Forging machine

Abstract

To provide a forging machine that is able to highly retain the quality to form a workpiece, by stabilizing the movement of a split die that performs a forging process on an outer peripheral surface of the workpiece.SOLUTION: A forging machine 1 includes: a plurality of split dies 4 that has a machining die (a knurling die 44) opposite to an outer peripheral surface of a workpiece W having a substantially axially symmetrical shape and is divided in a circumferential direction; a case 3 by which the plurality of split dies 4 is held so as to be relatively movable in an axial direction by surface contact and radially movable, throughout a time zone in which the machining die performs a forging process on outer peripheral surface of the workpiece W; a driving unit (a die driving unit 71) that relatively moves the plurality of split dies 4 and the case 3 in the axial direction, thereby moving the plurality of split dies 4 radially inward to perform the forging process on the outer peripheral surface of the workpiece W by means of the machining die; and a guide member (a guide pin 5) that restricts deflection in the circumferential direction while guiding the movement of the plurality of split dies 4.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a forging machine that performs forging by pressing a processing die against the outer peripheral surface of a workpiece having a substantially axisymmetric shape.

Background Art

[0002] In a general forging machine, a die holds a workpiece, and a punch moves in the axial direction and presses against the end face of the workpiece to perform forging. Therefore, it has been difficult to perform forging by pressing a processing die against the outer peripheral surface of the workpiece. When performing forging such as knurling or grooving on the outer peripheral surface of a workpiece, in the prior art, after forging the basic shape of the workpiece using a forging machine, the workpiece is transported to another processing machine such as a rolling machine to perform forming processing on the outer peripheral surface. However, this prior art requires capital investment in equipment such as a transport device for transporting the workpiece from the forging machine to another processing machine, or labor of an operator for performing the transport operation. Furthermore, production management and quality control become complicated, and the management level tends to decrease. In addition, in a rolling machine, there is a problem that the production efficiency does not increase because the production speed is slow. Technical examples corresponding to such problems are disclosed in Patent Documents Ⅰ and Ⅱ.

[0003] The former (forging machine) disclosed in Patent Document Ⅰ includes four forging stations, and a screw rolling device is attached to the space where the die block supporting the third die and the fourth die is removed, so that it can be selected as either a four-stage former or a former with a screw rolling device. According to this, it is said that it is possible to continuously perform forging to screw rolling as a former with a screw rolling device to manufacture bolts and the like, and to manufacture forged products that do not require screw rolling as a four-stage former.

[0004] Furthermore, the method for manufacturing a grooved nut disclosed in Patent Document 2 involves reducing the diameter of one end of a cylindrical material by press forming a small-diameter section, and then forming a circumferential groove in the small-diameter section using a split die. According to the description of the embodiment, the outer surfaces of the four split dies are shaped to form a conical surface where the diameter decreases towards the back when assembled, and the inner surface of the front part of the die case is also a similar conical surface. The four split dies move forward and approach each other, and the whole assembly comes together, making it possible to press form the circumferential groove. With this, a circumferential groove can be press formed on the outer surface of a cylindrical material. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Utility Model Registration No. 3145390 Gazette [Patent Document 2] Japanese Patent Publication No. 2002-139013 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] By the way, in the technical example of Patent Document 1, the replacement of the die block and screw rolling device is time-consuming due to the large scope of replacement, and the adjustment work after replacement is also complicated. In contrast, the split die (divided mold) disclosed in Patent Document 2 can be incorporated into one forging process of a multi-stage forging machine, and is preferable because the scope of replacement is limited. However, since the conical surfaces of the four split dies are in contact with the conical surface of the die case, there is a risk that the forging process using the split die will become unstable.

[0007] In detail, the four segmented dies can make surface contact with the die case when they move radially inward and converge (surface contact of both conical surfaces). However, before and during the movement of the four segmented dies radially inward, the radii of curvature of the opposing conical surfaces are slightly different. That is, the diameter of the conical surface of the die case is larger on the front side and smaller on the back side, and the segmented dies have conical surfaces that match the smaller diameter on the back side. Therefore, the segmented dies only make line contact with the die case except on the back side, and cannot make surface contact. Consequently, the movement of the four segmented dies becomes unstable, and one of the segmented dies may tilt relative to the axial direction, or there may be variations in the spacing between the dies. This raises concerns that the cold forging process using the segmented dies may become unstable, leading to a decrease in the forming quality of the workpiece.

[0008] This invention has been made in view of the problems of the background technology described above, and aims to provide a forging machine that can stabilize the movement of the split die used for forging the outer surface of a workpiece, thereby maintaining high molding quality of the workpiece. [Means for solving the problem]

[0009] The forging machine of the present invention has a processing die facing the outer circumferential surface of a workpiece with a substantially axially symmetrical shape, and a plurality of split dies divided in the circumferential direction , multiple The device comprises: a case that holds a number of the aforementioned split dies so that they can move relative to each other in the axial direction and so that they can move in the radial direction; a drive unit that moves the plurality of the split dies and the case relative to each other in the axial direction, thereby moving the plurality of split dies radially inward, and causing the processing die to perform press forging on the outer surface of the workpiece; and a guide member that guides the movement of the plurality of split dies while restricting circumferential runout. The guide member consists of a plurality of guide pins that are spaced apart from each other in the axial direction and extend parallel to the radial direction in which the splitting die moves.

[0010] Furthermore, the forging machine may also include a processing die facing the outer circumferential surface of a workpiece having a substantially axially symmetric shape, a plurality of split dies divided in the circumferential direction, a case that holds the plurality of split dies so that they can move relative to each other in the axial direction and so that they can move radially, a drive unit that moves the plurality of split dies and the case relative to each other in the axial direction, thereby moving the plurality of split dies radially inward and causing the processing die to perform forging on the outer circumferential surface of the workpiece, and a guide member that guides the movement of the plurality of split dies while restricting circumferential runout.

[0011] Furthermore, the forging machine may also include a plurality of split dies that are divided in the circumferential direction and have a processing die facing the outer circumferential surface of a workpiece with a substantially axially symmetric shape; a case that holds the plurality of split dies so that they can move relative to each other in the axial direction and move radially through surface contact throughout the time that the processing die performs forging on the outer circumferential surface of the workpiece; and a drive unit that moves the plurality of split dies radially inward by moving the plurality of split dies and the case relative to each other in the axial direction, thereby causing the processing die to perform forging on the outer circumferential surface of the workpiece. [Effects of the Invention]

[0012] In the forging machine of the present invention, the guide member guides the movement of the multiple split dies while restricting circumferential runout, thereby stabilizing the movement of the split dies. Furthermore, the case can be configured to hold the multiple split dies in a manner that allows for relative movement in the axial direction and radial movement through surface contact throughout the time that the processing die is performing forging on the outer surface of the workpiece. This ensures that surface contact between the case and the multiple split dies is maintained throughout the forging process, thereby stabilizing the movement of the split dies. Consequently, the movement of the split dies is stabilized by the action of at least one of the guide member and the case, allowing for the maintenance of high-quality workpiece molding. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic plan view showing the overall configuration of the forging machine according to the embodiment. [Figure 2]This is a side cross-sectional view showing the configuration of an outer surface forging process with multiple split dies and cases, and the initial state before workpiece insertion is shown. [Figure 3] This is a cross-sectional view taken along arrow AA in Figure 2, showing the arrangement of the split die and guide pins. For clarity, the hatching indicating the cross-section of the split die has been omitted. [Figure 4] This is a partial plan view showing the upper splitting die and guide pins. [Figure 5] This is a side cross-sectional view illustrating the operation of the outer surface forging process, starting from the initial state shown in Figure 2, and illustrating the workpiece insertion state. [Figure 6] This is a side cross-sectional view illustrating the operation of the outer surface forging process, following Figure 5, and shows the completed molding state where the split die is in the assembly position. [Figure 7] Figure 6 is a cross-sectional view taken along arrow AA, showing the arrangement of the split die, guide pins, and workpiece at the end of the cold forging process. For clarity, the hatching indicating the cross-section of the split die has been omitted. [Figure 8] This is a side cross-sectional view illustrating the operation of the outer surface forging process, following Figure 6, and shows the state in which the punch is retracting and the split die is in the process of returning from the assembly position to the separated position. [Figure 9] This is a side cross-sectional view illustrating the operation of the outer surface forging process, following Figure 8, and shows the state in which the split die has returned to its separated position. [Figure 10] This is a side cross-sectional view illustrating the operation of the outer surface forging process, which follows from Figure 9, showing the workpiece in a state where it is protruding backward. [Modes for carrying out the invention]

[0014] 1. Overall configuration of the forging machine 1 of the embodiment First, the overall configuration of the forging machine 1 of the embodiment will be described with reference to FIG. 1. The forging machine 1 includes a frame 21, a ram 24, six sets of dies 23 and punches 26, a transfer device 27, a wire supply device 8, and a main drive unit 9, etc. The forging machine 1 is a horizontal multi-stage forging machine in which the punch 26 reciprocates in the horizontal direction. The forging machine 1 has six sets of opposing dies 23 and punches 26 that form the first to sixth processes. The left-right direction in the drawing of FIG. 1 is the front-rear direction of the forging machine 1, and the up-down direction in the drawing is the width direction of the forging machine 1. The front-rear direction of the forging machine 1 coincides with the axial direction common to the die 23, the punch 26, and the workpiece. In FIG. No. 1, the first to sixth processes are arranged from the upper side to the lower side of the drawing in the width direction. Note that the number of processes of the forging machine 1 is not limited to six processes, and generally ranges from 1 to 8 processes.

[0015] The frame 21 is a housing for arranging each part. Six die holders 22 are provided side by side in the width direction at a position closer to the front of the frame 21. Each of the six dies 23 is detachably attached to the rear part of each die holder 22. A predetermined processing die is formed on the rear side of each die 23 facing the left direction in the drawing. The die 23 holds the workpiece inside the processing die.

[0016] The ram 24 is generally rectangular in plan view and is arranged approximately at the center of the frame 21. The ram 24 reciprocates in the front-rear direction. Six punch holders 25 are provided side by side in the width direction at a position closer to the front of the ram 24. Each of the six punches 26 is detachably attached to the front part of each punch holder 25. A predetermined processing die is formed on the front side of each punch 26 facing the right direction in the drawing. Each punch 26 reciprocates together with the ram 24. In each process, the punch 26 reciprocates in the front-rear direction (axial direction) while facing the die 23, and together with the die | 23, it performs forging processing on the workpiece.

[0017] The wire supply device 8 is positioned from the front of the frame 21, adjacent to the first process, towards the front. The wire supply device 8 consists of a cutting blade 81, a fixed gripping section 82, and a movable gripping section 83. The movable gripping section 83 grips the long wire supplied from the front and moves backward, feeding the wire to the cutting blade 81. While the movable gripping section 83 releases the wire and returns to the front, the fixed gripping section 82 grips the wire. The cutting blade 81 consists of an annular fixed blade and a movable blade through which the wire passes, cutting the wire to create a workpiece. The created workpiece is pushed towards the transfer device 27 by a pusher member (not shown). Typically, the wire has a circular cross-section, and the workpiece has a cylindrical initial shape. Examples of materials for the wire and workpiece include iron, aluminum, and various alloys. Alternatively, instead of the fixed gripping section 82 and the movable gripping section 83, a wire feeding mechanism having one or more rollers that rotate while gripping the wire may be used.

[0018] The transfer device 27 is positioned above the die holder 22 and behind the die 23. The transfer device 27 has seven pairs of fingers for gripping the workpiece. The first pair of fingers at the uppermost position grips the workpiece extruded from the wire feed device 8 and transports it to the first process. The second to sixth pairs of fingers grip the workpiece in the upstream process and transport it to the downstream process. The seventh pair of fingers at the lowermost position grips the workpiece in the sixth process and transports it to the unloading section (not shown).

[0019] A main drive unit 9 is provided to drive the reciprocating motion of the punch 26. The main drive unit 9 also drives the wire supply device 8 and the transfer device 27. The main drive unit 9 consists of a main drive source 91 and various transmission mechanisms and cam mechanisms. The main drive source 91 can be, for example, an induction motor or a synchronous motor that operates on a three-phase AC power supply. The driving force of the main drive source 91 is input to the crankshaft 96 via a flywheel 92, a clutch mechanism 93, a disc brake 94, and a reduction mechanism 95.

[0020] A connecting rod 29 is positioned between the crankshaft 96 and the ram 24. One end of the connecting rod 29 is connected to the crankshaft 96, and the other end is connected to the ram 24. When the crankshaft 96 rotates, driven by the main drive source 91, one end of the connecting rod 29 rotates along a circular orbit, and the other end of the connecting rod 29 reciprocates in the front-rear direction. As a result, the ram 24 reciprocates in the front-rear direction, and the six punches 26 on the ram 24 also reciprocate in the front-rear direction (axial direction).

[0021] Six kick-out cams 98 are provided above the connecting rod 29. The kick-out cams 98 are arranged at equal intervals in the width direction and correspond to the positions of the first to sixth strokes, respectively. The kick-out cams 98 drive the punch-side kick-out pins provided on each punch 26 in the forward and backward directions. In addition, the driving force is branched and transmitted from the crankshaft 96 to the side shaft 99 via a branch gear pair 97.

[0022] The side shaft 99 transmits the driving force in an upward direction. The driving force branched upward rotates the transfer cam 9A. The transfer cam 9A drives the reciprocating movement of the transfer device 27 between processes. In addition, seven open-close cams 9C are connected to the side shaft 99 via the transfer drive 9B so as to be rotated. The open-close cams 9C are arranged at equal intervals in the width direction. The open-close cams 9C drive each pair of finger in the transfer device 27 to open and close.

[0023] Furthermore, a cutter cam 9D is provided on the side shaft 99, and a pusher cam 9E, a feed cam 9F, and five kickout cams 9H are connected to it. The cutter cam 9D drives the cutting motion of the cutting blade 81. The pusher cam 9E drives the pushing motion of the pusher member. The feed cam 9F drives the reciprocating motion of the movable gripping part 83. The kickout cams 9H are arranged at equal intervals in the width direction and correspond to the positions of the first to sixth steps, respectively. The kickout cams 9H drive the motion of ejecting the workpiece from the die 23.

[0024] 2. Outer surface compaction process In this embodiment, one or more of the first to sixth steps are modified into the outer surface forging step shown in Figures 2 to 4. Note that Figure 2 corresponds to the cross-sectional view taken along arrow BB in Figure 3. The outer surface forging step is a process in which a forging process is performed on the outer surface of a workpiece with a substantially axially symmetric shape. Hereafter, the case of knurling on the outer surface of a cylindrical workpiece W will be used as an example. The outer surface forging step consists of a case 3, four split dies 4, multiple guide pins 5, kick-out pins 6, and a punch 26, etc.

[0025] As shown in Figure 2, the die holder 22 is formed in an annular shape with a central hole 221 that penetrates in the front-to-back direction along the axis AL. The die holder 22 also has a plurality of peripheral chambers 222 formed outside the central hole 221 and spaced apart in the circumferential direction. Each of the peripheral chambers 222 is open to the rear (left in Figure 2). The number of peripheral chambers 222 is generally three to six. Note that the peripheral chambers 222 may also be a single ring-shaped chamber that encircles the area outside the central hole 221.

[0026] Case 3 is attached to the rear of the die holder 22 (left side in Figure 2). Case 3 is about the same size as the die holder 22 and is formed in an annular shape around the axis AL. A mold storage space in the shape of a horizontally oriented pyramidal pyramid is provided in the center of the rear of Case 3. The four sides of the square upper and lower bases of the pyramidal pyramid are arranged horizontally or vertically. The front upper base is smaller than the rear lower base. Therefore, the mold storage space tapers towards the front (right side in Figure 2). The inside of the rear of Case 3 consists of four pressure-receiving surfaces in the shape of an isosceles trapezoid, corresponding to the sides of the pyramidal pyramid. Each of the pressure-receiving surfaces corresponds to a pressure-receiving inclined plane 31 that is inclined with respect to the axial direction.

[0027] The four split dies 4 are inserted into the aforementioned die storage space from the rear and positioned therein. Then, die stoppers 33 are attached to the rear of the case 3 using bolts 32. As shown in Figure 3, each of the four split dies 4 occupies a range of approximately 90° from the center position (axis AL) and has a shape divided into four equal parts in the circumferential direction. Each of the split dies 4 has a curved inner circumferential surface, two end faces 41 extending radially outward from both edges of the inner circumferential surface, two guide surfaces 42 connected to the two end faces 41, and an outer circumferential die-side inclined plane 43 connected to the outer edges of the two guide surfaces 42. The two end faces 41 widen radially outward at a 90° angle, and the two guide surfaces 42 are spaced apart and parallel to each other.

[0028] The split die 4 has a knurling die 44 on its inner circumferential surface. The knurling die 44 is a processing die mainly used for press forming fine bumps and notches for anti-slip purposes. The opposing end faces 41 of two adjacent split dies 4 are arranged to be parallel to each other, or are capable of surface contact with each other. A storage hole 45 is formed in each of the end faces 41. A biasing spring 46 is placed inside the two opposing storage holes 45. The biasing spring 46 is used, for example, a compressed coil spring, to bias the end faces 41 (the split dies 4) away from each other.

[0029] The die-side inclined plane 43 on the outer circumference is inclined with respect to the axial direction at the same inclination angle as the pressure-receiving side inclined plane 31 of case 3. Therefore, the split die 4 is formed with a smaller radial thickness dimension towards the front. On the other hand, the width dimension LG between the two guide surfaces 42 of the split die 4 remains the same whether it is on the front or rear side. The die-side inclined plane 43 has a rectangular shape in plan view (see Figure 4). Since the inclination angles of both inclined planes are the same, the die-side inclined planes 43 of the four split dies 4 each make surface contact with the pressure-receiving side inclined plane 31. When cold forging is performed by the knurling die 44, the pressure-receiving side inclined plane 31 receives radially outward surface pressure acting from the die-side inclined plane 43.

[0030] The split die 4 is held in the case 3 so as to be able to move relative to the axial direction (front-back direction) by surface contact between the mold-side inclined plane 43 and the pressure-receiving side inclined plane 31 (see arrow MA in Figure 4). Furthermore, the split die 4 is held in the case 3 so as to be able to move radially. Specifically, as shown by arrow MV in Figure 3, the upper and lower split die 4 are movable in the vertical direction corresponding to the radial direction. Also, as shown by arrow MH, the right and left split die 4 are movable in the horizontal direction corresponding to the radial direction. Here, the vertical direction corresponds to a second direction perpendicular to the axial direction, and the horizontal direction corresponds to a third direction perpendicular to the axial direction and the second direction.

[0031] A biasing member 47 and a plurality of biasing springs 48 are provided to bias the four split dies 4 toward the rear. As shown in Figure 2, the biasing member 47 is positioned on the front side of the split dies 4 on the inner circumference side of the case 3. The biasing member 47 consists of a front annular large-diameter portion 471 and a rear annular small-diameter portion 472. The front surface of the large-diameter portion 471 abuts against or separates from the rear surface of the die holder 22. The rear surface of the small-diameter portion 472 abuts against the front surface of the split dies 4.

[0032] Each of the multiple biasing springs 48 is positioned inside the surrounding chamber 222 of the die holder 22. The biasing springs 48 are, for example, compressed coil springs that bias the large-diameter portion 471 of the biasing material 47 backward. In the initial state shown in Figure 2, the biasing material 47 is biased backward so as to move away from the die holder 22. As a result, the biasing material 47 moves the four split dies 4 backward and brings them into contact with the die stopper 33. At this time, the four split dies 4 move radially outward due to the action of the biasing springs 46 and are positioned at spaced-out positions radially outward, separated from each other.

[0033] Multiple guide pins 5 are provided as guide members to guide the movement of the four split dies 4 while restricting circumferential movement. Parts of the guide pins 5 are fitted into the case 3 and fixed. Note that the guide pins 5 may be fixed by other fixing methods. The guide pins 5 are arranged on both sides of the split die 4 in the circumferential direction, separated by the aforementioned width dimension LG. Furthermore, two guide pins 5 are arranged spaced apart from each other in the axial direction. In other words, as shown in Figure 4, four guide pins 5 are provided for one split die 4. By using four guide pins 5, the rattle with the split die 4 is reduced, thereby stabilizing the movement of the split die 4.

[0034] Each of the guide pins 5 extends parallel to the radial direction in which the splitting die 4 moves. Specifically, as shown in Figure 3, guide pins 5 extending vertically are provided corresponding to the upper and lower splitting die 4 that move vertically in the direction of arrow MV. Guide pins 5 extending horizontally are also provided corresponding to the right and left splitting die 4 that move horizontally in the direction of arrow MH. By using four splitting die 4s and arranging the guide pins 5 vertically or horizontally rather than in an inclined direction, the structural design and manufacturing of the forging machine 1 are simplified, and it is also advantageous in terms of improving structural accuracy.

[0035] Furthermore, the guide pin 5 has a cylindrical or cylindrical shape (see Figure 4) and makes line contact with the guide surface 42 of the split die 4. Therefore, the guide pin 5 can guide the relative axial movement and radial movement of the split die 4 while restricting circumferential runout. In addition, the line contact reduces friction between the guide pin 5 and the moving split die 4. This makes the movement of the split die 4 smoother and suppresses unnecessary heat generation and temperature rise. To achieve line contact, the guide pin 5 may have other shapes, such as an elliptical cylinder. Furthermore, the guide pin 5 may have a smooth, uneven shape, such as a gourd shape, and make point contact with the split die 4 at multiple locations.

[0036] Furthermore, it is possible to modify the design by providing a guide groove extending axially at the center of the width direction (circumferential direction) of the inclined plane 43 on the mold side, and arranging the guide pins 5 fixed to the case 3 within the guide groove. This modification allows for a reduction in the number of guide pins 5. On the other hand, since the guide groove is formed in a location where the internal pressure of the split die 4 is high during the cold forging process, there is a risk of reduced mechanical strength. Alternatively, as a guide member to replace the guide pins 5, for example, a guide rail extending axially parallel to the guide surface 42 of the split die 4 may be used. By using a cylindrical or cylindrical guide rail, line contact can be achieved in the same way as with the guide pins 5.

[0037] The kickout pin 6 is positioned on axis AL and moves axially. As shown in Figure 2, the kickout pin 6 extends axially through the central hole 221 of the die holder 22, the center of the biasing member 47, and the central positions of the four split dies 4. The kickout pin 6 may be composed of multiple interconnected members.

[0038] A biasing spring 61 is provided around the kick-out pin 6 inside the central hole 221 of the die holder 22. The biasing spring 61 is used, for example, a compressed coil spring, which biases the kick-out pin 6 backward. The biased kick-out pin 6 contacts the workpiece W being forged and stabilizes its position. The aforementioned kick-out cam 9H drives the kick-out pin 6 from the front standby position to the rear protruding position. Figure 2 shows the protruding position of the kick-out pin 6. The kick-out pin 6 contacts and pushes the workpiece W after processing, protruding backward from the central position of the split die 4.

[0039] The punch 26 has a die drive unit 71 that moves the four split dies 4 and the case 3 relative to each other in the axial direction, and a workpiece insertion unit 72. In the initial state shown in Figure 2, the punch 26 is at its rear dead center. The die drive unit 71 is formed in a ring shape with a flat front surface. By moving forward, the die drive unit 71 pushes the rear surfaces of the four split dies 4 with its front surface, causing them to move forward in the axial direction.

[0040] The workpiece insertion section 72 has a stepped cylindrical shape consisting of a small diameter section 73 at the front and a large diameter section 74 at the rear (see Figure 8). The large diameter section 74 is fixed to the center of the mold drive section 71 and protrudes forward of the mold drive section 71. The small diameter section 73 fits inside the rear of the cylindrical workpiece W and holds the workpiece W. By moving forward, the workpiece insertion section 72 advances the workpiece W in the axial direction and inserts it into the central position of the four split molds 4.

[0041] 3. Operation of the forging machine 1 (outer surface forging process) Next, the operation of the forging machine 1, mainly the operation of the outer surface forging process, will be explained with reference to Figures 2 and 5 to 10. In the initial state shown in Figure 2, the workpiece W is fed in from the upstream process side by the transfer device 27. When the punch 26 starts moving forward from its rear dead center, the workpiece insertion section 72 holds the rear interior of the workpiece W with its small diameter section 73. The workpiece insertion section 72 then moves the workpiece W forward in the axial direction. The workpiece W moves forward towards the center position of the four split dies 4, pushing the kick-out pin 6. Therefore, the kick-out pin 6 returns from the ejected position to the standby position against the biasing spring 61. At this point, the die drive unit 71 and the split dies 4 are separated from each other.

[0042] As shown in Figure 5, when the workpiece W reaches the center position of the four split dies 4, the die drive unit 71 contacts the rear surface of the split dies 4. Subsequently, the punch 26 advances the workpiece W and the four split dies 4 simultaneously at a constant speed. This causes the split dies 4 to advance until the biasing material 47 contacts the die holder 22. At this time, the four split dies 4 move radially inward while advancing against the biasing spring 48, as the die-side inclined plane 43 advances along the pressure-receiving inclined plane 31. As a result, the four split dies 4 move radially inward from their separated positions against the biasing spring 46 and approach each other. Here, surface contact between the die-side inclined plane 43 and the pressure-receiving inclined plane 31 is maintained throughout the time that the split dies 4 advance. Furthermore, the movement of the split dies 4 is guided by the guide pin 5, and circumferential runout is restricted. Thus, the movement of the split dies 4 is stabilized.

[0043] As the four split dies 4 move radially inward, the knurling die 44 is pressed against the outer surface of the workpiece W to perform the cold forging process. At this time, the kick-out pin 6, through the action of the biasing spring 61, biases the workpiece W backward, stabilizing its position. Furthermore, since the workpiece W and the split dies 4 are moving at a constant velocity in the axial direction, the knurling die 44 moves radially inward relative to the workpiece W. In other words, the knurling die 44 is pressed perpendicularly toward the surface to be machined. Therefore, good machining accuracy is ensured. If the split dies 4 were to move axially while the workpiece W was stationary, the knurling die 44 would be pressed toward the surface to be machined from an oblique direction, which would tend to reduce machining accuracy.

[0044] As shown in Figures 6 and 7, when the punch 26 moves forward to its front dead center, the four split dies 4 are positioned in a radially inward junction where their end faces 41 are in contact with or closest to each other, and the forging process is completed. After this, the punch 26 begins to retract from its front dead center, leaving the workpiece W behind. As the punch 26 retracts, the biasing spring 48 causes the biasing material 47 to move the split dies 4 backward. The four split dies 4 move axially backward while the biasing spring 46 moves them from the junction to radially outward separated positions (see Figure 8).

[0045] As shown in Figure 9, after the four split dies 4 have returned to their separated positions, or while they are returning, the kick-out pin 6 is driven by the kick-out cam 9H to begin the ejection operation. That is, the kick-out pin 6 moves from the standby position to the ejection position. As a result, the knurled workpiece W is ejected behind the split dies 4, as shown in Figure 10. The biasing spring 61 also provides auxiliary biasing to the kick-out pin 6 backward. Therefore, the kick-out pin 6 may start its operation due to the biasing spring 61 and ultimately be driven by the kick-out cam 9H. After this, the ejected workpiece W is transported to the downstream process side by the transfer device 27.

[0046] In the forging machine 1 of this embodiment, the guide pins 5 guide the movement of the four split dies 4 while restricting circumferential runout, thereby stabilizing the movement of the split dies 4. Furthermore, the case 3 can be configured to hold the four split dies 4 so that they can move relative to each other in the axial direction and move radially through surface contact throughout the time that the knurling die 44 is performing forging on the outer surface of the workpiece W. Specifically, a configuration is adopted that maintains surface contact between the pressure-receiving inclined plane 31 and the die-side inclined plane 43. With this, surface contact between the case 3 and the four split dies 4 is maintained throughout the time that forging is performed, and the movement of the split dies 4 is stabilized. Therefore, the movement of the split dies 4 is stabilized by the action of at least one of the guide pins 5 and the case 3, and the molding quality of the workpiece W can be maintained at a high level. In addition, a faster production speed can be achieved compared to a rolling machine, thereby increasing production efficiency.

[0047] 4. Modifications and Applications of Embodiments Furthermore, the present invention can be applied to vertical forging machines, presses, and the like by reinterpreting the direction of movement of the punch 26 as vertical. In addition, the number of split dies 4 may be other than four. Moreover, since the movement of the split dies 4 is stabilized by using the guide pins 5, even if the die-side inclined plane 43 and the pressure-receiving side inclined plane 31 are replaced with conventional conical surfaces, the effect of maintaining high molding quality of the workpiece W is achieved. On the other hand, since the movement of the split dies 4 is stabilized by maintaining surface contact between the die-side inclined plane 43 and the pressure-receiving side inclined plane 31, the effect of maintaining high molding quality of the workpiece W is achieved even if the guide pins 5 are omitted.

[0048] Furthermore, in this embodiment, the split die 4 moves radially inward when the punch 26 (die drive unit 71) moves axially while the case 3 is stationary. Conversely, the same effect occurs when the case 3 and split die 4 move axially while the punch 26 is stationary. Also, the workpiece W is not limited to a cylindrical shape, but can be substantially axially symmetric, such as a stepped cylindrical shape or a polygonal prism shape. Moreover, the processing die on the inner circumferential surface of the split die 4 is not limited to a knurling die 44, but can be a processing die that press-forms indentations, holes, grooves, etc. on the outer circumferential surface of the workpiece W, or a processing die that performs marking, etc. The present invention can be modified and applied in various other ways. [Explanation of symbols]

[0049] 1: Forging machine 23: Die 26: Punch 3: Case 31: Pressure-receiving inclined plane 4: Split die 41: End face 42: Guide surface 43: Die side inclined plane 44: Knurled type 46: Biasing spring 5: Guide pin 6: Kick-out pin 71: Mold drive unit 72: Workpiece insertion unit W: Work AL: Axis

Claims

1. A workpiece with a substantially axially symmetrical shape has a machining die facing the outer circumferential surface, and comprises a plurality of split dies divided in the circumferential direction, A case for holding multiple split dies so that they can move relative to each other in the axial direction and move radially, A drive unit that moves a plurality of the split dies and the case relative to each other in the axial direction, thereby moving the plurality of split dies radially inward, and causing the processing die to perform press forging on the outer surface of the workpiece, The system includes a guide member that guides the movement of multiple split dies while restricting circumferential movement, The guide member consists of a plurality of guide pins that are spaced apart from each other in the axial direction and extend parallel to the radial direction in which the splitting die moves. Forging machine.

2. The forging machine according to claim 1, wherein the guide pin makes line contact with the splitting die.

3. The forging machine according to claim 2, wherein the guide pin has a cylindrical or cylindrical shape.

4. Multiple guide pins are arranged on both sides of the split mold in the circumferential direction, and four or more are provided for each split mold. The forging machine according to claim 1.

5. The plurality of split dies consist of two split dies that move in a radial direction in a second direction perpendicular to the axial direction, and two other split dies that move in a radial direction in a third direction perpendicular to the axial direction and the second direction. The guide pin extends parallel to the second or third direction. The forging machine according to claim 1.

6. The aforementioned case is, Throughout the time period in which the multiple split dies move radially inward, each of the split dies is held by surface contact, and the device has multiple pressure-receiving surfaces that receive radially outward surface pressure acting from the split dies. The forging machine according to claim 1.

7. Each of the multiple split dies has a die-side inclined plane that is inclined with respect to the axial direction, Each of the multiple pressure-receiving surfaces consists of a pressure-receiving inclined plane that makes surface contact with the mold-side inclined plane, The drive unit moves the multiple split dies radially inward by moving them relative to each other in the axial direction while bringing the mold-side inclined plane and the pressure-receiving side inclined plane into surface contact. The forging machine according to claim 6.

8. The forging machine according to claim 1, wherein the drive unit also serves as a workpiece insertion unit that moves the workpiece relative to the workpiece in the axial direction and inserts it into the central position of the plurality of split dies.

9. The forging machine according to claim 8, wherein the drive unit, which also serves as the workpiece insertion unit, moves the inserted workpiece, the plurality of split dies, and the case relative to each other in the axial direction, thereby moving the processing die radially inward with respect to the workpiece that is being moved relative to it.

10. The forging machine according to claim 1, wherein the processing die is a knurling die that performs knurling on the outer surface of the workpiece.

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