High-precision trimming die for engine single-cylinder crankshaft

Abstract

The utility model discloses a high-precision trimming die of engine single cylinder crankshaft, include: lower die seat, punch, set in the just above of lower die seat and have frame shape cutting edge, bag eccentric punch, and along the concentric punch of sliding in the both ends of eccentric punch plumb direction, the bottom surface of eccentric punch is eccentric positioning surface, and the both sides of eccentric positioning surface are eccentric cutting edge, and the bottom surface of concentric punch is concentric positioning surface, and the both sides of concentric positioning surface and the one end of back to eccentric positioning surface are concentric cutting edge, lift subassembly, output and punch are connected. The high-precision trimming die of engine single cylinder crankshaft through concentric punch pre -presses in the concentric axle of blank both ends and cuts the surrounding flash, and then eccentric punch drops and cuts the surrounding remaining flash, until the concentric punch is relative to eccentric punch and moves to the positioning station, and the concentric axle of blank both ends is positioned through eccentric positioning surface in the trimming process, prevents the upwarping or other deformation, guarantees the trimming quality.

Description

Technical Field

[0001] This utility model relates to the field of engine single-cylinder crankshaft trimming technology, and in particular to a high-precision trimming mold for engine single-cylinder crankshafts. Background Technology

[0002] The engine crankshaft is the core of the power transmission of an internal combustion engine. It is responsible for converting the reciprocating linear motion of the piston into rotational motion, thereby driving the operation of the whole vehicle and equipment. It is widely used in automobiles, engines, pumps, etc. The crankshaft is mostly made of alloy structural steel or ductile iron. During the forging process, excess metal will overflow from the gap of the forging die parting surface, forming flash around the crankshaft. Therefore, it is necessary to use a trimming die to remove it.

[0003] For forged single-cylinder crankshafts, if the final product rod is too slender (usually referring to a rod length-to-diameter ratio greater than 10), during edge trimming, the blank rod's rigidity is insufficient (significantly low bending rigidity), the lower die provides insufficient support to the blank (the blank end is prone to becoming suspended), and the flash is unevenly stressed during trimming (thicker flash areas, such as the eccentric block area, require greater shearing force and downward pressure, while thinner flash areas, such as the end of the rod, require less shearing force). This can easily cause the blank end to warp upwards, reducing the straightness of the crankshaft and, in severe cases, producing defective products.

[0004] In the prior art, such as the Chinese utility model patent with announcement number CN217647403U, an eccentric shaft trimming die is disclosed. By setting anti-warping protrusions on the cavity wall of the upper cavity of the concentric block, when trimming, the anti-warping protrusions press down on the blank, which can prevent the concentric block part with a smaller outer diameter of the blank from warping up, thereby ensuring the straightness of the product after trimming and forming, improving the trimming quality of the eccentric shaft and preventing the production of defective products.

[0005] While the aforementioned trimming die effectively prevents the smaller outer diameter portion of the blank from warping during trimming, the presence of the anti-warping protrusion alters the shape of the punch's bottom surface. This causes the blank to form a depression corresponding to the anti-warping protrusion during trimming, changing the overall shape of the blank and affecting subsequent blank shaping and production quality. When the depression is large or deep, it can also lead to defective products. Furthermore, in the aforementioned trimming die, the punch is a one-piece structure. After long-term use, the sharpness of some parts of the punch's cutting edge decreases, affecting the trimming process. Therefore, the entire punch needs to be replaced and maintained, increasing the cost of punch replacement and maintenance.

[0006] Therefore, it is necessary to improve the existing edge-cutting dies. Utility Model Content

[0007] The purpose of this invention is to overcome the defects in the existing technology and provide a high-precision edge trimming mold for engine single-cylinder crankshafts that prevents excessive deformation of the blank, ensures processing accuracy, and reduces replacement and maintenance costs.

[0008] To achieve the above technical effects, the technical solution of this utility model is as follows: the lower mold base is horizontally set, and a positioning lower cavity is opened on the top surface; A punch, positioned directly above the lower die base and having a frame-shaped cutting edge for removing flash from the blank, includes an eccentric die corresponding to the eccentric shaft and eccentric block of the blank, and a concentric die corresponding to the concentric shaft of the blank and sliding vertically at both ends of the eccentric die. The bottom surface of the eccentric die is an eccentric positioning surface, and the two sides of the eccentric positioning surface are eccentric cutting edges. The bottom surface of the concentric die is a concentric positioning surface, and the two sides of the concentric positioning surface and the end opposite to the eccentric positioning surface are concentric cutting edges. The two ends of the sliding trajectory of the concentric die relative to the eccentric die are respectively a trimming station and a positioning station. In the positioning station, the concentric positioning surface is located below the eccentric positioning surface. In the trimming station, the concentric cutting edge and the eccentric cutting edge combine to form the frame-shaped cutting edge. The projection of the frame-shaped cutting edge on the horizontal plane is located inside the projection of the edge of the lower cavity opening on the horizontal plane. The lifting assembly has its output end connected to the punch.

[0009] Preferably, in order to remove the flash from the blank, the output end of the lifting assembly is connected to the eccentric die, the eccentric die is connected to the concentric die through an axially vertical compression spring, and the eccentric die is also fixedly connected to a positioning element. In the trimming position, the concentric die abuts against the bottom of the positioning element.

[0010] Preferably, in order to reduce the replacement and maintenance costs of the punch, the output end of the lifting assembly is detachably connected to the eccentric die, and the eccentric die is detachably connected to the concentric die.

[0011] Preferably, in order to facilitate the replacement and maintenance of the eccentric die, the output end of the lifting assembly is a horizontal lifting plate. The eccentric die is fixedly connected to the lifting plate by a threaded locking bolt and a locking nut. The locking bolt includes a locking nut, a first screw, and a second screw, which are coaxially connected and have successively decreasing outer diameters. The locking nut and the locking nut are respectively clamped on both sides of the lifting plate. The locking nut is threadedly connected to the first screw, and the second screw is threadedly connected to the eccentric die.

[0012] Preferably, in order to facilitate the limitation of the sliding range of the concentric die relative to the eccentric die, the positioning member is a positioning plate clamped between the first screw and the eccentric die, and both ends of the positioning plate extend above the concentric die.

[0013] Preferably, in order to achieve a detachable connection between the concentric die and the eccentric die, the top of the concentric die is threaded with a fastening bolt that passes through the lifting plate, and the two ends of the compression spring abut against the concentric die and the lifting plate respectively.

[0014] Preferably, in order to facilitate the replacement of the compression spring and prevent the compression spring from dislodging from the lifting plate and the concentric die, the bottom end of the lifting plate and the top end of the concentric die are respectively provided with an upper limit tube and a lower limit tube with coaxial center lines, and the top and bottom ends of the compression spring are respectively disposed in the upper limit tube and the lower limit tube.

[0015] Preferably, in order to support the blank and prevent it from bending and deforming, a support assembly is provided on the inner side of the positioning cavity, and the support assembly is used to horizontally support the blank.

[0016] Preferably, in order to facilitate the support and positioning of the blank, the support assembly includes a telescopic unit and support members spaced apart along the length direction of the positioning cavity, wherein the telescopic unit drives the support members to move in the vertical direction.

[0017] Preferably, in order to facilitate the adjustment of the height position of the support, the telescopic unit includes an electromagnet and a permanent magnet distributed along the vertical direction, wherein one of the electromagnet and the permanent magnet is fixedly connected to the support and the other is fixedly connected to the lower mold base.

[0018] In summary, compared with the prior art, the high-precision trimming die for a single-cylinder crankshaft of this invention pre-presses the concentric shafts at both ends of the blank with a concentric die to remove the surrounding flash, and then the eccentric die descends to remove the remaining flash until the concentric die moves to the positioning position relative to the eccentric die. During the trimming process, the concentric shafts at both ends of the blank are positioned by the eccentric positioning surface to prevent warping or other deformations, thus ensuring the trimming quality. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of this utility model; Figure 2 yes Figure 1 An explosion diagram; Figure 3 yes Figure 1 An illustration of the explosion from another perspective; Figure 4 This is a schematic diagram of the structure of the present invention when the blank is placed; Figure 5 This is a schematic diagram of the structure of the blank after trimming. Figure 6 yes Figure 5 A schematic diagram of the cross-sectional structure; Figure 7This is a schematic diagram of the connection structure between the lifting assembly and the punch of this utility model; Figure 8 yes Figure 7 An explosion diagram; In the diagram: 1. Lower die base; 11. Positioning lower cavity; 2. Punch; 21. Eccentric die; 211. Eccentric positioning surface; 212. Eccentric cutting edge; 22. Concentric die; 221. Concentric positioning surface; 222. Concentric cutting edge; 223. Lower limit tube; 23. Compression spring; 24. Positioning component; 25. Locking bolt; 251. Locking cap; 252. First screw; 253. Second screw; 26. Locking nut; 27. 3. Fastening bolts; 4. Lifting assembly; 5. Hydraulic cylinder; 6. Lifting plate; 7. Upper limit tube; 8. Guide rod; 9. Limiting plate; 10. Support assembly; 11. Support component; 2. Guide hole; 32. Electromagnet; 43. Permanent magnet; 54. Base plate; 65. Guide column; 7. Frame; 8. Base; 9. Bracket; 10. Guide sleeve; 11. Blank; 12. Eccentric shaft; 13. Eccentric block; 14. Concentric shaft. Detailed Implementation

[0020] The specific embodiments of this utility model will be further described below with reference to the accompanying drawings and examples. The following examples are only used to more clearly illustrate the technical solution of this utility model and should not be construed as limiting the scope of protection of this utility model.

[0021] like Figure 1 and Figure 2 The diagram shows a structural schematic of a crankshaft blank 6 in the prior art, including an eccentric shaft 61. Two parallel eccentric blocks 62 are integrally connected to both ends of the eccentric shaft 61. A concentric shaft 63 is integrally connected to the side of each eccentric block 62 facing away from the eccentric shaft 61. The centerlines of the two concentric shafts 63 coincide and are parallel to the centerline of the eccentric shaft 61, but are spaced apart from the centerline of the eccentric shaft 61. The outer diameters of both concentric shafts 63 are smaller than the outer diameter of the eccentric shaft 61, and both concentric shafts 63 are slender rods, meaning the ratio of the length to the outer diameter of the concentric shaft 63 is greater than 10. After forging, the blank 6 develops flash on its outer periphery (not shown in the diagram).

[0022] like Figures 1-8 As shown, this utility model discloses a high-precision trimming die for a single-cylinder crankshaft of an engine, used for trimming the forged billet 6, including: The lower mold base 1 is horizontally set, and a positioning lower cavity 11 is opened on the top surface; Punch 2, located directly above the lower die base 1, has a frame-shaped cutting edge for removing the flash of the blank 6. It includes an eccentric die 21 corresponding to the eccentric shaft 61 and eccentric block 62 of the blank 6, and a concentric die 22 corresponding to the concentric shaft of the blank 6 and sliding vertically at both ends of the eccentric die 21. The bottom surface of the eccentric die 21 is an eccentric positioning surface 211, and the two sides of the eccentric positioning surface 211 are eccentric cutting edges 212. The bottom surface of the concentric die 22 is a concentric positioning surface 221. The two sides of 21 and one end opposite to the eccentric positioning surface 211 are concentric cutting blades 222. The two ends of the sliding trajectory of the concentric die 22 relative to the eccentric die 21 are the edge trimming station and the positioning station, respectively. In the positioning station, the concentric positioning surface 221 is located below the eccentric positioning surface 211. In the edge trimming station, the concentric cutting blade 222 and the eccentric cutting blade 212 are combined to form a frame-shaped cutting blade. The projection of the frame-shaped cutting blade on the horizontal plane is located inside the projection of the cavity opening edge of the positioning cavity 11 on the horizontal plane. The lifting assembly 3 has its output end connected to the punch 2.

[0023] When using the device, the forged blank 6 is placed on the horizontal lower die base 1. The length of the blank 6 is horizontal, with the lower part of the blank 6 located in the positioning lower cavity 11 and the upper part located above the positioning lower cavity 11. In the punch 2, without the influence of external force, the concentric die 22 of the punch 2 is located in the positioning position relative to the eccentric die 21. The lifting component 3 drives the punch 2 to descend, so that the eccentric die 21 and the concentric die 22 move downward synchronously. The concentric cutting edge 222 of the concentric die 22 first acts on the flash at the edge of the concentric shaft 63 of the blank 6. Since the flash material of the blank 6 is mainly concentrated around the eccentric block 62 and the eccentric shaft 61, the flash material around the end concentric shaft 63 is less and relatively thin, which helps the concentric cutting edge 222 to smoothly remove the thinner and less flash around the concentric shaft 63.

[0024] After the flash around the concentric shaft 63 is removed, the lifting assembly 3 continues to drive the punch 2 to move down, so that the concentric positioning surface 221 at the bottom of the concentric die 22 comes into contact with the upper part of the concentric shaft 63 at both ends of the blank 6, and acts on the concentric shaft 63 to prevent the concentric shaft 63 from tilting upward. The lifting assembly 3 continues to operate, causing the eccentric die 21 to move downwards, which in turn causes the eccentric cutting edges 212 on both sides of the eccentric die 21 to move downwards, cutting off the thicker flash around the eccentric shaft 61 and eccentric block 62 of the blank 6 until the eccentric positioning surface 211 is in contact with the upper part of the eccentric shaft 61 and eccentric block 62, thus completing the complete removal of the flash. Since the concentric positioning surface 221 on the concentric die 22 is in contact with the concentric shaft 63 at the end of the blank 6 before cutting off the flash around the eccentric block 62 and eccentric shaft 61, the concentric positioning surface 221 on the concentric die 22 is in contact with the concentric shaft 63 at the end of the blank 6, thereby achieving the positioning of the concentric shaft 63 and preventing the slender positioning shaft 63 from tilting upwards. Compared with the use of anti-tilting protrusions, this can effectively avoid the overall deformation of the blank 6 during the cutting process, which would affect the subsequent shaping operation. Thus, the cutting accuracy of the blank 6 is improved.

[0025] After the trimming is completed, as follows Figure 5 and Figure 6 As shown, at this time, the concentric die 22 moves to the trimming station relative to the eccentric die 21. At this time, the concentric cutting blade 222 and the eccentric cutting blade 212 combine to form a frame-shaped cutting blade. That is, the frame-shaped cutting blades are connected end to end to form a frame-shaped structure. The punch 2 is in contact with the upper part of the blank 6. Then, the lifting component 3 drives the punch 2 to move upward, so that the punch 2 is separated from the blank 6, making it convenient to take out the blank 6 after trimming.

[0026] like Figures 1-3 As shown, the trimming mold of this utility model also includes a frame 5. Specifically, the frame 5 includes a horizontal base 51, a lower mold base 1 fixed above the base 51, an inverted U-shaped bracket 52 fixed above the base 51, the lower mold base 1 located inside the bracket 52, and a guide sleeve 521 extending vertically fixed at the top of the bracket 52. The lifting assembly 3 includes a hydraulic cylinder 31, the cylinder of the hydraulic cylinder 31 fixed to the top of the bracket 52 and vertically downward, and a horizontal lifting plate 32 fixedly connected to the bottom end of the piston rod. The length of the lifting plate 32 is... The direction is parallel to the length direction of the lower mold base 1. Above the lifting plate 32, there is a guide rod 33 that extends vertically and slides in a corresponding manner with the guide sleeve 521. The top of the guide rod 33 is fixed with a limit plate 34. The outer diameter of the limit plate 34 is larger than the inner diameter of the guide sleeve 521 to prevent the guide rod 33 from disengaging from the guide sleeve 521. Thus, the output end of the lifting assembly 3 is the lifting plate 32 that moves vertically through the sliding engagement of the guide rod 33 and the guide sleeve 521. The lifting plate 32 is connected to the punch 2 to control the lifting and lowering movement of the punch 2.

[0027] A further improvement is that the lifting plate 32 is connected to the eccentric punch 21, and the eccentric punch 21 is connected to the concentric punch 22 through the axially vertical compression spring 23. The eccentric punch 21 is also fixedly connected to the positioning member 24. In the trimming position, the concentric punch 22 abuts against the bottom of the positioning member 24.

[0028] This design utilizes a compression spring 23 acting on the concentric die 22, allowing it to move relative to the eccentric die 21 to a positioning position without external force. At this position, the lifting assembly 3 lowers the punch 2, allowing the concentric cutting edge 222 of the concentric die 22 to first act on the flash around the concentric shaft 63 of the blank 6. The pressure of the compression spring 23 removes the flash around the concentric shaft 63, ensuring the concentric positioning surface 221 fits against the upper part of the concentric shaft 63 of the blank 6. The lifting assembly then... Part 3 continues to drive the eccentric die 21 of punch 2 to move downward, while the concentric positioning surface 221 abuts against the concentric shaft 63 to prevent the concentric shaft 63 from tilting upward when the subsequent eccentric cutting edge 212 cuts off the flash around the eccentric block 62 and the eccentric shaft 61. After the eccentric die 21 cuts off the flash around the eccentric block 62 and the eccentric shaft 61, the positioning part 24 above the eccentric die 21 abuts against the concentric die 22, limiting the relative position of the concentric die 22 and the eccentric die 21, so that the concentric die 22 moves to the cutting edge station.

[0029] A further improvement is that the lifting plate 32 is detachably connected to the eccentric die 21, and the eccentric die 21 is detachably connected to the concentric die 22. This design facilitates the replacement of either the eccentric die 21 or the concentric die 22 when the frame-shaped cutting edge of the punch 2 is damaged, avoiding the need to replace the entire punch 2, thus reducing maintenance costs.

[0030] To achieve a detachable connection between the lifting plate 32 and the eccentric die 21, the eccentric die 21 is fixedly connected to the lifting plate 32 by threaded locking bolts 25 and locking nuts 26. The locking bolt 25 includes a locking cap 251, a first screw 252, and a second screw 253, which are coaxially connected and have successively decreasing outer diameters. The locking nut 26 and the locking cap 251 are respectively clamped on both sides of the lifting plate 32. The locking nut 26 is threaded to the first screw 252, and the second screw 253 is threaded to the eccentric die 21. In this utility model, there are two locking bolts 25, which are distributed along the length direction of the lower die base 1.

[0031] After adopting the above structure, the locking bolt 25 and the eccentric die 21 are detachably connected by connecting the second screw 253 of the locking bolt 25 to the eccentric die 21. The locking nut 26 is screwed into the first screw 252, and the lifting plate 32 is fixed by clamping the locking nut 26 and the locking cap 251, thus achieving a fixed connection between the locking bolt 25 and the lifting plate 32. When the locking nut 26 is loosened, the locking bolt 25 and the lifting plate 32 can be easily separated. In this way, the detachable connection between the eccentric die 21 and the lifting plate 32 is achieved.

[0032] To achieve a detachable connection between the eccentric die 21 and the concentric die 22, a fastening bolt 27 penetrating the lifting plate 32 is threadedly connected to the top of the concentric die 22. The two ends of the compression spring 23 abut against the concentric die 22 and the lifting plate 32 respectively. Furthermore, as... Figure 7 and Figure 8 As shown, the concentric die 22 and the eccentric die 21 are integrally formed with a groove extending in the vertical direction on the side adjacent to each other, and the eccentric die 21 and the concentric die 22 are integrally formed with a protrusion extending in the vertical direction on the side adjacent to each other. The protrusion and the groove are adapted to each other and slide together, thus realizing the relative sliding connection between the concentric die 22 and the eccentric die 21; in addition, it also facilitates the replacement of the compression spring 23.

[0033] In order to limit the position of the concentric die 22, in this utility model, the positioning member 24 is a positioning plate clamped between the first screw 252 and the eccentric die 21. The two ends of the positioning plate extend to the top of the concentric die 22, so as to conveniently limit the top of the sliding position of the concentric die 22 relative to the eccentric die 21.

[0034] A further improvement is that the bottom end of the lifting plate 32 and the top end of the concentric die 22 are respectively provided with an upper limit tube 321 and a lower limit tube 223 with coaxial center lines, and the top and bottom ends of the compression spring 23 are respectively located inside the upper limit tube 321 and the lower limit tube 223. Specifically, the compression spring 23 is sleeved outside the fastening bolt 27, which facilitates the limitation of the position of the compression spring 23 and prevents it from dislodging from the lifting plate 32 and the concentric die 22.

[0035] A further improvement is that a support component 4 is provided on the inner side of the positioning cavity 11, which is used to horizontally support the blank 6.

[0036] By setting the support component 4, the blank 6 can be horizontally supported, avoiding the blank 6 from being easily skewed due to the burrs around the blank 6 contacting the top surface of the lower die base 1. In other words, by horizontally supporting the blank 6 with the support component 4, the horizontal placement angle of the blank 6 is guaranteed, which is beneficial to improving the cutting accuracy.

[0037] A further improvement is that the support assembly 4 includes a telescopic unit and support members 41 spaced apart along the length direction of the positioning lower cavity 11. The telescopic unit drives the support members 41 to move in the vertical direction. The telescopic unit includes an electromagnet 42 and a permanent magnet 43 distributed in the vertical direction. Of the two, one of the electromagnet 42 and the permanent magnet 43 is fixedly connected to the support member 41, and the other is fixedly connected to the lower mold base 1.

[0038] Specifically, the positioning cavity 11 is elongated, and the support members 41 are spaced apart along the length of the lower mold base 1. The top surfaces of the support members 41 are adapted to each other. The two support members 41 at the ends are close to the inner walls of the two ends of the positioning cavity 11. This ensures the support range of the support members 41, increases the support nodes, and ensures that the support members 41 can support the concentric shaft 63 at the end of the blank 6 and the eccentric block 62 and eccentric shaft 61 in the middle position. This avoids the slender concentric shaft 63 bending downwards due to the concentric die 22 pressing down on the concentric shaft 63 at the end of the blank 6 after the flash around the concentric shaft 63 is first removed. The top surfaces of the support members 41 are adapted to each other, which can further ensure that the blank 6 supported by the support members 41 remains in a horizontal state.

[0039] The telescopic unit can drive the support member 41 to move up and down. In the initial stage, such as Figure 1 As shown, the top of part of the support member 41 is higher than the top surface of the lower mold base 1, which facilitates the positioning of the placed blank 6. Then, the support member 41 is lowered by the telescopic unit to the position shown. Figure 4 The position facilitates the lifting assembly 3 to drive the punch 2 down to remove the flash.

[0040] More specifically, the bottom of each support member 41 is integrally fixedly connected by a horizontal base plate 44. Some support members 41 also have guide holes 411 extending in the vertical direction at their bottom. The guide holes 411 are blind holes. The support assembly 4 also includes guide posts 45 that correspond one-to-one with the guide holes 411. The guide posts 45 extend in the vertical direction and are fixed at their bottom ends above the base 51. The guide holes 411 and the guide posts 45 are slidably engaged. The electromagnet 42 is fixed at the top of the guide post 45, and the permanent magnet 43 is fixed at the bottom of the guide hole 411.

[0041] With the above structure, the sliding fit of the guide hole 411 and guide post 45 facilitates the stable lifting and lowering movement of the support member 41 in the vertical direction. By changing the current passing through the electromagnet 42, the magnetic field generated by the electromagnet 42 can be changed, thereby changing the magnetic repulsion force between the electromagnet 42 and the permanent magnet 43, so as to control the lifting and lowering movement of the support member 41. Thus, before trimming, the current of the electromagnet 42 is increased, so that the support member 41 moves up to the top and is located above the lower die base 1, which makes it convenient to place the blank 6 on the support member 41. Then the current is reduced, so that the support member 41 descends. While keeping the flash of the blank 6 in contact with the top surface of the lower die base 1, the current passing through the electromagnet 42 is maintained to support the blank 6. Then the lifting assembly 3 drives the punch 2 to descend, and the concentric punch 22 and the eccentric punch 21 are used to cut off the flash around the concentric shaft 63 of the blank 6 and the flash around the eccentric shaft 61 and the eccentric block 62, respectively.

[0042] In addition, the telescopic unit uses electromagnets 42 and permanent magnets 43 with magnetic repulsion, which allows the support 41 and the blank 6 to have a certain downward space during the trimming process. This avoids excessive downward pressure from the punch 2, which could cause deformation of the blank 6, especially at the position of the concentric shaft 63. The descent of the support 41 and the blank 6 provides a certain buffer, further ensuring the trimming quality and improving the final product molding quality.

[0043] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present utility model, and these improvements and modifications should also be considered within the protection scope of the present utility model.

Claims

1. A high-precision trimming die for a single-cylinder crankshaft of an engine, characterized in that, include: The lower mold base is horizontally positioned, and a positioning cavity is opened on the top surface; A punch, positioned directly above the lower die base and having a frame-shaped cutting edge for removing flash from the blank, includes an eccentric die corresponding to the eccentric shaft and eccentric block of the blank, and a concentric die corresponding to the concentric shaft of the blank and sliding vertically at both ends of the eccentric die. The bottom surface of the eccentric die is an eccentric positioning surface, and the two sides of the eccentric positioning surface are eccentric cutting edges. The bottom surface of the concentric die is a concentric positioning surface, and the two sides of the concentric positioning surface and the end opposite to the eccentric positioning surface are concentric cutting edges. The two ends of the sliding trajectory of the concentric die relative to the eccentric die are respectively a trimming station and a positioning station. In the positioning station, the concentric positioning surface is located below the eccentric positioning surface. In the trimming station, the concentric cutting edge and the eccentric cutting edge combine to form the frame-shaped cutting edge. The projection of the frame-shaped cutting edge on the horizontal plane is located inside the projection of the edge of the lower cavity opening on the horizontal plane. The lifting assembly has its output end connected to the punch.

2. The high-precision trimming die for a single-cylinder crankshaft of an engine according to claim 1, characterized in that: The output end of the lifting assembly is connected to the eccentric die. The eccentric die is connected to the concentric die via an axially vertical compression spring. The eccentric die is also fixedly connected to a positioning component. In the trimming position, the concentric die abuts against the bottom of the positioning component.

3. The high-precision trimming die for a single-cylinder crankshaft of an engine according to claim 2, characterized in that: The output end of the lifting component is detachably connected to the eccentric die, and the eccentric die is detachably connected to the concentric die.

4. The high-precision trimming die for a single-cylinder crankshaft of an engine according to claim 3, characterized in that: The output end of the lifting assembly is a horizontal lifting plate. The eccentric die is fixedly connected to the lifting plate by a threaded locking bolt and a locking nut. The locking bolt includes a locking nut, a first screw, and a second screw that are coaxially connected and have successively decreasing outer diameters. The locking nut and the locking nut are respectively clamped on both sides of the lifting plate. The locking nut is threadedly connected to the first screw, and the second screw is threadedly connected to the eccentric die.

5. The high-precision trimming die for a single-cylinder crankshaft of an engine according to claim 4, characterized in that: The positioning element is a positioning plate clamped between the first screw and the eccentric die, with both ends of the positioning plate extending above the concentric die.

6. The high-precision trimming die for a single-cylinder crankshaft of an engine according to claim 4, characterized in that: The top of the concentric die is threaded with a fastening bolt that passes through the lifting plate, and the two ends of the compression spring abut against the concentric die and the lifting plate, respectively.

7. The high-precision trimming die for a single-cylinder crankshaft of an engine according to claim 6, characterized in that: The bottom end of the lifting plate and the top end of the concentric die are respectively provided with an upper limit tube and a lower limit tube with a coaxial center line, and the top and bottom ends of the compression spring are respectively provided in the upper limit tube and the lower limit tube.

8. The high-precision trimming die for a single-cylinder crankshaft of an engine according to any one of claims 1-7, characterized in that: A support assembly is provided on the inner side of the positioning cavity, and the support assembly is used to horizontally support the blank.

9. The high-precision trimming die for a single-cylinder crankshaft of an engine according to claim 8, characterized in that: The support assembly includes a telescopic unit and support members spaced apart along the length direction of the lower cavity. The telescopic unit drives the support members to move in the vertical direction.

10. The high-precision trimming die for a single-cylinder crankshaft of an engine according to claim 9, characterized in that: The telescopic unit includes an electromagnet and a permanent magnet distributed along the vertical direction. Of the electromagnet and the permanent magnet, one is fixedly connected to the support member, and the other is fixedly connected to the lower mold base.

Images