JP6919345B2 - Fuel injection device - Google Patents

Description

The disclosure by this specification relates to a fuel injection device that injects fuel from a injection hole.

Conventionally, a hydraulic servo type fuel injection device and a needle direct motion type fuel injection device are known. In a hydraulic servo type fuel injection device, an actuator drives a valve body that controls the inflow and outflow of fuel into the control chamber. When the control chamber is depressurized by the operation of the valve body, the needle is displaced in the valve opening direction to open the injection hole.

On the other hand, in the needle direct-acting fuel injection device, for example, as disclosed in Patent Document 1, the actuator directly displaces the needle. More specifically, the body of the fuel injection device of Patent Document 1 is divided into a coupler chamber and a control chamber. The coupler chamber and the control chamber are located on both sides of the coupler piston and are connected to each other by a fuel passage formed in the coupler piston. When the coupler piston is displaced by the operation of the actuator, the volume of the coupler chamber increases, while decompression occurs in the control chamber connected to the coupler chamber. As a result, the needle is displaced in the valve opening direction that opens the injection hole.

European Patent Application Publication No. 2960487

By the way, in the needle direct-acting type fuel injection device, the mode of displacement of the needle in the valve opening direction can be changed by controlling the mode of the extension operation of the actuator. However, the driving energy required for the displacement of the needle in the needle direct-acting type fuel injection device tends to be higher than that in the hydraulic servo type fuel injection device. Therefore, the inventors of the present disclosure make it possible to change the mode of displacement of the needle in the valve opening direction even in the fuel injection device of the hydraulic servo type as in the fuel injection device of the needle direct motion type. investigated.

An object of the present disclosure is to provide a fuel injection device capable of changing the displacement mode of a needle even in a valve opening operation in which a valve opening operation is performed by utilizing decompression of a control chamber due to a fuel outflow.

In order to achieve the above object, one aspect disclosed is the first chamber (21a), in which the injection hole (23) for injecting the fuel is formed and the fuel of the first pressure is supplied, which is lower than the first pressure. The second chamber (22) to which the fuel of the second pressure is supplied, the first chamber and the valve chamber (25) connectable to the second chamber are connected to the main body (20) provided inside and the valve chamber. A control chamber member (60) provided with a control chamber (27) and a needle (50) that is pressed in the direction of closing the injection hole by the fuel pressure of the control chamber and is displaced in the valve opening direction by depressurizing the control chamber. ), The actuator (31) that expands and contracts along the valve opening direction, and the actuator is contracted to cut off the connection between the second chamber and the valve chamber and connect the first chamber and the control chamber. A valve body (110) that connects the valve chamber and the second chamber by an extension operation, a piston end face (131) that faces the inner wall surface of the main body along the valve opening direction and partitions the valve chamber together with the inner wall surface, and an actuator. It includes a piston (120) to have a seat surface portion (128) forming a gap (GP) along the opening direction between the valve body in a state where the contracting piston is displaced by the extending action of the actuator When the valve body comes into contact with the seat surface, the piston end surface is separated from the inner wall surface to increase the volume of the valve chamber before the needle starts to be displaced in the valve opening direction due to the depressurization of the control chamber. , it is a fuel injection device you displacement with the valve body.

In this aspect, when the valve chamber and the second chamber are connected by the displacement of the valve body, the fuel in the control chamber connected to the valve chamber flows out to the second chamber through the valve chamber. Due to the decompression of the control chamber due to the fuel outflow to the second chamber, the needle starts to be displaced in the valve opening direction, and the volume of the control chamber is reduced. After that, when the pressure in the control chamber recovers as the volume decreases, the displacement speed of the needle in the valve closing direction decreases.

Here, if the volume of the control chamber is increased, it becomes difficult for the pressure in the control chamber to recover due to the displacement of the needle in the valve opening direction. Therefore, in this aspect, the piston in contact with the valve body is displaced in the expansion direction to increase the volume of the valve chamber by the extension operation of the actuator. If the valve chamber is connected to the control chamber and the volume of the valve chamber is increased before the needle starts to be displaced in the valve opening direction, the fuel injection device can expand or contract the volume of the valve chamber. , The timing at which the displacement speed of the needle decreases can be adjusted. Therefore, the fuel injection device can change the mode of displacement of the needle even in the operation of displacementing the needle in the valve opening direction by utilizing the decompression of the control chamber due to the fuel outflow.

The reference numbers in parentheses are merely examples of the correspondence with the specific configuration in the embodiment described later, and do not limit the technical scope at all.

It is a figure which shows the whole structure of the fuel supply system including a fuel injection device and a control device. It is a vertical sectional view of a fuel injection device. It is a vertical cross-sectional view which shows the detailed structure of a pressure control mechanism. It is a figure which shows the detail of the pressure control mechanism in a low speed valve opening mode. It is a figure which shows the detail of the pressure control mechanism in a high-speed valve opening mode. It is a figure which shows the detail of the pressure control mechanism in a high-speed valve opening mode. It is a figure which shows the detail of the pressure control mechanism in a valve closing period. It is a time chart which shows the detail of a high-speed valve opening mode. It is a figure which compares and shows the transition of the needle lift amount in a low speed valve opening mode, and the transition of a needle lift amount in a high speed valve opening mode. It is a figure which compares and shows the transition of the injection rate in the low-speed valve opening mode, and the transition of the injection rate in the high-speed valve opening mode.

As shown in FIG. 1, the fuel injection device 10 according to the embodiment of the present disclosure is used in the fuel supply system 1. The fuel injection device 10 supplies the fuel stored in the fuel tank 4 to each combustion chamber 2b of a diesel engine (hereinafter, “engine 2”) which is an internal combustion engine. The fuel supply system 1 includes a feed pump 5, a high-pressure fuel pump 6, a common rail 3, a control device 70, and the like together with a fuel injection device 10.

The feed pump 5 is, for example, a trochoidal electric pump. The feed pump 5 is built in the high pressure fuel pump 6. The feed pump 5 pumps light oil as fuel stored in the fuel tank 4 to the high-pressure fuel pump 6. The feed pump 5 may be separate from the high-pressure fuel pump 6 and may be arranged inside, for example, the fuel tank 4.

The high-pressure fuel pump 6 is, for example, a plunger type pump. The high-pressure fuel pump 6 is driven by the output shaft of the engine 2. The high-pressure fuel pump 6 is connected to the common rail 3 by a fuel pipe 6a. The high-pressure fuel pump 6 further boosts the fuel supplied by the feed pump 5 and supplies it to the common rail 3 as high-pressure fuel.

The common rail 3 is connected to a plurality of fuel injection devices 10 via a high-pressure fuel pipe 3b. The common rail 3 is connected to the fuel tank 4 via a surplus fuel pipe 8a. The common rail 3 temporarily stores the high-pressure fuel supplied from the high-pressure fuel pump 6 and distributes the high-pressure fuel to each fuel injection device 10 while maintaining the pressure. The common rail 3 is provided with a pressure sensor 3a and a pressure reducing valve 8. The pressure sensor 3a detects the fuel pressure stored in the common rail 3. When the value detected by the pressure sensor 3a is higher than the target pressure, the pressure reducing valve 8 discharges the surplus fuel to the surplus fuel pipe 8a.

The control device 70 is an electronic control unit including an ECU (Electronic Control Unit) 70a and an EDU (Electronic Driver Unit) 70b shown in FIGS. 1 and 2. The control device 70 constitutes the fuel injection system 90 together with the fuel injection device 10. The control device 70 is electrically connected to each fuel injection device 10. The control device 70 controls the injection of fuel by each fuel injection device 10 according to the operating state of the engine 2.

The ECU 70a includes an arithmetic circuit mainly composed of a microcomputer or a microcontroller. The arithmetic circuit includes a processor, RAM, and a rewritable non-volatile memory device. The EDU 70b applies a drive voltage to the drive unit 30 of the fuel injection device 10 based on the command signal input from the ECU 70a.

The ECU 70a is provided with an injection pressure acquisition unit 71 and a charge control unit 72. The injection pressure acquisition unit 71 and the charge control unit 72 may be a functional block constructed based on an injection control program, or may be a dedicated electric circuit unit formed by combining a plurality of integrated circuits, passive elements, and the like. good.

The injection pressure acquisition unit 71 acquires the injection pressure in the fuel injection device 10. The injection pressure may be detected at any point between the common rail 3 and the fuel injection device 10. For example, the injection pressure may be the fuel pressure acquired by the pressure sensor 3a. The injection pressure may be the value of the fuel pressure detected by the pressure sensor built in each fuel injection device 10.

The charge control unit 72 controls charging / discharging of the piezo actuator 31, which will be described later. The charge control unit 72 increases or decreases the magnitude of the drive energy input from the EDU 70b to the piezo actuator 31 by increasing or decreasing the value of the command signal output to the EDU 70b (hereinafter, “command value”). The charge control unit 72 can adjust the command value to be output to the EDU 70b based on the injection pressure acquired by the injection pressure acquisition unit 71.

The fuel injection device 10 is attached to the head member 2a in a state of being inserted into the insertion hole of the head member 2a forming the combustion chamber 2b. The fuel injection device 10 injects the high-pressure fuel supplied through the high-pressure fuel pipe 3b directly from the injection hole 23 toward the combustion chamber 2b. The fuel injection device 10 includes a valve structure that controls the injection of fuel from the injection hole 23. The fuel injection device 10 uses a part of the high-pressure fuel to open and close the injection hole 23. A part of the fuel supplied to the fuel injection device 10 is returned to the fuel tank 4 through the return pipe 8b and the surplus fuel pipe 8a.

As shown in FIGS. 2 and 3, the fuel injection device 10 includes a valve body 20, a nozzle needle 50, a needle cylinder 60, a drive unit 30, and a pressure control mechanism 100 having a control valve body 110 and a piston 120. ..

The valve body 20 is formed by combining a plurality of metal members such as an injector turbo day member 20a, a flow path forming member 20b, a valve body member 20c, a nozzle body member 20d, and a retaining nut 20e. Inside the valve body 20, a high-pressure fuel passage 21, a low-pressure fuel passage 22, a high-pressure chamber 21a, a valve chamber 25, and a control chamber 27 are provided. In addition, the valve body 20 is formed with an injection hole 23.

The high-pressure fuel passage 21 is formed in the injector turbo day member 20a, the flow path forming member 20b, and the valve body member 20c. The high-pressure fuel passage 21 is connected to the high-pressure fuel pipe 3b (see FIG. 1). The high-pressure fuel passage 21 supplies the high-pressure fuel supplied from the common rail 3 (see FIG. 1) to the high-pressure chamber 21a through the high-pressure fuel pipe 3b.

The low-pressure fuel passage 22 is formed in the flow path forming member 20b. The low-pressure fuel passage 22 is a passage through which the fuel supplied to the fuel injection device 10 flows out to the return pipe 8b (see FIG. 1). The low-pressure fuel passage 22 is connected to a pin accommodating hole 20f penetrating the center of the channel forming member 20b in the axial direction, and extends in an inclined posture with respect to the pin accommodating hole 20f. An out-orifice 22a is formed at the inlet of the low-pressure fuel passage 22 facing the pin accommodating hole 20f. The out orifice 22a limits the flow rate of fuel flowing out of the pin accommodating hole 20f into the low pressure fuel passage 22. The fuel supplied to the low-pressure fuel passage 22 by passing through the out orifice 22a has a lower pressure than the high-pressure fuel flowing through the high-pressure fuel passage 21.

The high-pressure chamber 21a is a space formed in a columnar shape on the nozzle body member 20d. The nozzle needle 50 and the needle cylinder 60 are housed in the high pressure chamber 21a. The high pressure chamber 21a is connected to the high pressure fuel passage 21. The high pressure chamber 21a is filled with high pressure fuel supplied through the high pressure fuel passage 21. The high-pressure chamber 21a distributes high-pressure fuel to the injection hole 23. The fuel pressure in the high pressure chamber 21a is the "first pressure", and the fuel pressure in the low pressure fuel passage 22 which is lower than the first pressure is the "second pressure".

The valve chamber 25 is filled with fuel. The valve chamber 25 can be connected to the high pressure chamber 21a and the low pressure fuel passage 22. The valve chamber 25 is located between the drive unit 30 and the control chamber 27. The valve chamber 25 is divided into upper and lower parts by the control valve body 110. In the valve chamber 25, the space formed between the pressure control mechanism 100 and the flow path forming member 20b is the upper valve chamber portion 25b. In the valve chamber 25, the space partitioned inside the pressure control mechanism 100 is the lower valve chamber portion 25a. The upper valve chamber portion 25b and the lower valve chamber portion 25a are connected to each other.

Fuel is supplied to the control chamber 27 through the valve chamber 25. The control chamber 27 is connected to the valve chamber 25. The control chamber 27 can be connected to the high pressure chamber 21a and the low pressure fuel passage 22 via the valve chamber 25, respectively. The control chamber 27 is filled with fuel. The control chamber 27 is a flat columnar space partitioned by the piston 120, the nozzle needle 50, and the needle cylinder 60. The control chamber 27 is located on the opposite side of the injection hole 23 with the nozzle needle 50 in between.

The injection hole 23 is formed at the tip end portion in the insertion direction in the valve body 20 inserted into the head member 2a (see FIG. 1). The injection hole 23 is exposed in the combustion chamber 2b (see FIG. 1). The tip of the valve body 20 is formed in a conical or hemispherical shape. A plurality of injection holes 23 are provided radially from the inside to the outside of the valve body 20. Each injection hole 23 injects high-pressure fuel toward the combustion chamber 2b. The high-pressure fuel is atomized by passing through the injection hole 23, and is in a state where it can be easily mixed with air.

The nozzle needle 50 is formed in a cylindrical shape by a metal material. The tip of the nozzle needle 50 on the injection hole 23 side is formed in a conical shape. The nozzle needle 50 is housed in the high-pressure chamber 21a, and receives a force from the high-pressure fuel in the high-pressure chamber 21a in the direction of opening the injection hole 23 (hereinafter, “valve opening direction”). The nozzle needle 50 is formed with a needle pressure receiving surface 51, a spring seat portion 53, and a needle sliding surface 54.

The needle pressure receiving surface 51 is a circular end surface of the nozzle needle 50 facing the control chamber 27. The needle pressure receiving surface 51 receives a force in the direction of closing the injection hole 23 (hereinafter, “valve closing direction”) from the fuel filled in the control chamber 27. The nozzle needle 50 is pressed in the valve closing direction by the fuel pressure of the control chamber 27. The nozzle needle 50 is displaced relative to the valve body 20 along the axial direction due to the fluctuation of the fuel pressure in the control chamber 27, and opens and closes the injection hole 23.

The spring seat portion 53 is provided on the nozzle needle 50 in a collar shape. A needle spring 52 is installed between the spring seat portion 53 and the needle cylinder 60 in a state of being compressed in the axial direction. The needle spring 52 is a coil spring formed in a cylindrical spiral shape. The needle spring 52 applies an urging force to the spring seat portion 53 in the direction of closing the injection hole 23.

The needle sliding surface 54 is a portion of the outer peripheral wall surface of the nozzle needle 50 that is internally fitted into the needle cylinder 60. The needle sliding surface 54 is slidably supported with respect to the needle cylinder 60. The needle sliding surface 54 forms an oil tightness between the control chamber 27 and the high pressure chamber 21a with the inner peripheral wall surface of the needle cylinder 60.

The nozzle needle 50 is pushed up by the fuel in the high pressure chamber 21a due to the decompression of the control chamber 27, and is displaced in the valve opening direction. As a result, the high-pressure fuel filled in the high-pressure chamber 21a is injected from the injection hole 23 toward the combustion chamber 2b (see FIG. 1). On the other hand, according to the pressure recovery of the control chamber 27, the nozzle needle 50 is pushed down in the valve closing direction. As a result, fuel injection from the injection hole 23 is stopped. The valve opening direction and the valve closing direction are both displacement directions of the nozzle needle 50.

The needle cylinder 60 is formed in a cylindrical shape by a metal material or the like. The needle cylinder 60 is fitted onto the needle sliding surface 54. The needle cylinder 60 forms an oil tightness with the needle sliding surface 54. The needle cylinder 60 is pressed against the lower end surface of the piston 120 by the urging force of the needle spring 52. The needle cylinder 60 transmits the urging force of the needle spring 52 to the piston 120.

The drive unit 30 drives the pressure control mechanism 100. The drive unit 30 has a piezo actuator 31 and a drive transmission pin 32. The piezo actuator 31 is a laminated body in which layers composed of piezo elements and thin electrode layers are alternately stacked. A drive voltage defined based on the command signal is applied to the piezo actuator 31 by the EDU 70b. The piezo actuator 31 is extended by the reverse voltage effect, which is a characteristic of the piezo element, by charging the drive energy input by the EDU 70b. The piezo actuator 31 is in a contracted state due to the discharge of the input drive energy. As described above, the piezo actuator 31 expands and contracts along the displacement direction of the nozzle needle 50.

The drive transmission pin 32 is a pressing shaft portion that transmits the extension operation of the piezo actuator 31 to the pressure control mechanism 100. The drive transmission pin 32 is housed in a pin accommodating hole 20f formed in the flow path forming member 20b. The tip of the drive transmission pin 32 is abutted against the control valve body 110. The drive unit 30 displaces the drive transmission pin 32 in the direction of protruding into the valve chamber 25 by the piezo actuator 31 extended by the accumulation of electric charges. On the other hand, the drive unit 30 pulls the drive transmission pin 32 back to the pin accommodating hole 20f due to the contraction of the piezo actuator 31 due to the discharge of electric charge.

The pressure control mechanism 100 is housed in a mechanism accommodating hole 20g formed in the valve body member 20c. The pressure control mechanism 100 has a columnar shape as a whole, and is fitted inside the inner peripheral wall surface of the valve body member 20c. The mechanism accommodating hole 20g is a through hole formed in the center of the cylindrical valve body member 20c in the radial direction and penetrating the valve body member 20c in the axial direction. The mechanism accommodating hole 20 g forms a columnar accommodating space. A stopper portion 20s is formed in the mechanism accommodating hole 20g. The stopper portion 20s is a stepped portion in the radial direction provided on the inner peripheral wall surface of the valve body member 20c. The stopper portion 20s faces the outer edge of the lower end surface of the piston 120.

The pressure control mechanism 100 is a mechanism that increases or decreases the fuel pressure in the control chamber 27 by being pressed by the drive unit 30 in the valve closing direction. The pressure control mechanism 100 has a three-way valve function of switching between an inflow state in which fuel flows into the control chamber 27 and an outflow state in which fuel flows out from the control chamber 27, depending on the displacement of the drive transmission pin 32. In addition, the pressure control mechanism 100 has a function of a volume variable mechanism that increases or decreases the total volume of the control chamber 27 and the valve chamber 25 by the displacement of the drive transmission pin 32.

The pressure control mechanism 100 includes a control valve body 110, a piston 120, a valve spring 140, and the like. The control valve body 110 is formed by combining a valve closing member 111 and a transmission member 113 formed of a metal material. The piston 120 is a combination of a main piston member 120a and a sub-piston member 130 formed of a metal material.

The control valve body 110 has a columnar shape as a whole and is housed in the valve chamber 25. The control valve body 110 stops the outflow of fuel from the control chamber 27 to the low-pressure fuel passage 22 in a state where the piezo actuator 31 is contracted. The control valve body 110 enables fuel to flow out from the control chamber 27 to the low-pressure fuel passage 22 by displacement due to the extension operation of the piezo actuator 31.

The valve closing member 111 is a member that opens and closes the outflow opening 26 of the pin accommodating hole 20f facing the valve chamber 25. The valve closing member 111 is arranged in the upper valve chamber portion 25b in the valve chamber 25. The valve closing member 111 has a closing portion 112a and a spherical surface portion 112b.

The closing portion 112a is formed in a circular flat shape having a diameter larger than that of the outflow opening 26. The closing portion 112a faces the first sheet surface portion 28 that surrounds the outflow opening 26 in an annular shape. The drive transmission pin 32 is in contact with the center of the closing portion 112a. The extension operation of the piezo actuator 31 is transmitted to the valve closing member 111 through the drive transmission pin 32, so that the closing portion 112a is separated from the first seat surface portion 28. As a result, the outflow opening 26 is opened. On the other hand, with the piezo actuator 31 contracted, the closing portion 112a is seated on the first seat surface portion 28. As a result, the outflow opening 26 is closed. The spherical surface portion 112b is formed in a partially spherical shape continuous with the outer edge of the closed portion 112a.

The transmission member 113 is formed in a two-stage columnar shape having a large diameter portion 113a and a small diameter portion 113b. The small diameter portion 113b is located on the main piston member 120a side with respect to the large diameter portion 113a. The transmission member 113 is formed with a valve body sliding surface 114, a contact portion 115, and a valve connection passage 117.

The valve body sliding surface 114 is an outer peripheral wall surface of the large diameter portion 113a. The valve body sliding surface 114 is formed in a cylindrical surface shape. The valve body sliding surface 114 is internally fitted on the inner peripheral wall surface of the sub-piston member 130. The valve body sliding surface 114 is slidable with respect to the sub-piston member 130.

The contact portion 115 is a recess provided on the upper end surface of the transmission member 113 facing the valve body member 20c in the axial direction. The contact portion 115 is located at the center of the upper end surface in the radial direction and accommodates the valve closing member 111. The contact portion 115 is formed in a concave spherical shape, and is in surface contact with the spherical surface portion 112b. The sliding between the contact portion 115 and the spherical surface portion 112b allows the transmission member 113 to tilt relative to the valve closing member 111.

The valve connection passage 117 is formed by a through hole that penetrates the transmission member 113 along the axial direction. The valve connection passage 117 is arranged on the outer peripheral side of the contact portion 115. The valve connection passage 117 is a fuel passage that communicates the lower valve chamber portion 25a and the upper valve chamber portion 25b. The valve communication passage 117 always communicates between the lower valve chamber portion 25a and the upper valve chamber portion 25b regardless of the position of the control valve body 110.

The piston 120 is slidably supported on the inner peripheral wall surface of the valve body member 20c. The piston 120 can be displaced along the displacement direction of the nozzle needle 50. The piston 120 forms a gap GP in the displacement direction with the control valve body 110 in a state where the piezo actuator 31 is contracted. The size of the gap GP is, for example, about 10 to 30 μm. The gap GP disappears due to the displacement of the control valve body 110 in the valve closing direction due to the extension operation of the piezo actuator 31. The piston 120 comes into contact with the control valve body 110 displaced by the extension operation of the piezo actuator 31. The piston 120 is displaced in the valve closing direction by the force transmitted from the control valve body 110 to increase the volume of the upper valve chamber portion 25b. As a result, the piston 120 causes the control chamber 27 to be depressurized.

The main piston member 120a is formed in a columnar shape and is located between the sub-piston member 130 and the needle cylinder 60. The sub-piston member 130 and the valve spring 140 are mounted on the upper end surface of the main piston member 120a facing the control valve body 110. The lower end surface of the main piston member 120a faces the control chamber 27 and the high pressure chamber 21a. The lower end surface of the main piston member 120a comes into contact with the stopper portion 20s due to the displacement of the piston 120 in the valve closing direction, and limits the displacement of the piston 120 in the valve closing direction. The main piston member 120a is formed with an inflow flow path 122, a piston communication passage 127, a piston sliding surface 124, and a second seat surface portion 128.

The inflow flow path 122 is formed by a through hole extending from the outer edge portion of the lower end surface of the main piston member 120a toward the center of the upper end surface. The inflow flow path 122 forms a communication between the high pressure chamber 21a and the valve chamber 25. The inflow opening 122a of the inflow flow path 122 facing the valve chamber 25 opens in the center of the upper end surface. The inflow opening 122a allows fuel to flow from the high pressure chamber 21a into the lower valve chamber portion 25a. The inflow opening 122a is closed by the contact of the control valve body 110 with the main piston member 120a. Due to the closure of the inflow opening 122a, the connection between the high pressure chamber 21a and the valve chamber 25 is cut off. An in-orifice 123 is formed in the inflow flow path 122. The in orifice 123 limits the flow rate of fuel flowing from the high pressure chamber 21a into the valve chamber 25 when the inflow opening 122a is open.

The piston communication passage 127 is formed by a through hole that penetrates the sub-piston member 130 along the axial direction. The piston communication passage 127 is provided at a position deviated from the center of the sub-piston member 130. The piston communication passage 127 is a fuel passage that communicates the control chamber 27 and the lower valve chamber portion 25a. The piston communication passage 127 always communicates between the control chamber 27 and the lower valve chamber portion 25a regardless of the position of the control valve body 110. The control chamber 27 is always communicated with the upper valve chamber portion 25b by the piston communication passage 127 and the valve communication passage 117.

The piston sliding surface 124 is an outer peripheral wall surface of the main piston member 120a. The piston sliding surface 124 is formed in a cylindrical surface shape. The piston sliding surface 124 is fitted inside the inner peripheral wall surface of the valve body member 20c. The piston sliding surface 124 is slidable with respect to the valve body member 20c.

The second seat surface portion 128 is provided on the upper end surface of the main piston member 120a facing the lower end surface of the control valve body 110 in the axial direction. The second sheet surface portion 128 is formed in a flat flat shape. The second seat surface portion 128 is an annular shape surrounding the inflow opening 122a. With the piezo actuator 31 contracted, the above-mentioned gap GP is formed between the second seat surface portion 128 and the lower end surface of the control valve body 110. Due to the contact of the control valve body 110 with the piston 120, the second seat surface portion 128 forms an oil tightness with the lower end surface of the control valve body 110.

The sub-piston member 130 is formed in a cylindrical shape and is coaxially arranged with the main piston member 120a between the main piston member 120a and the valve body member 20c. The outer diameter of the sub-piston member 130 is substantially the same as the outer diameter of the main piston member 120a. The sub-piston member 130 is formed with a piston pressure receiving surface 131 and a cylindrical wall portion 132.

The piston pressure receiving surface 131 is an upper end surface of the sub-piston member 130 facing the flow path forming member 20b in the axial direction. The piston pressure receiving surface 131 is formed in an annular shape. The projected area of the piston pressure receiving surface 131 seen along the displacement direction of the nozzle needle 50 is larger than the projected area of the needle pressure receiving surface 51 seen along the displacement direction. The piston pressure receiving surface 131 is pressed against the lower end surface of the flow path forming member 20b by the urging force of the needle spring 52 in a state where the piezo actuator 31 is contracted.

The piston pressure receiving surface 131 is separated from the lower end surface of the flow path forming member 20b by the displacement of the piston 120 and the control valve body 110 in the valve closing direction, and the volume of the upper valve chamber portion 25b is expanded. On the other hand, the displacement of the piston 120 in the valve closing direction reduces the volume of the control chamber 27. As described above, since the projected area of the piston pressure receiving surface 131 is larger than the projected area of the needle pressure receiving surface 51, the increase in the volume of the upper valve chamber portion 25b is larger than the decrease in the volume of the control chamber 27. As a result, the total volumes of the valve chamber 25 and the control chamber 27 increase due to the displacement of the piston 120 and the control valve body 110 in the valve closing direction.

The cylindrical wall portion 132 supports the large-diameter portion 113a of the control valve body 110 so as to be displaceable in the axial direction, and is displaceably supported by the inner peripheral wall surface of the valve body member 20c. The axial length of the cylindrical wall portion 132 is longer than the axial length of the transmission member 113 by the interval of the gap GP. A cylindrical lower valve chamber portion 25a is formed between the cylindrical wall portion 132 and the small diameter portion 113b.

The valve spring 140 is a coil spring formed in a cylindrical spiral shape. The valve spring 140 is arranged between the large diameter portion 113a and the main piston member 120a in a state of being compressed in the axial direction. The valve spring 140 is housed in the lower valve chamber portion 25a and is located on the outer peripheral side of the small diameter portion 113b. The valve spring 140 urges the control valve body 110 toward the outflow opening 26.

The fuel injection device 10 described so far can change the mode of transition of the injection rate in fuel injection. As an example, the fuel injection device 10 performs fuel injection in a low-speed valve opening mode in which the injection rate is raised as standard, and fuel injection in a high-speed valve opening mode in which the injection rate is raised steeper than in the low-speed valve opening mode. It can be carried out. Hereinafter, the details of the operation of fuel injection by the fuel injection device 10 will be described with reference to FIGS. 3 to 7 with reference to FIGS. 2 while comparing the low-speed valve opening mode and the high-speed valve opening mode.

FIG. 3 shows a state in which the piezo actuator 31 is not energized, that is, the piezo actuator 31 is in a contracted state. The control valve body 110 in this state has the closing portion 112a seated on the first seat surface portion 28 as an initial position. The control valve body 110 at the initial position cuts off the connection between the low pressure fuel passage 22 and the valve chamber 25. Therefore, the outflow of fuel from the valve chamber 25 and the control chamber 27 to the low pressure fuel passage 22 is interrupted.

On the other hand, the lower end surface of the control valve body 110 is separated from the second seat surface portion 128, and forms a minute gap GP with the second seat surface portion 128. At such an initial position of the control valve body 110, the valve chamber 25 and the high pressure chamber 21a are in a communicating state, and the control chamber 27 is connected to the high pressure chamber 21a via the valve chamber 25. Therefore, the fuel pressure in the control chamber 27 is substantially the same as the fuel pressure in the high pressure chamber 21a. The nozzle needle 50 maintains the valve closed state of the injection hole 23 by the oil pressure received from the fuel in the control chamber 27.

As the initial position of the piston 120, the piston pressure receiving surface 131 is brought into contact with the lower end surface of the flow path forming member 20b. On the other hand, the lower end surface of the piston 120 is separated from the stopper portion 20s. A minute gap (hereinafter, "displacement section DGP") is formed between the lower end surface of the piston 120 and the stopper portion 20s. The distance secured as the displacement section DGP in the contracted state of the piezo actuator 31 is smaller than the distance secured as the gap GP. The displacement section DGP may be larger than the gap GP or may be substantially the same as the gap GP.

In the low-speed valve opening mode shown in FIG. 4, the first drive energy is applied to the piezo actuator 31. The first drive energy is drive energy that displaces the control valve body 110 but does not substantially cause displacement of the piston 120. Therefore, in the low-speed valve opening mode, the volume expansion of the valve chamber 25 by the pressure control mechanism 100 is not carried out.

The drive unit 30 in the low-speed valve opening mode pushes down the control valve body 110 by the drive transmission pin 32 by the extension operation of the piezo actuator 31. By opening the outflow opening 26 due to the displacement of the control valve body 110, the upper valve chamber portion 25b communicates with the low pressure fuel passage 22 through the pin accommodating hole 20f. Since the control chamber 27 and the valve chamber 25 are connected to each other by the piston communication passage 127, when the valve chamber 25 and the low pressure fuel passage 22 are connected by the displacement of the control valve body 110, the fuel in the control chamber 27 is released. , Flow out to the low pressure fuel passage 22 through the valve chamber 25.

Due to the depressurization of the control chamber 27 due to the outflow of fuel to the low pressure fuel passage 22, the oil pressure in the valve closing direction acting on the needle pressure receiving surface 51 is reduced. When the fuel pressure in the control chamber 27 falls below the valve opening pressure Po (see FIG. 8), the nozzle needle 50 starts displacement in the valve opening direction due to the hydraulic pressure of the high-pressure fuel. As a result, the injection hole 23 is opened.

Then, according to the displacement of the nozzle needle 50 in the valve opening direction, the volume of the control chamber 27 is reduced. Therefore, the fuel pressure in the control chamber 27, which has decreased due to the fuel outflow, is restored. When the displacement amount of the nozzle needle 50 reaches a specific lift amount (hereinafter, “balance lift amount”), the pressure of the control chamber 27 is restored due to the volume reduction, and the hydraulic pressure in the valve closing direction acting on the nozzle needle 50 and the opening of the nozzle needle 50 are caused. The oil pressure in the valve direction will be balanced. As a result, the displacement speed of the nozzle needle 50 that is displaced in the valve opening direction is reduced. After reaching the balance lift amount, the nozzle needle 50 continues to be displaced in the valve opening direction at a substantially constant speed according to the outflow amount of fuel flowing through the out orifice 22a.

The drive unit 30 in the low-speed valve closing mode presses the lower end surface of the control valve body 110 against the second seat surface portion 128 to close the inflow opening 122a. As a result, the connection between the high pressure chamber 21a and the valve chamber 25 is cut off. Therefore, the fuel leak from the high pressure chamber 21a to the low pressure fuel passage 22 is suppressed. According to the connection cutoff between the high pressure chamber 21a and the valve chamber 25, the connection between the high pressure chamber 21a and the control chamber 27 is also cut off.

In the high-speed valve opening mode shown in FIGS. 5 and 6, the second drive energy is input to the piezo actuator 31. The second drive energy is a drive energy larger than that of the first drive energy. The drive unit 30 causes the piezo actuator 31 to perform an extension operation larger than that in the low-speed valve opening mode, so that the control valve body 110 is further pushed down by the drive transmission pin 32. As a result, the control valve body 110 eliminates the gap GP between the piston 120 and the piston 120, and displaces the abutting piston 120 in the expansion direction. The expansion direction is substantially the same as the valve closing direction. Further, in the high-speed valve opening mode as well, as in the low-speed valve opening mode, the outflow of the fuel in the control chamber 27 to the low-pressure fuel passage 22 is started by the displacement of the control valve body 110 from the initial position.

As shown in FIG. 5, the control valve body 110 and the piston 120 expand while pushing down the needle cylinder 60 before the nozzle needle 50 starts to be displaced in the valve opening direction due to the decompression of the control chamber 27 due to the fuel outflow. Initiate an integral displacement in the direction. The piston 120 is displaced to a position where the lower end surface is brought into contact with the stopper portion 20s while eliminating the displacement section DGP. As a result, the upper valve chamber portion 25b between the lower end surface of the flow path forming member 20b and the upper end surface of the pressure control mechanism 100 is expanded. In this way, before the displacement of the nozzle needle 50 is started, the volume of the valve chamber 25, and by extension, the total volume of the valve chamber 25 and the control chamber 27 is expanded.

The pressure in the control chamber 27 drops due to the expansion of the total volume of the valve chamber 25 and the control chamber 27 and the outflow of fuel to the low pressure fuel passage 22. Then, when the pressure in the control chamber 27 falls below the valve opening pressure Po (see FIG. 8), as shown in FIG. 6, the nozzle needle 50 starts to be displaced in the valve opening direction, and the injection hole 23 is in the valve opening state. Become. According to the increase in the total volume of the valve chamber 25 and the control chamber 27 described above, the balance lift amount is increased, so that the period during which the displacement speed of the nozzle needle 50 can be maintained high (hereinafter, “accelerated valve opening period”) is long. Adjusted for a long time.

More specifically, the balance lift amount is a lift amount in which the axial oil pressure acting on the nozzle needle 50 is balanced by the pressure return of the control chamber 27 due to the displacement of the nozzle needle 50 in the valve opening direction. Therefore, as the volume of the control chamber 27 increases, the pressure return of the control chamber 27 due to the rise of the nozzle needle 50 is suppressed, so that the balance lift amount increases. In the configuration in which the valve chamber 25 is connected to the control chamber 27, the balance lift amount is increased even if the total volumes of the valve chamber 25 and the control chamber 27 are increased. As described above, if the total volumes of the valve chamber 25 and the control chamber 27 are increased or decreased by adjusting the drive energy applied to the piezo actuator 31, the balance lift amount and the accelerated valve opening period can be adjusted. Therefore, it is possible to change the mode of transition of the injection rate in fuel injection, for example, by making the rise of the injection rate steep.

During the valve closing period shown in FIG. 7, the energization of the piezo actuator 31 is cut off. When the electric charge stored in the piezo actuator 31 is released after the energization is stopped, the piezo actuator 31 contracts in the axial direction. In the valve closing period in the high-speed valve opening mode, the piston 120 is pushed by the restoring force of the needle spring 52 transmitted by the needle cylinder 60, the hydraulic pressure acting on the piston 120, and the like as the driving force of the driving unit 30 disappears. , Displace towards the outflow opening 26. As a result, the displacement section DGP is secured between the lower end surface of the piston 120 and the stopper portion 20s.

In addition, during the valve closing period of each valve opening mode, the control valve body 110 is displaced toward the outflow opening 26 with respect to the piston 120 due to the restoring force of the valve spring 140, the hydraulic pressure acting on the control valve body 110, and the like. do. The control valve body 110 seats the closing portion 112a on the first seat surface portion 28 and closes the outflow opening 26. As a result, the connection between the upper valve chamber portion 25b and the low-pressure fuel passage 22 is cut off, and the fuel outflow from the valve chamber 25 and the control chamber 27 to the low-pressure fuel passage 22 is stopped.

Further, the control valve body 110 separates the lower end surface from the second seat surface portion 128 and opens the inflow opening 122a. As a result, a gap GP is secured between the lower end surface of the control valve body 110 and the upper end surface of the main piston member 120a. As a result, the fuel in the high pressure chamber 21a flows into the control chamber 27 connected to the high pressure chamber 21a via the valve chamber 25 through the inflow passage 122, the gap GP, and the piston communication passage 127. As a result, the fuel pressure in the control chamber 27 is restored to the same initial pressure as the high pressure chamber 21a, and the nozzle needle 50 is pushed down in the valve closing direction by the restoring force of the needle spring 52, the oil pressure, and the like, and the injection hole 23 is closed. The valve is closed.

Next, the transition of the operation of the fuel injection device 10 in the high-speed valve opening mode will be described with reference to FIGS. 5 and 2 using the time chart of FIG.

At time t0, the charge control unit 72 starts charging the second drive energy to the piezo actuator 31 by outputting the command value toward the EDU 70b. The time t0 is a time when the driving energy is started to be charged to the piezo actuator 31, and is a charging start time when the charging of the piezo actuator 31 is started.

The displacement of the control valve body 110 is started by the extension operation accompanying the charging started at time t0. Then, the control valve body 110 displaced by the valve body idle distance corresponding to the gap GP comes into contact with the piston 120 and starts displacement integrally with the piston 120. Further, the piston 120 displaced by the piston idle distance corresponding to the displacement section DGP by being pushed by the control valve body 110 comes into contact with the stopper portion 20s at time t1. As a result, the displacement of the control valve body 110 and the piston 120 in the expansion direction is completed. In addition, charging of the piezo actuator 31 is completed at time t1. That is, the time t1 is the charging completion time of the piezo actuator 31. Then, the time from the time t0 to the time t1 is the boosting completion time Tu.

Due to the depressurization of the control chamber 27 that continues after the time t1, the pressure of the control chamber 27 reaches the valve opening pressure Po of the nozzle needle 50 at the time t2. As a result, at time t2, the nozzle needle 50 starts the lift displacement in the valve opening direction. That is, the time t2 is the valve opening start time of the nozzle needle 50. The time from the time t0 to the time t2 is the valve opening time Ts.

As described above, due to the configuration in which the boosting completion time Tu is set shorter than the valve opening time Ts, the displacement of the control valve body 110 and the piston 120 in the expansion direction causes the nozzle needle 50 to lift the valve displacement in the valve opening direction. It is started and completed before it starts. Such boosting completion time Tu is set to, for example, about 0.1 ms. On the other hand, the valve opening time Ts is set to about 0.25 to 0.3 milliseconds.

In the present embodiment described so far, the extension operation of the piezo actuator 31 causes the piston 120 in contact with the control valve body 110 to be displaced in the expansion direction to increase the volume of the valve chamber 25. If the valve chamber 25 is connected to the control chamber 27 and the volume of the valve chamber 25 is expanded before the nozzle needle 50 starts to be displaced in the valve opening direction, the fuel injection device 10 can move the valve chamber 25. The timing at which the displacement speed of the nozzle needle 50 decreases can be adjusted by expanding or contracting the volume of the nozzle needle 50. Therefore, even if the fuel injection device 10 is configured to open the nozzle needle 50 by utilizing the decompression of the control chamber due to the fuel outflow, the displacement mode of the nozzle needle 50 can be changed.

Specifically, as shown in FIG. 9, in the low-speed valve opening mode in which the volume of the valve chamber 25 is not expanded, the displacement amount of the nozzle needle 50 reaches the balance lift amount immediately after the valve opening starts. Therefore, the accelerated valve opening period is shortened. On the other hand, in the high-speed valve opening mode in which the volume of the valve chamber 25 is expanded, the accelerated valve opening period is secured longer than in the low-speed valve opening mode due to the expansion of the balance lift amount. As described above, by adopting the pressure control mechanism 100 capable of changing the volume of the valve chamber 25 by the extension operation of the piezo actuator 31, it is possible to realize a configuration in which the valve opening speed of the nozzle needle 50 is variable.

Then, as shown in FIG. 10, by changing the valve opening speed of the nozzle needle 50, it is possible to change the mode of transition of the injection rate. In the high-speed valve opening mode, the injection rate is increased more rapidly than in the low-speed valve opening mode because the accelerated valve opening period is continued for a long time. Therefore, the waveform of the injection rate has a high rectangular (boot type) shape that approximates a rectangle. On the other hand, in the low-speed valve opening mode, the injection rate rises more slowly than in the high-speed valve opening mode due to the early termination of the accelerated valve opening period. Therefore, the waveform of the injection rate has a low rectangular shape.

In addition, in the present embodiment, the displacement of the piston 120 in the expansion direction is completed before the valve opening start time t2 at which the displacement of the nozzle needle 50 is started. Therefore, the lift displacement of the nozzle needle 50 is started with the total volumes of the valve chamber 25 and the control chamber 27 expanded. According to the above, since the behavior of the nozzle needle 50 displaced in the valve opening direction can be stabilized, the accuracy and controllability of the injection amount can be ensured.

Further, in the present embodiment, the boosting completion time Tu is set shorter than the valve opening time Ts. The valve opening time Ts is roughly determined by the volume of the control chamber 27. Therefore, the valve opening time Ts is measured or calculated from the volume of the control chamber 27, and the boosting completion time Tu is adjusted to be shorter than the valve opening time Ts. According to such a setting, the displacement of the piston 120 is completed before the displacement of the nozzle needle 50 starts. Therefore, the accuracy and controllability of the injection amount can be more easily ensured.

Here, although the displacement amount of the piezo actuator 31 can be controlled by the input drive energy, the influence of temperature and the variation among individuals may inevitably exist. Therefore, in the present embodiment, the displacement of the piston 120 in the expansion direction is mechanically regulated by the stopper portion 20s. With such a configuration, the maximum displacement amount of the piston 120 can be maintained constant. In this way, the control shelf of the input drive energy is defined by the stopper portion 20s, so that the displacement mode of the nozzle needle 50 in the high-speed valve opening mode for expanding the volume of the valve chamber 25, and thus the change in the injection rate. The aspect of is stable. Therefore, the controllability of the injection amount can be ensured even in the configuration in which the valve opening speed of the nozzle needle 50 is variable.

Further, in the present embodiment, a valve spring 140 for urging the control valve body 110 toward the flow path forming member 20b is provided. Therefore, the control valve body 110 can return to the initial position as the piezo actuator 31 contracts. If the displacement of the control valve body 110 smoothly follows the operation of the piezo actuator 31, the pressure control mechanism 100 and the nozzle needle 50 operate stably even if the drive energy applied to the piezo actuator 31 is changed. be able to.

In addition, in the present embodiment, the control valve body 110 pushed down by the drive unit 30 closes the inflow opening 122a formed in the piston 120 and stops the inflow of fuel from the high pressure chamber 21a into the valve chamber 25. Therefore, the consumption of leaked fuel that is not used for driving the nozzle needle 50 can be reduced as compared with the form in which the inflow of fuel from the high pressure chamber 21a to the valve chamber 25 is not stopped.

Further, in the present embodiment, the piston communication passage 127 formed in the piston 120 communicates the control chamber 27 with the valve chamber 25. The piston communication passage 127 can connect the control chamber 27 and the valve chamber 25 at a short distance. As a result, the volume of the piston communication passage 127 is reduced, and by extension, the total volume of the control chamber 27 and the valve chamber 25 can be reduced. Based on the above, the pressure control mechanism 100 can secure a large variable ratio of the total volume realized by the displacement of the piston 120 in the expansion direction. Therefore, the fuel injection device 10 can change the displacement mode of the nozzle needle 50 more remarkably by controlling the driving energy applied to the piezo actuator 31.

In the above embodiment, the valve body 20 corresponds to the "main body", the high pressure chamber 21a corresponds to the "first chamber", the low pressure fuel passage 22 corresponds to the "second chamber", and the piezo actuator 31 " The nozzle needle 50 corresponds to the "actuator" and corresponds to the "needle". Further, the needle cylinder 60 corresponds to the "control chamber member", the control valve body 110 corresponds to the "valve body", the piston communication passage 127 corresponds to the "communication passage", and the valve spring 140 corresponds to the "valve body urging". Corresponds to "member".

(Other embodiments)
Although one embodiment of the present disclosure has been described above, the present disclosure is not construed as being limited to the above embodiment, and is applied to various embodiments and combinations without departing from the gist of the present disclosure. be able to.

In the above embodiment, the case where the second drive energy for bringing the piston 120 into contact with the stopper portion 20s is applied to the piezo actuator 31 has been described as the high-speed valve opening mode. However, the magnitude of the drive energy input from the control device to the piezo actuator can be changed as appropriate. For example, the charge control unit may charge the piezo actuator with driving energy that causes the piston to be displaced in the expansion direction to the extent that it does not abut on the stopper unit by setting the command value.

In the above embodiment, the drive unit 30 can open the outflow opening 26 without substantially displace the piston 120 due to the configuration in which the gap GP is provided between the control valve body 110 and the piston 120. However, the pressure control mechanism may be configured such that the gap GP is omitted and the piston is constantly displaced as the outflow opening is opened. Even with such a configuration, if the charge control unit controls the extension amount of the piezo actuator, the valve opening speed of the nozzle needle can be changed.

In the high-speed valve opening mode in the above embodiment, charging of the piezo actuator 31 is completed before the displacement of the nozzle needle 50 in the valve opening direction is started. However, charging of the piezo actuator under the control of the charge control unit may be continued even after the displacement of the nozzle needle is started. Further, the higher the injection pressure, the longer the valve opening time Ts. Therefore, the charge control unit may perform control to secure the boosting completion time Tu longer as the injection pressure becomes higher.

In the above embodiment, the maximum displacement amount of the piston 120 in the expansion direction is defined by the stopper portion 20s. However, the stopper portion may be omitted.

The control valve body 110 of the above embodiment was pressed by the valve spring 140. However, if one end of the needle cylinder penetrates the piston and a pressing force can be applied to the control valve body, the configuration corresponding to the valve spring may be omitted. By omitting the valve spring, the volume of the valve chamber can be further reduced. Therefore, a larger variable ratio of the total volumes of the valve chamber and the control chamber can be secured.

In the above embodiment, when the outflow opening 26 is opened due to the displacement of the control valve body 110, the communication between the high pressure chamber 21a and the valve chamber 25 is cut off, and the consumption of leaked fuel is suppressed. However, the connection between the high pressure chamber and the valve chamber may be maintained even when the outflow opening is open.

In the drive unit of the above embodiment, the piezo actuator 31 has been adopted as the actuator. However, the actuator may be, for example, a magnetron actuator or the like.

In the above embodiment, an example in which the pressure control mechanism and the like of the present disclosure are applied to a fuel injection device that injects light oil as fuel has been described. However, the above pressure control mechanism can also be applied to a fuel injection device that injects a fuel other than light oil, for example, a liquefied gas fuel such as dimethyl ether.

10 Fuel injection device, 20 valve body (main body), 20s stopper, 21a high pressure chamber (first chamber), 22 low pressure fuel passage (second chamber), 23 injection hole, 25 valve chamber, 27 control chamber, 31 piezo actuator (Actuator), 50 nozzle needle (needle), 60 needle cylinder (control chamber member), 110 control valve body (valve body), 120 piston, 122 inflow flow path, 122a inflow opening, 127 piston communication passage (communication passage), 140 Valve spring (valve body urging member), t0 charging start time, t1 charging completion time, t2 valve opening start time, Ts valve opening time, Tu boosting completion time

Claims (7)

A first chamber (21a) in which a fuel injection hole (23) is formed and a fuel of a first pressure is supplied, and a second chamber (22) in which a fuel of a second pressure lower than the first pressure is supplied. ), a body (20) to said first chamber and connectable to the second chamber valve chamber (25) is provided therein,
A control chamber member (60) provided with a control chamber (27) connected to the valve chamber, and a control chamber member (60).
A needle (50) that is pressed in the direction of closing the injection hole by the fuel pressure of the control chamber and displaced in the valve opening direction of opening the injection hole by the decompression of the control chamber.
In a state where the actuator (31) that expands and contracts along the valve opening direction and the actuator are contracted, the connection between the second chamber and the valve chamber is cut off, and the first chamber and the control chamber are connected. , A valve body (110) connecting the valve chamber and the second chamber by the extension operation of the actuator, and
The valve opening direction is between the inner wall surface of the main body and the piston end surface (131) facing the valve opening direction and partitioning the valve chamber together with the inner wall surface, and the valve body with the actuator contracted. a piston (120) to have a seat surface portion (128) forming a gap (GP) along comprises,
The piston has an end face of the piston before the needle starts to be displaced in the valve opening direction due to the decompression of the control chamber when the valve body displaced by the extension operation of the actuator comes into contact with the seat surface portion. in the expansion direction of increasing the volume of the valve chamber is separated from the inner wall surface, a fuel injection device you displaced together with the valve body. The fuel injection device according to claim 1, wherein the actuator completes the displacement of the piston in the expansion direction before the needle starts the displacement in the valve opening direction. The boosting completion time (Tu) from the charging start time (t0) when the drive energy is applied to the actuator to the charging completion time (t1) when charging is completed is the valve opening start of the needle from the charging start time (t0). The fuel injection device according to claim 1 or 2, which is shorter than the valve opening time (Ts) until the time (t2). The fuel injection device according to any one of claims 1 to 3, wherein the main body has a stopper portion (20s) that regulates the displacement of the piston in the expansion direction. The invention according to any one of claims 1 to 4, further comprising a valve body urging member (140) that urges the valve body in a direction that cuts off the connection between the valve chamber and the second chamber. Fuel injection device. The piston is formed with an inflow flow path (122) for allowing fuel to flow from the first chamber to the valve chamber.
The fuel injection device according to any one of claims 1 to 5, wherein the valve body closes the inflow opening (122a) of the inflow flow path facing the valve chamber by contacting the piston. The fuel injection device according to any one of claims 1 to 6, wherein a communication passage (127) communicating between the control chamber and the valve chamber is formed in the piston.

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