JP2018135821A - Fuel injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection device capable of improving controllability of a nozzle needle while suppressing an increase in a load on a drive unit. A first valve body 110 is housed in a pressure control chamber 25 to close and open an outflow opening 28. The second valve body 120 is housed in the pressure control chamber 25 and closes and opens the inflow opening 27. The pressure control chamber 25 is divided into an upper pressure control chamber portion 251a and a lower pressure control chamber portion 251b for accommodating the first valve body 110 by closing the valve of the second valve body 120. The second valve body 120 is formed with a communication passage 120a having a first throttle portion 120b that communicates the upper pressure control chamber portion 251a and the lower pressure control chamber portion 251b to generate a pressure difference. The second valve body 120 has an inflow opening 27 due to the force received from the fuel filled in the lower pressure control chamber portion 251b by communicating the upper pressure control chamber portion 251a and the outflow passage 24a by opening the valve of the first valve body 110. Fuel injection device that closes the valve. [Selection diagram] Fig. 3

Description

  The present invention relates to a fuel injection device that injects fuel from an injection hole toward a combustion chamber.

  Conventionally, as in Patent Document 1, an injector that injects fuel from an injection hole formed in a housing member has been proposed. This injector has a nozzle needle that opens and closes the nozzle hole, and a piezo actuator in addition to the housing member in which the control chamber is defined. The nozzle needle is displaced relative to the housing member by increasing and decreasing the fuel pressure in the valve closing direction received from the fuel filled in the control chamber.

  In addition, a valve chamber communicating with the control chamber is formed in the housing member. The valve chamber is connected to a passage through which high-pressure fuel flows into the control chamber and a communication passage through which fuel in the control chamber flows out.

  Furthermore, the valve body accommodated in the valve chamber is operated by the driving force transmitted from the piezo actuator, closes the opening of the passage facing the valve chamber, and opens the opening of the communication passage facing the valve chamber. Then, the flow of high-pressure fuel from the passage into the control chamber stops, and the fuel in the control chamber flows out from the communication passage. As a result, the fuel pressure in the control chamber drops and the nozzle needle opens.

JP 2006-46323 A

  As described above, the nozzle needle is displaced relative to the valve body as the fuel pressure in the control chamber changes. Therefore, the operating speed of the nozzle needle in the nozzle closing direction depends on the speed at which the fuel pressure in the control chamber is increased. Therefore, in order to improve the controllability of the nozzle needle, it is necessary to increase the inflow amount of the high-pressure fuel by increasing the opening area of the passage through which the high-pressure fuel flows into the control chamber, thereby improving the fuel pressure rising speed.

  However, the larger the opening area of the passage, the larger the contact area between the high-pressure fuel and the valve body in the passage. Therefore, in the configuration of Patent Document 1 in which the valve body closes the passage, the force with which the high-pressure fuel in the passage pushes the valve body in the valve opening direction also increases. Therefore, when the opening area of the passage is increased, there is a possibility that a load on a driving unit such as a piezo actuator increases.

  Therefore, the present invention has been made in view of the above matters, and an object of the present invention is to provide a fuel injection device capable of improving the controllability of the nozzle needle while suppressing an increase in the load on the drive unit. That is.

  The embodiment disclosed herein employs the following technical means to achieve the above object. The reference numerals in parentheses described in the claims and in this section indicate the correspondence with specific means described in the embodiments described later, and do not limit the technical scope of the invention. .

  One of the disclosed modes is a fuel injection device (10) for injecting fuel from an injection hole (23), the injection hole, a pressure control chamber (25) filled with fuel, and a high pressure fuel in the pressure control chamber. An inflow passage (21a) for letting in the fuel and an outflow passage (24a) for letting out the fuel in the pressure control chamber are formed. The valve body (20) in which the outflow opening (28) of the passage is opened, and the force in the valve closing direction is received from the fuel in the pressure control chamber, and the fuel pressure in the pressure control chamber increases and decreases with respect to the valve body. A nozzle needle (50) that opens and closes the nozzle hole by relative displacement, a first valve body (110) that is housed in the pressure control chamber and closes and opens the outflow opening, The first valve body is driven and the pressure is increased by opening the first valve body. A drive unit (30) for communicating the control chamber and the outflow passage and shutting off the communication between the pressure control chamber and the outflow passage by closing the first valve body, and an outer peripheral surface of the first valve body driven by the drive unit (110f) and a second valve body (120) that closes and opens the inflow opening, and the pressure control chamber is closed by the second valve body. It is divided into an upper pressure control chamber (251a) that accommodates one valve body, and a lower pressure control chamber (251b) that is located on the opposite side of the upper pressure control chamber across the second valve body. The two-valve body includes a first throttle portion (120b) that communicates the upper pressure control chamber portion and the lower pressure control chamber portion, and generates a pressure difference between the upper pressure control chamber portion and the lower pressure control chamber portion. A communication passage (120a) is formed, and the second valve body is formed by communication between the upper pressure control chamber and the outflow passage by opening the first valve body. A fuel injection device for closing the inlet opening by the force applied from fuel filled under pressure control chamber unit.

  According to the above aspect, the pressure control chamber is divided into the upper pressure control chamber portion and the lower pressure control chamber portion by the second valve body. Then, when the first valve element is opened by the drive unit and the upper pressure control chamber and the outflow passage are communicated with each other, the pressure in the upper pressure control chamber is reduced. A first throttle portion is formed in a communication passage that connects the upper pressure control chamber portion and the lower pressure control chamber portion. For this reason, even if the pressure in the upper pressure control chamber portion decreases, the pressure in the lower pressure control chamber portion does not drop immediately, and a pressure difference is generated between the upper pressure control chamber portion and the lower pressure control chamber portion. That is, the fuel in the lower pressure control chamber is higher in pressure than the upper pressure control chamber. Accordingly, the second valve body receives a larger force from the fuel in the lower pressure control chamber than the fuel in the upper pressure control chamber and the high pressure fuel in the inflow passage. That is, even if the second valve body is not driven by the drive unit, the inflow opening can be closed by the force received from the fuel filled in the lower pressure control chamber.

  Therefore, in order to improve the responsiveness when the nozzle needle is closed, even if the opening area of the inflow opening is increased and the force received by the high pressure fuel in the inflow passage increases, the drive unit The increase in load is difficult to cause.

  Therefore, it is possible to provide a fuel injection device capable of improving the controllability of the nozzle needle by increasing the amount of high-pressure fuel flowing into the pressure control chamber while suppressing an increase in the load on the drive unit. It is.

The figure which shows the whole structure of the fuel supply system in 1st embodiment. The longitudinal cross-sectional view of the fuel-injection apparatus in 1st embodiment. The enlarged view of the III section of FIG. Sectional drawing of the IV-IV line of FIG. The time chart which shows correlation, such as a displacement of a valve body and a nozzle needle. The enlarged view in 2nd embodiment. The time chart which shows correlation, such as a displacement of the valve body and nozzle needle in 2nd embodiment.

  Hereinafter, a plurality of modes for carrying out the invention will be described with reference to the drawings. In each embodiment, portions corresponding to the matters described in the preceding embodiment may be denoted by the same reference numerals and redundant description may be omitted. In each embodiment, when only a part of the configuration is described, the other configurations described above can be applied to other portions of the configuration.

(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS. The fuel supply system 1 shown in FIG. 1 uses a fuel injection device 10 according to the first embodiment. The fuel injection device 10 of the fuel supply system 1 supplies the fuel stored in the fuel tank 4 to each combustion chamber 2b of the diesel engine 2 that is an internal combustion engine. Hereinafter, the diesel engine 2 is simply referred to as the engine 2. The fuel supply system 1 includes a feed pump 5, a high-pressure fuel pump 6, a common rail 3, a control device 7, and the like together with a fuel injection device 10.

  The feed pump 5 is an electric pump built in the high-pressure fuel pump 6. The feed pump 5 is specifically a trochoid pump. 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 a separate body from the high-pressure fuel pump 6.

  The high-pressure fuel pump 6 is, for example, a plunger type pump that 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 from the feed pump 5 and supplies it to the common rail 3.

  The common rail 3 is connected to each fuel injection device 10 via a high-pressure fuel pipe 3b. 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 3 a and a pressure reducing valve 8. The pressure sensor 3 a detects the fuel pressure stored in the common rail 3. The pressure reducing valve 8 discharges the surplus fuel to the surplus fuel pipe 8 a connected to the fuel tank 4 when the detected value by the pressure sensor 3 a is higher than the target pressure.

  The control device 7 is configured by an arithmetic circuit mainly composed of a microcomputer or a microcontroller including a processor, a RAM, and a rewritable nonvolatile memory device. The control device 7 is electrically connected to each fuel injection device 10 as indicated by a broken line in FIG. The control device 7 controls the operation of each fuel injection device 10 according to the operating state of the engine 2.

  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 that forms the combustion chamber 2b. The fuel injection device 10 directly injects fuel supplied through the high-pressure fuel pipe 3b from the injection hole 23 toward the combustion chamber 2b. The fuel injection device 10 includes a valve structure that controls injection of fuel from the injection hole 23. The fuel injection device 10 uses part of the high-pressure fuel supplied via the high-pressure fuel pipe 3 b 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 from the surplus fuel pipe 8a through the return pipe 8b.

  Next, the detailed structure of the fuel injection device 10 will be described with reference to FIGS. As shown in FIG. 2, the fuel injection device 10 includes a valve body 20, a nozzle needle 50, a drive unit 30, and a valve body 100.

  The valve body 20 is configured by combining a plurality of members formed of a metal material. The valve body 20 includes a high pressure passage 21, a low pressure passage 24, a pressure control chamber 25, an inflow passage 21 a, an outflow passage 24 a, an injection hole 23, and a needle chamber 22.

  The high-pressure passage 21 is connected to the high-pressure fuel pipe 3b shown in FIG. The high-pressure passage 21 supplies high-pressure fuel supplied from the common rail 3 to the needle chamber 22 through the high-pressure fuel pipe 3b. The low pressure passage 24 is a passage through which the fuel supplied to the fuel injection device 10 flows out to the return pipe 8b. The fuel flowing through the low pressure passage 24 is at a lower pressure than the fuel flowing through the high pressure passage 21.

  The pressure control chamber 25 is filled with high-pressure fuel. Details of the pressure control chamber 25 will be described later. The inflow passage 21 a branches off from the high pressure passage 21. The inflow passage 21 a allows a part of the high-pressure fuel flowing through the high-pressure passage 21 to flow into the pressure control chamber 25. The outflow passage 24 a allows the fuel in the pressure control chamber 25 to flow out to the low pressure passage 24.

  The nozzle hole 23 is formed at the distal end in the insertion direction in the valve body 20 inserted into the head member 2a. The nozzle hole 23 is exposed to the combustion chamber 2b. The tip of the valve body 20 is formed in a conical or hemispherical shape. A plurality of nozzle holes 23 are provided radially from the inside to the outside of the valve body 20. The high-pressure fuel is injected from each nozzle hole 23 toward the combustion chamber 2b. The high-pressure fuel is atomized by passing through the nozzle hole 23, and is easily mixed with air.

  The needle chamber 22 is a space formed in a cylindrical shape. A nozzle needle 50 is accommodated in the needle chamber 22. The needle chamber 22 is connected to the high pressure passage 21. The needle chamber 22 is filled with high-pressure fuel supplied through the high-pressure passage 21.

  The nozzle needle 50 is formed in a cylindrical shape from a metal material. The tip of the nozzle needle 50 on the nozzle hole 23 side has a conical shape. The nozzle needle 50 is slidably held on a needle wall 51 formed in a cylindrical shape inside the needle chamber 22. A force in the valve opening direction is applied to the nozzle needle 50 from the high pressure fuel in the needle chamber 22. A force in the valve closing direction is applied to the nozzle needle 50 from the needle spring 52. The nozzle hole 50 opens and closes when the nozzle needle 50 is displaced relative to the valve body 20. When the nozzle hole 23 is opened, high-pressure fuel filled in the needle chamber 22 is injected from the nozzle hole 23 toward the combustion chamber 2b.

  The drive unit 30 includes a piezo actuator 31, a transmission mechanism 32, and the like. The piezo actuator 31 has a laminated body in which layers composed of piezo elements and thin electrode layers are alternately stacked. An input drive signal output from the control device 7 is input to the piezoelectric actuator 31. The piezo actuator 31 extends along the sliding direction of the nozzle needle 50 due to a reverse voltage effect that is a characteristic of the piezo element in accordance with a voltage corresponding to a drive signal (hereinafter, drive voltage).

  The transmission mechanism 32 is a mechanism that transmits the extension of the piezo actuator 31 to the valve body 100. The transmission mechanism 32 has a first piston 321 and a second piston 322. The first piston 321 and the second piston 322 are formed in a cylindrical shape. The second piston 322 has a smaller diameter than the first piston 321. The first piston 321 is in contact with the piezo actuator 31. The second piston 322 is formed with a protrusion 322a extending in the injection hole direction along the axial direction of the second piston. An oil tight chamber 323 is defined between the first piston 321 and the second piston 322. The oil tight chamber 323 is filled with fuel in a substantially oil tight state.

  In the drive unit 30, the first piston 321 is pushed by the piezo actuator 31 extended by the drive signal. The movement of the first piston 321 is transmitted to the second piston 322 by the fuel in the oil tight chamber 323. Since the second piston 322 has a smaller diameter than the first piston 321, the displacement of the first piston 321 due to the extension of the piezoelectric actuator 31 is expanded by the fuel in the oil-tight chamber 323 and transmitted to the second piston 322. That is, the displacement amount of the second piston 322 is larger than the displacement amount of the first piston 321.

  The details of the pressure control chamber 25 will be further described with reference to FIGS. The pressure control chamber 25 is provided inside the valve body 20 on the opposite side of the nozzle hole 23 with the nozzle needle 50 interposed therebetween. That is, the pressure control chamber 25 is formed between the drive unit 30 and the needle chamber 22. As shown in FIG. 3, the pressure control chamber 25 is partitioned by a partition wall 25 a formed in the valve body 20. A seating wall surface 25 b is formed on one surface of the partition wall 25 a that is perpendicular to the sliding direction of the driving unit 30 and closest to the driving unit 30. In the seating wall surface 25b, an outflow opening 28 of the outflow passage 24a and an inflow opening 27 of the inflow passage 21a are opened. As shown in FIG. 4, the outflow opening 28 is circular, and the inflow opening 27 is formed in an annular shape so as to surround the outflow opening 28.

  The pressure control chamber 25 includes a valve body accommodating space 251, an urging member accommodating space 254, and a pressure acting space 252 from the drive unit 30 toward the nozzle hole 23. Further, the pressure control chamber 25 has a pressure control communication path 253 between the biasing member accommodation space 254 and the pressure action space 252.

  The valve body accommodating space 251 is a cylindrical space. The valve body accommodating space 251 is coaxially arranged with the virtual center axis of each of the inflow opening 27 and the outflow opening 28. One side of the partition wall 25a that partitions the valve body accommodating space 251 corresponds to the seating wall surface 25b. The valve body 100 is housed in the valve body housing space 251. The biasing member accommodation space 254 is a cylindrical space having a smaller diameter than the valve body accommodation space 251. The height of the biasing member accommodation space 254 is lower than the height of the valve body accommodation space 251. The volume of the biasing member accommodation space 254 is smaller than the volume of the valve body accommodation space 251. The biasing member accommodating space 254 is formed on the opposite side to the seating wall surface 25b with the valve body 100 interposed therebetween.

  The urging member accommodating space 254 is a space that accommodates the urging member 130 that applies an urging force in the valve closing direction of the valve body 100. Details of the urging member 130 will be described later.

  The pressure acting space 252 is a disk-shaped space defined by the needle wall 51 and the end face of the nozzle needle 50. The pressure acting space 252 is formed on the opposite side of the valve body accommodating space 251 with the biasing member accommodating space 254 interposed therebetween. The fuel in the pressure acting space 252 applies a force in the valve closing direction to the nozzle needle 50. Therefore, the nozzle needle 50 is displaced relative to the valve body 20 as the fuel pressure in the pressure acting space 252 changes. Specifically, when the fuel pressure in the pressure acting space 252 decreases, the fuel pressure that applies a force in the valve closing direction to the nozzle needle 50 decreases, so that the nozzle needle 50 is displaced in the valve opening direction.

  The pressure control communication passage 253 is a fuel passage formed between the biasing member accommodation space 254 and the pressure action space 252. The pressure control communication path 253 communicates the urging member accommodating space 254 and the pressure acting space 252, and changes the fuel pressure in the pressure acting space 252 to the fuel pressure in the valve element accommodating space 251 and the urging member accommodating space 254. Follow.

  The valve body 100 includes a first valve body 110 and a second valve body 120. The first valve body 110 is housed in the valve body housing space 251 and closes and opens the outflow opening 28. The second valve body 120 is slidably disposed with respect to the outer peripheral surface 110 f of the first valve body 110, and closes and opens the inflow opening 27. The second valve body 120 is seated on the seating wall surface 25 b and closes the inflow opening 27, whereby an upper pressure control chamber 251 a that houses the first valve body 110 and a lower pressure that houses the second valve body 120. The valve body accommodating space 251 is divided into the control chamber 251b.

  The upper pressure control chamber portion 251a is a space formed between the valve body 100 and the seating wall surface 25b. The upper pressure control chamber 251 a is formed between the outflow opening 28 and the inflow opening 27, and is formed in an annular shape so as to surround the outflow opening 28. The upper pressure control chamber 251 a is formed so as to be coaxial with the outflow opening 28.

  The lower pressure control chamber 251b is located on the opposite side of the upper pressure control chamber 251a with the second valve body 120 interposed therebetween. The fuel filled in the lower pressure control chamber portion 251b applies a force in the valve closing direction to the first valve body 110.

  A biasing force in a valve closing direction is applied to the valve body 100 by a biasing member 130. The urging member 130 is accommodated in the urging member accommodation space 254 on the lower pressure control chamber 251b side with respect to the second valve body 120. The urging member 130 includes a first urging member 130a and a second urging member 130b. Both the first urging member 130 a and the second urging member 130 b are accommodated in a space other than the upper pressure control chamber portion 251 a in the pressure control chamber 25.

  The first urging member 130a is formed by winding a linear metal material into a cylindrical shape. The first urging member 130 a is accommodated in the urging member accommodation space 254 so as to be coaxial with the virtual central axis of the urging member accommodation space 254. The first urging member 130 a applies a force in the valve closing direction to the first valve body 110.

  The second urging member 130b is formed by winding a linear metal material into a cylindrical shape. The diameter of the second urging member 130b is larger than the diameter of the first urging member 130a, and is formed in a size that allows the first urging member 130a to be accommodated inside the cylindrical shape. The second urging member 130 b is accommodated in the urging member accommodation space 254 so as to be coaxial with the virtual central axis of the urging member accommodation space 254. The second urging member 130 b applies a force in the valve closing direction to the second valve body 120.

  The first valve body 110 is displaced by the driving force from the driving unit 30 and is seated and separated on the seating wall surface 25b. By opening the first valve body 110, the pressure control chamber 25 and the outflow passage 24a are in communication with each other. By closing the first valve body 110, the communication between the pressure control chamber 25 and the outflow passage 24a is cut off. The first valve body 110 includes a valve closing member 111 and a fitting member 112.

  The valve closing member 111 is made of, for example, a metal material. The valve closing member 111 has a valve closing portion 111a and a spherical portion 111b. The valve closing portion 111a is formed in a circular planar shape. The diameter of the valve closing portion 111 a is larger than the diameter of the outflow opening portion 28. The valve closing portion 111a closes the outflow opening 28 by being seated on the seating wall surface 25b. The spherical portion 111b is formed in a substantially spherical shape. The spherical surface portion 111b is in contact with the end portion of the fitting member 112 in the axial direction.

  The fitting member 112 is formed in a cylindrical shape from, for example, a metal material. The fitting member 112 has a fitting portion 112a. The fitting portion 112a is slidably fitted to the second valve body 120 while maintaining a liquid-tight state between the upper pressure control chamber portion 251a and the lower pressure control chamber portion 251b. The fitting member 112 transmits the urging force from the first urging member 130 a and the force in the valve closing direction received from the fuel in the valve body accommodating space 251 to the valve closing member 111.

  The second valve body 120 is formed in a cylindrical shape from a metal material. The second valve body 120 is housed in the valve body housing space 251. The second valve body 120 is arranged coaxially with the central axes of the inflow opening 27 and the outflow opening 28. Further, the second valve body 120 is arranged coaxially with the central axis of the valve body accommodating space 251. A cylindrical gap 120e is formed between the outer peripheral wall of the second valve body 120 and the inner peripheral wall of the valve body accommodating space 251. The gap 120e serves as a flow path for high-pressure fuel that flows from the inflow opening 27 toward the lower pressure control chamber 251b.

  The second valve body 120 is formed with a second seating surface 120d, a fitting hole 120c, and a communication passage 120a. The second seating surface 120d is formed as a plane parallel to the seating wall surface 25b. The second valve body 120 closes the inflow opening 27 by the second seating surface 120d seated on the seating wall surface 25b.

  The fitting hole 120c is a columnar through hole formed in the center of the second valve body 120 in the radial direction. The fitting hole 120c extends so as to be coaxial with the central axis of the second valve body 120. The fitting hole 120c penetrates the second valve body 120 in the axial direction. The diameter of the fitting hole 120c is formed such that the spherical portion 111b can be accommodated in the fitting hole 120c.

  The fitting portion 112a is slidably fitted into the fitting hole 120c. By fitting the fitting portion 112a into the fitting hole 120c, the liquid-tight state between the upper pressure control chamber portion 251a and the lower pressure control chamber portion 251b described above is maintained. Of the both ends of the fitting hole 120c, the inner diameter of one end continuous with the second seating surface 120d is larger than the other part, and is formed in a size that can accommodate the spherical portion 111b. .

  The communication passage 120 a penetrates the second valve body 120 in the axial direction. The communication passage 120a is a cylindrical through hole. The communication passage 120a communicates the upper pressure control chamber 251a and the lower pressure control chamber 251b. A first throttle portion 120b is formed in the communication passage 120a. The first throttle part 120b is formed at a position closer to the drive part 30 side than the center in the communication passage 120a. The first throttle portion 120b is a cylindrical through hole, and its diameter is smaller than the communication passage 120a. The first throttle unit 120b regulates the amount of fuel flow between the upper pressure control chamber unit 251a and the lower pressure control chamber unit 251b, so that the first throttle unit 120b is interposed between the upper pressure control chamber unit 251a and the lower pressure control chamber unit 251b. Create a pressure differential.

  The second valve body 120 is slidably disposed with respect to the outer peripheral surface 110 f of the first valve body 110. Even if the second valve body 120 is displaced, the first valve body 110 is not displaced. The second valve body 120 receives force in the valve closing direction from the fuel in the lower pressure control chamber 251b and the second urging member 130b. The second valve body 120 receives force in the valve opening direction from the high-pressure fuel in the inflow opening 27. The second valve body 120 closes the inflow opening 27 when a second seating surface 120d formed on the second valve body 120 is seated on the seating wall surface 25b.

  Next, the operation of the fuel injection device 10 will be described with reference to FIGS. 3 and 5.

  Before energization of the piezo actuator 31 is started at time t1, the first valve body 110 is applied to the seating wall surface 25b by the fuel pressure in the lower pressure control chamber 251b and the closing force received from the first urging member 130a. Sitting. That is, the first valve body 110 blocks communication between the outflow opening 28 and the upper pressure control chamber 251a. The second valve body 120 is seated on the seating wall surface 25b by the fuel pressure in the lower pressure control chamber 251b and the valve closing force received from the second urging member 130b. The second valve body 120 divides the pressure control chamber 25 into an upper pressure control chamber portion 251a and a lower pressure control chamber portion 251b.

  At time t1, when energization of the piezo actuator 31 is started, the protrusion 322a pushes the first valve body 110 in the nozzle hole direction, that is, in the valve opening direction due to the extension of the piezo actuator 31. When the first valve body 110 is displaced in the direction of the nozzle hole, the valve closing portion 111a is separated from the seating wall surface 25b. When the valve closing portion 111a is separated from the seating wall surface 25b, the outflow opening portion 28 is in communication with the upper pressure control chamber portion 251a.

  When the outflow opening 28 communicates with the upper pressure control chamber 251a, the fuel in the upper pressure control chamber 251a flows out of the outflow passage 24a through the outflow opening 28. As a result, the fuel pressure in the upper pressure control chamber 251a drops.

  The fuel in the lower pressure control chamber 251b flows into the upper pressure control chamber 251a through the communication passage 120a. Therefore, the fuel pressure in the lower pressure control chamber 251b also drops following the drop in the fuel pressure in the upper pressure control chamber 251a. Since the first throttle portion 120b is formed in the communication passage 120a, the fuel flow rate from the lower pressure control chamber portion 251b to the upper pressure control chamber portion 251a is compared with the outflow speed of the fuel from the upper pressure control chamber portion 251a. Distribution speed will be slow. Therefore, a difference occurs between the fuel pressure in the lower pressure control chamber 251b and the fuel pressure in the upper pressure control chamber 251a. That is, the fuel pressure in the lower pressure control chamber 251b is higher than the fuel pressure in the upper pressure control chamber 251a. The second valve body 120 is pressed against the inflow opening 27 by the force in the valve closing direction received from the fuel in the lower pressure control chamber 251b due to the pressure drop in the upper pressure control chamber 251a. To maintain.

  Here, when the fuel pressure in the lower pressure control chamber portion 251b decreases, the fuel pressure in the pressure acting space 252 connected to the lower pressure control chamber portion 251b via the biasing member accommodating space 254 and the pressure control communication path 253 also decreases. To do.

  At time t2, when the fuel pressure in the lower pressure control chamber 251b decreases to a predetermined pressure, the fuel pressure in the pressure acting space 252 also decreases to the predetermined pressure. Then, the force in the valve opening direction received from the fuel pressure in the needle chamber 22 is larger than the force received in the valve closing direction from the fuel pressure in the pressure acting space 252 and the needle spring 52 by the nozzle needle 50. Therefore, the nozzle needle 50 starts to open.

  At time t3, when energization to the piezo actuator 31 is stopped, the piezo actuator 31 contracts. As a result, the driving force from the drive unit 30 that pushes the first valve body 110 in the valve opening direction does not act, so the first valve body 110 starts displacement in the valve closing direction.

  At time t4, when the first valve body 110 is closed, the fuel outflow from the outflow opening 28 of the upper pressure control chamber 251a stops. Here, at time t4, there is a difference between the fuel pressure in the upper pressure control chamber 251a and the fuel pressure in the lower pressure control chamber 251b, and the fuel pressure in the lower pressure control chamber 251b is higher. Therefore, the fuel in the lower pressure control chamber portion 251b flows through the communication passage 120a and flows out to the upper pressure control chamber portion 251a. As the fuel in the lower pressure control chamber 251b flows into the upper pressure control chamber 251a, the fuel pressure in the upper pressure control chamber 251a increases.

  At time t5, the difference between the fuel pressure in the upper pressure control chamber portion 251a and the fuel pressure in the lower pressure control chamber portion 251b is reduced or substantially eliminated. Then, the force that the second valve body 120 receives in the valve closing direction from the fuel in the lower pressure control chamber 251b is smaller than the force that the second valve body 120 receives in the valve opening direction from the high pressure fuel in the inflow opening 27. As a result, the second valve body 120 starts to open. By opening the second valve body 120, the high-pressure fuel flows from the inflow opening 27 into the upper pressure control chamber 251a. Furthermore, when the second valve body 120 is opened, the high-pressure fuel flows from the inflow opening 27 into the lower pressure control chamber 251b through the predetermined gap 120e.

  At time t6, the fuel pressure in the upper pressure control chamber 251a and the lower pressure control chamber 251b rises to a predetermined pressure. Then, the fuel pressure in the pressure acting space 252 indirectly connected to the lower pressure control chamber portion 251b also rises in the same manner as the fuel pressure in the lower pressure control chamber portion 251b. Then, the fuel pressure in the pressure acting space 252 and the force acting from the needle spring 52 to the nozzle needle 50 in the valve closing direction are larger than the force acting from the fuel pressure in the needle chamber 22 to the nozzle needle 50 in the valve opening direction. Become. Therefore, the force applied in the valve closing direction of the nozzle needle 50 by the fuel in the pressure acting space 252 increases, and the nozzle needle 50 starts to close. In the period from time t6 to time t7, since the volume of the pressure acting space 252 is changed by the displacement of the nozzle needle 50 in the valve closing direction, it is assumed that fuel has flowed into the valve body accommodating space 251 from the inflow opening 27. In addition, the pressure in the valve body accommodating space 251 is kept constant.

  At time t7, the nozzle needle 50 is closed. After the nozzle needle 50 is opened, the fuel pressure in the valve body accommodating space 251 rises to the fuel pressure in the inflow passage 21a. Therefore, the difference between the force received by the second valve body 120 from the fuel in the lower pressure control chamber 251b in the valve closing direction and the force received from the fuel in the inflow opening 27 in the valve opening direction is reduced. Then, the force of the valve closing direction received from the fuel pressure of the lower pressure control chamber 251b and the second urging member 130b is larger than the force of the valve opening direction received by the second valve body 120 from the fuel pressure of the inflow opening 27. Will be bigger. Therefore, the second valve body 120 is seated on the seating wall surface 25b by the fuel pressure in the lower pressure control chamber 251b and the force in the valve closing direction received from the second urging member 130b, and the inflow opening 27 is closed.

  As described above, according to the present embodiment, the second valve body 120 closes the inflow opening 27 by the force received from the fuel charged in the lower pressure control chamber 251b without being driven by the drive unit 30. I can speak. Therefore, in order to improve the responsiveness when the nozzle needle 50 is closed, it is assumed that the opening area of the inflow opening 27 is increased and the force that the second valve body 120 receives from the high-pressure fuel in the inflow passage 21a is increased. However, it is difficult for the load of the drive unit 30 to increase. Therefore, it is possible to provide a fuel injection device 10 capable of improving the controllability of the nozzle needle 50 by increasing the amount of high-pressure fuel flowing into the pressure control chamber 25 while suppressing an increase in load on the drive unit 30. Is possible.

  Further, according to the present embodiment, when the first valve body 110 is closed, the fuel in the lower pressure control chamber 251b flows to the upper pressure control chamber 251a through the communication passage 120a, and the fuel pressure in the upper pressure control chamber 251a. And the fuel pressure in the lower pressure control chamber 251b becomes smaller. As a result, the force with which the fuel in the upper pressure control chamber portion 251a pushes the second valve body 120 in the valve closing direction is reduced, so that the second valve body 120 receives the inflow opening 27 by the force received from the high pressure fuel in the inflow passage 21a. Open the valve. Therefore, the second valve body 120 is subjected to valve closing control and valve opening control without being driven by the driving unit 30.

  Further, according to the present embodiment, the outflow opening 28 and the inflow opening 27 are open to the seating wall surface 25b on which the first valve body 110 and the second valve body 120 are seated together in the partition wall 25a. Therefore, it is difficult to form a gap between the first valve body 110 and the second valve body 120 and the seating wall surface 25b. Therefore, it is easy to reduce the volume of the upper pressure control chamber 251a.

  Further, according to the present embodiment, the fitting member 112 is slidably fitted to the second valve body 120, and between the upper pressure control chamber portion 251a and the lower pressure control chamber portion 251b. The liquid-tight state is maintained. Therefore, even if the first valve body 110 is slid by receiving the urging force from the urging member 130, the fitting member 112 causes a pressure difference between the upper pressure control chamber portion 251a and the lower pressure control chamber portion 251b. It is divided by. Therefore, the valve closing member 111 can be pushed in the valve closing direction by the urging force of the urging member 130 while the urging member 130 is housed in the lower pressure control chamber 251b. The liquid-tight state is a state where the amount of fuel flowing between the fitting member 112 and the second valve body 120 is smaller than the amount of fuel flowing through the first throttle portion 120b.

  Further, according to the present embodiment, the valve closing member 111 and the fitting member 112 are formed separately, and the valve closing member 111 includes the valve closing portion 111a and the spherical portion 111b. The spherical portion 111b receives a force in the valve closing direction from the fitting member 112 with which the spherical portion 111b is in contact. Accordingly, even if the displacement direction of the fitting member 112 is inclined with respect to the seating wall surface 25b, the fitting portion 112 is fitted at the contact portion between the end surface on the upper pressure control chamber portion 251a side and the spherical portion 111b. Relative rotation of the valve closing member 111 with respect to the member 112 is allowed. Therefore, the valve closing member 111 can seat the valve closing portion 111a on the seating wall surface 25b.

  Further, according to the present embodiment, the urging member 130 that applies the urging force in the valve closing direction to the second valve body 120 is accommodated in the lower pressure control chamber 251b. Further, the urging member 130 is not accommodated in the upper pressure control chamber 251a. Thus, if it is the structure which does not arrange | position the biasing member 130 in the upper pressure control chamber part 251a, compared with the case where the biasing member 130 is arrange | positioned in the upper pressure control chamber part 251a, of the upper pressure control chamber part 251a. It is possible to reduce the volume.

  According to the above volume reduction of the upper pressure control chamber 251a, after the first valve body 110 closes the outflow opening 28, the fuel pressure in the upper pressure control chamber 251a is quickly increased in the lower pressure control chamber 251b. Approaching fuel pressure. As a result, the time from the closing of the first valve body 110 to the opening of the second valve body 120 (see times t4 to t5 in FIG. 5) is shortened. According to such improvement of the valve opening response of the second valve body 120, the fuel pressure in the pressure acting space 252 can rise quickly. Therefore, the valve closing response of the nozzle needle 50 can be improved.

  In addition, according to the present embodiment, the valve body housing space 251 in which the first valve body 110 and the second valve body 120 are housed, and the pressure working space 252 in which fuel that applies pressure to the nozzle needle 50 is filled. I know. The valve body accommodation space 251 and the pressure action space 252 are communicated with each other through a pressure control communication path 253. With such a configuration, the volume of the valve body accommodating space 251 can be easily reduced, so that the fuel acting on the nozzle needle 50 can be raised and lowered in a short time.

  Moreover, according to this embodiment, the 2nd valve body 120 and the valve body accommodation space 251 are formed in the substantially similar shape. And the 2nd valve body 120 is accommodated in this valve body accommodation space 251 so that it may become coaxial with the center axis line of the valve body accommodation space 251. FIG. With these configurations, the volume of the space formed between the valve body accommodating space 251 and the second valve body 120, that is, the fuel space filled with fuel is easily reduced.

  Therefore, it is possible to increase and decrease the fuel pressure in the valve body accommodating space 251 in a short time as compared with a configuration having a large volume. Therefore, the responsiveness of the second valve body 120 can be improved, and as a result, the controllability of the nozzle needle 50 can be improved.

  Further, according to the present embodiment, the inflow opening 27 is formed in an annular shape, and the second valve body 120 is accommodated in the valve body accommodating space 251 so as to be coaxial with the inflow opening 27. Therefore, the second valve body 120 can receive the force received from the high-pressure fuel in the inflow passage 21a substantially uniformly in the circumferential direction. Therefore, when the second valve body 120 is opened by the force received from the high pressure fuel in the inflow passage 21a, the second valve body 120 is unlikely to be inclined with respect to the valve body accommodating space 251. Thereby, the 2nd valve body 120 can be opened smoothly.

(Second embodiment)
Next, a second embodiment will be described with reference to FIGS. In the present embodiment, the configuration of the pressure control chamber 25 is different from that of the first embodiment.

  As shown in FIG. 6, the fuel injection device 10 does not include the urging member 130. Therefore, the pressure control chamber 25 is not formed with an urging member accommodation space 254 for accommodating the urging member. Therefore, the valve body accommodation space 251 and the pressure action space 252 are directly connected by the pressure control communication path 253.

  A small protrusion 112b is formed on the end surface 112c formed on the lower pressure control chamber 251b side of the fitting member 112. The small protrusion 112b is formed on the end surface 112c of the fitting member 112 facing the bottom surface 25c of the lower pressure control chamber 251b, and protrudes from the end surface 112c in the direction of the bottom surface 25c. In the closed state of the first valve body 110, a gap is formed between the small protrusion 112b and the bottom surface 25c. Further, in the closed state of the first valve body 110, a gap wider than the gap formed between the small protrusion 112b and the bottom surface 25c is formed between the end surface 112c and the bottom surface 25c. When the first valve body 110 is opened and the fitting member 112 is displaced, the tip of the small protrusion 112b comes into close contact with the bottom surface 25c. In the state where the tip of the small protrusion 112b and the bottom surface 25c are in close contact with each other, the gap between the end surface 112c and the bottom surface 25c is maintained.

  Next, the operation of the fuel injection device 10 will be described with reference to FIG. The operation from time t2 to time t7 is substantially the same as in the first embodiment.

  Before energization of the piezo actuator 31 is started at time t1, there is no substantial difference in fuel pressure between the upper pressure control chamber 251a, the lower pressure control chamber 251b, and the inflow passage 21a. Therefore, the force in the valve opening direction that the second valve body 120 receives from the fuel pressure in the upper pressure control chamber portion 251a and the inflow opening 27, and the force in the valve closing direction that the second valve body 120 receives from the lower pressure control chamber portion 251b. And balance. Therefore, it is not pressed against the second valve body 120 and the seating wall surface 25b.

  At time t1, the extension of the piezo actuator 31 causes the protrusion 322a to push the first valve body 110 in the injection hole direction, that is, in the valve opening direction. When the first valve body 110 is displaced in the direction of the nozzle hole 23, the valve closing portion 111a is separated from the seating wall surface 25b. When the valve closing portion 111a is separated from the seating wall surface 25b, the outflow opening portion 28 is in communication with the upper pressure control chamber portion 251a. Therefore, the fuel pressure in the upper pressure control chamber 251a is a negative pressure relative to the fuel pressure in the lower pressure control chamber 251b. Therefore, the second valve body 120 is attracted to the fuel in the upper pressure control chamber 251a and receives the force in the valve closing direction and is seated on the seating wall surface 25b. As a result, the communication between the inflow opening 27 and the valve body accommodating space 251 is cut off.

  At time t8, due to the inflow of high pressure fuel started at time t5, there is no substantial difference in fuel pressure between the upper pressure control chamber portion 251a, the lower pressure control chamber portion 251b, and the inflow passage 21a. Therefore, the force in the valve closing direction that the second valve body 120 receives from the surrounding fuel is balanced. Therefore, the second valve body 120 is not seated on the seating wall surface 25b at time t8, and the communication state between the valve body accommodating space 251 and the inflow opening 27 is maintained. Then, when the outflow opening 28 is opened at the time t1 of the next injection, the second valve body 120 is closed.

  As described above, the second valve body 120 of the present embodiment is attracted in the valve closing direction by the fuel negative pressure generated by opening the first valve body 110. Therefore, the second valve body 120 can appropriately close the inflow opening 27 without being driven by the drive unit 30 and being biased by the second biasing member 130b.

  Further, according to the present embodiment, the urging member accommodating space 254 is not formed in the pressure control chamber 25. Therefore, the volume of the pressure control chamber 25 can be reduced as compared with the configuration in which the biasing member accommodating space 254 is formed. Therefore, it is possible to increase and decrease the fuel pressure in the valve body accommodating space 251 in a short time as compared with a configuration having a large volume. Therefore, the responsiveness of the second valve body 120 can be improved, and as a result, the controllability of the nozzle needle 50 can be improved.

  Further, according to the second embodiment, the small protrusion 112b is formed on the end surface 112c of the fitting member 112 on the lower pressure control chamber 251b side. Thereby, in the valve open state of the 1st valve body 110, the front-end | tip of the small projection part 112b contacts the bottom face 25c of the valve body accommodation space 251. FIG. Therefore, it is possible to maintain a gap formed between the end surface 112c and the bottom surface 25c when the first valve body 110 is open. That is, it can suppress that the whole end surface 112c adheres to the bottom face 25c of the valve body accommodating space 251. Thus, fuel can be interposed in the gap between the end surface 112c and the bottom surface 25c. Therefore, it is possible to apply a force in the valve closing direction received from the fuel pressure in the lower pressure control chamber 251b to the fitting member 112.

(Other embodiments)
The preferred embodiments of the present disclosure have been described above. However, the present disclosure is not limited to the above-described embodiments, and various modifications can be made as illustrated below. Not only combinations of parts that clearly show that combinations are possible in each embodiment, but also combinations of the embodiments even if they are not explicitly stated unless there is a problem with the combination. Is also possible.

  In the first embodiment, the first valve body 110 is formed of two members having a valve closing portion 111a and a fitting portion 112a. However, the first valve body 110 may be formed by one member having the valve closing portion 111a and the fitting portion 112a.

  In the first embodiment, the urging member 130 has the first urging member 130a and the second urging member 130b, but may not have the first urging member 130a.

  In the second embodiment, the small protrusion 112b is formed on the end surface 112c, but may be formed on the bottom surface 25c at a position facing the end surface 112c. That is, it may be formed at any position as long as the entire end surface 112c and the entire bottom surface 25c can be prevented from coming into close contact with each other.

DESCRIPTION OF SYMBOLS 10 Fuel injection apparatus 112 Fitting member 20 Valve body 110f Outer peripheral surface 21a Inflow passage 120 Second valve body 23 Injection hole 120a Communication passage 24a Outflow passage 120b First throttle part 25 Pressure control chamber 111a Closed valve part 25a Partition wall 111b Spherical surface part 25b Seat wall surface 130 Energizing member 27 Inflow opening 251 Valve body accommodating space 28 Outflow opening 251a Upper pressure control chamber 30 Drive unit 251b Lower pressure control chamber 50 Nozzle needle 252 Pressure action space 110 First valve body 253 Pressure control Communication passage 111 Valve closing member

Claims (10)

A fuel injection device (10) for injecting fuel from an injection hole (23),
The nozzle hole, a pressure control chamber (25) filled with fuel, an inflow passage (21a) for allowing high-pressure fuel to flow into the pressure control chamber, and an outflow passage (24a) for letting out fuel in the pressure control chamber are formed. A valve body (20) in which an inflow opening (27) of the inflow passage and an outflow opening (28) of the outflow passage are opened in a partition wall (25a) partitioning the pressure control chamber;
The nozzle hole is opened and closed by receiving a force in the valve closing direction from the fuel in the pressure control chamber and being displaced relative to the valve body by the increase and decrease of the fuel pressure in the pressure control chamber. A nozzle needle (50);
A first valve body (110) housed in the pressure control chamber and closing and opening the outflow opening;
The first valve body is driven, the pressure control chamber and the outflow passage are communicated by opening the first valve body, and the pressure control chamber and the outflow passage are closed by closing the first valve body. A drive unit (30) for blocking communication;
A second valve body (120) disposed to be slidable with respect to the outer peripheral surface (110f) of the first valve body driven by the drive section and closing and opening the inflow opening. ,
The pressure control chamber includes an upper pressure control chamber portion (251a) that houses the first valve body by closing the second valve body, and an upper pressure control chamber portion that sandwiches the second valve body. And the lower pressure control chamber (251b) located on the opposite side,
The second valve body communicates the upper pressure control chamber portion and the lower pressure control chamber portion, and generates a pressure difference between the upper pressure control chamber portion and the lower pressure control chamber portion. A communication passage (120a) having a throttle portion (120b) is formed,
The second valve body includes the inflow opening by a force received from fuel filled in the lower pressure control chamber due to the communication between the upper pressure control chamber and the outflow passage by opening the first valve body. A fuel injection device that closes the valve.   When the pressure difference is reduced by the flow of fuel through the communication passage from the lower pressure control chamber to the upper pressure control chamber after the first valve is closed, the second valve body The fuel injection device according to claim 1, wherein the valve is opened by a force received from the high-pressure fuel in the passage.   3. The fuel according to claim 1, wherein the outflow opening and the inflow opening are open to a seating wall surface (25 b) on which the first valve body and the second valve body are seated in the partition wall. Injection device. The first valve body is
A valve closing portion (111a) for closing the outflow opening;
2. A fitting portion (112 a) that slidably fits to the second valve body while maintaining a liquid-tight state between the upper pressure control chamber portion and the lower pressure control chamber portion. 4. The fuel injection device according to any one of 3. The first valve body has a valve closing member (111) and a fitting member (112),
The fitting member has the fitting portion,
The said valve closing member is provided with the said valve closing part and the spherical surface part (111b) on the substantially spherical surface which contacts the said fitting member and receives the force accompanying the sliding of the said fitting member. Fuel injection device.   The fuel injection device according to claim 5, further comprising a biasing member (130) that applies a biasing force in a direction of closing the outflow opening to the first valve body.   The fuel injection device according to claim 6, wherein the biasing member is accommodated in a space other than the upper pressure control chamber portion in the pressure control chamber. The pressure control chamber is
A valve body accommodating space (251) containing the first valve body and the second valve body and including the upper pressure control chamber;
A pressure acting space (252) filled with fuel for applying pressure to the nozzle needle;
The fuel injection device according to any one of claims 1 to 7, further comprising: a pressure control communication path (253) for communicating the valve body accommodation space and the pressure acting space. The valve body accommodating space is a cylindrical space,
The fuel injection device according to claim 8, wherein the second valve body is formed in a cylindrical shape and is accommodated in the valve body accommodating space so as to be coaxially disposed with a virtual central axis of the valve body accommodating space. The inflow opening is formed in an annular shape,
The fuel injection device according to claim 8 or 9, wherein the second valve body is housed in the valve body housing space so as to be coaxial with the inflow opening.

Images