KR20070037560A - Pressure pipe with formed connecting head - Google Patents

Abstract

For example, the pressure tube as a high pressure fuel injection tube has a connecting head 1 produced by cold forming at the end of the pipeline 16. The connecting head 1 is conical and has an annular sealing surface on its outer circumferential surface. The sealing surface exerts a preload introduced through the pressure shoulder 10 to the connection with the corresponding seat. The outer surface of the pipeline 16 forms an angle greater than 90 ° with the surface of the pressure shoulder 10.

High pressure fuel injectors, pressure tubes, connection heads, sealing surfaces, pressure shoulders, connections.

Description

PRESSURE PIPE WITH FORMED CONNECTING HEAD

1 is a cross sectional view of a pressure tube end with a connection head according to the prior art;

2 is a cross-sectional view of a pressure tube end with a connection head according to the invention.

3 is a cross-sectional view of a die in accordance with the present invention.

<Explanation of symbols for the main parts of the drawings>

1: connection head 2: pressure shoulder (prior art)

3: arched portion 4: compression deformation folding

5: inner diameter contraction part 6: cover surface of die

7: die 8: mandrel

9: internal cone 10: pressure shoulder (invention)

11: pressure ring 12: recess

13: sealing surface 14: bevel

15: slope 16: pipeline

17: Inside face 18: Cover face

19: opening 20: recess

The present invention relates to pressure tubes with molded connection heads, in particular high pressure fuel injection tubes with compression deformed connection heads.

The pressure pipe based on this invention is used as a fuel injection pipe or a hydraulic pipe for supplying fuel to an injection device. In order to connect the pressure tube to other parts in a sealing manner, the ends of the pressure tube are formed in the form of a cone. Cold forming is known as an economical method for producing such connection heads. The products of the processes known in the prior art are disclosed in published publications US 6,286,556 B1 and DE 103 58 373 A1, for example on the basis of fuel pipes.

The prior art is shown in cross section in FIG. 1. 1 shows the tube interior deformed by compression deformation of the cone-shaped connecting head and the pressure tube. Sealing of the part to be connected to the pressure tube is made in this embodiment according to the prior art via the inclined outer circumferential surface of the connection head and the union nut (not shown), which is preloaded via the pressure shoulder 2. Is applied to the pressure tube, the inclined outer circumferential surface of the pressure tube or connection head is pressed against the corresponding seat of the part to be connected.

However, in the prior art, a ring-shaped, sharp compressive deformation folding 4a occurs in the inner diameter of the tube due to the displacement of the outer circumference of the tube outward in the cold forming or compression deformation. However, since the fuel injection pipe is exposed to high, internal pressure during operation, the compression strain folding 4a can cause fatigue failure of the pressure pipe. In addition, the inner diameter in the area of the connection head is not uniform and has several shrinkages 5a, 5b, which cause a throttle of the fuel flow and there is a risk of pressure fluctuations and hence cavitation due to cross-sectional fluctuations. In the prior art, a conical reamer is used to ream the inner diameter of the tube at the end face until the compressive strain folding 4a and the constrictions 5a, 5b are removed to prevent the non-uniform inner diameter and compressive strain folding. reaming). In the aftertreatment which adversely affects the surface condition inside the tube, it should be ensured that the compressive deformation folding formed by cold forming is removed without leaving.

In the field of high pressure technology, the problem is particularly important at injection pressures of about 1600 bar or more, such as used in marine engines. A way to cope with high pressures is to form a thicker tube circumference by correspondingly adjusting the ratio of diameters between the outer and inner diameters of the tube, i.e. selecting a larger outer diameter than the inner diameter. However, this measure has the limitation that a tube of high strength material should be used. However, as the tensile strength increases, the ductility of the material and the likelihood of forming decrease. In the case of tubular materials with break elongation A <20%, there is a risk that the compression deformation folding will be formed very deep in forming the connecting head. Reaming by the conical reamer can no longer completely eliminate the compressive strain folding.

The publication 103 58 373 A1 proposes to use stepped connection plates in the pressure shoulder of the connection head to avoid such compressive deformation folding. A disadvantage of this prior art is the use of complicated stepped connecting plates and the fact that deformation of the inner diameter in cold forming cannot be prevented by the method chosen in the prior art. Therefore, in the prior art, the molding of the pressure tube is omitted in the case of high strength steel, and instead, the connection head of the pressure tube is formed by cutting.

An object of the present invention is to provide a pressure tube which does not have compression deformation folding and a contracted inner diameter even after cold forming of the connection head, and a tool for manufacturing the pressure tube.

The problem is solved by the independent claims of the present invention.

The dependent claims are a preferred embodiment of the invention.

According to a first aspect of the invention, for example, a pressure tube which can be used as a fuel injection tube of an injection device of a diesel engine has a connecting head shaped into a truncated cone. Thus, the pressure tube has a pipeline and a connection head. The connection head can be produced at the end of the pipeline, for example by cold forming. The connecting head forming the cone consists of an outer circumferential surface on the side, a cover surface at the end of the tube and a portion of the base surface of the cone. Since the inside of the base face is integrally connected with the rest of the pressure tube and the exposed, outer part of the base face does not lie in the same plane as the inside face of the base face, the connection head here is a cone but does not form a perfect cone. . The outer circumferential surface is formed with a surface for sealing the connection head to the corresponding portion. The corresponding part may for example be part of an injection system for a diesel engine. A tube opening is formed in the cover surface and a pressure shoulder for introducing a preload necessary for sealing the sealing surface is formed on the side opposite to the cover surface. The unformed pressure tube, ie the outer surface of the pipeline, forms an angle> 90 ° with the face of the pressure shoulder.

This arrangement of the pressure shoulder with the outer surface of the pressure tube causes the pressure shoulder to be at least slightly inclined, resulting in uniform bevel travel in the connection head. Uniform bevel progression improves the operating strength of the connection head, especially in the critical region of the transition from the pressure shoulder to the pressure tube outer surface. In addition, compression deformation folding formation is reduced by this embodiment of the pressure shoulder.

According to a preferred embodiment of the invention, the inner surface of the pressure tube is conically tapered from the outside to the inside in the region of the connection head. The taping takes place by the corresponding die mandrel during the compression deformation process. That is, the inner diameter of the pressure tube is slightly enlarged during the compression deformation. By using the mandrel in the die when manufacturing the pressure tube, since the inner surface of the pressure tube is not deformed, post-treatment by a conical reamer to form a uniform inner diameter is no longer necessary. Thus, the surface quality of the inner surface of the pressure tube is improved in the region of the connection head.

According to another embodiment of the invention the outer circumferential surface of the connection head has a recess in the area between the sealing surface and the pressure shoulder. In the cold forming, the recess of the connection head formed by the correspondingly formed die reduces the material volume under the pressure shoulder. Thereby, during cold forming, the material of the pressure tube is displaced away from it, not in the direction of the inner diameter, so that shrinkage of the inner diameter cannot occur.

 According to another embodiment of the present invention, a bevel is provided in the tube opening of the connection head as a radial expansion sealing surface. The bevel is used to prevent damage to the sealing surface during radial expansion.

Fuel pressure tubes are typically radially expanded to increase durability. To this end, the tube is exposed to high internal pressure for a short time and the internal pressure forms internal compressive stress after pressure relief due to plastic deformation. Since the radial expansion pressure is much higher than the subsequent working pressure of the pressure tube, the sealing against the actual sealing surface on the outer peripheral surface of the conical connection head should be avoided. The high force on the radial expansion sealing surface, which is necessary to ensure the tightness in the radial expansion, causes plastic deformation of the radial expansion sealing surface and thus damage in the absence of pressure. The bevel may already be formed by the corresponding design of the die upon compression deformation of the connection head. With the embodiments according to the invention mentioned here, when the connection head is produced using the die according to the invention described below in the manufacturing process described, the post-treatment of the pressure tube connection head is no longer necessary.

According to another embodiment of the present invention, the sealing surface on the outer circumferential surface is formed in a circular shape. This improves the pressure distribution at the sealing surface, especially when the axis of the connection head has an angular deviation from the axis of the corresponding part. In addition, there is a possibility of simply post-grinding at the time of mechanical damage of the sealing surface. In cooperation with the concave portion of the connection head, it is ensured that no grinding notch occurs in the outer peripheral surface of the connection head during the post grinding of the sealing surface.

According to another embodiment of the present invention, the pressure shoulder is formed flat, thereby simplifying the shape of the pressure ring contacting the pressure shoulder during assembly and installation of the pressure pipe.

According to a second aspect of the invention, the die for compressively deforming the pressure tube into the connecting head has an inwardly tapered conical recess, corresponding to the outer contour of the connecting head to be compression deformed. The die has a shape that forms a connection head upon compression deformation, the connection head having a pressure shoulder that forms an angle> 90 ° with the outer surface of the pipeline of the pressure tube.

Here, the die does not necessarily need to be formed integrally, but preferably consists of two parts. The first part is the corresponding part of the second part. That is, the first part is pressed against the tube end, and the second part forms a pressure shoulder of the connection head.

According to an embodiment of the second aspect of the invention, the recess has a convex arcuate in the first part of the die, so that the connecting head with the recess is formed on the outer circumferential surface.

According to another embodiment of the second aspect, the mandrel is provided in the first portion of the die, and because the mandrel is inserted into the tube opening of the pressure tube, the inner diameter of the pressure tube to be compression deformed may not be deformed. For this purpose, the outer diameter of the mandrel corresponds to the inner diameter of the pressure tube.

In addition, according to the second aspect of the present invention, the mandrel is formed conical. The base face of the mandrel has an outer diameter that is greater than the inner diameter of the pressure tube to be compression deformed. Therefore, the inner diameter of the pressure tube is enlarged during the compression deformation, thereby preventing the inner diameter from being deformed.

Further, according to the second aspect of the present invention, the die is formed so that another inclined portion is provided on the base face of the mandrel, so that the pressure tube opening can be beveled. As mentioned above, the bevel of the tube end can preferably be used as a seal of the pressure tube in radial expansion. Therefore, the later sealing surface of the pressure tube is not used as the sealing surface. For the lowest cost production of the bevel, since the bevel is formed by a cold forming process, a slope corresponding to the die is provided.

According to another embodiment, the mandrel of the die may be formed conical and another bevel is provided on the cover face of the mandrel, so that the mandrel can simply be aligned coaxially with respect to the pressure tube.

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

2 shows the tube end of a fuel injection tube with a connection head 1 and a pipeline 16. The inclined pressure shoulder 10 is supported on the pressure ring 5, which is required for installation by, for example, a union nut (not shown). The outer circumferential surface of the conical connection head has a bulge 12 on the one hand and a sealing surface 13 on the other hand. The sealing surface 13 seals the pressure tube against the corresponding part of the injection system (not shown). On the inner surface 17 of the pressure tube, an inner cone 9 is formed in the region of the connection head. The inner cone 9 forms a tube opening 19 at the sealing surface 18. The pressure shoulder 10 forms an angle greater than 90 ° with the outer surface of the pipeline 16 of the pressure tube. Preferably the angle is between 100 ° and 110 °. In each said range, the load of the pressure ring 11 is preferable. The height H of the connection head affects the compression deformation folding formation and lies in the range of 0.5 to 1.0 x outer diameter for pressure tubes with an outer diameter> 10 mm. The tube inner diameter at the base face of the inner cone 9, ie the enlargement at the end face of the pressure tube, lies within the range of 1.02 to 1.4 x pipeline inner diameter. Since the connecting head is formed in the shape of a ball at the sealing surface, even pressure deviation over the circumference of the sealing surface is achieved even if there is a deviation between the axes of the pressure tube and the corresponding portion.

An embodiment of the second aspect of the invention, ie the first part of the die pressed against the pressure tube end for compressive deformation, is shown in cross section in FIG. 3. The die 7 has a mandling 8, which mandrel is formed in a truncated cone shape. On the foot or base side of the mandrel, the inclined portion 15 for forming the bevel 14 is provided in the connection head. The cover surface 6 is connected to the outer circumferential surface of the cone by means of a bevel. The die has a recess 20, since the recess forms the negative of the connection head to be compression-deformed in the form of a barrel, so that an arch 3 appears in the profile of the barrel. The length of the mandrel shall be at least 1.5 x connection head height H.

According to the invention there is provided a pressure tube which does not have compressive deformation folding and a retracted inner diameter even after cold forming of the connection head.

Claims (13)

A pressure tube with a connecting head 1 shaped in the shape of a cone at the end of a pipeline 16 for connecting to the injection system of an internal combustion engine, which connects the connecting head 1 to the connecting part on its outer circumferential surface. An annular sealing surface 13 for sealing, a tube opening 19 on the cover surface 18, and a side surface disposed opposite to the sealing surface, in contact with the pipeline 16 and sealing the sealing surface 13. In a pressure tube, having a pressure shoulder 10 for introducing a preload necessary for Pressure tube with shaped connection head, characterized in that the outer surface of the pipeline (16) forms an angle greater than 90 ° with the surface of the pressure shoulder (10). 2. The pressure tube as claimed in claim 1, wherein the inner surface of the pressure tube is tapered conically from the outside to the inside in the region of the connection head. 3. 3. The molded part according to claim 1, wherein the outer circumferential surface of the connecting head 1 has a recess 12 in the region between the sealing surface 13 and the pressure shoulder 10. Pressure tube with connection head. 4. A pressure tube with a molded connection head according to any one of the preceding claims, characterized in that the tube opening (19) has a bevel (14) at its circumference. 5. The pressure tube with a molded connection head according to claim 1, wherein the connection head is a cold formed connection head. 6. 6. Pressure tube with molded connection head according to any one of the preceding claims, characterized in that the sealing surface (13) is formed in a ball shape. 7. Pressure tube with a molded connection head according to any one of the preceding claims, characterized in that the pressure shoulder (10) is formed flat. A die 7 consisting of two or more parts for compressively deforming the pressure tube into the connecting head 1, the first part having a conical recess 20 tapering inwardly, the inner contour of the recess being compressed In the die, which corresponds to the outer contour of the connection head 1 to be deformed, the second part has a recess for forming a pressure shoulder of the connection head 1 to be compression deformed, The second part is formed such that the connecting head 1 to be compressively deformed is formed to have a pressure shoulder with a surface forming an angle greater than 90 ° with the outer surface of the pipeline 16 as the connecting head. Die for compressive deformation. 9. Die according to claim 8, characterized in that the recess (20) has a convex arcuate (3) at the end face of the die (7). 10. The method according to claim 8 or 9, wherein the first portion of the die has a mandrel (8) for inserting into the tube opening (19), the outer diameter of the tube opening corresponding to the inner diameter of the pressure tube to be compression deformed. And a die for compressively deforming the pressure pipe to the connection head. 11. Compression deformation of a pressure tube with a connecting head according to claim 10, characterized in that the mandrel (8) is formed conical and the base face of the mandrel (8) has an outer diameter larger than the inner diameter of the pressure tube to be compressionally deformed. Die for. 12. The mandrel (8) according to claim 10 or 11, wherein the mandrel (8) has an inclined portion (22) in the region of the base face, in order to form the bevel (14) in the tube opening (19) of the pressure tube to be compression deformed. A die for compressively deforming a pressure tube to a connection head. 13. The mandrel according to any one of claims 10 to 12, wherein the mandrel (8) is formed in a conical shape, and a bevel is provided on the cover surface (6) for aligning the mandrel (8) coaxially with respect to the pressure tube. Die for compressively deforming the pressure pipe into the connection head.

Images