Patent Description:
Patent Literature <NUM> discloses a method of producing a metal product by forming a two-dimensional code on a surface of a metal member. The method includes forming a black marking having a predetermined pattern by repeating the process of irradiating a surface of a metal member with a laser beam to oxidize metal and printing circular dots on the surface, the dots corresponding to the beam shape. A two-dimensional code formed with a combination of a black cell that is a group of circular dots and a white cell that is a region not irradiated with the laser beam is thus formed on the surface of the metal member. The two-dimensional code has the function as an identification code that identifies each individual metal product (for example, product type, production date, materials used, and production line). Patent Literature <NUM> relates to a metal case used for electronic parts, comprising a base area with first recesses and second recesses formed by laser irradiation, wherein the second recesses have a different light reflection density from the first recesses and represent characters or figures in the base area. Patent Literature <NUM> describes a process of cleaning a marking area by irradiating a laser beam by scanning the marking area on the surface of an object with an energy lower than the energy of the laser beam for marking the area. Patent Literature <NUM> describes a method for laser marking on a metallic member. Patent Literature <NUM> describes a method of marking an article.

The metal member on which a two-dimensional code is to be formed is typically obtained by rolling a metal material through rolls. In this case, scratches on the surfaces of the rolls may be transferred onto the surface of the metal member to leave fine linear marks (also called rolling marks) on the surface of the metal member. Alternatively, the metal member may undergo a variety of surface treatment before an identification code is formed on the metal member. With this surface treatment, the gloss of the surface of the metal member may become uneven or the surface of the metal member may become a mirror surface.

In such a case, when the metal member is irradiated with flashlight in order to read the two-dimensional code formed on the metal surface by using a scanning camera, light may irregularly enter on the scanning camera due to rolling marks, gloss, and the like, or light specularly reflected on the metal surface may enter on the scanning camera. This reduces the readability of a two-dimensional code and in addition causes concern that the readability of a two-dimensional code varies for each metal product.

The present disclosure provides a method of manufacturing a metal product and a metal product with enhanced readability of an identification code.

In the method of manufacturing a metal product and the metal product according to the present disclosure, the readability of the identification code can be enhanced.

An exemplary embodiment according to the present disclosure will be described in detail below with reference to the drawings. In the following description, the same elements or the elements having the same functions are denoted by the same reference signs and an overlapping description will be omitted.

First of all, referring to <FIG> and <FIG>, a structure of a stacked rotor core <NUM>, which is an example of the metal product, is described. The stacked rotor core <NUM> is a part of a rotor. The rotor is formed by attaching end plates and a shaft (which are not illustrated) to the stacked rotor core <NUM>. As illustrated in <FIG>, the stacked rotor core <NUM> includes a stack <NUM> (metal member), connecting tab portions <NUM>, and an identification code <NUM>.

The stack <NUM> has a cylindrical shape. More specifically, as illustrated in <FIG>, a through hole 2a (center hole) extending along the center axis Ax is provided at the center portion of the stack <NUM>. A shaft may be disposed in the through hole 2a.

The stack <NUM> is a stack <NUM> in which a plurality of blanked members W are stacked. The blanked member W is a plate formed by blanking an electrical steel sheet (metal plate) into a predetermined shape. Since the electrical steel sheet is obtained by rolling by using rolls, the surface of the blanked member W may have rolling marks. The stack <NUM> may be formed by stacking a plurality of blanked members W while shifting the angles of the blanked members W from each other, which is called rotational stacking. The angle of rotational stacking may be set to a desired value.

In the present embodiment, the blanked members W adjacent in the stacking direction are fastened to each other by the connecting tab portions <NUM>. Specifically, as illustrated in <FIG>, the connecting tab portions <NUM> include a connecting tab 3a formed at a blanked member W forming a layer other than the bottom layer of the stack <NUM> and a through hole 3b formed at a blanked member W forming the bottom layer of the stack <NUM>. The connecting tab 3a has a depression formed on the front surface side of a blanked member W and a projection formed on the back surface side of the blanked member W. The depression of the connecting tab 3a of one blanked member W is joined to the projection of the connecting tab 3a of another blanked member W adjacent to the front surface side of the one blanked member W. The projection of the connecting tab 3a of one blanked member W is joined to the depression of the connecting tab 3a of still another blanked member W adjacent to the back surface side of the one blanked member W. The projection of the connecting tab 3a of the blanked member W adjacent to the bottom layer of the stack <NUM> is joined to the through hole 3b. The through hole 3b has the function of preventing the blanked member W subsequently formed from being fastened to the previously produced stack <NUM> by the connecting tab 3a when stacks <NUM> are continuously produced.

A plurality of blanked members W may be fastened to each other by a variety of known methods, instead of the connecting tab portions <NUM>. A plurality of blanked members W may be joined to each other, for example, by adhesive or a resin material or joined to each other by welding. Alternatively, the blanked member W may be provided with a temporarily-connecting tab, and the stack <NUM> may be obtained by fastening a plurality of blanked members W to each other through temporarily-connecting tabs to form a stack, and thereafter removing the temporarily-connecting tabs from the stack. The "temporarily-connecting tab" means a connecting tab used for temporarily integrating a plurality of blanked members W and removed in the process of producing a product (stack <NUM>).

At least one magnet insertion hole (not illustrated) extending along the extending direction (stacking direction) of the center axis Ax and passing through the stack <NUM> may be provided in the stack <NUM>. The magnet insertion hole may be filled with a resin material with a permanent magnet (not illustrated) disposed therein. The resin material has the function of fixing a permanent magnet in the magnet insertion hole and the function of joining the blanked members W adjacent in the vertical direction together.

As illustrated in <FIG>, one identification code <NUM> is provided on a surface 2b (upper surface or lower surface) of the stack <NUM>, that is, the outer surface of the blanked member W forming the top layer or the bottom layer of the stack <NUM>. The identification code <NUM> has the function of holding individual information (for example, product type, production date, materials used, and production line) for identifying each individual stacked rotor core <NUM> having the identification code <NUM>. The identification code <NUM> may be anything that can hold the individual information with a combination of light pattern and dark pattern. The identification code <NUM> may be a barcode or a two-dimensional code, for example. Examples of the two-dimensional code include QR code (registered trademark), DataMatrix, and Vericode. As illustrated in detail in <FIG>, the identification code <NUM> includes a base region <NUM> and a black marking <NUM>. The identification code <NUM> has a predetermined pattern with a combination of the base region <NUM> and the black marking <NUM>.

As illustrated in <FIG>, the identification code <NUM> has a plurality of virtual cells <NUM>. A plurality of cells <NUM> are arranged in a grid pattern and correspond to the size of the identification code <NUM> as a whole. Although lines in a grid pattern that define the cells <NUM> are illustrated in <FIG>, these lines are drawn for the sake of convenience to facilitate understanding of the invention and do not exist in the actual identification code <NUM>. The size of the cell <NUM> is not limited and may be a variety of sizes depending on the required performance of the identification code <NUM>. The shape of the cell <NUM> is not limited and may be, for example, square, rectangular, circular, polygonal, and any other undefined shapes. In the present embodiment, the cell <NUM> is set to, for example, a <NUM> by <NUM> square shape or a <NUM> by <NUM> square shape. In the present description, a cell <NUM> in which the base region <NUM> is formed is called white cell 16a, and a cell <NUM> in which the black marking <NUM> is formed is called black cell 16b.

The base region <NUM> is formed by irradiating the surface 2b of the stack <NUM> with a base laser beam. The size of the base region <NUM> is not limited and may be a variety of sizes depending on the size of the stack <NUM>, the kind of material of the blanked member W, the position of the identification code <NUM> formed, and the like. The shape of the base region <NUM> is not limited and may be, for example, square, rectangular, circular, polygonal, and any other undefined shapes. In the present embodiment, the base region <NUM> is set to, for example, a <NUM> by <NUM> square shape.

Examples of the base laser beam for forming the base region <NUM> include YAG laser, YVO<NUM> laser, and fiber laser. The base laser beam may be continuous wave (CW) laser or may be pulsed laser. The beam diameter (the diameter of light ray before the beam reaches a radiation target), the spot diameter (the diameter of light ray on the surface of a radiation target when the base laser beam radiates the radiation target), and the output level of the base laser beam are not limited and may be in various sizes depending on the kind of beam, the kind of material of the blanked member W, the thickness of the blanked member W, and the like. Even with the same beam diameter, the spot diameter may vary because the melting state by the beam varies depending on the kind of material of the radiation target irradiated with the base laser beam.

Since the surface 2b of the stack <NUM> (blanked member W) is treated by the base laser beam, as illustrated in <FIG>, the base region <NUM> has an extremely high flatness. For example, as illustrated in <FIG>, the surface of the blanked member W with rolling marks have protrusions and depressions with a height of approximately a few µm to a few tens of µm, whereas the height of protrusions and depressions present on the surface of the base region <NUM> is approximately <NUM> or less.

The base region <NUM> is formed by repeatedly scanning along a predetermined direction A (see <FIG>) while irradiating the surface of the stack <NUM> (blanked member W) with the base laser beam over multiple rows. That is, as illustrated in <FIG>, the base region <NUM> is configured such that laser grooves extending along the direction A (scan direction) are arranged in multiple rows. <FIG> illustrates a state of laser grooves when pulsed laser is used as the base laser beam, as an example. One laser groove in <FIG> is formed with a plurality of pulse marks (the marks produced when the surface of the blanked member W is irradiated with the pulsed base laser beam) continuous from the left side to the right side in <FIG>. That is, the laser groove in <FIG> is formed by scanning from the left side to the right side in <FIG> by the base laser beam.

In the row direction that is the direction in which the scan rows of the base laser beam are arranged (the direction in which the laser grooves are arranged), the arrangement pitch of the base laser beam (the arrangement pitch of laser grooves) may be equal to or smaller than the spot diameter of the base laser beam. That is, the laser grooves adjacent in the row direction at least partially overlap each other. When the base laser beam is pulsed laser, the pulse marks may be arranged at a feed pitch equal to or smaller than the spot diameter in the scan direction of the base laser beam.

In the present embodiment, the black marking <NUM> is formed by irradiating the base region <NUM> with a marking laser beam. The black marking <NUM> is the blanked member W oxidized by the marking laser beam and becoming black. The black marking <NUM> has a predetermined pattern and forms the identification code <NUM> together with the surrounding base region <NUM>. Specifically, as illustrated in <FIG>, the black marking <NUM> is a group of black cells 16b formed by irradiating the cells <NUM> with the marking laser beam and filling the cells <NUM> with black color.

Examples of the marking laser beam for forming the black marking <NUM> include YAG laser, YVO<NUM> laser, and fiber laser. The marking laser beam may be continuous wave laser or may be pulsed laser. The beam diameter (the diameter of light ray before the beam reaches a radiation target), the spot diameter (the diameter of light ray on the surface of a radiation target when the marking laser beam radiates the radiation target), and the output level of the marking laser beam are not limited and may be in various sizes depending on the kind of beam, the kind of material of the blanked member W, the thickness of the blanked member W, and the like. However, the output level of the marking laser beam may be greater than the output level of the base laser beam, for example, may be <NUM> times or more as large as the output level of the base laser beam. Even with the same beam diameter, the spot diameter may vary because the melting state by the beam varies depending on the kind of material of the radiation target irradiated with the marking laser beam.

The black cell 16b is formed by repeatedly scanning along a predetermined direction B (see <FIG>) while irradiating the base region <NUM> with the marking laser beam over multiple rows. That is, as illustrated in <FIG> and <FIG>, the base region <NUM> is configured such that laser grooves extending along the direction B (scan direction) are arranged in multiple rows. <FIG> and <FIG> both illustrate a state of laser grooves when pulsed laser is used as the marking laser beam, as an example. One laser groove in <FIG> and <FIG> is formed with a plurality of pulse marks (the marks produced when the surface of the base region <NUM> is irradiated with the pulsed marking laser beam) continuous from the upper side to the lower side in <FIG> and <FIG>. That is, the laser groove in <FIG> and <FIG> is formed by scanning from the upper side to the lower side in <FIG> and <FIG> by the marking laser beam.

In the row direction that is the direction in which the scan rows of the marking laser beam are arranged (the direction in which the laser grooves are arranged), the arrangement pitch of the marking laser beam (the arrangement pitch of laser grooves) may be set to a predetermined interval. For example, the arrangement pitch may be approximately equal to the spot diameter of the marking laser beam as illustrated in <FIG>, may be larger than the spot diameter of the marking laser beam as illustrated in <FIG>, or may be smaller than the spot diameter of the marking laser beam as illustrated in <FIG>. That is, the laser grooves adjacent to each other in the row direction may adjoin to each other (see <FIG>), may be spaced apart from each other (see <FIG>), or may at least partially overlap each other (see <FIG>). When the marking laser beam is pulsed laser, the pulse marks may be arranged at a feed pitch equal to or smaller than the spot diameter in the scan direction of the marking laser beam.

The scan direction of the marking laser beam is different from the scan direction of the base laser beam. That is, the scan direction of the marking laser beam may be opposite to or may intersect the scan direction of the base laser beam. In the example illustrated in <FIG>, the scan direction of the marking laser beam is orthogonal to the scan direction of the base laser beam.

A method of forming the identification code <NUM> on the stack <NUM>, that is, a method of manufacturing the stacked rotor core <NUM> will now be described. First of all, the stack <NUM> is formed by blanking and stacking blanked members W from an electrical steel sheet (workpiece plate) which is a strip-like metal plate.

Next, as illustrated in <FIG>, the base region <NUM> is formed on the surface 2b of the stack <NUM> (the outer surface of the blanked member W forming the top layer or the bottom layer of the stack <NUM>) by using the base laser beam. In this case, the base region <NUM> is formed by repeatedly scanning with the base laser beam along a predetermined direction A over multiple rows. In the present embodiment, the entire region where the identification code <NUM> is to be formed is irradiated with the base laser beam. That is, in the present embodiment, even the cells <NUM> in which the black marking <NUM> is to be formed are irradiated with the base laser beam.

Next, as illustrated in <FIG>, the cells <NUM> to serve as the black cells 16b are specified from among a plurality of cells <NUM>, in accordance with the identification code <NUM> to be formed. Next, the black marking <NUM> is formed on the base region <NUM> using the marking laser beam. The black marking <NUM> is formed by repeatedly scanning with the marking laser beam along a predetermined direction B different from the direction A over multiple rows.

In forming the black marking <NUM>, when parameters a, b, and n are defined as:.

the specified cells <NUM> may be irradiated with the marking laser beam such that Expression <NUM> is satisfied. <MAT> Expression <NUM> is satisfied when the irradiated area with the marking laser beam a × b × n relative to the area a<NUM> of the cell <NUM> (a × b × n/a<NUM>) is equal to or greater than <NUM>. Thus, when Expression <NUM> is satisfied, the filling ratio of each black cell 16b is equal to or greater than <NUM>% (see <FIG> as an example of the filling ratio of approximately <NUM>%). Since the filling ratio of each black cell 16b is relatively large, the contrast between the black marking <NUM> and the base region <NUM> is even more improved. Accordingly, the readability of the identification code <NUM> can be even more enhanced.

In forming the black marking <NUM>, the specified cells <NUM> may be irradiated with the marking laser beam such that the parameters a, b, and n satisfy Expression <NUM>, Expression <NUM>, or Expression <NUM>. <MAT> <MAT> <MAT> When Expression <NUM> is satisfied, the filling ratio of each black cell 16b is equal to or greater than <NUM>% (see <FIG> as an example of the filling ratio of about <NUM>%). When Expression <NUM> is satisfied, the filling ratio of each black cell 16b is equal to or greater than <NUM>%. When Expression <NUM> is satisfied, the filling ratio of each black cell 16b is equal to or greater than <NUM>% (see <FIG> as an example of the filling ratio of about <NUM>%). In these cases, since the filling ratio of each black cell 16b is sufficiently large, the contrast between the black marking <NUM> and the base region <NUM> is significantly improved. Accordingly, the readability of the identification code <NUM> can be significantly enhanced.

The length a is determined, for example, based on the size of the identification code <NUM> (base region <NUM>) and the data capacity of the identification code <NUM>. The pulse diameter b is determined, for example, based on the output level of the marking laser beam and the material of the irradiation target (stack <NUM>).

The stacked rotor core <NUM> is finished when the identification code <NUM> is formed on the surface 2b of the stack <NUM> through the steps described above.

A method of reading the identification code <NUM> will now be described. The identification code <NUM> is read, for example, by using a reader <NUM> illustrated in <FIG>. The reader <NUM> includes a transportation conveyor <NUM>, a camera <NUM> for reading, and a controller <NUM>.

The transportation conveyor <NUM> operates based on an instruction from the controller <NUM> and has the function of transporting the stacked rotor core <NUM> placed thereon in a predetermined direction. The camera <NUM> is positioned above the transportation conveyor <NUM>. The camera <NUM> operates based on an instruction from the controller <NUM> and captures an image of the identification code <NUM> when the stacked rotor core <NUM> transported by the transportation conveyor <NUM> passes through below the camera <NUM>. The controller <NUM> processes the captured image data captured by the camera <NUM> and reads the identification code <NUM>. When it is determined that the identification code <NUM> fails to be read, the controller <NUM> allows the camera <NUM> to repeatedly capture an image of the identification code <NUM> as long as the stacked rotor core <NUM> is present within the imaging range of the camera <NUM>.

Here, a test was conducted in which square cells <NUM> were irradiated with the marking laser beam, which was a pulsed laser with a spot diameter of <NUM>, to form the black marking <NUM> in the base region <NUM>, the resultant identification code <NUM> was read by the camera <NUM> from a predetermined direction (not from immediately above), and the reading success rate was determined with different sizes of the cell <NUM> and different numbers of scans. In the present description, "reading success rate" refers to the rate at which the reading by the camera <NUM> is successful when the identification code <NUM> is read <NUM> times by the camera <NUM>.

<FIG> illustrates the result when one side of the cell <NUM> was <NUM>, and the number of scans of the marking laser beam was changed from <NUM> to <NUM> (for <NUM> or more scans, only even number of scans). When the number of scans was four (the filling ratio was <NUM>%), the reading success rate was <NUM>%. When the number of scans was five (the filling ratio was <NUM>%), the reading success rate was <NUM>%. When the number of scans was six (the filling ratio was <NUM>%), the reading success rate was <NUM>%. When the number of scans was seven (the filling ratio was <NUM>%), the reading success rate was <NUM>%. When the number of scans was eight (the filling ratio was <NUM>%), the reading success rate was <NUM>%. When the number of scans was nine (the filling ratio was <NUM>%), the reading success rate was <NUM>%. When the number of scans was ten or more (the filling ratio was <NUM>% or more), the reading success rate was <NUM>%.

<FIG> illustrates the result when one side of the cell <NUM> was <NUM>, and the number of scans of the marking laser beam was changed from <NUM> to <NUM> (for <NUM> or more scans, only even number of scans). When the number of scans was six (the filling ratio was <NUM>%), the reading success rate was <NUM>%. When the number of scans was seven (the filling ratio was <NUM>%), the reading success rate was <NUM>%. When the number of scans was eight (the filling ratio was <NUM>%), the reading success rate was <NUM>%. When the number of scans was nine (the filling ratio was <NUM>%), the reading success rate was <NUM>%. When the number of scans was <NUM> (the filling ratio was <NUM>%), the reading success rate was <NUM>%. When the number of scans was eleven (the filling ratio was <NUM>%), the reading success rate was <NUM>%. When the number of scans was twelve (the filling ratio was <NUM>%), the reading success rate was <NUM>%. When the number of scans was thirteen (the filling ratio was <NUM>%), the reading success rate was <NUM>%. When the number of scans was fourteen (the filling ratio was <NUM>%), the reading success rate was <NUM>%. When the number of scans was fifteen (the filling ratio was <NUM>%), the reading success rate was <NUM>%. When the number of scans was sixteen (the filling ratio was <NUM>%), the reading success rate was <NUM>%. When the number of scans was eighteen (the filling ratio was <NUM>%), the reading success rate was <NUM>%. When the number of scans was twelve or more (the filling ratio was <NUM>% or more), the reading success rate was <NUM>%.

The test results above confirmed that when the filling ratio was <NUM>% or more, the reading of the identification code <NUM> is successful at least <NUM>%.

In the present embodiment as described above, the base region <NUM> is firstly formed on the surface 2b of the stack <NUM> and thereafter the black marking <NUM> is formed in the base region <NUM>. The stacked rotor core <NUM> is thus obtained in which the identification code <NUM> comprising a combination of the black marking <NUM> and the base region <NUM> is formed on the surface 2b of the stack <NUM>. The black marking <NUM> is therefore present in the base region <NUM> on the even surface 2b. Accordingly, the contrast between the black marking <NUM> and the base region <NUM> is improved. As a result, the readability of the identification code <NUM> can be enhanced.

In the present embodiment, the base region <NUM> is formed by repeatedly scanning with the base laser beam along the direction A over multiple rows, and the black marking <NUM> is formed by repeatedly scanning with the marking laser beam along the direction B different from the direction A over multiple rows. That is, the laser grooves that form the base region <NUM> extend in the same direction A in any rows. With this configuration, any incident light on the base region <NUM> is likely to be reflected approximately in the same direction. Similarly, the laser grooves that form the black marking <NUM> extend in the same direction B in any rows. With this configuration, any incident light on the black marking <NUM> is likely to be reflected approximately in the same direction. Accordingly, the contrast between the black marking <NUM> and the base region <NUM> is more improved. As a result, the readability of the identification code <NUM> can be more enhanced.

In the present embodiment, the direction B which is the scan direction of the marking laser beam intersects (is orthogonal to) the direction A which is the scan direction of the base laser beam. In this configuration, the direction of reflected light from the base region <NUM> and the direction of reflected light from the black marking <NUM> are different directions. Accordingly, the contrast between the black marking <NUM> and the base region <NUM> is further improved. As a result, the readability of the identification code <NUM> can be further enhanced. When the direction B which is the scan direction of the marking laser beam is the same as the direction A which is the scan direction of the base laser beam, as illustrated in <FIG>, the contrast is reduced and the captured image of the identification code <NUM> may be unclear.

According to the present invention, the contrast between the black marking <NUM> and the surrounding is enhanced, so that an image of the identification code <NUM> can be captured by the camera <NUM> not only from the position facing the identification code <NUM> but also from the diagonal direction. Specifically, since the stacked rotor core <NUM> has its form changed, for example, due to insertion of a shaft into the through hole 2a in the subsequent step, the imaging direction of the identification code <NUM> by the camera <NUM> tends to be limited. However, the present invention enables reading of the identification code <NUM> from various directions.

Although an embodiment according to the present disclosure has been described in detail above, the foregoing embodiment is susceptible to various modifications without departing from the present invention as defined in the claims.

Specifically, as illustrated in <FIG>, only white cells 16a are first obtained by repeatedly scanning along the direction A while irradiating only the cells <NUM> in which the base region <NUM> is to be formed in the identification code <NUM> with the base laser beam over multiple rows. As illustrated in <FIG>, only black cells 16b are then obtained by repeatedly scanning along the direction B while irradiating only the cells <NUM> in which the black marking <NUM> is to be formed in the identification code <NUM> with the marking laser beam over multiple rows. With this process, the base region <NUM> and the black marking <NUM> are individually formed with almost no overlap with each other.

Alternatively, as illustrated in <FIG>, only black cells 16b are first obtained by repeatedly scanning along the direction B while irradiating only the cells <NUM> in which the black marking <NUM> is to be formed in the identification code <NUM> with the marking laser beam over multiple rows. As illustrated in <FIG>, only white cells 16a are then obtained by repeatedly scanning along the direction A while irradiating only the cells <NUM> in which the base region <NUM> is to be formed in the identification code <NUM> with the base laser beam over multiple rows. With this process, the base region <NUM> and the black marking <NUM> are individually formed with almost no overlap with each other.

(<NUM>) The direction B which is the scan direction of the marking laser beam may not intersect the direction A which is the scan direction of the base laser beam. For example, the direction B may be approximately the same direction as the direction A or may be approximately the opposite direction.

(<NUM>) The scan direction of the base laser beam in forming the base region <NUM> may not be necessarily the direction A and may be a variety of directions. For example, the scan direction of the base laser beam in forming the base region <NUM> may be meandering, may be opposite between the forward path and the return path (see <FIG>), or may be spiral (see <FIG>). When the scan direction of the base laser beam is opposite between the forward path and the return path, the base region <NUM> is formed by scanning with the base laser beam so as to reciprocate in a direction A1 and a direction A2 that is the opposite direction to the direction A1 (see <FIG>). Thereafter, the marking laser beam is scanned along the direction B different from the directions A1 and A2 to form the black marking <NUM> (see <FIG>). When the scan direction of the base laser beam is spiral, the base region <NUM> is formed by repeatedly scanning with the base laser beam along a direction Al, scanning with the base laser beam from the end point along a direction A2 orthogonal to the direction Al, scanning with the base laser beam from the end point along a direction A3 orthogonal to the direction A2, and scanning with the base laser beam from the end point along a direction A4 orthogonal to the direction A3 (see <FIG>). Thereafter, the marking laser beam is scanned along the direction B different from the directions A1 and A3 to form the black marking <NUM> (see <FIG>). Similarly, the scan direction of the marking laser beam in forming the black marking <NUM> may not be necessarily the direction B and may be a variety of directions. For example, the scan direction of the marking laser beam in forming the black marking <NUM> may be meandering, may be opposite between the forward path and the return path, or may be spiral.

(<NUM>) The arrangement pitch of laser grooves in the black cell 16b may be constant or may be irregular. That is, the interval between adjacent laser grooves may be a regular interval or may not be a regular interval. When the interval between adjacent laser grooves is not a regular interval, the laser grooves are allocated uniformly to some extent in the cell <NUM>.

(<NUM>) The black marking <NUM> may be directly formed on the surface 2b of the stack <NUM> without forming the base region <NUM>.

(<NUM>) As long as the reading success rate of the identification code <NUM> exceeds <NUM>%, the filling ratio may be less than <NUM>% in the black cells 16b.

(<NUM>) When a permanent magnet is provided in the stack <NUM>, for example, a metal end plate made of stainless steel may be disposed on each of both end surfaces of the stack <NUM> in order to suppress demagnetization of the magnet, and the identification code <NUM> may be provided on the end plate. The metal end plate may undergo predetermined surface treatment, which may make the gloss of the surface of the end plate uneven or make the surface of the metal end plate into the mirror surface state. However, even in such a case, the present invention can enhance the contrast between the black marking <NUM> and the surrounding thereof and thereby enhance the readability of the identification code <NUM>.

(<NUM>) When an image of the identification code <NUM> is captured by the camera <NUM>, imaging conditions such as illumination may be changed as appropriate so as to capture a clear image of the identification code <NUM>.

(<NUM>) The identification code <NUM> may comprise anything other than a combination of the white cells 16a and the black cells 16b. That is, the identification code <NUM> may comprise a combination of other colors, in addition to or instead of white and black as long as the contrast is enhanced. For example, the identification code <NUM> may be a multilayered two-dimensional code (two-dimensional code formed by multilayering color information). An example of the multilayered two-dimensional code is PM code (registered trademark).

(<NUM>) The base region <NUM> may be formed as follows. First of all, a predetermined region of the surface 2b of the stack <NUM> (the outer surface of the blanked member W forming the top layer or the bottom layer of the stack <NUM>) is subjected to pretreatment (rough treatment) by using the base laser beam. Specifically, scanning along a predetermined direction A (see <FIG>) while irradiating the surface 2b with the base laser beam at a first output level is repeated over multiple rows. A preliminary region (not illustrated) is thus formed on the surface 2b. In the preliminary region, rolling marks on the surface Wa are roughly smoothed. For example, with the pretreatment, the protrusions and depressions with a height of approximately a few µm to a few tens of µm (see the broken line in <FIG>) due to rolling marks become protrusions and depressions with a height of approximately <NUM> or less (see the solid line in <FIG>).

Next, the preliminary region is subjected to main treatment (finishing) by using the base laser beam. Specifically, scanning along a predetermined direction A (see <FIG>) while irradiating the preliminary region with the base laser beam at a second output level lower than the first output level is repeated over multiple rows. The second output level may be, for example, equal to or lower than half of the first output level, may be equal to or lower than one-third of the first output level, or may be equal to or lower than one-fourth of the first output level. The base region <NUM> is thus formed on the surface 2b. In the base region <NUM>, the surface of the preliminary region is even more flattened. For example, with the main treatment, the protrusions and depressions with a height of about <NUM> or less in the preliminary region (see the broken line in <FIG>) become protrusions and depressions with a height of about <NUM> or less (see the solid line in <FIG>). The black marking <NUM> is formed in the thus formed base region <NUM>, whereby the contrast between the black marking <NUM> and the base region <NUM> is even more improved. As a result, the readability of the identification code <NUM> can be significantly enhanced.

(<NUM>) The present invention may be applied not only to the stacked rotor core <NUM> but also to a stacked stator core, or the present invention may be applied to any other various metal products.

Example <NUM>. A method of manufacturing a metal product according to an example of the present disclosure includes forming a base region on a surface of a metal member by repeatedly scanning along a predetermined first direction while irradiating the surface of the metal member with a base laser beam over multiple rows, and forming a marking by repeatedly scanning along a predetermined second direction while irradiating the surface of the metal member with a marking laser beam over multiple rows. The second direction is different from the first direction. An identification code having a predetermined pattern comprises a combination of the base region and the marking.

Example <NUM> comprises forming the base region on the surface of the metal member and forming the marking on the surface of the metal member. With this process, the metal product is obtained in which the identification code comprising the combination of the marking and the base region is formed on the surface of the metal member. Thus, the marking is present in a region surrounded by the base region with an even surface. Accordingly, the contrast between the marking and the base region is improved. As a result, the readability of the identification code can be enhanced.

Example <NUM> comprises forming the marking by repeatedly scanning with the base laser beam along the first direction over multiple rows, and forming the marking by repeatedly scanning with the marking laser beam along the second direction over multiple rows. That is, the laser grooves that form the base region extend in the same first direction in any rows. With this configuration, any incident light on the base region is likely to be reflected approximately in the same direction. Similarly, the laser grooves that form the marking extend in the same second direction in any rows. With this configuration, any incident light on the marking is likely to be reflected approximately in the same direction. Accordingly, the contrast between the marking and the base region is more improved. As a result, the readability of the identification code can be more enhanced.

According to Example <NUM>, the second direction which is the scan direction of the marking laser beam is a direction different from the first direction which is the scan direction of the base laser beam. With this configuration, the direction of reflected light from the base region and the direction of reflected light from the marking are different directions. Accordingly, the contrast between the marking and the base region is further improved. As a result, the readability of the identification code can be further enhanced.

Example <NUM>. In the method in Example <NUM>, forming the marking may include forming the marking by irradiating the base region with the marking laser beam.

Example <NUM>. In the method in Example <NUM>, the base region and the marking may be formed in regions that do not overlap each other.

Example <NUM>. In the method described in any one of Examples <NUM> to Example <NUM>, the second direction may intersect the first direction. In this case, the contrast between the marking and the base region is even more improved. As a result, the readability of the identification code can be even more enhanced.

Example <NUM>. In the method in any one of Example <NUM> to Example <NUM>, the base laser beam and the marking laser beam may comprise pulsed laser light, the base laser beam may be scanned at a feed pitch equal to or smaller than a spot diameter in the first direction and at an arrangement pitch equal to or smaller than a spot diameter in a row direction, and the marking laser beam may be scanned at a feed pitch equal to or smaller than a spot diameter in the second direction and at a predetermined arrangement pitch in a row direction.

Example <NUM>. In the method in Example <NUM>, the marking may comprise a combination of cells each having a square shape, and forming the marking may include irradiating each of the cells with the marking laser beam such that Expression <NUM> is satisfied: <MAT> where the parameters a, b, and n are defined as:.

In this case, the proportion of the total irradiated area with the second laser beam relative to the area of one cell that forms the marking, that is, the filling ratio by the second laser beam for one cell (which hereinafter may be simply referred to as "filling ratio") is equal to or greater than <NUM>%. Thus, since the filling ratio of each cell is relatively large, the contrast between the marking and the base region is even more improved. As a result, the readability of the identification code can be even more enhanced.

Example <NUM>. In the method in Example <NUM>, forming the marking may include irradiating each of the cells with the marking laser beam such that Expression <NUM> is satisfied. <MAT> In this case, the filling ratio is equal to or higher than <NUM>%. Thus, since the filling ratio of each cell is sufficiently large, the contrast between the marking and the base region is significantly improved. As a result, the readability of the identification code can be significantly enhanced.

Example <NUM>. In the method in any one of Example <NUM> to Example <NUM>, the marking may comprise a black marking formed by oxidizing the surface of the metal member by the marking laser beam.

Example <NUM>. In the method in any one of Example <NUM> to Example <NUM>, forming the base region may include repeatedly scanning along the first direction while irradiating the surface of the metal member with the base laser beam at a first output level over multiple rows, and repeatedly scanning along the first direction while irradiating a region with the base laser beam at a second output level lower than the first output level over multiple rows, the region being irradiated with the base laser beam at the first output level. In this case, in forming the base region, laser with a high output level is firstly emitted. With this process, rolling marks on the surface of the metal member are roughly smoothed (rough treatment). Thereafter, the region irradiated with laser with a high output level is irradiated with laser with a low output level. With this process, the protrusions and depressions of the roughly smoothed surface of the metal member are even more flattened (finishing). The marking is formed in the thus formed base region, whereby the contrast between the marking and the base region is even more improved. As a result, the readability of the identification code can be significantly enhanced.

Example <NUM>. A method of manufacturing a metal product according to another example of the present disclosure includes forming a marking by repeatedly scanning along a predetermined first direction while irradiating a surface of a metal member with a marking laser beam over multiple rows, the marking laser beam generated by a pulse-like laser light source. The marking laser beam is scanned at a feed pitch equal to or smaller than a spot diameter in the first direction and at a predetermined arrangement pitch in a row direction. The marking comprises a combination of cells each having a square shape. Forming the marking includes irradiating each of the cells with the marking laser beam such that Expression <NUM> is satisfied: <MAT> where parameters a, b, and n are defined as:.

According to Example <NUM>, each cell is irradiated with the marking laser beam such that Expression <NUM> is satisfied. In this configuration, the filling ratio is equal to or greater than <NUM>%. Accordingly, since the filling ratio of each cell is relatively large, the contrast between the marking and the surrounding region is even more improved. As a result, the readability of the identification code can be even more enhanced.

Example <NUM>. In the method in Example <NUM>, forming the marking may include irradiating each of the cells with the marking laser beam such that Expression <NUM> is satisfied. <MAT> In this case, the similar effects as in Example <NUM> can be achieved.

Example <NUM>. The method in Example <NUM> or Example <NUM> may further include, before forming the marking, forming a base region on the surface of the metal member by repeatedly scanning along a predetermined second direction while irradiating the surface of the metal member with a base laser beam over multiple rows. An identification code having a predetermined pattern may comprise a combination of the base region and the marking. Forming the marking may include irradiating the base region with the marking laser beam. In this case, the similar effects as in Example <NUM> can be achieved.

Example <NUM>. The method in Example <NUM> or Example <NUM> may further include forming a base region on the surface of the metal member by repeatedly scanning along a predetermined second direction while irradiating the surface of the metal member with a base laser beam over multiple rows. An identification code having a predetermined pattern may comprise a combination of the base region and the marking. The base region and the marking may be formed in regions that do not overlap each other. In this case, the similar effects as in Example <NUM> can be achieved.

Example <NUM>. In the method described in Example <NUM> or Example <NUM>, the first direction may intersect the second direction. In this case, the similar effects as in Example <NUM> can be achieved.

Example <NUM>. In the method in any one of Example <NUM> to Example <NUM>, the base laser beam may comprise pulse-like laser light and is scanned at a feed pitch equal to or smaller than a spot diameter in the second direction and at an arrangement pitch equal to or smaller than a spot diameter in a row direction.

Example <NUM>. In the method in any one of Example <NUM> to Example <NUM>, forming the base region may include repeatedly scanning along the first direction while irradiating the surface of the metal member with the base laser beam at a first output level over multiple rows, and repeatedly scanning along the first direction while irradiating a region with the base laser beam at a second output level lower than the first output level over multiple rows, the region being irradiated with the base laser beam at the first output level. In this case, the similar effects as in Example <NUM> can be achieved.

Example <NUM>. A metal product according to another example of the present disclosure comprises an identification code having a predetermined pattern comprising a combination of a base region and a marking, the identification code being formed on a surface of a metal member. The base region is configured such that laser grooves extending in a predetermined first direction are arranged in multiple rows. The marking is configured such that laser grooves extending in a predetermined second direction different from the first direction are arranged in multiple rows. Example <NUM> achieves the similar effects as Example <NUM>.

Example <NUM>. In the metal product in Example <NUM>, the second direction may intersect the first direction. In this case, the similar effects as in Example <NUM> can be achieved.

Example <NUM>. In the metal product in Example <NUM>, the base region may comprise pulse marks that are arranged at a feed pitch equal to or smaller than a spot diameter in the first direction and pulse marks that are arranged at an arrangement pitch equal to or smaller than a spot diameter in a row direction. The marking may comprise pulse marks that are arranged at a feed pitch equal to or smaller than a spot diameter in the second direction and pulse marks that are arranged at a predetermined arrangement pitch in a row direction.

Claim 1:
A method of manufacturing a marked metal product, the method comprising:
forming a base region on a surface of a metal member by repeatedly scanning along a predetermined first direction while irradiating the surface of the metal member with a base laser beam over multiple rows, wherein the base region is configured such that laser grooves extending along the predetermined first direction are arranged in multiple rows; and
forming a marking by repeatedly scanning along a predetermined second direction different from the first direction while irradiating the surface of the metal member with a marking laser beam over multiple rows, wherein the marking is configured such that laser grooves extending along the predetermined second direction are arranged in multiple rows,
wherein an identification code having a predetermined pattern comprising a combination of the base region and the marking is formed, wherein the base region is light pattern and the marking is dark pattern.