JP2025094774A - fuel injector - Google Patents

Abstract

To provide a fuel injection device which can suppress variation in radial positions of a floating plate and thus suppressing variation in an injection amount.SOLUTION: A floating plate 60 permits or blocks a communication between an in-orifice passage 502 and a pressure control chamber 500 by reciprocating inside an end part of an orifice plate 50 side of a cylinder 40 to separate from or contact an orifice plate body 51. The cylinder 40 includes: an annular groove 42 forming an annular space 420 from an outer peripheral wall of the floating plate 60 by being radially outwardly recessed from an inner peripheral wall of an end part on the orifice plate 50 side; and a guide part 43 which can guide the reciprocation of the floating plate 60 by sliding with the outer peripheral wall of the floating plate 60 on an opposite side to the orifice plate 50 of the groove 42.SELECTED DRAWING: Figure 5

Description

The present invention relates to a fuel injection device.

In recent years, in light of fuel regulations, it has become necessary to increase the fuel flow rate at the nozzle hole in order to increase the injection rate in order to shorten the combustion period. However, in a fuel injection device such as that described in Patent Document 1, for example, it was found that when the injection hole flow rate at the nozzle hole is increased, the variation in the injection amount becomes large. When the injection rate characteristics, which are the injection amount per unit time, were analyzed, it was found that this was caused by a large variation in the injection end timing, i.e., the nozzle needle closing timing.

The timing of the nozzle needle's closing is governed by the timing and flow rate of fuel flowing into the pressure control chamber. The timing of fuel flow is controlled by the opening and closing valve of the floating plate, i.e., its rising and falling motion, and the flow rate is controlled by the in-orifice passage. The floating plate is housed within the cylinder, but the gap between the outer peripheral wall of the floating plate and the inner peripheral wall of the cylinder is used as a fuel passage, and a large radial clearance must be secured in order to allow the floating plate to rise and fall smoothly even if the inner diameter of the cylinder shrinks in response to fuel pressure.

JP 2011-12670 A

In the fuel injection device of Patent Document 1, the clearance between the outer peripheral wall of the floating plate and the inner peripheral wall of the cylinder is large, so there is a risk that the radial position of the floating plate will vary when it descends for each injection. Structurally, the opening of the in-orifice passage on the pressure control chamber side is formed in an eccentric position relative to the center of the pressure control chamber, so the flow rate into the pressure control chamber changes due to the effect of the restriction depending on the radial position of the floating plate, and as a result, there is a risk that the variation in the injection amount will become large.

The object of the present invention is to provide a fuel injection device that can suppress variation in the radial position of the floating plate and suppress variation in the injection amount.

The present invention is a fuel injection device that injects high-pressure fuel accumulated in an accumulator pipe (2) into an internal combustion engine, and includes a nozzle body (20), a nozzle needle (30), a cylinder (40), an orifice plate (50), and a floating plate (60). The nozzle body has a nozzle chamber (200) into which high-pressure fuel flows, and a nozzle hole (23) that communicates with the nozzle chamber and injects high-pressure fuel. The nozzle needle is provided so as to be able to move back and forth within the nozzle chamber, and opens and closes the space between the nozzle chamber and the nozzle hole with one end, thereby intermittently spraying high-pressure fuel from the nozzle hole.

The cylindrical cylinder is provided radially inside the end of the nozzle body opposite the nozzle hole so as to be movable axially relative to the nozzle needle. The orifice plate is provided on the side opposite the nozzle body opposite the nozzle hole, and has an orifice plate body (51) that forms a pressure control chamber (500) between the inside of the cylinder and the other end of the nozzle needle, and an in-orifice passage (502) that opens on the surface of the orifice plate body facing the pressure control chamber and can supply high-pressure fuel to the pressure control chamber. The floating plate reciprocates inside the end of the cylinder facing the orifice plate, and allows or blocks communication between the in-orifice passage and the pressure control chamber by moving away from the orifice plate body or abutting against the orifice plate body.

The cylinder has an annular groove (42) that is recessed radially outward from the inner circumferential wall of the end on the orifice plate side and forms an annular space (420) between the inner circumferential wall of the floating plate and the groove, and a guide portion (43) that can guide the reciprocating movement of the floating plate by sliding against the outer circumferential wall of the floating plate on the side of the groove opposite the orifice plate. By allowing fuel to flow into the annular space formed by the groove, even if radial positional deviation occurs when the floating plate descends, a fluid action force acts in the direction of aligning the floating plate, suppressing variation in the radial position of the floating plate. This stabilizes the inflow flow rate into the pressure control chamber and suppresses variation in the injection amount.

1 is a cross-sectional view showing a fuel injection device according to a first embodiment; 1 is a cross-sectional view showing a portion of a fuel injection device according to a first embodiment; Cross-sectional view taken along line III-III in Figure 2. IV-IV line cross-sectional view of FIG. 2. Cross-sectional view of line VV in Figure 3. Cross-sectional view taken along line VI-VI in FIG. FIG. 6 is a cross-sectional view showing another state of FIG. 5 . FIG. 2 is a cross-sectional view showing a part of the fuel injection device according to the first embodiment in a state before the device is assembled; FIG. 11 is a cross-sectional view showing a part of a fuel injection device according to a comparative example. FIG. 10 is a cross-sectional view showing another state of FIG. 9 . 13 is a diagram showing changes over time in the drive signal and injection rate of a fuel injection device according to a comparative example. FIG. 13 is a diagram showing changes over time in the drive current, the pressure in the pressure control chamber, the lift position of the nozzle needle, and the injection rate of a fuel injection device according to a comparative example. FIG. 13A and 13B are diagrams showing a state in which the floating plate of a fuel injection device of a comparative embodiment is misaligned to one side in the radial direction, and FIG. 13C is a diagram showing the change over time in the lift position of the nozzle needle of a fuel injection device of a comparative embodiment. 13A and 13B are diagrams showing a state in which the floating plate of a fuel injection device of a comparative embodiment is shifted to the other radial position, and FIG. 13C is a diagram showing the change over time in the lift position of the nozzle needle of a fuel injection device of a comparative embodiment. 5A and 5B are diagrams showing a state in which the floating plate of the fuel injection device according to the first embodiment is misaligned in the radial direction; FIG. 6 is a cross-sectional view showing a portion of a fuel injection device according to a second embodiment. FIG. 11 is a cross-sectional view showing a portion of a fuel injection device according to a third embodiment. FIG. 13 is a cross-sectional view showing a portion of a fuel injection device according to a fourth embodiment. FIG. 13 is a cross-sectional view showing a portion of a fuel injection device according to a fifth embodiment. FIG. 13 is a cross-sectional view showing a portion of a fuel injection device according to a sixth embodiment. FIG. 13 is a cross-sectional view showing a portion of a fuel injection device according to a seventh embodiment.

Fuel injection devices according to several embodiments will be described below with reference to the drawings. Note that components that are essentially the same in several embodiments will be given the same reference numerals and descriptions will be omitted.

First Embodiment
A fuel injection device of a first embodiment is shown in Fig. 1. The fuel injection device 1 is applied to, for example, a four-cylinder diesel engine mounted on a vehicle (not shown). The fuel injection device 1 is provided in each cylinder and connected to a common rail 2 that stores diesel oil as pressurized fuel. The fuel injection device 1 injects high-pressure fuel supplied from the common rail 2 into the combustion chamber of each cylinder. In other words, the fuel injection device 1 is a fuel injection device that injects high-pressure fuel stored in the common rail 2 as an "accumulator pipe" into the diesel engine as an "internal combustion engine".

<1> As shown in Figures 1 and 2, the fuel injection device 1 includes a nozzle body 20, a nozzle needle 30 as a "valve member", a cylinder 40, an orifice plate 50, a floating plate 60, an injector body 70, a retaining nut 80, an opening/closing part 90, etc. The nozzle body 20 has a nozzle chamber 200 into which high-pressure fuel flows, and a nozzle hole 23 that communicates with the nozzle chamber 200 and injects high-pressure fuel. The nozzle needle 30 is provided so as to be able to move back and forth within the nozzle chamber 200, and opens and closes the space between the nozzle chamber 200 and the nozzle hole 23 with one end, thereby intermittently injecting high-pressure fuel from the nozzle hole 23.

The cylindrical cylinder 40 is provided radially inside the end of the nozzle body 20 opposite the injection hole 23, and is movable axially relative to the nozzle needle 30. The orifice plate 50 is provided on the opposite side of the nozzle body 20 opposite the injection hole 23, and has an orifice plate main body 51 that forms a pressure control chamber 500 between the inside of the cylinder 40 and the other end of the nozzle needle 30, and an in-orifice passage 502 that opens on the surface of the orifice plate main body 51 on the pressure control chamber 500 side and can supply high-pressure fuel to the pressure control chamber 500. The floating plate 60 reciprocates inside the end of the orifice plate 50 side of the cylinder 40, and allows or blocks communication between the in-orifice passage 502 and the pressure control chamber 500 by moving away from or coming into contact with the orifice plate main body 51.

The cylinder 40 has an annular groove 42 that is recessed radially outward from the inner circumferential wall of the end on the orifice plate 50 side and forms an annular space 420 between the inner circumferential wall of the floating plate 60 and the outer circumferential wall of the floating plate 60, and a guide portion 43 that can guide the reciprocating movement of the floating plate 60 by sliding against the outer circumferential wall of the floating plate 60 on the side of the groove 42 opposite the orifice plate 50.

The configuration of the fuel injection device 1 is explained in more detail below.

As shown in FIG. 1, the nozzle body 20 has a nozzle tube portion 21, a nozzle bottom portion 22, and a nozzle hole 23. The nozzle tube portion 21 is formed of, for example, metal. The nozzle tube portion 21 has a nozzle small diameter portion 211 and a nozzle large diameter portion 213. The nozzle small diameter portion 211 is formed in a substantially cylindrical shape. The nozzle large diameter portion 213 is formed in a substantially cylindrical shape integrally with the nozzle small diameter portion 211 so as to connect to one end of the nozzle small diameter portion 211. The outer diameter of the nozzle large diameter portion 213 is larger than the outer diameter of the nozzle small diameter portion 211. The inner diameter of the nozzle large diameter portion 213 is larger than the inner diameter of the nozzle small diameter portion 211. The inner peripheral wall of the nozzle small diameter portion 211 and the inner peripheral wall of the nozzle large diameter portion 213 are connected by a tapered wall surface.

The nozzle bottom 22 is formed integrally with the nozzle tube portion 21 so as to close the end of the nozzle small diameter portion 211 of the nozzle tube portion 21 opposite the nozzle large diameter portion 213. The nozzle hole 23 is formed to penetrate the nozzle bottom portion 22. For example, multiple nozzle holes 23 are formed at equal intervals in the circumferential direction of the nozzle bottom portion 22. The inner wall of the nozzle bottom portion 22 upstream of the nozzle hole 23 is formed in a tapered shape, forming a tapered valve seat 220.

The nozzle chamber 200 is formed inside the nozzle cylinder portion 21 and the nozzle bottom portion 22, and is connected to the nozzle hole 23.

The nozzle needle 30 has a needle body 31 and a flange portion 32. The needle body 31 is formed into a rod shape from, for example, metal. The needle body 31 is provided in the nozzle chamber 200 so as to be able to move back and forth in the axial direction. The needle body 31 is provided in the nozzle chamber 200 so that one end can abut against the valve seat 220 or move away from the valve seat 220. Hereinafter, the direction in which the needle body 31 abuts against the valve seat 220 will be referred to as the "valve closing direction" and the direction in which the needle body 31 moves away from the valve seat 220 will be referred to as the "valve opening direction" as appropriate.

The flange 32 is formed into a ring shape, for example, from metal, and is provided at a position a predetermined distance away from the end of the needle body 31 opposite the nozzle hole 23. When one end of the needle body 31 is in contact with the valve seat 220, the flange 32 is located radially inside the end of the nozzle large diameter portion 213 on the nozzle small diameter portion 211 side. In this state, the end face of the other end of the needle body 31 is a predetermined distance away from the end face of the nozzle large diameter portion 213 opposite the nozzle small diameter portion 211 on the nozzle hole 23 side.

As shown in FIG. 2, a cylinder 40, a needle spring 33, a floating plate 60, and a support spring 36 as a "spring" are provided radially inside the nozzle large diameter portion 213. The cylinder 40 is formed into a cylindrical shape from, for example, metal. The cylinder 40 is provided radially outside the end of the needle body 31 opposite the injection hole 23.

2, the cylinder 40 has a cylinder sliding part 411. The cylinder sliding part 411 is formed on the inner peripheral wall of the end of the cylinder 40 on the nozzle needle 30 side. The cylinder 40 is provided so that the cylinder sliding part 411 can slide on the outer peripheral wall of the end of the needle body 31 opposite the injection hole 23, and can move axially relative to the needle body 31. The outer diameter of the cylinder 40 is smaller than the inner diameter of the nozzle large diameter part 213. A roughly cylindrical gap is formed between the outer peripheral wall of the cylinder 40 and the inner peripheral wall of the nozzle large diameter part 213.

The needle spring 33 is, for example, a coil spring, and is provided between the flange 32 and the cylinder 40 on the radial outside of the needle body 31. One end of the needle spring 33 abuts against the flange 32, and the other end abuts against the cylinder 40. The needle spring 33 has a force that stretches in the axial direction. As a result, the needle spring 33 urges the cylinder 40 in the valve-opening direction relative to the needle body 31.

The floating plate 60 has a plate body 61 and a plate orifice passage 601. The plate body 61 is formed, for example, from metal in a substantially circular plate shape. The plate body 61 is provided on the radially inner side of the end of the cylinder 40 opposite the nozzle needle 30 so as to be able to reciprocate in the axial direction. The plate orifice passage 601 is formed so as to penetrate the center of the plate body 61 in the plate thickness direction. The plate orifice passage 601 has a plate orifice 602 formed in an orifice shape midway in the axial direction.

The support spring 36 is, for example, a coil spring, and is provided between the floating plate 60 and a spring seat 412, which is a portion extending radially inward from the inner peripheral wall of the cylinder 40. One end of the support spring 36 abuts against the spring seat 412, and the other end abuts against the floating plate 60. The support spring 36 has a force that stretches in the axial direction. As a result, the support spring 36 urges the floating plate 60 in the valve-opening direction relative to the cylinder 40.

The orifice plate 50 is provided on the nozzle body 20 on the opposite side to the nozzle hole 23. The orifice plate 50 has an orifice plate main body 51, a supply passage 501, an in-orifice passage 502, an out-passage 503, a plate annular recess 52, a plate annular passage 53, a plate recess 54, etc. The orifice plate main body 51 is formed, for example, from a metal in a substantially circular plate shape. The orifice plate main body 51 is provided so that the end face on the nozzle hole 23 side abuts against the end face of the nozzle large diameter portion 213 opposite the nozzle small diameter portion 211.

1 and 2, the supply passage 501 is inclined with respect to the axis of the orifice plate body 51 at the outer edge of the orifice plate body 51, and is formed to connect the end face of the orifice plate body 51 opposite the nozzle hole 23 to the end face on the nozzle hole 23 side. The in-orifice passage 502 is inclined with respect to the axis of the orifice plate body 51, and is formed to connect the end face of the orifice plate body 51 opposite the nozzle hole 23 to the center of the end face on the nozzle hole 23 side. An orifice-shaped in-orifice 504 is formed at the end of the in-orifice passage 502 on the nozzle hole 23 side. Here, the end of the in-orifice passage 502 opposite the nozzle hole 23 is adjacent to the end of the supply passage 501 opposite the nozzle hole 23. The out-passage 503 is inclined with respect to the axis of the orifice plate body 51, and is formed to connect the end face of the orifice plate body 51 opposite the nozzle hole 23 to the approximate center of the end face on the nozzle hole 23 side. The end of the outlet passage 503 opposite the nozzle hole 23 is formed in an orifice shape.

As shown in FIG. 2, the plate annular recess 52 is formed to be recessed in an annular shape from the end face of the orifice plate body 51 on the injection hole 23 side. The plate annular recess 52 is connected to the end of the supply passage 501 on the injection hole 23 side. The plate annular passage 53 is formed to be recessed in an annular shape from the end face of the orifice plate body 51 on the injection hole 23 side on the radial inner side of the plate annular recess 52. The plate annular passage 53 is connected to the in-orifice 504. The plate recess 54 is formed to be recessed in a circular shape from the center of the end face of the orifice plate body 51 on the injection hole 23 side on the radial inner side of the plate annular passage 53. The plate recess 54 is connected to the end of the out passage 503 on the injection hole 23 side.

The end face of the cylinder 40 opposite the nozzle hole 23 can abut against the end face of the orifice plate body 51 on the nozzle hole 23 side, or can be separated from the end face of the orifice plate body 51 on the nozzle hole 23 side. The pressure control chamber 500 is formed between the inner wall of the cylinder 40 and the end of the needle body 31 opposite the nozzle hole 23 and the end face of the orifice plate body 51 on the nozzle hole 23 side.

The end of the supply passage 501 on the nozzle hole 23 side is connected to the nozzle chamber 200 via the plate annular recess 52. The end of the in-orifice passage 502 on the nozzle hole 23 side, i.e., the in-orifice 504, is connected to the pressure control chamber 500 via the plate annular passage 53. The end of the out-passage 503 on the nozzle hole 23 side is connected to the pressure control chamber 500 via the plate recess 54.

The injector body 70 is provided on the opposite side of the orifice plate 50 from the nozzle hole 23. The injector body 70 has a main body 71, a body thread portion 72, a piping connection portion 73, and a high-pressure fuel passage 701. The main body 71 is formed into a cylindrical shape from, for example, metal. The end face of the main body 71 on the nozzle hole 23 side is provided so as to abut the end face of the orifice plate main body 51 on the opposite side from the nozzle hole 23. The body thread portion 72 is formed on the outer peripheral wall of the end of the main body 71 on the nozzle hole 23 side.

The high-pressure fuel passage 701 is formed between the inner and outer peripheral walls of the main body 71 so as to be approximately parallel to the axis of the main body 71. The high-pressure fuel passage 701 opens at a position corresponding to the openings of the supply passage 501 and the in-orifice passage 502 on the end face of the main body 71 on the injection hole 23 side. As a result, the high-pressure fuel passage 701 is in communication with the supply passage 501 and the in-orifice passage 502.

The pipe connection part 73 is formed at the end of the main body 71 opposite the injection hole 23 (see FIG. 1). A passage 731 that communicates with the high-pressure fuel passage 701 is formed inside the pipe connection part 73. A fuel pipe extending from the common rail 2 is connected to the pipe connection part 73. As a result, high-pressure fuel supplied from the common rail 2 flows into the high-pressure fuel passage 701 via the passage 731 in the pipe connection part 73. The fuel that flows into the high-pressure fuel passage 701 flows into the nozzle chamber 200 via the supply passage 501, and into the pressure control chamber 500 via the in-orifice passage 502. As a result, the nozzle chamber 200 and the pressure control chamber 500 are filled with high-pressure fuel.

The opening/closing part 90 is provided on the inside of the end of the main body 71 on the nozzle hole 23 side. The opening/closing part 90 has a drive part 91 and a movable member 92.

The movable member 92 is provided inside the end of the main body 71 on the nozzle hole 23 side so as to be able to move back and forth in a direction approximately parallel to the axis of the main body 71. The end of the movable member 92 on the nozzle hole 23 side is provided so as to be able to abut against a portion of the end face of the orifice plate main body 51 opposite the nozzle hole 23, which corresponds to the opening of the out passage 503, or to be able to move away from that portion.

The low-pressure side space 700 is formed radially outward of the end of the movable member 92 on the injection hole 23 side. The low-pressure side space 700 is connected to a low-pressure fuel passage (not shown). When the movable member 92 is in contact with a portion corresponding to the opening of the out passage 503 on the end face of the orifice plate body 51 opposite the injection hole 23, communication between the pressure control chamber 500 and the low-pressure side space 700 via the out passage 503 is blocked. On the other hand, when the movable member 92 is separated from the portion corresponding to the opening of the out passage 503 on the end face of the orifice plate body 51 opposite the injection hole 23, communication between the pressure control chamber 500 and the low-pressure side space 700 via the out passage 503 is permitted. In this way, the opening/closing unit 90 opens and closes between the pressure control chamber 500 and the low-pressure side space 700 by abutting the movable member 92 against the orifice plate body 51 or separating it from the orifice plate body 51.

The drive unit 91 is provided on the opposite side of the movable member 92 from the nozzle hole 23, and generates a magnetic attraction force when electricity is applied, which can attract the movable member 92 to the opposite side of the nozzle hole 23. An ECU 100 (see FIG. 1) provided in the vehicle can control the application of electricity to the drive unit 91. By controlling the application of electricity to the drive unit 91, the ECU 100 can control the operation of the movable member 92 of the opening/closing unit 90, and control the opening and closing between the pressure control chamber 500 and the low-pressure space 700.

The retaining nut 80 has a nut tube portion 81 and a nut thread portion 83. The nut tube portion 81 is formed of, for example, metal. The nut tube portion 81 has a nut small diameter portion 811, a nut medium diameter portion 812, and a nut large diameter portion 813. The nut small diameter portion 811 is formed in a substantially cylindrical shape. The nut medium diameter portion 812 is formed in a substantially cylindrical shape integral with the nut small diameter portion 811 so as to connect to one end of the nut small diameter portion 811. The outer diameter of the nut medium diameter portion 812 is the same as the outer diameter of the nut small diameter portion 811. The inner diameter of the nut medium diameter portion 812 is larger than the inner diameter of the nut small diameter portion 811. The nut large diameter portion 813 is formed in a substantially cylindrical shape integral with the nut medium diameter portion 812 so as to connect to the end of the nut medium diameter portion 812 opposite to the nut small diameter portion 811. The outer diameter of the nut large diameter portion 813 is the same as the outer diameter of the nut medium diameter portion 812. The inner diameter of the large diameter nut portion 813 is larger than the inner diameter of the medium diameter nut portion 812.

The nut thread portion 83 is formed on the inner peripheral wall of the end of the nut large diameter portion 813 opposite the nut medium diameter portion 812 so that it can be screwed into the body thread portion 72 of the injector body 70. The retaining nut 80 is provided such that the annular end face of the nut small diameter portion 811 on the nut large diameter portion 813 side abuts against the annular end face of the nozzle large diameter portion 213 on the nozzle small diameter portion 211 side, and the nut thread portion 83 is screwed into the body thread portion 72. This generates an axial force in a direction in which the nozzle body 20 and the injector body 70 approach each other. Therefore, the orifice plate 50 is sandwiched between the nozzle body 20 and the injector body 70, and a predetermined pressure is applied between the end face of the nozzle large diameter portion 213 on the orifice plate main body 51 side and the end face of the orifice plate main body 51 on the nozzle large diameter portion 213 side, and between the end face of the orifice plate main body 51 on the body main body 71 side and the end face of the body main body 71 on the orifice plate main body 51 side.

Next, the configuration of the cylinder 40 and its surroundings will be described in detail.

<1> As shown in FIG. 5, the groove 42 is recessed radially outward from the inner peripheral wall of the end of the cylinder 40 on the orifice plate 50 side, and forms an annular space 420 between the groove 42 and the outer peripheral wall of the floating plate 60. The guide portion 43 can guide the reciprocating movement of the floating plate 60 by sliding against the outer peripheral wall of the floating plate 60 on the opposite side of the groove 42 from the orifice plate 50. On the opposite side of the guide portion 43 from the groove 42, an annular escape recess 46 is formed that is recessed radially outward from the inner peripheral wall of the cylinder 40. The floating plate 60 has a plate tapered portion 62 and a plate cut surface 63. The plate tapered portion 62 is formed at the end of the plate body 61 opposite the orifice plate 50. The plate tapered portion 62 is formed in a tapered shape so as to approach the axis of the plate body 61 as it moves from the orifice plate 50 side to the opposite side of the orifice plate 50. The plate cut surface 63 is formed in a flat shape in the plate taper portion 62 so as to be inclined with respect to the axis of the plate body 61. Four plate cut surfaces 63 are formed at equal intervals in the circumferential direction of the plate body 61. The plate cut surfaces 63 allow the fuel on the orifice plate 50 side of the plate body 61 to easily flow to the opposite side of the orifice plate 50. The plate taper portion 62 indicated by the dashed line in FIG. 5 shows the plate taper portion 62 when the floating plate 60 is rotated 45 degrees in the circumferential direction.

The inner diameter of the guide portion 43 is larger than the outer diameter of the floating plate 60. Therefore, a substantially cylindrical clearance is formed between the inner peripheral wall of the guide portion 43 and the outer peripheral wall of the floating plate 60. A ring-shaped planar step surface 47 is formed on the radially inner side of the escape recess 46. The inner diameter of the step surface 47 is smaller than the outer diameter of the end face of the floating plate 60 opposite the orifice plate 50. Therefore, the outer edge of the end face of the floating plate 60 opposite the orifice plate 50 can abut against the step surface 47, and the floating plate 60 can move in the axial direction between the orifice plate 50 and the step surface 47. In other words, the axial movable range of the floating plate 60 is from the position where it abuts against the orifice plate 50 to the position where it abuts against the step surface 47.

<1-1> As shown in FIG. 7, when the floating plate 60 is at the farthest position from the orifice plate 50 within its axial movable range, the end of the outermost diameter part of the floating plate 60 on the orifice plate 50 side is located closer to the orifice plate 50 than the end of the guide part 43 on the orifice plate 50 side. At this time, the outer edge of the end face of the floating plate 60 opposite the orifice plate 50 abuts against the step surface 47. Note that even when the floating plate 60 abuts against the step surface 47, fuel near the relief recess 46 can flow between the plate cut surface 63 and the step surface 47 to the support spring 36 side.

<2> The groove 42 has a straight portion 421 that forms an inner wall parallel to the inner wall of the guide portion 43 (see Figure 5).

<3> The groove 42 has a connection portion 44 that connects the straight portion 421 and the guide portion 43. In a cross section taken along a plane including the axis of the cylinder 40, the connection portion 44 is formed to be linear (see FIG. 5). The connection portion 44 is formed to approach the axis of the cylinder 40 as it moves from the straight portion 421 side toward the guide portion 43 side. The inclination angle of the connection portion 44 with respect to the axis of the cylinder 40 is, for example, approximately 20 degrees.

<4> The cylinder 40 has a vertical groove 45 that extends along the axial direction of the cylinder 40 while recessing radially outward from the inner peripheral wall (see Figs. 3 and 6). As shown in Fig. 3, two vertical grooves 45 are formed at equal intervals in the circumferential direction of the cylinder 40. The vertical grooves 45 are formed so that the cross-sectional shape of a plane perpendicular to the axis of the cylinder 40 is approximately arc-shaped. As shown in Fig. 6, the vertical groove 45 connects the end face of the cylinder 40 on the orifice plate 50 side to the relief recess 46.

<5> When the annular space 420 is cut by a plane including the axis of the cylinder 40, the area S1 of one of the two cross sections is equal to or greater than half the minimum flow cross-sectional area S2 of the in-orifice passage 502 (see FIG. 5). Here, the minimum flow cross-sectional area S2 is equal to the flow cross-sectional area of the in-orifice 504.

<6> The support spring 36, which serves as a "spring," is provided on the floating plate 60 on the opposite side to the orifice plate 50, and biases the floating plate 60 toward the orifice plate 50 (see FIG. 5). For example, in a pre-assembly state in which the nozzle body 20 and the orifice plate 50 are not brought into contact with each other, when the support spring 36 is compressed only by the weight of the floating plate 60, the end of the outermost diameter portion of the floating plate 60 on the support spring 36 side is located on the opposite side to the groove 42 than the end of the guide portion 43 on the groove 42 side (see FIG. 8).

<7> The orifice plate 50 has an annular groove 55 that is recessed from the portion of the end face of the orifice plate body 51 facing the annular space 420 toward the opposite side of the cylinder 40 (see Figures 4 and 5). The annular groove 55 is also connected and communicates with the vertical groove 45 (see Figure 6).

Next, the operation of the fuel injection device 1 will be explained.

High-pressure fuel from the common rail 2 is supplied to the nozzle chamber 200 via the passage 731, the high-pressure fuel passage 701, the supply passage 501, and the plate annular recess 52 (see Figures 1 and 2). The needle spring 33 applies a load to the nozzle needle 30 in the valve closing direction.

A portion of the fuel in the high-pressure fuel passage 701 is supplied to the pressure control chamber 500 through the in-orifice 504 of the in-orifice passage 502 and the plate annular passage 53. As shown in FIG. 1, when the drive unit 91 is de-energized, the pressure control chamber 500 is filled with high-pressure fuel. The nozzle needle 30 receives a force in the valve closing direction from the load of the needle spring 33 and the fuel pressure in the pressure control chamber 500.

When the drive unit 91 is energized, the movable member 92 moves in the valve opening direction due to the magnetic attraction of the drive unit 91, and communication between the pressure control chamber 500 and the low pressure side space 700 is permitted via the out passage 503. As a result, fuel on the nozzle needle 30 side relative to the floating plate 60 of the pressure control chamber 500 flows through the plate orifice passage 601 to the orifice plate 50 side relative to the floating plate 60, and flows through the out passage 503 to the low pressure side space 700, and can be discharged to the low pressure fuel passage. As a result, the fuel pressure in the pressure control chamber 500 decreases. At this time, the floating plate 60 is pressed against the orifice plate 50 by the fuel pressure in the pressure control chamber 500 and the biasing force of the support spring 36.

When the fuel pressure in the pressure control chamber 500 drops, the force that the nozzle needle 30 receives in the valve opening direction from the fuel pressure in the nozzle chamber 200 becomes greater than the force that the nozzle needle 30 receives in the valve closing direction from the load of the needle spring 33 and the fuel pressure in the pressure control chamber 500. As a result, the nozzle needle 30 moves in the valve opening direction and moves away from the valve seat 220. As a result, the fuel in the nozzle chamber 200 is injected from the injection hole 23.

When the power supply to the drive unit 91 is turned off, the movable member 92 moves in the valve closing direction and abuts against the orifice plate 50, and the communication between the pressure control chamber 500 and the low pressure side space 700 via the out passage 503 is cut off. Therefore, the fuel pressure in the pressure control chamber 500 rises due to the fuel supplied from the in-orifice passage 502. As a result, the force that the nozzle needle 30 receives in the valve closing direction from the load of the needle spring 33 and the fuel pressure in the pressure control chamber 500 becomes greater than the force that the nozzle needle 30 receives in the valve opening direction from the fuel pressure in the nozzle chamber 200. Therefore, the nozzle needle 30 moves in the valve closing direction and abuts against the valve seat 220. As a result, the injection of fuel from the nozzle hole 23 of the nozzle chamber 200 stops. When high pressure fuel is supplied to the pressure control chamber 500 from the in-orifice passage 502, the floating plate 60 can move toward the nozzle needle 30 against the biasing force of the support spring 36.

Next, we will explain the advantages of this embodiment over the comparative embodiment.

As shown in FIG. 9, in the comparative embodiment, the cylinder 40 does not have a groove 42, but instead has a tapered portion 49. The tapered portion 49 is tapered on the inner edge of the end face of the cylinder 40 on the orifice plate 50 side, approaching the axis of the cylinder 40 as it moves from the orifice plate 50 side to the opposite side of the orifice plate 50.

In a fuel injection device such as the comparative embodiment, it was found that when the nozzle flow rate, which is the flow rate of fuel at the nozzle hole 23, is increased, the variation in the injection amount becomes greater (see FIG. 11C). When the injection rate characteristics, which is the injection amount per unit time, were analyzed, it was found that this was caused by the large variation in the injection end timing, i.e., the closing timing of the nozzle needle 30 (see arrows (4) and (5) in FIG. 11). This is because the variation in the area, which is the product of the injection rate and time, corresponds to the variation in the injection amount, and even if the changes in (4) and (5) are the same, the greater the nozzle flow rate, the greater this variation becomes (see FIG. 11C).

As shown in FIG. 12, variations in the closing timing of the nozzle needle 30 cause variations in the injection rate, which results in variations in the injection amount.

Structurally, the opening of the in-orifice passage 502 on the pressure control chamber 500 side is formed at a position eccentric to the center of the pressure control chamber 500. As shown in (A) and (B) of FIG. 13, when the floating plate 60 is located on the opening side of the in-orifice passage 502 with respect to the center of the pressure control chamber 500, a predetermined gap Sp1 is formed between the outer peripheral wall of the floating plate 60 and the inner peripheral wall of the cylinder 40 on the opposite side of the opening of the in-orifice passage 502 with respect to the floating plate 60. In this case, since the distance between the opening of the in-orifice passage 502 and the gap Sp1 is long, the flow rate of fuel flowing from the in-orifice passage 502 to the pressure control chamber 500 is small, and the pressure rise of the pressure control chamber 500 is slowed down (see (B) of FIG. 13). As a result, the closing speed of the nozzle needle 30 is slowed down (see (C) of FIG. 13).

On the other hand, as shown in (A) and (B) of FIG. 14, when the floating plate 60 is positioned on the opposite side of the opening of the in-orifice passage 502 from the center of the pressure control chamber 500, a predetermined gap Sp2 is formed between the outer peripheral wall of the floating plate 60 and the inner peripheral wall of the cylinder 40 on the opening side of the in-orifice passage 502 relative to the floating plate 60. In this case, since the distance between the opening of the in-orifice passage 502 and the gap Sp2 is short, the flow rate of fuel flowing from the in-orifice passage 502 to the pressure control chamber 500 increases, and the pressure rise of the pressure control chamber 500 becomes faster (see (B) of FIG. 14). As a result, the closing speed of the nozzle needle 30 becomes faster (see (C) of FIG. 14).

In addition, in the comparative embodiment, in the state shown in Figures 14(A) and 14(B), the fluid action force of the fuel that has flowed into the gap Sp2 acts on the outer peripheral wall of the floating plate 60, so that the floating plate 60 remains eccentric with respect to the center of the pressure control chamber 500.

In contrast, in this embodiment, as shown in (A) and (B) of FIG. 15, when the floating plate 60 is located on the opposite side of the opening of the in-orifice passage 502 with respect to the center of the pressure control chamber 500, the fluid action force of the fuel that flows from the in-orifice passage 502 into the annular space 420 of the groove 42 acts on the opposite side of the opening of the in-orifice passage 502 on the outer peripheral wall of the floating plate 60, and the floating plate 60 moves in the direction of alignment. As a result, the variation in the radial position of the floating plate 60 in the pressure control chamber 500 can be suppressed. Thus, this embodiment is advantageous over the comparative embodiment in that it can suppress the variation in the radial position of the floating plate 60.

9, in the comparative embodiment, the radial width of the space 490 formed between the outer peripheral wall of the floating plate 60 and the tapered portion 49 is relatively large and the axial length is relatively short, so that the centering effect of the floating plate 60 due to the fluid action force of the fuel flowing into the space 490 cannot be expected. If the tapered portion 49 is formed so as to increase the axial length of the space 490 in anticipation of an increase in the fluid action force, the axial length of the guide portion 43 is shortened, and the inclination of the floating plate 60 increases, which may increase the variation in the injection amount. If the outer diameter of the tapered portion 49, i.e., the seal diameter R1, which is the inner diameter of the contact surface between the orifice plate main body 51 and the cylinder main body 41, is enlarged in anticipation of an increase in the fluid action force in order to increase the radial size of the space 490, the seal function may be reduced and the variation in the injection amount may increase. Furthermore, if the tapered portion 49 is formed so that the axial length of the space 490 is increased while the radial width is decreased, the tip of the space 490 becomes narrower, and the fuel does not flow around due to the viscosity of the fuel, making it difficult for the fluid force to act on the floating plate 60.

In addition, in the comparative embodiment, when the floating plate 60 is at the farthest position from the orifice plate 50 within the axial movable range of the floating plate 60, the end of the outermost diameter portion of the floating plate 60 on the orifice plate 50 side is located at substantially the same position as the end of the guide portion 43 on the orifice plate 50 side (see FIG. 10). Therefore, as the floating plate 60 moves away from the orifice plate 50, the fluid action force acting on the outer peripheral wall of the floating plate 60 from the fuel flowing into the tapered portion 49 becomes smaller, and when the floating plate 60 is at the farthest position from the orifice plate 50, the fluid action force acting on the outer peripheral wall of the floating plate 60 becomes substantially zero.

On the other hand, in this embodiment, when the floating plate 60 is at the farthest position from the orifice plate 50 within the axial movable range of the floating plate 60, the end of the outermost diameter part of the floating plate 60 on the orifice plate 50 side is located closer to the orifice plate 50 than the end of the guide part 43 on the orifice plate 50 side (see FIG. 7). Therefore, regardless of the axial position of the floating plate 60, a fluid action force is applied to the outer peripheral wall of the floating plate 60 from the fuel that has flowed into the annular space 420 of the groove 42, and the floating plate 60 is centered at the center of the pressure control chamber 500. Thus, this embodiment is advantageous over the comparative embodiment in that it can suppress variation in the radial position of the floating plate 60 regardless of the axial position of the floating plate 60.

In this embodiment, the greater the depth of the groove 42, i.e., the greater the size of the groove 42 in the axial direction, the greater the area of the outer peripheral wall of the floating plate 60 on which the aligning force acts, and therefore the greater the aligning force acting on the floating plate 60. Therefore, the greater the depth of the groove 42, i.e., the greater the size of the groove 42 in the axial direction, the greater the amount of movement of the floating plate 60 in the aligning direction.

As described above, in the present embodiment, the cylinder 40 has an annular groove 42 that is recessed radially outward from the inner peripheral wall of the end portion on the orifice plate 50 side and forms an annular space 420 between the inner peripheral wall of the floating plate 60 and the outer peripheral wall of the floating plate 60, and a guide portion 43 that can guide the reciprocating movement of the floating plate 60 by sliding against the outer peripheral wall of the floating plate 60 on the opposite side of the groove 42 from the orifice plate 50. By allowing fuel to flow into the annular space 420 formed by the groove 42, even if a radial positional deviation occurs when the floating plate 60 descends, a fluid action force acts in a direction to center the floating plate 60, and the variation in the radial position of the floating plate 60 can be suppressed. This stabilizes the inflow flow rate into the pressure control chamber 500 and suppresses the variation in the injection amount.

<2> In this embodiment, the groove 42 has a straight portion 421 that forms an inner wall parallel to the inner wall of the guide portion 43. Therefore, the guide function of the guide portion 43 is ensured while the fluid action force acting on the floating plate 60 is also ensured.

<3> In this embodiment, the groove 42 has a connection portion 44 that connects the straight portion 421 and the guide portion 43. In a cross section taken along a plane including the axis of the cylinder 40, the connection portion 44 is formed to be linear. This improves the ease of inserting the floating plate 60 into the cylinder 40. It also improves the ease of processing between the connection portion 44 and the straight portion 421 and the guide portion 43, and suppresses the occurrence of burrs.

<4> In this embodiment, the cylinder 40 has a vertical groove 45 that extends along the axial direction of the cylinder 40 while being recessed radially outward from the inner peripheral wall. By using the vertical groove 45 as a fuel passage, the flow rate of fuel flowing radially outside the floating plate 60 can be ensured.

<5> In this embodiment, the area S1 of one of the two cross sections formed when the annular space 420 is cut by a plane including the axis of the cylinder 40 is equal to or greater than 1/2 the minimum flow passage cross-sectional area S2 of the in-orifice passage 502. Therefore, the flow rate of fuel from the in-orifice passage 502 to the pressure control chamber 500 of the groove 42 can be ensured.

<6> In this embodiment, the support spring 36 is provided on the opposite side of the floating plate 60 from the orifice plate 50, and biases the floating plate 60 toward the orifice plate 50. When the support spring 36 is compressed only by the weight of the floating plate 60, the end of the outermost diameter part of the floating plate 60 on the support spring 36 side is located on the opposite side of the groove 42 from the end of the guide part 43 on the groove 42 side. Therefore, it is possible to prevent the floating plate 60 from falling off the cylinder 40, for example, during transportation before assembly.

<7> In this embodiment, the orifice plate 50 has an annular groove 55 that is recessed from a portion of the end face of the orifice plate body 51 facing the annular space 420 on the cylinder 40 side toward the opposite side of the cylinder 40. Therefore, the flow rate of fuel from the in-orifice passage 502 to the annular space 420 of the groove 42 can be ensured.

Second Embodiment
A part of a fuel injection device of the second embodiment is shown in Fig. 16. The second embodiment differs from the first embodiment in the configuration of the groove 42.

<3> In this embodiment, in a cross section taken along a plane including the axis of the cylinder 40, the connection portion 44 is formed to be straight or curved. More specifically, in a cross section taken along a plane including the axis of the cylinder 40, the connection portion 44 is formed so that the center portion is straight and the end portion on the straight portion 421 side and the end portion on the guide portion 43 side are curved. In this embodiment, the insertion of the floating plate 60 into the cylinder 40 can be further improved. In addition, the occurrence of burrs between the connection portion 44 and the straight portion 421 and between the connection portion 44 and the guide portion 43 can be further suppressed.

Third Embodiment
A part of a fuel injection device of the third embodiment is shown in Fig. 17. The third embodiment differs from the first embodiment in the configuration of the groove 42.

<3> In this embodiment, the connection portion 44 is formed so as to be linear in a cross section taken along a plane including the axis of the cylinder 40. More specifically, the connection portion 44 is formed in an annular, planar shape between the straight portion 421 and the guide portion 43 so as to be perpendicular to the axis of the cylinder 40. In this embodiment, the tip of the annular space 420 formed by the groove 42 can be made wider, allowing the fuel to flow around, compared to the first embodiment in which the connection portion 44 is inclined with respect to the axis of the cylinder 40, for example. This allows the fluid action force to act even more strongly on the floating plate 60.

Fourth Embodiment
A part of a fuel injection device of the fourth embodiment is shown in Fig. 18. The fourth embodiment differs from the first embodiment in the configuration of the longitudinal grooves 45.

In this embodiment, four longitudinal grooves 45 are formed at equal intervals around the circumference of the cylinder 40. This further ensures the flow rate of fuel flowing radially outside the floating plate 60.

Fifth Embodiment
A part of a fuel injection device of the fifth embodiment is shown in Fig. 19. The fifth embodiment differs from the first embodiment in the configuration of the longitudinal grooves 45.

In this embodiment, the vertical groove 45 is formed so that the cross-sectional shape of the cylinder 40 taken along a plane perpendicular to the axis of the cylinder 40 is approximately triangular.

Sixth Embodiment
A part of a fuel injection device of the sixth embodiment is shown in Fig. 20. The sixth embodiment differs from the first embodiment in the configuration of the longitudinal grooves 45.

In this embodiment, the vertical groove 45 is formed so that the cross-sectional shape in a plane perpendicular to the axis of the cylinder 40 is approximately rectangular.

Seventh Embodiment
A part of a fuel injection device of the seventh embodiment is shown in Fig. 21. The seventh embodiment differs from the first embodiment in the configuration of the cylinder 40, the configuration of the nozzle needle 30, the arrangement of the support spring 36, and the like.

In this embodiment, the spring seat portion 412 shown in the first embodiment is not provided. On the other hand, the nozzle needle 30 has a spring seat portion 311. The spring seat portion 311 is formed so as to be recessed toward the nozzle hole 23 from the end face of the needle body 31 opposite the nozzle hole 23. One end of the support spring 36 abuts against the spring seat portion 311, and the other end abuts against the floating plate 60. The support spring 36 has a force that stretches in the axial direction. As a result, the support spring 36 urges the floating plate 60 in the valve opening direction relative to the cylinder 40.

The configuration of this embodiment can achieve the same effects as the first embodiment.

Other Embodiments
In other embodiments, the cylinder may have any number of longitudinal grooves in the circumferential direction of the cylinder, the longitudinal grooves extending along the axial direction of the cylinder while recessing radially outward from the inner circumferential wall. In other embodiments, the longitudinal grooves may have any shape in cross section taken along a plane perpendicular to the axis of the cylinder. In other embodiments, the cylinder may not have any longitudinal grooves.

In other embodiments, the groove does not have to have a straight portion that forms an inner wall parallel to the inner wall of the guide portion. That is, the inner wall of the groove does not have to be parallel to the inner wall of the guide portion.

In other embodiments, the area of one of the two cross sections formed when the annular space is cut by a plane including the axis of the cylinder does not have to be more than half the minimum flow cross-sectional area of the in-orifice passage.

In another embodiment, when the spring is compressed only by the weight of the floating plate, the spring side end of the outermost diameter part of the floating plate does not have to be located on the opposite side of the groove than the groove side end of the guide part.

In other embodiments, the orifice plate does not have to have an annular groove that is recessed from the portion of the end face of the orifice plate body facing the annular space toward the opposite side of the cylinder.

The features of the present disclosure are as follows:
"Disclosure 1"
A fuel injection device that injects high-pressure fuel accumulated in an accumulator pipe (2) into an internal combustion engine,
a nozzle body (20) having a nozzle chamber (200) into which the high-pressure fuel flows and a nozzle hole (23) communicating with the nozzle chamber and for injecting the high-pressure fuel;
a nozzle needle (30) provided reciprocally movable within the nozzle chamber, opening and closing a gap between the nozzle chamber and the injection hole at one end thereof to intermittently inject the high-pressure fuel from the injection hole;
a cylindrical cylinder (40) provided radially inside an end of the nozzle body opposite to the injection hole and movable axially relative to the nozzle needle;
an orifice plate (50) having an orifice plate main body (51) provided on the opposite side of the nozzle body from the injection hole and forming a pressure control chamber (500) between the inside of the cylinder and the other end of the nozzle needle, and an in-orifice passage (502) opening on a surface of the orifice plate main body facing the pressure control chamber and capable of supplying the high-pressure fuel to the pressure control chamber;
a floating plate (60) that reciprocates inside the end of the cylinder on the orifice plate side and moves away from or comes into contact with the orifice plate body to allow or block communication between the in-orifice passage and the pressure control chamber,
The cylinder has an annular groove (42) that is recessed radially outward from the inner wall of the end on the orifice plate side and forms an annular space (420) between the inner wall of the floating plate and the groove, and a guide portion (43) that can guide the reciprocating movement of the floating plate by sliding against the outer wall of the floating plate on the side of the groove opposite the orifice plate.
"Disclosure 2"
The fuel injection device according to Disclosure 1, wherein the groove has a straight portion (421) that forms an inner peripheral wall parallel to an inner peripheral wall of the guide portion.
"Disclosure 3"
The groove has a connection portion (44) that connects the straight portion and the guide portion,
The fuel injection device according to Disclosure 2, wherein the connection portion is formed so as to be straight or curved in a cross section taken along a plane including the axis of the cylinder.
"Disclosure 4"
The fuel injection device according to any one of Disclosures 1 to 3, wherein the cylinder has a longitudinal groove (45) that is recessed radially outward from an inner circumferential wall and extends along the axial direction of the cylinder.
"Disclosure 5"
The fuel injection device according to any one of Disclosures 1 to 4, wherein an area of one of two cross sections formed when the annular space is cut by a plane including an axis of the cylinder is equal to or larger than half of a minimum flow path cross-sectional area of the in-orifice passage.
"Disclosure 6"
a spring (36) provided on the floating plate opposite the orifice plate and biasing the floating plate toward the orifice plate;
A fuel injection device as described in any one of Disclosures 1 to 5, wherein, when the spring is compressed only by the weight of the floating plate, an end of the outermost diameter portion of the floating plate on the spring side is located on the opposite side to the groove than an end of the guide portion on the groove side.
"Disclosure 7"
The fuel injection device according to any one of Disclosures 1 to 6, wherein the orifice plate has an annular groove (55) that is recessed from a portion of an end face of the orifice plate body on the cylinder side that faces the annular space toward an opposite side to the cylinder.

As such, the present disclosure is not limited to the above-described embodiments, but can be implemented in various forms without departing from the spirit of the present disclosure.

1 Fuel injection device, 2 Accumulator pipe, 20 Nozzle body, 23 Injection hole, 30 Nozzle needle, 40 Cylinder, 42 Groove, 43 Guide part, 50 Orifice plate, 51 Orifice plate body, 60 Floating plate, 200 Nozzle chamber, 420 Annular space, 500 Pressure control chamber, 502 In-orifice passage

Claims (7)

A fuel injection device that injects high-pressure fuel accumulated in an accumulator pipe (2) into an internal combustion engine,
a nozzle body (20) having a nozzle chamber (200) into which the high-pressure fuel flows and a nozzle hole (23) communicating with the nozzle chamber and for injecting the high-pressure fuel;
a nozzle needle (30) provided reciprocally movable within the nozzle chamber, opening and closing a gap between the nozzle chamber and the injection hole at one end thereof to intermittently inject the high-pressure fuel from the injection hole;
a cylindrical cylinder (40) provided radially inside an end of the nozzle body opposite to the injection hole and movable axially relative to the nozzle needle;
an orifice plate (50) having an orifice plate main body (51) provided on the opposite side of the nozzle body from the injection hole and forming a pressure control chamber (500) between the inside of the cylinder and the other end of the nozzle needle, and an in-orifice passage (502) opening on a surface of the orifice plate main body facing the pressure control chamber and capable of supplying the high-pressure fuel to the pressure control chamber;
a floating plate (60) that reciprocates inside the end of the cylinder on the orifice plate side and moves away from or comes into contact with the orifice plate body to allow or block communication between the in-orifice passage and the pressure control chamber,
The cylinder has an annular groove (42) that is recessed radially outward from the inner wall of the end on the orifice plate side and forms an annular space (420) between the inner wall of the floating plate and the groove, and a guide portion (43) that can guide the reciprocating movement of the floating plate by sliding against the outer wall of the floating plate on the side of the groove opposite the orifice plate. The fuel injection device according to claim 1, wherein the groove has a straight portion (421) that forms an inner peripheral wall parallel to the inner peripheral wall of the guide portion. The groove has a connection portion (44) that connects the straight portion and the guide portion,
3. The fuel injection device according to claim 2, wherein the connection portion is formed so as to have a straight or curved shape in a cross section taken along a plane including an axis of the cylinder. The fuel injection device according to any one of claims 1 to 3, wherein the cylinder has a longitudinal groove (45) that extends along the axial direction of the cylinder while being recessed radially outward from the inner peripheral wall. The fuel injection device according to any one of claims 1 to 3, wherein the area (S1) of one of the two cross sections formed when the annular space is cut by a plane including the axis of the cylinder is equal to or greater than 1/2 of the minimum flow passage cross-sectional area (S2) of the in-orifice passage. a spring (36) provided on the floating plate opposite the orifice plate and biasing the floating plate toward the orifice plate;
4. The fuel injection device according to claim 1, wherein when the spring is compressed only by the weight of the floating plate, an end of the outermost diameter portion of the floating plate on the spring side is located on the opposite side to the groove than an end of the guide portion on the groove side. The fuel injection device according to any one of claims 1 to 3, wherein the orifice plate has an annular groove (55) that is recessed from a portion of the end face of the orifice plate body on the cylinder side that faces the annular space toward the opposite side of the cylinder.

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