JPH10141172A - Manufacture of common rail - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent projecting and recessed parts and fine cracks produced on the inner peripheral surface of a flow passage by rotating a roller relatively to a common rail to perform burnishing for the inner peripheral surface of a flow passage while tapping. SOLUTION: A roller burnishing device RB comprises plural rollers 2 for pulling a mandrel 1 axially relatively to a common rail 10 and engaging with the mandrel 1 on a conical surface 1a formed on the outer peripheral surface of the mandrel 1 to be freely rotated, and a retainer 3 for retaining the rollers 2 on the conical surface 1a of the mandrel 1. A burnishing device RB is introduced into a hollow part of a common rail 10 to be worked, so that plural rollers 2 rolling on the conical surface la of the mandrel 1 conducts rolling compaction for the inner peripheral surface 11 of the flow passage to perform roller burnishing. Thus, cracks and creased of the inner peripheral surface 11 of the flow passage can be prevented by rolling compact and tapping operation of the rollers 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high pressure fuel manifold which is connected to a branch connection such as a branch pipe or a branch fitting connected to an injection nozzle provided with an on-off valve or a high pressure pump, and which functions as a pressure accumulating chamber. The present invention relates to a method of manufacturing a common rail such as a pipe or a high pressure fuel block.

[0002]

In order to reduce the particulates and NO _x in the Background of the Invention Diesel engines, but the recent supply fuel has a tendency to high pressure, the fuel enough to be supplied at high pressure, the fuel injection pump in a fuel injection system It has become extremely difficult to control the timing between the fuel injection nozzle and the fuel injection nozzle, particularly the timing at the beginning of injection and the end of injection.
Therefore, the fuel is pressurized in advance by a high-pressure pump and stored in a pressure accumulator, and an injection nozzle is provided with a mechanically or electrically controlled on-off valve to supply the pressurized high-pressure fuel to the combustion chamber. A control method was proposed. In such a system, the high-pressure fuel manifold or high-pressure fuel block serving as a pressure accumulation chamber is called a common rail, and is connected to the pump or nozzle so as to be substantially perpendicular to the radial direction of the common rail. A branch connection body such as a branch fitting is connected.

In this case, the high-pressure fuel manifold or the high-pressure fuel block used for the common rail has conventionally been manufactured as follows. That is, in the case of the high-pressure fuel block, a thick-walled small-diameter block having a flow passage formed by performing a punching process by a gun drill on a metal block formed by forging is used. In the case of a high-pressure fuel manifold, a heat treatment and drawing process are repeated four to five times on a metal tube, and a thick-walled small-diameter tube having a flow passage is used.

[0004] However, since the inner peripheral surface of the passage of the common rail finished by using a gun drill is formed by cutting or grinding, rough unevenness remains on the finished surface, and the inside of the passage is circulated. 100 fuel to burn
Due to the high pressure of 0 kgf / cm ² or more and the rapid pressure fluctuation of the fuel inside the flow passage, cracks may be generated or grown on the inner peripheral surface of the flow passage. There is a possibility that a common rail breakage accident or the like may occur due to the repeated fatigue of sudden high-pressure fluctuations caused by the high pressure generated on the inner peripheral surface of the flow passage or the vibration of the engine.

[0005] Further, in the case of using a thick-walled small-diameter tube having a flow passage formed by repeating heat treatment and drawing for 4 to 5 times on a metal tube, the thick-walled small-diameter tube is formed by hot working. Therefore, a black scale layer having fine cracks and concave wrinkles due to plugs or the like must be present on the inner peripheral surface of the flow passage during processing. In this case, even if the finishing treatment is performed by immersion treatment in a chemical solution, it is not easy to completely remove black scale from the inner peripheral surface of the flow passage and finish the peripheral wall into a uniform smooth surface. When the fuel passes through the flow passage, the black scale remaining on the inner surface may peel off from the inner peripheral surface, causing the fuel injection nozzle of the diesel engine to be closed.

[0006] In order to prevent such a situation from occurring, the present applicant has previously proposed a manufacturing method in which mechanical means such as cutting and grinding are introduced in a process prior to the final drawing process.
No. 1 and further disclosed in Japanese Patent Application Laid-Open No. 5-154536, a core metal having a cutting blade at one end is pulled relatively to a pipe to be processed, and moved inside the pipe. The manufacturing method which finishes the inner peripheral surface of the flow passage of the pipe to be processed by relatively rotating is proposed.

[0007]

However, in any of the above-mentioned manufacturing methods, since the inner peripheral surface of the flow passage is finished by cutting or grinding, irregularities or fine cracks generated on the finished surface are completely eliminated. In addition, it is difficult to avoid the drawback that the residual compressive stress applied to the inner peripheral surface of the flow passage at the stage of final drawing is released by cutting or grinding.

According to the present invention, it is possible to substantially eliminate unevenness or fine cracks generated on the inner peripheral surface of the flow passage of the common rail, and to leave a compressive stress on the inner peripheral surface of the flow passage by roller burnishing, thereby improving durability. It is an object of the present invention to provide a method of manufacturing a common rail having a high level.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, according to the present invention, through holes are formed at a plurality of axial positions in a peripheral wall of an axially extending flow passage through which high-pressure fuel flows. In the through-hole, a pressure receiving seat surface is formed which is enlarged and opened in the circumferential direction so as to be connected to a branch connector having a flow path communicating with the flow passage, and a connection end portion of the branch connector is formed in the pressure receiving seat surface. The method of manufacturing a common rail in which the pressing seat surface formed in the above is brought into contact with and connected to the branch connection body, characterized in that the common rail is manufactured by performing burnishing on the inner peripheral surface of the flow passage. Things.

In the present invention, the burnishing device is pulled relatively in the axial direction with respect to the common rail, and the burnishing process is performed by rotating the burnishing device relative to the common rail, or while the inner peripheral surface of the flow passage is hit with a roller. It is preferable to apply burnishing to finish.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a partially cutaway side view of a roller burnishing process according to the present invention, and FIG. FIG. 3A is a cross-sectional view taken along the line A, FIG. 3A is a diagram illustrating an embodiment of a burnishing device, FIG. 3B is a diagram illustrating another embodiment, and FIG. 3 is an embodiment of a burnishing device with a coil spring interposed. (A) is a diagram showing one embodiment thereof, (b) is a diagram showing another embodiment, and FIGS. 4 to 7 are longitudinal sectional front views of main parts of various embodiments of the common rail. .

The present invention relates to a mandrel 1 which is rotationally driven by a rotary drive mechanism via a shank (not shown) as shown in FIG. 1 and a conical surface 1a formed on the outer peripheral surface of the mandrel 1. And a roller burnishing apparatus RB having a plurality of rollers 2 rotatably disposed in engagement with the mandrel 1 and a retainer 3 for holding the rollers 2 on the conical surface 1a of the mandrel 1. The burnishing device RB is introduced into the hollow portion of the processing common rail 10, and a plurality of rollers 2 rolling on the conical surface 1 a of the mandrel 1 perform rolling processing on the inner circumferential surface 11 of the flow passage to perform inner rolling of the common rail. 11 is subjected to roller burnishing.

The roller burnishing apparatus RB used in carrying out the present invention is a motor (not shown) for pulling the mandrel 1 relative to the common rail 10 in the axial direction and rotating the mandrel 1 relative to the common rail 10. Alternatively, a shaft 5 connected to a fixing tool (not shown) for fixing is attached to the mandrel 1, but the present invention is not limited to such a roller burnishing device shown in the drawings, but is also applicable to a real open flat 7-. A known device as disclosed in Japanese Patent No. 42681 can also be used.

The inner peripheral surface 11 of the passage of the common rail obtained by implementing the present invention is not cut or ground,
The fine cracks and wrinkles generated by the rolling operation of the roller 2 as shown in FIG. 2A or the rolling operation and the hitting operation of the roller 2 as shown in FIG. Is pressed into the concave portion to obtain a mirror finish, so that the surface has a smooth surface free from the fine cracks and wrinkles, improves the corrosion resistance so that electrolytic corrosion is unlikely to occur, and further compresses and remains on the inner peripheral surface of the common rail flow passage. Since the stress is applied, the fatigue resistance of the common rail is also improved. At the same time, the inner peripheral surface 11 of the passage of the common rail, the surface of which has been processed by the rolling operation of the roller 2, exhibits excellent wear resistance due to work hardening, and the finishing accuracy is further improved. Further, since the roller burnishing process can be performed in a shorter time than the cutting process, the production efficiency can be improved.

As described above, almost no irregularities or fine cracks are generated on the inner peripheral surface 11 of the flow passage of the common rail 10, and the residual compressive stress is applied to the inner peripheral surface 11 of the flow passage by roller burnishing. Grant,
Further, a large and deep compressive residual stress is applied to the inner peripheral surface 11 of the flow passage by a tapping burnishing process as shown in FIG. 2B, thereby making it possible to provide a method of manufacturing a highly durable common rail. is there.

Further, as shown in FIG. 3, between the bearing 4 and the annular flange 1b of the mandrel 1 (see FIG. 3 (a)) or between the retainer 3 and the bearing 4 (see FIG. 3 (b)).
The roller 2 is pulled through the coil spring 12 with the coil spring 12 interposed therebetween, so that the inner peripheral surface 11 of the flow passage formed by the plug at the time of drilling at the time of drilling with a gun drill is formed. Since the roller 2 follows eccentricity and uneven thickness due to slight variations in inner diameter accuracy and undulation, a smooth surface finish can be obtained over the entire surface by burnishing.

FIGS. 4 to 7 show examples of the use of the common rail 10 having the inner peripheral surface 11 subjected to the roller burnishing process.

FIG. 4 shows an example in which the common rail 10 is formed as a high-pressure fuel manifold 10a. A branch branch pipe 12a serving as a branch connecting body is tightened with a fastening nut 1 through a joint fitting 13.
4 is connected to the high-pressure fuel manifold 10a. FIG. 5 shows an example in which the common rail 10 is formed as a high-pressure fuel block 10 b having a projecting portion 15. A branch branch pipe 12 a as a branch connector is provided on a screw surface 15 a provided on the outer periphery of the projecting portion 15. 16 is screwed and connected to the high-pressure fuel manifold 10b. Further, FIG. 6 has a configuration similar to that of the embodiment of FIG. 5, but in this example, the fastening nut 14 is screwed into a threaded surface 15b provided on the inner surface of the projection 15 instead of the cap nut 16 to branch. The branch pipe 12a is connected. Furthermore, FIG.
Shows an example in which a branch fitting 12b is used as a branch connector, and in the case of using a branch fitting such as an elbow to bend the branch branch pipe in order to avoid interference with other parts caused by a large curvature. Further, the present invention has been made in consideration of a case where a branch fitting having a mechanism such as an equal pressure valve, a damping valve, a delivery valve, and a discharge valve is installed.

[0019]

As described above, according to the present invention, burnishing is applied to finish the inner peripheral surface of the flow passage of the common rail.
In particular, by introducing hitting burnishing processing, irregularities or fine cracks generated on the inner peripheral surface of the flow passage can be almost eliminated, and by interposing a coil spring, when drilling with a gun drill during pipe drawing Since the roller follows eccentricity and uneven thickness due to slight variations in the inner diameter accuracy of the inner peripheral surface of the hollow part caused by the plug and undulation, the inner peripheral surface becomes a mirror surface, so that electrolytic corrosion hardly occurs and corrosion resistance improves. A method for producing a highly durable common rail by imparting compressive residual stress to the inner peripheral surface of the flow passage by roller burnishing to suppress the progress of internal fatigue and increase the internal fatigue strength. Can be.

[Brief description of the drawings]

FIG. 1 is a partially cutaway side view at the time of burnishing processing according to the present invention.

FIGS. 2A and 2B are cross-sectional views taken along the line AA in FIG. 1, wherein FIG. 2A is a diagram illustrating an embodiment of a burnishing apparatus, and FIG. 2B is a diagram illustrating another embodiment.

FIGS. 3A and 3B are partially cutaway views showing an embodiment of a burnishing apparatus in which a coil spring is interposed. FIG. 3A is a view showing one embodiment, and FIG. 3B is a view showing another embodiment.

FIG. 4 is a vertical sectional front view of a main part of one embodiment of the common rail.

FIG. 5 is a vertical sectional front view of a main part of another embodiment of the common rail.

FIG. 6 is a longitudinal sectional front view of a main part of still another embodiment of the common rail.

FIG. 7 is a longitudinal sectional front view of a main part of still another embodiment of the common rail.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mandrel 1a Conical surface 2 Roller 3 Retainer 10 Common rail to be processed 11 Peripheral wall 12 Coil spring RB Burnishing machine

Claims (3)

[Claims] 1. A through-hole is formed at a plurality of positions in an axial direction on a peripheral wall of an axially extending flow passage through which high-pressure fuel flows, and the through-hole has a flow passage communicating with the flow passage. A pressure-receiving seat surface is formed which is expanded and opened in the circumferential direction so that the branch connection body is connected, and a pressure seat surface formed at a connection end of the branch connection body is brought into contact with the pressure-receiving seat surface, and A method of manufacturing a common rail connected to a branch connector, wherein burnishing is applied to an inner peripheral surface of the flow passage to finish the common rail. 2. The method for manufacturing a common rail according to claim 1, wherein the burnishing device is pulled relatively in the axial direction with respect to the common rail, and burnishes by rotating the burnishing device relative to the common rail. 3. The method for manufacturing a common rail according to claim 1, wherein burnishing is performed while hitting an inner peripheral surface of the flow passage with a roller.