JP7676901B2 - Manufacturing method of plastic gear and plastic gear - Google Patents

Description

The present invention relates to a method for manufacturing plastic gears and plastic gears.

Resin gears are lightweight and quiet, and are widely used, for example, as gears for vehicles or industry. A known method for manufacturing such resin gears is to use a molding material for resin gears that contains fibers and a thermosetting resin. For example, the manufacturing method described in Patent Document 1 includes a process in which phenolic resin powder and aramid fibers, etc. are dispersed in water and paper-formed to obtain a sheet-shaped molding material, and a process in which the obtained molding material is cut into gear shapes and a plurality of sheets are stacked to form a blank body that is compression molded while being heated.

JP 2014-51097 A

In recent years, there are cases where high strength is desired for plastic gears using the above-mentioned technology.

Therefore, the present invention aims to provide a method for manufacturing plastic gears that can increase the strength of plastic gears, and to provide plastic gears with increased strength.

The method for manufacturing a resin gear according to one aspect of the present invention is a method for manufacturing a resin gear having an annular resin member and a metal bushing using a resin gear molding material, and includes a first step of filling a mold with the resin gear molding material and applying pressure to form a first annular intermediate body, a second step of placing the first intermediate body and the metal bushing between an upper die and a lower die and heating and compressing them to form a second annular intermediate body, and a third step of forming a tooth profile by gear cutting on the outer periphery of the second intermediate body, and in the second step, recesses are formed at multiple locations to be cut in the gear cutting process by multiple first protrusions on the upper die and multiple second protrusions on the lower die.

According to the manufacturing method for resin gears according to one aspect of the present invention, in the second step in which an annular second intermediate body is formed, recesses are formed at multiple planned cutting locations in the gear cutting process by the multiple first protrusions of the upper mold and the multiple second protrusions of the lower mold. The compression ratio of the resin is high in the area in which such recesses are formed. By increasing the compression ratio of the resin in the area in which the recesses are formed, the filling rate of the fibers in the area surrounding the recesses is increased. This makes it possible to improve the strength of the resin in the area surrounding the recesses, i.e., the area in which the tooth profile is formed after the gear cutting process. As described above, according to the manufacturing method for resin gears according to one aspect of the present invention, it is possible to realize high strength in the manufactured resin gears.

In the method for manufacturing a resin gear according to one aspect of the present invention, in the second step, multiple recesses may be formed over the entire circumferential area of the second intermediate body. This makes it possible to appropriately improve the strength of each tooth profile formed over the entire circumferential area.

In the manufacturing method of a resin gear according to one aspect of the present invention, in the second step, the recesses formed by the first convex portion and the recesses formed by the second convex portion may be formed alternately in the circumferential direction of the second intermediate body. By forming the recesses by the first convex portion and the recesses by the second convex portion alternately in the circumferential direction in this manner, it is possible to appropriately form recesses corresponding to each tooth profile when manufacturing a helical gear with a twisted tooth profile. In other words, such a manufacturing method makes it possible to suitably manufacture a helical gear with improved strength of each tooth profile.

In the manufacturing method of a resin gear according to one aspect of the present invention, in the second step, the recess may be formed so that it tapers toward the bottom of the recess. By making the recess tapered, it becomes easier to overlap the cut area formed by the gear cutting process that forms the twisted tooth profile with the recess area, and it is possible to prevent the area whose strength has been improved by forming the recess from being cut by the subsequent gear cutting process. In other words, this manufacturing method makes it possible to suitably manufacture helical gears with improved strength for each tooth profile.

A resin gear according to one aspect of the present invention includes a metal bush and an annular resin member arranged around the metal bush, and a plurality of teeth are formed in the circumferential direction on the outer periphery of the resin member, and at least a portion of the region in which the teeth are formed in the resin member may have a higher fiber filling rate than a region in which the teeth are not formed. In the resin gear according to one aspect of the present invention, the fiber filling rate of the region in which the teeth are formed is higher. This can improve the strength of the resin in the region in which the teeth are formed.

The present invention provides a method for manufacturing plastic gears that can increase the strength of plastic gears, and plastic gears with increased strength.

FIG. 1 is a perspective view showing a resin gear according to an embodiment. Fig. 2(a) is a diagram for explaining a method for producing a resin gear molding material according to an embodiment, and Fig. 2(b) is a diagram continuing from Fig. 2(a). Fig. 3(a) is a photograph showing a resin gear molding material according to an embodiment, and Fig. 3(b) is a photograph showing an enlarged portion of Fig. 3(a). FIG. 4 is a schematic perspective view showing a mold used for molding a preform according to the embodiment. FIG. 5 is a perspective view showing a preform according to the embodiment. Fig. 6(a) is a schematic cross-sectional view showing a mold for heat compression molding, and Fig. 6(b) is a cross-sectional view showing a molded product as a second intermediate body. FIG. 7 is a perspective view showing an upper mold for heat compression molding. FIG. 8 is a perspective view showing a lower mold for heat compression molding. FIG. 9 is a perspective view showing a molded product as a second intermediate body after the heat compression molding. FIG. 10 is a diagram illustrating the filling rate of fibers in a molded article as the second intermediate body. FIG. 11 is a graph showing the relationship between fiber filling rate (fiber volume rate) and strength.

The following describes the embodiments in detail with reference to the attached drawings. In the description of the drawings, the same or corresponding elements are given the same reference numerals, and duplicate descriptions are omitted.

As shown in FIG. 1, the resin gear 1 manufactured by the manufacturing method according to this embodiment is a so-called high-strength resin gear, and is used as a gear for vehicles or industrial use. For example, the resin gear 1 can be used as a balance shaft gear or a camshaft gear in an engine. The resin gear 1 includes a metal bush 8 and a resin member 9. The resin gear 1 is a helical gear with twisted teeth.

The metal bush 8 is a member that is attached to, for example, a rotating shaft (not shown). The metal bush 8 is annular. The metal bush 8 is made of a metal such as stainless steel. The metal bush 8 is provided with a through hole 8h. The rotating shaft is inserted into the through hole 8h. The resin member 9 is a member that meshes with another gear. The resin member 9 is annular. The resin member 9 is made of resin. The resin member 9 is provided around the metal bush 8. A plurality of tooth shapes 9a are formed along the circumferential direction on the outer periphery of the resin member 9. A plurality of tooth shapes 9a are formed at predetermined intervals around the entire circumference of the resin member 9. As described above, the resin gear 1 is a helical gear, and the tooth shapes 9a are formed obliquely with respect to the rotating shaft. In the resin member 9, at least a portion of the region where the tooth shapes 9a are formed has a higher fiber filling rate than a region where the tooth shapes 9a are not formed (a portion other than the outer periphery of the resin member 9). Such a difference in fiber filling rate is realized by a manufacturing method described later (details will be described later).

Next, an example of a manufacturing method according to this embodiment will be described.

The manufacturing method according to this embodiment includes a manufacturing method for manufacturing a molding material for a resin gear 1, which is a molding material for the resin gear 1, and a manufacturing method for manufacturing the resin gear 1 using the molding material for the resin gear.

[Production of molding material for plastic gears]
First, a molding material for a resin gear is manufactured by preparing a raw material 5 containing (i) a thermosetting resin powder 2, (ii) wet fibers 3 having a moisture content of 10 to 25% by weight, and (iii) an additive (or a filler) 4, as shown in Fig. 2(a).

Examples of the resin powder 2 include phenol resin, imide resin, melamine resin, and epoxy resin. The resin powder 2 preferably has a particle size of about 1 to 200 μm. As the resin powder 2, one type of resin or a combination of two or more types of resins can be used. The amount of the resin powder 2 in the raw material 5 is preferably 30 to 80% by weight, and more preferably 45 to 65% by weight.

The wet fiber 3 includes, as fibrous materials, a first fiber 3P which is a para-aramid fiber and a second fiber 3M which is a meta-aramid fiber. The fiber length of the first fiber 3P is 3 mm ± 1 mm. The fiber length of the second fiber 3M is longer than the fiber length of the first fiber 3P. The fiber length of the second fiber 3M is at least twice the fiber length of the first fiber 3P. The fiber length of the second fiber 3M is 6 mm ± 1 mm. The wet fiber 3 may include other fibrous materials. For example, the wet fiber 3 may include acrylic fiber, cellulose fiber, carbon fiber, phenolic resin fiber, polyimide fiber, inorganic fiber, etc. Examples of inorganic fibers include carbon fiber, alumina fiber, alumina-silica fiber, glass fiber, mineral fiber, ceramic fiber, etc.

The fiber volume fraction (fiber volume content) of the raw material 5 is preferably 40% by volume or more, and more preferably 40-60% by volume. The fiber volume fraction is the volume ratio of the fibrous material contained in the raw material 5. The sum of the volume of the first fibers 3P and the volume of the second fibers 3M is more than half of the total volume of the wet fibers 3. The weight of the wet fibers 3 in the raw material 5 is preferably 25-55% by weight, and more preferably 35-45% by weight.

Examples of additives 4 include montanic acid esters, zinc stearate, talc, silicone rubber, zirconia, alumina, silica, barium sulfate, calcium carbonate, mica, potassium titanate, graphite, antimony trioxide, and antimony disulfide. The amount of additive 4 in raw material 5 is preferably 0 to 20% by weight, and more preferably 0.5 to 15% by weight.

As shown in FIG. 2(b), the raw material 5 is mixed for a predetermined time by the mixer 10. This forms the resin gear molding material 6 shown in FIG. 3(a) and FIG. 3(b). The resin gear molding material 6 contains a plurality of fine granules (fiber balls) as part of it. The resin gear molding material 6 forms a three-dimensional shape rather than a two-dimensional planar shape. The mixer 10 and its mixing method are not particularly limited as long as the raw materials can be mixed uniformly. For example, a Lödige mixer (manufactured by Lödige) and an Einrich mixer (manufactured by Nippon Eirich) can be used as the mixer 10.

In this embodiment, as shown in FIG. 2(b), an Einrich mixer is used as the mixer 10. The mixer 10 has a base 11, a mixing pan 12, a rotor 13, and a blade 14. The base 11 rotatably supports the mixing pan 12 and the rotor 13. The mixing pan 12 is a container that contains the raw material 5. The rotor 13 is a stirring blade that stirs the raw material 5. The rotor 13 is disposed in the mixing pan 12. In this mixer 10, the rotor 13 and the mixing pan 12 rotate at high speed, so that there is little dead zone in the mixing pan 12. In addition, in this mixer 10, the blade 14 scrapes off the material that is biased to the side of the mixing pan 12 due to centrifugal force, and further, because the mixing pan 12 is tilted, the scraped off material is brought into contact with the rotor 13, so that efficient mixing is performed.

[Manufacturing of plastic gears]
Next, the resin gear 1 is manufactured using the formed resin gear molding material 6 .
(Formation of preform)
First, the resin gear molding material 6 is preformed to form a preform as a first intermediate. Specifically, as shown in Fig. 4, a mold 20 including a lower mold 20B and an upper mold 20T is prepared, and the mold 20 is preheated to, for example, 80°C. The lower mold 20B has a cylindrical cavity 21. The upper mold 20T has a cylindrical protrusion 22 that fits into the cavity 21.

The required amount of resin gear molding material 6 is measured and the resin gear molding material 6 is uniformly filled into the cavity 21 of the lower die 20B. After filling, for example, a force is applied to the upper die 20T using a press machine or the like to pressurize the resin gear molding material 6. For example, the pressing conditions are such that the filled resin gear molding material 6 is pressed at a pressure of 70 MPa for 10 seconds. As a result, as shown in FIG. 5, a preform 25 is formed by preforming the resin gear molding material 6. Then, the preform 25 is removed from the die 20. The preform 25 is, for example, an annular object with an outer diameter of 90 mm and an inner diameter of 60 mm. The above-mentioned filling and pressurization of the resin gear molding material 6 are repeated to form two preforms 25. In this way, the resin gear molding material 6 is filled into the die 20 and pressurized to form the preform 25 as an annular first intermediate body (first step).

(Heat compression molding)
A tooth forming die 30 including a lower die 30B and an upper die 30T as shown in FIG. 6(a) is prepared, and the tooth forming die 30 is heated to 200±5°C. In FIG. 6(a), the detailed configuration of the lower die 30B and the upper die 30T is omitted (the detailed configuration will be described later with reference to FIG. 7 and FIG. 8). The two preforms 25 are dried in a dryer. The metal bush 8 is preheated to 90°C in a dryer. The dried preform 25 and the metal bush 8 are molded into the heated tooth forming die 30 without cooling. In the molding, the protrusion 8a provided on the outer circumferential surface of the metal bush 8 is sandwiched between the two (upper and lower) preforms 25, and these are placed in the tooth forming die 30. The mold is clamped in the tooth forming die 30, and the preform 25 and the metal bush 8 are heated and compressed. As a result, a molded product 40 is formed as a second intermediate body as shown in FIG. 6(b). In this manner, the two preforms 25 and the metal bush 8 are placed between the lower die 30B and the upper die 30T and heated and compressed to form a molded product 40 as an annular second intermediate body (second step).

When clamping the mold, for example, the molded product 40 is held for 30 seconds at a position 10 mm before the cut-off position (target thickness), then compressed with a pressure of 100 MPa up to the cut-off position, and held in this state for approximately 6 minutes to harden the resin. The molded product 40 is then removed from the tooth-forming mold 30, and any resin burrs are removed using scissors or the like. The molded product 40 is an annular object. In the molded product 40, the resin member 9 is composed of two preforms 25 that have been heated and compressed.

Here, as shown in FIG. 7, the upper die 30T has a disk-shaped pressing portion 33 that presses the preform 25 from above during heat compression. The pressing portion 33 has a plurality of first protrusions 33x formed on its outer periphery over the entire circumferential area. The first protrusions 33x extend toward the lower die 30B (downward). The first protrusions 33x are formed in a tapered shape toward their lower ends. The first protrusions 33x are configured to form recesses 25x (see FIG. 9) in the upper preform 25 during heat compression of the two preforms 25 and the metal bush 8 due to their shape. The shape of the first protrusions 33x corresponds to the shape of the recesses 25x desired to be obtained in the molded product 40. The position of each first protrusion 33x corresponds to the position of each recess 25x desired to be obtained in the molded product 40.

8, the lower die 30B has a hollow cylindrical housing 31 that houses the preform 25 and the metal bush 8 during heat compression. A plurality of second protrusions 31x are formed on the bottom surface 31a of the housing 31 over the entire circumferential area of the outer periphery. The second protrusions 31x extend toward the upper die 30T (upward). The second protrusions 31x are tapered toward their upper ends. The second protrusions 31x are configured to form recesses 25y (see FIG. 9) in the lower preform 25 during heat compression of the two preforms 25 and the metal bush 8 due to their shape. The shape of the second protrusions 31x corresponds to the shape of the recesses 25y to be obtained in the molded product 40. The position of each second protrusion 31x corresponds to the position of each recess 25y to be obtained in the molded product 40.

In the second step, the multiple first protrusions 33x of the upper mold 30T and the multiple second protrusions 31x of the lower mold 30B form recesses 25x and recesses 25y at multiple locations to be cut in the gear cutting process described below (see FIG. 9). That is, in the second step, recesses 25x and recesses 25y are formed at locations to be cut and discarded in the gear cutting process. In the second step, as shown in FIG. 9, multiple recesses 25x and multiple recesses 25y are formed over the entire circumferential area of the molded product 40.

In the second step, as shown in FIG. 9, the recesses 25x formed by the first protrusions 33x of the upper mold 30T and the recesses 25y formed by the second protrusions 31x are formed alternately in the circumferential direction of the molded product 40. By cutting along such recesses 25x and recesses 25y, a helical gear in which the tooth profile 9a is formed obliquely with respect to the rotation axis can be appropriately manufactured.

In the second step, the recesses 25x and 25y are formed so that they are tapered toward the bottom side of the recesses 25x and 25y. The bottom of the recess 25x is the region at the lower end of the recess 25x, and the bottom of the recess 25y is the region at the upper end of the recess 25y.

Figure 10 is a partially enlarged view of Figure 9, and is a diagram explaining the fiber filling rate in the molded product 40. As shown in Figure 10, when the recesses 25x and 25y are formed, the compression rate of the resin increases in the region where the recesses 25x and 25y are formed, and the fiber filling rate increases in the peripheral region of the region where the recesses 25x and 25y are formed. Specifically, for example, the fiber filling rate increases in the peripheral region, that is, region SA (region indicated by thick lines in Figure 10) along the shape of the recesses 25x and 25y, and region AA (region indicated by diagonal lines in Figure 10) between the recesses 25x and 25y. Such regions with a high fiber filling rate have higher strength than other regions (details will be described later).

Here, when the molded product 40 is cut so that the recesses 25x and recesses 25y formed alternately in the circumferential direction are connected to each other in the gear cutting process described later, the molded product 40 is cut along, for example, two cutting lines CL shown in FIG. 10. In this case, of the area AA between the recesses 25x and recesses 25y, the area A1 included between the two cutting lines CL is cut, but the area A2 not included between the two cutting lines CL remains uncut. In addition, since the molded product 40 is cut so that the recesses 25x and recesses 25y formed alternately in the circumferential direction are connected to each other, the cutting line CL is inclined with respect to the rotation axis, making it easier to overlap the cutting area with the area of the tapered recesses 25x and recesses 25y. As a result, as shown in Figure 10, it is possible to form the cutting line CL along a portion of region S1 of region SA that follows the shape of recess 25x and along a portion of region S2 of region SA that follows the shape of recess 25y (specifically, inside regions A1 and S2), and these regions S1 and S2 can remain even after cutting. In this way, at least a portion of the high-strength regions created by the formation of recess 25x and recess 25y (regions A2, S1, and S2 in the example shown in Figure 10) can remain even after gear cutting.

(gear cutting)
The thickness, outer diameter, and inner diameter of the molded product 40 are processed to a predetermined dimension by lathe processing. The molded product 40 is washed, and the outer periphery of the molded product 40 is subjected to gear cutting processing. Specifically, the molded product 40 is cut (gear cutting processing) so that the recesses 25x and the recesses 25y in the molded product 40 are connected to each other. That is, the cutting processing is performed by matching the phase of the parts with unevenness by the tooth forming shape, and the tooth shape shape of a predetermined dimension is finished. Examples of the gear cutting processing that can be applied include processing by a hobbing machine or a shaving machine. As a result, a tooth profile 9a (see FIG. 1) is formed on the outer periphery of the resin member 9 in the molded product 40. The manufacturing of the resin gear 1 is completed by the above.

[Action and Effect]
As described above, the manufacturing method of the resin gear 1 according to this embodiment is a method for manufacturing the resin gear 1 having the annular resin member 9 and the metal bush 8 using the resin gear molding material 6, and includes the following steps: a first step of filling the resin gear molding material 6 into the die 20 and pressurizing it to form a preform 25 as a first annular intermediate; a second step of arranging the two preforms 25 and the metal bush 8 between the lower die 30B and the upper die 30T and heating and compressing them to form a molded product 40 as a second annular intermediate; and a third step of forming a tooth profile 9a on the outer periphery of the molded product 40 by gear cutting. In the second step, recesses 25x and recesses 25y are formed at multiple planned cutting locations in the gear cutting by a plurality of first protrusions 33x of the upper die 30T and a plurality of second protrusions 31x of the lower die 30B.

According to the manufacturing method of the resin gear 1 of this embodiment, in the second step in which the annular molded product 40 is formed, the first protrusions 33x of the upper mold 30T and the second protrusions 31x of the lower mold 30B form recesses 25x and recesses 25y at the locations to be cut in the gear cutting process. The compression ratio of the resin is high in the region where such recesses are formed. By increasing the compression ratio of the resin in the region where the recesses 25x and recesses 25y are formed, the filling rate of the fibers in the peripheral region of the recesses 25x and recesses 25y is increased. This makes it possible to improve the strength of the resin in the peripheral region of the recesses, i.e., the region where the tooth profile 9a is formed after the gear cutting process. As described above, according to the manufacturing method of the resin gear 1 of this embodiment, it is possible to realize high strength of the manufactured resin gear 1.

The relationship between the fiber filling rate and strength will be described with reference to FIG. 11. FIG. 11 is a graph showing the relationship between the fiber filling rate (fiber volume fraction) and strength. The upper graph in FIG. 11 shows the relationship between the fiber filling rate (fiber volume fraction) and bending strength, and the lower graph in FIG. 11 shows the relationship between the fiber filling rate (fiber volume fraction) and impact strength. In order to evaluate the bending strength and impact strength of the resin gear 1 manufactured using the resin gear molding material 6, a demonstration test was conducted to evaluate the bending strength and impact strength of multiple test pieces manufactured using the resin gear molding material 6. In this demonstration test, multiple test pieces with different fiber filling rates (fiber volume fractions) were prepared. FIG. 11 is a graph showing the bending strength and impact strength of these test pieces. The bending strength was evaluated in accordance with the test method for bending strength and bending modulus described in "JIS K 6911 General Test Method for Thermosetting Plastics". The impact strength was evaluated according to the flatwise impact test method described in "JIS K 7062 Izod impact test method for glass fiber reinforced plastics."

As shown in the upper diagram of FIG. 11, it can be seen that the bending strength tends to increase as the fiber filling rate (fiber volume rate) increases. Also, as shown in the lower diagram of FIG. 11, it can be seen that the impact strength tends to increase as the fiber filling rate (fiber volume rate) increases. In this way, the higher the fiber filling rate, the greater the bending strength and impact strength. Therefore, as described above, according to the manufacturing method of the resin gear 1 according to this embodiment, which can increase the resin filling rate in the area where the tooth profile 9a is formed, it is possible to achieve high strength of the tooth profile 9a in the resin gear 1.

In the manufacturing method of the resin gear 1 according to this embodiment, in the second step, multiple recesses 25x and 25y may be formed over the entire circumferential area of the molded product 40. This makes it possible to appropriately improve the strength of each tooth profile 9a formed over the entire circumferential area.

In the manufacturing method of the resin gear 1 according to this embodiment, in the second step, the recesses 25x formed by the first protrusions 33x and the recesses 25y formed by the second protrusions 31x may be formed alternately in the circumferential direction of the molded product 40. In this way, the recesses 25x and 25y formed by the first protrusions 33x and the second protrusions 31x are formed alternately in the circumferential direction, so that when manufacturing a helical gear with twisted tooth profiles 9a, the recesses 25x and 25y corresponding to each tooth profile 9a can be appropriately formed. In other words, according to this manufacturing method, a helical gear with improved strength of each tooth profile 9a can be suitably manufactured.

When manufacturing a helical gear, for example, a method of forming the teeth by compression molding can be considered in which a base body preformed into a helical tooth shape is filled into a mold to form the teeth. However, with such a manufacturing method, it is difficult to fill the base body with the tooth shape, and the problem is that the mold structure becomes complicated. In this regard, with the manufacturing method of the resin gear 1 according to this embodiment, it is not necessary to fill the mold with a base body preformed into a helical tooth shape when manufacturing a helical gear, so it is possible to avoid the mold structure becoming complicated.

In the manufacturing method of the resin gear 1 according to this embodiment, in the second step, the recesses 25x and 25y may be formed so that they are tapered toward the bottom side of the recesses 25x and 25y. By making the recesses 25x and 25y tapered, it becomes easier to overlap the cutting area by the gear cutting process that forms the twisted tooth profile 9a with the area of the recesses 25x and 25y, and it is possible to prevent the area whose strength has been improved by forming the recesses 25x and 25y from being cut by the subsequent gear cutting process. In other words, according to this manufacturing method, it is possible to suitably manufacture a helical gear with improved strength of each tooth profile 9a.

The resin gear 1 according to this embodiment includes a metal bush 8 and an annular resin member 9 arranged around the metal bush 8. A plurality of teeth 9a are formed in the circumferential direction on the outer periphery of the resin member 9. At least a portion of the region in which the teeth 9a are formed in the resin member 9 may have a higher fiber filling rate than a region in which the teeth 9a are not formed. In the resin gear 1 according to this embodiment, the fiber filling rate in the region in which the teeth 9a are formed is higher. This can improve the strength of the resin in the region in which the teeth 9a are formed.

The manufacturing method of the resin gear 1 and the resin gear 1 according to this embodiment have been described above, but the present invention is not limited to the above embodiment. For example, the resin gear manufactured by the manufacturing method according to one aspect of the present invention may be a spur gear instead of a helical gear. Furthermore, the manufacturing method according to one aspect of the present invention may be used in a manufacturing method for manufacturing a resin gear from a papermaking base body formed by a so-called papermaking method.

1...resin gear, 6...molding material for resin gear, 8...metal bushing, 9...resin member, 9a...tooth profile, 20...mold (die), 25...preliminary molded body (first intermediate), 25x, 25y...recess, 30B...lower die, 30T...upper die, 31x...second protruding portion, 33x...first protruding portion, 40...molded product (second intermediate).

Claims (3)

A method for manufacturing a resin gear having an annular resin member and a metal bushing by using a resin gear molding material, comprising the steps of:
a first step of filling a mold with the resin gear molding material and pressurizing it to form an annular first intermediate body;
a second step of disposing the first intermediate body and the metallic bush between an upper die and a lower die and compressing them by heating to form an annular second intermediate body;
and a third step of forming a tooth profile by gear cutting on an outer periphery of the second intermediate body,
In the second step, recesses are formed at a plurality of intended cutting locations in the gear cutting process by a plurality of first protrusions of the upper die and a plurality of second protrusions of the lower die,
In the second step, the recesses formed by the first convex portions and the recesses formed by the second convex portions are alternately formed in the circumferential direction of the second intermediate body. The method for manufacturing a resin gear according to claim 1, wherein in the second step, a plurality of recesses are formed over the entire circumferential area of the second intermediate body. The method for manufacturing a plastic gear according to claim 1 or 2, wherein in the second step, the recess is formed so as to have a tapered shape toward the bottom side of the recess.

Images