JP2009222073A - Two layer bearing and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a two layer bearing having improved performance and productivity, enabling to suppress a great change in the inner diameter size of a sliding face layer during press-in by suppressing great outer force on the sliding face layer, and to provide its manufacturing method. <P>SOLUTION: The two layer bearing 21 includes the sliding face layer 23 formed mainly of carbon, and a sintered body layer 22 joined to the sliding face layer 23. The sintered body layer 22 has alloy particles and/or metal particles, and cavity portions existing between the alloy particles and/or the metal particles. When a press-in allowance is 0.10 mm during press-in, an inner diameter change rate C (%) of the sliding face layer 23, shown by an expression (1): the inner diameter change rate C of the sliding face layer=[(the inner diameter of the sliding face layer after press-in-the inner diameter of the sliding face layer before press-in)/the inner diameter of the sliding face layer before press-in]×100(%), is restricted to be 0≥C≥-0.12. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a two-layer bearing used for a sliding portion. More specifically, the present invention comprises a sliding surface layer mainly made of carbon and a sintered body layer bonded around the sliding surface layer. The present invention relates to a two-layer bearing and a manufacturing method thereof.

  Conventionally, there is a bearing having a multilayer structure disclosed in Patent Document 1 below. Patent Document 1 discloses a fuel pump bearing comprising a sliding contact layer mainly made of carbon and a support layer mainly made of carbon and metal and bonded to the sliding contact layer to support the sliding contact layer. Is disclosed.

  However, since the support layer is mainly composed of carbon and metal in Patent Document 1, the strength of the bearing is lower than when the support layer is made of metal alone, and the dimensional accuracy when the support layer is post-processed is deteriorated. Further, since the support layer is bonded after the slidable contact layer is roughly formed, the interface between the slidable contact layer and the support layer can be clearly defined, and sufficient adhesive force cannot be obtained. There is a problem that cracks occur. Furthermore, the thing of patent document 1 has to press-mold twice, and there exists a problem that productivity is bad.

  Therefore, the applicant of the present application has proposed a bearing having a multilayer structure disclosed in Patent Document 2 below. Specifically, to make use of the advantages of both carbon and ceramics, which are excellent in self-lubricating and corrosion resistance, but weak in strength, and strong in strength, but not self-lubricating and have problems with corrosion resistance. Instead of separately preparing and integrating the carbon layer and the metal and / or ceramic layer, the carbon layer and the metal and / or ceramic layer are formed by integral molding that simultaneously forms the carbon layer and the metal and / or ceramic layer. The structure is such that the interface between the two layers is unclear.

  With the above configuration, the sliding surface layer can take advantage of the characteristics of carbon with excellent self-lubrication and corrosion resistance, and the sintered body layer made of metal and / or ceramic can increase the strength of the composite material, and after good dimensional accuracy. A composite material that can be processed can be provided. Further, by integrally forming the carbon layer and the metal and / or ceramic layer, it is possible to improve productivity at the time of forming.

JP 2003-286922 A JP 2006-57138 A

  However, since the proposal of the above-mentioned Patent Document 2 has a large pressing force of the metal and / or ceramic layer as 300 MPa, the metal and / or ceramic layer is not sufficiently compressed and deformed when the two-layer bearing is press-fitted into the bearing device. (Especially when ceramic is used) Since a large external force is applied to the carbon layer, there may be a problem that the inner diameter of the carbon layer changes greatly. Therefore, there is room for improvement. In consideration of this, it is conceivable to calculate the amount of decrease in the inner diameter of the carbon layer in advance and press-fit under this assumption. However, since the tolerance of the carbon bearing is extremely small, There are cases where it does not pass. In such a case, it is necessary to cut the carbon layer after press-fitting the bearing so as to obtain a desired inner diameter, and thus there is a problem that the productivity of the bearing is lowered.

  Accordingly, an object of the present invention is to suppress a large external force from being applied to the sliding surface layer while improving productivity, and to suppress a large change in the inner diameter of the sliding surface layer during press-fitting. It is to provide a layer bearing and a manufacturing method thereof.

In order to achieve the above object, the present inventor is constituted by a cylindrical sliding surface layer mainly made of carbon and a sintered body layer bonded to the sliding surface layer, and the bearing device includes A two-layer bearing having a press-fit structure, wherein the sintered body layer has alloy particles and / or metal particles, and voids existing between the alloy particles and / or metal particles, and When the press-fitting allowance at the time of press-fitting is 0.10 mm, the inner diameter change rate C (%) of the sliding surface layer expressed by the following equation (1) is regulated to 0 ≧ C ≧ −0.12. Features.
Change rate of inner diameter of sliding surface layer C = [(inner diameter of sliding surface layer after press-fitting-inner diameter of sliding surface layer before press-fitting) / inner diameter of sliding surface layer before press-fitting] × 100 (%) ..・ (1)

  If the sintered body layer has a gap as in the above configuration, a two-layer bearing is press-fitted into the bearing device to form alloy particles and / or metal particles (hereinafter sometimes referred to as alloy particles). When an external force is applied, the alloy particles and the like can be easily deformed, so that the external force is absorbed by the deformation. Accordingly, since the external force applied to the sliding surface layer is reduced, it is possible to suppress the inner diameter dimension of the sliding surface layer from becoming smaller than a predetermined value. As a result, it is not necessary to cut the carbon layer after press-fitting the bearing, and the productivity of the bearing is improved.

  However, if the sintered body layer has alloy particles or the like and voids existing between the alloy particles or the like, the above effect cannot be sufficiently exhibited. Is 0.10 mm, the inner diameter change rate C (%) of the sliding surface layer expressed by the equation (1) needs to be regulated to 0 ≧ C ≧ −0.12.

The reason for regulating the inner diameter change rate C of the sliding surface layer on the basis of the case where the press-fitting allowance is 0.10 mm is that if the press-fitting allowance is too small, the fixing force of the bearing with respect to the bearing device becomes small, and the bearing On the other hand, if the press-fitting allowance is too large, the pressure applied to the sliding surface layer increases, and the sliding surface layer is chipped.
Further, “mainly composed of carbon” means that the ratio of the weight of carbon to the total weight of the sliding surface layer is 50% or more.
Furthermore, in the specification of the present invention, it is expressed as “layer”, but this is a wide concept including not only a clear interface but also a slightly unclear interface.

As the alloy particles, iron-based, copper-based, stainless-based, or tungsten-based particles are preferably used, and copper, iron, zinc, and tin are preferably used as the metal particles.
In view of cost and the like, it is desirable to use the above-mentioned alloy particles and the like, but the present invention is not limited to these.

The sliding surface layer includes at least one oxide selected from an oxide group consisting of silicon dioxide (SiO ₂ ), ferric oxide (Fe ₂ O ₃ ), and aluminum oxide (Al ₂ O ₃ ). Is desirable.
As described above, if the sliding surface layer contains an oxide such as silicon dioxide, the silicon dioxide or the like has a self-lubricating property and is difficult to wear. While being able to rotate, the wear in the sliding surface layer is suppressed. In addition, as for the addition ratio of silicon dioxide etc. with respect to 100 weight part of graphite powders, it is desirable that it is 3-6 weight part. This is because if the proportion is less than 3 parts by weight, the effect of adding an oxide may not be sufficiently exerted. On the other hand, if the proportion exceeds 6 parts by weight, the amount of carbon is relatively reduced. This is because the smooth rotation of the motor may be hindered.

The thickness ratio between the sliding surface layer and the sintered body layer is preferably 5:95 to 70:30.
In this way, when the ratio of the thickness of the sliding surface layer to the sintered body layer is less than 5:95, the sliding surface layer is thin, so the life as a sliding material is shortened and practically used. Problems can arise. On the other hand, when the ratio of the thickness of the sliding surface layer to the sintered body layer exceeds 70:30, the ratio of the sintered body layer becomes too small, and when the two-layer bearing is press-fitted into the bearing device, the alloy particles and / Or the deformation amount of the metal particles is reduced. For this reason, the external force applied to the sliding surface layer may not be reduced much, and the reinforcing effect of the sintered body layer may be reduced.

  A two-layer bearing composed of a cylindrical sliding surface layer mainly made of carbon and a sintered body layer bonded to the sliding surface layer, and having a structure press-fitted into a bearing device, The sintered body layer is composed of copper-nickel-zinc alloy particles and voids existing between the alloy particles, and the ratio of the density of the sintered body layer to the theoretical density of the alloy is 63. % To 72%.

Further, a two-layer bearing composed of a cylindrical sliding surface layer mainly made of carbon and a sintered body layer bonded to the sliding surface layer and having a structure press-fitted into a bearing device. The sintered body layer is composed of copper-tin alloy particles and voids existing between the alloy particles, and the ratio of the density of the sintered body layer to the theoretical density of the alloy particles is as follows. It is characterized by being restricted to 63% to 69%.
With these configurations, the inner diameter change rate C of the sliding surface layer is surely within the range of the above formula (1).

The sliding surface layer preferably contains at least one oxide selected from an oxide group consisting of silicon dioxide, ferric oxide, and aluminum oxide, and the sliding surface layer The ratio of the thickness of the sintered body layer is preferably 5:95 to 70:30.
The reason for this configuration is the same reason as described above.

  First, copper-nickel-zinc alloy particles are filled into a mold, and further, a molding powder mainly composed of carbon is filled into a mold existing inside the portion filled with the alloy particles. And a second step of producing a molded body by press-molding the alloy particles and the molding powder at a pressure of 127 to 137 MPa, and a third step of firing the molded body. It is characterized by.

In addition, the mold is filled with copper-tin alloy particles, and further, a molding powder mainly composed of carbon is filled into a mold existing inside the portion filled with the alloy particles. And a second step of producing a molded body by press-molding the alloy particles and the molding powder at a pressure of 147 to 157 MPa, and a third step of firing the molded body. It is characterized by.
With these manufacturing methods, the above-described two-layer bearing can be manufactured.

  According to the present invention, while improving performance and productivity as a sliding member, it is possible to suppress a large external force from being applied to the carbon layer, and to suppress a large change in the inner diameter of the carbon layer during press-fitting. There is an excellent effect of being able to.

Next, the present invention will be described in more detail with reference to embodiments. The present invention can be changed in design without departing from the scope of the claims, and is not limited to the following embodiments or examples described later.
The two-layer bearing of the present invention comprises a sliding surface layer mainly made of carbon and a sintered body layer bonded around the sliding surface layer.

  The sliding surface layer is preferably obtained by mixing and baking 5 to 80 parts by weight of a binder with respect to 100 parts by weight of graphite powder (carbon) having an average particle diameter of 1 to 200 μm. As the graphite powder (carbon), Although artificial graphite, natural graphite, soot, etc. are mentioned, it does not specifically limit. The average particle size of the graphite powder is preferably 1 to 200 μm. If the average particle size is less than 1 μm, the fluidity of the molding powder is deteriorated and the moldability is lowered, while the average particle size exceeds 200 μm. This is because not only the strength is lowered but also the sliding surface layer is easily peeled off. Considering this, the average particle diameter of the graphite powder is more preferably 10 to 100 μm.

  Examples of the binder include pitch, tar, and synthetic resin. As the synthetic resin, any of a thermosetting resin and a thermoplastic resin can be used. Particularly suitable synthetic resins include phenolic resins, epoxy resins, and furan resins.

  There are no particular limitations on the type of metal powder or alloy powder used in the present invention, and commercially available powders can be used. As the metal powder, copper, iron, zinc, tin and the like are preferably used, and as the alloy powder, copper-based, iron-based, stainless-based and tungsten-based powders are preferably used.

Next, the manufacturing process of the composite material of this invention is demonstrated. As a first step, a production step of a material used for the sliding surface layer of the composite material of the present invention will be described.
First, the graphite powder and the binder are kneaded. The compounding ratio of the graphite powder and the binder is 5 to 80 parts by weight, preferably 10 to 50 parts by weight of the binder with respect to 100 parts by weight of the graphite powder. When the amount of the binder is less than 5 parts by weight, the sliding surface layer is easily peeled off, and the amount of wear during sliding increases. On the other hand, if the amount of the binder exceeds 80 parts by weight, the shrinkage during firing is large and cracking is likely to occur. Further, since the amount of graphite is reduced, the sliding characteristics are deteriorated. When kneading, an appropriate amount of an organic solvent such as alcohol or acetone may be added as necessary. Moreover, you may add an additive, such as a solid lubricant and a film | membrane regulator, to graphite powder as needed. That is, solid lubricants such as molybdenum disulfide and tungsten disulfide may be added, and a film modifier such as silicon dioxide, ferric oxide, aluminum oxide is added in an amount of 3 to 6 parts by weight based on 100 parts by weight of graphite powder. May be. Next, the kneaded mass is pulverized and adjusted to a molding powder (hereinafter referred to as a molding powder). In addition, you may add additives, such as a mold release agent and a lubricant, to the obtained shaping | molding powder.

  Next, a molding process for producing the composite material of the present invention will be described as a second process. As shown in the schematic cross-sectional view of FIG. 1A, a mold 11 used in this molding step is a cylindrical die 5 and a cylindrical shape that is fitted into the die 5 from below and has a pressing ring at the lower end. The lower punch 2 is fitted along the cylinder inner wall of the lower punch 2 and has a cylindrical threshold member 6 having a pressing ring at the lower end, and is fitted along the cylinder inner wall of the threshold member 6 at the lower end. A cylindrical lower punch 3 having a pressing ring, a rod-like lower punch 4 fitted along the cylinder inner wall of the lower punch 3, and an upper punch 1 that can be fitted to the die 5 from above. Become.

Next, the step of forming a molded body using the mold 11 will be specifically described.
First, a metal powder and / or alloy powder 9 indicated by oblique lines is filled in a space surrounded by the die 5, the lower punch 2 and the threshold member 6 of the mold 11 (see FIG. 1A).
Next, the lower punch 3 is moved downward until the upper end of the lower punch 3 and the upper end of the lower punch 2 are in the same position, and the molding powder 10 mainly made of carbon is cut into the cutting member 6 and the lower punches 3, 4. The space surrounded by is filled (see FIG. 1B).

  Then, the threshold member 6 is moved downward until the upper end of the threshold member 6 between the molding powder 10 and the metal powder and / or alloy powder 9 is at the same position as the upper end of the lower punch 3 and the upper end of the lower punch 2. Move (see FIG. 1C). As described above, when the threshold member 6 is lowered, the molding powder 10 and the metal powder and / or the alloy powder 9 can be integrally molded, and the interface between the two layers does not occur.

Thereafter, the upper punch 1 is fitted into the die 5 from above and pressed downward, and the respective press rings are pressed upward while preventing the positions of one end of each of the lower punches 2 and 3 and the threshold member 6 from being displaced. Is pressed and the metal powder and / or alloy powder 9 and the molding powder 10 are pressure-molded (see FIG. 1D). In this way, both layers of the metal powder and / or alloy powder 9 and the molding powder 10 are firmly bonded and molded to form a metal and / or alloy layer 8 and a molding powder layer 7.
After molding, the upper punch 1 is removed upward from the die 5 and pushed upward so that the positions of the lower punches 2 and 3 and the squeeze member 6 are not displaced, and the lower punch 4 is moved downward from the molded body and pulled out. (See FIG. 1 (e)), a cylindrical molded body composed of the metal and / or alloy layer 8 and the molding powder layer 7 is taken out from the mold 11. A molded body is thus obtained.

Next, the molded body is fired as a third step. Thereby, the metal and / or alloy layer 8 becomes a sintered body layer, and the molding powder layer 7 becomes a sliding surface layer.
Here, it is preferable that the compact is fired in a non-oxidizing atmosphere or a reducing atmosphere. The firing temperature is a temperature at which the metal or alloy does not melt or decompose, and is, for example, 500 to 2000 ° C. By calcination in a non-oxidizing atmosphere or a reducing atmosphere, oxidative deterioration of the molded product is prevented. The firing temperature can be appropriately selected according to the melting point of the metal or alloy used for the metal and / or alloy layer 8. The fired molded article may be subjected to a rust prevention treatment such as applying an antioxidant.

  According to the above embodiment, the sliding surface layer can make use of the characteristics of carbon excellent in self-lubricating and corrosion resistance, and the sintered body layer made of metal and / or alloy can increase the strength of the composite material, and has good dimensions. It is possible to provide a composite material that enables post-processing with accuracy. Further, by integrally molding the sliding surface layer and the sintered body layer, productivity can be improved during molding. Further, in the finishing process for dimensioning the molded product obtained in the above embodiment, it is possible to use sizing that can obtain excellent dimensional accuracy. Furthermore, since cracks do not occur in the sliding surface layer due to sizing, it can be produced efficiently and inexpensively.

  Here, the molding pressure in the second step is preferably 127 to 200 MPa, and particularly preferably 127 to 157 MPa. This is because if the molding pressure is less than 127 MPa, the mold may be deformed due to insufficient pressure, and the molding may not be performed sufficiently. On the other hand, when the molding pressure exceeds 200 MPa, the space existing in the sintered body layer becomes small, and the alloy particles and / or metal particles cannot be easily deformed when the bearing is press-fitted. This is because the external force applied cannot be sufficiently reduced, and as a result, the inner diameter of the sliding surface layer may be smaller than a predetermined value.

  The composite material of the present invention can be used for a bearing, and preferably for a bearing used in a liquid, a gas atmosphere, and a high-temperature atmosphere up to about 300 ° C. However, the molding method shown in FIG. 1 is a method in which the sliding surface layer is formed inside the sintered body layer, but the sliding surface layer is formed outside the sintered body layer. It doesn't matter.

Hereinafter, the present invention will be specifically described with reference to two examples.
[First embodiment]
Example 1
Carbon graphitic powder is blended with 25 parts by weight of phenolic resin with respect to 100 parts by weight of carbon graphite powder (carbon is 95% by mass, ash content is 5% by mass, and average particle size is 10 μm). The mixture was kneaded at room temperature so that the powder and the resin were uniformly mixed. The obtained kneaded product was pulverized to an average particle size of 40 μm to obtain a molding powder.

  After the copper-nickel-zinc (Cu-Ni-Zn) -based alloy powder (average particle diameter 40 μm) having the composition shown in Table 1 is filled in a mold as shown in FIG. The body was filled into a mold as shown in FIG. 1B, and compression molded at a normal pressure of 127 MPa at a normal temperature by the molding process described in the above embodiment. Thereafter, the obtained molded product was fired at 800 ° C. in a reducing atmosphere, and the fired molded product was further sized. At this time, no crack occurred in the sliding surface layer of the molded product.

Here, as shown in FIG. 2, the obtained two-layer bearing 21 has an outer diameter L1 of 10 mm, a height L2 of 10 mm, an inner diameter L3 of the sintered body layer 22 of 7 mm, and an inner diameter L4 of the sliding surface layer 23. Is 5 mm. Further, since the density of the sintered body layer 22 is 5.5 g / cm ³ and the theoretical density of the Cu—Ni—Zn-based alloy powder is 8.73 g / cm ³ , The ratio to the theoretical density was 63% ([5.5 / 8.73] × 100). The sliding surface layer 23 is provided with the hook-shaped portion 23a, but the portion 23a may not be provided.
The two-layer bearing produced in this way is hereinafter referred to as the present invention bearing A1.

(Example 2)
A two-layer bearing was produced in the same manner as in Example 1 except that the pressing force in the molding step was 137 MPa.
Further, since the applied pressure was changed, the density of the sintered body layer 22 was 6.3 g / cm ^3. As a result, the ratio of the sintered body layer 22 to the theoretical density was 72% ([6.3 / 8 .73] × 100). The porosity of the sintered body layer 22 was 25.6%.
The two-layer bearing produced in this way is hereinafter referred to as the present invention bearing A2.

(Comparative Example 1)
A two-layer bearing was produced in the same manner as in Example 1 except that the applied pressure in the molding step was 235 MPa.
Further, since the applied pressure was changed, the density of the sintered body layer 22 was 6.5 g / cm ^3. As a result, the ratio of the sintered body layer 22 to the theoretical density was 75% ([6.5 / 8 .73] × 100).
The two-layer bearing produced in this way is hereinafter referred to as a comparative bearing Z1.

(Comparative Example 2)
A two-layer bearing was produced in the same manner as in Example 1 except that the pressing force in the molding step was 343 MPa.
Further, since the applied pressure was changed, the density of the sintered body layer 22 was 7.0 g / cm ³ , and as a result, the ratio of the sintered body layer 22 to the theoretical density was 80% ([7.0 / 8 .73] × 100). The porosity of the sintered body layer 22 was 17.4%.
The two-layer bearing produced in this way is hereinafter referred to as a comparative bearing Z2.

(Comparative Example 3)
A two-layer bearing was produced in the same manner as in Example 1 except that the sintered body layer 22 was not provided (consisting only of the sliding surface layer 23).
The sliding surface layer 23 has an outer diameter of 10 mm, a height of 10 mm, and an inner diameter L3 of 5 mm.
The two-layer bearing produced in this way is hereinafter referred to as a comparative bearing Z3.

(Experiment)
FIG. 5 and Table 2 show the results of examining the amount of decrease in the inner diameter (the inner diameter of the sliding surface layer 23) when the bearings A1 and A2 and the comparative bearings Z1 to Z3 are pressed into the bearing device.
In the experiment, as shown in FIG. 3, a press-fit member 24 having an inner diameter of L1-α (α is a press-fit allowance and is changed in a range of 0.02 to 0.18 mm) is prepared. As shown in FIG. 4, the bearing 21 was press-fitted into the press-fitted member 24.

As apparent from Table 2 and FIG. 5, when the press-fitting allowance is 0.10 mm, the inner diameter reduction amounts of the bearings A1 and A2 of the present invention are 0.002 mm and 0.004 mm, respectively. It is recognized that the inner diameter change rate C (%) of the sliding surface layer is -0.04 and -0.08, and is -0.12 or more. Therefore, it is not necessary to cut the sliding surface layer after the press-fitting of the two-layer bearing, and the productivity is improved.
Change rate of inner diameter of sliding surface layer C = [(inner diameter of sliding surface layer after press-fitting-inner diameter of sliding surface layer before press-fitting) / inner diameter of sliding surface layer before press-fitting] × 100 (%) ..・ (1)

  On the other hand, when the press-fitting allowance is 0.10 mm, the inner diameter reduction amounts of the comparative bearings Z1 and Z2 are 0.010 mm and 0.018 mm, respectively, and the inner diameter of the sliding surface layer shown in the above equation (1) It is recognized that the rate of change C (%) is −0.20 and −0.36, and is less than −0.12. Therefore, it is necessary to cut the sliding surface layer after the press-fitting of the two-layer bearing, and the productivity is lowered. In the comparative bearing Z3, when the press-fitting allowance exceeded 0.08 mm, the outer peripheral portion was scraped or the bearing was chipped, so the inner diameter reduction amount was not measured.

  Although a dimensional error of about 0.04 mm (maximum dimensional error of about 0.06 mm) may occur between the press-fitted member and the bearing, the inner diameter reduction amount is 0.02 mm or less (maximum 0). Less than 0.03 mm). Therefore, when looking at the case where the press-fit allowance is 0.14 mm and 0.16 mm in Table 2, in the bearings A1 and A2 of the present invention, the inner diameter reduction amount when the press-fit allowance is 0.14 mm is 0.005 mm or less, While it is recognized that the inner diameter reduction amount when the press-fitting allowance is 0.16 mm is 0.007 mm or less, in the comparative bearings Z1 and Z2, the inner diameter reduction amount when the press-fitting allowance is 0.14 mm is 0. It is recognized that the inner diameter reduction amount is 0.030 mm or more when 021 mm or more and the press-fitting allowance is 0.16 mm. Accordingly, when a dimensional error occurs to some extent between the press-fitted member and the bearing, the bearings A1 and A2 of the present invention suppress the change in the inner diameter (bearing inner diameter tolerance [preferably 0.02 mm, preferably 0.03 mm at the maximum]]. It can be seen that the two-layer bearing can be press-fitted (while keeping it inside), but the comparative bearings Z1 to Z3 cannot press-fit the two-layer bearing while suppressing changes in the inner diameter.

[Second Embodiment]
Example 1
The first embodiment described above except that the alloy powder is a copper-tin (Cu-Sn) -based alloy powder (average particle diameter of 40 μm) having the composition shown in Table 1 and the pressure in the forming step is 147 MPa. A two-layer bearing was prepared in the same manner as in Example 1 of the example.
The density of the sintered body layer 22 is 5.6 g / cm ³ , and the theoretical density of the Cu—Sn alloy powder is 8.83 g / cm ^3. The ratio to was 63% ([5.6 / 8.83] × 100).
The two-layer bearing produced in this way is hereinafter referred to as the present invention bearing B1.

(Example 2)
A two-layer bearing was produced in the same manner as in Example 1 except that the pressing force in the molding step was 157 MPa.
Further, since the applied pressure was changed, the density of the sintered body layer 22 was 6.1 g / cm ³ , and as a result, the ratio of the sintered body layer 22 to the theoretical density was 69% ([6.1 / 8]. .83] × 100). The porosity of the sintered body layer 22 was 25.2%.
The two-layer bearing produced in this way is hereinafter referred to as the present invention bearing B2.

(Comparative Example 1)
A two-layer bearing was produced in the same manner as in Example 1 except that the pressing force in the molding step was 225 MPa.
Further, since the applied pressure was changed, the density of the sintered body layer 22 was 6.3 g / cm ^3. As a result, the ratio of the sintered body layer 22 to the theoretical density was 72% ([6.3 / 8 .83] × 100).
The two-layer bearing produced in this way is hereinafter referred to as a comparative bearing Y1.

(Comparative Example 2)
A two-layer bearing was produced in the same manner as in Example 1 except that the applied pressure in the molding step was 265 MPa.
Further, since the applied pressure was changed, the density of the sintered body layer 22 was 6.7 g / cm ^3. As a result, the ratio of the sintered body layer 22 to the theoretical density was 76% ([6.7 / 8 .83] × 100). The porosity of the sintered body layer 22 was 15.4%.
The two-layer bearing produced in this way is hereinafter referred to as a comparative bearing Y2.

(Comparative Example 3)
A two-layer bearing was produced in the same manner as in Example 1 except that the pressing force in the molding step was 300 MPa.
Further, since the applied pressure was changed, the density of the sintered body layer 22 was 7.0 g / cm ³ , and as a result, the ratio of the sintered body layer 22 to the theoretical density was 79% ([7.0 / 8 .83] × 100).
The two-layer bearing produced in this way is hereinafter referred to as a comparative bearing Y3.

(Experiment)
FIG. 6 and Table 3 show the results of examining the amount of decrease in the inner diameter (the inner diameter of the sliding surface layer 23) when the bearings B1 and B2 and the comparative bearings Y1 to Y3 are pressed into the bearing device. The experiment was performed in the same manner as the experiment in the first embodiment. For reference, the results of the comparative bearing Z3 are also shown in FIG.

  As apparent from Table 3 and FIG. 6, when the press-fitting allowance is 0.10 mm, the inner diameter reduction amounts of the bearings B1 and B2 of the present invention are 0.002 mm and 0.006 mm, respectively. It is recognized that the change rate C (%) of the inner diameter of the sliding surface layer is −0.04 and −0.12, and is −0.12 or more. Therefore, it is not necessary to cut the sliding surface layer after the press-fitting of the two-layer bearing, and the productivity is improved.

  On the other hand, when the press-fitting allowance is 0.10 mm, the inner diameter reduction amounts of the comparative bearings Y1 to Y3 are 0.030 mm, 0.030 mm, and 0.035 mm, respectively, and the sliding shown in the above equation (1) It can be seen that the inner diameter change rate C (%) of the face layer is less than -0.12. Therefore, it is necessary to cut the sliding surface layer after the press-fitting of the two-layer bearing, and the productivity is lowered.

  As in the experiment of the first embodiment, when the press-fitting allowances are 0.14 mm and 0.16 mm, the bearings B1 and B2 of the present invention have an inner diameter when the press-fitting allowance is 0.14 mm. When the reduction amount is 0.015 mm or less and the press-fitting allowance is 0.16 mm, the inner diameter reduction amount is recognized to be 0.023 mm or less, whereas in the comparative bearings Y1 to Y3, the press-fitting allowance is 0.14 mm. In this case, the inner diameter reduction amount is 0.050 mm or more, and the inner diameter reduction amount when the press-fitting allowance is 0.16 mm is 0.055 mm or more. Therefore, when a certain dimensional error occurs between the press-fitted member and the bearing, the bearings B1 and B2 of the present invention can press-fit the two-layer bearing while suppressing the inner diameter change, but the comparative bearings Y1 to Y3 suppress the inner diameter change. However, it can be seen that the two-layer bearing cannot be press-fitted.

(Other matters)
(1) Alloy particles are not limited to copper-based particles such as Cu-Ni-Zn and Cu-Sn, but iron-based particles such as Fe-C and Fe-Cu-C, Fe-Cr A stainless steel material such as -Ni or a tungsten material such as W-Ni-Cr or W-Ni-Fe may be used. The present invention is not limited to alloy particles, and may be metal particles such as Fe, Cu, Zn, Sn. Furthermore, the present invention can also be used by mixing alloy particles and metal particles.
(2) Although the diameter of the two-layer bearing is not limited to 10 mm, the present invention is preferably applied to a two-layer bearing of about 1 mm to 100 mm, particularly a two-layer bearing of about 5 mm to 20 mm.

  The present invention can be used for a bearing of a fuel pump.

FIGS. 1A to 1E are views showing a manufacturing process of a two-layer bearing, and FIG. 1A is a schematic cross-sectional view when a metal and / or alloy powder is filled in a mold; FIG. 6B is a schematic cross-sectional view when the molding powder is filled, and FIG. 5C shows a threshold member between the molding powder and the metal and / or alloy powder. FIG. 4D is a schematic cross-sectional view at the time of pressure molding, and FIG. 4E is a schematic cross-sectional view at the end of molding. It is sectional drawing of the two-layer bearing of this invention. It is sectional drawing which shows the relationship between a two-layer bearing and a press-fit member. It is sectional drawing which shows the state which press-fitted the two layer bearing to the to-be-fitted member. It is a graph which shows the relationship between the press-fitting allowance and internal-diameter reduction | decrease when this invention bearing A1, A2 and comparative bearing Z1-Z3 are press-fitted in a to-be-fitted member. It is a graph which shows the relationship between the press-fitting allowance when the present invention bearings B1 and B2 and the comparative bearings Y1 to Y3 and Z3 are press-fitted into the press-fitted member, and the inner diameter reduction amount.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper punch 2, 3, 4 Lower punch 5 Die 6 Cutting member 7 Molding powder layer 8 Metal and / or alloy layer 9 Metal and / or alloy powder 10 Molding powder 11 Mold 21 Two-layer bearing 22 Firing Bonded layer 23 Sliding surface layer 24 Press-fit member

Claims (10)

A two-layer bearing composed of a cylindrical sliding surface layer mainly made of carbon and a sintered body layer bonded to the sliding surface layer, and having a structure press-fitted into a bearing device,
The sintered body layer has alloy particles and / or metal particles, and voids existing between the alloy particles and / or metal particles, and the press-fitting allowance at the time of the press-fitting is 0.10 mm. Further, the inner diameter change rate C (%) of the sliding surface layer represented by the following formula (1) is regulated to 0 ≧ C ≧ −0.12, and the two-layer bearing is characterized in that:
Change rate of inner diameter of sliding surface layer C = [(inner diameter of sliding surface layer after press-fitting-inner diameter of sliding surface layer before press-fitting) / inner diameter of sliding surface layer before press-fitting] × 100 (%) ..・ (1)   2. The alloy particles may be iron-based, copper-based, stainless-based, or tungsten-based, and the metal particles may be copper, iron, zinc, or tin. 2 layer bearing.   3. The two-layered structure according to claim 1, wherein the sliding surface layer includes at least one oxide selected from an oxide group consisting of silicon dioxide, ferric oxide, and aluminum oxide. bearing.   The two-layer bearing according to any one of claims 1 to 3, wherein a thickness ratio between the sliding surface layer and the sintered body layer is 5:95 to 70:30. A two-layer bearing composed of a cylindrical sliding surface layer mainly made of carbon and a sintered body layer bonded to the sliding surface layer, and having a structure press-fitted into a bearing device,
The sintered body layer is composed of copper-nickel-zinc alloy particles and voids existing between the alloy particles, and the ratio of the density of the sintered body layer to the theoretical density of the alloy is as follows. A two-layer bearing characterized by being restricted to 63% to 72%. A two-layer bearing composed of a cylindrical sliding surface layer mainly made of carbon and a sintered body layer bonded to the sliding surface layer, and having a structure press-fitted into a bearing device,
The sintered body layer is composed of copper-tin alloy particles and voids existing between the alloy particles, and the ratio of the density of the sintered body layer to the theoretical density of the alloy particles is 63. A two-layer bearing characterized by being restricted to% to 69%.   The two-layered material according to claim 5 or 6, wherein the sliding surface layer contains at least one oxide selected from the group consisting of silicon dioxide, ferric oxide, and aluminum oxide. bearing.   The two-layer bearing according to any one of claims 5 to 7, wherein a thickness ratio between the sliding surface layer and the sintered body layer is 5:95 to 70:30. First, copper-nickel-zinc alloy particles are filled into a mold, and further, a molding powder mainly composed of carbon is filled into a mold existing inside the portion filled with the alloy particles. Process,
A second step in which the alloy particles and the molding powder are pressure-molded at a pressure of 127 to 137 MPa to form a molded body;
A third step of firing the molded body;
A method for producing a two-layer bearing, comprising: A first step of filling copper-tin-based alloy particles in a mold and further filling a molding powder mainly composed of carbon into a mold existing inside a portion filled with the alloy particles; ,
A second step in which the alloy particles and the molding powder are pressure-molded at a pressure of 147 to 157 MPa to form a molded body;
A third step of firing the molded body;
A method for producing a two-layer bearing, comprising:

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