve provided to be able to abut on the valve seat 50. It comprises a body 45, a shaft 46 integrally provided with the valve body 45 and extending from the valve body 45, and a step motor 32 for moving the shaft 46 together with the valve body 45 in its axial direction.

  Both ends of the EGR gas flow path 44 formed in the housing 43 are an inlet 41 into which the EGR gas is introduced, and an outlet 42 from which the EGR gas is drawn out. The valve seat 50 is provided in the middle of the EGR gas passage 44 and has a valve hole 50 a communicating with the EGR gas passage 44.

  The shaft 46 is provided between the step motor 32 and the valve body 45, and is disposed penetrating the housing 43 in the vertical direction in the drawing. The valve body 45 is fixed to the lower end of the shaft 46 and has a conical shape such that the conical surface abuts or is separated from the valve seat 50. A spring receiver 48 is fixed to the upper end of the shaft 46. A compression coil spring 49 is mounted between the spring bearing 48 and a spring bearing 43 a provided on the housing 43. The compression coil spring 49 urges the valve 45 in contact with the valve seat 50 to close the EGR passage 44.

  The shaft 46 is supported slidably by the slide bearing 1 in the vertical direction. The slide bearing 1 is incorporated in an inner diameter hole provided in the housing 43 and slidably fitted with the outer diameter surface of the shaft 46. The slide bearing 1 is a sintered bearing for an EGR valve according to the present embodiment. Details will be described later.

  The step motor 32 has a configuration in which the cylindrical rotor 35 is disposed on the inner diameter side of the stator 34 in which the exciting coil 33 is mounted in the slot, and N pole and S pole are alternately magnetized on the outer periphery of the rotor 35 A cylindrical magnet is mounted. The rotor 35 is rotatably supported by a pivot bearing 39 at the upper end and a radial bearing 40 at the lower end. An inner diameter of the rotor 35 is formed with a female screw 36, and an inner diameter side of the rotor 35 is provided with an output shaft 37 in which a male screw 38 to be screwed with the female screw 36 is formed. The rotational movement of the rotor 35 is configured to be converted to the up and down movement of the output shaft 37 via the female screw 36 and the male screw 38. A connector 52 projecting laterally is integrally formed on the casing 51 of the step motor 32, and a terminal 53 extending from the exciting coil is provided.

  The electronic control unit on the engine side sends a control signal to the step motor 32, and the operation amount of the step motor 32 corresponding to the control signal causes the shaft 46 to be lowered against the biasing force of the compression coil spring 49 to And the EGR gas whose flow rate is adjusted is returned to the intake side on the engine side through the EGR gas passage 44 (not shown).

  The EGR valve 31 is disposed in the vicinity of the combustion chamber of the engine, and may be exposed to a high-temperature environment reaching 300 ° C. or more, in combination with an increase in the amount of heat generated by the engine. The sintered bearing 1 for an EGR valve of the present embodiment, which supports the shaft 46 slidably in the vertical direction in the drawing, under such conditions of use and environment, has corrosion resistance, wear resistance, and high temperature dry environment. Slidability is required.

  The longitudinal cross-sectional view of the sintered bearing for EGR valve | bulbs of this embodiment is shown in FIG. The EGR valve sintered bearing (hereinafter, also simply referred to as a sintered bearing) 1 is formed in a cylindrical shape having a bearing surface 1 a on the inner periphery. A shaft 46 (see FIG. 1) having a valve body 45 is inserted into the inner periphery of the sintered bearing 1. The shaft 46 is axially slidably supported by the bearing 1 in a high temperature dry environment.

  The sintered bearing 1 for an EGR valve according to the present embodiment is formed by filling raw material powder in which various powders are mixed into a mold, compressing it to form a green compact, and then sintering the green compact. Be done.

  The raw material powder is a mixed powder of aluminum-copper alloy powder, copper powder, phosphorus-copper alloy powder, graphite powder, and aluminum fluoride and calcium fluoride as a sintering aid. Details of each powder are described below.

[Aluminum-Copper Alloy Powder]
The 40 to 60% by weight aluminum-copper alloy powder was ground and particle size adjusted. The particle size of the aluminum-copper alloy powder is 100 μm or less, and the average particle size is 35 μm. Here, in the present specification, the average particle diameter means an average value of particle diameters measured by laser diffraction. Specifically, 5000 powder is measured by laser diffraction using SALD-3100 manufactured by Shimadzu Corporation as an average value of particle diameters.

  By using the aluminum-copper alloy powder, the effects of additives such as graphite and phosphorus are derived, and the sintered bearing material is excellent in corrosion resistance, strength, sliding characteristics and the like. Moreover, since it is alloyed, there is no problem in handling associated with the scattering of a single powder of aluminum having a small specific gravity.

  In the aluminum bronze structure, the alpha phase is most excellent in corrosion resistance against sulfidation corrosion and organic acid corrosion. By using a 40 to 60% by weight aluminum-copper alloy powder, even if graphite is added, strength is obtained and a sintered bearing can be manufactured. When the structure is in the γ phase, although the wear resistance is excellent, the organic acid corrosion resistance is deteriorated. In the aluminum bronze structure, it is preferable to set the ratio γ phase / α phase of the γ phase to the α phase to 0.10 ≦ γ phase / α phase ≦ 0.25. If the ratio of the γ phase / α phase is less than 0.10, the abrasion resistance is unfavorably reduced, while if it exceeds 0.25, the organic acid corrosion resistance is unfavorably reduced.

[Copper powder]
The copper powder includes atomized powder, electrolytic powder and pulverized powder, but in order to sufficiently diffuse aluminum into copper, dendritic electrolytic powder is effective and is excellent in moldability, sinterability and sliding property. Therefore, in the present embodiment, an electrolytic powder is used as the copper powder. Also, in order to sufficiently diffuse aluminum into copper, using two types of electrolytic copper powder having different powder shapes, the ratio W1 of electrolytic copper powder having an aspect ratio of 2 or more and the ratio W2 of electrolytic copper powder having an aspect ratio less than 2 It is preferable to set the ratio W2 / W1 to 3 to 9. Electrolytic copper powder having an aspect ratio of 2 or more is effective for the diffusion of aluminum, but has poor formability. If the ratio W2 / W1 is less than 3, it is not preferable from the viewpoint of formability. On the other hand, if it exceeds 9, the diffusion of aluminum becomes insufficient, which is not preferable.

  In the present embodiment, the average particle diameter of the electrolytic copper powder is 85 μm. It is preferable to set ratio d2 / d1 of the average particle diameter d1 of aluminum-copper alloy powder mentioned above and the average particle diameter d2 of electrolytic copper powder to 2-3. When the ratio d2 / d1 is in this range, aluminum can be sufficiently diffused in copper, and the corrosion resistance is excellent. For this reason, in the present embodiment, the average particle diameter d1 of the aluminum-copper alloy powder is 35 μm, and the average particle diameter d2 of the electrolytic copper powder is 85 μm. However, the average particle diameter of the aluminum-copper alloy powder is not limited to this, and those of about 20 to 65 μm can be used, the particle diameter of the electrolytic copper powder is 200 μm or less, and the average particle diameter is about 60 to 120 μm Are available.

[Phosphorus alloy powder]
As a phosphorus alloy powder, 7 to 10% by weight of phosphorus-copper alloy powder was used. Phosphorus has the effect of enhancing the wettability between solid and liquid phases at the time of sintering. The blending amount of phosphorus is preferably 0.1 to 0.6% by weight, specifically 0.1 to 0.4% by weight. If it is less than 0.1% by weight, the sintering promoting effect between the solid and liquid phases is poor, while if it exceeds 06% by weight, which is a preferable value, 0.4% by weight, sintering proceeds too much and aluminum segregates. The precipitation of the phase increases and the sintered body becomes brittle.

[Graphite powder]
Graphite exists as free graphite mainly in pores dispersed and distributed in a matrix, imparts excellent lubricity to a sintered bearing, and contributes to the improvement of wear resistance. 3 to 10 weight% is preferable and, as for the compounding quantity of graphite, 6 to 10 weight% is more preferable. If the amount is less than 6% by weight, it is difficult to obtain the effect of improving the lubricity and wear resistance by the addition of graphite as a sintered bearing for an EGR valve, which is in a high temperature dry environment. If it is less than 3% by weight, the effect of improving the lubricity and the abrasion resistance by the addition of graphite can not be obtained as a sintered bearing for an EGR valve which is in a high temperature dry environment. On the other hand, if it exceeds 10% by weight, the material strength is lowered and the diffusion of aluminum into copper is not preferable. Generally, when 4% by weight or more of graphite is added, it can not be molded, but by using granulated graphite, molding was made possible. In the present embodiment, as the graphite powder, fine powder of natural graphite or artificial graphite is granulated with a resin binder and then crushed, and graphite powder having a particle size of 145 mesh or less is used.

[Aluminum fluoride and calcium fluoride]
In aluminum-copper alloy powder, a film of aluminum oxide formed on the surface at the time of sintering significantly inhibits sintering, but aluminum fluoride and calcium fluoride as a sintering aid cause sintering of aluminum-copper alloy powder. Sintering is promoted and diffusion of aluminum is promoted by gradually evaporating while melting at a sintering temperature of 850 to 900 ° C. to protect the surface of the aluminum-copper alloy powder to suppress the formation of aluminum oxide. Aluminum fluoride and calcium fluoride evaporate and volatilize during sintering, so they hardly remain in the finished product of the sintered bearing.

  Aluminum fluoride and calcium fluoride as sintering aids are 0.05 to 0 in total with respect to a total of 100% by weight of aluminum powder, phosphorus, graphite, raw material powder containing copper as the main component of the balance and unavoidable impurities It is preferable to add at about 2% by weight. When the amount is less than 0.05% by weight, the effect as a sintering aid is insufficient, and a compact sintered body having appropriate strength can not be obtained. On the other hand, if it exceeds 0.2% by weight, the effect as a sintering aid will be plateaued even if it is added more than 0.2% by weight from the viewpoint of cost.

  In the sintered bearing for an EGR valve of the present embodiment and the manufacturing method to be described later, the aluminum content is 9 to 12% by weight, the phosphorus is 0.1 to 0.4% by weight, the graphite is 6 to 10% by weight, Aluminum-copper alloy powder, electrolytic copper powder, phosphorus alloy powder and graphite powder were mixed at a ratio such that the main component was copper, to obtain a raw material powder. A total of 0.05 to 0.2% by weight of aluminum fluoride and calcium fluoride as a sintering aid with respect to 100% by weight of this total, zinc stearate, calcium stearate and the like to facilitate formability 0.1 to 1% by weight of the lubricant was added.

  Specifically, for example, in the sintered bearing for an EGR valve according to the present embodiment and the manufacturing method described later, the aluminum content is 9 to 12 parts by weight, the phosphorus is 0.1 to 0.4 parts by weight, and the graphite is 6 to 10 The aluminum-copper alloy powder, the electrolytic copper powder, the phosphorus alloy powder and the graphite powder are mixed to give a raw material powder in a proportion such that the main component of the remaining part is copper in parts by weight. A total of 0.05 to 0.2 parts by weight of aluminum fluoride and calcium fluoride as a sintering aid with respect to 100 parts by weight of the total, zinc stearate, calcium stearate and the like to facilitate formability 0.1 to 1 part by weight of the lubricant was added.

  The blending amount of phosphorus is preferably 0.1 to 0.6 parts by weight, specifically 0.1 to 0.4 parts by weight. If the amount is less than 0.1 part by weight, the sintering promoting effect between the solid and liquid phases is poor, while if it exceeds 0.6 part by weight, the preferable value is 0.4 parts by weight, the sintering progresses too much and aluminum segregates The precipitation of the γ phase increases and the sintered body becomes brittle.

  The blending amount of graphite is preferably 3 to 10 parts by weight, and more preferably 6 to 10 parts by weight. If the amount is less than 6 parts by weight, it is difficult to obtain the effect of improving the lubricity and the abrasion resistance by the addition of graphite as a sintered bearing for an EGR valve which is in a high temperature dry environment. If the amount is less than 3 parts by weight, the effect of improving the lubricity and the wear resistance by the addition of graphite can not be obtained as a sintered bearing for an EGR valve which is in a high temperature dry environment. On the other hand, if it exceeds 10 parts by weight, the strength of the material is lowered, and the diffusion of aluminum into copper is not preferable. Generally, when 4 parts by weight or more of graphite is added, it can not be molded, but by using granulated graphite, molding was made possible.

  In the sintered bearing 1, in the manufacturing method described later, both the outer diameter surface 1 b of the bearing and the bearing surface 1 a on the inner diameter side are subjected to sizing after sintering. Therefore, the inner diameter and the outer diameter are corrected to improve the accuracy. In addition, the surface roughness of the inner diameter surface is improved, and the slidability is improved.

  The compression layer of the surface layer of the sintered bearing 1 is shown by hatching in FIG. Hatching is applied only to the upper half of the bearing 1 in the radial direction, and the lower half is not shown. The surface layer of the sintered bearing 1 has a compression layer. The density ratio αo of the compression layer Po of the surface layer on the outer diameter surface 1b side and the density ratio αb of the compression layer Pb of the surface layer on the bearing surface 1a are both higher than the density ratio αi inside, and both of the density ratios αo and αb Is set in the range of 80% ≦ αo and αb ≦ 95%. If the density ratios αo and αb are less than 80%, the bearing strength is insufficient, while if it exceeds 95%, the residual stress due to the correction becomes large and the stress may be released at high temperature, which is not preferable.

The average value of the depth of the compressed layer Po of the surface layer on the outer diameter surface 1b side is To, and the average of the depth of the compressed layer Pb of the surface layer on the bearing surface 1a is Tb. Assuming that the ratios are To / D1 and Tb / D1, respectively, it is preferable to set 1/100 ≦ To / D1 and Tb / D1 ≦ 1/15. Here, the density ratio α is expressed by the following equation.
α (%) = (ρ1 / ρ0) × 100
However, if ρ1: density of porous body, ρ0: density To / D1 and Tb / D1 assuming that there is no pore in the porous body is less than 1/100, pore crush is insufficient, while If it exceeds 1/15, the pores will be crushed too much, which is not preferable.

Next, verification results up to the present embodiment will be described based on FIGS. Material combination specifications of the conventional bronze-based standard products in FIGS. 3 to 7 and the prototypes 1 to 3 according to the present embodiment are shown in Table 1.

  Figures 3 and 4 show the results of torque tests of bronze-based standard products and prototypes. FIG. 3 shows the result of the torque test (1), and FIG. 4 shows the result of the torque test (2). The torque tests (1) and (2) were all performed in the state of no oil and no oil (dry). The ambient temperature was normal temperature. In a dry environment, the tendency of the sliding characteristics of the EGR valve in a high temperature environment (about 350 ° C.) and the sliding characteristics at normal temperature are considered to be the same. In addition, focusing on the fact that the usual aluminum blending amount (9 to 11 wt%) can be applied as an aluminum bronze sintered bearing under the use conditions in a dry environment, the trial amount 1 to 3 has a median aluminum blending amount of 10 Each test was carried out by fixing the weight percentage and changing the addition amount of graphite.

図３に示すトルク試験結果より、ドライ環境下において、試作品１〜３は、いずれも青銅系標準品よりも摩擦係数が低く、摺動性に優れている。また、黒鉛の添加量を増やすほど摩擦係数が低くなる傾向があることが分かった。 [Torque test (1)]
The speed was fixed and a load was added every 5 minutes. The specific test conditions are as follows.

From the torque test results shown in FIG. 3, in the dry environment, all of the prototypes 1 to 3 have a lower coefficient of friction than the bronze-based standard product, and are excellent in slidability. It was also found that the coefficient of friction tends to be lower as the amount of addition of graphite is increased.

[Torque test (2)]
In the torque test (2), after applying a load of 60 N in the above-mentioned torque test (1), the torque test was continued for about 90 minutes with the load and the number of revolutions remaining. Similar to the torque test (1), as shown in FIG. 4, all of the prototypes 1 to 3 have a lower coefficient of friction than the standard bronze-based product, and are excellent in slidability. In particular, it was found that in the prototypes 1 and 2 in which the additive amount of graphite was 8% by weight or more, the increase in the coefficient of friction was suppressed even after the test time elapsed.

[Block on ring test]
Test pieces in the form of blocks were prepared using material combination specifications of bronze-based standard products and prototypes 1 to 3, and the wear resistance was evaluated using a block-on-ring tester.
<Test conditions>
Test machine: Block on ring test machine (manufactured by NTN Co., Ltd.)
・ Load: 14.7N
・ Rotational speed: 430 rpm (54.0 m / min)
Test time: 60 min
· Lubrication method: No oil, no oil (dry)
-Counterpart material: Material: SUS420J2 Soaking (hardness HV 550-650), rotational diameter (outer diameter) and width: Outer diameter 40 mm × width 4 mm, surface roughness: 0.02 μm Ra

  The results of the block on ring test are shown in FIG. In this test also, the ambient temperature is normal temperature, but the wear resistance and tendency in the high temperature dry environment of the EGR valve are considered to be the same. From the test results, it is found that all of the prototypes 1 to 3 have less wear than the bronze-based standard and are excellent in wear resistance. The prototype 2 in which the additive amount of graphite is 8% by weight is the most excellent in wear resistance. Although the wear amount of the trial product 3 in which the amount of added graphite was 10% by weight was increased, it seems that the strength of the material was slightly decreased and it was easy to scrape because the amount of added graphite was large. From this test result, it was found that the additive amount of graphite usable as the bearing for the EGR valve is 3 to 10% by weight, preferably 6 to 10% by weight.

[Organic acid corrosion test]
Test pieces were manufactured with material combination specifications of bronze-based standard product and prototype products 1 to 3 and an organic acid corrosion test was performed. The evaluation method is to immerse each test piece in a corrosive solution and leave it in a 60 ° C. high temperature bath for a predetermined time. After standing, each test piece is removed from the solution and allowed to dry for 1 hour. After drying, the weight of the test piece was measured, and the weight change rates calculated from the measured values were compared. In the comparison of weight change rates, the maximum value and the minimum value were also compared with the average value of the weight change rates of the five test pieces. The specific test conditions are as follows.
<Test conditions>
Test specimen size: Inner diameter φ 6 mm × outer diameter φ 12 mm × width 6 mm
· Number of test pieces: 5 · Corrosion solution: 1% aqueous solution of formic acid + 1% acetic acid · Ambient temperature: 60 ° C

  FIG. 6 shows the weight change rate after leaving for 24 hours. The prototypes 1 to 3 all had a smaller weight change rate than the bronze standard. In particular, Prototype 3 in which the additive amount of graphite was 10% by weight had the smallest weight change rate.

  FIG. 7 shows the weight change rate after leaving for 72 hours. All of prototypes 1 to 3 have a smaller weight change rate than the bronze-based standard product. The prototype 3 in which the additive amount of graphite was 10% by weight had the smallest weight change rate, and there was almost no change as compared with the result after leaving for 24 hours.

  From the test results shown in FIGS. 3 to 7, it is possible to use 3 to 10% by weight, preferably 6 to 10% by weight, of the additive amount of graphite as a sintered bearing for an EGR valve used in a high temperature dry environment It was confirmed. Further, if the addition amount of graphite exceeds 10% by weight, the diffusion of aluminum to copper is inhibited, which is not preferable also in the sintering surface.

  As described above, although the compounding amount of aluminum was set to 9 to 11% by weight, as the sintered bearing for an EGR valve, the diffusion of aluminum to copper due to the increase of the graphite is inhibited with the test results of FIGS. In consideration of the above, it was found that the upper limit of the blending amount of aluminum is preferably 12% by weight.

The result of having measured the hardness of the sintering bearing for EGR valves in 1st Embodiment in Table 3 is shown. The hardness values shown in Table 3 are values evaluated based on Vickers hardness (Hv) at a test load of 25 g. Hereinafter, the hardness value will be described as a value based on the Vickers hardness (Hv). In addition, the hardness of the copper-based sintered bearing is also described as Comparative Example 1 as a comparison.

  As shown in Table 3, while the hardness of the copper-based sintered bearing is approximately 70 to 80, the hardness of the sintered bearing for an EGR valve in the first embodiment is approximately 120 to 220, for example. From the results, it can be determined that the sintered bearing for an EGR valve in the first embodiment is a sintered bearing having better wear resistance than a copper-based sintered bearing. This is because the hardness of the soft phase α phase is approximately 120 to 140, and the hardness of the hard phase γ phase is approximately 200 to 220, and the sintered bearing for the EGR valve in the first embodiment The hardness of either phase is also harder than the hardness of the copper-based sintered bearing.

  Next, a first embodiment of a method of manufacturing a sintered bearing for an EGR valve will be described. It manufactures through the raw material powder preparation process S1 as shown in FIG. 8, the mixing process S2, the shaping | molding process S3, the sintering process S4, and the sizing process S5.

[Raw material powder preparation step S1]
In the raw material powder preparation step S1, the raw material powder of the sintered bearing 1 is prepared and generated. Raw material powder: 18 to 24% by weight of 40 to 60% by weight of aluminum-copper alloy powder, 2 to 4% by weight of 7 to 10% by weight of phosphorus-copper alloy powder, 6 to 10% by weight of graphite powder, electrolytic copper powder The total amount of aluminum fluoride and calcium fluoride as a sintering aid is 0.05 to 0.2% by weight to facilitate the formability of the graphite powder, with respect to the total 100% by weight. A lubricant such as zinc stearate or calcium stearate was added in an amount of 0.1 to 1% by weight. By adding a lubricant, it is possible to smoothly release the green compact described later, and it is possible to avoid the collapse of the shape of the green compact caused by the release.

  For example, 18 to 24 wt% of 40 to 60 wt% aluminum-copper alloy powder, 2 to 4 wt% of 7 to 10 wt% phosphorous-copper alloy powder, 6 to 10 wt% of graphite powder, and remaining electrolytic copper powder The content of aluminum is, for example, 8.5% by weight or more and 10% by weight or less, and specifically 9% by weight or more and 9.5% by weight or less, based on 100% by weight of the total weight%.

  For example, the raw material powder is 18 to 24 parts by weight of 40 to 60% by weight of aluminum-copper alloy powder, 2 to 4 parts by weight of 7 to 10% by weight of phosphorus-copper alloy powder, and 3 to 10 parts by weight of graphite powder. Is 6 to 10 parts by weight, and 0.05 to 0.2 parts by weight in total of aluminum fluoride and calcium fluoride as a sintering aid with respect to a total of 100 parts by weight containing the electrolytic copper powder as the remaining part by weight, In order to make the graphite powder formability easy, 0.1 to 1 part by weight of a lubricant such as zinc stearate or calcium stearate can be used.

  For example, 18 to 24 parts by weight of 40 to 60% by weight of aluminum-copper alloy powder, 2 to 4 parts by weight of 7 to 10% by weight of phosphorus-copper alloy powder, 6 to 10 parts by weight of graphite powder, and electrolytic copper powder The content of aluminum is, for example, 8.5 parts by weight or more and 10 parts by weight or less, specifically 9 parts by weight or more and 9.5 parts by weight or less based on 100 parts by weight in total as parts by weight.

[Mixing step S2]
The raw material powder M described above is introduced into, for example, the can 11 of the V-type mixer 10 shown in FIG. 9, and the can 11 is rotated to be uniformly mixed.

[Forming step S3]
In the forming step S3, a green compact having the shape of the sintered bearing 1 is formed by compacting the above-mentioned raw material powder. The green compact is compression molded so that the density ratio α of the sintered body formed by heating at a sintering temperature or higher is 70% or more and 80% or less.

  Specifically, for example, a molding die having a cavity according to a green compact shape is set in a CNC press using a servomotor as a drive source, and the above-mentioned raw material powder filled in the cavity is 200 to 200 A green compact is formed by compression at a pressure of 700 MPa. During molding of the green compact, the molding die may be heated to 70 ° C. or higher.

  In the method of manufacturing the sintered bearing 1 for an EGR valve according to the present embodiment, the problem of insufficient strength of the green compact due to the decrease in formability due to the flowability is improved by using the aluminum-copper alloy powder as the aluminum source. There are no handling problems associated with the scattering of single particles of aluminum having a low specific gravity. In addition, the production efficiency is good and suitable for mass production.

[Sintering step S4]
In the sintering step S4, the green compact is heated at a sintering temperature to sinter and bond adjacent raw material powders to form a sintered body. Using a mesh belt type continuous furnace 15 shown in FIG. 10, a large amount of green compact 1 ′ is introduced into the mesh belt 16 to form a sintered body. Thus, stable quality and manufacturing method can be realized.

  What is important in the sintering step is to sufficiently diffuse aluminum into copper to improve corrosion resistance, and to improve the corrosion resistance and bearing performance by making the aluminum bronze structure into an α phase. When it becomes the γ phase, it becomes hard and has excellent abrasion resistance, but the organic acid corrosion resistance decreases. Therefore, it was found that it is necessary to reduce the amount of aluminum so as to suppress the precipitation of the γ phase as much as possible.

  Furthermore, it has been found that the aluminum structure preferably has a ratio of γ phase to α phase of γ phase / α phase of 0.10 ≦ γ phase / α phase ≦ 0.25. If the ratio of the γ phase / α phase is less than 0.10, the abrasion resistance is unfavorably reduced, while if it exceeds 0.25, the organic acid corrosion resistance is unfavorably reduced.

  As sintering conditions satisfying the above, the sintering temperature is preferably 900 to 950 ° C., and more preferably 900 to 920 ° C. (eg, 920 ° C.). The atmosphere gas is hydrogen gas, nitrogen gas or a mixed gas of these, and the longer the sintering time, the better the corrosion resistance, and the sintered bearing for an EGR valve for 20 to 60 minutes (for example, 30 minutes) Is preferred.

  Various liquid phases are generated in the aluminum-copper alloy powder when the eutectic temperature is 548 ° C. or higher. When the liquid phase is generated, it expands, and the generated liquid phase forms a sintering neck, which leads to densification and shrinks in size. In the present embodiment, by sintering in the mesh belt type continuous furnace 15, the surface of the sintered body is oxidized and the sintering is inhibited, so densification is not achieved, and the dimension remains expanded. However, since the inside of the sintered body is sintered without being oxidized, the strength of the sintered body can be sufficiently secured. Since the mesh belt type continuous furnace 15 is used, the sintering time from input to extraction of the green compact 1 'can be short and mass-produced, and cost reduction can be achieved. In addition, in terms of the function of the sintered bearing, sufficient strength can be secured.

  In the above-mentioned sintering process, a sintered body of good quality can be formed by the effect of the added phosphorus alloy powder. Phosphorus improves the wettability between solid and liquid phases during sintering, and a good sintered body can be obtained. As a compounding quantity of phosphorus, 0.1 to 0.6 weight%, specifically 0.1 to 0.4 weight% is preferable. If it is less than 0.1% by weight, the effect of promoting sintering between solid and liquid phases is poor, while if it exceeds 0.6% by weight, which is a preferable value, 0.4% by weight, the obtained sintered body is segregated. It becomes brittle.

  Furthermore, graphite exists as free graphite mainly in pores dispersed and distributed in a matrix, imparts excellent lubricity to a sintered bearing, and contributes to the improvement of wear resistance. 3 to 10 weight% is preferable and, as for the compounding quantity of graphite, 6 to 10 weight% is more preferable. If the amount is less than 6% by weight, it is difficult to obtain the effect of improving the lubricity and wear resistance by the addition of graphite as a sintered bearing for an EGR valve, which is in a high temperature dry environment. If it is less than 3% by weight, the effect of improving the lubricity and the abrasion resistance by the addition of graphite can not be obtained as a sintered bearing for an EGR valve which is in a high temperature dry environment. On the other hand, if it exceeds 10% by weight, the material strength is lowered and the diffusion of aluminum into copper is not preferable.

[Sizing step S5]
In the sizing step S5, the expanded sintered body is dimensioned in comparison with the green compact by sintering. The detail of sizing process S5 is shown in FIG. The mold for sizing processing is composed of a die 20, an upper punch 21, a lower punch 22 and a core 23. With the core 23 and the upper punch 21 retracted upward as shown in FIG. 11 (a), the sintered body 1 '' is set on the lower punch 22. As shown in FIG. 11 (b), first, as shown in FIG. The core 23 enters the inner diameter of the sintered body 1 ′ ′, and then the sintered body 1 ′ ′ is pressed into the die 20 by the upper punch 21 and compressed by the upper and lower punches 21 and 22 as shown in FIG. Thereby, the surface of the sintered body 1 ′ ′ is dimensioned.

  The mold of the above-mentioned sizing process is constituted by a die 20, a pair of punches 21 and 22 and a core 23, and compressed from both sides in the axial direction of the sintered body 1 ′ ′ and the outer diameter side by the punches 21 and 22 and the die 20 By forming the inner diameter side of the sintered body 1 ′ ′ with the core 23, the expansion due to sintering of the aluminum bronze-based sintered bearing is effectively used to form the desired pores together with the dimensioning of the sintered bearing 1. it can. Since free graphite is distributed in the pores, the slidability is excellent.

  The sintered bearing 1 for an EGR valve according to the present embodiment manufactured by the above-described steps is excellent in wear resistance, corrosion resistance, and slidability in a high temperature dry environment, thereby achieving compactness and cost reduction. be able to.

  Next, a second embodiment of the sintered bearing for an EGR valve according to the present invention and a second embodiment of the manufacturing method will be described. In the sintered bearing for an EGR valve and the manufacturing method according to the first embodiment, aluminum-copper alloy powder and electrolytic copper powder are used as raw material powders to be an aluminum source and a copper source, but in the second embodiment, copper is used. This embodiment differs from the first embodiment in that aluminum-copper alloy powder is used without adding a single electrolytic copper powder.

  In a more severe use environment, it was found that when adding powder of copper alone, there is a problem of corrosion resistance due to the occurrence of a portion where copper alone is biased. As a result of various studies based on this finding, the present embodiment has been made based on the idea that aluminum-copper alloy powder is used as a raw material powder to be an aluminum source and a copper source, and no powder of copper alone is added.

  In the sintered bearing for an RGR valve and the manufacturing method of the present embodiment, the aluminum content is 9 to 12% by weight, the phosphorus is 0.1 to 0.4% by weight, the graphite is 6 to 10% by weight, and the remaining portion is mainly The composition of which the component is copper is the same as that of the first embodiment. However, the raw material powder is different as follows. That is, the aluminum-copper alloy powder, the phosphorus alloy powder and the graphite are mixed in such a ratio that the above composition can be obtained without adding electrolytic copper powder of copper alone, and the sintering aid is added to the total of 100% by weight. Added aluminum fluoride and calcium fluoride in total 0.05 to 0.2% by weight, and lubricants such as zinc stearate and calcium stearate 0.1 to 1% by weight to facilitate formability did.

  For example, in a sintered bearing for an RGR valve and a manufacturing method, the aluminum content is 9 to 12 parts by weight, phosphorus is 0.1 to 0.4 parts by weight, graphite is 6 to 10 parts by weight, and the remaining main components are The composition of copper can be used. In this case, for example, the raw material powder is as follows. That is, the aluminum-copper alloy powder, the phosphorus alloy powder and the graphite are mixed in such a ratio that the above composition can be obtained without adding electrolytic copper powder of copper alone, and the sintering aid is added to the total 100 parts by weight. Add 0.05 to 0.2 parts by weight of aluminum fluoride and calcium fluoride in total, and 0.1 to 1 part by weight of a lubricant such as zinc stearate and calcium stearate to facilitate formability did.

  The description of the blending amount of phosphorus and the description of the blending amount of graphite are the same as those of the first embodiment, and thus the redundant description will be omitted here.

  In addition, since the state of the compression layer of the surface layer of the sintered bearing 1 of the present embodiment is also the same as that of the sintered bearing of the first embodiment shown in FIG. 2, the contents described above with reference to FIG. Omit.

  Moreover, although illustration is abbreviate | omitted, about the organic acid-corrosion resistance, a favorable result was confirmed by the sintered bearing in 2nd Embodiment rather than the sintered bearing in 1st Embodiment. Further, with regard to the relationship of the coefficient of friction, the test results of the sintered bearing in the first embodiment and the test results of the sintered bearing in the second embodiment are substantially equivalent to each other. The detailed description is omitted.

  The aluminum bronze structure of the present embodiment using aluminum-copper alloy powder as a copper source and not adding powder of copper alone has a ratio of γ phase to α phase, γ phase / α phase, 0 ≦ γ phase / α phase It is preferable to set it as ≦ 0.10. If it is the range of 0 <= (gamma) phase / (alpha) phase <= 0.10, it is excellent in organic acid-proof corrosion resistance.

Table 4 shows the results of measuring the hardness of the sintered bearing for an EGR valve in the second embodiment. Since the method of evaluation of hardness shown in Table 4 and the method of evaluation of hardness shown in Table 3 are the same, the detailed description thereof is omitted here.

  As shown in Table 4, while the hardness of the copper-based sintered bearing is approximately 70 to 80, the hardness of the sintered bearing for an EGR valve in the second embodiment is approximately 100 to 240, for example. From the results, it can be determined that the sintered bearing for an EGR valve in the second embodiment is a sintered bearing having better wear resistance than a copper-based sintered bearing. This is because the hardness of the soft phase α phase is approximately 100 to 140, and the hardness of the hard phase γ phase is approximately 200 to 240, and the sintered bearing for an EGR valve in the second embodiment The hardness of either phase is also harder than the hardness of the copper-based sintered bearing.

  The sintered bearing for an EGR valve according to the present embodiment can ensure corrosion resistance even in a more severe use environment.

  Next, a second embodiment of the manufacturing method will be described. The manufacturing method of the second embodiment is also the same as the manufacturing method of the sintered bearing of the first embodiment, so the contents described above are applied mutatis mutandis, and only the difference between the raw material powder preparation step S1 and the forming step S2 is Explain.

[Raw material powder preparation step S1]
In the raw material powder preparation step S1, the raw material powder of the sintered bearing 1 is prepared. Raw material powder is 85 to 93% by weight of 7 to 11% by weight of aluminum-copper alloy powder, preferably 8 to 10% by weight of aluminum to copper alloy powder, and 1 to 5% of 7 to 10% by weight of phosphorus-copper alloy powder. % And total of 0.05% to 0.2% by weight of aluminum fluoride and calcium fluoride as a sintering aid, with respect to 100% by weight of the total of 6 to 10% by weight of graphite powder 0.1 to 1% by weight of zinc stearate was added as a lubricant for this purpose. The 7 to 11 wt% aluminum-copper alloy powder was used after being ground and adjusted in particle size. As in the first embodiment, for example, the raw material powder described above is introduced into the can 11 of the V-shaped mixer 10 shown in FIG. 9, and the can 11 is rotated and uniformly mixed.

  For example, 85 to 93% by weight of 7 to 11% by weight of aluminum-copper alloy powder, 1 to 5% by weight of 7 to 10% by weight of phosphorus-copper alloy powder, and 6 to 10% by weight of graphite powder Content of aluminum is, for example, 8.5 parts by weight or more and 10 parts by weight or less, specifically 9 parts by weight or more and 9.5 parts by weight or less with respect to 100 parts by weight in total. Make it

  For example, as the raw material powder, 7 to 11 wt% aluminum-copper alloy powder, preferably 8 to 10 wt% aluminum-copper alloy powder 85 to 93 parts by weight, 7 to 10 wt% phosphorus-copper alloy powder 1 to 5 Aluminum fluoride and calcium fluoride as a sintering aid in total of 0.05 to 0. 5 parts by weight with respect to 100 parts by weight in total of 3 to 10 parts by weight, preferably 6 to 10 parts by weight of graphite powder. It is possible to use 2 parts by weight and 0.1 to 1 part by weight of zinc stearate added as a lubricant for facilitating moldability.

  The sintered bearing according to the present embodiment is, for example, a sintered bearing for an EGR valve which does not contain an oil such as lubricating oil depending on the type of the EGR valve, a sintered bearing for an EGR valve containing a small amount of lubricating oil. Is available.

  The present invention is not limited to the embodiment described above, and it is needless to say that the present invention can be practiced in various forms without departing from the scope of the present invention, and the scope of the present invention is not limited to the patent The scope of the present invention is defined by the claims, and further includes the meaning of equivalents described in the claims, and all changes within the scope.

DESCRIPTION OF SYMBOLS 1 Sintering bearing for EGR valve 1 'Compacted powder 1 "Sintered body 1a Bearing surface 1b Outer diameter surface 1c End surface 15 Mesh belt type continuous furnace 20 Die 21 Upper punch 22 Lower punch 23 Core 31 EGR valve 46 Shaft D1 Bearing surface Inner diameter dimension of Ti compression layer To compression layer

The present invention, abrasion resistance, relates to the sliding excellent in EGR valve for sintering bearings under corrosion resistance and high-temperature dry environment.

In view of the conventional problems, the present invention improves the wear resistance, the corrosion resistance, and the slidability in a high-temperature dry environment, as well as the aluminum bronze-based sintered bearing for an EGR valve, which achieves downsizing and cost reduction. an object of the present invention and provide child a.

As technical means for achieving the foregoing objects, the present invention contain 9-12% by weight of aluminum and 0.1 to 0.4% by weight of phosphorus and from 3 to 10% by weight of graphite, the remaining portion there a EGR sintered bearing valve made of copper and not avoidable impurities, the entirety of the sintered bearing, aluminum - tissue copper alloy powder is sintered is dispersed, the sintered bearing It is characterized in that there is no biased part of copper alone in the whole, and free graphite is distributed in the pores formed by dispersion. Also, it contains 9 to 12% by weight of aluminum, 0.1 to 0.4% by weight of phosphorus and 3 to 10% by weight of graphite, with the balance being copper, aluminum fluoride and calcium fluoride, and unavoidable impurities A sintered bearing for an EGR valve, comprising: a structure in which an aluminum-copper alloy powder is sintered is dispersed in the whole of the sintered bearing; And free graphite distributed in pores formed by dispersion. As a result, it is possible to realize an aluminum bronze-based sintered bearing for an EGR valve which is excellent in wear resistance, corrosion resistance, and slidability in a high-temperature dry environment, and is made compact and cost-reduced.

It is a method for producing a sintered bearing EGR valve, contains 9-12% by weight of aluminum and 0.1 to 0.6% by weight of phosphorus and from 3 to 10% by weight of graphite, copper main component of the balance And a method of manufacturing a sintered bearing for an EGR valve containing unavoidable impurities, wherein the manufacturing method does not add powder of copper alone as raw material powder, aluminum-copper alloy powder, phosphorus-copper alloy powder And forming at least a green compact having a sintering aid added to the raw material powder using graphite powder, and a sintering process for obtaining a sintered body having an aluminum-copper alloy structure from the green compact. And a sizing step of dimensioning the sintered body. Here, not adding the powder of copper alone as the raw material powder means that the powder of copper alone which is inevitably contained in the manufacturing site is acceptable.

Above production how the productivity is good, at low cost, it is possible to realize a manufacturing method of a preferred EGR aluminum bronze based sintered bearing valve mass production. Moreover, the sintered bearing for an EGR valve manufactured by this is excellent in abrasion resistance, corrosion resistance, and slidability in a high-temperature dry environment, and can achieve downsizing and cost reduction. Furthermore, since the powder of copper alone is not added, the portion where copper alone is biased is almost eliminated, the occurrence of corrosion due to this portion is avoided, and the corrosion resistance of each grain of the aluminum-copper alloy powder is By the improvement, it is possible to secure corrosion resistance even in a more severe use environment.

Sintered bearing EGR valve according to the present invention, wear resistance, corrosion resistance and excellent sliding properties in a high-temperature dry environment, compact, Ru can be reduced in cost.

Moreover, without the addition of pure copper powder, aluminum - with According to the copper alloy powder prepared how using eliminates substantially the portion of copper alone is biased, the occurrence of corrosion due to this portion is avoided, aluminum - By improving the corrosion resistance of each particle of the copper alloy powder, the corrosion resistance can be ensured even in a more severe use environment.

Claims (11)

  Sintered for an EGR valve containing 9 to 12% by weight of aluminum, 0.1 to 0.4% by weight of phosphorus and 3 to 10% by weight of graphite, with the balance being copper as the main component and unavoidable impurities A sintered bearing having a structure in which an aluminum-copper alloy is sintered, wherein free graphite is distributed in pores formed by dispersion, which is a sintered bearing for an EGR valve. Bearing.   The sintered bearing for an EGR valve according to claim 1, wherein the structure of the aluminum-copper alloy has an alpha phase.   The structure of the aluminum-copper alloy is characterized in that the ratio γ phase / α phase of the γ phase and the α phase is 0 ≦ γ phase / α phase ≦ 0.10. The sintered bearing for an EGR valve as described above.   The sintered bearing for an EGR valve according to any one of claims 1 to 3, wherein tin as a sintering aid is not added to the sintered bearing for an EGR valve.   Sintered for an EGR valve containing 9 to 12% by weight of aluminum, 0.1 to 0.4% by weight of phosphorus and 3 to 10% by weight of graphite, with the balance being copper as the main component and unavoidable impurities A manufacturing method of a bearing, which uses aluminum-copper alloy powder, electrolytic copper powder, phosphorus-copper alloy powder and graphite powder as raw material powder, and at least a sintering aid is added to the raw material powder. It is characterized by including a forming step of forming a green compact, a sintering step of obtaining a sintered body having an aluminum-copper alloy structure from the green compact, and a sizing step of dimensioning the sintered body. Method for producing a sintered bearing for an EGR valve.   The total amount of aluminum fluoride and calcium fluoride is 0 as a total of 100% by weight of the raw material powder consisting of the aluminum-copper alloy powder, electrolytic copper powder, phosphorus-copper alloy powder and graphite powder as the sintering aid. The method of manufacturing a sintered bearing for an EGR valve according to claim 5, wherein 0.5 to 0.2% by weight is added.   7. The EGR valve according to claim 5, wherein a ratio d2 / d1 of the average particle diameter d1 of the aluminum-copper alloy powder and the average particle diameter d2 of the electrolytic copper powder is set to 2 to 3. Manufacturing method of sintered bearing.   The electrolytic copper powder has different powder shapes, and the ratio W2 / W1 of the ratio W1 of the electrolytic copper powder having an aspect ratio of 2 to 2 and the ratio W2 of the electrolytic copper powder less than 2 is 3 to 9 The manufacturing method of the sintered bearing for EGR valves as described in any one of the Claims 5-7 characterized by these.   The said graphite powder granulated the fine powder of natural graphite or artificial graphite with a resin binder and then ground it to a graphite powder having a particle size of 145 mesh or less. Of manufacturing a sintered bearing for an EGR valve.   Sintering for an EGR valve containing 9 to 12% by weight of aluminum, 0.1 to 0.6% by weight of phosphorus and 3 to 10% by weight of graphite, with the balance being copper as the main component and unavoidable impurities A manufacturing method of a bearing, wherein the manufacturing method does not add powder of copper alone as raw material powder, but uses aluminum-copper alloy powder, phosphorus-copper alloy powder and graphite powder, and at least sintered to the raw material powder A forming step of forming a green compact to which an auxiliary agent is added, a sintering step of obtaining a sintered body having an aluminum-copper alloy structure from the green compact, and a sizing step of dimensioning the sintered body A method of manufacturing a sintered bearing for an EGR valve, comprising:   The method for producing a sintered bearing for an EGR valve according to claim 10, wherein the aluminum-copper alloy powder as the raw material powder is 7 to 11 wt% aluminum-copper alloy powder.

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