A design method for trimming die of crankshaft forgings

Abstract

The present invention proposes a method for designing a trimming die for a crankshaft forging, comprising the following steps: S1, drawing a hot forging drawing of the crankshaft forging without a rounded corner design; S2, oversizing the dimensions of the balancing block, journal step, flywheel end, and gear end in the hot forging drawing of the crankshaft obtained in step S1 by 1.5 mm to 3 mm in both directions along the length of the crankshaft; S3, rounding the hot forging drawing in step S2; S4, obtaining the maximum outer contour of the hot forging drawing; S5, designing an outer contour drawing of a trimming punch according to step S4; S6, obtaining a final outer contour drawing of the desired trimming punch; S7, drawing a die structure drawing of a mounting base of the crankshaft trimming punch to form the trimming punch; S8, performing a Boolean operation design on the hot forging drawing of the crankshaft obtained in step S3 and the die structure drawing of the trimming punch in step S7 to obtain a trimming punch structure drawing having a die cavity surface. The present invention can effectively prevent the trimming punch cavity contour and the crankshaft forging from sticking.

Description

Technical Field

[0001] The invention relates to the technical field of crankshaft forging production, and in particular to a crankshaft forging trimming die design method. Background Art

[0002] During the production of crankshaft forgings, trimming is an essential process, and a trimming die is required for this process. Currently, the design of a trimming die for crankshaft forgings requires drawing a hot forging drawing for the crankshaft forging, a hot forging drawing for the trimming die, and the outline of the forging punch for trimming. The design process has the problems of long design cycle, unreasonable matching between the hot forging drawing used in the trimming process and the hot forging drawing used in the crankshaft forging, product quality problems such as indentation and die sticking during the process, and only the gap between the punch and die is considered in the design process of the punch outline and the trimming die (blanking die / maximum outline of the crankshaft forging), while the cavity outline of the punch is consistent with the surface shape of the crankshaft forging. This leads to the problem of the order of contact points between the crankshaft forging and the trimming punch during the trimming production process, which makes it easy for the outline of the trimming punch and the main journal and connecting rod neck on the crankshaft forging to get stuck, causing the crankshaft forging to be unable to be blanked from the die, (and during the trimming punch and the forging flash cutting process, due to uneven force, the rounded corner part of the punch die structure and the maximum outline of the forging flash form a bond, causing the flash to be unable to separate from the punch), thereby affecting the normal trimming of the crankshaft forging.

[0003] In the prior art, a Chinese patent with publication number CN103352912B discloses a V-type six-cylinder engine crankshaft forging and a forging method thereof. In the patent, an appropriate amount of process allowance is added to the connecting rod neck to change the parting surface of the crankshaft forging, so that each crank is parted along the curved surface formed by the center plane of the connecting rod neck and the center plane of the main journal, thereby controlling the position of the connecting rod neck in the mold cavity. In addition, although the trimming punch in the above patent has a single-sided increase of 2mm, the mold design process does not reveal the matching relationship between the punch and the crankshaft forging surface. Therefore, it is not clear how the connecting rod neck and the main journal solve the problem of sticking in the convex mold cavity contour.

[0004] In addition, the design of crankshaft forging dies, especially the trimming punch modeling design requirements, requires more precise design requirements for the hot forging drawings used in crankshaft forging, the hot forging drawings used in the trimming die, and the design of the trimming punch profile. The drawing design requires that the clearance between the two sides of the crankshaft be 1.5mm to 3mm in the longitudinal direction, and the clearance between the two sides be 0.5mm to 1mm in the die width direction, depending on the size of the crankshaft product. At the same time, the design dimensions of the crankshaft balance block, journal step, flywheel end, and gear end in the die width direction must be fully considered. The maximum profile of the crankshaft hot forging and the clearance requirements of the trimming punch must be fully considered when designing the punch profile. Depending on the size of the crankshaft, the clearance is generally required to be within the range of 0.5mm to 2.5mm. At the same time, all convex fillets in the punch profile design process must be larger than all convex fillets in the maximum profile. These design requirements increase the design time of the die drawings. Summary of the Invention

[0005] In view of this, the present invention proposes a crankshaft forging trimming die design method to solve the problem in the prior art that the trimming die is prone to the cavity contour of the punch and the crankshaft forging is stuck.

[0006] The technical solution of the present invention is achieved as follows:

[0007] The present invention discloses a crankshaft forging trimming die, which is used for trimming crankshaft forgings. The die comprises a concave die and a convex die matched with the convex die. The concave die comprises a blanking hole. The surface of the concave die is provided with a parting surface matched with the parting surface of the crankshaft forging. The parting surface surrounds the blanking hole. The blanking hole is matched with the maximum outer contour of the crankshaft forging. The blanking hole is used to place the crankshaft forging with flash, and the parting surface is used to bear the flash of the crankshaft forging.

[0008] The maximum outer contour of the punch in contact with the crankshaft forging is smaller than the maximum outer contour of the parting line of the crankshaft forging. The surface of the punch has multiple cavities that are adapted to the surface contour of the crankshaft forging. The multiple cavities have corresponding clearance fits with the balance block, journal step, flywheel end and gear end on the crankshaft forging.

[0009] The present invention provides a method for designing a trimming die for a crankshaft forging, comprising the following steps:

[0010] S1. Draw a hot forging drawing of a crankshaft forging without a fillet design;

[0011] S2, enlarging the dimensions of the balance block, journal step, flywheel end, and gear end of the crankshaft hot forging obtained in step S1 by 1.5 mm to 3 mm on both sides along the length direction of the crankshaft;

[0012] S3. Design fillets for the offset hot forging drawing according to the requirements of convex and concave fillets for the hot forging drawing of the crankshaft, and complete the hot forging drawing of the crankshaft required for the design of the trimming punch die.

[0013] S4, rounding the hot forging drawing in step S1 to obtain the maximum outline of the hot forging drawing;

[0014] S5. Design the contour drawing of the trimming punch according to the maximum contour of the hot forging drawing;

[0015] S6. The outer contour of the trimming punch is offset inward by 0.5 mm to 2.5 mm to obtain the final outer contour of the required trimming punch;

[0016] S7. Optimize the rounded corners of the final outline of the trimming punch, and draw a mold structure diagram of the trimming punch formed by the mounting base of the crankshaft trimming punch;

[0017] S8. Perform Boolean operation design on the crankshaft hot forging drawing obtained in step S3 and the die structure drawing of the trimming punch in step S7 to obtain a trimming punch structure drawing having a die cavity surface.

[0018] On the basis of the above technical solution, preferably, in step S4, a parting line of the forging is drawn according to the forging direction of the crankshaft hot forging, and the parting line is used as the maximum outer contour of the hot forging drawing.

[0019] On the basis of the above technical solution, preferably, the hot forging drawing obtained in step S1 without fillet design is further included in the rounded corner design, wherein the rounded corner design includes designing convex fillets and concave fillets on the surface contour of the forging drawing, and obtaining the maximum outer contour of the forging through the parting surface.

[0020] Furthermore, preferably, in step S7, the fillet of the final outer contour of the trimming punch is increased by 0.5 mm to 2.5 mm.

[0021] On the basis of the above technical solution, preferably, the crankshaft forging in step S3 is subjected to Boolean difference design through its parting surface and the mold structure diagram of the trimming punch in step S7 to draw a trimming punch structure diagram with a mold surface.

[0022] On the basis of the above technical solution, preferably, the mold drawing is optimized for the irregular shapes of the journals, balancing blocks and other parts in the trimming punch structure diagram with the mold surface in step S8 according to the design and production practice.

[0023] On the basis of the above technical solution, preferably, the journals, balance blocks and other parts in the trimming punch structure diagram having the mold profile are offset by 0.5 mm to 1 mm in the mold width direction.

[0024] On the basis of the above technical solution, preferably, the method further includes offsetting the blanking opening on the die outward along its edge contour by 2 mm to 5 mm to form a step structure.

[0025] The present invention has the following beneficial effects compared to the prior art:

[0026] (1) The crankshaft forging trimming die disclosed in the present invention has a corresponding clearance fit between the convex mold cavity and the balancing block, journal step, flywheel end and gear end on the crankshaft forging. When the convex mold cavity surface contacts the crankshaft surface, the balancing block, journal step, flywheel end and gear end on the crankshaft will not get stuck with the convex mold cavity contour. At the same time, the maximum outer contour of the convex mold in contact with the crankshaft forging is smaller than the maximum outer contour of the parting line of the crankshaft forging. When the trimming convex mold contacts the crankshaft forging surface to the maximum extent, the convex mold and the concave mold can avoid air gaps, thereby ensuring that the crankshaft flash can be effectively removed and that the crankshaft does not get stuck with the convex mold and the concave mold.

[0027] (2) The crankshaft forging trimming die design method disclosed in the present invention obtains the maximum outer contour of the hot forging drawing by offsetting the dimensions of the balancing blocks, journal steps, flywheel ends, and gear ends of the crankshaft forging drawing along the length direction of the crankshaft, and draws a punch die structure drawing based on the maximum outer contour of the hot forging drawing. The crankshaft forging to be formed and the punch die structure drawing are used for Boolean operation to obtain a trimming punch die structure drawing with a mold cavity surface. When the punch die cavity contour contacts the crankshaft surface, the balancing blocks, journal steps, flywheel ends, and gear ends on the crankshaft are clearance-matched with the punch die cavity contour. Compared with directly drawing the trimming punch by the crankshaft forging to be formed, this design method has high design efficiency and shortened cycle time. At the same time, it can effectively avoid the problem of the trimming punch die cavity contour and the crankshaft forging being stuck during the contact and downward pressing process between the trimming punch and the crankshaft, thereby realizing that the crankshaft forging can be effectively trimmed with the cooperation of the punch and the die.

[0028] (3) When drawing the crankshaft hot forging drawing, by not designing the rounded corners in advance, it is convenient to design the dimensions of the balance block, journal step, flywheel end, and gear end in the crankshaft hot forging drawing on both sides along the crankshaft length direction. This design method improves the drawing efficiency of the crankshaft hot forging drawing required for the trimming punch die design;

[0029] (4) By offsetting the trimming punch contour inward by 0.5 mm to 2.5 mm, the final contour of the trimming punch is obtained, which can avoid air between the trimming punch and the die, and reduce the shear loss of the punch to the die edge;

[0030] (5) By optimizing the mold drawing according to the design and production practice for the irregular shapes of the journals, balance blocks and other parts in the trimming punch structure diagram with the mold profile, the convex mold cavity surface can be in smooth contact with the crankshaft surface, ensuring that the sharp parts of the convex mold cavity surface are prevented from causing pressure damage to the crankshaft surface during the trimming process;

[0031] (6) By offsetting the journals, balance blocks and other parts of the trimming punch structure with the die profile by 0.5 mm to 1 mm in the die width direction, the edge of the convex die cavity can be horizontally thickened, thereby improving the structural strength of the edge of the convex die cavity, avoiding deformation of the cutting edge of the convex die cavity, and preventing the edge of the convex die cavity from forming an indentation with the forging surface during the trimming process;

[0032] (7) By offsetting the blanking hole on the die outward by 2 mm to 5 mm along its edge contour to form a step structure, on the one hand, it is convenient for the crankshaft to fall smoothly along the blanking hole of the die after trimming, and on the other hand, it can also improve the structural strength of the cutting edge at the blanking hole. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1 It is a schematic diagram of the three-dimensional structure of the crankshaft forging trimming die disclosed in the present invention;

[0035] Figure 2 This is a schematic diagram of the three-dimensional structure of the punch of the crankshaft forging trimming die disclosed in the present invention;

[0036] Figure 3 This is a flow chart of the crankshaft forging trimming die design method disclosed in the present invention;

[0037] Figure 4 The crankshaft forging diagram in step S1 disclosed in the present invention;

[0038] Figure 5 A diagram of a crankshaft forging after the offset in step S1 disclosed in the present invention;

[0039] Figure 6 A diagram of a crankshaft forging with rounded corners in step S2 disclosed in the present invention;

[0040] Figure 7 This is a diagram of a crankshaft forging after rounding in step S1 disclosed in the present invention;

[0041] Figure 8 Designing a trimming punch outline drawing for the maximum outline of the hot forging drawing disclosed in the present invention;

[0042] Figure 9 The final outline diagram of the trimming punch disclosed in the present invention;

[0043] Figure 10 A diagram showing the structure of a mold for forming a trimming punch for a mounting base of the crankshaft trimming punch disclosed in the present invention;

[0044] Figure 11 A diagram showing the design steps of a trimming punch structure diagram having a mold cavity surface disclosed in the present invention;

[0045] Figure 12 This is a diagram showing the offset of various journals, balancing blocks and other parts in the width direction of the die in the structure diagram of the trimming punch disclosed in the present invention;

[0046] Figure 13 This is a structural design diagram of the die disclosed in the present invention. DETAILED DESCRIPTION

[0047] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0048] In the prior art, after the crankshaft is forged by a forging die, flash is usually formed at the parting line of the crankshaft, which needs to be removed by a crankshaft trimming die. The crankshaft trimming die is composed of a die and a punch. The die is also called a blanking die. The top surface shape of the die is processed by the parting surface of the crankshaft forging, and the blanking hole of the die is formed by the maximum outer contour of the parting line of the crankshaft forging. The crankshaft forging is placed on the blanking hole of the die during trimming. The trimming on the crankshaft is located on the top surface shape of the die, and the trimming punch contacts the surface of the crankshaft forging downward, thereby utilizing the relative shearing of the punch and the die to achieve the cutting of the crankshaft flash at the blanking edge (cutting edge) of the die. Finally, the flash remains on the die, and the crankshaft falls through the blanking hole.

[0049] Since the punch needs to act on the crankshaft and cooperate with the die to remove flash from the crankshaft, the punch and crankshaft surface must be in full contact to ensure stable force when the punch presses down on the crankshaft. Currently, the punch cavity surface is usually made to match the surface contour of the crankshaft. The most common mold design for trimming punches is to cut the punch cavity surface directly from the crankshaft forging. This design method makes it easy for the punch cavity contour and the crankshaft surface contour to get stuck when the punch contacts the crankshaft, which usually causes jamming at the crankshaft main journal and connecting rod journal. Directly designing a cavity on the punch that adapts to the crankshaft contour to avoid jamming on the main journal and connecting rod journal requires a long design time. Because the crankshaft shape is relatively complex, the cavity surface on the punch needs to be designed piece by piece, which results in a long design cycle.

[0050] To this end, the present invention discloses a crankshaft forging trimming die, Figure 1 and 2 As shown, it includes a die 1 and a punch 2 that cooperates with the punch 1. The die 1 includes a blanking hole 11. The top surface of the die 1 is provided with a parting surface 12 that is adapted to the parting surface of the crankshaft forging. The parting surface 12 surrounds the blanking hole 11. The blanking hole 11 is adapted to the maximum outer contour of the crankshaft forging S. The blanking hole 11 is used to place the crankshaft forging with flash, and the parting surface is used to support the flash of the crankshaft forging.

[0051] The maximum outer contour of the punch 2 in contact with the crankshaft forging is smaller than the maximum outer contour of the parting line of the crankshaft forging S. The surface of the punch 2 has multiple cavities 21 that are adapted to the surface contour of the crankshaft forging. The multiple cavities 21 have corresponding clearance fits with the balance block, journal step, flywheel end and gear end on the crankshaft forging S.

[0052] In this embodiment, the die is a fixed die and the punch is a movable die. The punch can be connected to the trimming and punching machine by setting a base plate. When performing crankshaft trimming operations, the forged crankshaft forging is placed on the die, and the flash contacts the parting surface of the die. The outer surface of the crankshaft is pressed down by the punch, and the punch is in contact with the surface of the crankshaft forging to the maximum extent, ensuring that the punch can apply downward pressure to all surfaces of the crankshaft when pressing down. At the same time, the maximum outer contour of the contact between the punch and the crankshaft forging is smaller than the maximum outer contour of the parting line of the crankshaft forging. Thus, when the trimming punch contacts the surface of the crankshaft forging to the maximum extent, the punch and the die avoid each other, ensuring that the crankshaft flash can be effectively removed and that the crankshaft is not stuck with the punch and the die. In addition, by making the convex model cavity and the balance block, journal step, flywheel end and gear end on the crankshaft forging have corresponding clearance fit, when the convex model cavity surface contacts the crankshaft surface, the balance block, journal step, flywheel end and gear end on the crankshaft will not get stuck with the contour of the convex model cavity.

[0053] The present invention also discloses a method for designing a trimming die for a crankshaft forging, which is mainly innovative in the design of a trimming punch. Figure 3-13 As shown, the design steps of the present invention are as follows:

[0054] S1. Draw a hot forging diagram of a crankshaft forging without fillet design.

[0055] This step belongs to the crankshaft product model design. When designing the crankshaft forging die, the hot forging diagram of the crankshaft can be drawn through 3D software. This hot forging diagram can be used as the design of the trimming punch and can also be used as the crankshaft forging die. Figure 4 As shown, in this embodiment, when designing the crankshaft hot forging drawing, no rounded corners are designed for the crankshaft surface contour in advance, which is convenient for model redesign or optimization design in the subsequent punch design.

[0056] S2. Enlarge the dimensions of the balance block, journal step, flywheel end, and gear end in the crankshaft hot forging obtained in step S1 by 1.5 mm to 3 mm in both directions along the length direction of the crankshaft.

[0057] Since the balancing weight, journal step, flywheel end, and gear end on the crankshaft forging are all raised portions on the crankshaft, and adjacent to these raised portions are the mainshaft journal and connecting rod journal, and the rotation radius of the aforementioned raised portions is larger than that of the mainshaft journal and connecting rod journal, in some prior art, when designing the punch, the outer contour surface of the designed crankshaft forging drawing is directly copied onto the punch mold to cut out the punch cavity surface, which results in a long design cycle. This causes the recessed cavities on the punch reflecting the balancing weight, journal step, flywheel end, and gear end to become stuck with the balancing weight, journal step, flywheel end, and gear end on the crankshaft, and the cavity surfaces on the punch reflecting the mainshaft journal and connecting rod journal to become stuck with the mainshaft journal and connecting rod journal on the crankshaft.

[0058] Refer to the attached Figure 5 As shown, in this embodiment, by performing step S2, the dimensions of each balancing block, journal step, flywheel end, and gear end on the crankshaft forging diagram are pre-offset by 1.5mm to 3mm along the length direction of the crankshaft, that is, the thickness dimensions of the balancing block, journal step, flywheel end, and gear end are 1.5mm to 3mm larger on one side. At the same time, the length dimensions of the main journal and connecting rod journal on the corresponding crankshaft are 1.5mm to 3mm smaller on one side. This step is designed so that when the subsequent punch is designed, the offset crankshaft hot forging diagram can be used to draw a punch structure diagram with a cavity. Then the cavity of the punch and the surface contour of the crankshaft hot forging are clearance fit, also known as air avoidance. Then when the punch contacts the crankshaft, there will be no problem of the convex mold cavity surface and the crankshaft contour surface getting stuck.

[0059] S3. Design the fillet of the offset hot forging drawing according to the requirements of the convex fillet and concave fillet of the crankshaft hot forging drawing, and complete the crankshaft hot forging drawing required for the trimming punch mold design.

[0060] If the offset is performed directly on the crankshaft forging drawing, the design operation cannot be performed, or there are design difficulties. In this embodiment, step S1 is first performed, and then step S2 is performed. After completing step S2, the crankshaft hot forging has corners or sharp edges, which are not conducive to the use in the subsequent punch design and do not meet the design requirements of the crankshaft product. At this time, according to the design requirements of the crankshaft fillet, the convex fillet and concave fillet of the offset hot forging are designed. Refer to the attached figure. Figure 6 As shown, specifically, convex fillets are designed at the outer edges of each balancing block, journal step, flywheel end, and gear end, and concave fillets are designed at the roots of the main journal and connecting rod journal.

[0061] At the same time, by not performing rounded corner design in advance, it is convenient to perform bilateral offset design of the dimensions of each balance block, journal step, flywheel end, and gear end in the crankshaft hot forging drawing along the length direction of the crankshaft. This design method improves the efficiency of drawing the crankshaft hot forging drawing required for the trimming punch mold design.

[0062] In order to make the punch contact with the maximum contour of the crankshaft surface and maintain the force stable when the trimming is pressed down, this embodiment is implemented through step S4. Specifically, the hot forging drawing in step S1 is rounded, and the rounded corners are designed with reference to the attached drawing. Figure 7 , obtain the maximum outline of the hot forging diagram. What is obtained in step S4 is the hot forging diagram of the crankshaft forging, which is a complete three-dimensional model diagram of the crankshaft product.

[0063] In order to make the cavity contour of the punch contact with the maximum contour of the crankshaft, this embodiment is implemented through step S5. Specifically, the trimming punch contour diagram is designed according to the maximum contour of the hot forging diagram; refer to the attached Figure 8 As shown, in this embodiment, the maximum outer contour of the hot forging figure can be obtained by the crankshaft parting line.

[0064] Since the maximum outer contour diagram obtained in step S5 is based on the crankshaft parting line, if the final outer contour diagram of the punch is directly based on the maximum outer contour diagram of the crankshaft, the final outer contour of the punch will correspond to the blanking hole of the die, which will cause shear wear on the punch and die.

[0065] To this end, this embodiment designs step S6. Specifically, refer to the attached Figure 9 As shown, the trimming punch profile is offset inward by 0.5mm to 2.5mm to obtain the final profile of the trimming punch. This setting allows the trimming punch and die to avoid air gaps, reducing shear loss from the punch to the die edge.

[0066] Since the contour of the trimming punch is biased inward during step S6, this results in a smaller rounded corner. Therefore, in this embodiment, the rounded corner of the final contour of the trimming punch is optimized and designed. Figure 10 As shown in the figure, the radius of the final contour of the trimming punch is increased by 0.5mm to 2.5mm. In other words, the radius increases in proportion to the inward offset of the trimming punch contour. With this setting, the radius of the punch contour is designed to be larger than the forming radius of the crankshaft forging. When the punch and the flash contour come into contact after trimming, the punch and the flash will not get stuck, facilitating the smooth completion of the process.

[0067] The mounting base of the crankshaft trimming punch is then drawn to form the die structure diagram of the trimming punch. This step is to design the die structure diagram by projecting the trimming punch outline onto the base plate. At this point, the outer surface of the punch is a closed surface along the outline.

[0068] In order to enable the trimming punch to contact the crankshaft surface and realize the subsequent pressing operation, this embodiment performs Boolean operation design on the mold structure diagram of the crankshaft forging in step S3 and the trimming punch in step S7 to draw a trimming punch structure diagram with a mold surface.

[0069] For details, please refer to the attached Figure 11 As shown, this embodiment makes the parting surface formed by the maximum outer contour of the crankshaft forging in S3 correspond to the curved surface formed by the outer contour of the trimming punch in S7, and draws a trimming punch structure diagram with a mold surface through Boolean difference design.

[0070] Through the above scheme, a structural diagram of a trimming punch with a mold surface is formed. When the contour of the convex model cavity contacts the surface of the crankshaft, the balance block, journal step, flywheel end and gear end on the crankshaft are clearance-fitted with the contour of the convex model cavity. Compared with drawing the trimming punch directly through the crankshaft forging to be formed, this design method has high design efficiency and shortened cycle. At the same time, it can effectively avoid the problem of the cavity contour of the trimming punch and the crankshaft forging getting stuck during the contact and downward pressing process of the trimming punch and the crankshaft. In addition, the radius of the outer contour of the punch is designed to be larger than the forming radius of the crankshaft forging. When the punch and the flash contour contact after trimming, the punch and the flash will not get stuck, thereby realizing that the crankshaft forging can be effectively trimmed with the cooperation of the convex and concave dies.

[0071] In the above step S8, the punch structure diagram designed by Boolean difference has some uncut or sharp edges on the cavity surface. If the punch is not used, there will be a problem of edge breakage.

[0072] To this end, this embodiment further includes steps for optimizing the mold drawing based on design and production practices, taking into account the irregular shapes of the journals, balancing weights, and other parts of the trimming punch structure diagram with the mold profile in step S8. This ensures that the convex mold cavity surface can smoothly contact the crankshaft surface, preventing sharp areas of the convex mold cavity from causing damage to the crankshaft surface during the trimming process.

[0073] Since the maximum outer contour of the punch is offset inward, the edge of the maximum outer contour where the punch contacts the crankshaft surface will form a sharp-angle structure. During the pressing operation of the punch and the crankshaft, the long-term punching pressure, coupled with the high temperature of the crankshaft after forging, will cause the edge of the punch outer contour to curl or deform, affecting its service life.

[0074] For this purpose, refer to the attached Figure 12 As shown, in this embodiment, the various journals, balance blocks and other parts in the trimming punch structure diagram with a mold surface are offset by 0.5mm to 1mm in the mold width direction, which can horizontally thicken the edge of the convex model cavity, improve the structural strength of the edge of the convex model cavity, avoid deformation of the cutting edge of the edge of the convex model cavity, and avoid the edge of the convex model cavity from forming indentations with the forging surface during the trimming process.

[0075] It is worth noting that the offset size in this step is smaller than the offset size in step S6 to avoid interference between the offset punch and the die.

[0076] In order to facilitate the crankshaft to fall smoothly from the blanking hole after the crankshaft forging is trimmed, refer to the attached Figure 13 As shown, in this embodiment, the blanking hole on the die is offset outward by 2mm to 5mm along its edge contour to form a step structure. On the one hand, it is convenient for the crankshaft to fall smoothly along the blanking hole of the die after trimming. On the other hand, it can also improve the structural strength of the cutting edge at the blanking hole.

[0077] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for designing a trimming die for a crankshaft forging, characterized in that: The steps are as follows: S1. Draw a hot forging drawing of a crankshaft forging without a fillet design; S2. Increase the size of the balance block, journal step, flywheel end, and gear end of the crankshaft hot forging by 1.5mm to 3mm on both sides along the length of the crankshaft; S3. Design fillets for the offset hot forging drawing according to the requirements of convex and concave fillets for the hot forging drawing of the crankshaft, and complete the hot forging drawing of the crankshaft required for the design of the trimming punch die. S4, rounding the hot forging drawing in step S1 to obtain the maximum outline of the hot forging drawing; S5. Design the contour drawing of the trimming punch according to the maximum contour of the hot forging drawing; S6. The outer contour of the trimming punch is offset inward by 0.5 mm to 2.5 mm to obtain the final outer contour of the required trimming punch; S7. Optimize the rounded corners of the final outline of the trimming punch, and draw a mold structure diagram of the trimming punch formed by the mounting base of the crankshaft trimming punch; S8, performing Boolean operation design on the crankshaft hot forging drawing obtained in step S3 and the die structure drawing of the trimming punch in step S7 to obtain a trimming punch structure drawing having a die cavity surface; The crankshaft forging trimming die designed by the crankshaft forging trimming die design method is used for trimming crankshaft forgings. The trimming die includes a die and a punch matched with the die. The die includes a blanking hole. The die surface is provided with a parting surface matched with the parting surface of the crankshaft forging. The parting surface surrounds the blanking hole. The blanking hole is matched with the maximum outer contour of the crankshaft forging. The blanking hole is used to place the crankshaft forging with flash. The parting surface is used to bear the flash of the crankshaft forging. The maximum outer contour of the punch in contact with the crankshaft forging is smaller than the maximum outer contour of the parting line of the crankshaft forging. The surface of the punch has multiple cavities that are adapted to the surface contour of the crankshaft forging. The multiple cavities have corresponding clearance fits with the balance block, journal step, flywheel end and gear end on the crankshaft forging.

2. The method for designing a trimming die for a crankshaft forging according to claim 1, wherein: In step S4, a parting line of the crankshaft hot forging is drawn according to the forging direction of the crankshaft hot forging, and the parting line is used as the maximum outer contour of the hot forging drawing.

3. The method for designing a trimming die for a crankshaft forging according to claim 1 or 2, wherein: The method also includes performing fillet design on the hot forging drawing obtained in step S1 without fillet design, wherein the fillet design includes performing convex fillet design and concave fillet design on the surface contour of the hot forging drawing, and obtaining the maximum outer contour of the forging through the parting surface.

4. The method for designing a trimming die for a crankshaft forging according to claim 3, wherein: In step S7, the radius of the final outer contour of the trimming punch is increased by 0.5 mm to 2.5 mm.

5. The crankshaft forging trimming die design method according to claim 4, characterized in that: The crankshaft forging in step S3 is subjected to Boolean difference design through its parting surface and the die structure diagram of the trimming punch in step S7 to draw a trimming punch structure diagram with the die profile.

6. The crankshaft forging trimming die design method according to claim 5, characterized in that: The mold drawing of the irregular shapes of the journals and balancing blocks in the trimming punch structure diagram with the mold surface in step S8 is optimized according to the design and production practice.

7. The method for designing a trimming die for a crankshaft forging according to claim 6, wherein: The journals and balance block parts in the trimming punch structure diagram with the mold surface are offset by 0.5mm to 1mm in the mold width direction.

8. The crankshaft forging trimming die design method according to claim 1, wherein: The method also includes offsetting the blanking hole on the die outward by 2 mm to 5 mm along the edge contour thereof to form a step structure.

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