JP4582025B2 - Manufacturing method of fuel injection valve - Google Patents

Description

  The present invention relates to a method of manufacturing a fuel injection valve applied to a diesel engine using dimethyl ether as a fuel.

  2. Description of the Related Art Conventionally, in a diesel engine, fuel pressurized by a high pressure pump is temporarily stored in a common rail, and fuel is supplied from the common rail to an injector.

  In general, in an injector applied to a common rail type diesel engine, a needle is accommodated in an injector body so as to be movable up and down, and the needle is driven up and down to open and close the injection hole.

  As a driving method of the needle, there are a pressure balance type (for example, refer to Patent Documents 1 and 2) and a direct acting type.

  The direct-acting type injector is configured to pull up the needle by directly driving the needle with an actuator such as a solenoid or a piezoelectric element.

  In the direct acting type injector, when the needle is pulled up, the actuator pulls up the needle against the downward fuel pressure applied to the nozzle seat portion of the needle and the like, so that the actuator requires a strong driving force.

  However, in general, an actuator tends to increase in size when the driving force becomes strong, and a large actuator has a problem that it is difficult to arrange. For example, in order to improve the volumetric efficiency of the engine, it is preferable to use two intake valves and two exhaust valves, and therefore the space for arranging the injectors is limited. Therefore, it is the mainstream to arrange the injectors at the engine center. In this case, since the size of the injector is restricted by the dimensions of the intake valve and the exhaust valve, the mountability of a large actuator such as a large driving force solenoid or a piezoelectric element is deteriorated.

  Further, when the engine speed and load are high, the required common rail pressure becomes high. If the driving force of the actuator is lower than the descending force due to the common rail pressure, the needle cannot be pulled up. In general, in a linear motion type injector, the common rail pressure can be used only up to around the upper limit of about 30 MPa.

  The pressure balance type injector applies / releases fuel pressure from the pressure control chamber to the needle, changes the force balance against the needle, and lowers / lifts the needle.

  As shown in FIG. 4, the pressure balance type injector 51 includes an injector body 10 that accommodates the needle 30, a nozzle 12 that is attached to the tip of the injector body 10 and has a plurality of injection holes 2, and the needle 30 is lowered and raised. A balance chamber 5 that introduces and discharges pressurized fuel from the common rail 4, an intermediate chamber 6 that stores leaked fuel through the needle 30, and a leak passage 8 that returns the leaked fuel in the intermediate chamber 6 to the fuel tank 7. Is provided.

  The needle 30 of the pressure balance type injector 51 is connected to the command piston 31 urged by the fuel in the balance chamber 5, the needle member 33 that opens and closes the nozzle hole 2, and the needle member 33 and the command piston 31. It consists of three members with the intermediate rod 32.

JP-A-10-77924 JP 2000-18119 A

  By the way, in recent years, in addition to general light oil, for example, use of liquefied gas fuel such as dimethyl ether (hereinafter referred to as DME) has been studied.

  When the DME is injected by the pressure balance type injector 51 described above, since DME has a lower viscosity than light oil, there is a problem that more fuel leaks from the gap between the injector body 10 and the needle 30. there were.

  That is, the balance chamber 5 and the nozzle 12 connected to the common rail 4 are high pressure, while the intermediate chamber 6 connected to the fuel tank 7 is low pressure. The fuel leaks through the needle 30 toward the intermediate chamber 6.

  The leaked DME vaporizes in the intermediate chamber 6, and the injector parts are frozen by the latent heat of vaporization at that time.

  Further, since the amount of leakage is larger than that of light oil, it is necessary to increase the discharge amount of the high-pressure pump that supplies pressurized fuel to the common rail 4, resulting in an increase in size of the high-pressure pump.

  As described above, the injector 51 of FIG. 4 has problems such as poor sliding at the intermediate rod 32 portion and the upper portion of the command piston 31, and an increase in the required discharge amount of the high-pressure fuel pump.

  Therefore, it is conceivable that an intermediate chamber 62 communicating with the common rail 4 is formed in the injector body 10 as in the injector 61 shown in FIG.

  In this case, since the intermediate chamber 62 has a high pressure similar to the balance chamber 5 and the nozzle 12, there is no leakage of fuel from the balance chamber 5 and the nozzle 12 due to the pressure difference, and there is no problem of freezing of the injector parts.

  However, the injector 61 shown in FIG. 5 is significantly different from the conventional light oil injector as shown in FIG.

  Accordingly, an object of the present invention is to provide a method for manufacturing a fuel injection valve that can solve the above-described problems and can use a low-viscosity fuel such as DME and can reduce the manufacturing cost.

In order to achieve the above object, the present invention provides an injection hole for injecting fuel, and a needle valve for opening and closing the injection hole is provided to be movable up and down, and is added from the common rail to the proximal end side of the needle valve. There is a balance chamber that introduces and discharges pressurized fuel and lowers and raises the needle valve, and an intermediate chamber that stores leaked fuel from the balance chamber through the needle valve. The intermediate chamber communicates with the fuel tank and leaks. In order to use a fuel injection valve for light oil having a leak passage for returning fuel to the fuel tank for fuel having a viscosity lower than that of light oil, the leak passage is closed to shut off the intermediate chamber and the fuel tank. In order to introduce the pressurized fuel of the common rail into the intermediate chamber, a high pressure passage is provided for communicating the intermediate chamber with the common rail.

Preferably, the fuel having a viscosity lower than that of the light oil is dimethyl ether.

  Preferably, the needle valve is formed as a single member from the nozzle hole side distal end to the balance chamber side proximal end.

  According to the present invention, it is possible to use a low-viscosity fuel such as DME, and to exhibit an excellent effect that the manufacturing cost can be reduced.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  The injector (fuel injection valve) of the present embodiment is applied to, for example, a diesel engine using dimethyl ether (hereinafter referred to as DME) as fuel.

  As shown in FIG. 1, the injector 1 of this embodiment forms the nozzle hole 2 which injects a fuel, and provides the needle valve (henceforth a needle) 3 for opening and closing the nozzle hole 2 so that raising / lowering is possible, A balance chamber 5 for introducing and discharging pressurized fuel from the common rail 4 to lower and raise the needle 3 is provided on the proximal end side of the needle 3, and the leaked fuel is accumulated from the balance chamber 5 through the needle 3. An intermediate chamber 6 is provided, and the intermediate chamber 6 is connected to a fuel tank 7 to provide a leak passage 8 for returning leaked fuel to the fuel tank 7. In order to shut off the intermediate chamber 6 and the fuel tank 7. In order to close the leak passage 8 and introduce the pressurized fuel of the common rail 4 into the intermediate chamber 6, a high-pressure passage 9 that connects the intermediate chamber 6 to the common rail 4 is provided.

  Further, the needle 3 of the present embodiment is formed as a single member from the nozzle hole side distal end to the balance chamber side proximal end.

  The injector 1 is attached to an injector body 10 having an accommodation hole 11 for accommodating the needle 3 so that the needle 3 can be moved up and down (movable in the vertical direction in FIG. 1), and the tip (lower end in FIG. 1) of the injector body 10. And a nozzle 12 having a plurality of nozzle holes 2 formed therein. The injector body 10 is configured by assembling a first piece 101, a second piece 102, and a third piece 103 in order from the top (solenoid 23 side).

  A fuel supply path 41 for supplying pressurized fuel stored in the common rail 4 to the balance chamber 5, the intermediate chamber 6, and the nozzle 12 is connected to the injector body 10.

  More specifically, in the injector body 10, an introduction path 14 connected to a fuel supply path 41 and provided with a filter (a bar filter in the illustrated example) 13, and a first in which the balance chamber 5 communicates with the introduction path 14. A supply path 15 and a second supply path 16 that allows the intermediate chamber 6 and the nozzle 12 to communicate with the introduction path 14 are formed. An orifice 151 is provided in the first supply path 15 of the present embodiment.

  The pressurized fuel from the common rail 4 is introduced into the balance chamber 5 (or the intermediate chamber 6 and the nozzle 12) by the introduction path 14 and the first supply path 15 (or the second supply path 16). Therefore, in this embodiment, the balance chamber 5, the intermediate chamber 6, and the inside of the nozzle 12 are maintained at a high pressure (common rail pressure) and substantially the same pressure.

  The balance chamber 5 is provided in the injector body 10 on the proximal end side of the needle 3 (above the needle 3 in FIG. 1). More specifically, the balance chamber 5 includes an orifice plate 18 that closes the upper surface of the needle 3, the side surface of the hole 17 that is formed in the upper part of the receiving hole 11 and has a diameter larger than the receiving hole 11, and the upper portion of the hole 17. A partition is formed with the lower surface.

  The outlet of the first supply passage 15 opens on the side surface of the hole portion 17, and pressurized fuel is introduced into the balance chamber 5 from the first supply passage 15. The orifice plate 18 is formed with an orifice hole 19 for communicating the balance chamber 5 and an amateur chamber 20 described later.

  As will be described in detail later, when the fuel injection is stopped, the needle 3 is urged downward by the pressure of the fuel in the balance chamber 5 to close the nozzle hole 2, and at the time of fuel injection, the fuel in the balance chamber 5 is amateur. The pressure is reduced to the chamber 20 and the needle 3 is lifted.

  The amateur room 20 is formed in the injector body 10 above the balance chamber 5. An armature 21 is provided in the armature chamber 20 so as to be movable in the vertical direction. The armature 21 opens and closes the orifice hole 19 of the orifice plate 18, and the armature 21 is biased downward to close the orifice hole 19. An amateur spring (coil spring in the illustrated example) 22 and a solenoid 23 for opening the orifice hole 19 by lifting the armature 21 against the biasing force of the armature spring 22 are provided. The solenoid 23 is connected to an engine control device (not shown), and the engine control device controls the injection amount and injection timing of the injector 1 by moving the armature 21 up and down.

  The amateur room 20 is connected to the fuel tank 7 via the fuel return path 71. Here, since the fuel discharged from the balance chamber 5 to the amateur chamber 20 is throttled by the orifice hole 19, the amateur chamber 20 is kept at a lower pressure than the balance chamber 5.

  An intermediate chamber 6 is formed in the injector body 10 below the balance chamber 5. The intermediate chamber 6 is provided at an intermediate position between the balance chamber 5 and the nozzle 12 in the vertical direction. The intermediate chamber 6 of the present embodiment is partitioned by partially expanding the accommodation hole 11 between the balance chamber 5 and the nozzle 12.

  A leak passage 8 is connected to the intermediate chamber 6. One end of the leak passage 8 is connected to the intermediate chamber 6 and the other end is connected to the amateur chamber 20. In this embodiment, a plug member 26 that closes the leak passage 8 is provided at the other end of the armature chamber 20. Provided. The plug 26 blocks the flow of fuel between the intermediate chamber 6 and the amateur chamber 20.

  As shown in FIG. 2, the plug member 26 according to the present embodiment includes a sleeve 261 whose one end is closed and a ball member 262 fitted into the sleeve 261.

  As shown in FIG. 3, the intermediate chamber 6 is connected to the second supply path 16 through the high pressure passage 9, and pressurized fuel is introduced into the intermediate chamber 6 through the high pressure passage 9 and the second supply path 16.

  Returning to FIG. 1, the nozzle 12 is formed in a hollow shape and accommodates the lower portion of the needle 3 therein. An outlet of the second supply path 16 is opened on the inner surface of the nozzle 12, and pressurized fuel from the second supply path 16 is introduced between the nozzle 12 and the needle 3.

  The lower end portion (tip portion) of the nozzle 12 is formed in a tapered shape that is reduced in diameter as it goes downward, and the inner surface of the lower end portion forms a seat portion for seating the needle 3. A plurality of nozzle holes 2 are formed on the lower end (tip) side of the sheet portion at intervals in the circumferential direction.

  A needle spring 28 for biasing the needle 3 downward is provided between the intermediate chamber 6 and the nozzle 12.

  The needle 3 is urged downward by the elastic force of the needle spring 28 and the pressure of the fuel in the balance chamber 5. On the other hand, the needle 3 is biased upward by the pressure of the fuel in the nozzle 12.

  When the fuel injection is stopped, the descending force due to the fuel in the needle spring 28 and the balance chamber 5 exceeds the ascending force due to the fuel in the nozzle 12, and the needle 3 is seated on the seat portion. On the other hand, at the time of fuel injection, the fuel in the balance chamber 5 is discharged, the downward force becomes weaker than the upward force, and the needle 3 is lifted.

  Next, the manufacturing method of the injector 1 of this embodiment is demonstrated.

  The injector 1 of the present embodiment is manufactured based on, for example, an injector 51 for light oil as shown in FIG.

  First, the schematic structure of the light oil injector 51 will be described with reference to FIG. In addition, about the same element as the injector 1 of this embodiment, it attaches | subjects the same code | symbol in a figure, and abbreviate | omits detailed description.

  As shown in FIG. 4, the light oil injector 51 has a nozzle hole 2 for injecting fuel to the nozzle 12, and a needle 30 for opening and closing the nozzle hole 2 can be moved up and down in the injector body 10. A balance chamber 5 is provided on the proximal end side of the needle 30 to introduce and discharge pressurized fuel from the common rail 4 to lower and raise the needle 30, and below the balance chamber 5 the needle from the balance chamber 5. An intermediate chamber 6 for storing the fuel leaked through 30 is provided, and an amateur chamber 20 is provided above the balance chamber 5, which can communicate with the balance chamber 5 through an orifice 19 and communicate with the fuel tank 7. The intermediate chamber 6 is communicated with the fuel tank 7 through the amateur chamber 20 to return the leaked fuel to the fuel tank 7. Configured to provide a passage 8.

  Further, the needle 30 of the light oil injector 51 is composed of three members, ie, a command piston 31, an intermediate rod 32, and a needle member 33 as a pressure balance valve structure.

  Here, when DME is used as fuel, the viscosity of DME is lower than that of light oil. Therefore, if the light oil injector 51 in FIG. 4 is directly used as a DME injector, the high pressure side balance chamber 5 and the low pressure side intermediate chamber are used. 6 Leakage amount of DME is larger than that of light oil.

  Therefore, in this embodiment, the intermediate chamber 6 is changed to the same pressure as the balance chamber 5 by increasing the pressure to the intermediate chamber 6, so that the DME leak from the balance chamber 5 to the intermediate chamber 6 is suppressed. gave.

  That is, in the manufacturing method of the injector 1 of this embodiment, the leak passage 8 is closed so as to shut off the intermediate chamber 6 and the fuel tank 7 of the light oil injector 51 described above, and the pressurized fuel of the common rail 4 is placed in the intermediate chamber 6. Is provided with a high-pressure passage 9 for communicating the intermediate chamber 6 with the common rail 4.

  As shown in FIG. 2, the leak passage 8 is closed by fitting a plug material 26 (in the illustrated example, a plug plug) into the leak passage 8 from the opening on the amateur chamber 20 side. Specifically, a fitting hole 81 having the same diameter as the outer diameter of the sleeve 261 and a stepped portion having a smaller diameter than the fitting hole 81 (the outer diameter of the sleeve 261) are provided in advance at the end of the leak passage 8 on the amateur chamber 20 side. 82. Next, the sleeve 261 is fitted into the fitting hole 81. A ball member 262 having a diameter larger than the inner diameter of the sleeve 261 is pushed into the fitted sleeve 261 to fix the sleeve 261.

  As shown in FIG. 3, the high-pressure passage 9 is formed, for example, by subjecting the injector body 10 to hole processing or groove processing to the lower surface of the second piece 102.

  Returning to FIG. 1, in this embodiment, the needle 3 is formed as a single member from the nozzle hole side distal end to the balance chamber side proximal end.

  As described above, the present embodiment is based on the mass-produced intermediate-chamber low-pressure type light oil injector 51, and has minimal processing (blocking of the leak passage 8, formation of the high-pressure passage 9) and minimum recombination parts (integrated nozzle 12). Thus, the intermediate chamber high-pressure type DME injector 1 can be realized.

  Next, the operation of the injector 1 of this embodiment will be described based on FIG.

  As shown in FIG. 1, during operation of the diesel engine, pressurized fuel (high pressure fuel) stored in the common rail 4 passes through the introduction path 14 of the injector 1 and is introduced into the first supply path 15 and the second supply path 16. Is done. The pressurized fuel in the first supply path 15 is introduced into the balance chamber 5, and the pressurized fuel in the second supply path 16 is introduced into the nozzle 12.

  Furthermore, in this embodiment, since the high pressure passage 9 for communicating the second supply passage 16 and the intermediate chamber 6 is formed, the pressurized fuel in the second supply passage 16 passes through the high pressure passage 9 and is intermediate. It is introduced into the chamber 6. On the other hand, in the present embodiment, the leak passage 8 extending from the intermediate chamber 6 to the amateur chamber 20 is closed by the plug material 26, and the fuel in the intermediate chamber 6 does not flow out to the amateur chamber 20.

  From the above, in the present embodiment, the pressure in the balance chamber 5 and the nozzle 12 and the pressure in the intermediate chamber 6 are maintained at substantially the same pressure.

  Here, a gap through which DME can flow is formed between the accommodation hole 11 from the balance chamber 5 to the intermediate chamber 6 and the needle 3, but in this embodiment, the balance chamber 5 and the intermediate chamber 6 are connected to each other. Since the same pressure is maintained, the fuel does not leak from the balance chamber 5 to the intermediate chamber 6. Similarly, since the inside of the nozzle 12 and the intermediate chamber 6 are maintained at the same pressure, there is no fuel leakage from the nozzle 12 to the intermediate chamber 6.

  Although switching leakage occurs when the solenoid 23 is switched, it is not a problem because it is at the same level as the conventional light oil injector 51.

  Further, when fuel is injected from the nozzle hole 2, fuel corresponding to the injection amount is newly supplied from the common rail 4 to the injector 1. At this time, the introduction path 14, the first and second supply paths 15, Pressure pulsation due to fluid inertia occurs in the pressure of the fuel flowing through 16.

In the present embodiment, the leak passage 8 connected to the intermediate chamber 6 is closed at the end on the amateur chamber 20 side, so that a sufficient capacity to absorb pressure pulsation is secured in the leak passage 8, Pressure pulsation accompanying fuel injection is reduced. That is, the intermediate portion of the fuel flow path from the introduction path 14 provided with the bar filter 13 that is the inlet and the orifice of the injector 1 to the nozzle hole 2 at the nozzle tip that is the outlet is provided by the leak passage 8 of the present embodiment. In addition, a buffer volume for buffering the pressure pulsation is secured.

  Thus, in the present embodiment, a relatively small change is made to the conventional light oil injector 51 in that the high pressure passage 9 is formed, the leak passage 8 is closed, and the needle 3 is formed as a single member. Thus, the mass-produced light oil injector 51 can be diverted to the DME injector 1.

  Furthermore, since most of the components of the light oil injector 51 (for example, the solenoid and the engine control device that controls the solenoid) are diverted, the number of parts of the new component is significantly larger than when a new DME injector is designed. Reduction is possible.

  As a result, it is possible to produce the DME injector 1 by substantially diverting the existing production facility for the light oil injector 51.

  From the above, the manufacturing cost of the injector 1 can be reduced.

  Further, since the light oil injector 51 is used, engine technology development such as NOx emission reduction measures currently applied to light oil engines can be smoothly applied to DME engines with slight changes. As a result, the development cost of the DME engine can be reduced.

  Further, in the present embodiment, when a low viscosity liquid such as DME is used as fuel, fuel leakage from the intermediate chamber 6 can be prevented.

  As a result, freezing due to latent heat of vaporization can be prevented, and the common rail pressure and the like can be set to a pressure range equivalent to that of light oil.

  That is, when DME, which is clean energy, is used as a fuel for a diesel engine, the DME has a low viscosity. Therefore, when the conventional pressure balance type light oil injector 51 is diverted, the fuel leaks from the intermediate chamber 6. In addition, the direct-acting type injector has a problem that the injectable pressure becomes low because the actuator driving force cannot be sufficiently secured. On the other hand, in the injector 1 of this embodiment, since the leak from the intermediate chamber 6 is prevented, a pressure balance type needle drive structure can be adopted and the jettable pressure can be increased.

  In addition, the pressure pulsation accompanying fuel injection can be reduced by connecting the leak passage 8 (buffer chamber) that absorbs the pressure pulsation to the high-pressure side fuel flow paths 13 to 15 communicating with the common rail 4. .

  In addition, when the needle is divided as in the prior art, a high pressure is applied to the divided surfaces. Therefore, unless the design is made in consideration of the pressure difference between the surfaces, force is applied to the needle by the differential pressure. On the other hand, in this embodiment, since the needle 3 is formed as one member, the differential pressure due to the division does not occur, and the design of the needle 3 can be facilitated.

  In addition, this invention is not limited to the above-mentioned embodiment, Various modifications and application examples can be considered.

  For example, the fuel is not limited to DME. The injector of the present invention can also be used as a high-pressure injector for injecting other liquid fuels (for example, light oil, gasoline, LPG, etc.).

  Further, a damper member constituted by a piston in which an orifice is formed and a return spring for restoring the piston may be provided in the leak passage 8. In this case, pressure pulsation associated with fuel injection can be reduced by the damper member.

FIG. 1 shows a fuel injection valve according to an embodiment of the present invention. FIG. 2 is a detailed view of part II in FIG. FIG. 3 is a detailed view of part III in FIG. FIG. 4 shows a conventional fuel injection valve for light oil. FIG. 5 shows a fuel injection valve for DME devised by the present inventors.

Explanation of symbols

1 Fuel injector (injector)
2 Injection hole 3 Needle valve (needle)
4 Common rail 5 Balance chamber 6 Intermediate chamber 7 Fuel tank 8 Leak passage 9 High pressure passage 26 Plug material

Claims (3)

An injection hole for injecting fuel is formed, and a needle valve for opening and closing the injection hole is provided so that it can be moved up and down, and pressurized needle fuel is introduced and discharged from the common rail to the base end side of the needle valve. A balance chamber for lowering and raising is provided, an intermediate chamber for storing leaked fuel from the balance chamber through the needle valve is provided, and a leak passage is provided for returning the leaked fuel to the fuel tank by communicating the intermediate chamber with the fuel tank. In order to use a fuel injection valve for light oil that has a lower viscosity than light oil, the leak passage is closed to shut off the intermediate chamber and the fuel tank, and the common rail is pressurized to the intermediate chamber. A method for manufacturing a fuel injection valve, characterized in that a high-pressure passage is provided for communicating the intermediate chamber with a common rail in order to introduce fuel. The method for producing a fuel injection valve according to claim 1, wherein the fuel having a viscosity lower than that of the light oil is dimethyl ether.     The method of manufacturing a fuel injection valve according to claim 1 or 2, wherein the needle valve is formed as a single member from the injection hole side distal end to the balance chamber side proximal end.

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