CN116529475A - Two-component joint and method for manufacturing same - Google Patents

Abstract

The present invention provides a two-component joint, comprising: a 1 st member having a through hole; a 2 nd member inserted into the through hole of the 1 st member; and an annular weld metal formed on the facing portions of the 1 st member and the 2 nd member, and joining the 1 st member and the 2 nd member, wherein an amount of overlap between a start end and an end of a back bead of the weld metal is smaller than a width of the back bead.

Description

Two-component joint and method for manufacturing same

Technical Field

The present invention relates to a joined body of two members and a joining method, and more particularly, to a joined body in which sealing performance of an annular welded portion between two members is emphasized, and a method for manufacturing the same.

Background

As a technique of inserting one member into the other member and welding the two members along the outer periphery of the other member, for example, a technique described in patent document 1 is known.

Prior art literature

Patent literature

Patent document 1: international publication No. 2018/142930

Disclosure of Invention

Problems to be solved by the invention

The welding disclosed in patent document 1 is penetration welding penetrating the plate thicknesses of two members, and the welded portion is formed in a ring shape. In such welding, the facing surfaces of the two members may be welded to each other in more than 1 turn, so that a portion where the 2 nd turn of the weld metal overlaps with a part of the 1 st turn of the weld metal may be formed. However, the overlapping portion tends to be prone to internal cracking or air holes.

The present invention provides a two-component joined body and a method for manufacturing the same, wherein occurrence of internal cracks or pores of a weld metal joining the two components can be suppressed.

Technical means for solving the problems

To achieve the above object, the present invention provides a two-component joint comprising: a 1 st member having a through hole; a 2 nd member inserted into the through hole of the 1 st member; and an annular weld metal formed on the facing portions of the 1 st member and the 2 nd member, and joining the 1 st member and the 2 nd member, wherein an amount of overlap between a start end and an end of a back bead of the weld metal is smaller than a width of the back bead.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, the occurrence of internal cracks or pinholes in the weld metal joining the two members can be suppressed.

Drawings

Fig. 1 is a schematic diagram of a fuel supply system including a high-pressure fuel supply pump as an application example of a joined body of two members and a manufacturing method thereof according to an embodiment of the present invention.

Fig. 2 is a sectional view of the high-pressure fuel supply pump shown in fig. 1.

Fig. 3 is a cross-sectional view taken along line III-III of fig. 2.

Fig. 4 is a cross-sectional view taken along line IV-IV in fig. 3.

Fig. 5 is a cross-sectional view taken along line V-V in fig. 3.

Fig. 6 is an enlarged view of the VI portion of fig. 4.

Fig. 7 is an enlarged view showing a state before welding of the portion shown in fig. 6.

Fig. 8 is a conceptual diagram illustrating a mechanism of generation of keyhole by vapor pressure of metal vapor at the time of soldering.

Fig. 9A is an explanatory diagram of a mechanism of occurrence of solidification cracks in the weld metal.

Fig. 9B is an explanatory diagram of a mechanism of occurrence of solidification cracks in the weld metal.

Fig. 9C is an explanatory diagram of a mechanism of occurrence of solidification cracks in the weld metal.

Fig. 9D is an explanatory diagram of a mechanism of occurrence of solidification cracks in the weld metal.

Fig. 9E is an explanatory diagram of a mechanism of occurrence of solidification cracks in the weld metal.

Fig. 10 is an explanatory view of a joining method of two members according to an embodiment of the present invention.

Fig. 11A is an explanatory diagram of a phenomenon occurring in each stage of the joining method of fig. 10.

Fig. 11B is an explanatory diagram of a phenomenon occurring in each stage of the joining method of fig. 10.

Fig. 11C is an explanatory diagram of a phenomenon occurring in each stage of the joining method of fig. 10.

Fig. 11D is an explanatory diagram of a phenomenon occurring in each stage of the joining method of fig. 10.

Fig. 12A is a schematic view of a back bead of a joined body of two members manufactured by the manufacturing method according to the embodiment of the present invention.

Fig. 12B is an enlarged view of the portion XIIB in fig. 12A.

Detailed Description

Next, embodiments of the present invention will be described with reference to the drawings.

Note that, although the description will be given with reference to the vertical direction, the vertical direction does not mean the vertical direction in the mounted state of the high-pressure fuel supply pump.

Fuel supply system

Fig. 1 is a schematic diagram of a fuel supply system including a high-pressure fuel supply pump as an application example of a joined body of two members and a manufacturing method thereof according to an embodiment of the present invention. Hereinafter, the high-pressure fuel supply pump will be simply referred to as a high-pressure pump. The high-pressure pump illustrated in the present embodiment is applied to an engine system in which fuel is directly injected into a cylinder block of an engine.

The dashed box shown in this figure represents the body of the high-pressure pump, i.e. the pump body 1, the mechanisms and components shown in this box being integrally mounted on the pump body 1. The feed pump 21 is driven according to a signal from an engine control unit 27 (hereinafter referred to as ECU), and fuel in the fuel tank 20 is drawn by the feed pump 21. The fuel is pressurized and supplied to the fuel suction port 10a of the high-pressure pump through the suction pipe 28 at a predetermined feed pressure. After passing through the fuel suction port 10a, the fuel reaches the suction port 31b of the electromagnetic suction valve unit 300 constituting the capacity variable mechanism via the suction joint 51, the pressure pulsation reducing mechanism 9, and the suction passage 10 d.

The fuel flowing into the electromagnetic suction valve unit 300 flows into the pressurizing chamber 11 via the suction valve 30. The plunger 2 is powered for reciprocating movement by means of a cam 93 (fig. 2) of the engine. When the plunger 2 reciprocates, fuel is sucked into the pressurizing chamber 11 from the suction valve 30 in a descending stroke of the plunger 2, and the fuel is pressurized in an ascending stroke. The fuel pressurized in the pressurizing chamber 11 is discharged from the high-pressure pump through the discharge valve 8 and the fuel discharge port 12, and is pressure-fed to the common rail 23. The common rail 23 is provided with a pressure sensor 26 and a plurality of injectors 24. The injectors 24 are mounted on the common rail 23 in a number corresponding to the number of cylinders of the internal combustion engine, and are opened and closed in accordance with a control signal from the ECU 27 to inject fuel into the cylinders (combustion chambers) of the engine by performing an opening operation. The discharge flow rate of the fuel of the high-pressure pump is adjusted by the ECU 27 to control the electromagnetic suction valve unit 300.

When the pressure of the common rail 23 excessively increases due to a failure of the injector 24 or the like, for example, and the differential pressure between the pressure of the fuel discharge port 12 and the pressurizing chamber 11 becomes equal to or higher than the valve opening pressure of the relief valve unit 200, the ball valve 202 opens. The excessively pressurized fuel is returned from the relief passage 200a to the pressurizing chamber 11 through the relief valve unit 200, thereby protecting the high-pressure piping such as the common rail 23.

High-pressure pump

Fig. 2 is a sectional view of the high-pressure fuel supply pump shown in fig. 1, fig. 3 is a sectional view taken along line III-III in fig. 2, and fig. 4 is a sectional view taken along line IV-IV in fig. 3.

As shown in fig. 3 and 4, the high-pressure pump of the present embodiment fixes a mounting flange 1e provided on the pump body 1 to the outer wall surface of a cylinder head 90 of the internal combustion engine by a plurality of bolts (not shown). An O-ring 61 is embedded in the pump body 1, and the space between the cylinder cover 90 and the pump body 1 is sealed by the O-ring 61, so that engine oil is prevented from leaking.

As shown in fig. 3, the pump body 1 is provided with a suction fitting 51. The suction joint 51 is connected to a suction pipe 28 (fig. 1) that supplies low-pressure fuel from the fuel tank 20 of the vehicle, from which the fuel is supplied into the high-pressure pump. The fuel flowing in from the fuel suction port 10a of the suction joint 51 flows through a low-pressure flow path formed inside the pump body 1 to the buffer chambers formed in the buffer upper portion 10b and the buffer lower portion 10 c. The buffer chamber is delimited by a buffer cover 14 mounted on the pump body 1. The fuel flowing into the buffer chamber suppresses pressure pulsation by the pressure pulsation reducing mechanism 9 provided in the buffer chamber, and reaches the suction port 31b of the electromagnetic suction valve unit 300 via the suction passage 10 d. The pressure pulsation reducing mechanism 9 is a metal diaphragm buffer in which 2 corrugated disc-shaped metal plates are bonded and inert gas (for example, argon gas) is injected into the inside, and absorbs and reduces pulsation of the flow of fuel by expanding and contracting the metal buffer. Fig. 3 illustrates an example in which the suction fitting 51 is provided on the side of the pump body 1, and the suction fitting 51 is sometimes provided on the upper surface of the damper cap 14.

The pump body 1 is equipped with an electromagnetic suction valve unit 300 and a discharge valve 8. The fuel is supplied to the pressurizing chamber 11 via a pressurizing chamber inlet flow path 1a formed in the pump body 1 by the electromagnetic suction valve unit 300. The backflow of the fuel that has been discharged from the pressurizing chamber 11 to the discharge passage 12b (fig. 3) is prevented by the discharge valve 8. The fuel after passing through the discharge valve 8 is supplied to the engine through the fuel discharge port 12 of the discharge joint 12 c.

Further, a cylinder 6 for guiding the reciprocating motion of the plunger 2 is mounted on the pump body 1. The cylinder 6 is pressed into the pump body 1 and is fixed by caulking. The cylinder 6 is pressed to seal the cylinder so that the pressurized fuel does not leak from the pressurizing chamber 11 through the space between the cylinder 6 and the pump body 1. In addition, not only the outer peripheral surface of the cylinder 6 is in contact with the pump body 1, but also the upper end surface is in contact with the pump body 1, and the metal contact of the upper end surface of the cylinder 6 with the pump body 1 also contributes to the sealing of the pressurized fuel.

A tappet 92 is provided at the lower end of the plunger 2, and rotational movement of a cam 93 mounted on a camshaft of the internal combustion engine is transmitted to the plunger 2 by being converted into up-down movement by the tappet 92. The plunger 2 is mounted with a catch 15, and the catch 15 is pressed by the spring 4 to press the plunger 2 against the tappet 92. Thereby, the plunger 2 reciprocates up and down with the rotational movement of the cam 93.

Further, a plunger seal 13 is held at the lower end of the inner periphery of the seal holder 7, and the plunger seal 13 is provided at the lower side in the drawing of the cylinder 6. The fuel of the sub-chamber 7a when the plunger 2 slides is sealed by the plunger seal 13 slidably contacting the outer periphery of the plunger 2, thereby preventing the fuel from flowing into the inside of the internal combustion engine. At the same time, by means of the plunger seal 13, lubricating oil (also including engine oil) that lubricates sliding parts in the internal combustion engine is also prevented from flowing into the pump body 1.

The discharge valve 8 provided at the outlet of the pressurizing chamber 11 is composed of a valve seat 8a, a valve body 8b, a spring 8c, a discharge valve plug 8d, and a discharge valve stopper 8 e. The valve body 8b is biased toward the valve seat 8a by a spring 8c, and the valve body 8b contacts and separates from the valve seat 8a to open and close the discharge valve 8. The stroke (moving distance) of the valve body 8b is defined by the discharge valve stopper 8 e. The discharge valve plug 8d is a body of the discharge valve 8, and is joined to the pump body 1 by a weld metal 407. The weld metal 407 blocks the inner space of the pump body 1, through which the fuel flows, from the outer space of the pump body 1.

In a state where there is no differential pressure of the fuel pressure between the pressurizing chamber 11 and the discharge valve chamber 12a, the valve body 8b is pressed against the valve seat 8a by the spring 8c, and the discharge valve 8 is in a valve-closed state. When the fuel pressure in the pressurizing chamber 11 becomes greater than the fuel pressure in the discharge valve chamber 12a by a certain degree or more, the valve body 8b moves against the spring 8c, and the discharge valve 8 opens. At this time, the high-pressure fuel in the pressurizing chamber 11 is discharged to the common rail 23 (fig. 1) through the discharge valve chamber 12a, the discharge passage 12b, and the fuel discharge port 12 shown in fig. 3. The movement of opening and closing the valve body 8b is guided by the outer peripheral surface of the discharge valve stopper 8e to be limited in the stroke direction, and the discharge valve 8 also functions as a check valve.

The pressurizing chamber 11 is defined by the pump body 1, the electromagnetic suction valve unit 300, the plunger 2, the cylinder 6, the discharge valve 8, and the relief valve unit 200. The rotation of the cam 93 reciprocates the plunger 2, and when the plunger 2 moves in a direction to expand the volume of the pressurizing chamber 11, fuel is sucked into the pressurizing chamber 11, and the fuel pressure inside the pressurizing chamber 11 decreases. When the fuel pressure inside the pressurizing chamber 11 becomes lower than the pressure of the suction passage 10d in this stroke, the suction valve 30 opens.

After the intake stroke, the plunger 2 changes the operation direction in the direction of the contracting pressure chamber 11, and at this time, the compression stroke is switched. Here, in a state where the electromagnetic coil 43 of the electromagnetic suction valve unit 300 is not energized, the suction valve 30 is biased by the stem biasing spring 40 to be opened. In a state where the volume of the pressurizing chamber 11 is reduced, the fuel sucked into the pressurizing chamber 11 is once returned to the suction passage 10d through the opening of the suction valve 30 in the valve-opened state, so that the pressure of the pressurizing chamber 11 does not rise. This stroke is called the return stroke.

Next, the electromagnetic suction valve unit 300 will be described with reference to fig. 5. Fig. 5 is a cross-sectional view taken along line V-V in fig. 3, showing a state in which the suction valve is opened.

The electromagnetic intake valve unit 300 drives the intake valve 30 disposed in parallel with the magnetic core (fixed core) 39, the movable core 36, and the valve stem 35 by energizing the electromagnetic coil 43, thereby sucking fuel and delivering the fuel to the pressurizing chamber 11. In the non-energized state, the suction valve 30 is urged in the valve opening direction by the valve stem urging spring 40, and when a control signal from the ECU 27 is applied to the electromagnetic suction valve unit 300, an electric current flows to the electromagnetic coil 43 via the terminal 46, and the magnetic core 39 generates a magnetic attraction force. With this, the movable iron core 36 is pulled by the magnetic attraction force of the magnetic iron core 39 in the valve closing direction on the magnetic attraction surface S. The valve rod 35 is disposed between the movable core 36 and the suction valve 30, and a flange portion 35a that engages with the movable core 36 is disposed on the valve rod 35. The electromagnetic coil chamber in which the electromagnetic coil 43 is disposed is covered with a cover member 44, and the magnetic core 39 also serves as a member for holding the cover member 44. The valve stem energizing spring 40 is covered by a portion of the magnetic core 39 that holds the cover member 44.

The valve rod 35 is engaged with the movable core 36 by the flange 35a, and moves together with the movable core 36 when the movable core 36 moves toward the magnetic core 39 side. Therefore, when the magnetic attractive force acts on the movable core 36, the valve rod 35 moves in the valve closing direction. A valve closing biasing spring 41 that biases the movable core 36 in a valve closing direction and a stem guide member 37 that guides the stem 35 in the opening/closing direction are disposed between the movable core 36 and the suction valve 30. The stem guide member 37 constitutes a spring seat 37b of the closing valve urging spring 41. Further, the stem guide member 37 is provided with a fuel passage 37a so that fuel can flow in and out to a space where the movable core 36 is disposed.

The movable core 36, the valve closing biasing spring 41, the valve rod 35, and the like are enclosed in an electromagnetic suction valve unit case 38 fixed to the pump body 1. Further, a magnetic core 39, a stem biasing spring 40, a solenoid 43, a stem guide member 37, and the like are supported on the electromagnetic suction valve unit case 38. The stem guide member 37 is attached to the electromagnetic suction valve unit case 38 on the side opposite to the magnetic core 39 and the electromagnetic coil 43. The stem guide member 37 encloses the suction valve 30, the suction valve biasing spring 33, and the stopper 32, and forms a part of the electromagnetic suction valve unit case 38.

The suction valve 30, the suction valve biasing spring 33, and the stopper 32 are provided on the opposite side of the magnetic core 39 on the valve stem 35. The suction valve 30 is provided with a guide portion 30b protruding toward the pressurizing chamber 11, and the guide portion 30b is guided by a suction valve biasing spring 33. With the movement of the valve rod 35, the suction valve 30 moves by the valve body stroke 30e in the valve opening direction (direction away from the valve seat 31 a) to the valve opening state, and fuel is supplied from the suction passage 10d to the pressurizing chamber 11. The guide portion 30b stops moving by colliding with the stopper 32. The stopper 32 is press-fitted and fixed inside the housing (stem guide member 37) of the electromagnetic suction valve unit 300. The valve rod 35 and the suction valve 30 are separate members.

The suction valve 30 closes the flow path to the pressurizing chamber 11 by contacting the valve seat 31a of the valve seat member 31 disposed on the suction side, and opens the flow path to the pressurizing chamber 11 by leaving the valve seat 31 a. When the magnetic force overcomes the force of the valve stem urging spring 40 to move the valve stem 35 in a direction away from the intake valve 30, the force of the intake valve urging spring 33 and the fluid force of the fuel flowing into the intake passage 10d cause the intake valve 30 to close. After the valve is closed, the volume of the pressurizing chamber 11 decreases by the operation of the plunger 2, the fuel pressure in the pressurizing chamber 11 increases, and when the pressure in the pressurizing chamber 11 becomes equal to or higher than the pressure in the fuel discharge port 12, the high-pressure fuel is discharged from the high-pressure pump through the discharge valve 8 and supplied to the common rail 23. This stroke is called the discharge stroke. The fuel discharged from the high-pressure pump can be controlled by the timing of energization of the electromagnetic coil 43.

The relief valve unit 200 includes a relief valve sleeve 201, a ball valve 202, a relief valve pressing block 203, a spring 204, and a spring seat 205. The relief valve unit 200 opens the ball valve 202 and returns the fuel to the pressurizing chamber 11 only when the common rail 23 or a member on the downstream side thereof has a problem and becomes high pressure beyond an allowable value.

Weld metal-

The pump body 1 is formed with a plurality of through holes for fitting components, and fitting components are inserted into the through holes, respectively, and joined by welding. The discharge valve 8, the discharge joint 12c, and the like are examples thereof. The body (discharge plug 8 d) of the discharge valve 8 and the discharge joint 12c are joined to the pump body 1 via a weld metal 407 formed by laser welding. The weld metal 407 is formed in a ring shape around the outer periphery of the discharge plug 8d along the facing portion of the pump body 1 and the discharge plug 8 d. The weld metal 407 joining the discharge joint 12c and the pump body 1 is formed in a ring shape along the facing portion of the pump body 1 and the discharge joint 12c around the outer peripheral portion of the discharge joint 12 c. It is important to suppress the occurrence of defects such as solidification cracks and pinholes in the weld metal 407, in order to sufficiently ensure the reliability of the welded portion. In particular, the reliability of the welded portion facing the flow path of the fuel inside the pump body 1 is important from the viewpoint of preventing the fuel from leaking out of the pump body 1, and the welded portion needs to have sufficient strength.

Fig. 6 is an enlarged view of the VI portion of fig. 4, that is, an enlarged view of the welded portion of the pump body 1 and the discharge plug 8 d. Fig. 7 is an enlarged view showing a state before welding of the portion shown in fig. 6. Here, the structure of the welded portion between the pump body 1 and the discharge plug 8d will be described with reference to fig. 6 and 7, and the welded portion between the pump body 1 and the discharge joint 12c is also configured in the same manner.

As shown in fig. 7, the discharge plug 8d inserted into the through hole 413 for component mounting formed in the pump body 1 is press-fitted and fixed to the pump body 1 by a press-fitting portion 405 formed separately from a portion to be welded (a portion where the weld metal 407 is formed after welding). The press-fit portion 405 is located on the inner side of the pump body 1 than the portion to be welded in the direction of the center line O of the discharge plug 8 d. At this time, the flange 414 is provided on the discharge plug 8d before welding, and the discharge plug 8d is press-fitted into the pump body 1 until the flange 414 comes into contact with the press-fit receiving surface 406 of the outer wall of the pump body 1. In the stage before welding, a slight gap GP is provided between the inner peripheral surface of the through hole 413 of the pump body 1 and the outer peripheral surface of the discharge plug 8d facing the inner peripheral surface, unlike the press-fit portion 405. The gap GP is tapered toward the inside of the pump body 1, and is inclined with respect to the center line O so as to approach the center line O of the discharge plug 8d as going toward the inside of the pump body 1, as viewed in the cross section of fig. 7. A gap 400 is formed between the gap GP (the portion facing the pump body 1 and the discharge plug 8 d) and the press-fitting portion 405. When the pump body 1 and the discharge plug 8d are welded, the gap GP is aligned in the state of fig. 7, the laser beam LB is irradiated onto the laser irradiation surface 404 of the flange 414 of the discharge plug 8d, and the laser beam LB is turned around the annular gap GP. In the cross section of fig. 7, the optical axis of the laser beam LB is inclined with respect to the center line O of the discharge plug 8d according to the inclination of the gap GP.

As a result of this welding, as shown in fig. 6, the portion of the pump body 1 opposite to the discharge plug 8d melts and solidifies around the portion where the gap GP was previously present, thereby forming a weld metal 407 joining the pump body 1 and the discharge plug 8 d. Since the void 400 is present, the weld metal 407 forms a back bead 416 exposed to the void 400 in addition to a surface bead 415, which is a surface (exposed to the space outside the pump body 1) on the incidence side of the laser beam LB. In the cross section of fig. 6, a straight line 407a passing through the center of the surface bead 415 in the width direction and the center of the back bead 416 in the width direction is inclined with respect to the center line O of the discharge plug 8d in correspondence with the gap GP before welding. The weld metal 407 is formed on the entire circumference of the discharge plug 8d, and the portion of the pump body 1 facing the discharge plug 8d is sealed by the weld metal 407, thereby suppressing leakage of fuel from the pump body 1.

Mechanism for generating defects in weld metal

Fig. 8 is a conceptual diagram illustrating a mechanism of generation of keyhole by vapor pressure of metal vapor at the time of soldering. As shown in the figure, when the laser beam LB is irradiated to the metal member, the metal member is heated by the laser beam LB to reach a melting point and melt, and a part of the metal member becomes liquid to form a molten pool MP. Thereafter, the metal member in the vicinity of the laser beam axis of the liquefied melting tank MP is further heated by the laser beam LB, and is heated and evaporated to become metal vapor MV. The vapor pressure of the metal vapor MV is believed to push away the molten pool MP to form the keyhole KH. The keyhole KH is not generated immediately by irradiation of the metal member with the laser beam LB, but is generated through the formation of the molten pool MP and the generation of the metal vapor MV. The laser beam LB is considered to penetrate the metal member plate thickness TP at a stage after the generation of the keyhole KH, and after the generation of the keyhole KH, the keyhole KH gradually deepens with an increase in energy of the laser beam LB, so that the molten pool MP gradually deepens to penetrate the metal member plate thickness TP.

Fig. 9A to 9E are views for explaining the mechanism of occurrence of solidification cracking of the weld metal in stages. In these figures, a metal 2 nd member B (for example, a discharge plug 8d in the example of fig. 1 to 7) is pressed into a cylindrical through hole TH of a metal 1 st member a (in the example of fig. 1 to 7, a pump body 1). Fig. 9A to 9E show a process of irradiating the facing portions of the 1 st member a and the 2 nd member B with the laser beam LB, rotating the 1 st member a and the 2 nd member B, and scanning the cylindrical facing portions of the two members with the laser beam LB.

In the example of fig. 9A to 9E, the position of the penetration start point P1 of the plate thickness TP (fig. 8) at which the key hole KH penetrates the 1 st member a and the 2 nd member B is set to be the azimuth θ=0° with respect to the center line O of the annular facing portion (in other words, the gap GP) of the 1 st member a and the 2 nd member B. The penetration welding start point P1 becomes the start of the back weld bead 416. The molten pool MP and the keyhole KH advance from the penetration welding start point P1 along with the laser beam LB in a circular orbit, and the laser beam LB is sequentially solidified to form the weld metal WM. Fig. 9A shows a case during which the laser LB advances at a position of azimuth angle 0 deg. or more θ. or less 270 deg.. During this time, the gap GP is sufficiently left in the advancing direction of the laser beam LB, and the metal vapor MV generated inside the keyhole KH flows into the gap GP in the advancing direction of the laser beam. When the laser beam LB further advances and reaches the region having the azimuth angle θ equal to or larger than 270 ° as shown in fig. 9B, the gap GP in the advancing direction of the laser beam LB gradually disappears as the laser beam LB approaches the penetration welding start point P1 filled with the welding metal WM. When the laser beam LB approaches the penetration welding start point P1, as shown in fig. 9C, a part of the metal vapor MV flowing into the gap GP in the advancing direction of the laser beam LB collides with the welding metal WM penetrating the welding start point P1. Then, the metal vapor MV that has collided with the welding metal WM is pushed back in the direction opposite to the advancing direction of the laser beam LB by the reaction force, and is contained in the molten pool MP as shown in fig. 9D. Solidification of the molten pool MP containing the metal vapor MV in this manner may generate blowholes in the weld metal WM as shown in fig. 9E, which may cause an internal crack IC of the metal vapor MV.

Method for producing a bonded body

In contrast, the weld metal 407 of the high-pressure pump described in fig. 1 to 7 is formed by a special welding method that aims to suppress the occurrence of such internal cracks. Thereby, a firm joint body of the pump body 1 corresponding to the 1 st component a and the discharge plug 8d (or the discharge joint 12 c) corresponding to the 2 nd component B in the example of fig. 9A to 9E is produced. The method for manufacturing the joint of the two members includes a laser energy increasing step, a penetration welding step, a laser energy switching step, and a laser energy reducing step.

The laser energy increasing step is a step of moving the laser beam from the start of the surface bead (laser irradiation start position) of the weld metal along the facing portions of the 1 st and 2 nd members while increasing energy. During this period, the energy of the laser beam LB is increased to a set penetration energy for forming the back bead. In the laser energy increasing step, the melting depth does not reach the plate thicknesses of the 1 st and 2 nd members, so that the back weld bead is not formed.

The subsequent penetration welding step is a step of surrounding the laser beam LB by 1 turn along the facing portions of the 1 st and 2 nd members while maintaining the penetration energy from the position where the energy of the laser beam LB reaches the penetration energy, that is, from the start of the back bead. In the penetration welding step, the penetration welding is performed so that the molten depth reaches the plate thickness of the 1 st member and the 2 nd member, and thus a back bead is formed.

The laser energy switching step subsequent to the penetration welding step is a step of switching the energy of the laser beam LB to a set non-penetration energy at which the back bead is not formed when the laser beam LB reaches the end of the back bead (in other words, when the laser beam LB returns to the start of the back bead after 1 turn of penetration welding). Thus, the melting depth again does not reach the plate thicknesses of the 1 st and 2 nd members, and the back weld bead is interrupted at this point.

The laser energy reduction step is a step of moving the laser beam LB along the facing portions of the 1 st and 2 nd members while reducing the energy from the non-penetrating energy after the laser energy switching step. In this period, as the energy of the laser beam LB decreases, the melting depth becomes shallow, and the weld metal (the 2 nd turn weld metal) becomes thin. When the laser beam LB reaches a predetermined end position of the surface bead, the irradiation of the laser beam LB is stopped, and the welding is completed.

A specific example of the above method for producing the joined body will be described with reference to the drawings.

Fig. 10 is an explanatory view of a joining method of two members according to an embodiment of the present invention, and shows energy control of laser beam LB in an example of irradiating laser beam LB clockwise along an annular facing portion of pump body 1 and discharge plug 8 d. Fig. 11A to 11D are explanatory views of phenomena occurring at each stage of the joining method of fig. 10. The azimuth angles shown in these figures correspond to the azimuth angles shown in fig. 9A-9E. Here, the welding of the pump body 1 to the discharge plug 8D will be described with reference to fig. 10 and 11A to 11D, and the same applies to the welding of the pump body 1 to the discharge joint 12 c.

First, in fig. 10, the energy of the laser beam LB is increased from 0 to the penetrating energy while the laser beam LB advances from the laser irradiation start point X along the annular facing portion of the pump body 1 and the discharge plug 8d by a predetermined laser beam energy increasing rotation angle Ru. The step of increasing the laser energy by the interval of the rotation angle Ru is a laser energy increasing step.

Thereafter, while the laser beam LB is further advanced by the main welding rotation angle Fp (360 °) along the annular facing portion of the pump body 1 and the discharge plug 8d, the two members of the pump body 1 and the discharge plug 8d are penetration welded by the laser beam LB of penetration energy. The step of the interval of the main welding rotation angle Fp is a penetration welding step. The back bead 416 is formed only in the range of the main welding rotation angle Fp. In this example, when the laser beam LB approaches the penetration welding start point P1, as shown in fig. 11A, a part of the metal vapor MV flowing into the gap GP in the advancing direction of the laser beam LB collides with the welding metal WM penetrating the welding start point P1 (as in fig. 9C).

After the main welding rotation angle Fp is passed, the energy of the laser beam LB is switched from the penetration energy to the non-penetration energy while the laser beam LB is further advanced along the annular facing portion of the pump body 1 and the discharge plug 8d by the rotation angle Fd. The step of rapidly decreasing the laser energy by the interval of the rotation angle Fd is a laser energy switching step. Here, for example, the laser energy rapid decrease rotation angle Fd is set to about 5 to 10 °, and the energy of the laser beam LB is rapidly decreased by about 15 to 20% between about 5 to 10 °. As a result, as shown in fig. 11B, the keyhole KH is narrowed, the amount of the metal vapor MV inside the keyhole KH is reduced, and the vapor pressure is lowered, thereby leaving the metal vapor MV in the keyhole KH.

After the energy of the laser beam LB is reduced to the non-penetrating energy, the energy of the laser beam LB is gradually reduced while the laser beam LB advances along the annular facing portion of the pump body 1 and the discharge plug 8d by the rotation angle Rd. The step of reducing the laser energy by the rotation angle Rd is a laser energy reduction step. As a result, as shown in fig. 11C, the metal vapor MV inside the keyhole KH is released from the laser light incidence side to the atmosphere, and during this time, the keyhole KH disappears and the welding ends.

Joint body

The two-component joined body manufactured by the method described in fig. 10 to 11D has: a 1 st member having a through hole; a 2 nd member inserted into the through hole of the 1 st member; and an annular weld metal formed on the facing portions of the 1 st member and the 2 nd member, and joining the 1 st member and the 2 nd member. Then, the laser energy switching step leaves a specific weld mark having a smaller overlap amount between the start and end of the back bead of the weld metal than the width of the back bead.

On the other hand, by performing the laser energy reduction step subsequent to the laser energy switching step, the amount of overlap between the start and end of the surface bead of the weld metal becomes larger than the width of the surface bead. As a result, the through weld portion where the back bead is formed overlaps the end portion of the 2 nd turn of the surface bead, and as a result, the azimuth angle range between the start and end portions of the overlapping portion with respect to the center of the annular weld metal is 30 degrees or more. The fusion depth of the overlapping portion between the through-welded portion and the end portion of the 2 nd round surface bead becomes shallow toward the end. In the high-pressure pump described in fig. 1 to 7, the pump body 1 corresponds to the 1 st component described herein, and a component mounted on the pump body 1, for example, the discharge valve plug 8d (or the discharge joint 12 c) which is the body of the discharge valve corresponds to the 2 nd component.

The above joined body will be described with reference to the drawings.

Fig. 12A is a schematic view of a back bead of a joined body of two members manufactured by the manufacturing method (fig. 10) according to the embodiment of the present invention, and fig. 12B is an enlarged view of the portion XIIB in fig. 12A.

As described above, the penetration welding is performed by making the melting depth to the plate thickness (penetration plate thickness) only in the section of the main welding rotation angle Fp (fig. 10), and therefore the back bead 416 is formed only in this section. That is, only the back bead 416 of 360 ° is formed. When the laser beam LB passes through the start of the section of the main welding rotation angle Fp, that is, the penetration welding start point P1 (fig. 10), a back bead start end 411 is formed. When the laser beam LB passes through the end of the section of the main welding rotation angle Fp, the rear bead end portion 412 is formed. Since the laser beam LB has a circular cross section, the tip end portions 411a and 412a of the back bead start end portion 411 and the back bead end portion 412 each have a circular arc shape according to the cross section of the laser beam LB. In the present embodiment, the back bead leading end 411 and the back bead trailing end 412 overlap only at the semicircular leading end 411a and 412a, and the overlap amount OL1 is smaller than the bead width BW1 of the back bead 416 as shown in fig. 12B.

On the other hand, the surface bead 415 is continuously formed in the interval of the laser energy increasing rotation angle Ru, the main welding rotation angle Fp, the laser energy decreasing rotation angle Fd, and the laser energy decreasing rotation angle Rd with respect to the back bead 416 formed only with the main welding rotation angle Fp. Thus, the end portion of the 2 nd surface bead 415 overlaps with the penetration weld formed in the section of the main welding rotation angle Fp in the total section of the laser energy rapid decrease rotation angle Fd and the laser energy decrease rotation angle Rd. The overlap amount OL2 (fig. 11D) is wider than the bead width BW2 (fig. 11D) of the surface bead 415. As described above, the azimuth range Φ (fig. 11D) between the start and end of the overlapping portion of the end portion of the surface bead 415 and the through-welded portion is 30 degrees or more.

Effects-

(1) According to the present embodiment, as described above, after the penetration welding is started, the energy of the laser beam LB is suddenly reduced to the non-penetration energy at the point that the laser beam LB returns to the penetration welding start point P1 after surrounding the 1 st member and the 2 nd member by 1 turn along the facing portion. Thus, the overlapping amount OL1 between the start and end of the back bead of the weld metal is smaller than the bead width BW1 of the back bead. In the process of forming the weld metal, the energy of the laser beam LB is suddenly reduced to the non-penetrating energy, and the metal vapor MV is suddenly reduced and remains in the keyhole KH as described above, thereby suppressing the occurrence of the phenomenon that the molten pool MP is solidified by packing the metal vapor MV. In this way, the occurrence of cracks and pinholes in the weld metal joining the two members can be suppressed, and the effects such as improvement in the reliability of the joined body of the two members, reduction in the maintenance and management costs of the weld quality in mass production, and the like can be expected. Since the internal cracking of the weld metal is effectively suppressed, the high-pressure fuel can be effectively sealed by the weld metal.

(2) In the case of the present embodiment, the back surface bead of the weld metal is overlapped only at the end, whereas the overlap amount OL2 of the surface bead of the weld metal is larger than the bead width BW2 of the surface bead 415. In particular, in the present embodiment, since a large range of 30 degrees or more is secured in the azimuth range at the overlapping portion of the through-welded portion of the weld metal and the end portion of the surface bead, the two members can be firmly joined, and the reliability in terms of the strength of the joined body of the two members is also sufficiently secured. In this case, the welding is completed by passing through the laser energy reduction step so that the molten depth of the overlapping portion passing through the welded portion and the end portion of the surface bead becomes shallower toward the end, and the occurrence of the air holes can be more effectively suppressed in the overlapping portion.

(3) As described in the above embodiment, the above method can be suitably applied to the joined body of the pump body 1 of the high-pressure fuel pump and the components (e.g., the discharge plug 8 d) mounted thereon, particularly the portion facing the high-pressure fuel. Specifically, since the interior of the pump body 1 of the high-pressure pump is pressurized, sealing performance of the fitting member such as the discharge plug 8d is also important from the viewpoint of suppressing leakage of fuel, and the like, and a structure in which the fitting member is firmly fixed by interference fit and welding as described in fig. 6 and 7 may be adopted. However, it is not easy to manufacture the components precisely so that the facing surfaces of the pump body 1 and the mounting component are in contact with each other at both the interference fit portion and the welded portion. Therefore, as described with reference to fig. 7, the portion to be welded may be a clearance fit structure. In this case, however, a high-density laser is used to obtain a sufficient melt depth, and the use of the high-density laser tends to cause a large amount of metal vapor to be generated during welding and enter the melt pool. For such reasons, the above-described method of effectively suppressing the inclusion of metal vapor in the molten pool can be suitably applied to the joining of the pump body 1 of the high-pressure pump with the components mounted thereon, as described above.

Modification-

While the above embodiment has been described with respect to the case of applying the invention to the joining of the pump body 1 and the discharge plug 8d of the high-pressure pump, the same effect can be obtained by applying the invention to the joining of the pump body 1 and the discharge joint 12c of the high-pressure pump as described above. The present invention is not limited to the high-pressure pump, and other products may be used. For example, the same effect can be obtained by applying the present invention to a case where a fuel injection valve (the injector 24 of fig. 1, etc.) is assembled and joined by welding. Furthermore, a so-called normally open high-pressure pump is illustrated in fig. 1 to 7, but the invention can also be applied to normally closed high-pressure pumps.

In the above example, the through-welding is performed to a degree of 360 °, and an increase or decrease in the range of the through-welding, for example, about 360±5°, is allowable. The reason for this is that the molten pool formed by the laser beam LB is not a dot but a solid having a circular cross-section of a volume. Thus, for example, the energy of the laser beam LB may be suddenly reduced to a non-penetrating energy at a position where 355 ° penetration welding is performed while suppressing the penetration welding range to about 355 °. Further, the example in which the surface welding beads 415 are overlapped by 30 ° or more is described, but this overlapping amount is considered to be an appropriate example, and the design of the overlapping amount OL2 of the surface welding beads 415 may be changed as appropriate.

Symbol description

1 … pump body, 8d … bleed plug (assembled component, body of bleed valve), 12c … bleed fitting (assembled component), 411 … back bead start, 415 … surface bead, 416 … back bead, a … 1 st component, B … 2 nd component, BW1, BW2 … back bead width, LB … laser, OL1, OL2 … overlap, WM … weld metal, Φ … azimuthal range.

Claims (7)

1. A two-component joint, comprising:

a 1 st member having a through hole;

a 2 nd member inserted into the through hole of the 1 st member; and

a ring-shaped weld metal formed on the facing portions of the 1 st member and the 2 nd member, for joining the 1 st member and the 2 nd member,

the amount of overlap between the beginning and the end of the back bead of the weld metal is smaller than the width of the back bead.

2. A two-part joint according to claim 1, wherein,

the amount of overlap between the beginning and end of the surface bead of the weld metal is greater than the width of the surface bead.

3. A two-part joint according to claim 2, wherein,

the overlapping portion of the through-welded portion on which the back bead is formed and the distal end portion of the surface bead is in an azimuth range of 30 degrees or more from the start end to the end with respect to the center of the annular weld metal.

4. A two-part joint according to claim 3, wherein,

the fusion depth of the overlapping portion between the penetration weld and the distal end portion of the surface bead becomes shallow toward the distal end.

5. A two-part joint according to claim 1, wherein,

the 1 st component is a pump body of a high-pressure fuel pump,

the 2 nd part is a part assembled on the pump body.

6. A two-part joint according to claim 5, wherein,

the 2 nd component is the main body of the discharge valve.

7. A method for producing a joined body, which is the two-component joined body according to claim 2, characterized in that,

moving the laser beam from the start of the surface bead along the facing portion of the 1 st member and the 2 nd member while increasing energy,

the laser beam is made to surround 1 turn by holding the penetrating energy along the facing portions of the 1 st member and the 2 nd member from the start end of the back bead, where the energy of the laser beam reaches the penetrating energy set to form the back bead,

when reaching the end of the back bead, switching the energy of the laser to a set non-penetrating energy which does not form the back bead,

then, while lowering the energy from the non-penetrating energy, moving the laser beam along the facing portions of the 1 st member and the 2 nd member,

when the laser reaches the end of the surface bead, the irradiation of the laser is stopped to complete the welding.