Fuel Injectors

Abstract

The injector comprises a tubular nozzle body (1) having a nozzle side (1b) and an actuator side (1a), the nozzle side (1b) receiving a needle valve member (2), the actuator side (1a) receiving a tubular magnetic armature (3) and receiving an armature side (4b) of a tubular pole piece (4) above the magnetic armature, wherein the nozzle body and the pole piece are welded together by a seam weld line (5, 5a) between a tubular inner surface (6) of the actuator side (1a) of the tubular nozzle body (1) and a tubular outer surface (7) of the armature side (4b) of the pole piece (4), wherein the actuator side (1a) of the tubular nozzle body comprises a constriction area (8) and the outer surface of the armature side (4b) of the pole piece comprises a recessed area (9, 10), such constriction area (8) and such recessed area (9, 10) contact each other at the level of the seam weld line and provide a friction area for transferring hydraulic loads away from the seam weld line.

Description

Technical Field

[0001] The present invention relates to fuel injectors for internal combustion engines designed to withstand internal gasoline pressures above 300 bar. Background Art

[0002] The assembly of the injector generally comprises attaching a tubular pole piece and a tubular nozzle body. The first type of design, in which the end of the pole piece is received in the end of the nozzle body, uses an annular weld in which a continuous annular weld line is located between the inner surface of the nozzle body and the outer surface of the pole piece. The welding is done by means of a laser beam through the tubular nozzle body. This welding method is hereinafter referred to as a seam weld. In the second type of design, the annular end of the nozzle body is butt welded face to face with the annular end of the pole piece.

[0003] Both welding methods provide a sealed joint between the two parts in order to withstand the gasoline pressure inside the injector. Butt welding is stronger than seam welding, but is more difficult to perform because the position of the laser welding the ends of the two parts must be more accurate.

[0004] In gasoline engines, the injector can be held into the cylinder head by spring compression and connected to the supply rail by a fluid-tight connection without mechanical locking. The injector can also be fixed to the supply rail and inserted into the hole of the cylinder head without mechanical locking to the cylinder head. In the case of butt welding, the hydraulic load creates tensile stresses on the weld line. In the case of seam welding, the hydraulic load inside the injector provides shear forces on the weld line. The shear forces lead to reduced weld line durability, which reduces the hydraulic pressure that a seam welded injector can withstand compared to a butt welded injector.

[0005] As a result, injectors that use seam welding to attach the pole piece to the injector body are more limited in pressure than injectors that butt weld these parts. Current designs of seam welded injectors are limited to pressures of around 250 bar and cannot be used in high pressure gasoline injection systems, such as 350 bar pressure injection systems, particularly when the injector is attached to an injection rail system and received in a bore of a cylinder head without being secured to said cylinder head. Summary of the invention

[0006] The present invention aims to increase the pressure that can be withstood by an injector in which the pole piece and the injector body are seam welded.

[0007] More precisely, the invention relates to an injector comprising a tubular nozzle body having a nozzle side and an actuator side, the nozzle side receiving a needle valve member, the actuator side receiving a tubular magnetic armature and receiving an armature side of a tubular pole shoe above the magnetic armature, wherein the nozzle body and the pole shoe are welded together by a seam weld line between a tubular inner surface of the actuator side of the tubular nozzle body and a tubular outer surface of the armature side of the pole shoe, and wherein the actuator side of the tubular nozzle body comprises a constriction area and the outer surface of the armature side of the pole shoe comprises a recessed area, such constriction area and such recessed area being in contact with each other at the level of the seam weld line and providing a friction area that reduces the hydraulic load on the seam weld line.

[0008] Providing the constricted area and the recessed area at or around the weld line provides a retaining force around the weld line so that the injector can withstand higher hydraulic pressures inside the injector.

[0009] Among the implementation modes that can be used alone or in combination:

[0010] The recessed area may be formed by chamfering the outer surface of the tubular pole piece in the axial direction from the nozzle to the inlet, the diameter of the tubular pole piece decreasing in the axial direction from the nozzle to the inlet.

[0011] Along the nozzle to inlet axis, the armature side of the pole piece may include a first diameter and a second diameter above the first diameter, the first diameter providing a contact surface with the inner diameter of the actuator side of the tubular nozzle, the second diameter being smaller than the first diameter and forming the recessed area.

[0012] The constriction region provided at the upper end of the actuator side of the tubular nozzle body may reduce the diameter of the nozzle body toward the top of the actuator side of the nozzle body until the top of the actuator side of the nozzle body.

[0013] The constricted area and the recessed area may extend around the seam weld line.

[0014] The seam weld line may be provided at an actuator-side upper end of the tubular nozzle body and may terminate the constriction region.

[0015] The seam weld line may be a continuous annular weld line.

[0016] The present disclosure also relates to a method for manufacturing an injector as described above, the method comprising: applying pressure on at least a portion of the top end of the nozzle body using a tool adapted to apply a preload on the upper end of the actuator side of the nozzle body while laser welding the nozzle body and the pole shoe.

[0017] The tool may press the actuator-side upper end of the nozzle body to deform the tip of the nozzle body in a centripetal direction into the contraction area during laser welding of the nozzle body and the pole piece until the contraction area contacts the concave area of ​​the pole piece.

[0018] The tool may have a tubular wall provided with an inner tapered end which presses against the upper end of the actuator side of the nozzle body, and wherein the tool, nozzle body and pole piece are rotated about a common axis during laser welding while the beam of the laser is fixed to provide the annular seam weld line and the contraction area in contact with the recessed area.

[0019] The tool may include at least one roller that presses said upper end of the actuator side of the nozzle body while the nozzle body and the pole piece rotate about a common axis during laser welding, and the beam of the laser is fixed, thereby providing said annular seam weld line and said constriction area in contact with said recessed area. In a preferred mode, the tool includes three rollers to balance the pressure around the injector. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] A detailed description of exemplary embodiments of the present invention will now be discussed with reference to the accompanying drawings, in which:

[0021] Figure 1 shows a longitudinal cross-sectional view of an ejector according to the present disclosure;

[0022] Figure 2A Shows details of the first embodiment before welding;

[0023] Figure 2B Shown after welding Figure 2A the implementation method;

[0024] Figure 2C shows details of the second embodiment before welding;

[0025] Figure 2D Shown after welding Figure 2C the implementation method;

[0026] Figure 2E shows details of the third embodiment after welding;

[0027] Figure 3 shows a longitudinal cross-sectional view of a portion of an injector during a first embodiment of the welding process of the present disclosure;

[0028] Figure 4 A microscopic view of a section at the level of a seam weld joint is shown;

[0029] Figure 5shows a schematic side view of a portion of an injector during a second embodiment of the welding process of the present disclosure;

[0030] Figure 6 Shows Figure 5 Schematic diagram of a part of the injector from the top during the welding process. DETAILED DESCRIPTION

[0031] The present invention relates to an electromagnetic injector, in particular an injector for a gasoline engine, wherein the injection pressure is in the range of 200 to 400 bar. Figure 1 Such an injector shown in a longitudinal cross-sectional view of comprises an electromagnetic actuator having an actuator body 15, a solenoid 11, a tubular magnetic armature 3 and a tubular pole shoe 4. The electromagnetic actuator actuates a needle valve member 2 biased by a needle valve member core spring to inject gasoline into a cylinder of an engine. The needle valve member and the core spring are located in an axial bore 16 of the injector.

[0032] The bottom portion of the needle valve member is received in the tubular nozzle body 1. The tubular nozzle body has an enlarged upper portion or actuator side 1a which accommodates the tubular magnetic armature 3 and the bottom portion 4b of the pole shoe 4. The bottom portion of the pole shoe accommodates the head 2a of the needle valve member, its core spring 14 and the calibration sleeve 21.

[0033] In the design, the actuator side 1a of the nozzle body 1 is surrounded by the solenoid assembly 11. The pole piece 4 includes an upper portion that extends above the middle portion and provides an inlet for gasoline in the injector. This upper portion or inlet side 4a of the pole piece is introduced into a dispensing pipe, not shown, and receives a sealing gasket 17 to provide a leak-proof fluid connection.

[0034] The injector also comprises a sleeve 23 provided with an electrical connector held by a weld.Another configuration of the pole piece is possible, depending on the type of petrol distribution system.

[0035] The inlet side 4 a of the pole piece 4 may also comprise attachment means, such as holes 12 , to a petrol distributor circuit.

[0036] On the nozzle side 1 b of the nozzle body, a ball 19 and a nozzle 20 are provided below the needle valve member 2 .

[0037] Such injectors must prevent leakage at internal gasoline pressures from 200 bar to approximately 400 bar. Figure 1, fluid enters the injector from the inlet side 4a of the pole piece, which is the top side of the axial hole 16 in the pole piece. When the needle valve member is extended under the force of the spring 14, the fluid flows around the needle valve member and down to the ball 19 and is held under pressure. When the needle valve member is retracted when the solenoid 11 is energized, the gasoline leaves the injector through the nozzle 20. In the design of the present invention, the assembly of the pole piece and the nozzle body must withstand the pressure of the gasoline inside the injector, which results in hydraulic loads on the interface between these components.

[0038] Assembly of the injector may include positioning the tubular magnetic armature 3, the nozzle 20 with the ball 19, the needle valve member 2 in the tubular nozzle body, positioning the pole shoe with the needle valve member core spring 14 and the calibration sleeve 21 in the pole shoe, and assembling the equipped pole shoe and tubular nozzle body.

[0039] Assembling the nozzle body and the pole piece is done at the armature side 4b of the pole piece and the actuator side 1a of the nozzle body. This assembly of the actuator side 1a of the tubular nozzle body 1 and the armature side 4b of the pole piece 4 is done by welding these parts together, as shown in FIG. Figure 3 Schematically, Figure 3 A simplified cross-section of the welding area is shown. The welding is laser beam welding W wherein the nozzle body and pole piece are rotated about a common axis A in front of a stationary laser 22, thereby providing a seam weld line 5 which may be a continuous weld line, preferably an annular weld line.

[0040] Figure 4 A microscopic view of a section of material at the level of a weld line 5 between a tubular inner surface 6 of the tubular nozzle body near the actuator side 1 a of the tubular nozzle body and a tubular outer surface 7 of the armature side 4 b of the pole piece 4 is shown.

[0041] According to the present disclosure, the upper end or actuator side 1a of the tubular nozzle body includes a constricted region 8, while the outer surface of the bottom portion or armature side 4b of the pole piece includes a concave region.

[0042] The contraction region refers to the portion of the tubular body having reduced outer and inner diameters. Figure 2B and Figure 2D In the example of , the constriction region is an annular region around the weld line between the pole piece and the nozzle body where the tubular nozzle body has a reduced diameter. Figure 2E In the example shown, the contraction area starts below the weld line and ends at the weld line.

[0043] A concave area refers to a portion of the outer surface of the pole shoe which has a locally reduced diameter or at least a locally reduced diameter.

[0044] Figure 2A and Figure 2CTwo possible types of recessed areas 9, 10 of the welding zone of the pole piece are shown.

[0045] exist Figure 2A In the embodiment, the recessed area is formed by chamfering 9 on the outer surface of the pole shoe in the welding area. Figure 2C In the embodiment, the recessed area is achieved by utilizing the reduced diameter area of ​​the tubular outer surface of the pole piece 4 in the welding area.

[0046] On the tubular nozzle body side, the upper end of the actuator side 1a of the nozzle body is straight before welding ( Figure 2A , Figure 2C in), and bending after welding (such as Figure 2B , Figure 2D ). This provides a contraction area 8 so that the contraction area 8 and the recessed areas 9, 10 surround the seam weld line 5, contact each other and provide a friction area. The friction area transfers the hydraulic load or pressure inside the injector away from the seam weld line, which allows for higher fluid pressures in the injector and injection circuit, while the weld line provides a leak-proof seal for the injector.

[0047] With this configuration, the permissible pressure can be increased to above 350 bar, whereas similar ejectors without such friction areas are typically limited to approximately 250 bar.

[0048] In the following paragraphs, the ejector is Figure 1 As shown, its nozzle side is at the bottom and its inlet side is at the top. The words bottom, below and top, above refer to such an orientation.

[0049] return Figure 2A The chamfer 9 of the tubular outer surface starts below the seam weld line and continues along Figure 3 The longitudinal axis direction A of the tubular pole piece shown ends above the seam weld line, and the tubular pole piece has a diameter that decreases in a bottom-to-top direction (ie, nozzle-side to inlet-side direction) around the annular weld line.

[0050] Return with Figure 3 Corresponding Figure 2C , the pole shoe has a first diameter 4a below the seam weld line, the first diameter providing a contact surface with the inner diameter of the actuator side of the tubular nozzle, and a second diameter 4b above the first diameter, the second diameter being smaller than the first diameter and forming the recessed area 10. Here, too, the recessed area extends from below the seam weld line to above the weld line.

[0051] With this design, a constriction region 8 provided at the upper end of the actuator side 1 a of the tubular nozzle body reduces the diameter of the nozzle body towards the upper end, up to the upper end.

[0052] This design is of particular concern when the injector is "hung" on the gasoline distribution system, which means that the injector is fixed to the gasoline distribution system and the nozzle side 1b of the nozzle body is inserted into the hole of the cylinder head without axial locking. In this case, the internal pressure in the injector is not offset by this axial locking.

[0053] To provide the constriction region, the method used in the present disclosure includes applying a preload P using a tool 13 to the upper end of the actuator side 1 a of the nozzle body.

[0054] In the first embodiment of the present disclosure, Figure 3 As shown, the tool has a tubular wall provided with an inner tapered end 14 adapted to press the upper end of the nozzle body on the actuator side 1a to provide a preload during laser welding W of the nozzle body to the pole shoe, the preload being approximately 150 to 250 Newtons, preferably approximately 200 Newtons.

[0055] The inner tapered end portion presses the upper end of the nozzle body in a centripetal direction during laser welding W of the nozzle body and the pole piece. This deforms the top end of the nozzle body into the constricted area that contacts the concave area of ​​the pole piece.

[0056] As the parts rotate about axis A in front of the welding laser 22, the tool 13 rotates with the welded parts to avoid friction with the nozzle body. The preload is preferably maintained until the weld line is complete. This pressure, together with the laser welding heat, creates a constricted area at the end of the tubular nozzle body.

[0057] Using this process, a nozzle body end having a relatively thick wall (eg, a wall thickness between 0.45 mm and 1.0 mm, depending on material strength) can be shrunk without degrading the weld line between the nozzle body and the pole piece.

[0058] In accordance with Figure 5 and Figure 6 In another embodiment, the tool comprises rollers 25 separated by gaps to provide a path for the laser beam 22a. This embodiment with rollers is used when a simple tool as described above would cover the area to be welded. This is the case for welds near or at the edge of the upper side of the tubular nozzle body.

[0059] The gap separating the rollers allows the laser beam to be directed towards the upper end of the actuator side 1a of the tubular nozzle body. This allows welding of the pole piece and the nozzle body at the upper end of the nozzle body, such as Figure 2E In the embodiment shown, the concave area of ​​the pole shoe is as shown. Figure 2A The chamfer in Figure 2CThe constriction area 8a starts below the weld line and ends with the weld line 5a, and the friction area between the tubular nozzle body and the pole shoe ends with the weld line.

[0060] In this embodiment, the laser is fixed and the injector assembly rotates, which causes the roller 25 to apply pressure on the heated seam weld line 5a while rolling over the edge of the upper end of the tubular nozzle body. This pressure combined with the heat of the weld causes the upper end of the tubular nozzle body to deform and create a constriction area.

[0061] The rollers are made of a hard material such as steel or a material such as ceramic to limit heat losses at the point of contact with the edge of the upper end of the nozzle body.

[0062] The invention is not limited to the examples described above, in particular the configuration of the solenoid 11, whose housing and / or sleeve 23 may differ from the examples shown. In particular, although the description relates to laser welding, the welding process may use an electron beam welding process which also allows welding of components positioned side by side.

[0063] Reference numerals list

[0064] 1- Tubular nozzle body

[0065] 1a - Actuator side of tubular nozzle body

[0066] 1b - Nozzle side of tubular nozzle body

[0067] 2- Needle valve component

[0068] 2a- Head of needle valve member

[0069] 3- Tubular magnetic armature

[0070] 4- Pole Shoes

[0071] 4a - Inlet side of pole piece

[0072] 4b - Armature side of pole piece

[0073] 5- Seam welding line

[0074] 5a- End seam weld line

[0075] 6- Tubular inner surface of the tubular nozzle body

[0076] 7- The tubular outer surface of the bottom portion

[0077] 8, 8a - Contraction area

[0078] 9, 10- Recessed area

[0079] 11- Solenoid

[0080] 12- Hole

[0081] 13- Tools

[0082] 14- Needle valve member core spring

[0083] 15- Actuator body

[0084] 16- Axial hole

[0085] 17- Sealing gasket

[0086] 18- Spring clamp

[0087] 19- Ball

[0088] 20- Nozzle

[0089] 21- Calibration sleeve

[0090] 22- Welding laser

[0091] 22a- Laser beam

[0092] 23- Sleeve

[0093] 24a- First diameter

[0094] 24b - Second diameter

[0095] 25- Roller

[0096] A- Public axis

[0097] P - Preload

[0098] R - Rotate

[0099] W - Welding

Claims

1. An injector, comprising a tubular nozzle body (1), the tubular nozzle body (1) having a nozzle side (1b) and an actuator side (1a), the nozzle side (1b) receiving a needle valve member (2), the actuator side (1a) receiving a tubular magnetic armature (3) and receiving an armature side (4b) of a tubular pole piece (4) above the tubular magnetic armature, wherein: The tubular nozzle body and the tubular pole shoe are welded together via a seam welding line (5, 5a) between the tubular inner surface (6) of the actuator side (1a) of the tubular nozzle body (1) and the tubular outer surface (7) of the armature side (4b) of the tubular pole shoe (4), characterized in that the actuator side (1a) of the tubular nozzle body includes a contraction area (8), while the tubular outer surface of the armature side (4b) of the tubular pole shoe includes a recessed area (9, 10), the contraction area (8) and the recessed area (9, 10) contact each other at the level of the seam welding line and provide a friction area for reducing the hydraulic load on the seam welding line.

2. The injector according to claim 1, wherein: The recessed area is formed by chamfering the tubular outer surface of the tubular pole piece (4) along the axial direction (A) from the nozzle to the inlet, and the diameter of the tubular pole piece decreases along the axial direction (A) from the nozzle to the inlet.

3. The injector according to claim 1, wherein: Along the axial direction (A) from the nozzle to the inlet, the armature side (4b) of the tubular pole piece (4) includes a first diameter and a second diameter above the first diameter, wherein the first diameter provides a contact surface with the inner diameter of the actuator side (1a) of the tubular nozzle body, and the second diameter is smaller than the first diameter and forms the recessed area.

4. The injector according to any one of claims 1 to 3, wherein: The contraction area (8) provided at the upper end of the actuator side (1a) of the tubular nozzle body reduces the diameter of the tubular nozzle body toward the top of the actuator side (1a) of the tubular nozzle body until the top of the actuator side (1a) of the tubular nozzle body.

5. The injector according to claim 4, wherein: The constricted area and the recessed area extend around the seam weld line.

6. The injector according to claim 4, wherein: The seam weld line is provided at the upper end of the actuator side (1a) of the tubular nozzle body and terminates the constriction region (8).

7. The injector according to any one of claims 1 to 3, wherein: The seam weld line is a continuous annular weld line.

8. A method of manufacturing an injector, the injector being an injector according to any one of the preceding claims, characterized in that The method comprises: while laser welding (W) the tubular nozzle body and the tubular pole shoe, applying pressure (P) on the top end of the tubular nozzle body (1) using a tool (13) adapted to apply a preload on the upper end of the actuator side (1a) of the tubular nozzle body, wherein the tool presses the upper end of the actuator side of the tubular nozzle body during laser welding of the tubular nozzle body and the tubular pole shoe so that the top end of the tubular nozzle body (1) is deformed into the contraction area (8) in the centripetal direction until the contraction area contacts the recessed area (9, 10) of the tubular pole shoe (4).

9. The method for manufacturing an injector according to claim 8, wherein: The tool has a tubular wall provided with an inner tapered end which presses against the upper end of the actuator side of the tubular nozzle body, and wherein the tool, the tubular nozzle body and the tubular pole piece are rotated about a common axis during the laser welding (W) while the beam of the laser (22) is fixed to provide the seam weld line and the constricted area (8) in contact with the recessed areas (9, 10).

10. The method for manufacturing an injector according to claim 8, wherein: The tool comprises at least one roller which presses the upper end of the tubular nozzle body on the actuator side while the tubular nozzle body and the tubular pole piece are rotated about a common axis during the laser welding (W), and the beam of the laser (22) is fixed, thereby providing the seam weld line and the constricted area (8) in contact with the recessed areas (9, 10).

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