JP7611288B2 - Device and method for non-contact detection of grinding wheel clogging during machining - Google Patents

Description

The present invention relates to a detection device and a detection method for non-contact detection of clogging or dulling of a grinding wheel during processing. More specifically, the present invention relates to a detection device and a detection method suitable for monitoring the progress level of clogging (a state in which shavings from the workpiece are clogged around the abrasive grains or in holes in the abrasive grains) or dulling (a state in which the tips of the abrasive grains are worn down or chipped) of a grinding wheel in a grinding machine such as a grinding machine or a dicer [both of which are also referred to simply as "clogging" in this application] in real time without contacting the grinding wheel while the grinding wheel is rotating during processing.

When the grinding wheel of a grinding machine becomes clogged, good processing cannot be achieved. For this reason, regular dressing is performed to sharpen the wheel and restore it before processing can begin. However, frequent dressing is undesirable from the standpoint of efficiency. Therefore, there is a strong need to monitor the clogging of the grinding wheel during processing in order to perform efficient dressing.

Conventionally, to monitor the clogging of the grinding wheel during processing, the load on the grinding wheel has been monitored by the amount of current in the motor that rotates the grinding wheel, as described in, for example, Patent Document 1 below. However, particularly in processing machines such as dicers, which have a small processing load to begin with, the change in load due to clogging is extremely small, making it nearly impossible to monitor by the amount of current.

Patent Document 2 below discloses a device for measuring the surface condition of a grinding wheel, in which a contactor is brought into contact with the surface of the rotating wheel, and the vibrations transmitted to the contactor are detected by a vibration sensor to measure the surface condition of the wheel. The contactor is arranged so that it can come into contact with and separate from the surface of the wheel, and the contact and separation are performed by a shape memory alloy that is deformed by heat from a heater.

However, such mechanical means are prone to malfunction in the machining area, which is easily contaminated by grinding fluid and machining debris, and the contacts, which repeatedly come into contact with and separate from the grinding wheel surface, are prone to wear and breakage.

In addition, the following Patent Document 3 describes a device that determines the wear state of a grinding wheel by collecting grinding sounds using an AE sensor (ultrasonic detector) attached to the support part of the workpiece, converting them into electrical signals, and inputting these signals to a grinding wheel wear determination circuit via a pulse height level analysis circuit and/or a frequency analysis circuit.

However, determining whether the grinding wheel is worn or not based on such audio signals is easily affected by environmental noise and the material of the grinding wheel, and frequency analysis and other advanced calculations are required, making it difficult to determine the wear state in real time during processing.

Furthermore, the following Patent Document 4 describes a device that uses light reflection to detect the presence or absence of surface defects in a rolling roll, although it is not a grinding wheel like the present invention. However, the detection device in Patent Document 4 is for inspecting the surface of a rolling roll after the rolling roll has stopped rolling or after repairs, not during the rolling process. Furthermore, the detection device in Patent Document 4 performs analysis based solely on the difference in the intensity of the reflected light between normal and defective parts of the surface, regardless of the regular reflection component and diffuse reflection component contained in the reflected light, and also performs complex arithmetic processing to make the judgment for the analysis, making it difficult to obtain and use the judgment results in real time during processing.

Japanese Patent Application Publication No. 6-304865 JP 2003-334756 A JP 2006-281402 A JP 2006-208347 A

As described above, conventional technology has not achieved the ability to accurately measure the clogging state of the grinding wheel surface directly and in real time during processing.

The object of the present invention is therefore to solve the problems of the prior art, that is, to provide a grinding wheel clogging detection device and detection method that can accurately measure the clogging state of the grinding wheel surface directly and in real time during processing.

In such cases, performing contact measurements on the grinding wheel during processing would result in wear and tear or damage to the contacts, so non-contact measurements are desirable. In addition, the grinding wheel itself is made of a variety of materials, such as metal and resin, so non-contact measurements using electrical methods are difficult. Furthermore, since there is a risk of contact if the detection device is installed too close to the grinding wheel, it is desirable to have a means that can measure at a distance from the grinding wheel. From these perspectives, it is desirable to use light as the measurement means of the present invention.

The configuration of the present invention to achieve the above objective is as follows:

[1] A non-contact detection device for detecting clogging of a grinding wheel used to process a workpiece by contacting the workpiece while rotating, the non-contact detection device for detecting clogging of the grinding wheel comprising: a light-projecting unit that emits projected light onto a grinding surface of the grinding wheel; a light-receiving sensor that receives reflected light from the grinding surface; and a discrimination circuit that discriminates the state of clogging of the grinding surface based on the received light intensity distribution of each of the specular reflection component and diffuse reflection component detected by the light-receiving sensor.
[2] The non-contact sensing device according to [1], wherein the received light intensity distribution is detected by a reflection pattern formed on the light receiving sensor by the specular reflection component and the diffuse reflection component.
[3] A processing apparatus comprising the grindstone and the non-contact detection device according to [1] or [2].
[4] A non-contact detection method for detecting clogging of a grinding wheel used to process a workpiece by bringing the workpiece into contact with the workpiece while rotating, the non-contact detection method including: emitting projected light from a light-projecting unit toward a grinding surface of the grinding wheel; receiving the reflected light from the grinding surface by a light-receiving sensor; and discriminating the clogging state of the grinding surface by a discrimination circuit based on the received light intensity distribution of each of the specular reflection component and diffuse reflection component detected by the light-receiving sensor.
[5] The non-contact sensing method according to [4], in which the received light intensity distribution is detected by a reflection pattern formed on the light receiving sensor by the specular reflection component and the diffuse reflection component.

Another aspect of the present invention is a non-contact detection device for detecting clogging of a grinding wheel during processing, which includes a light-projecting unit having a light source and arranged near the periphery of the rotating grinding wheel, and which emits projected light toward a predetermined position on the grinding surface of the rotating grinding wheel other than the contact point with the workpiece during processing; a light-receiving unit having a light-receiving sensor and arranged near the periphery of the rotating grinding wheel in a position where the projected light can receive reflected light reflected from the grinding surface of the rotating grinding wheel; and a discrimination circuit that discriminates the clogging state of the grinding surface of the rotating grinding wheel based on a reflection pattern formed on the light-receiving sensor by the specular reflection component and diffuse reflection component that constitute the reflected light from the grinding surface of the rotating grinding wheel.

The light projecting light source and light receiving sensor may be one-dimensional or two-dimensional. Considering light collection efficiency and intensity, a laser is preferable as the light projecting light source, but an LED or the like may also be used. Furthermore, the light projecting light source need only have directionality and does not need to be monochromatic light. A CCD or the like is preferably used as the light receiving sensor, but is not limited to this.

The light projected by the light-projecting unit onto the grinding surface of the rotating grinding wheel is reflected from the grinding surface and forms a reflection pattern on the light-receiving sensor. Since the reflection pattern differs between a noticeable state (normal state) and a clogged state, the current clogged state can be measured in real time by detecting the reflection pattern with the light-receiving sensor.

In other words, in the normal state where the grains are prominent, the abrasive grains are exposed on the grinding wheel surface, resulting in fine irregularities, which results in a large amount of diffusely reflected light. Also, because the grinding wheel rotates during processing, the reflected light is not only reflected at a specific point on the light receiving sensor, but is dispersed in various directions, and a gradual, evenly spread reflection pattern is projected onto the light receiving sensor, such as a CCD.

On the other hand, when the grinding surface of the grinding wheel is clogged or damaged, the grinding surface is relatively flat and smooth, resulting in less diffuse reflection and more regular reflection, resulting in a reflection pattern in which the reflected light is concentrated in a relatively narrow area. Therefore, by monitoring the reflection pattern, it is possible to detect whether the condition of the grinding surface is good or bad.

In this way, in the present invention, light is projected from a light projection unit toward the grinding surface of the rotating grinding wheel, and the clogged state of the grinding wheel is determined based on the reflection pattern of the light reflected from the grinding surface of the rotating grinding wheel, making it possible to accurately measure the clogged state of the grinding wheel surface directly in real time during processing.

In addition, because this detection operation is performed in a non-contact manner with the grinding wheel using the optical means described above, there is no risk of the contactor being damaged as occurs with devices that use contactors, and stable measurements can be achieved even for grinding wheels made of a variety of materials, including metal and resin.

In addition, by changing the setting value of the discrimination circuit, it is easy to accommodate grinding wheels with various different characteristics.

Furthermore, in the above-mentioned embodiment, the present invention is characterized in that the criterion for discriminating the reflection pattern by the discrimination circuit is the concentration of the reflected light on the light receiving sensor.

As the amount of clogged areas on the grinding surface of the grinding wheel increases, the amount of smooth surface increases, and the amount of diffuse reflection decreases, causing the reflection pattern to become more concentrated. The higher the concentration, the more clogged or dulled the pattern is.

Furthermore, in the above, it is recommended that the barometer of the concentration of the reflected light be the peak intensity value and/or the half-width of the received light intensity of the reflection pattern formed on the light receiving sensor. This is because it can be a simple and reliable barometer without requiring complex calculations, etc.

Furthermore, in order to achieve the above object, the present invention provides a non-contact detection device for detecting clogging of a grinding wheel during processing, comprising: a light-projecting unit having a light source for projecting light, which is arranged near the periphery of the rotating grinding wheel and emits projected light toward a predetermined position on the grinding surface of the rotating grinding wheel other than the contact point with the workpiece during processing; a light-receiving unit having a light-receiving sensor and arranged near the periphery of the rotating grinding wheel in a position where the projected light can receive reflected light reflected from the grinding surface of the rotating grinding wheel; and a discrimination circuit that discriminates the clogging state of the grinding surface of the rotating grinding wheel based on a correlation coefficient between the characteristics of the reflected light from the grinding surface of the rotating grinding wheel and the corresponding characteristics of the reflected light during similar rotation when the grinding surface is in a normal state.

This allows a variety of different characteristics to be used as the characteristics of the reflected light for which the correlation coefficient is to be calculated, which has the advantage of making it possible to detect the clogging state from a variety of perspectives.

In the above device, it is recommended that the spectrum be used as the characteristic of the reflected light for which the correlation coefficient is to be calculated.

The advantage of using a spectrum is that it is possible to directly detect and determine the amount of light of a specific wavelength component based on the output data of the three primary colors detected by the light receiving sensor, and there is no need to add special components.

Furthermore, in the above, it is recommended that the device further include an alarm circuit that generates a processing stop signal and/or an alarm signal based on the output signal when the discrimination circuit detects clogging at a level equal to or greater than a predetermined value.

This effectively prevents the production of defective products caused by the continued use of clogged grinding wheels.

Furthermore, in the above, it is preferable that the light projection unit includes an optical element that collects light rays from the light projection light source and forms the projection light as parallel light.

This increases the amount of light projected onto the grinding surface of the grinding wheel, optimizing the formation of specular and diffuse reflections from the grinding surface.

Furthermore, in the above, it is preferable that the light receiving unit includes a light collecting element for collecting the reflected light from the grinding surface of the rotating grinding wheel and forming an image on the light receiving sensor.

This allows an appropriate reflection pattern to be formed on the light receiving sensor, improving detection accuracy.

Furthermore, in order to achieve the above object, the present invention provides a non-contact method for detecting clogging of a grinding wheel during processing, in which a light-projecting unit emits projected light toward a predetermined position on the grinding surface of the rotating grinding wheel other than the contact point with the workpiece during processing, and the projected light is received by a light-receiving unit having a light-receiving sensor that receives reflected light reflected from the grinding surface of the rotating grinding wheel near the periphery of the rotating grinding wheel, and a discrimination circuit discriminates the clogging state of the grinding surface of the rotating grinding wheel based on the reflection pattern formed on the light-receiving sensor by the specular reflection component and diffuse reflection component that make up the reflected light.

As a result, just like in the case of the non-contact detection device, the light projected from the light-emitting unit onto the grinding surface of the rotating grinding wheel is reflected by the grinding surface and forms a reflection pattern on the light-receiving sensor. Since the reflection pattern differs between the normal state and the clogged state, the reflection pattern is detected by the light-receiving sensor, making it possible to measure the current degree and presence of clogging in real time.

Furthermore, in the above-mentioned embodiment, the present invention is characterized in that the criterion for discriminating the reflection pattern by the discrimination circuit is the concentration of the reflected light on the light receiving sensor.

As mentioned above, the concentration of the reflection pattern increases due to the increase in the smooth surface area caused by the increase in clogged areas, so the higher the concentration, the more clogged the area is.

Furthermore, in the above, the barometer of the concentration of the reflected light is the peak intensity value and/or the half-value width of the received light intensity of the reflection pattern formed on the light receiving sensor.

As mentioned above, this does not require complex calculations and can be a simple and reliable barometer.

Furthermore, in order to achieve the above object, the present invention provides a non-contact method for detecting clogging of a grinding wheel during processing, in which a light-projecting unit emits projected light toward a predetermined position on the grinding surface of the rotating grinding wheel other than the contact point with the workpiece during processing, and the projected light is received by a light-receiving unit having a light-receiving sensor that receives reflected light reflected from the grinding surface of the rotating grinding wheel near the periphery of the rotating grinding wheel, and a discrimination circuit discriminates the clogging state of the grinding surface of the rotating grinding wheel based on a correlation coefficient between the characteristics of the reflected light from the grinding surface of the rotating grinding wheel and the corresponding characteristics of the reflected light during similar rotation when the grinding surface is in a normal state.

As a result, as described above, various types of characteristics can be used as the characteristics of the reflected light for which the correlation coefficient is to be calculated, which has the advantage that the clogging state can be detected from various perspectives.

Furthermore, in the above, the characteristic of the reflected light for which the correlation coefficient is to be calculated is a spectrum.

The spectrum of reflected light reflects the properties of the reflector, and as mentioned above, the spectrum has the advantage that it is possible to directly detect and determine the amount of light of a specific wavelength component based on the output data of the three primary colors detected by the light receiving sensor, and there is no need to add special components.

According to the present invention, the light projecting unit projects light onto the grinding surface of the rotating grinding wheel during actual grinding, and the clogged state of the grinding wheel is judged based on the reflection pattern of the light reflected from the grinding surface of the rotating grinding wheel. This makes it possible to accurately measure the clogged state of the grinding wheel surface directly during processing in real time. This effectively prevents the generation of defective products caused by the continued use of a clogged grinding wheel. In addition, since the above-mentioned detection operation is performed by the optical means described above in a non-contact manner with the grinding wheel, there is no risk of the contactor being damaged as in devices using contactors, and stable measurement can be achieved even for grinding wheels made of various materials such as metal and resin. Furthermore, since the device of the present invention has few components, it can be constructed compactly, has a high degree of freedom in the installation position on a processing machine such as a grinding machine, and has few causes of failure. In addition, by changing the setting value of the discrimination circuit, it is easy to handle grinding wheels with various different properties.

FIG. 1 is a schematic diagram of a non-contact grinding wheel clogging detection device according to an embodiment of the present invention. Enlarged cross-sectional image of the grinding surface of a grinding wheel under normal conditions Enlarged cross-sectional image of the grinding surface of a clogged or damaged grinding wheel An enlarged cross-sectional image showing the reflection state of the grinding surface of a grinding wheel under normal conditions An enlarged cross-sectional image showing the regular reflection area on the grinding surface of a normal grinding wheel An enlarged cross-sectional image showing the reflection state of the grinding surface of a clogged or glazed grinding wheel An enlarged cross-sectional image showing the regular reflection areas on the grinding surface of a clogged or glazed grinding wheel Image of the reflection pattern formed on the light receiving sensor when the grinding surface of the grinding wheel is in a normal state An image of the reflection pattern formed on the light receiving sensor when the grinding surface of the grinding wheel is clogged or damaged. Enlarged photo of the grinding surface of a new grinding wheel in normal condition Enlarged photo of grinding surface of grinding wheel with clogged/glazed grinding wheel after use

Below, a preferred embodiment of the non-contact grinding wheel clogging detection device according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the illustrated embodiment, and includes various modified embodiments within the scope of the claims.

Figure 1 shows a state in which the clogging state of the grinding surface 7a (the outer peripheral surface of the grinding wheel 7 in the illustrated embodiment) of a rotating grinding wheel 7 is monitored in real time by a non-contact detection device 1 according to the present invention when grinding a workpiece 8 such as a semiconductor wafer. As shown in the figure, the non-contact detection device 1 of the present invention has a light-emitting unit 2 and a light-receiving unit 3 that are arranged near the periphery of the rotating grinding wheel 7 in a non-contact state with the grinding wheel 7, a discrimination circuit 4, and an alarm circuit 5.

In the illustrated state, the grinding wheel 7 rotates clockwise around the grinding wheel rotation axis 7e, and abuts against the workpiece 8 at a contact point 7b of the grinding surface 7a, thereby grinding the processed portion 8a of the workpiece 8. A predetermined position on the grinding surface 7a other than the contact point 7b with the workpiece 8 serves as a projection portion 7c, from which the projection light 2f from the light projection unit 2 is projected. The grinding surface 7a of the grinding wheel 7 that grinds the workpiece 8 may be the outer peripheral surface of the grinding wheel 7 as in the illustrated example, or it may be a flat side surface or edge portion of the grinding wheel 7 depending on the processing purpose and the object to be processed.

The light projection unit 2 is composed of a light projection light source 2a such as a laser or LED, an optical element 2b consisting of a condenser lens 2c and a slit plate 2d, 2d, etc., and a casing 2e, etc., and is provided near the periphery of the grinding wheel 7 in a non-contact state with the grinding wheel 7 as described above. The light projection light source 2a does not necessarily have to be monochromatic light, and may be one-dimensional or two-dimensional. The light from the light projection light source 2a is condensed by the condenser lens 2c and made into parallel light, and then becomes a projection light 2f of a predetermined diameter having directionality through the slit plates 2d, 2d, and is projected to the projection part 7c, which is a point on the grinding surface 7a of the grinding wheel 7, as described above. The light beam diameter and radiation direction of the projection light 2f are kept constant, but the projection part 7c scans or traces the grinding surface 7a in the circumferential direction as the grinding wheel 7 rotates. The optical element 2b is not limited to the one shown in the figure, and various known means can be used. If the projecting light source 2a itself emits a directional light beam with a constant diameter, the optical element 2b does not need to be provided.

The projection position of the projected light 2f, i.e., the position of the projection part 7c on the grinding surface 7a, may be any position other than the contact point 7b where the grinding surface 7a contacts the workpiece 8 during processing (including the area immediately adjacent to the contact point 7b if grinding fluid is applied there), and there is no problem even if the grinding surface 7a is wet with grinding fluid.

The projection light 2f emitted from the projection unit 2 is projected onto the projection part 7c on the grindstone 7, and is reflected at the projection part 7c to form reflected light 2g, 2h, and 2i. At that time, regular reflection and diffuse reflection occur depending on the surface condition of the projection part 7c. That is, in the illustrated example, when the projection part 7c is a smooth surface, the projection light 2f is reflected as reflected light 2g (shown by a solid line in the figure) that is regularly reflected with a reflection angle α equal to the angle of incidence α with respect to the normal line 7d at the projection part 7c, that is, reflected light 2g as a regular reflection component, and is emitted. On the other hand, when the projection part 7c is a rough surface, the projection light 2f is reflected as reflected light 2h, 2i (shown by a dashed line in the figure) that is diffusely reflected in various directions at the rough surface of the projection part 7c, that is, reflected light 2h, 2i as a diffuse reflection component, and is emitted.

As will be described later with reference to Figures 2 to 7, when the grinding surface 7a of the grinding wheel 7 is normal, the abrasive grains are prominent on the grinding surface, there is no clogging or dulling, the surface is rough, and there are few smooth areas, so the projected light 2f is mostly emitted as diffusely reflected light 2h, 2i, and the regular reflection component is small. On the other hand, if the grinding process is continued and the grinding surface 7a becomes clogged or dulled due to wear, the grinding surface 7a becomes smooth and is no longer rough, so the proportion of the projected light 2f that is emitted as diffusely reflected light 2h, 2i (shown by dashed lines in the figures) decreases, and the proportion of the regular reflection component reflected light 2g (shown by solid lines in the figures) increases.

Therefore, in the illustrated embodiment of the present invention, a light receiving unit 3 having a light receiving sensor 3a of a size capable of receiving the reflected light 2g as the specular reflection component and the reflected light 2h, 2i as the diffuse reflection components is disposed in a position where it can receive them, and the discrimination circuit 4 is configured to discriminate the clogging state of the rotating grinding wheel 7 based on the reflection pattern formed by these reflected lights.

That is, the reflection pattern formed by the reflected light 2g, 2h, 2i, etc. on the light receiving sensor 3a made of a CCD or the like presents a curve 62 of the received light intensity as exemplified by the reference reflection pattern graph 6 in FIG. 1. That is, this curve 62 is a curve of the received light intensity with the light receiving position of the regular reflection component on the light receiving sensor 3a as the central origin, as will be described later with reference to FIG. 8 and FIG. 9, and indicates that the more the reflected light is concentrated in the central area, the more the regular reflection component in the reflected light increases and the diffuse reflection component decreases, that is, the clogging state of the grinding wheel surface progresses and worsens. Therefore, the level of clogging of the grinding wheel surface can be detected by determining the concentration of this reflection pattern in the central area by the determination circuit 4. For example, the light receiving intensity for each coordinate on the light receiving sensor is detected from the output data of the line sensor type light receiving sensor 3a, and the discrimination circuit 4 discriminates whether the peak intensity value at the center origin reaches a preset level. If the level is exceeded, it can be determined that the regular reflection component in the reflected light exceeds a predetermined level and that the clogging exceeds the predetermined level. The discrimination criterion is not limited to the peak intensity value h (see Figures 8 and 9) in the light receiving intensity of the reflection pattern, but may be the half-width w described later. Also, the light receiving sensor 3a is not limited to a line sensor type (one-dimensional) but may be a two-dimensional one.

It is recommended that a focusing element 3b be provided in front of the light receiving sensor 3a to focus the reflected light 2g, 2h, and 2i and form an image on the light receiving sensor 3a.

Furthermore, as shown in FIG. 1, it is recommended to provide an alarm circuit 5 that operates based on the output signal of the discrimination circuit 4, and that generates a processing stop signal and/or an alarm signal based on the output signal when the discrimination circuit 4 detects clogging of the grinding wheel 7. The processing stop signal is sent to the control device of the processing machine to automatically stop processing, preventing the occurrence of defective grinding products, and also to automatically replace the grinding wheel or to issue an alarm based on the above alarm signal to alert the operator.

Next, with reference to Figures 2 to 9, we will explain the comparison between the normal state of the grinding surface 7a of the grinding wheel and the clogged/glazed state, and the changes in the reflection pattern.

Figure 2 is an enlarged cross-sectional image of the grinding surface 7a of the grinding wheel in a normal (noticeable) state. The grinding wheel 7 is made by mixing and fixing abrasive grains 7g, 7g made of diamond particles, alumina particles, etc., in a binder 7f made of resin, metal, etc., and the sharp ends of many abrasive grains 7g, 7g protrude and stand out on the surface of the grinding surface 7a of the grinding wheel 7, and there are also many holes 7h, 7h where the abrasive grains have fallen out. In addition, smooth surfaces 71, 71 of the top of the binder 7f are exposed between the sharp ends of the abrasive grains 7g, 7g and the holes 7h, 7h where the abrasive grains have fallen out. In this normal state (noticeable state), the grinding surface 7a has a rough surface overall, and when the grinding wheel 7 rotates and moves continuously in the direction of the arrow A in Figure 2, the workpiece 8 is efficiently ground at the contact point 7b (see Figure 1) where the grinding surface 7a of the grinding wheel 7 comes into contact with the workpiece 8.

Figure 3 is an enlarged cross-sectional image of the grinding surface 7a in a clogged or dulled state. In this state, the grinding surface 7a of the grinding wheel 7 is worn down to the position shown by line B-B in Figure 1 due to processing the workpiece, and the tips of the abrasive grains 7g, 7g that protrude from the surface are chipped, worn away, or chipped (dulled state), and smooth surfaces 73, 73 are formed on the tops of the abrasive grains 7g, 7g. In addition, the abrasive grain drop holes 7h, 7h and the sides of the abrasive grains are clogged with shavings and the like (clogged state), resulting in clogged portions 7i, 7i. In this state, smooth surfaces 72, 72 are formed on the tops of the binder 7f, and smooth surfaces 74, 74 are also formed on the tops of the clogged portions 7i, 7i. As a result, the grinding wheel 7 is not suitable for continued processing and needs to be replaced or dressed.

Figure 4 shows the reflection state of the grinding surface 7a of the grinding wheel 7 shown in Figure 2 in a normal state. In such a normal state without clogging or glare, when the projected light 2f emitted from the light projecting unit 2 is projected onto the grinding surface 7a of the grinding wheel 7 that is moving continuously in the direction of arrow A, as the grinding wheel moves, the projected light 2f is specularly reflected by the smooth surfaces 71, 71 at the top of the binder, and becomes reflected light 2g as a specular reflection component shown by a solid line and heads toward the light receiving unit 3, but the projected light 2f projected to other places becomes reflected light 2h, 2i, etc. as a diffuse reflection component shown by a dashed line and heads toward the light receiving unit 3 (see also Figure 1).

Figure 5 shows the locations where specular reflection occurs on the grinding surface 7a when the grinding wheel 7 is in a normal state with no clogging or dulling, with indicators 75, 75 drawn with dashed lines for easy understanding. That is, the indicators 75, 75 in Figure 5 are dashed lines drawn at positions corresponding to the smooth surfaces 71, 71 at the top of the binder that cause specular reflection when the grinding surface 7a is in a normal state as shown in Figures 2 and 4. In this way, when the grinding wheel is in a normal state, the surface roughness is high, resulting in a large amount of diffuse reflection components.

On the other hand, Figure 6 shows the reflection state of the clogged or glazed grinding wheel 7 shown in Figure 3. In such a clogged or glazed state, when the projected light 2f emitted from the light projecting unit 2 is projected onto the grinding surface 7a of the grinding wheel 7, which is moving continuously in the direction of the arrow A, as the grinding wheel moves, the projected light 2f is specularly reflected by the smooth surfaces 72, 72 of the binder top, the smooth surfaces 73, 73 of the abrasive grain top, and the smooth surfaces 74, 74 of the clogged top, and becomes reflected light 2g as a specular reflection component toward the light receiving unit 3, while the projected light 2f projected to other places becomes reflected light 2h as a diffuse reflection component toward the light receiving unit 3 (also see Figure 1).

Figure 7 shows the locations where specular reflection occurs on the grinding surface 7a when the grinding wheel 7 shown in Figure 6 is clogged or dulled, as clearly shown by dashed line indicators 76, 76. That is, the indicators 76, 76 in Figure 7 are dashed lines drawn at positions corresponding to the smooth surfaces 72, 72 at the top of the binder, the smooth surfaces 73, 73 at the top of the abrasive grains, and the smooth surfaces 74, 74 at the top of the clogged area, which cause specular reflection when the grinding surface 7a is clogged or dulled as shown in Figures 3 and 6. In this way, when the grinding wheel is clogged or dulled, there are many smooth areas on the surface, resulting in a high specular reflection component.

In Figure 5, when the grindstone is in a normal state, the total length of the indicators 75, 75 in the specular reflection generating portion is approximately 52% of the total, whereas in Figure 7, when the grindstone is in a clogged or damaged state, the total length of the indicators 76, 76 in the specular reflection generating portion is approximately 92% of the total. This shows that the proportion of specular reflection components in the reflected light is higher when the grindstone is in a clogged or damaged state compared to when the grindstone is in a normal state.

Figures 8 and 9 show that the reflection pattern obtained by the light receiving sensor 3a changes based on the difference in the ratio of specular reflection components to diffuse reflection components in the reflected light from the grinding surface 7a of the grinding wheel 7.

That is, Figure 8 shows an image of the reflection pattern 61 obtained by the light receiving sensor 3a when the grinding surface 7a of the grinding wheel is in a normal state. This is a graph with the coordinate on the light receiving sensor on the horizontal axis and the received light intensity on the vertical axis. The coordinate center is the regular reflection position. As mentioned above, when the grinding surface 7a is in a normal state, there is a lot of diffuse reflection components, so the peak intensity value h of the reflection pattern 61 is low and the half-width w (half-width w at a specified received light intensity of 0.1) is a wide pattern. Also, since this is the received light intensity obtained while the grinding wheel is rotating, there are no strong components in specific locations, and the distribution is smooth and average.

On the other hand, Figure 9 shows an image of the reflection pattern 62 obtained by the light receiving sensor 3a when the grinding surface 7a of the grinding wheel is clogged or damaged. The coordinates etc. are the same as in Figure 8. When the grinding surface 7a is clogged or damaged, as mentioned above, there is a lot of regular reflection component, so the peak intensity value h of the reflection pattern 62 is high and the half-width w (half-width w at a specified light receiving intensity of 0.1) is a narrow pattern. Since this is the light receiving intensity obtained when the grinding wheel is rotating, it has an average smooth distribution.

As described above, the level of clogging on the surface of the grinding wheel can be detected by determining the concentration of the central region (region showing the amount of regular reflection components) of the reflection patterns 61 and 62 by the discrimination circuit 4. That is, as described above, the light receiving intensity for each coordinate on the light receiving sensor is detected from the output data of the light receiving sensor 3a such as a CCD, and the discrimination circuit 4 determines whether the peak intensity value h at the center origin reaches a preset level, and when it exceeds that level, it can be determined that the regular reflection component in the reflected light exceeds a predetermined level and the clogging exceeds a predetermined level. The discrimination criterion is not limited to the peak intensity value h, but may be the half-width w. Alternatively, it may be both the peak intensity value h and the half-width w, or the ratio of both. That is, the peak intensity value and/or the half-width in the light receiving intensity of the reflection pattern can be used as a barometer of the concentration of the reflected light. In this way, the present invention can determine the level of clogging without performing any special calculations, simply by reading the peak intensity value h and half-width w of the reflection patterns 61 and 62 obtained by the light receiving sensor 3a and determining with the discrimination circuit 4 whether they have reached a predetermined level.

Figure 10 is an enlarged photograph of the grinding surface 7a of a new grinding wheel in a normal state, from which it can be seen that there is no clogging of the binder portion or dulling of the abrasive grains. In contrast, Figure 11 is an enlarged photograph of the surface of the grinding surface 7a of a used grinding wheel in a clogged or dulled state, from which it can be seen that there is clogging of the binder portion (long linear streaks) and dulling of the abrasive grains (dot-like white shiny areas). In the present invention, by utilizing the fact that reflected light containing a large amount of regular reflection components is generated from such clogged and dulled areas, it is possible to detect the clogged and dulled state of the grinding surface 7a in real time during processing without contact, as described above.

As described above, the reflection pattern differs between a grinding wheel in a normal state and a grinding wheel with clogging or the like due to the difference in surface properties, so the clogging state can be monitored by reading the peak intensity value h or half-width w in the reflection pattern. In this case, if the grinding wheel is stationary, spot reflections will be present and will hinder the measurement, so it is desirable to measure while the wheel is rotating as described above. With the above-mentioned configuration, clogging or the like can be monitored in real time without contact, using simple optical and circuit means, without the need for complex calculations, etc., while the grinding wheel is rotating for processing.
In addition, since the device as a whole has few components, there is a high degree of freedom in the mounting position on the processing equipment, and it is easy to install it, for example, on the opposite side of the processing surface, thereby reducing the causes of failure.

Furthermore, the present invention is not limited to a configuration in which the level of clogging is determined based on the peak intensity and half-width of the reflected light, which is composed of a specular reflection component and a diffuse reflection component, as described above.

That is, in another embodiment of the present invention, a light-projecting unit 2 and a light-receiving unit 3 are provided as in the above case, but unlike the above, the discrimination circuit 4 is configured to discriminate the clogged state of the rotating grinding wheel based on a correlation coefficient between the characteristics of the reflected light from the grinding surface 7a of the rotating grinding wheel and the corresponding characteristics of the reflected light during rotation when the grinding surface is in a normal state. It is preferable to use the spectrum of the reflected light as the characteristic of the reflected light for which the correlation coefficient is to be calculated. By using such a correlation coefficient, it is possible to numerically analyze to what extent the measurement results of the spectrum of the reflected light from the rotating grinding wheel during processing match the spectrum in the normal state, and thus it is possible to discriminate the clogged state of the grinding wheel without contact. This is because the spectrum of the reflected light reflects the properties of the reflector.

Such a configuration has the advantage that various types of characteristics can be used as the characteristics of the reflected light for which the correlation coefficient is to be calculated, making it possible to detect the clogging state from various perspectives. In addition, there is the advantage that the spectrum of the reflected light can be obtained as output data of the three primary colors detected by the light receiving sensor, so there is no need to add special components. If necessary, a spectroscopic means, filter, etc. may be included in the light collecting element 3b.

The present invention has the above-mentioned configuration, and thus has many industrial applicability, as follows. That is, it is possible to accurately measure the clogging state of the grinding surface of the grinding wheel directly during processing in real time. This effectively prevents the generation of defective products caused by the continued use of a clogged grinding wheel. In addition, since the detection operation is performed by the optical means as described above in a non-contact manner with the grinding wheel, there is no risk of the contactor being damaged or worn out as in devices using contactors, and stable measurement can be achieved even for grinding wheels made of various materials such as metal and resin. Furthermore, since there are few components, the configuration can be made compact, there is a high degree of freedom in the installation position on a processing machine such as a grinding machine, and there are few causes of failure. In addition, by changing the setting value of the discrimination circuit, it is easy to handle grinding wheels with various different properties.

REFERENCE SIGNS LIST 1 Non-contact detection device 2 Light-projecting unit 2a Light-projecting light source 2b Optical element 2c Condenser lens 2d, 2d Slit plate 2e Casing 2f Projected light 2g Reflected light as regular reflection component 2h, 2i Reflected light as diffuse reflection component 3 Light-receiving unit 3a Light-receiving sensor 3b Condenser element 4 Discrimination circuit 5 Alarm circuit 6 Reference reflection pattern graph 61, 62 Reflection pattern 7 Grinding wheel 7a Grinding surface 7b Contact point with workpiece 7c Projecting portion 7d Normal line 7e Grinding wheel rotation axis 7f Binder 7g Abrasive grain 7h Abrasive grain dropout hole 7i Clogged portion 71 Smooth surface of binder top when grinding wheel is in normal state 72 Smooth surface of binder top when grinding wheel is in clogged state 73 Smooth surface of the top of the abrasive grain when the grinding wheel is dulled 74 Smooth surface of the top of the clogged grinding wheel when the grinding wheel is clogged 75 Indicator showing the location where regular reflection occurs when the grinding wheel is in a normal state 76 Indicator showing the location where regular reflection occurs when the grinding wheel is clogged 8 Workpiece 8a Worked part h Peak intensity value w Half width

Claims (3)

A non-contact detection device that detects clogging of a grinding wheel that processes a workpiece by contacting the workpiece while rotating, comprising:
a light projection unit that emits light onto the grinding surface of the grindstone;
a light receiving sensor that receives light reflected from the grinding surface;
a determination circuit that determines a clogging state of the grinding surface based on a concentration degree of the regular reflection component in a central region and/or a light receiving intensity distribution of the diffuse reflection component detected by the light receiving sensor ,
the concentration of the regular reflection component in a central region and/or the light receiving intensity distribution of the diffuse reflection component is detected by a reflection pattern formed on the light receiving sensor;
The non-contact grinding wheel clogging detection device, wherein the discrimination circuit discriminates that the clogging state exists when a peak intensity value of a peak at a central origin, which is a light receiving position of a specular reflection component in the reflection pattern, exceeds a predetermined level, and/or discriminates that the clogging state exists when a half-width of the peak does not satisfy a predetermined level . The grindstone;
A processing device comprising the non-contact detection device according to claim 1 . A non-contact detection method for detecting clogging of a grinding wheel that is brought into contact with a workpiece while rotating and processes the workpiece, comprising the steps of:
Emitting projection light from a light projection unit toward the grinding surface of the grindstone;
receiving light reflected from the grinding surface with a light receiving sensor;
and determining a clogging state of the grinding surface by a determination circuit based on a concentration degree of the regular reflection component in a central region and/or a light receiving intensity distribution of the diffuse reflection component detected by the light receiving sensor ,
the concentration of the regular reflection component in a central region and/or the light receiving intensity distribution of the diffuse reflection component is detected by a reflection pattern formed on the light receiving sensor;
A non-contact detection method in which the clogging state is determined to exist when the peak intensity value of a peak at the central origin, which is the light receiving position of the specular reflection component in the reflection pattern, exceeds a predetermined level and/or when the half-width of the peak is less than a predetermined level .