JP2020069510A - Stress dispersion structure for hot forging mold - Google Patents

Abstract

To provide a spacer that is less likely to cause stress concentration therein even when a mold-releasing agent flow passage is formed in the spacer in order to feed a mold-releasing agent for smoothly releasing a work from a lower mold to a tip of a shaft part, and is less likely to cause the spacer to be broken.SOLUTION: A stress dispersion structure for a hot forging mold 1 includes an annular groove 46 along a circumferential direction of an inner wall surface 43c of a guide hole 43 upward a mold-release agent discharge port 44a that is opened in the inner wall surface 43c of the guide hole 43 of a spacer 4 that is communicated to a lower end opening 33b of a through-hole 33 of a lower mold 3.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a stress distribution structure of a hot forging die.

  A fixed pulley used for a belt type continuously variable transmission or the like of a vehicle includes a flange-shaped sheave portion that is a contact surface of a metal belt, and a shaft portion having a groove in which a plurality of balls are inserted. The fixed pulley can be manufactured by, for example, hot forging.

  In hot forging, a work made of a metal material heated to a high temperature is set in a lower mold, and the upper mold is pressed to mold the work. The lower mold has a through hole penetrating from the upper surface to the bottom surface, and the upper surface is inclined upward from the through hole toward the outer edge. When the upper mold was pressed against the lower mold, the sheave part of the fixed pulley was molded by the work inserted in the gap between the bottom surface of the upper mold and the upper surface of the lower mold, and was inserted into the through hole. The shaft portion of the fixed pulley is molded by the work.

  The lower mold is supported by the spacer on the bottom surface side. The spacer has a guide hole communicating with the lower end opening of the through hole of the lower mold. The guide hole extends coaxially with the through hole, and a knockout pin is arranged in the guide hole and the through hole so as to be vertically movable in the axial direction. At the time of molding the work, the upper end of the knockout pin is inserted into the through hole to hold the lower end of the shaft portion molded in the through hole. After molding, by removing the upper mold and moving the knockout pin upward, the work is released from the lower mold (see, for example, Patent Document 1).

JP-A-3-94947

  In order to smoothly release the work from the lower mold, a release agent is supplied to the work, but if it is supplied from above the through hole, it may not reach the tip side of the shaft. Therefore, a cavity serving as a release agent flow path is formed in the spacer, and a release agent discharge port is provided on the inner wall surface of the guide hole. This allows the release agent to be supplied to the work from below via the guide hole.

  However, when the work is molded, a stress is generated in the spacer that supports the lower mold by the load that presses the upper mold against the lower mold. The stress tends to concentrate in the cavity of the spacer provided to form the release agent flow path, and the discharge port of the release agent flow path that opens on the inner wall surface of the guide hole becomes the starting point of the spacer crack. there is a possibility.

  In a die for hot forging, it is required to reduce cracking of spacers and improve durability.

The stress distribution structure of the hot forging die of the present invention,
A lower mold having a through hole into which a work is inserted by pressing the upper mold,
A spacer provided with a guide hole that supports the lower mold and communicates with a lower end opening of the through hole and extends coaxially with the through hole.
A knockout pin that is provided movably in the axial direction within the guide hole and the through hole, and that holds the lower end of the work loaded in the through hole,
A release agent channel provided in the spacer and having a discharge port opened on the inner wall surface of the guide hole,
An annular groove formed along the circumferential direction of the inner wall surface of the guide hole,
The annular groove is provided on the lower mold side of the discharge port of the release agent flow path.

  According to the present invention, since the annular groove is provided on the lower die side of the discharge port of the release agent flow channel, stress that tends to concentrate near the discharge port is dispersed, and thus the occurrence of spacer cracking is reduced. Therefore, the durability of the mold can be improved.

It is sectional drawing which shows the structure of the metal mold | die for hot forging, and is a figure which shows the state at the time of workpiece | work shaping | molding. It is a figure which shows the structure of the pulley provided with the fixed pulley manufactured with the metal mold | die for hot forging. It is sectional drawing which shows the structure of a spacer. It is a figure which shows the state at the time of raising of a knockout pin of a hot forging die. It is a figure which shows the state of the metal mold | die for hot forging after raising a knockout pin. (A) is a figure explaining the stress which acts on a spacer, (b) is a figure explaining the stress distribution structure of the spacer by an annular groove, (c) is a figure of the scale into the through-hole by an annular groove. It is a figure explaining invasion control.

FIG. 1 is a cross-sectional view showing the structure of a hot forging die.
FIG. 2 is a diagram showing a configuration of a pulley including a fixed pulley manufactured by a hot forging die.
As shown in FIG. 1, the hot forging die 1 according to the embodiment is for molding a work W to manufacture a fixed pulley.
As shown in FIG. 2, the fixed pulley 110 is a component that constitutes the pulley 100 of the belt type continuously variable transmission, and includes a shaft portion 111 and a sheave portion 112 that extends radially outward from the outer circumference of the shaft portion 111. The pulley 100 is configured by mounting a movable pulley 120 on a shaft portion 111 of a fixed pulley 110. The movable pulley 120 is provided so as to be movable in the axis Xi direction in a state in which relative rotation with the fixed pulley 110 in the circumferential direction around the axis Xi is restricted.

  The movable pulley 120 has a cylindrical base portion 121 that is externally inserted into the shaft portion 111 of the fixed pulley 110, and a sheave portion 122 that extends radially outward from the outer periphery of the base portion 121. 122 and the sheave portion 112 of the fixed pulley 110 face each other with a space in the direction of the axis Xi.

  A V groove around which the belt V is wound is formed between the facing surfaces of the sheave portion 112 of the fixed pulley 110 and the sheave portion 122 of the movable pulley 120. In the belt type continuously variable transmission, the desired gear ratio is realized by changing the groove width of the V groove to change the winding radius of the belt V on the pulley 100.

As shown in FIG. 1, the hot forging die 1 includes a cylindrical upper die 2 and a columnar die 3 that are arranged coaxially (axis X) to face each other.
At the center of the bottom surface 21 of the upper mold 2, a circular recess 21a is formed when viewed in the axial direction.

  A through hole 33 penetrating from the upper surface 31 to the bottom surface 32 is formed at the axial center of the lower mold 3, and the diameter of the through hole 33 is gradually reduced from the upper surface 31 to the bottom surface 32. An upper surface 31 of the lower mold 3 facing the upper mold 2 is provided with an inclined surface that is inclined upward from the upper surface side opening end 33a of the through hole 33 toward the outer edge. In a state where the upper mold 2 and the lower mold 3 are arranged to face each other, a gap is formed between the bottom surface 21 of the upper mold 2 and the upper surface 31 of the lower mold 3.

  By setting the heated work W in the lower mold 3 and pressing the upper mold 2 against the lower mold 3 by the press P, the work W is plastically deformed and the fixed pulley 110 is molded. The portion of the work W that is inserted into the gap between the bottom surface 21 of the upper mold 2 and the upper surface 31 of the lower mold 3 becomes the sheave portion 112 (see FIG. 2) of the fixed pulley 110, and serves as the sheave portion 112 of the upper mold 2. The recess 21a and the portion inserted into the through hole 33 of the lower mold 3 serve as the shaft portion 111 (see FIG. 2) of the fixed pulley 110.

  The lower die 3 is fixed to the upper surface 41 of the columnar spacer 4 with bolts or the like, and the lower die 3 and the spacer 4 are housed in a die case 5 fixed on a hard plate (not shown).

FIG. 3 is a cross-sectional view showing the structure of the spacer 4.
As shown in FIG. 3, the spacer 4 is formed with a guide hole 43 that extends from the upper surface 41 to the bottom surface 42 and extends coaxially (axis line X) with the through hole 33 of the lower mold 3. The upper surface side opening end 43a of the guide hole 43 is connected to the bottom surface side opening end 33b of the through hole 33, and the through hole 33 and the guide hole 43 communicate with each other. The diameter D1 of the guide hole 43 is larger than the diameter D2 of the bottom surface side opening end 33b of the through hole 33.

  The knockout pin 6 is inserted into the guide hole 43 of the spacer 4. The knockout pin 6 includes a head portion 61 and a body portion 62 having a diameter smaller than that of the head portion 61 and extending upward from the head portion 61 in the axis X direction. The diameter D3 of the head portion 61 is slightly smaller than the diameter D1 of the guide hole 43 and larger than the diameter D2 of the bottom surface side opening end 33b of the through hole 33, and can slide on the inner wall surface 43c of the guide hole 43. In addition, the size is set so that entry into the through hole 33 is restricted. The diameter D4 of the body portion 62 is slightly smaller than the diameter D2 of the bottom surface side opening end 33b of the through hole 33, and is set to a size capable of sliding inside the through hole 33.

  The knockout pin 6 can be raised along the axis X direction by a drive mechanism (not shown) pushing up the head 61 of the knockout pin 6. The drive mechanism of the knockout pin 6 can be, for example, a mechanical drive mechanism using a lever that swings by rotation of a cam or a hydraulic drive mechanism using a hydraulic cylinder.

  When the work W is molded, the knockout pin 6 is not driven, the head portion 61 is located at the bottom surface side opening end 43b of the guide hole 43, and the tip end 62a of the body portion 62 is located at the position P1 in the through hole 33 in the axis X direction. At, the lower end of the work W loaded in the through hole 33 is held.

FIG. 4 is a diagram showing a state when the knockout pin 6 is raised.
After the work W is molded, the upper mold 2 is removed, and then the head 61 of the knockout pin 6 is pushed up to raise the knockout pin 6, as shown in FIG. As the knockout pin 6 rises, the work W held at the tip 62a of the knockout pin 6 also rises and is released from the lower die 3.

  The spacer 4 is provided with a release agent flow passage 44 for supplying a release agent L for smoothing the release of the work W. As the release agent L, for example, graphite-containing oil or the like can be used. The release agent flow channel 44 is a cavity that penetrates the interior of the spacer 4 in a direction orthogonal to the axis X direction, and is connected to a release agent supply source (not shown) provided in the die case 5. The release agent flow path 44 has an opening at a position in the vicinity of the upper surface side opening end 43a of the inner wall surface 43c of the guide hole 43, and this opening serves as a discharge port 44a of the release agent L.

  At the time of releasing the work W, the knockout pin 6 is raised and the release agent L is supplied from the ejection port 44 a of the release agent flow path 44. Since the ejection port 44a is located in the vicinity of the upper opening side end 43a of the guide hole 43, the release agent L sprayed from the ejection port 44a forms a gap between the knockout pin 6 and the guide hole 43 and the through hole 33. Through it is applied to the work W in the through hole 33. Although illustration is omitted, in addition to the supply from the release agent flow path 44, the release agent L may be supplied to the work W from the upper surface 31 side of the lower mold 3.

FIG. 5 is a diagram showing a state after the knockout pin 6 is lifted.
As described above, since the head portion 61 of the knockout pin 6 has a diameter larger than the diameter D2 of the bottom surface side opening end 33b of the through hole 33, as shown in FIG. The part 61 stops at the position where it abuts the bottom surface side opening end 33b of the through hole 33. The tip 62a of the body portion 62 rises from the position P1 in the axial direction X in the through hole 33 to the position P2, and the work W held by the tip 62a of the body portion 62 is lifted up from the lower die 3. Become. The work W lifted up by a transfer device (not shown) is held and carried out from the hot forging die 1.

  The spacer 4 is provided with an air supply passage 45 that supplies air A for holding the tip 62a of the knockout pin 6 at the position P2. The air supply passage 45 is a cavity that penetrates the interior of the spacer 4 in a direction orthogonal to the axis X direction, and is connected to an air supply source (not shown) provided in the die case 5. The air supply passage 45 has an opening near the bottom surface side opening end 43b of the inner wall surface 43c of the guide hole 43, and this opening serves as an air A supply port 45a.

  When the air A is supplied from the supply port 45a of the air supply passage 45, the air A circulates in the guide hole 43 and is blown onto the head 61 of the knockout pin 6 and pressed upward. As a result, the tip 62a of the knockout pin 6 is held at the position P2.

  As shown in FIG. 3, an annular groove 46 is formed along the circumferential direction of the inner wall surface 43c near the upper surface side opening end 43a of the inner wall surface 43c of the guide hole 43 of the spacer 4. The annular groove 46 is formed so as to expand the inner wall surface 43c in the radial direction, and is U-shaped in cross section. The annular groove 46 is formed above the supply port 45a of the air supply path 45 and the discharge port 44a of the release agent flow path 44, that is, on the lower mold 3 side.

6A is a diagram for explaining the stress applied to the spacer 4, FIG. 6B is a diagram for explaining the stress distribution of the spacer 4 by the annular groove 46, and FIG. FIG. 4 is a diagram for explaining how the annular groove 46 suppresses the intrusion of scale into the through hole 33.
As a comparative example, FIG. 6A shows a state in which the annular groove 46 is not formed in the spacer 4.
At the time of molding the work W, a stress is applied to the spacers 4 supporting the lower mold 3 by the load pressing the upper mold 2 against the lower mold 3. As shown in FIG. 6A, the stress is likely to be concentrated particularly on the hollow portion of the spacer 4. The discharge port 44a of the release agent flow path 44 and the supply port 45a of the air supply path 45, which are open to the inner wall surface 43c of the guide hole 43, may serve as starting points for cracking due to stress concentration.

  In the embodiment, the annular groove 46 is formed on the inner wall surface 43c of the guide hole 43 above the discharge port 44a of the release agent flow channel 44 and the supply port 45a of the air supply channel 45. As shown in FIG. 6B, the portion where the annular groove 46 is formed is in a state where the inner wall surface 43c is radially expanded. Therefore, the portion where the stress concentrates moves radially outward of the annular groove 46, so that the stress applied to the discharge port 44a of the release agent flow channel 44 and the supply port 45a of the air supply channel 45, which tends to be the starting point of cracking. Can be dispersed.

  The position of the annular groove 46 in the X-axis direction, the axial width, and the radial depth can be appropriately set in consideration of the stress distribution applied to the spacer 4, the strength required for the spacer 4, and the like. ..

  Further, the annular groove 46 has a function of suppressing the scale from entering the through hole 33. In hot forging, heating the work W produces scale (oxide film). As shown in (c) of FIG. 6, when the work W is molded, the scale S is peeled from the work W, falls into the guide hole 43 communicating with the through hole 33, and is discharged to the inner wall surface 43 c of the guide hole 43. May adhere. When the knockout pin 6 rises and slides in the guide hole 43, the scale S adhering to the inner wall surface 43c of the guide hole 43 may be scraped off and the scraped scale S may be brought into the through hole 33. .. When the scale S enters the through hole 33, friction between the work W and the wall surface of the through hole 33 increases when the work W is released from the mold, which may lead to lack of thickness of the work W or rough skin.

  In the embodiment, the scale S scraped off by the knockout pin 6 moves into the through hole 33 by entering into the annular groove 46 provided in the position near the upper surface side opening end 43a of the inner wall surface 43c of the guide hole 43. The invasion of the scale S can be suppressed.

As described above, the stress distribution structure of the hot forging die 1 is
(1) a lower mold 3 having a through hole 33 into which the work W is loaded by pressing the upper mold 2,
A spacer 4 that supports the lower mold 3 and that includes a guide hole 43 that communicates with the bottom surface side opening end 33b (lower end opening) of the through hole 33 and extends coaxially with the through hole 33;
A knockout pin 6 that is provided movably in the guide hole 43 and the through hole 33 in the axial direction and that holds the lower end of the work W loaded in the through hole 33;
A release agent flow channel 44 provided in the spacer 4 and having a discharge port 44a opened to the inner wall surface 43c of the guide hole 43;
An annular groove 46 formed along the circumferential direction of the inner wall surface 43c of the guide hole 43,
The annular groove 46 is provided on the upper side (lower mold side) of the discharge port 44 a of the release agent flow channel 44.

  When the release agent flow path 44 is provided in the spacer 4 that supports the lower mold 3, a cavity is formed in the spacer 4. The spacer 4 supporting the lower mold 3 is deformed by the load that presses the upper mold 2 against the lower mold 3 during molding of the work W, but is opened in the cavity of the spacer 4, especially in the inner wall surface 43c of the guide hole 43. The stress is likely to be concentrated on the ejection port 44a, which may become a starting point of cracking of the spacer 4.

  In the embodiment, by forming the annular groove 46 on the inner wall surface 43c of the guide hole 43 above the ejection port 44a, the stress in the vicinity of the ejection port 44a can be dispersed, and the durability of the spacer 4 is improved. be able to.

  Further, the scale S scraped off the work W and falling into the through hole 33 and scraped by the ascending knockout pin 6 enters the annular groove 46, thereby suppressing the invasion of the scale S into the through hole 33. Therefore, the wall thickness of the work W and the rough surface of the work W due to the friction between the wall surface of the through hole 33 and the work W can be reduced.

(2) The stress distribution structure of the hot forging die 1 is provided in the spacer 4 and includes the air supply passage 45 having the supply port 45a opened to the inner wall surface 43c, and the annular groove 46 corresponds to the air supply passage 45. It is provided on the lower mold 3 side of the supply port 45a.
A cavity is formed in the spacer 4 by the air supply passage 45, but like the release agent passage 44, stress tends to concentrate on the supply port 45a opened to the inner wall surface 43c, and the starting point of cracking of the spacer 4 is generated. There is a possibility that By forming the annular groove 46, the stress in the vicinity of the supply port 45a of the air supply passage 45 can be dispersed as in the case of the release agent flow passage 44, so that the durability of the spacer 4 can be improved.

  In the above-described embodiment, the annular groove 46 having a U-shaped cross section (see FIG. 3) is illustrated. However, the annular groove 46 radially expands the inner wall surface 43c in the radial direction so that the stress concentration portion is in the radial direction. It suffices if it can be moved outward, and for example, the annular groove 46 may have a C-shaped cross section.

1 Hot Forging Die 2 Upper Die 21 Bottom 21a Recess 3 Lower Die 31 Top 32 Bottom 33 33 Through Hole 33a Top Side Opening End 33b Bottom Side Opening End 4 Spacer 41 Top 42 Bottom 43 Guide Hole 43a Top Opening End 43b Bottom face side opening end 43c Inner wall surface 44 Release agent channel 44a Discharge port 45 Air supply channel 45a Supply port 46 Annular groove 5 Die case 6 Knockout pin 61 Head 62 Body 62a Tip 100 Pulley 110 Fixed pulley 111 Shaft 112 Sheave part 120 Movable pulley 121 Base part 122 Sheave part P Press S Scale V Belt W Work

Claims (2)

A lower mold having a through hole into which a work is inserted by pressing the upper mold,
A spacer provided with a guide hole that supports the lower mold and communicates with a lower end opening of the through hole and extends coaxially with the through hole.
A knockout pin that is provided movably in the guide hole and the through hole in the axial direction and that holds the lower end of the work loaded in the through hole,
A release agent channel provided in the spacer and having a discharge port opened on the inner wall surface of the guide hole,
An annular groove formed along the circumferential direction of the inner wall surface of the guide hole,
The stress distribution structure of the hot forging die, wherein the annular groove is provided on the lower die side of the discharge port of the release agent flow path. An air supply path provided in the spacer and having a supply port opening to the inner wall surface,
The stress distribution structure of the hot forging die according to claim 1, wherein the annular groove is provided on the lower die side of a supply port of the air supply path.

Images