JP5716459B2 - Cam surface observation method - Google Patents

Description

  The present invention relates to a cam surface observation method, and more particularly to a cam surface observation method using a wide-field laser microscope.

  In general, automobile engines have many parts that require high safety and reliability. In particular, the camshaft is an important part that controls intake and exhaust of the engine, and the shape of the camshaft is finished with high accuracy in order to influence the performance of the internal combustion engine. However, the condition and scratches on the cam surface affect the performance of the cam and cause factors such as increased friction and seizure. Therefore, it is very important to observe the surface of the cam, such as grasping the state of the cam surface and inspecting the scratch. The problem with the current camshaft inspection is that an inspection by a skilled worker is mainly performed. Therefore, inspection mistakes such as oversight of scratches and defects are inevitable. In addition, it takes time to acquire technical skills for visual inspection. Therefore, an apparatus that can observe the entire cam surface is required. Here, in order to observe the surface in detail, an apparatus capable of observation at a certain magnification such as a microscope is desired.

  However, with a general microscope, it is difficult to observe a curved surface such as a cam shape in a short time. Further, since the field of view becomes narrower when the resolution of the observation apparatus is increased, more time is required to observe a wide area. For this reason, no means for efficiently observing the entire circumference of the cam has been developed at present.

  So far, the present inventors have developed a wide-field laser microscope in the past and developed a method for observing a cylindrical surface using the same (Non-Patent Document 1). This method uses a wide-field laser microscope developed by the present inventors, performs laser scanning at high speed in the direction of the generatrix of the cylinder, and rotates the cylindrical surface in a short time. In this method, the image distortion can be suppressed and observed.

  However, this method can be used when the cross section of the cylindrical surface is completely circular, and it has been difficult to observe the surface of the cam having a non-circular cross section by this method.

Rintaro Ebuchi, Isamu Nitta: Cylindrical surface evaluation using a wide-field laser microscope, Proceedings of the 47th General Meeting and Lecture Meeting of the Japan Society of Mechanical Engineers Hokuriku Shin-etsu, (2010), pp.541-542 Isamu Nitta, Akihiro Kanno, Rinya Okamoto, Yasushi Nagaoka: Wide-field laser microscope using shrink fitter, Journal of Precision Engineering, 73 (11), pp.1226-1232

  Accordingly, an object of the present invention is to provide a novel cam surface observation method using a wide-field laser microscope that can observe the cam surface.

The cam surface observation method of the present invention guides laser light from a laser light source as a parallel beam to a scanning mirror via a beam splitter, and converts the laser light into scanning light by the scanning mirror and makes it incident on a telecentric fθ lens. The reflected light from the cam surface arranged close to the focal plane of the telecentric fθ lens is converted into a parallel light beam by the telecentric fθ lens, reflected by the scanning mirror, and then reflected from the laser light from the laser light source by the beam splitter. A cam surface that is separated, condensed by an imaging lens, passed through a pinhole located at a position conjugate with the focal plane of the telecentric fθ lens, and the amount of reflected light that has passed through the pinhole is measured by a light receiving element. The camshaft having the cam surface is rotated about its axis, and , Based on the data of the rough shape of the acquired in advance the cam surface moves the cam shaft the cam surface is always perpendicular to such so that with respect to the laser beam, and the laser beam focus is always characterized by observing while moving the pre Symbol camshaft so as to be positioned on the cam surface in the optical axis direction of the laser beam.

  The scanning light may be scanned along a generatrix on the cam surface.

  Further, each time the scanning light scans the bus surface of the cam surface once, the cam shaft is centered on the axis in an amount corresponding to the spot diameter of the scanning light in a direction orthogonal to the scanning direction of the scanning light. It is characterized by rotating it.

  Further, based on the light amount signal corresponding to the light amount measured by the light receiving element and the positional information on the cam surface from which the light amount signal is obtained, a three-dimensional image of the cam surface is created and displayed on the display means. It is characterized by that.

  According to the cam surface observation method of the present invention, the cam shaft having the cam surface is rotated about its axis, the cam surface is always perpendicular to the laser beam, and the focus of the laser beam is always the cam. By measuring while moving the camshaft so as to be located on the surface, the entire surface of the cam surface can be measured easily and in a short time.

  Further, by scanning the scanning light along the generatrix of the cam surface, the cam surface can be observed only by rotating the cam surface once, and measurement can be performed in a short time.

Further, each time the scanning light scans the bus surface of the cam surface once, the camshaft is rotated around the axis by an amount corresponding to the spot diameter of the scanning light in a direction orthogonal to the scanning direction of the scanning light. The shape of the cam surface can be accurately measured over the entire surface of the cam surface, and at the same time, a surface image of the cam surface can be obtained.

  Further, based on the light amount signal corresponding to the light amount measured by the light receiving element and the position information on the cam surface from which the light amount signal was obtained, a three-dimensional image of the cam surface is created and displayed on the display means. The measurement results can be displayed visually and clearly.

It is the schematic which shows the whole structure of the wide-field laser microscope used for the observation method of the cam surface of this invention. It is sectional drawing of the cam observed by the observation method of the cam surface of this invention. It is sectional drawing of the cam in a certain rotation angle same as the above. It is sectional drawing of the cam in another rotation angle same as the above. It is a two-dimensional image which shows the observation result of the cam surface. 6 is an enlarged image of a portion A in FIG. 5. It is a three-dimensional image which shows the observation result of the cam surface.

  Hereinafter, an embodiment of a method for observing a cam surface according to the present invention will be described with reference to the accompanying drawings.

  In FIG. 1 showing an example of a wide field laser microscope using the principle of a confocal laser scanning microscope used in the cylindrical surface shape measuring method of the present invention, reference numeral 1 denotes a laser light source (for example, a solid-state laser having a wavelength of 488 nm). The laser light output from the laser light source 1 is converted into a parallel laser beam by the collimator lens 2, and the parallel laser beam is reflected by the fixed mirror 3 and changes its direction, and the beam splitter 4 and the quarter wavelength plate 5 are changed. It is guided to a scanning mirror 7 that passes and rotates by a motor 6. The parallel laser light beam is converted into scanning light by being reflected by the scanning mirror 7 rotating in the direction of arrow A, passes through the telecentric fθ lens 8, and closes to the focal plane of the camshaft 9 disposed in the vicinity. Reflected by the cam surface 10. Here, when the scanning mirror 7 rotates in the direction of arrow A, the scanning light scans the cam surface 10 in the direction of arrow B along the generatrix of the cam surface 10. The camshaft 9 is held by holding means (not shown), rotated around the axis z by a rotating means (not shown) in the direction of arrow C, and moved in the optical axis direction x of the laser light by an optical axis direction moving means (not shown). It moves and moves in the vertical direction y by a vertical direction moving means (not shown). FIG. 1 is a plan view, and the optical axis direction x, the vertical direction y, and the axis z are orthogonal to each other.

  The measurement light, which is the reflected light reflected by the cam surface 10, passes through the telecentric fθ lens 8, is converted into a reflected parallel light beam, is reflected by the scanning mirror 7, passes through the quarter-wave plate 5, and is reflected by the beam. It is guided to the splitter 4. Then, the reflected parallel light beam is reflected by the beam splitter 4 to be branched from the laser light from the laser light source 1, is incident on the imaging lens 11, is condensed, and is conjugate with the focal plane of the telecentric fθ lens 8. The light passes through the pinhole 12a of the pinhole plate 12 installed in the light and enters the light receiving element 13 such as photomaru.

  The light receiving element 13 measures the light quantity of the incident reflected parallel light flux, performs photoelectric conversion, and transmits a light quantity signal corresponding to the light quantity to the A / D conversion board 14, and the A / D conversion board 14 receives the light quantity signal. A / D conversion is performed and the result is transmitted to the calculation means 15.

  Further, the operation of the motor 6 for rotating the scanning mirror 7 and the rotation and movement of the camshaft 9 are controlled by a control means (not shown). To the computing means 15. Then, the calculation means 15 calculates position information on the cam surface 10 from which the light amount signal is obtained from the rotation angle of the scanning mirror 7, the rotation angle of the camshaft 9, and the movement amount, and based on the light amount signal and the position information. Image data is created, and this image data is output to the display means 16.

  Next, the principle of the method for observing the cam surface of the present invention using the above wide field laser microscope will be described.

  An example of the cross section of the cam to be observed is shown in FIG. The cross section of the cam is oval instead of circular. Since half of the cross section of the cam is circular, the laser beam is reflected vertically in this circular portion and returns to the original path, so that the cam surface can be observed. However, as shown in FIG. 3, since the laser beam does not reflect vertically except in a circular portion, the cam surface cannot be observed. Therefore, as shown in FIG. 4, the cam is moved to a position where the laser beam is vertically reflected by the optical axis direction moving means and the vertical direction moving means, and the cam surface is observed.

  Hereinafter, the cam surface observation method of the present invention will be described in detail.

  The camshaft 9 is held by the holding means. Then, a command is given to a control means (not shown) to turn on the laser light from the laser light source 1 and to rotate the motor 6 in the direction of arrow A. As a result, the scanning light is scanned in the direction of the arrow B along the generatrix of the cam surface 10 and the measurement light reflected by the cam surface 10 is generated.

  Further, every time the scanning light scans the bus surface of the cam surface 10 once, the cam corresponding to the spot diameter of the scanning light in the direction of the arrow C that is orthogonal to the arrow B that is the scanning direction of the scanning light. The shaft 9 is rotated about its axis z. The camshaft 9 may be continuously rotated in the direction of the arrow C, or may be rotated discontinuously for each scanning of the scanning light. In the case of continuous rotation, the scanning line on the cam surface 10 is twisted due to the rotation of the camshaft 9, and therefore it is necessary to correct by data processing.

  Here, simply rotating the camshaft 9 causes a focus shift in the optical axis direction, and an observation image cannot be acquired. This is because there are cases where the reflected light cannot be detected because the laser light does not strike the cam surface 10 perpendicularly. For this purpose, data of the rough shape of the cam surface 10 acquired in advance is used. The rough shape data of the cam surface 10 can be measured using, for example, a digital gauge or a laser measuring instrument. Then, the control means operates the rotating means to rotate the camshaft 9 so that the cam surface 10 is always perpendicular to the laser light based on the rough shape data of the cam surface 10. The vertical movement means is operated to move the camshaft 9 in the vertical direction y. At the same time, the optical axis direction movement means is operated so that the focal point of the laser beam is always located on the cam surface 10 to light the camshaft 9. Move in the axial direction x.

  The measurement light becomes a reflected parallel light beam by the telecentric fθ lens 8 and is branched from the laser light from the laser light source 1 by the beam splitter 4. Then, the measurement light is condensed by the imaging lens 11, excess light is cut by the pinhole 12 a, and only the focused light enters the light receiving element 13. The light amount signal transmitted from the light receiving element 13 is A / D converted by the A / D conversion board 14 and then transmitted to the calculation means 15.

  Further, the calculation means 15 calculates position information on the cam surface 10 from which the light amount signal is obtained based on information such as the rotation angle of the scanning mirror 7 and the rotation angle of the camshaft 9 transmitted from the control means (not shown). . The computing means 15 stores the light quantity signal and its position information. Then, by continuing the measurement until the camshaft 9 makes one rotation, the light amount signal of the entire circumference of the cam surface 10 and its position information are accumulated in the computing means 15. The computing means 15 creates image data based on the light amount signal and its position information and outputs it to the display means 16. As a result, image data of the entire circumference of the cam surface 10 is obtained. The image data obtained here is displayed on the display means 16 as a two-dimensional image in which the cam surface 10 is developed. In addition, a cam-shaped three-dimensional image in which the cam surface 10 is not expanded is created by data processing by the calculation means 15 and displayed on the display means 16. The coordinate value of this three-dimensional image can be specified in submicron units.

  Hereinafter, an actual observation example will be described.

  First, data of a rough shape of the cam surface 10 was acquired using a digital gauge having a resolution of 0.1 μm. A digital gauge was brought into contact with the cam surface 10 and the camshaft 9 was rotated at a constant pulse amount by a rotating means. The displacement for each pulse amount was measured with a digital gauge and output to a personal computer. Note that FIG. 2 shows a rough shape of the cam surface 10 created based on the amount of displacement. Then, from the obtained data, the tangent of the laser beam irradiation position on the cam surface 10 in each pulse is obtained, so that the cam surface 10 is always perpendicular to the laser beam, and the focal point of the laser beam is always cam. Data of absolute positions in the optical axis direction, vertical direction, and rotation direction in each pulse was created so as to be positioned on the surface 10. Using the data, observation was performed by operating the rotating means, the vertical direction moving means, and the optical axis direction moving means.

  The observation result of the entire circumference of the cam surface 10 is shown in FIG. In some cases, the reflection intensity of the laser beam becomes too strong, and a portion appears white, but the entire circumference was observed. Further, the cam surface 10 had numerous scratches, and polishing marks could be confirmed in the rotation direction of the camshaft 9. The polishing marks are undulating in the generatrix direction, and it can be assumed that this is due to the movement of the tool during polishing. When the portion A in FIG. 5 was enlarged, small scratches could be confirmed as shown in FIG. Here, each pixel in the observation image can be associated with the coordinates of the three-dimensional space and the submicron unit from the data of the absolute position in the optical axis direction, the vertical direction, and the rotation direction for moving the cam. Therefore, the position of the flaw can be specified with high accuracy.

  Next, the observation image was displayed three-dimensionally using a three-dimensional display program created using DirectX. That is, a mesh having a three-dimensional framework structure on the cam surface 10 was created, and an observation image was pasted on the mesh to perform three-dimensional display. For the creation of the mesh, data on the cam surface 10 previously obtained with a digital gauge was used. An example of three-dimensional display is shown in FIG. Compared to the observed image in FIG. 5, the position of the flaw is intuitively easier to understand. In addition, it was possible to check the state of the entire circumference of the cam surface and scratches by freely enlarging and rotating the program.

  As described above, the cam surface observation method of the present embodiment guides the laser light from the laser light source 1 to the scanning mirror 7 through the beam splitter 4 as a parallel light flux, and the scanning mirror 7 scans the laser light with the scanning light. And is incident on the telecentric fθ lens 8, and the reflected light from the cam surface 10 arranged close to the focal plane of the telecentric fθ lens 8 is converted into a parallel light beam by the telecentric fθ lens 8. After being reflected, it is separated from the laser light from the laser light source 1 by the beam splitter 4, condensed by the imaging lens 11, and passed through a pinhole 12 a placed at a position conjugate with the focal plane of the telecentric fθ lens 8. A cam surface observation method for measuring the amount of reflected light that has passed through the pinhole 12a with a light receiving element 13, wherein the cam surface 10 The camshaft 9 is rotated around its axis z, the cam surface 10 is always perpendicular to the laser light, and the camshaft 9 is always focused on the cam surface 10. The observation is performed while moving, and the entire surface of the cam surface 10 can be observed easily and in a short time.

  In addition, by scanning the scanning light along the generatrix of the cam surface 10, the cam surface 10 can be observed with only one rotation of the cam surface 10 and can be measured in a short time.

Further, each time the scanning light scans the generatrix of the cam surface 10, the camshaft 9 is rotated about the axis z in an amount corresponding to the spot diameter of the scanning light in a direction orthogonal to the scanning direction of the scanning light. By doing so, the shape of the cam surface 10 can be accurately measured over the entire surface of the cam surface 10, and at the same time, a surface image of the cam surface 10 can be obtained.

  Further, based on the light amount signal corresponding to the light amount measured by the light receiving element 13 and the position information on the cam surface 10 from which the light amount signal is obtained, a three-dimensional image of the cam surface 10 is created and displayed on the display means. As a result, the measurement result can be displayed visually and in an easily understandable manner.

  As mentioned above, although this invention was demonstrated based on the said Example, this invention is not limited to the said Example, A various deformation | transformation implementation is possible within the range of the thought of this invention. In the above embodiment, only basic elements of the optical system used in the laser scanning interferometer are illustrated, and various members installed in this type of optical system may be added as necessary. The arrangement may be changed as appropriate. Further, a laser light source may be arranged on the reflection side of the beam splitter, and a light receiving element may be arranged on the passage side. Furthermore, a pinhole is used to cut off excess light, but a slit may be used instead.

DESCRIPTION OF SYMBOLS 1 Laser light source 4 Beam splitter 7 Scanning mirror 8 Telecentric f (theta) lens 9 Cam shaft
10 Cam surface
10a Cylindrical surface to be observed
10b Cylindrical shaft
11 Imaging lens
12a pinhole
13 Photo detector
16 Display means
x Optical axis direction z axis

Claims (4)

Laser light from a laser light source is guided to a scanning mirror through a beam splitter as a parallel light beam, and the laser light is converted into scanning light by the scanning mirror and is incident on a telecentric fθ lens, near the focal plane of the telecentric fθ lens. The reflected light from the cam surface arranged in close proximity is converted into a parallel light beam by the telecentric fθ lens, reflected by the scanning mirror, separated from the laser light from the laser light source by the beam splitter, and condensed by the imaging lens. A method for observing a cam surface, wherein a pinhole installed at a position conjugate with a focal plane of the telecentric fθ lens is passed through, and the amount of reflected light passing through the pinhole is measured by a light receiving element. the cam rotates the cam shaft about its axis, acquired in advance with Based on the data of the rough shape of the surface, wherein the cam surface is always perpendicular to such so that moving the camshaft, and located at the focal point of the laser beam is always the cam surface relative to the laser beam observation method of the cam surface, characterized in that the observation while moving the pre Symbol camshaft in the direction of the optical axis of the laser light so. The cam surface observation method according to claim 1, wherein the scanning light is scanned along a generatrix of the cam surface. Each time the scanning light scans the generatrix on the cam surface, the camshaft is rotated about the axis in the direction orthogonal to the scanning direction of the scanning light by an amount corresponding to the spot diameter of the scanning light. The method for observing a cam surface according to claim 2, wherein: Based on the light amount signal corresponding to the light amount measured by the light receiving element and the position information on the cam surface from which the light amount signal is obtained, a three-dimensional image of the cam surface is created and displayed on the display means. The method for observing a cam surface according to any one of claims 1 to 3.