The present invention relates to a fuel injection valve, and a fuel injection apparatus provided with the same.
Conventionally, a fuel injection nozzle including a spiral passage that is formed between a wall surface of a hollow hole of a nozzle main body and a sliding surface of a needle valve has been known (Patent Document 1, for example). In such a fuel injection nozzle, fuel that has passed through the spiral passage generates a rotational flow. The fuel in the rotational flow is injected via an injection opening through a space that is formed between the needle valve and the nozzle main body when the needle valve is lifted.
Patent Document
Patent Document 1: Japanese Patent Application Publication No. 10-141183 (JP 10-141183 A)
The fuel in the rotational flow is injected via the injection opening while the rotational flow is maintained. Accordingly, dispersion of a spray and mixture with the air are aimed by the fuel injection nozzle disclosed in Patent Document 1. Here, the fuel passing through the spiral passage is supplied to the space between the needle valve and the nozzle main body in a state that a fuel thickness corresponds to a cross-sectional shape of the spiral passage, that is, in a state that a cross-sectional dimension of the fuel flow is maintained. Thus, when the fuel thickness becomes larger than a maximum lift amount of the needle valve, the needle valve may hinder maintenance of the rotational flow of the fuel. In other words, a decrease in a swirl velocity of the fuel that is caused by collision of the fuel flow with a portion of the needle valve is concerned.
In view of the above, a problem of the fuel injection valve that is disclosed in this specification is to suppress a decrease in a flow velocity of the fuel that swirls through the spiral groove.
In order to solve such a problem, a fuel injection valve disclosed in this specification includes: a needle valve with a seat surface on a distal end side; a nozzle body with a seat section on which the seat surface rests and with an injection opening disposed downstream of the seat section; and a swirl flow generating section with a spiral groove for causing fuel injected via the injection opening to swirl. The seat surface includes a first contact point, and the first contact point contacts a second contact point included in the seat section during valve closing. A line segment drawn by connecting the first contact point and the second contact point during valve opening intersects a virtual straight line passing a bottom of a first groove, section that appears the most downstream side of a cross section of the swirl flow generating portion in a plane including a central axis of the needle valve and a bottom of a second groove section that appears one-step upstream side of the first groove section.
The first contact point and the second contact point contact each other when the needle valve is closed. Then, when the needle valve is lifted to be in a valve opening state, the line segment that connects the first contact point and the second contact point is drawn in parallel with the central axis of the needle valve. Since such a line segment is set to intersect the virtual straight line, a fuel flow that passes through the spiral groove and turns into a swirl flow can avoid collision with the needle valve. Consequently, a decrease in a swirl velocity of the fuel flow is suppressed.
The swirl flow generating section can have a plurality of the spiral grooves, and the first groove section and the second groove section can respectively be contained in the different spiral grooves.
Since the swirl flow generating section includes the plurality of the spiral grooves, a cross-sectional area of the one spiral groove can be decreased while a necessary injection amount is secured. More specifically, a depth of the spiral groove can be set shallow, and the collision of the fuel flow with the needle valve can easily be avoided.
A flow passage area of the spiral groove can be set to be the smallest at an exit. Since an area of an entry of the spiral groove can be set larger than the exit of the spiral groove, pressure loss in the fuel flow can be decreased. Consequently, the fuel can be injected at a low combustion pressure.
The fuel injection valve disclosed in this specification can be mounted in an engine that is installed in a vehicle. At this time, the fuel injection valve becomes a part of a fuel injection apparatus. The fuel injection apparatus disclosed in this specification includes the fuel injection valve and pressure adjusting means for fuel supplied to the fuel injection valve. The injection opening provided in the fuel injection valve satisfies a condition that bubbles produced in the fuel injected by the fuel injection valve are broken in a desired time, and is set to have an injection opening diameter at which a set combustion pressure becomes the lowest. The pressure adjusting means for fuel changes a combustion pressure according to an operation state of the engine in which the fuel injection valve is mounted.
Since the combustion pressure is changed according to the operation state of the engine, for example, energy consumed by a fuel pump can be decreased, and a fuel atomization effect can be maintained.
According to a fuel injection valve that is disclosed in this specification, a decrease in a flow velocity of fuel that swirls through a spiral groove can be suppressed.
A description will hereinafter be made on an embodiment of the present invention with reference to the accompanying drawings. It should be noted however that a dimension, a ratio, or the like of each component in the drawings may not correspond perfectly to the actual dimension, ratio, or the like. In addition, details may not be drawn in the drawings.
A state of a spray that is realized by the fuel injection valve 1 is described first before a detailed description is made on a configuration of the fuel injection valve 1 of the first example. As will be described later, the fuel injection valve 1 includes the swirl flow generating section 30 and applies a swirl flow to fuel to be injected. As purposes of applying the swirl flow, favorable dispersion of the fuel and atomization of the fuel can be raised. The first example is one example of the fuel injection valve that injects the fuel by using such a swirl flow, and is preferred to achieve the atomization of the fuel. A principle of the atomization of the fuel is as follows. The swirl flow at a high swirl velocity is formed in the fuel injection valve, and the swirl flow is introduced into the injection opening. Then, a negative pressure is generated at swirl center of the strong swirl flow. Once the negative pressure is generated, the air on the outside of the fuel injection valve 1 is suctioned into the injection opening. Accordingly, an air column is generated in the injection opening. Air bubbles are generated on an interface between the thus-generated air column and the fuel. The thus-generated bubbles are mixed in the fuel that flows around the air column, and are injected together with the fuel flow that flows on an outer peripheral side as a bubble mixing flow.
At this time, conical sprays of the fuel flow and the bubble mixing flow that are dispersed from the center due to a centrifugal force of the swirl flow are formed. A diameter of the conical spray is increased as it separates from the injection opening, and thus, a spray liquid film is stretched to be thin. Consequently, the spray can no longer be retained as the liquid film and is disrupted. Then, the diameter of the spray after disruption is decreased due to a self-pressurizing effect of fine bubbles, and the spray is crumbled into an ultrafine spray. Since the spray of the fuel that is injected by the fuel injection valve 1 is atomized just as described, rapid flame propagation is realized in a combustion chamber, and stable combustion is thereby performed. The fuel injection valve 1 of the first example adopts a fuel injection mode as described above.
The fuel injection valve 1 is embedded in a fuel injection apparatus 100 and is mounted in an engine that is installed in a vehicle. The fuel injection valve 1 includes: a needle valve 10 with a seat surface 11 on the distal end side; and a nozzle body 20 with a seat section 21 on which the seat surface 11 rests and with an injection opening 22 disposed downstream of the seat section 21. The injection opening 22 is a single injection opening, and an injection opening diameter is set to φa. In addition, a drive mechanism for executing drive control of the needle valve 10 is provided. The drive mechanism is a conventionally known mechanism that includes a part suitable for operation of the needle valve 10, such as an actuator using a piezoelectric element, an electromagnet, or the like, or an elastic member for applying an appropriate pressure to the needle valve 10.
The fuel injection valve 1 includes the swirl flow generating section 30 with a spiral groove 32 for swirling the fuel that is injected via the injection opening 22. The swirl flow generating section 30 is a member housed in the nozzle body 20, and includes three spiral grooves, that is, a first spiral groove 32a, a second spiral groove 32b, and a third spiral groove 32c in a conical section formed at the distal end. The number of the spiral grooves is not limited to three; however, it is desired that the plurality of grooves is provided. By providing the plurality of the spiral grooves, an overall injection flow rate is secured, and flexibility in determining a cross-sectional area of the each spiral groove (a flow passage area) is increased. In addition, a rotational angle from an entry to an exit of the spiral groove is desirably set to 180° or larger. By setting the rotational angle to be 180° or larger, the swirl flow can be applied to the fuel that is introduced into the injection opening 22. In the fuel injection valve 1 of the first example, a rotational angle of the first spiral groove 32a from an entry 32a1 to an exit 32a2 is set to 180° or larger. Similarly, a rotational angle of the second spiral groove 32b from an entry 32b1 to an exit 32b2 is set to 180° or larger. Furthermore, a rotational angle of the third spiral groove 32c from an entry 32c1 to an exit 32c2 is set to 180° or larger.
A depth of the first spiral groove 32a becomes gradually shallow as it is headed from the entry 32a1 to the exit 32a2. A flow passage area of the first spiral groove 32a is gradually decreased as the first spiral groove 32a is headed from the entry 32a1 to the exit 32a2. The flow passage area of the first spiral groove 32a is the smallest at the exit 32a2. The same applies to the second spiral groove 32b and the third spiral groove 32c.
Referring to
The fuel is supplied to the fuel injection valve 1 through a fuel pump Po that is included in the fuel injection apparatus 100. The fuel pump Po includes a first pump Po1 and a second pump Po2 that are connected in series. The fuel pump Po is electrically connected to an electronic control unit (ECU) 40. In accordance with an operation state of the engine, the ECU 40 selects either to only drive the first pump Po1 or to drive both of the first pump Po1 and the second pump Po2. In other words, the fuel pump Po and the ECU 40 each have a function as pressure adjusting means for fuel. It should be noted that a mode of the pressure adjusting means for fuel is not limited to what has been described above, and any mode may be applied, such as adopting a regulator or the like.
As described above, the fuel injection valve 1 of the first example includes the needle valve 10, the nozzle body 20, and the swirl flow generating section 30 with the first spiral groove 32a to the third spiral groove 32c. A further detailed description will hereinafter be made on relationships among these components.
As described above;
When a virtual straight line L2 passing through a bottom of the first spiral groove 32a, which corresponds to the, first groove section, and a bottom of the third spiral groove 32c, which corresponds to the second groove section, is drawn, the line segment L1 intersects the virtual straight line L2. When a condition just as described is satisfied, a seat section fuel thickness Sf becomes a smaller value than a length of the line segment L1 that corresponds to a lift amount of the needle valve 10, that is, a distance SL from the first contact point P1 to the second contact point P2 during the valve opening. Consequently, the collision of the fuel flow that passes through the spiral groove and turns into the swirl flow with the needle valve 10 is avoided. Thus, a decrease in a flow velocity of the fuel is suppressed. The seat section fuel thickness Sf can be defined as a distance from the second contact point P2 to a point of an intersection P3 between the line segment L1 and the virtual straight line L2.
Here, a description will be made on setting of the virtual straight line L2 in the first example. Referring to
A virtual straight line that is drawn by using another reference can be used instead of the virtual straight line L2. For example, referring to
A description is now made on effects of the fuel injection valve 1, which is described above, together with comparative examples.
The fuel injection valve 1 of the first example injects the fuel that has passed through the swirl flow generating section 30. The fuel that has passed through the swirl flow generating section 30 and thus turned into the swirl flow receives such a force that it is pressed against the inner peripheral surface of the nozzle body 20 due to a centrifugal force of the flow. Furthermore, the fuel injection valve 1 has such a relationship that the line segment L1 and the virtual straight line L2 intersect each other. Accordingly, a state that the fuel can easily pass through a space between the needle valve 10 and the nozzle body 20 is developed from an initial period of the valve opening in which the lift amount of the needle valve 10 is small.
A cross-sectional area of the first spiral groove 32a is decreased as the first spiral groove 32a is headed from the entry 32a1 to the exit 32a2. Accordingly, the fuel that passes through the first spiral groove 32a turns into a contracted flow. Even after being injected from the exit 32a2, the fuel maintains a contracted flow effect due to the centrifugal force that is caused by swirling of the fuel, and passes through the space between the seat surface 11 and the seat section 21 while the decrease in the fuel thickness is continued. Then, while a velocity of the swirl flow is maintained, the fuel is introduced into the injection opening 22. The fuel that passes through each of the second spiral groove 32b and the third spiral groove 32 also turns into the contracted flow and is introduced into the injection opening 22.
As described above, in the fuel injection valve of the first example, the line segment L1 and the virtual straight line L2 intersect each other, and the fuel thickness/the maximum lift amount of the seat section is set to 1 or smaller. Thus, a favorable spray mode can be realized.
In the fuel injection valve 1 of the first example, since the decrease in the swirl velocity of the swirl flow is suppressed, the spiral groove can be shortened. In order to generate the fine bubbles in the fuel, it is necessary to increase the swirl velocity of the fuel. In order to increase the swirl velocity, it is considered to increase the length of the spiral groove. However, if the length of the spiral groove is increased, pressure loss is increased. Meanwhile, in the fuel injection valve 1 of the first example, the swirl velocity of the fuel for generating the fine bubbles can be maintained even without increasing the length of the spiral groove. Consequently, the pressure loss in the spiral groove is suppressed, and a low combustion pressure can be realized. Thus, driving loss at a time when a high-pressure fuel pump is used can be decreased, and low cost can be realized.
As described above, since the fine bubbles can be generated without using the high-pressure fuel pump, the fuel injection valve 1 of the first example can also be applied to an electric fuel injection (EFI).
Furthermore, the swirl flow for generating the fine bubbles can be generated even in the transition to increase a pressure of the fuel pump in a state that the combustion pressure is low, such as when the engine is started. Thus, the fuel that contains the fine bubbles can be injected immediately after the engine is started, and the fuel can be atomized.
The fuel injection valve 1 of the first example includes the three spiral grooves of the first spiral groove 32a to the third spiral groove 32c. When the plurality of spiral grooves is provided like in this case, the number of positions at which the fuel spews out to the downstream side of the seat section 21 is increased. Consequently, the uniform swirl flow can be generated, and the fine bubbles in the fuel that is injected via the injection opening 22 are less likely to be distributed coarsely and densely. In addition, since wave-like injection is suppressed, particle diameter distribution is uniformed. Furthermore, since the fine bubbles are uniformly dispersed, air-fuel mixture is homogenized.
The effects of the fuel injection valve 1 will further be described together with a second comparative example.
In the first example shown in
Referring to
On the other hand, referring to
Next, the fuel injection apparatus 100 that includes the above-mentioned fuel injection valve 1 will be described. As described above, the fuel is supplied to the fuel injection valve 1 through the fuel pump Po that is included in the fuel injection apparatus 100. The fuel injection apparatus 100 is embedded in the engine that is installed in the vehicle. As described above, the fuel injection apparatus 100 includes the fuel injection valve 1 as well as the fuel pump Po and the ECU 40 that correspond to the pressure adjusting means for fuel. Here, the injection opening diameter of the injection opening 22, which is provided in the fuel injection valve 1, is set as follows. That is, the injection opening diameter satisfies such a condition that the bubbles generated in the fuel, which is injected from the fuel injection valve 1, is broken in a desired time. The injection opening diameter is also set such that a set combustion pressure becomes the lowest. Then, the fuel pump Po and the ECU 40 change the combustion pressure in accordance with the operation state of the engine, in which the fuel injection valve 1 is mounted.
Here, referring to
Here, 0.95 MPa is set as the maximum combustion pressure of the electric fuel injection. When such setting is done and the maximum combustion pressure is 0.95 MPa, the diameter of the fine bubble is 9.7 μm, and the injection flow rate is 11 mm3/ms. The diameter of the fine bubble, which is 9.7 μm, is a value that corresponds to the breakage time of 20 ms. When the electric fuel injection is used and operated at the maximum combustion pressure of 0.95 MPa or at a pressure near the maximum combustion pressure, both of the first pump Po1 and the second pump Po2 in the fuel pump Po are driven. However, when both of the first pump Po1 and the second pump Po2 are driven, energy consumption is increased, and the fuel economy thereby worsens.
Thus, only when the high injection flow rate is required, for example, during wide open throttle (WOT) or in a cold time in which vaporization promotion is requested, both of the first pump Po1 and the second pump Po2 are driven at the maximum combustion pressure or the pressure near the maximum combustion pressure. In a partial state, for example, the combustion pressure is set to 0.6 MPa. Accordingly, the energy consumption can be suppressed, and consequently, worsening of the fuel economy can be suppressed.
Referring to
In addition, in an idle state of the engine, the combustion pressure is approximately 0.4 MPa, the injection flow rate is the minimum value of 4.3 mm3/ms, and the diameter of the fine bubble is approximately 16 μm. Just as described, the diameter of the fine bubble is increased in the idle state. However, in consideration of a fact that the diameter of the bubble is conventionally 70 μm, it is considered that the sufficient atomization can be realized.
When such a fuel injection valve 1 is used for cylinder direct injection, the combustion pressure is increased to 1.8 MPa. Accordingly, the diameter of the fine bubble becomes approximately 6.6 μm, and the injection flow rate becomes 15 mm3/ms.
Next, a description will be made on a second example with reference to
As described above, in the fuel injection valve that is disclosed in this specification, the spiral groove provided in the swirl flow generating section can adopt any shape. In other words, the flexibility of design is high. The contracted flow effect can be adjusted by adjusting the cross-sectional shape of the spiral groove in various ways. For example, for the fuel injection valve that is operated at the low combustion pressure like a port injection valve, the area of the entry is increased. Accordingly, the contracted flow effect can be enhanced, and the pressure loss can also be reduced. Consequently, the fuel, the swirl velocity of which is maintained to be sufficiently high, can be introduced into the injection opening even at the low combustion pressure. Thus, it is possible to uniformly inject the fuel that contains the fine bubbles.
Next, a description will be made on a third example with reference to
The above examples are merely examples to carry out the present invention. Thus, the present invention is not limited thereto, and various modifications of these examples fall into the scope of the present invention. Furthermore, it is apparent from the above description that various other examples can also be made.
1/Fuel Injection Valve
10/Needle Valve
11/Seat Surface
20/Nozzle Body
21/Seat Section
22/Injection Opening
W1/Seat Diameter
30/Swirl Flow Generating Section
31/Sliding Surface
32
a/First Spiral Groove
32a1/Entry
32a2/Exit
32b1/Second Spiral Grove
32b1/Entry
32b2/Exit
32
c/Third Spiral Groove
32c1/Entry
32c2/Exit
33/Fuel Supply Groove
34/Pressure Chamber
40/ECU
Po1/First Pump
Po2/Second Pump
L1/Line Segment
L2 to L6/Virtual Vertical Straight Line
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/JP2012/053562 | 2/15/2012 | WO | 00 | 8/12/2014 |