JP5405899B2 - Surface inspection device - Google Patents

Description

  The present invention relates to a surface inspection apparatus for inspecting the surface of a workpiece.

In an automobile manufacturing process, a bore is cut in a cylinder block of an engine, and then a cylinder head, a crankcase, and the like are assembled to the cylinder block. In boring, the bore is formed by moving the boring tool back and forth with respect to the cylinder block, forming a bore on the inner surface of the bore, which is used as an engine oil passage (oil pit). ing.
In addition, since the inner surface of the bore becomes the sliding surface of the piston, it is necessary to maintain the sliding surface with an appropriate surface roughness and surface properties in order to suppress the sliding resistance and to exert the desired performance on the engine. is there. Therefore, after the boring process, a honing process is performed to polish and finish the inner surface of the bore so that oil pits remain. Then, after the honing process, in order to inspect the polishing residue that causes the sliding resistance, an inspection of the smooth state of the inner surface of the bore is performed.

In this inspection, an optical unit is inserted into the bore, a reflected image of laser light emitted from the optical unit is photographed by a camera through the optical unit, and a digital image of the inner surface of the bore is generated. For example, image processing for detecting a smooth state, such as binarization processing or power spectrum processing, is performed, and the smooth state is evaluated (for example, see Patent Document 1).
Japanese Patent Publication No. 2004-132900

However, since the image processing is performed on the digital image over the entire inner surface of the bore, the time required for the inspection is increased, which hinders improvement in engine productivity. In addition to this, there is a problem that when foreign matter such as water droplets or dust adheres to the inner surface of the bore, the foreign matter is reflected in the digital image and erroneously determined as a defect.
The present invention has been made in view of the circumstances described above, and is a surface inspection that is not affected by foreign matter on the surface and that can reduce the time required for the inspection by accurately narrowing down the area to be image-processed. An object is to provide an apparatus.

In order to achieve the above object, the present invention scans the surface of a workpiece with a sensor head that irradiates the surface with laser light, generates a digital image of the surface based on a reflected image of the laser light, and In a surface inspection apparatus that inspects the surface by performing image processing for detecting defects on the surface of a digital image, an eddy current flaw detection sensor that is provided in the sensor head and scans the surface together with the laser beam ; The image generation means for generating the digital image based on the reflected image of the laser light and the defect map image based on the output of the eddy current flaw detection sensor in association with the mutual position coordinates as the sensor head scans, identifying a defective portion of the workpiece based on a defect map image, the image processing range determined for determining an image processing range in the digital image comprising said defective portion And means, and to said image processing range in the digital image, and detects a defect of the image processing performed by said surface for determining the presence or absence of a defect.

  According to the present invention, the defect portion on the surface of the workpiece is detected by the eddy current flaw detection sensor without being affected by foreign matters such as water droplets and dust on the surface. Further, although the size of the detected defect and whether the defect is a surface defect or an internal defect such as a cast hole cannot be determined from the output of the eddy current flaw detection sensor, the image processing range including the defect portion Since image processing is performed on the image, the size of the defect can be determined. Therefore, the defect can be detected without being affected by the presence or absence of foreign matter on the surface, and the size of the defect can be reduced while reducing the time required for inspection by narrowing the range to be subjected to image processing to the image processing range. Can be determined.

In order to achieve the above-mentioned object, the present invention scans the inner surface of a bore formed and polished on a cylinder block with a sensor head that emits laser light, and based on the reflected image of the laser light, In a surface inspection apparatus for inspecting the inner surface by generating a digital image of the inner surface and performing image processing on the digital image to detect defects on the inner surface, the inner surface is provided with the sensor head, The eddy current flaw detection sensor that scans the surface together with the laser light, the digital image based on the reflected image of the laser light and the defect map image based on the output of the eddy current flaw detection sensor as the sensor head scans each other. image generating means for generating in correspondence the coordinates, to identify the defective portion on the basis of the defect map image, said digital include the defective portion And an image processing range determination means for determining an image processing range in the image, to the image processing range in the digital image to detect a defect of the inner surface is subjected to image processing for determining the presence or absence of a defect It is characterized by that.

  According to the present invention, a defect portion on the inner surface of the bore is detected by the output of the eddy current flaw detection sensor without being affected by foreign matters such as water droplets and dust on the inner surface. Although the size of the detected defect and whether the defect is a surface defect or an internal defect such as a cast hole cannot be determined from the output of the eddy current flaw detection sensor, the image processing range including the defect portion Since the image processing is performed on the image, the size of the defect and the like can be determined, and the dent, the polishing residue, the oil pit, and the like can be determined. As a result, defects can be detected without being affected by the presence or absence of foreign matter on the surface, and the time required for inspection is shortened by narrowing the range to be subjected to image processing to the image processing range, while making dents and polishing. The remaining oil pits can be identified.

According to the above invention, it is possible to detect a defect by the digital image of the workpiece surface and the eddy current flaw detection sensor in one scan.

According to the present invention, a defect of a workpiece can be detected by an eddy current flaw detection sensor without being affected by a foreign matter such as a water droplet or dust attached to the surface of the workpiece. Further, since the image processing can be performed only in the image processing range including the defective portion, the size of the defect can be determined and the time required for the inspection can be shortened.
Further, when inspecting the inner surface of the bore of the cylinder block, it is possible to efficiently discriminate the defective bore from the oil pit and harmful defects such as dents and polishing residues.
Further, by providing the sensor head with an eddy current flaw detection sensor, it is possible to detect a defect with the digital image of the workpiece surface and the eddy current flaw detection sensor in one scan.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a schematic configuration of a bore inner surface inspection system 1 according to an embodiment of the present invention and a cylinder block 5 in which a bore 3 to be inspected is formed.
The bore 3 is a so-called boring process in which a cutting tool is protruded in a radial direction on a boring head provided on a rotating shaft, and the boring head is moved forward and backward with respect to an aluminum alloy casting cylinder block 5 while rotating the boring head. It is formed by. By this boring, a spiral cutting trace having directionality is formed on the inner surface 3A of the bore 3. After that, honing is performed using a machining head provided with a honing grindstone so as to obtain surface roughness and surface properties capable of exhibiting desired engine performance while leaving an oil pit on the inner surface 3A of the bore 3. Processing has been applied.

The bore inner surface inspection system 1 detects defects on the inner surface 3A based on a digital image obtained by photographing the inner surface 3A of the bore 3, and evaluates the quality of the bore 3.
That is, the bore inner surface inspection system 1 detects a defect on the inner surface 3A of the bore 3 based on an output signal of the sensor head 7 that scans the inner surface 3A of the bore 3, and evaluates the quality. A device 9 and a drive mechanism 11 for moving and driving the sensor head 7 are provided.
The sensor head 7 is formed in a cylindrical shape that can enter the bore 3, and is attached to the drive mechanism 11 so as to be rotatable around the central axis 12 and movable in the direction of the central axis 12.
The sensor head 7 irradiates laser light toward the inner surface 3A of the bore 3 from the opening 15 provided on the peripheral surface, detects the amount of reflected light according to the uneven shape of the inner surface 3A, and outputs it to the surface inspection apparatus 9. At the same time, an eddy current is passed through the inner surface 3 </ b> A of the bore 3 to detect the generated electromagnetic induction and output it to the surface inspection device 9.

  Specifically, the sensor head 7 includes an LD (laser diode) 17 as a light source, an optical fiber 19, and a condensing optical unit 21, and guides the light from the LED 17 to the condensing optical unit 21 through the optical fiber 19. The light is condensed by the optical unit 21 and emitted from the opening 15. The sensor head 7 includes a light receiving sensor 23 that receives the reflected light, and a plurality of optical fibers 25 that guide the reflected light returning through the condensing optical unit 21 to the light receiving sensor 23 are adjacent to the optical fiber 19. Arranged.

Further, the sensor head 7 incorporates an eddy current flaw detection sensor 26. The eddy current flaw detection sensor 26 includes a coil for detecting an eddy current flowing through the inner surface 3A of the bore 3 and detecting a current generated by electromagnetic induction, and the current is amplified by the ET amplifier 28 and input to the surface inspection apparatus 9. Is done. That is, since the current due to electromagnetic induction changes depending on the unevenness of the inner surface 3A of the bore 3 and the presence / absence of the internal cavity, a defect is detected by detecting a location where the current due to electromagnetic induction changes. In addition, since the current due to electromagnetic induction is not easily affected by water droplets or dust attached to the inner surface 3A of the bore 3, it is possible to prevent erroneous determination due to water droplets or dust, etc., compared to defect determination by laser light irradiation.
The eddy current flaw detection sensor 26 is provided in the sensor head 7 so as to be able to detect the same height position as the laser light irradiation position. Thereby, digital image generation at the same height position of the bore 3 and defect detection by the eddy current flaw detection sensor 26 can be simultaneously performed by one scan.

The drive mechanism 11 includes a rotation drive mechanism 31 that rotates the sensor head 7 and an advance / retreat mechanism 33 that advances and retracts the rotation drive mechanism 31.
The rotation drive mechanism 31 includes a housing 34, a shaft 35 provided with the sensor head 7 at the tip and penetrating the housing 34 vertically, and a shaft that rotates the shaft 35 under the control of the surface inspection apparatus 9. A motor 37 and a rotary encoder 39 that detects the rotation speed and rotation angle of the shaft 35 and outputs the detected rotation speed to the surface inspection device 9 are provided.
The advancing / retreating mechanism 33 is a feed screw mechanism, and detects a shaft portion 41 in which a screw is engraved, an advancing / retreating motor 43 that rotationally drives the shaft portion 41, and a rotation speed and a rotation angle of the shaft portion 41 to detect a surface. 9 and a rotary encoder 45 that outputs to N. The shaft portion 41 is screwed into the nut portion 36 of the housing 34, and the shaft portion 41 is rotated by driving the advance / retreat motor 43, so that the rotation drive mechanism 31 is advanced and retracted.

  The surface inspection apparatus 9 includes a position control unit 51 that controls the position of the sensor head 7 by controlling the drive mechanism 11, a eddy current flaw detection unit 53 that detects a defect in the bore 3 based on a detection signal from the eddy current flaw detection sensor 26, A laser inspection unit 55 that generates a digital image of the inner surface 3A of the bore 3 based on the light reception signal of the sensor head 7 and evaluates the quality of the bore 3 based on the digital image is provided. The surface inspection apparatus 9 can be configured by causing a personal computer to execute a program for realizing each unit, for example.

  The parts of the surface inspection apparatus 9 will be described in more detail. The position control unit 51 includes a servo mechanism that drives the shaft motor 37 and the advance / retreat motor 43, and controls the position and rotation angle of the sensor head 7 on the central axis 12. To do. That is, the position control unit 51 inserts the sensor head 7 into the bore 3 at the start of inspection, and positions the opening 15 and the eddy current flaw detection sensor 26 at the lower end position Ka of the inspection range K. Then, the movement of raising the sensor head 7 while rotating it around the central axis 12 so as to follow the trajectory of the boring tool at the time of boring, the opening 15 of the sensor head 7 and the eddy current flaw sensor 26 are within the inspection range K. The process is performed until the upper end position Kb is reached, and the entire surface of the inspection range K is spirally scanned by the sensor head 7. This inspection range K is determined by a range that functions as a sliding surface with the cylinder.

The eddy current flaw detection unit 53 A / D converts the detection signal of the eddy current flaw detection sensor 26 of the sensor head 7 and outputs it as a digital signal having an intensity value corresponding to the presence or absence of a defect. An imaging unit 59 that generates a defect map image 70 based on the defect map unit 70 and a defect detection unit 61 that detects a defect location P based on the defect map image 70 are provided.
As shown in FIG. 2A, the defect map image 70 is obtained by imaging the detection signal of the eddy current flaw detection sensor 26 in correspondence with the inspection position. In this embodiment, the height position X of the sensor head 7 is detected. The rotation angle θ of the sensor head 7 is imaged with the vertical axis and the horizontal axis, respectively. In the defect map image 70, a portion where the detection signal of the eddy current flaw detection sensor 26 has changed due to a defect such as a dent, a cutting mark, or a cast hole on the inner surface 3 </ b> A of the bore 3 appears as a defect portion P. The defect portion P is detected by the defect detection unit 61, and position coordinates (X, θ) defined by the height position X and the rotation angle θ are output to the laser inspection unit 55.

The laser inspection unit 55 performs A / D conversion on the light reception signal from the sensor head 7 and outputs it as a digital signal indicating luminance, and an image for generating a digital luminance image 71 based on the digital signal. An image processing range determination unit 67 that determines an image processing range T for the digital luminance image 71 based on the position coordinates of the defect portion P detected by the conversion unit 65 and the defect detection unit 61 of the eddy current flaw detection unit 53. An evaluation unit 69 that performs image processing on the image processing range T and evaluates the quality of the bore 3 based on the result of the image processing is provided.
As shown in FIG. 2B, the digital luminance image 71 is obtained by imaging the reflected light intensity obtained by the sensor head 7 at each inspection position in the bore 3 in correspondence with the inspection position. In the embodiment, similarly to the defect map image 70, the height position X of the sensor head 7 and the rotation angle θ of the sensor head 7 are imaged with the vertical axis and the horizontal axis, respectively.

  Here, while moving the sensor head 7 from the lower end position Ka to the upper end position Kb in the bore 3, both the laser light irradiation and the detection by the eddy current flaw detection sensor 26 are performed simultaneously. Accordingly, a phase difference α corresponding to the mounting interval between the opening 15 and the eddy current flaw detection sensor 26 is generated between the laser light irradiation position and the detection position of the eddy current flaw detection sensor 26. Therefore, when generating the digital luminance image 71, the imaging unit 65 corrects the rotation angle θ of the detection position with the phase difference α so that the position coordinates are equal to the position coordinates of the defect map image 70, and forms an image.

In the digital luminance image 71, as shown in FIG. 2B, a cutting mark Q at the time of boring, a dent mark R formed by a collision of a tool such as a boring tool, etc. are displayed. In the conventional surface inspection, the entire digital luminance image 71 is subjected to binarization processing and power spectrum calculation processing to exclude oil pits from the detected cutting trace Q and to perform cutting processing such as polishing residue. In order to extract harmful defects such as the mark Q and the dent mark R, processing takes time.
On the other hand, in the present embodiment, as described above, the image processing range determination unit 67 limits the range on which image processing is performed to the defective portion P, thereby enabling high-speed processing.

More specifically, when the position coordinate (X, θ) of the defect location P detected by the eddy current flaw detection sensor 26 is input from the defect detection unit 61, the image processing range determination unit 67 receives the position coordinate (X, θ). A rectangular area within a predetermined range centering on is defined as an image processing range T.
Accordingly, for example, as shown in FIG. 2C, when the dent R exists on the inner surface 3 </ b> A of the bore 3, a range including the dent R is determined as the image processing range T. Further, in the eddy current flaw detection, internal defects such as a casting hole are detected in addition to surface defects such as the dent mark R and the cutting mark Q, and these cannot be distinguished only by the result of the eddy current flaw detection. For this reason, when an internal defect such as a cast hole is detected by the eddy current flaw detection unit 53, as shown in FIG. 2C, the digital luminance image 71 is conspicuous such as the dent mark R and the cutting mark Q. The image processing range T is also determined for a range where unevenness is not seen.

  Note that the size of the image processing range T may be a fixed value or a variable value. That is, when a rough range of the defect portion P is input from the defect detection unit 61 to the image processing range determination unit 67, the image processing range T is varied to include the range. In addition, when the defect detection unit 61 is configured to input, for example, only the center position of the defect portion P to the image processing range determination unit 67, a range defined in advance in consideration of a dent R and a polishing residue that may normally occur. An image processing range T (for example, 10 μm square) is used.

  The evaluation unit 69 performs image processing on each image processing range T, thereby discriminating between surface defects and internal defects and extracting only surface defects such as the dent mark R and the cutting mark Q. Then, the size (dimensions) of these dents R and cutting marks Q is obtained by image processing, and it is identified whether these are oil pits or harmful defects that hinder the function of the sliding surface. However, in the case of a harmful defect, the bore 3 is evaluated as defective.

In the image processing of the evaluation unit 69, for example, the image is binarized using a luminance value when the dent mark R or the cutting mark Q is present as a threshold value, and an image indicating the presence or absence of the dent mark R or the cutting mark Q is obtained. A binarization process can be used, and the binarization process can detect the presence or absence of the dent mark R or the cutting mark Q and specify the size thereof. By this binarization process, when the dent mark R or the cutting mark Q is not detected, an internal defect such as a cast hole is detected by eddy current flaw detection, and the internal defect can be distinguished.
In addition to the binarization processing, a power spectrum image is obtained for the image processing range T, and the unevenness of the image processing range T is determined based on the power spectrum image, and the unevenness is generated according to the proportion of the unevenness. The bore 3 can also be evaluated.

FIG. 3 is a flowchart of the bore inner surface inspection process performed by the bore inner surface inspection system 1.
After the cylinder block 5 in which the bore 3 to be inspected is formed is set at a predetermined position directly below the drive mechanism 11, the position control unit 51 causes the sensor head 7 to enter the bore 3 and advance and retract while rotating the bore 3. The inner surface 3A is scanned over the inspection range K (step S1). The eddy current flaw detection unit 53 generates a defect map image 70 based on the detection signal of the eddy current flaw detection sensor 26 obtained during the scanning, and the laser inspection unit 55 generates the digital luminance image 71 based on the reflected light amount of the laser light. Generate (step S2).

  Next, the eddy current flaw detection unit 53 detects the defect location P and the position information (X, θ) of the defect location P from the defect map image 70 (step S3) and outputs them to the laser inspection unit 55. Then, based on the positional information (X, θ) of the defective portion P, the laser inspection unit 55 determines that the image processing range T to be image-processed includes the defective portion P (step S4). Image processing such as binarization processing for detecting defects is performed on the image processing range T (step S5). When a relatively large defect such as a dent mark R or a cutting mark Q such as a polishing residue is detected by this image processing and a harmful defect that inhibits the function of the sliding surface is detected (step S6: YES), If the bore 3 is determined to be defective (step S7), and no harmful defect is detected (step S6: NO), the bore 3 is determined to be non-defective (step S8).

As described above, according to the present embodiment, since the inner surface 3A of the bore 3 is scanned by the eddy current flaw detection sensor 26, even when foreign matter such as water droplets or dust adheres to the inner surface 3A, the influence of the foreign matter is affected. Defects can be detected without receiving them.
Furthermore, although the exact size of the defect detected by the eddy current flaw detection and whether the defect is a surface flaw or an internal defect such as a cast hole cannot be determined from the detection signal of the eddy current flaw detection sensor 26, the defect Since image processing is performed on the image processing range T including the portion P, the size of the defect can be determined, and the detected cutting trace Q can be distinguished from the oil pit and the polishing residue. As a result, it is possible to accurately determine only harmful defects such as polishing residues and dents R, and the time required for inspection is shortened by narrowing the range to be subjected to image processing to the image processing range T. be able to.

  Further, according to the present embodiment, since the eddy current flaw detection sensor 26 is provided in the sensor head 7, the generation of the digital luminance image 71 by the laser light irradiation and the defect detection by the eddy current flaw detection sensor 26 can be performed by one scan.

In addition, embodiment mentioned above shows the one aspect | mode of this invention to the last, and can change arbitrarily within the scope of the present invention.
For example, in the embodiment, the apparatus for inspecting the inner surface 3 </ b> A of the bore 3 is illustrated, but the present invention is not limited to the apparatus for inspecting the machined surface of the hole like the bore 3. That is, the present invention can be applied to an apparatus for inspecting a planar surface of a workpiece. In this case, since the surface is a flat surface, a digital luminance image can be obtained by photographing the entire surface at once with a camera or the like.

It is a figure which shows schematic structure of the cylinder block in which the bore | bore inner surface inspection system which concerns on one Embodiment of this invention, and the bore | bore used as test object were formed. It is the figure which showed the image produced | generated by a bore | bore inner surface inspection along the flow of inspection. It is a flowchart of a bore | bore inner surface inspection process.

DESCRIPTION OF SYMBOLS 1 Bore inner surface inspection system 3 Bore 3A inner surface 5 Cylinder block 7 Sensor head 9 Surface inspection apparatus 26 Eddy current flaw detection sensor 51 Position control part 53 Eddy current flaw detection part 55 Laser inspection part 61 Defect detection part 67 Image processing range determination part 69 Evaluation part 70 Defect map image 71 Digital luminance image P Defect location Q Cutting trace R Imprint T Image processing range

Claims (2)

The surface of the workpiece is scanned with a sensor head that irradiates the surface with laser light, a digital image of the surface is generated based on the reflected image of the laser light, and defects on the surface are detected with respect to the digital image. In the surface inspection apparatus for inspecting the surface by performing image processing for
An eddy current flaw detection sensor provided on the sensor head for scanning the surface together with the laser beam ;
An image generating means for generating the digital image based on the reflected image of the laser light and the defect map image based on the output of the eddy current flaw detection sensor in association with the mutual position coordinates in accordance with the scanning of the sensor head;
Image processing range determination means for determining a defect location of the workpiece based on the defect map image , and determining an image processing range in the digital image including the defect location,
A surface inspection apparatus for detecting defects on the surface by performing image processing for determining the presence or absence of defects in the image processing range in the digital image . The inner surface of the bore formed and polished in the cylinder block is scanned with a sensor head that emits laser light, and a digital image of the inner surface is generated based on the reflected image of the laser light. In the surface inspection apparatus that inspects the inner surface by performing image processing for detecting defects on the inner surface,
An eddy current flaw sensor provided on the sensor head and scanning the inner surface together with the laser beam ;
An image generating means for generating the digital image based on the reflected image of the laser light and the defect map image based on the output of the eddy current flaw detection sensor in association with the mutual position coordinates in accordance with the scanning of the sensor head;
An image processing range determining means for identifying a defect location based on the defect map image and determining an image processing range in the digital image including the defect location;
A surface inspection apparatus for detecting a defect on the inner surface by performing image processing for determining the presence or absence of a defect with respect to the image processing range in the digital image .

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