A method and device for on-line measurement of parallelism of a crankshaft

Abstract

The application discloses a kind of crankshaft parallelism online measurement method and device, comprising the following steps: S1: establish hexahedron.S2: acquisition hexahedron and the displacement variation data of crank pin or main shaft neck;S3: obtain the base circle size of hexahedron;S4: obtain the rotation angle of crank pin and main shaft neck;S5: obtain crankshaft center line parallelism.Through the design of hexahedron, non-contact laser sensor is used to solve, the mapping relationship of each crank pin and main shaft neck and the rotation angle and size transmission of hexahedron is established, the online accurate measurement of crankshaft crank pin and main shaft neck parallelism is realized, the problem of surface loss caused by crankshaft shutdown detection and contact measurement is avoided, the difficulty of crankshaft parallelism error measurement is reduced, and the error caused by multiple clamping and manual measurement is also avoided, and the measurement speed and accuracy are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of crankshaft parallelism online measurement method and device, belong to parallelism measurement technical field. BACKGROUND

[0002] In the process of crankshaft splicing and processing, it is difficult to measure the rotating crankshaft parts. Traditional manual measurement methods, such as using a level tool, need to stop the rotation of the crankshaft for manual measurement and reading, which has human error and reduces production efficiency. Therefore, it is crucial to quickly and accurately measure each workpiece of the crankshaft. Timely and accurate measurement of the parallelism of the crankpin and the main journal helps to identify crankshaft wear and other issues early in production and provides guidance for subsequent processing of the workpiece, thereby ensuring the quality of the crankshaft and improving production efficiency.

[0003] However, there are many challenges in measuring the parallelism of the crankshaft. First, the crankshaft rotates at variable speed during processing, making it difficult to measure online using traditional manual methods, and human error is introduced during manual measurement, resulting in insufficient measurement accuracy. In addition, using contact measuring instruments to measure the parallelism of the crankpin of the crankshaft can cause surface wear of the part during multiple measurements, affecting accuracy, making it difficult to accurately collect surface information, and preventing online measurement. Currently, three-coordinate measuring machines are commonly used to measure the parallelism of shaft parts, but there are some limitations, such as not being suitable for large parts and being relatively expensive. When using visual and laser non-contact detection methods to measure rotating workpieces during processing, the rotation angle cannot be accurately calculated, the circumferential sampling point position cannot be obtained, and tracking measurement cannot be achieved. SUMMARY

[0004] The present application provides a kind of crankshaft parallelism online measurement method and device, which is used to solve the problems in the prior art. The method for obtaining the rotation angle and the size transmission is used to accurately measure the parallelism of the crankpin and the main journal of the rotating crankshaft.

[0005] Technical solution: a kind of crankshaft parallelism online measurement method, comprising the following steps:

[0006] S1: establish a hexagonal prism: according to the diameter size of the crankpin and the main journal, obtain the side length size of the hexagonal prism and establish the corresponding hexagonal prism, mark the angle of each crankpin in the hexagonal prism, and evenly distribute A, B, C, D, E, F, H, I, J, K, L, M points on the side length of the hexagonal prism.

[0007] S2: collect displacement data: set up laser displacement sensor and line laser displacement sensor to measure the displacement change data of the hexagonal prism and the crankpin or the main journal;

[0008] S3: Obtain the base circle size of the hexahedron: the hexahedron is coaxially arranged with the crankshaft main journal, when the crankshaft rotates, the hexahedron rotates coaxially with the crankshaft, the base circle size is obtained through size and angle transmission;

[0009] S4: Obtain the rotation angle of the crank pin and the main journal: based on the angle transmission, size transmission and geometric principle, the rotation angle of each crank pin and main journal is solved by using the geometric characteristic size and displacement change data of the hexahedron and the base circle size;

[0010] S5: Obtain the parallelism of the crankshaft center line: move the linear laser displacement sensor, collect the surface profile information of each crank pin under the same angle of rotation of the crank pin, and solve the center line by the rotation angle and coordinates by adopting the reverse method for the main journal, so as to obtain the parallelism of the crankshaft center line.

[0011] Preferably, the S3 is specifically:

[0012] The point inside the main journal profile surface irradiated by the linear laser displacement sensor is set as the zero point, the distance between the zero point and the horizontal axis of the shaft center is d, the zero point rotates around the shaft center to obtain the reference circle with a radius of r, the distance deviated from the shaft center is r0, the crankshaft rotates clockwise with the hexahedron,

[0013] When the linear laser displacement sensor irradiates the crank pin profile surface, the profile cross section data is recorded, the distance l of the hexahedron is known HK and l LI , according to the geometric characteristic relationship of the hexahedron, the following can be obtained:

[0014] (1)

[0015] Wherein, 、 、 、 are the displacements displayed by the laser spot irradiating to H, K, L and I points respectively.

[0016] The values of d and r0 can be obtained by solving formula (1), and the distance r between the zero point position and the rotation center can be obtained by formula (2):

[0017] (2)

[0018] Preferably, the S4 is specifically:

[0019] According to the geometric principle, the distance from the P1 point on the hexahedron to the rotation center O measured by the laser displacement sensor can be obtained as follows:

[0020] (3)

[0021] wherein, is the displacement of the first arbitrary point read by the laser sensor.

[0022] Setting point C as the starting point, the rotation angle of the point can be obtained , which can be obtained by (4):

[0023] (4)

[0024] distance and the rotation angle is:

[0025] (5)

[0026] wherein, is the displacement of the second arbitrary point read by the laser sensor.

[0027] the rotated angle is:

[0028] (6)

[0029] Preferably, the S5 comprises:

[0030] S501: obtaining the spatial coordinates of the crank pin axis;

[0031] S502: obtaining the spatial coordinates of the main shaft neck axis;

[0032] S503: obtaining the parallelism of the crank pin through the crank pin axis and obtaining the parallelism of the main shaft neck through the main shaft neck axis.

[0033] Preferably, the S501 is specifically:

[0034] For the crank pin axis, the linear laser displacement sensor is moved to any crank pin, and when the crank pin rotates to the range of the linear laser displacement sensor light path, the linear laser light path profile appears on the surface of the crank pin. At this time, the crank pin profile cross-section data is recorded. According to the measurement principle of the linear laser displacement sensor, the semi-cross-section profile arc can be measured, and the crank pin axis can be calculated through the following formula. The profile coordinates corresponding to the crank pin measurement points are substituted into the general equation of an ellipse:

[0035] (7)

[0036] According to the principle of the least square method, the target function to be fitted is:

[0037] (8)

[0038] Make the partial derivatives of f equal to 0, that is:

[0039] (9)

[0040] Thus, the values of linear equations A, B, C, D, E and F can be obtained, and the coordinates of the geometric center point of the ellipse are set as (x u1 ,z u1 ):

[0041] (10)

[0042] That is, the spatial coordinates of the first axis center point are (x u1 ,y u1 ,z u1 ),;

[0043] The linear laser displacement sensor is horizontally moved y u2 , and the spatial coordinates of the second axis center point are (x u2 ,y u2 ,z u2 ) according to formulas (7-9):

[0044] (11)

[0045] Preferably, the S502 is specifically:

[0046] For measuring the spindle neck axis, the linear laser displacement sensor is moved to the spindle neck, the spindle neck is rotated clockwise, and the coordinates and rotation angle of any three points S1(m1, y1, n1), S2(m2, y2, n2), S3(m3, y3, n3) on the spindle neck are recorded by the reverse method , the coordinates of the center of the spindle neck are set as (m e1 ,y e1, n e1 ), and the coordinates are brought into the following formula:

[0047] (12)

[0048] By arranging the above formula, we can get:

[0049] (13)

[0050] The center of the circle is:

[0051] (14)

[0052] That is, the spatial coordinates of the first spindle neck axis are (m e1 ,y e1 ,n e1 ), and the spatial coordinates of the second spindle neck axis are (me2 y e2 n e2 ).

[0053] Preferably, S503 is specifically:

[0054] Let the coordinates of the two center points of the crankshaft be and , and the coordinates of the two center points of the crankpin or main journal be and , respectively connecting and , so that the straight line on which is located is the center line of the crankshaft, and the direction vector of the straight line is :

[0055] (15)

[0056] The straight line on which is located is the center line of the crankpin or main journal, and the direction vector of the straight line is :

[0057] (16)

[0058] The included angle between the two spatial vectors is :

[0059] (17)

[0060] Given that the length of the crankpin or main journal is H, the parallelism of the center line of the crankpin or main journal to the center line of the crankshaft is , and the calculation formula is:

[0061] (18)

[0062] A device for realizing online measurement of the parallelism of a crankshaft, comprising a laser displacement sensor, a line laser displacement sensor, a moving assembly, a clamp, and a processing module, wherein the crankshaft is installed on the clamp, a six-faced prism is installed at the end of the crankshaft and coaxially arranged with the main journal of the crankshaft, the moving assembly is arranged in parallel with the clamp, the laser displacement sensor and the line laser displacement sensor are sequentially and slidingly installed on the moving assembly, and the processing module is respectively signal-connected with the laser displacement sensor and the line laser displacement sensor.

[0063] Preferably, the moving assembly comprises a grating slide and a sliding block, the sliding block is coaxially arranged on the grating slide, and the laser displacement sensor and the line laser displacement sensor are respectively installed on the sliding block.

[0064] Beneficial effects: the present application adopts non-contact laser sensor joint solution through the design of hexahedron, establishes the mapping relationship of the rotation angle and size transmission of each crank pin and main shaft neck and hexahedron, realizes the online accurate measurement of the parallelism of crank pin and main shaft neck of crankshaft, avoids the problems of surface loss caused by crankshaft shutdown detection and contact measurement, reduces the difficulty of crankshaft parallelism error measurement, and avoids the errors caused by multiple clamping and manual measurement, and improves the measurement speed and accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0065] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are only a part of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the provided drawings.

[0066] Figure 1 The method flowchart of the present application;

[0067] Figure 2 The schematic diagram of the line laser displacement sensor and the laser displacement sensor irradiation position of the present application;

[0068] Figure 3 The schematic diagram of the position relationship of the feature points of the hexahedron;

[0069] Figure 4 The schematic diagram of the rotation angle of the hexahedron;

[0070] Figure 5 The schematic diagram of the laser measurement main shaft neck;

[0071] Figure 6 The schematic diagram of the crank pin axis;

[0072] Figure 7 The device structure diagram of the present application;

[0073] Figure 8 The hexahedron structure diagram of the present application. DETAILED DESCRIPTION

[0074] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0075] In the description of the present application, it needs to be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0076] In the present application, unless otherwise explicitly specified and limited, "on" or "under" of a first feature to a second feature can include that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, "on", "above" and "above" of the first feature to the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. "Below", "below" and "below" of the first feature to the second feature includes that the first feature is directly below and obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0077] As shown in Figure 1 and Figure 2 A crankshaft parallelism online measurement method, comprising the following steps:

[0078] S1: Establishing a hexagonal prism: according to the diameter size of the crankpin and the main shaft neck, the length size of the hexagonal prism is obtained and the corresponding hexagonal prism is established, the angle of each crankpin is marked in the hexagonal prism, and A, B, C, D, E, F, H, I, J, K, L, M points are uniformly arranged on the length of the hexagonal prism.

[0079] S2: Collecting displacement data: setting laser displacement sensor and line laser displacement sensor to measure the displacement change data of the hexagonal prism and the crankpin or the main shaft neck respectively;

[0080] As shown in Figure 3 S3: Obtaining the base circle size of the hexagonal prism: the hexagonal prism is coaxially arranged with the crankshaft main shaft neck, when the crankshaft rotates, the hexagonal prism rotates coaxially with the crankshaft, the base circle size is obtained through size and angle transmission;

[0081] The point inside the main shaft neck profile surface irradiated by the line laser displacement sensor is set as the zero point, the distance between the zero point and the horizontal axis of the shaft center is d, the zero point rotates around the shaft center to obtain a reference circle with a radius of r, the distance deviated from the shaft center is r0, the crankshaft rotates clockwise with the hexagonal prism,

[0082] When the line laser displacement sensor irradiates to the crankpin profile surface, the profile cross section data is recorded, and the distance l HK and lLI According to the geometric feature relationship of the hexahedron, the following can be obtained:

[0083] (1)

[0084] wherein, , , , are displacements of the laser spot irradiated to H, K, L, I points, respectively.

[0085] The solution of formula (1) can obtain the values of d and r0, and the distance r of the zero point position from the rotation center can be obtained by formula (2):

[0086] (2)

[0087] As shown in Figure 4 , S4: obtaining the rotation angles of the crank pin and the main shaft neck: based on the angle transmission, size transmission and geometric principle, the geometric feature size of the hexahedron and the displacement change data, the base circle size are used to solve the rotation angle of each crank pin and main shaft neck.

[0088] According to the geometric principle, the distance of P1 point on the hexahedron measured by the laser displacement sensor to the rotation center O can be obtained as follows:

[0089] (3)

[0090] wherein, is the displacement of the first arbitrary point read by the laser sensor.

[0091] Taking point C as the starting point, the corresponding rotation angle of the point can be obtained by (4):

[0092] (4)

[0093] The distance and the rotation angle are:

[0094] (5)

[0095] wherein, is the displacement of the second arbitrary point read by the laser sensor.

[0096] The rotated angle is:

[0097] (6)

[0098] S5: Obtain the parallelism of the crankshaft centerline: Move the linear laser displacement sensor to collect surface contour information of each crankpin when the crankpin rotates at the same angle. Then, use the reverse method to solve the centerline of the main journal by rotating the angle and coordinates to obtain the parallelism of the crankshaft centerline.

[0099] S501: Obtain the spatial coordinates of the crank pin centerline;

[0100] To measure the crankpin centerline, a linear laser displacement sensor is moved to any crankpin. When the crankpin rotates into the optical path range of the linear laser displacement sensor, the profile of the linear laser path appears on the crankpin surface. At this point, the cross-sectional data of the crankpin profile is recorded. Based on the measurement principle of the linear laser displacement sensor, the half-section profile arc can be measured. The crankpin centerline can be calculated using the following formula. Substituting the profile coordinates corresponding to the crankpin measurement point into the general equation of an ellipse:

[0101] (7)

[0102] Based on the principle of least squares, the fitted objective function is:

[0103] (8)

[0104] This makes the partial derivatives of f equal to 0, that is:

[0105] (9)

[0106] Therefore, the values ​​of the linear equation system A, B, C, D, E, and F can be obtained. Let the coordinates of the geometric center point of the ellipse be (x... u1 ,z u1 ):

[0107] (10)

[0108] That is, the spatial coordinates of the first axis point are (x u1 ,y u1 ,z u1 ),;

[0109] Horizontal movement of the linear laser displacement sensor y u2 According to formula (7-9), the spatial coordinates of the second axis center point are (x... u2 ,y u2 ,z u2 ):

[0110] (11)

[0111] like Figure 5 As shown, S502: Obtain the spatial coordinates of the spindle journal axis;

[0112] For the spindle neck axis line measurement, the linear laser displacement sensor is moved to the spindle neck, the spindle neck is rotated clockwise, and the coordinates and rotation angle of any three points S1(m1, y1, n1), S2(m2, y2, n2), S3(m3, y3, n3) on the spindle neck are recorded by reverse rotation method , let the center coordinates of the spindle neck be (m e1 ,y e1, n e1 ), and the coordinates are brought into the following formula:

[0113] (12)

[0114] By arranging the above formula, we can get:

[0115] (13)

[0116] The center is:

[0117] (14)

[0118] That is, the first spindle neck axis space coordinates are (m e1 ,y e1 ,n e1 ), and the second spindle neck axis space coordinates are obtained according to formulas (12-13) (m e2 ,y e2 ,n e2 ).

[0119] S503: Find the parallelism of the crank pin through the crank pin axis line, and find the parallelism of the spindle neck through the spindle neck axis line;

[0120] Let the coordinates of the two center points of the crankshaft be and , and the coordinates of the two center points of the crank pin or spindle neck be and , respectively connecting and , so that The straight line on which the center line of the crankshaft is located, and the direction vector of the straight line is:

[0121] (15)

[0122] The straight line on which the center line of the crank pin or spindle neck is located, and the direction vector of the straight line is:

[0123] (16)

[0124] Calculate the included angle of two space vectors is:

[0125] (17)

[0126] As shown in Figure 6 , the crank pin or main journal length is known as H, the crank pin axis or main journal axis is parallel to the crankshaft centerline The calculation formula is:

[0127] (18)

[0128] As shown in Figure 7 and Figure 8 , a device for realizing online measurement of crankshaft parallelism includes a laser displacement sensor 1, a line laser displacement sensor 2, a moving assembly 3, a clamp 4, a processing module, the crankshaft is installed on the clamp 4, a six-faced prism is installed at the end of the crankshaft and coaxially arranged with the crankshaft main journal, the moving assembly 3 is coaxially and parallel arranged with the clamp 4, the laser displacement sensor 1 and the line laser displacement sensor 2 are sequentially and slidingly installed on the moving assembly 3, and the processing module is respectively signal connected with the laser displacement sensor 1 and the line laser displacement sensor 2.

[0129] The moving assembly 3 includes a grating slide 31 and a sliding block 32, the sliding block 32 is coaxially arranged on the grating slide 31, and the laser displacement sensor 1 and the line laser displacement sensor 2 are respectively installed on the sliding block 32.

[0130] In this embodiment, the installation process of the measuring device is that the clamp 4 is a three-jaw chuck and a thimble, the crankshaft is fixed through the three-jaw chuck and the thimble, the crankshaft rotation axis and the three-jaw chuck axis are overlapped according to the adjustment of the crankshaft position, the six-faced prism is installed in the thimble direction at the end of the crankshaft, the crankshaft is rotated, and the base circle size is obtained by using the known size six-faced prism;

[0131] The grating slide 31 is placed parallel to one side of the crankshaft and fixed, the line laser sensor 2 and the laser displacement sensor 1 are installed on the grating slide 31, the laser displacement sensor 1 is located on the right side of the line laser sensor 2, the light path is perpendicular to the side surface of the six-faced prism, the line laser sensor 2 is placed opposite to any crank pin by moving the sliding block 32 left and right, and the light path of the line laser sensor 2 is parallel to the normal section of the crank pin or main journal.

[0132] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same or similar parts between various embodiments can be referred to each other. For the device disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple, and the related parts can be referred to the method part.

[0133] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Numerous modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without the use of the inventive faculty. Therefore, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for on-line measurement of crankshaft parallelism, characterized by: The method comprises the following steps: S1: establishing a hexagonal prism: according to the diameter size of the crank pin and the main shaft neck, the size of the edge length of the hexagonal prism is obtained, and the corresponding hexagonal prism is established, the angle of each crank pin is marked in the hexagonal prism, and A, B, C, D, E, F, H, I, J, K, L and M points are uniformly arranged on the edge length of the hexagonal prism; S2: collecting displacement data: a laser displacement sensor and a line laser displacement sensor are arranged to measure the displacement change data of the hexagonal prism and the crank pin or the main shaft neck; S3: obtaining the base circle size of the hexagonal prism: the hexagonal prism is coaxially arranged with the crankshaft main shaft neck, when the crankshaft rotates, the hexagonal prism rotates coaxially with the crankshaft, the base circle size is obtained through size and angle transmission; S4: obtaining the rotation angle of the crank pin and the main shaft neck: based on angle transmission, size transmission and geometric principles, the rotation angle of each crank pin and main shaft neck is solved by using the geometric characteristic size of the hexagonal prism and the displacement change data, the base circle size; S5: obtaining the parallelism of the crankshaft center line: moving the line laser displacement sensor, collecting surface profile information of each crank pin under the condition that the crank pin rotates by the same angle, and solving the center line by using the rotation angle and coordinates, so as to obtain the parallelism of the crankshaft center line; The S5 comprises: S501: obtaining the spatial coordinates of the crank pin axis; The S501 is specifically: The crank pin axis is measured, the line laser displacement sensor is moved to any crank pin, when the crank pin rotates to the range of the line laser displacement sensor light path, the line laser light path profile appears on the surface of the crank pin, at this time, the crank pin profile cross-section data is recorded, according to the measurement principle of the line laser displacement sensor, the semi-cross-section profile arc can be measured, and the crank pin axis can be calculated by the following formula: (7) According to the principle of the least square method, the target function to be fitted is: (8) So that the partial derivatives of f are 0, that is: (9) Thereby, values of linear equations A, B, C, D, E and F can be obtained, and the coordinates of the geometric center point of the ellipse are set as (x u1 ,z u1 ): (10) The spatial coordinates of the first axis core point are (x u1 ,y u1 ,z u1 ). Linear laser displacement sensor horizontal movement y u2 According to formula (7-9), the spatial coordinates of the second axis center point are (x u2 ,y u2 ,z u2 ): (11) S502: obtaining the spatial coordinates of the main shaft neck axis; The S502 is specifically: For the spindle neck axis measurement, the linear laser displacement sensor is moved to the spindle neck, the spindle neck is rotated clockwise, and the coordinates and rotation angle of any three points S1(m1, y1, n1), S2(m2, y2, n2), S3(m3, y3, n3) on the spindle neck are recorded by the reverse method , assuming that the center coordinates of the spindle neck are (m e1 ,y e1, n e1 ), the coordinates are brought into the following formula: (12) The above formula can be obtained by sorting: (13) The center of the circle is: (14) That is, the first main journal axis space coordinate is (m e1 ,y e1 ,n e1 ), and the second main journal axis space coordinate is obtained according to formulas (12-13) (m e2 ,y e2 ,n e2 ). S503: obtaining the parallelism of the crank pin through the crank pin axis, and obtaining the parallelism of the main shaft neck through the main shaft neck axis; The S503 is specifically: Let the coordinates of the two center points of the crankshaft be and , and the coordinates of the two center points of the crankpin or main journal be and , respectively connecting and , so that the straight line is the center line of the crankshaft, and the direction vector of the straight line is: (15) The straight line is the crank pin axis or the spindle neck axis, and the direction vector of the straight line is: ​ (16) Computing the angle between two spatial vectors is: (17) Given the length of the crankpin or main journal as H, the parallelism of the crankpin or main journal centerline to the crankshaft centerline The formula is: (18)。 2. The on-line measurement method of the parallelism of a crankshaft according to claim 1, characterized in that: The S3 is specifically: The point inside the main shaft neck profile surface irradiated by the line laser displacement sensor is set as a zero point, the distance between the zero point and the axis horizontal axis is d, the reference circle with a radius of r is obtained by rotating the zero point around the axis, the distance between the reference circle and the axis is r0, the crankshaft and the hexagonal prism rotate clockwise, When the linear laser displacement sensor is irradiated to the crank pin wheel profile surface, the profile cross section data is recorded, and the distance l of the hexahedron is known HK and l LI According to the geometric feature relationship of the hexahedron, the following can be obtained: (1) wherein, , , , are the displacements shown by the laser spot irradiation to points H, K, L, I, respectively. The values of d and r0 can be obtained by solving formula (1), and the distance r between the zero point position and the rotation center can be obtained by formula (2): (2)。 3. The on-line measurement method of the parallelism of a crankshaft according to claim 2, characterized in that: The S4 is specifically: According to the principle of geometry, the distance from the P1 point on the hexahedron measured by the laser displacement sensor to the rotation center O This can be obtained as follows: (3) wherein, reading the displacement of the first arbitrary point for the laser sensor; Setting point C as the starting point, the rotation angle corresponding to the point can be obtained , can be obtained by (4): (4) Distance and the angle of rotation is: (5) wherein, reading the displacement of the second arbitrary point for the laser sensor; rotated angle is: (6)。 4. An apparatus for implementing the on-line measurement method of the parallelism of a crankshaft according to any one of claims 1 to 3, characterized in that, The application relates to a laser displacement sensor (1), a linear laser displacement sensor (2), a moving assembly (3), a clamp (4) and a processing module, wherein a crankshaft is installed on the clamp (4), a six-surface prism is installed at the end of the crankshaft and coaxially arranged with the crankshaft main journal, the moving assembly (3) is coaxially and parallel arranged with the clamp (4), the laser displacement sensor (1) and the linear laser displacement sensor (2) are sequentially and slidingly installed on the moving assembly (3), and the processing module is respectively signal-connected with the laser displacement sensor (1) and the linear laser displacement sensor (2).

5. The apparatus for realizing online measurement of parallelism of a crankshaft according to claim 4, wherein, The moving assembly (3) comprises a grating slide (31) and a sliding block (32), the sliding block (32) is coaxially arranged on the grating slide (31), and the laser displacement sensor (1) and the linear laser displacement sensor (2) are respectively installed on the sliding block (32).

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