JP6292944B2 - Mold strengthening method and forging mold - Google Patents

Description

  The present invention relates to a forging die suitable for forging a bevel gear.

  A bevel gear is used in a portion where the drive shaft and the driven shaft are orthogonal or intersecting. Bevel gears are manufactured by forging as well as by machining. Forging requires a mold, but mass production can reduce manufacturing costs. Forging dies having various structures are known (see, for example, Patent Document 1 (FIG. 1)).

  As shown in FIG. 1B of Patent Document 1, a tooth forming portion (12) in the circumferential direction (the numbers in parentheses indicate the symbols described in Patent Document 1. The same applies hereinafter) and a convex for forming the tooth bottom of the product. The parts (14) are arranged alternately. During forging, since a large pressure and friction are applied to the tooth forming portion (12) and the convex portion (14), the life of the mold is shortened. Since the mold is expensive, it is desired to extend its life.

  Various mold structures have been proposed that take measures to extend the life (see, for example, Patent Document 2 (FIG. 11)).

  As shown in FIG. 11 of Patent Document 2, a shaft press-fitting hole (24) is opened in the reinforcing case (2) (the numbers in parentheses indicate the symbols described in Patent Document 2. The same applies hereinafter). The shaft (25) is press-fitted into the press-fitting hole (24) to reduce the inner diameter of the reinforcing case (2). Inevitably, the outer diameter of the reinforcing case (2) increases.

When press-fitting to such an extent that the inner diameter and outer diameter of the reinforcing case (2) are changed, the axial force of the shaft (25) increases, and there is a concern that the shaft (25) bends or falls. Therefore, an advanced press-fitting technique is required, and the press-fitting man-hour is increased.
From the technique of Patent Document 2, a technique capable of easily strengthening the mold is required.

JP-A-6-198381 Japanese Patent No. 2624629

  An object of the present invention is to provide a strengthening technique capable of easily strengthening a forging die.

The invention according to claim 1 is a mold strengthening method for strengthening a forging mold in which molding concave portions and molding convex portions are alternately arranged in the circumferential direction,
The forging die is subjected to a drilling step of making a hole in the molding convex portion and a pin fitting step of fitting a pin having higher hardness than the molding convex portion into the hole.

  The invention according to claim 2 is characterized in that the hole is formed by laser processing in the hole making step.

  The invention according to claim 3 is characterized in that in the pin fitting step, at least one end of the pin protrudes from the forming convex portion, and the removing step of removing the protruding portion is performed after the pin fitting step. And

The invention according to claim 4 is a forging die in which molding concave portions and molding convex portions are alternately arranged in the circumferential direction,
The molding convex part is provided with a hole, and a pin having a higher hardness than the molding convex part is fitted into the hole.

  The invention according to claim 5 is characterized in that the outer diameter of the pin and the diameter of the hole are the same size.

  In the invention which concerns on Claim 6, a hole is a through-hole which penetrates a shaping | molding convex part, It is characterized by the above-mentioned.

  The invention according to claim 7 is characterized in that the pin is a pointed pin having a conical portion at one end.

  In the invention according to claim 8, the forging die has a cylindrical hole in the center, the molding concave portion and the molding convex portion are arranged so as to surround the cylindrical hole, and with respect to a central axis passing through the center of the cylindrical hole. The central axis of the through hole is inclined at an inclination angle selected from a range of 30 ° to 60 °, and the cone angle of the cone portion is set to be twice the inclination angle.

  The invention according to claim 9 is characterized in that the hole is a non-through hole having a bottom and the pin is a round tip pin.

  The invention according to claim 10 is characterized in that the forging die is a die for forging a bevel gear, and the pins are arranged on a pitch circle of the bevel gear.

In the invention according to claim 1, a hole is made in the molding convex portion, and a pin having high hardness is fitted into this hole.
Since a pin having higher hardness than the molding convex portion is added to the molding convex portion, the pin exhibits a reinforcing action and strengthens the molding convex portion.
Therefore, according to this invention, the reinforcement | strengthening technique which can reinforce the metal mold | die for forging easily is provided.

  According to a second aspect of the present invention, the hole is formed by laser processing in the hole making process. Even a very hard material can be drilled in a mold if it is a laser. Therefore, the degree of freedom in selecting the mold material is increased.

  In the invention which concerns on Claim 3, a removal process is implemented after a pin fitting process, and the protrusion part of a pin is removed by this removal process. To fit all the pins into the holes, advanced fitting techniques are required. In this regard, if it is allowed to leave a protruding portion in the pin fitting process, a pin hitting tool that chucks one end of the pin can be employed. This type of pin hitting tool is inexpensive and can reduce the cost associated with pin fitting.

In the invention which concerns on Claim 4, a hole is made in a shaping | molding convex part and a pin is fitted in this hole. Since a pin having higher hardness than the molding convex portion is added to the molding convex portion, the pin exhibits a reinforcing action and strengthens the molding convex portion.
Therefore, according to this invention, the reinforcement | strengthening technique which can reinforce the metal mold | die for forging easily is provided.

  In the invention which concerns on Claim 5, since the outer diameter of a pin and the diameter of a hole are the same magnitude | sizes, a pin can be easily fitted to a hole and a pin fitting man-hour can be reduced.

  In the invention which concerns on Claim 6, a hole is a through-hole which penetrates a shaping | molding convex part. In the case of drilling a hole by laser processing, the through-hole is easier to manage the laser irradiation time than the bottomed hole, and the drilling operation becomes easier.

  In the invention which concerns on Claim 7, a pin is a pointed pin which has a cone part in one end. Since the tip is sharp, the pin can be easily fitted into the hole, and the pin fitting work becomes easy.

  In the invention according to claim 8, the forging die has a cylindrical hole in the center and the central axis of the through hole is selected from a range of 30 ° to 60 ° with respect to the central axis passing through the center of the cylindrical hole. It is inclined at an inclination angle, and the cone angle of the cone portion is set to twice the inclination angle. A dummy shaft that fits into the cylindrical hole is prepared, and the dummy shaft is fitted into the cylindrical hole. One end of the through hole is closed with a dummy shaft. When a pointed pin is fitted from the other end of the through hole, the tip of the pin stops when it hits the dummy shaft. Since 1/2 of the inclination angle of the tip of the pin is located at the inclination angle formed by the central axis of the cylindrical hole and the central axis of the through hole, the conical surface of the conical portion is flush with the surface of the cylindrical hole. As a result, it is not necessary to remove the tip of the pin, and the number of removal steps can be reduced.

  In the invention which concerns on Claim 9, a hole is a non-through hole which has a bottom part, and a pin is a round-tip pin. It is not necessary to remove the tip of the pin, and the number of removal steps can be reduced.

  In the invention according to claim 10, the forging die is a die for forging the bevel gear, and the pin is arranged on the pitch circle of the bevel gear. The position of the pin is important, and in general, the position of the pin is determined by repeated strength calculations. On the other hand, in the present invention, the position of the pin is determined on the pitch circle without performing strength calculation. Since the pin position is uniquely determined and there is no need for troublesome calculations and examinations, the design cost can be reduced.

It is sectional drawing of the metal mold | die for forging which concerns on this invention. It is an effect | action figure of the metal mold | die for forging. FIG. 3 is a view taken in the direction of arrow 3 in FIG. 2. FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. It is a figure explaining a drilling process and a pin fitting process. It is a figure explaining the reinforcement effect of a pin. It is a figure explaining the pin fitting process different from a drilling process. It is a figure explaining another another drilling process and pin fitting process. It is a figure explaining the pin of another form. It is a figure explaining the correlation of a pin and a pitch circle.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, the forging die 10 includes a die 20 and a punch 30.
The die 20 is provided on the base 11, a cylindrical die 21 extending upward from the base 11, a floating die 22 that surrounds the cylindrical die 21 from the outside and moves up and down with respect to the cylindrical die 21, and the base 11. A hydraulic cylinder 23 that pushes up the floating die 22 with a predetermined force, a knockout pin 24 that penetrates the base 11 and penetrates the cylindrical die 21, and a knockout cylinder 25 that moves the knockout pin 24 in the axial direction. And.

The cylindrical die 21 has a concave portion 26 that accommodates the back surface of the bevel gear 40 as a workpiece.
The floating die 22 has an annular protrusion 27 on the top. The annular protrusion 27 has an inclined surface 28 that restricts the outer peripheral end 42 of the tooth 41 of the bevel gear 40.

  The punch 30 includes a center punch 31 that dents the front central portion 41 of the bevel gear 40, a ring punch 34 that surrounds the center punch 31 and has a molding convex portion 32 and a molding concave portion 33, and the ring punch 34 and the center punch 31. And a punch support plate 35 for supporting.

  The punch 30 moves relative to the die 20. Because of relative movement, the base 11 is stationary and the punch support plate 35 is moved (lifted / lowered), the base 11 is moved and the punch support plate 35 is stationary, the base 11 and Any system in which the punch support plate 35 moves together may be used.

A system in which the base 11 is stationary and the punch support plate 35 moves (lifts) will be described below as an example.
In FIG. 2, when the forging process is completed, the punch support plate 35 is raised. The center punch 31 and the ring punch 34 rise together. As this rises, the floating die 22 rises a certain distance. When the knockout pin 24 is lifted by the knockout cylinder 25, the knockout pin 24 pushes up the bevel gear 40 and floats from the die 20. Thus, the bevel gear 40 can be paid out from the forging die 10.

After FIG. 2, returning to FIG. 1, forging is performed, and a large load is applied to the forming convex portion 32 during this forging. An example of taking measures against this load will be described below.
As shown in FIG. 3, the ring punch 34 has a cylindrical hole 36 at the center, and includes molding convex portions 32 and molding concave portions 33 that are alternately arranged on a circumference surrounding the cylindrical hole 36. That is, the molding convex portions 32 and the molding concave portions 33 are alternately arranged in the circumferential direction. Further, a pin 50 is embedded in the molding convex portion 32.

As shown in FIG. 4, the pin 50 is a pointed pin having a conical portion 51 at the tip.
The forming convex part 32 is manufactured by alloy tool steel (for example, SKD61) prescribed | regulated by JISG4404. SKD61 has a quenching and tempering hardness of 53 or less in HRC (Rockwell C scale).
On the other hand, the pin 50 is made of cemented carbide. Although the hardness of the cemented carbide varies depending on the components, it is 84 or more in terms of HRA (Rockwell A scale) and 65 or more in terms of HRC.
Therefore, the pin 50 is made of a material having higher hardness than the molding convex portion 32.

  As shown to Fig.5 (a), the laser beam 53 is irradiated from the laser gun 52, and the through-hole 54 is opened (drilling process). The through hole 54 may be opened by electric discharge machining or machining by a drill in addition to laser machining. However, when the ring punch 34 is particularly hard, the frequency of exchanging the drill is increased, and therefore laser processing is more suitable.

As shown in FIG. 5B, a dummy shaft 56 having the same diameter as the cylindrical hole 36 is fitted into the cylindrical hole 36. Further, a pointed pin 50 having a cone angle of 2.times..theta. Twice the inclination angle .theta. Formed by the center axis 57 of the cylindrical hole 36 and the center axis 55 of the through hole 54 is prepared. The inclination angle θ is selected from the range of 30 ° to 60 °.
The outer diameter of the pointed pin 50 is the same as the diameter of the through hole 54.
The base portion 59 of the pointed pin 50 is chucked with the pin hitting tool 58 and fitted into the through hole 54 (pin fitting step).

The relationship between the outer diameter of the pointed pin 50 and the hole diameter of the through hole 54 for this pin fitting process will be described.
A light press-fitting method and an insertion method can be applied to the pin fitting process.
In the light press-fitting method, a pointed pin 50 having an outer diameter such that the press-fitting allowance is 1% or less is prepared, and the pointed pin 50 is press-fitted into the through hole 54 with a pin hitting tool 58. Since the press-fitting allowance is 1% or less, the press-fitting work is not so difficult.

  In the insertion method, a pointed pin 50 having the same diameter as the through hole 54 is inserted. As a recommended operation method, a list is prepared by measuring all the outer diameters of the pointed pins 50. Next, the hole diameter of the through hole 54 is measured, and a pointed pin 50 having an outer diameter approximate to the hole diameter is selected and inserted.

As shown in FIG. 5C, the tip of the pointed pin 50 hits the dummy shaft 56 and stops. The base portion 59 protrudes outward from the molding convex portion 32. The protruding portion 61 is cut out by machining (removal process).
As shown in FIG. 5D, since one surface of the conical portion 51 is flush with the peripheral surface of the cylindrical hole 36, it is not necessary to remove the tip of the sharp tip pin 50. The number of man-hours for the removal process can be reduced.

The effect of the pin 50 will be described with reference to FIG.
In the comparative example shown in FIG. 6A, no pin is fitted on the molding convex portion 101. Although it is difficult to predict the deformation of the molding convex portion 101, it is assumed here that the vertex 102 has fallen to the left by L1 during forging. Due to this collapse, stress concentrates on the bottom of the molding convex portion 101, that is, the molding concave portions 103, 103. If stress is repeatedly concentrated and becomes excessive, cracks occur in the concentrated part and the mold life is reached.

  In the embodiment shown in FIG. 6B, the pin 50 is made of a material having a higher hardness than the molding convex portion 32, and therefore contributes to an increase in the rigidity (bending rigidity, deflection rigidity) of the molding convex portion 32. As a result, even if the same load is applied, the vertex 62 falls to the left by L2. Since L2 is much smaller than L1, there is no fear that excessive stress is generated in the molding recesses 33 and 33, and the life of the mold can be extended.

A modification to FIG. 5 will be described with reference to FIG.
In FIG. 7A, the through hole 54 is opened in the same manner as in FIG.
In FIG. 7B, a pin 50 </ b> B that is sufficiently longer than the through hole 54 is prepared. Since the tip shape of the pin 50B is arbitrary, a commercially available pin can be used as it is, and the procurement cost of the pin 50B can be reduced.

The pin 50B is fitted into the through hole 54. The tip 63 and the base 59 of the pin 50 </ b> B protrude from the through hole 54. That is, the protruding portions 61 and 61 exist before and after the pin 50B. Therefore, the protruding portions 61 and 61 at the tip and the base are cut off by machining or the like. The form after excision is as shown in FIG.
As shown in FIG.7 (d), the front end cut surface 64 of the pin 50B becomes an ellipse. Since the tip cut surface 64 is elliptical with respect to the through-hole 54 that is a round hole of a perfect circle, there is no fear that the pin 50 idles (spins).

A further modification to FIG. 5 will be described with reference to FIG.
As shown in FIG. 8A, a non-through hole 66 having a bottom 65 is opened by laser processing.
As shown in FIG. 8B, the round tip pin 50 </ b> C having a round tip is fitted into the non-through hole 66. As the round tip pin 50C, a commercially available pin can be used as it is, and the procurement cost of the pin 50C can be reduced. Further, by using the round tip pin 50C, the corner of the pin 50C does not hit the bottom 65, so that stress can be prevented from concentrating.

Next, the protruding portion 61 on the base 59 side is cut off.
Since laser processing becomes difficult, the processing cost in the drilling process is higher than the through holes shown in FIGS. However, since it is not necessary to cut off the tip of the pin 50C, the processing cost can be reduced in the removal man-hours.

As shown in FIG. 9A, the pin 50 </ b> D having a length L <b> 4 shorter than the length L <b> 3 of the through hole 54 is fitted into the through hole 54.
As shown in FIG. 9B, all the pins 50 </ b> D are accommodated in the through holes 54. As a result, there is no need to remove the front and rear of the pin 50D, and the number of removal steps can be reduced to zero.

  By the way, the pins 50, 50B, 50C and 50D can be fitted at arbitrary positions of the forming convex portion 32, and the positions are generally determined by repeating the strength calculation. However, the simple figure which can reduce the cost required for determination can be provided in the following figure.

When a bevel gear is forged with the forging die of the present invention, a pitch circle exists in the bevel gear.
Therefore, as shown in FIG. 10, the pins 50, 50 </ b> B, 50 </ b> C, and 50 </ b> D are arranged on the pitch circle 67 of the bevel gear 32 in the forming convex portion 32. That is, the pins 50, 50 </ b> B, 50 </ b> C, 50 </ b> D are positioned on the center line 68 of the width (width in the horizontal direction in the drawing) W of the forming convex portion 32 and on the pitch circle 67. Since the positions of the pins 50, 50B, 50C, and 50D are uniquely determined and it is not necessary to perform troublesome calculations and examinations, the design cost can be reduced.

  The present invention is suitable for forging of the bevel gear 40, but can also be applied to forging of a cup member of a constant velocity ball joint. That is, in the cup member, the track grooves for storing the steel balls (balls) are arranged in an annular shape, and the track grooves are formed by the forming convex portions. Therefore, the workpiece is not limited to the bevel gear 40.

  The present invention is suitable for forging of bevel gears.

  DESCRIPTION OF SYMBOLS 10 ... Die for forging, 20 ... Die, 30 ... Punch, 32 ... Molding convex part, 36 ... Cylindrical hole, 40 ... Workpiece (bevel gear), 50 ... Pin (pointed tip pin), 50B ... Pin (long pin) , 50C ... pin (round tip pin), 50D ... pin (short pin), 51 ... conical part, 52 ... laser gun, 53 ... laser beam, 54 ... hole (through hole), 55 ... central axis of through hole, 57 ... Central axis of cylindrical hole, 61... Projecting portion, 66... Hole (non-through hole), 67... Pitch circle, .theta.

Claims (10)

A mold strengthening method for strengthening a forging mold in which molding concave portions and molding convex portions are alternately arranged in the circumferential direction,
A hole making step of making a hole in the molding convex part;
A die strengthening method comprising: applying a pin fitting step of fitting a pin having a hardness higher than that of the molding convex portion into the hole to the forging die.   2. The mold strengthening method according to claim 1, wherein the hole is formed by laser processing in the hole making step. In the pin fitting step, at least one end of the pin protrudes from the molding convex portion,
3. The mold strengthening method according to claim 1, wherein the removing step of removing the protruding portion is performed after the pin fitting step. A forging die in which molding concave portions and molding convex portions are alternately arranged in the circumferential direction,
A forging die, wherein a hole is provided in the molding convex portion, and a pin having a higher hardness than the molding convex portion is fitted into the hole.   The forging die according to claim 4, wherein the outer diameter of the pin and the diameter of the hole are the same.   The forging die according to claim 4 or 5, wherein the hole is a through-hole penetrating the forming convex portion.   The forging die according to any one of claims 4 to 6, wherein the pin is a pointed pin having a conical portion at one end.   The forging die has a cylindrical hole in the center, and the molding concave portion and the molding convex portion are arranged so as to surround the cylindrical hole, and the through-hole with respect to a central axis passing through the center of the cylindrical hole The central axis of each of the first and second cones is inclined at an inclination angle selected from a range of 30 ° to 60 °, and the cone angle of the cone portion is set to be twice the inclination angle. The forging die described.   The forging die according to claim 4 or 5, wherein the hole is a non-through hole having a bottom portion, and the pin is a round tip pin.   The said forging metal mold | die is a metal mold | die used for forging of a bevel gear, The said pin is arrange | positioned on the pitch circle | round | yen of the said bevel gear, The any one of Claims 4-9 characterized by the above-mentioned. Die for forging.

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