JP2011027081A - Fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection device capable of restricting hindrance to fuel injection in an injection hole by optimizing a seat part flow passage area being a flow passage area in a seat part when a needle is lifted to the maximum. <P>SOLUTION: Fuel injection is controlled to cut fuel supply to an injection hole 13 by moving a needle valve 20 forward to the maximum so that a tip part 24 of the needle valve 20 and a seat surface of a nozzle body 10 abut on each other, and controlled to allow fuel supply to the injection hole 13 by moving the needle valve 20 backward so that the tip part 24 of the needle valve 20 and the seat surface of the nozzle body 10 separate from each other. A seat part flow passage area 62 being a flow passage area in a seat part 33, in which the tip part 24 of the needle valve 20 and the seat surface of the nozzle body 10 abut on each other, is formed to be at least ten times or more as large as the flow passage area of the injection hole 13 when the needle valve 20 is positioned at the most retreated position. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a fuel injection device. More specifically, the present invention relates to a fuel injection device in which a seat portion flow passage area is formed to be 10 times or more as large as a flow passage area of an injection hole when a needle valve is at a last retracted position.

  2. Description of the Related Art Conventionally, in a fuel injection device having a nozzle body and a needle valve, a seat portion (needle valve tip and nozzle body seat) is in a low lift state (a state in which the amount of upward movement from the closed position of the needle valve is small). By forming the downstream throttle flow passage area S3, which is the flow passage area downstream from the seat portion, to be larger than the flow passage area S1 of the contact portion with the surface), fuel injection is performed in a low lift state. A fuel injection device with improved responsiveness is known (see, for example, Patent Document 1).

JP 2007-231771 A

  However, in Patent Document 1, although the fuel injection responsiveness is improved in the low lift state, the flow passage area S1 of the seat portion is a predetermined value (the fuel injection responsiveness is good) during the needle maximum lift. Therefore, the fuel injection amount may be insufficient.

  Therefore, the present invention has an object to provide a fuel injection device that suppresses the inhibition of fuel injection at the injection hole by optimizing the flow passage area of the seat portion, which is the flow passage area of the seat portion, at the time of maximum needle lift. And

  (1) A fuel injection device comprising: a nozzle body having a nozzle hole at a tip; and a needle valve that is movably held in a needle valve insertion hole formed in the nozzle body, wherein the needle valve is advanced a maximum By causing the tip of the needle valve and the seating surface of the nozzle body to contact each other, the fuel supply to the nozzle hole is shut off, and the needle valve is retracted, so that the tip of the needle valve and the tip of the needle valve A seat portion that is a contact portion between the tip end portion of the needle valve and the seat surface of the nozzle body that performs fuel injection control by allowing fuel supply to the nozzle hole by separating the seat surface of the nozzle body The flow path area of the seat portion is formed so that the sheet area is at least 10 times the flow area of the nozzle hole when the needle valve is in the last retracted position. Fuel injection system.

  Here, the sheet flow area and the nozzle flow coefficient have a positive correlation (the larger the sheet flow area, the larger the nozzle flow coefficient), and the sheet flow area is 10 times the total nozzle hole area. It was found that the nozzle flow coefficient becomes substantially constant and maximum at the above. Therefore, according to the invention of (1), when the needle valve is in the last retracted position, it is set to 10 times or more, so that the nozzle flow coefficient can be maximized.

  (2) In the fuel injection device according to (1), the nozzle body has a sac portion on the tip side of the contact portion, the injection hole is formed in the sac portion, and the inlet of the sac portion The flow path area of the sac inlet portion is formed so as to be at least 5 times the flow area of the nozzle hole when the needle valve is in the last retracted position. Fuel injection device.

  Here, there is a positive correlation between the sac inlet flow area and the nozzle flow coefficient (the larger the sack inlet flow area, the larger the nozzle flow coefficient), and the sac inlet flow area is the total nozzle hole area. It has been found that the nozzle flow coefficient becomes a substantially constant value and the maximum when it is 5 times or more. Therefore, according to the invention of (2), when the needle valve is in the last retracted position, it is set to 5 times or more, so that the nozzle flow coefficient can be maximized.

  (3) In the fuel injection device according to (1) or (2), the needle valve side tip surface, which is the tip side of the seat portion of the needle valve tip portion, and the tip of the nozzle body seat surface than the seat portion The needle valve side tip surface and the nozzle body side tip surface are formed so that the tip scissor angle, which is an angle formed by the nozzle body side tip surface that is the side, is 6 degrees or less. apparatus.

  Here, it was found that as the tip scissor angle increases, wear of the seat portion with time increases (the collapse width of the tip portion of the needle valve increases). Therefore, according to the invention of (3), it is possible to minimize the wear (crush width) by setting the tip scissor angle to 6 degrees or less.

  (4) In the fuel injection device according to (2), the needle valve side tip surface which is the tip side of the seat portion of the needle valve tip portion and the nozzle which is the tip side of the seat portion of the nozzle body seat surface When the needle valve side tip surface and the nozzle body side tip surface are formed such that the tip scissor angle, which is an angle formed with the body side tip surface, is 6 degrees or less, and the needle valve is in the most advanced position Further, the inlet diameter and the tip scissor angle of the sac inlet portion are set so that the downstream volume of the seat portion formed downstream from the seat portion and upstream from the nozzle hole inlet is minimized. A fuel injection device.

  Here, there is a positive correlation between the downstream volume of the seat portion and the deterioration of exhaust emission (HC emission increases) (the relationship that the exhaust emission deteriorates as the downstream volume of the seat increases). Therefore, according to the invention of (4), the seat portion downstream volume is minimized under conditions satisfying other constraints (the sac inlet portion flow area is not less than a predetermined value and the tip scissor angle is not more than a predetermined value). Furthermore, since the inlet diameter of the sac inlet portion and the tip scissor angle are set, deterioration of exhaust emission can be suppressed.

  (5) In the fuel injection device according to (2), when the needle valve is in the most advanced position, the sac inlet channel area is formed to be larger than the channel area of the nozzle hole. A fuel injection device characterized by the above.

  According to the invention of (5), since the needle valve can draw a high nozzle flow coefficient from the low lift amount state, the fuel injection rises well.

  (6) In the fuel injection device according to (1) to (5), the first guide portion that holds the first guide shaft portion of the needle valve in the first guide hole portion of the needle valve insertion hole; A second guide that is spaced apart from the first guide part and is formed on the tip side of the first guide part, and holds the second guide shaft part of the needle valve in the second guide hole part of the needle valve insertion hole. And at the front end side of the second guide portion, spaced apart from the second guide portion, and at the time of maximum advancement of the needle valve, the tip portion of the needle valve and the seating surface of the needle valve insertion hole A fuel that is formed by separating an inner circumferential surface of the needle valve insertion hole and an outer circumferential surface of the needle valve between the first guide portion and the seat portion. A flow path is provided, and the second guide portion includes a needle valve axis. A second guide contact portion where the inner peripheral surface of the needle valve insertion hole and the outer peripheral surface of the needle valve are in contact with each other, and the inner peripheral surface of the needle valve insertion hole and the needle valve; A second guide portion fuel passage that is spaced apart from the outer peripheral surface of the second guide portion, and a second guide portion passage area that is a passage area of the second guide portion fuel passage is defined as a passage area of the nozzle hole. A fuel injection device, wherein the fuel injection device is formed so as to be at least 16 times as large.

According to the invention of (6), by providing the second guide part in addition to the first guide part, it is possible to further suppress the tilting (inclination) of the needle valve (the needle valve can be stably advanced and retracted). It becomes.
By the way, when the fuel flow path area in the second guide portion is small, there is a possibility that the fuel injection from the nozzle hole may be hindered. Here, according to the invention of (6), by setting the flow path area of the second guide part to 16 times or more of the flow path area of the injection hole, the guide part that does not hinder fuel injection at the injection hole is provided. In addition, since the effects of the inventions (1) to (5) are also achieved, the nozzle flow coefficient can be maximized.

  (7) A fuel injection device comprising: a nozzle body having a nozzle hole at a tip; and a needle valve that is movably held in a needle valve insertion hole formed in the nozzle body, wherein the needle valve is advanced a maximum By causing the tip of the needle valve and the seating surface of the nozzle body to contact each other, the fuel supply to the nozzle hole is shut off, and the needle valve is retracted, so that the tip of the needle valve and the tip of the needle valve When the needle valve is in the last retracted position, the tip of the needle valve and the nozzle body are controlled by separating the seat surface of the nozzle body and allowing fuel supply to the nozzle hole to perform fuel injection control. The last retracted position is set such that the flow passage area of the seat portion, which is the contact portion with the seat surface, is at least 10 times the flow passage area of the nozzle hole. A fuel injection apparatus characterized by.

  Here, there is a positive correlation between the sheet flow area and the nozzle flow coefficient, and when the sheet flow area is 10 times or more of the total nozzle hole area, the nozzle flow coefficient is substantially constant and maximum. There was found. Therefore, according to the invention of (7), since the last retracted position is set so as to be 10 times or more when the needle valve is in the last retracted position, the nozzle flow coefficient can be maximized. .

  (8) In the fuel injection device according to (7), the nozzle body has a sac portion on the tip side of the contact portion, the injection hole is formed in the sac portion, and the needle valve is the last The last retracted position is set such that when in the retracted position, the sac inlet channel area, which is the channel area at the inlet of the sack section, is at least five times the channel area of the nozzle hole. A fuel injection device characterized by that.

  Here, there is a positive correlation between the sac inlet channel area and the nozzle flow coefficient, and when the sac inlet channel area is more than five times the total nozzle hole area, the nozzle flow coefficient is substantially constant and maximum. Turned out to be. Therefore, according to the invention of (8), since the last retracted position is set to be 5 times or more when the needle valve is in the last retracted position, the nozzle flow coefficient can be maximized. .

  (9) In the fuel injection device according to (7) or (8), the last flow path is configured so that the flow path area of the seat portion is the smallest among at least 10 times the flow path area of the nozzle holes. A fuel injection device characterized in that a retreat position is set.

  According to the invention of (9), since the last retracted position of the needle valve (maximum lift amount of the needle valve) is set so as to be the smallest among the above 10 times or more, the amount of movement of the needle valve is made as much as possible. It is possible to reduce it to a very low level. Therefore, it is possible to reduce the size of the injector and improve the responsiveness of fuel injection.

  (10) In the fuel injection device according to (8), the last retracted position is set such that the flow path area of the sac inlet portion is the smallest among at least five times the flow path area of the nozzle hole. A fuel injection device characterized by being set.

  According to the invention of (10), since the last retracted position of the needle valve (maximum lift amount of the needle valve) is set so as to be the smallest among the above five times or more, the same effect as the invention of (9) Play.

  According to the present invention, it is possible to provide a fuel injection device that suppresses the inhibition of fuel injection at the nozzle hole by optimizing the flow passage area of the seat portion, which is the flow passage area of the seat portion, at the time of needle maximum lift. it can.

It is a longitudinal cross-sectional view of the fuel-injection apparatus which concerns on one Embodiment of this invention. It is a cross-sectional view which follows the AA line of FIG. It is a graph which shows the relationship between the magnification of a flow-path area with respect to a nozzle hole total area, and a flow coefficient. It is an enlarged view showing the state in which the needle valve was seated on the nozzle body in the vicinity of the tip of the fuel injection device. It is an enlarged view showing the state where the needle valve is separated from the nozzle body in the vicinity of the tip of the fuel injection device. It is a formula for calculating a sac inlet channel area and a sheet channel area. It is the graph showing the relationship between the sac inlet part flow path area of a fuel injection device, the sheet | seat part flow path area, the flow path area of a nozzle hole, and the lift amount of a needle valve. It is a graph which shows the relationship between the magnification of the sheet | seat part flow path area with respect to a nozzle hole total area, and a flow coefficient. It is a graph which shows the relationship between the magnification | multiplying_factor of a sac inlet part channel area with respect to a nozzle hole total area, and a flow coefficient. It is an enlarged view showing a seat part downstream volume. It is the graph which contrasted the relationship between HC discharge | emission amount and an EGR rate with the magnitude | size of the sheet | seat part downstream volume. It is a graph showing the relationship between the sac inlet part flow area, the seat part flow area, the flow area of the injection hole, and the lift amount of the needle valve of the fuel injection device according to the modification of the present embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
First, the fuel injection device 1 according to this embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a longitudinal sectional view of a fuel injection device 1 according to this embodiment. FIG. 2 is a cross-sectional view taken along line AA in FIG. In the following drawings, the positional relationship and dimensions of each member are exaggerated and simplified for easy understanding.

The fuel injection device 1 includes a nozzle body 10 having a nozzle hole 13 at the tip, a needle valve insertion hole 2 formed in the nozzle body 10, a needle valve 20 held in the needle valve insertion hole 2 so as to be able to advance and retract, A drive device (not shown) for moving the needle valve 20 back and forth.
When the needle valve 20 is seated on the nozzle body 10 by this driving device, the injection of fuel from the nozzle hole 13 stops, and when it is separated, the fuel is injected from the nozzle hole 13.
FIG. 1 shows a state where the needle valve 20 is seated on the nozzle body 10.

  Further, the fuel injection device 1 is separated from the first guide portion 31 and the first guide portion 31 that holds the first guide shaft portion 21 of the needle valve 20 in the first guide hole portion 11 of the needle valve insertion hole 2. A second guide portion 32 that is formed on the tip side of the first guide portion 31 and holds the second guide shaft portion 22 of the needle valve 20 in the second guide hole portion 12 of the needle valve insertion hole 2; 2 A sheet that is spaced apart from the guide portion 32 and is formed on the tip side of the second guide portion 32, and contacts the tip portion of the needle valve 20 and the seat surface of the needle valve insertion hole 2 when the needle valve 20 is fully advanced. Unit 33.

  In addition, the needle valve axial direction length of the 2nd guide part 32 is formed larger than the advancing / retreating movement width of the needle valve 20.

  In addition, a fuel flow path formed between the first guide portion 31 and the seat portion 33 by separating the inner peripheral surface of the needle valve insertion hole 2 and the outer peripheral surface of the needle valve 20 (described later, 1 fuel channel 41, second guide fuel channel 35, and second fuel channel 42).

The second guide portion 32 is a second guide in which the inner peripheral surface of the needle valve insertion hole 2 and the outer peripheral surface of the needle valve 20 abut on a cross section (AA cross section) perpendicular to the axis of the needle valve 20. And a second guide portion fuel flow path 35 in which the inner peripheral surface of the needle valve insertion hole 2 and the outer peripheral surface of the needle valve 20 are separated from each other.
In the present embodiment, the second guide portion abutment portion 34 and the second guide portion fuel flow path 35 are provided alternately at three locations in the circumferential direction.

  The second guide portion flow passage area (the total flow passage area of all second guide portion fuel flow passages 35), which is the flow passage area of the second guide portion fuel flow passage 35, is the flow passage area of the injection holes 13 (injection at the same time). It is formed so as to be at least 16 times the total flow passage area of the possible nozzle holes 13).

  The fuel flow path will be described. Among the fuel flow paths, the first fuel flow path 41 is formed on the upstream side of the second guide section fuel flow path 35 and between the first guide section 31 and the second guide section 32, and the second fuel section. The flow path 42 is formed between the second guide part 32 and the seat part 33 on the downstream side of the second guide part fuel flow path 35.

The first fuel flow path 41 has a fuel reservoir 51 in which the inner peripheral surface of the needle valve insertion hole 2 is recessed over the entire circumference in a position adjacent to the second guide portion 32.
The second fuel flow path 42 has a polishing relief portion 52 in which the inner peripheral surface of the needle valve insertion hole 2 is recessed over the entire circumference in a position adjacent to the second guide portion 32.

  The relationship between the areas of the fuel flow paths will be described. The flow area (first flow area) of the first fuel flow path 41 and the flow area (second flow area) of the second fuel flow path 42 are formed larger than the flow area of the second guide portion. Yes.

  In a cross section (AA cross section) perpendicular to the needle valve axis of the second guide portion 32, the circumferential length of the second guide portion abutting portion 34 is not more than half of the total circumferential length. A second guide portion fuel flow path 35 is formed.

  Further, the second guide portion fuel flow path 35 is formed such that the inner peripheral surface of the needle valve insertion hole 2 (nozzle body 10) formed in a circular cross-section and a circular cross-section as a reference shape, and a part thereof is linearly recessed. And the outer peripheral surface of the formed needle valve 20.

  In the present embodiment, the second guide portion fuel flow path 35 is formed by denting the outer peripheral surface side of the needle valve 20, but is not limited to this, and the inner peripheral surface of the needle valve insertion hole 2. May be formed, or may be formed by denting the inner peripheral surface of the needle valve insertion hole 2 and the outer peripheral surface of the needle valve 20.

  In addition, a plurality (three in the present embodiment) of the second guide portion fuel flow paths 35 are formed in parallel, and in a cross section (AA cross section) perpendicular to the needle valve axis of the second guide portion 32, A plurality (three in this embodiment) of the second guide portion fuel flow paths 35 are equally arranged in the circumferential direction.

  As described above, the flow path area of the second guide portion is formed to be at least 16 times the flow area of the injection hole 13 (total flow area of the injection holes 13 that can be ejected simultaneously) You may form so that it may become the smallest among at least 16 times. That is, it may be formed to be 16 times.

  FIG. 3 is a graph showing the relationship between the magnification of the flow path area of the second guide portion with respect to the total nozzle hole area and the flow coefficient (a graph representing the contribution of the flow coefficient).

According to FIG. 3, until the magnification of the second guide portion channel area with respect to the total nozzle hole area becomes 16 times, the flow coefficient increases as the magnification increases, and the magnification should be 16 times or more. For example, the flow coefficient is substantially constant and maximum.
Here, since the second guide portion fuel flow path area and the circumferential length of the second guide portion abutment portion 34 are inversely correlated, the smaller the second guide portion fuel flow passage area, the smaller the second guide portion. The circumferential length of the part contact part 34 is large. Furthermore, the fall prevention effect of the needle valve 20 is higher as the circumferential length of the second guide portion contact portion 34 is larger.
Accordingly, if the second guide portion fuel flow path 35 is formed so that the magnification of the second guide portion flow passage area with respect to the flow passage area of the nozzle hole 13 is 16 times, under the condition that the flow coefficient is maximum. Since the minimum flow path area can be obtained, it is possible to provide the fuel injection device 1 that suppresses the fuel injection from the injection hole 13 to the maximum and further suppresses the tilt (inclination) of the needle valve 20. it can.

  FIG. 4 is an enlarged view showing a state in which the needle valve 20 is seated on the nozzle body 10 in the vicinity of the tip of the fuel injection device 1 shown in FIG.

  According to FIG. 4, the distal end portion 24 of the needle valve 20 is in contact with the seat surface of the nozzle body 10. Here, the contact portion on the seating surface of the nozzle body 10 is referred to as a nozzle body side contact portion 14. Further, the sheet portion 33 includes both the front end portion 24 and the nozzle body side contact portion 14.

  In the needle valve 20, the tip side from the tip portion 24 (seat portion 33) is referred to as a needle valve side tip surface 25, and in the nozzle body 10, the tip side from the nozzle body side contact portion 14 (sheet portion 33) is a nozzle. This is referred to as a body-side tip surface 15.

  Further, the nozzle body 10 has a sac portion 71 on the tip side of the nozzle body side contact portion 14. A bent portion 16 is formed at the boundary between the sac portion 71 and the nozzle body side distal end surface 15. The bent portion 16 serves as an entrance of the sack portion 71. The nozzle hole 13 is formed in the sack portion 71.

  Further, a clearance area formed when a perpendicular is dropped from the bent portion 16 which is the inlet of the sac portion 71 to the needle valve side distal end surface 25 is referred to as a sac inlet portion flow passage area 61 (see FIG. 5). It should be noted that the sac inlet channel area 61 is not shown because it is very small in the seated state in FIG.

  FIG. 5 is an enlarged view showing a state where the needle valve 20 is separated from the nozzle body 10 in the vicinity of the tip of the fuel injection device 1 shown in FIG.

  FIG. 5 shows a state where the needle valve 20 is raised by a distance L from the seated state in FIG. As a result of this rise, the distal end portion 24 and the nozzle body side contact portion 14 are separated by a distance L. That is, the sheet portion 33 is separated by a distance L. The distance L is a needle valve lift amount (L) described later.

  At this time, the gap area formed when a perpendicular is drawn from the nozzle body side contact portion 14 (the seat portion 33 on the nozzle body 10 side when L = 0) to the needle valve side distal end surface 25 is defined as the sheet portion flow. It is called a road area 62.

  Here, the sac inlet channel area 61 and the seat channel area 62 are calculated by the equations shown in FIG.

  However, the radius of the circumference formed by the bent portion 16 that is the inlet of the sack portion 71 is the sac inlet diameter (Dsac), the radius of the circumference formed by the nozzle body side contact portion 14 is the seat diameter (Dseat), The lift amount of the needle valve is the needle valve lift amount (L), the half angle between the nozzle body side end surfaces 15 is the nozzle body seat surface angle (θseat), and the half angle between the needle valve side end surfaces 25 is the needle. The valve tip surface angle (θneedle) and the angle formed by the needle valve side tip surface 25 and the nozzle body side tip surface 15 are defined as the tip scissor angle (θns).

  The sac inlet channel area 61 is at least five times the channel area of the nozzle hole 13 when the needle valve 20 is in the last retracted position (when the needle valve lift (L) is maximized). The sheet portion channel area 62 is formed to be 10 times or more the channel area of the nozzle hole 13. Further, the tip scissor angle (θns) is formed to be 6 degrees or less.

  FIG. 7 shows the relationship between the sac inlet flow area 61, the seat flow area 62, the flow area of the injection hole 13 and the lift amount of the needle valve 20 of the fuel injection device 1 according to this embodiment. It is a graph.

  According to FIG. 7, when the needle valve lift amount is the maximum lift amount (the maximum lift amount is set to 200 μm, for example), the sac inlet portion flow passage area 61 is five times the flow passage area of the nozzle hole 13, and the seat portion flow The passage area 62 is 10 times the passage area of the nozzle hole 13.

  When the needle valve lift amount is 0 μm, the sac inlet portion flow passage area 61 is smaller than the flow passage area of the injection hole 13 and larger than zero. Further, when the needle valve lift amount is 0 μm, the size of the seat portion channel area 62 is zero.

  Further, the flow passage area of the nozzle hole 13 is constant regardless of the needle valve lift amount. The sac inlet channel area 61 and the seat channel area 62 are substantially proportional to the needle valve lift amount, and the rate of increase of the seat channel area 62 is greater than the rate of increase of the sac inlet channel area 61. .

  FIG. 8 is a graph showing the relationship between the magnification of the sheet flow area 62 and the flow coefficient with respect to the total nozzle hole area.

According to FIG. 8, the flow coefficient increases as the magnification increases until the magnification of the sheet flow path area 62 with respect to the total nozzle hole area becomes 10 times. The flow coefficient is substantially constant and maximum.
Therefore, if the last retracted position (maximum lift amount) of the needle valve 20 is set so that the magnification becomes 10 times, the movement amount of the needle valve 20 is minimized under the condition that the flow coefficient is maximum. Therefore, the fuel injection device 1 can be downsized and the fuel injection response can be improved.

  FIG. 9 is a graph showing the relationship between the magnification of the sac inlet channel area 61 and the flow coefficient with respect to the total nozzle hole area.

According to FIG. 9, until the magnification of the sac inlet channel area 61 with respect to the total area of the nozzle hole becomes five times, the flow coefficient increases as the magnification increases, and the magnification is 5 times or more. For example, the flow coefficient is substantially constant and maximum.
Therefore, if the last retracted position (maximum lift amount) of the needle valve 20 is set so that the magnification is 5 times, the movement amount of the needle valve 20 is minimized under the condition that the flow coefficient is maximum. Therefore, the fuel injection device 1 can be downsized and the fuel injection response can be improved.

  FIG. 10 is an enlarged view showing the seat portion downstream volume. In FIG. 10, the angle and shape are exaggerated for easy understanding.

  According to FIG. 10, the front end portion 24 and the nozzle body side abutting portion 14 are in contact with each other, and a sheet portion downstream volume is formed downstream of the sheet portion 33 and upstream of the inlet of the injection hole 13. Yes. The seat portion downstream volume is the sum of the volume of the seat gap region 72 that is a region of the gap formed by the needle valve side tip surface 25 and the nozzle body side tip surface 15 and the volume of the sack portion 71.

  Here, the volume of the sheet gap area 72 correlates with the tip scissor angle (θns), and the sac portion 71 correlates with the sac inlet diameter (Dsac). In the present embodiment, the sac inlet diameter is such that the downstream volume of the seat portion is minimized under conditions that satisfy other constraints (the sac inlet channel area 61 is not less than a predetermined value and the tip scissor angle is not more than a predetermined value). And the tip scissor angle is set.

  FIG. 11 is a graph in which the relationship between the HC emission amount and the EGR rate is compared with the size of the seat portion downstream volume.

  According to FIG. 11, a broken line graph and a solid line graph are drawn. The broken line graph has a sheet portion downstream volume three times that of the solid line graph. As a result, it can be seen that the larger the downstream volume of the seat portion, the larger the HC emission amount.

According to this embodiment, there are the following effects.
(1) There is a positive correlation between the sheet flow area 62 and the nozzle flow coefficient, and when the sheet flow area 62 is 10 times or more the total nozzle hole area, the nozzle flow coefficient is substantially constant and maximum. Turned out to be. Therefore, according to the present embodiment, when the needle valve 20 is in the last retracted position, the ratio is set to 10 times or more, so that the nozzle flow coefficient can be maximized.

  (2) There is a positive correlation between the sac inlet flow path area 61 and the nozzle flow coefficient, and when the sac inlet flow area 61 is 5 times or more of the total nozzle hole area, the nozzle flow coefficient is substantially constant and It turned out to be the maximum. Therefore, according to the present embodiment, when the needle valve 20 is in the last retracted position, the nozzle flow coefficient is set to 5 times or more, so that the nozzle flow coefficient can be maximized.

  (3) It was found that as the tip scissor angle (θns) increases, wear of the seat portion 33 with time increases (the collapse width of the tip portion 24 of the needle valve 20 increases). Therefore, according to the present embodiment, it is possible to minimize wear (crush width) by setting the tip scissor angle (θns) to 6 degrees or less.

  (4) There is a positive correlation between the downstream volume of the seat portion and the deterioration of exhaust emission (HC emission increases). Therefore, according to the present embodiment, the seat portion downstream volume is minimized under conditions satisfying other constraints (the sac inlet portion flow passage area 61 is equal to or larger than a predetermined value and the tip scissor angle is equal to or smaller than a predetermined value). Since the inlet diameter (Dsac) and the tip scissor angle (θns) of the sac inlet are set, it is possible to suppress the deterioration of exhaust emission.

(5) In addition to the first guide portion 31, the second guide portion 32 is provided. Therefore, it is possible to further suppress the tilting (tilting) of the needle valve 20 (the needle valve 20 can be moved forward and backward stably).
By the way, when the fuel flow path area in the second guide portion 32 is small, fuel injection from the nozzle hole may be hindered. According to the present embodiment, the flow passage area of the second guide portion 32 is set to 16 times or more the flow passage area of the injection hole 13, so that it can be a guide portion that does not inhibit fuel injection in the injection hole 13. Furthermore, since the effects (1) to (4) are exhibited, the nozzle flow coefficient can be maximized.

  (6) There is a positive correlation between the sheet flow area 62 and the nozzle flow coefficient, and when the sheet flow area 62 is 10 times or more the total nozzle hole area, the nozzle flow coefficient is substantially constant and maximum. Turned out to be. Therefore, according to the present embodiment, since the last retracted position is set to be 10 times or more when the needle valve 20 is in the last retracted position, the nozzle flow coefficient can be maximized.

  (7) There is a positive correlation between the sac inlet flow path area 61 and the nozzle flow coefficient, and when the sac inlet flow area 61 is 5 times or more of the total nozzle hole area, the nozzle flow coefficient is substantially constant and It turned out to be the maximum. Therefore, according to this embodiment, when the needle valve 20 is in the last retracted position, the last retracted position is set to be 5 times or more, so that the nozzle flow coefficient can be maximized.

  (8) According to the present embodiment, since the last retracted position of the needle valve 20 (the maximum lift amount of the needle valve 20) is set so as to be the smallest among at least 10 times or more, the moving amount of the needle valve 20 Can be reduced as much as possible. Therefore, the fuel injection device 1 can be downsized and the fuel injection response can be improved.

  (9) According to the present embodiment, since the last retracted position of the needle valve 20 (the maximum lift amount of the needle valve 20) is set so as to be the smallest among the above five times or more, the same as (8) There is an effect.

  In addition, this invention is not limited to the above-mentioned embodiment, The deformation | transformation in the range which can achieve the objective of this invention, improvement, etc. are included in this invention.

  Further, in the present embodiment, in the second guide portion 32, the second guide portion fuel flow path 35 is formed by a concave groove on the needle valve 20 side, but the present invention is not limited to this, and the concave groove is on the nozzle body 10 side or It may be formed on both sides.

  Further, in the present embodiment, the second guide portion fuel flow path 35 is formed by three fuel flow paths in which the needle valve 20 side is linear. However, the present invention is not limited to this. The fuel flow path may be a “spiral shape” formed in a spiral shape in the needle valve axial direction.

  In the present embodiment, the first fuel flow path 41 has a fuel reservoir shape, but is not limited to this.

  In the present embodiment, the polishing escape portion 52 having a diameter larger than that of the second guide portion 32 is formed in the second fuel flow path 42, but the present invention is not limited to this.

  Further, in this embodiment, as shown in FIG. 7, when the needle valve lift amount is 0 μm (when the needle valve is at the most advanced position), the sac inlet channel area 61 is the flow path of the nozzle hole 13. However, the present invention is not limited to this, and the sac inlet channel area 61 may be formed to be larger than the channel area of the nozzle hole 13.

  In this case, since the needle valve can draw a high nozzle flow coefficient from the low lift amount state, the fuel injection rises well. FIG. 12 is a graph showing the relationship between the sac inlet channel area 61, the seat channel area 62, the nozzle area 13, and the lift amount of the needle valve 20 in this modification.

  According to FIG. 12, as in FIG. 7, when the needle valve lift amount is the maximum lift amount (the maximum lift amount is set to 200 μm, for example), the sac inlet portion flow passage area 61 is 5 of the flow passage area of the nozzle hole 13. The sheet portion channel area 62 is 10 times the channel area of the nozzle hole 13.

  However, as a difference from FIG. 7, when the needle valve lift amount is 0 μm, the sac inlet channel area 61 according to this modification is larger than the channel area of the nozzle hole 13, and the rate of increase of the channel area is It is smaller than the increase rate of the sac inlet portion flow passage area 61 according to the main embodiment.

  Note that the “flow channel area of the injection hole” is the total flow area of the injection holes that can be injected simultaneously when there are a plurality of injection holes.

DESCRIPTION OF SYMBOLS 1 Fuel injection apparatus 2 Needle valve insertion hole 10 Nozzle body 11 1st guide hole part 12 2nd guide hole part 13 Injection hole 14 Nozzle body side contact part 15 Nozzle body side front end surface 16 Bending part 20 Needle valve 21 1st guide Shaft portion 22 Second guide shaft portion 24 Tip portion 25 Needle valve side tip surface 31 First guide portion 32 Second guide portion 33 Seat portion 34 Second guide portion abutting portion 35 Second guide portion fuel flow path 41 First fuel Flow path 42 Second fuel flow path 51 Fuel pool 52 Polishing relief part 61 Suck inlet part flow path area 62 Seat part flow path area 71 Suck part 72 Seat clearance area

Claims (10)

A fuel injection device comprising: a nozzle body having a nozzle hole at a tip; and a needle valve that is movably held in a needle valve insertion hole formed in the nozzle body,
By advancing the needle valve to the maximum extent, the tip of the needle valve and the seat surface of the nozzle body are brought into contact with each other, and the fuel supply to the nozzle hole is shut off,
By retreating the needle valve, the tip of the needle valve and the seat surface of the nozzle body are separated to allow fuel supply to the nozzle hole, and fuel injection control is performed.
When the needle valve is in the last retracted position, the nozzle hole has a flow passage area that is a flow passage area in a seat portion that is a contact portion between a tip portion of the needle valve and a seating surface of the nozzle body. A fuel injection device formed so as to be at least 10 times as large as a flow passage area. The fuel injection device according to claim 1,
The nozzle body has a sack portion on the tip side of the contact portion,
The nozzle hole is formed in the sack portion,
The flow path area at the inlet of the sac part is formed so that the flow area of the sac inlet part is at least 5 times the flow area of the nozzle hole when the needle valve is in the last retracted position. The fuel-injection apparatus characterized by the above-mentioned. The fuel injection device according to claim 1 or 2,
A tip scissor angle that is an angle formed by a needle valve side tip surface that is the tip side of the seat portion of the needle valve tip portion and a nozzle body side tip surface that is the tip side of the seat portion of the nozzle body seat surface is The fuel injection device characterized in that the needle valve side tip surface and the nozzle body side tip surface are formed to be 6 degrees or less. The fuel injection device according to claim 2, wherein
A tip scissor angle that is an angle formed by a needle valve side tip surface that is the tip side of the seat portion of the needle valve tip portion and a nozzle body side tip surface that is the tip side of the seat portion of the nozzle body seat surface is Forming the needle valve side tip surface and the nozzle body side tip surface to be 6 degrees or less,
When the needle valve is at the most advanced position, the inlet diameter of the sac inlet part and the seat part downstream volume formed downstream of the seat part and upstream of the nozzle hole inlet are minimized. A fuel injection device characterized in that the tip scissor angle is set. The fuel injection device according to claim 2, wherein
The fuel injection device, wherein the flow path area of the sac inlet portion is larger than the flow path area of the nozzle hole when the needle valve is at the most advanced position. The fuel injection device according to any one of claims 1 to 5,
A first guide portion for holding the first guide shaft portion of the needle valve in the first guide hole portion of the needle valve insertion hole;
A second guide shaft is formed on the distal end side of the first guide part and spaced from the first guide part, and holds the second guide shaft part of the needle valve in the second guide hole part of the needle valve insertion hole. A guide part;
It is spaced apart from the second guide part and is formed on the tip side from the second guide part, and the tip part of the needle valve and the seat surface of the needle valve insertion hole come into contact with each other when the needle valve is fully advanced. A seat portion,
Between the first guide portion and the seat portion, a fuel flow path is provided that is formed by separating an inner peripheral surface of the needle valve insertion hole and an outer peripheral surface of the needle valve,
The second guide portion has a second guide portion abutting portion in which an inner peripheral surface of the needle valve insertion hole and an outer peripheral surface of the needle valve abut on the cross section perpendicular to the needle valve axis, and the needle A second guide portion fuel flow path in which an inner peripheral surface of the valve insertion hole and an outer peripheral surface of the needle valve are separated from each other;
2. The fuel injection device according to claim 1, wherein a second guide portion flow passage area, which is a flow passage area of the second guide portion fuel flow passage, is formed to be at least 16 times the flow passage area of the nozzle hole. A fuel injection device comprising: a nozzle body having a nozzle hole at a tip; and a needle valve that is movably held in a needle valve insertion hole formed in the nozzle body,
By advancing the needle valve to the maximum extent, the tip of the needle valve and the seat surface of the nozzle body are brought into contact with each other, and the fuel supply to the nozzle hole is shut off,
By retreating the needle valve, the tip of the needle valve and the seat surface of the nozzle body are separated to allow fuel supply to the nozzle hole, and fuel injection control is performed.
When the needle valve is in the last retracted position, a sheet portion flow area that is a flow passage area in a seat portion that is a contact portion between a tip portion of the needle valve and a seating surface of the nozzle body is the injection hole. The fuel injection device is characterized in that the last retracted position is set so as to be at least 10 times or more of the flow path area. The fuel injection device according to claim 7, wherein
The nozzle body has a sack portion on the tip side of the contact portion,
The nozzle hole is formed in the sack portion,
When the needle valve is in the last retracted position, the sac inlet portion flow passage area, which is the flow passage area at the inlet of the sac portion, is at least five times the flow passage area of the nozzle hole. A fuel injection device characterized in that a last retreat position is set. The fuel injection device according to claim 7 or 8,
The fuel injection device characterized in that the last retracted position is set so that the seat portion channel area is the smallest of at least 10 times the channel area of the nozzle hole. The fuel injection device according to claim 8, wherein
2. The fuel injection device according to claim 1, wherein the last retracted position is set such that the flow path area of the sac inlet is the smallest among at least five times the flow path area of the nozzle hole.

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