WO2008044343A1 - Common rail - Google Patents

Abstract

A common rail in which localized stress concentrations in the intersections between a flow passage and branched passages is prevented to avoid damage, such as cracks, to the intersections. The common rail used for the fuel injection system of an internal combustion engine has a rail body in which the flow passage is formed along the axial direction of the rail body, branched pipes arranged along the axial direction of the rail body, formed integrally with the rail body so as to project from it, and in which the branched passages branched from the flow passage are formed. The rail body has, at the intersection between the flow passage and each branched passage, a thick wall portion where the wall thickness around the flow passage is greater than the wall thickness around the flow passage of the other portions of the rail body.

Description

 Common-lay technology

 TECHNICAL FIELD [0001] The present invention relates to a common rail used in a fuel injection system for an internal combustion engine, and more particularly, to a common rail including a branch pipe portion integrally formed by protruding a rail body portion force.

Background art

 Conventionally, there has been a pressure accumulation type fuel injection device in which fuel that is pumped by a high pressure is stored in a common rail as an accumulator, and fuel of an equal pressure is distributed to a plurality of fuel injection valves. Are known. FIG. 9 shows an example of such a common rail, which is arranged along the rail body 312 and the axial direction (X direction) of the rail body 312 and formed integrally with the rail body 312. And a plurality of branch pipe portions 314 (five in the example of FIG. 9) projecting outward in the circumferential direction of the rail body portion 312. The rail body portion 312 has a flow passage 318 formed therein along the axial direction, and a branch passage 316 branched from the flow passage 318 is formed inside the branch pipe portion 314. Further, a fuel pipe (not shown) is connected to the branch pipe part 314, and the other end side of the fuel pipe (not shown) connected to the injection branch pipes 314a to 314d in the branch pipe part 314 is a fuel pipe. The other end of a fuel pipe (not shown) connected to an injection valve (not shown) and connected to the inflow branch pipe 314e is connected to a fuel supply pump (not shown).

 [0003] In such a common rail, the internal pressure of the high-pressure fuel acts on the inner surfaces of the flow passage and the branch passage. In addition, stress is concentrated at the intersection where the branch path branches from the flow passage, and a larger stress is applied immediately than other parts. Increased risk of breakage.

Therefore, common rail knowing has been proposed that can significantly improve the pressure resistance by reducing the stress value at the stress concentration part. More specifically, as shown in FIG. 10, the cross-sectional shape of the pressure accumulation chamber 302 for accumulating high-pressure fuel supplied from the fuel supply pump is made elliptical, so that the pressure accumulation chamber 302 and each second fuel passage hole are formed. 306, accumulator with a circular cross section Disclosed is a common rail housing in which the stress value at the intersection (stress concentration portion) 309 can be reduced by arranging it so as to intersect in the orthogonal direction at a position where the curvature is larger than that of a true circular tube having a chamber. (For example, see Patent Document 1).

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 2001-295723 (Claims Fig. 1)

 Disclosure of the invention

 Problems to be solved by the invention

 [0005] However, in the common rail nosing disclosed in Patent Document 1, the stress value in the axial direction of the housing among the stresses acting on the intersection between the pressure accumulating chamber and the second fuel passage hole, and the axial direction In some cases, there is a difference between the stress value in the direction perpendicular to and the stress concentration may not be sufficiently reduced. That is, as shown in FIG. 11, in the vicinity of the intersection 417 between the flow passage 418 and the branch passage 416, the direction perpendicular to the axial direction (in the X direction) is perpendicular to the axial direction (X direction) of the rail body 412 ( Since the wall thickness in the Y direction is thin, deformation in the Y direction is more likely to occur than in the X direction. As a result, the stress in the Y direction acting on the edge in the X direction at the entrance of the branch 416 is greater than the stress in the X direction acting on the edge in the Y direction. Therefore, there was a possibility that the durability of the common rail might be lowered due to a crack at the edge in the X direction at the entrance of the intersection 417.

 [0006] In addition to the method described in Patent Document 1, there is a force S in which the constituent material is changed to a high-strength material or the hardness is increased by applying heat treatment to the common rail. Then, there is a possibility that material cost and production cost will become high. In addition, there is a method of increasing the strength by increasing the wall thickness of the entire common rail. In addition to the increase in production cost, there is a problem that the overall weight increases.

 [0007] Therefore, the inventors of the present invention diligently worked on the common rail by providing a predetermined thick portion at the intersection of the flow passage of the rail main body portion and the branch passage of the branch pipe portion. The present invention has been completed by finding that the above problems can be solved.

 In other words, the object of the present invention is to prevent local stress concentration from occurring at the intersection between the flow path and the branch path without significantly increasing the production cost or increasing the weight. It is providing the common rail which can reduce.

Means for solving the problem [0008] According to the present invention, a common rail used in a fuel injection system for an internal combustion engine, the rail main body having a flow passage inside along the axial direction, and the rail main body arranged along the axial direction of the rail main body. Rail main body force projecting and integrally molded, each having a branch pipe portion having a branch passage that branches into the distribution passage force, and at the intersection of the flow passage and the branch passage in the rail body portion, A common rail provided with a thick portion where the thickness around the flow passage is thicker than the thickness around the other portion of the flow passage is provided, and the above-mentioned problems can be solved.

 [0009] Further, in configuring the common rail of the present invention, it is preferable that the thick portion is provided evenly on both sides in the axial direction of the rail body portion with the intersection portion as the center.

 [0010] Further, in configuring the common rail of the present invention, it is preferable that the thickness of the branching direction side of the branch path in the thick portion is thicker than the thickness on the side opposite to the branching direction.

 [0011] Further, in configuring the common rail of the present invention, the curvature of the outer periphery of the rail body in the outer periphery of the rail body in the cross section cut in the direction orthogonal to the axial direction is the opposite side to the branch direction. It is preferable to make it smaller than the curvature of the outer periphery.

 [0012] Another aspect of the present invention is a common rail used in a fuel injection system for an internal combustion engine, the rail main body having a flow passage therein along the axial direction, and the axial direction of the rail main body. And a branch pipe portion having a branch passage that branches out from the rail body portion and is formed integrally with each other, each branching from the flow passage force. The common rail is provided with a thin wall portion at a portion other than the intersection with the road where the thickness around the flow passage is thinner than the thickness around the flow passage near the branch pipe.

 The invention's effect

 [0013] According to the common rail of the present invention, by providing a predetermined thick portion at the intersection of the flow passage and the branch path, in other words, by providing a predetermined thin portion at a portion other than the intersection. At the intersection, the stress value acting in the axial direction of the rail body portion and the stress value acting in the direction intersecting the axial direction can be approximated to obtain a stress balance. Therefore, the stress concentration at the predetermined location of the intersection is reduced, the occurrence of cracks and the like can be suppressed, and the durability of the common rail can be improved.

[0014] In the common rail of the present invention, the thick wall portion is leveled along the axial direction of the rail body. By arranging them equally, it is possible to eliminate variations in the stress acting in the axial direction of the rail body at the intersection, and to effectively reduce the stress concentration.

 [0015] Further, in the common rail of the present invention, by increasing the thickness of the thick portion in a predetermined direction, a compressive stress can be applied to the intersecting portion in a direction intersecting the axial direction. Therefore, the tensile stress acting in the direction can be reduced, and the stress concentration at a predetermined location at the intersection can be reduced more effectively.

 [0016] Further, in the common rail of the present invention, the cross-sectional shape of the thick wall portion is set to a predetermined shape, whereby a compressive stress in a direction intersecting the axial direction can be easily applied to the intersecting portion.

 Brief Description of Drawings

[0017] FIG. 1 is a perspective view of a common rail that is applied to an embodiment of the present invention.

 FIG. 2 is a cross-sectional view of a common rail that is applied to the embodiment of the present invention.

 FIG. 3 is a view showing an example of a pressure accumulation type fuel injection device provided with a common rail.

 FIG. 4 is a diagram showing an example of a method for forming a thick portion.

 FIG. 5 is a diagram showing another example of a method for forming a thick portion.

 FIG. 6 is a diagram for explaining an arrangement configuration of thick portions.

 FIG. 7 is a diagram showing an example in which the thickness of the thick part is varied (part 1).

 FIG. 8 is a diagram showing an example in which the thickness of the thick part is varied (part 2).

 FIG. 9 is a diagram for explaining the configuration of a conventional common rail (part 1).

 FIG. 10 is a diagram for explaining the configuration of a conventional common rail (part 2).

 FIG. 11 is a diagram for explaining the action of tensile stress in a common rail having a conventional configuration.

 BEST MODE FOR CARRYING OUT THE INVENTION

[0018] An embodiment according to the present invention is a common rail used in a fuel injection system for an internal combustion engine. A rail main body having a flow passage therein along the axial direction, and an axial direction of the rail main body. And a branch pipe part having a branch path that branches from the flow path inside each, and is integrally formed by protruding from the rail main body part, and the flow path and the branch path in the rail main body part. At the intersection of the flow path, the thickness around the flow path is the other part of the flow path It is a common rail characterized by providing a thick part thicker than the surrounding thickness. In other words, the rail main body is provided with a thin wall portion in a portion other than the vicinity of the branch pipe portion in which the thickness around the flow passage is thinner than the thickness around the flow passage in the vicinity of the branch pipe portion. It is a common rail.

 Hereinafter, the common rail of the present embodiment will be specifically described with reference to the drawings.

 However, this embodiment shows one aspect of the present invention, and can be arbitrarily changed within the scope of the present invention, which is not intended to limit the present invention.

 In addition, in each figure, what has attached the same code | symbol has shown the same member, and description is abbreviate | omitted suitably.

 [0020] 1. Overall configuration

 1 and 2 (a) to 2 (b) show the common rail 10 of the present embodiment. Fig. 1 is a perspective view of the common rail 10, Fig. 2 (a) is a cross-sectional view of the common rail 10 cut along the axial direction, and Fig. 2 (b) is a branch from the flow path. 2 is a cross-sectional view of a portion to be cut in a direction perpendicular to the axial direction of the common rail 10. FIG.

 A common rail 10 of this embodiment shown in FIGS. 1 and 2 (a) to 2 (b) is configured by using a steel material such as a conventionally used alloy steel or pig iron, and the rail main body 12 And a plurality of branch pipe portions 14 (five in the figure) that are arranged along the axial direction (X direction) of the rail body portion 12 and project from the rail body portion 12 and are integrally formed. ing. Among these, the rail main body 12 has a flow passage 18 opened at both ends 10a and 10b along the axial direction. Of the plurality of branch pipe portions 14, four injection branch pipes 14a to 14d internally have injection branch paths 16a to 16d branched from the flow passage 18 and opened at the other end side. Similarly, the inflow branch pipe 14e in the branch section 14 has an inflow branch path 16e branched from the flow path 18 and opened at the other end side.

[0022] In addition, screw grooves are formed on the outer peripheral surfaces of end portions 10a on one side in the axial direction of each branch pipe portion 14 and rail body 12. The end 10a of the rail body 12 is connected to an electromagnetic controller 54 that controls the amount of fuel discharged from the discharge passage 15 to control the pressure in the rail. Each of the injection branch pipes 14a to 14d is connected to a fuel pipe (not shown) leading to a fuel injection valve (not shown) for injecting fuel into a cylinder of an internal combustion engine (not shown). Further, a fuel pipe (not shown) that leads to a discharge valve (not shown) of a fuel supply pump (not shown) is connected to the inflow branch pipe 14e (see FIG. 3). On the other hand, the other end portion 10b of the rail body 12 is formed with a thread groove on the inner peripheral surface, and a pressure sensor 52 for detecting the pressure in the rail is connected (see FIG. 3).

[0023] Fig. 3 shows a configuration example of a pressure accumulating fuel injection device 50 using such a common rail 10. In this pressure accumulation type fuel injection device 50, the fuel in the fuel tank 82 is pumped up by the feed pump 84 of the fuel supply pump 60, passes through a metering valve 68 for adjusting the injection amount, and then pressurized ( Then, the pressure is increased in a pressurizing chamber (not shown) and fed to the common rail 10. The high-pressure fuel pumped to the common rail 10 flows into the common rail 10 via an inflow branch path (not shown) in the inflow branch pipe 14e. The high-pressure fuel is accumulated in the common rail 10 and is supplied to each fuel injection valve 56 at an equal pressure through the injection branch passages (not shown) in the injection branch pipes 14a to 14b. . The pressure in the common rail 10 is controlled by discharging a considerable amount of fuel by the electromagnetic control unit 54 while being detected by a pressure sensor 52 connected to the common rail 10.

 [0024] The nozzle-dollar 101 of the fuel injection valve 56 is urged in the direction to close the injection hole 64 by the high-pressure fuel supplied to the pressure control chamber 67 in the fuel injection valve 56, and is controlled by the valve 71. By releasing a part of the high-pressure fuel in the pressure control chamber 67, the urging force of the nozzle-dollar 101 is weakened. As a result, the fuel is injected from the injection hole 64 into the cylinder of the internal combustion engine. As a result, high-pressure fuel can be supplied to each fuel injection valve 56 without the injection pressure being affected by fluctuations in the engine speed, and fuel can be injected into the internal combustion engine at a desired timing. . Therefore, noise can be reduced and the content of environmental pollutants can be reduced.

 [0025] 2. Thick part (thin part)

Here, in the common rail 10 of this embodiment shown in FIG. 1 and FIG. 2 (a) to (b), the wall thickness around the flow path 18 is increased at the intersection 17 between the flow path 18 and the branch path 16. It has a thick-walled part 20 that is thicker than the wall thickness around the distribution channel 18 of other parts. In other words, the thickness around the flow passage 18 is larger than the thickness around the flow passage 18 near the intersection 17 in the portion other than the intersection 17. It has a thin thin part 21.

 That is, the thickness of the rail body portion 12 at a portion other than the intersection portion 17 between the flow passage 18 of the rail body portion 12 and the branch passage 16 of the branch pipe portion 14 is relatively compared with the vicinity of the intersection portion 17. By reducing the thickness, the thickness of the rail main body 12 becomes uniform as a whole. Compared with the case where the rail main body 12 is thick, the direction intersecting the axial direction of the rail main body 12 around the intersection 17 (Y direction) ) Deformation can be relaxed. Therefore, it is possible to balance the tensile stress acting in the X direction centering on the intersection 17 and the tensile stress acting in the Y direction, without using high-strength materials or increasing production costs. Stress concentration at the location can be prevented.

 More specifically, as described above, high-pressure fuel is always accumulated inside the common rail, and internal pressure is generated on the inner surface of the flow passage and the inner surface of the branch passage. In particular, at the intersection of the flow path and the branch path, stress tends to concentrate on the edge of the branch path entrance. At this time, the thickness of the rail body in the axial direction (X direction) is relatively thick compared to the thickness in the direction perpendicular to the axial direction (Y direction). Is also deformed in the Y direction. As a result, the stress in the Y direction concentrates on the edge in the X direction among the edges of the entrance of the branch path at the intersection, and damage such as cracks is likely to occur.

 Therefore, in the present invention, the thick portion 20 is provided at the intersection 17 between the flow passage 18 and the branch passage 16, and the stress acting in the X direction and the stress acting in the Y direction with a good balance are created. The stress concentration at a specific location is reduced.

[0027] In constructing a common rail having such a thick portion 20, as shown in FIG. 4 (a), the thickness of the portion other than the portion to be the thick portion 20 is removed from the conventional common rail. The thin-walled portion 21 may be formed by adding the thickness near the intersection 17 to the conventional common rail as shown in Fig. 4 (b). Among them, as shown in Fig. 4 (a), when it is configured by reducing the thickness of the portion other than the thick portion 20, the amount of raw materials can be reduced and the manufacturing cost can be reduced. Since the common rail can be reduced in weight, this is a more preferable aspect. [0028] Further, in configuring the thick portion 20, as shown in FIG. 5, the axial direction (X direction) of the rail body 12 is centered on the intersection 17 between the flow passage 18 and the branch passage 16. It is preferable to provide them equally on both sides.

 With the thick portion 20 configured as described above, the stress values on both sides along the axial direction (X direction) of the tensile stress acting on the intersecting portion 17 can be made equal. Therefore, it is possible to reduce damage to the common rail where stress does not concentrate on one edge in the axial direction among the edges of the entrance portion of the branch path 16.

[0029] In constructing the thick portion 20, as shown in Fig. 2 (b), the thickness t2 on the branch direction side (upper side in the figure) of the branch path 16 is set on the side opposite to the branch direction (Fig. It is preferable to make it thicker than the wall thickness tl of the middle lower side.

 With the thick wall portion 20 configured in this way, as shown in FIG. 6, when an internal pressure is generated in the common rail 10, the side opposite to the branching direction is positively deformed. 17, compressive stress can be applied in the direction (Y direction) intersecting the axial direction. Therefore, the internal pressure cancels a part of the tensile stress acting in the Y direction on the intersection 17 and balances the stress value with the tensile stress acting in the X direction. Can be reduced. As a result, damage to the common rail can be reduced.

[0030] As an example of a thick portion in which the thickness of the branching path 16 on the branching direction side (upper side in the figure) is thicker than the thickness on the opposite side (lower side in the figure) of the branching direction, FIG. Besides b), it can be configured as shown in Fig. 7 (a) to (b). Fig. 2 (b) shows an example in which the outer peripheral surface of the branch path 16 opposite to the branch direction is a curved surface, and Fig. 7 (a) is a plan view of the outer peripheral surface of the branch path 16 opposite to the branch direction. FIG. 7B shows an example in which the position of the flow path 18 in the rail body 12 is offset to the side opposite to the branch direction of the branch path 16.

[0031] Above all, due to the fact that compressive stress can be efficiently applied to the intersecting portion 17 in the Y direction, the thick portion 20 is orthogonal to the axial direction as shown in FIG. 2 (b). In the cross section cut along the direction, the curvature force of the outer periphery of the rail body 12 on the branch direction side of the branch path 16 is smaller than the curvature of the outer periphery of the rail body 12 on the side opposite to the branch direction of the branch path 16. Is preferred. As shown in Fig. 7 (a), the curvature force of the outer periphery of the rail body 12 on the branch direction side is smaller than the curvature of the outer periphery of the rail body 12 on the opposite side to the branch direction. The rail body 12 on the opposite side of the direction includes a linear outer periphery, and even with this configuration, the cross section 17 has a predetermined direction compared to the conventional circular configuration. Compressive stress can be applied to

 However, in the present invention, in the thick portion 20, the thickness on the branch direction side (upper side in the figure) of the branch path 16 is made thicker than the thickness on the side opposite to the branch direction (lower side in the figure). As shown in Fig. 8 (a) to (b), even if the wall thickness around the flow path 18 in the thick wall portion 20 is equal, compared with the conventional common rail. The balance in the direction in which the tensile stress acts can be taken and damage to the common rail can be reduced.

 [0033] Needless to say, if a rise in production cost and a decrease in production workability are not taken into consideration, a common rail may be formed using a material having higher strength than conventional materials, or heat treatment may be performed. Well, when configured in this way, it is possible to more effectively prevent damage such as cracks due to the stress acting on the internal pressure at the intersection of the flow path and the branch path.

Claims

The scope of the claims  [1] A common rail used in the fuel injection system of an internal combustion engine,  A rail body having an internal flow passage along the axial direction;  A branch pipe part that is arranged along the axial direction of the rail body part, protrudes from the rail body part, is integrally formed, and has a branch path that branches from the flow path inside.  At the intersection of the flow passage and the branch path in the rail body portion, a thicker portion is provided where the thickness around the flow passage is thicker than the thickness around the flow passage in other portions. Common rail characterized by  [2] The common rail according to claim 1, wherein the thick portion is provided equally on both sides in the axial direction of the rail body portion with the intersection portion as a center.  [3] In the first or second aspect of the present invention, the thickness on the branch direction side of the branch path in the thick portion is made thicker than the thickness on the opposite side to the branch direction. Common Lenore listed.  [4] In the outer periphery of the rail main body in a cross section obtained by cutting the thick portion in a direction orthogonal to the axial direction, the curvature of the outer periphery on the branch direction side is determined from the curvature of the outer periphery on the side opposite to the branch direction. The common rail according to any one of claims 1 to 3, wherein the common rail is also made smaller.  [5] A common rail used for the fuel injection system of an internal combustion engine,  A rail body having an internal flow passage along the axial direction;  A branch pipe part that is arranged along the axial direction of the rail body part, protrudes from the rail body part, is integrally formed, and has a branch path that branches from the flow path inside.  In a portion of the rail body other than the intersection between the flow passage and the branch path, a thin wall portion having a thickness around the flow passage that is smaller than a thickness around the flow passage in the vicinity of the branch pipe portion. A common rail characterized by providing.