JP2015000415A - Welding member, fuel injection valve and laser welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a welding member reduced in welding deformation, a fuel injection valve with the welding member, and a laser welding method.SOLUTION: A welding member includes: a first welding target material 1 having a recess 13; a second welding target material 2; and a weld bead 3 which is formed by deep penetration laser welding by irradiating with laser beam 5 from the first welding target material 1 side by superposing the first welding target material 1 and the second welding target material 2. When a surface width of the weld bead 3 is W1, a weld penetration width to be a width of the weld bead 3 in a boundary surface 4 of the first welding target material 1 and the second welding target material 2 is W2, and board thickness of the first welding target material 1 is t, a ratio W1/t of the surface width W1 to the board thickness t is equal or less than a first threshold value, and a ratio (W1-W2)/t of a difference between the surface width W1 and the weld penetration width W2 to the board thickness t is equal or less than a second threshold value.

Description

  The present invention relates to a welding member obtained by laser welding a plurality of workpieces, a fuel injection valve including the welding member, and a laser welding method.

  Laser welding is used in various directions because the energy density of the laser beam as a heat source is high, and a weld joint with low distortion, high speed, and high accuracy can be obtained. In the automotive field, a plurality of materials to be welded are overlapped and welded to a steel material such as stainless steel or carbon steel, or a metal material such as an aluminum alloy or a nickel alloy.

  For example, an injection nozzle (welding member) of a fuel injection valve is manufactured by welding a nozzle plate (material to be welded) having fuel injection holes and a nozzle body (material to be welded) that provides a fuel path. Laser welding is used for welding the nozzle plate and the nozzle body because low distortion and high accuracy are required, and it is desirable that the welding speed be high.

  In Patent Document 1, the oxygen gas content of the assist gas is adjusted to 5 to 50% by volume, and the surface width of the weld bead and the width (penetration width) of the joint portion (boundary surface) of a plurality of members (materials to be welded). It is disclosed that the ratio of) is close to 1.

JP-A-10-85974

  By the way, there are two types of laser welding methods: heat conduction type laser welding and deep penetration type (keyhole mode) laser welding. Incidentally, the laser welding method disclosed in Patent Document 1 is heat conduction type laser welding.

  In thermal conduction type laser welding, the surface of the workpiece is irradiated with laser light, the irradiated laser light is absorbed by the workpiece, and the laser light is converted into heat so that heat energy is transferred to the inside of the material. Then, the material to be welded is welded by melting the material to be welded. This welding method is a type of welding in which the surface width of the weld bead is wider than the penetration depth of the weld bead, and a weld bead having a shallow penetration depth and a wide surface width is easily formed. For this reason, heat conduction type laser welding cannot be applied when welding with a deep penetration depth, a narrow surface width, and small welding deformation is required.

On the other hand, in deep penetration type (keyhole mode) laser welding, when the power density (laser output per unit area) of the laser beam irradiated onto the surface of the workpiece is 10 ⁶ W / cm ² or more, the metal material The temperature of the metal surface of the welded material consisting of becomes higher than the boiling point of the metal, and with the generation of plasma, the metal vapor jumps out of the laser beam irradiation point, and the molten metal surface is dented by the reaction force of the metal vapor. In this method, the laser beam is incident while repeating reflection in a recess (keyhole) to form a deep and thin keyhole, thereby welding the material to be welded. This welding method can make the penetration depth of the weld bead deeper than that of the heat conduction type laser welding. Moreover, this welding method can make the penetration depth of a weld bead several times the surface width of a weld bead.

  Here, the cross-sectional shape of the weld bead 3 of the conventional deep penetration type | mold (keyhole mode) laser welding is demonstrated using FIG. FIG. 10 is a sectional view of a conventional bead 3 of deep penetration type (keyhole mode) laser welding. Although FIG. 10 shows a cross-sectional view, hatching is not shown for convenience of explanation. Here, a material to be welded (nozzle plate) 1 and a material to be welded (nozzle body) 2 are welded by deep penetration type (keyhole mode) laser welding to form a weld bead 3. W1 is the surface width of the weld bead 3, W2 is the width (penetration width) of the weld bead 3 at the boundary surface 4 between the welded material 1 and the welded material 2, and H is the melt width of the weld bead 3. It is a penetration depth, D is a penetration depth from the boundary surface 4, and t is a plate thickness of the workpiece 1.

  As shown in FIG. 10, in the conventional deep penetration type (keyhole mode) laser welding, the cross section of the wine cup-shaped weld bead 3 in which the surface width W1 of the weld bead 3 is larger than the penetration width W2 of the weld bead 3. Easy to form. This has the effect of spreading the molten pool surface by transferring heat from the high-temperature metal vapor (plasma) ejected from the keyhole to the metal surface of the workpiece 1 during deep penetration (keyhole mode) laser welding. Because. Moreover, it is because the molten metal flow turns outward by pushing the molten pool around the keyhole outward from the keyhole by jetting metal vapor. By these two actions, the cross-sectional shape of the weld bead 3 becomes a wine cup-shaped cross-sectional shape having a wide surface width W1 and a narrow penetration width W2.

  The weld bead 3 having such a wine cup-like cross-sectional shape has an area melted in the vicinity of the surface of the material to be welded (nozzle plate) 1 during laser welding, and the material to be welded (nozzle plate) 1 and the material to be welded. (Nozzle body) 2 greatly exceeds the area melted in the vicinity of the boundary surface 4 of the nozzle 2. For this reason, the amount of shrinkage between the vicinity of the surface of the material to be welded (nozzle plate) 1 and the vicinity of the boundary surface 4 between the material to be welded (nozzle plate) 1 and the material to be welded (nozzle body) 2 is greatly different. Deformation may occur.

  Then, this invention makes it a subject to provide the welding member which reduced welding deformation, a fuel injection valve provided with this welding member, and a laser welding method.

  In order to solve such a problem, a welding member according to the present invention includes a first welded material provided with a recess, a second welded material, the first welded material, and the second welded material. And a weld bead formed by deep penetration type laser welding by irradiating a laser beam from the side of the first workpiece to be welded, and the weld bead has a surface width of the weld bead. W1 is the penetration width that is the width of the weld bead at the boundary surface between the first welded material and the second welded material, W2, and the plate thickness of the first welded material is t. W1 / t, which is the ratio between W1 and the plate thickness t, is equal to or less than the first threshold, and is the difference between the surface width W1 and the penetration width W2 and the plate thickness t (W1- W2) / t is less than or equal to the second threshold value.

  The fuel injection valve according to the present invention includes a nozzle plate provided with a swirl chamber for swirling fuel, a nozzle body, the nozzle plate and the nozzle body, and a laser beam from the nozzle plate side. And a weld bead formed by deep penetration laser welding, wherein the weld bead has a surface width of the weld bead as W1, and the weld bead at the boundary surface between the nozzle plate and the nozzle body. The penetration width which is the width of the nozzle plate is W2, the plate thickness of the nozzle plate is t, W1 / t which is the ratio of the surface width W1 and the plate thickness t is not more than a first threshold value, and the surface The difference between the width W1 and the penetration width W2 and the ratio of the plate thickness t (W1-W2) / t is equal to or less than a second threshold value.

  Further, the laser welding method according to the present invention includes a first welded material provided with a recess and a second welded material overlapped, and a laser beam is irradiated from the side of the first welded material to perform deep melting. A weld bead is formed by embedded laser welding, and the weld bead is a width of the weld bead at a boundary surface between the first welded material and the second welded material, where W1 is a surface width of the weld bead. The penetration width is W2, the plate thickness of the first material to be welded is t, and the ratio of the surface width W1 and the plate thickness t is W1 / t, which is equal to or less than a first threshold value. The difference between W1 and the penetration width W2 and the ratio of the plate thickness t (W1-W2) / t is not more than a second threshold value.

  ADVANTAGE OF THE INVENTION According to this invention, the welding member which reduced welding deformation, a fuel injection valve provided with this welding member, and a laser welding method can be provided.

(A) is a longitudinal cross-sectional view of the welding member which concerns on this embodiment, (b) is the top view seen from the front end side of the welding member which concerns on this embodiment. It is sectional drawing explaining the structure of the lap weld joint of the welding member which concerns on this embodiment. It is sectional drawing which shows the outline | summary of deep penetration type laser welding. It is a graph which shows the relationship between the temperature of the molten pool 3a, and surface tension. It is sectional drawing explaining the shape of the weld bead of the welding member which concerns on this embodiment. It is sectional drawing explaining the shape of the weld bead of the welding member which concerns on the comparative example 1. FIG. It is sectional drawing explaining the shape of the weld bead of the welding member which concerns on the comparative example 2. FIG. It is a graph which shows the relationship between the deformation | transformation amount by welding deformation, and the ratio of the surface width of a weld bead, and the plate | board thickness of a nozzle plate. It is a graph which shows the relationship between the deformation amount by welding deformation, and the welding bead width change rate. It is sectional drawing of the welding bead of the conventional deep penetration type laser welding. It is sectional drawing explaining the structure of the lap weld joint of the welding member using the conventional deep penetration type laser welding.

  Hereinafter, modes for carrying out the present invention (hereinafter referred to as “embodiments”) will be described in detail with reference to the drawings as appropriate. In each figure, common portions are denoted by the same reference numerals, and redundant description is omitted.

≪Injection nozzle (welding member) F of fuel injection valve≫
The welding member F which concerns on this embodiment is demonstrated using FIG. In addition, the welding member F which concerns on this embodiment is the injection nozzle F of the fuel injection valve (it is also called an injector) used for the internal combustion engine of a motor vehicle, for example. Hereinafter, the welding member F which concerns on this embodiment is demonstrated as what is the injection nozzle F of a fuel injection valve. Fig.1 (a) is a longitudinal cross-sectional view of the welding member F which concerns on this embodiment, FIG.1 (b) is the top view seen from the front end side of the welding member F which concerns on this embodiment. 1A is a longitudinal sectional view taken along line AA in FIG. 1B, and FIG. 1B is a plan view of the welding member F viewed in the direction of arrow B in FIG. 1A. FIG.

  As shown in FIG. 1 (a), an injection nozzle (welding member) F of a fuel injection valve includes a nozzle plate (welded material) 1 and a nozzle body (welded material) 2 which are deep-penetrating (keyholes). Mode) A welding member in which a weld bead 3 is formed by laser welding and joined by a lap joint (lap weld joint). In FIG. 1, only the injection nozzle F at the tip of the fuel injection valve is shown, and other components of the fuel injection valve, such as a needle (valve element), a plunger, a solenoid, etc., are well-known in the art. Description is omitted as it is configured.

<Nozzle plate 1, nozzle body 2>
The nozzle plate 1 is a thin plate material made of a steel material such as austenitic stainless steel in a disc shape and having a plate thickness t of, for example, 0.35 mm. The nozzle body 2 is formed in a substantially cylindrical shape with a steel material such as martensitic stainless steel.

  As shown in FIG. 1 (a), a nozzle body 2 formed in a substantially cylindrical shape has a valve seat 21 with which a needle (valve element) abuts a communication path inside the nozzle body, and a nozzle to be described later in the center of the tip. A communication hole 22 communicating with the central chamber 11 of the plate 1 is formed.

  As shown in FIG. 1A, a concave portion is provided on the back surface of the nozzle plate 1 (the surface in contact with the nozzle body 2), and the central chamber is formed by joining the nozzle plate 1 and the nozzle body 2 together. 11, a communication passage 12 (see FIG. 1B), and a swirl chamber (swirl chamber) 13 are formed. In addition, an injection hole 14 that communicates from the swirl chamber 13 to the surface of the nozzle plate 1 (the surface opposite to the side in contact with the nozzle body 2) is formed. The central chamber 11 is formed at a position corresponding to the communication hole 22 of the nozzle body 2. As shown in FIG. 1B, the communication path 12 extends from the central chamber 11 in the radial direction of the nozzle plate 1 and is formed to communicate with the swirl chamber 13. Four swirl chambers 13 are formed, and an injection hole 14 for injecting fuel is formed at the center of each swirl chamber 13.

  The fuel injected from the injection nozzle (welding member) F flows from the communication hole 22 of the nozzle body 2 to the central chamber 11 of the nozzle plate 1 and then flows to the swirl chamber 13 via the four communication paths 12. The fuel that has flowed into the swirl chamber 13 from the communication path 12 swirls inside the swirl chamber 13 and is injected from the injection hole 14 at the center of the swirl chamber 13. In FIG. 1A, fuel is injected from the injection hole 14 above the plane of the drawing.

  In FIG. 1, the injection nozzle (welding member) F has been described as having four injection holes 14 formed in the nozzle plate 1. However, the present invention is not limited to this, and the number of injection nozzles F may be three or less. It may be 5 or more. In addition, although it has been described that one injection hole 14 is formed for one swirl chamber 13, the present invention is not limited to this, and two or more injection holes 14 are provided for one swirl chamber 13. It may be formed. Further, the injection hole 14 may be formed in the central chamber 11. Moreover, the shape of the injection hole 14 is not limited to a circle, and can be appropriately changed to an ellipse, a polygon, a long hole, an arc, or the like. Further, the position and diameter of the injection hole 14 can be changed as appropriate.

<Welding bead 3>
FIG. 2 is a schematic cross-sectional view illustrating the structure of the lap weld joint of the welding member F according to this embodiment.
As shown in FIG. 2, the injection nozzle (welding member) F of the fuel injection valve overlaps the nozzle plate 1 and the nozzle main body 2, and the surface of the overlapping nozzle plate 1 (the side in contact with the nozzle main body 2). The weld bead 3 (see FIG. 1 (a)) is formed by deep penetration type (keyhole mode) laser welding by irradiating the laser beam 5 from the opposite side) to form a molten pool 3a in which the metal material is melted. ) And the nozzle plate 1 and the nozzle body 2 are joined by a lap joint (lap weld joint). Further, as shown in FIG. 1B, the weld bead 3 is circumferentially welded (entirely welded) along the peripheral edge of the nozzle plate 1 (the area surrounding the central chamber 11, the communication path 12, and the swirl chamber 13). ing. By circumferential welding in this way, the gap between the boundary surface 4 between the nozzle plate 1 and the nozzle body 2 is sealed, so that fuel can be reliably prevented from leaking from the boundary surface 4.

  In order to prevent the nozzle plate 1 and the nozzle body 2 from slipping or shifting during laser welding, a restraining jig (not shown) is used in advance before laser welding, so that the nozzle plate 1 and the nozzle The joint on which the main body 2 is overlapped is restrained (fixed).

  Here, when the nozzle plate 1 and the nozzle body 2 are restrained (fixed) by a restraining jig (not shown), the nozzle plate 1 and the nozzle body 2 are not formed so that no gap is formed between the nozzle plate 1 and the nozzle body 2. The chamfer L at the edge of the main body 2 is set to zero as much as possible. For example, it is desirable that the chamfer L is 0.1 mm or less. This is because, when the chamfering L of the nozzle edge is set to 0.1 or more, the nozzle body 2 is positioned near the swirl chamber 13 of the nozzle plate 1 due to the influence of a restraining jig (not shown) before welding. This is because a gap is formed between them, and this gap remains after welding, greatly affecting the flow of fuel.

After the attachment of the restraining jig (not shown), the laser welding process is started. The deep penetration type (keyhole mode) laser welding will be further described with reference to FIG. FIG. 3 is a sectional view showing an outline of deep penetration type (keyhole mode) laser welding. 3 shows a cross-sectional view, but hatching is not shown for convenience of explanation.
When the power density (laser output per unit area) of the laser light applied to the surface of the nozzle plate 1 is, for example, 10 ⁶ W / cm ² or more, the temperature of the metal surfaces of the nozzle plate 1 and the nozzle body 2 is metal. As the plasma is generated, the metal vapor 7 jumps out of the irradiation point of the laser beam 5, and the molten metal surface of the molten pool 3 a is recessed by the reaction force of the metal vapor 7 to form the keyhole 6. Then, the laser beam 5 is incident while being repeatedly reflected in the keyhole 6 to form the deep and thin keyhole 6, thereby forming the deep and thin molten pool 3a. Thereafter, the deep and thin molten pool 3a is solidified again, whereby a deep and thin weld bead 3 (see FIG. 1A) can be obtained.

  In this deep penetration type (keyhole mode) laser welding, for example, a fiber laser having a wavelength of 1070 to 1080 nm can be used, but laser light 5 of other wavelengths may be used. Further, laser light is generated from a laser transmitter (not shown), is condensed by a condenser lens (not shown) via a transfer path, and the surface of the nozzle plate 1 is irradiated with the laser light 5.

  As welding conditions, for example, the laser peak output is 100 W to 600 W, the welding speed is 4.0 mm / s to 100 mm / s, and the spot diameter of the laser beam 5 irradiated on the surface of the nozzle plate 1 is 0.05 mm to It can be set appropriately at 0.3 mm. In this laser welding, either continuous wave or pulse wave may be used.

  Further, a mixed gas of nitrogen and oxygen is used as the shielding gas. The shielding gas is not limited to a mixed gas of nitrogen and oxygen, and nitrogen, Ar (argon), He (helium), Air, or a mixed gas thereof may be used.

Here, in this embodiment, a mixed gas of oxygen and nitrogen is used as the shielding gas, but the shielding gas may not be used. That is, it is obtained as a result of using a shielding gas containing a gas (for example, oxygen, CO ₂ ) that can oxidize with a metal element such as Fe (iron). That is, when shield gas is not used, when using shield gas as described above, it is necessary to select an appropriate material to be welded, such as stainless steel containing a large amount of iron (Fe), as in the embodiment, etc. Can be applied to.

FIG. 4 is a graph showing the relationship between the temperature of the molten pool 3a and the surface tension.
In general, when a shielding gas (nitrogen or the like: low oxygen amount) is used, the surface tension of molten iron (Fe) decreases as the temperature T increases, as shown in graph A (solid line) in FIG. Therefore, the hot water flow (molten metal flow) on the surface of the molten pool 3a flows from the central portion having a high temperature toward the outer peripheral portion having a low temperature. As a result, a wide welding width (surface width W1) is formed. On the other hand, when oxygen or CO ₂ is contained in the shielding gas, the amount of oxygen in the molten metal increases (the amount of oxygen is high). Thereby, as shown in the graph B (broken line) in FIG. 4, the surface tension of the molten metal increases as the temperature T increases, contrary to the graph A. As a result, the hot water flow on the surface of the molten pool 3a flows from the outer periphery of the molten pool 3a having a low temperature toward the central portion having a high temperature. Thus, as a result of the hot water flow toward the center, the width of the molten pool 3a becomes narrow, and the spread of the surface width W1 of the weld bead 3 formed after solidification can be suppressed. Even when the shield gas is not used, the amount of oxygen in the molten metal is increased by the oxygen contained in the air, so that a weld bead 3 having a narrow surface width W1 is similarly obtained.

[Conventional weld bead]
Here, the case where the conventional wine cup-shaped welding bead 3 (refer FIG. 10) is applied to the welding of the nozzle plate 1 and the nozzle main body 2 is demonstrated using FIG. FIG. 11 is a cross-sectional view illustrating the structure of a lap weld joint of welded members using conventional deep penetration type (keyhole mode) laser welding. The X direction in FIG. 11 is the axial direction of the nozzle plate 1 and the nozzle body 2, and the R direction is the radial direction of the nozzle plate 1 and the nozzle body 2.

As described above, the weld bead 3 having such a wine cup-like cross-sectional shape has an area melted in the vicinity of the surface of the nozzle plate 1 during laser welding of the boundary surface 4 between the nozzle plate 1 and the nozzle body 2. Significantly greater than the area melted nearby. For this reason, the amount of shrinkage between the vicinity of the surface of the nozzle plate 1 and the vicinity of the boundary surface 4 between the nozzle plate 1 and the nozzle body 2 is greatly different, so that welding deformation occurs. In particular, when applied to the welding of the nozzle plate 1 and the nozzle body 2 according to the present embodiment, the surface width W1 of the weld bead 3 is widened and the distance from the swirl chamber 13 is very small. Further, since the concave portion is formed in the nozzle plate 1 to form the swirl chamber 13, the plate thickness t ₁₃ of the swirl chamber 13 is thinner than the plate thickness t of the nozzle plate 1. For this reason, deformation is likely to occur near the swirl chamber 13.

Here, as a result of the simulation of welding deformation using the finite element method, as shown in FIG. 11, deformation ε _x occurs in the negative direction in the axial direction (X direction) in the vicinity of the swirl chamber 13 after welding. . That is, when viewed from the surface of the nozzle plate 1, a dent deformation occurs near the center of the nozzle plate 1.
Further, a deformation ε _y1 occurs in the negative direction in the radial direction (R direction) near the surface of the nozzle plate 1, and the deformation in the positive direction in the radial direction (R direction) occurs in the vicinity of the boundary surface 4 between the nozzle plate 1 and the nozzle body 2. ε _y2 is generated. As a result, waviness deformation occurs in the entire nozzle plate 1 and the swirl chamber 13 for swirling the fuel is also deformed, which greatly affects the swirl pattern or swirl stability of the fuel. As a result, the fuel injection performance of the fuel injection valve may also decrease.

[Welding bead of this embodiment]
On the other hand, in this embodiment, the nozzle plate 1 and the nozzle body 2 are welded using a shield gas containing an oxidation reaction gas, or welded in an air atmosphere without using a seal gas. By obtaining the bead 3, a thin weld bead 3 can be obtained. Thereby, it can apply suitably to the welding of the part which cannot widen welding width (surface width W1) like the injection nozzle F. FIG. Further, by suppressing the spread of the surface width W1 of the weld bead 3, the width of the weld bead 3 can be made uniform in the depth direction. That is, the difference between the surface width W1 which is the width of the weld bead 3 on the one end surface side of the nozzle plate 1 and the penetration width W2 which is the width of the weld bead 3 on the other end surface side of the nozzle plate 1 is reduced. By doing so, the deformation | transformation which arises in the swirl chamber 13 can be suppressed, and the fuel injection performance of a fuel injection valve can be ensured.

(Cross-sectional shape of weld bead 3 according to this embodiment)
FIG. 5 is a cross-sectional view illustrating the shape of the weld bead 3 of the welding member F according to the present embodiment. 5 (and FIG. 6 and FIG. 7 described later) are sectional views, but hatching is not shown for convenience of explanation.

  As shown in FIG. 5, the lap weld joint provided with the weld bead 3 was obtained by the deep penetration type | mold (keyhole mode) laser welding which concerns on this embodiment. In this lap weld joint, for example, the surface width W1 of the cross-sectional shape of the weld bead 3 formed on the surface of the nozzle plate 1 is 0.32 mm, and the entire surface from the surface of the nozzle plate 1 to the bottom of the weld bead 3 is formed. The penetration depth H was 0.42 mm. The penetration width W2 of the weld bead 3 at the depth position of the boundary line (boundary surface 4) that forms the boundary between the nozzle plate 1 and the nozzle body 2 was 0.28 mm. The thickness t of the nozzle plate 1 is 0.35 mm, and the depth D from the boundary line (boundary surface 4) to the bottom of the weld bead 3 (the penetration depth on the nozzle body 2 side below the boundary surface 4) is 0.07 mm.

As a result, the ratio W1 / t between the surface width W1 of the weld bead 3 and the plate thickness t of the nozzle plate 1 was 0.91, and the threshold value was 1.0 or less. The relationship (W1-W2) / t of the surface width W1 of the weld bead 3, the penetration width W2 of the weld bead 3 at the boundary surface 4 between the nozzle plate 1 and the nozzle body 2 and the plate thickness t of the nozzle plate 1 is It was 0.114, and the threshold value was 0.4 or less.
In the following description, (W1-W2) / t is referred to as a welding bead width change rate. Further, the significance of the threshold value 1.0 of the ratio W1 / t and the threshold value 0.4 of the weld bead width change rate will be described later with reference to FIGS.

  About the lap weld joint which has such a weld bead 3 (cross-sectional shape of the weld bead 3), the deformation | transformation of the nozzle plate 1, especially the swirl chamber 13 vicinity was measured after welding. As a result, it was confirmed that the nozzle plate 1 or the swirl chamber 13 hardly deformed. Further, the structure and defects of the weld were observed with a microscope. As a result, no weld defects such as weld cracks, porosity, and poor bonding were found in the weld.

(Cross-sectional shape of weld bead 3 according to comparative example)
FIG. 6 is a cross-sectional view illustrating the shape of the weld bead 3 of the welding member F according to Comparative Example 1. FIG. 7 is a cross-sectional view illustrating the shape of the weld bead 3 of the welding member F according to Comparative Example 2.

  The cross-sectional shape of the weld bead 3 of Comparative Example 1 shown in FIG. 6 is that the surface width W1 is 0.65 mm, the entire penetration depth H is 0.46 mm, and the penetration width W2 is 0.53 mm. The depth D was 0.11 mm. Note that. The thickness t of the nozzle plate 1 is 0.35 mm.

As a result, the weld bead width change rate (W1-W2) / t was 0.34, and the threshold value was 0.4 or less. On the other hand, the ratio W1 / t was 1.86, which was larger than the threshold value 1.0.
As described above, when the surface width W1 and the penetration width W2 of the weld bead 3 are both larger than the plate thickness t of the nozzle plate 1, the thermal influence on the periphery of the swirl chamber 13 is increased during welding, and the welding deformation of the swirl chamber 13 is increased. Is also getting bigger.

  The cross-sectional shape of the weld bead 3 of Comparative Example 2 shown in FIG. 7 is that the surface width W1 is 0.30 mm, the entire penetration depth H is 0.38 mm, and the penetration width W2 is 0.12 mm. The depth D was 0.03 mm. Note that. The thickness t of the nozzle plate 1 is 0.35 mm.

As a result, the ratio W1 / t was 0.86, and the threshold value was 1.0 or less. On the other hand, the weld bead width change rate (W1-W2) / t was 0.51, which was larger than the threshold value 0.4.
The shape of the weld bead 3 is such that the surface width W1 is smaller than the plate thickness t of the nozzle plate 1 and the thermal effect on the swirl chamber 13 is small, but the difference between the surface width W1 and the penetration width W2 is large. The difference between the deformation near the surface of the nozzle plate 1 (near the upper part of the swirl chamber 13) and the deformation near the boundary surface 4 (near the lower part of the swirl chamber 13) between the nozzle plate 1 and the nozzle body 2 is large. There is a greater possibility of deformation such as a dent in the inner peripheral edge.

  A summary of these results is shown in FIGS. FIG. 8 is a graph showing the relationship between the amount of deformation caused by welding deformation and the ratio W1 / t of the surface width W1 of the weld bead 3 and the plate thickness 5 of the nozzle plate 1. FIG. 9 is a graph showing the relationship between the amount of deformation due to welding deformation and the weld bead width change rate (W1-W2) / T.

  As shown in FIG. 8, when the ratio W1 / t is equal to or less than the threshold value 1.0, the deformation amount due to welding deformation becomes smaller than the deformation allowable amount, and the injection performance of the fuel injection valve can be ensured. On the other hand, when the ratio W1 / t is larger than the threshold value 1.0, the deformation amount due to welding deformation is larger than the deformation allowable amount, and the deformation amount is rapidly increased.

  As shown in FIG. 9, when the weld bead width change rate (W1-W2) / t is equal to or less than the threshold value 0.4, the deformation amount due to welding deformation becomes smaller than the allowable deformation amount, and the injection performance of the fuel injection valve Can be secured. On the other hand, when the welding bead width change rate (W1-W2) / t becomes larger than the threshold value 0.4, the deformation amount due to welding deformation becomes larger than the deformation allowable amount, and the deformation amount suddenly increases.

  As described above, by setting the ratio W1 / t and the weld bead width change rate (W1-W2) / t within a predetermined range, the laser of the nozzle plate 1 provided with the swirl chamber 13 and the nozzle body 2 is provided. In welding, welding deformation of the swirl chamber 13 can be suppressed, and a high-quality fuel injection valve can be obtained.

≪Modification≫
In addition, the welding member F which concerns on this embodiment is not limited to the structure of the said embodiment, A various change is possible within the range which does not deviate from the meaning of invention.

  The threshold value of the ratio W1 / t has been described as being 1.0, but is not limited to this, and may be changed according to the deformation allowable amount of the swirl chamber 13.

  Although the threshold value of the weld bead width change rate (W1-W2) / t has been described as 0.4, it is not limited to this and may be changed according to the deformation allowance of the swirl chamber 13.

1 Nozzle plate (material to be welded, first material to be welded)
2 Nozzle body (welded material, second welded material)
3 weld bead 3a molten pool 4 boundary surface 5 laser beam 6 keyhole 7 metal vapor 11 central chamber 12 communication path 13 swirl chamber (recess, swirl chamber)
14 Injection hole 21 Valve seat 22 Communication hole F Injection nozzle (welding member, fuel injection valve)
W1 Surface width W2 Penetration width H Penetration depth D Depth t Plate thickness L Chamfering

Claims (13)

A first material to be welded provided with a recess;
A second welded material;
A welding bead formed by deep penetration laser welding by irradiating a laser beam from the side of the first welded material with the first welded material and the second welded material overlapped with each other. ,
The weld bead is
The surface width of the weld bead is W1, the penetration width that is the width of the weld bead at the boundary surface between the first welded material and the second welded material is W2, and the plate thickness of the first welded material. T
W1 / t which is a ratio of the surface width W1 and the plate thickness t is equal to or less than a first threshold value,
The welding member, wherein (W1−W2) / t, which is a ratio between the difference between the surface width W1 and the penetration width W2 and the thickness t, is equal to or less than a second threshold value. The welding member according to claim 1, wherein the first threshold value and the second threshold value are set based on a deformation allowable amount of the recess. The first threshold is 1.0,
The welding member according to claim 2, wherein the second threshold value is 0.4. The chamfer formed at the edge of the surface of the second workpiece to be overlapped with the first workpiece is:
The welding member according to claim 1, wherein the welding member is 0.1 mm or less. A nozzle plate provided with a swirl chamber for swirling fuel;
A nozzle body;
The nozzle plate and the nozzle body are overlapped, and a welding bead formed by deep penetration laser welding by irradiating laser light from the nozzle plate side,
The weld bead is
W1 is the surface width of the weld bead, W2 is the penetration width of the weld bead at the interface between the nozzle plate and the nozzle body, and t is the thickness of the nozzle plate.
W1 / t which is a ratio of the surface width W1 and the plate thickness t is equal to or less than a first threshold value,
A fuel injection valve characterized in that a difference between the surface width W1 and the penetration width W2 and a ratio of the plate thickness t (W1-W2) / t is equal to or less than a second threshold value. 6. The fuel injection valve according to claim 5, wherein the first threshold value and the second threshold value are set based on a deformation allowable amount of the swirl chamber. The first threshold is 1.0,
The fuel injection valve according to claim 6, wherein the second threshold value is 0.4. The chamfer formed at the edge of the surface of the nozzle body that is overlapped with the nozzle plate is:
6. The fuel injection valve according to claim 5, wherein the fuel injection valve is 0.1 mm or less. The first welded material provided with the recess and the second welded material are overlapped, a laser beam is irradiated from the first welded material side to form a weld bead by deep penetration laser welding,
The weld bead is
The surface width of the weld bead is W1, the penetration width that is the width of the weld bead at the boundary surface between the first welded material and the second welded material is W2, and the plate thickness of the first welded material. T
W1 / t which is a ratio of the surface width W1 and the plate thickness t is equal to or less than a first threshold value,
A laser welding method characterized in that (W1-W2) / t, which is a ratio of the difference between the surface width W1 and the penetration width W2 and the plate thickness t, is equal to or less than a second threshold value. The laser welding method according to claim 9, wherein the first threshold value and the second threshold value are set based on an allowable deformation amount of the swirl chamber. The first threshold is 1.0,
The laser welding method according to claim 10, wherein the second threshold value is 0.4. The deep penetration type laser welding is
The laser welding method according to claim 9, wherein a mixed gas of oxygen and nitrogen is used as the shielding gas. The deep penetration type laser welding is
The laser welding method according to claim 9, wherein the method is performed in an air atmosphere without using a shielding gas.