JP4408179B2 - Orifice pipe for fuel injection pipe - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is an injection of high-pressure fuel used in connection with a common rail system of a diesel internal combustion engine, a PLD (pump line delivery) injection system (hereinafter referred to as a “PLD injection system”), or the like. The present invention relates to an orifice pipe provided in the pipe.
[0002]
[Prior art]
Conventionally, as a fuel injection pipe for a diesel engine of this type, for example, as shown in FIG. 6, a truncated conical connection head having an outer peripheral surface provided at the end of a thick steel pipe 41 as a seat surface 43. 42, or as shown in FIG. 7, the connection heads 52 having the outer peripheral surface provided at the end of the thick-walled steel pipe 51 as the spherical sheet surface 53 are respectively directed in the axial direction by the punch member from the outside. In relation to being formed by the buckling process by pressing, an annular pocket 45-1 (FIG. 6) or an annular shape on the inner side of the head due to the outward expansion of the peripheral wall accompanying the buckling process by pressing. The notch 55-1 (FIG. 7) is formed and used in this state. Reference numerals 44 and 54 denote sleeve washers fitted behind the connection head, and reference numerals 46 and 56 denote tightening nuts.
[0003]
In a fuel injection system employing such a diesel engine fuel injection pipe, the fuel injection pipe can inject a sufficient amount into the combustion chamber without causing a pressure loss in the pipe and convenience on the pipe. Considering this, it has become shorter. However, even with such a short injection pipe, when the valve after fuel injection is closed, pressure fluctuation occurs in the injection pipe. This pressure fluctuation pulsates and reaches from the inside of the pipe to the inside of the common rail, and also affects the injection pipe of the next cylinder, so that there is a problem that stable fuel injection cannot be performed.
[0004]
As such a countermeasure, for example, the pressure fluctuation can be reduced by increasing the inner diameter of the injection pipe or common rail to increase the volume of the pipe, but there is a drawback that the pulsation is transmitted quickly. Therefore, a method has been developed in which an orifice is provided in the common rail in order to keep pulsation low and to slow and reduce propagation.
In this method, there are known a method of imparting an orifice function by reducing the diameter of the branch hole provided in the common rail, and a method of interposing a metal ring member (piece) with an orifice in the branch hole portion of the common rail. Any method can suppress pulsation and slow propagation. However, the method of making the orifice function by making the diameter of the branch hole smaller in the common rail is 7 mm or more even at the thinnest part because a high pressure is repeatedly applied to the branch hole, and the position deeper from the end face of the common rail. Therefore, there is a problem that it is not easy to form an orifice. In addition, a method in which a metal ring member (piece) with an orifice is interposed in the branch hole portion is that an axial force generated by a single tightening nut incorporated on the injection pipe side is between the common rail and the metal ring member and between the injection pipe and the metal. In order to seal two places between the ring members, there is a drawback that the stability of the seal is poor.
[0005]
Therefore, the present inventors have provided a fuel injection pipe for a diesel engine that can perform stable fuel injection by suppressing the pulsation and slowing and reducing propagation by providing an orifice pipe at the pipe end of the injection pipe. Proposed earlier (2000-344055).
This fuel injection pipe is a diesel engine fuel injection pipe having a head having a conical or spherical seat surface and a tightening nut, preferably at least one side, preferably a common rail side, and a pump side pipe in the PLD injection system. In the pipe near the end, an orifice pipe having an outer diameter smaller than or equal to the pipe diameter is provided inside the pipe end or the pipe end. The orifice pipe is provided from the outside. It is fixed inside the pipe by a diameter reducing force, or has a protruding part with one end protruding outside from the pipe end, and the protruding part has a flange part larger in diameter than the pipe diameter, or is hard It consists of a metal tube and a soft metal ring that is externally fitted to one end of the tube that protrudes outward from the tube end, or a hard metal inner tube that protrudes outward from the tube end. It is used one made of an outer tube made of soft metal having the flange portion.
[0006]
That is, this fuel injection pipe is provided with an orifice pipe at the front end opening of the connecting head or on the inner side of the front end opening, so that the orifice pipe serves as an orifice and does not adversely affect the sealing performance, thereby reducing pulsation. It is configured so that stable fuel injection can be performed while suppressing and slowing propagation. Further, if the flange portion and the ring are soft, the axial force of the tightening nut is not canceled and the seal surface pressure is not lowered.
[0007]
[Problems to be solved by the invention]
By the way, as the means for fixing the orifice pipe, means such as press-fitting, caulking, rolling, shrink fitting, brazing, welding or sandwiching the flange portion with the mating sheet surface can be used. Among these fixing means, the means for fixing the orifice pipe by press-fitting requires a very large press-fitting allowance so that it does not move due to pulsation pressure. Therefore, the outer peripheral surface of the orifice pipe, the inner wall of the pipe, There is a possibility that friction powder is generated by sliding contact, and the friction powder adheres to the branch hole on the common rail side or falls into the main rail and is mixed into the fuel.
[0008]
The present invention has been made to solve such a problem, and provides an orifice pipe for a fuel injection pipe capable of fixing an orifice pipe to a tip opening of a connection head portion of the fuel injection pipe so that friction powder is not generated. It is something to try.
[0009]
[Means for Solving the Problems]
An orifice pipe for a fuel injection pipe according to the present invention is an orifice pipe having a double-pipe structure that is fixed to a tip opening of a connecting head by a diameter-expansion method. The outer tube having a tapered hole, and preferably an inner tube having a flange portion at one end and having an outer diameter larger than the minimum diameter of the tapered hole of the outer tube. The inner tube is structured to expand the diameter of the outer tube by press-fitting the inner tube.
The orifice pipe of the present invention is an orifice pipe provided in a pipe near a pipe end portion on at least one side of a fuel injection pipe having a connection head having a conical or spherical seat surface and a clamping nut, one end of which is a pipe end. The outer tube has a flange portion that protrudes more outward and has an inner diameter that is a tapered hole, and preferably has a flange portion that protrudes outward from the tube end, and the outer diameter of the main body portion is a taper of the outer tube. An inner pipe having a diameter larger than the minimum diameter of the hole, and the inner pipe is press-fitted into the outer pipe to expand the diameter of the outer pipe, so that the inner pipe is pressed and fixed in the vicinity of the pipe end of the fuel injection pipe. It is characterized by having a structure.
Further, in the above-described orifice pipe of the present invention, a ring-shaped protrusion projecting in the radial direction is provided on the outer peripheral surface on the inner pipe side so that the outer pipe can be easily expanded, and a plurality of cuts are formed on the side surface on the outer pipe side. Can be put.
Furthermore, the inner tube and the outer tube of the orifice tube can be made of hard metal and soft metal, respectively.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
1 and 2 show an example of an orifice pipe for a fuel injection pipe according to the present invention. FIG. 1 is a longitudinal sectional view showing a state before the inner pipe is press-fitted into the outer pipe, and FIG. 2 shows the inner pipe in the outer pipe. FIG. 3 is a view corresponding to FIG. 2 showing another example of the present invention, and FIG. 4 is an embodiment in which the orifice pipe for a fuel injection pipe shown in FIG. 1 is applied to a fuel injection pipe for a diesel engine. FIG. 5 is a longitudinal sectional view showing an example of a connection structure in which the diesel engine fuel injection pipe shown in FIG. 4 is applied to a common rail. 1, 11 is an orifice pipe, 1a, 11a are outer pipes, 1b 11b is an inner pipe, 21 is a fuel injection pipe, 22 is a connection head, 23 is a tightening nut, 24 is a sleeve washer, and 25 is a main rail.
[0011]
1 and 2 includes an outer tube 1a and an inner tube 1b. The outer tube 1a has a flange portion 1a-1 at one end and an inner diameter of the flange portion 1a-1. The inner tube 1b has a flange portion 1b-1 at one end like the outer tube 1a, and the outer diameter of the main body portion is a tapered hole of the outer tube 1a. The diameter is larger than the minimum diameter of 1a-2, and the length in the axial direction is substantially equal to that of the outer tube 1a. Both flange portions 1a-1, 1b-1 preferably have substantially the same outer diameter. 1b-2 is an orifice hole.
The inner diameter of the outer tube 1a is a tapered hole 1a-2, and the outer diameter of the body portion of the inner tube 1b is larger than the minimum diameter of the tapered hole 1a-2 of the outer tube 1a. This is to increase the diameter of the outer tube 1a by press-fitting 1b.
[0012]
FIG. 1 shows a state before the inner tube 1b is press-fitted into the outer tube 1a. When the inner tube 1b is press-fitted into the outer tube 1a in this state, the inner diameter of the outer tube 1a becomes a tapered hole 1a-2. As a result, the outer tube 1a is expanded in diameter as the inner tube 1b is press-fitted, and when the inner tube 1b is completely press-fitted, the main body of the outer tube 1a expands outward as shown in FIG. In this case, since the inner tube 1b is a press fit that simply expands the diameter of the outer tube 1a, the friction between the inner surface of the outer tube 1a and the outer surface of the inner tube 1b is small, and therefore friction powder is hardly generated. The flange portion 1b-1 of the inner pipe 1b may not be provided.
[0013]
An orifice tube 11 for a fuel injection tube shown in FIG. 3 has a ring-shaped projection 11b-3 projecting radially on the outer peripheral surface of an inner tube 11b having a flange portion 11a-1 at one end so that the outer tube 11a can be easily expanded. The outer tube 11a having a flange portion 11a-1 at one end is provided with a plurality of cuts (slits or the like) 11a-3 on the side surface. When the inner tube 11b is press-fitted into the outer tube 11a, a ring-shaped protrusion is formed. By 11b-3, the outer tube 11a provided with the cut 11a-3 is applied with an outward pressing force, and the diameter of the outer tube 11a can be expanded relatively easily. 11b-2 is an orifice hole. In this case, the flange portion 11b-1 of the inner tube 11b may not be provided.
[0014]
As materials of the outer pipes 1a and 11a and the inner pipes 1b and 11b of the orifice pipe, a combination of hard metal and soft metal is generally used. The hard metal is generally steel, and the soft metal is copper, brass, or the like. The outer tubes 1a and 11a and the inner tubes 1b and 11b are not necessarily made of metal, and hard resin and soft resin such as NG6 and PP can be used, and metal and resin such as bronze and PPG can be used. It may be a combination.
[0015]
The diesel engine fuel injection pipe 21 shown in FIG. 4 has an opening end portion of a truncated conical connecting head portion 22 having an outer peripheral surface provided at an end portion of the thick steel tube 21-1 as a seat surface 22-1a. Further, an orifice tube 1 made of a soft metal having a long outer tube 1a and a hard metal inner tube 1b having an outer diameter substantially equal to the diameter of the pipe 21-3 of the thick steel pipe 21-1 is fitted inside. The orifice tube 1 is formed by adhering to the outer tube 1a first at the opening end of the connection head 32, and the inner end of the orifice tube 1 in the annular recess of the pocket portion 22-2 existing inside the head. The inner tube 1b is inserted into the outer tube 1a so as to protrude, and the outer tube 1a is press-fitted into the outer tube 1a to expand the diameter of the outer tube 1a. At this time, since the inner end of the outer tube 1a of the orifice tube 1 is expanded toward the inner wall side of the pocket portion 22-2, when the orifice tube 1 is pushed outward by the pulsation pressure, the inner tube Although the diameter reducing force acts on 1b, since the inner tube 1b is highly rigid and resists this diameter reducing force and does not deform, the orifice tube 1 does not come out while being simply press-fitted.
[0016]
Next, an example of a connection structure in which the diesel engine fuel injection pipe shown in FIG. 4 is applied to a common rail will be described with reference to FIG.
That is, the connection structure shown in FIG. 5 has a flow passage 25 of the main rail 25 in a plurality of boss portions 25-4 provided at intervals on an axial peripheral wall portion on the main rail 25 side made of a circular pipe. 1 and a branch hole 25-2 having a pressure receiving seat surface 25-3 that opens outward, and a seat surface (pressing force) formed by the connection head 22 of the fuel injection pipe 21 for a diesel engine shown in FIG. (Seat surface) 22-1a is brought into contact with and engaged with the pressure-receiving seat surface 25-3 on the main rail 25 side, and a tightening nut 23, which is assembled in advance on the fuel injection tube side via a sleeve washer 24, is attached to the boss portion 25. -4 is screwed into the connection head 22 so as to be fastened together with the pressure under the neck of the connection head 22 to form a connection structure.
[0017]
The main rail 25 as a common rail in the connection structure example shown in FIG. 5 is a forged product such as a material S45C having a relatively thick tubular portion having a diameter of 28 mm and a thickness of 9 mm, for example, In the case of multiple integrated boss parts or separate boss parts, block rail type, with the inside of the shaft core as a flow passage by machining such as boring, gun drill, etc., keeping a space in the axial peripheral wall part Connection holes are respectively provided. The common rail having the integrated boss portion is not limited to the connection structure described above, but a branch hole that is not shown is extended to the vicinity of the free end of the boss portion, and the pressure receiving seat surface is extended to the boss portion. It is formed so as to be exposed at the free end of the part, and a female screw is machined on the inner periphery of the boss part, and a nut is screwed into the female screw to tighten the fuel injection pipe with the pressure below the connection head neck. Needless to say, the present invention can also be applied to a system that is connected and configured. Furthermore, the orifice pipe of the present invention can be provided in the portion of the common rail branch hole 25-2 in the connection structure example shown in FIG.
The flange portion of the orifice pipe 1 may be brought into contact with the main rail 25 side pressure receiving seat surface side 25-3. In addition, although the inner tube and the outer tube are shown to have the same length here, they are not necessarily the same.
[0018]
【The invention's effect】
As described above, the orifice tube for a fuel injection pipe according to the present invention can be firmly fixed at the tip opening of the connection head of the fuel injection pipe at room temperature so that friction powder is not generated, so that pulsation is kept low. In addition to the effect of the orifice tube that can slow down and reduce the propagation, there is an excellent effect that the friction powder is not mixed in the fuel and that clean fuel can always be supplied to the combustion chamber.
[Brief description of the drawings]
FIG. 1 shows an example of an orifice pipe for a fuel injection pipe according to the present invention, and is a longitudinal sectional view showing a state before an inner pipe is press-fitted into an outer pipe.
2 is a longitudinal sectional view showing a state in which an inner pipe is press-fitted into an outer pipe of the orifice pipe shown in FIG. 1;
FIG. 3 is a view corresponding to FIG. 2, showing another example of the present invention.
4 is a longitudinal sectional view showing an embodiment in which the fuel injection pipe orifice pipe shown in FIG. 1 is applied to a diesel engine fuel injection pipe. FIG.
5 is a longitudinal sectional view showing a connection structure example in which the fuel injection pipe for a diesel engine shown in FIG. 4 is applied to a common rail.
FIG. 6 is a longitudinal sectional view showing an example of a conventional fuel injection pipe for a diesel engine as a subject of the present invention.
FIG. 7 is a longitudinal sectional view showing another example of a conventional fuel injection pipe for a diesel engine as a subject of the present invention.
[Explanation of symbols]
1, 11 Orifice pipes 1a, 11a Outer pipes 1b, 11b Inner pipe 21 Fuel injection pipe 22 Connection head 23 Tightening nut 24 Sleeve washer 25 Main rail

Claims (4)

An orifice pipe provided in a pipe near the pipe end on at least one side of a fuel injection pipe having a connection head having a conical or spherical seat surface and a tightening nut, and having a flange portion with one end projecting outside from the pipe end. and an outer tube which vital internal diameter is no tapered hole, the body outer diameter is from a larger diameter and forms the tube is less than the minimum diameter of the tapered hole of the outer tube, the outer the inner tube is pressed into the outer tube An orifice pipe for a fuel injection pipe, wherein the diameter of the pipe is increased and the structure is fixed in pressure contact within a pipe near the end of the fuel injection pipe. The inner tube, the fuel injection pipe orifice tube according to claim 1, wherein a flange portion having one end protruding outward from the pipe end. A ring-shaped projection projecting radially on the outer peripheral surface provided on the inner tube, the fuel injection pipe orifice tube according to claim 1 or 2, wherein the containing the plurality of cuts on the sides to the outer tube . The inner and outer tubes of the orifice tube, the fuel injection pipe orifice tube according to any one of claims 1 to 3, characterized in that each is made of hard metal and soft metal.

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