JP2012093316A - Surface evaluation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface evaluation device which can quantitatively evaluate workpiece surface unevenness using all coordinate point data of power spectra.SOLUTION: A surface evaluation device 10 which evaluates a workpiece surface based on workpiece surface unevenness data includes: means of obtaining power spectra by the Fourier transform of the workpiece surface unevenness data; means of digitizing the power spectra using cross-correlation functions; and the means of evaluating the workpiece surface using the maximum value of the digitized values.

Description

  The present invention relates to a surface evaluation apparatus for quantitatively evaluating the uneven state of a workpiece surface.

  Conventionally, the surface condition of a cylinder bore of an internal combustion engine after honing has been closely related to engine seizure and piston friction, and is therefore an important quality evaluation item for the engine. Specifically, the spiral streak formed when the cylinder bore is honed has a function of holding engine oil, and the formation state of the spiral streak changes to the lubrication state of the piston portion (oil consumption, friction). Since it contributes, the quality evaluation is performed in the machining process of the cylinder block.

  As a means for evaluating the surface condition of the cylinder bore, visual quality evaluation using a transfer image by SUMP or the like, and two-dimensional roughness measurement results such as Rz (ten-point average roughness), Ra (centerline average roughness) are used. However, the former has poor reproducibility of evaluation results, and the latter has the problem that the obtained information is line information, and the accuracy is insufficient as an index for evaluating the aforementioned engine performance.

  In recent years, three-dimensional roughness (shape) measuring machines that can measure the roughness of the machined surface at the surface level have also become widespread, but the cost is high, the measurement time is long, and the sensor head is installed in the bore. There is a problem that the full-scale application to the quality evaluation of the bore surface is not expected. In other words, there is a need for a technology that can quickly and easily evaluate the bore surface quality in multiple dimensions.

  In the inspection of the state of the cylinder bore surface after the honing process, in recent years, image diagnosis has been used to improve the inspection efficiency.

  For example, Patent Document 1 discloses a technique for selecting a coordinate point having a power value having a power spectrum equal to or greater than a certain value and evaluating the workpiece surface.

JP 2004-340805 A

  However, since the surface analysis apparatus described in Patent Document 1 is a surface evaluation performed by selecting a coordinate point having a power value equal to or greater than a certain value, the accuracy is poor. Therefore, instead of selecting only specific coordinate points of the power spectrum, it is desirable to improve accuracy by performing surface evaluation using all coordinate point data of the power spectrum.

  Therefore, the present invention has been made in view of the above problems, and an object thereof is to provide a surface evaluation apparatus capable of quantitatively evaluating the uneven state of the workpiece surface using all coordinate point data of the power spectrum. And

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

That is, in claim 1,
In the surface evaluation device that evaluates the workpiece surface based on the unevenness data of the workpiece surface,
Means for Fourier transforming the unevenness data of the workpiece surface to obtain a power spectrum;
Means for digitizing the power spectrum using a cross-correlation function;
Means for evaluating the workpiece surface using a maximum value of the digitized values;
Is a surface evaluation apparatus.

In claim 2,
The workpiece surface is a surface evaluation device that is a cylinder bore surface of an internal combustion engine.

  When the workpiece surface is evaluated as in the present invention, by using the cross-correlation function, the surface evaluation including all coordinate point data can be performed, and the evaluation accuracy is improved.

The schematic diagram which shows schematic structure of the surface evaluation apparatus which concerns on one Embodiment of this invention. It is explanatory drawing explaining the surface evaluation method applied to the surface evaluation apparatus which concerns on embodiment, (a) is a figure which shows imaging data, (b) is a figure which shows 3D shape data, (c) shows a power spectrum. Figure. Explanatory drawing for demonstrating applying a cross correlation function with respect to the power spectrum of FIG.2 (c), and quantifying. The figure which shows the flow of the quality determination of a bore surface.

  Next, embodiments of the invention will be described.

  Hereinafter, as one embodiment of the surface evaluation apparatus of the present invention, a surface evaluation apparatus for evaluating the surface processing quality of a workpiece surface will be described with reference to the drawings. In the present embodiment, the surface of the cylinder bore 2 in the cylinder block 1 of the internal combustion engine will be described as an example of the workpiece surface to be evaluated.

  The surface evaluation apparatus 10 is an apparatus that evaluates the inner peripheral surface of the cylinder bore 2 based on unevenness data relating to the unevenness state of the inner peripheral surface of the cylinder bore 2, and as shown in FIG. Means 3 and a computer 5 that evaluates the unevenness of the inner peripheral surface of the cylinder bore 2 based on the imaging signal output from the imaging means 3. Specifically, the surface evaluation device 10 is a device that performs a pass / fail determination on the formation state of the spiral streaks among the uneven components on the inner peripheral surface of the cylinder bore 2.

  The image pickup means 3 is inserted into the cylinder bore 2 to reciprocate the CCD camera for picking up an image of the inner peripheral surface of the cylinder bore 2 and the CCD camera in the height direction of the cylinder bore 2, and the CCD camera is rotated around the center axis of the cylinder bore 2. Driving means for rotationally driving the motor. The operation of the CCD camera and the driving unit included in the imaging unit 3 is controlled in accordance with a command from the computer 5. The imaging unit 3 can acquire an image signal of a predetermined inspection range on the inner peripheral surface of the cylinder bore 2 by rotating and driving the CCD camera in a predetermined pattern by the driving unit and reciprocating in the height direction of the cylinder bore 2. . The image signal obtained by the CCD camera is synthesized by the computer 5 according to the predetermined pattern, thereby creating one analysis image representing the entire inspection range of the inner peripheral surface of the cylinder bore 2. The imaging unit 3 is connected to the computer 5 via the data transfer unit 4.

  The computer 5 stores a CPU for executing various processes relating to surface evaluation and various processes relating to data analysis, a program for various surface evaluation / analysis processes, and storing information necessary for the analysis process such as the imaging signal. And an output means 6 such as a monitor for outputting an image of the inner peripheral surface of the cylinder bore 2 imaged by the imaging means 3 (for example, bore surface unevenness data indicated by arrows in FIG. 1), analysis results, evaluation results, and the like. . Further, the computer 5 outputs a command signal for controlling an input port for inputting an image pickup signal output from the image pickup means 3 via the data transfer unit 4 and a CCD camera and a driving device of the image pickup means 3. An output port is provided.

  The data analysis unit is an analysis unit included in the computer 5 for executing a predetermined analysis process on the unevenness data that is an analysis image, and the computer 5 executes a program to evaluate the quality of the inner peripheral surface of the cylinder bore 2. Each analysis process for performing can be performed.

Specifically, the data analysis unit obtains the power spectrum calculation unit, which is a means for obtaining a power spectrum (also referred to as a frequency spectrum) by Fourier transforming the unevenness data on the inner peripheral surface of the cylinder bore 2, and obtains the power spectrum calculation unit. A cross-correlation function Rxy (i, j, kx, ky) that is a means for obtaining a cross-correlation function Rxy (i, j, kx, ky) of the obtained power spectrum, and the cross-correlation function Rxy (i, j, kx, ky), a maximum value calculation unit that is a means for obtaining the maximum value, and the cross correlation function Rxy (i, j, kx, ky) obtained by the cross correlation function calculation unit is the maximum value of kx, ky Maximum time variable calculation unit that is a means for calculating the value of each variable, the maximum value of the cross-correlation function Rxy (i, j, kx, ky) calculated by the maximum value calculation unit, and the maximum time variable calculation Is a means for determining the quality evaluation of the inner peripheral surface of the cylinder bore 2 based on the values of the variables kx and ky when the cross-correlation function Rxy (i, j, kx, ky) obtained in (1) becomes the maximum value. While being comprised by the evaluation calculating part and the display part which displays the calculation result of the said evaluation calculating part, the calculation function of each calculating part is made executable by a program.
The details of the cross-correlation function Rxy (i, j, kx, ky) will be described later.

The cross-correlation function calculation unit, the maximum value calculation unit, and the maximum time variable calculation unit may use the cross-correlation function Rxy (i, j) for the power spectrum obtained by the power spectrum calculation unit. , Kx, ky) and means for digitizing the value of each variable of kx, ky at that time.
Further, the evaluation calculation unit uses the maximum value of the cross-correlation function Rxy (i, j, kx, ky), which is the digitized value, and the value of each variable of kx, ky at that time to determine the cylinder bore 2 It is a means for evaluating the inner peripheral surface.
In the present embodiment, the evaluation calculation unit uses the maximum value of the cross-correlation function Rxy (i, j, kx, ky) as a numerical value and the values of the variables kx and ky at that time. The inner peripheral surface of the cylinder bore 2 is evaluated, but is not particularly limited, and the maximum value of the cross-correlation function Rxy (i, j, kx, ky) or each variable of kx, ky at that time is expressed as a numerical value. It is also possible to evaluate the inner peripheral surface of the cylinder bore 2 using any one of the values.

  The power spectrum calculation unit performs discrete two-dimensional Fourier transform on the unevenness data that is the analysis image, and generates a two-dimensional or three-dimensional power spectrum image based on the result (see FIG. 2C). The image shown is a two-dimensional image). That is, the power spectrum calculation unit converts the unevenness data, which is an image of the inner peripheral surface of the cylinder bore 2, into a spectrum image in the frequency space. The two-dimensional power spectrum image shown in FIG. 2C is an image in which the horizontal axis and the vertical axis are the spatial frequencies in the x-axis and y-axis directions, respectively. At each coordinate point on the xy coordinate of the power spectrum, power values (convolution integral values) of frequency components of luminance levels in the circumferential direction and height direction of the inner peripheral surface of the cylinder bore 2 are plotted. . The power spectrum image calculation method itself is known, and for example, a conventional method (for example, the method disclosed in Patent Document 1) can be used.

  Next, a method for evaluating the surface of the concave / convex state on the inner periphery of the cylinder bore 2 using the surface evaluation apparatus 10 will be specifically described. Here, as a specific example, a method for quantitatively evaluating the formation state of the spiral streaks on the inner peripheral surface of the cylinder bore 2 formed during the honing process will be described with reference to FIG.

  In the evaluation of the formation state of the spiral streak on the surface of the cylinder bore 2, first, the imaging means 3 is inserted into the cylinder bore 2 of the cylinder block 1, and the inner peripheral surface of the cylinder bore 2 is imaged. Imaging is performed while the CCD camera is rotated about the central axis of the cylinder bore 2 and moved in the height direction of the cylinder bore 2 to sequentially scan the entire inner peripheral surface of the cylinder bore 2 in the circumferential direction and the height direction. . The imaging signal output from the imaging means 3 is input to the computer 5 through the data transfer unit 4 and the input port.

  When the imaging signal is input to the data analysis unit included in the computer 5, the computer 5 processes the signal, generates unevenness data on the inner peripheral surface of the cylinder bore 2, and stores it in the storage means.

  The imaging data shown in FIG. 2 (a) shows an example of unevenness data on the inner peripheral surface of the cylinder bore 2. In the imaging data, the x axis indicates the circumferential direction in the cylinder bore 2, and the y axis indicates the cylinder bore 2. The vertical height direction is shown. In addition, in the imaging data shown in FIG. 2A, it can be confirmed that there are a plurality of periodic spiral stripes in two different oblique directions, that is, an upward right direction and a downward right direction. That is, according to the imaging data shown in FIG. 2A, it can be seen that a spiral streak of a so-called cross hatch pattern is formed on the inner peripheral surface of the cylinder bore 2.

Also, the 3D shape data shown in FIG. 2B is an example of the unevenness data on the inner peripheral surface of the cylinder bore 2, and in the 3D shape data, the x-axis indicates the vertical height direction in the cylinder bore 2. The y axis indicates the circumferential direction in the cylinder bore 2, and in FIG. 2B, the z axis indicates the unevenness level (the level of unevenness). In the 3D shape data shown in FIG. 2B, it can be confirmed that there are a plurality of periodic spiral stripes in two different directions (basically oblique directions). That is, according to the 3D shape data shown in FIG. 2 (b), a plurality of honing grooves appearing regularly at substantially regular intervals, so-called cross-hatch pattern spiral stripes, are three-dimensionally formed on the inner peripheral surface of the cylinder bore 2. You can see that it is formed.
Note that as the unevenness data, any data (RGB data, 3D shape measurement data, etc.) indicating the unevenness state of the surface of the cylinder bore 2 can be applied, and is acquired by an imaging means such as a CCD camera as in this embodiment. It is not limited to unevenness data (imaging data shown in FIG. 2 (a)), for example, unevenness data (for example, 3D roughness measuring instrument, other surface shape measuring instrument, etc., which is acquired using a surface roughness measuring instrument) The 3D shape data shown in FIG. 2B may also be used.

  Then, by executing a two-dimensional Fourier transform process on the cylinder bore 2 inner circumferential surface irregularity data stored in the storage means, a power spectrum based on imaging data which is irregularity data on the inner circumferential surface of the cylinder bore 2 (FIG. 2C). Reference) is acquired and stored in the storage means.

  FIG. 2C shows a power spectrum obtained by performing two-dimensional Fourier transform on imaging data which is unevenness data on the inner peripheral surface of the cylinder bore 2. The x-axis and y-axis in FIG. 2C indicate frequency components after two-dimensional Fourier transform in the x-axis direction and the y-axis direction in the imaging data, respectively. At each coordinate point on the xy coordinate of such a power spectrum, the power value (convolution integral value) of each frequency component of the luminance level in the circumferential direction and the height direction of the inner peripheral surface of the cylinder bore 2 is plotted. Yes. In such a power spectrum, the first quadrant, the third quadrant, the second quadrant, and the fourth quadrant are point-symmetric with respect to the origin of the xy coordinates (power spectrum origin).

  After obtaining the power spectrum of the imaging data on the inner peripheral surface of the cylinder bore 2 as described above, the computer 5 performs processing by applying a cross-correlation function (see Equation 1) to the frequency component in the obtained power spectrum. . Here, the cross-correlation function is, for example, for obtaining a correlation between two functions f (i, j) and g (i, j). In other words, it is a means applied to examine how similar two coordinate points are, or how far the two coordinate points are located. In the function (Equation 1) according to the present embodiment, the coordinates of f (i, j) are left as they are, the coordinates of g (i, j) are shifted by kx and ky, and the inner product of both is obtained in a predetermined section. It is. The correlation value of the inner product is a function having coordinate deviations kx and ky as variables. This function is a cross-correlation function applied in the present embodiment. That is, in this embodiment, a cross-correlation function is applied in order to see the correlation between data plotted on two coordinates. Hereinafter, an example in which the cross-correlation function is applied to the power spectrum will be specifically described with reference to FIG.

  In the power spectrum shown in FIG. 3 (a) (the same as the power spectrum shown in FIG. 2 (c)), the first quadrant and the third quadrant indicate the downward-sloping components of the spiral streak in the image data. On the other hand, the quadrant II and quadrant IV indicate the components that rise to the right of the spiral streak in the imaging data. Thus, the first quadrant and the third quadrant, and the second quadrant and the fourth quadrant are symmetrical with respect to the origin.

  In order to quantitatively evaluate the formation state of the spiral streaks formed on the inner peripheral surface of the cylinder bore 2, the quadrature that does not have the symmetrical relationship of the power spectrum shown in FIG. Investigate the correlation between quadrants that do not become. That is, in order to quantitatively evaluate the formation state of the spiral streak, the correlation between the two quadrants that are not symmetrical to each other is examined, and the right lowering component and the right rising component of the spiral streak are Determine the formation balance. In this embodiment, when evaluating the formation balance of the right-down component and the right-up component of the spiral streak, as an example, a cross-correlation function with respect to the first quadrant having the right-down component and the second quadrant having the right-up component Is applied to evaluate the formation balance.

  FIG. 3B is an explanatory diagram imaged for understanding the case where the cross-correlation function is applied to the first and second quadrants of the power spectrum of FIG. As shown in FIG. 3B, when the cross-correlation function is applied to the first and second quadrants, the first quadrant (function f (i, j)) and the second quadrant (function g (i) , J), and the data in the second quadrant shown in FIG. 3B is obtained by superimposing the frequency vertical axis) with kx and ky as variables, and the cross-correlation function Rxy corresponding to the variables kx and ky. A change in the size of (i, j, kx, ky) is observed. FIG. 3C shows a three-dimensional relationship between the value of the cross-correlation function Rxy (i, j, kx, ky) and the value of each variable kx, ky. As can be seen from these figures, when the cross-correlation function is applied to the quadrant I having the downward-sloping component and the quadrant II having the upward-sloping component, Rxy (i, i, i) at kx = m and ky = n. j, kx, ky) is the largest, and the higher the value of Rxy (i, j, kx, ky) at that time, the more closely the formation state of the spiral stripes falling to the right and the spiral stripes rising to the right Become. Also, kx = m and ky = n when Rxy (i, j, kx, ky) is the maximum represent the positional deviation amount between the right-down spiral stripe and the right-up spiral stripe. The smaller the values of, m, and n, the more similar the formation state of the spiral stripes falling to the right and the spiral stripes rising to the right. That is, if the maximum value of Rxy (i, j, kx, ky) is larger and kx and ky at that time are smaller, the spiral streak formation state will be very similar, and the right-down spiral streak It can be said that this is a well-formed and well-balanced state where the spiral stripes rising to the right are balanced. The surface evaluation apparatus 10 according to the present embodiment obtains the maximum value of these Rxy (i, j, kx, ky) and each value of kx, ky at that time, and forms the spiral streak based on each value. The state is quantitatively evaluated.

  As described above, when the cross-correlation function is applied to the first quadrant having the right-down component and the second quadrant having the right-up component, Rxy (i, j, kx, ky at kx = m and ky = n. ) Is the maximum, and the larger the value of Rxy (i, j, kx, ky) at that time, and the smaller each value of kx, ky at that time, It shows that the formation state is very similar. As for the honing quality of the inner peripheral surface of the cylinder bore 2, the spiral streak has a function of retaining engine oil, and the formation of the spiral streak contributes to the lubrication state (oil consumption, friction) of the piston part. Therefore, there is a cross-hatch pattern in which the clean and well-balanced spiral streak formation state, that is, the formation state of the right downward spiral streak and the right upward spiral streak on the inner peripheral surface of the cylinder bore 2 is very similar. It is required to be formed. Therefore, as an evaluation method of the formation state of the spiral streak, the formation state of the spiral streak on the inner peripheral surface of the cylinder bore 2 is digitized by the above-described method using the cross-correlation function. It is preferable to use it as a new determination standard value for determining pass / fail of this. Specifically, when determining the quality of the inner peripheral surface of the cylinder bore 2 in the production line of the internal combustion engine, the maximum value of the cross-correlation function Rxy (i, j, kx, ky) and the cross-correlation function Rxy (i, j, kx) , Ky) is set to a standard value for use in quality determination in advance for the values of the variables kx and ky when the maximum value is obtained, and the quality determination of the inner peripheral surface of the cylinder bore 2 is performed based on the standard value. And the result of the quality determination of the inner peripheral surface of the cylinder bore 2 is output via an output means 6 such as a monitor.

  In this way, the data analysis unit of the computer 5 allows the maximum value of the cross-correlation function Rxy (i, j, kx, ky) and the cross-correlation function Rxy (i, j, kx, ky) to be the maximum value. The honing quality is evaluated based on kx and ky.

  That is, the computer 5 uses a cross-correlation function for quadrants having a right-up component and a right-down component of the spiral streak in the power spectrum shown in FIG. By performing the processing, the maximum value of the cross-correlation function Rxy (i, j, kx, ky) and the kx and ky when the cross-correlation function Rxy (i, j, kx, ky) is maximized are calculated. The maximum value of the cross-correlation function Rxy (i, j, kx, ky), the kx, ky at that time, and the maximum value of the cross-correlation function Rxy (i, j, kx, ky) preset in the computer 5 By comparing the values of kx and ky at that time with each other, it is possible to evaluate the quality of the formation of the spiral streak on the inner peripheral surface of the cylinder bore 2.

  Next, FIG. 4 shows a flowchart of the surface evaluation processing steps executed by the surface evaluation apparatus 10 of the present embodiment described above. This process is executed by the data analysis unit of the computer 5. Each processing step will be described with reference to the flowchart of FIG.

  The surface evaluation processing step includes a standard value determination step for determining a quality determination standard value in advance and a main measurement step for performing a main measurement for determining pass / fail of the cylinder bore 2 in the production line of the internal combustion engine. Hereinafter, each step will be described.

  In the standard value determining step, a predetermined standard value for performing a pre-evaluation on a predetermined workpiece in advance using the surface evaluation device 10 to determine whether or not a spiral streak is formed on the inner peripheral surface of the cylinder bore 2 is determined. It is a step of determining.

  In the standard value determining step, first, a master work serving as a standard value determining standard is selected (S100), and the imaging means 3 is used to photograph the inner peripheral surface of the cylinder bore 2 to be inspected to obtain unevenness data on the inner peripheral surface of the cylinder bore 2. (S110). Next, the data analysis unit performs a two-dimensional Fourier transform on the unevenness data on the surface of the cylinder bore 2, and obtains a power spectrum from the conversion result (S120). Next, a cross-correlation function Rxy (i, j, kx, ky) between the right-down component (I quadrant or III quadrant) and the right-up component (II quadrant or IV quadrant) of the power spectrum is obtained (S130). Next, the maximum value of the cross-correlation function Rxy (i, j, kx, ky) and kx and ky at that time are obtained (S140). Then, a predetermined quality evaluation criterion value is determined from the maximum value of the obtained cross-correlation function Rxy (i, j, kx, ky) and each value of kx, ky at that time (S150). The determined quality evaluation determination standard value is used in this measurement process, and becomes a determination standard value in the quality determination of the formation state of the spiral streaks on the inner peripheral surface of the cylinder bore 2 after the honing process.

  This measurement process is a process applied to inspect the workpiece in the production line of the internal combustion engine, that is, to determine the quality of the inner peripheral surface of the cylinder bore 2 after the honing process.

In this measurement process, first, a workpiece to be evaluated is selected (S200), and the imaging means 3 photographs the inner peripheral surface of the cylinder bore 2 to be inspected to obtain unevenness data on the inner peripheral surface of the cylinder bore 2 (S210). Next, the data analysis unit performs a two-dimensional Fourier transform on the unevenness data on the surface of the cylinder bore 2, and obtains a power spectrum from the conversion result (S220). Next, a cross-correlation function Rxy (i, j, kx, ky) between the right-down component (I quadrant or III quadrant) and the right-up component (II quadrant or IV quadrant) of the power spectrum is obtained (S230). Subsequently, the maximum value of the cross-correlation function Rxy (i, j, kx, ky) and kx and ky at that time are obtained (S240), and the maximum value of the obtained cross-correlation function Rxy (i, j, kx, ky) and Then, it is determined whether kx and ky at that time are within the standard values (S250). That is, the data analysis unit of the computer 5 uses the quality evaluation determination standard value determined in the quality evaluation determination determined as described above, and uses the maximum value of the cross-correlation function Rxy (i, j, kx, ky). If the value and the values of kx and ky at that time are within the quality evaluation determination standard value (Yes), it is determined that the formation of the spiral streaks on the inner peripheral surface of the cylinder bore 2 is good (OK determination), and the cross-correlation If the maximum value of the function Rxy (i, j, kx, ky) and the values of kx and ky at that time are not within the quality evaluation judgment standard value (No), the formation state of the spiral streaks on the inner peripheral surface of the cylinder bore 2 is It is determined to be defective (No) (NG determination).
As the standard value, for example, when the maximum value of the cross-correlation function Rxy (i, j, kx, ky) is equal to or larger than the standard value of the maximum value determined in the standard value determination step, the maximum value is obtained. The values of kx and ky are preferably equal to or less than the standard values of the values of kx and ky determined in the standard value determining step, and the range of standard values used in this measurement step may be determined.

  As described above, according to this embodiment, it is possible to evaluate the spiral streak state on the inner peripheral surface of the cylinder bore 2 of the internal combustion engine formed during the honing process based on the frequency information of the unevenness data. For example, in the power spectrum obtained by Fourier transforming the imaging data of the bore surface or 3D unevenness data, the symmetry (correlation) of the frequency components between quadrants that are not symmetrical is obtained by the cross correlation function, and the honing quality Can be evaluated.

  The present invention pays attention to the fact that the spiral streaks formed during the honing process are formed with regularity, and the frequency of the uneven state of the engine bore surface is analyzed to simplify the formation of the spiral streaks. And can be quantitatively evaluated.

  According to the present invention, when a workpiece surface is evaluated, by using a cross-correlation function, an evaluation using all coordinate points of a power spectrum, that is, a surface evaluation including all coordinate point data can be performed. Evaluation accuracy is improved as compared with conventional surface evaluation using coordinate points.

DESCRIPTION OF SYMBOLS 1 Cylinder block 2 Cylinder bore 3 Imaging means 5 Computer 10 Surface evaluation apparatus

Claims (2)

In the surface evaluation device that evaluates the workpiece surface based on the unevenness data of the workpiece surface,
Means for Fourier transforming the unevenness data of the workpiece surface to obtain a power spectrum;
Means for digitizing the power spectrum using a cross-correlation function;
Means for evaluating the workpiece surface using a maximum value of the digitized values;
A surface evaluation apparatus comprising:   The surface evaluation apparatus according to claim 1, wherein the workpiece surface is a cylinder bore surface of an internal combustion engine.

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