JP2006070799A - Fuel injection system of diesel engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection system of a diesel engine in which piping constitution is simplified to perform an efficient installation work, in addition to suppressing pressure pulsation in an injector. <P>SOLUTION: In the fuel injection system 1A of a diesel engine, fuel is injected in each cylinder by feeding pressurized fuel FE to a plurality of injectors 2a-2d by a fuel pump 3. A volume chamber is provided in each injector in order to damp the pulsation of fuel pressure, and all the injectors are connected to a single fuel-feeding common pipe 4. In the fuel injection system 1A, pulsation is suppressed, because each injector is provided with the volume chamber. Further, since all the injectors are connected to the single common pipe, piping construction is simplified, and the installation work can be performed efficiently. Thus, fuel pressure pulsation can be suppressed, and cost reduction is achieved. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel injection system. More particularly, the present invention relates to a fuel injection system for a diesel engine configured without using a common rail.

  2. Description of the Related Art In recent years, an accumulator fuel injection system in which high-pressure fuel supplied by a fuel pump is once stored in a common rail (accumulation chamber) and high-pressure fuel is supplied from the common rail to an injector of each cylinder has been widely adopted. FIG. 10 is a view showing an example of a fuel injection system having a conventional common rail. In this fuel injection system 100, fuel FE in a fuel tank 105 is supplied to a common rail 101 by a fuel pump 103 to store high-pressure fuel. The fuel in the common rail 101 is supplied to the injectors 102a to 102d via the branch pipes 104a to 104d. Since the fuel at a constant pressure is stored in the common rail 101, the fuel can be injected evenly without variations among the injectors. The common rail 101 also functions as a pressure pulsation buffer chamber that attenuates the pressure pulsation (pressure fluctuation) of the fuel that is generated when the injector performs an opening / closing operation. Therefore, by providing the common rail, the interference between the cylinders can be reduced and the fuel can be stably injected.

  However, even if the common rail 101 is provided, it is difficult to completely remove the fuel pressure pulsation. Therefore, in the conventional fuel injection system, as shown in FIG. 10, measures such as making the lengths of the branch pipes 104a to 104d the same are taken to attenuate the pulsation as much as possible. A technique related to suppressing pressure pulsation is disclosed in Patent Document 1.

  Patent Document 1 proposes a structure for reducing a radiated sound generated based on a pulsation caused by an opening / closing operation of an injector, with respect to a fuel injection device having a common rail. In this apparatus, a damping case serving as a pulsation reducing means is provided at the center of the branch supply pipe connecting the common rail and the injector to reduce the pressure pulsation of the injector and suppress noise.

  Conventionally, as disclosed in Patent Document 2, a structure in which a buffer chamber that absorbs pressure pulsation is provided in a fuel supply branch path in an injector has been proposed for a fuel injection device that does not use a common rail. As described above, a plurality of techniques for reducing pressure pulsation generated during the opening / closing operation of an injector have been proposed in a fuel injection device having a common rail and a fuel injection device not having a common rail.

Japanese Patent Laid-Open No. 10-30521 JP-A-11-257184

  As described above, suppressing the pressure pulsation of the injector is one of the important issues in the fuel injection system of a diesel engine. However, as with other configurations included in the fuel injection system, it is necessary to consider cost reduction, mountability, and assembly man-hours for the configuration for suppressing pressure pulsation. Since the common rail included in the fuel injection device of Patent Document 1 is an expensive part and has a large outer shape, there is a potential demand to abolish the common rail.

  Since the fuel injection device of Patent Document 2 supplies the fuel directly from the fuel pump to the injector via the regulator, the cost can be suppressed in that no common rail is used. However, in the devices of Patent Document 1 and Patent Document 2, a branch pipe is connected to a main pipe from a common rail or a fuel pump, and an injector is fixed to an end of each branch pipe. Therefore, in the techniques proposed in these documents, the number of pipes increases and the pipe configuration becomes complicated. Therefore, there is a problem that the number of parts increases, the assembly work becomes complicated, and the cost increases.

  Accordingly, an object of the present invention is to provide a fuel injection system for a diesel engine that not only suppresses the pressure pulsation of an injector but also simplifies the piping configuration and allows efficient assembly work.

  An object of the present invention is a fuel injection system of a diesel engine that supplies fuel pressurized by a fuel pump to a plurality of injectors and injects the fuel into each cylinder, and attenuates fuel pressure pulsation in each of the injectors. This can be achieved by a fuel injection system for a diesel engine in which all of the injectors are connected to one common pipe for supplying the fuel.

  According to the present invention, since each of the injectors has a volume chamber, pulsation can be suppressed, and all the injectors are connected to one common pipe, so that the piping configuration can be simplified and efficient assembling work can be performed. Therefore, according to the present invention, it is possible to provide a diesel engine fuel injection system that can realize suppression of fuel pressure pulsation and cost reduction.

  The common pipe has a small hole at a position where the injector is installed, the injector has a seal member having a fuel passage corresponding to the small hole, and fastening means for tightening the common pipe toward the seal member And can be formed. Further, when the injector is provided with a predetermined space through which the fuel passes, the predetermined space may be used as a storage chamber.

  Further, the fastening means includes a pressing member that presses the common pipe and a tightening member that moves the pressing member toward the pipe, and the volume chamber is formed in the pressing member. Can do. A structure in which an orifice for restricting the flow of the fuel is formed in at least one of the fuel passage and the small hole may be adopted. Furthermore, the volume chamber may be provided outside the injector.

  According to the fuel injection system of the present invention, since each injector has a volume chamber, pressure pulsation can be attenuated, and since all the injectors are connected to one common pipe, the number of pipes is reduced and the assembly work is performed. Can be performed efficiently.

  A diesel engine fuel injection system (hereinafter simply referred to as a fuel injection system) according to an embodiment of the present invention will be described below with reference to the drawings.

  FIG. 1 is a perspective view showing a main part of the fuel injection system 1A, and FIG. 2 is a view showing a configuration relating to fuel piping of the fuel injection system 1A. The fuel injection system 1A is formed so that the fuel FE stored in the fuel tank 5 is sucked by the fuel pump 3 through the suction pipe 7, and fuel of a predetermined pressure is supplied to, for example, four injectors 2a to 2d. It is. Here, the four injectors 2 a to 2 d are connected to one common pipe 4 that supplies fuel from the fuel pump 3. A structure in which all of the injectors 2a to 2d can be connected to one common pipe 4 will be described later.

  As shown in FIG. 2, a relief valve 9 and a return pipe 8 are connected to the fuel pump 3. A fuel pressure sensor 6 that detects the pressure of the high-pressure fuel supplied from the fuel pump 3 is connected to the fuel pump 3. The fuel injection system 1 </ b> A is entirely controlled by an ECU (electronic control unit) 10. The ECU 10 uses the fuel pump 3 and injectors 2a to 2d based on output signals PS from various sensors installed in a diesel engine (not shown) to which the fuel injection system 1A is applied and outputs from the fuel pressure sensor 6. The optimal amount of fuel is injected by controlling the opening / closing operation of the fuel.

  In addition, as shown in FIG. 1, each injector 2a-2d is provided with connectors 12a-12d for electrically connecting with ECU10. The injectors 2a to 2d are fixed to a cylinder head of a diesel engine (not shown) by clamps 11a to 11d, and are arranged so that respective tip portions (injection holes) face each cylinder.

  As described above, the fuel injection system requires a configuration for suppressing fuel pressure pulsation caused by the opening / closing operation of the injector. The fuel injection system 1A includes a structure for suppressing the pressure pulsation in each of the injectors 2a to 2d. Since the structure of each injector is the same, the structure for suppressing a pulsation is shown by showing the cross section of the 1st injector 2a in FIG.

  In the first injector 2a, a fuel supply port 20 for supplying fuel is formed at one end (upper side in FIG. 3). The injector 2a includes an injector main body portion 21a and a nozzle portion 21b connected to the distal end portion in the longitudinal direction of the injector main body portion 21a. The injector 2a includes a space 22 that continues from the main body portion 21a to the nozzle portion 21b. The fuel FE supplied from the common pipe 4 flows into the space 22.

  A needle valve 23 is disposed in the space 22, and the needle valve 23 extends into the nozzle portion 21b. A first magnetic circuit M1 and a second magnetic circuit M2 are disposed in the space on the main body 21a side. The first magnetic circuit M1 includes a first electromagnet (M1a, M1c) including a cylindrical first magnetic core M1a and a first coil M1c embedded in the first magnetic core M1a. . The first magnetic circuit M1 includes an annular magnetic body (armature) M1b. A needle valve 23 is positioned in the opening of the armature M1b so as to be relatively movable. The armature M1b is connected to a stopper member 27 fixed to the needle valve 23 via the first spring S1, and is elastically coupled to the needle valve 23.

  On the upper side of the first magnetic circuit M1, a second magnetic circuit M2 having the same configuration is formed. The second magnetic circuit M2 includes a second electromagnet (M2a, M2c) including a cylindrical second magnetic core M2a and a second coil M2c embedded in the second magnetic core M2a. . The second magnetic circuit M2 includes an annular magnetic body (armature) M2b. A needle valve 23 is fixed in the opening of the armature M2b, and the armature M2b is elastically connected to the upper portion in the injector main body 21a via the second spring S2.

  The fuel FE introduced from the fuel supply port 20 includes an inner region α of the second magnetic core M2a, a fuel passage β provided in the armature M2b, an inner region γ of the first magnetic core M1a, and a fuel passage provided in the armature M1b. Through δ, it reaches the nozzle portion 21b side and moves to just before the fuel seal portion 24. An ejection hole 25 is provided at the tip of the nozzle portion 21b, and the fuel FE is ejected from the ejection hole 25 when the valve is opened.

  In the first injector 2 a shown in FIG. 3, the fuel FE introduced from the fuel supply port 20 passes through the internal space 22 and reaches the ejection hole 25. Since the first magnetic circuit M1, the second magnetic circuit M2, and the needle valve 23 are arranged in the space 22, the volume is reduced, but the lower part of the first magnetic circuit M1 and the first magnetic circuit M1 and the second magnetic circuit M2 Meanwhile, a relatively large space having a predetermined volume (hereinafter referred to as a predetermined space) remains in the periphery of the needle valve 23 or the like. In the injector 2a, this predetermined space functions as a volume chamber that attenuates pressure pulsation. In the fuel injection system 1A, each of the injectors 2a to 2d is provided with the predetermined space in advance, so that it is not necessary to provide a separate volume chamber for pressure pulsation attenuation. As will be described later, since this volume chamber functions in the same manner as a conventional common rail, the common rail can be eliminated, so that the configuration of the fuel injection system 1A can be simplified as compared with the conventional fuel injection system (see FIG. 10) ( (See FIG. 2).

  Further, a structure for connecting the injector 2a shown in FIG. 3 and other injectors 2b to 2d having the same configuration to the single common pipe 4 will be described. FIG. 4 is an enlarged view of the periphery of the fuel supply port 20 of the injector 2a shown in FIG. Here, the first injector 2a will be described as a representative example. 4A is a view showing a state where the injector 2a is connected to the common pipe 4, and FIG. 4B is a cross-sectional view taken along line AA in FIG.

  The fuel supply port 20 is partly cut out at the end, and as shown in FIG. 4, a part of the common pipe 4 is housed in the cut out part. The common pipe 4 accommodated in the injector 2a is formed with a small hole 4a for supplying fuel. A gasket 30 formed in a shape for receiving the common pipe 4 is arranged on the inner side (opposite to the fuel supply port 20) than the common pipe 4. The upper surface of the gasket 30 is formed in a semicylindrical concave shape, and is designed so as to be in close contact with the outer peripheral surface of the common pipe 4 for sealing. The lower surface side of the gasket 30 is in contact with the injector main body 21a.

  Further, the gasket 30 has a fuel passage 31 at a position corresponding to the small hole 4 a of the common pipe 4. Therefore, the fuel FE flowing in the common pipe 4 exits from the small hole 4 a and flows into the space 22 inside the injector 2 a through the fuel passage 31 of the gasket 30. Note that an orifice for regulating the flow rate of the fuel FE may be formed in the small hole 4 a of the common pipe 4 or the fuel passage 31. If an orifice is formed during the passage of fuel, the pressure pulsation can be further attenuated by reducing the flow rate of the fuel FE. FIG. 4B shows an example in which an orifice is formed by making the small hole 4 a of the common pipe 4 smaller than the diameter of the fuel passage 31 as a preferable form.

  The fuel supplied by the common pipe 4 is at a high pressure. When high-pressure fuel flows out from the small hole 4a, a structure is required that allows the fuel to flow into the injector 2a without leaking into the peripheral portion. For this purpose, a pressing member 40 that presses the back side (the upper side in FIG. 4) of the common pipe 4 is inserted into the fuel supply port 20. A nut 45 is disposed on the back side of the pressing member 40. A male screw 26 is formed on the outer periphery of the fuel supply port 20, and a corresponding female screw 46 is formed on the inner periphery of the nut 45. Therefore, when the nut 45 is screwed into the fuel supply port 20, the pressing member 40 can be moved toward the common pipe 4. As a result, since the lower surface of the common pipe 4 is pressed against the upper surface of the gasket 30, the surfaces can be brought into close contact with each other to form a sealed state. Therefore, the fuel FE that has flowed out from the common pipe 4 can be caused to flow into the injector 2a via the gasket 30 without leaking to the peripheral portion.

  In the example shown in FIG. 4, the gasket 30 functions as a seal member, and the pressing member 40 and the nut 45 function as fastening means. The pressing member 40 includes a guide protrusion 41, and a guide hole 47 that fits with the guide protrusion 41 is formed on the nut 45 side. Thus, if the guide protrusion 41 and the guide hole 47 are formed, workability at the time of assembly can be improved. Further, the injector 2 a shown in FIG. 4 has a fuel supply port 20 formed at the end, and the nut 45 is designed to be screwed into the upper portion of the fuel supply port 20. In this way, by adopting a structure in which the nut 45 is disposed at a position where the axial end of the injector can be easily tightened, for example, an impact wrench can be used for easy tightening, so that workability is improved.

  The fastening structure to the common pipe 4 shown in FIG. 4 is the same for the other injectors 2b to 2d. Therefore, as shown in FIG. 1, all four injectors can be easily connected to one common pipe 4. Moreover, each of the injectors 2a to 2d has a structure provided with a volume chamber for suppressing pressure pulsation inside. Therefore, the fuel injection system 1A can not only suppress the pressure pulsation even if the common rail is eliminated, but can also reduce the cost by reducing the number of parts and improving the workability due to the simplified piping configuration. The injectors 2 a to 2 d employed in the fuel injection system 1 </ b> A are so-called direct acting injectors, and do not require a return pipe for returning the fuel to the fuel tank 5. Therefore, it is only necessary to perform a tightening operation for fastening the injectors 2 a to 2 d to the common pipe 4. Therefore, the number of assembling steps can be further reduced as compared with the case where a type of injector that requires a return pipe is employed.

  In addition, the fastening structure of the injector 2a to the common pipe 4 shown in FIG. 4 is an example. A screw portion may be formed on the outer peripheral portion of the pressing member 40 without using the nut 45, and the pressing member 40 may be screwed into the fuel supply port 20. Further, as in the modification shown in FIG. 5, instead of providing an opening at the end of the injector 2a, a structure in which a communication hole 33 is provided in the width direction and the common pipe 4 is inserted into the communication hole 33 may be adopted. . In the case of adopting this modification, members corresponding to the gasket 30 and the pressing member 40 shown in FIG. 4B are arranged in advance in the injector 2a at a predetermined interval, and the common pipe 4 is interposed therebetween. Insert it. The outer joint portion 34 between the common pipe 4 and the injector 2a may be brazed or laser welded to ensure sealing performance.

  In the fuel injection system 1A shown in the first embodiment, an example in which the injectors 2a to 2d having a predetermined space functioning as a volume chamber are used is shown, but the present invention is not limited to this. . Conventionally, an injector called a differential pressure injector has been widely adopted. The differential pressure injector opens and closes the needle valve by generating a fuel pressure difference inside. This differential pressure injector generally does not have a space for storing fuel that contributes to buffering pressure pulsations. The fuel injection system 1B of the second embodiment shows a fuel injection system configured using the differential pressure injector that does not have a pulsation buffering space as described above.

  FIG. 6 is a view showing a fuel piping configuration of the fuel injection system 1B. FIG. 7 is an enlarged sectional view showing the periphery of the fuel supply port 20 of the first injector 2e shown in FIG. In addition, about the fuel-injection system 1B of Example 2, the overlapping description is abbreviate | omitted by attaching | subjecting the same code | symbol to the site | part similar to the fuel-injection system 1A of Example 1. FIG.

  As shown in FIG. 6, the fuel injection system 1B includes four differential pressure injectors 2e to 2h. These injectors 2 e to 2 h are also connected to one common pipe 4. Note that branch pipes 50e to 50h for returning fuel are connected to the injectors 2e to 2h. These branch pipes 50 e to 50 h are connected to the return pipe 8. As shown in FIG. 6, each of the injectors 2e to 2h includes volume chambers 49e to 49h therein. Since the injectors 2e to 2h have the same structure, the injector 2e will be described.

  As shown in FIG. 7, the injector 2 e is partially cut away on the fuel supply port 20 side, and a part of the common pipe 4 is housed in the cutout portion. The common pipe 4 is disposed between the first gasket 35 and the second gasket 37. The upper surface of the first gasket 35 has a semicylindrical concave shape, and the lower surface of the second gasket 37 has a semicylindrical concave shape. Therefore, the common pipe 4 is sandwiched between the first gasket 35 and the second gasket 37 from above and below to form a sealed state. A pressing member 40 is disposed on the upper side of the second gasket 37 so as to hold the second gasket 37 from above. Inside the pressing member 40, a space 49e having a predetermined volume serving as a volume chamber is formed.

  Similar to the first embodiment, the common pipe 4 has a small hole 4a (first small hole) for fuel supply. The first gasket 35 has a fuel passage 36 at a position corresponding to the small hole 4 a of the common pipe 4. Therefore, the fuel FE flowing in the common pipe 4 exits from the small hole 4a and enters the space 22 inside the injector 2e through the fuel passage 36 of the first gasket 35.

  Furthermore, in the case of the common pipe 4 of the second embodiment, the second small hole 4b is formed in the direction opposite to the first small hole 4a. A fuel passage 38 is formed in the second gasket 37 at a position corresponding to the small hole 4 b of the common pipe 4. The second small hole 4 b and the fuel passage 38 communicate the space 49 e formed in the pressing member 40 disposed above the second gasket 37 and the common pipe 4. Therefore, the fuel FE supplied by the common pipe 4 is stored in the space 49 through the second small hole 4b. Since the space 49e functions as a volume chamber, pressure pulsation can be suppressed.

  Also in the injector 2e of the second embodiment, an orifice may be formed in the first small hole 4a, the second small hole, or the fuel passages 36, 38 of the common pipe 4 in order to suppress the pressure pulsation more reliably. FIG. 7 shows an example in which an orifice is formed by making the first small hole 4a and the second small hole 4b of the common pipe 4 smaller than the diameter of the fuel passages 36 and 38 as a more preferable form.

  In the fuel injection system 1B of the second embodiment, a volume chamber (space 49) is provided in the differential pressure type injector, and all the injectors 2e to 2h are provided in one common pipe 4 as in the fuel injection system 1A of the first embodiment. Connected. Therefore, the fuel injection system 1B can be provided as an injection system that suppresses pressure pulsation without using a common rail, and that can further reduce the cost by improving the work efficiency and reducing the number of parts by simplifying the piping configuration.

  FIG. 8 is a diagram illustrating a fuel pipe configuration of a fuel injection system 1C according to the third embodiment. In the first and second embodiments, the structure example in which the volume chamber is provided in the injector is shown. However, in the fuel injection system 1C shown in FIG. 8, the volume chambers 55i to 55l connected to the differential pressure injectors 2i to 2l from the outside. Is provided. Thus, even if the volume chambers attached to the injectors are connected from the outside, the same effects as in the first and second embodiments can be obtained. That is, even in the fuel injection system 1C having the configuration shown in FIG. 8, the common rail can be eliminated to suppress pressure pulsation, and the cost can be reduced by simplifying the piping configuration.

  In addition, although the fuel injection systems 1B and 1C of the second and third embodiments described above exemplify a case where a differential pressure injector that does not include a predetermined space that is generally a volume chamber is used, When the injector does not have a predetermined space, the fuel injection system can be similarly formed by applying the configurations of the second and third embodiments. However, in the case of the direct acting type, it is not necessary to return the fuel, so the branch pipe for fuel return can be deleted from the configuration shown in FIGS.

  FIG. 9 is a diagram showing the results of a test conducted to confirm the pulsation suppressing effect when a volume chamber is provided in the differential pressure injector. FIG. 9 (B) and FIG. 9 (C) show changes in the injection amount when the pilot interval interval is changed with the drive signal shown in FIG. 9 (A). FIG. 9B shows a result obtained when a fuel pump and a differential pressure injector are connected without providing a common rail. FIG. 9C shows a result obtained when a fuel pump without a common rail is connected to the differential pressure injectors 2i to 2l with external volume chambers shown in FIG.

  FIG. 9B shows that the reflection of the pressure pulsation varies among the injectors, and the injection amount varies from cylinder to cylinder due to the interval variation. However, when the injector includes a volume chamber, the pressure pulsation is reflected in the volume chamber as shown in FIG. From the results shown in FIG. 9, it can be seen that if a volume chamber attached to the injector is provided, pressure fluctuation can be suppressed even if the common rail is eliminated. From the results shown in FIG. 9, it can be confirmed that the volume chamber of each injector used in the above-described embodiment functions in the same manner as the common rail.

  In the fuel injection system of the embodiment described above, each of the injectors has a volume chamber, so that pulsation can be suppressed without using a common rail, and all the injectors are connected to one common pipe, so the piping configuration is simplified. Can be assembled efficiently. Therefore, the fuel injection system of the embodiment can be provided as a fuel injection system capable of suppressing the pressure pulsation of the fuel and reducing the cost.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

It is the perspective view which showed the principal part of the fuel-injection system which concerns on Example 1. FIG. It is the figure which showed the fuel piping structure of the fuel-injection system of FIG. It is a figure which shows the cross section of the 1st injector included in the fuel-injection system of FIG. It is the figure which expanded and showed the periphery of the fuel supply port of the injector shown in FIG. It is a figure which shows the modification of the injector included in the fuel-injection system of FIG. It is the figure which showed the fuel piping structure of the fuel-injection system which concerns on Example 2. FIG. It is sectional drawing which expanded and showed the periphery of the fuel supply port of the 1st injector included in the fuel-injection system shown in FIG. FIG. 6 is a diagram illustrating a fuel pipe configuration of a fuel injection system according to a third embodiment. It is the figure shown about the test result which confirmed the pulsation suppression effect at the time of providing a volume chamber in a differential pressure type injector. It is the figure which showed an example of the fuel-injection system provided with the conventional common rail.

Explanation of symbols

1A, 1B, 1C Fuel injection system 2a to 2d Injector 3 Fuel pump 4 Common piping 4a Small hole 22 Space 30 Gasket (seal member)
40 Pressing member 45 Nut (tightening member)
49, 55 Volume chamber FE fuel

Claims (6)

A fuel injection system for a diesel engine that supplies fuel pressurized by a fuel pump to a plurality of injectors and injects the fuel into each cylinder,
A fuel injection system for a diesel engine, wherein each of the injectors is provided with a volume chamber for attenuating a pressure pulsation of fuel, and all of the injectors are connected to one common pipe for supplying the fuel. A small hole is formed in the common pipe at a position where the injector is installed,
2. The diesel engine according to claim 1, wherein the injector includes a seal member having a fuel passage corresponding to the small hole, and fastening means for tightening the common pipe toward the seal member. Fuel injection system. The fuel injection system for a diesel engine according to claim 1 or 2, wherein the injector includes a predetermined space through which the fuel passes, and the predetermined space is used as the volume chamber. The fastening means includes a pressing member that presses the common pipe, and a tightening member that moves the pressing member toward the pipe,
The diesel engine fuel injection system according to claim 2, wherein the volume chamber is formed in the pressing member. The diesel engine fuel injection system according to any one of claims 2 to 4, wherein an orifice for restricting the flow of the fuel is formed in at least one of the fuel passage and the small hole. The diesel engine fuel injection system according to claim 1, wherein the volume chamber is provided outside the injector.

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