Internal combustion engine component and method for manufacturing an internal combustion engine component

Abstract

Internal combustion engine component, comprising: a metallic component (30); a mark (40) formed from an oxide film produced on a surface (39) of the metallic component (30), or formed from the metallic component (30) and the oxide film; and a coating material (60) that covers the entire marking (40) and allows light transmission.

Description

AREA OF INVENTION

[0001] The present disclosure relates to an internal combustion engine component and a method for manufacturing the internal combustion engine component, in particular to an internal combustion engine component to which a marking is attached, and a method for manufacturing the internal combustion engine component to which a marking is attached. BACKGROUND OF THE INVENTION

[0002] A technique has been proposed in which a predefined identifier (mark) is applied to an industrial product, allowing information about the product's history, including procurement, processing, production, distribution, sale, disposal, and similar processes, to be traced. Even a spark plug, which ignites an air-fuel mixture in an internal combustion engine, requires marking to enhance traceability. As a technique for applying the mark to the industrial product, Japanese utility model registration JP 3 078 913 U ("PTL 1") discloses a technique for printing a mark by irradiating the surface of a ceramic substrate with a laser beam. EP 3 401 051 A1 discloses a spark plug and a method for manufacturing a spark plug that has a mark formed from an oxide layer.DE 10 2018 210 257 A1 discloses a spark plug and a method for marking a spark plug. SUMMARY OF THE INVENTION

[0003] Since the related technique described above involves creating a mark by irradiating the surface of the brittle ceramic substrate with a laser beam, it is possible to create a clearly legible mark. However, the mark can become a starting point for fracture of the substrate, and there is concern that the strength of a component to which the mark is applied could decrease.

[0004] Therefore, the explanatory aspects of this disclosure relate to the provision of a spark plug that can prevent a reduction in the strength of the component on which the marking is applied, while ensuring the legibility of the marking, and to a method for manufacturing the spark plug.

[0005] The following are examples of embodiments according to the invention, namely application examples 1 to 13. <Anwendungsbeispiel 1>

[0006] Internal combustion engine component, wherein part of the component consists of a metallic component, the component comprising: a marking formed from an oxide film produced on a surface of the metallic component, or formed from the metallic component and the oxide film; and a coating material covering the entire marking and allowing light transmission.

[0007] Since the marking is formed from the oxide layer created on the surface of the metallic component or from the metallic component and the oxide layer, it is possible under this configuration to prevent a decrease in the strength of a part to which the marking is applied, compared to a case in which the marking is applied to a ceramic part.

[0008] Since the oxide layer or the metallic component forming the marking is covered with the coating material, it is also possible to prevent the oxide layer or the metallic component from rusting due to contact with the air. This prevents the oxide layer or the metallic component from discoloring due to rust or similar processes, thus preventing the marking from becoming less legible. Therefore, it is possible to prevent a decrease in the strength of the component to which the marking is attached while simultaneously ensuring the marking's legibility.

[0009] The coating material is made of a translucent material. The light can contain various wavelengths, including infrared, visible, and ultraviolet rays. If the marking is visually verified, a material that transmits visible light can be used. If the marking is read and verified by a code reader, a translucent material that can be read by the code reader can be used. <Anwendungsbeispiel 2>

[0010] The internal combustion engine component according to application example 1, wherein the entire outermost edge of the coating material on the surface of the metallic component is located outside an outermost edge of the marking.

[0011] Since the oxide layer and the metallic component forming the marking are more reliably covered by the coating material, this configuration prevents discoloration of the oxide layer or the metallic component due to rust or similar substances, thus preventing further deterioration of the marking's legibility. This makes it possible to prevent a decrease in the strength of the component to which the marking is attached while simultaneously ensuring the marking's legibility. <Anwendungsbeispiel 3>

[0012] The internal combustion engine component according to application example 1 or 2, wherein an uneven section is provided around the marking in the surface of the metallic component and the coating material covers the uneven section.

[0013] According to this configuration, the removal of the coating material can be made more difficult by covering the uneven section with the coating material. <Anwendungsbeispiel 4>

[0014] The internal combustion engine component according to one of application examples 1 to 3, wherein a hollowed-out section (such as a recessed section) is formed on the surface of the metallic component and wherein the marking is formed on a bottom surface of the hollowed-out section.

[0015] Since the coating material covers the mark formed on the underside of the hollowed-out section (e.g., a depression), removing the coating material may be more difficult compared to a case where the coating material is applied to a flat surface. <Anwendungsbeispiel 5>

[0016] The internal combustion engine component according to application example 4, wherein the outermost edge of the coating material is located within an outermost edge of the hollowed-out section.

[0017] According to this configuration, the application area of ​​the coating material can be determined by the hollowed-out section in comparison to a case where the coating material is applied by spreading it over an area. <Anwendungsbeispiel 6>

[0018] The internal combustion engine component according to one of application examples 1 to 5, wherein the internal combustion engine component is a spark plug configured to ignite an air-fuel mixture in an internal combustion engine.

[0019] In this configuration it is possible to prevent the loss of strength of the component that is attached with the marking formed on the metallic component that forms part of the spark plug, while ensuring the legibility of the marking. <Anwendungsbeispiel 7>

[0020] The internal combustion engine component according to application example 6, wherein the internal combustion engine component is a spark plug, wherein the spark plug extends axially from a front end to a rear end and has a metal housing with a projection section extending radially outward over its entire circumference, wherein the projection section has a projection: a surface facing the front end (orsurface), which is locked directly or via a seal to the motor head when mounted on a motor; and a marking-forming surface on which the marking is formed adjacent to a rear end face of the surface facing the front end face, and wherein a portion of the coating material with maximum thickness is arranged at a rear end face of a center of the marking in a direction along the marking-forming surface, wherein a thickness of the coating material is maximum at the portion with maximum thickness.

[0021] Since the area of ​​maximum thickness is located relatively far from the end face that forms an interlocking surface with the motor head, the coating material is prevented from adhering to the end face during application or drying. This ensures an airtight seal between the motor head and the surface facing the front end face. <Anwendungsbeispiel 8>

[0022] The internal combustion engine component according to application example 6 or 7, wherein the internal combustion engine component is a spark plug extending axially from a front end to a rear end and having a projecting section extending radially outward over its entire circumference, wherein the projecting section comprises: a front end-facing surface (or area) that is locked to the engine head directly or via a seal; and a marking-forming surface on which the marking is formed adjacent to a rear end of the front end-facing surface, and wherein a portion of the coating material with maximum thickness is arranged outside an outermost edge of the marking in a direction along the marking-forming surface, wherein the thickness of the coating material is at its maximum at the portion with maximum thickness.

[0023] With this configuration, the variation in thickness of a section of the coating material applied to the marking can be reduced compared to a case where sections of maximum thickness lie within the outermost edge of the marking. Therefore, the visibility of the marking can be further improved. <Anwendungsbeispiel 9>

[0024] The internal combustion engine component according to one of application examples 6 to 8, wherein the internal combustion engine component is a spark plug extending axially from a front end to a rear end and having a projecting section extending radially outward over its entire circumference, wherein the projecting section comprises: a front end-facing surface (or area) that is locked to the engine head directly or via a seal; and a marking-forming surface on which the marking is formed adjacent to a rear end of the front end-facing surface, and wherein a length of the coating material in a direction perpendicular to the axial direction along the marking-forming surface is longer than a length in the axial direction along the marking-forming surface.

[0025] This configuration allows for an increased coverage area of ​​the coating material without increasing its length towards the end surface. This prevents the coating material from adhering to the end-facing surface during application or drying. Furthermore, the increased coverage area allows for more reliable coverage of the oxide layer or metallic component forming the marking. <Anwendungsbeispiel 10>

[0026] A method for manufacturing an internal combustion engine component, wherein part of the component is composed of a metallic part, the method comprising: a preparation step for preparing the metallic part; a marking step for irradiating a surface of the metallic part with a laser beam to form a marking, wherein the marking is formed from an oxide film or is formed from the metallic part and the oxide film; and a coating step for applying a coating material that allows light transmission to cover the entire marking.

[0027] Since the marking is formed from the oxide layer created on the surface of the metallic component or from the metallic component and the oxide layer, it is possible under this configuration to prevent a decrease in the strength of a part to which the marking is applied, compared to a case in which the marking is applied to a ceramic part.

[0028] Since the oxide layer or the metallic component forming the marking is covered with the coating material, rust formation through contact with the air is prevented. This prevents the oxide layer or the metallic component from discoloring due to rust or similar substances, thus preventing the marking from becoming less legible. Consequently, the strength of the component to which the marking is attached is not compromised, while the legibility of the marking remains undetectable.

[0029] The coating material is made of a translucent material. The light can contain various wavelengths, including infrared, visible, and ultraviolet rays. If the marking is visually verified, a material that transmits visible light can be used. If the marking is read and verified by a code reader, a translucent material that can be read by the code reader can be used. <Anwendungsbeispiel 11>

[0030] Method for manufacturing an internal combustion engine component according to application example 10, wherein the internal combustion engine component is a spark plug configured to ignite an air-fuel mixture in an internal combustion engine.

[0031] In this configuration it is possible to prevent the loss of strength of the component that is attached with the marking formed on the metallic component that forms part of the spark plug, while ensuring the legibility of the marking. <Anwendungsbeispiel 12>

[0032] Method for manufacturing the internal combustion engine component according to application example 11, wherein the internal combustion engine component is a spark plug extending axially from a front end to a rear end and having a projecting section extending radially outward over its entire circumference, wherein the projecting section comprises: a front end-facing surface (or area) that is locked to the engine head directly or via a seal when mounted on an engine; and a marking-forming surface on which the marking is formed adjacent to a rear end of the front end-facing surface, wherein the coating step is carried out in a state in which the front end-facing surface is vertically upward.

[0033] According to this configuration, although the coating material hangs vertically downwards during the coating step due to its own weight, adhesion of the coating material to the surface facing the front end is prevented. This ensures an airtight seal between the engine head and the surface facing the front end. <Anwendungsbeispiel 13>

[0034] Method for manufacturing the internal combustion engine component according to application example 13, wherein the internal combustion engine component is a spark plug extending axially from a front end to a rear end and having a metal housing with a projecting section extending radially outward over its entire circumference, wherein the projecting section comprises: a surface facing the front end which is locked to the engine head directly or via a seal; and a marking-forming surface on which the marking is formed adjacent to a rear end of the surface facing the front end, wherein the coating step is carried out in a state in which the marking-forming surface is pointing vertically upward.

[0035] This configuration prevents the coating material from sagging towards the front end due to its own weight during the coating process. This ensures an airtight seal between the motor head and the front end.

[0036] Since the coating material spreads essentially uniformly along the marking-forming surface during the coating step due to its own weight, this configuration also prevents the thickness of any portion of the coating material on the marking from being uneven. This improves the legibility of the marking. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a one-sided section of a spark plug in a first illustrative embodiment. Fig. Figure 2 is a side view of the spark plug near a mark in the first illustrative embodiment. The Fig. Figures 3A to 3F are explanatory views of a marking step, an uneven surface forming step, and a coating step. Fig. 4A is a schematic representation of the light reflected by the marking, and Fig. Figure 4B is a schematic representation of the reflectivity distribution captured by a light receiving element that receives the light reflected from the marker. The Fig. 5A and Fig. Figure 5B shows explanatory views of the coating step in a second illustrative embodiment. Fig. Figure 6 is an explanatory view of the coating step in a third illustrative embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0037] In the following, selected embodiments of the invention are described as illustrative embodiments with reference to the present figures. A. First illustrative embodiment:

[0038] The following describes a first illustrative embodiment of the present disclosure. Fig. Figure 1 is a one-sided section of a spark plug 10 in the first illustrative embodiment. Fig. Figure 1 refers to the underside of a drawing sheet as the front end of the spark plug 10 and the top side of the drawing sheet as the rear end of the spark plug 10. The spark plug 10 is designed for igniting an air-fuel mixture in an internal combustion engine (not shown). The spark plug 10 consists of an insulator 11, a metal terminal 20, a metal housing 30 and a ground electrode 31.

[0039] The insulator 11 is a cylindrical component made of aluminum oxide or a similar material, exhibiting excellent mechanical and insulating properties at high temperatures. The insulator 11 has an axial hole 12 shaped to penetrate along an axis O. A central electrode 14 is arranged at the end face of the axial hole 12.

[0040] The central electrode 14 is a rod-shaped component extending along axis O. The central electrode 14 is manufactured by coating a core material of copper, or a core material with copper as the main component, with nickel or a nickel-based alloy. The central electrode 14 is held by the insulator 11. The central electrode 14 has a front end that protrudes from the axial hole 12. A precious metal-containing tip 15 is connected to a front end of the central electrode 14.

[0041] The metal connector 20 is a rod-shaped component to which a high-voltage cable (not shown) is connected. The metal connector 20 is made of a conductive metal material (e.g., low-carbon steel). The metal connector 20 is connected to a shaft section 21, which is inserted into the axial hole 12, a fastening section 22, which fits into the axial hole 12, and a head section 23, which abuts a rear end face 13 of the insulator 11. The head section 23 is disc-shaped. The outer diameter of the head section 23 is larger than the outer diameter of the shaft section 21. The head section 23 is provided with a cylindrical wall section 25 that surrounds an end face 24 in the direction of the axis O of the metal connector 20.

[0042] To improve the corrosion resistance of the metal connection 20, nickel plating of the metal connection 20 is carried out in the present illustrative embodiment. The height T of the wall section 25 in the direction of the axis O from the end surface 24 is set, for example, to 2 mm or less.

[0043] The metal housing 30 is a substantially cylindrical body made of a conductive metal material (e.g., low-carbon steel). A section of a surface layer consisting of a zinc layer or a nickel-plated layer (not shown) is formed in the metal housing 30 by zinc plating or nickel plating. The metal housing 30 is upsetting and attached to the end face of an outer circumference of the insulator 11 at a distance in the direction of axis O from the head 23 of the metal terminal 20.

[0044] The metal housing 30 has an external thread 36 which is screwed to an internal thread of a cylinder head (not shown) of the internal combustion engine on an outer circumferential surface of the metal housing 30. The metal housing 30 has a projecting section 37 which extends radially outwards at the rear end face of the external thread 36.

[0045] The projecting section 37 has a surface 38 facing the front end, which, when screwed onto the cylinder head of the internal combustion engine, is locked to the cylinder head directly or via a seal 70. The projecting section 37 has a marking-forming surface 39, which adjoins a rear end of the surface 38 facing the end, and on which a marking 40 is formed from an oxide layer or from the oxide layer and a surface of the metal housing 30.

[0046] The surface of the metal housing 30 corresponds in the requirements to “a surface of the metallic component”.

[0047] The ground electrode 31 is a rod-shaped component made of metal (e.g., a nickel-based alloy). The ground electrode 31 has a first section 32 located on the front side and a second section 33 on the back side of the first section 32.

[0048] In the ground electrode 31, a precious metal-containing tip 35 is connected to the first section 32. In the present example embodiment, the front end of the ground electrode 31 is bent, and the first section 32 faces the center electrode 14 (tip 15). A spark gap is formed between the tip 35, which is connected to the first section 32, and the center electrode 14 (tip 15).

[0049] The spark plug 10 is manufactured, for example, according to the following procedure. First, the center electrode 14, to whose front end the tip 15 has been previously connected, is inserted into the axial hole 12 of the insulator 11 and positioned so that a front end of the center electrode 14 is exposed to the outside of the axial hole 12. The shaft portion 21 of the metal terminal 20 is inserted into the shaft hole 12 to ensure the connection between the metal terminal 20 and the center electrode 14, and then the metal housing 30, to which the ground electrode 31 has been previously connected, is mounted to the outer circumference of the insulator 11. The tip 35 is connected to the ground electrode 31, and then the ground electrode 31 is bent so that the tip 35 faces the center electrode 14 (tip 15) to form the spark plug 10.

[0050] Fig. 2 is a side view of spark plug 10, in which the area around the mark in Fig. Figure 1 is enlarged. The marking 40 is formed on the marking-forming surface 39 of the projecting part 37 of the metal housing 30. In the present illustrative embodiment, the marking 40 is a two-dimensional code. Examples of two-dimensional codes are PDF 417, Micro PDF 417, CODE 49, Maxicode, Data Matrix, QR code, and Aztec. Incidentally, it is of course possible to form a one-dimensional code on the metal connector 20.

[0051] The marker 40 comprises a first section 41, consisting of a series of rectangular cells, and a second section 42, which covers a perimeter of the first section 41 and has a higher reflectivity than the first section 41. In the present illustrative embodiment, the first section 41 is a dark module and the second section 42 is a light module. The combination of the first section 41 and the second section 42 displays unique historical information for the product or component. A quiet zone 43, which is a boundary part of the marker 40, is a portion of the second section 42 that has a higher reflectivity than the first section 41.

[0052] In the present illustrative embodiment, the first section 41 is an oxide layer and the second section 42 is a surface (marking-forming surface 39) of the projecting section 37 of the metal housing 30, which is a metallic component.

[0053] A coating material 60 is applied to the marking-forming surface 39 in such a way that it covers the entire marking 40. The coating material 60 can be a rust-preventive oil, a water-repellent coating agent, a resin, or similar. In the present example, a UV-curing resin is used, which is cured by irradiation with ultraviolet (UV) rays.

[0054] The coating material 60 consists of a material capable of transmitting light in such a way that the reflected light of the light emitted for marking 40 is read by a code reader. In the present illustrative embodiment, a colorless and transparent UV-cured resin is used.

[0055] The coating material 60 covers the marking 40 such that an outermost edge 61 of the coating material 60 lies completely outside an outermost edge 43 of the marking 40.

[0056] On the marking-forming surface 39 of the projecting section 37, an uneven section 34 is formed at the periphery of the mark 40. In the first illustrative embodiment, the coating material 60 covers the marking-forming surface 39, so that it covers the entire mark 40 and the entire uneven section 34.

[0057] In the coating material, a length D2 in a direction perpendicular to the direction of the axis O along the marking-forming surface 39 is longer than a length D1 in the direction of the axis O along the marking-forming surface 39.

[0058] With reference to Fig. 3 describes a marking step to form the marking 40 on the marking-forming surface 39 of the protrusion section 37, a step to form an uneven section on the marking-forming surface 39 and a coating step to apply the coating material 60 to cover the entire marking 40 and the entire uneven section 34.

[0059] In Fig. 3. The marking step, the step for forming the uneven section, and the coating step are described with reference to a cross-sectional view of the projecting section 37 of the metal housing 30. In the first illustrative embodiment, during the coating step, a spark plug (in the machining state) is positioned during manufacturing such that the marking-forming surface 39 is oriented vertically upwards. Fig. 3 is the upward direction of a paper surface in a vertical direction upwards and a downward direction of the paper surface in a vertical direction downwards (direction of gravity).

[0060] Fig. Figure 3A is an explanatory representation of a step in which a base region 44 is formed by irradiation with a laser beam 51 in the marking step. Fig. Figure 3B is an explanatory representation of a step in which the first section 41 of the marking 40 is formed by irradiation with the laser beam 51 in the marking step. Fig. 3C is an explanatory representation of a step to clarify a boundary between the first section 41 and the second section 42 by irradiating the second section 42 of the marker 40 with the laser beam 51 in the marking step.

[0061] Fig. 3D is an explanatory representation for the step of forming the uneven section, in which the uneven section 34 is formed by irradiating the perimeter of the marking 40 in the marking-forming surface 39 with the laser beam 51.

[0062] Fig. 3E is an explanatory representation of a step in which a liquid coating material 601 is applied prior to curing to cover the entire marking 40 in the coating step. Fig. Figure 3F is an explanatory representation of an irradiation step with UV 53 using a UV irradiation device 52 to form the liquid coating material 601 as solid coating material 60 in the coating step.

[0063] In the step of Fig. In 3A, the marking-forming surface 39 is irradiated with the laser beam 51 emitted by the processing head 50, and a section of the surface layer is ablated to form the base region 44. This allows the reflectivity in the base region to be made essentially constant, thus improving the readability of the marking. By moving the processing head 50 relatively along the marking-forming surface 39 (see Fig. 1) and scanning of the laser beam 51, the rectangular base region 44 (background) is formed in an area where the marker 40 (see Fig. 2) arises.

[0064] When the base region 44 is formed, the laser power of the processing head 50, or a scanning speed and a focus diameter, depth of field, or similar parameters of the laser beam 51 are adjusted so that sufficient energy is delivered to remove the section of the surface layer onto the marking-forming surface 39. This is intended to minimize the re-oxidation of the section irradiated with the laser beam 51. This increases the reflectivity while further reducing the variation in the shading of the background (base region 44) of the marking 40.

[0065] In the step of Fig. In step 3B, the base region 44 is irradiated with the laser beam 51 emitted by the processing head 50, partially heating the base region 44. This promotes the formation of the oxide layer in the section heated by the laser beam 51. By moving the processing head 50 relatively along the marking-forming surface 39 and scanning the laser beam 51, the first section 41 is formed.

[0066] When the first section 41 is formed, the laser power of the processing head 50 or the scanning speed and the focus diameter, depth of field, or similar parameters of the laser beam 51 are adjusted so that the energy on the marking-forming surface 39 is higher than during the formation of the base region 44. Accordingly, the oxidation of the section irradiated with the laser beam 51 is promoted, and the oxide layer is formed and blackened on the first section 41.

[0067] Since the oxidation level of the first section 41 can be controlled by the laser power, the thickness or density of the oxide layer of the first section 41 can be made essentially uniform.

[0068] Since the first section 41 is formed on the base region 44 with a small variation in shading, irregularities of the first section 41 can be eliminated and the contrast of the first section 41 can be increased compared to a case in which the first section 41 is formed directly on the marking-forming surface without forming the base region 44.

[0069] In the step of Fig. 3C will be a section not irradiated with the laser beam 51 with the processing head 50 in a step of Fig. The laser beam 51 emitted by 3B illuminates the surface, and an oxide layer formed in a contour section of the second section 42 is removed by a thermal effect during the formation of the first section 41. The boundary between the first section 41 and the second section 42 is formed by the relative movement of the processing head 50 along the marking-forming surface 39 and the scanning of the laser beam 51.

[0070] In the step of Fig. In step 3C, the laser power of the processing head 50, or the scan speed and the focus diameter, depth of field, etc., of the laser beam 51 are adjusted so that the energy used corresponds to that used during the formation of the base region 44. The dirt generated during the formation of the first section 41 of the second section 42 can be removed. Therefore, the contrast between the first section 41 and the second section 42 can be increased, and at the same time, the dimensional accuracy of the first section 41 and the second section 42 can be improved.

[0071] In the step of Fig. In the 3D process, the laser beam 51 emitted by the processing head 50 is directed onto a section of the marking-forming surface around the marking 40 to create the uneven section 34. At this point, the energy input is adjusted by modifying the focus diameter, depth of field, or similar parameters of the laser beam 51 to obtain a different reflectivity than that of the first section 41 or the second section 42 of the marking 40. In the present illustrative embodiment, the energy is supplied at a focus diameter larger than the focus diameter in the marking step or at a depth of field deeper than the depth of field in the marking step. This can negatively affect the reading of the marking 40 in a code reader because the reflectivity in the uneven section 34 is not uniform.

[0072] In the step of Fig. Step 3E shows the application of the liquid coating material 601 prior to UV curing. In this illustrative embodiment, the processing state is set such that the marking-forming surface 39 points vertically upwards. The liquid coating material 601 then distributes itself substantially evenly due to its own weight. The liquid coating material 601 covers the entire marking 40 and is applied in such a way that it covers the entire area. Fig. 3D formed uneven section 34 covers.

[0073] In the step of Fig. Figure 3F shows a UV irradiation step in which the liquid coating material 601 is irradiated with UV 53 before curing with the UV irradiation device 52 to form the solid coating material 60.

[0074] Next, the reflected light from marker 40 will be analyzed using... Fig. 4 described. Fig. Figure 4A is a schematic representation of the reflected light from the marker 40. The marker 40 is read by illuminating it with light source 54 and detecting the light 55, 56, and 57 reflected from the marker 40 by a light-receiving element 58. The light-receiving element 58 is part of an image sensor, such as a CCD or CMOS sensor, with a condenser lens, color filter, or similar component. Since the first section 41 absorbs more light source 54 than the second section 42, the light-receiving element 58 can receive more reflected light 56 ​​from the second section 42 than reflected light 55 from the first section 41.

[0075] Fig. Figure 4B is a schematic representation of the reflectivity distribution (degree of reflection) detected by the light-receiving element 58, which receives the reflected light 55 and 56 from the marker 40, and the distribution of reflectivity values ​​representing the amount of light received by each pixel of the light-receiving element 58 is shown schematically. Fig. 4B, the reflectance is taken as the horizontal axis and the number of pixels (frequency) of the light receiving element 58 that has detected light is taken as the vertical axis.

[0076] In the spark plug of the first illustrative embodiment, as shown in Fig. As shown in Figure 4B, the variation in the reflection distribution of the reflected light 55 of the first section 41 can be made smaller than the variation in the reflection distribution of the reflected light 57 in a section around the marker 40. The variation in the reflection distribution of the reflected light 56 ​​of the second section 42 can be made smaller than the variation in the reflection distribution of the reflected light 57 around the marker 40. This is because the oxidation state of a surface of the first section 41 or the surface condition of the second section 42 and the uneven section 34 can be controlled by adjusting the laser power or similar means.

[0077] The reflectance of the reflected light 56 ​​of the second section 42 is higher than the reflectance of the reflected light 55 of the first section 41. Therefore, by setting a reflectance threshold between the distribution of reflected light 56 ​​and the distribution of reflected light 55, the first section 41 (dark module) and the second section 42 (light module) can be read accurately, in contrast to a case where the variation in the reflectance distribution of the second section 42 is not reduced. This ensures a consistent reading rate by the light receiving element 58 and protects against misreadings.

[0078] According to the spark plug 10 of the first illustrative embodiment, since the marking 40 is formed from the first section 41 (oxide layer) and the second section 42 (surface of the metal housing 30), it is possible to prevent a decrease in the strength of a component on which the marking is applied, compared to a case in which the marking is applied to a ceramic component.

[0079] Furthermore, since the first section 41 (oxide layer) or the second section 42 (surface of the metal housing 30), which forms the marker 40, is covered with the coating material 60, it is possible to prevent the first section 41 or the second section 42 from rusting due to contact with the open air. This prevents the first section 41 (oxide layer) or the second section (surface of the metallic component) from becoming discolored by rust or similar substances, thus preventing a decrease in the readability of the marker 40. Therefore, it is possible to prevent a decrease in the strength of the component to which the marker 40 is attached while simultaneously ensuring the readability of the marker 40.

[0080] Since the first section 41 (oxide layer) and the second section 42 (surface of the metal housing 30), which form the marking 40, are more reliably covered by the coating material 60 after the spark plug 10 of the first illustrative embodiment, it is further prevented that the first section 41 (oxide layer) or the second section (surface of the metallic component) becomes discolored by rust or similar substances, and the readability of the marking 40 is further prevented from decreasing. This makes it possible to prevent a decrease in the strength of the component to which the marking 40 is attached while simultaneously ensuring the readability of the marking 40.

[0081] Furthermore, after the spark plug 10 of the first illustrative embodiment, the coverage area of ​​the coating material 60 can be increased without increasing the length of the coating material 60 in the direction of the surface 34 facing the front end. This prevents the coating material 60 from adhering to the surface 38 facing the front end during application or drying. Since the coverage area of ​​the coating material 60 can be increased, the first section 41 (oxide layer) or the second section 42 (surface of the metal housing), which forms the marking 40, can also be more reliably covered by the coating material 60.

[0082] According to the spark plug 10 of the first illustrative embodiment, flaking of the coating material can be made more difficult by covering the uneven section 34 with the coating material 60.

[0083] Furthermore, after the spark plug 10 of the first illustrative embodiment, it is possible in the coating step to prevent the coating material 60 from hanging towards the end face 38 due to its own weight. This ensures airtightness between the engine head and the surface 38 facing the front end face.

[0084] Since the coating material 601 spreads substantially uniformly along the marking-forming surface 39 after the spark plug 10 of the first illustrative embodiment due to its own weight during the coating step, it is also possible to prevent the thickness of the portion of the coating material 601 located on the marking 40 from being uneven. This improves the readability of the marking 40. B Second illustrative embodiment:

[0085] A second illustrative embodiment of the present disclosure is described below with reference to the Fig. 5A and Fig. 5B described. Fig. 5A and Fig. Figure 5B shows explanatory views of the coating step in the second illustrative embodiment.

[0086] One difference from the first illustrative embodiment is that the processing state in the application step of applying the coating material is set such that the front end face of surface 38 points vertically upwards. Other configurations are the same as those of the first illustrative embodiment. This can be understood, for example, by comparing the Fig. 3E and Fig. 3F and the Fig. 5A and Fig. 5B. In Fig. 5A and Fig. 5B represents the top of the paper surface pointing vertically upwards and the bottom of the paper surface pointing vertically downwards (in the direction of gravity). That is, although in the Fig. 5A and Fig. With 5B omitted, the surface 38 facing the front end is on the top side of the Fig. 5A and Fig. 5B available.

[0087] In contrast to the first illustrative embodiment, in the second illustrative embodiment, before curing, a part 621 of maximum thickness is located in the liquid coating material 601a on the rear end face of a center 40c of the marking 40 in a direction along the marking-forming surface 39. The part 621 of the coating material 601a, which has maximum thickness, is located outside an outer edge 43 of the marking 40 in the direction of the marking-forming surface 39.

[0088] In contrast to the first illustrative embodiment, in the second illustrative embodiment, after curing, the coating material 60a also contains a part 621 of maximum thickness, the thickness of which is maximal, located on the rear end face of a center 40c of the marking 40 in a direction along the marking-forming surface 39. The part 621 of the coating material 60a, the thickness of which is maximal, is located outside an outermost edge 43 of the marking 40 in the direction of the marking-forming surface 39.

[0089] According to the spark plug 10a of the second illustrative embodiment, since the part 621 with the maximum thickness of the liquid coating material 601a is arranged at a location relatively far from the surface 38 facing the front end, which is an interlocking surface with the engine head, the coating material 601a is prevented from adhering to the surface 38 facing the front end at the time of application or drying. This ensures an airtight seal between a spark plug hole and the surface 38 facing the front end.

[0090] Furthermore, according to the spark plug 10a of the second illustrative embodiment, the thickness variation of the portion of the coating material 60a located on the marking 40 can be reduced compared to a case where the portions 62 and 621 lie with their maximum thickness within the outermost edge 43 of the marking 40. Therefore, the visibility of the marking 40 can be further improved. C Third illustrative embodiment:

[0091] A third illustrative embodiment of the present disclosure is described below with reference to Fig. 6 described. Fig. Figure 6 is an explanatory view of the coating step in the third illustrative embodiment.

[0092] The third illustrative embodiment differs from the first illustrative embodiment in that a hollowed-out section 371 (e.g., a recess) is formed in a projecting section 37a. Other configurations are the same as those of the first illustrative embodiment. This becomes clear, for example, by comparing Fig. 3F and Fig. 6. A marking is formed on a base surface 372 of the hollowed-out section 371 (the base surface 372 of the hollowed-out section 371 corresponds to the marking-forming surface 39). Furthermore, the outermost edge 62 of the coating material 60 is located within an outermost edge 373 of the hollowed-out section 371.

[0093] According to the spark plug 10b of the third illustrative embodiment, since the coating material 60 covers the marking 40 formed on the underside 372 of the hollowed-out section 371, the removal of the coating material 60 may be more difficult compared to a case in which the coating material 60 is applied to a plane.

[0094] According to the spark plug 10b of the third illustrative embodiment, the hollowed-out section 371 allows an application range of the coating material 60 to be determined, in comparison to a case in which the coating material 60 is disposed of by scattering in a plane. D modification:

[0095] In the present illustrative embodiment, the mark 40 is a two-dimensional code, but it can also be a one-dimensional barcode. Furthermore, the mark 40 can not be a code, but a symbol for visual confirmation (a circle, a triangle, a square, a star, a logo, or similar).

[0096] In the present illustrative embodiment, the UV-cured resin 60 and 60a is used as the coating material, but a thermosetting or time-curing resin can also be used. In this case, instead of the UV irradiation device 52, the liquid coating material 601a can be cured before curing using a heating or blowing device.

[0097] Furthermore, the coating materials 60 and 60a can be in liquid form, e.g., as rust-preventive oil. In this case, one step of curing the liquid coating materials 601 and 601a is omitted, and the coating configuration is completed with the application of the liquid coating materials 601 and 601a.

[0098] Furthermore, in the present illustrative embodiment, a colorless and transparent material is used as coating material 60 and 60a, but the present disclosure is not limited to this. The coating materials 60 and 60a need only be able to transmit the light emitted by the code reader. For example, a slightly tinted, semi-transparent material can be used. If the code reader is configured to read reflected ultraviolet or infrared light, the coating materials 60 and 60a can be a material that does not transmit visible light.

[0099] In the present illustrative embodiment, the surface of the projecting section 37 of the metal housing 30 is defined as the marking-forming surface 39, but it can be a surface of another metallic component. Examples of metallic components used in the spark plug are the ground electrode 31, the center electrode 14, and the metal terminal 20. The marking 40 can be formed on these surfaces.

[0100] In the present illustrative embodiment, the first section 41 is set as a dark module and the second section 42 as a light module, but the first section 41 can also be set as a light module and the second section 42 as a dark module. This can be achieved by swapping the laser conditions of Fig. 3A and the laser conditions of Fig. 3B will be implemented.

[0101] Although the oxide layer is used as the first section 41 and the surface of the metallic section as the second section 42 in the present illustrative embodiment, the first section 41 and the second section 42 can be formed from the oxide layer. In this case, the brightness of the first section 41 and the second section 42 can be adjusted by changing one oxidation state.

[0102] As in the present illustrative embodiment, it is preferable for the coating materials 60 and 60a to cover the entire marking 40 and the entire uneven section 34. However, it is not always necessary for the coating materials 60 and 60a to cover the entire uneven section 34. This is because it prevents the coating materials 60 and 60a from flaking off, even if they cover at least a portion of the uneven section 34.

[0103] The method for manufacturing the spark plug of the present illustrative embodiment includes the step of forming the uneven sections, but this step can be omitted. The step of forming the uneven section can be performed before the marking step.

[0104] In the method for manufacturing the spark plug of the present illustrative embodiment, the marking step is the step of Fig. 3C is included, in which the boundary between the first section 41 and the second section 42 is clearly illustrated; however, this step can also be omitted. This is because if the oxide layer in the step of Fig. Since 3B can be shaped exactly, it is not necessary to remove the oxide layer produced in the contour section of the second section 42 under the influence of heat when forming the first section 41.

[0105] In the present illustrative embodiment, the spark plug has been described as an internal combustion engine component, but the internal combustion engine component forming part of the metallic component includes a glow plug for a diesel engine used to assist in the ignition of light oil, an oxygen sensor measuring the oxygen concentration of the exhaust gas exiting the internal combustion engine, or the like, and the present disclosure can be applied to these internal combustion engine components.

[0106] The present invention has been described based on the foregoing illustrative embodiments and modifications. The illustrative embodiments of the invention are intended to facilitate understanding of the present invention and do not limit its scope. The present invention can be modified and improved without departing from the scope of the claims and includes equivalents thereof.

Claims

[1] Internal combustion engine component comprising: a metallic component (30); a mark (40) formed from an oxide film produced on a surface (39) of the metallic component (30), or formed from the metallic component (30) and the oxide film; and a coating material (60) that covers the entire marking (40) and allows light transmission. [2] Internal combustion engine component according to claim 1, wherein an outermost edge (62) of the coating material (60) is arranged on the surface (39) of the metallic component (30) outside an outermost edge (43) of the marking (40). [3] Internal combustion engine component according to claim 1 or 2, wherein an uneven section (34) is provided around the marking (40) in the surface of the metallic component (30) and the coating material (60) covers the uneven section (34). [4] Internal combustion engine component according to any one of claims 1 to 3, wherein a hollowed-out section (371) is formed on the surface (39) of the metallic component (30), and wherein the marking (40) is formed on a floor surface (372) of the hollowed-out section (371). [5] Internal combustion engine component according to claim 4, wherein an outermost edge (62) of the coating material (60) is arranged within an outermost edge (373) of the hollowed-out section (371). [6] Internal combustion engine component according to any one of claims 1 to 5, wherein the internal combustion engine component is a spark plug (10) configured to ignite an air-fuel mixture in an internal combustion engine. [7] Internal combustion engine component according to claim 6, wherein the spark plug (10) extends in an axial direction from a front end to a rear end and has a metal housing (30) with a radially outwardly projecting section (37) over its entire circumference, where the leading section (37) has: a surface (38) facing the front end, which, when mounted on a motor, is locked to a motor head directly or via a seal (70); and a marking-forming surface (39) on which the marking (30) is formed adjacent to a rear end face of the surface (38) facing the front end face, and wherein a part (621) with maximum thickness of the coating material (60) is arranged at a rear end side of a center (40c) of the marking (40) in a direction along the marking-forming surface (39), wherein the thickness of the coating material (60) is maximum at the part (621) with maximum thickness. [8] Internal combustion engine component according to claim 6 or 7, wherein the spark plug (10) extends in an axial direction from a front end to a rear end and has a projecting section (37) that extends radially outwards over its entire circumference, where the leading section (37) has: a surface (38) facing the front end, which, when mounted on a motor, is locked to a motor head directly or via a seal (70); and a marking-forming surface (39) on which the marking (30) is formed adjacent to a rear end face of the surface (38) facing the front end face, and wherein a part (621) with maximum thickness of the coating material (60) is arranged outside an outermost edge (43) of the marking (40) in a direction along the marking-forming surface (39), wherein the thickness of the coating material (60) is maximum at the part (621) with maximum thickness. [9] Internal combustion engine component according to any one of claims 6 to 8, wherein the spark plug (10) extends in an axial direction from a front end to a rear end and has a projecting section (37) that extends radially outwards over its entire circumference, where the leading section (37) has: a surface (38) facing the front end, which is locked to a motor head directly or via a seal (70); and a marking-forming surface (39) on which the marking (40) is formed adjacent to a rear end face of the surface (38) facing the front end face, and wherein a length of the coating material (60) in a direction perpendicular to the axial direction along the marking-forming surface (39) is longer than a length in the axial direction along the marking-forming surface (39). [10] Method for manufacturing an internal combustion engine component, wherein part of the component is composed of a metallic part, the method comprising: a preparatory step for preparing the metallic component (30); a marking step of irradiating a surface (39) of the metallic component (30) with a laser beam to form a marking (40), wherein the marking (40) is formed from an oxide film or from the metallic component (40) and the oxide film; and a coating step in which a coating material (60) is applied which allows light transmission so that the entire marking (40) is covered. [11] Method for manufacturing an internal combustion engine component according to claim 10, wherein the internal combustion engine component is a spark plug (10) configured to ignite an air-fuel mixture in an internal combustion engine. [12] Method for manufacturing the internal combustion engine component according to claim 11, wherein the spark plug extends in an axial direction from a front end to a rear end and has a projection section (37) that projects radially outwards over its entire circumference, the projection section (37) comprising: a front end-facing surface (38) which is locked directly or via a seal (70) to a motor head when mounted on an engine; and a marking-forming surface (39) on which the marking (40) is formed adjacent to a rear end of the front end-facing surface (38), the coating step being carried out in a state in which the front end-facing surface (38) is vertically upwards. [13] Method for manufacturing the internal combustion engine component according to claim 11, wherein the spark plug (10) extends in an axial direction from a front end to a rear end and has a metal housing (30) with a projection section (37) that projects radially outwards over its entire circumference, wherein the projection section (37) has: a surface (38) facing the front end which is locked directly or via a seal (70) to a motor head; and a marking-forming surface (39) on which the marking (40) is formed adjacent to a rear end of the surface facing the front end, wherein the coating step is carried out in a state in which the marking-forming surface (39) points vertically upwards.

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