JP4386867B2 - High pressure fuel injection accumulator / distributor for automobile and manufacturing method thereof - Google Patents

Description

  The present invention relates to an automobile high-pressure fuel injection / accumulation distributor and a method for manufacturing the same, and more particularly, an automobile high-pressure fuel injection / accumulation distributor (common rail) that can withstand a pressure exceeding 1200 atm is assembled by liquid phase diffusion bonding or other welding. The joint strength reduction and breakage from the joint caused by the joint failure inevitably occurring at the joint can be reliably prevented by increasing the fastening force in the joint site shape design. The present invention relates to a high-pressure fuel injection accumulator / distributor for automobiles and a manufacturing method thereof.

  In the case of using light oil as fuel for automobiles, a common rail system is used as a technology for mixing light oil into each combustion chamber and uniformly injecting it, and converting the explosion combustion effect into engine power most efficiently. This is an effective technique for reducing harmful substances in exhaust gas by uniformly injecting fuel into each combustion chamber of an engine as a mixture with gas at high pressure and adjusting the injection pressure by electronic control. In Europe, it is often used in passenger cars, and the development of system technology has continued, such as using high-power, low fuel consumption, and high torque by using light oil with few impurity components. The main configuration of this system is to draw light oil from a fuel tank with a pump, hold it temporarily at a high pressure in a fuel accumulator called a common rail, and from here to an injection nozzle via a small-diameter discharge port called an orifice and piping Sent. The injection nozzle is provided with a collecting pipe and an injection function for mixing the pumped fuel with combustion air and feeding it uniformly into the engine combustion chamber. The fuel discharged from the injection nozzle has a higher combustion efficiency as it is sprayed uniformly, and the higher the pressure, the easier it is to achieve this purpose. That is, forming a high-pressure fuel injection system as much as possible is an important technical element in developing an automobile engine that emits less harmful substances. However, in the current common rail system, when fuel is injected into the first accumulator, the accumulator itself cannot withstand the pressure of the fuel in the process of reaching the discharge port, and internal pressure fatigue failure may occur. In order to solve this, with the recognition that it is important to increase the steel strength of the common rail material, the corresponding technological development has progressed by adjusting the chemical composition of the steel material and adjusting the heat treatment, and the injected fuel pressure is up to 1200 atm. A sufficiently reliable common rail system has already been put into practical use.

  However, the common rail for high pressure exceeding 1200 atm is currently manufactured by integrally forming by forming forging and performing complicated machining on it. This means that if the material strength is increased, the moldability is inferior and the processing is difficult, which causes a large increase in cost, and remains an unsolved problem for practical application of the high-pressure common rail. At present, high-pressure common rails up to 1500 atm have been put into practical use, but the manufacturing method cannot adopt a method other than a combination of forging and machining, so the above-mentioned problems still remain unsolved. . FIG. 1 shows an example of the shape of the common rail. 1A is a plan view, and FIG. 1B is a front view.

  The present inventors have fundamentally reviewed the manufacturing method of this high-voltage common rail, focused on a method of dividing each part into simple-shaped parts, mass-producing each part, and assembling them into a product by welding. Parts are originally formed by one-piece molding, and if the shape is complicated, the parts to be manufactured through stamping forging, upsetting forging, casting or partial cutting processes are divided into simple shaped parts. Patent Documents 1 and 2 describe a technique for manufacturing these components and assembling them by liquid phase diffusion bonding. These technologies use the advantages of precision bonding technology called liquid phase diffusion bonding, and realize parts with complex shapes by bonding. However, liquid phase diffusion bonding has the property that it progresses at the diffusion rate-determining point of the melting point lowering element. However, the stress must be continuously applied to the joint surfaces at a high temperature, the process time is relatively long, and the cost of the joining apparatus is high, so that the situation is not widespread industrially.

JP 2002-086279 A JP 2002-263857 A

  However, the inventions described in Patent Documents 1 and 2 occur when the load stress on the joining surface is not uniform due to the problem of the joining jig or part shape and processing accuracy, or when heating is not performed uniformly. There is no disclosure about a technique for stably forming a precision butt of a joint surface by local deformation. The high-pressure fuel injection / accumulation / distribution distributor for automobiles is the most important part for obtaining the reliability of the engine because the joint strength is strictly reflected in the design due to the nature of the part to be applied. Therefore, for example, in the event that an incomplete joint due to a cause that is difficult to manage in the joining process, such as the above, should occur, the yield can be improved from the viewpoint of production cost even if the subsequent inspection technique is perfected. It has not been solved, and the cost of parts has risen, and the problem that only a manufacturing method that is not preferable as an industrial product can be used has not been solved.

  Surface bonding technology such as liquid phase diffusion bonding can form precision joints, but on the other hand, it is also sensitive to slight groove shape abnormalities, and there remains a problem to be solved in order to obtain a reliable joint. ing.

  Therefore, the present invention provides a liquid phase diffusion bonding, other bonding techniques, or a holder necessary for connecting a fuel branch pipe of a common rail, which is an automobile fuel injection component, to the rail body without fuel pressure loss or leakage. Provided are a high-pressure fuel injection accumulator / distributor for automobiles and a method for manufacturing the same, which can greatly increase the reliability when joining by a composite technique.

The present invention cannot be confirmed by non-destructive inspection or the like even if the above-mentioned problems of the prior art, that is, the joint between the common rail body formed by joining and the holder satisfies the mechanical properties such as tensile strength. It was designed to prevent the occurrence of micro-defects and defects based on human errors, and the characteristics required of parts, especially the long-term internal pressure fatigue durability characteristics cannot be realized. The main points are as follows.
(1) Piping attachment parts for attaching piping to the injection nozzle inserted into the combustion chamber of the engine from a plurality of branch passages for distributing fuel at an equal pressure to the rail body of the high pressure fuel injection accumulator / distributor (common rail) for automobiles (Holder) is a welded common rail joined by liquid phase diffusion bonding or the like, and the holder extends to the weld joint surface side end of the outer peripheral surface over a length of 2 mm or more in the axial direction of the holder. Over the holder main body outer peripheral surface and formed with a projection having a large outer diameter of 1 mm or more on one side, and the rail main body is positioned at the holder joint position at the holder joint position. A groove for determination, the groove having an inner peripheral wall of a diameter that can be fitted to the inner periphery of the holder joint, a groove bottom surface that serves as a joint surface with the holder, and a depth of 3 mm or more from the groove bottom surface. Diameter And a groove outer peripheral wall having a diameter with a clearance of 1.5 mm or less on one side, and further, the groove outer peripheral wall has a hollow portion that fits into a protruding portion at the end of the joint outer surface of the holder outer peripheral surface. A high-pressure fuel injection / accumulation / distribution distributor for an automobile, wherein a fastening force between the holder and the rail body is enhanced by an anchor effect caused by fitting between the recess of the outer peripheral wall of the groove and the protrusion of the holder.
(2) The holder and the rail body are steel materials having a tensile strength of 800 MPa or more and 1500 MPa or less at room temperature, and 200 MPa or less at a temperature of 1000 ° C. or more, and are generated when an internal pressure is applied to the fuel injection system. The high-pressure fuel injection and accumulation distributor for automobiles according to (1) above, wherein the plastic deformation starting stress (elastic limit) of pulling out the holder is 200 MPa or more in the range up to 100 ° C.
(3) Piping fittings that attach piping to the injection nozzles that are inserted into the combustion chamber of the engine from a plurality of branch passages for distributing fuel at the same pressure to the rail body of the high-pressure fuel injection accumulator / distributor (common rail) for automobiles A method of manufacturing a high pressure fuel injection and accumulation distributor for an automobile, in which (holder) is joined by liquid phase diffusion joining or the like, wherein the rail body has a holder joining position determining groove at a holder joining position, The inner wall of the groove that can be fitted to the inner periphery of the holder joint, the groove bottom surface that becomes the weld joint surface with the holder, and a clearance of 1.5 mm or less on one side of the holder outer diameter at a depth of 3 mm or more from the groove bottom surface A groove outer peripheral wall having an added diameter, and further, the groove outer peripheral wall has a length extending from the groove bottom surface to a groove depth direction length of 2 mm or more and over the entire circumference, 1 mm from the groove outer peripheral wall surface on one side. After processing the rail body so as to have a recess having a large outer diameter, the joint is exposed to a high temperature of 1000 ° C. or higher when the holder is bonded to the rail body by liquid phase diffusion bonding or the like. In the meantime, a stress of 10 MPa or more is applied to the entire holder for 0.1 to 60 seconds in addition to the required stress application time at the time of joint joining, so that the holder shaft is attached to the end of the holder on the joint surface side. A protrusion having a large outer diameter of 1 mm or more on one side from the outer peripheral surface of the holder body is formed by hot plastic deformation over the entire circumference in a range extending in a direction length of 2 mm or more, and the protrusion of the holder is formed on the rail body. A manufacturing method of a high-pressure fuel injection / accumulation / distribution distributor for an automobile, characterized in that the fastening force between the holder and the rail body is increased by an anchor effect caused by fitting with a recess in the outer peripheral wall of the groove.
(4) The protrusion of the holder is formed in advance by 1 mm or more on one side, machining, cold pressing or cold forging, hot forging or a combination of hot pressing and machining, and grinding of the holder protrusion. The method for producing a high-pressure fuel injection / accumulation / distribution distributor for an automobile according to (3) above, wherein an angle formed between the outer peripheral surface of the slope and the outer peripheral surface of the holder is 45 ° or more.
(5) The holder and the rail body are steel materials having a tensile strength of 800 MPa or more and 1500 MPa or less at room temperature, and 200 MPa or less at a temperature of 1000 ° C. or more, and are generated when an internal pressure is applied to the fuel injection system. The manufacturing of the high-pressure fuel injection and accumulation distributor for automobiles according to (3) or (4) above, wherein the plastic deformation starting stress (elastic limit) of pulling out the holder is 200 MPa or more in the range up to 100 ° C. Method.

  According to the present invention, particularly when an automobile high pressure fuel injection pressure accumulation distributor (common rail) that can withstand an internal pressure exceeding 1200 atm is assembled and manufactured by liquid phase diffusion bonding or other welding, it is inevitably generated at the joint. The industrial effect is immeasurable because it can advantageously compensate for the strength reduction of the joint and the destruction from the joint caused by the joint failure.

  In the present invention, when a common rail, which is a fuel injection system for automobiles, is assembled and manufactured by joining, if the joint technology cannot inevitably detect a joint defect that is unavoidably present in the joint, reliable joint reliability is ensured for the common rail. It is for giving and fully exhibiting its functions. The present invention includes a rail main body (hereinafter, also simply referred to as rail in the present invention) including a common rail pressure accumulating structure and a fuel branch path and capable of connecting an internal pressure detection or pressure feedback mechanism, and a fuel distribution path thereof. Inner screw type or external screw type connection projection that is a connector that connects the pipe and the pipe (hereinafter, this part is manufactured separately from the rail body of the common rail and the part that is joined to the rail body by joining is also simply called a holder) Consists of. Here, the detailed shape and configuration of the joint between the holder and the rail, and the fastening force improving mechanism of the joint will be specifically described.

FIG. 1 already shows one form of the common rail (inner screw type holder type), and shows the rail body 2 and the holder 1. The rail has a through hole inside, and an orifice for distributing fuel in a direction perpendicular to the axial direction of the hole. Here, the common rail in FIG. 1 will be described as an example, but the shape of the rail that is a fuel pressure accumulator is basically not limited, and the cross section may be rectangular or circular as in this time, and the fuel supply to the engine The form can be changed as appropriate according to the convenience of the piping. However, only the through hole and the branch pipe structure are essential elements. 2 is a cross-sectional configuration diagram when the rail is cut in the width direction, FIG. 3 is a projection formed by plastic deformation of the joint end, and FIG. 4 is a case where the projection is formed in advance by machining. The state of the fitting of the joint was shown in detail. That is,
(1) A rail and a holder were manufactured separately to form a joining-type assembly part.
(2) The rail and the holder are joined with a tensile strength equivalent to that of the base material by forming a joint by surface joining such as liquid phase diffusion joining. When welding, the holder and rail orifices are connected with high precision, and the holder joining position for joining the holder to the rail accurately without misalignment to prevent fuel leakage when connecting pipes with metal seals. A determination groove (guide groove) (see a partially enlarged view (b) in FIG. 2) is provided. The depth of the guide groove is 3 mm or more because of its function. If the depth is less than this, the holder axis will be greatly displaced from the axis of the pipe connected by the metal seal, and tightening cannot be achieved at the time of fastening. The injection function may not be sufficient, or a protrusion on the holder outer surface side that reaches the end of the holder weld joint surface, and an outer peripheral wall recess provided in the rail main body guide groove to match the protrusion (in FIG. 2) It was confirmed experimentally that the pull-out stress of the holder might be less than 200 MPa without sufficient fitting after joining.
(3) The protruding portion of 1 mm or more molded on the joining end side of the outer peripheral surface of the holder needs to have a height of 2 mm or more and a guide groove depth of the rail body in the holder axial direction, and the protruding portion is a machine When pre-molded by processing, the holder outer wall and the protrusion must be connected to the holder outer wall with a taper surface of 45 ° or more, and the rail body side also has a groove outer wall recess that matches this. Need to be. When the pulling stress is generated in the holder, the aligned rail body groove outer peripheral wall depression and the tapered portion of the holder projecting portion exhibit the effect of improving the fastening force by the frictional force and the anchor effect by the fitting. When the taper angle is less than 45 °, when the height of the holder protrusion in the axial direction of the holder is 2 mm, the 1 mm protrusion cannot be geometrically processed in advance. The shape of the groove outer wall recess is also subject to the same restrictions. In addition, machining at an angle of 90 ° or more becomes impossible because machining on the groove outer peripheral wall recess portion side of the rail body is not possible, but is not realistic.
(4) The fitting of the holder protrusion to the rail body groove outer peripheral wall recess is achieved by high-temperature plastic deformation utilizing preheating at 1000 ° C. or higher during welding joining. In the case of liquid phase diffusion bonding, this stress for high-temperature plastic deformation can be applied simultaneously when stress is applied to the joint groove. For example, in other welding (electric resistance welding, friction welding), the stress Since the addition is indispensable at the time of joining, the stress necessary for joint joint deformation is formed by further plastic deformation immediately after the addition, and the fitting of the holder protrusion and the rail body groove outer peripheral wall recess is achieved . To achieve this fitting, cut the joint after fitting and observe the cross-section, determine the magnitude of the stress and the time to apply the stress based on the observation results, and manage the stress or the time to apply the stress. However, it is possible to secure the fastening force. In addition, it can be confirmed by ultrasonic inspection or X-ray inspection whether a void remains. The stress and the stress application time are factors determined by the material of the common rail, the mechanical properties of the material at 1000 ° C. or higher, particularly the deformation yield stress, and can be determined as needed.
(5) If welding conditions between the holder and the rail body are selected with sufficient joining conditions and defect detection is performed by nondestructive inspection, characteristics can be guaranteed using an industrial safety factor. However, it guarantees 100% of small defects that cannot be detected by non-destructive inspection, or extremely small defects compared to the ultrasonic wave incident from the flaw detector, and various micro defects and weld cracks caused by the welding method. Difficult to do. The properties required for the joint are fatigue properties that can withstand repeated tensile stress perpendicular to the joint surface that occurs when the internal pressure varies. Fatigue failure due to repeated stress accumulation is the most difficult to predict and is the most important guarantee item in common rail component design. In order to prevent this fatigue failure, a holder protrusion and a rail body groove outer peripheral wall recess are provided at the joint, and the fastening effect can be secured sufficiently by the anchor effect, but complete fatigue failure In order to prevent this, the residual tensile stress that occurs when the pipe is fastened with a metal seal and the repeated tensile stress caused by fluctuations in the internal pressure applied to it, the plastic deformation start stress (elastic limit) when the holder is pulled out. In addition, if fatigue fracture is taken into consideration, the plastic deformation starting stress at the time of pulling out needs to be twice the holder pulling stress applied to the joint. Even if the internal pressure increases, fatigue fracture does not theoretically occur if the fastening stress exceeds twice the yield starting stress when the holder is pulled out due to the internal pressure. The plastic deformation initiation stress at the time of pulling out of the holder and the rail body fastened by the method of the present invention is not limited to the surface where the fastening force is generated, By being dispersed on the surface, the internal pressure fatigue characteristics are excellent as compared with a conventional welded common rail having no protrusion.
(6) Regarding the material of the holder, there are no specific chemical component provisions. However, as a common rail for high pressure, it is necessary to have excellent internal pressure fatigue characteristics. For this reason, the tensile strength of the material is appropriately adjusted by chemical treatment, tempering treatment such as heat treatment, or cold working, etc. In the final product form after completion, 800 MPa or more is required. The upper limit of the tensile strength is that when the present invention uses welding / joining technology, a very small amount of hydrogen that penetrates into this part diffuses over a long distance and accumulates at the maximum stress generation position inside the common rail. Assuming that the upper limit of strength from the viewpoint of hydrogen embrittlement susceptibility is set to 1500 MPa or less so that hydrogen-induced embrittlement does not occur. Further, in order to substantially enable the forming or projecting of the protruding portion by high-temperature plastic deformation of the holder end portion using the residual heat immediately after joining, which is the greatest feature of the present invention, It is necessary that the above strength (at 1000 ° C. or higher, the strength substantially decreases as the temperature increases, and the tensile strength at 1000 ° C. represents this) is 200 MPa or less. However, the only material with high temperature strength exceeding this is ceramics and special alloys for ultra-high temperatures, but this value is specified because it is a required specification for important materials. Based on the prescription of these material strengths, when evaluating the effect of the present invention described above, that is, the plastic deformation yield start stress when the holder is pulled out (the direction in which the holder is substantially separated from the rail in the direction perpendicular to the weld joint surface). The maximum heating temperature is estimated to be that the common rail will be exposed when it is mounted on the engine. Up to 200 MPa, the bonded holder is not practically broken from the bonded portion due to the anchor effect of the protruding portion and the bonded strength of the bonded portion of the present invention.

  In the present invention, the shape of the protruding portion provided at the end portion on the joint surface side of the holder outer peripheral surface is 1 mm or more in the outer diameter direction, and the taper angle of 45 ° or more formed by the holder main body outer peripheral surface and the inclined surface of the protruding portion is limited. Was determined based on the following experiment. That is, first, an inner screw type holder having an outer diameter of 24 mm and a thickness of 6 mm was prepared by gradually increasing the protrusion outer diameter from 24 mm in units of 0.1 mm. The guide groove for determining the holder joint position on the rail body side corresponding to this has an inner diameter of 17.8 mm, an outer diameter of 24.5 mm, a depth of 3 mm, and a recess portion following the holder protrusion is provided on the outer periphery of the rail body groove. The wall was prepared by processing according to the type of test level of the outer diameter of the holder protrusion. Also, a holder having no protrusion on the outer peripheral surface of the holder, and a holder main body in which only the hollow portion of the outer peripheral wall of the rail main body corresponding to the holder was changed in units of 0.1 mm were prepared.

  These parts were subjected to liquid phase diffusion bonding, electric resistance welding or liquid phase diffusion bonding after resistance welding, composite bonding was performed to produce a common rail, and the plastic deformation starting stress was measured when the holder was pulled out. Note that the amount of deformation required when the holder protrusion fully aligns with the recess in advance is determined by measuring the decrease in holder height that occurs when stress is indirectly applied to the holder, and obtaining the optimum value. Managed by decreasing height.

  FIG. 5 shows the relationship between the one-side increment from the outer peripheral surface of the holder parallel portion of the outer diameter of the initial protrusion and the plastic deformation start stress (elastic limit) at the time of pulling-out stress of the holder when the protrusion is provided in advance when cutting the holder. Indicated. It can be seen that the one-side increment from the outer peripheral surface of the parallel portion of the protrusion is just 1 mm, and the plastic deformation starting stress at the time of drawing exceeds 200 MPa. With this data, when forming the protrusion by machining, the required one-side incremental amount of the holder outer diameter of the protrusion was determined to be 1 mm or more. In addition, although there is no upper limit on one side increment, if it is too large (it has been experimentally found that it is substantially 3 mm or more), the cutting allowance becomes too large in the case of prior machining. There are limitations due to material processing cost issues. However, there is no practical upper limit on the mechanism.

  FIG. 6 shows the result of actually measuring the amount of protrusion when forming the protrusion by plastic deformation at the time of joining when the protrusion is not provided, by cutting the common rail in the width direction at the axial position of the holder after joining, It is a figure which shows the relationship of the plastic deformation start stress at the time of holder extraction in the case of the same deformation amount. Even if the protrusion is not provided in advance, the plastic deformation portion will eventually overhang so as to align with the recess on the rail body side, so that the plastic deformation start stress when the holder is pulled out exceeds 200 MPa when the holder outer diameter is increased by 1 mm. . In this case, the amount of plastic deformation at the joint end of the holder is substantially larger than when the protruding portion is pre-processed, and the height change of the holder is large, but the completed joint shape is not provided with the protruding portion in advance. It was similar to the case. Even when the amount of plastic deformation is different, the shape of the protrusion is similar because the outer peripheral surface of the holder connected to the protrusion is also increased in outer diameter due to plastic deformation.

  The common rail shown in FIG. 1 was prototyped as follows. That is, a material having the chemical components shown in Table 1 is a 230 mm long, 30 mm square rail body, a holder for branch pipe connection for distributing fuel with a maximum thread height of 2 mm to the inner diameter side on a holder of 24 mm outer diameter and thickness 5 mm. Were separately processed from steel plate or steel bar by rolling, drawing, cutting, etc. In the rail body, a guide groove for determining a holder joint position having a depth of 3 mm shown in FIG. 2 was processed. 2A is a view showing a rail body, and FIG. 2B is an enlarged view of a holder joint portion. The holder end was prepared for both the case where the protrusions as shown in FIGS. 3 and 4 were provided in advance and the case where the protrusions were not provided. In FIG. 3, (a) shows the state A: as-bonded, (b) state B: stress is applied immediately after joining, the joint surface is plastically deformed, and the outer wall of the holder bulges to the rail slit The figure which showed the state which started, (c) is the figure which continued applying stress further to the state C: state B, and the state which completed the shaping | molding by completely filling a protrusion part into a slit in the state whose temperature is 1000 degreeC or more It is. 4A is a diagram showing a state A: as-joined, and FIG. 4B is a state B: a protruding portion that is pre-processed by applying a stress immediately after joining and plastically deforming the joining end portion. (C) shows a state in which bulging is disclosed to the rail slit, and (c) shows a state where the stress is continuously applied to the state B, and the protrusion is completely filled in the slit in a state where the temperature is 1000 ° C. or higher and the molding is completed. FIG. 4B, the hatched portion is the bulging portion 8 ′, and similarly, the hatched portion in FIG. 4C is the bulging portion 8 ″, and the pre-processed protrusion matches the slit. 3 and FIG. 4, the holder and the rail body are welded together by liquid phase diffusion bonding or resistance welding, or combined welding of resistance welding and liquid phase diffusion bonding. In the case of the first resistance welding in the case, the joint end of the holder is 1000 ° C or higher due to the residual heat), and the temperature is measured simultaneously with a radiation thermometer at a position where the holder outer wall is 0.2 mm higher than the rail body surface position. While confirming, add stress from the end surface opposite to the joint surface of the holder, measure the amount of decrease in holder height that was set separately by measuring in advance by the amount of displacement of the crosshead that applies stress to the holder, Required holder end After confirming that the plastic deformation has reached the required amount of deformation with and without the protrusions, remove the stress, and then cool to satisfy the specifications that require the height of the holder The load stress for forming the protrusion at this time or for completely fitting the protrusion to the recess of the outer wall of the rail body groove is the stress value added to the holder, in the case of resistance welding. 18 MPa, 15 MPa in the case of liquid phase diffusion bonding Further, after reheating the entire common rail to 1150 ° C. in an inert atmosphere and holding it for 10 minutes, the structure was tempered by normalizing and tempering, and the tensile strength of the common rail The pressure was set at 1000 MPa so that it could withstand internal pressure fatigue of 2000 atm.20 common rails manufactured under exactly the same conditions were manufactured, and one was cut in the width direction of the common rail, passing through the holder central axis. The protrusion fits into the rail body groove outer peripheral wall recess, and the one-side increment of the outer diameter of the protrusion at the both ends of the holder joint with the rail body groove outer peripheral wall is in the range of 1.12 to 1.47 mm. In this range, the outer diameter of all the holder protrusions of one common rail fluctuated, but it did not fall below 1.0 mm, and the height of the holder protrusion was 2.0 mm. The holder end is processed in this way, and the one-side increment before joining the protrusion outer diameter and the holder outer diameter is controlled to 1.1 ± 0.05 mm, and regardless of whether the holder end protrusion is processed or not, The clearance of the recess on the outer peripheral wall of the rail body groove was processed to 1.1 ± 0.05 mm by plastic deformation of the holder end, and the taper angle at which the protrusion of the holder end connects to the outer periphery of the holder body is 60 °. The concave part of the outer peripheral wall of the rail body groove to be joined was provided with the same reverse taper. In addition, the clearance between the outer diameter of the outer peripheral wall of the rail body and the outer diameter of the holder was set to 1.2 mm on one side when the protrusion was provided in advance, and 1.0 mm when the protrusion was not processed in advance.

  We conducted an evaluation test to pull out the common rail holder assembled in the above process, measured the pulling stress excluding the pulling force in the area of the end side where the holder is not joined, and the deformation changed from elastic to plastic When the stress was measured, it was 400 MPa.

  In addition, 10 or more completed common rails were set in an internal pressure fatigue test apparatus via a fixing jig that was separately processed and attached, and an internal pressure fatigue test was performed 10 million times at 15 Hz at a maximum injection pressure of 3000 atm. . In the test, the screw that closes the opening end of the upper part of the holder was selected so as to match the shape of the screw machined on the inner diameter side of the holder and fastened with a maximum torque of 3 tons to reproduce the actual use environment in the engine.

  FIG. 7 shows the relationship between the number N of repeated internal pressure loads that lead to fatigue failure and the joint stress calculated from the applied pressure as an internal pressure-fatigue failure life diagram. In this case, the maximum applied pressure applied to the joint is determined by the shape and the internal pressure, but the joint maximum principal stress generated at an internal pressure of 2000 atmospheres can be estimated to be 190 MPa, and similarly at 3,000 atmospheres it is 270 MPa. In the results of FIG. 7, black circles indicate damage from the rail body, black circles with → indicate data in which fatigue failure did not occur even after 10 million cycles, and black triangles indicate the case where damage occurred from the joint between the holder and the rail. . The internal pressure applied to the actual common rail is the largest among those assumed to be 2200 atm. According to the data in FIG. 7, the fatigue limit pressure can be read as 2300 atm, and the manufactured common rail has a maximum of 2200 atm. It can be seen that it can withstand the internal pressure of 10 million times of fatigue test. Further, in the figure, the result of the case where the protrusion is not attached to the holder with a dotted line and the recess is not attached to the outer peripheral wall of the rail body groove is also shown as a representative line. The stress at the fatigue limit is slightly reduced, but this is because the fatigue limit value is obtained from the data fractured from the joint at 3.7 million times and 5.6 million times. It is clear that the joint rail reliability of the common rail is clearly improved over the prior art.

It is a figure which shows the structure of a common rail in detail including the inside, (a) is a top view, (b) is a front view. (A) is a cross-sectional view in the width direction of a welded common rail according to the present invention, and (b) is a cross-section in a mating state between a holder provided with a part of the protrusion and a recess provided in the outer wall of the rail body groove. It is a figure which shows an enlarged view. (A), (b), (c) is a figure which shows the process of applying a stress to the joining edge part of a holder from upper direction immediately after welding joining, and plastically deforming at 1000 degreeC or more, and shape | molding a protrusion part. (A), (b), and (c), a protrusion is processed in advance at the end of the outer peripheral surface of the holder, and immediately after joining, stress is applied from above and plastic deformation is performed at 1000 ° C. or more to bulge the protrusion. It is a figure which shows the process made to fit and the rail main-body groove | channel outer peripheral wall hollow part. It is a figure which shows the relationship between the one-side increment from the holder outer diameter of the protrusion outer diameter processed beforehand, and the plastic deformation start stress at the time of the extraction stress of a holder. It is a figure which shows the relationship between the one side increment from the holder outer diameter of the protrusion part outer diameter in the case of forming a protrusion part by the plastic deformation at the time of joining, and the plastic deformation start stress at the time of the extraction stress of a holder. It is the figure which showed the comparison of the internal pressure fatigue test result of the common rail manufactured with the method of this invention, and a prior art.

Explanation of symbols

1 Piping mounting parts (holder)
2 Rail body 3 Branch capillary (orifice)
4 Guide groove depth when the holder is joined to the rail body 5 Holder axial height of the protrusion of the holder 6 Recessed portion of the outer wall of the rail body groove 7 Taper angle of the holder protrusion 8 Holder protrusion 8 'Holder outer surface Forming process of protruding part due to high temperature plastic deformation at the end 8 "Final shape of protruding part due to high temperature plastic deformation at the end of holder outer surface

Claims (5)

  Piping fittings (holders) that install piping from multiple branch passages for distributing fuel at the same pressure to the injection nozzles that are inserted into the combustion chamber of the engine to the rail body of the high-pressure fuel injection accumulator / distributor (common rail) for automobiles Are welded common rails joined by liquid phase diffusion bonding or the like, wherein the holder has a length in the holder axial direction of 2 mm or more at the end of the outer peripheral surface on the weld joint surface side, and over the entire circumference. It has a protrusion with a large outer diameter of 1 mm or more on one side from the outer peripheral surface of the holder body, which is formed in the heat during welding such as liquid phase diffusion bonding, and the rail body is used for determining the holder bonding position at the holder bonding position. The groove has a groove inner peripheral wall having a diameter that can be fitted to the inner periphery of the holder joint, a groove bottom surface that serves as a joint surface with the holder, and a depth of 3 mm or more from the groove bottom surface. Fragment A groove outer peripheral wall having a diameter with a clearance of 1.5 mm or less, and further, the groove outer peripheral wall has a hollow portion that fits into a protruding portion of the joint outer surface side end portion of the holder outer peripheral surface, A high-pressure fuel injection / accumulation / distribution distributor for an automobile, wherein a fastening force between the holder and the rail body is enhanced by an anchor effect caused by fitting of the recess of the outer peripheral wall of the groove and the protrusion of the holder.   The holder and the rail body are steel materials having a tensile strength of 800 MPa or more and 1500 MPa or less at room temperature, and 200 MPa or less at a temperature of 1000 ° C. or more, and the holder pull-out generated when an internal pressure is applied to the fuel injection system. 2. The high-pressure fuel injection / accumulation / distribution distributor for an automobile according to claim 1, wherein a plastic deformation initiation stress (elastic limit) is 200 MPa or more in a range up to 100 ° C. 3.   Piping fittings (holders) that install piping from multiple branch passages for distributing fuel at the same pressure to the injection nozzles that are inserted into the combustion chamber of the engine to the rail body of the high-pressure fuel injection accumulator / distributor (common rail) for automobiles A high pressure fuel injection / accumulation / accumulator / distributor for automobiles, wherein the rail body has a holder joint position determination groove at a holder joint position, and the groove is a holder joint. A groove inner peripheral wall with a diameter that can be fitted to the inner periphery of the groove, a groove bottom surface that becomes a weld joint surface with the holder, a depth of 3 mm or more from the groove bottom surface, and a diameter that is less than 1.5 mm on one side of the holder outer diameter Further, the groove outer peripheral wall has a length extending from the groove bottom surface to the groove depth direction length of 2 mm or more and over the entire circumference from the groove outer peripheral wall by 1 mm or more on one side. After processing the rail body so as to have a large depression, the joint is exposed to a high temperature of 1000 ° C. or higher when the holder is bonded to the rail body by liquid phase diffusion bonding or the like. By applying a stress of 10 MPa or more to the entire holder for 0.1 to 60 seconds in addition to the required stress application time at the time of joint joining, the length of the holder in the axial direction on the joint surface side end of the outer peripheral surface of the holder A protrusion having a large outer diameter of 1 mm or more on one side from the outer peripheral surface of the holder main body is formed by hot plastic deformation in a range extending over 2 mm and over the entire circumference, and the protrusion of the holder is formed as a groove outer peripheral wall of the rail main body. A method of manufacturing a high-pressure fuel injection / accumulation / distribution distributor for an automobile, wherein the fastening effect between the holder and the rail body is increased by an anchor effect.   The holder protrusion is formed in advance by machining, cold pressing or cold forging, hot forging, or a combination of hot pressing and grinding by machining, and the holder outer peripheral surface of the holder protrusion is 1 mm or more on one side. The manufacturing method of the high-pressure fuel-injection / accumulation-distributor for automobiles according to claim 3, wherein an angle formed between the inclined surface connected to the holder and the outer peripheral surface of the holder is 45 ° or more.   The holder and the rail body are steel materials having a tensile strength of 800 MPa or more and 1500 MPa or less at room temperature, and 200 MPa or less at a temperature of 1000 ° C. or more, and the holder pull-out generated when an internal pressure is applied to the fuel injection system. 5. The method for manufacturing a high-pressure fuel injection accumulator / distributor for an automobile according to claim 3 or 4, wherein a plastic deformation starting stress (elastic limit) is 200 MPa or more in a range up to 100 ° C.

Images