JP2005214179A - Common rail - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a common rail 1 excellent in screw workability of a pipe connector 21 and easily proving strong connection strength of a rail main body 20 and a stay 22. <P>SOLUTION: The pipe connector 21 is connected to a rail main body 20 by connection technology. Consequently, since the pipe connector 21 can be connected to the rail main body 20 after working mail thread 33 on the pipe connector 21, efficiency of threading the pipe connector 21 is excellent and manufacturing cost for forming mail thread 33 on the pipe connector 21 can be lowered. Although heavy load and stress act on the connection part of the rail main body 20 and the stay 22, connection strength of the rail main body 20 and the stay 22 is strengthened and high strength warranty can be easily obtained by forming the rail main body 20 and the stay 22 as one piece by either of forging or cutting. Namely, workability and strength of the common rail 1 can be compatibly established. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a common rail that is mounted on an accumulator fuel injection device that injects fuel into a diesel engine and accumulates high-pressure fuel.

(Conventional technology)
As common rails for storing high-pressure fuel, those shown in FIGS. 5 and 6 are known.
(1) The common rail J1 shown in FIG. 5 includes a rail body J2, a pipe connector J3 for connecting a plurality of pipes, and a stay J4 for mounting an engine (an example of a fixing member) by at least one of forging and cutting. It is integrally molded (no patent document etc.).
(2) The common rail J1 shown in FIG. 6 is formed by joining a rail body J2, a plurality of pipe connection pipe connectors J3, and an engine mounting stay J4 by resistance welding (Patent Literature). Etc.)

(Trouble of conventional technology)
(1) The common rail J1 (see Fig. 5), which is integrally formed by at least one of forging or cutting, the rail body J2, the pipe connector J3, and the stay J4, provides high strength at each joint. Is easy.
On the other hand, the pipe connector J3 needs to be formed with a screw J6 for screwing the pipe fastener J5 after forging, and this screw J6 is required to be threaded with high accuracy. However, since the pipe connector J3 integrated with the rail body J2 has poor workability, the processing efficiency of the screw J6 becomes inefficient and the processing cost increases.

(2) The common rail J1 (see Fig. 6), in which the rail body J2, piping connector J3, and stay J4 are joined by welding or other joining technology, is joined to the rail body J2 after forming the screw J6 on the piping connector J3. Therefore, the processing efficiency of the screw J6 is excellent and the processing cost can be reduced.
The rail body J2 can be made of a thick hollow pipe material. Alternatively, a round hole or square bar is processed with a central hole serving as an internal passage (pressure accumulation chamber) for accumulating high-pressure fuel, and the cost of the rail body J2 can be suppressed.

When the stay J4 is fixed to a fixing member such as an engine, the vibration of the engine and the vibration of the vehicle are transmitted to the rail body J2 having a large mass through the stay J4. Therefore, at the joint between the rail body J2 and the stay J4, The largest load or stress acts on the common rail J1. For this reason, high joint strength and high welding quality are required at the joint between the rail body J2 and the stay J4.
However, assuring high joint strength and high welding quality at the joint between the rail body J2 and the stay J4 requires a large man-hour, which is more costly than when the common rail J1 is integrally formed by forging technology. There are concerns.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a common rail that is excellent in workability of a screw of a pipe connector and that can easily guarantee high joint strength between a rail body and a stay.

[Means of Claim 1]
Since the common rail of Claim 1 joins a piping connector to a rail main body by joining technique, it can join to a rail main body, after giving a screw process to a piping connector. Thereby, the efficiency of threading in the pipe connector is excellent, and the processing cost for threading the pipe connector can be reduced. Further, since the rail body and the stay are integrally provided by at least one of forging and cutting, the joint strength between the rail body and the stay is high, and high strength assurance can be easily obtained.

[Means of claim 2]
In the common rail according to claim 2, members other than the pipe connector are provided integrally with the rail body by at least one of forging and cutting without using a joining technique.

[Means of claim 3]
The common rail of claim 3 includes at least one of laser welding, resistance welding, friction welding, or brazing as a joining technique for joining the rail body and the pipe connector.

[Means of claim 4]
Since the rail body including the stay is manufactured by at least one of forging and cutting, the degree of freedom of the shape of the rail body can be increased. For this reason, the connector joint surface for joining a pipe connector can be easily formed around the outside of the inner and outer communication holes of the rail body by adopting claim 4.

[Means of claim 5]
Since the rail body including the stay is manufactured by at least one of forging and cutting, the degree of freedom of the shape of the rail body can be increased. For this reason, when the shaft core of the internal passage is offset by a predetermined amount from the center of the tube of the rail body to the side different from the connector joint surface, the shape in which the unnecessary thickness is eliminated is adopted. The shape of the rail body can be easily formed.

  The common rail of the best mode 1 has an internal passage for accumulating high-pressure fuel in the longitudinal direction, an internal / external communication hole for communicating the internal passage and the outside, and a rail body having a substantially cylindrical shape, A screw for screwing a pipe fastener is formed on the outer periphery or inner periphery, and a pipe connector joined to the rail body by a joining technique in a state of surrounding the inner and outer communication holes, and the rail body by at least one of forging or cutting And a stay that is integrally provided and fixed to the fixing member.

  In the first embodiment, first, the system configuration of the accumulator fuel injection device will be described with reference to FIG. 3, and then the structure of the common rail will be described with reference to FIGS.

(Description of accumulator fuel injection system)
3 is a system that injects fuel into each cylinder of a diesel engine (not shown), and includes a common rail 1, an injector 2, a supply pump 3, an ECU 4 (engine control unit), and an EDU 5 (drive unit). ) Etc.

  The common rail 1 is a pressure accumulating container that accumulates high-pressure fuel supplied to the injector 2, and discharges from the supply pump 3 that pumps high-pressure fuel through the high-pressure pump pipe 6 so that the common rail pressure corresponding to the fuel injection pressure is accumulated. In addition to being connected to the outlet, a plurality of injector pipes 7 for supplying high-pressure fuel to each injector 2 are connected. The connection structure between the common rail 1 and the high-pressure pump pipe 6 and the connection structure between the common rail 1 and the injector pipe 7 will be described later.

A pressure limiter 10 is attached to a relief pipe 9 that returns fuel from the common rail 1 to the fuel tank 8. This pressure limiter 10 is a pressure safety valve, and opens when the fuel pressure in the common rail 1 exceeds the limit set pressure, and suppresses the fuel pressure in the common rail 1 to be equal to or lower than the limit set pressure.
A pressure reducing valve 11 is attached to the common rail 1. The pressure reducing valve 11 is opened by a valve opening instruction signal given from the ECU 4 and rapidly reduces the common rail pressure via the relief pipe 9. Thus, by mounting the pressure reducing valve 11 on the common rail 1, the ECU 4 can quickly control the common rail pressure to a pressure corresponding to the vehicle running state. There is also a type in which the pressure reducing valve 11 is eliminated from the common rail 1.

The injector 2 is mounted in each cylinder of the engine and supplies fuel into each cylinder. The injector 2 is connected to the downstream ends of a plurality of injector pipes 7 branched from the common rail 1 and accumulated in the common rail 1. A fuel injection nozzle that injects high-pressure fuel into each cylinder and an electromagnetic valve that performs lift control of a needle accommodated in the fuel injection nozzle are mounted.
The leaked fuel from the injector 2 is also returned to the fuel tank 8 through the relief pipe 9.

  The supply pump 3 is a high-pressure fuel pump that pumps high-pressure fuel to the common rail 1, and is equipped with a feed pump that sucks fuel in the fuel tank 8 into the supply pump 3 through the filter 12, and is sucked up by this feed pump. The fuel is compressed to a high pressure and pumped to the common rail 1. The feed pump and the supply pump 3 are driven by a common cam shaft 13. The camshaft 13 is rotationally driven by the engine.

  In the supply pump 3, an SCV 14 (suction metering valve) for adjusting the degree of opening of the fuel flow path is attached to a fuel flow path that guides the fuel into a pressurizing chamber that pressurizes the fuel to a high pressure. The SCV 14 is a valve that adjusts the amount of fuel sucked into the pressurizing chamber and changes the discharge amount of fuel pumped to the common rail 1 by being controlled by a pump drive signal from the ECU 4. The common rail pressure is adjusted by adjusting the discharge amount of fuel to be pumped to the vehicle. That is, the ECU 4 can control the common rail pressure to a pressure corresponding to the vehicle running state by controlling the SCV 14.

The ECU 4 includes a CPU, a RAM, a ROM, and the like (not shown), and performs various arithmetic processes based on a program stored in the ROM and sensor signals (vehicle driving state) read into the RAM. I do.
An example of a specific calculation is as follows. For each fuel injection, the ECU 4 determines each cylinder based on a program stored in the ROM and a sensor signal (vehicle operating state) read into the RAM. The target injection amount, the injection mode, and the valve opening timing of the injector 2 are determined.

  The EDU 5 is a drive circuit that applies a valve opening drive current to the electromagnetic valve of the injector 2 based on an injector valve opening signal given from the ECU 4, and supplies high pressure fuel to the cylinder by supplying the valve opening drive current to the electromagnetic valve. The fuel injection is stopped by stopping the valve opening drive current.

  In addition to the pressure sensor 15 that detects the common rail pressure, the ECU 4 includes an accelerator sensor that detects the accelerator opening, an engine speed sensor that detects the engine speed, Sensors such as a water temperature sensor for detecting the cooling water temperature are connected.

(Description of Common Rail 1) As shown in FIG. 1, the common rail 1 is a pipe for connecting the high-pressure pump pipe 6 and the injector pipe 7 and the like to the rail body 20 having a substantially cylindrical shape in which ultrahigh pressure fuel is stored. A connector 21 and a stay 22 for attaching the rail body 20 to a fixing member such as an engine are provided.

As shown in FIGS. 1 and 2, the rail body 20 is a member in which members other than the pipe connector 21 are integrally provided by at least one of forging or cutting without using a joining technique. Since the member other than the pipe connector 21 is only the stay 22, the rail body 20 and the stay 22 are integrally provided by at least one of forging or cutting.
After the rail body 20 including the stay 22 is formed by at least one of forging and cutting, the internal passage 23 and the plurality of internal and external communication holes 24 are cut. The connector joint surface 25 may be formed only by a forging technique, but the connector joint surface 25 may be cut for finishing.

In the rail body 20, an internal passage 23 serving as a pressure accumulating chamber for high-pressure fuel is formed so as to penetrate in the axial direction. The axial center α of the internal passage 23 is offset from the center β of the cylinder of the rail body 20 by a predetermined amount on the side different from the connector joint surface 25.
Screw holes 26 to which the pressure limiter 10, the pressure sensor 15 and the like can be attached are formed at both ends of the rail body 20, and in this embodiment 1, a sealing plug 27 using a sealing ball is provided in the screw hole 26. It is attached and both ends of the internal passage 23 are closed.

A plurality of inner and outer communication holes 24 are formed in the rail body 20 in the radial direction. The plurality of inner and outer communication holes 24 are formed by forming holes at appropriate intervals in the axial direction of the rail body 20. The inside of each internal / external communication hole 24 communicates with the internal passage 23, and the outside of each internal / external communication hole 24 opens at the approximate center of the connector joint surface 25 formed on the side surface of the rail body 20.
Further, a pressure receiving seat surface 29 having a substantially conical taper shape into which a tapered taper portion 28 (described later) formed at the tip of the pipes 6 and 7 is inserted in the outer opening (outside opening portion) of the inner and outer communication holes 24. Is formed.

Next, a pipe joint 30 for connecting the pipes 6 and 7 to the rail body 20 using the pipe connector 21 will be described.
The pipe joint 30 includes a pipe connector 21, a pressing sleeve 31, and a pipe fastening nut 32 (corresponding to a pipe fastener), and has a tapered shape that has a substantially conical shape (or a substantially spherical shape) formed at the ends of the pipes 6 and 7. The tapered portion 28 is fixed in a state where it is pressed against the pressure receiving seat surface 29 of the outer opening of the inner and outer communication holes 24.

The pipe connector 21 has a substantially cylindrical shape in which a male screw 33 is formed on the outer peripheral surface of the pipe connector 21 to be engaged with the pipe fastening nut 32. The pipe connector 21 is firmly joined to the connector joining surface 25 by resistance welding (an example of joining technique) in a state of concentrically surrounding the inner and outer communication holes 24.
The pressing sleeve 31 is mounted around the pipes 6 and 7 and inserted into the pipe connector 21, and the lower end is engaged with the step 34 at the back of the tip of the pipes 6 and 7. A large-diameter portion 35 is provided at the upper end of the pressing sleeve 31 so as to be engaged with the pipe fastening nut 32 without being inserted into the pipe connector 21.
The pipe fastening nut 32 includes a female screw 36 that engages with the male screw 33 of the pipe connector 21 and a step portion 37 that engages with the large-diameter portion 35 of the pressing sleeve 31. The pipe fastening nut 32 is connected to the rail body. The tapered taper portion 28 of the pipes 6 and 7 is strongly pressed against the pressure-receiving seat surface 29 of the rail body 20 by being screwed into the male screw 33 of the pipe connector 21 joined to the seal connector (oil-tight surface). Form.

  The stay 22 is a connecting means for mounting the rail body 20 to a fixing member such as an engine. FIGS. 1 and 2 show an example in which two stays 22 are provided on the rail body 20. As described above, the stay 22 is provided integrally with the rail body 20 by at least one of forging and cutting. Specifically, although it is possible only by forging if a precision forging technique is used, in many cases, it is formed by performing cutting after forging. The stay 22 has a bolt insertion hole 38 for fixing the stay 22 to a fixing member such as an engine. The bolt insertion hole 38 and the surrounding flat portion 39 may be formed by cutting, or may be forged during forging.

(Effect of Example 1)
Since the common rail 1 shown in the first embodiment is for joining the pipe connector 21 to the rail body 20 by the joining technique, the pipe connector 21 can be joined to the rail body 20 after the male screw 33 is processed. it can. Thereby, the processing efficiency of the male screw 33 in the pipe connector 21 is excellent, and the processing cost for forming the male screw 33 on the pipe connector 21 can be reduced.
In the state where the common rail 1 is fixed to a fixing member such as an engine via the stay 22, the vibration of the engine and the vibration of the vehicle are transmitted to the rail main body 20 having a large mass via the stay 22. The largest load or stress in the common rail 1 acts on the joint portion 20. For this reason, high joint strength and high welding quality are required for the joint between the rail body 20 and the stay 22. In the first embodiment, since the rail body 20 and the stay 22 are integrally provided by at least one of forging or cutting, the bonding strength between the rail body 20 and the stay 22 is high, and high strength assurance can be easily obtained. .
That is, since the common rail 1 of Example 1 can achieve both workability and strength, the common rail 1 can be provided at low cost and with high strength guarantee.

Since resistance welding is used as a joining technique between the rail body 20 and the pipe connector 21, the joining cost of the pipe connector 21 can be reduced as compared with the case where laser welding or the like is used as the joining technique, and the cost of the common rail 1 can be reduced. Can do.
Since the rail body 20 including the stay 22 is manufactured by at least one of forging and cutting, the degree of freedom of the shape of the rail body 20 can be increased. For this reason, the connector joint surface 25 to which the pipe connector 21 is joined can be easily formed.
Similarly, since the rail main body 20 including the stay 22 is manufactured by at least one of forging and cutting, the degree of freedom of the shape of the rail main body 20 can be increased. For this reason, when the axis α of the internal passage 23 is offset by a predetermined amount from the center β of the cylinder of the rail body 20 to the side different from the connector joint surface 25, the rail body has a shape in which the thickness unnecessary for securing the strength is deleted. The shape of 20 can be made easy (see FIGS. 2 and 4).

Example 2 will be described with reference to a cross-sectional view of the common rail 1 shown in FIG. In addition, in Example 2, the same code | symbol as the said Example 1 shows the same function thing.
In the second embodiment, the pressing sleeve 31 and the pipe fastening nut 32 in the first embodiment are replaced with one pipe fastening bolt 41 (corresponding to a pipe fastener). The pipe fastening bolt 41 is provided so as to be screwed into the pipe connector 21, and a male screw (not shown) is formed around the pipe fastening bolt 41 of the second embodiment. A female screw (not shown) for fastening the pipe is formed.

(Modification)
In the above embodiment, as an example of the pipe joint 30, the ends of the pipes 6 and 7 are directly pressed by the rail body 20 to form a liquid-tight seal surface between the rail body 20 and the ends of the pipes 6 and 7. Although an example is shown, a joint member may be interposed between the pipes 6 and 7 and the rail body 20, and the pipes 6 and 7 and the rail body 20 may be connected via the joint member. In that case, a flat part of the end face of the joint member may be pressed against the connector joint surface 25 provided on the rail body 20 to form a liquid-tight seal surface, or a substantially conical taper part may be formed on the joint member. Then, it may be strongly pressed against the pressure receiving seat surface 29 of the rail body 20 to form a liquid-tight seal surface.

In the above embodiment, an example in which resistance welding is used as a joining technique between the rail body 20 and the pipe connector 21 has been described. However, other joining techniques such as laser welding, friction welding, brazing, and the like other than resistance welding may be used. Further, a combination of joining techniques such as laser welding, resistance welding, friction welding, and brazing may be used.
In the above embodiment, the rail main body 20 and the stay 22 are formed only by forging using a precision forging technique, and the example is formed by cutting after forging. The rail main body 20 and the stay 22 may be cut out integrally by the drawing process.

It is sectional drawing which follows the axial direction of a common rail (Example 1). (Example 1) which is a schematic perspective view of the rail main body provided integrally with the stay. 1 is a system configuration diagram of an accumulator fuel injection device (Example 1). FIG. (Example 2) which is sectional drawing of the direction orthogonal to the axial direction of a common rail. It is sectional drawing which follows the axial direction of a common rail (conventional example). It is sectional drawing which follows the axial direction of a common rail (conventional example).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Common rail 20 Rail main body 21 Piping connector 22 Stay 23 Internal passage 24 Internal / external communication hole 25 Connector joint surface 32 Piping fastening nut (piping fastener)
33 Male thread (Screw to which the pipe fastener is screwed)
41 Piping fastening bolt (piping fastener)
α Axis of internal passage β Center of cylinder of rail body

Claims (5)

An internal passage for accumulating high-pressure fuel inside is formed in the longitudinal direction, an internal / external communication hole for communicating the internal passage and the outside is formed, and a rail body having a substantially cylindrical shape,
A screw for screwing a pipe fastener to the outer periphery or the inner periphery is formed, and a pipe connector joined to the rail body by a joining technique in a state surrounding the inner and outer communication holes,
And a stay provided integrally with the rail body by at least one of forging and cutting and fixed to a fixing member. The common rail according to claim 1,
The rail main body is a common rail in which members other than the pipe connector are integrally provided by at least one of forging and cutting without using a joining technique. In the common rail according to claim 1 or 2,
A common rail characterized in that the joining technique for joining the rail body and the pipe connector includes at least one of laser welding, resistance welding, friction welding, or brazing. In the common rail in any one of Claims 1 thru | or 3,
The common rail is characterized in that the pipe connector is joined to a connector joining surface formed around the outside of the inner and outer communication holes in the rail body by a joining technique. In the common rail according to claim 4,
The common rail is characterized in that the axis of the internal passage is provided by a predetermined amount offset from the center of the tube of the rail body on a side different from the connector joint surface.

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