JP2011220133A - Fuel injection valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the occurrence of cavitation of fuel injected from a fuel injection valve.SOLUTION: The fuel injection valve 1 includes: a hollow cylindrical nozzle body 2 on which a nozzle hole 21 is formed; a needle valve 3 which is slidably arranged in the nozzle body 2 and forms a fuel passage 4 through which fuel passes between the nozzle body 2 and itself; and a movable piece 5 for adjusting a throttle 41 of the fuel passage 4 on the basis of a pressure in the fuel passage 4. This configuration causes the fuel injection valve 1 to control the fuel cavitation and to adjust penetration strength of spray.

Description

  The present invention relates to a fuel injection valve provided in an internal combustion engine.

  In an internal combustion engine, fuel injected from a fuel injection valve is mixed with air to form an air-fuel mixture, which is ignited and ignited for combustion. The injected fuel is more easily mixed with air as the particles are made finer, and the combustion efficiency is improved as it is mixed well with air. For this reason, the improvement which accelerates | stimulates atomization of the injected fuel conventionally has been performed. As a method of promoting atomization of fuel, there is a method of generating cavitation in the fuel in the fuel injection valve. Patent Document 1 discloses an improved fuel injection valve that generates such cavitation.

  The fuel injection valve of Patent Document 1 generates a cavitation by reducing the curvature radius of the edge at the inflow opening of the injection hole to sharply change the flow direction of the fuel flowing into the injection hole.

JP 2009-114925 A

  In a conventional fuel injection valve that generates such cavitation, the fuel always passes through a passage that generates cavitation, so that the spray is always atomized. However, when the internal combustion engine is operated at a medium load or a high load, penetration that is strong against spraying is required so that the fuel diffuses over a wide area. The spray from the fuel injection valve causes cavitation to occur inside the injection valve, resulting in a decrease in penetration, so that an appropriate spray cannot be injected when the internal combustion engine is operated at a medium or high load. It can be aggravated or insufficient output.

  Therefore, an object of the present invention is to control generation of cavitation of fuel injected from a fuel injection valve.

  The fuel injection valve of the present invention that solves such a problem is disposed so as to be slidable in a hollow cylindrical nozzle body in which an injection hole is formed, and the nozzle body, and fuel passes between the nozzle body. A needle valve forming a fuel passage, and a throttle adjusting means for adjusting a throttle of the fuel passage based on a pressure in the fuel passage are provided.

  Cavitation occurs when the fuel passes through the throttle formed in the fuel passage. With the above configuration, it is possible to promote the occurrence of cavitation by reducing the aperture, and to suppress the occurrence of cavitation by enlarging the aperture. In this way, the occurrence of cavitation can be adjusted, and the strength of the spray penetration can be adjusted.

  In the fuel injection valve, the throttle adjusting means may expand the throttle when the fuel in the fuel passage is high pressure, and reduce the throttle when the fuel in the fuel passage is low pressure. it can. By adopting such a configuration, it is possible to suppress the occurrence of fuel cavitation during high-pressure injection and to promote the occurrence of fuel cavitation during low-pressure injection.

In the fuel injection valve, the throttle adjusting means includes a movable piece that is held by the needle valve and protrudes into the fuel passage to form a throttle, and the movable piece increases the fuel pressure in the fuel passage. In this case, the needle valve can be immersed. Alternatively, in the fuel injection valve, the throttle adjusting means includes a movable piece that is held by the nozzle body and projects into the fuel passage to form a throttle.
The movable piece may be configured to be immersed in the nozzle body when the fuel pressure in the fuel passage increases.

  According to the present invention, it is possible to control whether or not a throttle portion is formed in a fuel passage for supplying fuel to an injection hole, and to control generation of cavitation of injected fuel.

It is explanatory drawing which showed the cross section of the front-end | tip part by which the nozzle hole of the fuel injection valve of Example 1 was pierced. It is explanatory drawing which showed the state of the fuel injection valve at the time of low pressure injection. It is explanatory drawing which expanded and showed the movable piece periphery at the time of low pressure injection. It is explanatory drawing which showed the state of the fuel injection valve at the time of high pressure injection. It is explanatory drawing which expanded and showed the movable piece periphery at the time of high pressure injection. It is explanatory drawing which showed the cross section of the front-end | tip part in which the nozzle hole of the fuel injection valve of Example 2 was pierced.

  Hereinafter, an embodiment for carrying out the present invention will be described in detail with reference to the drawings.

  Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view showing a cross-section of a tip portion in which a nozzle hole 21 of a fuel injection valve 1 of this embodiment is formed. For example, the fuel injection valve 1 is mounted on a cylinder head of an engine so that a tip portion projects into a cylinder, and is used as a part of a fuel injection device. The fuel injection valve 1 includes a hollow cylindrical nozzle body 2 in which an injection hole 21 is formed, a slidable arrangement within the nozzle body 2, and a needle valve 3 having a pointed tip 31.

  The nozzle hole 21 is formed so as to communicate the sack portion 22 formed on the tip end side of the nozzle body 2 and the outside of the nozzle body 2. A plurality of nozzle holes 21 are formed around the axis of the nozzle body 2. A seat portion 23 is provided on the proximal end side of the sack portion 22. Further, a convex portion 24 is formed on the base end side of the sheet portion 23.

  When the valve is closed, the needle valve 3 has a tapered portion 32 seated on the seat portion 23 of the nozzle body 2. The needle valve 3 is formed with a large diameter portion 35. A fuel passage 4 through which fuel can pass is defined between the outer periphery of the needle valve 3 and the inner periphery of the nozzle body 2. The fuel passage 4 is connected to a common rail (not shown) for supplying fuel to the fuel injection valve 1 or a fuel supply device (not shown) to supply the fuel.

  An accommodation portion 33 is formed at a location corresponding to the root of the large diameter portion 35 of the needle valve 3. The movable piece 5 is slidably assembled and held in the housing portion 33. Further, the base end side of the accommodating portion 33 is connected to a low pressure path of fuel. The movable piece 5 receives the pressure of the fuel in the fuel passage 4 from the front end side of the movable piece 5. Further, a spring 34 is disposed on the proximal end side of the movable piece 5, and the movable piece 5 is biased toward the distal end side. As such a spring 34, when the fuel injection valve 1 is closed or when the fuel supply pressure is low, the force by which the spring 34 biases the movable piece 5 is directed toward the base end side that the movable piece 5 receives from the fuel. On the other hand, when the fuel supply pressure is high, the force by which the spring 34 biases the movable piece 5 is selected to be smaller than the force toward the proximal end that the movable piece 5 receives from the fuel. Has been. Thus, the movable piece 5 protrudes into the fuel passage 4, and the throttle 41 is formed in the fuel passage 4 by the convex portion 24 of the nozzle body 2.

  Next, the state at the time of operation | movement of the fuel injection valve 1 is demonstrated. First, a case where fuel is injected at a low pressure will be described. FIG. 2 is an explanatory diagram showing the state of the fuel injection valve 1 during low pressure injection. FIG. 3 is an explanatory diagram showing the periphery of the movable piece 5 during low-pressure injection in an enlarged manner.

  Since the needle valve 3 is raised for injection, the fuel in the fuel passage 4 flows toward the injection hole 21. When the fuel supplied to the fuel passage 4 is at a low pressure, the movable piece 5 is biased toward the distal end side because the force received from the spring 34 is greater than the force received from the fuel in the fuel passage 4. Therefore, a throttle 41 is formed in the fuel passage 4, and the passage of the fuel passing through the throttle 41 is subsequently expanded, and cavitation occurs. That is, atomization of the fuel flowing through the position indicated by the arrow A is promoted by the occurrence of cavitation. For this reason, the fuel injected from the injection hole 21 forms a spray that is easy to mix with air and has excellent diffusibility.

  Next, the case where the pressure of the fuel supplied to the fuel passage 4 rises and fuel is injected at a high pressure will be described. FIG. 4 is an explanatory view showing the state of the fuel injection valve 1 during high-pressure injection. FIG. 5 is an explanatory diagram showing the periphery of the movable piece 5 during high-pressure injection in an enlarged manner.

  When the fuel supplied to the fuel passage 4 rises to a high pressure, the force received from the fuel in the fuel passage 4 is greater than the force received from the spring 34, so the movable piece 5 moves to the base end side, Immerse in the accommodating part 33. For this reason, as shown in FIG. 5, the passage 42 where the throttle 41 of the fuel passage 4 was located is enlarged. As a result, the fuel passing through 42 indicated by the arrow B is sent to the nozzle hole 21 while maintaining the high pressure while suppressing the occurrence of cavitation. For this reason, the fuel injected from the nozzle hole 21 forms a high-penetration spray.

  The fuel injection valve 1 can promote the occurrence of cavitation when the movable piece 5 is located on the distal end side in this way, and can suppress the occurrence of cavitation when the movable piece 5 is located on the proximal end side. The movement of the movable piece 5 is determined by the pressure of the fuel supplied to the fuel passage 4, and the pressure of the fuel to which the movable piece 5 moves can be determined by the engine specifications and operating conditions. As described above, the fuel injection valve 1 adjusts the generation of fuel cavitation by the pressure of the fuel supplied to the fuel passage 4 and adjusts the strength of the spray penetration.

  In particular, when high penetration is required, it is a high-load operation and the amount of fuel supply increases, so that the fuel injection pressure inevitably increases and the fuel supplied to the fuel passage 4 is increased. The pressure increases. On the other hand, when high penetration is not required, the operation is a low load, the amount of fuel supplied is small, the injection pressure is low, and the pressure of the fuel supplied to the fuel passage 4 is low. Therefore, the fuel injection valve 1 suppresses the occurrence of cavitation, and the conditions during operation to form a high-penetration spray coincide with those during high-load operation. The fuel injection valve 1 promotes the occurrence of cavitation and atomizes the spray. The conditions at the time of driving to promote low load operation are the same.

  Even in the case of a conventional fuel injection valve that does not have a special shape for generating cavitation, when the needle valve leaves the seat, the gap between the seat and the needle valve is narrow. And cavitation occurred in the fuel flowing to the wide sack. However, in the conventional fuel injection valve, as the lift amount of the needle valve increases, the gap between the seat portion and the needle valve increases, so that cavitation does not occur, and cavitation occurs even in low-pressure fuel injection. The spray could not be atomized. On the other hand, in the fuel injection valve 1 of the present embodiment, when the fuel pressure is low, the throttle 41 is formed in the fuel passage 4 even if the lift amount of the needle valve 3 is increased. The occurrence of cavitation can be promoted.

  In addition, by changing the pressure in the low pressure path provided on the base end side of the accommodating portion 33, the balance of the force applied to the distal end side and the base end side of the movable piece 5 is changed to move the movable piece 5. Also good.

  Next, a second embodiment of the present invention will be described. FIG. 6 is an explanatory view showing a cross-section of the tip portion where the injection hole 121 of the fuel injection valve 11 of this embodiment is formed. The fuel injection valve 11 of the present embodiment is different from the first embodiment in that the movable piece 15 is provided on the nozzle body 12 side. The fuel injection valve 11 includes a hollow cylindrical nozzle body 12 in which an injection hole 121 is formed, and a needle valve 13 that is slidably disposed in the nozzle body 12 and has a pointed tip. A fuel passage 14 through which fuel can pass is defined between the outer periphery of the needle valve 13 and the inner periphery of the nozzle body 12. The nozzle body 12 is formed with a housing portion 123 that holds the movable piece 15, and a spring 124 is disposed in the housing portion 123 on the tip side of the movable piece 15. Further, the accommodating portion 123 is connected to a low pressure path on the proximal end side of the fuel injection valve 11.

  In the fuel injection valve 11, as in the first embodiment, when the fuel supplied to the fuel passage 14 is at a low pressure, the movable piece 15 receives a greater force from the spring 124 than the force received from the fuel in the fuel passage 14. Therefore, it is biased toward the base end side. Accordingly, a throttle 141 is formed in the fuel passage 14, and the fuel passing through the throttle 141 is subsequently expanded in flow path, so that cavitation occurs and atomization is promoted. For this reason, the fuel injected from the nozzle hole 121 forms a spray that is easily mixed with air and excellent in diffusibility.

  On the other hand, when the fuel supplied to the fuel passage 14 rises and becomes a high pressure, the force received from the fuel in the fuel passage 14 becomes larger than the force received from the spring 124, so the movable piece 15 moves to the tip side. Immerse into the housing part 123. For this reason, the passage of the portion of the fuel passage 14 where the throttle 141 is located is enlarged, and the fuel is sent to the nozzle hole 121 while maintaining the high pressure while suppressing the occurrence of cavitation. For this reason, the fuel injected from the nozzle hole 121 forms a spray with high penetration.

  The fuel injection valve 11 promotes the occurrence of cavitation when the movable piece 15 is located on the proximal end side, and suppresses the occurrence of cavitation when the movable piece 15 is located on the distal end side. The movement of the movable piece 15 is determined by the pressure of the fuel supplied to the fuel passage 14, and the pressure of the fuel to which the movable piece 15 moves can be determined by the engine specifications and operating conditions. As described above, the fuel injection valve 11 adjusts the generation of fuel cavitation by the pressure of the fuel supplied to the fuel passage 14, and adjusts the strength of the spray penetration.

  The above-described embodiments are merely examples for carrying out the present invention, and the present invention is not limited thereto. Various modifications of these embodiments are within the scope of the present invention. It is apparent from the above description that various other embodiments are possible within the scope.

DESCRIPTION OF SYMBOLS 1, 11 Fuel injection valve 2 Nozzle body 21 Injection hole 3 Needle valve 4 Fuel passage 41 Restriction 5 Movable piece

Claims (4)

A hollow cylindrical nozzle body in which a nozzle hole is formed;
A needle valve that is slidably disposed within the nozzle body and forms a fuel passage through which fuel passes with the nozzle body;
Throttle adjusting means for adjusting the throttle of the fuel passage based on the pressure in the fuel passage;
A fuel injection valve comprising: The fuel injection valve according to claim 1, wherein
The fuel injection valve according to claim 1, wherein the throttle adjusting means expands the throttle when the fuel in the fuel passage is high pressure, and reduces the throttle when the fuel in the fuel passage is low pressure. The fuel injection valve according to claim 1 or 2,
The throttle adjusting means includes a movable piece that is held by the needle valve and projects into the fuel passage to form a throttle.
The fuel injection valve according to claim 1, wherein the movable piece is immersed in the needle valve when the fuel pressure in the fuel passage increases. The fuel injection valve according to claim 1 or 2,
The throttle adjusting means includes a movable piece that is held by the nozzle body and protrudes into the fuel passage to form a throttle.
The fuel injection valve according to claim 1, wherein the movable piece is immersed in the nozzle body when the fuel pressure in the fuel passage increases.

Images