Fuel injection device

Abstract

This fuel injection device comprises a nozzle holder, a magnetic core, an anchor, a plunger rod, a retainer, a stopper, a plate, and a biasing member. The retainer is provided on the plunger rod, and the anchor abuts on the retainer when a valve is opened. The stopper is provided on the plunger rod and is disposed on the opposite side of the anchor from the retainer. The plate is disposed between the stopper and the anchor. The biasing member biases the plate to the anchor. The contact area of a contact surface of the plate that contacts the anchor is set smaller than the contact area of a contact surface of the plate that contacts the stopper.

Description

fuel injector

[0001] The present invention relates to a fuel injection device.

[0002] Conventionally, internal combustion engines have been used as direct-injection internal combustion engines, in which fuel is directly injected into the cylinder by a fuel injection device. In recent years, fuel injection devices equipped with a pre-stroke mechanism have become more common to accommodate higher speeds and higher fuel pressures. A typical fuel injection device uses an electromagnet to attract an anchor, which is a moving element held in a valve-closed state by a first spring. A plunger rod is engaged with the anchor, and the valve is opened by energizing it.

[0003] The anchor generates force in response to the magnetic flux created by the electromagnet. The plunger rod is driven by the anchor, and a valve body is formed at the axial end. The preliminary stroke is the space (play) provided between the anchor and the plunger rod. While the anchor is moving through the preliminary stroke due to the application of electromagnetic force, the structure is such that it is less susceptible to reaction forces from the plunger rod. This allows the anchor to accelerate and collide with the plunger rod in a nearly unloaded state.

[0004] In this way, in addition to the electromagnetic energy acting on the anchor, the kinetic energy stored in the anchor also contributes to accelerating the plunger rod, enabling the valve to open at high speed. Also, in a valve structure in which fuel pressure acts on the plunger rod, energy must be applied to the plunger rod to open the valve against the fuel pressure during the valve opening operation. For this reason, a valve structure with a pre-stroke can be said to be suitable for high fuel pressure.

[0005] An example of such a conventional technology relating to a fuel injection device is described in Patent Document 1. Patent Document 1 describes a technology including a valve seat, a valve element, a movable core separate from the valve element, and a magnetic core that stops the movement of the movable core. Patent Document 1 also describes a technology including a valve element portion that opens and closes a flow path by abutting against and separating from the valve seat, a plunger rod that transmits power from the valve element portion to a drive portion, an anchor that is displaceable relative to the plunger rod, and a magnetic core with a through hole formed therein.

[0006] In the technology described in Patent Document 1, when the valve is opened, the anchor initially contacts a first flange-shaped structural member (stopper) formed on the plunger rod. After energization, the anchor begins to move due to the electromagnetic force generated between it and the magnetic core, and disengages from the first flange-shaped structural member. The anchor then collides with a second flange-shaped structural member (retainer) formed on the plunger rod. The kinetic energy of the anchor at this time moves the plunger rod to open the valve. On the other hand, when the valve is closed, the anchor moves in the opposite direction, and after the valve is closed, the anchor collides with the stopper and returns to its initial state.

[0007] Japanese Patent Application Laid-Open No. 2014-227958

[0008] However, with the technology described in Patent Document 1, after the anchor collides with the stopper when returning to its initial position, it repeatedly bounces back while attenuating, resulting in a damped vibration known as bouncing. If the next valve-opening operation is initiated during bouncing, the initial position and initial velocity of the anchor cannot be determined, resulting in variations in the valve-opening time and valve-opening amount. As a result, with the technology described in Patent Document 1, bouncing causes variations in the injection amount, making stable fuel injection impossible.

[0009] In consideration of the above problems, an object of the present invention is to provide a fuel injection device that is capable of performing stable fuel injection.

[0010] To solve the above problems and achieve the object, a fuel injection device includes a nozzle holder provided with an injection hole forming member, a magnetic core arranged in the nozzle holder, an anchor, a plunger rod, a retainer, a stopper, a plate, and an urging member. The anchor is arranged opposite the magnetic core. The plunger rod is movably arranged in the nozzle holder and has a valve body. The retainer is provided on the plunger rod and the anchor abuts against it when the valve is opened. The stopper is provided on the plunger rod and is arranged on the opposite side of the anchor from the retainer. The plate is arranged between the stopper and the anchor. The urging member urges the plate toward the anchor. The contact area of ​​the contact surface of the plate that contacts the anchor is set smaller than the contact area of ​​the contact surface of the plate that contacts the stopper.

[0011] According to the fuel injection device having the above configuration, it is possible to suppress variations in the initial position and initial velocity of the anchor caused by bouncing, thereby enabling stable fuel injection.

[0012] FIG. 1 is a cross-sectional view showing a fuel injection device according to a first embodiment; FIG. 2 is a cross-sectional view showing the structure in the vicinity of the anchor in a conventional fuel injection device; FIG. 3 is a cross-sectional view showing the operating states of the anchor and plunger rod in a conventional fuel injection device; FIG. 4 is a time chart showing the operating states of the anchor and plunger rod of a conventional fuel injection valve; FIG. 5 is a diagram and formulas for explaining squeeze force; FIG. 6 is a cross-sectional view showing the structure in the vicinity of the anchor in a fuel injection device according to a first embodiment; FIG. 7 is a diagram showing a plate in a fuel injection device according to a first embodiment; FIG. 8 is a cross-sectional view showing the operating states of the anchor, plunger rod, and plate in a fuel injection device according to a first embodiment; FIG. 9 is a time chart showing the operating states of the anchor, plunger rod, and plate in a fuel injection device according to a first embodiment; FIG. 10 is a cross-sectional view showing the structure in the vicinity of the anchor in a fuel injection device according to a second embodiment; FIG. 11 is a cross-sectional view showing the structure in the vicinity of the anchor in a fuel injection device according to a third embodiment; FIG. 12 is a cross-sectional view showing the structure in the vicinity of the anchor in a fuel injection device according to a fourth embodiment; FIG. 13 is a diagram showing a plate in a fuel injection device according to a fourth embodiment; FIG. 14 is a cross-sectional view showing the structure in the vicinity of the anchor in a fuel injection device according to a fifth embodiment.

[0013] Hereinafter, an embodiment of a fuel injection device will be described with reference to Figures 1 to 14. Note that common members in the figures are given the same reference numerals.

[0014] 1. First Embodiment 1-1. Configuration of Fuel Injection Device First, the configuration of a fuel injection device according to a first embodiment (hereinafter referred to as "this example") will be described with reference to Fig. 1. Fig. 1 is a cross-sectional view showing the fuel injection device.

[0015] The fuel injection device shown in FIG. 1 is used in a four-stroke internal combustion engine that repeats four strokes: intake stroke, compression stroke, combustion (expansion) stroke, and exhaust stroke. The fuel injection device is also applied to a direct-injection internal combustion engine that injects fuel into each cylinder. Fuel supplied from a fuel pump is supplied to the rear end (upper part in FIG. 1 ) of the fuel injection device 100 via a manifold (omitted in this embodiment). The fuel injection device 100 then injects fuel into the cylinder from the tip end (lower part in FIG. 1 ) during a valve opening operation. The fuel injection device 100 has a generally axisymmetric structure.

[0016] 1, the fuel injection device 100 includes a first housing 101, an O-ring 102, a second housing 103, a coil 104, a magnetic core 105, an anchor (movable core) 106, and a nozzle holder 107. The fuel injection device 100 also includes a plunger rod 108, an injection hole forming member 109, a valve body 110, a first spring 111, a second spring 115, and a third spring 116 which serves as a biasing member. The fuel injection device 100 of this example also includes a plate 117.

[0017] The first housing 101 is formed in a cylindrical shape with a hollow interior. One axial end (upper end) of the first housing 101 is connected to a manifold (not shown). An O-ring 102 is disposed at the upper end of the first housing 101. The O-ring 102 is interposed between the first housing 101 and the manifold. The O-ring 102 seals the gap between the first housing 101 and the manifold to prevent fuel leakage.

[0018] The second housing 103 is connected to the other axial end (tip) of the first housing 101. The second housing 103 is formed in a cylindrical shape. The second housing 103 is in close contact with the outer circumferential surface of the first housing 101 at the other axial end of the first housing 101, and a coil 104 is wound around the outer circumferential surface of the second housing 103.

[0019] The coil 104 is wound around a cylindrical coil bobbin. The coil 104 is wound around the coil bobbin and disposed so as to cover a portion of the outer peripheral surface of the second housing 103. The start and end of the coil 104 are connected to power supply terminals via wiring (not shown). When current is supplied from the outside, the coil 104 generates a magnetic field. The coil 104 is also covered by a nozzle holder 107.

[0020] The nozzle holder 107 is formed in a cylindrical shape with a hollow interior. One axial end (upper end) of the nozzle holder 107 is connected to the other axial end (tip) of the second housing 103. The internal space of the nozzle holder 107 is connected to the internal space of the second housing 103. An injection hole forming member 109 is attached to the other axial end (tip) of the nozzle holder 107 by insertion or press fitting. An injection hole for injecting fuel is formed in this injection hole forming member 109.

[0021] The injection hole forming member 109 is also formed with a valve seat that the tip of a valve element 110 (described later) comes into contact with and separates from, and the injection hole forming member 109 seals the fuel when the valve element 110 is seated on the valve seat. The valve element 110 also seals the fuel when it comes into contact with the valve seat, and allows the fuel to pass through when it moves away from the valve seat.

[0022] The nozzle holder 107 accommodates a third spring 116 , an anchor 106 , and a plate 117 .

[0023] The magnetic core 105 is made of a magnetic material and is formed into a substantially cylindrical shape. The magnetic core 105 is fixed in a state where it is fitted into the inner circumferential surface of the first housing 101. The magnetic core 105 also protrudes from the other axial end of the first housing 101. The part of the magnetic core 105 that protrudes from the first housing 101 is inserted into the second housing 103. The outer circumferential surface of the magnetic core 105 faces the coil 104 across the second housing 103. An anchor 106 is disposed opposite the other axial end of the magnetic core 105.

[0024] The anchor 106 is made of a magnetic material and is formed into a substantially cylindrical shape. A plunger rod 108 is inserted into a cylindrical hole in the anchor 106. The anchor 106 is disposed in the internal space of the nozzle holder 107 and the internal space of the second housing 103. One axial end of the anchor 106 faces the other axial end of the magnetic core 105. Furthermore, minute gaps are formed between the outer circumferential surface of the anchor 106 and the inner circumferential surfaces of the nozzle holder 107 and the second housing 103.

[0025] An eccentric through-hole (not shown) is formed in the anchor 106. The eccentric through-hole is formed at a position offset from the center of the anchor 106 in the radial direction. The eccentric through-hole penetrates the anchor 106 from one end to the other end in the axial direction. This eccentric through-hole serves as a flow path through which fuel passes. A stopper 114, which will be described later, is disposed below the anchor 106.

[0026] Next, the plunger rod 108 will be described. The plunger rod 108 is formed in a substantially cylindrical shape. The plunger rod 108 is inserted into the cylindrical holes of the magnetic core 105, the second housing 103, the anchor 106, and the nozzle holder 107. The plunger rod 108 is arranged in the internal space of the nozzle holder 107 and the internal space of the second housing 103 so as to be movable in the axial direction of the nozzle holder 107 and the second housing 103.

[0027] Furthermore, a valve body 110 is fixed to the other axial end (lower end) of the plunger rod 108. That is, in this embodiment, the plunger rod 108 and the valve body 110 are integrated and slidably supported by the nozzle holder 107 and the second housing 103.

[0028] An adjustment member 112 is inserted into the cylindrical hole of the first housing 101. The adjustment member 112 is press-fitted into the cylindrical hole of the first housing 101 and fixed inside the first housing 101. The adjustment member 112 is formed in a cylindrical shape. The cylindrical hole of the adjustment member 112 serves as a flow path through which fuel passes.

[0029] One axial end (upper end) of adjustment member 112 faces an opening at one end of first housing 101. The other axial end (lower end) of adjustment member 112 faces one axial end of plunger rod 108. A first spring 111 is disposed between the other axial end of adjustment member 112 and one axial end of plunger rod 108.

[0030] One end (upper end) of the first spring 111 abuts against the other axial end of the adjustment member 112. The other end (lower end) of the first spring 111 abuts against a retainer 113 fixed to the plunger rod 108, which will be described later. The first spring 111 urges the plunger rod 108 toward the injection hole forming member 109. As a result, the valve body 110 is pressed against the seat portion of the injection hole forming member 109.

[0031] The retainer 113 is fixed to one axial end of the plunger rod 108. The retainer 113 is formed in a substantially cylindrical shape. An outer flange portion is formed at one axial end of the retainer 113. The other end of the first spring 111 abuts against the outer flange portion of the retainer 113. A second spring 115 is disposed around the retainer 113. The upper end of the second spring 115 abuts against the outer flange portion of the retainer 113. The second spring 115 biases the retainer 113 upward.

[0032] The second spring 115 is disposed between the outer flange portion of the retainer 113 and the anchor 106. The lower end of the second spring 115 abuts against the anchor 106. The second spring 115 biases the anchor 106 downward. The spring constant of the second spring 115 is set to be smaller than the spring constant of the first spring 111.

[0033] A stopper 114 is disposed below the anchor 106 on the opposite side to the second spring 115 and the retainer 113. The stopper 114 is fixed to the plunger rod 108.

[0034] 1-2. Conventional Fuel Injection Device A conventional fuel injection device will now be described with reference to Figures 2 to 4. Figure 2 is a cross-sectional view showing the structure in the vicinity of the anchor 106 in a conventional fuel injection device. Figure 3 is a cross-sectional view showing the operating state of the anchor 106 and plunger rod 108 in a conventional fuel injection device. Figure 4 is a time chart showing the operating state of the anchor 106 and plunger rod 108 in a conventional fuel injection device. Note that Figure 2 shows the initial position where no current flows through the coil 104.

[0035] As shown in Figure 2, the anchor 106 is biased downward by the second spring 115 and pressed against the stopper 114. In this state, a gap is formed between the top of the anchor 106 and the bottom of the retainer 113. This gap is called the preliminary stroke (st1). The vertical distance between the bottom of the retainer 113 and the bottom of the magnetic core 105 is called the stroke (st2).

[0036] FIG. 3(a) shows the initial position before current is applied to the coil 104. As shown in FIG. 3(a), the anchor 106 is stationary and in contact with the stopper 114. When current flows through the coil 104, an electromagnetic force is generated between the magnetic core 105 and the anchor 106, and the anchor 106 is attracted upward. As a result, the anchor 106 separates from the stopper 114. The anchor 106 then accelerates upward, ascends a distance equivalent to the preliminary stroke (st1), and collides with the retainer 113. The state at this moment is shown in FIG. 3(b). This causes the fuel injection device to start opening the valve.

[0037] From the state shown in FIG. 3(b), the anchor 106 further pushes up the retainer 113, thereby pushing up the plunger rod 108 and continuing to open the valve. After the anchor 106 rises by the stroke (st2) from the start of the valve opening shown in FIG. 3(b), it collides with the magnetic core 105. Thereafter, the anchor 106 is attracted to maintain the open valve state. That is, the state shown in FIG. 3(c) is reached. Then, the fuel injection device maintains the open valve state and injects fuel for a certain period of time, and then starts the valve closing operation.

[0038] The plunger rod 108 is urged downward by a first spring 111, and at the same time, urges the anchor 106 downward via a retainer 113. When the current is cut off and the electromagnetic force between the anchor 106 and the magnetic core 105 decreases, the anchor 106 separates from the magnetic core 105. The anchor 106 then begins to move downward together with the plunger rod 108. When the anchor 106 descends by the stroke (st2), it changes from the state shown in FIG. 3(c) to the state shown in FIG. 3(b), at which point the valve is completely closed and the fuel injection device stops.

[0039] At this point, a downward inertial force and a downward spring force from the second spring 115 act on the anchor 106. As a result, the anchor 106 separates from the retainer 113 and moves further downward. After moving downward by the preliminary stroke (st1), the anchor 106 collides with the stopper 114, causing bouncing.

[0040] FIG. 4 is a time chart showing the series of operations described above. The horizontal axis in FIG. 4 indicates time, graph 401 indicates changes in current, and graph 402 indicates changes in displacement. State (A) shown on the horizontal axis of graph 402 in FIG. 4 corresponds to the state in FIG. 3( a), state (B) corresponds to the state in FIG. 3( b), and state (C) corresponds to the state in FIG. 3( c). In addition, dashed line Q1 in graph 402 indicates the displacement of anchor 106, and solid line P1 indicates the displacement of plunger rod 108.

[0041] As shown in graph 402 in Fig. 4, when current begins to flow at time 0, the anchor 106 begins to displace from state (A) due to electromagnetic force. The anchor 106 rises while accelerating, and collides with the retainer 113 at time t1 (state (B)). Thereafter, the anchor 106 rises together with the plunger rod 108 fastened to the retainer 113, and begins to open the valve. At time t2, the anchor 106 collides with the magnetic core 105 and stops (state (C)).

[0042] Here, the plunger rod 108 overshoots due to inertial force, but quickly settles due to the spring force of the first spring 111 and the fuel pressure, maintaining state (C) for a while. State (C) is maintained even after the current becomes zero due to the influence of residual magnetism. However, when the electromagnetic force acting on the anchor 106 becomes equal to or less than the repulsive force (the sum of the spring force of the first spring 111 and the fuel pressure), the anchor 106 and plunger rod 108 leave the magnetic core 105 and begin to descend. Then, at time t3, the valve element 110 is pressed against the seat portion of the injection hole forming member 109, resulting in a valve-closed state. Therefore, the plunger rod 108 stops (state (B)). At this time, the anchor 106 leaves the retainer 113 due to its own inertial force and the spring force of the second spring 115, and continues to descend. The anchor 106 then collides with the stopper 114 at time t4 (state (A)). As shown in graph 402 in FIG. 4, after the anchor 106 and the stopper 114 collide, they repeat separation and collision, resulting in damped vibration (bouncing).

[0043] If a current starts to flow and the valve opening operation begins while the anchor 106 is bouncing, the initial speed and initial position of the anchor 106 become unstable. As a result, the valve opening characteristics of the fuel injection device vary, causing variations in the injection amount. Thus, it is clear that suppressing the bouncing of the anchor 106 is necessary to prevent variations during high-speed operation.

[0044] 1-3. Fluid Force (Squeezing Force) Next, fluid force (squeezing force) will be explained with reference to Fig. 5. Fig. 5 shows a diagram and a mathematical formula illustrating the magnitude of the fluid force (squeezing force) acting on an object.

[0045] One possible method for suppressing the above-mentioned bouncing is to utilize the fluid force (squeeze force) that occurs in a narrow gap. Here, the squeeze force is a fluid force that occurs when two objects approach or separate, accompanying the expulsion or introduction of fluid between the objects. The squeeze force is a force that occurs in a direction that prevents the two objects from approaching or separating.

[0046] A state in which a flat plate approaches a flat surface and a spherical object 501 shown in Fig. 5 will be described. Here, formula 502 is a theoretical formula expressing the magnitude of the squeeze force. In formula 502, F represents the squeeze force, μ represents the viscosity coefficient, v represents the approach speed, h represents the size of the gap between object 501 and the flat plate, and R represents the radius of object 501. Formula 503 is a transformation of formula 502 using the projected area S (=π*R^2) of the sphere that is object 501.

[0047] 5 is formed in a substantially circular disk shape. Equations 505 and 506 are theoretical equations that express the magnitude of the squeeze force F when a flat plate approaches the plane of object 504.

[0048] From equation 503, it can be seen that the squeeze force F is proportional to the projected area S and the approach speed v, and inversely proportional to the gap size h. From equation 506, it can be seen that, similarly to equation 503, the squeeze force F is proportional to the area S and the approach speed v, and inversely proportional to the cube of the gap size h. As described above, since bouncing is caused by the collision between anchor 106 and stopper 114, bouncing can be suppressed by suppressing the collision speed. Furthermore, as shown in FIG. 5, increasing the squeeze force F is effective in suppressing the collision speed. To achieve this, it can be said that increasing the area S of objects 501 and 504 is effective, as shown in equations 503 and 506.

[0049] As described above, bouncing can be suppressed by increasing the contact area between the anchor 106 and the stopper 114. Note that the squeeze force generates a repulsive force when the anchor 106 and the stopper 114 approach each other (during the valve closing operation), and is effective in decelerating the anchor 106. However, a similar squeeze force is also generated when the anchor 106 separates from the stopper 114 (during the valve opening operation). As a result, the separation of the anchor 106 is hindered, and the separation speed decreases, which hinders the high-speed operation required of the fuel injection device.

[0050] 1-4. Structure in the Vicinity of the Anchor 106 of the Fuel Injection Device of the Present Example Next, the structure in the vicinities of the anchor 106 of the present example will be described with reference to Figures 6 and 7. Figure 6 is a cross-sectional view showing the structure in the vicinities of the anchor 106. Figure 7 is a diagram showing the plate 117.

[0051] As shown in FIG. 6 , a plate 117 is disposed between the anchor 106 and the stopper 114. The plate 117 is disposed so as to be able to move up and down independently relative to the anchor 106 and the stopper 114. A third spring 116 is disposed below the plate 117. The third spring 116 contacts the plate 117 and biases it upward, i.e., toward the anchor 106. The lower side of the third spring 116 contacts the nozzle holder 107. The spring constant of the third spring 116 is set to be smaller than the spring constant of the second spring 115. Therefore, the plate 117 is sandwiched between the anchor 106 and the stopper 114 and is in contact with both, and maintains this state when not energized.

[0052] As shown in FIG. 7 , the plate 117 is formed in a substantially circular plate shape with an opening in the radial center. The plunger rod 108 is inserted through the opening of the plate 117. A convex portion 701 that protrudes upward in the vertical direction is formed at one axial end of the plate 117. The convex portion 701 is a ridge that continues along the circumferential direction of the plate 117. The convex portion 701 comes into contact with the anchor 106. A contact surface 702 is formed at the other axial end of the plate 117. The contact surface 702 is formed in a flat shape. The contact surface 702 comes into contact with the stopper 114.

[0053] 1-5. Operation of the Fuel Injection Device of the Present Example Next, the operation of the fuel injection device 100 of the present example having the above-described configuration will be described with reference to Figures 8 and 9. Figure 8 is a cross-sectional view showing the operating states of the anchor 106, plunger rod 108, and plate 117 in the fuel injection device 100 of the present example. Figure 9 is a time chart showing the operating states of the anchor 106, plunger rods 108, 117 of the fuel injection device 100 of the present example. Note that Figure 8, like Figure 3, shows the operation from valve opening to valve closing.

[0054] The state shown in Fig. 8(a) is the initial state. As shown in Fig. 8(a), the anchor 106, plunger rod 108, and plate 117 are held in place by the repulsive forces of the first spring 111 to the third spring 116. The plate 117 is sandwiched between the anchor 106 and the stopper 114 and remains stationary (state (A) shown in Fig. 9).

[0055] The state shown in Figure 8(b) is the moment when the anchor 106 starts to rise after energization and hits the retainer 113 (state (B) shown in Figure 9). Immediately after energization, the plate 117 is urged upward by the third spring 116, but its rise is hindered by the squeeze force, and it lags behind the anchor 106. As a result, the anchor 106 separates from the plate 117 and rises.

[0056] After the anchor 106 is released, the plate 117 follows the anchor 106 due to the repulsive force of the third spring 116, releases from the stopper 114, and begins to rise. After reaching state (B) shown in FIG. 8(b), the anchor 106, plunger rod 108, and retainer 113 continue to rise. Then, the anchor 106 collides with and is attracted to the magnetic core 105, stopping its rise. This results in the completely open state shown in FIG. 8(c) (state (C) shown in FIG. 9).

[0057] After this, the rising plate 117 collides with the anchor 106, resulting in state (D) shown in FIG. 8( d). The fuel injection device 100 maintains the valve open state for a certain period of time to inject fuel, and then begins the valve closing operation. The plunger rod 108 is urged downward by the first spring 111, which simultaneously urges the anchor 106 and plate 117 downward via the retainer 113. When the current is interrupted and the electromagnetic force between the anchor 106 and magnetic core 105 decreases, the anchor 106 separates from the magnetic core 105. The anchor 106 then begins to move downward together with the plunger rod 108 and plate 117.

[0058] When the anchor 106 descends by the stroke (st2), it reaches the state (E) shown in FIG. 8(e). At this point, the valve is completely closed and the fuel injection device 100 stops. At this point, a downward inertial force and a downward spring force from the second spring 115 act on the anchor 106. As a result, the anchor 106 separates from the retainer 113 and continues to descend. After descending by the preliminary stroke (st1), the plate 117 collides with the stopper 114 and returns to the state shown in FIG. 8(f), i.e., the initial state.

[0059] Figure 9 is a time chart showing the operating states of the anchor 106, plunger rod 108, and plate 117 of this example. The horizontal axis in Figure 9 represents time, with graph 901 showing changes in current and graph 902 showing changes in displacement. State (A) shown on the horizontal axis of graph 902 corresponds to the state shown in Figure 8(a), state (B) corresponds to the state shown in Figure 8(b), and state (C) corresponds to the state shown in Figure 8(c). State (D) corresponds to the state shown in Figure 8(d), state (E) corresponds to the state shown in Figure 8(e), and state (F) corresponds to the state shown in Figure 8(f).

[0060] In addition, the dashed line Q2 shown in the graph 902 indicates the displacement of the anchor 106, the solid line P2 indicates the displacement of the plunger rod 108, and the dashed dotted line K2 indicates the displacement of the plate 117.

[0061] 9, when current begins to flow at time 0, the anchor 106 begins to be displaced from state (A) by electromagnetic force. The anchor 106 rises while accelerating and collides with the retainer 113 at time t1 (state (B)). Thereafter, the anchor 106 rises together with the plunger rod 108 fastened to the retainer 113, and begins to open the valve. At time t2, the anchor 106 collides with the magnetic core 105 and stops (state (C)).

[0062] The plunger rod 108 overshoots due to inertial force, but is quickly stabilized by the spring force of the first spring 111 and the pressure of the fuel, and maintains state (D) for a while. After the anchor 106 is released, the plate 117 starts to rise, and follows the anchor 106, colliding with it at time t3 (state (D)). After that, the plate 117 moves integrally with the anchor 106.

[0063] Even after the current becomes zero, state (D) is maintained due to the influence of residual magnetism. However, when the electromagnetic force acting on the anchor 106 becomes equal to or less than the repulsive force (the sum of the spring force of the first spring 111 and the fuel pressure), the anchor 106 and plunger rod 108 separate from the magnetic core 105 and begin to descend. When they descend until time t4, the valve element 110 is pressed against the seat portion of the injection hole forming member 109, resulting in a closed valve state. The plunger rod 108 then stops (state (E)). The anchor 106 and plate 117 separate from the retainer 113 due to their own inertial force and the spring force of the second spring 115, and continue to descend. Then, at time t5, the plate 117 collides with the stopper 114 (state (F)).

[0064] 7, the contact area of ​​the plate 117 with the anchor 106 is reduced by the protrusion 701 compared to the contact surface 702 with the stopper 114. As a result, when the valve starts to open, the contact area is reduced by the protrusion 701, so the plate 117 smoothly releases from the anchor 106. This prevents the plate 117 from interfering with the rising (release) movement of the anchor 106.

[0065] Furthermore, during the valve closing operation, the plate 117 descends integrally with the anchor 106. At this time, the contact surface 702 of the plate 117 that comes into contact with the stopper 114 is formed into a flat surface, thereby increasing the squeezing force. As a result, when the anchor 106 and the stopper 114 approach each other (during the valve closing operation), the squeezing force generated by the plate 117 can reduce the collision speed and suppress bouncing. As a result, it is possible to suppress bouncing while performing high-speed operation, thereby reducing the variation in the injection amount.

[0066] 2. Second Embodiment Next, a fuel injection device according to a second embodiment will be described with reference to Fig. 10. Fig. 10 is a cross-sectional view showing the structure of the vicinity of the anchor in the fuel injection device according to the second embodiment.

[0067] The fuel injection device according to the second embodiment differs from the fuel injection device 100 according to the first embodiment in the shape of the plate. Therefore, parts common to the fuel injection device 100 according to the first embodiment are designated by the same reference numerals and redundant explanations will be omitted.

[0068] 10 , in a fuel injection device 1001 according to the second embodiment, a plate 117B is disposed between the anchor 106 and the stopper 114. The surface of the plate 117B that comes into contact with the stopper 114 is formed in a flat plate shape. In contrast, the surface of the plate 117B that faces the anchor 106 is formed in an arc shape. In other words, the contact area of ​​the plate 117B with the anchor 106 is smaller than the contact area of ​​the plate 117B with the stopper 114.

[0069] The other configurations are the same as those of the fuel injection device 100 according to the first embodiment, and therefore description thereof will be omitted. The fuel injection device 1001 having such a plate 117B can also obtain the same effects as those of the fuel injection device 100 according to the first embodiment described above.

[0070] In the plate 117B according to the second embodiment, the contact surface with the stopper 114 may be formed in an arc shape, similar to the surface facing the anchor 106. In this case, it is preferable that the radius of curvature of the contact surface with the stopper 114 of the plate 117B is larger than the radius of curvature of the surface (contact surface) of the plate 117B facing the anchor 106.

[0071] 3. Third Embodiment Next, a fuel injection device according to a third embodiment will be described with reference to Fig. 11. Fig. 11 is a cross-sectional view showing the structure of the vicinity of the anchor in the fuel injection device according to the third embodiment.

[0072] The fuel injection device according to the third embodiment differs from the fuel injection device 100 according to the first embodiment in the shapes of the plate and anchor. Therefore, parts common to the fuel injection device 100 according to the first embodiment are designated by the same reference numerals and redundant explanations will be omitted.

[0073] As shown in FIG. 11 , in a fuel injection device 1002 according to the third embodiment, a plate 117C is disposed between an anchor 106C and a stopper 114. The plate 117C is formed in a substantially flat plate shape. The plate 117C has a constant thickness. A protrusion 106k is formed on the surface of the anchor 106C that faces the plate 117C (contact surface). Therefore, the contact area between the plate 117C and the anchor 106C is set smaller than the contact area between the plate 117C and the stopper 114.

[0074] The other configurations are the same as those of the fuel injection device 100 according to the first embodiment, and therefore description thereof will be omitted. The fuel injection device 1002 having such plate 117C and anchor 106C can also achieve the same effects as those of the fuel injection device 100 according to the first embodiment described above.

[0075] According to the fuel injection device 1002 of the third embodiment, the manufacturing cost of the plate 117C can be reduced compared to the fuel injection device 100 of the first embodiment.

[0076] 4. Fourth Embodiment Next, a fuel injection device according to a fourth embodiment will be described with reference to Figures 12 and 13. Figure 12 is a cross-sectional view showing the structure near the anchor in the fuel injection device according to the fourth embodiment. Figure 13 is a view showing the plate of the fuel injection device according to the fourth embodiment.

[0077] The fuel injection device according to the fourth embodiment differs from the fuel injection device 100 according to the first embodiment in the shape of the plate and in the elimination of the third spring. Therefore, parts common to the fuel injection device 100 according to the first embodiment are designated by the same reference numerals and redundant explanations will be omitted.

[0078] 12, in a fuel injection device 1003 according to the fourth embodiment, a plate 117D is disposed between the anchor 106 and the stopper 114. Note that a third spring is not provided below the stopper 114 in the axial direction.

[0079] 13 , the plate 117D according to the fourth embodiment is similar to the plate 117 according to the first embodiment, except that it is provided with a support portion 1102 and a plurality of beam structures 1101. The beam structures 1101, which are an example of a biasing member, are provided on the outer periphery of the plate 117D in the radial direction. The plurality of beam structures 1101 are spaced apart in the circumferential direction of the plate 117D. The beam structures 1101 protrude radially outward from the outer periphery of the plate 117D.

[0080] A support portion 1102 is provided at the radially outer end of the plate 117D of the beam structure 1101. The support portion 1102 is formed in a substantially annular shape. The support portion 1102 is fixed to the nozzle holder 107. That is, the beam structure 1101 is disposed between the plate 117D and the support portion 1102. The beam structure 1101 has elasticity. The beam structure 1101 biases the plate 117D toward the anchor 106. This allows the plate 117D to be biased toward the anchor 106 without providing the third spring 116. As a result, the number of parts of the fuel injection device 1003 can be reduced.

[0081] The other configurations are the same as those of fuel injection device 100 according to the first embodiment, and therefore description thereof will be omitted. Fuel injection device 1003 in which beam structure 1101 and support portion 1102 are provided on plate 117D can also achieve the same effects as fuel injection device 100 according to the first embodiment described above.

[0082] 5. Fifth Embodiment Next, a fuel injection device according to a fifth embodiment will be described with reference to Fig. 14. Fig. 14 is a cross-sectional view showing the structure of the vicinity of the anchor in the fuel injection device according to the fourth embodiment.

[0083] The fuel injection device according to the fifth embodiment differs from the fuel injection device 100 according to the first embodiment in the shape of the stopper 114 and the support structure of the third spring. Therefore, parts common to the fuel injection device 100 according to the first embodiment are designated by the same reference numerals and redundant explanations will be omitted.

[0084] 14, a fuel injection device 1004 according to the fifth embodiment is characterized by the support structure of the third spring 116. In the first to fourth embodiments described above, the third spring 116 or the support portion 1102 is fixed to the nozzle holder 107. In contrast, in the fuel injection device 1004 according to the fifth embodiment, the third spring 116 is fixed to the stopper 114E.

[0085] 14, stopper 114E is fixed to plunger rod 108 and disposed in a recess formed in nozzle holder 107. A spring bearing portion 114a is formed at the other axial end of stopper 114E. Spring bearing portion 114a is a flange portion that protrudes radially outward from the outer circumferential surface of stopper 114E.

[0086] One end of the third spring 116 abuts against the plate 117, and the other end of the third spring 116 is fixed to the spring bearing portion 114a of the stopper 114E. The third spring 116 biases the plate 117 toward the anchor 106.

[0087] In the assembly process of the fuel injection device 1004 according to the fifth embodiment, first, the stopper 114E is fixed to the plunger rod 108. Then, the plunger rod 108 is inserted into the third spring 116, and the third spring 116 is fixed to the spring receiving portion 114a of the stopper 114E. Furthermore, the plunger rod 108 is inserted in the order of the plate 117, anchor 106, second spring 115, and retainer 113. Then, the retainer 113 is fixed in a predetermined position on the plunger rod 108, thereby completing the assembly around the plunger rod 108. This eliminates the need for a step of fixing the third spring 116 to the nozzle holder 107, making the assembly process easier.

[0088] The other configurations are the same as those of the fuel injection device 100 according to the first embodiment, and therefore a description thereof will be omitted. Even with this configuration in which the third spring 116 is fixed to the stopper 114E and biases the plate 117 toward the anchor 106, it is possible to obtain the same effects as those of the fuel injection device 100 according to the first embodiment described above.

[0089] The present invention is not limited to the embodiments described above and shown in the drawings, and various modifications can be made without departing from the spirit of the invention as defined in the claims.

[0090] In this specification, the words "parallel" and "orthogonal" are used, but these do not mean only "parallel" and "orthogonal" in the strict sense, but also include "parallel" and "orthogonal" and may also mean a "substantially parallel" or "substantially orthogonal" state within a range in which the functions can be exerted.

[0091] DESCRIPTION OF SYMBOLS 100, 1001, 1002, 1003, 1004...Fuel injection device, 101...First housing, 102...O-ring, 103...Second housing, 104...Coil, 105...Magnetic core, 106, 106C...Anchor, 106k...Protrusion, 107...Nozzle holder, 108...Plunger rod, 109...Injection hole forming member, 110...Valve body, 111...First spring, 112...Adjusting member, 113...Retainer, 114, 114E...Stopper, 114a...Spring receiving portion, 115...Second spring, 116...Third spring (biasing member), 117, 117B, 117C, 117D...Plate, 701...Contact portion, 702...Contact surface, 1101... beam structure (biasing member), 1102... support portion

Claims

1. A fuel injection device comprising: a nozzle holder provided with an injection hole forming member, a magnetic core arranged in said nozzle holder, an anchor arranged opposite said magnetic core, a plunger rod movably arranged in said nozzle holder and having a valve body, a retainer arranged on said plunger rod and against which said anchor abuts when a valve is opened, a stopper arranged on said plunger rod and arranged on the opposite side of said anchor to said retainer, a plate arranged between the stopper and the anchor, and a biasing member that biases said plate against said anchor, wherein the contact area of ​​a contact surface of said plate that comes into contact with said anchor is set smaller than the contact area of ​​a contact surface of said plate that comes into contact with said stopper.

2. The fuel injection device according to claim 1, wherein a convex portion protruding toward said anchor is formed on a surface of said plate facing said anchor.

3. The fuel injection device according to claim 1, wherein a protrusion protruding toward said plate is formed on a surface of said anchor that faces said plate.

4. The fuel injection device according to claim 1, wherein the surface of said plate facing said anchor is formed in an arc shape.

5. The fuel injection device according to claim 4, wherein a surface of said plate that comes into contact with said stopper is formed in an arc shape, and a radius of curvature of said surface of said plate that comes into contact with said stopper is larger than a radius of curvature of a surface of said plate that faces said anchor.

6. The fuel injection device according to claim 1, wherein the biasing member is a spring disposed on the opposite side of the plate from the anchor.

7. The fuel injection device according to claim 1, comprising: a support portion fixed to said nozzle holder; and a beam structure disposed between said support portion and said plate, said beam structure biasing said plate towards the anchor.

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