JP5094083B2 - Pressure tube with molded connection head - Google Patents

Description

  The present invention relates to a pressure tube with a molded connection head, and more particularly, to a high-pressure fuel injection tube with an upset connection head.

  The pressure pipe which is the subject of the present invention is used as a fuel injection pipe for supplying fuel to the fuel injection device, or is also used as a hydraulic pressure pipe. In order to hermetically connect the pressure tube to other components, the tip of the pressure tube is formed in a frustoconical shape. Conventionally, a cold forming method has been demonstrated as an inexpensive manufacturing example of such a connection head. For example, Patent Document 1 and Patent Document 2 show products by a conventionally known manufacturing method using a fuel pipe as an example.

  This prior art is also shown in the attached FIG. 1, which shows in cross-section the inside of a tube which has been deformed by swaging the frustoconical connection head and the pressure tube. In this conventional example, the parts to be connected to the pressure pipe are sealed by an inclined outer peripheral surface of the connection head and a cap nut (not shown). The cap nut applies a biasing force to the pressure pipe via the pressurizing step portion 2, whereby the inclined outer peripheral surface of the pressure pipe or the connection head is pressed against the seat of the connected component.

  However, in the prior art, due to the displacement of the tube wall in the radial direction at the time of cold forming or swaging, an annular wrinkle 4 that is deeply sharpened on the inner peripheral surface of the tube is generated. In addition, the fuel injection pipe is subjected to a large inflating internal pressure during operation, and the swaging rod 4 causes fatigue failure in the pressure pipe. Further, the inner diameter in the region of the connection head is not uniform, and has various narrow portions 5a and 5b. These narrow portions 5a and 5b cause a restriction in the fuel flow, and there is a risk of pressure fluctuation and accompanying cavitation due to changes in the cross-sectional area. Conventionally, this unequal inner diameter and upset rod have been addressed by passing the reamer through the tube until the upset rod 4 and the narrowed portions 5a, 5b are removed by the conical reamer at the end face. Yes. This reworking has a detrimental effect on the surface properties inside the tube, in which case the upsets that occur during cold working must be removed without fail.

  In the high-pressure technical field, for example, the above-mentioned problems are particularly surfaced at fuel injection pressures above about 1600 bar, such as used in marine engines. In order to cope with the possibility of high pressure, the diameter ratio between the outer diameter and the inner diameter of the tube must be adapted accordingly. That is, an outer diameter that is larger than the inner diameter must be selected, thereby forming a thick-walled tube wall. However, this procedure is limited and requires the use of a tube made of high tensile material. However, the greater the tensile strength, the lower the ductility of the material and hence the formability. In the case of a tube material with an elongation A of A <20%, there is a risk that apparent deep wrinkles will occur when the connection head is formed. Such upset wrinkles cannot be completely removed by reaming through the above-described conical reamer.

The above-mentioned Patent Document 2 proposes to use a stepped connection washer on the pressurization step portion of the connection head in order to prevent such upset wrinkles. This prior art has the disadvantages of using an expensive stepped connection washer and that the method selected in this prior art does not avoid deformation of the inner diameter during cold forming. Therefore, it is conventionally known that the deformation process of the pressure tube in high-strength steel is completely abandoned, and instead the connection head of the pressure tube is formed by cutting.
US Pat. No. 6,286,556 German Patent Application No. 10358373

  Starting from the above-mentioned prior art, the object of the present invention is to provide a pressure tube and a tool for manufacturing the pressure tube, which have no upset or narrow inner diameter after cold forming of the connection head.

  This problem is solved according to the independent claims of the present invention. Advantageous embodiments of the invention are described in the dependent claims.

  As a first aspect of the present invention, for example, a pressure head used as a fuel injection pipe of a fuel injection device of a diesel engine is provided with a connection head formed in a truncated cone shape. Accordingly, the pressure pipe has a pipe and a connection head. In that case, the connection head is made, for example, by a cold forming method at the tip of the pipe. The connection head, which is mainly a truncated cone, consists of an outer peripheral surface at the side, an end surface at the tube end, and a part of the base surface of the geometric truncated cone. The interior of this geometric foundation surface is: integrally joined with the rest of the pressure tube, the outer exposed part of the foundation surface is not located on the same plane as the interior of the foundation surface. Accordingly, the connection head is referred to herein as a frustoconical shape and does not form a geometrically perfect frustoconical. A surface for sealing the connection head with respect to the opposing member is formed on the outer peripheral surface. The opposing member is, for example, a part of a fuel injection device of a diesel engine. A tube opening is formed in the end face, and a pressure step for introducing a bias force necessary for sealing the seal face is formed on the side opposite to the end face. The outer peripheral surface of the non-molded pressure pipe, that is, the outer peripheral surface of the pipe forms an angle larger than 90 ° with the surface of the pressurizing step portion.

  According to the arrangement of the pressurizing step portion and the outer peripheral surface of the pressure pipe, the pressurizing step portion is at least slightly inclined, thereby obtaining a uniform chamfered slope course in the connection head. Due to the uniform chamfered slope, the operating strength of the connection head is improved, especially at the critical part of the transition from the pressure step to the outer periphery of the pressure tube. In addition, the shape of this pressurization step reduces the occurrence of upset wrinkles.

  In an advantageous embodiment of the invention, the inner peripheral surface of the pressure tube gradually narrows conically from the outside to the inside in the region of the connection head. This taper taper is formed by a corresponding upset mandrel during the upset process. That is, the inner diameter of the pressure tube is slightly widened during swaging. Therefore, the use of a swivel mandrel in the manufacture of the pressure tube does not cause deformation on the inner surface of the pressure tube, thereby eliminating the need for rework with a conical reamer to form a uniformly extending inner diameter. Thus, the surface quality at the inner surface of the pressure tube in the area of the connection head is improved.

  In another embodiment of the present invention, the outer peripheral surface of the connection head has a concave curved portion at a portion between the sealing surface and the pressurizing step. The curved portion in the connection head formed during cold forming with a correspondingly shaped upset reduces the material volume below the pressure step. Correspondingly, it is noted that during cold forming, the material of the pressure tube is not moved in the direction of the inner diameter but is moved away from it, so that no narrowing occurs in the inner diameter.

  In another embodiment of the present invention, a chamfered slope is provided as a self-sealing seal surface in the tube opening of the connection head. This chamfered slope is used to prevent damage to the seal surface during self-tightening. Fuel pressure tubes are generally self-tightened to increase fatigue strength. For this purpose, the pipe is temporarily subjected to a high internal pressure, which generates a residual compressive stress due to plastic deformation after the pressure is removed. Since the self-tightening pressure is considerably higher than the future operating pressure of the pressure tube, sealing at the original sealing surface of the outer peripheral surface of the frustoconical connection head is avoided. The large force on the self-sealing seal surface necessary to guarantee the sealing performance during self-tightening causes plastic deformation in the non-pressure state, thereby causing damage to the self-sealing seal surface. In that case, the chamfered slope is already formed when the connection head is set up, due to the corresponding shape of the set-up type. Accordingly, according to the embodiment based on the present invention described here, the connection head is manufactured in the above-described manufacturing process by the upset mold based on the present invention described later, so that reworking of the pressure pipe connection head is unnecessary. Become.

  In another embodiment of the present invention, the sealing surface on the outer peripheral surface is formed in a spherical shape. This improves the pressure distribution on the sealing surface even when there is an angle deviation between the axis of the connection head and the axis of the opposing member. Further, when the sealing surface is mechanically damaged, the sealing surface can be easily reground. In combination with the concave curved portion of the connection head, it is ensured that no grinding notch is produced on the outer peripheral surface of the connection head when the sealing surface is reground.

  In another embodiment of the invention, the pressure step is formed mainly flat, which simplifies the assembly and geometry of the pressure ring that contacts the pressure step when the pressure tube is wrapped.

  In the second aspect of the present invention, the upsetting for setting up the pressure pipe with the concave portion gradually narrowing inward in a frustoconical shape corresponding to the outer contour of the connecting head to be set up in the shape of the connecting head. A type is proposed. The upsetting type has a shape that occurs when the connection head including the pressurizing step portion formed at an angle larger than 90 ° with the outer surface of the pipe of the pressure pipe is set up.

  Here, the upset type is not necessarily formed as a single product, but preferably consists of two parts, the first part being a counter member for the second part. That is, the first part is pressed against the tube end, and the second part forms the pressure step of the connection head.

  In an embodiment of the second aspect of the present invention, the recess has a convex bulging portion in the upset first portion, whereby the connecting head is formed with the curved portion described above on the outer peripheral surface.

  In another embodiment of the second aspect of the present invention, the upset first part is provided with a mandrel inserted into the tube opening of the pressure tube, thereby changing the inner diameter of the pressure tube to be set up. Disappear. For this purpose, the outer diameter of the mandrel must substantially match the inner diameter of the pressure tube.

  Further, according to a second aspect of the present invention, the mandrel is formed in a conical shape. In that case, the base surface of the mandrel has an outer diameter larger than the inner diameter of the pressure tube to be swept up. Therefore, the inner diameter of the pressure tube is widened during swaging, thereby preventing deformation of the inner diameter.

  Furthermore, the upsetting mold according to the second aspect of the present invention is formed such that another inclined surface is provided on the base surface of the mandrel in order to form a chamfered inclined surface at the tube opening of the pressure tube. As already mentioned, the chamfered slope at the tube end has the advantage that it is used as a pressure tube seal during the self-tightening process. Therefore, according to the present invention, the sealing surface after the pressure tube is not used as the sealing surface. In order to produce the chamfered slope as cheaply as possible, the chamfered slope is formed in the cold forming process, and therefore a slope corresponding to the upset mold must be provided.

  In another embodiment, the upright mandrel is also formed in a frustoconical shape, and another chamfered bevel is provided at the end face of the mandrel for easy coaxial alignment with the pressure tube.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 2 shows a pipe end of a fuel injection pipe provided with a connection head (1) and a pipe (16). For example, a pressure ring (11) required for wrapping with an inclined pressure step (10) with a cap nut (not shown), for example, is contact-supported. The outer peripheral surface of the frustoconical connection head has on one hand a recess (12) and on the other hand a sealing surface (13). The sealing surface (13) seals the pressure tube against an opposing member comprising a fuel injection device (not shown). An internal taper (9) is formed on the inner peripheral surface (17) of the pressure tube in the region of the connection head (1). The internal taper (9) forms a tube opening (19) in the end face (18). The pressurization step (10) forms an angle greater than 90 ° with the outer peripheral surface of the pipe (16). This angle is preferably between 100 ° and 110 °. This angular range is advantageous for the load of the pressure ring (11). Similarly, the height H of the connection head affects the generation of upset wrinkles, and is in the range of (0.5 to 1.0) × tube outer diameter for a pressure tube having an outer diameter larger than 10 mm. The pipe inner diameter at the base surface of the internal taper (9), that is, the spread at the end face of the pressure pipe, must be in the range of (1.02-1.4) x pipe inner diameter. By forming the sealing surface of the connection head into a spherical shape, a uniform pressure distribution can be obtained over the circumference of the sealing surface even when there is an angular deviation between the axis of the pressure tube and the axis of the opposing member.

  FIG. 3 shows an embodiment of the second aspect of the invention, i.e. the first part of the upset (forging) mold. This first part is pressed against the pressure tube end to swallow the pressure tube. The upsetting mold (7) has a mandrel (8) formed in a truncated cone shape. A slope (15) is provided on the leg or base surface of the mandrel (8) to form a chamfered slope (14) on the connection head. The end face (6) is connected to the outer peripheral surface of the truncated cone through a chamfered slope. The upset part has a recess (20), which forms the base of the connection head to be set up in a bowl shape, and thus has a bulge (3) in the form of a bowl. Prepare. The length of the mandrel (8) must be at least 1.5 × (connection head height H).

Sectional drawing of the pressure pipe end with the conventional connection head. Sectional drawing of the pressure pipe end with a connection head based on this invention. Sectional drawing of the upset part based on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Connection head 2 Conventional pressurization step part 3 Expansion part 4 Upset wrinkle
5a, 5b Narrow part at inner diameter 6 End face of upset type 7 Upset type 8 Mandrel 9 Internal taper 10 Pressure step part 11 according to the present invention Pressure ring 12 Recess 13 of outer peripheral surface Seal surface 14 Chamfered slope 15 Slope 16 Piping 17 Inner peripheral surface 18 End surface 19 Opening 20 Recess

Claims (8)

A cold -formed truncated conical shaped connection head (1) is provided at the tip of a pipe (16) for connection to a fuel injection device of an internal combustion engine, and the connection head (1) is connected to the connection head on the outer peripheral surface. (1) has an annular sealing surface (13) for sealing against the connecting member, the end surface (18) has a tube opening (19), and a seal is formed on the surface opposite to the end surface (18). pressurizing the pressure stage section pipes (16) are in contact for introducing a biasing force necessary for the sealing surface (13) has a (10), the outer peripheral surface of the piping (16) is pressurized pressure stage section ( 10) a pressure tube with a molded connection head that forms an angle of 100 ° to 110 ° with the plane of
The inner peripheral surface (17) of the pressure pipe forms an internal taper (9) in the region of the connection head, and the pipe inner diameter at the base surface of the internal taper (9) is 1.02 to 1.4 of the inner diameter of the pipe. A molded connection characterized in that the outer peripheral surface of the connection head (1) has a concave curved portion (12) between the sealing surface (13) and the pressurizing step portion (10). Pressure tube with head. The pressure tube according to claim 1 tube opening (19) is characterized in that it has a chamfer inclined surface (14) on its periphery. 3. Pressure tube according to claim 1 or 2 , characterized in that the sealing surface (13) is formed in a spherical shape. 4. Pressure tube according to any one of claims 1 to 3 , characterized in that the pressurization step (10) is formed flat. A swivel type (7) consisting of at least two parts for swaging the pressure tube into the shape of the connection head (1), the first part of which is gradually narrowed inward in a substantially frustoconical shape A recess (20), the inner contour of the recess (20) corresponds to the outer contour of the connection head (1) to be swept, and the second part of the connection head (1) to be swallowed a pressurized pressure stage portion (10) swaging type having a recess for forming the (7), the outer surface of the second portion, connected to upsetting head (1) is pipe (16) And a pressurizing step (10) having a surface with an angle of 100 ° to 110 ° with the concave portion (20) having a swollen (7) convex bulge on its side surface. The first part of the upset type has a mandrel (8) for insertion into the tube opening (19). A swaging type for swaging the pressure pipe into the shape of the connection head (1), characterized in that the outer diameter of the mandrel (8) corresponds to the inner diameter of the pressure pipe to be swept . 6. Pressure tube according to claim 5 , characterized in that the mandrel (8) is conically formed and the base surface of the mandrel (8) has an outer diameter larger than the inner diameter of the pressure tube to be swept up. A swivel type for swaging into the shape of the connection head (1). The mandrel (8) has a bevel (15) at the base surface in order to form a chamfered bevel (14) in the tube opening (19) when the pressure tube is swept up. A swaging type for swaging the pressure pipe according to 5 or 6 into the shape of the connection head (1). The mandrel (8) is formed in a frustoconical shape and is provided with a chamfered bevel on the end face (6) to align the mandrel (8) coaxially with the pressure tube. Item 8. A swivel type for swaging the pressure pipe according to any one of items 5 to 7 into the shape of the connection head (1).

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