JP2009102988A - Fuel injection device for internal combustion engine - Google Patents

Abstract

A fuel injection device for an internal combustion engine capable of facilitating fuel vaporization by generating fine cavitation in the fuel and injecting the fuel.
An injection hole, a fuel chamber, a valve body that opens to inject fuel in the fuel chamber from the injection hole and closes to stop fuel injection, a high-frequency vibration member, And the fuel in the fuel chamber is vibrated at high frequency by the high-frequency vibrating member when the valve body is closed.
[Selection] Figure 1

Description

  The present invention relates to a fuel injection device for an internal combustion engine.

  In a fuel injection device having a valve body coupled to a piezoelectric actuator and injecting fuel by opening the valve body by contracting the piezoelectric actuator, the piezoelectric actuator is operated at a high frequency when the valve body is opened to the maximum. It has been proposed to vibrate the injected fuel at a high frequency by oscillating it to remove deposits deposited in the nozzle holes (see, for example, Patent Document 1).

JP2003-97390 JP 2003-105343 A 4-76968 JP 63-268952 A

  By the way, when the fuel is vibrated at high frequency, fine cavitation is generated in the fuel. By injecting fuel containing fine cavitation in this way, cavitation rapidly expands after injection to atomize the fuel and facilitate fuel vaporization. In the fuel injection device disclosed in Patent Document 1, the fuel vibrates at high frequency only in a short period while the valve element is opened to the maximum. With this, fine cavitation can be sufficiently generated in the fuel. Therefore, there is room for improvement in the vaporization of the injected fuel.

  Accordingly, an object of the present invention is to provide a fuel injection device for an internal combustion engine that can facilitate fuel vaporization by generating fine cavitation in the fuel and injecting the fuel.

  According to a first aspect of the present invention, there is provided a fuel injection device for an internal combustion engine, wherein an injection hole, a fuel chamber, and a fuel in the fuel chamber are opened to inject fuel from the injection hole, and fuel injection is stopped. A valve body for closing the valve and a high-frequency vibration member are provided, and the fuel in the fuel chamber is vibrated at high frequency by the high-frequency vibration member when the valve body is closed.

  According to a second aspect of the present invention, there is provided the fuel injection device for an internal combustion engine according to the first aspect, wherein the high-frequency vibration member is the first set period immediately before the valve body is opened. The fuel in the fuel chamber is vibrated at high frequency.

  According to a third aspect of the present invention, there is provided the fuel injection device for an internal combustion engine according to the first aspect, wherein the high-frequency vibration member is the first set period immediately after the valve body is closed. The fuel in the fuel chamber is vibrated at high frequency.

  The fuel injection device for an internal combustion engine according to claim 4 according to the present invention is the fuel injection device for an internal combustion engine according to claim 2 or 3, wherein the first set period is lengthened as the engine temperature is low. To do.

  A fuel injection device for an internal combustion engine according to a fifth aspect of the present invention is the fuel injection device for an internal combustion engine according to any one of the second to fourth aspects, wherein the fuel contains alcohol, The higher the alcohol concentration is, the longer the first setting period is.

  According to a sixth aspect of the present invention, there is provided a fuel injection device for an internal combustion engine, wherein an injection hole, a fuel chamber, and the fuel in the fuel chamber are opened to inject fuel from the injection hole, and the fuel injection is stopped. A valve body for closing the valve and a high-frequency vibration member are provided, and the fuel in the fuel chamber is vibrated at high frequency by the high-frequency vibration member while the valve body is closed.

  A fuel injection device for an internal combustion engine according to a seventh aspect of the present invention is the fuel injection device for an internal combustion engine according to the second or sixth aspect, wherein the high-frequency vibration member is in a second set period shorter than the first set period. The fuel accumulated on the downstream side of the nozzle hole is vibrated at a high frequency immediately after the valve body is closed.

  An internal combustion engine fuel injection device according to an eighth aspect of the present invention is the internal combustion engine fuel injection device according to any one of the first to seventh aspects, wherein the high-frequency vibration member opens the valve body to a maximum. The fuel in the fuel chamber is vibrated at a high frequency even when being valved.

  An internal combustion engine fuel injection device according to a ninth aspect of the present invention is the internal combustion engine fuel injection device according to any one of the first to eighth aspects, wherein the high-frequency vibration member opens the valve body and It is a piezo actuator for closing the valve.

  According to the fuel injection device for an internal combustion engine according to claim 1 of the present invention, the fuel in the fuel chamber is sufficiently long to vibrate at high frequency in order to vibrate the fuel in the fuel chamber by the high-frequency vibrating member when the valve body is closed. Thus, fine cavitation can be sufficiently generated in the fuel. Thus, if fine cavitation is sufficiently generated in the fuel and the fuel is injected, the cavitation expands rapidly after injection to atomize the fuel and facilitate fuel vaporization.

  According to the fuel injection device for an internal combustion engine according to claim 2 of the present invention, in the fuel injection device for internal combustion engine according to claim 1, the high-frequency vibration member is a fuel in a first setting period immediately before the valve body is opened. The fuel in the room is vibrated at a high frequency, and the first setting period can be set sufficiently long to sufficiently generate fine cavitation in the fuel in the fuel chamber.

  According to a fuel injection device for an internal combustion engine according to claim 3 of the present invention, in the fuel injection device for internal combustion engine according to claim 1, the high-frequency vibration member is a fuel in a first setting period immediately after the valve body is closed. The fuel in the room is vibrated at a high frequency, and the first setting period can be set sufficiently long to sufficiently generate fine cavitation in the fuel in the fuel chamber.

  According to the fuel injection device of the internal combustion engine according to claim 4 of the present invention, in the fuel injection device of the internal combustion engine according to claim 2 or 3, the lower the engine temperature, the longer the first setting period, Thereby, the lower the engine temperature at which the fuel is less likely to vaporize, the more fine cavitation is generated in the fuel in the fuel chamber, and the atomization of the injected fuel can be promoted.

  According to a fuel injection device for an internal combustion engine according to claim 5 of the present invention, in the fuel injection device for an internal combustion engine according to any one of claims 2 to 4, the fuel contains alcohol, The higher the alcohol concentration is, the longer the first setting period is. As a result, the higher the alcohol concentration at which the fuel is hard to vaporize, the more fine cavitation is generated in the fuel in the fuel chamber and the atomization of the injected fuel is reduced. Can be promoted.

  According to the fuel injection device for an internal combustion engine according to claim 6 of the present invention, the fuel in the fuel chamber is vibrated at high frequency by the high frequency vibrating member while the valve body is being closed. The atomization of the injected fuel can be promoted by generating even a small amount of fine cavitation in the fuel in the fuel chamber when the injected fuel pressure immediately before closing the valve is lowered.

  According to the fuel injection device for an internal combustion engine according to claim 7 of the present invention, in the fuel injection device for internal combustion engine according to claim 2 or 6, the high-frequency vibration member is in a second setting period shorter than the first setting period. The fuel accumulated on the downstream side of the valve body immediately after the valve is closed is caused to vibrate at high frequency, so that the fuel accumulated on the downstream side of the valve body flows out of the nozzle hole by the high frequency vibration, It becomes difficult to generate deposits in the nozzle holes.

  According to a fuel injection device for an internal combustion engine according to an eighth aspect of the present invention, in the fuel injection device for an internal combustion engine according to any one of the first to seventh aspects, the high-frequency vibration member opens the valve body to the maximum. Even when the valve is being operated, the fuel in the fuel chamber is vibrated at a high frequency, so that even during fuel injection, fine cavitation is further generated in the fuel, which can further promote atomization of the injected fuel. it can.

  According to a fuel injection device for an internal combustion engine according to claim 9 of the present invention, in the fuel injection device for internal combustion engine according to any one of claims 1 to 8, the high-frequency vibration member opens the valve body and Since the piezoelectric actuator for closing the valve is used, it is not necessary to provide a new member as the high-frequency vibration member.

  FIG. 1 is a schematic cross-sectional view showing a fuel injection device according to the present invention. In the figure, reference numeral 1 denotes a main body of the fuel injection device. A fuel reservoir 3 that communicates with the nozzle hole 2 is formed at the tip of the main body 1. The fuel reservoir 3 has a hemispherical portion on the distal end side and a cylindrical portion on the proximal end side, and the cylindrical portion is connected to a truncated cone-shaped portion of the fuel chamber 4, and a connecting corner portion of both forms a seat portion 5. A cylindrical portion on the base end side of the fuel chamber 4 is connected to the high-pressure fuel passage 6. The high-pressure fuel passage 6 is always supplied with high-pressure fuel in a pressure accumulation chamber (not shown) pressurized by a high-pressure pump, whereby the fuel chamber 4 is filled with high-pressure fuel via the high-pressure fuel passage 6. It is filled.

  A valve body 7 is disposed in the fuel chamber 4. When the valve body 7 is closed, the conical tip of the valve body 7 comes into contact with the seat portion 5, and as a result, the injection hole 2 is closed. Is stopped. On the other hand, when the valve body 7 is opened, the tip of the conical shape of the valve body 7 is separated from the seat portion 5, and when the fuel chamber 4 and the fuel reservoir 3 are communicated to open the injection hole 2, fuel injection is performed. Is done. The valve body 7 has a small-diameter portion 7a on the distal end side, an intermediate-diameter portion 7b, and a large-diameter portion 7c on the proximal end side, and the end surface of the large-diameter portion 7c contains high-pressure fuel via a high-pressure fuel passage 6. The fuel pressure acts in the valve closing direction, and the pressing force of the spring 8 also acts in the valve closing direction.

  A control chamber 10 whose volume is changed by the piston 9 is provided, and the fuel pressure in the control chamber 10 acts on the step portion between the middle diameter portion 7b and the large diameter portion 7c of the valve body 7 in the valve opening direction. ing. The control chamber 10 is connected to the high-pressure fuel passage 6 via the check valve 11 so that the inside of the control chamber 10 does not fall below the fuel pressure of the high-pressure fuel (the moment when the volume increases, the high-pressure fuel pressure is reduced). May be less). The piston 9 is moved in the direction of decreasing the volume of the control chamber 10 by the extension of the piezo actuator 12 via the operating rod 9a, and the volume of the control chamber 10 is increased by the spring 13 by contraction of the piezo actuator 12. Moved in the direction.

  When the volume of the control chamber 10 is reduced and the inside of the control chamber 10 is sufficiently increased from the fuel pressure of the high-pressure fuel, the force acting on the valve body 7 in the valve opening direction is greater than the force acting on the valve body 7 in the valve closing direction. The valve element 7 opens as the valve body becomes larger. On the other hand, when the volume of the control chamber 10 is increased and the inside of the control chamber 10 becomes the fuel pressure of the high-pressure fuel, the force acting in the valve closing direction by the pressing force of the spring 8 becomes larger than the force acting in the valve opening direction. The body 7 is closed.

  Thus, by applying a voltage to the piezo actuator 12 and extending it, the valve body 7 is opened to start fuel injection, and by stopping the voltage application to the piezo actuator 12 and contracting, the valve body 7 is closed. Thus, the fuel injection can be stopped. FIG. 2 is a time chart showing the lift amount of the valve body 7. The valve body 7 starts to open at time t1, closes at time t2, then starts to open at time t5, and closes at time t8. At time t6 after a while from time t5, the valve element 7 is lifted to the maximum, and is lifted to the maximum until time t7 when the valve closing is started.

  By the way, when the fuel is vibrated at high frequency, fine cavitation is generated in the fuel. By injecting fuel containing fine cavitation in this way, cavitation rapidly expands after injection to atomize the fuel and facilitate fuel vaporization. Further, when the generated cavitation collapses, the disrupted energy causes turbulence in the injected fuel, or the fuel is lightened, facilitating fuel vaporization. In the fuel injection device according to the present embodiment, the piezoelectric actuator 12 vibrates at a high frequency by superimposing a voltage or current having a slight amplitude that vibrates at a high frequency on the control voltage or control current of the piezoelectric actuator 12. The fuel in the fuel chamber 4 can be vibrated at a high frequency via

  Further, the piezo actuator 12 vibrates the piston 9 at high frequency, and vibrates the fuel in the back pressure chamber 14 of the piston 9 at high frequency. Since the back pressure chamber 14 communicates with the fuel chamber 4 via the high pressure fuel passage 6, the high frequency vibration of the fuel in the back pressure chamber 14 is propagated to the fuel in the fuel chamber 4, and the fuel in the fuel chamber 4 Is vibrated at high frequency.

  FIG. 5 shows that when a constant voltage is applied to the piezo actuator 12, that is, when the valve body is closed (for example, an applied voltage of 0 V) and when the valve body is fully opened (lifted), a slight amount of high frequency is shown. This shows a case where a voltage with a large amplitude is superimposed. FIG. 6 shows a case where the voltage applied to the piezo actuator 12 is changing, for example, a case where a high-frequency voltage with a slight amplitude is superimposed on the valve body during closing. The piezoelectric actuator 12 can be vibrated at a high frequency not by such voltage control but by similar current control.

  For example, even when the piezo actuator 12 is vibrated at a high frequency while the valve element 7 is lifted to the maximum (between time t6 and time t7), fine cavitation is sufficiently generated in the fuel in the fuel chamber 4. It is not possible to promote vaporization of injected fuel.

  Accordingly, in the present embodiment, the fuel in the fuel chamber 4 is vibrated at high frequency by the piezo actuator 12 when the valve body 7 is closed (between time t2 and time t5). When the valve body 7 is closed, the fuel in the fuel chamber 4 can be sufficiently vibrated at a high frequency to sufficiently generate fine cavitation in the fuel. Thus, if fine cavitation is sufficiently generated in the fuel and the fuel is injected, the cavitation expands rapidly after injection to atomize the fuel and facilitate fuel vaporization. Of course, the fuel in the fuel chamber 4 may be vibrated at a high frequency during the entire period when the valve body 7 is closed, but the fuel in the fuel chamber 4 may be vibrated at a high frequency during a partial period when the valve body 7 is closed. Also good.

  In the fuel injection device of the present embodiment, the piezo actuator 12 is not directly connected to the valve body 7, and the valve body 7 is opened and closed by the fuel pressure in the control chamber 10 controlled by the piezo actuator 12. When the piezoelectric actuator 12 is vibrated at high frequency, that is, when the piezo actuator 12 repeats slight expansion and contraction for a short time, the fuel pressure in the control chamber 10 is changed by the piston 9 until the valve body 7 is opened. The fuel pressure in the control chamber 10 does not increase. Thereby, even if the piezo actuator 12 is vibrated at high frequency while the valve body 7 is closed, the valve body 7 does not open.

  The partial period described above can be a first setting period (for example, between time t2 and time t3) immediately after the valve body 7 is closed. Of course, the first setting period immediately after the valve body 7 is closed may not start from the valve closing timing (time t2) of the valve body 7. Further, the partial period can be a first setting period (for example, between time t4 and time t5) immediately before the valve element 7 is opened. Of course, the first setting period immediately before the opening of the valve body 7 does not have to end at the valve opening timing (time t5) of the valve body 7. The first setting period when the valve body 7 is closed can be set sufficiently long, and fine cavitation can be sufficiently generated in the fuel in the fuel chamber 4. In addition, by generating cavitation immediately before the valve element 7 is opened, a large amount of cavitation can surely exist in the fuel even at the time of injection.

  By the way, the lower the engine temperature is, the more difficult it is to vaporize the injected fuel. Therefore, as shown in FIG. 3, the lower the cooling water temperature, the larger the water temperature coefficient a is set. The period may be corrected by multiplication by the water temperature coefficient a. As a result, the lower the engine temperature, the longer the first set period, and the lower the engine temperature at which the fuel is less likely to vaporize, the more fine cavitation is generated in the fuel in the fuel chamber, which promotes atomization of the injected fuel. be able to. Such high-frequency vibration of the piezo actuator 12 may be performed only when the engine is started.

  In addition, when alcohol (for example, ethanol or methanol) is included in the injected fuel, the alcohol requires a large amount of latent heat of vaporization. Therefore, the higher the alcohol concentration of the fuel, the more difficult it is to vaporize. Thereby, as shown in FIG. 4, the higher the alcohol concentration, the larger the concentration coefficient b may be set, and the reference period may be multiplied and corrected by the concentration coefficient b in the first setting period described above. As a result, the higher the alcohol concentration at which the fuel is less likely to vaporize, the longer the first setting period, and a large amount of fine cavitation is generated in the fuel in the fuel chamber, which can promote atomization of the injected fuel. . Such high-frequency vibration of the piezo actuator 12 may be performed only when the engine is started. Further, the reference period of the first set period may be corrected by multiplication with the concentration coefficient b and the water temperature coefficient a.

  By the way, during the valve closing of the valve body 7 (from time t7 to time t8), the injected fuel pressure gradually decreases, so that the atomization of the injected fuel worsens as the injected fuel pressure decreases. As a result, if the fuel in the fuel chamber 4 is vibrated at a high frequency while the valve body 7 is being closed, the fuel in the fuel chamber 4 will be fine when the injected fuel pressure immediately before the valve body 7 is closed. Even a slight cavitation can be generated to promote atomization of the injected fuel. Of course, the fuel in the fuel chamber 4 may be vibrated at a high frequency during the entire period when the valve body 7 is being closed. However, the fuel within the fuel chamber 4 may be vibrated at a high frequency during a part of the period when the valve body 7 is being closed. May be.

  Further, immediately after the valve body 7 is closed, the fuel reservoir 3 and the injection hole 2 are filled with fuel. When this fuel is exposed to a high temperature in the combustion chamber, it may become a deposit and reduce the inner diameter of the nozzle hole 2. Thereby, immediately after the valve body 7 is closed, the fuel in the fuel reservoir 3 and the nozzle hole 2, that is, the fuel accumulated on the downstream side of the valve body 7 is preferably discharged immediately.

  In the first setting period immediately after the valve body 7 is closed, when the piezo actuator 12 is vibrated at high frequency and the fuel in the fuel chamber 4 is vibrated at high frequency, the high frequency vibration of the piezo actuator 12 is downstream of the valve body 7. The accumulated fuel is also vibrated at a high frequency, and can automatically flow out of the nozzle hole 2. However, in the first setting period immediately before the valve element 7 is opened or when the fuel in the fuel chamber 4 is vibrated at a high frequency while the valve element 7 is being closed, in the second setting period immediately after the valve element 7 is closed. It is preferable to make it difficult for deposits to be generated in the injection hole 2 by causing the piezoelectric actuator 12 to vibrate at high frequency to cause the fuel accumulated on the downstream side of the valve body 7 to vibrate at high frequency and to flow out of the injection hole 2. This second setting period can be shorter than the first setting period described above.

  Of course, the fuel in the fuel chamber 4 may be vibrated at a high frequency even when the valve element 7 is opened to the maximum, so that fine cavitation is generated in the fuel in the fuel chamber 4 during fuel injection. And can further promote atomization of the injected fuel.

  In the fuel injection device of the present embodiment, a piezoelectric actuator for opening and closing the valve body 7 as a high-frequency vibration member that vibrates the fuel in the fuel chamber 4 or the fuel accumulated on the downstream side of the valve body 7 at a high frequency. Therefore, it is not necessary to provide a new member as the high-frequency vibration member. Of course, the actuator that opens and closes the valve body 7 may or may not be a piezoelectric actuator. Such a high-frequency vibration member may be provided.

It is a schematic sectional drawing of the fuel-injection apparatus of the internal combustion engine by this invention. It is a time chart which shows the lift amount of a valve body. It is a map for setting a water temperature coefficient. It is a map for setting a density coefficient. It is a time chart which shows the case where the voltage of the small amplitude of a high frequency is superimposed on the fixed control voltage. It is a time chart which shows the case where the voltage of the slight amplitude of a high frequency is superimposed on the control voltage which changes.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main body 2 Injection hole 3 Fuel reservoir 4 Fuel chamber 7 Valve body 9 Piston 10 Control chamber 12 Piezo actuator

Claims (9)

  Comprising a nozzle hole, a fuel chamber, a valve body that opens to inject fuel in the fuel chamber from the nozzle hole, and closes to stop fuel injection, and a high-frequency vibration member, A fuel injection device for an internal combustion engine, wherein the high-frequency vibration member vibrates the fuel in the fuel chamber at high frequency when the valve body is closed.   2. The fuel injection device for an internal combustion engine according to claim 1, wherein the high-frequency vibration member vibrates the fuel in the fuel chamber at a high frequency in a first setting period immediately before the valve body is opened.   2. The fuel injection device for an internal combustion engine according to claim 1, wherein the high-frequency vibration member vibrates the fuel in the fuel chamber at a high frequency in a first setting period immediately after the valve body is closed.   The fuel injection device for an internal combustion engine according to claim 2 or 3, wherein the first set period is lengthened as the engine temperature is lower.   The fuel injection apparatus for an internal combustion engine according to any one of claims 2 to 4, wherein the fuel contains alcohol, and the first setting period is lengthened as the alcohol concentration of the fuel is higher.   Comprising a nozzle hole, a fuel chamber, a valve body that opens to inject fuel in the fuel chamber from the nozzle hole, and closes to stop fuel injection, and a high-frequency vibration member, A fuel injection device for an internal combustion engine, wherein the high-frequency vibration member vibrates the fuel in the fuel chamber at a high frequency while the valve body is closed.   7. The high-frequency vibrating member vibrates high-frequency vibrations of fuel accumulated on the downstream side of the nozzle hole immediately after the valve element is closed in a second setting period shorter than the first setting period. 2. A fuel injection device for an internal combustion engine according to 1.   The fuel injection of the internal combustion engine according to any one of claims 1 to 7, wherein the high-frequency vibration member vibrates the fuel in the fuel chamber at a high frequency even when the valve body is opened to a maximum. apparatus.   9. The fuel injection device for an internal combustion engine according to claim 1, wherein the high-frequency vibration member is a piezo actuator for opening and closing the valve body.

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