JP4740226B2 - Common rail - Google Patents

Description

  The present invention relates to a common rail provided with a holder for attaching a pipe (hereinafter referred to as an injection pipe) connected to an injection nozzle mounted in a combustion chamber of an automobile engine.

  In recent years, passenger cars equipped with diesel engines have been increasing in Europe, which is largely due to technological development of fuel injection devices. In particular, high performance (high pressure) of the common rail is used as the core part, and light oil with less impurity components is used, resulting in high output, low fuel consumption, and large torque. .

  In a diesel engine fuel injection system that uses light oil as fuel, the common rail temporarily holds the light oil sucked by the pump from the fuel tank at a high pressure, and supplies the light oil through the injection pipe from the orifice to the injection nozzle of each combustion chamber. Used as a fuel accumulator / distributor for pumping

  The light oil pumped to the injection nozzle is mixed with the combustion air, and then injected into the engine combustion chamber for explosive combustion. In order to improve the combustion efficiency, the light oil pressure in the common rail may be increased. It is desired.

  Therefore, conventionally, the strength has been improved by controlling the manufacturing conditions such as the chemical composition and heat treatment of the steel used for the common rail, and until now, a sufficiently reliable common rail has been developed up to a fuel injection pressure of 150 MPa. Has already been put to practical use. In the manufacturing method of the high-pressure common rail exceeding 150 MPa, at the present time, the common rail body is integrally formed by forging, and then a complicated distribution pipe is machined.

  However, development of common rail manufacturing technology that replaces conventional forging integrated molding and machining methods from the viewpoint of increased formability and workability due to higher strength of common rail materials, and increased costs due to higher performance. Has become an issue.

  The biggest problem with the increase in fuel injection pressure is fatigue at the end of the orifice, which is due to the area where the diameter of the oil flow passage becomes narrower. In the conventional common rail, an orifice 13 is provided at the boundary between the rail hole 11 and the branch hole 12 as shown in the longitudinal sectional view of FIG. In this boundary portion, the diameter of the oil flow passage is abruptly narrowed, so that the stress concentration becomes large and fatigue becomes a problem. As a countermeasure against this, as disclosed in Patent Document 1, compressive stress is applied by applying a laser peening process by irradiation with a pulsed laser beam near the entrance of the orifice 13 on the rail hole 11 side, thereby improving fatigue strength. There is a way. However, since the laser beam is transmitted to the rail hole 11 of the rail body 1 to be a narrow portion and processing is performed, there is a problem that productivity is low.

  On the other hand, instead of drilling the orifice in the rail body, as shown in FIG. 16, the orifice tube 3 is fixedly fitted into the branch hole 12 of the rail body 1 and connected to the injection nozzle outside the orifice tube 3. The structure which installs the connection head of the injection pipe 2 to be performed is disclosed in Patent Document 2, for example. Increasing the strength of the orifice itself is one solution for increasing the pressure of the injected fuel. However, the higher the strength, the higher the cost of the material, and the inner fitting fixing process to the branch hole is required. There is a problem that becomes difficult.

JP 2006-322446 A Japanese Patent No. 3806302

  An object of the present invention is to solve the above-described problems, and to provide a common rail that can withstand high injected fuel pressure and has low manufacturing cost and high productivity.

  As a result of investigations to solve the above-mentioned problems, the inventors of the present invention installed an orifice pipe between the rail body and the injection pipe connected to the injection nozzle, and placed a laser around the opening end of the orifice hole of the orifice pipe. It has been found that if compressive stress is introduced by a peening method or the like, a high-pressure common rail with low manufacturing cost and high productivity can be obtained. That is, the present invention is as follows.

  According to a first aspect of the present invention, an injection nozzle is provided in a rail body in which a rail hole through which a fluid passes is formed at a central portion, and a plurality of branch holes opening outward are formed in a cylindrical wall portion surrounding the rail hole. An orifice pipe for distributing the fluid at an equal pressure is provided in the middle of the flow path from the boundary between the rail hole and the branch hole to the injection pipe. The common rail is characterized in that residual compressive stress is applied to the periphery of one or both of the two openings on the rail hole side and the injection pipe side that are provided and communicated with the orifice pipe. is there.

  According to a second aspect of the present invention, the introduction depth of the residual compressive stress with respect to the circumferential direction is 0.1 mm or more in the periphery of the orifice hole opening of the orifice pipe, and the circumferential residual stress on the surface is It is characterized by being 30% or more of the tensile strength of the material constituting the tube.

  The third aspect of the present invention is characterized in that the residual compressive stress is applied by a laser peening process.

  According to a fourth aspect of the present invention, the surface layer of the material on the laser-treated surface is removed after the laser peening treatment.

  The fifth aspect of the present invention is characterized in that the surface layer is removed by an electrolytic polishing method or a fluid polishing method.

  According to a sixth aspect of the present invention, the yield strength of the orifice pipe is smaller than that of the rail body.

  According to the present invention, a common rail with increased fatigue strength can be obtained by applying residual compressive stress to the periphery of the opening end of the orifice hole in the orifice pipe. Moreover, since the strength of the orifice itself can be kept low, the workability of the orifice can be ensured.

  Below, the detail of the common rail of this invention is demonstrated. In the present specification and drawings, elements having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 shows a schematic cross section of a common rail body 1. A rail hole 11 is formed at the center of the rail body 1, and a plurality of branch holes 12 that are opened outward from the cylindrical wall portion 14 surrounding the rail hole 11 are formed.

  FIG. 2 illustrates a part of the common rail according to the present invention. A holder 4 that is an attachment part for attaching an injection pipe 2 connected to an injection nozzle (not shown) is joined to the rail body 1. A guide groove 15 for precisely joining the holder 4 to a required position is formed on the outer wall of the rail body 1. The holder 4 has a small-diameter cylindrical portion on the injection tube 2 side and a large-diameter cylindrical portion on the side joined to the outer wall of the rail body 1, and has a coaxial two-stage cylindrical outer shape as a whole. A screw 4a for fitting a tightening nut 5 described later is formed on the outer side of the injection pipe 2 side. In addition, as a metal material used for the common rail main body 1 and the holder 4, a steel material is generally used.

  As a joining method of the rail main body 1 and the holder 4, there are liquid layer diffusion joining, resistance welding, or a joining method combining them. The liquid layer diffusion bonding method is a method in which a bonding layer having a uniform structure is formed by holding at about 1000 ° C. or higher via a low melting point amorphous alloy foil between the bonding surfaces of the rail body 1 and the holder 4. .

  Of course, the rail body 1 and the holder 4 may be integrally formed. However, if the reliability of the joint is ensured, the rail body 1 and the holder 4 can be made as separate parts as described here. However, it is desirable from the viewpoint of processability and processing cost.

  An orifice pipe 3 and an injection pipe 2 connected to an injection nozzle are connected to the outlet of the branch hole 12 outside the rail body 1 in this order toward the outside. The orifice tube 3 is made of a metal material such as steel, and after the orifice hole 21 and the tapered portions 22 and 23 are machined, a compressive stress is applied to the periphery of the opening end of the orifice hole 21 as will be described in detail later. Is done. In the example shown in FIG. 2, when the tightening nut 5 described above is tightened, between the pressing seat surface 26 of the connection head of the injection tube 2 and the upper portion of the orifice tube 3, the lower portion of the orifice tube 3 and the rail body 1. A metal touch seal is provided between the pressure receiving seat surface 16 provided at the outlet of the branch hole 12.

  While the common rail is in operation, vibrations of the engine and vehicle body occur, but stable sealing is required even under such conditions. For this purpose, it is desirable that the yield strength of the orifice tube 3 is made smaller than that of the rail body 1 and a metal touch seal is realized by deformation of the orifice tube 3. In the common rail of the present invention, fatigue characteristics can be ensured by locally reinforcing the orifice tube 3 without increasing the strength of the material itself. For this reason, if the magnitude relationship of the yield strength described above is taken into account, the strength of the rail body 1 can be suppressed and the cost merit is great. For the same reason, it is desirable to make the yield strength of the injection pipe 2 smaller than that of the orifice pipe 3.

  The structure for connecting the injection tube 2 to the holder 4 is not necessarily limited to the method described above. As an example, the structure shown in FIG. 3 differs from the structure shown in FIG. 2 only in that the injection tube 2 is directly fastened to a screw 4 b formed on the inner surface of the holder 4. The structure of FIG. 3 is complicated in that a screw is formed on the outer periphery of the injection tube 2, but has an advantage that the number of parts can be reduced as compared with the structure of FIG. Furthermore, as a method for installing the orifice pipe 3, a configuration in which the orifice pipe 3 is fitted and fixed to the branch hole 12 as shown in FIG. 16 may be used.

  Next, taking the orifice pipe 3 shown in FIG. 2 as an example, a method for introducing compressive stress into the periphery of the opening end of the orifice hole 21 of the orifice pipe 3 will be described with reference to the enlarged view of the orifice pipe 3 shown in FIG. explain. 4A is a cross-sectional view of the orifice hole 21 in the longitudinal direction, and FIG. 4B is a plan view of the orifice hole 21 viewed from the central axis direction. Compressive stress is introduced by forming the orifice hole 21 and the tapered portions 22 and 23, the pressure seating surface 26 (see FIG. 2) of the connection head of the injection pipe 2, and the pressure receiving seat provided at the outlet of the branch hole 12 of the rail body 1. This is performed after machining such as processing of the seat surfaces 24 and 25 for metal touch sealing with the surface 16 and before connecting to the branch hole 12 of the rail body 1. The compressive stress is applied to one or both peripheral portions of the opening ends 21 a and 21 b at both ends of the orifice hole 21. This is selected in consideration of the load stress distribution determined from the opening diameter of the orifice hole 21 and the shape of the periphery thereof.

  Examples of a method for applying compressive stress to the periphery of the opening end of the orifice hole 21 include a laser peening process, a method of hitting with a vibration terminal that vibrates ultrasonically, and a coining process of pressing with a spherical metal punch. From the viewpoint of easy access to narrow holes, laser peening treatment, which is non-contact treatment, is easy to construct.

  Below, the laser peening processing method is demonstrated. An example of the irradiation apparatus is shown in FIG. 5 (plan view) and FIG. 6 (side view). As shown in the figure, the orifice tube 3 that has been machined is immersed in a water tank 35, and a laser beam 32 is irradiated from a laser beam oscillator 31. The laser beam 32 is condensed by a condensing lens 33 made of a convex lens, and irradiated to the orifice tube 3 through an optical window 34. The rear side of the orifice tube 3 is attached to a guide 40 slidable in the vertical direction (V direction) as shown in FIG. Moreover, the guide 40 is connected to the support part 41 attached to the guide 42 which can be slid to a horizontal direction (H direction), as shown in FIG. The orifice tube 3 is installed so as to be movable in both the H and V directions along the guides 40 and 42 under the control of the scanning device 43.

The laser peening process requires (1) a laser beam having a high peak power density and (2) installation of a transparent medium such as water near the irradiated surface. About (1), the peak power density in the surface of the rail hole inner periphery which is an irradiation point shall be 1-100 TW / m < ² >. In order to obtain this peak power density, the laser device uses a pulse laser that oscillates intermittently with a pulse time width of about 10 ps to 100 ns and a pulse energy of about 0.1 mJ to 100 J. An example of such a laser device is an Nd: YAG laser, but any laser device that satisfies the above condition (1) may be used. When the above conditions (1) and (2) are satisfied, the plasma generated by the irradiation of the pulse laser beam having a high peak power density is suppressed by the presence of a transparent medium such as water near the irradiated surface. And the plasma pressure is increased. By the reaction force of the plasma that has become high pressure, plastic deformation can be applied in the vicinity of the irradiation point, and residual compressive stress can be applied.

  In order to improve the internal pressure fatigue strength, it is effective to apply a particularly large compressive stress in the circumferential direction over the entire circumference of the opening end of the orifice hole 21. For this purpose, it is desirable to perform processing while superimposing the beam spot of the pulse laser as follows. In the irradiation apparatus shown in FIGS. 5 and 6, the movement of the beam spot position of the pulse laser is realized by the scanning device 43.

  One method is to form a laser beam irradiation spot 51 along a circle centered on the orifice hole 21 as shown in FIG. If one scanning area cannot be covered, a plurality of scanning areas are formed. At this time, it is desirable to perform processing so that adjacent scanning regions overlap so that an unprocessed region does not occur. By setting the area of the overlapping portion of adjacent laser beam irradiation spots 51 in the same circle to 20% or more of the area of each laser beam irradiation spot 51, the stress in the circumferential direction of the orifice hole 21 around the opening ends 21a and 21b is increased. Selectively enhanced.

  In another method, as shown in FIG. 8, the laser beam irradiation spot 51 is scanned in a plane including the axis of the orifice hole 21, and the scanning of the laser beam irradiation spot 51 is shifted in the circumferential direction of the orifice hole 21. However, it is performed several times. The laser beam irradiation spots 51 are scanned so that adjacent laser beam irradiation spots 51 in the same scanning region overlap each other. In addition, processing is performed so that adjacent scanning regions overlap each other. By performing the treatment under the condition that the average number of times of irradiation of the pulse laser beam to the same point is two times or more, anisotropy is generated in the residual compressive stress on the surface, and the circumference of the orifice hole 21 around the open ends 21a and 21b. The compressive stress in the direction can be selectively strengthened.

  The area where compressive stress is applied around the opening of the orifice hole 21 depends on the design philosophy of the parts such as the inclination of the taper portions 22 and 23 and how much the stress concentration is relaxed. As shown in the figure, it is often sufficient to laser treat a region where the distance from the center of the orifice hole 21 is within 1.5 times the diameter d of the orifice hole 21. Although depending on the laser processing conditions, in the laser peening process, compressive stress can be introduced to a depth of about 1 mm, and therefore the inner surface of the orifice hole 21 also corresponds to this introduction depth from the open ends 21a and 21b. The residual compressive stress in the circumferential direction is applied to the region up to the distance.

Below, the experimental result which demonstrates the effect of this invention is demonstrated. In the experiment, the orifice tube 3 having the shape shown in FIG. 9 was manufactured using a steel material having a tensile strength of 800 MPa, and laser peening was performed. In the laser peening process, the apparatus shown in FIGS. 5 and 6 was used, and the orifice tube 3 immersed in the water tank 35 was irradiated with a laser beam. As the laser beam, a second harmonic (wavelength: 532 nm) of an Nd: YAG laser having good underwater permeability was used. The laser beam was condensed with a convex lens having a focal length of 100 mm. Laser beam irradiation is performed from the direction indicated by the arrow in FIG. 9 with respect to the tapered portion 22 that is the periphery of the opening end of the orifice hole 21, and the shape of the beam spot on the tapered portion 22 is 0.8 mm It was an ellipse with a diameter of 0.6 mm. The laser pulse energy was 150 mJ and the peak power density was 40 TW / m ² . The pulse time width was 10 ns and the pulse repetition frequency was 30 Hz. The method of superimposing the beam spot of the pulse laser used the method shown in FIG. As shown in FIG. 10, the treatment area is an area where the distance from the center of the orifice hole 21 is 1.5 times the diameter d = 0.7 mm of the orifice hole 21, that is, within 1.1 mm. The depth direction distribution of the residual stress in the circumferential direction of the orifice hole 21 was measured using an X-ray residual stress measuring device. The stress measurement region is as shown in FIG. The measurement results are shown in FIG. When viewed from the axial direction of the orifice hole 21, the stress measurement region looks elliptical as shown in FIG. 10, but is circular when viewed from the direction perpendicular to the tapered portion bc, and its diameter is 0.7 mm. . The stress near the point c was measured as a representative point, but the residual stress was almost the same over the entire circumference. The stress distribution in the depth direction was measured while removing the steel material successively by electrolytic polishing. Polishing was performed in the direction of the bisector of the angle acb as indicated by an arrow cz in FIG. 9, and the stress on this cz was measured. The depth shown on the horizontal axis in FIG. 11 is defined as the distance from the point c on cz. In the present invention, the depth at which the residual stress changes from compression to tension is called the introduction depth of the residual compression stress. Looking at the measurement results, the introduction depth of the residual compressive stress in the circumferential direction of the orifice hole 21 is 0.6 mm. The residual stress on the surface is -604 MPa. This result shows that the laser peening process is effective in applying compressive stress to the periphery of the opening end of the orifice hole 21. Considering that the tensile strength of the steel material is 800 MPa, the injected fuel pressure is a level applicable to a 200 MPa class common rail.

  Further, as shown in FIG. 11, the residual compressive stress becomes maximum at a depth of 30 μm (−712 MPa), which exceeds the residual stress on the surface. This is because when the surface of the sample is irradiated with a laser beam, the vicinity of the surface area of the irradiated spot is melted and re-solidified, and the residual stress on the outermost surface is reduced compared to the inside. In order to suppress the occurrence of fatigue cracks, it is effective to maximize the compressive stress on the outermost surface. Therefore, after applying the laser peening process described above, the material on the outermost surface with reduced residual stress is used. By removing, the effect of the laser peening process can be further increased. The removal of the material by mechanical polishing or the like may leave a tensile stress on the surface after the removal and adversely affect the fatigue characteristics. Therefore, an electrolytic polishing method or a fluid polishing method is desirable as the removal method.

  It is effective to set the removal thickness within the following range. First, the removal thickness is set to 0.01 mm or more in order to remove the vicinity of the surface that is melted and re-solidified by laser irradiation and the stress is shifted to the tension side. On the other hand, as shown in FIG. 11, the compressive stress introduced by laser peening tends to decrease as the depth from the surface increases. For example, from the stress depth distribution shown in FIG. 11, if the material is removed from the surface to a depth of about 0.1 mm or more, it is expected that the surface stress after the removal will be rather smaller than before the removal. . Decreasing the compressive stress in the depth direction can be mitigated by increasing the pulse energy (150 mJ under the present conditions). That is, it is possible to obtain a larger removal thickness by increasing the pulse energy, but it is effective to keep the removal thickness at about 0.3 mm or less.

  Although the method for applying compressive stress to the orifice tube of the present invention has been described above, it should be noted that the shape of the orifice tube is not limited to the example described here. For example, like the orifice tube 3 shown in FIG. 16, the orifice tube 3 having no tapered portion can be applied with compressive stress by the same method as described above.

  Below, the fatigue test which simulated the repeated load concerning an orifice hole opening peripheral part was performed, and the result of having verified the effect of this invention is demonstrated. In the test, as shown in FIG. 12, an Ono type rotating bending fatigue test was performed using a test piece 91 having a through hole 92 having a diameter of 1 mm in the center of a constricted portion 93 having a diameter of 6 mm. The test piece 91 was created using an 800 MPa class steel material. In such a test piece 91, stress concentration occurs in the vicinity of the through hole 92. The load stress is maximized in the direction along the circumference of the through hole 92 (hereinafter, the circumferential direction). This circumferential stress becomes maximum at points A and B in FIG.

  The apparatus shown in FIGS. 5 and 6 was used for the laser peening process. A test piece 91 (not shown in FIGS. 5 and 6) was attached to the support portion 38, and laser peening was performed on the opening peripheral portions on both sides of the through hole 92. As the laser beam, the second harmonic of an Nd: YAG laser or the second harmonic of an Nd: YVO4 laser was used. Both laser beams have a wavelength of 532 nm. The time width of the pulse laser beam was 10 ns for the Nd: YAG laser and 1 ns for the Nd: YVO4 laser. The pulse repetition frequency was 30 Hz for the Nd: YAG laser and 100 Hz for the Nd: YVO4 laser. The spot shape on the test piece 91 was almost circular in any laser.

  In order to increase the compressive stress in the circumferential direction around the opening of the through hole 92, the beam spot is scanned in a plane including the axis of the through hole 92 as shown in FIG. The pulsed laser beam was irradiated by a method performed several times while shifting the position in the circumferential direction. As shown in FIG. 13, the laser-treated region has a distance from the axis of the through hole 92 within 1.5 times the diameter d of the through hole, that is, within 1.5 mm, on the outer surface of the constricted portion 93 having a diameter of 6 mm. It is an area. The average value of the number of times of irradiation with the pulse laser beam for the same point was set to 25 times for all laser processing conditions. In the test, laser peening treatment was performed for several conditions with different pulse energies, the introduced stress was measured, and the fatigue strength was evaluated.

Table 1 shows the fatigue test results. The table also shows the result of measuring the circumferential residual stress σ _A of the through hole 92 at the point A (outside of the through hole at φ 6 mm outer surface) on the outer peripheral surface of the constricted portion 93 for each laser processing condition. . The residual stress was measured using an X-ray residual stress measuring device. As shown in FIG. 13, the X-ray spot diameter corresponding to the stress measurement region was 1.0 mm. The stress at point A was measured as a representative point, but the residual stress was substantially the same over the entire circumference. Further, the depth direction distribution of the circumferential stress in the through hole was measured while removing the steel material successively by electrolytic polishing. FIG. 14 shows a method of measuring the depth direction distribution. As in the case of the stress measurement in the periphery of the orifice hole 21 in FIG. 10, polishing is performed in the direction of the bisector of the angle EAC (angle EAC = 90 °) as shown by the arrow Az in FIG. The circumferential stress on the top was measured. Table 1 shows the introduction depth of residual compressive stress as a measurement result. This depth is defined as the distance from the point A on Az.

Condition 1 is a comparative example, and is a result for a test piece that was not subjected to laser peening. Conditions 2 to 5 are examples corresponding to embodiments of the present invention that have been subjected to laser peening. Under conditions 2, 3, and 4, 15 to 25% improvement in fatigue strength was observed with respect to condition 1. On the other hand, in condition 5, the improvement in fatigue strength was only 5%. In order to increase the fatigue strength, the larger the surface compressive stress, that is, σ _A , and the greater the introduction depth of the compressive stress, the more effective. Looking at the results in Table 1, in the order of condition 2, condition 3, condition 4, and condition 5, as the pulse energy decreases, σ _A increases and the depth of introduction of residual compressive stress decreases. Condition 5 was the largest of the four conditions (conditions 2 to 5) regarding the compressive stress on the surface, but the improvement in fatigue strength was small. This is probably because the introduction depth of the compressive stress was small (0.08 mm). Therefore, in the present invention, the preferable range of the introduction depth of the compressive stress is set to 0.1 mm or more.

In addition, Condition 6 which is an example corresponding to another embodiment of the present invention is one in which the material is removed by electropolishing after laser peening is performed under the same condition as Condition 2. Polishing was performed concentrically around the axis of the through hole 92 while pressing the spherical protrusion and energizing. The polishing area was within a radius of 1.7 mm from the axis of the through hole 92, and the material was removed from the outer surface of the constricted portion 93 to a depth of about 50 μm. Since the vicinity of the surface where the stress was shifted to the tension side due to melting and re-solidification by laser irradiation was removed, σ _A was larger than in condition 2 and the fatigue strength was further improved (33% improvement over condition 1) )was gotten.

Furthermore, Table 2 shows the results of the Ono-type rotating bending fatigue test described above performed for laser processing conditions different from those in Table 1. In this test, in the laser peening process, the average value of the number of times of irradiation of the pulse laser beam with respect to the same point (average number of superpositions) was changed. The laser beam used was a second harmonic (wavelength: 532 nm) of an Nd: YAG laser, the laser pulse energy was 200 mJ, and the beam spot diameter was 0.8 mm. The time width of the pulse laser beam was 10 ns, and the pulse repetition frequency was 30 Hz. The laser-treated region, the residual stress σ _A, and the method for measuring the introduction depth are the same as in Table 1 above. Further, in Table 2, Condition 1 which is a comparative example in which the laser peening treatment was not performed is the same as that in Table 1.

From the results of conditions 7 to 10 on which the laser peening treatment was performed, it can be seen that as the average number of superpositions increases, both σ _A and the introduction depth increase, and the fatigue strength also increases. In condition 7, although the introduction depth of compressive stress exceeds 0.1 mm (0.15 mm), σ _A is small because the number of average superposition times is insufficient, and the improvement in fatigue strength is small (compared to condition 1) 5% improvement). This, sigma _A is, because smaller relative tensile strength of the steel material constituting the test piece (sigma _b), i.e. (σ _{A /} σ _b) can be interpreted that this is because the smaller. Under condition 7, (σ _A / σ _b ) was 0.14. On the other hand, in condition 8 where fatigue strength improvement was obtained, (σ _A / σ _b ) was 0.33. Therefore, in the present invention, the preferred range of _{σ A (σ A / σ b} ) was 0.3 or more.

  The present invention can be applied to a common rail used in an accumulator fuel injection system.

It is sectional drawing of the rail hole longitudinal direction of a common rail main body. It is sectional drawing of the rail hole longitudinal direction which shows embodiment of the common rail concerning this invention. It is sectional drawing of the rail hole longitudinal direction which shows different embodiment of the common rail concerning this invention. FIG. 3 is an enlarged view showing the orifice of FIG. 2, (A) is a sectional view in the longitudinal direction of the orifice hole, and (B) is a plan view seen from a direction perpendicular to (A). It is a top view which shows a laser beam irradiation apparatus. FIG. 6 is a side view of FIG. 5. It is a top view explaining the laser beam irradiation method to an orifice hole periphery. It is a top view explaining the different laser beam irradiation method to an orifice hole periphery. It is sectional drawing of the orifice hole longitudinal direction of the orifice pipe which implemented the laser beam process. It is a top view explaining the laser beam process area and stress measurement area | region around an orifice hole. It is a graph which shows the residual stress of the orifice pipe | tube which carried out the laser peening process. It is a top view which shows a test piece. It is explanatory drawing which shows the laser irradiation method to a through-hole opening peripheral part. It is sectional drawing of the constriction part of FIG. 12 explaining a grinding | polishing direction. It is sectional drawing of the rail hole longitudinal direction which shows the prior art example of a common rail. It is sectional drawing of the rail hole radial direction which shows the prior art example from which a common rail differs.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rail main body 2 Injection pipe 3 Orifice pipe 4 Holder 5 Nut 11 Rail hole 12 Branch hole 13 Orifice 14 Cylindrical wall part 16 Pressure-receiving seat surface 21 Orifice hole 21a, 21b Open end peripheral part 22, 23 Taper part 24, 25 Seat 26 Press seat surface 31 Laser beam oscillator 32 Laser beam 33 Condensing lens 34 Optical window 35 Water tank 38, 39, 41 Support section 40, 42 Guide 43 Scanning apparatus 51 Laser beam irradiation spot 91 Test piece 92 Through hole 93 Constriction

Claims (6)

A rail hole in which a fluid passes is formed in the center, and a jet pipe connected to the jet nozzle is attached to a rail body in which a plurality of branch holes opening outward are formed in a cylindrical wall portion surrounding the rail hole. Is a common rail to which the holder is connected,
In the middle of the flow path from the boundary between the rail hole and the branch hole to the injection pipe connected to the injection nozzle, an orifice pipe for delivering the fluid at an equal pressure is provided and communicates with the orifice pipe The common rail is characterized in that residual compressive stress is applied to the periphery of one or both of the two openings on the rail hole side and the injection tube side.   In the periphery of the orifice hole opening of the orifice pipe, the introduction depth of the residual compressive stress in the circumferential direction is 0.1 mm or more, and the circumferential residual stress on the surface is the tensile strength of the material constituting the orifice pipe. It is 30% or more, The common rail of Claim 1 characterized by the above-mentioned.   The common rail according to claim 1, wherein the residual compressive stress is applied by a laser peening process.   The common rail according to claim 3, wherein a surface layer of a material of a laser processing surface is removed after the laser peening processing.   5. The common rail according to claim 4, wherein the surface layer is removed by an electrolytic polishing method or a fluid polishing method.   The common rail according to claim 1, wherein the yield strength of the orifice pipe is smaller than that of the rail body.

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