JP2006029259A - Fuel injection valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve durability of the welded part of an upper casing to an injection valve body. <P>SOLUTION: In a fuel injection valve, the upper end part of the injection valve body 1 has a cylindrical inner peripheral surface 8 and an annular upper end face 9, and the lower end part 10 of an upper casing 2 has a cylindrical protrusion part 11 and an annular lower end face 12. The cylindrical inner peripheral surface 8 of the upper end part 7 of the injection valve body is pressed in the surroundings of the cylindrical protrusion part 11 of the lower end part 10 of the upper casing, and the annular upper end face 9 of the injection valve body upper end part 7 and the the annular lower end face 12 of the upper casing lower end part 10, which are butted against each other, are welded to each other for jointing with each other. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel injection valve for an internal combustion engine.

In order to reduce the manufacturing cost, a fuel injection valve in which components are joined to each other by welding is known (see, for example, Patent Document 1).
JP 2002-48032 A

  By the way, when the engine is repeatedly operated, the fuel pressure in the fuel injection valve repeatedly becomes high, and when the fuel pressure in the fuel injection valve becomes repeatedly high, a large stress is repeatedly generated in the welded joints of the respective parts. In this case, when the fuel pressure repeatedly generated in the fuel injection valve becomes a high pressure of 10 MPa or more, and in some cases 100 MPa or more, the stress repeatedly generated in the weld joint becomes extremely large, and as a result, a crack occurs in the weld joint, At the end, there is a problem that the welded joint is destroyed.

  In order to solve the above problems, according to the present invention, an injection valve main body that accommodates a needle valve, and an upper portion that is attached to an upper end portion of the injection valve main body and in which fuel pressure acts in a direction away from the injection valve main body. A fuel injection valve comprising a casing, wherein the upper end of the injection valve main body extends around the central axis of the injection valve main body, and outwards at a right angle from the upper edge of the cylindrical inner peripheral surface. A cylindrical annular protrusion having a flat annular upper end surface extending to the upper casing, the lower end of the upper casing being formed at the center of the lower end, and an outer side substantially perpendicular to the root of the cylindrical protrusion. The cylindrical inner peripheral surface of the upper end portion of the injection valve body is press-fitted around the cylindrical projection of the lower end portion of the upper casing, and the annular upper surface of the upper end portion of the injection valve body that is abutted with each other Annular below the end face and the lower end of the upper casing It is welded to the surface.

  Stress generated at the welded joint between the injection valve body and the upper casing when the fuel pressure in the injection valve body becomes high by press-fitting the cylindrical inner peripheral surface of the upper end of the injection valve body around the cylindrical projection Can be reduced, thereby preventing the weld joint from breaking.

  Referring to FIG. 1 showing the upper part of the fuel injection valve, 1 is an injection valve body, and 2 is an upper casing attached to the upper end of the injection valve body 1. A cylindrical inner chamber 3 filled with high-pressure fuel is formed in the injection valve main body 1, and a pair of cores (not shown) having a needle valve (not shown) and a solenoid (see FIG. (Not shown) is housed. High pressure fuel is supplied into the inner chamber 3 via a fuel supply passage 4 formed in the upper casing 2, and the upper casing 2 is separated from the injection valve body 1 in the direction of separating the upper casing 2 from the injection valve body 1. Fuel pressure acts. Reference numeral 5 denotes a connector for supplying power to the solenoid.

  As shown in FIG. 1, in this embodiment, the upper portion 6 of the injection valve body 1 is formed of a thin hollow cylindrical body. On the other hand, the inner diameter of the upper end portion 7 of the injection valve main body 1 is the same as the inner diameter of the upper portion 6 of the injection valve main body 1, but the outer diameter is larger than the outer diameter of the upper portion 6 of the injection valve main body 1. The upper end portion 7 of the injection valve main body 1 is formed thicker than the upper portion 6. As can be seen from FIG. 1, the upper end portion 7 of the injection valve main body 1 is formed at a right angle from the cylindrical inner peripheral surface 8 extending around the central axis of the injection valve main body 1 and the upper edge of the cylindrical inner peripheral surface 8. It has a flat annular upper end surface 9 extending outward.

  On the other hand, a lower end portion 10 of the upper casing 2 has a cylindrical projection 11 formed at the center of the lower end portion 10 and a flat annular shape extending outwardly at a right angle from the root portion of the cylindrical projection 11. And a lower end surface 12. In addition, the lower end surface 13 of the cylindrical protrusion 11 is formed flat, and the outer peripheral surface 14 of the cylindrical protrusion 11 is formed in a cylindrical shape. As can be seen from FIG. 2 (A) showing an enlarged view of the portion A in FIG. 1, the connecting portion 15 between the annular lower end surface 12 and the cylindrical outer peripheral surface 14 of the upper casing lower end portion 10 is rounded, and injection is performed. The connecting portion 16 between the cylindrical inner peripheral surface 8 and the annular upper end surface 9 of the upper end portion 7 of the valve body is chamfered at least necessary to avoid contact with the rounded portion 15. The chamfered portion 16 is substantially 45 degrees with respect to the annular upper end surface 9 and the cylindrical inner peripheral surface 8.

  Next, a method for fixing the upper casing 2 to the upper end portion 7 of the injection valve body 1 will be described. In the present invention, first, the cylindrical inner peripheral surface 8 of the upper end portion 7 of the injection valve body is press-fitted around the cylindrical projection 11 of the lower end portion 10 of the upper casing. In this case, in the embodiment according to the present invention, the press-fitting allowance of the cylindrical inner peripheral surface 8 to the cylindrical protrusion 11 is the radial expansion of the cylindrical inner peripheral surface 8 when the maximum fuel pressure is applied in the injection valve body 1. It is set almost equal to the amount. Next, after press-fitting, the annular upper end surface 9 of the injection valve main body upper end portion 7 and the annular lower end surface 12 of the upper casing lower end portion 10 which are abutted to each other as shown by the thick black line 17 are welded. This welding operation is performed, for example, by irradiating the joint portion between the injection valve main body 1 and the upper casing 2 with laser or the like from the outside over the entire circumference.

  Usually, when the injection valve main body upper end portion 7 as shown in FIG. 1 is welded to the upper casing 2, the cylindrical inner peripheral surface 8 of the injection valve main body upper end portion 7 is fitted into the cylindrical projection 11, Next, as shown by reference numeral 17, welding is performed. In this case, when a high fuel pressure is applied to the inner chamber 3, the upper portion 6 of the injection valve main body 1 expands radially outward. As a result, the cylindrical inner peripheral surface 8 of the upper end portion 7 of the injection valve body is separated from the cylindrical outer peripheral surface 14 of the cylindrical protrusion 11, and a counterclockwise moment acts on the welded portion 17 in FIG. become.

  When a counterclockwise moment acts on the welded portion 17 in this way, tensile stress is generated at the inner end portion of the welded portion 17. Therefore, when the engine is repeatedly operated and the fuel pressure in the inner chamber 3 is repeatedly increased, a large tensile stress is repeatedly generated at the inner end portion of the welded portion 17, and as a result, a crack is generated at the inner end portion of the welded portion 17. At the end, the weld 17 is destroyed.

  On the other hand, in the present invention, the cylindrical inner peripheral surface 8 of the upper end portion 7 of the injection valve body is press-fitted around the cylindrical protrusion 11 of the upper casing lower end portion 10, and the cylindrical inner surface with respect to the cylindrical protrusion 11 is further increased. The press-fitting allowance of the peripheral surface 8 is set substantially equal to the amount of expansion in the radial direction of the cylindrical inner peripheral surface 8 when the maximum fuel pressure is applied in the injection valve body 1. In this way, when the cylindrical inner peripheral surface 8 of the upper end portion 7 of the injection valve body is press-fitted around the cylindrical projection 11, the stress state is completely different from the case of the normal clearance fit as described above.

  That is, when the cylindrical inner peripheral surface 8 of the upper end portion 7 of the injection valve body is press-fitted around the cylindrical projection 11 of the lower end portion 10 of the upper casing 10, the upper end portion 7 of the injection valve body is expanded in the radial direction, as described above. The annular upper end surface 9 of the injection valve main body upper end portion 7 is welded to the annular lower end surface 12 of the upper casing lower end portion 10 in a state where the injection valve main body upper end portion 7 is expanded in the radial direction.

  Now, when the fuel pressure in the internal chamber 3 increases, the upper portion 6 of the injection valve main body 1 expands radially outward. However, as described above, the press-fitting allowance of the cylindrical inner peripheral surface 8 to the cylindrical protrusion 11 is substantially equal to the amount of expansion in the radial direction of the cylindrical inner peripheral surface 8 when the maximum fuel pressure is applied to the injection valve body 1. Therefore, the upper end portion 7 of the injection valve main body 7 is radially outward with the amount of expansion when the fuel pressure in the inner chamber 3 reaches the maximum regardless of whether the fuel pressure in the inner chamber 3 is high or low. It is held in an expanded state. Therefore, even if the fuel pressure in the inner chamber 3 increases and the upper portion 6 of the injection valve body 1 expands radially outward, the upper end portion 7 of the injection valve body is held in a state where it is press-fitted without further expansion. The Accordingly, no moment is applied to the welded portion 17 and no tensile stress is generated at the inner end portion of the welded portion 17, so that the welded portion 17 is not destroyed.

  As described above, even if the fuel pressure in the inner chamber 3 increases, no moment is applied to the welded portion 17, but when the stress generated in the upper end portion 7 of the injection valve body is reduced by the creep phenomenon, the fuel in the inner chamber 3 is reduced. When the pressure is increased, the cylindrical inner peripheral surface 8 of the upper end portion 7 of the injection valve body is separated from the cylindrical outer peripheral surface 14 of the cylindrical protrusion 11, and a moment acts on the welded portion 17. In this case, in order to reduce the moment acting on the welded portion 17, it is only necessary to absorb the deformation of the upper portion 6 of the injection valve body so that the upper end portion 7 of the injection valve body around the welded portion 17 is not deformed. In the embodiment shown in B), an annular groove 19 having a rectangular cross section extending over the entire length is formed on the cylindrical outer peripheral surface 18 of the upper end portion 7 of the injection valve body.

It is side surface sectional drawing of a fuel injection valve upper part. It is an expanded sectional view of the A section shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Injection valve main body 2 Upper casing 3 Internal chamber 7 Upper end part 8 Cylindrical inner peripheral surface 9 Annular upper end surface 10 Lower end part 11 Cylindrical protrusion 12 Annular lower end surface 13 Lower end surface 14 Cylindrical outer peripheral surface 17 Welding part 18 Cylindrical outer periphery Face 19 annular groove

Claims (3)

  A fuel injection valve comprising: an injection valve body that houses a needle valve; and an upper casing that is attached to an upper end portion of the injection valve body and in which fuel pressure acts in a direction away from the injection valve body. An upper casing having a cylindrical inner peripheral surface whose upper end extends around the central axis of the injection valve main body, and a flat annular upper end surface extending outward at a substantially right angle from the upper edge of the cylindrical inner peripheral surface. An injection valve having a cylindrical protrusion formed at a central portion of the lower end, and a flat annular lower end surface extending substantially outward from the root of the cylindrical protrusion. The cylindrical inner peripheral surface of the upper end of the main body is press-fitted around the cylindrical projection of the lower end of the upper casing, and the annular upper end surface of the upper end of the injection valve body and the annular lower end surface of the lower end of the upper casing are welded together. Fuel injection valve.   The press-fitting allowance of the cylindrical inner peripheral surface to the cylindrical protrusion is set to be approximately equal to the radial expansion amount of the cylindrical inner peripheral surface when the maximum fuel pressure is applied in the injection valve body. The fuel injection valve according to 1.   In order to absorb the deformation of the injection valve body that occurs when fuel pressure is applied to the injection valve body, an annular groove extending over the entire length is formed on the cylindrical inner peripheral surface of the upper end portion of the injection valve body. Item 4. The fuel injection valve according to Item 1.

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