JP2017089438A - Fuel injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection device capable of preventing malfunction caused by deposit even with a simple constitution.SOLUTION: A fuel injection device 100 includes a control body 40 and a nozzle needle 60. The control body 40 is provided with an injection hole 44, a pressure control chamber 53, and an armature chamber 54. The armature chamber 54 accommodates an armature 33 for controlling outflow of a liquefied gas fuel from the pressure control chamber 53 to the armature chamber 54. The nozzle needle 60 is reciprocated and displaced with pressure fluctuations in the pressure control chamber 53 for opening and closing the injection hole 44. The fuel injection device 100 discharges part of the supplied liquefied gas fuel to a return flow channel. A pressure maintaining portion 80 is disposed midway through a low-pressure fuel passage 51b for discharging the liquefied gas fuel from the armature chamber 54 to the return flow channel. The pressure maintaining portion 80 maintains a pressure in the armature chamber 54 at not less than a saturated vapor pressure of the liquefied gas fuel.SELECTED DRAWING: Figure 2

Description

  The disclosure according to this specification relates to a fuel injection device that injects liquefied gas fuel from an injection hole.

  In general, liquefied gas fuel has a lower viscosity than liquid fuel such as light oil, and therefore contains an additive for ensuring lubricating performance. However, the additive contained in the liquefied gas fuel is deposited by evaporation of the liquefied gas fuel. For example, in the pressure release chamber of the fuel injection device, if the deposited additive residue adheres to the armature as a deposit, the armature will malfunction.

  For this reason, the fuel injection system disclosed in Patent Document 1 is provided with a pressure pump that pumps liquid liquefied gas fuel to the fuel injector separately from an injection pump that pressurizes liquefied gas fuel and supplies the fuel gas to the fuel injector. ing. The liquefied gas fuel pumped by the pressure pump dissolves the deposit deposited in the pressure release chamber and pushes it toward the return flow path. In this way, the fuel injection system of Patent Document 1 can clean the deposited deposit with liquefied gas fuel.

JP2015-90123A

  However, in Patent Document 1, the configuration of the fuel injection system is complicated due to the addition of a pumping pump or the like for removing the generated deposit. In addition, the fuel injection system of Patent Document 1 is configured to clean the deposit once deposited, and cannot prevent the additive deposition itself from the liquefied gas fuel. Therefore, there remains a possibility that the residue of the deposited additive adheres to the structure of the fuel injection device as a deposit and causes malfunction of the fuel injection device.

  The present disclosure has been made in view of such problems, and an object of the present disclosure is to provide a fuel injection device that can prevent a malfunction due to deposit even with a simple configuration.

  In order to achieve the above object, according to a first aspect disclosed, a liquefied gas fuel supplied through a fuel flow path (15) is injected from an injection hole (44), and a part of the supplied liquefied gas fuel is returned. A fuel injection device that discharges to a flow path (16), a nozzle, a pressure control chamber (53) into which liquefied gas fuel supplied through the fuel flow path flows, and a fuel from which liquefied gas fuel in the pressure control chamber flows out A valve body (40) forming an outflow chamber (54), a valve body (60) accommodated in the valve body and reciprocally displaced by pressure fluctuations in the pressure control chamber, thereby opening and closing the nozzle hole; and fuel A control member (33) which is accommodated in the outflow chamber and controls the outflow of the liquefied gas fuel from the pressure control chamber to the fuel outflow chamber to change the pressure of the pressure control chamber; and from the fuel outflow chamber to the return flow path Discharge passage (51b) for discharging liquefied gas fuel Provided in the middle of 251b), is a pressure maintaining unit for maintaining the pressure of the fuel outlet chamber on the saturated vapor pressure of the liquefied gas fuel and (80,281), a fuel injection device comprising a.

  According to this aspect, the pressure in the fuel outflow chamber is maintained at or above the saturated vapor pressure of the liquefied gas fuel by the pressure maintaining unit. Therefore, evaporation of the liquefied gas fuel in the fuel outflow chamber is suppressed, and the fuel outflow chamber is maintained in a state of being filled with the liquefied scum fuel that remains liquid. According to the above, precipitation of the additive from the liquefied gas fuel is prevented. As a result, it is difficult for the residue of the additive to adhere to the control member as a deposit. Therefore, it is possible to prevent malfunction of the control member due to the deposit by a simple configuration in which the pressure maintaining unit is provided.

  Note that the reference numbers in the parentheses merely show an example of a correspondence relationship with a specific configuration in an embodiment described later, and do not limit the technical scope at all.

It is a figure showing the whole fuel supply system composition to which the fuel injection device by a first embodiment is applied. It is a longitudinal section showing a fuel injection device by a first embodiment. It is a longitudinal cross-sectional view which shows the fuel-injection apparatus by 2nd embodiment.

  Hereinafter, a plurality of embodiments of the present disclosure will be described based on the drawings. In addition, the overlapping description may be abbreviate | omitted by attaching | subjecting the same code | symbol to the corresponding component in each embodiment. When only a part of the configuration is described in each embodiment, the configuration of the other embodiment described above can be applied to the other part of the configuration. Moreover, not only the combination of the configurations explicitly described in the description of each embodiment, but also the configuration of a plurality of embodiments can be partially combined even if they are not explicitly described, as long as there is no problem in the combination. And the combination where the structure described in several embodiment and the modification is not specified shall also be disclosed by the following description.

(First embodiment)
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 a 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 12, a high-pressure fuel 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 an electric pump that pumps the fuel stored in the liquefied gas fuel tank 11 to the high-pressure fuel pump 13. The feed pump 12 is connected to the high-pressure fuel pump 13 by a fuel pipe 12a. The liquefied gas fuel tank 11 stores dimethyl ether (hereinafter referred to as DME fuel) which is a kind of liquefied gas fuel. The DME fuel is filled in the liquefied gas fuel tank 11 while being pressurized at a pressure equal to or higher than the saturated vapor pressure. The DME fuel contains additives such as fatty acids, for example, in order to improve lubrication of the sliding parts of the pumps 12 and 13 and the fuel injection device 100.

  The high-pressure fuel pump 13 is driven by the output shaft of the diesel engine. The high-pressure fuel pump 13 is connected to the common rail 14 by a fuel pipe 13a. The high-pressure fuel pump 13 further boosts the pressure of the DME fuel supplied by the feed pump 12 and supplies it to the common rail 14.

  The common rail 14 is connected to each fuel injection device 100 via a fuel pipe 14a. The fuel pipe 14 a forms a fuel flow path 15 that supplies DME fuel to each fuel injection device 100. The common rail 14 temporarily stores high-pressure DME fuel supplied from the high-pressure fuel pump 13 and distributes the fuel to each fuel injection device 100 while maintaining the pressure. The surplus DME fuel in the common rail 14 is discharged to the surplus fuel pipe 14b while being decompressed. The surplus fuel pipe 14 b forms a return flow path 16 that recirculates surplus fuel to the liquefied gas fuel tank 11.

  The engine control device 17 is configured to include a processor or RAM as an arithmetic circuit, a microcomputer or a microcontroller including a rewritable nonvolatile storage medium, and a drive circuit that drives each fuel injection device 100. The engine control device 17 controls the operation of each fuel injection device 100 according to the operating state of the diesel engine 20.

  A fuel pipe 14 a and a return pipe 14 c are connected to the fuel injection device 100. 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 the DME fuel supplied through the fuel flow path 15 into the combustion chamber 22 from the plurality of injection holes 44. The fuel injection device 100 includes a valve mechanism that controls injection of DME fuel from the injection hole 44. The valve mechanism includes a pressure control valve 35 (see FIG. 2 and the like) that operates based on a drive signal from the engine control device 17, and a main valve portion 50 that opens and closes the injection hole 44. The fuel injection device 100 uses a part of the DME fuel supplied through the fuel flow path 15 in order to open and close the injection hole 44. The DME fuel used for opening and closing the nozzle hole 44 is discharged to the return pipe 14c while being decompressed. The return pipe 14 c and the surplus fuel pipe 14 b form a return flow path 16 for returning DME fuel that has not been used for combustion to the liquefied gas fuel tank 11.

  As shown in FIG. 2, the fuel injection device 100 includes a control body 40, a nozzle needle 60, an armature 33, a drive unit 30, a return spring 66, and a floating plate 70. The control body 40 is formed with an injection hole 44, a high pressure fuel passage 51a, an inflow passage 52a, an outflow passage 52b, a supply passage 52c, a pressure control chamber 53, an armature chamber 54, and a low pressure fuel passage 51b.

  As shown in FIGS. 1 and 2, the injection hole 44 is formed at the distal end in the insertion direction in the control body 40 inserted into the combustion chamber 22. The tip is formed in a conical or hemispherical shape. A plurality of nozzle holes 44 are provided radially from the inside to the outside of the control body 40. High-pressure DME fuel is injected into the combustion chamber 22 through the injection hole 44. By passing through the nozzle hole 44, the DME fuel is vaporized and easily mixed with air.

  The high-pressure fuel passage 51 a is connected to the fuel passage 15. The high pressure fuel passage 51a distributes the high pressure DME fuel supplied from the common rail 14 to the inflow passage 52a and the supply passage 52c. The inflow passage 52a allows the high pressure fuel passage 51a and the pressure control chamber 53 to communicate with each other. The inflow passage 52 a allows high-pressure DME fuel to flow into the pressure control chamber 53. The outflow passage 52b allows the pressure control chamber 53 and the armature chamber 54 to communicate with each other. The outflow passage 52 b allows the DME fuel in the pressure control chamber 53 to flow out to the armature chamber 54. The supply passage 52 c allows high-pressure DME fuel supplied through the high-pressure fuel passage 51 a to flow to the injection hole 44.

  The pressure control chamber 53 is provided inside the control body 40 on the opposite side of the nozzle hole 44 with the nozzle needle 60 interposed therebetween. High-pressure DME fuel supplied through the fuel flow path 15 and the inflow passage 52a flows into the pressure control chamber 53. The pressure of the DME fuel in the pressure control chamber 53 varies depending on the inflow of high-pressure DME fuel from the inflow passage 52a and the outflow of DME fuel into the armature chamber 54 through the outflow passage 52b. The pressure control chamber 53 reciprocates the nozzle needle 60 by utilizing the pressure fluctuation of the DME fuel.

  DME fuel flows out from the pressure control chamber 53 into the armature chamber 54 through the outflow passage 52b. The armature chamber 54 accommodates the armature 33 so as to be capable of reciprocating displacement. The pressure of the DME fuel in the armature chamber 54 is lower than the pressure of the DME fuel in the pressure control chamber 53.

  The low pressure fuel passage 51 b is connected to the armature chamber 54 and the return passage 16. The low pressure fuel passage 51 b extends along the high pressure fuel passage 51 a in the control body 40. The low pressure fuel passage 51 b discharges the DME fuel in the armature chamber 54 to the return passage 16. The pressure of the DME fuel flowing through the low-pressure fuel passage 51 b is lower than the pressure of the DME fuel in the armature chamber 54.

  The control body 40 includes a nozzle body 41, a cylinder 56, an orifice plate 46, a holder 48, and the like formed of a metal material. The nozzle body 41, the orifice plate 46, and the holder 48 are arranged in this order from the distal end side in the direction of insertion into the head member 21 (see FIG. 1).

  The nozzle body 41 is a bottomed cylindrical member. The nozzle body 41 has a nozzle hole 44 and a supply passage 52c. The nozzle body 41 has a nozzle needle housing chamber 43 and a seat portion 45. The nozzle needle storage chamber 43 is formed in a cylindrical hole shape, and stores the nozzle needle 60 and the cylinder 56. The nozzle needle storage chamber 43 defines a supply passage 52 c together with the cylinder 56. The seat portion 45 is formed in a conical shape inside the tip portion and faces the supply passage 52c.

  The cylinder 56 is formed in a cylindrical shape. The cylinder 56 defines the pressure control chamber 53 together with the orifice plate 46 and the nozzle needle 60. The cylinder 56 is disposed on the inner peripheral side of the nozzle body 41 so as to be coaxial with the nozzle body 41.

  The orifice plate 46 is formed in a disc shape. In the orifice plate 46, an inflow passage 52a and an outflow passage 52b are formed. The orifice plate 46 has a control sheet portion 46a. The control sheet portion 46a is formed so as to surround the opening of the outflow passage 52b in the top surface of the orifice plate 46 facing the holder 48 side. The control seat portion 46 a forms a pressure control valve 35 together with the armature 33.

  The holder 48 is formed in a cylindrical shape. The holder 48 is formed with two vertical holes extending along the axial direction. Each vertical hole forms a high-pressure fuel passage 51a and a low-pressure fuel passage 51b. The holder 48 accommodates the drive unit 30.

  The nozzle needle 60 is formed in a cylindrical shape as a whole by a metal material. The nozzle needle 60 is accommodated in the nozzle body 41. One end of the nozzle needle 60 is inserted into the cylinder 56. The nozzle needle 60 can reciprocate in the axial direction along a support surface 41 a formed on the inner peripheral wall of the nozzle body 41.

  The nozzle needle 60 has a valve pressure receiving surface 61 and a face portion 65. The nozzle needle 60 is reciprocally displaced along the axial direction of the nozzle body 41 due to a change in the fuel pressure in the pressure control chamber 53 received by the valve pressure receiving surface 61, so that the face portion 65 is seated on the seat portion 45. The face portion 65 forms a main valve portion 50 that opens and closes the nozzle hole 44 together with the seat portion 45.

  The armature 33 is a two-stage cylindrical member formed of a metal material that is a ferromagnetic material. The armature 33 is accommodated in the armature chamber 54 and can be reciprocally displaced in the armature chamber 54. The armature 33 varies the pressure in the pressure control chamber 53 by controlling the outflow of DME fuel from the pressure control chamber 53 to the armature chamber 54. The armature 33 has a suction part 33a and a control face part 33b. The suction part 33a is formed in a circular plate shape. The suction unit 33 a is sucked toward the drive unit 30 by the magnetic force generated by the drive unit 30. The control face portion 33b is formed at the tip of a cylindrical portion that protrudes from the center of the suction portion 33a toward the opening of the outflow passage 52b. The control face portion 33 b is pressed against the control sheet portion 46 a by the displacement of the armature 33, and can close the opening of the outflow passage 52 b that faces the armature chamber 54.

  The drive unit 30 is connected to the armature 33 and drives the armature 33. The drive unit 30 includes a solenoid 31a, a magnetic pole face plate 31b, and a spring 31c. The solenoid 31a is a coil wound in a cylindrical shape. A pulsed drive signal is supplied from the engine control device 17 to the solenoid 31a. The solenoid 31a generates a magnetic field that circulates along the axial direction by supplying a drive signal. The magnetic pole surface plate 31b is a circular plate-like member made of a magnetic material. The magnetic pole surface plate 31b faces the suction portion 33a. The magnetic pole face plate 31b is magnetized in the magnetic field generated by the solenoid 31a, and attracts the attracting part 33a by magnetic force. The spring 31c is a coil spring in which a metal wire is wound spirally. The spring 31c biases the armature 33 in a direction in which the armature 33 is separated from the magnetic pole face plate 31b.

  When the power supply from the engine control device 17 is not supplied, the above drive unit 30 seats the control face portion 33b on the control seat portion 46a by the urging force of the spring 31c. As a result, the pressure control valve 35 is in a closed state where communication between the pressure control chamber and the fuel outflow chamber is blocked. On the other hand, when power is supplied from the engine control device 17, the drive unit 30 sucks the armature 33 and separates the control face unit 33b from the control seat unit 46a. As a result, the pressure control valve 35 enters an open state in which the pressure control chamber 53 and the armature chamber 54 are in communication. As described above, the drive unit 30 opens and closes the pressure control valve 35 by reciprocating the armature 33 under the control of the engine control device 17. As a result, the outflow of DME fuel from the pressure control chamber 53 to the armature chamber 54 is controlled by the pressure control valve 35.

  The return spring 66 is a coil spring in which a metal wire is wound spirally. The return spring 66 urges the nozzle needle 60 toward the nozzle hole 44 to seat the face portion 65 on the seat portion 45.

  The floating plate 70 is formed in a disk shape from a metal material. The floating plate 70 is disposed in the pressure control chamber 53 so as to be reciprocally displaced along the axial direction of the nozzle body 41. The floating plate 70 is biased toward the orifice plate 46 by a spring 72. A first out orifice 71 is formed in the floating plate 70. The first out orifice 71 is a through hole that penetrates the floating plate 70 in the plate thickness direction. The channel area of the first out orifice 71 is defined to be narrower than the channel area of the outflow passage 52b. The first out orifice 71 allows the flow of DME fuel from the pressure control chamber 53 to the outflow passage 52b and the flow rate of the DME fuel flowing out into the outflow passage 52b when the floating plate 70 is in close contact with the orifice plate 46. Limit.

  In the fuel injection device 100 described above, when the pressure control valve 35 is opened, the DME fuel in the pressure control chamber 53 flows out to the armature chamber 54 through the first out orifice 71 and the outflow passage 52b. As a result, the fuel pressure in the pressure control chamber 53 decreases, and the nozzle needle 60 moves to the pressure control chamber 53 side to open the nozzle hole 44. When the communication between the pressure control chamber 53 and the armature chamber 54 is cut off by closing the pressure control valve 35, the DME fuel supplied through the inflow passage 52a flows into the pressure control chamber 53 while pushing down the floating plate 70. To do. As a result, the fuel pressure in the pressure control chamber 53 is restored, and the nozzle needle 60 quickly moves toward the seat portion 45 to close the nozzle hole 44.

  Next, the details of the second out orifice 81 provided in the control body 40 will be described. The second out orifice 81 functions as a pressure maintaining unit 80 that maintains the pressure in the armature chamber 54. The pressure maintaining unit 80 is configured to maintain the pressure of the DME fuel filling the armature chamber 54 at or above the saturated vapor pressure of the DME fuel in both the valve closing period and the valve opening period of the pressure control valve 35.

  The saturated vapor pressure of DME fuel increases gradually as the temperature of DME increases. Therefore, it is desirable that the pressure maintaining unit 80 is set based on the maximum temperature assumed to be used in the fuel injection device 100. The maximum operating temperature of the fuel injection device 100 is set in relation to the temperature environment assumed to be used in a vehicle equipped with the diesel engine 20 and the maximum ambient temperature in the engine room assumed in the temperature environment. The

  The second out orifice 81 is configured in the middle of the low pressure fuel passage 51b. In the first embodiment, the upstream end of the low pressure fuel passage 51b connected to the armature chamber 54, that is, the low pressure fuel. It is provided at the entrance of the passage 51b. The second out orifice 81 is configured to narrow the flow passage area of the flow passage through which the DME fuel flows smaller than the flow passage area of the low pressure fuel passage 51b. The second out orifice 81 restricts the discharge flow rate of the DME fuel discharged from the armature chamber 54 to the low pressure fuel passage 51b. The flow area of the second out orifice 81 is defined to be narrower than the flow area of the first out orifice 71. Specifically, the channel area of the second out orifice 81 is about half of the channel area of the first out orifice 71.

  According to such correlation between the flow path areas, the flow rate of DME fuel flowing out from the armature chamber 54 during the valve opening period of the pressure control valve 35 is suppressed to be less than the flow rate of DME fuel flowing into the armature chamber 54. Is done. Therefore, when the pressure control valve 35 is closed, the fuel pressure in the armature chamber 54 is maintained high. As a result, even after the pressure control valve 35 is closed, the fuel pressure in the armature chamber 54 is maintained to be equal to or higher than the saturated vapor pressure of the DME fuel even in a state where the outflow of DME fuel from the armature chamber 54 continues.

  In addition, the correlation between the respective flow passage areas described above is set so that the locally decreased fuel pressure can be maintained at or above the saturated vapor pressure even when the fuel pressure locally decreases in the armature chamber 54. . More specifically, when the pressure control valve 35 starts to open, that is, immediately after the control face portion 33b is separated from the control seat portion 46a, the DME fuel flowing into the armature chamber 54 from the outflow passage 52b passes through these at high speed. Circulate at. Therefore, the fuel pressure between the control seat part 46a and the control face part 33b falls locally. Even in such a case, the fuel pressure between the control seat portion 46a and the control face portion 33b is maintained at or above the saturated vapor pressure of the DME fuel.

  As described so far, the pressure in the armature chamber 54 in the first embodiment is maintained at or above the saturated vapor pressure of the DME fuel by the second out orifice 81 functioning as the pressure maintaining unit 80. Therefore, the evaporation of the DME fuel in the armature chamber 54 is suppressed, and the armature chamber 54 can be maintained in a state where it is filled with the DME fuel that remains liquid. According to the above, since precipitation of the additive from the DME fuel is prevented, a situation in which the residue of the additive adheres to the armature 33 as a deposit is less likely to occur. Therefore, it is possible to prevent the armature 33 from malfunctioning due to the deposit by a simple configuration in which the pressure maintaining unit 80 is provided.

  In addition, in the first embodiment, the discharge flow rate of the DME fuel to the return flow path 16 is limited by the second out orifice 81. Therefore, the pressure of the armature chamber 54 on the upstream side of the second out orifice 81 can be maintained high. In addition, since the second out orifice 81 has a simple configuration that reduces the flow path area, it is difficult to complicate the configuration of the fuel injection device 100. Therefore, the second out orifice 81 of the first embodiment is suitable as the pressure maintaining unit 80 that maintains the pressure in the armature chamber 54 at or above the saturated vapor pressure of the DME fuel.

  Further, according to the first embodiment, the flow rate of the DME fuel flowing out from the pressure control chamber 53 to the armature chamber 54 is limited by the upstream first out orifice 71 provided separately from the second out orifice 81. . Therefore, immediately after the pressure control valve 35 is opened, the flow rate of the DME fuel flowing between the control seat portion 46a and the control face portion 33b is suppressed, so that the pressure drop that occurs between them can also be suppressed. According to the above, even if the pressure between the control seat portion 46a and the control face portion 33b is locally reduced, the pressure in the gap portion can be maintained at or above the saturated vapor pressure of DME fuel. According to the above, since local evaporation of the DME fuel in the armature chamber 54 can also be suppressed, malfunction of the armature 33 due to deposit can be prevented more reliably.

  Furthermore, in the first embodiment, the flow area of the second out orifice 81 is narrower than the flow area of the first out orifice 71. Therefore, the amount of DME fuel flowing into the armature chamber 54 during the valve opening period of the pressure control valve 35 can be maintained higher than the amount of DME fuel discharged from the armature chamber 54. Therefore, the pressure in the armature chamber 54 can be determined by the flow rate ratio between the first out orifice 71 and the second out orifice 81. According to the above, the fuel pressure in the armature chamber 54 is maintained to be equal to or higher than the saturated vapor pressure of the DME fuel throughout the valve opening period of the pressure control valve 35. Therefore, precipitation of the additive from the DME fuel can be prevented.

  In addition, in the first embodiment, since the flow of DME fuel into the armature chamber 54 can be continued until just before the pressure control valve 35 is closed, the fuel pressure in the armature chamber 54 is high when the pressure control valve 35 is closed. Become. Therefore, even when the discharge of DME fuel from the armature chamber 54 is continued during the valve closing period of the pressure control valve 35, the armature chamber 54 can maintain a pressure that does not fall below the saturated vapor pressure of the DME fuel. Therefore, precipitation of the additive from the DME fuel can be prevented.

  In the first embodiment, a second out orifice 81 as the pressure maintaining unit 80 is provided in the holder 48. As described above, the pressure maintaining unit 80 embedded in the configuration of the control body 40 is less affected by the external environment, and can stably exhibit the function of maintaining the pressure in the armature chamber 54. In addition, since the increase in the number of parts of the fuel injection device 100 is also minimized, the fuel injection device 100 can easily maintain a simple configuration.

  In the first embodiment, the armature 33 corresponds to a “control member”, the control body 40 corresponds to a “valve body”, the low pressure fuel passage 51b corresponds to a “discharge passage”, and the armature chamber 54 corresponds to a “fuel”. Corresponds to the “outflow chamber”. The nozzle needle 60 corresponds to a “valve element”, the first out orifice 71 corresponds to an “upstream orifice portion”, and the second out orifice 81 corresponds to a “downstream orifice portion”.

(Second embodiment)
The second embodiment shown in FIG. 3 is a modification of the first embodiment. The fuel injection device 200 according to the second embodiment is provided with a discharge control valve 280. On the other hand, a configuration corresponding to the second out orifice 81 (see FIG. 2) is omitted from the fuel injection device 200.

  The discharge control valve 280 has a valve housing 282 and a pressure regulating valve portion 281. The valve housing 282 is a housing formed of a metal material and accommodates the pressure regulating valve portion 281. The valve housing 282 is assembled to the holder 48 and is a part of the control body 40. The valve housing 282 forms a low-pressure fuel passage 251 b together with the holder 48. The valve housing 282 is connected to the return pipe 14c (see FIG. 1), and distributes the DME fuel discharged from the armature chamber 54 to the return flow path 16 (see FIG. 1).

  The pressure regulating valve portion 281 is disposed in the valve housing 282. The pressure regulating valve portion 281 is provided at the downstream end of the low pressure fuel passage 251b connected to the return flow passage 16 (see FIG. 1), that is, at the outlet portion of the low pressure fuel passage 251b. The pressure regulating valve portion 281 is a one-way valve that allows only the flow of DME fuel from the low-pressure fuel passage 251b to the return flow path 16, and depressurizes the DME fuel that flows through the low-pressure fuel path 251b to the return flow path 16. Circulate. The pressure regulating valve portion 281 is closed due to a pressure drop in the low pressure fuel passage 251 on the upstream side, and prevents a pressure drop in the low pressure fuel passage 251. By such an operation, the pressure regulating valve unit 281 maintains the pressure in the upstream low-pressure fuel passage 251b and hence the armature chamber 54 at or above the saturated vapor pressure of DME fuel.

  Even in the second embodiment described so far, the same effects as in the first embodiment can be obtained, and the pressure in the armature chamber 54 is maintained to be equal to or higher than the saturated vapor pressure of the DME fuel. Therefore, precipitation of the additive from the DME fuel is prevented, and the malfunction of the armature 33 due to the deposit is less likely to occur. In the second embodiment, the low pressure fuel passage 251b corresponds to a “discharge passage”, and the pressure regulating valve portion 281 corresponds to a “pressure maintaining portion”.

(Other embodiments)
Although a plurality of embodiments have been described above, the present disclosure is not construed as being limited to the above-described embodiments, and can be applied to various embodiments and combinations without departing from the scope of the present disclosure. it can.

  In the first embodiment, the second out orifice 81 is formed at the end closest to the armature chamber 54 in the low pressure fuel passage 51b. However, the position of the second out orifice can be changed as appropriate. For example, the second out orifice may be provided in the middle of the low pressure fuel passage. Furthermore, the 2nd out orifice may be provided in the edge part nearest to return piping among low pressure fuel passages like the pressure regulation valve part 281 of said 2nd embodiment.

  Further, the flow path area of the second out orifice can be changed as appropriate, and may be defined to be approximately the same as the flow area of the first out orifice, for example. Furthermore, the flow path shape of the throttle portion formed by the second out orifice is not limited to the cylindrical shape as described above, and can be changed as appropriate.

  In the above embodiment, the floating plate 70 that controls the outflow of DME fuel from the pressure control chamber 53 to the armature chamber 54 is provided, but the floating plate and the first out orifice may be omitted. The floating plate may be provided with a plurality of first out orifices. Similarly, there may be a plurality of second out orifices. In such a case, it is desirable that the sum of the flow path areas of the plurality of first out orifices is larger than the sum of the flow path areas of the second out orifices.

  In the above embodiment, the DME fuel is introduced as an example of the liquefied gas fuel. However, the characteristic configuration of the present disclosure can also be applied to a fuel injection device that injects a liquefied gas fuel other than the DME fuel. For example, the characteristic configuration of the present disclosure can be applied to a fuel injection device that injects Liquefied Petroleum Gas (LPG). Furthermore, the characteristic configuration of the present disclosure can also be applied to a fuel injection device that can switch between DME fuel and light oil that is liquid fuel.

DESCRIPTION OF SYMBOLS 15 Fuel flow path, 16 Return flow path, 33 Armature (control member), 40 Control body (valve body), 44 Injection hole, 46a Control seat part, 51b, 251b Low pressure fuel path (discharge path), 53 Pressure control chamber, 54 Armature chamber (fuel outflow chamber), 60 Nozzle needle (valve element), 71 First out orifice (upstream orifice portion), 80 Pressure maintaining portion, 281 Pressure regulating valve portion (pressure maintaining portion), 81 Second out orifice ( (Downstream orifice part, orifice part), 100, 200 Fuel injection device

Claims (7)

A fuel injection device for injecting liquefied gas fuel supplied through a fuel flow path (15) from a nozzle hole (44) and discharging a part of the supplied liquefied gas fuel to a return flow path (16),
A valve forming the nozzle hole, a pressure control chamber (53) into which liquefied gas fuel supplied through the fuel flow path flows, and a fuel outflow chamber (54) from which the liquefied gas fuel in the pressure control chamber flows out Body (40),
A valve body (60) which is accommodated in the valve body and opens and closes the nozzle hole by reciprocating displacement due to pressure fluctuations in the pressure control chamber;
A control member (33) housed in the fuel outflow chamber and configured to change the pressure of the pressure control chamber by controlling the outflow of liquefied gas fuel from the pressure control chamber to the fuel outflow chamber;
Pressure maintenance is provided in the middle of discharge passages (51b, 251b) for discharging liquefied gas fuel from the fuel outflow chamber to the return flow path, and maintains the pressure in the fuel outflow chamber above the saturated vapor pressure of liquefied gas fuel. Part (80, 281).   2. The fuel injection device according to claim 1, wherein the pressure maintaining unit includes an orifice part (81) for limiting a discharge flow rate of the liquefied gas fuel discharged from the fuel outflow chamber to the return flow path.   The upstream orifice part (71) which restrict | limits the flow volume of the liquefied gas fuel which flows out out of the said pressure control chamber to the said fuel outflow chamber separately from the downstream orifice part which is the said orifice part, The Claim 2 characterized by the above-mentioned. Fuel injection device.   4. The fuel injection device according to claim 3, wherein a flow passage area of the downstream orifice portion is narrower than a flow passage area of the upstream orifice portion.   The fuel injection device according to any one of claims 1 to 4, wherein the pressure maintaining unit is formed in the valve body. The control member switches between a state in which the pressure control chamber and the fuel outflow chamber communicate with each other and a state in which the communication between the pressure control chamber and the fuel outflow chamber is blocked,
The pressure maintaining unit maintains the pressure of the fuel outflow chamber at or above a saturated vapor pressure of liquefied gas fuel even in a state where the communication between the pressure control chamber and the fuel outflow chamber is blocked by the control member. The fuel injection device according to any one of 1 to 5. The valve body forms a control seat portion (46a) for seating the control member,
The control member blocks communication between the pressure control chamber and the fuel outflow chamber by being seated on the control seat portion.
The said pressure maintenance part maintains the pressure between the said control sheet part and the said control member which fell locally by the seating of the said control member from the said control sheet part more than the saturated vapor pressure of liquefied gas fuel. Item 7. The fuel injection device according to any one of Items 1 to 6.

Images