JPS6037161B2 - Manufacturing method for high-precision sintered gears - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement on the conventionally known manufacturing method for forming gears, in which iron powder or the like is placed in a mold, pressure-molded at a predetermined pressure, and then formed at a predetermined temperature. The purpose of this is to minimize the dimensional change of the fine-toothed and complex gear surface to the green compact after the powder compaction is applied during the morning refinement, and to provide a highly accurate high-precision anti-coagulation gear. .

Mix 1 to 2% nickel powder (weight ratio) and 0.5% carbon (weight ratio) with iron powder and put it into a mold.
Pressure molding was carried out at a temperature of 5°C, and then competitive bonding was performed at 1130°C to produce scale-stripe gears, but since nickel was added, strength was obtained, but due to the undesirable fringes, the scale-stripe gears were produced. It shrinks by 5% and there is variation in shrinkage, so no matter how much you increase the precision of the mold, it is useless, and the quality varies significantly, making it impossible to achieve high precision.
The drum gears mentioned above could not be manufactured by grinding and had to be manufactured by cutting, which was extremely costly.

In the present invention, when steel powder is added to iron powder and the mixture is combined after pressure molding, 1 to 2
Known technology that may expand when adding %C
As a result of various experiments, we applied steel powder and nickel powder in approximately equal amounts (within 1 to 10%) for large-diameter, high-precision (JIS or higher) office machine gears, especially large-sized gears for driving photoreceptors. A mixed powder consisting of iron powder containing 0.5% carbon (weight ratio), the balance being 0.5% carbon, was placed in an extremely high-precision mold and pressure-molded at exactly the same pressure as the well-known Toshijima Sukikin method, and then When bonded, the precision of the tooth surface of the gear could be made extremely high.

Next, one embodiment of the present invention will be described.

Figure 1 shows a mold used in the method of the present invention, in which a highly accurate tooth pattern 2 of JIS standard 0 grade is formed on the inner surface of the center hole of die 1 using a gear grinder, and a similar tooth pattern 2 of JIS standard 2 to 3 grade is formed below. tooth type 3
The lower punch 4 which has been formed is iron-fitted, and a recess 5 with a height of approximately 14 is formed in the upper part, and the mixed powder is stored in this recess 5 until the upper surface becomes approximately flush with the upper part, and the powder is punched from above in the same manner as the lower mold. After forming the tooth pattern 6, a punch 7 is press-formed at a pressure of about 5 n/.

Then, it was sintered at 113,000. In addition, the clearance between punch 4 and die 1 is set to 2/10 or less. As a result, the shape of the shape shown in Figures 2 and 3 was 6.7.
After 7 days, a gear 8 with the following accuracy was obtained. Module 1 The amount of nickel powder used to increase strength is limited to 10%, and if it exceeds 10%, the machinability deteriorates and the teeth become chipped, making it impossible to put it to practical use.

According to the method of the present invention, by mixing approximately equal amounts (weight ratio) of copper powder and nickel powder within 1 to 10% with 0.5% carbon-containing iron powder, the nickel powder shrinks easily during sintering. In particular, the impolute surface is intricately balanced and the density distribution inside is uniform.Especially, the teeth have stepped portions 8a on both sides, so the compression ratio is higher than that of the main body, and the surface Dimensional accuracy can be increased, and gears with more than 1,000 modules can be manufactured by competitive bonding, which meets the gear accuracy level 5 of the JIS standard, which was impossible with conventional sintered products. .

As a result, compared to the gear manufacturing method using the hob cutting method, which had no choice but to be adopted, the manufacturing time was approximately 1'3, making it possible to reduce the overall cost by 40 to 50%. It is effective.

Note that the pressing force of the upper punch and the brazing temperature are almost the same as in the conventional coagulation method.

[Brief explanation of the drawing]

Fig. 1 is a front cross-sectional view of the mold used in the present invention, Fig. 2 is a front view of a high-precision heating gear obtained by the method of the present invention, and Fig. 3 is a side cross-sectional view taken along line A-A in Fig. 2. be. 8... Race gear. Figure 2 Figure 1 Figure 3

Claims (1)

[Claims] 1 The thickness of the tooth part is made slightly thinner than the main body part, and when compacting with the same punch, the tooth part becomes relatively denser, and like a chamfered part, it can be made parallel to or perpendicular to the pressing direction. For powder metallurgy gears with a profile that has a continuous surface that is partially perpendicular to the pressing direction, Ni powder and Cu powder with equal weights and 0.5% C of iron are used. A method for manufacturing a high-precision sintered gear in which a mixed powder consisting of powder is press-formed at a predetermined pressure and sintered at a predetermined temperature.