Clamp for turning crank throw

Abstract

The utility model discloses a clamp for turning a crank throw, which is matched with a turning lathe for installation and comprises a first clamping assembly, the first clamping assembly comprises a fixed clamping block and a movable clamping block which are clamped along the Z direction, and the movable clamping block and the fixed clamping block are detachably fixed through at least one connecting piece. The fixed clamping block is connected with a plurality of first balancing weights which are detachably connected, the fixed clamping block is further provided with a first positioning piece and a second positioning piece which are used for conducting Y-direction positioning on the turning crank throw, and the first positioning piece and the second positioning piece are both detachably connected with the fixed clamping block. The crankshaft crank throw turning device solves the problem that in the prior art, a hydraulic pressing mode is unstable in pressure, and consequently the precision and efficiency of turning operation of a crank throw on a crankshaft are affected.

Description

Technical Field

[0001] The utility model relates to the technical field of clamps, in particular to a clamp used for turning a crank. Background Art

[0002] The crankshaft is one of the most difficult core parts of the internal combustion engine to process, and mainly includes the front end shaft, connecting rod journal, crank, crankshaft journal, crank throw and rear end shaft. In the prior art, the main journal, connecting rod journal and crank throw of the crankshaft are all processed by turning technology.

[0003] During the processing of the crankshaft's crank, the crankshaft needs to be fixed and positioned. In the prior art, the crankshaft is mostly fixed by hydraulic fixing. Since the crank is eccentric in both directions, it needs to be oriented and aligned; since hydraulic clamping is used, the crank is heavy and the hydraulic pressure varies, which will cause the hydraulic clamping force to be unreliable, and the crankshaft will move during the processing, affecting the accuracy and efficiency of the crank turning operation on the crankshaft. Utility Model Content

[0004] In view of the deficiencies in the prior art, the utility model provides a clamp for turning a crankshaft, which solves the problem of unstable pressure in the hydraulic clamping method in the prior art, which affects the accuracy and efficiency of the crank turning operation on the crankshaft.

[0005] To achieve the above-mentioned purpose, the utility model adopts the following technical solutions: a clamp for turning a crank, which is installed in cooperation with a turning lathe, and the clamp includes a first clamping assembly, and the first clamping assembly includes a fixed clamping block and a movable clamping block for clamping along the Z direction, and the movable clamping block and the fixed clamping block are detachably fixed by at least one connecting piece, and a plurality of first counterweight blocks that are detachably connected are connected to the fixed clamping block, and a first positioning piece and a second positioning piece for positioning the turned crank in the Y direction are also provided on the fixed clamping block, and the first positioning piece and the second positioning piece are both detachably connected to the fixed clamping block.

[0006] Compared with the prior art, the utility model has the following beneficial effects:

[0007] During the crankshaft cranking process, the two ends of the crankshaft are connected to the main shaft and tailstock of the lathe respectively, the fixture and the main shaft of the turning lathe are relatively fixed, and the rotation of the main shaft drives the fixture and the crankshaft to rotate to turn the crankshaft's crank.

[0008] In order to achieve the relative fixation of the crankshaft and the lathe spindle, the connecting piece of the utility model adopts a mechanical connecting piece, such as screws, bolts, screws, etc., which can realize the detachable fixation of the movable clamp and the fixed clamp, and can eliminate the problem of poor pressure stability during hydraulic clamping. The mechanical locking method can effectively lock the crankshaft, and the locking effect is better than the hydraulic clamping method; and the setting of multiple counterweights can reduce vibration, ensure the processing accuracy of the turning process, and ensure product quality; the setting of the first locating piece and the second locating piece is based on the layout of two cranks with opposite convex directions on the crankshaft. The first locating piece and the second locating piece are respectively positioned in cooperation with the two cranks to ensure that the clamped crankshaft and the turning lathe are adapted to the position.

[0009] Furthermore, the connecting piece includes a connecting bolt and a fixing nut threadedly connected to the connecting bolt, the connecting bolt is hinged to the fixed clamp block and clamped to the movable clamp block, the connecting bolt is clamped to the movable clamp block, and the fixing nut is rotated to lock the fixed clamp block and the movable clamp block.

[0010] Furthermore, the first clamping assembly further comprises a connecting plate, on which a mounting through hole is provided along the X direction.

[0011] The fixed clamp block is slidably connected to the connection plate along the Z direction, and the clamping space formed by the fixed clamp block and the movable clamp block is arranged opposite to the through hole direction of the installation through hole.

[0012] Furthermore, a plurality of strip-shaped through grooves arranged along the Z direction are formed on the fixed clamping block, at least one locking screw is clamped in each strip-shaped through groove, and the locking screw and the connecting plate thread are detachably fixed.

[0013] Furthermore, the first positioning member includes a positioning block detachably connected to the fixed clamp block and a first positioning rod connected to the positioning block, and the first positioning rod moves along the Y direction to abut and fix with the crank.

[0014] Furthermore, the second positioning member includes a protrusion detachably connected to the fixed clamp block and a second positioning rod connected to the protrusion, the second positioning rod is located above the first positioning rod, and the second positioning rod moves along the Y direction to abut and fix with the crank.

[0015] Furthermore, the multiple first counterweight blocks are divided into a main configuration block and multiple auxiliary counterweight blocks. The main counterweight block is located in the direction of the fixed clamp block and is detachably connected to the fixed clamp block. The multiple auxiliary counterweight blocks are arranged in an overlapping manner along the X direction, and the main counterweight block and the auxiliary counterweight blocks or any two adjacent auxiliary counterweight blocks can be detachably connected.

[0016] Furthermore, the bottoms of the main counterweight block and the auxiliary counterweight block are both in an arc-shaped structure protruding away from the fixed clamping block.

[0017] Furthermore, it also includes a second clamping assembly, the second clamping assembly and the first clamping assembly are spaced and arranged relative to each other along the X direction,

[0018] The second clamping assembly includes a fixed clamping seat and a movable clamping seat for clamping along the Z direction. The movable clamping seat and the fixed clamping seat are detachably fixed through a connecting piece. The fixed clamping seat is connected to a plurality of detachably connected second counterweight blocks.

[0019] Furthermore, it also includes a fixed plate, which is provided with a connecting through hole arranged along the X direction. The fixed clamp seat is slidably connected to the fixed plate along the Z direction, and the clamping space formed by the fixed clamp seat and the movable clamp seat is arranged opposite to the through hole direction of the connecting through hole. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic structural diagram of a crankshaft of the utility model;

[0021] Figure 2 It is a structural schematic diagram of the fixture and crankshaft of the utility model;

[0022] Figure 3 for Figure 2 A schematic diagram of a structure in which the crankshaft is removed;

[0023] Figure 4 This is an exploded view of the structure of the first clamping assembly of the utility model;

[0024] Figure 5 It is a structural explosion diagram of the second clamping assembly of the utility model.

[0025] In the figure: connecting plate 1, mounting through hole 110, slide groove 12, connecting bolt 2, fixing nut 21, first counterweight 3, main counterweight 31, auxiliary counterweight 32, fixing clamp block 4, locking screw 41, strip through groove 42, positioning block 51, first positioning rod 52, protrusion 62, second positioning rod 61, movable clamp block 7, movable clamp seat 8, fixing clamp seat 9, second counterweight 10, fixing plate 11, connecting through hole 111, crankshaft 101, cylindrical structure 102, second crank 103, first crank 104. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0027] like Figure 1As shown, it is the structure of the crankshaft 101 processed and formed by the utility model. The crankshaft 101 is provided with two cranks along its length direction. The two cranks are divided into a first crank 104 and a second crank 103. Since the two cranks are eccentrically opposite, in order to ensure that the two cranks can rotate simultaneously with the main shaft of the turning lathe during the processing and are relatively fixed to improve the processing accuracy, it is necessary to ensure that the fixture can clamp and fix the crankshaft 101, and to ensure that the crankshaft 101 can be positioned on the fixture when different cranks on the crankshaft 101 are processed. Based on this, the utility model provides a fixture for turning cranks.

[0028] like Figure 2 , 3 As shown in , 4, a clamp for turning a crankshaft includes a first clamping assembly, wherein the first clamping assembly includes a fixed clamping block 4 and a movable clamping block 7 for clamping along the Z direction, wherein the movable clamping block 7 is detachably fixed to the fixed clamping block 4 by at least one connecting member, wherein a plurality of first counterweight blocks 3 that are detachably connected are connected to the fixed clamping block 4, and a first positioning member and a second positioning member for positioning the turned crankshaft in the Y direction are also provided on the fixed clamping block 4, wherein the first positioning member and the second positioning member are both detachably connected to the fixed clamping block 4. The crankshaft 101 is horizontally arranged in the turning lathe, and the length direction of the crankshaft 101 is arranged along the X direction. In theory, the movable clamping block 7 and the fixed clamping block 4 can clamp the crankshaft 101 in any direction perpendicular to the X direction. In order to facilitate the movable clamping block 7 and the fixed clamping block 4, and also to limit the installation position of other components, the utility model limits the movable clamping block 7 and the fixed clamping block 4 to clamp along the Z direction. Correspondingly, the movable clamp block 7 and the fixed clamp block 4 are used to clamp the cylindrical structure 102 of the crankshaft 101. To this end, one side of the movable clamp block 7 and the fixed clamp block 4 used to clamp the crankshaft 101 is an arc groove structure adapted to the cylindrical structure 102. In the present utility model, the fixed clamp block 4 and the main shaft of the turning lathe are relatively fixed, ensuring that the crankshaft 101 fixed by the first clamping assembly can rotate simultaneously with the main shaft of the turning lathe. In order to avoid the problem of unstable pressure caused by hydraulic clamping in the prior art, the movable clamp block 7 and the fixed clamp block 4 of the utility model are detachably connected by mechanical connecting parts, such as screws, bolts, screws, etc., which can realize the detachable fixation of the movable clamp block 7 and the fixed clamp block 4, and can eliminate the problem of poor pressure stability during hydraulic clamping. The mechanical locking method can effectively lock the crankshaft 101, and the locking effect is better than that of the hydraulic clamping method; and the setting of multiple counterweights can reduce vibration, ensure the processing accuracy of the turning process, and ensure product quality; the setting of the first positioning member and the second positioning member is based on two cranks with opposite directions on the crankshaft 101, and the first positioning member and the second positioning member are respectively positioned in cooperation with the two cranks to ensure that the clamped crankshaft 101 and the turning lathe are adapted to the position.

[0029] The main function of the connecting piece is to realize the detachable connection between the fixed clamp block 4 and the movable clamp block 7. For this purpose, the connecting piece can adopt other structures that can realize the above functions in addition to the threaded rod. Figure 3 , 4 As shown, the connecting member of the utility model is a connecting bolt 2, and there are also multiple ways to connect the connecting bolt 2 with the fixed clamp block 4 and the movable clamp block 7. The connecting bolt 2 can be connected with the fixed clamp block 4 and the movable clamp block 7 by threaded holes. A threaded hole with a through hole structure and a threaded hole with a blind hole structure are respectively provided on the fixed clamp block 4 and the movable clamp block 7. The connecting bolt 2 is passed through the two threaded holes to achieve a fixed connection between the fixed clamp block 4 and the movable clamp block 7. Of course, two through holes can also be provided on the fixed clamp block 4 and the movable clamp block 7, respectively, and the connecting bolt 2 is passed through the two through holes and fixed by a nut. In this embodiment, in order to avoid the connection bolt 2 from being lost during use, the connecting member includes a connecting bolt 2 and a fixing nut 21 threadedly connected to the connecting bolt 2, the connecting bolt 2 is hinged to the fixed clamp block 4 and clamped with the movable clamp block 7, the connecting bolt 2 is clamped with the movable clamp block 7, and the fixing nut 21 is rotated to lock the fixed clamp block 4 and the movable clamp block 7. The connecting bolt 2 is hinged to the fixed clamp block 4. The connecting bolt 2 and the movable clamp block 7 can be separated or clamped by rotating the connecting bolt 2, and the fixed clamp block 4 and the movable clamp block 7 can be fixed or separated by rotating the fixing nut 21. Of course, if a connecting screw is provided, the fixed clamp block 4 and the movable clamp block 7 can also be hinged to achieve effective clamping of the crankshaft 101. In this embodiment, the number of connecting members is two, and the two connecting members are arranged at intervals along the Y direction. Each connecting member includes a connecting bolt 2 and a fixing nut 21 threadedly connected to the connecting bolt 2. The provision of two connecting members can completely separate the movable clamp block 7 from the fixed clamp block 4. At the same time, this method is also adapted to the crankshaft 101. When the diameter of the cylindrical structure 102 of the crankshaft 101 changes, the crankshaft 101 can be calibrated.

[0030] Since there are two cranks on the crankshaft 101, the diameters of the two adjacent cylindrical structures 102 of the two cranks are different. Therefore, after the first crank 104 of the crankshaft 101 is processed, the second crankshaft 101 needs to be clamped and fixed. After the crankshaft 101 is clamped and fixed, it is also necessary to ensure that the center line of the cylindrical structure 102 at this end is in line with the center line of the main shaft. Therefore, the fixed clamp block 4 needs to be able to slide along the Z direction to adapt to the cylindrical structures 102 of the crankshaft 101 with different diameters. Figure 4As shown, for this purpose, the first clamping assembly of the utility model also includes a connecting plate 1, on which a mounting through hole 110 is opened along the X direction, and the fixed clamp block 4 is slidably connected to the connecting plate 1 along the Z direction, and the clamping space formed by the fixed clamp block 4 and the movable clamp block 7 is arranged relative to the through hole direction of the mounting through hole 110. The arrangement of the mounting through hole 110 is to facilitate the placement of cylindrical structures 102 of different lengths of the crankshaft 101. The connecting plate 1 is fixed to the main shaft of the turning lathe, so that the main shaft and the fixed clamp block 4 are relatively fixed. Figure 4 As shown, the connection plate 1 is a disc structure, the mounting through hole 110 is arranged along the center direction of the connection plate 1, the fixed clamp block 4 is arranged on one of the circular side walls of the connection plate, and the other circumferential side wall of the connection plate 1 is fixed to the main shaft (dial) of the lathe. The fixed clamp block 4 is slidably connected on the connection plate 1 along the Z direction, and the two cylindrical structures 102 of different diameters of the crankshaft 101 can be calibrated and fixed, ensuring that the center line of the cylindrical structure 102 fixed by the fixed clamp block 4 and the movable clamp block 7 is arranged in a colinear manner with the center line of the main shaft.

[0031] In order to adjust the fixed clamp block 4 in a specific direction, the utility model provides a plurality of strip-shaped through slots 42 arranged along the Z direction on the fixed clamp block 4, and at least one locking screw 41 is clamped in each strip-shaped through slot 42, and the locking screw 41 and the connecting plate 1 are threadably fixed. Figure 3 , 4 As shown, two locking screws 41 are provided in each strip-shaped through groove 42, and the locking screws 41 can be single-headed bolts, double-headed bolts, etc., which can realize the locking of the fixed clamping block 4 and the connecting plate 1 by threaded connection. The movement of the fixed clamping block 4 can be adjusted by loosening the locking screws 41, or by changing the weight of the first counterweight 3.

[0032] The multiple first counterweight blocks 3 are divided into a main counterweight block and multiple auxiliary counterweight blocks 32. The main counterweight block 31 is located in the direction of the fixed clamp block 4 and is detachably connected to the fixed clamp block 4. The multiple auxiliary counterweight blocks 32 are arranged in sequence and overlapped along the X direction, and the main counterweight block 31 and the auxiliary counterweight block 32 or any two adjacent auxiliary counterweight blocks 32 can be detachably connected. The main function of the multiple first counterweight blocks 3 is to reduce vibration. Because the crankshaft 101 rotates and the crank is eccentrically arranged, there is an eccentric force to the outside during the rotation process. Arranging multiple first counterweight blocks 3 on the opposite side of the crank protrusion can reduce the centrifugal effect during the rotation process. For this reason, Figure 3 , 4As shown, the main counterweight block 31 provided in the utility model is located below the fixed clamp block 4 and fixed to the fixed clamp block 4, and a plurality of auxiliary counterweight blocks 32 are arranged in sequence and overlapped along the X direction. By changing the different numbers of auxiliary counterweight blocks 32, the adjustment of the counterweight of the fixed clamp block 4 can be realized, which can change the position of the fixed clamp block 4 in the vertical direction without changing the position of the locking bolt, and can adapt to the crank structure to reduce the vibration during the rotation process. In order to make the centrifugal force of the main counterweight block 31 and the auxiliary counterweight smaller during the rotation process, the bottom of the main counterweight block 31 and the auxiliary counterweight block 32 in the utility model are both in an arc-shaped structure protruding away from the fixed clamp block 4.

[0033] In order to make the fixed clamp block 4 slide on the connection disk 1 along a specific direction, a limit slider can be set between the connection disk 1 and the fixed clamp block 4. The limit slider is fixed to the fixed clamp block 4 (or the connection disk 1). A slide groove 12 set in the Z direction is opened on the connection disk 1 (or the fixed clamp block 4). The limit slider and the slide groove 12 are slidably connected to limit the sliding direction of the fixed clamp block 4 along the connection disk 1. Figure 4 As shown, in this embodiment, the slide groove 12 is opened on the connecting disk 1.

[0034] After the movable clamp 7 and the fixed clamp 4 are in place, the first crank 104 or the second crank 103 needs to be positioned by the first positioning member or the second positioning member. For this purpose, the utility model provides a first positioning member adapted to the first crank 104 and a second positioning member adapted to the second crank 103.

[0035] Specifically, Figure 3 , 4 As shown, the first positioning member includes a positioning block 51 detachably connected to the fixed clamp block 4 and a first positioning rod 52 connected to the positioning block 51, and the first positioning rod 52 moves along the Y direction and is fixed against the crank. The first positioning rod 52 is a screw structure, and the first positioning rod 52 is threadedly connected to the positioning block 51. Rotating the first positioning rod 52 can realize the movement of the first positioning rod 52 along the Y direction, and the first positioning rod 52 is fixed against the position of the first crank 104 close to the cylindrical structure 102 of the crankshaft 101, so as to realize the positioning function. The positioning block 51 is detachably fixed to the fixed clamp block 4 by bolts. When processing the first crank 104, the positioning block 51 and the fixed clamp block 4 are fixed, and the first positioning rod 52 is in action, and the second positioning member and the fixed clamp block 4 are disassembled. When processing the second crank 103, the positioning block 51 and the fixed clamp block 4 are disassembled, and the second positioning member and the fixed clamp block 4 are connected.

[0036] like Figure 3 , 4As shown, the second positioning member includes a protrusion 62 detachably connected to the fixed clamp block 4 and a second positioning rod 61 connected to the protrusion 62. The second positioning rod 61 is located above the first positioning rod 52, and the second positioning rod 61 moves along the Y direction and is fixed against the crank. The second positioning member is mainly used in conjunction with the cylindrical structure 102 of the crankshaft 101. For this purpose, the second positioning rod 61 is located above the first positioning rod 52. The overall structure of the second positioning member is similar to that of the first positioning member. The protrusion 62 and the fixed clamp block 4 are detachably connected. The second positioning rod 61 adopts a bolt structure. The second positioning rod 61 and the protrusion 62 are threadedly connected. Rotating the second positioning rod 61 can realize the movement of the second positioning rod 61 along the Y direction, and the second positioning rod 61 is against the cylindrical structure 102 adjacent to the second crank 103 to achieve the positioning function.

[0037] In another embodiment of the present invention, since the crankshaft 101 has a certain length, even if the first clamping assembly fixes one end of the crankshaft 101 and the other end of the crankshaft 101 is connected to the tailstock of the lathe, there is still a problem of rotation shaking. Therefore, in order to further improve the stability of the crankshaft 101 during rotation, this embodiment further provides a second clamping assembly. Figure 2 , 3 As shown in , 5, the second clamping assembly and the first clamping assembly are spaced and arranged relatively along the X direction, and the second clamping assembly includes a fixed clamp seat 9 and a movable clamp seat 8 clamped along the Z direction, the movable clamp seat 8 is detachably fixed to the fixed clamp seat 9 by a connecting piece, and the fixed clamp seat 9 is connected to a plurality of detachably connected second counterweight blocks 10. The structure of the second clamping assembly is similar to the overall structure of the second clamping assembly, and the role of the second counterweight block 10 on the fixed clamp seat 9 is the same as the role of the first counterweight block 3 on the fixed clamp block 4. With reference to the use of the various components of the first clamping assembly (excluding the first positioning member and the second positioning member), the use, positional relationship, and connection relationship of the various components of the second clamping assembly are all the same, and for this reason, the use principle and matching relationship of the second clamping assembly will not be described in detail.

[0038] Of course, in order to facilitate the connection between the second clamping assembly and the lathe tailstock, the second clamping assembly also includes a fixing plate 11, such as Figure 3 , 5 As shown, the fixed disk 11 is provided with a connecting through hole 111 arranged along the X direction, the fixed clamp seat 9 is connected to the fixed disk 11 by sliding along the Z direction, and the clamping space formed by the fixed clamp seat 9 and the movable clamp seat 8 is arranged opposite to the through hole direction of the connecting through hole 111. The fixed disk 11 is equivalent to the connecting disk 1, the function of the connecting through hole 111 is equivalent to the installation through hole 110, and the setting mode of the fixed clamp seat 9 on the fixed disk 11 is equivalent to the setting mode of the fixed clamp block 4 on the connecting disk 1. Therefore, referring to the connection mode of the fixed clamp block 4 and the connecting disk 1, the same structure can be used to realize the sliding and connection of the fixed clamp seat 9 on the fixed disk 11.

[0039] The coordinated use of the first clamping assembly and the second clamping assembly can make the crankshaft 101 more fixed during the turning process, so as to rotate coaxially with the main shaft of the lathe for turning processing.

[0040] In summary, the clamp of the utility model adopts mechanical locking, and has a good locking effect; moreover, it can ensure that the center line of the crankshaft 101 (the center line of the cylindrical structure 102 fixed by the first clamping assembly) can be coaxially fixed with the center line of the main shaft, while also reducing the rotational vibration.

[0041] In the present invention, unless otherwise clearly specified and limited, the terms "install", "connect", "connect", "fix" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0042] In the description of the present utility model, it should be noted that the terms "center", "upper", "lower", "left", "right", "inner", "outer", etc. indicate the orientation or position relationship based on the orientation or position relationship shown in the drawings, or the orientation or position relationship in which the utility model product is usually placed when in use, which is only for the convenience of describing the utility model and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present utility model. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0043] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-restrictive from any point of view, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention. Any reference numeral in a claim should not be regarded as limiting the claim to which it relates.

Claims

1. A fixture for turning a crankshaft, mounted in conjunction with a turning lathe, the fixture comprising a first clamping assembly, the first clamping assembly comprising a fixed clamping block (4) and a movable clamping block (7) for clamping along the Z direction, characterized in that: The movable clamp block (7) and the fixed clamp block (4) are detachably fixed via at least one connecting piece, a plurality of first counterweight blocks (3) are detachably connected to the fixed clamp block (4), and a first positioning piece and a second positioning piece for positioning the crankshaft in the Y direction are also provided on the fixed clamp block (4), and the first positioning piece and the second positioning piece are both detachably connected to the fixed clamp block (4).

2. A fixture for turning a crank according to claim 1, characterized in that: The connecting member comprises a connecting bolt (2) and a fixing nut (21) threadedly connected to the connecting bolt (2); the connecting bolt (2) is hingedly connected to the fixing clamp block (4) and clamped to the movable clamp block (7); the connecting bolt (2) is clamped to the movable clamp block (7); the fixing nut (21) is rotated to lock the fixing clamp block (4) and the movable clamp block (7).

3. A fixture for turning a crank according to claim 1 or 2, characterized in that: The first clamping assembly further comprises a connection plate (1), on which a mounting through hole (110) is provided along the X direction. The fixed clamp block (4) is slidably connected to the connection plate (1) along the Z direction, and the clamping space formed by the fixed clamp block (4) and the movable clamp block (7) is arranged opposite to the through hole direction of the installation through hole (110).

4. A fixture for turning a crank according to claim 3, characterized in that: The fixed clamp block (4) is provided with a plurality of strip-shaped through grooves (42) arranged along the Z direction, and at least one locking screw (41) is clamped in each strip-shaped through groove (42). The locking screw (41) and the connecting plate (1) are detachably fixed by threads.

5. A fixture for turning a crank according to claim 1, 2 or 4, characterized in that: The first positioning member comprises a positioning block (51) detachably connected to the fixed clamp block (4) and a first positioning rod (52) connected to the positioning block (51); the first positioning rod (52) moves along the Y direction and abuts against the crank to be fixed.

6. A fixture for turning a crank according to claim 5, characterized in that: The second positioning member comprises a protrusion (62) detachably connected to the fixed clamp block (4) and a second positioning rod (61) connected to the protrusion (62); the second positioning rod (61) is located above the first positioning rod (52), and the second positioning rod (61) moves along the Y direction to abut against the crank and be fixed.

7. A fixture for turning a crank according to claim 1, 2, 4 or 6, characterized in that: The plurality of first counterweight blocks (3) are divided into a main counterweight block and a plurality of auxiliary counterweight blocks (32); the main counterweight block (31) is located in the direction of the fixed clamp block (4) and is detachably connected to the fixed clamp block (4); the plurality of auxiliary counterweight blocks (32) are arranged in sequence and overlapped along the X direction; and the main counterweight block (31) and the auxiliary counterweight block (32) or any two adjacent auxiliary counterweight blocks (32) are detachably connected.

8. A fixture for turning a crank according to claim 7, characterized in that: The bottoms of the main counterweight block (31) and the auxiliary counterweight block (32) are both in an arc-shaped structure that protrudes away from the fixed clamp block (4).

9. A fixture for turning a crank according to claim 1, 2, 4, 6 or 8, characterized in that: The second clamping assembly is also included. The second clamping assembly and the first clamping assembly are spaced and arranged relative to each other along the X direction. The second clamping assembly comprises a fixed clamping seat (9) and a movable clamping seat (8) for clamping along the Z direction. The movable clamping seat (8) and the fixed clamping seat (9) are detachably fixed via a connecting piece. The fixed clamping seat (9) is connected to a plurality of detachably connected second counterweight blocks (10).

10. A fixture for turning a crank according to claim 9, characterized in that: It also includes a fixed disk (11), on which a connecting through hole (111) arranged along the X direction is opened, and the fixed clamp seat (9) is slidably connected to the fixed disk (11) along the Z direction, and the clamping space formed by the fixed clamp seat (9) and the movable clamp seat (8) is arranged opposite to the through hole direction of the connecting through hole (111).

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