Fuel injection device

Abstract

To provide a fuel injection device capable of stably injecting fuel.SOLUTION: A fuel injection device includes a nozzle holder, a magnetic core, an anchor 106, a plunger rod 108, a retainer 113, a stopper 114, a plate 117, and an energizing member 116. The retainer 113 is provided on the plunger rod 108, and the anchor 106 comes into contact therewith when a valve is opened. The stopper 114 is provided on the plunger rod 108, and is disposed on a side of the anchor 106 opposite the retainer 113. The plate 117 is disposed between the stopper 114 and the anchor 106. The energizing member 116 energizes the plate 117 to the anchor 106. A contact area of a contact surface of the plate 117 in contact with the anchor 106 is set to be smaller than a contact area of a contact surface of the plate 117 in contact with the stopper 114.SELECTED DRAWING: Figure 6

Description

Technical Field

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

Background Art

[0002] Conventionally, as an internal combustion engine, an in-cylinder injection type internal combustion engine that directly injects fuel into a cylinder by a fuel injection device has been used. In recent years, in order to cope with high speed and high fuel pressure, fuel injection devices equipped with a pre-stroke mechanism have been increasing. Generally, a fuel injection device attracts an anchor, which is a mover held in a valve-closed state by a first spring, by an electromagnet. Then, a plunger rod is engaged with the anchor, and a valve opening operation is performed by energization.

[0003] The anchor generates a force according to the magnetic flux created by the electromagnet. Also, the plunger rod is driven by the anchor, and a valve body is formed at an axial end portion. And the pre-stroke is a space (play) provided between the anchor and the plunger rod. When the electromagnetic force acts and the anchor is moving the pre-stroke, it has a structure that is less likely to receive a reaction force from the plunger rod. Thereby, the anchor can be accelerated in a state close to no load and made to collide with the plunger rod.

[0004] Thus, in addition to the electromagnetic energy acting on the anchor, the kinetic energy accumulated in the anchor also contributes to the acceleration of the plunger rod, enabling a high-speed valve opening operation. Also, in a valve structure where fuel pressure acts on the plunger rod, it is necessary to apply energy to the plunger rod to open the valve against the fuel pressure during the valve opening operation. Therefore, it can be said that a valve structure having a pre-stroke is suitable for high fuel pressure.

[0005] As a technology related to such a conventional fuel injection device, there is one described in Patent Document 1. Patent Document 1 describes a technology including a valve seat, a valve body, a movable core separated from the valve body, and a magnetic core that stops the movement of the movable core. Further, Patent Document 1 describes that it includes a valve body portion that opens and closes a flow path by contacting and separating from the valve seat, a plunger rod that transmits power from the valve body portion to a drive portion, an anchor that can be relatively displaced with respect to the plunger rod, and a magnetic core in which a through hole is formed.

[0006] And in the technology described in Patent Document 1, at the time of valve opening, first, the anchor is in contact with a first flange-shaped structural member (stopper) formed on the plunger rod. After energization, the anchor starts to move due to the electromagnetic force generated between the anchor and the magnetic core and separates from the first flange-shaped structural member. Then, the anchor 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, at the time of valve closing, the anchor moves in the reverse direction, and after valve closing, the anchor collides with the stopper and returns to the initial state.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, in the technique described in Patent Document 1, when the anchor returns to the initial position and collides with the stopper, damped vibration that continuously bounces back while decaying, so-called bouncing, occurs. And when the next valve opening operation is started during bouncing, the initial position and initial velocity of the anchor cannot be defined, and there is a problem that variations occur in the valve opening time and valve opening amount. As a result, the technique described in Patent Document 1 has a problem that variations in the injection amount occur due to bouncing, and stable fuel injection cannot be performed.

[0009] An object of the present invention is to provide a fuel injection device capable of performing stable fuel injection in consideration of the above problems.

Means for Solving the Problems

[0010] In order to solve the above problems and achieve the object, the fuel injection device includes a nozzle holder provided with an injection hole forming member, a magnetic core disposed in the nozzle holder, an anchor, a plunger rod, a retainer, a stopper, a plate, and a biasing member. The anchor is disposed to face the magnetic core. The plunger rod is movably disposed 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 disposed on the side of the anchor opposite to the retainer. The plate is disposed between the stopper and the anchor. The biasing member biases the plate toward the anchor. And the contact area of the contact surface of the plate that contacts the anchor is set to be smaller than the contact area of the contact surface of the plate that contacts the stopper.

Effects of the Invention

[0011] According to the fuel injection device having the above configuration, variations in the initial position and initial velocity of the anchor due to bouncing can be suppressed, and stable fuel injection can be achieved.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Embodiments for Carrying Out the Invention

[0013] Hereinafter, an embodiment example of a fuel injection device will be described with reference to FIGS. 1 to 14. In each figure, common members are denoted by the same reference numerals.

[0014] 1. First Embodiment Example 1-1. Configuration of Fuel Injection Device First, the configuration of the fuel injection device according to the first embodiment example (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 as an internal combustion engine in a four-cycle engine that repeats four strokes of an intake stroke, a compression stroke, a combustion (expansion) stroke, and an exhaust stroke. Further, the fuel injection device is applied to an in-cylinder injection type internal combustion engine that injects fuel into the cylinder of each cylinder. The fuel supplied from the fuel pump is supplied to the rear end portion (upper portion in FIG. 1) of the fuel injection device 100 via a manifold (omitted in this embodiment). Then, the fuel injection device 100 injects fuel into the cylinder from the tip end portion (lower portion in FIG. 1) during the valve opening operation. Further, the fuel injection device 100 has a substantially axisymmetric structure.

[0016] As shown in FIG. 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. Further, the fuel injection device 100 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 serving as a biasing member. Furthermore, the fuel injection device 100 of this example includes a plate 117.

[0017] The first housing 101 is formed in a cylindrical shape with a hollow structure inside. One axial end (upper end) of the first housing 101 is connected to a manifold (not shown). Also, 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. And the O-ring 102 seals between the first housing 101 and the manifold to prevent fuel leakage.

[0018] A second housing 103 is connected to the other axial end (tip end) 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 peripheral surface of the first housing 101 at the other axial end of the first housing 101. Also, a coil 104 is wound around the outer peripheral surface of the second housing 103.

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

[0020] The nozzle holder 107 is formed in a cylindrical shape with a hollow structure inside. One axial end (upper end) of the nozzle holder 107 is connected to the other axial end (tip end) of the second housing 103. And the internal space of the nozzle holder 107 communicates with the internal space of the second housing 103. Also, an injection hole forming member 109 is attached to the other axial end (tip end) of the nozzle holder 107 by insertion or press-fitting. Injection holes for injecting fuel are formed in this injection hole forming member 109.

[0021] In addition, the injection hole forming member 109 is formed with a valve seat with which the tip of a valve body 110 described later makes contact. When the valve body 110 seats on the valve seat, the injection hole forming member 109 seals the fuel. Also, when the valve body 110 abuts against the valve seat, it seals the fuel, and when it separates from the valve seat, it permits the passage of the fuel.

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

[0023] The magnetic core 105 is formed in a substantially cylindrical shape by a magnetic material. The magnetic core 105 is fixed in a state of being fitted to the inner peripheral surface of the first housing 101. Also, the magnetic core 105 protrudes from the other axial end of the first housing 101. And the portion of the magnetic core 105 that protrudes from the first housing 101 is inserted into the second housing 103. Further, the outer peripheral surface of the magnetic core 105 faces the coil 104 via the second housing 103. An anchor 106 is disposed opposite the other axial end of the magnetic core 105.

[0024] The anchor 106 is formed in a substantially cylindrical shape by a magnetic material. A plunger rod 108 is inserted into the cylindrical hole of 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. Also, a minute gap is formed between the outer peripheral surface of the anchor 106 and the inner peripheral surfaces of the nozzle holder 107 and the second housing 103.

[0025] In addition, the anchor 106 is formed with an eccentric through-hole (not shown). The eccentric through-hole is formed at a position deviated from the center in the radial direction of the anchor 106. And the eccentric through-hole penetrates the anchor 106 from one axial end to the other end. This eccentric through-hole serves as a flow path through which the fuel passes. Also, a stopper 114 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, respectively. And the plunger rod 108 is disposed movably in the axial direction of the nozzle holder 107 and the second housing 103 in the internal spaces of the nozzle holder 107 and the second housing 103.

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

[0028] Further, 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. Also, the adjustment member 112 is formed in a cylindrical shape. And the cylindrical hole of the adjustment member 112 serves as a flow path through which fuel passes.

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

[0030] One end (upper end) of the first spring 111 abuts against the other end portion in the axial direction 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 described later. The first spring 111 biases the plunger rod 108 toward the injection hole forming member 109 side. Thereby, 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. Also, 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. Further, 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. And the second spring 115 biases the retainer 113 upward.

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

[0033] A stopper 114 is disposed below the anchor 106 on the side opposite 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 Here, a conventional fuel injection device will be described with reference to FIGS. 2 to 4. FIG. 2 is a cross-sectional view showing the structure near the anchor 106 in a conventional fuel injection device. FIG. 3 is a cross-sectional view showing the operating states of the anchor 106 and the plunger rod 108 in a conventional fuel injection device. FIG. 4 is a time chart showing the operating states of the anchor 106 and the plunger rod 108 of a conventional fuel injection device. Note that FIG. 2 shows the initial position where no current is flowing through the coil 104.

[0035] As shown in Fig. 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 upper part of the anchor 106 and the lower part of the retainer 113. This gap is referred to as the preliminary stroke (st1). Also, the vertical distance between the lower part of the retainer 113 and the lower part of the magnetic core 105 is referred to as the stroke (st2).

[0036] Fig. 3(a) shows the initial position before energizing the coil 104. As shown in Fig. 3(a), the anchor 106 is stationary in contact with the stopper 114. When an electric 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 detaches from the stopper 114. Then, the anchor 106 accelerates upward and rises by a distance corresponding to the preliminary stroke (st1) and collides with the retainer 113. The state at this moment is shown in Fig. 3(b). Thereby, the fuel injection device starts valve opening.

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

[0038] The plunger rod 108 is biased downward by the first spring 111 and simultaneously biases the anchor 106 downward via the retainer 113. When the electric current is cut off and the electromagnetic force between the anchor 106 and the magnetic core 105 decreases, the anchor 106 detaches from the magnetic core 105. Then, the anchor 106 starts to move downward together with the plunger rod 108. When it descends by the stroke (st2), it changes from the state shown in Fig. 3(c) to the state shown in Fig. 3(b), and at this point, it completely closes the valve and the fuel injection device stops.

[0039] At this point, a downward inertial force and a downward spring force due to the second spring 115 act on the anchor 106. Therefore, the anchor 106 detaches from the retainer 113 and further descends. After descending by the amount of the preliminary stroke (st1), the anchor 106 collides with the stopper 114, causing bouncing.

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

[0041] As shown in graph 402 of Figure 4, when current starts to flow at time 0, the anchor 106 starts to displace from state (A) due to the electromagnetic force. The anchor 106 rises while accelerating and collides with the retainer 113 at time t1 (state (B)). After that, the anchor 106 becomes integrated with the plunger rod 108 fastened to the retainer 113 and rises to start valve opening. 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 reaches a static state due to the spring force of the first spring 111 and the fuel pressure, and maintains state (C) for a while. And even after the current becomes zero, state (C) 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 the plunger rod 108 disengage from the magnetic core 105 and start to descend. Then, when they descend until time t3, the valve body 110 is pressed against the seat portion of the injection hole forming member 109 to be in a closed valve state. Therefore, the plunger rod 108 stops (state (B)). At this time, the anchor 106 disengages from the retainer 113 due to its own inertial force and the spring force of the second spring 115, and continues to descend further. Then, the anchor 106 collides with the stopper 114 at time t4 (state (A)). As shown in the graph 402 of FIG. 4, after the anchor 106 and the stopper 114 collide, they repeatedly separate and collide, undergoing damped vibration (bouncing).

[0043] When current starts to flow and the valve opening operation starts while the anchor 106 is in a bouncing state, the initial velocity and initial position of the anchor 106 become indeterminate. As a result, the valve opening characteristics of the fuel injection device vary, leading to variations in the injection amount. Thus, it can be seen that it is necessary to suppress the bouncing of the anchor 106 in order to prevent variations during high-speed operation.

[0044] 1-3. Regarding the fluid force (squeeze force) Next, the fluid force (squeeze force) will be described with reference to FIG. 5. FIG. 5 is a diagram and mathematical formula showing the magnitude of the fluid force (squeeze force) applied to an object.

[0045] As a method for suppressing the above-described bouncing, a method of utilizing the fluid force (squeeze force) generated in a narrow gap can be considered. Here, the squeeze force is a fluid force generated when an object approaches or separates, accompanied by the exclusion and introduction of the fluid between the objects. And the squeeze force is a force generated in a direction to prevent the approach and separation of two objects.

[0046] The state where a flat plate approaches a plane with respect to the object 501 composed of a spherical body shown in FIG. 5 will be described. Here, Equation 502 is a theoretical formula representing the magnitude of the squeeze force. In Equation 502, F represents the squeeze force, μ represents the viscosity coefficient, v represents the approaching speed, h represents the magnitude of the gap between the object 501 and the flat plate, and R represents the radius of the object 501. And Equation 503 is a transformation of Equation 502 using the projected area S (= π*R^2) of the sphere which is the object 501.

[0047] Also, the object 504 shown in FIG. 5 is formed in a substantially disc shape. And Equations 505 and 506 are theoretical formulas representing the magnitude of the squeeze force F in the state where the flat plate approaches the plane with respect to the object 504.

[0048] Looking at Equation 503, it can be seen that the squeeze force F is proportional to the projected area S and the approaching speed v, and inversely proportional to the magnitude of the gap h. Looking at Equation 506, similar to Equation 503, it can be seen that the squeeze force F is proportional to the area S and the approaching speed v, and inversely proportional to the cube of the magnitude of the gap h. As described above, since the cause of bouncing is the collision between the anchor 106 and the stopper 114, bouncing can be suppressed by suppressing the collision speed. And to suppress the collision speed, as shown in FIG. 5, it is effective to increase the squeeze force F. For that purpose, it can be said that it is effective to increase the area S of the objects 501 and 504 as shown in Equations 503 and 506.

[0049] As described above, it is possible to suppress bouncing 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, the same squeeze force is generated even when the anchor 106 separates from the stopper 114 (during the valve opening operation). As a result, the separation of the anchor 106 is obstructed and the separation speed decreases, which hinders the high-speed operation required for the fuel injection device.

[0050] 1-4. Structure near the anchor 106 of the fuel injection device of this example Next, with reference to FIGS. 6 to 7, the structure near the anchor 106 of this example will be described. FIG. 6 is a cross-sectional view showing the structure near the anchor 106. FIG. 7 is a view 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 arranged so as to be movable independently in the vertical direction with respect to the anchor 106 and the stopper 114. Below the plate 117, a third spring 116 is disposed. The third spring 116 contacts the plate 117 and biases the plate 117 upward, that is, toward the anchor 106. Also, the lower part of the third spring 116 is in contact with the nozzle holder 107. Note that the spring constant of the third spring 116 is set 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 of them, and this state is maintained when not energized.

[0052] As shown in FIG. 7, the plate 117 is formed in a substantially disc shape having an opening at the center in the radial direction. A plunger rod 108 is inserted through the opening of the plate 117. At one end portion in the axial direction of the plate 117, a convex portion 701 protruding upward in the vertical direction is formed. The convex portion 701 is a ridge continuous along the circumferential direction of the plate 117. And the convex portion 701 contacts the anchor 106. Also, a contact surface 702 is formed at the other end portion in the axial direction of the plate 117. The contact surface 702 is formed in a planar shape. And the contact surface 702 contacts the stopper 114.

[0053] 1-5. Operation of the fuel injection device of this example Next, with reference to FIGS. 8 to 9, the operation of the fuel injection device 100 of this example having the above-described configuration will be described. FIG. 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 this example. FIG. 9 is a time chart showing the operating states of the anchor 106, plunger rods 108 and 117 of the fuel injection device 100 of this example. Note that in FIG. 8, similar to FIG. 3, the operation from valve opening to valve closing is shown.

[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 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 is stationary (state (A) shown in FIG. 9).

[0055] The state shown in FIG. 8(b) is the moment when the anchor 106 starts to rise and collides with the retainer 113 after energization (state (B) shown in FIG. 9). Immediately after energization, the plate 117 is urged upward by the third spring 116, but its upward movement is inhibited by the squeeze force and it lags behind the anchor 106. Therefore, the anchor 106 detaches from the plate 117 and rises.

[0056] After the anchor 106 detaches, the plate 117 follows the anchor 106 due to the repulsive force of the third spring 116, detaches from the stopper 114, and rises. After the 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 adsorbed by the magnetic core 105, and the upward movement stops. As a result, the complete valve-open state shown in FIG. 8(c) is achieved (state (C) shown in FIG. 9).

[0057] After that, the rising plate 117 collides with the anchor 106, reaching the 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 starts the valve closing operation. The plunger rod 108 is biased downward by the first spring 111, and at the same time, biases the anchor 106 and the plate 117 downward via the 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 disengages from the magnetic core 105. Then, the anchor 106 starts to move downward together with the plunger rod 108 and the 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 fully closed and the fuel injection device 100 stops. At this time, a downward inertial force and a downward spring force due to the second spring 115 act on the anchor 106. Therefore, the anchor 106 disengages from the retainer 113 and further descends. 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), that is, the initial state.

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

[0060] Also, the dashed line Q2 shown in 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] As shown in Fig. 9, when current starts to flow at time 0, the anchor 106 starts to displace from state (A) due to the electromagnetic force. The anchor 106 rises while accelerating and collides with the retainer 113 at time t1 (state (B)). After that, the anchor 106 is integrated with the plunger rod 108 fastened to the retainer 113 and rises to start valve opening. At time t2, the anchor 106 collides with the magnetic core 105 and stops (state (C)).

[0062] The plunger rod 108 overshoots due to the inertial force, but quickly stabilizes due to the spring force of the first spring 111 and the fuel pressure, and maintains state (D) for a while. The plate 117 starts to rise after the anchor 106 detaches, and collides with the anchor 106 at time t3 in a form following the anchor 106 (state (D)). After that, the plate 117 moves integrally with the anchor 106.

[0063] Even after the current becomes 0, state (D) is maintained due to the influence of the residual magnetism, but when the electromagnetic force acting on the anchor 106 becomes less than or equal to the repulsive force (the sum of the spring force of the first spring 111 and the fuel pressure), the anchor 106 and the plunger rod 108 detach from the magnetic core 105 and start to descend. When it descends until time t4, the valve body 110 is pressed against the seat portion of the injection hole forming member 109 to be in a closed valve state. Then, the plunger rod 108 stops (state (E)). The anchor 106 and the plate 117 detach from the retainer 113 due to their own inertial forces and the spring force of the second spring 115 and continue to descend further. Then, at time t5, the plate 117 collides with the stopper 114 (state (F)).

[0064] Here, as shown in Fig. 7, the plate 117 reduces the contact area with the anchor 106 by the convex portion 701 compared to the contact surface 702 with the stopper 114. Thereby, at the start of valve opening, since the convex portion 701 reduces the contact area, the plate 117 smoothly detaches from the anchor 106. Thereby, it is possible to prevent the plate 117 from interfering with the rising (detaching) operation of the anchor 106.

[0065] Also, during the valve closing operation, the plate 117 descends integrally with the anchor 106. At this time, the contact surface 702 that contacts the stopper 114 on the plate 117 is formed in a planar shape, increasing the squeezing force. As a result, when the anchor 106 and the stopper 114 approach each other (during the valve closing operation), the collision speed can be reduced and bouncing can be suppressed by the squeezing force generated by the plate 117. Consequently, it is possible to suppress bouncing while performing high-speed operation and reduce variations in the injection amount.

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

[0067] The difference between the fuel injection device according to the second embodiment example and the fuel injection device 100 according to the first embodiment example lies in the shape of the plate. Therefore, here, the same reference numerals are given to the parts common to the fuel injection device 100 according to the first embodiment example, and duplicate explanations are omitted.

[0068] As shown in FIG. 10, in the fuel injection device 1001 according to the second embodiment example, a plate 117B is disposed between the anchor 106 and the stopper 114. The contact surface of the plate 117B with the stopper 114 is formed in a flat plate shape. On the other hand, the surface of the plate 117B facing the anchor 106 is formed in an arc shape. That is, the plate 117B is formed such that the contact area with the anchor 106 is smaller than the contact area with the stopper 114.

[0069] Since the other configurations are the same as those of the fuel injection device 100 according to the first embodiment example, their descriptions are omitted. Even with the fuel injection device 1001 having such a plate 117B, the same operational effects as those of the fuel injection device 100 according to the first embodiment example described above can be obtained.

[0070] In addition, in the plate 117B according to the second exemplary 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 of the plate 117B with the stopper 114 is larger than the radius of curvature of the surface (contact surface) of the plate 117B facing the anchor 106.

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

[0072] The fuel injection device according to the third exemplary embodiment is different from the fuel injection device 100 according to the first exemplary embodiment in the shapes of the plate and the anchor. Therefore, herein, the same reference numerals are given to the parts common to the fuel injection device 100 according to the first exemplary embodiment, and the overlapping description is omitted.

[0073] As shown in FIG. 11, in the fuel injection device 1002 according to the third exemplary embodiment, a plate 117C is disposed between the anchor 106C and the stopper 114. The plate 117C is formed in a substantially flat plate shape. And the plate 117C has a constant thickness. Further, a protrusion 106k is formed on the surface (contact surface) of the anchor 106C facing the plate 117C. 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] Since the other configurations are the same as those of the fuel injection device 100 according to the first exemplary embodiment, the description thereof is omitted. Also with the fuel injection device 1002 having such a plate 117C and an anchor 106C, the same operational effects as those of the fuel injection device 100 according to the above-described first exemplary embodiment can be obtained.

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

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

[0077] The difference between the fuel injection device according to the fourth exemplary embodiment and the fuel injection device 100 according to the first exemplary embodiment is that the shape of the plate and the third spring are eliminated. Therefore, here, the same reference numerals are given to the parts common to the fuel injection device 100 according to the first exemplary embodiment, and the overlapping description is omitted.

[0078] As shown in FIG. 12, in the fuel injection device 1003 according to the fourth exemplary embodiment, a plate 117D is disposed between the anchor 106 and the stopper 114. Note that no third spring is provided below the stopper 114 in the axial direction.

[0079] As shown in FIG. 13, the plate 117D according to the fourth exemplary embodiment is provided with a support portion 1102 and a plurality of beam structures 1101 on the plate 117 according to the first exemplary embodiment. The beam structure 1101, which is an example of a biasing member, is provided on the outer peripheral portion on the outer side in the radial direction of the plate 117D. The plurality of beam structures 1101 are arranged at intervals in the circumferential direction of the plate 117D. Further, the beam structure 1101 protrudes radially outward from the outer peripheral portion of the plate 117D.

[0080] At the radially outer end of the plate 117D in the beam structure 1101, a support portion 1102 is provided. The support portion 1102 is formed in a substantially annular shape. And 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. Also, the beam structure 1101 has elasticity. And the beam structure 1101 biases the plate 117D toward the anchor 106. Thereby, without providing the third spring 116, the plate 117D can be biased toward the anchor 106. As a result, the number of components of the fuel injection device 1003 can be reduced.

[0081] Other configurations are the same as those of the fuel injection device 100 according to the first embodiment example, so their descriptions are omitted. Also by the fuel injection device 1003 provided with the beam structure 1101 and the support portion 1102 on such a plate 117D, the same operational effects as those of the fuel injection device 100 according to the first embodiment example described above can be obtained.

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

[0083] The differences between the fuel injection device according to the fifth embodiment example and the fuel injection device 100 according to the first embodiment example are the shape of the stopper 114 and the support structure of the third spring. Therefore, here, the same reference numerals are given to the parts common to the fuel injection device 100 according to the first embodiment example, and the overlapping descriptions are omitted.

[0084] As shown in Fig. 14, the fuel injection device 1004 according to the fifth exemplary embodiment has a feature in the support structure of the third spring 116. In the first to fourth exemplary 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 exemplary embodiment, the third spring 116 is fixed to the stopper 114E.

[0085] As shown in Fig. 14, the stopper 114E is fixed to the plunger rod 108 and is disposed in a recess formed in the nozzle holder 107. Further, a spring receiving portion 114a is formed at the other end in the axial direction of the stopper 114E. The spring receiving portion 114a is a flange portion that protrudes radially outward from the outer peripheral surface of the 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 receiving portion 114a of the stopper 114E. And the third spring 116 biases the plate 117 toward the anchor 106.

[0087] In the fuel injection device 1004 according to the fifth exemplary embodiment, in the assembly process, 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. Further, the plunger rod 108 is inserted in the order of the plate 117, the anchor 106, the second spring 115, and the retainer 113. And by fixing the retainer 113 to a predetermined position of the plunger rod 108, the assembly around the plunger rod 108 is completed. Thereby, the process of fixing the third spring 116 to the nozzle holder 107 becomes unnecessary, and the assembly work can be easily performed.

[0088] Since the other configurations are the same as those of the fuel injection device 100 according to the first exemplary embodiment, the descriptions thereof are omitted. Even in a structure where such a third spring 116 is fixed to the stopper 114E and biases the plate 117 toward the anchor 106, the same operational effects as those of the fuel injection device 100 according to the first exemplary embodiment described above can be obtained.

[0089] Note that 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 gist of the invention described in the claims.

[0090] In this specification, words such as "parallel" and "orthogonal" are used, but these do not mean only strict "parallel" and "orthogonal", and may be in a state of "substantially parallel" or "substantially orthogonal" including "parallel" and "orthogonal" and within a range where their functions can be exerted.

Explanation of Reference Numerals

[0091] 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... adjustment member, 113... retainer, 114, 114E... stopper, 114a... spring receiving portion, 115... second spring, 116... third spring (biasing member), 117, 117B, 117C, 117D... plate, 701... convex portion, 702... contact surface, 1101... beam structure (biasing member), 1102... support portion

Claims

1. A nozzle holder provided with a jet hole forming member, a magnetic core disposed in the nozzle holder, an anchor disposed to face the magnetic core, a plunger rod movably disposed in the nozzle holder and having a valve body, a retainer provided on the plunger rod and against which the anchor abuts when the valve is opened, a stopper provided on the plunger rod and disposed on the side of the anchor opposite to the retainer, a plate disposed between the stopper and the anchor, and a biasing member that biases the plate toward the anchor, wherein 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. A fuel injection device.

2. On the surface of the plate facing the anchor, a convex portion protruding toward the anchor is formed. The fuel injection device according to Claim 1.

3. On the surface of the anchor facing the plate, a protrusion protruding toward the plate is formed. The fuel injection device according to Claim 1.

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

5. The surface of the plate that contacts the stopper is formed in an arc shape, and the radius of curvature of the contact surface of the plate with the stopper is larger than the radius of curvature of the surface of the plate facing the anchor. The fuel injection device according to Claim 4.

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

7. a support portion fixed to the nozzle holder, and a beam structure disposed between the support portion and the plate and biasing the plate toward the anchor. The fuel injection device according to Claim 1, comprising the above.

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