JP7327799B2 - Manufacturing method of cylindrical sintered member - Google Patents

Description

The present disclosure relates to a method for manufacturing a tubular sintered member.

Patent Literature 1 discloses a method of manufacturing a rotor for an internal gear pump. A rotor for an internal gear pump is configured by combining an inner rotor and an outer rotor. The inner rotor and the outer rotor are required to have high dimensional accuracy in order to mesh smoothly with each other. Therefore, the inner rotor and the outer rotor are configured by sizing a sintered member having a predetermined shape.

Sizing is done using a mold that includes a die, top and bottom punches, and a core rod. Sizing is generally performed by placing a cylindrical sintered member in a space formed by a die, a lower punch, and a core rod, and pressurizing the sintered member with an upper punch to improve dimensional accuracy. In the case of pressurization by the upper punch, a difference in stress may occur between the area on the upper punch side and the area on the lower punch side of the sintered member. Due to this difference, the amount of springback of the sintered member after extraction from the mold may also differ. Therefore, the sintered member extracted from the mold can have an outer peripheral surface that expands radially outward from the lower punch side region toward the upper punch side region. That is, as shown in FIG. 6 of Patent Document 1, the sintered member after sizing tends to deteriorate the perpendicularity of the side surface with respect to the end surface.

Therefore, Patent Document 1 discloses sizing the same sintered member twice. Between the first sizing and the second sizing, the direction in which the sintered member is accommodated in the space formed by the die, the lower punch, and the core rod is reversed.

JP 2009-162105 A

The technique disclosed in Patent Document 1 can improve the perpendicularity of the side surface to the end surface of the sintered member, but the sizing operation is complicated and the productivity is poor.

Accordingly, one object of the present disclosure is to provide a method for manufacturing a cylindrical sintered member that efficiently obtains a high-accuracy squareness with respect to the squareness of the side surface of the sintered member with respect to the end surface.

The manufacturing method of the tubular sintered member of the present disclosure includes:
preparing a tubular sintered member;
sizing the sintered member;
The sintered member has an inner peripheral surface, an outer peripheral surface, and a first end surface and a second end surface connecting the inner peripheral surface and the outer peripheral surface,
In the preparing step, the sintered member having, on at least one of the inner peripheral surface and the outer peripheral surface, an inclined surface that gradually becomes radially inward from the first end surface side toward the second end surface side. prepare and
In the sizing step, the sintered member is accommodated in a space formed by a die, a lower punch, and a core rod so that the first end face faces the lower punch, and the second end face is pressed by the upper punch.

The manufacturing method of the cylindrical sintered member of the present disclosure can efficiently obtain high-precision squareness with respect to the squareness of the side surface of the sintered member with respect to the end surface.

FIG. 1 is an explanatory diagram illustrating a sizing step in a method for manufacturing a tubular sintered member according to Embodiment 1. FIG. FIG. 2 is an explanatory view of the squareness of the cylindrical sintered member obtained by the sizing step in the manufacturing method of the cylindrical sintered member of the first embodiment. 3A and 3B are explanatory diagrams for explaining a forming step in the method for manufacturing a cylindrical sintered member according to Embodiment 1. FIG. 4A and 4B are explanatory diagrams for explaining a sintering step in the method for manufacturing a cylindrical sintered member according to Embodiment 1. FIG. FIG. 5 is an explanatory diagram illustrating another form of the sintering step in the method for manufacturing a cylindrical sintered member of Embodiment 1. FIG. 6A and 6B are explanatory diagrams for explaining the forming step in the method for manufacturing a tubular sintered member according to the second embodiment. FIG. 7 is a schematic plan view showing a rotor for a general internal gear pump.

[Description of Embodiments of the Present Disclosure]
First, the embodiments of the present disclosure are listed and described.

(1) A method for manufacturing a cylindrical sintered member according to one aspect of the present disclosure includes:
preparing a tubular sintered member;
sizing the sintered member;
The sintered member has an inner peripheral surface, an outer peripheral surface, and a first end surface and a second end surface connecting the inner peripheral surface and the outer peripheral surface,
In the preparing step, the sintered member having, on at least one of the inner peripheral surface and the outer peripheral surface, an inclined surface that gradually becomes radially inward from the first end surface side toward the second end surface side. prepare and
In the sizing step, the sintered member is accommodated in a space formed by a die, a lower punch, and a core rod so that the first end face faces the lower punch, and the second end face is pressed by the upper punch.

For sizing, as described above, the sintered member is accommodated in the space formed by the die, the lower punch, and the core rod, and the sintered member is pressed by the upper punch. In the method of manufacturing a cylindrical sintered member of the present disclosure, a sintered member having an inclined surface on at least one of the inner peripheral surface and the outer peripheral surface is prepared, and the sintered member is accommodated in the space in a specific direction, Do sizing. Specifically, the sintered member is housed in the space so that the first end surface of the sintered member located on the radially outer side of the inclined surface faces the lower punch. When the sintered member is accommodated in the space in this direction, the upper punch presses the second end surface of the sintered member located on the radially inner narrow side of the inclined surface.

The area on the second end surface side of the sintered member pressed by the upper punch is subjected to greater stress by sizing than the area on the first end surface side facing the lower punch, and the diameter of the sintered member is increased after being extracted from the mold. The amount of springback that spreads outward in the direction increases. That is, in the sintered member after sizing, the perpendicularity of the side surface to the end surface tends to deteriorate. In the method for manufacturing a cylindrical sintered member of the present disclosure, sizing is performed on the sintered member having the inclined surface that is inclined radially inward from the first end surface side toward the second end surface side. Therefore, even if the second end face side region of the sintered member expands radially outward due to springback, the inclination angle of the inclined surface is moderated, and deterioration of the perpendicularity after sizing can be suppressed. In the method for manufacturing a cylindrical sintered member of the present disclosure, a sintered member having an inclined surface is prepared, and the sintered member is accommodated in the space in a specific direction and sized. can suppress the deterioration of That is, according to the method for manufacturing a cylindrical sintered member of the present disclosure, a cylindrical sintered member having the above perpendicularity with high accuracy can be efficiently obtained by one sizing.

(2) As an example of a method for manufacturing a cylindrical sintered member of the present disclosure,
The preparing step includes:
a step of pressure-molding the powder to produce a cylindrical powder compact;
sintering the powder compact to produce the sintered member;
In the step of producing the powder compact, at least one of the inner peripheral surface and the outer peripheral surface of the powder compact may be provided with the inclined surface of the sintered member.

Press molding can easily produce a powder compact having a slanted surface in the sintered member. By sintering this powder compact, a sintered member having the inclined surface can be easily prepared.

(3) As an example of a method for manufacturing a cylindrical sintered member of the present disclosure,
In the step of producing the sintered member, there is a mode in which a plurality of the powder compacts are stacked and sintered.

The above configuration is excellent in productivity because a plurality of powder compacts can be sintered simultaneously. The sintered member obtained by sintering can change in dimension with respect to the powder compact due to hardening during sintering. When a plurality of powder compacts are stacked and sintered, the sintered member may vary in dimensional change. For example, when three powder compacts are stacked and sintered, the sintered member located in the upper stage, the sintered member located in the middle stage, and the sintered member located in the lower stage differ in area and amount of sintering. Variation in dimensional change can occur. In the manufacturing method of the cylindrical sintered member of the present disclosure, as described above, the powder compact is provided with the inclined surface. Therefore, even if variation occurs in dimensional change during sintering, it is easy to suppress radially outward expansion of the region on the second end surface side in the obtained sintered member. In other words, even in the case of stacking, it is possible to obtain a sintered member having an inclined surface that inclines radially inward from the first end surface side toward the second end surface side.

(4) As an example of a method for manufacturing a cylindrical sintered member of the present disclosure,
The sintered member may be an inner rotor or an outer rotor that constitutes a rotor for an internal gear pump.

A rotor for an internal gear pump is configured by combining an inner rotor and an outer rotor. The inner rotor and the outer rotor are required to have high dimensional accuracy in order to mesh smoothly with each other. Specifically, regarding the perpendicularity of the side surface to the end face, a highly accurate perpendicularity is required. The method for manufacturing a tubular sintered member according to the present disclosure can suppress deterioration of squareness after sizing, and is therefore suitable for obtaining inner rotors and outer rotors that require highly accurate squareness.

[Details of the embodiment of the present disclosure]
Details of embodiments of the present disclosure are described below with reference to the drawings. The same reference numerals in the drawings indicate the same names. In each drawing, part of the configuration may be exaggerated or simplified for convenience of explanation. The dimensional ratio of each part in the drawings may also differ from the actual one. The present invention is not limited to these examples, but is indicated by the scope of the claims, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.

<Embodiment 1>
A method for manufacturing a cylindrical sintered member according to Embodiment 1 will be described with reference to FIGS. 1 to 4. FIG. A method for manufacturing a tubular sintered member includes a preparation step and a sizing step. In the preparation step, a cylindrical sintered member is prepared. In the sizing step, the prepared sintered member is sized.

≪Preparation process≫
In the preparation step, a cylindrical sintered member is prepared. The sintered member has an inner peripheral surface, an outer peripheral surface, and a first end surface and a second end surface connecting the inner peripheral surface and the outer peripheral surface. In the preparation step, a sintered member is prepared which has, on at least one of the inner peripheral surface and the outer peripheral surface thereof, an inclined surface that gradually becomes radially inward from the first end surface side toward the second end surface side. In this example, a sintered member having an inclined surface on its outer peripheral surface is prepared. The preparation process includes a molding process and a sintering process. A cylindrical sintered member is obtained by a molding process and a sintering process.

<Molding process>
In the molding step, as shown in FIG. 3, a molding die 7 is used to pressure-mold the raw material powder 4 to produce a cylindrical powder compact 3 (FIG. 4).

[Molding mold]
The molding die 7 includes a die 71 , a lower punch 72 , an upper punch 73 and a core rod 74 . The lower punch 72 and the upper punch 73 are fitted into the die 71 from below and above. Core rod 74 is inserted into the center of die 71 . In this example, the die 71 is cylindrical and the core rod 74 is cylindrical. By combining the die 71 , the lower punch 72 , and the core rod 74 , the inner peripheral surface of the die 71 , the upper surface of the lower punch 72 , and the outer peripheral surface of the core rod 74 form a cylindrical space 70 . This space 70 is filled with the raw material powder 4 . The shape and dimensions of the space 70 can be appropriately set according to the shape and dimensions of the powder compact 3 (FIG. 4) to be manufactured.

The inner peripheral surface of the die 71 is composed of an inclined surface 710 and straight surfaces 711 and 712 . The straight surfaces 711 and 712 are provided in areas where the lower punch 72 and the upper punch 73 are fitted. The straight surface 711 is a surface that rubs against the outer peripheral surface of the lower punch 72 , and the straight surface 712 is a surface that rubs against the outer peripheral surface of the upper punch 73 . By providing the die 71 with the straight surfaces 711 and 712, it is possible to prevent the lower punch 72 or the upper punch 73 from interfering with the inclined surface 710, and the compression allowance by the lower punch 72 and the upper punch 73 can be secured well. Further, by providing the die 71 with the straight surfaces 711 and 712, it is possible to prevent the raw material powder 4 from being bitten between the die 71 and the lower punch 72 and between the die 71 and the upper punch 73. It is possible to prevent the formation of burrs on the powder compact 3 (FIG. 4). The straight surface 711 located on the lower punch 72 side is located radially inside the straight surface 712 located on the upper punch 73 side.

The inclined surface 710 is provided so as to connect the straight surfaces 711 and 712 . That is, the inclined surface 710 is gradually inclined radially inward from the upper punch 73 side toward the lower punch 72 side. The length of the inclined surface 710 in the axial direction is three times or more, more preferably five times or more the length of the straight surfaces 711 and 712 in the axial direction. The inclination angle of the inclined surface 710 will be described in detail in the sizing process, which will be described later.

It should be noted that the "slanted" and "straight" referred to here are contour lines shown in a cross section cut along a plane parallel to the axial direction of the object, for example, the die 71, and do not represent the shape of a three-dimensional surface. do not have. In other words, the inclined surface is a truncated cone-shaped peripheral surface, not a flat inclined surface. Also, the straight surface is a cylindrical surface, not a flat vertical surface. The truncated conical shape and cylindrical shape include not only a circular shape but also an elliptical shape in a cross-sectional shape cut along a plane orthogonal to the axial direction. The truncated cone shape and cylindrical shape also include shapes having a plurality of teeth on the peripheral surface.

In this example, the outer peripheral surface of the core rod 74 is configured with a straight surface over the entire length in the axial direction. Further, the upper surface of the lower punch 72 and the lower surface of the upper punch 73 are formed flat over the entire surface.

[Pressure molding]
The space 70 is filled with the raw material powder 4, and the powder compact 3 (FIG. 4) is formed by compressing the raw material powder 4 from above and below with the upper punch 73 and the lower punch 72. As shown in FIG. The molding pressure is, for example, 400 MPa or more and 800 MPa or less. After molding the powder compact 3 , the upper punch 73 is raised, and the die 71 and the core rod 74 are lowered relative to the lower punch 72 to extract the powder compact 3 from the molding die 7 .

The powder compact 3 (FIG. 4) obtained by pressure molding with the molding die 7 has a cylindrical shape. FIG. 4 shows a state in which three powder compacts 3 are stacked. Each powder compact 3 shown in FIG. 4 is upside down from the compact of the raw material powder 4 in the space 70 shown in FIG.

As shown in FIG. 4 , the powder compact 3 has an inner peripheral surface 33 , an outer peripheral surface 34 , and a first end surface 31 and a second end surface 32 connecting the inner peripheral surface 33 and the outer peripheral surface 34 . The outer peripheral surface 34 is composed of an inclined surface 35 and straight surfaces 36 and 37 . The straight surface 36 is located on the second end surface 32 side, and the straight surface 37 is located on the first end surface 31 side. The straight surface 36 located on the second end surface 32 side is located radially inward of the straight surface 37 located on the first end surface 31 side. The inclined surface 35 is provided so as to connect the straight surfaces 36 and 37 . That is, the inclined surface 35 is gradually inclined radially inward from the first end surface 31 side toward the second end surface 32 side. The inclined surface 35 and the straight surfaces 36, 37 of the powder compact 3 correspond to the inclined surface 710 and the straight surfaces 711, 712 of the mold 7, respectively.

<Sintering process>
In the sintering step, as shown in FIG. 4, the powder compact 3 obtained in the molding step is sintered to produce the sintered member 2 (FIG. 1).

Sintering is performed by placing the powder compact 3 on the mounting table 8 . The mounting table 8 is composed of a fireproof net or a fireproof plate. Sintering can be performed by stacking a plurality of powder compacts 3 . By stacking a plurality of powder compacts 3, the plurality of powder compacts 3 can be sintered simultaneously, resulting in excellent productivity. In this example, three powder compacts 3 are stacked.

When n is an integer of 2 or more and n powder compacts 3 are stacked and sintered, the n-th powder compact 3, which is the uppermost tier, can be stacked so that the second end surface 32 faces upward. preferable. The powder compacts 3 from the first stage to the (n-1)th stage at the bottom may be oriented in the vertical direction. In this example, all the powder compacts 3 are oriented in the same vertical direction.

The sintered member 2 obtained by sintering may change in dimension with respect to the powder compact 3 due to densification during sintering. When a plurality of powder compacts 3 are stacked and sintered, dimensional changes of the sintered member 2 may vary. For example, the n-th stage sintered member 2, which is the uppermost stage, tends to be smaller in size in the upper region than in the lower region. In the n-th stage powder compact 3, which is the uppermost stage, the lower area is less susceptible to dimensional change due to contact resistance with the (n-1)th stage powder compact 3 below, and the upper area is This is because, since it is free, dimensional change is likely to occur. The powder compacts 3 from the first stage to the (n−1)th stage of the lowest stage are in contact with the adjacent powder compacts 3 or the mounting table 8 in both the upper side area and the lower side area, so that they are the uppermost stage. The dimensional change can be different from that of the n-th stage powder compact 3 .

Each powder compact 3 has an inclined surface 35 as described above. Therefore, even if there are variations in dimensional changes during sintering, in the obtained sintered member 2, it is easy to suppress the radially outward expansion of the region on the second end surface 22 side. That is, even in the case of stacking, the sintered member 2 (FIG. 1) having the inclined surface 25 inclined radially inward from the first end surface 21 side toward the second end surface 22 side can be obtained.

When stacking a plurality of powder compacts 3, as shown in FIG. 5, the vertically adjacent powder compacts 3 may be alternately oriented in the vertical direction. In this case, the first end surfaces 31 or the second end surfaces 32 of the vertically adjacent powder compacts 3 are in contact with each other.

A sintered member 2 (FIG. 1) obtained by sintering has a cylindrical shape. As shown in FIG. 1 , the sintered member 2 includes an inner peripheral surface 23 , an outer peripheral surface 24 , and a first end surface 21 and a second end surface 22 connecting the inner peripheral surface 23 and the outer peripheral surface 24 . The outer peripheral surface 24 is composed of an inclined surface 25 and straight surfaces 26 and 27 . The straight surface 26 is located on the second end surface 22 side, and the straight surface 27 is located on the first end surface 21 side. The straight surface 26 located on the second end surface 22 side is located radially inside the straight surface 27 located on the first end surface 21 side. The inclined surface 25 is provided so as to connect the straight surfaces 26 and 27 . That is, the inclined surface 25 is gradually inclined radially inward from the first end surface 21 side toward the second end surface 22 side. The inclined surface 25 and straight surfaces 26, 27 of the sintered member 2 correspond to the inclined surface 35 and straight surfaces 36, 37 of the powder compact 3 (FIG. 4), respectively.

≪Sizing process≫
In the sizing step, as shown in FIG. 1, a sizing mold 6 is used to size the sintered member 2 obtained in the sintering step.

[Sizing mold]
The sizing die 6 comprises a die 61 , a lower punch 62 , an upper punch 63 and a core rod 64 . The lower punch 62 and the upper punch 63 are fitted into the die 61 from below and above. Core rod 64 is inserted into the center of die 61 . In this example, the die 61 is cylindrical and the core rod 64 is cylindrical. By combining the die 61 , the lower punch 62 and the core rod 64 , a cylindrical space 60 is formed by the inner peripheral surface of the die 61 , the upper surface of the lower punch 62 and the outer peripheral surface of the core rod 64 . The space 60 accommodates the sintered member 2 . The shape and dimensions of the space 60 can be appropriately set according to the shape and dimensions of the sintered member 1 (FIG. 2) to be dimensionally corrected by sizing.

In this example, the inner peripheral surface of the die 61 and the outer peripheral surface of the core rod 64 are straight surfaces over the entire length in the axial direction. Moreover, the upper surface of the lower punch 62 and the lower surface of the upper punch 63 are configured to be entirely flat surfaces.

The sizing die 6 generally corrects the dimension of the object, which is the sintered member 2 in this example, by applying downward pressure with the upper punch 63 while the lower punch 62 is fixed.

[Sizing]
First, the sintered member 2 is accommodated in the space 60 described above. At this time, the sintered member 2 is accommodated in the space 60 so that the first end surface 21 of the sintered member 2 faces the lower punch 62 . Then, the second end face 22 of the sintered member 2 is pressed by the upper punch 63 . The pressure to be applied may be, for example, 500 MPa or more and 1100 MPa or less. After pressurization, the upper punch 63 is raised, and the die 61 and the core rod 64 are lowered relative to the lower punch 62 to extract the sintered member from the sizing die 6 .

When the lower punch 62 is fixed and the sintered member 2 is pressed by the upper punch 63, the area on the side of the second end surface 22 pressurized by the upper punch 63 becomes the area on the side of the first end surface 21 facing the lower punch 62. In comparison, the stress imparted by sizing is greater. Therefore, when the sintered member 2 is extracted from the sizing die 6, the amount of springback that spreads radially outward in the region on the second end face 22 side of the sintered member 2 is greater than that in the region on the first end face 21 side. Become. The sintered component 2 to be sized comprises an inclined surface 25 . Therefore, when the region of the sintered member 2 on the side of the second end surface 22 expands radially outward due to springback, this expansion relaxes the inclination angle of the inclined surface 25 .

The sintered member 1 (FIG. 2) obtained by sizing has a cylindrical shape. As shown in FIG. 2 , the sintered member 1 includes an inner peripheral surface 13 , an outer peripheral surface 14 , and a first end surface 11 and a second end surface 12 connecting the inner peripheral surface 13 and the outer peripheral surface 14 . The sintered member 1 shown in FIG. 2 is illustrated such that the outer diameter of the second end surface 12 is larger than the outer diameter of the first end surface 11 for convenience of explanation. Actually, the diameter difference between the outer diameter of the first end face 11 and the outer diameter of the second end face 12 is sufficiently smaller than the diameter difference shown in FIG. In addition, actually, the angular difference between the corner formed by the first end surface 11 and the outer peripheral surface 14 and the corner formed by the second end surface 12 and the outer peripheral surface 14 is larger than the angular difference shown in FIG. Small enough.

The outer peripheral surface 14 of the sintered member 1 obtained by sizing has a small perpendicularity to the first end surface 11 or the second end surface 12 . The perpendicularity is determined by the amount of displacement δ in the direction orthogonal to the longitudinal direction of the sintered member 1 with the first end surface 11 or the second end surface 12 as a reference. The squareness is preferably 10 μm or less, more preferably 8 μm or less, especially 5 μm or less, or 0 μm.

The angle of inclination of the inclined surface 35 given to the powder compact 3 described above, that is, the angle of inclination of the inclined surface 710 of the die 71 in the molding die 7, takes account of the amount of springback after sizing. The thickness may be set to 10 μm or less, further 8 μm or less, particularly 5 μm or less, preferably 0 μm.

≪Effect≫
In the manufacturing method of the cylindrical sintered member of Embodiment 1, as shown in FIG. Further, in the method for manufacturing a cylindrical sintered member of Embodiment 1, as shown in FIG. When the second end surface 22 is pressed by the upper punch 63, when the sintered member 2 is extracted from the sizing die 6, the area on the second end surface 22 side is larger than the area on the first end surface 21 side in the radial direction. The amount of springback that spreads outward increases. Since the region on the side of the second end face 22 is located radially inwardly of the region on the side of the first end face 21, even if the region expands radially outward due to springback, the inclination angle of the inclined surface 25 is moderated. As a result, it is possible to suppress the deterioration of the squareness of the sintered member 1 (FIG. 2).

In the method for manufacturing a cylindrical sintered member according to Embodiment 1, a sintered member 2 having an inclined surface 25 is prepared, and this sintered member 2 is placed in a space 60 of a sizing mold 6 in a specific direction for sizing. only, it is possible to suppress the deterioration of the squareness. In other words, in the method for manufacturing a cylindrical sintered member according to the first embodiment, the cylindrical sintered member 2 (FIG. 2) having the above-described perpendicularity can be efficiently obtained by one sizing.

<Embodiment 2>
A method for manufacturing a cylindrical sintered member according to Embodiment 2 will be described with reference to FIG. In Embodiment 2, a sintered member having inclined surfaces on both the inner peripheral surface and the outer peripheral surface is prepared in the preparation step. A sintered member having inclined surfaces on both the inner peripheral surface and the outer peripheral surface is obtained by producing a powder compact using the molding die 7 shown in FIG. 6 and sintering the powder compact. In the following description, differences from the above-described first embodiment will be mainly described, and descriptions of similar items will be omitted.

[Molding mold]
The molding die 7 includes a die 71 , a lower punch 72 , an upper punch 73 and core rods 74 and 75 . Basic configurations of the die 71, the lower punch 72, and the upper punch 73 are the same as in the first embodiment. The core rod 74 is fitted into the die 71 from below and forms a recess together with the die 71 . The core rod 75 is fitted into the die 71 from above, and its lower end is fitted into the recess. The core rod 75 is a tapered cylinder whose one end tapers toward the distal end. In this molding die 7, the die 71, the lower punch 72, and the core rods 74 and 75 are combined to form a cylindrical space with the inner peripheral surface of the die 71, the upper surface of the lower punch 72, and the outer peripheral surface of the core rod 75. is configured. This space is filled with raw material powder 4 .

The inner peripheral surface of the die 71 is composed of an inclined surface 710 and straight surfaces 711 and 712 as in the first embodiment.

The outer peripheral surface of the core rod 75 is composed of an inclined surface 750 and straight surfaces 751 and 752 . The straight surfaces 751 and 752 are provided in areas where the lower punch 72 and the upper punch 73 are fitted. The straight surface 751 is a surface that rubs against the outer peripheral surface of the lower punch 72 , and the straight surface 752 is a surface that rubs against the outer peripheral surface of the upper punch 73 . The straight surface 751 located on the lower punch 72 side is located radially inside the straight surface 752 located on the upper punch 73 side. The inclined surface 750 is provided so as to connect the straight surfaces 751 and 752 . That is, the inclined surface 750 is gradually inclined radially inward from the upper punch 73 side toward the lower punch 72 side. In this example, the inclination angle of the inclined surface 750 of the core rod 75 and the inclination angle of the inclined surface 710 of the die 71 are the same. The inclination angle of the inclined surface 750 on the core rod 75 and the inclination angle of the inclined surface 710 on the die 71 may be different. In addition, the axial lengths of the inclined surface 750 and the straight surfaces 751 and 752 of the core rod 75 are substantially the same as the axial lengths of the inclined surface 710 and the straight surfaces 711 and 712 of the die 71 .

The upper surface of the lower punch 72 and the lower surface of the upper punch 73 are entirely flat surfaces.

[Pressure molding]
The space is filled with the raw material powder 4, and the powder compact is formed by compressing the raw material powder 4 from above and below with the upper punch 73 and the lower punch 72. As shown in FIG. The powder compact obtained by pressure molding with the molding die 7 is configured in a cylindrical shape, and has an inner peripheral surface, an outer peripheral surface, and a first end surface and a second end surface connecting the inner peripheral surface and the outer peripheral surface. Prepare. Each of the inner peripheral surface and the outer peripheral surface is composed of an inclined surface and a straight surface. The inclined surface and straight surface of the outer peripheral surface of the powder compact correspond to the inclined surface 710 and straight surfaces 711 and 712 of the die 71 of the molding die 7, respectively. The inclined surface and straight surface of the inner peripheral surface of the powder compact correspond to the inclined surface 750 and straight surfaces 751 and 752 of the core rod 75 of the mold 7, respectively.

The sintered member obtained by sintering the powder compact has inclined surfaces and straight surfaces on the inner peripheral surface and the outer peripheral surface, respectively, similarly to the powder compact.

When sizing a sintered member having inclined surfaces on both the inner peripheral surface and the outer peripheral surface as in the method for manufacturing a cylindrical sintered member according to the second embodiment, the inclined surfaces are formed similarly to the first embodiment. The upper punch presses the second end surface located on the side that narrows radially inward. By pressing the second end surface with the upper punch, the inclination angle of the inclined surface is relaxed by the springback when the sintered member is extracted from the sizing die, and the perpendicularity of the outer peripheral surface to the first end surface or the second end surface is reduced. You can control the deterioration.

The method of manufacturing the cylindrical sintered member described in Embodiments 1 and 2 is suitable for obtaining the inner rotor 91 or the outer rotor 92 that constitutes the internal gear pump rotor 9 (FIG. 7).

The internal gear pump rotor 9 includes an inner rotor 91 and an outer rotor 92, as shown in FIG. The inner rotor 91 and the outer rotor 92 are arranged eccentrically. The inner rotor 91 and the outer rotor 92 are composed of sintered members made of ferrous materials. The inner rotor 91 has a plurality of external teeth on its outer circumference. The outer rotor 92 has a plurality of internal teeth on its inner circumference. The number of teeth of the internal teeth is one more than the number of teeth of the external teeth. Therefore, when the inner rotor 91 and the outer rotor 92 are combined, a closed space 90 is created by the tips of the external teeth and the internal teeth.

A shaft hole 91h is provided in the center of the inner rotor 91 . A shaft (not shown) is inserted into the shaft hole 91h, and the inner rotor 91 is rotationally driven by this shaft. By this rotational drive, the outer rotor 92 receives a rotational force due to the meshing of the inner teeth with the rotating outer teeth, and rotates in the same direction as the inner rotor 91 .

High dimensional accuracy is required for the inner rotor 91 and the outer rotor 92 to mesh smoothly with each other. Specifically, regarding the perpendicularity of the side surface to the end face, a highly accurate perpendicularity is required. Therefore, according to the method of manufacturing the cylindrical sintered member described in the first and second embodiments, the inner rotor 91 or the outer rotor 92 having highly accurate squareness can be obtained. In particular, since the inner rotor 91 meshes with the outer rotor 92 on the outer peripheral side, there is a problem of deterioration of the perpendicularity on the outer peripheral side due to springback after sizing. Therefore, the inner rotor 91 having highly precise squareness can be efficiently obtained by the method of manufacturing the tubular sintered member described in the first and second embodiments.

Reference Signs List 1 sintered member 11 first end surface 12 second end surface 13 inner peripheral surface 14 outer peripheral surface δ displacement amount 2 sintered member 21 first end surface 22 second end surface 23 inner peripheral surface 24 outer peripheral surface 25 inclined surface , 26, 27 straight surface 3 powder compact 31 first end surface 32 second end surface 33 inner peripheral surface 34 outer peripheral surface 35 inclined surface 36, 37 straight surface 4 raw material powder 6 sizing mold 60 space 61 die 62 Lower punch 63 Upper punch 64 Core rod 7 Mold 70 Space 71 Die 710 Inclined surface 711, 712 Straight surface 72 Lower punch 73 Upper punch 74, 75 Core rod 750 Inclined surface 751, 752 Straight surface 8 Mounting Table 9 Rotor for internal gear pump 90 Space 91 Inner rotor 91h Shaft hole 92 Outer rotor

Claims (3)

preparing a tubular sintered member;
sizing the sintered member;
The sintered member has an inner peripheral surface, an outer peripheral surface, and a first end surface and a second end surface connecting the inner peripheral surface and the outer peripheral surface,
The preparing step includes :
a step of pressure-molding the powder to produce a cylindrical powder compact;
By sintering the powder compact, at least one of the inner peripheral surface and the outer peripheral surface has an inclined surface that gradually becomes radially inward from the first end surface side toward the second end surface side. A step of producing a sintered member,
In the step of producing the powder compact, at least one of an inner peripheral surface and an outer peripheral surface of the powder compact is provided with a surface to be the inclined surface of the sintered member,
In the sizing step, the sintered member is housed in a space composed of a die, a lower punch, and a core rod such that the first end face faces the lower punch, and the second end face is pressed by the upper punch.
A method for manufacturing a cylindrical sintered member. 2. The method of manufacturing a cylindrical sintered member according to claim 1 , wherein in the step of producing the sintered member, a plurality of the powder compacts are stacked and sintered. 3. The method of manufacturing a cylindrical sintered member according to claim 1, wherein the sintered member is an inner rotor or an outer rotor that constitutes a rotor for an internal gear pump.

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