CN111895938A - Automatic measuring method for position deviation of cold oil duct in piston - Google Patents
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Abstract
The invention relates to an automatic measuring method for position deviation of a cold oil duct in a piston, which comprises the following steps: s1, scanning the piston with the wavy inner cooling oil duct by adopting an X-ray linear array detector industrial CT system to obtain a DR image of the piston; s2, searching the position of the wavy inner cooling oil duct on the DR image, setting the height of the inner cooling oil duct as h, and respectively performing CT scanning at h/2, h/m and h/n (n is more than m & gt 2) to obtain corresponding tomographic images which are respectively marked as a first tomographic CT image, a second tomographic CT image and a third tomographic CT image; wherein a plurality of local oil passages exist in the second tomographic CT image and the third tomographic CT image; s3, measuring the radial deviation of the inner cooling oil passage through the first tomography CT image; and S4, measuring the axial deviation of the internal cooling oil channel through the second fault CT image and the third fault CT image. The traditional area array CT system has the advantages of low cost, high efficiency and high measurement precision.
Description
Technical Field
The invention relates to the field of pistons, in particular to an automatic measuring method for position deviation of a cold oil duct in a piston.
Background
The piston in the engine needs to bear periodical thermal load and mechanical load impact, and the working environment of the piston is more severe along with the increase of the power and the rotation speed of the internal combustion engine. The oil passage arranged in the piston is an important structure playing a role in cooling in the piston, and the heat is taken away through the flowing of the engine oil to forcibly cool the head area of the piston, so that the temperature and the thermal deformation of important parts such as the periphery of a combustion chamber, a piston ring groove and the like are effectively reduced. Therefore, the shape and the position of the cooling oil passage in the piston have important influence on the working temperature of each part of the piston.
The piston in the prior art is generally formed by adopting the methods of metal die casting, forging, hydraulic die forging and the like at one step, the position of an internal cooling oil duct is easy to generate relative movement due to the performance fluctuation of forming equipment, and when the deviation of the internal position of the internal cooling oil duct in the piston is larger than the design requirement, the cooling effect of the piston is influenced, so that the strength of the head part of the piston is reduced. Therefore, the shape and position detection of the piston cooling oil cavity is very important, and is directly related to the performance and the service life of the internal combustion engine.
Because the inner cooling oil duct is positioned in the piston, contact measurement means such as a three-coordinate instrument cannot be used. Therefore, nondestructive testing is adopted in the industry to detect the position of the inner cooling oil duct. The method mainly comprises industrial CT detection and ultrasonic detection aiming at the position nondestructive detection method of the traditional shape internal cooling oil duct (circular ring). In the industrial CT detection method, DR and CT scanning is carried out on a piston with an annular inner cooling oil passage to obtain DR and CT images, and axial deviation measurement of the oil passage can be realized only by acquiring 2 DR images (0 degree and 90 degrees). The measuring method comprises the steps of observing the position of the whole top of the oil duct on a DR image, subtracting the highest position and the lowest position of the top of the oil duct to obtain the axial deviation of the piston oil duct, and measuring the circle center deviation of the oil duct and the excircle of the piston on a CT image to calculate and obtain the radial deviation; in addition, the ultrasonic detection method adopts a water immersion method to obtain the position of the oil passage in the piston by vertically incident ultrasonic waves from the top of the piston, axial deviation of the oil passage of the piston can be obtained by measuring the distance between the top of the inner cooling oil passage and the top of the piston, an oil passage C scanning image is formed by ultrasonic detection, and radial deviation can be measured on the C scanning image. When the inner cooling oil duct is in a wave shape, the partial area of the top of the oil duct is not perpendicular to the incident direction of the ultrasonic wave, and the ultrasonic wave cannot return, so that the ultrasonic detection method cannot be developed. Ghost images of the wavy oil duct on a DR image are serious, and high positions and low positions of the oil duct are difficult to distinguish. The above-described conventional methods have too large measurement errors or cannot be effectively implemented, and thus further improvement is required.
Disclosure of Invention
The invention aims to solve the technical problem of providing an automatic measuring method for the position deviation of an inner cooling oil duct in a piston aiming at the current situation of the prior art, the automatic measuring method has low cost and high measuring precision, and can realize the measurement of the axial deviation and the radial deviation of the inner cooling oil duct with a complex structure.
The technical scheme adopted by the invention for solving the technical problems is as follows: a method for automatically measuring the position deviation of a cold oil duct in a piston is characterized by comprising the following steps of: the method is used for automatically measuring the position deviation of the wavy inner cooling oil channel in the piston and comprises the following steps:
s1, scanning a piston with a wavy inner-cooling oil duct by adopting an X-ray linear array detector industrial CT system to obtain a DR image of the piston;
s2, searching the position of the wavy inner cooling oil duct on the DR image, setting the height of the inner cooling oil duct as h, respectively performing CT scanning at h/2, h/m and h/n (n is more than m & gt 2) to obtain corresponding tomographic images, and sequentially marking the tomographic images obtained at h/2, h/m and h/n as a first tomographic CT image, a second tomographic CT image and a third tomographic CT image respectively; wherein a plurality of local oil passages exist in the second tomographic CT image and the third tomographic CT image;
step S3, performing radial deviation measurement of the internal cooling oil passage by the first tomographic CT image: the method comprises the following specific steps:
s3-1, processing the first tomography image by using an automatic threshold segmentation method to obtain a binary image corresponding to the first tomography image, and recording the binary image as a first binary image;
step S3-2, when the number of the inner cooling oil passages in the first binary image is one, respectively extracting the edge of the piston and the edge of the inner cooling oil passage in the first binary image to obtain an outer contour line of the piston, an outer contour line of the inner cooling oil passage and an inner contour line of the inner cooling oil passage;
when the inner cooling oil duct in the first binary image has the left inner cooling oil duct and the right inner cooling oil duct, respectively extracting the edge of the piston, the edge of the left inner cooling oil duct and the edge of the right inner cooling oil duct from the first binary image to obtain an outer contour line of the piston, an outer contour line of the left inner cooling oil duct, an inner contour line of the left inner cooling oil duct, an outer contour line of the right inner cooling oil duct and an inner contour line of the right inner cooling oil duct;
s3-3, fitting the outer contour line of the piston extracted in the step S3-2 to calculate the circle center of the outer contour of the piston;
step S3-4, when the number of the inner cooling oil duct in the first binary image is one, calculating a central axis of the inner cooling oil duct according to an outer contour line of the inner cooling oil duct and an inner contour line of the inner cooling oil duct, fitting the central axis to calculate the center of the inner cooling oil duct, and calculating the distance between the center of the outer contour of the piston and the center of the inner cooling oil duct, wherein the distance is the radial deviation of the inner cooling oil duct;
when the inner cooling oil duct in the first binary image has the left inner cooling oil duct and the right inner cooling oil duct, calculating a central axis of the left inner cooling oil duct according to an outer contour line of the left inner cooling oil duct and an inner contour line of the left inner cooling oil duct, calculating a central axis of the right inner cooling oil duct according to an outer contour line of the right inner cooling oil duct and an inner contour line of the right inner cooling oil duct, fitting the central axis of the left inner cooling oil duct and the central axis of the right inner cooling oil duct respectively to obtain a circle center of the left inner cooling oil duct and a circle center of the right inner cooling oil duct, calculating a distance between a circle center of a piston outer contour and a circle center of the left inner cooling oil duct and a distance between a circle center of the piston outer contour and a circle center of the right inner cooling oil duct respectively to obtain a radial deviation of the left inner cooling oil duct and a radial deviation of the right inner cooling oil duct, and finally calculating a middle point of the circle center of the left inner cooling, calculating the distance between the middle point and the circle center of the outer contour of the piston, wherein the distance is the integral radial deviation of the inner cooling oil duct;
step S4, carrying out axial deviation measurement of the internal cooling oil passage through the second tomography image and the third tomography image: the method comprises the following specific steps:
s4-1, processing the second tomographic CT image and the third tomographic CT image by using an automatic threshold segmentation method respectively to obtain a binary image corresponding to the second tomographic CT image and a binary image corresponding to the third tomographic CT image, and marking the binary images as the second binary image and the third binary image respectively;
step S4-2, when the number of the internal cooling oil ducts is one, calculating the area of each local oil duct in the second binary image and the area of the local oil duct at the corresponding same position in the third binary image, and searching the maximum value S in all the local oil duct areas in the second binary image or the third binary imagemaxAnd minimum value SminIf the axial deviation σ of the internal cooling oil passage is:
wherein,
S1(i) is the area of the ith local oil passage in the second binary image, S2(i) The area of the local oil duct in the third binary image, which is at the same position as the ith local oil duct in the second binary image, is M, and the total number of the local oil ducts in the second binary image and the third binary image, which are at the same position, is M;
when the inner cooling oil duct of the piston has a left inner cooling oil duct and a right inner cooling oil duct, respectively calculating the area of each local oil duct corresponding to the left inner cooling oil duct in the second binary image, the area of each local oil duct corresponding to the same position of the left inner cooling oil duct in the third binary image, the area of each local oil duct corresponding to the right inner cooling oil duct in the second binary image and the area of each local oil duct corresponding to the same position of the right inner cooling oil duct in the third binary image; then, searching out the maximum value S 'of the areas of all the local oil passages in the left internal cooling oil passage in the second binary image or the third binary image'maxAnd a minimum value of S'minAnd the maximum value S' of the areas of all local oil passages in the right inner cooling oil passagemaxAnd a minimum value S ″minThen, the axial deviation sigma of the left inner cooling oil passage is calculated respectively1And axial deviation sigma of right inner cooling oil passage2；
Wherein,
S′1(j) is the area, S 'of the jth local oil passage in the left internal cooling oil passage of the second binary image'2(j) The local oil in the same position in the left inner cooling oil duct of the third binary image as the jth local oil duct in the left inner cooling oil duct of the second binary imageThe area of the oil duct is N, and the N is the total number of local oil ducts which have the same position in the left inner cooling oil duct of the second binary image and the left inner cooling oil duct of the third binary image;
S″1(q) is the area of the q-th local oil passage in the right internal cooling oil passage of the second binary image, S ″2(q) is the area of the local oil duct at the same position in the right internal cooling oil duct of the third binary image as the q-th local oil duct in the right internal cooling oil duct of the second binary image, and K is the total number of the local oil ducts at the same position in the right internal cooling oil duct of the second binary image and the right internal cooling oil duct of the third binary image;
the calculation formula of the integral axial deviation sigma' of the inner cooling oil passage is as follows:
wherein,
or
Or
Preferably, the automatic threshold segmentation method used in the steps S3-1 and S4-1 is a maximum inter-class variance method.
Preferably, the method used for fitting the outer contour line of the piston in step S3-3 is a circular fitting method.
Preferably, the method used for the centering axis fitting in step S3-4 is an ellipse fitting method.
Compared with the prior art, the invention has the advantages that: selecting 3 layers in the area where the piston is located to perform linear array CT scanning imaging, and extracting the oil duct boundary and the piston outer contour by utilizing a CT image of the middle position of the oil duct so as to calculate the radial deviation of the oil duct; and sequentially scanning 2 layers of CT images on one side of the central position of the oil duct, calculating the area of a local area of the oil duct on the CT images, and calculating the relation between the area of the local area and the axial displacement so as to obtain the axial deviation. The method can be used for calculating the axial deviation and the radial deviation of the complex inner cooling oil duct in the piston of the high-energy industrial CT, and has the advantages of low cost, high efficiency, high measurement precision and the like compared with the traditional area array CT system.
Drawings
FIG. 1 is a schematic diagram of three positions, namely h/2, h/m and h/n, of a wave-shaped inner cooling oil passage in a DR image according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a DR image of a piston in an embodiment of the present invention;
FIG. 3 is a first tomographic CT image obtained by CT scanning at a position h/2 of the wavy inner cooling oil passage in FIG. 2;
FIG. 4 is a second tomographic CT image obtained by CT scanning at the h/m position of the wavy inner cooling oil passage in FIG. 2;
FIG. 5 is a second cross-sectional CT image obtained by CT scanning at the h/n position of the wavy inner cooling oil passage in FIG. 2;
FIG. 6 is a schematic illustration of the outer contour line of the piston, the central axis of the left inner cooling gallery and the central axis of the right inner cooling gallery extracted from FIG. 3;
FIG. 7 is a schematic illustration of the calculation of the local oil gallery areas in the left and right internal cooling galleries of FIG. 4;
fig. 8 is a schematic diagram illustrating calculation of the local oil passage areas in the left and right inner cooling passages in fig. 5.
Detailed Description
The invention is described in further detail below with reference to the accompanying examples.
A method for automatically measuring the position deviation of a wavy inner cooling oil duct in a piston comprises the following steps:
s1, scanning a piston with a wavy inner-cooling oil duct by adopting an X-ray linear array detector industrial CT system to obtain a DR image of the piston;
s2, searching the position of the wavy inner cooling oil duct on the DR image, setting the height of the inner cooling oil duct as h, respectively performing CT scanning at h/2, h/m and h/n (n is more than m & gt 2) to obtain corresponding tomographic images, and sequentially marking the tomographic images obtained at h/2, h/m and h/n as a first tomographic CT image, a second tomographic CT image and a third tomographic CT image respectively; wherein a plurality of local oil passages exist in the second tomographic CT image and the third tomographic CT image; as shown in fig. 1, corresponding to images at h/2, h/m, h/n (n > m >2), respectively;
step S3, performing radial deviation measurement of the internal cooling oil passage by the first tomographic CT image: the method comprises the following specific steps:
s3-1, processing the first tomography image by using an automatic threshold segmentation method to obtain a binary image corresponding to the first tomography image, and recording the binary image as a first binary image;
step S3-2, when the number of the inner cooling oil passages in the first binary image is one, respectively extracting the edge of the piston and the edge of the inner cooling oil passage in the first binary image to obtain an outer contour line of the piston, an outer contour line of the inner cooling oil passage and an inner contour line of the inner cooling oil passage;
when the inner cooling oil duct in the first binary image has the left inner cooling oil duct and the right inner cooling oil duct, respectively extracting the edge of the piston, the edge of the left inner cooling oil duct and the edge of the right inner cooling oil duct from the first binary image to obtain an outer contour line of the piston, an outer contour line of the left inner cooling oil duct, an inner contour line of the left inner cooling oil duct, an outer contour line of the right inner cooling oil duct and an inner contour line of the right inner cooling oil duct;
in the existing production process, an inner cooling oil passage in a piston is divided into two conditions, one is as follows: the whole circle of inner cooling oil channel is communicated, and the other circle of inner cooling oil channel is as follows: the left inner cooling oil duct and the right inner cooling oil duct are not communicated with each other, in addition, the left inner cooling oil duct and the right inner cooling oil duct are independently communicated, and in order to ensure that the piston is uniformly cooled, an upper oil duct and a lower oil duct do not exist in the actual production;
s3-3, fitting the outer contour line of the piston extracted in the step S3-2 to calculate the circle center of the outer contour of the piston;
step S3-4, when the number of the inner cooling oil duct in the first binary image is one, calculating a central axis of the inner cooling oil duct according to an outer contour line of the inner cooling oil duct and an inner contour line of the inner cooling oil duct, fitting the central axis to calculate the center of the inner cooling oil duct, and calculating the distance between the center of the outer contour of the piston and the center of the inner cooling oil duct, wherein the distance is the radial deviation of the inner cooling oil duct;
when the inner cooling oil duct in the first binary image has the left inner cooling oil duct and the right inner cooling oil duct, calculating a central axis of the left inner cooling oil duct according to an outer contour line of the left inner cooling oil duct and an inner contour line of the left inner cooling oil duct, calculating a central axis of the right inner cooling oil duct according to an outer contour line of the right inner cooling oil duct and an inner contour line of the right inner cooling oil duct, fitting the central axis of the left inner cooling oil duct and the central axis of the right inner cooling oil duct respectively to obtain a circle center of the left inner cooling oil duct and a circle center of the right inner cooling oil duct, calculating a distance between a circle center of a piston outer contour and a circle center of the left inner cooling oil duct and a distance between a circle center of the piston outer contour and a circle center of the right inner cooling oil duct respectively to obtain a radial deviation of the left inner cooling oil duct and a radial deviation of the right inner cooling oil duct, and finally calculating a middle point of the circle center of the left inner cooling, calculating the distance between the middle point and the circle center of the outer contour of the piston, wherein the distance is the integral radial deviation of the inner cooling oil duct;
step S4, carrying out axial deviation measurement of the internal cooling oil passage through the second tomography image and the third tomography image: the method comprises the following specific steps:
s4-1, processing the second tomographic CT image and the third tomographic CT image by using an automatic threshold segmentation method respectively to obtain a binary image corresponding to the second tomographic CT image and a binary image corresponding to the third tomographic CT image, and marking the binary images as the second binary image and the third binary image respectively;
step S4-2, when the number of the internal cooling oil ducts is one, calculating the area of each local oil duct in the second binary image and the area of the local oil duct at the corresponding same position in the third binary image, and searching all the local oil ducts in the second binary image or the third binary imageMaximum value S in local oil passage areamaxAnd minimum value SminIf the axial deviation σ of the internal cooling oil passage is:
wherein,
S1(i) is the area of the ith local oil passage in the second binary image, S2(i) The area of the local oil duct in the third binary image, which is at the same position as the ith local oil duct in the second binary image, is M, and the total number of the local oil ducts in the second binary image and the third binary image, which are at the same position, is M;
when the inner cooling oil duct of the piston has a left inner cooling oil duct and a right inner cooling oil duct, respectively calculating the area of each local oil duct corresponding to the left inner cooling oil duct in the second binary image, the area of each local oil duct corresponding to the same position of the left inner cooling oil duct in the third binary image, the area of each local oil duct corresponding to the right inner cooling oil duct in the second binary image and the area of each local oil duct corresponding to the same position of the right inner cooling oil duct in the third binary image; then, searching out the maximum value S 'of the areas of all the local oil passages in the left internal cooling oil passage in the second binary image or the third binary image'maxAnd a minimum value of S'minAnd the maximum value S' of the areas of all local oil passages in the right inner cooling oil passagemaxAnd a minimum value S ″minThen, the axial deviation sigma of the left inner cooling oil passage is calculated respectively1And axial deviation sigma of right inner cooling oil passage2；
Wherein,
S′1(j) is the area, S 'of the jth local oil passage in the left internal cooling oil passage of the second binary image'2(j) The local oil duct area of the same position in the left inner cooling oil duct of the third binary image as the jth local oil duct in the left inner cooling oil duct of the second binary image is obtained, and N is the total number of the local oil ducts with the same position in the left inner cooling oil duct of the second binary image and the left inner cooling oil duct of the third binary image;
S″1(q) is the area of the q-th local oil passage in the right internal cooling oil passage of the second binary image, S ″2(q) is the area of the local oil duct at the same position in the right internal cooling oil duct of the third binary image as the q-th local oil duct in the right internal cooling oil duct of the second binary image, and K is the total number of the local oil ducts at the same position in the right internal cooling oil duct of the second binary image and the right internal cooling oil duct of the third binary image;
the calculation formula of the integral axial deviation sigma' of the inner cooling oil passage is as follows:
wherein,
or
Or
the specific steps of the automatic measurement method are described below with specific examples, as shown in fig. 2 to 8, the inner cooling oil duct is a wavy oil duct, the radial deviation and the axial deviation of the inner cooling oil duct are difficult to observe from the DR image, but the height of the inner cooling oil duct can be directly observed through the DR image to obtain h which is 12mm, in this embodiment, n which is 6 and m which is 3 are selected, and CT scanning is performed on the heights of 6mm, 4mm and 2mm respectively to obtain the tomographic images shown in fig. 3 to 5;
measuring the radial deviation of the inner cooling oil duct on the image in fig. 3, wherein the inner cooling oil duct has a left inner cooling oil duct and a right inner cooling oil duct, extracting the edge of the piston, the edge of the left inner cooling oil duct and the edge of the right inner cooling oil duct respectively to obtain the outer contour line of the piston, the outer contour line of the left inner cooling oil duct, the inner contour line of the left inner cooling oil duct, the outer contour line of the right inner cooling oil duct and the inner contour line of the right inner cooling oil duct, and calculating the central axis of the left inner cooling oil duct and the central axis of the right inner cooling oil duct, as shown in fig. 6, fitting the outer contour lines of the piston by a least square method to calculate the outer contour line of the piston, and calculating the outer contour circlepistonIs x 1826 and y 1991 (pixel). Respectively fitting the central axis of the left inner cooling oil duct and the central axis of the right inner cooling oil duct by adopting a least square ellipse fitting method to obtain the circle center O of the left inner cooling oil ductvittaIs x 1854, y 1993 (pixel), and the center of the right inner cooling oil duct is OvittaIs x 1753, y 1987 (pel); calculating the distance between the circle center of the outer contour of the piston and the circle center of the left inner cooling oil duct, wherein the distance is the radial deviation of the left inner cooling oil duct; calculating the distance between the circle center of the outer contour of the piston and the circle center of the right inner cooling oil duct, wherein the distance is the radial deviation of the right inner cooling oil duct;
the radial deviation of the left inner cooling oil duct is as follows:
the radial deviation of the right inner cooling oil duct is as follows:
in addition, the middle point of the distance between the circle center of the left inner cooling oil duct and the circle center of the right inner cooling oil duct is calculated to be x 1804, y 1990 (pixel), and the integral radial deviation of the piston oil duct is as follows:
the images in fig. 4 and 5 were subjected to the measurement of the axial deviation of the inner cooling oil passage, which had left and right inner cooling oil passages, as shown in fig. 7 and 8, in which the three partial areas of the left inner cooling oil passage in the image corresponding to the 4mm position were 44839, 43893, and 45666, respectively, the three partial areas of the right inner cooling oil passage were 53559, 54609, and 51675, the three partial areas of the left inner cooling oil passage in the image corresponding to the 2mm position were 31939, 30894, and 32588, respectively, and the three partial areas of the right inner cooling oil passage were 41550, 42938, and 3939, respectively, and then the three partial areas of the left inner cooling oil passage correspond to the three partial areas of the left inner cooling oil passage, respectively
The axial deviation of the left inner cooling oil duct is as follows:
or
Similarly, the three local areas of the right inner cooling oil passage are respectively corresponding
The axial deviation of the right inner cooling oil duct is as follows:
or
With three local areas of the left inner cooling gallery corresponding to each other
Three local areas of right inner cooling oil duct respectively correspond
The integral axial deviation of the inner cooling oil duct is as follows:
in the method, the calculation error can be reduced to a certain extent by calculating the k value mean value and the b value mean value corresponding to all the local areas, but in the actual calculation process, because the difference value between each pair of local areas can be in a certain range, in order to reduce the workload, a group of local oil passages can be randomly selected to calculate the axial deviation of the inner cooling oil passage within a certain error allowable range.
In the method, when the left inner cooling oil duct and the right inner cooling oil duct exist in the inner cooling oil duct, the radial deviation and the axial deviation of a single oil duct in the left inner cooling oil duct and the right inner cooling oil duct need to be calculated respectively, and the radial deviation and the axial deviation of the whole oil duct need to be calculated simultaneously.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the technical principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (4)
1. A method for automatically measuring the position deviation of a cold oil duct in a piston is characterized by comprising the following steps of: the method is used for automatically measuring the position deviation of the wavy inner cooling oil channel in the piston and comprises the following steps:
s1, scanning a piston with a wavy inner-cooling oil duct by adopting an X-ray linear array detector industrial CT system to obtain a DR image of the piston;
s2, searching the position of the wavy inner cooling oil duct on the DR image, setting the height of the inner cooling oil duct as h, respectively performing CT scanning at h/2, h/m and h/n (n is more than m & gt 2) to obtain corresponding tomographic images, and sequentially marking the tomographic images obtained at h/2, h/m and h/n as a first tomographic CT image, a second tomographic CT image and a third tomographic CT image respectively; wherein a plurality of local oil passages exist in the second tomographic CT image and the third tomographic CT image;
step S3, performing radial deviation measurement of the internal cooling oil passage by the first tomographic CT image: the method comprises the following specific steps:
s3-1, processing the first tomography image by using an automatic threshold segmentation method to obtain a binary image corresponding to the first tomography image, and recording the binary image as a first binary image;
step S3-2, when the number of the inner cooling oil passages in the first binary image is one, respectively extracting the edge of the piston and the edge of the inner cooling oil passage in the first binary image to obtain an outer contour line of the piston, an outer contour line of the inner cooling oil passage and an inner contour line of the inner cooling oil passage;
when the inner cooling oil duct in the first binary image has the left inner cooling oil duct and the right inner cooling oil duct, respectively extracting the edge of the piston, the edge of the left inner cooling oil duct and the edge of the right inner cooling oil duct from the first binary image to obtain an outer contour line of the piston, an outer contour line of the left inner cooling oil duct, an inner contour line of the left inner cooling oil duct, an outer contour line of the right inner cooling oil duct and an inner contour line of the right inner cooling oil duct;
s3-3, fitting the outer contour line of the piston extracted in the step S3-2 to calculate the circle center of the outer contour of the piston;
step S3-4, when the number of the inner cooling oil duct in the first binary image is one, calculating a central axis of the inner cooling oil duct according to an outer contour line of the inner cooling oil duct and an inner contour line of the inner cooling oil duct, fitting the central axis to calculate the center of the inner cooling oil duct, and calculating the distance between the center of the outer contour of the piston and the center of the inner cooling oil duct, wherein the distance is the radial deviation of the inner cooling oil duct;
when the inner cooling oil duct in the first binary image has the left inner cooling oil duct and the right inner cooling oil duct, calculating a central axis of the left inner cooling oil duct according to an outer contour line of the left inner cooling oil duct and an inner contour line of the left inner cooling oil duct, calculating a central axis of the right inner cooling oil duct according to an outer contour line of the right inner cooling oil duct and an inner contour line of the right inner cooling oil duct, fitting the central axis of the left inner cooling oil duct and the central axis of the right inner cooling oil duct respectively to obtain a circle center of the left inner cooling oil duct and a circle center of the right inner cooling oil duct, calculating a distance between a circle center of a piston outer contour and a circle center of the left inner cooling oil duct and a distance between a circle center of the piston outer contour and a circle center of the right inner cooling oil duct respectively to obtain a radial deviation of the left inner cooling oil duct and a radial deviation of the right inner cooling oil duct, and finally calculating a middle point of the circle center of the left inner cooling, calculating the distance between the middle point and the circle center of the outer contour of the piston, wherein the distance is the integral radial deviation of the inner cooling oil duct;
step S4, carrying out axial deviation measurement of the internal cooling oil passage through the second tomography image and the third tomography image: the method comprises the following specific steps:
s4-1, processing the second tomographic CT image and the third tomographic CT image by using an automatic threshold segmentation method respectively to obtain a binary image corresponding to the second tomographic CT image and a binary image corresponding to the third tomographic CT image, and recording the binary images as the second binary image and the third binary image in sequence;
step S4-2, when the number of the internal cooling oil ducts is one, calculating the area of each local oil duct in the second binary image and the area of the local oil duct at the corresponding same position in the third binary image, and searching the maximum value S in all the local oil duct areas in the second binary image or the third binary imagemaxAnd minimum value SminIf the axial deviation σ of the internal cooling oil passage is:
wherein,
S1(i) is the area of the ith local oil passage in the second binary image, S2(i) The area of the local oil duct in the third binary image, which is at the same position as the ith local oil duct in the second binary image, is M, and the total number of the local oil ducts in the second binary image and the third binary image, which are at the same position, is M;
when the inner cooling oil duct of the piston has a left inner cooling oil duct and a right inner cooling oil duct, respectively calculating the area of each local oil duct corresponding to the left inner cooling oil duct in the second binary image, the area of each local oil duct corresponding to the same position of the left inner cooling oil duct in the third binary image, the area of each local oil duct corresponding to the right inner cooling oil duct in the second binary image and the area of each local oil duct corresponding to the same position of the right inner cooling oil duct in the third binary image; then, searching out the maximum value S 'of the areas of all the local oil passages in the left internal cooling oil passage in the second binary image or the third binary image'maxAnd a minimum value of S'minAnd the maximum value S' of the areas of all local oil passages in the right inner cooling oil passagemaxAnd a minimum value S ″minThen, the axial deviation sigma of the left inner cooling oil passage is calculated respectively1And axial deviation sigma of right inner cooling oil passage2；
Wherein,
S′1(j) is the area, S 'of the jth local oil passage in the left internal cooling oil passage of the second binary image'2(j) The local oil duct area of the same position in the left inner cooling oil duct of the third binary image as the jth local oil duct in the left inner cooling oil duct of the second binary image is obtained, and N is the total number of the local oil ducts with the same position in the left inner cooling oil duct of the second binary image and the left inner cooling oil duct of the third binary image;
S″1(q) is the area of the q-th local oil passage in the right internal cooling oil passage of the second binary image, S ″2(q) is the area of the local oil duct at the same position in the right internal cooling oil duct of the third binary image as the q-th local oil duct in the right internal cooling oil duct of the second binary image, and K is the total number of the local oil ducts at the same position in the right internal cooling oil duct of the second binary image and the right internal cooling oil duct of the third binary image;
the calculation formula of the integral axial deviation sigma' of the inner cooling oil passage is as follows:
wherein,
or
2. The method for automatically measuring the positional deviation of the cold oil passage in the piston as set forth in claim 1, wherein: the automatic threshold segmentation method used in the steps S3-1 and S4-1 is a maximum inter-class variance method.
3. The method for automatically measuring the positional deviation of the cold oil passage in the piston as set forth in claim 1, wherein: the method used for fitting the outer contour line of the piston in step S3-3 is a circular fitting method.
4. The method for automatically measuring the positional deviation of the cold oil passage in the piston as set forth in claim 1, wherein: the method used for the centering axis fitting in step S3-4 is an ellipse fitting method.
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| US20020178593A1 (en) * | 2001-05-31 | 2002-12-05 | Yasunaga Corporation | Position sensor for a hydraulic actuator and hydraulic system using the same |
| CN109254137A (en) * | 2018-09-21 | 2019-01-22 | 青岛海洋地质研究所 | The hydrate sediment stream solid output measuring device and measuring method of joint X-CT technology |
| CN209706770U (en) * | 2019-06-03 | 2019-11-29 | 西安康博新材料科技有限公司 | A kind of piston binary channels undaform oil duct ultrasonic detection device |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US20020178593A1 (en) * | 2001-05-31 | 2002-12-05 | Yasunaga Corporation | Position sensor for a hydraulic actuator and hydraulic system using the same |
| CN109254137A (en) * | 2018-09-21 | 2019-01-22 | 青岛海洋地质研究所 | The hydrate sediment stream solid output measuring device and measuring method of joint X-CT technology |
| CN209706770U (en) * | 2019-06-03 | 2019-11-29 | 西安康博新材料科技有限公司 | A kind of piston binary channels undaform oil duct ultrasonic detection device |
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