mold

Abstract

To provide a metal die not requiring the removal of burr after forming a green compact having a slide surface formed in a U-shape in cross section.SOLUTION: A metal die for forming a green compact having a slide surface having an U-shape in section, comprises an annular die and a lower punch. The lower punch comprises a first lower punch and two second lower punches. The first lower punch has a first upper-end face forming a bottom face of the slide surface, first right-side and left-side faces forming an inner face of the slide surface, and first front and back faces to be slide-contacted with the die. Each of the second lower punches has a second upper-end face arranged lower than the first upper-end face, a second left-side face to be slide-contacted with the first right-side face or a second right-side face to be slide-contacted with the first left-side face, and second front and back faces to be slide-contacted with the die. A first edge extending along a left-right direction of the first upper-end face has a first protrusion and a second edge extending along a vertical direction of the first right-side and left-side faces has a second protrusion.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] This disclosure relates to a mold.

Background Art

[0002] Compressed powders or sintered compacts are used for various parts such as machine parts and electrical equipment parts. Compressed powders are produced, for example, by compression molding metal powders using a mold as described in Patent Documents 1 and 2. Sintered compacts are produced by sintering compressed powders. A mold for molding a compressed powder typically includes a cylindrical die, an upper punch, and a lower punch that fits into the die. The molding of the compressed powder is performed by filling the internal space of the die with metal powder and then compressing the powder with the upper punch and the lower punch. The die forms the outer peripheral surface of the compressed powder. The lower punch forms the lower surface of the compressed powder. The upper punch forms the upper surface of the compressed powder.

[0003] Burrs may occur on the compressed powder formed by the mold. Patent Document 1 describes removing burrs generated on the compressed powder using a sizing mold. Patent Document 2 describes removing burrs generated on the compressed powder using a deburring brush.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] It is desired to improve the productivity of compressed powders.

[0006] The compacted powder formed by the above mold is prone to burrs forming at the corners. The reason for burr formation is as follows: A clearance is provided in the fitting portion between the die and the punch so that the punch slides against the die. When powder enters this clearance, burrs are formed.

[0007] When forming a compacted powder having a groove with a U-shaped cross-section, a lower punch with an upper end corresponding to the groove is used. When the groove is formed with such a lower punch, burrs are generated that protrude from the opening edge of the groove. These burrs remain on the compacted powder even after it has been sintered.

[0008] Burrs protruding from the opening edge of a groove can damage or hinder the sliding of other components when they slide within the groove of the compacted or sintered body. On the other hand, removing burrs is time-consuming and laborious.

[0009] One of the objectives of this disclosure is to provide a mold that eliminates the need to remove burrs after molding a powder compact having a U-shaped sliding surface in cross-section. [Means for solving the problem]

[0010] The mold disclosed herein is A mold for forming a compacted powder having a sliding surface with a U-shaped cross-section, An annular die having a space in which the compacted powder is formed, It comprises a lower punch fitted into the lower part of the aforementioned space, The aforementioned lower punch, First low punch, The first lower punch is further comprising two second lower punches positioned to sandwich it from the left and right, The aforementioned first lower punch is A first upper end surface that forms the bottom surface of the sliding surface, The first right side and the first left side form the inner surface of the sliding surface, It has a first front surface and a first back surface that slide against the die, Each of the aforementioned second lower punches is A second upper surface disposed below the first upper surface, a second left side surface slidably contacting the first right side surface, or a second right side surface slidably contacting the first left side surface, and second front and rear surfaces slidably contacting the die, a first edge along the left - right direction of the first upper surface has a first ridge, a second edge along the up - down direction of the first right side surface and the first left side surface has a second ridge.

Advantages of the Invention

[0011] The mold of the present disclosure can eliminate the need for deburring after forming a compacted powder body having a U - shaped sliding surface in cross - section.

Brief Description of the Drawings

[0012] [Figure 1] FIG. 1 is an exploded perspective view schematically showing the configuration of a mold according to an embodiment. [Figure 2] FIG. 2 is a cross - sectional view schematically showing the mold according to an embodiment. [Figure 3] FIG. 3 is a top view schematically showing a first punch of the mold according to an embodiment. [Figure 4] FIG. 4 is a schematic view exaggerating the shape of the first punch of the mold according to an embodiment. [Figure 5] FIG. 5 is an enlarged cross - sectional view schematically showing the V - V cross - section of FIG. 4. [Figure 6] FIG. 6 is an enlarged cross - sectional view schematically showing the VI - VI cross - section of FIG. 4. [Figure 7] FIG. 7 is a perspective view schematically showing a compacted powder body. [Figure 8] FIG. 8 is another perspective view schematically showing a compacted powder body. [Figure 9] FIG. 9 is a plan view schematically showing a compacted powder body. [Figure 10] FIG. 10 is a schematic view exaggerating the shape of the compacted powder body. [Figure 11] FIG. 11 is an enlarged cross - sectional view schematically showing the XI - XI cross - section of FIG. 10. [Figure 12] FIG. 12 is a cross-sectional view schematically showing an enlarged XII-XII cross-section of FIG. 10.

BEST MODE FOR CARRYING OUT THE INVENTION

[0013] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described.

[0014] (1) The mold according to an embodiment of the present disclosure is a mold for forming a compacted powder having a sliding surface with a U-shaped cross-section, an annular die having a space in which the compacted powder is formed, and a lower punch fitted to the lower part of the space, wherein the lower punch includes a first lower punch, and two second lower punches arranged so as to sandwich the first lower punch from the left and right, wherein the first lower punch has a first upper end surface for forming the bottom surface of the sliding surface, a first right side surface and a first left side surface for forming the inner side surface of the sliding surface, and a first front surface and a first back surface slidably contacting the die, wherein each of the second lower punches has a second upper end surface arranged below the first upper end surface, a second left side surface slidably contacting the first right side surface or a second right side surface slidably contacting the first left side surface, and a second front surface and a second back surface slidably contacting the die, wherein a first edge portion along the left-right direction of the first upper end surface has a first ridge, and a second edge portion along the up-down direction of the first right side surface and the first left side surface has a second ridge. ...

[0015] The mold of this disclosure forms a compacted material having a U-shaped sliding surface in cross-section using a lower punch. The shape having a U-shaped sliding surface is, for example, a groove. The lower punch comprises a first lower punch and two second lower punches. The first lower punch has a first upper end surface that forms the bottom surface of the U-shaped sliding surface constituting the groove, and a first right side surface and a first left side surface that form the inner surface. In the mold of this disclosure, the first lower punch has a first projection on the first edge of the first upper end surface along the left-right direction, and a second projection on the second edge of the first right side surface and the first left side surface along the up-down direction. With this configuration, a chamfered portion can be formed on the opening edge of the groove in the compacted material. By providing a chamfered portion on the opening edge of the groove, even if burrs are generated on the opening edge of the groove, it is possible to suppress the burrs from protruding from the chamfered portion. By preventing burrs from protruding from the chamfered portion, it is possible to suppress interference between burrs and other members when other members are assembled to the groove. As a result, damage to other components or obstruction of sliding of other components due to burrs can be suppressed. Therefore, with the mold of this disclosure, it is possible to eliminate the need to remove burrs after molding a powder compact having a U-shaped sliding surface in cross-section.

[0016] (2) In the mold described in (1) above, The first upper end surface has a main end surface, a first top surface of the first projection, and a first connecting surface that connects the main end surface and the first top surface. Each of the first right side and the first left side may have a main side surface, a second top surface of the second projection, and a second connecting surface connecting the main side surface and the second top surface.

[0017] According to the configuration of (2) above, the first and second protrusions make it easy to form a predetermined chamfered portion on the opening edge of the groove portion of the compacted powder.

[0018] (3) In the mold described in (2) above, The first connecting surface and the second connecting surface may be inclined surfaces.

[0019] According to the configuration of (3) above, it is possible to suppress damage to the first and second protrusions due to the reaction force when compressing the powder.

[0020] (4) In the mold described in (3) above, The angle of the first connecting surface with respect to the main end surface, and the angle of the second connecting surface with respect to the main side surface, may be 60° or less.

[0021] According to the configuration described in (4) above, damage to the first and second protrusions can be effectively suppressed.

[0022] (5) In any of the molds described in (2) to (4) above, The width of the first top surface and the width of the second top surface may be 0.1 mm or more.

[0023] According to the configuration of (5) above, the strength of the first and second protrusions can be increased, and damage to the first and second protrusions due to the reaction force when compressing the powder can be suppressed.

[0024] (6) In any of the molds described in (1) to (5) above, The height of the first protrusion and the height of the second protrusion may be 0.1 mm or more.

[0025] According to the configuration described in (6) above, the depth of the chamfer formed by the first and second protrusions can be set to 0.1 mm or more. By having a chamfer depth of 0.1 mm or more, the protrusion of burrs from the chamfer can be effectively suppressed.

[0026] [Details of the embodiments of this disclosure] Hereinafter, specific examples of molds according to the embodiments of this disclosure will be described with reference to the drawings. The same reference numerals in the drawings indicate the same or corresponding parts. However, the present invention is not limited to these examples, and is intended to include all modifications within the meaning and scope of the claims as shown, and equivalents thereof.

[0027] <Mold> The outline of mold 1 will be described with reference to Figures 1, 2, and 7 to 9. Mold 1 is a mold for molding the compacted body 6 shown in Figures 7 and 8. The compacted body 6 has a first surface 61, a second surface 62, and an outer peripheral surface 63. Of the first surface 61 and the second surface 62, one is the top surface and the other is the bottom surface. The outer peripheral surface 63 connects the first surface 61 and the second surface 62. In this example, the first surface 61 is the bottom surface and the second surface 62 is the top surface. The top and bottom of the compacted body 6 refer to the top and bottom when the compacted body 6 is placed inside mold 1. The compacted body 6 has a groove 7. In this example, one groove 7 is provided on the first surface 61. The groove 7 has a sliding surface 70 with a U-shaped cross-section. The sliding surface 70 has a bottom surface 71 and two inner surfaces 72 facing each other. In this example, the bottom surface 71 is rectangular in shape. The sliding surface 70 that constitutes the groove 7 is not included in the first surface 61.

[0028] In this example, the groove 7 opens to the first surface 61 and the outer circumferential surface 63. As shown in Figure 9, the groove 7 penetrates from the front surface 63a to the back surface 63b of the outer circumferential surface 63. The shape of the groove 7 is that of a rectangular parallelepiped. The shape of the groove 7 is the shape of the space enclosed by the bottom surface 71, the inner surface 72, a virtual surface extended from the first surface 61, and a virtual surface extended from the outer circumferential surface 63.

[0029] As shown in Figure 1, mold 1 comprises an annular die 10, a lower punch 21, and an upper punch 22. As shown in Figure 2, die 10 has a space 100 (see Figure 1) in which the compacted body 6 is formed. The lower punch 21 is fitted into the lower part of the space 100. The upper punch 22 is fitted into the upper part of the space 100. The lower punch 21 and the upper punch 22 are spaced apart in the vertical direction. Figure 2 shows the state in which the compacted body 6 has been formed by mold 1. Figure 2 is a longitudinal cross-sectional view of mold 1 from the front. A longitudinal cross-section is a cross-section obtained by cutting mold 1 along the vertical direction.

[0030] In this embodiment, the mold 1 uses a lower punch 21 to form a U-shaped sliding surface 70 into the compacted powder 6. The upper end of the lower punch 21 has a shape corresponding to the groove 7. The lower punch 21 comprises a first lower punch 21a and two second lower punches 21b. As shown in Figure 2, the first lower punch 21a has a first upper end surface 31 (described later), a first right side surface 33a, and a first left side surface 33b. One of the features of the mold 1 in this embodiment is that the first lower punch 21a has a specific shape. Specifically, as will be described later with reference to Figure 4, the first edge 40 of the first upper end surface 31 has a first protrusion 41, and the second edges 50 of the first right side surface 33a and the first left side surface 33b have a second protrusion 51. In Figure 4, for the sake of explanation, the first protrusion 41 and the second protrusion 51 are exaggerated. In Figures 1 and 4, the first left side surface 33b is hidden and therefore not visible. The configuration of mold 1 will be described in detail below with reference to Figures 1 to 6.

[0031] In this embodiment, the vertical, horizontal, and front-to-back directions in the mold 1 are defined as follows. The vertical direction of the mold 1 is the direction in which the space 100 penetrates the annular die 10. That is, the vertical direction is the Z direction shown in Figure 1. The vertical direction is also the direction along the axial direction of the lower punch 21 and the upper punch 22, respectively. The horizontal direction of the mold 1 is the direction in which the two second lower punches 21b are aligned on either side of the first lower punch 21a. That is, the horizontal direction is the X direction shown in Figure 1. The front-to-back direction of the mold 1 is the direction perpendicular to the vertical and horizontal directions. That is, the front-to-back direction is the Y direction shown in Figure 1.

[0032] (Thailand) As shown in Figure 1, the die 10 is an annular member having a space 100 that penetrates in the vertical direction. As shown in Figure 2, the inner circumferential surface 101 of the die 10 forms the outer circumferential surface 63 of the compacted body 6. The shape of the die 10 in this embodiment is rectangular, as shown in Figure 1, and the shape of the space 100 as viewed from the vertical direction is rectangular. The rectangle includes a square. The die 10 in this embodiment has a front frame portion 10a, a rear frame portion 10b, a left frame portion 10c, and a right frame portion 10d. The front frame portion 10a constitutes the front part of the die 10. The rear frame portion 10b constitutes the rear part of the die 10. The left frame portion 10c constitutes the left part of the die 10. The right frame portion 10d constitutes the right part of the die 10. The shape of the space 100 is appropriately selected according to the shape of the compacted body 6. The shape of the compacted body 6 is the shape of the compacted body 6 (see Figures 7 and 8) as viewed from the vertical direction. The shape of space 100 may be, for example, a circle, or a polygon other than a rectangle. A circle includes an ellipse.

[0033] (Lower punch) The upper end of the lower punch 21 is movable vertically relative to the die 10 while sliding against the die 10. The upper end of the lower punch 21 is the part that fits into the space 100 of the die 10. As shown in Figures 1 and 2, the lower punch 21 is a split punch composed of a first lower punch 21a and two second lower punches 21b. The two second lower punches 21b are arranged to sandwich the first lower punch 21a from the left and right. The first lower punch 21a and the second lower punches 21b are independently movable vertically. The first lower punch 21a and the second lower punches 21b are columnar members that extend vertically. In this embodiment, the shape of the lower punch 21 is rectangular. The shape of the lower punch 21 is the shape of the contour when viewed from the axial direction, i.e., the vertical direction. The shape of the lower punch 21 is appropriately selected according to the shape of the die 10. The shape of the lower punch 21 may be, for example, circular or a polygon other than a rectangle.

[0034] <First lower punch> As shown in Figure 3, the first lower punch 21a has a first upper end surface 31, a first right side surface 33a and a first left side surface 33b, a first front surface 34a and a first back surface 34b. In Figures 1 and 4, the first left side surface 33b and the first back surface 34b are hidden and therefore not visible. The first upper end surface 31 forms the bottom surface 71 of the sliding surface 70 on the compacted powder 6 shown in Figure 2. The first right side surface 33a and the first left side surface 33b form the inner surface 72 of the sliding surface 70. The first right side surface 33a and the first left side surface 33b are not in contact with the die 10. The first right side surface 33a is provided at a distance from the right frame portion 10d of the die 10. The first left side surface 33b is provided at a distance from the left frame portion 10c of the die 10. The first front surface 34a and the first back surface 34b are in sliding contact with the die 10, as shown in Figure 3. The first front surface 34a slides against the front frame portion 10a of the die 10. The first rear surface 34b slides against the rear frame portion 10b of the die 10. The first upper end surface 31, the first right side surface 33a, and the first left side surface 33b are connected to the first front surface 34a and the first rear surface 34b, respectively.

[0035] The shape of the first upper surface 31 in this embodiment is rectangular. The shape of the first upper surface 31 is the shape of the first upper surface 31 when viewed from above. The shape of the first upper surface 31 corresponds to the shape of the bottom surface 71 of the sliding surface 70 in the compacted powder 6 shown in Figure 8. The shape of the first upper surface 31 is appropriately selected according to the shape of the bottom surface 71. The shape of the first upper surface 31 may be a polygon other than a rectangle, for example.

[0036] The upper end of the first lower punch 21a forms a groove 7 having a sliding surface 70 into the compacted powder 6. In this embodiment, the shape of the upper end of the first lower punch 21a is a rectangular parallelepiped corresponding to the groove 7. The shape of the upper end of the first lower punch 21a is the shape of the portion enclosed by the first upper end surface 31, the upper parts of the first right side surface 33a and the first left side surface 33b, and the upper parts of the first front surface 34a and the first back surface 34b.

[0037] <Second lower punch> Each of the second lower punches 21b has a second upper end surface 32, a second left side surface 35a and a second right side surface 35b, a second front surface 36a and a second back surface 36b, as shown in Figure 3. In Figure 1, the second left side surface 35a and the second right side surface 35b and the second back surface 36b are hidden and therefore not visible. In Figure 4, the second left side surface 35a and the second back surface 36b are hidden and therefore not visible. The second upper end surface 32 is positioned below the first upper end surface 31 of the first lower punch 21a, as shown in Figure 2. The second left side surface 35a slides against the first right side surface 33a of the first lower punch 21a. The second right side surface 35b slides against the first left side surface 33b of the first lower punch 21a. The second front surface 36a and the second back surface 36b slide against the die 10, as shown in Figure 3. The second front surface 36a slides against the front frame portion 10a of the die 10. The second rear surface 36b slides against the rear frame portion 10b of the die 10. The second upper end surface 32, the second left side surface 35a, and the second right side surface 35b are connected to the second front surface 36a and the second rear surface 36b, respectively.

[0038] The shape of the second upper surface 32 in this embodiment is rectangular. The shape of the second upper surface 32 is the shape of the second upper surface 32 when viewed from above. The shape of the second upper surface 32 corresponds to the shape of the first surface 61, i.e., the bottom surface, of the compacted powder 6 shown in Figure 8. The shape of the second upper surface 32 is appropriately selected according to the shape of the first surface 61. The shape of the second upper surface 32 may be a polygon other than a rectangle, for example.

[0039] <First Protrusion> As shown in Figure 4, the first upper surface 31 has a first projection 41. In this embodiment, the first upper surface 31 has a pair of first edges 40, which are the outer edges along the left-right direction among the outer edges of the four sides. The first projection 41 is provided on these first edges 40. The first projection 41 is provided along the entire length of the first edges 40. The first edges 40 are edges that are connected to the first front surface 34a or the first back surface 34b of the first upper surface 31. The first edges 40 are located near the front edge and rear edge of the first upper surface 31, respectively. In other words, there are two first edges 40 on one first upper surface 31.

[0040] The first upper end surface 31 has a main end surface 310, a first top surface 411 of the first projection 41, and a first connecting surface 412. The first connecting surface 412 connects the main end surface 310 and the first top surface 411. The main end surface 310 is the largest surface constituting the first upper end surface 31. The length of the main end surface 310 in the front-rear direction is, for example, 50% or more of the length of the first upper end surface 31 in the front-rear direction. The length of the first upper end surface 31 in the front-rear direction is equal to the distance along the front-rear direction between the first front surface 34a and the first back surface 34b. The above length of the main end surface 310 may further be 60% or more, 70% or more, 80% or more, or 90% or more of the above length of the first upper end surface 31. The upper limit of the above length of the main end surface 310 is not particularly limited as long as it is shorter than the above length of the first upper end surface 31.

[0041] The first projection 41 forms a first chamfer 81 on the first edge 80 of the bottom surface 71 of the sliding surface 70, as will be described later with reference to Figure 10. The first projection 41 protrudes beyond the main end surface 310, as shown in Figure 4. In this embodiment, the first top surface 411 of the first projection 41 is perpendicular to the first front surface 34a or the first back surface 34b. The first top surface 411 is parallel to the main end surface 310. In this embodiment, the first connecting surface 412 is an inclined surface. The first connecting surface 412 may also be a vertical surface. This vertical surface is a surface that is aligned in both the vertical and horizontal directions.

[0042] The shape and dimensions of the first projection 41 will be described with reference to Figure 5. Figure 5 shows a cross-section obtained by cutting the vicinity of the first edge portion 40 of the first upper end surface 31 in a direction perpendicular to the left-right direction. In the cross-section shown in Figure 5, the shape of the first projection 41 is trapezoidal, having a flat first top surface 411 and an inclined surface consisting of a first connecting surface 412. The angle α1 of the first connecting surface 412 with respect to the main end surface 310 is, for example, 60° or less. The smaller the angle α1, the longer the first connecting surface 412 becomes, and therefore the shorter the length of the main end surface 310 becomes. The lower limit of the angle α1 is, for example, 10° or more and 60° or less, 15° or more and 45° or less, or 20° or more and 40° or less. In this embodiment, the angle α1 is 30°.

[0043] The width y1 of the first top surface 411 is, for example, 0.1 mm or more. The upper limit of the width y1 is, for example, 1 mm. The width y1 may also be, for example, 0.1 mm or more and 1 mm or less, or 0.2 mm or more and 0.5 mm or less. The width y1 is the length of the first top surface 411 along the longitudinal direction of the first projection 41, that is, the direction perpendicular to the left-right direction. The height z1 of the first protrusion 41 is, for example, 0.1 mm or more. The upper limit of the height z1 is, for example, 1 mm. The height z1 may also be, for example, 0.1 mm or more and 1 mm or 0.2 mm or more and 0.5 mm or less. The height z1 is the distance along the vertical direction between the main end face 310 and the first top face 411. The height z1 of the first protrusion 41 is selected to be greater than the height of the burr B1 formed on the sub-bottom face 811 of the first chamfer 81, which will be described later with reference to Figure 11. In this embodiment, the width y1 and height z1 are each 0.2 mm.

[0044] <Second Protrusion> Each of the first right side surface 33a and the first left side surface 33b has a second projection 51, as shown in Figure 4. In this embodiment, each of the first right side surface 33a and the first left side surface 33b has a pair of second edges 50, which are outer edges aligned vertically among the outer edges of the four sides. The second projection 51 is provided on these second edges 50. The second projection 51 extends along the entire length of the second edges 50. The second edges 50 are edges that connect to the first front surface 34a or the first back surface 34b on the first right side surface 33a and the first left side surface 33b. The second edges 50 are located near the front edge and rear edge of each of the first right side surface 33a and the first left side surface 33b. In other words, each of the first right side surface 33a and the first left side surface 33b has two second edges 50. In this embodiment, there are a total of four second edges 50. The upper end of each second projection 51 is connected to the left or right end of the first projection 41.

[0045] Each of the first right side 33a and the first left side 33b has a main side 330, a second top surface 511 of the second projection 51, and a second connecting surface 512. The second connecting surface 512 connects the main side 330 and the second top surface 511. The main side 330 is the largest surface constituting the first right side 33a or the first left side 33b. The length of the main side 330 in the front-rear direction is, for example, 50% or more of the length of the first right side 33a or the first left side 33b in the front-rear direction. The length of the first right side 33a or the first left side 33b in the front-rear direction is equal to the distance between the first front surface 34a and the first back surface 34b. The above length of the main side 330 may further be 60% or more, 70% or more, 80% or more, or 90% or more of the above length of the first right side 33a or the first left side 33b. The upper limit of the length of the main side surface 330 is not particularly limited, as long as it is shorter than the length of the first right side surface 33a or the first left side surface 33b.

[0046] As will be described later with reference to Figure 10, the second projection 51 forms a second chamfer 91 on the second edge 90 of the inner surface 72 of the sliding surface 70. The second projection 51 protrudes beyond the main surface 330, as shown in Figure 4. In this embodiment, the second top surface 511 of the second projection 51 is perpendicular to the first front surface 34a or the first back surface 34b. The second top surface 511 is parallel to the main surface 330. In this embodiment, the second connecting surface 512 is an inclined surface. The second connecting surface 512 may also be a vertical surface. This vertical surface is a surface that is aligned in both the vertical and horizontal directions.

[0047] The shape and dimensions of the second projection 51 will be described with reference to Figure 6. Figure 6 shows a cross-section of the first left side surface 33b near the second edge 50, cut in a direction perpendicular to the vertical direction. In the cross-section shown in Figure 6, the shape of the second projection 51 is trapezoidal, having a flat second top surface 511 and an inclined surface consisting of a second connecting surface 512. The angle α2 of the second connecting surface 512 with respect to the main side surface 330 is, for example, 60° or less. The smaller the angle α2, the longer the second connecting surface 512 becomes, and therefore the shorter the length of the main side surface 330 becomes. The lower limit of the angle α2 is, for example, 10° or more and 60° or less, 15° or more and 45° or less, or 20° or more and 40° or less. In this embodiment, the angle α2 is 30°.

[0048] The width y2 of the second top surface 511 is, for example, 0.1 mm or more. The upper limit of the width y2 is, for example, 1 mm. The width y2 may also be, for example, 0.1 mm or more and 1 mm or less, or 0.2 mm or more and 0.5 mm or less. The width y2 is the length of the second top surface 511 along the longitudinal direction of the second projection 51, that is, the direction perpendicular to the vertical direction. The height x2 of the second protrusion 51 is, for example, 0.1 mm or more. The upper limit of the height x2 is, for example, 1 mm. The height x2 may also be, for example, 0.1 mm or more and 1 mm or 0.2 mm or more and 0.5 mm or less. The height x2 is the distance along the left-right direction between the main side surface 330 and the second top surface 511. The height x2 of the second protrusion 51 is selected to be greater than the height of the burr B2 formed on the sub-bottom surface 911 of the second chamfer 91, which will be described later with reference to Figure 12. In this embodiment, the width y2 and height x2 are each 0.2 mm.

[0049] As shown in Figure 10, the first upper surface 31 has a first projection 41, and the first right surface 33a and the first left surface 33b each have a second projection 51, so that in the groove 7 of the compacted body 6, a first chamfer 81 and a second chamfer 91 can be formed on the first edge 80 of the bottom surface 71 and the second edge 90 of the inner surface 72. As shown in Figures 11 and 12, even if burrs B1 and B2 occur on the first edge 80 of the bottom surface 71 and the second edge 90 of the inner surface 72, it is possible to suppress the protrusion of each burr from the first chamfer 81 and the second chamfer 91. Because burrs do not protrude from the first chamfer 81 and the second chamfer 91, as will be described later, problems caused by burrs are less likely to occur even without removing the burrs. Therefore, the mold 1 can eliminate the need to remove burrs after forming the compacted body 6.

[0050] Furthermore, if the outer surface of the compacted powder 6 or the sintered body obtained by sintering the compacted powder 6 is subjected to processing such as polishing, burrs may form on the first edge 80 of the bottom surface 71 and the second edge 90 of the inner surface 72. Even if burrs are formed by the above processing, it is possible to suppress the burrs from protruding from the first chamfer 81 and the second chamfer 91.

[0051] In addition, the first lower punch 21a is provided with a first ridge 41 and a second ridge 51. When the metal powder that is the raw material for the compacted body 6 is compressed, the reaction force causes the first ridge 41 and the second ridge 51 to elastically deform in a direction that brings them closer to the inner circumferential surface 101 of the die 10. As a result, the clearance between the die 10 and the first ridge 41 and the second ridge 51 is reduced. Consequently, burrs B1 and B2 are less likely to occur on the first edge 80 of the bottom surface 71 and the second edge 90 of the inner surface 72 of the compacted body 6, and the height of each burr is reduced.

[0052] The fact that the first connecting surface 412 of the first upper end surface 31 and the second connecting surfaces 512 of the first right side surface 33a and the first left side surface 33b are inclined surfaces prevents the first protrusion 41 and the second protrusion 51 from being damaged by the reaction force when the powder is compressed. The fact that the angle α1 of the first connecting surface 412 and the angle α2 of the second connecting surface 512 are 60° or less effectively prevents the first protrusion 41 and the second protrusion 51 from being damaged. The above effect is easier to obtain when the angles α1 and α2 are 45° or less, and even 40° or less.

[0053] The smaller the angles α1 and α2, the longer the first connecting surface 412 and the second connecting surface 512 become, thus shortening the length of the main end surface 310 of the first upper end surface 31 and the main side surfaces 330 of the first right side surface 33a and the first left side surface 33b. If angles α1 and α2 are 10° or more, and even 20° or more, it is easier to secure the length of the main end surface 310 and the main side surfaces 330. The main end surface 310 and the main side surfaces 330 form the main bottom surface 710 of the bottom surface 71 and the main inner surface 720 of the inner surface 72 of the sliding surface 70 of the compacted powder body 6 shown in Figure 10. By securing the length of the main end surface 310 and the main side surfaces 330, the length of the main bottom surface 710 and the main inner surface 720 in the groove 7 can be secured.

[0054] By having a width y1 of the first top surface 411 and a width y2 of the second top surface 511 of 0.1 mm or more, the strength of the first protrusion 41 and the second protrusion 51 can be increased, and damage to the first protrusion 41 and the second protrusion 51 due to the reaction force when compressing the powder can be suppressed. The above effect is easier to obtain when the widths y1 and y2 are 0.2 mm or more. The first top surface 411 and the second top surface 511 form the sub-bottom surface 811 of the first chamfer 81 and the sub-bottom surface 911 of the second chamfer 91 shown in Figure 10 in the groove portion 7 of the compacted powder body 6. The larger the widths y1 and y2, the larger the widths a1 of the sub-bottom surface 811 and a2 of the sub-bottom surface 911 become, and thus the larger the size of the first chamfer 81 and the second chamfer 91. If widths y1 and y2 are 1 mm or less, and further 0.5 mm or less, the first chamfer 81 and the second chamfer 91 can be made smaller to some extent.

[0055] By having a height z1 of the first protrusion 41 and a height x2 of the second protrusion 51 of 0.1 mm or more, the depth b1 of the first chamfer 81 and the depth b2 of the second chamfer 91 shown in Figures 11 and 12 can be set to 0.1 mm or more in the groove portion 7 of the compacted powder 6. By having depths b1 and b2 of 0.1 mm or more, the burrs B1 and B2 generated on the first edge portion 80 and the second edge portion 90 can be effectively suppressed from protruding from the first chamfer 81 and the second chamfer 91. If depths b1 and b2 are 0.2 mm or more, the protrusion of each burr from the first chamfer 81 and the second chamfer 91 can be sufficiently suppressed. The larger the heights z1 and x2, the larger the depths b1 and b2 become, and therefore the larger the size of the first chamfer 81 and the second chamfer 91. If heights z1 and x2 are 1 mm or less, and further 0.5 mm or less, the first chamfer 81 and the second chamfer 91 can be made smaller to some extent.

[0056] The second lower punch 21b, which slides against the first right side surface 33a or first left side surface 33b of the first lower punch 21a, has a second groove 39 (see Figure 4) provided along the vertical direction on its second left side surface 35a and second right side surface 35b, corresponding to the second ridge 51.

[0057] (Upper punch) As shown in Figure 1, the upper punch 22 is a columnar member extending in the vertical direction. The upper end of the upper punch 22 is movable in the vertical direction relative to the die 10 while sliding against the die 10. The lower end of the upper punch 22 is the part that fits into the space 100 of the die 10. The upper punch 22 has a lower end surface 222 and an outer peripheral surface 224. As shown in Figure 2, the lower end surface 222 forms the second surface 62 of the compacted body 6. The outer peripheral surface 224 slides against the die 10. In this embodiment, the shape of the lower end surface 222 is rectangular. The shape of the lower end surface 222 is the shape of the lower end surface 222 when viewed from below. The shape of the lower end surface 222 corresponds to the shape of the second surface 62 in the compacted body 6 shown in Figure 8. The shape of the lower end surface 222 is appropriately selected according to the shape of the second surface 62. The shape of the lower end surface 222 may be a polygon other than a rectangle, for example.

[0058] In this embodiment, the shape of the upper punch 22 is rectangular. The shape of the upper punch 22 refers to the shape of the outline when viewed from the axial direction, i.e., the vertical direction. The shape of the upper punch 22 is appropriately selected according to the shape of the die 10. The shape of the upper punch 22 may be, for example, circular or a polygon other than a rectangle.

[0059] Referring to Figure 2, the operation of the mold 1 described above will be explained. The lower punch 21 is fitted into the space 100 of the die 10 (see Figure 1). At this time, the upper punch 22 is positioned above the die 10 and is not fitted into the space 100 of the die 10. Metal powder, which will be the raw material for the compacted body 6, is filled into the space formed by the die 10 and the lower punch 21. After the metal powder is filled, the upper punch 22 descends and compresses the powder with the upper punch 22 and the lower punch 21. After compressing the powder and forming the compacted body 6, the compacted body 6 is removed from the die 10.

[0060] As in this embodiment, when the lower punch 21 is a split punch comprising a first lower punch 21a and a second lower punch 21b, the first lower punch 21a and the second lower punch 21b can be controlled individually. Therefore, when filling with the powder, the vertical positions of the first upper end surface 31 and the second upper end surface 32 can be adjusted, respectively. This makes it possible to reduce the difference between the compression ratio of the powder compressed by the first lower punch 21a and the upper punch 22 and the compression ratio of the powder compressed by the second lower punch 21b and the upper punch 22. By reducing the difference in compression ratio, the density difference between the part of the compacted body 6 with grooves 7 and the part without grooves 7 can be reduced. As a result, the density of the compacted body 6 can be made uniform.

[0061] <Compacted powder> The details of the compact 6 will be described with reference to Figures 7 to 12. The compact 6 is formed by the mold 1 of the embodiment described above. As shown in Figures 7 and 8, the compact 6 has a first surface 61, a second surface 62, and an outer peripheral surface 63. In this embodiment, the first surface 61 is the bottom surface, and the second surface 62 is the top surface. The shape of the compact 6 of this embodiment when viewed from above is rectangular. The outer peripheral surface 63 includes a front surface 63a and a back surface 63b, as shown in Figure 9. Figure 7 is a perspective view of the compact 6 with the second surface 62, i.e., the top surface, facing upwards. Figure 8 is a perspective view of the compact 6 shown in Figure 7 with the first surface 61, i.e., the bottom surface, facing upwards. Figure 9 is a plan view of the compact 6 viewed from below.

[0062] (Mizobe) The compacted body 6 has grooves 7. As shown in Figure 8, the grooves 7 open to the first surface 61 and the outer peripheral surface 63. The grooves 7 penetrate from the front surface 63a to the back surface 63b. In other words, the grooves 7 open to both the front surface 63a and the back surface 63b. The grooves 7 have a sliding surface 70 with a U-shaped cross-section. The sliding surface 70 has a bottom surface 71 and two inner surfaces 72 facing each other. The inner surfaces 72 are provided between the first surface 61 and the bottom surface 71. The bottom surface 71 and the inner surfaces 72 are connected to the front surface 63a and the back surface 63b, respectively. The shape of the compacted body 6 in this embodiment, when viewed from the front-rear direction, is U-shaped. The shape of the bottom surface 71 in this embodiment is rectangular.

[0063] In this embodiment, as shown in Figure 8, the first surface 61 is divided into left and right sections by the groove 7. The shape of the first surface 61 is rectangular. As shown in Figure 7, the shape of the second surface 62 is rectangular.

[0064] As shown in Figure 10, the compacted powder body 6 has a first chamfer 81 and a second chamfer 91 on the opening edge of the groove 7 on the outer circumferential surface 63. The opening edge of the groove 7 is the edge that connects to the outer circumferential surface 63 on the sliding surface 70. In Figure 10, the first chamfer 81 and the second chamfer 91 are shown in an exaggerated manner for ease of explanation.

[0065] <First chamfering> The first chamfer 81 is provided on the first edge portion 80 of the bottom surface 71. The first edge portion 80 is a pair of outer edges along the left-right direction, among the outer edges of the four sides constituting the bottom surface 71. The left-right direction is a direction perpendicular to the up-down direction and the front-back direction, respectively. The first chamfer 81 is provided along the entire length of the first edge portion 80. The first edge portion 80 is an edge that connects to the front surface 63a or the back surface 63b of the bottom surface 71. The first edge portion 80 is located near the front edge and the rear edge of the bottom surface 71, respectively. In other words, there are two first edge portions 80 on one bottom surface 71.

[0066] The base surface 71 has a main base surface 710, a sub-base surface 811 of the first chamfer 81, and a first connecting surface 812. The first connecting surface 812 connects the main base surface 710 and the sub-base surface 811. The main base surface 710 is the largest surface constituting the base surface 71. The length of the main base surface 710 in the front-to-back direction is, for example, 50% or more of the length of the base surface 71 in the front-to-back direction. The length of the base surface 71 in the front-to-back direction is equal to the distance along the front-to-back direction between the front surface 63a and the back surface 63b of the outer peripheral surface 63. The above length of the main base surface 710 may further be 60% or more, 70% or more, 80% or more, or 90% or more of the above length of the base surface 71. The upper limit of the above length of the main base surface 710 is not particularly limited as long as it is shorter than the above length of the base surface 71.

[0067] The first chamfer 81 is recessed compared to the main base surface 710. In this embodiment, the sub-base surface 811 of the first chamfer 81 is perpendicular to the outer peripheral surface 63. The sub-base surface 811 of the first chamfer 81 is parallel to the main base surface 710. The first connecting surface 812 is an inclined surface. The first connecting surface 812 may also be a surface perpendicular to the main base surface 710.

[0068] The shape and dimensions of the first chamfer 81 will be described with reference to Figure 11. Figure 11 shows a cross-section of the base surface 71 near the first edge 80, cut in a direction perpendicular to the first edge 80. In the cross-section shown in Figure 11, the shape of the first chamfer 81 is trapezoidal, having a flat sub-base surface 811 and an inclined surface consisting of a first connecting surface 812. The angle β1 of the first connecting surface 812 with respect to the main base surface 710 is, for example, 60° or less. The smaller the angle β1, the longer the first connecting surface 812 becomes, and therefore the shorter the length of the main base surface 710 becomes. The lower limit of the angle β1 is, for example, 10° or more and 60° or less, 15° or more and 45° or less, or 20° or more and 40° or less.

[0069] The width a1 of the sub-base 811 is, for example, 0.1 mm or more. The upper limit of the width a1 is, for example, 1 mm. The width a1 may also be, for example, 0.1 mm or more and 1 mm or 0.2 mm or more and 0.5 mm or less. The width a1 is the length of the sub-base 811 along the direction perpendicular to the longitudinal direction of the first edge portion 80. The depth b1 of the first chamfer 81 is, for example, 0.1 mm or more. The upper limit of the depth b1 is, for example, 1 mm. The depth b1 may also be, for example, 0.1 mm or more and 1 mm or 0.2 mm or more and 0.5 mm or less. The depth b1 is the distance along the vertical direction between the main base surface 710 and the sub-base surface 811. The depth b1 of the first chamfer 81 is greater than the height of the burr B1 formed on the sub-base surface 811 of the first chamfer 81.

[0070] The first chamfer 81 is formed by the first ridge 41 provided on the first edge 40 of the first upper end surface 31 of the first lower punch 21a shown in Figures 4 and 5 above. The main bottom surface 710 is formed by the main end surface 310 of the first upper end surface 31. The secondary bottom surface 811 is formed by the first top surface 411 of the first ridge 41. The first connecting surface 812 is formed by the first connecting surface 412 that connects the main end surface 310 and the first top surface 411. The shape of the first chamfer 81 is substantially the same as the shape of the first ridge 41. The angle β1 of the first connecting surface 812 is substantially equal to the angle α1 of the first connecting surface 412 shown in Figure 11 above, and the width a1 of the secondary bottom surface 811 is substantially equal to the width y1 of the first top surface 411 shown in Figure 11 above. The depth b1 of the first chamfer 81 is substantially equal to the height z1 of the first projection 41 shown in Figure 11 above. In this embodiment, the angle β1 is 30°. The width a1 and depth b1 are 0.2 mm each.

[0071] <Second chamfering> The second chamfer 91 is provided on the second edge portion 90 of the inner surface 72. The second edge portion 90 is a pair of outer edges aligned vertically, near the outer edges of the four sides constituting the inner surface 72. The second chamfer 91 is provided along the entire length of the second edge portion 90. The second edge portion 90 is an edge that connects to the front surface 63a or the back surface 63b of the inner surface 72. The second edge portion 90 is located near the front edge and the rear edge of the inner surface 72, respectively. In other words, there are two second edge portions 90 on one inner surface 72. In this embodiment, there are a total of four second edge portions 90. The upper end of each second chamfer 91 is connected to the left end or the right end of the first chamfer 81.

[0072] The inner surface 72 has a main inner surface 720, a secondary bottom surface 911 of the second chamfer 91, and a second connecting surface 912. The second connecting surface 912 connects the main inner surface 720 and the secondary bottom surface 911. The main inner surface 720 is the largest surface constituting the inner surface 72. The length of the main inner surface 720 in the front-rear direction is, for example, 50% or more of the length of the inner surface 72 in the front-rear direction. The length of the inner surface 72 in the front-rear direction is equal to the distance along the front-rear direction between the front surface 63a and the back surface 63b of the outer peripheral surface 63. The above length of the main inner surface 720 may further be 60% or more, 70% or more, 80% or more, or 90% or more of the above length of the inner surface 72. The upper limit of the above length of the main inner surface 720 is not particularly limited as long as it is shorter than the above length of the inner surface 72.

[0073] The second chamfer 91 is recessed compared to the main inner surface 720. In this embodiment, the sub-bottom surface 911 of the second chamfer 91 is perpendicular to the outer circumferential surface 63. The sub-bottom surface 911 of the second chamfer 91 is parallel to the main inner surface 720. The second connecting surface 912 is an inclined surface. The second connecting surface 912 may also be a surface perpendicular to the main inner surface 720.

[0074] The shape and dimensions of the second chamfer 91 will be described with reference to Figure 12. Figure 12 shows a cross-section of the inner surface 72 near the second edge 90, cut in a direction perpendicular to the second edge 90. In the cross-section shown in Figure 12, the shape of the second chamfer 91 is trapezoidal, having a flat sub-bottom surface 911 and an inclined surface consisting of a second connecting surface 912. The angle β2 of the second connecting surface 912 with respect to the main inner surface 720 is, for example, 60° or less. The smaller the angle β2, the longer the second connecting surface 912 becomes, and therefore the shorter the length of the main inner surface 720 becomes. The lower limit of the angle β2 is, for example, 10° or more and 60° or less, 15° or more and 45° or less, or 20° or more and 40° or less.

[0075] The width a2 of the sub-base 911 is, for example, 0.1 mm or more. The upper limit of the width a2 is, for example, 1 mm. The width a2 may also be, for example, 0.1 mm or more and 1 mm or 0.2 mm or more and 0.5 mm or less. The width a2 is the length of the sub-base 911 along the direction perpendicular to the longitudinal direction of the second edge portion 90. The depth b2 of the second chamfer 91 is, for example, 0.1 mm or more. The upper limit of the depth b2 is, for example, 1 mm. The depth b2 may also be, for example, 0.1 mm or more and 1 mm or 0.2 mm or more and 0.5 mm or less. The depth b2 is the distance between the main inner surface 320 and the sub-bottom surface 911 along the direction perpendicular to the main inner surface 320. The depth b2 of the second chamfer 91 is greater than the height of the burr B2 formed on the sub-bottom surface 911 of the second chamfer 91.

[0076] The second chamfer 91 is formed by a second ridge 51 provided on the second edge 50 of the first right side 33a or the first left side 33b of the first lower punch 21a shown in Figures 4 and 6 above. The main inner surface 720 is formed by the main side surface 330 of the first right side 33a or the first left side 33b. The secondary bottom surface 911 is formed by the second top surface 511 of the second ridge 51. The second connecting surface 912 is formed by the second connecting surface 512 that connects the main side surface 330 and the second top surface 511. The shape of the second chamfer 91 is substantially the same as the shape of the second ridge 51. The angle β2 of the second connecting surface 912 is substantially equal to the angle α2 of the second connecting surface 512 shown in Figure 12 above, and the width a2 of the secondary bottom surface 911 is substantially equal to the width y2 of the second top surface 511 shown in Figure 12 above. The depth b2 of the second chamfer 91 is substantially equal to the height x2 of the second projection 51 shown in Figure 12 above. In this embodiment, the angle β2 is 30°. The width a2 and depth b2 are 0.2 mm each.

[0077] The compacted powder 6 having the groove 7 described above, or the sintered body obtained by sintering this compacted powder 6, can be used, for example, as a sliding part. Although not shown in the figures, the sliding part includes a movable member inserted into the groove 7. The movable member slides within the groove 7 while in contact with the main bottom surface 710 of the bottom surface 71 and the main inner surface 720 of the inner surface 72 of the inner surface 72 of the sliding surface 70. A specific example of a sliding part is an electric actuator used in the parking lock mechanism of an automobile.

[0078] (Bali) Burrs may form on the compacted body 6 formed by the mold 1 of the above-described embodiment. Burrs form, for example, on the opening edge of the groove 7 on the outer peripheral surface 63 shown in Figure 10. Specifically, as shown in Figure 11, burr B1 is generated on the first edge 80 of the bottom surface 71. Burr B1 protrudes from the sub-bottom surface 811 of the first chamfer 81 along the outer peripheral surface 63. Also, as shown in Figure 12, burr B2 is generated on the second edge 90 of the inner surface 72. Burr B2 protrudes from the sub-bottom surface 911 of the second chamfer 91 along the outer peripheral surface 63. The reason why burrs B1 and B2 are generated is that when the compacted body 6 is formed by the mold 1, metal powder, which is the raw material for the compacted body 6, gets into the fitting portion between the die 10 and the first lower punch 21a. The fitting portion between the die 10 and the first lower punch 21a is specifically the portion where the die 10 and the first front surface 34a and first back surface 34b of the first lower punch 21a slide into contact. The height of the burr is, for example, 0.05 mm or more and 0.2 mm or less.

[0079] As shown in Figure 10, the compacted powder body 6 is provided with a first chamfer 81 and a second chamfer 91 on the first edge 80 of the bottom surface 71 and the second edge 90 of the inner surface 72 of the sliding surface 70. Therefore, as shown in Figure 11, it is possible to suppress the protrusion of burr B1 from the first chamfer 81 on the first edge 80 of the bottom surface 71. In other words, even if burr B1 protrudes from the sub-bottom surface 811 of the first chamfer 81, it can be prevented from protruding beyond the extended surface of the main bottom surface 710. Also, as shown in Figure 12, it is possible to prevent burr B2 from protruding from the second chamfer 91 on the second edge 90 of the inner surface 72. In other words, even if burr B2 protrudes from the sub-bottom surface 911 of the second chamfer 91, it can be prevented from protruding beyond the extended surface of the main inner surface 720.

[0080] By preventing burrs B1 and B2 from protruding from the first chamfer 81 and the second chamfer 91, interference between burrs B1 and B2 and the movable member when the aforementioned movable member is assembled to the groove 7 can be suppressed. Therefore, burrs B1 and B2 are less likely to come into contact with the movable member, preventing damage to the movable member or obstruction of its sliding motion. Thus, even if burrs remain, the impact of burrs on performance can be reduced, and the decrease in the reliability of sliding parts due to burrs can be suppressed. In other words, it is not necessary to remove burrs from the compacted powder 6. [Explanation of Symbols]

[0081] 1. Mold 10 Dies 100 space, 101 inner surface 10a Front frame section, 10b Rear frame section, 10c Left frame section, 10d Right frame section 21. Down punch, 22. Up punch 21a First lower punch, 21b Second lower punch 222 Lower end surface, 224 Outer surface 31 First upper end surface, 310 Main end surface 32 Second upper end surface 33a First right side, 33b First left side, 330 Main side 34a First front, 34b First back 35a second left side, 35b second right side 36a 2nd front, 36b 2nd back 39 Second groove 40 First edge, 41 First projection 411 First top surface, 412 First connecting surface 50 Second edge, 51 Second protrusion 511 Second top surface, 512 Second connecting surface 6. Compacted powder 61 First surface, 62 Second surface, 63 Outer surface 63a front, 63b back 7 Groove 70 Sliding surface 71 bottom, 710 main bottom 72 inner surface, 720 main inner surface 80 First edge, 81 First chamfer 811 Secondary bottom surface, 812 First connecting surface 90 Second edge, 91 Second chamfer 911 Sub-bottom surface, 912 Second connection surface B1, B2 Bali α1, α2, β1, β2 angles y1, y2, a1, a2 width z1, x2 height b1, b2 depth

Claims

1. A mold for forming a compacted powder having a sliding surface with a U-shaped cross-section, An annular die having a space in which the compacted powder is formed, It comprises a lower punch fitted into the lower part of the aforementioned space, The aforementioned lower punch, First low punch, The first lower punch is further comprising two second lower punches positioned to sandwich it from the left and right, The aforementioned first lower punch is A first upper end surface that forms the bottom surface of the sliding surface, The first right side and the first left side form the inner surface of the sliding surface, It has a first front surface and a first back surface that slide against the die, Each of the aforementioned second lower punches is A second upper surface located below the first upper surface, A second left side that slides against the first right side, or a second right side that slides against the first left side, It has a second front surface and a second back surface that slide against the die, The first edge portion of the first upper end surface, along the left-right direction, has a first projection, The second edge portions along the vertical direction of the first right side and the first left side have a second projection, The first upper end surface has a main end surface, a first top surface of the first projection, and a first connecting surface that connects the main end surface and the first top surface. Each of the first right side and the first left side has a main side surface, a second top surface of the second projection, and a second connecting surface that connects the main side surface and the second top surface. Mold.

2. The mold according to claim 1, wherein the first connecting surface and the second connecting surface are inclined surfaces.

3. The mold according to claim 2, wherein the angle of the first connecting surface with respect to the main end surface and the angle of the second connecting surface with respect to the main side surface are 60° or less.

4. The mold according to claim 1, wherein the width of the first top surface and the width of the second top surface are 0.1 mm or more.

5. The mold according to claim 1, wherein the height of the first protrusion and the height of the second protrusion are 0.1 mm or more.

Images