Sintered gear and speed reducer

Abstract

To improve the silentness on a sintered gear.SOLUTION: A sintered gear 1 has a coating amount of Cu to a copper-covered iron powder in a range of 5 to 65 (wt)%. This makes it possible to improve the silentness while suppressing the reduction in dimensional accuracy. Particularly, the sintered gear 1 has a surface roughness of a tooth surface in a range of 0.5 to 1.3 Ra / μm. This makes it possible to improve the silentness while suppressing the reduction in productivity. Besides, the sintered gear 1 has a void ratio in a range of 15 to 35%. This makes it possible to attenuate the propagation of sound.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a sintered gear and a reducer that are excellent in quietness. [Background technology]

[0002] BACKGROUND ART Conventionally, a sintered gear that uses copper-coated iron powder to achieve both improved quietness and improved strength has been known (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-36745 Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventional sintered gears have not achieved sufficient improvement in noise reduction. An object of the present invention is to improve noise reduction in sintered gears. [Means for solving the problem]

[0005] In order to solve the above problems, the sintered gear according to the first invention is a sintered gear obtained by sintering a raw material powder mainly composed of copper-coated iron powder, and is characterized in that the sintered gear is made of an iron-copper sintered material with a Cu content of 5% (by weight) or more, the Cu coating amount in the copper-coated iron powder is in the range of 5 to 65% (by weight), and the surface roughness of the tooth flank is in the range of 0.5 to 1.3 Ra / μm. In the sintered gear according to the first aspect of the present invention, the amount of Cu coated in the copper-coated iron powder is 5 to 65% (by weight), which makes it possible to improve noise reduction while suppressing a decrease in dimensional accuracy. In particular, the sintered gear according to the first aspect of the present invention has a tooth surface roughness in the range of 0.5 to 1.3 Ra / μm, which makes it possible to improve noise reduction while suppressing a decrease in productivity. Here, the sintered gear corresponds to, for example, the sintered gear 1 described below.

[0006] A sintered gear according to a second aspect of the present invention is the sintered gear according to the first aspect of the present invention, characterized in that the porosity is in the range of 15 to 35%. In the sintered gear according to the second aspect of the present invention, the porosity is in the range of 15 to 35%, which makes it possible to attenuate the propagation of sound while maintaining strength.

[0007] A sintered gear according to a third aspect of the present invention is the sintered gear according to the first or second aspect of the present invention, wherein the density is 5.6 to 7.0 g / cm 3 and contains Sn in the range of 5 to 12 (by weight) % relative to the Cu content. A sintered gear according to a third aspect of the present invention contains Sn in a range of 5 to 12 (by weight)% relative to the Cu content, and has a tooth density of 5.6 to 7.0 g / cm 3 This makes it possible to appropriately adjust the strength, hardness, and wear resistance on the one hand, and the quietness on the other.

[0008] The sintered gear according to the fourth invention is the sintered gear according to the first or second invention, characterized in that it contains Sn in a range of 2 to 10 (weight)% relative to the Cu content, and C in a range of 1 to 5 (weight)% relative to the total amount. A sintered gear according to a fourth aspect of the present invention contains 2 to 10% by weight of Sn relative to the Cu content, and 1 to 5% by weight of C (carbon / graphite) relative to the total content, which allows for appropriate adjustment of improvements in strength, hardness, and wear resistance, as well as quietness.

[0009] A reducer according to a fifth aspect of the present invention is characterized by including the sintered gear according to the first or second aspect of the present invention. In the reducer according to the fifth aspect of the present invention, it is possible to improve quietness. [Effects of the Invention]

[0010] The sintered gear according to the present invention can improve noise reduction. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view of a sintered gear 1. [Figure 2] FIG. 2 is a diagram showing the compositions of sintered gears according to Examples 1 to 4 and Comparative Examples 1 to 5. [Figure 3] FIG. 1 is a schematic diagram of a test device 100 used in a sound pressure evaluation test. [Figure 4] FIG. 3 is a graph comparing the results of a sound pressure evaluation test for the sintered gear according to Example 1 and the sintered gear according to Comparative Example 1. [Figure 5] FIG. 10 is a graph comparing the results of a sound pressure evaluation test for the sintered gear according to Example 2 and the sintered gear according to Comparative Example 2. [Figure 6] FIG. 10 is a graph comparing the results of a sound pressure evaluation test for the sintered gear according to Example 3 and the sintered gear according to Comparative Example 3. [Figure 7] FIG. 10 is a graph comparing the results of a sound pressure evaluation test for the sintered gear according to Example 4 and the sintered gear according to Comparative Example 4. [Figure 8] FIG. 10 is a graph comparing the results of a sound pressure evaluation test for the sintered gear of Example 1 and the sintered gear of Comparative Example 5. [Figure 9] FIG. 10 is a graph comparing the results of a sound pressure evaluation test for the sintered gear of Example 2 and the sintered gear of Comparative Example 5. [Figure 10] FIG. 10 is a graph comparing the results of a sound pressure evaluation test for the sintered gear of Example 3 and the sintered gear of Comparative Example 5. [Figure 11] FIG. 10 is a graph comparing the results of a sound pressure evaluation test for the sintered gear of Example 4 and the sintered gear of Comparative Example 5. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The sintered gear according to the present invention can be applied to various types of gears such as spur gears, helical gears, etc. In this embodiment, an example will be described in which the sintered gear according to the present invention is applied to a sintered gear 1, which is a type of helical gear. FIG. 1 is a perspective view of a sintered gear 1. As shown in Fig. 1, the sintered gear 1 includes a plurality of tooth traces (teeth) 20 arranged at equal intervals on the outer circumferential surface. The sintered gear 1 also has a shaft hole h formed along the central axis. Each tooth trace 20 is inclined with respect to the central axis and extends spirally.

[0013] The sintered gear 1 is made of a sintered body and has a porous structure. The sintered gear 1 is an iron-copper based sintered material obtained by sintering raw material powder mainly composed of copper-coated iron powder, and is made of an iron-copper based sintered material with a Cu content of 5% (by weight) or more. In particular, in the sintered gear 1, the amount of Cu coated on the copper-coated iron powder is set to a range of 5 to 65% by weight. That is, if the amount of Cu coated on the copper-coated iron powder is less than 5% by weight, the amount of Cu coated will be insufficient, exposing the iron and potentially reducing quietness. On the other hand, if the amount of Cu coated on the copper-coated iron powder exceeds 65% by weight, there is a risk of reduced dimensional accuracy. Therefore, by setting the amount of Cu coated on the copper-coated iron powder to a range of 5 to 65% by weight, it is possible to improve quietness while suppressing a reduction in dimensional accuracy.

[0014] In addition, the surface roughness of the tooth flank (surface of the tooth trace 20) of the sintered gear 1 is set to a range of 0.5 to 1.3 Ra / μm. That is, if the surface roughness of the tooth flank is less than 0.5 Ra / μm, the number of steps increases, which may reduce productivity. On the other hand, if the surface roughness of the tooth flank exceeds 1.3 Ra / μm, the friction on the tooth flank increases, which may reduce quietness. Therefore, by setting the surface roughness of the tooth flank within a range of 0.5 to 1.3 Ra / μm, it is possible to improve quietness while suppressing a decrease in productivity. Furthermore, the sintered gear 1 has a porosity (particularly the porosity of the tooth trace 20) in the range of 15 to 35%. A porosity of less than 15% could result in sound propagation not being attenuated, resulting in loud noise. On the other hand, a porosity of more than 35% could result in insufficient strength due to a decrease in density, potentially leading to gear damage. Therefore, by setting the porosity in the range of 15 to 35%, sound propagation can be attenuated while maintaining strength.

[0015] Here, in the sintered gear 1, the iron-copper sintered material has a composition containing Sn in a range of 5 to 12 (by weight) % relative to the Cu content, and the density (particularly the density of the tooth trace 20) is 5.6 to 7.0 g / cm 3 It is preferable that the content of Cu is within this range. This makes it possible to appropriately adjust the strength, hardness, and wear resistance of the sintered gear 1, as well as the noise reduction. Here, the "Cu content" refers to the amount of Cu alone in the total amount of the iron-copper sintered material (excluding components other than Cu (iron, etc.)) (the same applies in the following description). That is, in the iron-copper sintered material, when the composition contains Sn in the range of 5 to 12 (by weight)% relative to the Cu content, the density is 5.6 g / cm 3 If the density is less than 7.0 g / cm, the required strength may not be ensured. 3 If it exceeds this value, the effect of attenuating the drive noise may decrease. The density is 5.6 to 7.0 g / cm 3 Within this range, if the Sn content in the iron-copper sintered material is less than 5% (by weight) relative to the Cu content, there is a risk that the improvement in strength, hardness, and wear resistance will be insufficient. On the other hand, if the Sn content in the iron-copper sintered material exceeds 12% (by weight) relative to the Cu content, there is a risk that the material will become brittle. Therefore, the iron-copper sintered material is configured to contain Sn in the range of 5 to 12 (by weight)% relative to the Cu content, and the tooth density is set to 5.6 to 7.0 g / cm 3By keeping the value within this range, it is possible to improve strength, hardness, and abrasion resistance while also improving quietness, making it possible to appropriately adjust the improvements in strength, hardness, and abrasion resistance and the improvements in quietness.

[0016] Alternatively, in the sintered gear 1, the iron-copper sintered material preferably contains 2 to 10% by weight of Sn relative to the Cu content, and 1 to 5% by weight of C (carbon or graphite) relative to the total amount (total amount or weight). This allows the sintered gear 1 to be appropriately adjusted to improve strength, hardness, and wear resistance, as well as quietness. That is, in the case of an iron-copper sintered material, when the composition contains 1 to 5% by weight of C relative to the total amount (total amount / weight), if the Sn content is less than 2% by weight relative to the Cu content, there is a risk that the improvement in strength, hardness, and wear resistance will be insufficient. On the other hand, if the Sn content exceeds 10% by weight relative to the Cu content, there is a risk that the material will become brittle. Furthermore, in the case of an iron-copper sintered material, when the Sn content is within the range of 2-10% (by weight) relative to the Cu content, if the C content is less than 1% (by weight) relative to the total amount (total amount / weight), the improvement in wear resistance will be insufficient, and lubricity and quietness may decrease. On the other hand, if the C content exceeds 5% (by weight) relative to the total amount (total amount / weight), the sintered strength may decrease. Therefore, by using a composition in which the iron-copper sintered material contains Sn in the range of 2 to 10 (weight)% relative to the Cu content and C (carbon) in the range of 1 to 5 (weight)% relative to the total amount (total amount / weight), it becomes possible to improve strength, hardness, and wear resistance while also improving quietness, making it possible to appropriately adjust the improvements in strength, hardness, and wear resistance, and the improvements in quietness. In addition, when the iron-copper sintered material has a composition that contains 2 to 10 (weight)% Sn relative to the Cu content and 1 to 5 (weight)% C (carbon) relative to the total amount (total amount / weight), it is preferable to further contain 0.3 to 0.7 (weight)% P relative to the Cu content. This lowers the eutectic point during sintering, making it possible to lower the sintering temperature.

[0017] The sintered gear 1 can be used, for example, in a reducer. That is, the sintered gear 1 is applied to at least one type of gear among multiple types of gears (pinion gear, planetary gear, internal gear, etc.) included in the reducer. This makes it possible to reduce the production cost of the reducer and improve noise reduction.

[0018] (Method of manufacturing sintered gear 1) Next, a method for manufacturing the sintered gear 1 will be described. In manufacturing the sintered gear 1, first, raw material powder (raw material) is produced. The raw material powder is mainly composed of copper-coated iron powder, and is particularly configured so that the Cu content in the sintered body is 5% by weight or more. Specifically, raw material powder A can be used as the raw material powder, which is produced by stirring and mixing copper-coated iron powder and bronze powder. Raw material powder A contains 5% or more by weight of Cu. Raw material powder A also contains 5 to 12% by weight of Sn relative to the Cu content. Furthermore, in raw material powder A, the amount of Cu coated on the copper-coated iron powder is 5 to 65% by weight. Here, the "Cu content" refers to the amount of Cu alone in the total amount of the raw material powder (excluding components other than Cu (iron, etc.)) (the same applies in the following description). Alternatively, raw material powder B can be used, which is produced by stirring and mixing copper-coated iron powder, bronze powder, phosphorus copper powder, and graphite powder. Raw material powder B has a Cu content of 5% or more (by weight). Raw material powder B also contains Sn in the range of 2-10% by weight relative to the Cu content, C (carbon / graphite) in the range of 1-5% by weight relative to the total amount (total amount / weight), and P in the range of 0.3-0.7% by weight relative to the Cu content. Furthermore, in raw material powder B, the amount of Cu coating on the copper-coated iron powder is in the range of 5-65% by weight.

[0019] Next, a compacting step is carried out. In the compacting step, the raw material powder is compression-molded using a helical gear-shaped die to form a green compact. Specifically, the raw material powder thus produced is placed in the die. The raw material powder placed in the die is then press-molded at a predetermined compression ratio to form a green compact. At this time, the density of the sintered body after the sizing step described below is set to 5.6 to 7.0 g / cm. 3 The compression ratio is adjusted so that the compression ratio is within the range of Next, a sintering step is carried out. In the sintering step, the green compact is sintered to form a sintered body. Specifically, the green compact is sintered in a mesh belt sintering furnace under a predetermined atmosphere (in this embodiment, a H2-N2 atmosphere) and a predetermined temperature condition (in this embodiment, the sintering temperature is 855°C) to form a sintered body. Next, an oil immersion step is carried out, in which processing oil is applied to the surface of the sintered compact by dipping.

[0020] Next, the sizing process is carried out. In the sizing process, the sintered body is sized (re-compressed) using a helical gear-shaped mold. By sizing the sintered body, the dimensional accuracy and surface roughness are improved. In particular, the surface roughness of the sintered body before the sizing step is in the range of 1.35 to 2.15 Ra / μm, and by carrying out the sizing step, the surface roughness of the sintered body is set to be in the range of 0.5 to 1.3 Ra / μm. Furthermore, the sintered body before the sizing step has a porosity in the range of 17 to 33%, and by carrying out the sizing step, the porosity of the sintered body is set to a range of 15 to 35%. Next, a de-oiling and cleaning process is carried out. In this process, ultrasonic cleaning is carried out using a hydrocarbon-based cleaning solution to remove the processing oil adhering to the sintered body, and then the sintered body is dried in a dryer at 100°C. Next, a vacuum oil immersion process is carried out in which the sintered compact is immersed in lubricating oil, and after vacuuming in a desiccator for a predetermined time (20 minutes in this embodiment), the lubricating oil adhering to the surface of the sintered compact is removed. In this way, the sintered gear 1 is formed.

[0021] (Example) Next, an embodiment of the present invention will be described. FIG. 2 is a diagram showing the compositions of the sintered gears according to Examples 1 to 4 and Comparative Examples 1 to 5. FIG. 3 is a schematic diagram of a testing device 100 used in the sound pressure evaluation test. FIG. 4 is a diagram comparing the results of the sound pressure evaluation test for the sintered gear according to Example 1 and the sintered gear according to Comparative Example 1. FIG. 5 is a diagram comparing the results of the sound pressure evaluation test for the sintered gear according to Example 2 and the sintered gear according to Comparative Example 2. FIG. 6 is a diagram comparing the results of the sound pressure evaluation test for the sintered gear according to Example 3 and the sintered gear according to Comparative Example 3. FIG. 7 is a diagram comparing the results of the sound pressure evaluation test for the sintered gear according to Example 4 and the sintered gear according to Comparative Example 4. FIG. 8 is a diagram comparing the results of the sound pressure evaluation test for the sintered gear according to Example 1 and the sintered gear according to Comparative Example 5. FIG. 9 is a diagram comparing the results of the sound pressure evaluation test for the sintered gear according to Example 2 and the sintered gear according to Comparative Example 5. FIG. 10 is a diagram comparing the results of the sound pressure evaluation test for the sintered gear according to Example 3 and the sintered gear according to Comparative Example 5. FIG. 11 is a diagram comparing the results of the sound pressure evaluation test for the sintered gear according to Example 4 and the sintered gear according to Comparative Example 5. Four types of sintered gears (Examples 1 to 4) were manufactured as examples of the present invention. Five types of sintered gears (Comparative Examples 1 to 5) were manufactured as comparative examples. Then, a sound pressure evaluation test was conducted on the sintered gears of Examples 1 to 4 and Comparative Examples 1 to 5 using the testing device 100.

[0022] The sintered gears of Examples 1 to 3 were manufactured using the above-mentioned raw material powder A according to the manufacturing method of the sintered gear 1. Specifically, as shown in Fig. 2, the sintered gears of Examples 1 to 3 were manufactured using raw material powder A having a composition, by weight ratio relative to the total weight of the raw material powder, of 64% Fe, 34% Cu, and 2% Sn. The sintered gears of Examples 1 to 3 had a composition containing 5.91% (by weight) of Sn relative to the Cu content. In particular, for the sintered gear according to Example 1, the green density of the compact was 5.45 g / cm 3 The sintered density of the sintered body after the sizing process is 5.68 g / cm 3 The sintered body after the sizing process had a porosity of 30.7% and a surface roughness of 0.78 Ra / μm. In the sintered gear of Example 1, the change in porosity before and after the sizing process was 1.79%. On the other hand, for the sintered gear according to Example 2, the green density of the green compact was 5.70 g / cm 3 The sintered density of the sintered body after the sizing process is 5.96 g / cm 3 The sintered gear according to Example 2 had a porosity of 27.4% and a surface roughness of 0.63 Ra / μm after the sizing process. The sintered gear according to Example 2 had a porosity change of 1.41% before and after the sizing process. On the other hand, for the sintered gear according to Example 3, the green density of the green compact was 5.85 g / cm 3 The sintered density of the sintered body after the sizing process is 6.07 g / cm 3The sintered gear according to Example 3 had a porosity of 26.0% and a surface roughness of 1.28 Ra / μm after the sizing process. The sintered gear according to Example 3 had a porosity change of 0.68% before and after the sizing process.

[0023] The sintered gear of Example 4 was manufactured using the above-mentioned raw material powder B according to the manufacturing method of the sintered gear 1. Specifically, the sintered gear of Example 4 was manufactured using raw material powder B having a composition, by weight ratio relative to the total weight of the raw material powder, of 39.7% Fe, 53% Cu, 5% Sn, 0.3% P, and 2% C. The sintered gear of Example 4 had a composition containing 7.97 (by weight) % Sn, 0.52 (by weight) % P, and 3.29 (by weight) % C relative to the Cu content. In particular, for the sintered gear according to Example 4, the green density of the compact was 5.85 g / cm 3 The sintered density of the sintered body after the sizing process is 6.13 g / cm 3 The sintered body after the sizing process had a porosity of 22.2% and a surface roughness of 0.57 Ra / μm. In the sintered gear of Example 4, the change in porosity before and after the sizing process was 3.26%. Here, the density of the sintered gear according to Example 4 is 5.6 to 7.0 g / cm 3 By keeping the thickness within this range, it is possible to ensure strength.

[0024] The sintered gears of Comparative Examples 1 to 3 were manufactured using the raw material powder A according to the method for manufacturing the sintered gear 1. However, for the sintered gears of Comparative Examples 1 to 3, the sizing step of the method for manufacturing the sintered gear 1 was omitted. In particular, the sintered gear according to Comparative Example 1 had a green density of 5.45 g / cm 3 The sintered density of the sintered body after the sizing process is 5.54 g / cm 3The porosity of the sintered body after the sizing process was 32.5%, and the surface roughness of the sintered body after the sizing process was 1.83 Ra / μm. On the other hand, for the sintered gear according to Comparative Example 2, the green density of the green body was 5.70 g / cm 3 The sintered density of the sintered body after the sizing process is 5.84 g / cm 3 The porosity of the sintered body after the sizing process was 28.8%, and the surface roughness of the sintered body after the sizing process was 1.51 Ra / μm. On the other hand, for the sintered gear according to Comparative Example 3, the green density of the green compact was 5.85 g / cm 3 The sintered density of the sintered body after the sizing process is 6.02 g / cm 3 The porosity of the sintered body after the sizing process was 26.6%, and the surface roughness of the sintered body after the sizing process was 2.05 Ra / μm.

[0025] The sintered gear of Comparative Example 4 was manufactured using the raw material powder B according to the manufacturing method of the sintered gear 1. However, for the sintered gear of Comparative Example 4, the sizing step of the manufacturing method of the sintered gear 1 was omitted. In particular, the sintered gear according to Comparative Example 4 had a green density of 5.85 g / cm 3 The sintered density of the sintered body after the sizing process is 5.87 g / cm 3 The porosity of the sintered body after the sizing process was 25.4%, and the surface roughness of the sintered body after the sizing process was 1.34 Ra / μm. The sintered gear of Comparative Example 5 was manufactured using raw material powder containing iron powder as the main material, according to the above-described manufacturing method for the sintered gear 1. Specifically, the sintered gear of Comparative Example 5 was manufactured using raw material powder having a composition consisting of 97.5% Fe (atomized iron powder), 1.5% Cu (electrolytic copper powder), 1.0% C (graphite powder), and 0.75% lubricant (zinc stearate) by weight relative to the total weight of the raw material powder. In particular, the sintered gear according to Comparative Example 5 had a green density of 6.80 g / cm 3 The sintered density of the sintered body after the sizing process is 6.75 g / cm 3 The porosity of the sintered body after the sizing process was 13.7%, and the surface roughness of the sintered body after the sizing process was 1.50 Ra / μm.

[0026] As shown in FIG. 3, the test device 100 includes a drive motor 110, a drive gear shaft 130 connected to the drive shaft of the drive motor 110 via a coupling 120, a brake unit 140, a driven gear shaft 160 connected to the rotation shaft of the brake unit 140 via a coupling 150, and a microphone 170. The drive motor 110 , the coupling 120 , the brake unit 140 , and the coupling 150 are arranged on the upper surface of an installation table 190 supported by a vibration isolation table 180 . In the testing apparatus 100, a sintered gear g1 to be tested (specifically, the sintered gears according to Examples 1 to 4 and Comparative Examples 1 to 5) is press-fitted onto a drive gear shaft 130, and a mating gear g2 (a resin gear in this example) is press-fitted onto a driven gear shaft 160. The sintered gear g1 and mating gear g2 are meshed with each other at a predetermined center distance. A predetermined amount of grease is applied to the sintered gear g1 and mating gear g2 to be tested. This grease is used to reduce friction and wear during gear meshing and to prevent rust. When the drive motor 110 is driven, the drive gear shaft 130 rotates via the coupling 120. This causes the sintered gear g1 to be tested, which is press-fitted onto the drive gear shaft 130, to rotate, which in turn causes the mating gear g2 meshing with the sintered gear g1 to rotate. A sound pressure evaluation test was conducted using each of the sintered gears according to Examples 1 to 4 and Comparative Examples 1 to 5 as the test sintered gear g1. In the sound pressure evaluation test, a microphone 170 was placed at a position approximately 80 mm away from the meshing portion between the test sintered gear g1 and the mating gear g2, and the drive motor 110 was driven at 2000 rpm, and sound pressure was measured for 6 seconds by the microphone 170. The measurement frequency was 1200 to 2000 Hz.

[0027] As a result of the sound pressure evaluation test, as shown in Fig. 4, it was confirmed that in the frequency range of 1200 to 2000 Hz, the sound pressure value of the sintered gear of Example 1 was lower than that of the sintered gear of Comparative Example 1. In Fig. 4, the sound pressure value measured for the sintered gear of Example 1 is shown by a solid line, and the sound pressure value measured for the sintered gear of Comparative Example 1 is shown by a dashed line. 5, it was confirmed that in the frequency range of 1200 to 2000 Hz, the sound pressure value of the sintered gear of Example 2 was lower than that of the sintered gear of Comparative Example 2. In FIG. 5, the sound pressure value measured for the sintered gear of Example 2 is shown by a solid line, and the sound pressure value measured for the sintered gear of Comparative Example 2 is shown by a dashed line. 6, it was confirmed that in the frequency range of 1200 to 2000 Hz, the sound pressure value of the sintered gear of Example 3 was lower than that of the sintered gear of Comparative Example 3. In FIG. 6, the sound pressure value measured for the sintered gear of Example 3 is shown by a solid line, and the sound pressure value measured for the sintered gear of Comparative Example 3 is shown by a dashed line. 7, it was confirmed that in the frequency range of 1200 to 2000 Hz, the sound pressure value of the sintered gear of Example 4 was lower than that of the sintered gear of Comparative Example 4. In FIG. 7, the sound pressure value measured for the sintered gear of Example 4 is shown by a solid line, and the sound pressure value measured for the sintered gear of Comparative Example 4 is shown by a dashed line. 8, it was confirmed that in the frequency range of 1200 to 2000 Hz, the sound pressure value of the sintered gear of Example 1 was lower than that of the sintered gear of Comparative Example 5. In FIG. 8, the sound pressure value measured for the sintered gear of Example 1 is shown by a solid line, and the sound pressure value measured for the sintered gear of Comparative Example 5 is shown by a dashed line. 9, it was confirmed that in the frequency range of 1200 to 2000 Hz, the sound pressure value of the sintered gear of Example 2 was lower than that of the sintered gear of Comparative Example 5. In FIG. 9, the sound pressure value measured for the sintered gear of Example 2 is shown by a solid line, and the sound pressure value measured for the sintered gear of Comparative Example 5 is shown by a dashed line. 10, it was confirmed that in the frequency range of 1200 to 2000 Hz, the sound pressure value of the sintered gear of Example 3 was lower than that of the sintered gear of Comparative Example 5. In FIG. 10, the sound pressure value measured for the sintered gear of Example 3 is shown by a solid line, and the sound pressure value measured for the sintered gear of Comparative Example 5 is shown by a dashed line. 11, it was confirmed that in the frequency range of 1200 to 2000 Hz, the sound pressure value of the sintered gear of Example 4 was lower than that of the sintered gear of Comparative Example 5. In FIG. 11, the sound pressure value measured for the sintered gear of Example 4 is shown by a solid line, and the sound pressure value measured for the sintered gear of Comparative Example 5 is shown by a dashed line.

[0028] (Function of Sintered Gear 1) The sintered gear 1 is a sintered gear made by sintering raw material powder mainly composed of copper-coated iron powder. It is made of an iron-copper sintered material with a Cu content of 5% (by weight) or more, the Cu coating amount in the copper-coated iron powder is in the range of 5 to 65% (by weight), and the surface roughness of the tooth surface is in the range of 0.5 to 1.3 Ra / μm. That is, the amount of Cu coated in the copper-coated iron powder is within a range of 5 to 65% (by weight) in the sintered gear 1. This makes it possible to improve noise reduction while suppressing a decrease in dimensional accuracy. In particular, the surface roughness of the tooth surface of the sintered gear 1 is within the range of 0.5 to 1.3 Ra / μm, which makes it possible to improve noise reduction while suppressing a decrease in productivity. Furthermore, the sintered gear 1 has a porosity in the range of 15 to 35%, which allows for attenuation of sound propagation. The sintered gear 1 contains 5 to 12% by weight of Sn relative to the Cu content, and has a density of 5.6 to 7.0 g / cm 3 This makes it possible to improve strength, hardness, and abrasion resistance while also improving quietness, and allows for an appropriate adjustment between improvements in strength, hardness, and abrasion resistance and improvements in quietness. The sintered gear 1 contains 2 to 10% by weight of Sn relative to the Cu content, and 1 to 5% by weight of C (carbon) relative to the total content. This makes it possible to improve strength, hardness, and wear resistance while also improving quietness, and thus allows appropriate adjustment of the improvements in strength, hardness, and wear resistance, and the improvements in quietness. [Explanation of symbols]

[0029] 1 Sintered gears 20 Tooth line h Shaft hole

Claims

1. A sintered gear made by sintering raw material powder mainly composed of copper-coated iron powder, The material is an iron-copper sintered material having a Cu content of 5% (by weight) or more, the amount of Cu coated in the copper-coated iron powder is within the range of 5 to 65 (wt%); A sintered gear characterized in that the surface roughness of the tooth surface is within the range of 0.5 to 1.3 Ra / μm.

2. 2. The sintered gear according to claim 1, wherein the porosity is in the range of 15 to 35%.

3. Density 5.6 to 7.0 g / cm ３ is within the range of 3. The sintered gear according to claim 1, wherein the Sn content is in the range of 5 to 12% (by weight) relative to the Cu content.

4. Contains Sn in the range of 2 to 10% (by weight) relative to the Cu content, 3. The sintered gear according to claim 1, further comprising 1 to 5% by weight of C based on the total amount.

5. A reducer comprising the sintered gear according to claim 1 or 2.

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