JP2010242517A - Fuel injection valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection valve capable of reducing a valve open time. <P>SOLUTION: The fuel injection valve includes a nozzle body 8 including an injection hole 6 formed at a tip part a high pressure fuel passage 30 supplying fuel to the tip, a needle 10 slidably disposed in a nozzle body 8, a first control chamber 22 which is connected to the high pressure fuel passage 30 and in which fuel generating pressure for biasing the needle 10 to a tip side is introduced, a valve 44 reducing generated pressure, a piezoelectric stack 38 operating the valve 44, a second valve open means applying pressure in a valve open direction on the needle 10 according to the action of the piezoelectric stack 38. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a fuel injection valve.

  In a common rail fuel injection device for an internal combustion engine, a nozzle is opened and closed by operating a needle to inject fuel in the common rail. As an actuator for controlling the open / close state of the fuel injection valve, a piezo stack that expands and contracts in response to application of a voltage may be used.

  Patent Document 1 discloses a technique for continuously adjusting the lift amount of a needle by charging and discharging a piezo element.

JP 2007-231770 A

  The valve opening pressure of the fuel injection valve is a pressure when the force for pushing down the needle (force in the valve closing direction) is equal to the force for pushing up (force in the valve opening direction). That is, when the force in the valve opening direction becomes larger than the force in the valve closing direction, the needle is pushed up and the fuel injection valve is opened. As the force in the valve closing direction, for example, the pressure of the fuel in the control chamber and the force of the spring in the control chamber are applied to the needle. At this time, if the fuel pressure in the common rail is low, the force from the spring out of the force in the valve closing direction applied to the needle increases. That is, the influence of the force by the spring is greater than the force resulting from the pressure. In this case, since it takes time until the spring is compressed, the valve opening time of the fuel injection valve may become long. For this reason, the opening of the fuel injection valve may become unstable.

  This invention makes it a subject to shorten the valve opening time of a fuel injection valve.

  The present invention includes a nozzle body provided with a nozzle hole provided at a tip portion, a fuel passage for supplying fuel to the tip portion, a needle slidably disposed in the nozzle body, and the fuel passage. And a control chamber into which a fuel for creating a pressure for urging the needle toward the tip side is introduced, a first valve opening means for reducing the created pressure, and the first valve opening means are operated. And a second valve opening means for applying a pressure in the valve opening direction to the needle in accordance with the operation of the actuator. According to the present invention, since the pressure in the valve opening direction acts on the needle according to the operation of the actuator, the valve opening time of the fuel injection valve can be shortened.

  In the above configuration, the needle includes a pressure receiving portion having a pressure receiving surface on the distal end side, and the second valve opening means increases the pressure of internal fuel acting on the pressure receiving surface in accordance with the operation of the actuator. It can be set as the structure provided with an oil-tight chamber. According to this configuration, since the pressure of the fuel in the oil-tight chamber that has been increased acts on the pressure receiving surface in accordance with the operation of the actuator, the valve opening time of the fuel injection valve can be shortened.

  In the above configuration, the needle includes a pressure receiving portion having a pressure receiving surface on the distal end side, and the second valve opening means includes a first oil-tight chamber in which an internal pressure is increased according to an operation of the actuator, A second oil-tight chamber that is connected to the oil-tight chamber and that increases the pressure of the internal fuel acting on the pressure-receiving surface in accordance with the operation of the actuator. According to this configuration, the increased fuel pressure in the second oil-tight chamber acts on the pressure-receiving surface in accordance with the operation of the actuator, so that it is possible to shorten the valve opening time of the fuel injection valve.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel injection valve which can shorten valve opening time can be provided.

FIG. 1 is a cross-sectional view illustrating a fuel injection valve according to the first embodiment. FIG. 2 is a cross-sectional view illustrating the operation of the fuel injection valve according to the first embodiment. FIG. 3 is a cross-sectional view illustrating the operation of the fuel injection valve according to the first embodiment. 4A and 4B are schematic views illustrating the relationship between the pressure in the control chamber of the fuel injection valve and time, and FIG. 4C relates to the conventional fuel injection valve and the first embodiment. It is the figure compared with the fuel injection valve.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view illustrating a fuel injection valve 100 according to the first embodiment. In FIG. 1, the fuel injection valve 100 is in a closed state, and no voltage is applied to a piezo stack 38, which will be described later.

  As shown in FIG. 1, the fuel injection valve 100 is connected to an ECU (Engine Control Unit) 2 via an EDU 4. The fuel injection valve 100 includes a nozzle body 8, a needle 10, and a piezo stack 38.

  In the nozzle body 8, the actuator chamber 12, the first piston chamber 14, the first oil-tight chamber 16, the second piston chamber 18, the valve chamber 20, the first control chamber 22 ( A control chamber), a second control chamber 24, a second oil-tight chamber 26 (oil-tight chamber), and a fuel reservoir chamber 28 are provided. A nozzle hole 6 is provided in a fuel reservoir chamber 28 provided at the tip of the nozzle body 8. A high pressure fuel passage 30 (fuel passage) connected to the common rail is provided in the nozzle body 8. A high pressure fuel passage 30 is connected to the valve chamber 20, the first control chamber 22, and the fuel reservoir chamber 28, and fuel is introduced from the high pressure fuel passage 30.

  The valve chamber 20 and the first control chamber 22 are connected by a fuel passage 32. The first oil tight chamber 16 and the second oil tight chamber 26 are connected by an oil tight passage 34. A return passage 36 is connected to the actuator chamber 12, the second piston chamber 18 and the second control chamber 24. The pressure of the fuel in the high pressure fuel passage 30 is higher than the pressure of the fuel in the return passage 36.

  The actuator chamber 12 is provided with a piezo stack 38 (actuator). A first piston 40 is connected to the front end side of the piezo stack 38, and the first piston 40 is disposed in the first piston chamber 14. A second piston 42 is connected to the distal end side of the first piston 40, and the second piston 42 is disposed in the second piston chamber 18. A valve 44 is connected to the distal end side of the second piston 42, and the valve 44 is disposed in the valve chamber 20. The first piston chamber 14 is provided with a spring 46a, the second piston chamber 18 is provided with a spring 46b, and the first control chamber 22 is provided with a spring 46c. The elastic force of the spring 46a urges the first piston 40, and the elastic force of the spring 46b urges the second piston 42 toward the base end side of each slidable body 8. The elastic force of the spring 46 c biases the needle 10 toward the tip end side of the nozzle body 8.

  The distal end side of the needle 10 is disposed in the fuel reservoir chamber 28, and the proximal end side of the needle 10 is disposed in the first control chamber 22. Further, the flange portion 11 (pressure receiving portion) formed in the middle of the needle 10 is slidably disposed in the first control chamber 22 and the second oil tight chamber 26. That is, the needle 10 is slidably disposed in the nozzle body. The pressure receiving surface 11 a that is the surface on the distal end side of the flange portion 11 receives pressure urging from the fuel in the second oil tight chamber 26 toward the proximal end side. A tapered portion 10 a is formed at the tip of the needle 10. When the fuel injection valve 100 is in a closed state, the seat portion 10b (illustrated by a solid line) of the tapered portion 10a is seated on the inner wall of the nozzle body 8. That is, the fuel supply to the nozzle hole 6 is interrupted and fuel is not injected. When the needle 10 is lifted to the proximal end side, the seat portion 10 b is separated from the inner wall of the nozzle body 8. In this case, fuel is supplied to the nozzle hole 6 and fuel is injected.

  As shown in FIG. 1, the valve 44 cuts off the connection between the second piston chamber 18 and the valve chamber 20 when no voltage is applied to the piezo stack 38. In other words, the connection between the first control chamber 22 connected to the valve chamber 20 by the fuel passage 32 and the return passage 36 connected to the second piston chamber 18 and the second piston chamber 18 is cut off. In this case, the fuel pressure in the first control chamber 22 and the fuel pressure in the fuel reservoir chamber 28 are both the fuel pressure in the high-pressure fuel passage 30.

  The taper portion 10 a of the needle 10 receives a pressure for urging the needle 10 toward the proximal end side of the nozzle body 8 from the fuel in the fuel reservoir chamber 28, in other words, a pressure in the valve opening direction. On the other hand, the pressure receiving surface 10c on the proximal end side of the needle 10 receives a pressure for urging the needle 10 toward the distal end side from the fuel in the first control chamber 22, in other words, a pressure in the valve closing direction. That is, the fuel introduced into the first control chamber 22 from the high-pressure fuel passage 30 creates a pressure that urges the needle 10 toward the distal end side. In addition, the spring 46c provided in the first control chamber 22 applies a force in a direction for urging the needle 10 toward the distal end side to the pressure receiving surface 10c. In FIG. 1, the force that urges the needle 10 toward the distal end (force in the valve closing direction) exceeds the force that urges the needle 10 toward the proximal end (force in the valve opening direction). For this reason, the needle 10 is pressed toward the distal end side, and the seat portion 10 b is seated on the inner wall of the nozzle body 8. That is, the supply of fuel to the nozzle hole 6 is shut off, and the fuel injection valve 100 is closed.

  Next, consider a case where a voltage is applied to the piezo stack 38. 2 and 3 are cross-sectional views illustrating the operation of the fuel injection valve 100 according to the first embodiment. The description of the same configuration as that described above is omitted.

  As shown in FIG. 2, the ECU 2 determines the fuel injection timing and the fuel injection amount, and sends a command to the EDU 4. In response to a command from the ECU 2, the EDU 4 applies a voltage to the piezo stack 38. The piezo stack 38 to which the voltage is applied operates. Specifically, the piezo stack 38 extends in the distal direction. Due to the extension of the piezo stack 38, the first piston 40, the second piston 42, and the valve 44 move to the tip side of the nozzle body 8. In other words, the piezo stack 38 operates the first piston 40, the second piston 42, and the valve 44. The valve chamber 20 and the second piston chamber 18 are connected by moving the valve 44 toward the distal end side. A return passage 36 is connected to the valve chamber 20 via the second piston chamber 18. Further, the return passage 36 is connected to the first control chamber 22 through the fuel passage 32, the valve chamber 20 and the second piston chamber 18. Further, the connection between the valve chamber 20 and the high-pressure fuel passage 30 is cut off by the valve 44.

  As shown in FIG. 3, the fuel in the first control chamber 22 flows out to the return passage 36 via the fuel passage 32, the valve chamber 20, and the second piston chamber 18. For this reason, the pressure of the fuel in the 1st control chamber 22 reduces. That is, the valve chamber 20 connects the first control chamber 22 and the return passage 36. The valve 44 controls the open / closed state of the valve chamber 20 and the return passage 36. That is, the valve chamber 20 and the valve 44 function as first valve opening means. In accordance with the operation of the piezo stack 38, the valve chamber 20 and the valve 44 reduce the pressure of fuel in the first control chamber 22. On the other hand, when the first piston 40 moves in accordance with the extension of the piezo stack 38, the pressure of fuel in the first oil tight chamber 16, the oil tight passage 34, and the second oil tight chamber 26 increases. That is, according to the operation of the piezo stack 38, the pressure of the fuel in the second oil tight chamber 26 acting on the pressure receiving surface 11a is increased. In other words, the pressure of the fuel in the first oil tight chamber 16 and the second oil tight chamber 26 increases in accordance with the operation of the piezo stack 38.

  Since the fuel pressure in the first control chamber 22 is reduced, the force in the valve closing direction received by the needle 10 is reduced. On the other hand, since the pressure of the fuel in the second oil tight chamber 26 increases, the force in the valve opening direction received by the needle 10 increases. That is, the first oil-tight chamber 16, the oil-tight passage 34, and the second oil-tight chamber 26 function as second valve opening means. When the force in the valve opening direction becomes larger than the force in the valve closing direction, the needle 10 is pushed up to the proximal end side. That is, the seat portion 10 b of the needle 10 is separated from the inner wall of the nozzle body 8. At this time, fuel is supplied to the nozzle hole 6. That is, the fuel injection valve 100 is opened and fuel is injected.

  Next, the time until the fuel injection valve is opened will be described with reference to the drawings. 4A shows the pressure in the closing direction of the fuel injection valve when the fuel pressure in the high-pressure fuel passage 30 is 200 MPa, and FIG. 4B shows the pressure in the valve closing direction of the fuel injection valve when the fuel pressure in the high-pressure fuel passage 30 is 40 MPa. It is a schematic diagram which illustrates the relationship between time and time. In each figure, the vertical axis represents the pressure in the valve closing direction applied to the needle 10, and the horizontal axis represents time. Also, the broken line indicates the valve opening pressure (the pressure at which the valve closing direction pressure and the valve opening direction pressure are equal), and the horizontal dotted line indicates the valve opening pressure when there is no spring 46c (see, for example, FIG. 1). To express. Assume that the elastic force of the spring 46c provided in the first control chamber 22 corresponds to a pressure of 10 MPa, and voltage application to the piezo stack 38 is started at time t1.

  As shown in FIG. 4A, when voltage application to the piezo stack 38 is started at time t1, the fuel pressure in the first control chamber 22 decreases (see FIGS. 2 and 3). In other words, the pressure in the valve closing direction is reduced. When the pressure in the valve closing direction becomes lower than the valve opening pressure represented by the solid line in the figure, the needle 10 is pushed up and the fuel injection valve 100 is opened (see FIG. 3). The time for reaching the valve opening pressure is t2.

  As shown in FIG. 4B, when the pressure of the fuel in the high pressure fuel passage 30 is 40 MPa, the elastic force of the spring 46c contributes to the pressure in the valve closing direction as compared with the example of FIG. The proportion increases. In this case, the time until the spring 46c is compressed by the needle 10 is longer than the time during which the fuel in the first control chamber 22 flows out into the return passage 36 and the pressure of the fuel in the first control chamber 22 decreases. Sometimes. In this case, it takes time to open the valve. Especially when the fuel pressure in the high-pressure fuel passage 30 is low as in the example of FIG. 4B, the contribution of the elastic force of the spring to the force in the valve closing direction increases, so that the valve opening pressure is reached. This time t2 is longer than in the case of FIG.

  Next, the fuel injection valve 100 according to the first embodiment and the fuel injection vent according to the comparative example are compared, and the time until the fuel injection valve is opened will be described. The comparative example is an example in which the needle does not receive pressure from the oil-tight chamber.

  FIG. 4C is a diagram comparing the time until the fuel injection valve opens between the fuel injection valve according to the comparative example and the fuel injection valve 100 according to the first embodiment. The pressure of the fuel in the high-pressure fuel passage 30 is 40 MPa. The broken line represents the valve opening pressure in the fuel injection valve according to the comparative example (same as that shown in FIG. 4B), and the dotted line represents the valve opening pressure in the fuel injection valve 100 according to the first embodiment.

  As shown in FIG.4 (c), time t3 until reaching valve opening pressure in Example 1 is shorter than time t2 until reaching valve opening pressure in the comparative example. This cause will be described. According to the first embodiment, as shown in FIG. 3, the pressure of the fuel in the second oil tight chamber 26 increases due to the extension of the piezo stack 38, and the pressure receiving surface 11 a of the needle 10 receives the pressure of the second oil tight chamber 26. . Since the pressure of the fuel in the second oil-tight chamber 26 is the pressure in the valve opening direction, according to Example 1, the pressure in the valve opening direction is higher than that in the comparative example. Therefore, the pressure in the valve closing direction and the pressure in the valve opening direction reach an equilibrium earlier than in the comparative example. That is, the time until the valve opening pressure is reached is shortened. Thereby, the opening of the fuel injection valve is stabilized.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such 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.

ECU 2
EDU 4
Hole 6
Nozzle body 8
Needle 10
Isobe 11
Pressure receiving surface 10c, 11a
Actuator room 12
First oiltight chamber 16
Valve chamber 20
First control room 22
Second oiltight chamber 26
Fuel reservoir 28
High pressure fuel passage 30
Return passage 36
Piezo stack 38
Valve 44
Spring 46a, 46b, 46c
Fuel injection valve 100

Claims (3)

A nozzle body provided with a nozzle hole provided at the tip, and a fuel passage for supplying fuel to the tip;
A needle slidably disposed in the nozzle body;
A control chamber that is connected to the fuel passage and into which fuel is introduced to create a pressure that biases the needle toward the distal end;
First valve opening means for reducing the created pressure;
An actuator for operating the first valve opening means;
And a second valve opening means for applying a pressure in the valve opening direction to the needle according to the operation of the actuator. The needle includes a pressure receiving portion having a pressure receiving surface on the tip side,
2. The fuel injection valve according to claim 1, wherein the second valve opening means includes an oil tight chamber in which a pressure of an internal fuel acting on the pressure receiving surface is increased according to an operation of the actuator. The needle includes a pressure receiving portion having a pressure receiving surface on the tip side,
The second valve opening means includes a first oil-tight chamber in which an internal pressure is increased according to the operation of the actuator;
2. The fuel according to claim 1, further comprising: a second oil-tight chamber connected to the first oil-tight chamber, wherein the pressure of the internal fuel acting on the pressure receiving surface is increased according to the operation of the actuator. Injection valve.

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