Method and device for producing an element with a through hole

Abstract

A method of manufacturing an element (93) having a through-hole (88, 98), the method comprising: a primary forming step of irradiating a laser beam onto a workpiece member (7, 8) to form a pilot hole (981) having a smaller inner diameter than the through hole (88, 98) in the workpiece member (7, 8) while receiving light from the workpiece member (7, 8) by a light detecting unit (17); an intensity determining step for determining whether an intensity of the light detected by the light detecting unit (17) is less than or equal to a predetermined threshold value; a laser modulation step for modulating a spatial light phase of the laser beam irradiated onto the workpiece element (7, 8) in response to determining that the intensity of the light detected by the light detection unit is less than or equal to the predetermined threshold value; and a secondary forming step of irradiating the laser beam having the modulated spatial light phase onto an edge portion of the pilot hole (981) to form the through hole (88, 98).

Description

Technical FieldThe present disclosure relates to a method for manufacturing an element and an apparatus for manufacturing an element.General State of the ArtMethods for manufacturing elements having through holes using a laser beam are conventionally known. In this method of manufacturing a workpiece member, when a through hole is drilled through the workpiece member, a laser beam penetrates the drilled through hole toward a side opposite to an irradiated side of the workpiece. In this case, an object on the side opposite to the irradiated side of the workpiece may be damaged by the laser beam. In order to prevent such damage by the laser beam, a laser shielding member capable of shielding the laser beam is provided on the side opposite to the irradiated side of the workpiece.For example, U.S. Pat. No. 8,242,408 B2 describes a method for manufacturing a member into which a laser shielding member is inserted when an injection hole is formed in a fuel injection valve using a laser beam. A laser shielding member formed of a material having a high melting point such as corundum and cubic zirconia is inserted into a workpiece member that is processed into a nozzle body.Further, DE 11 2004 002 827 T5 discloses a differential diameter hole drilling method comprising: generating a first laser output power having sufficient energy density over a first spatial spot size to remove target material within a first spot area defined by the first spatial spot size; directing the first laser output power to impinge on the target material and thereby form a pre-hole having a first diameter corresponding to the diameter of the first spot area and less than the predetermined diameter of the through-hole; generating a second laser output power having sufficient energy density over a second spatial spot size to remove target material within a second spot area defined by the second spatial spot size; directing the second laser output to impinge upon the target material such that the resulting second spot area is greater than the first spot area of the pre-hole to form a through-hole having the predetermined diameter and extending through the thickness of the target material, wherein forming the through-hole includes adding thermal energy that escapes through the pre-hole.EP 0 792 717 B1 discloses a method for laser beam cutting of workpieces, in which the thermal radiation of the cutting region is detected by a sensor and the measurement signals of said sensor are fed to an evaluation unit, with which a method parameter of the cutting effected with continuous laser radiation is influenced if a measurement signal exceeds a set threshold value. In order to optimize the cutting speed, the method is such that the cutting speed is reduced by a predetermined step if the threshold value is exceeded by a predetermined time and / or by a predetermined amount, that the stepwise reduction of the cutting speed is repeatedly carried out as required until the threshold value is not exceeded during the predetermined time, and that cutting is continued with the reduced, not increased again cutting speed.Further relevant prior art is known from the publications JP 2014-012 290 A, WO 2015 / 152 156 A1, U.S. Pat. No. 6,433,301 B1, JP 2000-126 880 A and US 2009 / 0 045 180 A1.Summary of the InventionAccording to the method for manufacturing an element described in U.S. Pat. No. 8,242,408 B2, the laser shielding element is gradually damaged by irradiation of a laser beam and thus has to be frequently replaced. Therefore, it is necessary to take man-hours in the machining steps machining a workpiece member with the laser beam to replace the laser shielding member. The laser shielding member is formed of a relatively expensive material that can restrict the amount of damage to the laser beam in the method used to manufacture the member described in US 8242408 B2. Since laser shielding members are replaced with a certain number of times as mentioned above, the manufacturing cost of the members increases.An object of the present disclosure is to provide a method and an apparatus for manufacturing a member in which damage caused by a laser beam is prevented when a through hole is formed in a workpiece member.The above object is achieved by the subject matter of claims 1 and 9. Advantageous further developments of the invention are the subject of the dependent claims that follow.A method for manufacturing an element according to a first aspect of the present disclosure includes a primary forming step, an intensity determining step, a laser modulating step, and a secondary forming step. The primary forming step includes emitting a laser beam to a workpiece member (7, 8) to form a pilot hole (981) having a smaller diameter than a through hole while receiving light from the workpiece member (7, 8) by a light detecting unit (17).The intensity determination step includes determining whether an intensity of the light detected by the light detection unit ( 17) is less than or equal to a predetermined threshold value. The laser modulating step includes modulating a spatial light phase of the laser beam emitted to the workpiece ( 7, 8) when the light detected by the light detecting unit ( 17) is detected as having a light intensity less than or equal to the predetermined threshold. The secondary forming step includes emitting the laser beam having the modulated spatial light phase onto a circumferential part of the pilot hole ( 981) to form the through hole.The method for manufacturing a member according to the present disclosure includes the primary forming step of forming a pilot hole using the laser beam. The pilot hole has a smaller inner diameter than a through hole in a workpiece member. A beam intensity picked up by the light detection unit after the pilot hole is drilled through the workpiece member is smaller than a beam intensity picked up by the light detection unit before the pilot hole penetrates the workpiece. In this connection, when it is determined in the intensity determination step that the intensity of the beam detected by the light detection unit is less than or equal to a predetermined threshold value, in the laser modulation step, the spatial light phase of the laser beam emitted onto the workpiece member is modulated. The laser modulating step includes modulating the spatial light phase of the laser beam to reduce the intensity of the laser beam that penetrates the completed pilot hole when the peripheral portion of the pilot hole is machined and to change the spread angle of the laser beam so that a machining amount for the element per unit time is reduced. The laser beam entering an interior of the workpiece member through the pilot hole therefore has reduced energy. Consequently, damage to the workpiece by the laser beam and an object located on the side of the workpiece member opposite to the side on which the laser beam is irradiated is prevented when the laser beam penetrates the pilot hole.BRIEF DESCRIPTION OF THE DRAWINGSThe foregoing and other objects, features and advantages of the present disclosure will be further understood from the following detailed technologies with reference to the drawings. In the accompanying drawings, FIG. 1 is a schematic diagram of an apparatus for manufacturing an element according to a first embodiment of the present disclosure; FIG. 2 is a cross-sectional view of a fuel injection valve provided with a nozzle body manufactured using a manufacturing method of an element according to the first embodiment of the present disclosure; FIG. 3 is an enlarged cross-sectional view of the nozzle body of FIG. 2 ; FIG. 4 is a flowchart of the method for manufacturing an element according to the first embodiment of the present disclosure; FIG. 5 is a characteristic diagram illustrating an intensity distribution of a laser beam related to the method of manufacturing an element according to the first embodiment of the present disclosure; FIG. 6A is a schematic diagram describing a step of the method for manufacturing the element according to the first embodiment of the present disclosure; FIG. 6B is a diagram viewed from a direction of an arrow VIb of FIG. 6A ; FIG. 7 is a characteristic diagram illustrating the intensity distribution of the laser beam different from the intensity distribution of the laser beam of FIG. 5 according to the method for manufacturing an element of the first embodiment of the present disclosure; FIG. 8A is a schematic diagram describing a step of the method for manufacturing an element different from the step of FIG. 6A according to the first embodiment of the present disclosure; FIG. 8B is a diagram viewed from a direction of an arrow VIIIb of FIG. 8A ; FIG. 9A is a diagram illustrating the intensity distribution of the laser beam according to the method for manufacturing an element of a second embodiment of the present disclosure; FIG. 9B is a schematic diagram describing a step of the method for manufacturing an element according to the second embodiment of the present disclosure; FIG. 10 is a flowchart of a method for manufacturing an element according to a third embodiment of the present disclosure; FIG. 11A is a schematic diagram describing a step of the method for manufacturing an element according to the third embodiment of the present disclosure; FIG. 11B is a diagram viewed in a direction of an arrow XIb of FIG. 11A ; FIG. 12A is a schematic diagram describing a step of the method for manufacturing an element different from a step of FIG. 11A according to the third embodiment of the present disclosure; FIG. 12B is a diagram viewed in a direction of an arrow XIIb of FIG. 12A ; FIG. 13 is a schematic diagram of the device for manufacturing an element according to a fourth embodiment of the present disclosure; FIG. 14 is a schematic diagram of the device for manufacturing an element according to a fifth embodiment of the present disclosure; FIG. 15 is a schematic diagram of the device for manufacturing an element according to a sixth embodiment of the present disclosure; FIG. 16 is a flowchart of the method for manufacturing an element according to the sixth embodiment of the present disclosure; FIG. 17 is an enlarged cross-sectional view of the workpiece member according to the method for manufacturing a member of the sixth embodiment of the present disclosure; FIG. 18 is a schematic diagram of the device for manufacturing an element according to a seventh embodiment of the present disclosure; FIG. 19 is a schematic diagram describing a step of the method for manufacturing an element according to the seventh embodiment of the present disclosure; FIG. 20 is a schematic diagram describing a step of the method for manufacturing an element according to the seventh embodiment of the present disclosure, which is different from the step of FIG. 19 ; FIG. 21 is a characteristic diagram illustrating the intensity distribution of the laser beam in connection with a method for manufacturing an element according to a comparative example; FIG. 22A is a schematic diagram describing a step of the method for manufacturing an element according to the comparative example; and FIG. 22B is a diagram viewed in a direction of an arrow XXIIb of FIG. 22A.DESCRIPTION OF EMBODIMENTSHereinafter, embodiments of the present disclosure will be described based on the drawings.(First Embodiment)A laser processing apparatus 1 as an "element manufacturing apparatus" according to the first embodiment is used for manufacturing a nozzle body 93 illustrated in FIG. 2 as an "element" of a fuel injection valve 90 for diesel fuel.First, a configuration of the fuel injection valve 90 will be described. As shown in FIGS. 2 and 3, the fuel injection valve 90 includes the nozzle body 93, a needle 95, and an electromagnetic driving unit 96. the needle 95 is provided so as to be able to abut against a valve seat 94 of the nozzle body 93. The electromagnetic drive unit 96 may drive the needle 95 in an axial direction.A chamber 97 is partitioned between the needle 95 abutting against the valve seat 94 and the nozzle body 93. The nozzle body 93 has injection holes 98 or "through holes" communicating with an exterior of the nozzle body 93 and the blind chamber 97. Fuel introduced into the nozzle body 93 passes through the blind chamber 97 and the injection holes 98 when the needle 95 disengages from the valve seat 94 to be injected to the outside. The laser processing apparatus 1 can form the injection holes 98 in a workpiece member 7.Next, a configuration of the laser processing apparatus 1 will be described with reference to FIG. 1. The laser processing apparatus 1 includes an element holding unit 11, a laser oscillator 13, an optical element unit 15, a beam detection unit 17, a control unit 19, and the like. Note that, in FIG. 1, a course of a laser beam in the laser processing apparatus 1 is indicated by a dotted line L 0 representing an outer edge of the laser beam. The course of the light from the workpiece element 7 is indicated by a dotted line L 7.The element holding unit 11 is configured such that the workpiece element 7 having a bottomed cylindrical shape can be held thereon. The element holding unit 11 holds the workpiece element 7 such that a laser beam is irradiated thereon from the outside of the workpiece element 7.The laser oscillator 13 oscillates the laser beam that can form the injection holes 98 in the workpiece member 7. The laser oscillator 13 is electrically connected to the control unit 19. The laser oscillator 13 oscillates laser beams based on a command signal output by the control unit 19. The laser beams oscillated by the laser oscillator 13 pass through a collimator 141 provided between the laser oscillator 13 and the optical element unit 15. The laser beams pass through the collimator 141 to become a collimated beam with adjusted parallel light beams. The collimated beam reaches the optical element unit 15.The optical element unit 15 corresponds to a so-called liquid crystal reflective panel including a front glass substrate 151, a liquid crystal layer 152, a rear reflective plate 153, electrodes 154 electrically connected to the control unit 19, and the like. In the optical element unit 15, a collimated beam incident through the front glass substrate 151 to an inside of the optical element unit 15 is reflected by the rear reflecting plate 153 in a predetermined direction. At this time, a direction of an array of liquid crystal molecules in the liquid crystal layer 152 is changed by a voltage applied to the electrodes 154. Consequently, the optical element unit 15 can modulate the spatial light phase of the laser beam directed from the optical element unit 15 toward the workpiece element 7. The laser beam directed from the optical element unit 15 toward the workpiece member 7 is condensed by a condenser lens 142 provided between the optical element unit 15 and the workpiece member 7, and is emitted to a desired position at the workpiece member 7.The light detecting unit 17 is electrically connected to the control unit 19. The light detection unit 17 is provided on an outer side of the workpiece member 7 in the vicinity of a portion of the workpiece member 7. This portion of the workpiece member 7 corresponds to a portion where the injection hole 98 is machined. The light detection unit 17 can receive reflection light of the laser beam reflected by the outer wall surface of the workpiece member 7 or plasma light of fine particles generated from the workpiece member 7 via the laser beam processing. The light detection unit 17 of the first embodiment can detect, for example, light in a wavelength range of 200 to 1200 nm, thus enabling detection of plasma light generated by a reaction between fine particles of the workpiece member 7 and the laser beam. The light detecting unit 17 outputs an electric signal corresponding to a detected intensity to the control unit 19.The control unit 19 is electrically connected to the laser oscillator 13, the optical element unit 15, and the light detection unit 17. The control unit 19 controls the laser oscillator 13 and the optical element unit 15 according to an electric signal output by the light detection unit 17.Hereinafter, a method of machining the workpiece member 7 will be described as a "method of manufacturing a member" according to the present embodiment based on FIGS. 4, 5, 6A, 6B, 7, 8A, and 8B. FIG. 4 is a flowchart illustrating the method for machining the workpiece member 7.First, at step 101 (hereinafter, step is simply referred to as "S"), the workpiece member 7 is set in the member holding unit 11.Subsequently, at S 102, the laser beam is radiated as a "primary forming step" to a desired position on the workpiece member 7. The term "desired position" corresponds to a substantially middle position of the injection hole 98 of the nozzle body 93 to which the workpiece member 7 is processed.Here, the intensity distribution of the laser beam emitted to the workpiece member 7 at S 102 will be described based on FIG. 5. FIG. 5 is a diagram illustrating the intensity distribution of the laser beam emitted to the workpiece member 7 through the condenser lens 142, the intensity of the laser beam being distributed in a direction perpendicular to a propagation direction of the laser beam. In FIG. 5, a horizontal axis represents a distance L from a center cL 0 of the laser beam. The vertical axis represents the intensity SoL of the laser beam.At S 102, the workpiece member 7 is irradiated with the laser beam having a beam diameter twice the distance L 1. The region in which the laser beam has an intensity of more than zero is hereinafter referred to as a laser irradiation region Rm 1. Specifically, the shape of the laser irradiation region Rm 1 substantially corresponds to a circular shape having a radius of the distance L 1.The laser beam irradiated on the workpiece member 7 at S 102 has the strongest intensity at the center cL 0 of the laser beam, and the intensity of the laser beam decreases as the distance from the center cL 0 increases. In the present embodiment, assuming that the lowest laser intensity with which the workpiece member 7 can be machined using the method for machining the workpiece member 7 is set as an intensity SoL 9, a range extending from the center cL 0 toward a distance L 21 corresponds to a machining range Rm 21. This region Rm 21 corresponds in particular to a region in which the laser beam has an intensity that enables machining of the workpiece element 7. At S 102, the laser beam irradiated on the workpiece member 7 has the region Rm 21 in which the process can be performed substantially in the center of the laser irradiation region Rm 1.At S 102, the control unit 19 controls the optical element unit 15 so as to irradiate the workpiece element 7 with the laser beam having the intensity distribution illustrated in FIG. 5. In the optical element unit 15, a voltage is applied to the electrodes 154, and the liquid crystal layer 152 is operated such that the laser beam oscillated by the laser oscillator 13 has an intensity distribution shown in FIG. 5.Next, based on FIGS. 6A and 6B, it will be described how the workpiece member 7 is machined at S 102. FIG. 6A is an enlarged cross-sectional view illustrating a portion of the workpiece member 7 irradiated with the laser beam. In FIG. 6A, the propagation direction of the laser beam is indicated by a solid arrow Ld 1. FIG. 6B corresponds to a diagram viewed from a direction of an arrow VIb of FIG. 6A. In FIGS. 6A and 6B, an outer edge of the laser irradiation region Rm 1 defined in FIG. 5 is indicated by a broken line Lw 1. The outer edge of Rm21 which can be processed as defined in FIG. 5 is indicated by a two-dot chain line Lw2.At S 102, the laser beam having the intensity distribution of FIG. 5 is emitted substantially at a center of the injection hole 98 to be formed at the workpiece member 7, as illustrated in FIG. 6B. At this time, an inner diameter of a pilot hole 981 (which may also be referred to as a primary hole or an output hole) provided as a pilot hole for the injection hole 98 to be manufactured with the laser beam having the intensity distribution of FIG. 5 is smaller than the inner diameter of the injection hole 98 indicated by the dotted lines in FIGS. 6A and 6B. Since the laser beam does not have intensity in regions other than the region Rm 21 that enables the workpiece member 7 to be machined, damage is not caused to the outer wall. Thus, at S 102, the pilot hole 981 is formed at the portion of the workpiece member 7 irradiated with the laser beam in the machining area Rm 21, that is, the area Rm 21 that can be machined, as illustrated in FIGS. 6A and 6B.At S 102, reflection of light or plasma light from the workpiece member 7 is captured by the light detection unit 17 when the workpiece member 7 is irradiated with the laser beam. The light detection unit 17 outputs an electric signal according to the intensity of the picked-up light to the control unit 19.Subsequently, at S 103, as an "intensity determination step", it is determined whether the intensity of reflection of light or plasma light from the workpiece member 7 is less than or equal to a first threshold value as a "predetermined threshold value".Once the pilot hole 981 is formed through the workpiece member 7, a part of the laser beam irradiated on the workpiece member 7 enters the workpiece member 7 through the completed pilot hole 981. Therefore, an intensity of the light reflected from the workpiece member 7 decreases once the pilot hole 981 is completed and passes through the workpiece member 7. In other words, based on a change in intensity of reflection light, it is determined whether the pilot hole 981 is completed to pass through the workpiece member 7.When the workpiece member 7 is machined with a laser beam, atoms constituting fine particles of the workpiece member 7 generated by this process are excited by the laser beam, and plasma light is generated due to the excitation. Therefore, the intensity of plasma light from the workpiece member 7 decreases because an amount of the fine particles generated is reduced once the pilot hole 981 is formed through the workpiece member 7. In other words, based on a change in intensity of plasma light, it is determined whether the pilot hole 981 is completed and passes through the workpiece member 7.At S 103, the control unit 19 determines whether the intensity of reflection light or plasma light from the workpiece member 7 captured by the light detection unit 17 is less than or equal to the preset first threshold value. If it is determined that the intensity of the light received by the light detection unit 17 is less than or equal to the first threshold, the process proceeds to S 104. If it is determined that the intensity of the light received by the light detection unit 17 is equal to or higher than the first threshold value, the process returns to S 102 and proceeds to irradiate the workpiece 7 with the laser beam having the intensity distribution illustrated in FIG. 5.Next, if it is determined at S 103 that the intensity of the reflection light or plasma light from the workpiece member 7 captured by the light detection unit 17 is less than or equal to the first threshold value, at S 104, as a "laser modulation step", the intensity distribution of the laser beam is changed.Here, the intensity distribution of the laser beam changed in S 104 will be described based on FIG. 7. FIG. 7 is a diagram illustrating the intensity distribution of the laser beam irradiated to the workpiece member 7 through the condenser lens 142. The intensity of the laser beam is distributed in the direction perpendicular to the propagation direction of the laser beam. In FIG. 7, a horizontal axis represents the distance from the center cL 0 of the laser beam. A vertical axis represents the intensity SoL of the laser beam. Note that, in FIG. 7, an intensity distribution of the laser beam changed at S 104 is indicated with a solid line AL 1, and the intensity distribution of the laser beam used at S 102 to form the pilot hole 981 is indicated with a two-dot chain line VL 1.Although the laser beam modulated at S 104 has a laser diameter twice as large as the distance L 1, the laser beam has the strongest intensity at a position deviating from the center cL 0 of the laser beam, as illustrated in FIG. 7. Specifically, the spatial distribution of the laser beam is modulated such that the energy of the center region Rm 4 that is closer to the center cL 0 in terms of the distance (L 1 / 2) is distributed to be lower than the energy of the outer peripheral region Rm 3. Consequently, the processing area Rm 21 located between a distance L 3 and a distance L 4 is shifted to the center of the laser irradiation area Rm 1.At S 104, the control unit 19 controls the optical element unit 15 so that the workpiece element 7 is irradiated with a laser beam having the spatial distribution illustrated in FIG. 7. In the optical element unit 15, a voltage is applied to the electrodes 154, and the liquid crystal layer 152 is operated so that the laser beam oscillated by the laser oscillator 13 has the intensity distribution shown in FIG. 7.Subsequently, at S 105, as a "secondary forming step", the laser beam is radiated to a peripheral part 982 constituting the pilot hole 981. At S 105, a focal point position is moved by modulating the spatial light phase of the laser beam modulated at S 104, and the peripheral part 982 is irradiated with the laser beam. Here, a process state of the workpiece member will be described based on FIGS. 8A and 8B. FIG. 8A is an enlarged cross-sectional view illustrating a portion of the workpiece member 7 irradiated with the laser beam. FIG. 8B is a diagram viewed in the direction of an arrow VIIIb of FIG. 8A.The laser beam having obtained the intensity distribution of FIG. 7 from S 104 is irradiated on the outer wall of the workpiece member 7 so that the peripheral part 982 is irradiated with the laser beam in the machining area Rm 21, as illustrated in FIG. 8B. Consequently, at S 105, the peripheral part 982 is machined with the laser beam, and an expanded hole 983 communicating with the pilot hole 981 is formed in a direction radially outside the pilot hole 981, as illustrated in FIGS. 8A and 8B. At this time, a part of the laser beam in the region outside the machining region Rm 21 in the laser irradiation region Rm 1 passes through the completed pilot hole 981 to enter the workpiece member 7, as illustrated in FIG. 8A. However, since the laser beam does not have an intensity in the laser irradiation region Rm 1 except for the machining region Rm 21 that enables machining of the workpiece member 7, damage is not caused to the inner wall surface of the workpiece member 7.At S 105, the focal point position of the laser beam is moved along the circumferential direction of the pilot hole 981 to process portions of the circumferential part 982 in order as indicated by a solid arrow Ld 2 of FIG. 8B, thereby moving the processing area Rm 21. Consequently, widened holes 983 are formed around the pilot hole 981 in the radially outer direction thereof.Subsequently, at S 106, it is determined whether a light intensity is less than or equal to a second threshold. At S 106, in the same manner as at S 103, the control unit 19 determines whether the intensity of reflection light or plasma light from the workpiece member 7 picked up by the light detection unit 17 is less than or equal to the preset second threshold value. In other words, it is determined whether the extended hole 983 has been formed through the workpiece member 7 based on a change in intensity of reflection light or plasma light.If it is determined at S 106 that the intensity of the light received by the light detection unit 17 is less than or equal to the second threshold, the process proceeds to S 107. If it is determined that the intensity of the light received by the light detection unit 17 is greater than or equal to the second threshold value, the process returns to S 105 and continues irradiating the workpiece member 7 with the laser beam having the intensity distribution illustrated in FIG. 7.If it is determined at S 106 that the intensity of reflection light or plasma light from the workpiece member 7 captured by the light detection unit 17 is less than or equal to the second threshold value, then at S 107, the control unit 19 determines whether the laser beam having the intensity distribution illustrated in FIG. 7 has been irradiated to the entire circumferential part 982. The control unit 19 determines whether the laser beam having the intensity distribution shown in FIG. 7 has been irradiated to the entire peripheral part 982 based on a program input in advance. If the control unit 19 determines that the laser beam has been irradiated to the entire circumferential part 982, the present routine is ended. If the control unit 19 determines that the laser beam has not been irradiated to the entire peripheral part 982, the process returns to S105 and irradiates a portion of the peripheral part 982 which has not been processed to the widened hole 983 with the laser beam having the intensity distribution shown in FIG. 7.According to the method for machining the workpiece member 7 of the present embodiment, the injection hole 98 is formed in the workpiece member 7 in this manner, and the nozzle body 93 is manufactured.Conventionally, when an injection hole is formed in a workpiece member using a laser beam, the laser beam used to form the injection hole enters the workpiece member through the completed injection hole. When the laser beam that has entered the workpiece member is irradiated to the inner wall surface of the workpiece member disposed in the emitting direction of the laser beam, there is a risk that the inner wall surface of the workpiece member may be damaged.Here, a method of machining a workpiece member according to a comparative example will be described in detail based on FIGS. 21, 22A, and 22B.According to the method for machining a workpiece member of the comparative example, first, the pilot hole 981 is formed using the laser beam having a beam diameter that is twice the length of the distance L 1, as in the present embodiment. After the pilot hole 981 is formed, the expanded hole 983 is formed by irradiating the circumferential part 982 of the pilot hole 981 with the laser beam. According to the workpiece member processing method of the comparative example, an intensity distribution of the laser beam for forming the extended hole 983 is not changed from the intensity distribution of the laser beam for forming the pilot hole 981. Specifically, the laser beam used in the workpiece member processing method according to the comparative example has the strongest intensity at the center cL 1 of the laser beam, as illustrated in FIG. 21, and the intensity of the laser beam decreases as the distance from the center cL 1 increases. Therefore, a range from the center cL 1 toward the distance L 20 corresponds to a machining range Rm 20 having an energy that allows the workpiece member 7 to be machined. The processing region Rm 20 is disposed substantially at the center of the laser irradiation region Rm 1. The diameter of the machining area Rm 20 is equal to the diameter of the pilot hole 981.FIGS. 22A and 22B illustrate a machining state of the workpiece member 7 when the extended hole 983 is formed with the method for machining a workpiece member according to the comparative example. FIG. 22A corresponds to an enlarged cross-sectional view illustrating a portion of the workpiece member 7 irradiated with the laser beam. FIG. 22B is a diagram viewed from a direction of an arrow XXIIb of FIG. 22A. In FIGS. 22A and 22B, the outer edge of the machining area Rm 20 defined in FIG. 21 is indicated with a two-dot chain line Lw 3.As illustrated in FIG. 22B, when the expanded hole 983 is formed, the laser beam is irradiated on the workpiece member 7 so that the circumferential part 982 of the pilot hole 981 is irradiated with the laser beam in the machining area Rm 20. At this time, the laser beam enters the workpiece member 7 via the pilot hole 981 in a partial region Rm 0 of the machining region Rm 20 that is not used for machining the peripheral part 982. The laser beam in the region Rm 0 that has entered the workpiece member 7 is irradiated to the inner wall surface of the workpiece member 7, causing damage to the inner wall surface of the workpiece member 7.(1) In the method for machining the workpiece member 7 according to the present embodiment, a light intensity from the workpiece member 7 taken by the light detection unit 17 after the pilot hole 981 is completed and penetrates the workpiece member 7 is lower than a light intensity before the pilot hole 981 is provided to penetrate the workpiece member 7. In this regard, after it is determined that the intensity of the light detected by the light detection unit 17 is less than or equal to the first threshold value, the spatial phase of the light of the laser beam oscillated by the laser oscillator 13 is modulated so that the outer peripheral area Rm 3 has a higher intensity than the central area Rm 4. Subsequently, the laser beam having the modulated spatial light phase is irradiated on the peripheral part 982 to form the expanded hole 983 communicating with the pilot hole 981. At this time, since the laser beam reaching an inside of the workpiece member 7 through the pilot hole 981 corresponds to a laser beam in the range that is outside the machining range Rm 21 and inside the laser irradiation range Rm 1, the workpiece member 7 is not damaged even when the inner wall surface of the workpiece member 7 is irradiated with such light. Consequently, the inner wall surface of the workpiece member 7 can be prevented from being damaged by the laser beam passing through the pilot hole 981 or the extended hole 983.(2) According to the method for machining the workpiece member 7 of the present embodiment, there is no need to provide a laser shielding member for preventing damage to the inner wall surface of the workpiece member 7 since the laser beam reaches the inside of the workpiece member 7, since the inner wall surface of the workpiece member 7 can be prevented from being damaged by the laser beam passing through the pilot hole 981. Consequently, the manufacturing cost of the nozzle body 93 can be reduced, and a number of steps necessary for inserting and removing a laser shielding member when the injection hole 98 is formed can also be reduced.(3) In the laser processing apparatus 1 according to the present embodiment, the optical element unit 15 is provided so that modulation of a focal point position can be performed by changing the spatial light phase of a laser beam. Consequently, when extended holes 983 are formed, positional displacement can be prevented as compared with a case where a rotator and a galvano scanner which needs to be driven are used to change the focal point position of the laser beam. Therefore, the injection hole 98 can be formed with a high degree of accuracy.(4) The laser processing apparatus 1 according to the present embodiment controls the intensity distribution of the laser beam based on the detection result provided by the light detection unit 17 when the corresponding pilot hole 981 and the extended hole 983 are provided through the workpiece member 7. Consequently, the intensity distribution of the laser beam can be changed immediately after the pilot hole 981 and the extended hole 983 are formed by the workpiece member 7, and therefore, the required power consumption for forming the injection hole 98 can be reduced. Consequently, the cost for manufacturing the nozzle body 93 can be reduced.(5) The light detection unit 17 is provided so that plasma light of fine particles generated from the workpiece member 7 via the laser beam processing can be captured. Consequently, a determination as to whether the pilot hole 981 and the extended hole 983 have been created to pass through the workpiece member 7 is easily made with plasma light as compared with a reflection light of the laser beam reflected by the outer wall surface of the workpiece member 7, and therefore can be changed according to the shape of the workpiece member 7. The pilot hole 981 and the expanded hole 983 can therefore be reliably provided by the workpiece member 7.(Second Embodiment)Next, a method of machining a workpiece member according to the second embodiment of the present disclosure will be described based on FIGS. 9A and 9B. The intensity distribution of the laser beam for forming an extended hole in the second embodiment is different from that in the first embodiment. Note that portions substantially identical to those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.The intensity distribution of the laser beam irradiated on the workpiece member 7 will be described based on FIG. 9A when the extended hole 983 is formed in the method for machining the workpiece member 7 according to the second embodiment. FIG. 9A is a diagram illustrating the intensity distribution of the laser beam irradiated onto the workpiece member 7 via the condenser lens 142, the intensity of the laser beam being distributed in the direction perpendicular to the propagation direction of the laser beam. In FIG. 9A, a horizontal axis represents the distance L from the center cL 0 of the laser beam. A vertical axis represents the intensity SoL of the laser beam.As illustrated in FIG. 9A, the spatial distribution of the laser beam forming the extended hole 983 in the present embodiment is modulated such that the central region Rm 4 has a smaller intensity than the outer peripheral region Rm 3. In the present embodiment, the laser beam is further modulated such that two machining areas Rm 21 are provided between the distance L 5 and the distance L 6 at outer edge areas Rm 3. Consequently, the two processing areas Rm 21 are arranged at positions shifted to the center of the laser irradiation area Rm 1.In the optical element unit 15, a voltage is applied to the electrodes 154, and the liquid crystal layer 152 is operated so that the laser beam oscillated by the laser oscillator 13 has the intensity distribution shown in FIG. 9A.A machining state of the workpiece member 7 is illustrated in FIG. 9B when the extended hole 983 is formed with the laser beam having the intensity distribution illustrated in FIG. 9A. FIG. 9B is a schematic diagram of the pilot hole 981 and the extended holes 983 viewed from the direction of laser beam emission. In FIG. 9B, a cross-sectional line of a laser beam having the intensity distribution shown in FIG. 9A is indicated as a line IXa-IXa.As shown in FIG. 9B, two widened holes 983 may be formed simultaneously in the peripheral part 982 when the laser beam having the intensity distribution shown in FIG. 9A is irradiated to the peripheral part 982 of the pilot hole 981. Consequently, the method of machining the workpiece member 7 according to the present embodiment can shorten a necessary time for forming the expanded holes 983. Therefore, the second embodiment can achieve the same effects as the first embodiment and further reduce the necessary number of steps for manufacturing the nozzle body 93.(Third Embodiment)Next, an element manufacturing apparatus and a method for manufacturing an element according to the third embodiment of the present disclosure will be described based on FIGS. 10, 11A, 11B, 12A, and 12B. The working effect of the optical element of the third embodiment is different from that of the first embodiment. Note that portions substantially identical to those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.The optical element unit 15 of the laser processing apparatus according to the third embodiment can modulate the spatial light phase of the laser beam directed from the optical element unit 15 toward the workpiece element 7 and change the spread angle of the laser beam by changing the arrangement direction of the liquid crystal molecules of the liquid crystal layer 152.Next, the method of machining the workpiece member 7 according to the present embodiment will be described based on FIGS. 10, 11A, 11B, 12A, and 12B. FIG. 10 is a flowchart illustrating the method for machining the workpiece member 7. FIGS. 11A and 12A are cross-sectional diagrams of an enlarged view of portions of the workpiece member 7 irradiated with the laser beam. FIGS. 11B and 12B are diagrams respectively viewed via an arrow XIb of FIG. 11A and an arrow XIIb of FIG. 12A.The method of machining the workpiece member 7 according to the present embodiment can be used to form the injection hole 98 in which the cross-sectional shape of the inner wall surface on a plane including the central axis C 981 of the pilot hole 981 is non-linear. For example, the injection hole 98 formed with the method for machining the workpiece member 7 according to the present embodiment has substantially a center of the injection hole 98 having a smaller cross-sectional area than an inner opening 984 of the injection hole 98 and an outer opening 985 of the injection hole 98. The cross-sectional area of the inner opening 984 may vary from or be equal to the cross-sectional area of the outer opening 985.First, at S 201, the workpiece member 7 is set in the member holding unit 11 in the same manner as at S 101 of the first embodiment. Subsequently, at S 202, as a "primary forming step", a laser beam forming the pilot hole 981 is radiated to a desired position on the workpiece member 7 in the same manner as at S 102 of the first embodiment. At S 203 following S 202, in the same manner as at S 103 of the first embodiment, it is determined whether the intensity of light from the workpiece member 7 is less than or equal to the first threshold value.If it is determined at S 203 that the intensity of the light from the workpiece 7 received by the light detection unit 17 is less than or equal to the first threshold value, the optical element unit 15 changes the propagation angle of the laser beam at S 204 as a "laser modulation step.".Subsequently, at S 205, as a "secondary forming step", a laser beam is irradiated to the pilot hole 981 or an inner wall surface 986 of a currently machined injection hole 98 having a partially machined pilot hole 981. Specifically, at S 205, the laser beam is incident on the pilot hole 981, with the center cL 0 of the laser beam being inclined with respect to the center axis C 981 of the pilot hole 981.Here, a process of changing the spread angle of the laser beam at S 204 will be described based on FIGS. 11A, 11B, 12A, and 12B together with a process of irradiating the inner wall surface 986 with the laser beam at S 205. FIGS. 11A and 11B are diagrams illustrating a state in which the workpiece member 7 is processed using a laser beam having a relatively small spread angle, and FIGS. 12A and 12B are diagrams illustrating how the workpiece member 7 is processed using a laser beam having a relatively small spread angle. Note that the method for machining the workpiece member 7 according to the present embodiment uses a laser beam having a relatively high energy in which reflection with respect to the irradiation-exposed inner wall surface 986 predominates over absorption. As illustrated in FIGS. 11A, 11B, 12A, and 12B, the inner wall surface 986 is not parallel to the central axis C 991.As illustrated in FIG. 11A, a laser beam incident on the pilot hole 981 or the currently machined injection hole 98 is reflected by the inner wall surface 986 and guided into the workpiece member 7. In the present embodiment, the reflected laser beam is compressed at a peripheral part 987 of the inner opening 984 as a "predetermined portion of the member", and the workpiece member 7 is machined so that the inner opening 984 has a desired shape. At this point, the laser beam reflected by the inner wall surface 986 has a relatively large beam diameter L 31 in the vicinity of the circumferential part 987 of the inner opening 984, as illustrated in FIG. 11A, if the spread angle SA 31 of the laser beam is relatively small. Consequently, a large amount of processing is necessary for the peripheral part 987 per unit time. Moreover, for example, the relatively large inner diameter portion R 31 is formed as illustrated in a region A 31 of FIG. 11B.In contrast, in a case where the spread angle SA 32 of the laser beam incident at the pilot hole 981 or at the currently machined injection hole 98 is larger than the spread angle SA 31, as illustrated in FIG. 12A, the laser beam reflected by the inner wall surface 986 has a beam diameter L 32 smaller than the beam diameter L 31 in the vicinity of the circumferential part 987 of the inner opening 184. Consequently, an amount of time per unit time required for processing the peripheral part 987 is reduced. Moreover, for example, the portion having an inner diameter R 32 smaller than the inner diameter R 31 is formed as illustrated in a region A 32 of FIG. 12B, for example.Note that, in the present embodiment, the area of the reflection surface on the inner wall surface 986 at which the laser beam having the spread angle SA 31 is reflected and the area of the reflection surface on the inner wall surface 986 at which the laser beam having the spread angle SA 32 is reflected correspond to the same size. Since the laser beam has a constant energy regardless of its spread angle, a fixed energy per unit area of the laser beam is irradiated to the reflecting surface on the inner wall surface 986.At S 206 following S 205, in the same manner as at S 106 of the first embodiment, it is determined whether the intensity of light is less than or equal to the second threshold value. If it is determined at S 206 that the intensity of the light from the workpiece member 7 received by the light detection unit 17 is less than or equal to the second threshold value, the control unit 19 determines at S 207 whether the laser beam has been irradiated to a predetermined position of the circumferential part 987 of the inner opening 984.According to the method for machining the workpiece member 7 of the present embodiment, the injection hole 98 is machined on the workpiece member 7 in this manner, and the nozzle body 93 is manufactured.According to the method for machining the workpiece member 7 of the present embodiment, the inner opening 984 is formed by irradiating the circumferential part 987 of the inner opening 984 using the laser beam reflected by the inner wall surface 986. At this time, the machining amount per unit time at the circumferential part 987 of the inner opening 984 is changed by changing the propagation angle of the laser beam incident at the pilot hole 981 or the injection hole 98 currently machined. Consequently, only a laser beam that is required for forming the inner opening 984 is incident on the pilot hole 981 or the currently machined injection hole 98, whereby it is difficult for the laser beam that has not been used for machining to be irradiated on the inner wall surface of the workpiece member 7. Damage to the inner wall surface of the workpiece member 7 can also be prevented. The third embodiment can therefore achieve the effects (1), (2), (4) and (5) of the first embodiment.Since the machining amount per unit time can be changed in the present embodiment, the inner opening 984 having a desired shape as illustrated in FIGS. 11B and 12B can be provided without being influenced by the shape of the outer opening 985. In this way, the present embodiment can increase areas that can be machined, particularly on an inner side of the outer opening 985. Consequently, the flexibility of the shape of the injection hole 98 can be improved.(Fourth Embodiment)Next, a laser processing apparatus according to the fourth embodiment of the present disclosure will be described based on FIG. 13. The configuration of the optical element unit of the fourth embodiment is different from that of the first embodiment. Note that portions substantially identical to those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.The schematic diagram of the laser processing apparatus 2 according to the present embodiment is illustrated in FIG. 13. The laser processing apparatus 2 includes the element holding unit 11, the laser oscillator 13, an optical element unit 25, the light detecting unit 17, the control unit 19, and the like. Note that, in FIG. 13, the pattern of the laser beam in the laser processing apparatus 2 is indicated with a dotted line L 0 representing the outer edge of the laser beam. The course of the light from the workpiece element 7 is indicated by a dotted line L 7.The optical element unit 25 includes the front glass substrate 151, a plurality of diffraction lenses 252, the rear reflective plate 153, and a drive unit 254 electrically connected to the control unit 19, and the like. In the optical element unit 25, when a beam collimated by the rear reflecting plate 153 passes through the plurality of diffraction lenses 252, the diffraction lenses 252 are rotated by the driving unit 254. Consequently, the light diffraction pattern of the laser beam directed from the optical element unit 25 toward the workpiece member 7 can be changed. The laser beam directed from the optical element unit 25 toward the workpiece element 7 is irradiated to a desired position on the workpiece element 7 via the condenser lens 142.The laser processing apparatus 2 can modulate the spatial light phase of the laser beam with the plurality of diffraction lenses 252 used in combination with each other. Thus, the fourth embodiment achieves the same effects as the first embodiment.(Fifth Embodiment)Next, a laser processing apparatus according to a fifth embodiment of the present disclosure will be described based on FIG. 14. The number of light detecting units of the fifth embodiment is different from that of the first embodiment. Note that portions substantially identical to those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.The schematic diagram of the laser processing apparatus 3 according to the present embodiment is illustrated in FIG. 14. The laser processing apparatus 3 includes the element holding unit 11, the laser oscillator 13, the optical element unit 15, a plurality of light detection units 17, the control unit 19, and the like. Note that, in FIG. 14, the pattern of the laser beam in the laser processing apparatus 3 is indicated with a dotted line L 0 representing the outer periphery of the laser beam. The course of the light from the workpiece element 7 is indicated by a dotted line L 7.In the laser processing apparatus 3, as illustrated in FIG. 14, the plurality of light detection units 17 are arranged at different angles relative to the workpiece member 7. Thus, according to the method for machining the workpiece member 7 of the present embodiment, an overall determination based on changes in the laser reflection light as to whether the pilot hole 981 and the extended hole 983 have been created to pass through the workpiece member 7 can be detected by the plurality of light detection units 17. Therefore, the fifth embodiment can achieve the same effects as the first embodiment and can form the injection hole 98 with a high degree of accuracy.(Sixth Embodiment)Next, a laser processing apparatus according to the sixth embodiment of the present disclosure will be described based on FIGS. 15, 16, and 17. The sixth embodiment includes a laser shielding member, which is different from the first embodiment. Note that portions substantially identical to those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.The schematic diagram of the laser processing apparatus 4 according to the present embodiment is illustrated in FIG. 15. The laser processing apparatus 4 includes the element holding unit 11, a laser shielding member 12, the laser oscillator 13, the optical element unit 15, the laser detection unit 17, the control unit 19, and the like. Note that, in FIG. 15, the pattern of the laser beam in the laser processing apparatus 4 is indicated with a dotted line L 0 representing the outer periphery of the laser beam. The course of the light from the workpiece element 7 is indicated by a dotted line L 7.The laser shielding member 12 is supported by a support unit 121 and is configured such that the laser shielding member can be inserted into the workpiece member 7. The support unit 121 can rotate the laser shielding member 12 inside the workpiece member 7.Next, a method of machining the workpiece member 7 according to the present embodiment will be described based on FIG. 16. FIG. 16 is a flowchart illustrating the method for machining the workpiece member 7.First, at S 301, the workpiece member 7 is installed in the member holding unit 11 in the same manner as at S 101 of the first embodiment. Following S 301, the laser shielding member 12 is inserted into the workpiece member 7 as a "member installation step" at S 302. At this time, an outer wall surface 122 of the laser shielding member 12 is provided at a position where the laser beam having passed through the completed pilot hole 981 or the extended hole 983 is irradiated, as shown in an enlarged cross-sectional image of the workpiece member 7 illustrated in FIG. 17.Subsequently, at S 303, in the same manner as at S 102 of the first embodiment, as a "primary forming step", the laser beam forming the pilot hole 981 is irradiated to a desired position on the workpiece member 7.At S 304 following S 303, in the same manner as at S 103 of the first embodiment, it is determined whether the intensity of light from the workpiece member 7 is less than or equal to the first threshold value.If it is determined at S 304 that the intensity of light from the workpiece member 7 picked up by the light detection unit 17 is less than or equal to the first threshold value, the intensity distribution of the laser beam is changed at S 305 in the same manner as at S 104 of the first embodiment as the "laser modulation step".After it is determined that the intensity of light from the workpiece member 7 is less than or equal to the first threshold value, as illustrated in FIG. 17, the laser beam is irradiated to the outer wall surface 122 of the laser shielding member 12 through the completed pilot hole 981 until the intensity distribution of the laser beam is changed. Consequently, the laser beam is not irradiated on an inner wall surface 71 of the workpiece member 7 facing an outer wall surface 123 opposite to the outer wall surface 122 of the laser shielding member 12.Subsequently, at S 306, in the same manner as at S 105 of the first embodiment, as the "secondary forming step", the laser beam forming the expanded hole 983 is irradiated to the circumferential part 982 forming the pilot hole 981. At S 307 following S 306, in the same manner as at S 106 of the first embodiment, it is determined whether the intensity of light is less than or equal to the second threshold value. If it is determined at S 307 that the intensity of the light from the workpiece member 7 received by the light detection unit 17 is less than or equal to the second threshold value, the control unit 19 determines at S 308 whether the laser beam has been irradiated to the entire peripheral part 982 in the same manner as at S 107 of the first embodiment.According to the method for machining the workpiece member 7 of the present embodiment, the injection hole 98 is formed in the workpiece member 7 in this manner, and the nozzle body 93 is manufactured.The laser processing apparatus 4 includes the laser shielding member 12 irradiated with the laser beam passing through the pilot open hole 981 or the extended hole 983. Consequently, reliable inhibition of irradiation on the inner wall surface 71 of the workpiece member 7 by the laser beam that has entered the workpiece member 7 can be achieved immediately after the pilot hole 981 is provided by the workpiece member 7 or immediately after the widened hole 983 is provided by the workpiece member 7. Therefore, the sixth embodiment can achieve the effects (1) and (3) to (5) of the first embodiment and can reliably prevent damage to the inner wall surface of the workpiece member 7.(Seventh Embodiment)Next, the method for machining a workpiece member according to the seventh embodiment of the present disclosure will be described based on FIGS. 18, 19, and 20. The method for machining a workpiece member according to the seventh embodiment is different from that of the first embodiment. Note that portions substantially identical to those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.The schematic diagram of a laser processing apparatus 5 according to the present embodiment is illustrated in FIG. 18. The laser processing apparatus 5 includes an element holding unit 31, the laser oscillator 13, an optical element unit 35, the light detecting unit 17, the control unit 19, and the like. The laser processing apparatus 5 may form a plurality of through holes 88 in a workpiece member 8 having a substantially disk-shaped shape. Note that, in FIG. 18, the pattern of the laser beam in the laser processing apparatus 5 is indicated with a dotted line L 0 representing the outer periphery of the laser beam. The course of the light from the workpiece element 8 is indicated by a dotted line L 8.The element holding unit 31 can hold the workpiece element 8 so that the workpiece element 8 cannot move relative to the optical element unit 35. The optical element unit 35 corresponds to a so-called liquid crystal reflective panel, and includes the front glass substrate 151, a liquid crystal layer 36, the rear reflective plate 153, a plurality of electrodes 371, 372, 373, and 374, and the like. The liquid crystal layer 36 includes a plurality of liquid crystal molecules 361, 362, 363, and 364 (refer to FIGS. 19 and 20 ). In the optical element unit 35, the arrangement directions of the liquid crystal molecules 361, 362, 363, and 364 are individually changed by voltages applied to the electrodes 371, 372, 373, and 374 corresponding to the liquid crystal molecules 361, 362, 363, and 364, respectively.The method for machining the workpiece member 8 according to the present embodiment will be described based on FIGS. 19 and 20. According to the method for processing the workpiece member 8 of the present embodiment, the spatial light phase of the laser beam irradiated on the workpiece member 8 is modulated by controlling the arrangement directions of the liquid crystal molecules 361, 362, 363, and 364, and the focal point position of the laser beam is changed.For example, as illustrated in FIG. 19, a part of the laser beam reflected by the rear reflecting plate 153 is blocked by the liquid crystal molecules 361. Consequently, since the laser beam is focused through the condenser lens 142 on a part of the outer edge of the workpiece member 8 that is away from a base 311 of the member holding unit 31, the laser beam forms a through hole 881 as one of the through holes 88 at this part of the outer edge away from the base 311. The through hole 881 is formed by forming a pilot hole first and then an expanded hole at the pilot hole forming peripheral part as described in the first embodiment.After the through hole 881 is formed, as illustrated in FIG. 20, a part of the laser beam reflected by the rear reflecting plate 153 is blocked by the liquid crystal molecules 364. Consequently, since the laser beam is focused through the condenser lens 142 on a part of the outer edge of the workpiece member 8 close to the base 311, the laser beam forms a through hole 882 as one of the through holes 88 at this part of the outer edge close to the base 311. The through hole 882 is formed by forming a pilot hole and forming an expanded hole in the pilot hole forming peripheral part as in the first embodiment.When the through holes 88 are formed, the laser processing apparatus 5 forms expanded holes using a laser beam having an intensity of the processing area in the outer peripheral area. Consequently, damage to the element holding unit 31 supporting the workpiece element 8 by the laser beam having passed through the pilot holes and widened holes can be prevented.Conventionally, in a case where a plurality of through holes are formed using the laser beam in a single workpiece member, the workpiece member needs to be precisely positioned (aligned) with respect to the focal point position of the laser beam. This creates a need for an element holding unit to precisely position the workpiece element, and thus results in an increase in the number of steps for positioning.The laser processing apparatus 5 can change the arrangement of a plurality of liquid crystal molecules of the optical element unit 35 to change the focal point position of the laser beam. Consequently, the plurality of through holes 88 can be formed in a single fixed workpiece member 8. The need for an element holding unit to position a workpiece element with respect to the focal position of the laser beam is eliminated, and the cost of equipment for machining the workpiece element 8 can therefore be reduced.The laser processing apparatus 5 electrically controls arrangement directions of a plurality of liquid crystal molecules of the optical element unit 15 to change the focal point position of the laser beam. Consequently, the through holes 88 can be formed in a relatively short time as compared with when precise positioning is performed by an element holding unit. Therefore, the number of steps required for manufacturing an element having through holes can be reduced.(Other Embodiments)In the above-mentioned embodiments, the "member" corresponds to the nozzle body of a fuel injection valve. However, the "element" is not limited to this example. The "element" need only have a "through hole".In the above-mentioned embodiments, the processing area of the laser beam is located in the outer edge area when an expanded hole is formed. However, the machining area is not necessarily disposed in this area. That is, the processing region may be disposed in any region as long as the laser beam in the processing region does not reach the side opposite to the side of the workpiece member irradiated by the laser beam through a completed pilot hole.In the above-mentioned embodiments, the light detecting unit can receive reflection light and plasma light. However, the light detection unit may be capable of receiving reflection light and / or plasma light. The light detecting unit may receive any light as long as the intensity thereof is changed when a pilot hole or an extended hole is provided by a workpiece member.In the above-mentioned embodiments, the optical element unit comprises a liquid crystal layer or diffraction lenses. However, the configuration of the optical element unit is not limited to this example. The optical element unit may have any configuration as long as the spatial light phase of the laser beam can be modulated via the optical element unit.In the first to sixth embodiments, a plurality of injection holes may be formed by changing the focal point position of the laser beam as in the seventh embodiment.In the second embodiment, the laser beam has two machining regions at the outer edge regions. However, the number of machining areas is not limited to this example. The number of machining areas may be three or more.In the third embodiment, the propagation angle of the laser beam is changed by modulating the spatial light phase of the laser beam in the optical element unit. However, the method of changing the propagation angle of the laser beam is not limited to this example. That is, changing the position of the condenser lens relative to a workpiece member may change the propagation angle of the laser beam. In the third embodiment, the intensity distribution of the laser beam can be varied as in the first and second embodiments.In the third embodiment, the laser beam desirably has a relatively high energy. However, the energy of the laser beam is not limited to this example. That is, the laser beam may have a relatively low energy.In the third embodiment, the beam diameter in the vicinity of the circumferential part of the inner opening is relatively large when the spread angle of the laser beam is small, and the beam diameter in the vicinity of the circumferential part of the inner opening is relatively small when the spread angle of the laser beam is large. The relationship between spread angles and beam diameters in the vicinity of the circumferential part of the inner opening is not limited to this example. That is, the beam diameter in the vicinity of the circumferential part of the inner opening may also be relatively small when the spread angle of the laser beam is small, and the beam diameter in the vicinity of the circumferential part of the inner opening may be relatively large when the spread angle of the laser beam is large, with respect to the angle between the inner wall surface of an injection hole and the center of the laser beam.Although the description of the third embodiment relates only to the machining of the circumferential part of the inner opening, the inner wall surface of an injection hole may be machined while changing the machining amount per unit time by changing the spread angle of the laser beam.In the third embodiment, the circumferential part of the inner opening is machined using the laser beam reflected by the inner wall surface of the injection hole which is not parallel to the central axis of the pilot hole. However, the inner wall surface of the injection hole reflecting the laser beam may be parallel to the central axis of the pilot hole.In the third embodiment, the area of the reflecting surface on the inner wall surface of the injection hole where the laser beam is reflected at a certain propagating angle and the area of the reflecting surface on the inner wall surface of the injection hole where the laser beam is reflected at a different propagating angle correspond to the same size. However, the areas of the reflecting surfaces may deviate from each other.In the third and fourth embodiments, as in the fifth embodiment, a plurality of light detecting units may be provided, and as in the sixth embodiment, a laser shielding member may be provided.In the fifth embodiment, like the sixth embodiment, a laser shielding member may be provided.In the seventh embodiment, as in the sixth embodiment, a laser shielding member may be provided between a workpiece member and the member holding unit.The present disclosure is not limited to the above-mentioned embodiments, and may be implemented in various forms without departing from the spirit of the disclosure.The present disclosure has been described with reference to Examples. However, the present disclosure is not limited to the embodiments and structures. The present disclosure covers various modifications and equivalent variations. In addition to various combinations and forms, other combinations and forms having one or more / fewer elements thereof are also within the spirit and scope of the present disclosure.

Claims

A method for manufacturing an element (93) having a through hole (88, 98), the method comprising: a primary forming step of radiating a laser beam onto a workpiece element (7, 8) to form, on the workpiece element (7, 8), a pilot hole (981) having a smaller inner diameter than the through hole (88, 98) while receiving light from the workpiece element (7, 8) by a light detecting unit (17); an intensity determining step of determining whether an intensity of the light detected by the light detecting unit (17) is less than or equal to a predetermined threshold; a laser modulating step of modulating a spatial phase of light of the laser beam radiated onto the workpiece element (7, 8) in response to determining that the intensity of the light detected by the light detecting unit is less than or equal to the predetermined threshold; and a secondary forming step of radiating the laser beam having the modulated spatial light phase onto a peripheral part of the pilot hole (981) to form the through hole (88, 98).The method for manufacturing an element according to claim 1, wherein in the laser modulating step, the spatial light phase of the laser beam is modulated such that an outer edge region (Rm3) in a beam diameter of the laser beam has a higher intensity than a central region (Rm4) in the beam diameter of the laser beam.The method for manufacturing an element according to claim 2, wherein in the laser modulating step, the spatial light phase of the laser beam is modulated such that a plurality of the outer peripheral regions (Rm3) having the higher intensity than the central region (Rm4) are formed in the beam diameter of the laser beam.The method for manufacturing an element according to any one of claims 1 to 3, wherein in the laser modulating step, the spatial light phase of the laser beam is modulated so as to change a propagation angle of the laser beam, and wherein in the secondary forming step, a predetermined portion (987) of the workpiece element (7, 8) is machined with the laser beam reflected by an inner wall surface (986) of the through hole (88, 98).The method for manufacturing an element according to any one of claims 1 to 4, wherein in the primary forming step, the light detecting unit (17) receives a reflection light of the laser beam reflected by the workpiece element (7, 8) and / or a plasma light generated by a reaction between the laser light and the workpiece element (7, 8).The method for manufacturing an element according to any one of claims 1 to 5, wherein in the laser modulating step, the spatial light phase of the laser beam is modulated so as to change an irradiation position on the workpiece element (7, 8).The method for manufacturing a member according to any one of claims 1 to 6, further comprising: a member installation step before the primary forming step, wherein the member installation step provides a laser shielding member (12) on a side of the workpiece member (7, 8) opposite to a side on which the laser beam is irradiated.The method for manufacturing an element according to any one of claims 1 to 7, wherein a nozzle body having an injection hole is provided, which is manufactured as the element (93) having the through hole (88, 98).An apparatus (1, 2, 3, 4, 5) for manufacturing an element (93) having a through hole (88, 98), the apparatus comprising: a laser oscillator (13) that oscillates a laser beam capable of forming the through hole (88, 98) in a workpiece element (7, 8); an optical element unit (15, 25, 35) capable of modulating a spatial light phase of the laser beam emitted by the laser oscillator (13); a light detection unit (17) in which light can be received by the workpiece element (7, 8), wherein the light detection unit (17) can output an electrical signal according to an intensity of the received light; and a control unit (19) electrically connected to the laser oscillator (13), the optical element unit (15, 25, 35), and the light detection unit (17), wherein the control unit (19) is provided, to control the laser oscillator (13) and the optical element unit (15, 25, 35) according to the electric signal output by the light detection unit (17), wherein the control unit (19) is further configured to control the laser oscillator (13) to irradiate the laser beam to the workpiece element (7, 8) to form, at the workpiece element (7, 8), a pilot hole (981) having a smaller inner diameter than the through hole (88, 98) that receives the electric signal from the light detection unit (17), determines whether the intensity of the detected light is less than or equal to a predetermined threshold, controls the optical element unit (15, 25, 35) to modulate the spatial phase of light of the laser beam irradiated to the workpiece element (7, 8) in response to determining that the intensity of the detected light is less than or equal to the predetermined threshold, and drives the laser oscillator (13) to emit the laser beam having the modulated spatial light phase to an edge part of the pilot hole (981) to form the through hole (88, 98).The device for manufacturing an element according to claim 9, wherein the optical element unit (15, 25, 35) can change a light diffraction pattern of the laser beam.The device for manufacturing an element according to claim 9 or 10, wherein the optical element unit (15, 25, 35) can change a propagation angle of the laser beam.The device for manufacturing an element according to any one of claims 9 to 11, wherein the optical element unit (15, 25, 35) corresponds to a reflective liquid crystal panel.The device for manufacturing an element according to any one of claims 9 to 11, wherein the optical element unit (15, 25, 35) has a plurality of diffraction lenses (252).The device for manufacturing an element according to any one of claims 9 to 13, wherein the optical element unit (15, 25, 35) is capable of modulating the spatial light phase of the laser beam so that an outer edge region (Rm3) that is within a beam diameter of the laser beam has a higher intensity than a central region (Rm4) that is within the beam diameter of the laser beam.The device for manufacturing an element according to any one of claims 9 to 14, wherein a plurality of light detecting units (17) are provided.The device for manufacturing a member according to any one of claims 9 to 15, further comprising: a laser shielding member (12) provided on a side opposite to a side on which the laser beam of the workpiece member (7, 8) is irradiated, wherein the laser shielding member (12) is configured to shield the side of the workpiece member (7, 8) opposite to the side on which the laser beam is irradiated.

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