WO2018037713A1

WO2018037713A1 - Fuel injection device

Info

Publication number: WO2018037713A1
Application number: PCT/JP2017/023908
Authority: WO
Inventors: 戸田　直樹; 利明稗島; 友基藤野
Original assignee: 株式会社デンソー
Priority date: 2016-08-24
Filing date: 2017-06-29
Publication date: 2018-03-01
Also published as: JP6508146B2; JP2018031298A

Abstract

A fuel injection device including: a valve body (31) having formed therein an injection hole (30), a supply flow path (40), a pressure control chamber (43), and an outflow flow path (42); a valve member (32) that opens and closes the injection hole; a switching valve mechanism (36) that has a first valve body (38) and a second valve body (37) and switches the flow path area of the outflow flow path; a drive unit (33) that controls the amount of lift of the first valve body to a first lift amount or a second lift amount; and a third valve body (35) that has switching chambers (44, 45) and a communication path (57) formed therein and opens and closes the communication path in accordance with the lift amount for the first valve body. The switching valve mechanism restricts to a first throttle state when the first valve body is not lifting and restricts to a second throttle state when the first valve body is positioned at the second lift amount. The third valve body separates from the first valve body and opens the communication path when the first valve body is not lifting and comes in contact with the first valve body and blocks the communication path when the first valve body is at the first lift amount position or the second lift amount position.

Description

Fuel injection device

Cross-reference of related applications

This application is based on Japanese Patent Application No. 2016-164004 filed on August 24, 2016, the contents of which are incorporated herein by reference.

This disclosure relates to a fuel injection device that injects fuel from an injection hole toward a combustion chamber.

Conventionally, as disclosed in Patent Document 1, for example, the needle opening speed for injecting fuel is made variable. As a specific mechanism for making the needle valve opening speed variable, two solenoids are installed, and the solenoids are operated independently to control the discharge speed of the fuel flowing out from the control chamber in two stages.

US Patent Application Publication No. 2013/0233941

In the above-described prior art, since the discharge speed is varied by mounting two solenoids, there is a possibility that the fuel injection device may be increased in size as compared with the configuration having one solenoid.

The present disclosure aims to provide a fuel injection device capable of variably controlling the fuel discharge speed while suppressing an increase in size.

The fuel injection device according to one aspect of the present disclosure injects fuel from the injection hole toward the combustion chamber. The fuel injection device includes an injection hole, a supply flow path for supplying fuel to the injection hole, a pressure control chamber into which a part of the fuel flowing through the supply flow path flows, and an outflow flow path for discharging the fuel in the pressure control chamber to the low pressure side , A valve member that opens and closes the nozzle hole by being relatively displaced with respect to the valve body due to fluctuations in fuel pressure in the pressure control chamber, and a first valve body disposed in the outflow passage And a switching valve mechanism for switching the flow area of the outflow passage and a valve body, and a driving force is applied to the first valve body for switching the flow passage area by the switching valve mechanism. The first valve body is lifted, and the first valve body and the second valve body house the drive unit that controls the lift amount of the first valve body to the first lift amount or the second lift amount larger than the first lift amount. A communication passage is formed to communicate the switching chamber and the supply flow path, and the first valve body Including a third valve body for opening and closing the communication passage in accordance with the shift amount. When the first valve body is not lifted, the switching valve mechanism is seated on the valve body to close the outflow passage, and the first valve body is at the position of the first lift amount. The first valve body is separated from the valve body, the first valve body is in contact with the first contact portion of the third valve body, and the second valve body is not separated from the valve body. Thus, when the outflow channel is limited to the first throttle state, and the first valve body is in the second lift amount, the first valve body is separated from the valve body, and the first valve body first The third valve body is displaced by the pressing of the contact portion, and the second valve body is in a position away from the valve body due to the pressing of the second valve body to the second contact portion by the first valve body. The flow path is limited to a second throttle state having a different channel area from the first throttle state. When the first valve body is not lifted, the third valve body is separated from the first valve body to open the communication passage, and the first valve body is positioned at the first lift amount or the second lift amount. If it is in the position, it contacts the first valve body and closes the communication passage.

According to the present disclosure as described above, when the first valve body is at the position of the first lift amount and the outflow passage is in the first throttle state, the first valve body that is separated from the valve body is the second valve body. It is set as the state contact | abutted to the 1st contact part of the 3rd valve body so that a valve body may not be separated. As a result, the position of the first valve body is held by contact with the first contact portion of the third valve body, so that the flow area of the outflow passage in the first throttled state, and hence the fuel from the pressure control chamber The outflow will be stable.

Further, when the first valve body is in the second lift amount and the outflow channel is in the second throttle state, the third valve body is displaced by the pressing of the first contact portion by the first valve body, The second valve body is separated from the valve body by pressing the second valve body against the second contact portion by the first valve body. As described above, since the position of the second valve body is maintained by the pressing of the first valve body, the flow area of the outflow passage in the second throttled state, and hence the amount of fuel discharged from the pressure control chamber is stable. Become.

Thus, the switching valve mechanism can switch the channel area of the outflow channel by adjusting the lift amount of the first valve body. And the lift amount of a 1st valve body can be controlled by one drive part. Therefore, since the drive part should just be the structure which controls the lift amount of one 1st valve body, a drive part can suppress an enlargement.

Furthermore, when the first valve body is in the position of the first lift amount or the second lift amount, the third valve body is in contact with the first valve body and closes the communication passage. When the first valve body is not lifted, the third valve body is separated from the first valve body and opens the communication passage, so that the first valve body is separated from the valve body. When seated from above, the fuel from the supply channel can be immediately allowed to flow into the switching chamber. Therefore, the fuel that has flowed out to the low pressure side when the first valve body is separated from the valve body can be filled with the high pressure fuel supplied from the communication passage of the third valve body in a short time. Thereby, the time from when the first valve body is seated on the valve body to when the valve member is closed can be shortened.

The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description with reference to the accompanying drawings. The drawing
FIG. 1 is a diagram showing an overall configuration of a fuel supply system, FIG. 2 is a longitudinal sectional view showing the fuel injection device, FIG. 3 is an enlarged longitudinal sectional view showing the vicinity of the three-way valve and the bypass valve, FIG. 4 is a diagram showing the operation of the three-way valve, FIG. 5 is a time chart showing the correlation between the displacement of the three-way valve and the nozzle needle.

(First embodiment)
A first embodiment of the present disclosure will be described with reference to FIGS. 1 to 5. The fuel supply system 10 shown in FIG. 1 uses the fuel injection device 100 according to the first embodiment. The fuel supply system 10 supplies fuel to each combustion chamber 22 of a diesel engine 20 that is an internal combustion engine by a fuel injection device 100. The fuel supply system 10 includes a feed pump (F / P) 12, a supply pump 13, a common rail 14, an engine control device 17, a plurality of fuel injection devices 100, and the like.

The feed pump 12 is, for example, a trochoid pump built in the supply pump 13. The feed pump 12 pumps light oil as fuel stored in the fuel tank to the supply pump 13. The feed pump 12 may be a separate body from the supply pump 13.

The supply pump 13 is, for example, a plunger type pump that is driven by the output shaft of the diesel engine 20. The supply pump 13 is connected to the common rail 14 by a fuel pipe 13a. The supply pump 13 further boosts the fuel supplied from the feed pump 12 and supplies the fuel to the common rail 14.

The common rail 14 is connected to each fuel injection device 100 via a high-pressure fuel pipe 14a. The common rail 14 temporarily stores high-pressure fuel supplied from the supply pump 13 and distributes the fuel to each fuel injection device 100 while maintaining the pressure. The common rail 14 is provided with a pressure reducing valve 14b. The pressure reducing valve 14b discharges the surplus fuel in the common rail 14 to the surplus fuel pipe connected to the fuel tank.

The engine control device 17 includes an arithmetic circuit mainly composed of a microcomputer or a microcontroller including a processor, a RAM, and a rewritable nonvolatile storage medium, and a drive circuit that drives each fuel injection device 100. It is. The engine control device 17 is electrically connected to each fuel injection device 100 as indicated by a broken line in FIG. The engine control device 17 controls the operation of each fuel injection device 100 according to the operating state of the diesel engine 20.

The fuel injection device 100 is attached to the head member 21 in a state of being inserted into the insertion hole of the head member 21 that forms the combustion chamber 22. The fuel injection device 100 directly injects fuel supplied through the high-pressure fuel pipe 14 a from the plurality of injection holes 30 toward the combustion chamber 22. The fuel injection device 100 includes a valve mechanism that controls fuel injection from the injection hole 30. The fuel injection device 100 uses part of the fuel supplied through the high-pressure fuel pipe 14 a to open and close the injection hole 30.

Next, the fuel injection device 100 will be described with reference to FIGS. As shown in FIG. 2, the fuel injection device 100 includes a valve body 31, a nozzle needle 32, a drive unit 33, a high-pressure valve 34, an in-orifice body 35, and a switching valve mechanism 36. The switching valve mechanism 36 includes a bypass valve 37 and a three-way valve 38.

The valve body 31 is configured by combining a plurality of members such as a cylinder formed of a metal material. The valve body 31 includes an injection hole 30, a seat portion 39, a high-pressure passage 40, an inflow passage 41, a low-pressure passage 42, a pressure control chamber 43, a bypass valve chamber 44, a three-way valve chamber 45, a drive portion accommodation chamber 46, and An orifice chamber 47 is formed.

The injection hole 30 is formed at the distal end in the insertion direction in the valve body 31 inserted into the combustion chamber 22. The tip is formed in a conical or hemispherical shape. A plurality of nozzle holes 30 are provided radially from the inside to the outside of the valve body 31. High-pressure fuel is injected from each injection hole 30 toward the combustion chamber 22. The high-pressure fuel is atomized by passing through the nozzle holes 30 and is easily mixed with air. The seat part 39 is formed in a conical shape inside the tip part of the valve body 31. The seat portion 39 faces the high-pressure channel 40 on the upstream side of the nozzle hole 30.

The high-pressure channel 40 supplies high-pressure fuel supplied from the common rail 14 to the nozzle hole 30 through the high-pressure fuel pipe 14a shown in FIG. The inflow channel 41 allows the high-pressure channel 40 and the pressure control chamber 43 to communicate with each other. The inflow channel 41 causes a part of the fuel flowing through the high-pressure channel 40 to flow into the pressure control chamber 43. The inflow channel 41 is provided with a second in orifice 48 as an inflow orifice. The second in-orifice 48 restricts the flow rate of fuel flowing from the high-pressure channel 40 to the pressure control chamber 43.

The low pressure channel 42 extends in the valve body 31 along the high pressure channel 40. The low-pressure channel 42 is a part of the outflow channel that allows the fuel (leak fuel) in the pressure control chamber 43 to flow out to the surplus fuel pipe on the low-pressure side outside the fuel injection device 100. The outflow passage is constituted by a low pressure passage 42, a bypass valve chamber 44 and a three-way valve chamber 45, an upstream communication passage 51, an intermediate communication passage 52, a downstream communication passage 53, and the like. The pressure of the fuel flowing through the low pressure channel 42 is lower than the pressure of the fuel in the pressure control chamber 43.

The pressure control chamber 43 is provided inside the valve body 31 on the opposite side of the nozzle hole 30 with the nozzle needle 32 interposed therebetween. The pressure control chamber 43 is a cylindrical space defined by the high pressure valve 34, the cylinder 49, and the nozzle needle 32. High pressure fuel flows into the pressure control chamber 43 through the inflow passage 41. The fuel pressure in the pressure control chamber 43 varies depending on the inflow of high-pressure fuel from the inflow passage 41 and the outflow of fuel to the bypass valve chamber 44. The nozzle needle 32 is reciprocated by the fluctuation of the fuel pressure in the pressure control chamber 43.

The bypass valve chamber 44 is a cylindrical space that houses the bypass valve 37. The axial direction of the bypass valve chamber 44 is along the axial direction of the pressure control chamber 43 and the cylinder 49. An upstream communication path 51 is formed between the bypass valve chamber 44 and the pressure control chamber 43. The fuel discharged from the pressure control chamber 43 flows into the bypass valve chamber 44 through the upstream communication passage 51. The fuel pressure in the upstream communication passage 51 is substantially the same as the fuel pressure in the bypass valve chamber 44. In addition, a cylindrical hole-shaped intermediate communication passage 52 is formed between the bypass valve chamber 44 and the three-way valve chamber 45. The fuel in the bypass valve chamber 44 is discharged to the three-way valve chamber 45 through the intermediate communication passage 52.

A second seat portion 50 is formed on a partition wall that partitions the bypass valve chamber 44. The second seat portion 50 is an annular region surrounding the periphery of the opening of the intermediate communication path 52 in the partition wall of the bypass valve chamber 44. The second seat portion 50 is a region where the bypass valve 37 is seated.

The three-way valve chamber 45 is a cylindrical space that houses the three-way valve 38. The three-way valve chamber 45 is located between the bypass valve chamber 44 and the drive unit accommodation chamber 46. The axial direction of the three-way valve chamber 45 is along the axial direction of the bypass valve chamber 44. The three-way valve chamber 45, the bypass valve chamber 44, and the intermediate communication passage 52 are formed so as to be coaxial with each other. The volume of the three-way valve chamber 45 is larger than the volume of the bypass valve chamber 44. A downstream communication passage 53 is formed between the three-way valve chamber 45 and the drive unit accommodation chamber 46. The downstream side communication passage 53 mainly causes the fuel discharged from the three-way valve chamber 45 to flow through the low pressure passage 42.

A first sheet portion 54 and a first placement portion 55 are formed on a partition wall that partitions the three-way valve chamber 45. The first seat portion 54 is an annular region surrounding the periphery of the opening of the downstream communication passage 53 in the partition wall of the three-way valve chamber 45. The first seat portion 54 is a region where the three-way valve 38 is seated. The first placement portion 55 is a region surrounding the periphery of the opening of the intermediate communication passage 52 in the partition wall of the three-way valve chamber 45. The lower end of the three-way valve spring 56 is placed on the first placement portion 55.

The orifice chamber 47 is a cylindrical space that houses the in-orifice body 35. The axial direction of the orifice chamber 47 is along the axial direction of the pressure control chamber 43 and the cylinder 49. An in-orifice passage 57 is formed between the orifice chamber 47 and the high-pressure channel 40. The fuel supplied from the high-pressure channel 40 flows into the orifice chamber 47 through the in-orifice passage 57. The fuel pressure in the orifice chamber 47 is substantially the same as the fuel pressure in the high-pressure channel 40.

A second mounting portion 58 is formed on the partition wall that partitions the orifice chamber 47. The second placement portion 58 is an area surrounding the periphery of the opening of the in-orifice passage 57 in the partition wall of the orifice chamber 47. The lower end of the orifice spring 59 is placed on the second placement portion 58.

The drive unit accommodation chamber 46 is a columnar space that houses the drive unit 33. The drive unit accommodation chamber 46 is filled with part of the fuel discharged from the three-way valve chamber 45. The axial direction of the drive unit accommodating chamber 46 is along the axial directions of the bypass valve chamber 44 and the three-way valve chamber 45. The drive unit accommodation chamber 46, the three-way valve chamber 45, and the bypass valve chamber 44 are provided so as to be coaxial with each other.

The nozzle needle 32 is formed in a cylindrical shape as a whole by a metal material. The nozzle needle 32 is accommodated in the valve body 31. The nozzle needle 32 is urged toward the nozzle hole 30 by a coiled nozzle spring 60 in which a metal wire is spirally wound. The nozzle needle 32 has a valve pressure receiving surface 61 and a face portion 62. The nozzle needle 32 is reciprocally displaced in the axial direction along the inner peripheral wall surface of the cylinder 49 formed in a cylindrical shape by receiving the fuel pressure in the pressure control chamber 43 on the valve pressure receiving surface 61. The nozzle needle 32 is displaced relative to the valve body 31, thereby causing the face portion 62 to be separated from and seated on the seat portion 39. The face portion 62 forms a main valve portion that opens and closes the nozzle hole 30 together with the seat portion 39.

The drive unit 33 is accommodated in the drive unit accommodation chamber 46. The drive unit 33 generates a driving force for driving the three-way valve 38 and the bypass valve 37 of the switching valve mechanism 36, so that the pressure control chamber 43 and the low-pressure flow path 42 are switched from the cut-off state to the communication state. Switch. The driving unit 33 can change the magnitude of the driving force to be generated based on the driving signal output from the engine control device 17, and can generate the first driving force or the second driving force. The second driving force is a force larger than the first driving force.

The driving unit 33 includes a piezoelectric element laminate 63, a transmission mechanism 64, and the like. The piezoelectric element laminate 63 is a laminate in which, for example, layers called PZT (PbZrTiO3) and thin electrode layers are alternately stacked. The piezoelectric element laminate 63 receives an input drive signal output from the engine control device 17. The piezoelectric element stacked body 63 expands and contracts along the axial direction of the drive unit accommodation chamber 46 by the inverse piezoelectric effect that is a characteristic of the piezoelectric element, according to the drive voltage that is a voltage corresponding to the drive signal.

The transmission mechanism 64 is a mechanism that transmits expansion and contraction of the piezoelectric element laminate 63. The transmission mechanism 64 includes a piston 65, a buffer cylinder 66, and a piston spring 67. The piston 65 is formed in a cylindrical shape. The piston 65 is in contact with the piezoelectric element laminate 63. The movement of the piezoelectric element laminate 63 that expands and contracts is input to the piston 65. The piston 65 is formed with a first drive transmission pin 68 that protrudes in a cylindrical shape toward the three-way valve chamber 45. The first drive transmission pin 68 is inserted through the downstream communication path 53. The distal end surface of the first drive transmission pin 68 is in contact with the three-way valve 38.

The buffer cylinder 66 is formed in a cylindrical shape and is fitted on the piston 65. The piston spring 67 is a metal spring that generates an elastic force in the axial direction. The piston spring 67 urges the piston 65 toward the three-way valve 38 with respect to the buffer cylinder 66.

Thus, the drive unit 33 reciprocally displaces the first drive transmission pin 68 in the axial direction by transmitting the expansion and contraction of the piezoelectric element stack 63 along the axial direction by the transmission mechanism 64. As the drive voltage input to the drive unit 33 increases, the drive force input from the first drive transmission pin 68 to the three-way valve 38, and thus the lift amount of the first drive transmission pin 68 and the three-way valve 38, increases.

The high-pressure valve 34 is formed in a disk shape from a metal material. The high-pressure valve 34 is disposed on the inner peripheral side of the cylinder 49 in a state where the high-pressure valve 34 can be reciprocally displaced along the axial direction of the valve body 31. A space between the high pressure valve 34 and the valve pressure receiving surface 61 is substantially the pressure control chamber 43. The high pressure valve 34 is urged toward the upstream communication path 51 with respect to the cylinder 49 by a high pressure valve spring 69. A first out orifice 70 is formed in the high pressure valve 34. The first out orifice 70 is formed in a through hole that penetrates the high-pressure valve 34 in the plate thickness direction. The first out orifice 70 is a flow rate of fuel flowing from the pressure control chamber 43 to the upstream communication passage 51 and the bypass valve chamber 44 in a state where the high pressure valve 34 closes the second in orifice 48 of the inflow passage 41. Limit.

The switching valve mechanism 36 is a mechanism for switching the channel area of the outflow channel by opening and closing the bypass valve 37 and the three-way valve 38. When the drive unit 33 generates neither the first drive force nor the second drive force, the switching valve mechanism 36 closes the outflow channel. On the other hand, when the drive unit 33 generates the first driving force, the switching valve mechanism 36 restricts the outflow channel to the first throttle state. Further, when the drive unit 33 generates the second driving force, the switching valve mechanism 36 restricts the outflow channel to the second throttle state.

The bypass valve 37 is formed in a disk shape from a metal material or the like. The bypass valve 37 is disposed in the bypass valve chamber 44 and can be displaced along the axial direction in the bypass valve chamber 44. A through hole 71 that penetrates the bypass valve 37 in the axial direction is formed in the center of the bypass valve 37 in the radial direction. A small diameter cylindrical portion 72 of the three-way valve 38 is inserted into the through hole 71 of the bypass valve 37, and guides the small diameter cylindrical portion 72 of the three-way valve 38 along the inner wall of the through hole 71 in the axial direction.

The bypass valve 37 is provided with an upper end side contact portion 73, a lower end side contact portion 74, and a second out orifice 75. The upper end side contact portion 73 is formed on the upper end surface of the bypass valve 37 facing the intermediate communication path 52. The upper end side contact portion 73 is formed in a flat annular shape. The upper end side contact portion 73 contacts the second sheet portion 50 by the elastic force of the orifice spring 59. The bypass valve 37 is closed by the seating of the upper end side contact portion 73 on the second seat portion 50.

The lower end side contact portion 74 is formed on the end surface of the bypass valve 37 facing the opening of the upstream communication passage 51 in both axial end surfaces. In the lower end side contact portion 74, the tip portion of the in-orifice body 35 comes into contact with the elastic force of the orifice spring 59. When the three-way valve 38 is in the closed position, the in-orifice body 35 and the lower end side contact portion 74 are in contact with each other.

The second out orifice 75 is configured to restrict the flow area from the bypass valve chamber 44 to the intermediate communication path 52. The second out orifice 75 restricts the flow rate of fuel flowing out from the bypass valve chamber 44 to the intermediate communication passage 52 when the bypass valve 37 is in a closed state, so that the flow of the outflow passage in the first throttle state is reduced. Define the road area. The throttle area that is the flow path area throttled by the second out orifice 75 is defined to be narrower than that of the first out orifice 70. That is, the second out orifice 75 is an orifice having a smaller diameter than the first out orifice 70.

The three-way valve 38 is formed of a metal material or the like into a three-stage cylindrical shape having a smaller diameter than the bypass valve 37. The three-way valve 38 and the bypass valve 37 are arranged in series in the outflow channel. The three-way valve 38 has a large-diameter disk portion 76, a medium-diameter column portion 77, and a small-diameter column portion 72. The large-diameter disk portion 76 is formed with a larger diameter than the intermediate communication path 52. On the other hand, the medium diameter cylindrical portion 77 and the small diameter cylindrical portion 72 are formed to have a smaller diameter than the intermediate communication path 52. The medium-diameter cylindrical portion 77 protrudes from the large-diameter disk portion 76 in a cylindrical shape along the axial direction. The small diameter cylindrical portion 72 protrudes in a cylindrical shape from the medium diameter cylindrical portion 77 along the axial direction.

The axial length of the medium-diameter cylindrical portion 77 is longer than the axial length of the intermediate communication path 52. The axial length of the small diameter cylindrical portion 72 is longer than the length of the through hole 71 of the bypass valve 37. The diameter of the medium diameter cylindrical portion 77 is larger than the diameter of the through hole 71 of the bypass valve 37. Therefore, the step between the middle diameter cylindrical portion 77 and the small diameter cylindrical portion 72 becomes a portion in contact with the bypass valve 37.

The medium-diameter cylindrical portion 77 is formed with a flat portion 77a including the axial direction so that a part of the outer peripheral portion is concave in the radially inward direction. The flat surface portion 77a is formed in order to secure a flow path area in the intermediate communication path 52. The plane portion 77a is set in position and size so as not to block fuel flowing out from the second out orifice 75 of the bypass valve 37.

The three-way valve 38 is disposed in the three-way valve chamber 45. The three-way valve 38 can be displaced in the three-way valve chamber 45 along the axial direction. The three-way valve 38 is urged toward the drive unit accommodation chamber 46 with respect to the first placement unit 55 by a three-way valve spring 56 formed in a coil spring shape.

The pilot face portion 78 is formed on the three-way valve 38. The pilot face portion 78 is formed on the upper end surface of the three-way valve 38 that faces the downstream communication passage 53. The pilot face portion 78 is formed in a flat annular shape. The pilot face portion 78 comes into contact with the first seat portion 54 by the elastic force of the three-way valve spring 56. The pilot face portion 78 is pressed against the first seat portion 54 by the urging force of the three-way valve spring 56 and the fuel pressure difference between the three-way valve chamber 45 and the low pressure passage 42. The three-way valve 38 is closed by the seating of the pilot face portion 78 on the first seat portion 54.

The three-way valve 38 uses the distance that is displaced in the axial direction when the driving unit 33 generates the first driving force as the first lift amount, and is displaced in the axial direction when the driving unit 33 generates the second driving force. The distance to be used is the second lift amount. The first lift amount is longer than the second lift amount.

The in-orifice body 35 is formed in a cylindrical shape from a metal material or the like. The in-orifice body 35 is disposed in the orifice chamber 47 and can be displaced along the axial direction in the orifice chamber 47. A through-hole 35 a that penetrates the in-orifice body 35 in the axial direction is formed in the center of the in-orifice body 35 in the radial direction. The in-orifice body 35 is urged toward the bypass valve chamber 44 with respect to the second placement portion 58 by an orifice spring 59 formed in a coil spring shape.

The in-orifice body 35 has a recess 79 and a first in-orifice 80 formed therein. The recess 79 is formed so as to be recessed from the upper end side of the in-orifice body 35. At the bottom of the recess 79, an opening of the through hole 35a is formed. A plurality of insertion holes 81 are formed in the side wall of the recess 79.

The tip of the recess 79 comes into contact with the bypass valve 37 by the elastic force of the orifice spring 59. The inner diameter of the recess 79 is larger than the diameter of the small-diameter cylindrical portion 72 of the three-way valve 38. Therefore, the tip of the small diameter cylindrical portion 72 of the three-way valve 38 can contact the bottom of the recess 79 to close the through hole 35a.

The first in-orifice 80 is configured to restrict the flow area of the through-hole 35a of the in-orifice body 35. The first in-orifice 80 restricts the flow rate of the fuel flowing out from the high-pressure channel 40 to the bypass valve chamber 44 when the three-way valve 38 is in a closed state.

In the bypass valve 37 and the three-way valve 38, the direction from the bypass valve chamber 44 toward the drive unit accommodation chamber 46 along the axial direction is the valve closing direction, and the direction from the drive unit storage chamber 46 toward the bypass valve chamber 44 along the axial direction. The direction is the valve opening direction. When the driving unit 33 does not generate a driving force, the outflow passage is closed by the seating of the three-way valve 38 and the bypass valve 37 on the valve body 31. A valve opening gap 82 is formed between the three-way valve 38 in the valve closing position and the in-orifice body 35 in the valve closing position. The valve opening gap 82 functions as a space that allows displacement in the valve opening direction only by the three-way valve 38.

Next, details of the injection operation of the fuel injection device 100 will be described with reference to FIGS. As shown in FIG. 3, the application of the drive voltage from the engine control device 17 to the drive unit 33 is interrupted before the start of injection. Therefore, the drive unit 33 does not substantially generate forces such as the first drive force and the second drive force. Therefore, the three-way valve 38 and the bypass valve 37 are both stationary at the valve closing position where the pilot face portion 78 and the upper end side contact portion 73 are in contact with the first seat portion 54 and the second seat portion 50. A valve opening gap 82 is formed between the three-way valve 38 and the in-orifice body 35. Since both the three-way valve 38 and the bypass valve 37 are closed, the fuel pressures in the three-way valve chamber 45 and the bypass valve chamber 44 are substantially increased to the same level as the fuel pressure in the pressure control chamber 43. . In the above state, the high pressure valve 34 is pressed against the wall surface around the opening of the inflow passage 41 by the elastic force of the high pressure valve spring 69. The nozzle needle 32 is stationary at the valve closing position where the face portion 62 is in contact with the seat portion 39.

First, we will explain when the valve opens at low speed. As shown in FIGS. 4 and 5, when the valve is opened at low speed, application of a drive voltage from the engine control device 17 to the drive unit 33 is started. As a result, the drive unit 33 generates the first drive force. The engine control device 17 applies a drive voltage applied to the drive unit 33 so that a first drive force that is greater than the opening force of the three-way valve 38 and does not displace the in-orifice body 35 acts on the three-way valve 38. Control.

When the drive unit 33 generates the first driving force, the first drive transmission pin 68 is displaced over the first lift amount. The three-way valve 38 pushed down by the first drive transmission pin 68 causes the pilot face portion 78 to be separated from the first seat portion 54 due to the displacement in the valve opening direction over the first lift amount. In addition, the three-way valve 38 causes the tip of the small-diameter cylindrical portion 72 to contact the in-orifice body 35 so that the bypass valve 37 is not separated from the valve body 31. Due to the displacement of the three-way valve 38 in the valve opening direction, the valve opening gap 82 disappears.

By opening the three-way valve 38 as described above, the pressure control chamber 43 and the low-pressure channel 42 are switched from the shut-off state to the communication state as shown in the first lift position of FIG. As a result, the high-pressure fuel in the pressure control chamber 43 flows through the first out orifice 70, the upstream communication passage 51, the second out orifice 75, the intermediate communication passage 52, and the three-way valve chamber 45 of the high pressure valve 34 in this order. It is discharged to the path 42.

At this time, the flow area of the outflow flow path is defined by the throttle area of the first out orifice 70 and the throttle area of the second out orifice 75 which is smaller than the pilot opening area of the three-way valve 38. Therefore, the outflow passage is in the first throttle state in which the outflow flow rate of the fuel from the pressure control chamber 43 to the low pressure passage 42 is limited by the second out orifice 75.

The pilot opening area is a flow area between the first seat part 54 and the pilot face part 78. In order to enable flow control by the second out orifice 75, the valve opening gap 82 is defined in advance so that the pilot opening area is larger than the throttle area of the second out orifice 75.

In the first throttle state, the orifice spring 59 urges the in-orifice body 35 and the bypass valve 37 toward the three-way valve 38 in the valve closing direction, thereby separating the bypass valve 37 from the valve body 31. I won't let you. As a result, the small-diameter cylindrical portion 72 of the three-way valve 38 is pressed against the bottom of the concave portion 79 of the in-orifice body 35 and can be stationary while being sandwiched between the first drive transmission pin 68 and the in-orifice body 35. It becomes. In addition, since the driving force generated by the drive unit 33 is maintained at the first driving force, the closed state of the bypass valve 37 in the first throttle state is maintained.

The fuel pressure in the bypass valve chamber 44 and the pressure control chamber 43 gradually decreases due to the outflow of fuel through the outflow passage in the first throttle state. As a result, the nozzle needle 32 is displaced in the valve opening direction while being gradually accelerated toward the pressure control chamber 43 by the pressure of the high-pressure fuel acting on the face portion 62. The fuel injection from the nozzle hole 30 is started by opening the main valve portion as described above.

Next, a description will be given of when the valve is opened at high speed. When the valve is opened at high speed, the drive voltage applied from the engine control device 17 to the drive unit 33 is increased. As a result, the drive unit 33 generates a second drive force that exceeds the opening force of the bypass valve 37. The engine control device 17 controls the drive voltage applied to the drive unit 33 so that the generation of the second drive force larger than the opening force of the bypass valve 37 is maintained.

When the drive unit 33 generates the second driving force, the first drive transmission pin 68 is displaced over the second lift amount. The three-way valve 38 pushed down by the first drive transmission pin 68 causes the pilot face portion 78 to be separated from the first seat portion 54 by displacement in the valve opening direction over the second lift amount. Further, due to the displacement of the three-way valve 38, the bypass valve 37 is displaced in the valve opening direction by the upper end side contact portion 73 being pushed by the step of the three way valve 38, and the upper end side contact portion 73 is separated from the second seat portion 50. Sit down.

By opening the bypass valve 37 as described above, as in the second lift position of FIG. 3, the fuel in the pressure control chamber 43 passes through the first out orifice 70, the upstream communication passage 51, and the second seat in the bypass valve chamber 44. The bypass passage between the portion 50 and the upper end side contact portion 73, the intermediate communication passage 52, and the three-way valve chamber 45 are sequentially circulated. As a result, the configuration that defines the flow passage area of the outflow passage and restricts the outflow flow rate of the fuel is switched from the second out orifice 75 to the first out orifice 70. Since the first out orifice 70 has a larger throttle area than the second out orifice 75, the flow area of the outflow channel in the second throttle state is larger than that in the first throttle state. As a result, the flow rate of the fuel flowing out from the pressure control chamber 43 in the second throttle state increases more than in the first throttle state.

Both the opening area of the bypass passage and the pilot opening area of the three-way valve 38 are made larger than the throttle area of the first out orifice 70. In order to enable the flow rate control by the first out orifice 70, the second lift amount is defined in advance so that the opening area thereof is larger than the throttle area of the first out orifice 70.

The fuel pressure in the bypass valve chamber 44 and the pressure control chamber 43 drops significantly due to the outflow of fuel whose flow rate is controlled by the first out orifice 70. As a result, the nozzle needle 32 accelerates in the valve opening direction, and rapidly expands the gap between the seat portion 39 and the face portion 62. As described above, the flow area of the high-pressure flow path 40 connected to the injection hole 30 is increased, so that the fuel injection amount injected from the injection hole 30 is increased. As a result, a clear change occurs in the characteristics of the injection amount (injection rate) of the fuel injected from the injection hole 30 per unit time.

Next, the valve closing operation will be described. During the valve closing operation, the application of the drive voltage from the engine control device 17 to the drive unit 33 is interrupted. Then, the driving force of the driving unit 33 falls below the valve opening force of the three-way valve 38 and the bypass valve 37 and eventually disappears. As described above, the three-way valve 38 and the bypass valve 37 are displaced in the valve closing direction by the respective elastic forces of the three-way valve spring 56 or the orifice spring 59 and the fuel pressure. As a result, the pilot face portion 78 and the upper end side contact portion 73 are returned to the closed state in which the first seat portion 54 and the second seat portion 50 are contacted. As a result, the pressure control chamber 43 and the low-pressure channel 42 are switched from the communication state to the cutoff state, and the outflow channel returns to the closed state.

On the other hand, the high pressure valve 34 is pushed down by the fuel pressure of the high pressure fuel flowing from the inflow passage 41. When the three-way valve 38 is displaced in the valve closing direction and separated from the in-orifice body 35, the first in-orifice 80 of the in-orifice body 35 is opened. As a result, the high-pressure fuel in the pressure control chamber 43 flows through the in-orifice passage 57, the first in-orifice 80, the bypass valve chamber 44, the second out-orifice 75, the intermediate communication passage 52, and the three-way valve chamber 45 in this order.

Thereby, each fuel pressure in the three-way valve chamber 45, the bypass valve chamber 44, and the pressure control chamber 43 is recovered integrally. As a result, the nozzle needle 32 is pushed down by the fuel pressure in the pressure control chamber 43 and returns to the state where the face portion 62 is brought into contact with the seat portion 39 at the valve closing position. The fuel injection from the nozzle hole 30 is interrupted by closing the main valve portion.

In the first embodiment described so far, the flow area of the outflow flow path is switched by the switching valve mechanism 36 due to an increase in the generated drive force of the drive unit 33 from the first drive force to the second drive force. As described above, the displacement speed of the nozzle needle 32 is clearly changed by changing the pressure drop mode of the pressure control chamber 43. Therefore, the passage area rapidly increases in the orifice portion between the face portion 62 and the seat portion 39 through which the high-pressure fuel supplied to the injection hole 30 passes. As a result, the injection amount injected from the nozzle hole 30 per unit time also clearly changes before and after the driving force is switched by the driving unit 33. Therefore, the fuel injection device 100 can change the injection rate characteristic of the fuel injection by controlling the driving force generated by the single drive unit 33.

Further, in the first embodiment, when the three-way valve 38 is in the first lift amount position and the outflow passage is in the first throttle state, the three-way valve 38 separated from the valve body 31 separates the bypass valve 37. The in-orifice body 35 is in contact with the recess 79 so as not to be seated. As a result, the position of the three-way valve 38 is maintained by contact with the recess 79 of the in-orifice body 35, so that the flow area of the outflow passage in the first throttled state, and hence the outflow amount of fuel from the pressure control chamber 43, is , Become stable. In the present embodiment, the position of the first lift amount is also referred to as a first lift position.

Further, when the three-way valve 38 is at the second lift amount and the outflow channel is in the second throttle state, the in-orifice body 35 is displaced by pressing the recess 79 by the three-way valve 38. Then, the bypass valve 37 is separated from the valve body 31 by pressing the upper end side contact portion 73 of the bypass valve 37 by the three-way valve 38. In this way, the position of the bypass valve 37 is held by the pressing of the three-way valve 38, so that the flow area of the outflow passage in the second throttle state, and hence the amount of fuel discharged from the pressure control chamber 43, is also stable. .

Thus, the switching valve mechanism 36 can switch the channel area of the outflow channel by adjusting the lift amount of the three-way valve 38. The lift amount of the three-way valve 38 can be controlled by one drive unit 33. Therefore, since the drive part 33 should just be the structure which controls the lift amount of the one three-way valve 38, the drive part 33 can suppress enlargement.

Further, the in-orifice body 35 is in contact with the three-way valve 38 and closes the in-orifice passage 57 when the three-way valve 38 is in the first lift amount position or the second lift amount position. When the three-way valve 38 is not lifted, the in-orifice body 35 is separated from the three-way valve 38 to open the in-orifice passage 57. When the three-way valve 38 is seated from the state where it is separated from the valve body 31, the fuel from the high-pressure flow path 40 can immediately flow into the bypass valve chamber 44. Therefore, the fuel that has flowed out to the low pressure side when the three-way valve 38 is separated from the valve body 31 can be filled with the high pressure fuel supplied from the in-orifice passage 57 of the in-orifice body 35 in a short time. As a result, the time from when the three-way valve 38 is seated on the valve body 31 until the nozzle needle 32 is closed can be shortened.

Furthermore, the drive unit 33 of the first embodiment switches between the first throttle state and the second throttle state of the outflow channel not by the lift amount of the first drive transmission pin 68 but by the generated driving force of the drive unit 33. Yes. With the above configuration, the positions of the three-way valve 38 and the bypass valve 37 can be maintained even if the driving force varies to some extent in the first throttle state and the second throttle state. Therefore, since the highly accurate control of the lift amount of the first drive transmission pin 68 is not necessarily required, the control of the drive unit 33 can be simplified. Further, the dimensional accuracy required for each member can be relaxed.

In addition, in the first embodiment, in each of the first throttle state and the second throttle state, the first out orifice 70 and the second out orifice 75, which are throttle holes provided in a specific member, The road area is specified. As described above, if the flow path area is not defined by the gap between the plurality of members, the variation in the flow rate of the fuel flowing through the outflow flow path in each throttled state is further reduced.

Furthermore, in the switching valve mechanism 36 of the first embodiment, a valve opening gap 82 is formed as a space that allows a stroke in the valve opening direction of the three-way valve 38. Therefore, the fuel injection device 100 can displace the three-way valve 38 and the bypass valve 37 in the valve opening direction at different timings by a simple linear operation of the single drive unit 33.

In addition, according to the first embodiment, one end portion of the three-way valve spring 56 is placed on the first placement portion 55. Therefore, the elastic force of the three-way valve spring 56 does not urge the bypass valve 37 in the valve opening direction. Therefore, even if the spring constant of the orifice spring 59 is kept low, the bypass valve 37 can maintain the closed state when the valve is opened at low speed. According to the above, the drive energy consumed by the drive unit 33 for opening the bypass valve 37 can be reduced.

In the first embodiment, the three-way valve 38 is separated from the in-orifice body 35, and the in-orifice body 35 abuts on the lower end side abutting portion 74 of the bypass valve 37 by pressing by the orifice spring 59. The service passage 57 is opened. When the three-way valve 38 is in the first lift amount position or the second lift amount position, the state in which the three-way valve 38 is in contact with the recess 79 of the in-orifice body 35 is maintained by the pressure by the orifice spring 59. Thus, the in-orifice passage 57 is closed. The closed state can be maintained by maintaining the contact state between the three-way valve 38 and the recess 79 by the orifice spring 59. In the present embodiment, the position of the second lift amount is also referred to as a second lift position.

Furthermore, in the first embodiment, the flow area of the first in-orifice 80 is set smaller than the flow area of the second in-orifice 48 that flows into the pressure control chamber 43 from the high-pressure flow path 40. As a result, the fuel flowing into the bypass valve chamber 44 at the valve closing position can be restricted by the first in orifice 80. This facilitates control of the valve closing speed.

In the first embodiment, the high-pressure channel 40 corresponds to a supply channel, the first placement portion 55 corresponds to a recess, and the nozzle needle 32 corresponds to a valve member. The three-way valve 38 corresponds to the first valve body, the bypass valve 37 corresponds to the second valve body, the in-orifice body 35 corresponds to the third valve body, and the orifice spring 59 corresponds to the biasing member. . Further, the recess 79 corresponds to the first contact portion, the upper end side contact portion 73 corresponds to the second contact portion, and the lower end side contact portion 74 corresponds to the third contact portion. Further, the bypass valve chamber 44 and the three-way valve chamber 45 correspond to a switching chamber, and the in-orifice passage 57 corresponds to a communication passage.

(Other embodiments)
The preferred embodiments of the present disclosure have been described above. However, the present disclosure is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present disclosure.

The structure of the above-described embodiment is merely an example, and the scope of the present disclosure is not limited to the scope of these descriptions. The scope of the present disclosure is indicated by the description of the scope of claims, and further includes meanings equivalent to the description of the scope of claims and all modifications within the scope.

In the first embodiment described above, the channel area of the outflow channel in each throttled state is defined by each orifice formed in a hole shape. However, the channel area of the outflow channel in each throttled state may be defined by a gap provided between the two members.

In the first embodiment described above, the present invention is applied to the fuel injection device 100 that injects light oil as fuel, but it can also be applied to a fuel injection device that injects fuel other than light oil, for example, liquefied gas fuel such as dimethyl ether.

Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments and structures. The present disclosure includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, as well as other combinations and forms including only one element, more or less, are within the scope and spirit of the present disclosure.

Claims

A fuel injection device (100) for injecting fuel from a nozzle hole (30) toward a combustion chamber (22),
The nozzle hole, a supply channel (40) for supplying fuel to the nozzle hole, a pressure control chamber (43) into which a part of the fuel flowing through the supply channel flows, and the fuel in the pressure control chamber to the low pressure side A valve body (31) formed with an outflow channel (42) for allowing outflow;
A valve member (32) for opening and closing the nozzle hole by relative displacement with respect to the valve body due to a change in fuel pressure in the pressure control chamber;
A switching valve mechanism (36) having a first valve body (38) and a second valve body (37) disposed in the outflow passage, and for switching a flow passage area of the outflow passage;
The first valve body is lifted by applying a driving force to the first valve body in order to switch the flow passage area by the switching valve mechanism, and the lift amount of the first valve body is set to a first amount. A drive unit (33) for controlling the lift amount or a second lift amount larger than the first lift amount;
A communication passage (57) that connects the switching chamber (44, 45) in which the first valve body and the second valve body are accommodated and the supply flow path is formed, and the lift of the first valve body A third valve body (35) for opening and closing the communication passage according to the amount,
The switching valve mechanism is
When the first valve body is not lifted, the first valve body is seated on the valve body to close the outflow channel,
When the first valve body is in the position of the first lift amount, the first valve body is separated from the valve body, and the first valve body is a first contact portion of the third valve body. (79), and the second valve body is not separated from the valve body, thereby restricting the outflow passage to the first throttle state,
When the first valve body is in the second lift amount, the first valve body is separated from the valve body, and the first abutting portion is pressed by the first valve body to The three valve bodies are displaced, and the second valve body is in a position separated from the valve body by the pressing of the second valve body to the second contact portion (73) by the first valve body. Limiting the outflow channel to a second throttled state having a different channel area from the first throttled state,
The third valve body is
When the first valve body is not lifted, it is separated from the first valve body to open the communication passage,
A fuel injection device that contacts the first valve body and closes the communication passage when the first valve body is in the position of the first lift amount or the second lift amount.
2. The fuel injection device according to claim 1, wherein the second throttle state is a throttle state having a larger flow path area than the first throttle state.
The fuel injection device according to claim 1 or 2, wherein a flow passage area of the communication passage is smaller than a flow passage area when flowing from the supply flow passage into the pressure control chamber.
A biasing member (59) for biasing the third valve body toward the first valve body;
When the first valve body is not lifted, the first valve body is separated from the third valve body, and the third valve body is moved to the second valve body by pressing by the urging member. The third abutment portion to open the communication passage,
When the first valve body is at the position of the first lift amount or the position of the second lift amount, the first valve body is the first of the third valve body by pressing by the biasing member. The fuel injection device according to any one of claims 1 to 3, wherein a state of contact with the contact portion is maintained and the communication passage is closed.