Crankshaft machining clamp and machine tool

Abstract

The application discloses a crankshaft machining clamp and a machine tool. The crankshaft machining clamp is provided with a pair of eccentric clamps and limiting mechanisms arranged at the head end and the tail end of the machine tool clamp. One crankshaft machining clamp comprises an eccentric clamp and a limiting mechanism. The eccentric clamp is arranged at one end of the machine tool clamp. The eccentric clamp is provided with a first hole and is used for clamping the main journal of the crankshaft. The center line of the first hole is arranged with an eccentric distance relative to the rotation center line of the machine tool clamp, so that the axis of the connecting rod journal of the crankshaft is collinear with the rotation center line of the machine tool clamp. The eccentric distance is used for being equal to the distance between the axis of the main journal and the axis of the connecting rod journal. The limiting mechanism is connected with one end of the main journal. The limiting mechanism is matched with the eccentric clamp and is used for limiting the rotation of the main journal relative to the eccentric clamp. The machine tool comprises the crankshaft machining clamp.

Description

Technical Field

[0001] This application relates to the field of crankshaft machining fixture technology, and in particular to a crankshaft machining fixture and machine tool. Background Technology

[0002] The crankshaft crankshaft, also known as the connecting rod journal, is a core component for engine power transmission. Its machining accuracy directly affects the engine's operational stability and lifespan. This is especially true for crankshafts with an odd number of crankshafts, such as 5-cylinder crankshafts, where the crankshafts are asymmetrically distributed, making machining significantly more difficult than for crankshafts with an even number of crankshafts. Current technologies primarily use traditional fixtures designed for symmetrically distributed even-numbered crankshafts. When machining the odd-numbered crankshafts of a 5-cylinder crankshaft, the lack of symmetrical crankshaft balance loads results in insufficient stability for the odd-numbered crankshafts. Severe vibrations can also lead to deterioration of the crankshaft surface roughness, resulting in poor cutting quality. Furthermore, adjusting parameters is difficult when changing to produce crankshafts of different specifications, leading to poor adaptability. Utility Model Content

[0003] To solve at least one of the above-mentioned technical problems, this application provides a crankshaft machining fixture and machine tool, and the technical solution adopted is as follows.

[0004] The crankshaft machining fixture provided in this application is arranged in pairs at the head and tail ends of a machine tool fixture. One crankshaft machining fixture includes: An eccentric clamp is provided at one end of the machine tool fixture. The eccentric clamp has a first hole for clamping the main journal of the crankshaft. The center line of the first hole is used to set an eccentric distance relative to the rotation center line of the machine tool fixture so that the axis of the connecting rod journal of the crankshaft is collinear with the rotation center line of the machine tool fixture. The eccentric distance is equal to the distance between the axis of the main journal and the axis of the connecting rod journal. A limiting mechanism is used to connect to one end of the main journal. The limiting mechanism cooperates with the eccentric clamp and is used to limit the rotation of the main journal relative to the eccentric clamp.

[0005] In some embodiments of this application, the eccentric fixture includes a first connecting structure and a second connecting structure. The first connecting structure is used to connect to one end of the machine tool fixture. The first connecting structure is connected to the second connecting structure. The second connecting structure is used to clamp the main journal of the crankshaft. The first connecting structure is used to rotate with the connecting rod journal around the centerline of the machine tool fixture, and the second connecting structure is used to rotate with the main journal around the centerline of the main journal. The distance between the centerline of the machine tool fixture and the centerline of the main journal is the eccentric distance.

[0006] In some embodiments of this application, the first connecting structure includes a transition plate, one side of which is used to connect with the machine tool fixture, and the transition plate is provided with a plurality of bolt holes for adjusting the installation position of the transition plate on the machine tool fixture; the second connecting structure is provided on the other side of the transition plate, and the second connecting structure is provided with the first hole.

[0007] In some embodiments of this application, the transition plate has a boss on the side for connecting with the machine tool fixture. The boss is used to position itself at the edge of the chuck inner hole of the machine tool fixture and to position the transition plate at its installation position.

[0008] In some embodiments of this application, the second connecting structure includes a base and a cover, the base being connected to the first connecting structure, and the base and the cover being connected and used to form a first hole.

[0009] In some embodiments of this application, the base includes a first connecting portion, a mounting portion, and a second connecting portion for connecting the first connecting portion and the mounting portion. The mounting portion is connected to the cover and is used to form a first hole. The second connecting portion is used to create a gap between the first connecting portion and the mounting portion. One end of the first hole communicates with the gap. The limiting mechanism is used to be disposed within the gap and is used to be connected to the end of the main journal. The limiting mechanism acts on the second connecting portion.

[0010] In some embodiments of this application, the limiting mechanism includes a limiting rod and a limiting screw. One end of the limiting rod is connected to one end face of the main journal, and the other end of the limiting rod is provided with a threaded hole perpendicular to the center line of the limiting rod and the main journal. The limiting screw cooperates with the threaded hole and cooperates with the eccentric clamp to limit the rotation of the main journal relative to the eccentric clamp.

[0011] In some embodiments of this application, the limiting rod is installed on a preset plane, the preset plane being parallel to the plane where a crank of the crankshaft is located, the limiting screw being perpendicular to the preset plane, and the limiting rod being used to correspond to different crank settings.

[0012] In some embodiments of this application, the crankshaft machining fixture is provided with an eccentric support frame, which is disposed between two pairs of eccentric fixtures. The eccentric support frame is provided with a fixed frame and an eccentric ring structure. The eccentric ring structure is provided with a second hole for the main journal to pass through. The eccentric ring structure is used to rotate around the center line of the machine tool fixture. The fixed frame is provided with a plurality of elastic support devices, which contact the outer ring surface of the eccentric ring structure and are used to support the eccentric ring structure.

[0013] This application also provides a machine tool including the crankshaft machining fixture as described above.

[0014] This application has at least the following beneficial effects: the paired eccentric fixtures are set at the head and tail ends of the machine tool fixture. Through the preset eccentric distance between the center line of the first hole and the center line of the machine tool fixture, the spindle journal can be driven to rotate stably around the center line of the machine tool fixture, ensuring that the machining trajectory of the connecting rod journal is precisely aligned with the tool feed path. The eccentric fixture has a synergistic effect on the stable clamping of the spindle journal and the reverse rotation restriction of the limiting mechanism, which can limit the spindle journal wobbling caused by the cutting force. Because the vibration is effectively suppressed, the cutting amount can be safely increased.

[0015] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0016] The present application will be further illustrated below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments illustrated in the following drawings are exemplary and are only used to explain the present application, and should not be construed as limiting the present application.

[0017] Figure 1 This is a schematic diagram of the crankshaft machining fixture in one embodiment of this application; Figure 2 This is a side view of a crankshaft machining fixture according to one embodiment of this application. Figure 3 This is a schematic diagram of the limiting mechanism in one embodiment of this application; Figure 4 This is a schematic diagram of an eccentric scaffold structure in one embodiment of this application.

[0018] Reference numerals: eccentric clamp 100; first hole 110; transition plate 120; connecting screw 121; pin 122; positioning shaft 123; second connecting structure 130; base 131; mounting part 1311; second connecting part 1312; gap 1313; cover 132; Limiting mechanism 200; limiting rod 210; limiting screw 220; Eccentric support frame 300; fixed frame 310; lower fixed frame 311; upper fixed frame 312; elastic support device 313; eccentric ring structure 320; second hole 321; gasket 322; V-shaped support block 330; Crankshaft 400; main journal 410; connecting rod journal 420; third connecting part 411. Detailed Implementation

[0019] The following is combined with Figures 1 to 4The embodiments of this application are described in detail below, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0020] In the description of this application, it should be understood that the terms "center", "middle", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0021] In the description of this application, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0022] In the description of this application, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0023] In the description of this application, the use of terms such as "one embodiment," "some embodiments," "an example," "some instances," "some embodiments," "illustrative embodiment," "example," "specific example," and "some examples" indicates that the specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0024] Combination Figure 1 , Figure 3As shown, the crankshaft machining fixture provided in this application is arranged in pairs at the head and tail ends of a machine tool fixture. One crankshaft machining fixture includes: An eccentric clamp 100 is used to be set at one end of a machine tool clamp. The eccentric clamp 100 is provided with a first hole 110 for clamping the main journal 410 of the crankshaft 400. The center line of the first hole 110 is used to set an eccentric distance relative to the rotation center line of the machine tool clamp, so that the axis of the connecting rod journal 420 of the crankshaft 400 is collinear with the rotation center line of the machine tool clamp. The eccentric distance is equal to the distance between the axis of the main journal 410 and the axis of the connecting rod journal 420. The limiting mechanism 200 is used to connect to one end of the main journal 410. The limiting mechanism 200 cooperates with the eccentric clamp 100 and is used to limit the rotation of the main journal 410 relative to the eccentric clamp 100.

[0025] The first hole 110 of the eccentric fixture 100 clamps the main journal 410. During normal crankshaft machining, the first hole 110 prevents relative sliding of the outer wall of the main journal 410. The eccentric fixture 100 rotates around the center line of the machine tool fixture under the drive of the machine tool fixture, thereby causing the main journal 410 to rotate around the center line of the machine tool fixture. The eccentric distance is also the distance between the center line of the connecting rod journal 420 of the crankshaft 400 and the center line of the machine tool fixture. The eccentric distance is set by the eccentric fixture 100 so that the center line of the connecting rod journal 420 coincides with the center line of the machine tool fixture, simplifying the machining trajectory of the connecting rod journal 420 and reducing machining errors. After the connecting rod journal 420 coincides with the center line of the machine tool fixture, the cutting force is always transmitted in a fixed direction, the tool is subjected to more stable force, and a larger cutting amount can be achieved stably. It can also machine crankshafts 400 without asymmetrical cranks.

[0026] The limiting mechanism 200 is connected to one end of the main journal 410. The limiting mechanism 200 is stationary relative to the first hole 110. When the main journal 410 tends to rotate relative to the eccentric jig 100 in the opposite direction of rotation due to the cutting force, the limiting mechanism 200 contacts the eccentric jig 100 and forms a mechanical limit, restricting the relative rotation.

[0027] The paired eccentric fixtures 100 are positioned at the head and tail ends of the machine tool fixture. Through a preset eccentric distance between the centerline of the first hole 110 and the centerline of the machine tool fixture, the main spindle journal 410 can be driven to rotate stably around the centerline of the machine tool fixture. This ensures precise alignment between the machining trajectory of the connecting rod journal 420 and the tool feed path. After the connecting rod journal 420 coincides with the centerline of the machine tool fixture, the cutting force is always transmitted in a fixed direction, resulting in more stable tool force and enabling the stable achievement of larger cutting volumes. It also allows for the machining of crankshafts 400 without asymmetrical cranks. The eccentric fixtures 100 provide stable clamping of the main spindle journal 410, while the limiting mechanism 200 restricts reverse rotation. This limits the wobbling of the main spindle journal 410 caused by the cutting force. Because the vibration is effectively suppressed, the cutting volume can be safely increased.

[0028] In some embodiments, the eccentric clamp 100 includes a first connecting structure and a second connecting structure 130. The first connecting structure is used to connect to one end of the machine tool clamp, and the first connecting structure is connected to the second connecting structure 130. The second connecting structure 130 is used to clamp the main journal 410 of the crankshaft 400. The first connecting structure is used to rotate with the connecting rod journal 420 around the center line of the machine tool fixture, and the second connecting structure 130 is used to rotate with the main journal 410 around the center line of the main journal 410. The distance between the center line of the machine tool fixture and the center line of the main journal 410 is the eccentric distance.

[0029] Before machining the crankshaft 400, the first and second connecting structures 130 are installed on the machine tool fixture to set the required eccentric distance. The separate design of the first and second connecting structures 130 simplifies the control of the machining accuracy of the eccentric distance and makes it easier to adapt to the machining requirements of crankshafts 400 with different eccentric distances.

[0030] Specifically, in combination Figure 2 As shown, the first connecting structure includes a transition plate 120 for connecting to a machine tool fixture. A second connecting structure 130 is located on the opposite side of the transition plate 120 from the machine tool fixture. The second connecting structure 130 has a first hole 110. The transition plate 120 is a flat plate with multiple bolt holes for connecting screws 121. The connecting screws 121 are used to mount the transition plate 120 onto the machine tool fixture. The mounting position of the transition plate 120 on the machine tool fixture can be adjusted before being fixed by the connecting screws 121. The first hole 110 is formed on the second connecting structure 130 for clamping the main journal 410 of the crankshaft 400. The centerline of the first hole 110 is perpendicular to the connecting surface of the transition plate 120. Specifically, the transition plate 120 is fixed around its perimeter by connecting screws 121, and the heads of the connecting screws 121 are concealed within the transition plate 120 through countersunk holes, resulting in a stable connection and a compact structure.

[0031] Furthermore, the transition plate 120 has a boss on the side for connecting to the machine tool fixture. The boss is used to position the transition plate 120 in the machine tool fixture. The machine tool fixture has a chuck, and the boss of the transition plate 120 is positioned at the edge of the chuck's inner hole. The boss positions the transition plate 120 in the machine tool fixture and is fixed in place with the connecting screw 121, thereby improving the stability of the eccentric fixture 100's rotation.

[0032] The transition plate 120 is also provided with a pin hole, through which a pin shaft 122 passes to position the transition plate 120 at the machine tool fixture connection position.

[0033] Combination Figure 1 , Figure 2 As shown, in some embodiments, the second connection structure 130 includes a base 131 and a cover 132. The base 131 is connected to the first connection structure, and the base 131 and the cover 132 are connected and used to form a first hole 110.

[0034] The base 131 is used to connect with the transition plate 120. The transition plate 120 is provided with a protruding positioning shaft 123. The base 131 is provided with a positioning hole, through which the positioning shaft 123 passes for positioning. Alternatively, the transition plate 120 is also provided with a positioning hole, and the positioning shaft 123 passes through the positioning holes of both the transition plate 120 and the base 131 for positioning. The base 131 and the transition plate 120 are connected by screws. The screws can be inserted from one side of the base 131 and reach the transition plate 120, screwing into the threaded holes of the transition plate 120.

[0035] During installation, the main journal 410 is placed on the base 131, and then the cover 132 is placed on the main journal 410. The cover 132 and the base 131 are connected by bolts. The clamping degree of the first hole 110 on the main journal 410 can be adjusted by adjusting the preload of the bolts.

[0036] A shim is added in the first hole 110 to accommodate spindle journals 410 of different diameters.

[0037] Furthermore, the base 131 includes a first connecting portion, a mounting portion 1311, and a second connecting portion 1312 for connecting the first connecting portion and the mounting portion 1311. The mounting portion 1311 is connected to the cover 132 and is used to form a first hole 110. The second connecting portion 1312 is used to create a gap 1313 between the first connecting portion and the mounting portion 1311. One end of the first hole 110 communicates with the gap 1313. The limiting mechanism 200 is used to be disposed in the gap 1313 and is used to be connected to the end of the main journal 410. The limiting mechanism 200 acts on the second connecting portion 1312.

[0038] The first connecting part can be a chassis, which is used to connect with the transition plate 120. The transition plate 120 is provided with a protruding positioning shaft 123, and the chassis is provided with positioning holes. The positioning shaft 123 passes through the positioning holes and is used for positioning. Alternatively, the transition plate 120 is also provided with positioning holes, and the positioning shaft 123 passes through the positioning holes of the transition plate 120 and the chassis for positioning. The chassis and the transition plate 120 are connected by screws. The screws can be inserted from one side of the chassis and reach the transition plate 120, and screwed into the threaded holes of the transition plate 120.

[0039] The mounting portion 1311 is arranged along the center line of the first hole 110, and the second connecting portion 1312 is used to create a gap 1313 between the first connecting portion and the mounting portion 1311.

[0040] The mounting portion 1311, the second connecting portion 1312, and the cover 132 can all be configured as semi-cylindrical structures. The limiting mechanism 200 includes a plate-like component, one end of which is connected to the main journal 410, and the other end contacts the end face of the semi-cylindrical structure of the second connecting portion 1312. The side of the second connecting portion 1312 that contacts the limiting mechanism 200 forms a limiting surface, used to limit the main journal 410 from rotating relative to the eccentric clamp 100 in the opposite direction to the rotation direction of the crankshaft 400. The limiting mechanism 200 is positioned in the gap 1313 to avoid interference with the cutting tool or other components, ensuring safety and saving space.

[0041] Specifically, in combination Figure 3 As shown, the limiting mechanism 200 includes a limiting rod 210 and a limiting screw 220. One end of the limiting rod 210 is connected to one end face of the main journal 410, and the other end of the limiting rod 210 is provided with a threaded hole perpendicular to the center line of the limiting rod 210 and the main journal 410. The limiting screw 220 is engaged with the threaded hole, and one end of the limiting screw 220 is engaged with the mounting part 1311 and is used to limit the main journal 410 from rotating relative to the eccentric clamp 100 in the opposite direction of the rotation direction of the crankshaft 400.

[0042] The side of the main journal 410 connected to the limiting rod 210 is connected to one end of the limiting rod 210 via a pin. A third connecting part 411 is provided on the end face of the main journal 410. The third connecting part 411 is a pin hole or a pin shaft. The limiting rod 210 is fitted with a pin shaft or a pin hole, and the pin shaft is inserted into the pin hole for positioning and connection. If the third connecting part 411 is a pin shaft, there are at least two pin shafts to prevent the limiting rod 210 from deflecting on the end face of the main journal 410.

[0043] The other end of the limiting rod 210 is provided with a threaded hole, which can be used to limit the movement by engaging the end cap of the limiting screw 220 with the limiting surface of the mounting part 1311. The center line of the limiting screw 220 is perpendicular to the limiting surface. The extension length can be adjusted by rotating the limiting screw 220. By pressing the limiting screw 220 against the limiting surface, the main journal 410 is restricted from rotating relative to the eccentric clamp 100 in the opposite direction of the rotation direction of the crankshaft 400, thus preventing slippage.

[0044] Specifically, the limiting rod 210 is installed on a preset plane, which is parallel to the plane where a crank of the crankshaft 400 is located. The limiting screw 220 is perpendicular to the preset plane. The crank consists of a connecting rod journal 420 and crank arms on both sides. The plane where the crank is located is the preset plane. A set of third connecting parts 411 is provided at the intersection of the main journal 410 and the preset plane, and the limiting rod 210 is installed on the main journal 410. The limiting rod 210 is used to correspond to different crank settings. The number of sets of third connecting parts 411 provided on the main journal 410 is the same as the number of cranks of the crankshaft 400. The tightening force of the limiting screw 220 on the mounting part 1311 is directly transmitted in the opposite direction of the cutting force, avoiding the loss of component force due to the deviation of the force direction, improving the anti-slip reliability, and reducing phase deviation.

[0045] When machining different connecting rod journals 420, the limiting rod 210 is connected to the corresponding third connecting part 411. The switching is simple and can be adapted to odd-numbered crankshafts and even-numbered crankshafts, or other asymmetrically distributed crankshafts, such as machining five-cylinder crankshafts. The design of the limiting mechanism 200 is adaptable.

[0046] Combination Figure 4 As shown, in some embodiments, the crankshaft machining fixture is provided with an eccentric support 300, which is disposed between two pairs of eccentric fixtures 100. The eccentric support 300 is provided with a fixing frame 310 and an eccentric ring structure 320. The eccentric ring structure 320 is provided with a second hole 321 for the main journal 410 to pass through. The eccentric ring structure 320 is used to rotate around the center line of the machine tool fixture. The fixing frame 310 is used to support the eccentric ring structure 320.

[0047] The eccentric support 300 is used to support the main journal 410 located in the middle of the crankshaft 400 between the two eccentric clamps 100. The eccentric ring structure 320 is a disc structure with a second hole 321 on the disc. The fixing frame 310 includes a lower fixing frame 311 and an upper fixing frame 312. The bottom of the lower fixing frame 311 is fixed to the machine tool clamp guide rail by bolts. The fixing frame 310 has a circular hole for the rotation of the eccentric ring structure 320. During installation, the lower fixing frame 311 is fixed first, then the eccentric ring structure 320 is installed, and finally the fixing frame 312 is covered and the upper fixing frame 312 is connected to the lower fixing frame 311.

[0048] Specifically, the fixed frame 310 is provided with several elastic support devices 313. The elastic support devices 313 contact the outer ring surface of the eccentric ring structure 320 and are used to support the eccentric ring structure 320. The elastic support devices 313 can be evenly distributed around the circumference of the fixed frame 310. Two elastic support devices 313 can be provided on the lower fixed frame 311 to support the eccentric ring structure 320, and two elastic support devices 313 can be provided on the upper fixed frame 312 to clamp the eccentric ring structure 320. By adjusting the distance of the elastic support devices 313 extending towards the center of the circular hole of the fixed frame 310, the outer ring of the eccentric ring structure 320 is made coaxial with the circular hole of the fixed frame 310. At the same time, the circular hole of the fixed frame 310 is made coaxial with the center line of the machine tool fixture, thereby reducing the radial sway of the eccentric ring structure 320 during rotation and ensuring rotational stability.

[0049] The eccentric ring structure 320 also has a base and a cover, which are connected to form the second hole 321. The base of the eccentric ring structure 320 is a V-shaped support block 330, which is used to support the main journal 410. By replacing the V-shaped support block 330 with one of different thicknesses, it can support the main journal 410 of different sizes in different processes. A shim 322 can also be set between the V-shaped support block 330 and the cover to accommodate the main journal 410 of different sizes, thereby improving support stability and making it versatile.

[0050] This application also provides a machine tool, including the crankshaft machining fixture as described above. A pair of eccentric fixtures 100 are disposed at the head and tail ends of the machine tool fixture. Through a preset eccentric distance between the centerline of the first hole 110 and the centerline of the machine tool fixture, the main journal 410 can be driven to rotate stably around the centerline of the machine tool fixture, ensuring precise alignment of the machining trajectory of the connecting rod journal 420 with the tool feed path. After the connecting rod journal 420 coincides with the centerline of the machine tool fixture, the cutting force is always transmitted in a fixed direction, resulting in more stable tool force and enabling the stable achievement of a larger cutting amount. It can also machine crankshafts 400 without asymmetrical crankshafts. The eccentric fixture 100 has a synergistic effect on the stable clamping of the main journal 410 and the reverse rotation restriction of the limiting mechanism 200, which can limit the shaking of the main journal 410 caused by the cutting force. Because the vibration is effectively suppressed, the cutting amount can be safely increased.

[0051] The embodiments of this application have been described in detail above with reference to the accompanying drawings. However, this application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this application. Furthermore, unless otherwise specified, the embodiments and features described in the embodiments of this application can be combined with each other.

Claims

1. A crankshaft machining fixture, arranged in pairs at the head and tail ends of a machine tool fixture, characterized in that, One of the crankshaft machining fixtures includes: An eccentric clamp is provided at one end of the machine tool fixture. The eccentric clamp has a first hole for clamping the main journal of the crankshaft. The center line of the first hole is used to set an eccentric distance relative to the rotation center line of the machine tool fixture so that the axis of the connecting rod journal of the crankshaft is collinear with the rotation center line of the machine tool fixture. The eccentric distance is equal to the distance between the axis of the main journal and the axis of the connecting rod journal. A limiting mechanism is used to connect to one end of the main journal. The limiting mechanism cooperates with the eccentric clamp and is used to limit the rotation of the main journal relative to the eccentric clamp.

2. The crankshaft machining fixture according to claim 1, characterized in that: The eccentric fixture includes a first connecting structure and a second connecting structure. The first connecting structure is used to connect to one end of the machine tool fixture. The first connecting structure is connected to the second connecting structure. The second connecting structure is used to clamp the main journal of the crankshaft. The first connecting structure is used to rotate with the connecting rod journal around the centerline of the machine tool fixture, and the second connecting structure is used to rotate with the main journal around the centerline of the main journal. The distance between the centerline of the machine tool fixture and the centerline of the main journal is the eccentric distance.

3. The crankshaft machining fixture according to claim 2, characterized in that: The first connecting structure includes a transition plate, one side of which is used to connect with the machine tool fixture. The transition plate is provided with a plurality of bolt holes for adjusting the installation position of the transition plate on the machine tool fixture. The second connecting structure is provided on the other side of the transition plate and is provided with the first hole.

4. The crankshaft machining fixture according to claim 3, characterized in that: The transition plate has a boss on the side that connects to the machine tool fixture. The boss is positioned at the edge of the chuck inner hole of the machine tool fixture and is used to position the transition plate.

5. The crankshaft machining fixture according to claim 2 or 3, characterized in that: The second connecting structure includes a base and a cover. The base is connected to the first connecting structure, and the base and the cover are connected to form a first hole.

6. The crankshaft machining fixture according to claim 5, characterized in that: The base includes a first connecting part, a mounting part, and a second connecting part for connecting the first connecting part and the mounting part. The mounting part is connected to the cover and forms a first hole. The second connecting part is used to create a gap between the first connecting part and the mounting part. One end of the first hole communicates with the gap. The limiting mechanism is disposed within the gap and connected to the end of the main journal. The limiting mechanism acts on the second connecting part.

7. The crankshaft machining fixture according to claim 6, characterized in that: The limiting mechanism includes a limiting rod and a limiting screw. One end of the limiting rod is connected to one end face of the main journal, and the other end of the limiting rod is provided with a threaded hole perpendicular to the center line of the limiting rod and the main journal. The limiting screw cooperates with the threaded hole and cooperates with the eccentric clamp to limit the rotation of the main journal relative to the eccentric clamp.

8. The crankshaft machining fixture according to claim 7, characterized in that: The limiting rod is installed on a preset plane, which is parallel to the plane where a crank of the crankshaft is located. The limiting screw is perpendicular to the preset plane, and the limiting rod is used to correspond to different crank settings.

9. The crankshaft machining fixture according to claim 1, characterized in that: The crankshaft machining fixture is provided with an eccentric support frame, which is disposed between two pairs of eccentric fixtures. The eccentric support frame is provided with a fixed frame and an eccentric ring structure. The eccentric ring structure is provided with a second hole for the main journal to pass through. The eccentric ring structure is used to rotate around the center line of the machine tool fixture. The fixed frame is provided with several elastic support devices, which contact the outer ring surface of the eccentric ring structure and are used to support the eccentric ring structure.

10. A machine tool, characterized in that, Includes the crankshaft machining fixture as described in any one of claims 1 to 9 above.

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