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CN-116234979-B - Method for assembling a fuel injector and tool for use in the method

CN116234979BCN 116234979 BCN116234979 BCN 116234979BCN-116234979-B

Abstract

The invention relates to a method for assembling a fuel injector (1) comprising a holding body (2) and a nozzle body (4), wherein a clamping shoulder (8) is formed at the transition of the stem (6) to the nozzle collar (5). The holding body (2) and the nozzle body (4) are clamped by a nozzle clamping nut (7). For assembling the fuel injector, the assembly tool (16) is pushed onto the stem (6) of the nozzle body (4) up to the clamping surface (4) of the nozzle body (4). Then, a pretensioning force (Fa) is applied to the nozzle body (4) by means of the assembly tool (16), so that the nozzle body (4) is pressed at least indirectly against the holding body (2), wherein the assembly tool (16) clamps the stem (6) of the nozzle body (4). Subsequently, the nozzle clamping nut (7) is screwed on until a defined contact pressure of the nozzle body (4) on the holding body (2) is reached. The clamping tool (16) used has a hollow cylindrical receptacle (17) for the stem (6) of the nozzle body (4), wherein the wall of the cylindrical receptacle (17) is designed such that it deforms inwardly when a longitudinal force is applied to the clamping tool (16).

Inventors

  • LEUKART MICHAEL
  • A. HAUG

Assignees

  • 罗伯特·博世有限公司

Dates

Publication Date
20260505
Application Date
20210707
Priority Date
20200730

Claims (12)

  1. 1. A method for assembling a fuel injector (1) comprising a holding body (2) and a nozzle body (4), wherein the outer side of the nozzle body (4) is rotationally symmetrical and has a larger diameter nozzle collar (5) and a smaller diameter rod (6), wherein a clamping shoulder (8) is formed at the transition of the rod (6) to the nozzle collar (5), and the fuel injector has a nozzle clamping nut (7) which can be screwed with an internal thread (10) into an external thread (11) on the holding body (2), wherein the nozzle clamping nut (7) is supported on the clamping shoulder (8) such that the nozzle body (4) is clamped at least indirectly against the holding body (2), It is characterized in that the method comprises the steps of, Providing the stem (6) of the nozzle body (4) with an assembly tool (16) having a receiving portion (17), Inserting the assembly tool (16) over the stem (6) of the nozzle body (4) until the assembly tool (16) rests against the clamping surface (13) of the nozzle body (4), Applying a pretension (F a ) to the nozzle body (4) by means of the assembly tool (16) such that the nozzle body (4) is pressed at least indirectly against the holding body (2), wherein the assembly tool (16) is configured such that it is deformed inwardly by the pretension (F a ) and thus grips the stem (6) of the nozzle body (4), -Screwing the nozzle clamping nut (7) until a defined pressing force is reached between the nozzle body (4) and the retaining body (2).
  2. 2. Method according to claim 1, characterized in that the nozzle body (4) is clamped by the assembly tool (16) such that the assembly tool (16) receives the torque transmitted by the nozzle clamping nut (7) onto the nozzle body (4) such that the nozzle body (4) does not rotate relative to the holding body (2) when screwing the nozzle clamping nut (7) until a defined pressing force is reached.
  3. 3. Method according to claim 1 or 2, characterized in that the assembly tool (16) is placed on a clamping surface (13) on the nozzle body (4), which clamping surface is formed at a circumferential flange (14) on the stem (6) of the nozzle body (4).
  4. 4. A method according to claim 3, characterized in that the receiving portion (17) of the assembly tool (16) is configured hollow-cylindrically and is concavely arched inwardly on the inside.
  5. 5. The method according to claim 1 or 4, characterized in that the assembly tool (16) is concavely arched inwardly on its outer side.
  6. 6. A method according to claim 3, characterized in that a hollow cylindrical intermediate piece (19) is introduced between the stem (6) of the nozzle body (4) and the assembly tool (16) before the assembly tool (16) is pressed, wherein clamping forces are transmitted between the assembly tool (16) and the stem (6) through the intermediate piece (19).
  7. 7. Method according to claim 6, characterized in that the intermediate piece (19) is conically configured on its inner side and/or outer side.
  8. 8. Method according to claim 6 or 7, characterized in that the assembly tool (16) is conically shaped on its inner side.
  9. 9. An assembly tool for use in a method according to any one of claims 1 to 8, characterized in that the assembly tool (16) has a hollow cylindrical receptacle for the stem (6) of the nozzle body (4), and that the walls of the hollow cylindrical receptacle are configured such that the inner walls of the hollow cylindrical receptacle deform inwardly upon application of a longitudinal force to the assembly tool (16).
  10. 10. Assembly tool according to claim 9, characterized in that the wall of the assembly tool (16) has a recess or groove on the outside.
  11. 11. The assembly tool according to claim 9, characterized in that the wall of the assembly tool (16) has a groove on the outside.
  12. 12. Assembly tool according to claim 9, characterized in that the hollow cylindrical receiving portion of the assembly tool (16) is constituted by an inner cylinder (21) and an outer cylinder (22) which are fixedly engaged with each other, wherein the inner cylinder (21) is constituted by a material having a lower modulus of elasticity than the outer cylinder (22).

Description

Method for assembling a fuel injector and tool for use in the method Technical Field The present invention relates to a method for assembling a fuel injector, for example for introducing fuel under high pressure into a combustion chamber of an internal combustion engine. The invention further relates to an assembly tool for use in the method according to the invention. Background A fuel injector, such as a fuel injector for injecting fuel under high pressure, is composed of a plurality of components, typically a holder and a nozzle. The nozzle contains an injection opening through which fuel is introduced into the combustion chamber. The nozzle is produced as a separate component and is screwed to the holder by a clamping nut. Since fuel is present in the holding body and the nozzle at a pressure of up to 2700bar (270 MPa), the sealing surfaces between the nozzle and the holding body must be reliably sealed so that fuel does not escape during operation of the fuel injector. For this purpose, the nozzle is clamped against the holding body by means of a nozzle clamping nut, so that the nozzle body is pressed against the holding body with a large force, which results in the required tightness. The nozzle clamping nut surrounds the nozzle body and rests against a shoulder on the outside of the nozzle body. In order to ensure precise positioning of the nozzle body in the rotational direction relative to the holder body, one or more clamping pins are provided which extend partially into the holder body and partially into the nozzle, so that precise positioning is ensured during assembly. However, by tightening the nozzle clamping nut, a torque is applied to the nozzle with the holding body fixed, so that the clamping pin, which should hold the nozzle in its position relative to the holding body, is subjected to a strong mechanical load. This can lead to overload of the clamping pin and the nozzle body, especially when the fuel injector is operated for a long period of time, ultimately leading to failure of the fuel injector. In order to avoid this, a method is known from EP 1 399 668 B1, in which the nozzle body is preloaded against the holding body in the longitudinal direction by means of a clamping tool. In this case, the nozzle body is pressed against the holding body with a large axial force, so that the nozzle clamping nut can be screwed down without applying a torque to the nozzle body or only with such a small torque that the nozzle body does not move relative to the holding body. Subsequently, the clamping tool is removed, wherein the nozzle body is held in its position by the nozzle clamping nut and clamped against the holding body. However, in some applications it has been shown that the necessary axial force with which the nozzle body must be pressed against the holding body is too high. The torque introduced by the nozzle clamping nut cannot be avoided, which in turn leads to the above-mentioned problems when assembling the fuel injector. Disclosure of Invention The invention has the advantages that: the assembly method according to the invention for a fuel injector has the advantage that the assembly of a high-pressure seal of the fuel injector can be achieved without overloading the clamping pin or other means during assembly, which avoids breakage or failure of the injector during operation. The assembly method is carried out on a fuel injector comprising a holder body and a nozzle body, wherein the outer side of the nozzle body is rotationally symmetrical and has a nozzle collar with a larger diameter and a rod with a smaller diameter. In this case, a clamping shoulder is formed at the transition from the stem to the nozzle collar. Furthermore, the fuel injector comprises a nozzle clamping nut which is screwed with an internal thread into an external thread on the holding body, wherein the nozzle clamping nut is supported on the clamping shoulder such that the nozzle body is clamped at least indirectly against the holding body. The assembly tool used in the method has a receptacle for the stem of the nozzle body and is pushed onto the stem of the nozzle body until the assembly tool rests against the clamping surface of the nozzle body. The nozzle body is then pressed against the holding body at least indirectly by means of an assembly tool, which clamps the stem of the nozzle body laterally. Subsequently, the nozzle clamping nut is screwed on until a defined pressing force is reached between the nozzle body and the holding body. An axial force is applied to the nozzle body in the direction of the holding body by means of a clamping tool, so that the nozzle body is held in the assembly position, wherein the assembly tool also laterally clamps the stem of the nozzle body. As a result, the assembly tool can receive a significantly greater torque acting on the nozzle body than in the case of axial compression alone. If the nozzle clamping nut is now screwed down, the nozzle clamping nut applies a tor