Fuel injection device

Abstract

A fuel injection device is provided that sets the electromagnetic attraction force generated in a magnetic gap between a magnetic core and a movable element to at least a desired value. The fuel injection device comprises a movable element attracted by the magnetic core and a housing provided opposite to the movable element in a direction orthogonal to an axial direction, wherein the movable element is designed such that its axial length is 1.25 to 1.46 times the axial length of the housing.

Description

Technical area

[0001] The present invention relates to a fuel injection device used for an internal combustion engine, particularly to a fuel injection device that performs fuel injection by opening and closing a fuel passage using an electromagnetically driven movable member. Technical Background

[0002] One of the technical backgrounds of the present technical field is disclosed in JP 2012-188977 A. In JP 2012-188977 A, an electromagnetic diaphragm having an inner diameter gradually increasing toward a movable element is provided on an inner peripheral surface of a magnetic core. This can reduce the magnetic delay time at valve opening after power is supplied to an electromagnetic coil and before magnetic fluxes increase, and the magnetic delay time at valve closing after power is cut off to the electromagnetic coil and before magnetic fluxes increase, and can improve the dynamic response at valve opening and closing (see abstract). Citation listPatent literature

[0003] PTL 1: JP 2012-188977 A

[0004] Other conventional fuel injection devices are described in JP 2011-052557 A, JP 2013-217307 A and WO 2013 / 121806 A1. Summary of the inventionTechnical problem

[0005] Automotive engineers have recently had to contend with stricter emissions regulations, higher fuel efficiency, and higher power output. Given this, the fuel injection device disclosed in PTL 1 requires atomization, thus requiring a fuel injection device capable of injecting into an area filled with fuel at a higher pressure.

[0006] For example, in a case where the fuel injection device according to PTL 1 is mounted on a common rail filled with high-pressure fuel, the high fuel pressure acts in a direction that closes a valve body to open and close a fuel passage. In this fuel injection device, by passing a current through the electromagnetic coil, magnetic fluxes are generated in a magnetic gap between the magnetic core and the movable element, thereby generating an electromagnetic attraction force. With the electromagnetic attraction force, the movable element is attracted to the magnetic core.

[0007] In this case, when the common rail is filled with fuel under very high pressure, the conventional electromagnetic attraction force generated by the current supply to the solenoid coil may not be sufficient to attract the movable element to the magnetic core, and the valve may fail to open. If the electromagnetic attraction force is weak, the opening speed of the valve body will be slow, so in this case, the injection of the desired small amount of fuel may fail.

[0008] In view of the above, it is an object of the present invention to provide a fuel injection device which sets the electromagnetic attractive force generated in the magnetic gap between the magnetic core and the movable member at least to a desired value. Solution to the problem

[0009] To solve the problems described above, a fuel injection device according to the present invention has the features defined in claim 1. Advantageous effects of the invention

[0010] The present invention can provide a fuel injection device that sets the electromagnetic attraction force generated in the magnetic gap between the magnetic core and the movable member to at least a desired value. Other structures, operations, and effects of the present invention will be described in detail below using an example of the present invention. Short description of the drawing

[0011] They show: Fig. 1 is a longitudinal sectional view of a fuel injection device according to Example 1 of the present invention, Fig. 2 is an enlarged view of a drive unit structure of the fuel injection device according to Example 1 of the present invention with the valve closed, Fig. 3 is an enlarged view of the drive unit structure of the fuel injection device according to Example 1 of the present invention with the valve closed, Fig. 4 is an enlarged view of one side of the drive unit structure of the fuel injection device according to Example 1 of the present invention with the valve closed, Fig. 5 is an enlarged view of a connecting part between a nozzle holder and a magnetic core of the fuel injection device according to Example 1 of the present invention, Fig. 6 is a graph showing the relationship between the ratio between the axial length of the movable member and the axial length of a housing of a fuel injection valve according to Example 1 of the present invention and the magnetic attraction force generated in the movable member, Fig. 7 is a diagram showing the magnetic flux density in a magnetic circuit of the fuel injection device according to Example 1 of the present invention, Fig. 8 is an enlarged view of the drive unit structure of the fuel injection device according to Example 1 of the present invention when the movable member collides with a magnetic core, Fig. 9 is an enlarged view of the drive unit structure of the fuel injection device according to Example 1 of the present invention when the movable member performs a valve closing movement, Fig. 10 is an enlarged view of a reference example of a drive unit structure of a fuel injection device and Fig. 11 is a graph showing the relationship between the radial cross-sectional area of ​​a housing and the radial cross-sectional area of ​​an electromagnetic coil. Description of embodiments

[0012] Examples of the present invention are described below with reference to Fig. 1 to 11 described. Examples

[0013] Fig. 1 is a diagram showing a basic structure of a fuel injection device according to Example 1 of the present invention. Fig. 2 and Fig. 3 are partially enlarged views of a drive unit structure and its periphery as shown in Fig. 1 shown. Fig. 4 is an enlarged view of one side of the drive unit structure and its periphery. Fig. 5 is an enlarged view of a connecting part in a magnetic circuit. Fig. 1 to 5 show details of the fuel injection device of the present example. With reference to Fig. 1 to 5 describe the structure and basic operation of the fuel injection device. Fig. 1 to 5 show a state in which no current is supplied to an electromagnetic drive unit (electromagnetic coil 105), the valve is closed, and the movable member remains stopped.

[0014] In the fuel injection device according to the present example, a valve body 114 is excited in the valve-closing direction by a spring 110. When no current is supplied to the solenoid coil 105, a fuel passage is closed. By supplying current to the solenoid coil 105, a movable element 102 is driven by an electromagnetic attraction force, and the fuel passage is opened, thus fuel injection occurs.

[0015] The fuel injection device according to the present example forms the magnetic passage with a magnetic core 107, the movable member 102, a nozzle holder 101, and a housing 103. A diaphragm 213 is formed in a portion corresponding to a space between the magnetic core 107 and the movable member 102 in the nozzle holder 101. An electromagnetic coil 105 wound around a bobbin 104 is attached to the outer peripheral side of the nozzle holder 101, and the insulating property is obtained by a resin molding 121.

[0016] As in Fig. As shown in Figure 1, the nozzle holder 101 includes a small-diameter cylindrical portion 22 and a large-diameter cylindrical portion 23. A guide member 115 and an orifice shell 116 having a fuel injection port 10 are inserted into one end portion of the small-diameter cylindrical portion 22. A guide member 115 is provided inside the orifice shell 116 and is press-fitted to the orifice shell 116, or plastically coupled to it, or integrally formed therewith. The orifice shell 116 is welded to the end portion of the small-diameter cylindrical portion 22 along an outer peripheral portion of an apex surface.

[0017] The guide member 115 guides an outer periphery 114B of the valve body provided at one end of the valve body 114, which is received in the movable part 106 described below. The orifice shell 116 is provided with a valve seat 39 having a circular conical shape on a side opposite the guide member 115. The valve body 114B provided at the end of the valve body 114 contacts this valve seat 39, and the fuel flow is guided or stopped toward the fuel injection port 10. A groove is formed along an outer periphery of the nozzle holder 101, and a sealing member 131, typically a resin chip seal, is fitted into this groove.

[0018] The magnetic core 107 is press-fitted into an inner peripheral part of the large-diameter cylindrical portion 23 of the nozzle holder 101 and welded to the press-fit contact portion. This seals the space between the outside air and the inside of the large-diameter cylindrical portion 23. A through hole (central hole) is provided in the center of the magnetic core 107, and fuel is supplied through the through hole. On the side of the magnetic core 107 facing the fuel supply port 118, another member (adapter) 108 is press-fitted and welded to the press-fit contact portion, sealing off the space between the outside air and the inside. The inner diameter of the adapter 108 is provided with a through hole similar to that of the magnetic core 107 and communicates with the fuel supply port 118.

[0019] The magnetic core 107 and the adapter 108 may be integrated to communicate with the fuel supply port 118 provided at the upper end of the fuel injector (at an end opposite the fuel injection port 10). A filter 113 is provided inside the fuel supply port 118. A sealing material 130 is provided on the other peripheral side of the fuel supply port 118 to maintain fluid tightness between the fuel supply port 118 and a connector on a fuel hose side.

[0020] Fig. 1 shows a normal state in which no current is supplied to the solenoid coil 105, and in this state, the valve body 114 is driven in the valve-closing direction by the spring 110. Therefore, the seat portion 114B of the valve body 114 on the downstream side of the nozzle holder contacts the valve seat 39 of the orifice cup, and the fuel is sealed. Here, the movable member 102 is supported by the valve body 114 and driven in the valve-opening direction by a neutral spring 112 supported by the nozzle holder between the nozzle holder 101 and the movable member 102.

[0021] Next, with reference to the Fig. 2 to 5, a structure of the drive unit when power is supplied to the fuel injector and the movable member 102 collides with the valve body 114 is described. When power is supplied to the electromagnetic coil 105, magnetic fluxes are generated in the magnetic passage, and a magnetic attraction force is generated between the magnetic core 107 and the movable member 102. In the fuel injection valve according to the present example, by supplying power to the electromagnetic coil 105, the magnetic fluxes are generated in the magnetic circuit including the magnetic core 107, the movable member 102, the nozzle holder 101, and the housing 103, and the magnetic attraction force is generated between the magnetic core 107 and the movable member 102.The magnetic fluxes passing through the magnetic core 107 are divided into magnetic fluxes flowing from a position of an end surface of the magnetic core 107 on the movable member 102 side toward the nozzle holder 101 side, and magnetic fluxes flowing toward the attraction surface side of the magnetic core 107, that is, toward a magnetic gap side between the magnetic core 107 and the movable member 102. At this time, the magnetic attraction force is determined based on the magnetic flux density and the number of magnetic fluxes passing between the magnetic core 107 and the movable member 102.

[0022] Next, a structure of the movable part 106 will be described with reference to Fig. 2, which is an enlarged view of the drive unit structure of the fuel injection device when the valve is closed. As described above, the magnetic core 107 is press-fitted into the inner peripheral part of the large-diameter cylindrical portion 23 of the nozzle holder 101 and welded to the press-fit contact portion. Here, the movable member 102 is received in the large-diameter cylindrical portion 23 of the nozzle holder 101. In a normal state where no power is supplied to the fuel injection device, the movable member 102 is pressed toward the magnetic core 107 side by the driving force of the neutral spring 112. The magnetic core 107 transmits the magnetic attraction force to the movable member 102 to pull it in the valve-opening direction.A lower end surface (collision surface) 107B of the magnetic core 107 and an upper end surface (collision surface) 102B of the movable element 102 can be plated as needed to improve durability. If the movable element 102 and the magnetic core 107 are made of soft magnetic stainless steel, which is relatively soft, durability and reliability can be maintained by using hard chrome plating or electroless nickel plating.

[0023] A through hole 107A, provided as a fuel passage in the center of the magnetic core 107, has a slightly larger diameter than a sliding part 114A of the valve body 114. A lower end of the spring 110 is in contact with a spring receiving surface provided on an upper end surface of the valve body 114 for initial load adjustment. The other end of the spring 110 is received by an adjusting member 54, which is press-fitted into a through hole 108A of the adapter 108. The spring 110 is fixed between the valve body 114 and the adjusting member, and the initial load of the spring 110 to press the valve body 114 against the valve seat 39 can be adjusted by adjusting the mounting position of the adjusting member 54.

[0024] The movable member 102 is inserted into the large-diameter cylindrical portion 23 of the nozzle holder 101, and the housing 103 and the electromagnetic coil 105 wound around the coil body 104 are attached to the outer periphery of the large-diameter cylindrical portion 23 of the nozzle holder 101. After that, the valve body 114 penetrates the through-hole 108A of the adapter 108 of the movable member 102 and the through-hole 107A of the fixing core 107. At this time, the valve body 114 is pressed into the valve-closing position by a jig, and the stroke of the movable part 106 is adjusted to an arbitrary position by determining the press-fitting position of the orifice cup 116 while detecting the stroke of the valve body 114 when current is supplied to the electromagnetic coil 105.

[0025] When the initial load of the spring 110 is adjusted, the lower end surface 107B of the magnetic core 107 faces the upper end surface 102A of the movable element 102 of the movable part 106 with a stroke G1 of about 40 to 100 micrometers.

[0026] The housing 103 is secured in a bowl-like shape along the outer circumference of the large-diameter cylindrical portion 23 of the nozzle holder 101. A through hole is provided in the center of the lower part of the housing 103, through which the large-diameter cylindrical portion 23 of the nozzle holder 101 is inserted. An outer peripheral wall of the housing 103 forms an outer peripheral yoke portion, which faces the outer peripheral surface of the large-diameter cylindrical portion 23 of the nozzle holder 101.

[0027] The electromagnetic coil 105, which has an annular or cylindrical shape, is arranged within a cylindrical space formed by the housing 103. The electromagnetic coil 105 includes the annular coil body 104 with a groove whose cross section is U-shaped and opens outward in the radial direction, and a copper wire (electromagnetic coil 105) wound in the groove. A rigid conductor is attached to one end portion where the winding of the electromagnetic coil 105 begins and one end portion where the winding of the electromagnetic coil 105 ends, and the conductor is led out from the through-hole provided in the magnetic core 107. On the outer periphery of the large-diameter cylindrical portion 23 of the nozzle holder 101, the magnetic core 107, and the conductor 109, insulating resin is injected and molded from an inner periphery of an opening in the upper end of the casing 103 so that they are covered with the resin molded body 121.An annular magnetic passage is formed in a portion of the magnetic core 107, the movable member 102 and the large diameter cylindrical portion 23 of the nozzle holder 101 and the housing 103 so as to surround the electromagnetic coil 105.

[0028] Although not illustrated here, the fuel injection device according to the present example is mounted on a common rail to which high-pressure fuel is supplied from a high-pressure fuel pump, and the high-pressure fuel is directly injected into the cylinder of the internal combustion engine. To meet the new, more stringent emission regulations and the demand for higher fuel efficiency, the fuel pressure of the common rail has been increased to 20 MPa or higher. It is expected that fuel pressure will continue to rise in the future, and a fuel injection device capable of achieving stable fuel injection even under such conditions will be required.

[0029] For example, it is assumed that the common rail fuel pressure at the Fig. 10 shown structure is 35 MPa. In Fig. 10, the axial length 201 of the movable element 102 of the fuel injector on opposite sides of the nozzle holder 101 is 2.1 times the axial length 202 of the housing 103.

[0030] Here shows Fig. 6 shows the relationship between the ratio between the axial length 201 of the movable element 102 and the axial length 202 of the housing 103 and the magnetic attraction force generated in the movable element 102. In the structure of Fig. 10 can be calculated assuming that the magnetic attraction force desired in this example, as in Fig. 6 is 80 N, but this magnetic attraction force cannot be maintained even when a current of 20 A or greater is applied. This means that valve opening may fail due to insufficient magnetic attraction force. Therefore, even if valve opening is possible, the valve opening speed is low, so that injection of the minimum required amount of fuel may fail.

[0031] In view of the above, as in Fig. 2, the axial length 201 of the movable member 102 of the fuel injection device according to the present example is set to 1.25 to 1.46 times the axial length 202 of the housing 103 on the opposite side of the nozzle holder 101. That is, the fuel injection device includes the movable member 102 attracted by the magnetic core 107 and the housing 103 disposed opposite to the movable member 102 orthogonal to the axial direction, and the movable member 102 and the housing 103 are designed such that the axial length 201 of the movable member 102 is 1.25 to 1.46 times the axial length 202 of the housing 103.

[0032] By making the axial length 201 of the movable element 102 greater than or equal to 1.25 times the axial length 202 of the housing 103, the cross-sectional area of ​​the movable element 102 in the magnetic circuit can be ensured. Because the magnetic resistance can be reduced, the magnetic attraction force generated in the movable element 102 can be improved, and the desired magnetic attraction force of 80 N can be achieved by applying a current of 19 A, as shown in Fig. 6 is shown.

[0033] As in Fig. 6, the magnetic attraction force tends not to increase when the axial length 201 of the movable element 102 is greater than or equal to 1.46 times the axial length 202 of the housing 103. Furthermore, the mass of the movable element 102 increases when the axial length 201 of the movable element 102 is increased. Because increasing the mass of the movable element 102 results in a deterioration in the response of the movable element 102, it is desirable that the axial length 201 of the movable element 102 be less than or equal to 1.46 times the axial length 202 of the housing 103.

[0034] Therefore, the magnetic attraction force generated in the movable member 102 can be effectively increased by designing the movable member 102 such that the axial length 201 of the movable member 102 is 1.25 to 1.46 times the axial length 202 of the housing 103.

[0035] Furthermore, as in Fig. 2, it is desirable that the total area 203 of the outer peripheral side of the movable member 102 of the fuel injection device according to the present example be 0.9 to 1.1 times the total axial cross-sectional area 204 of the housing 103 on the opposite side of the large-diameter cylindrical portion 23 of the nozzle holder 101.

[0036] When the total area 203 of the outer peripheral side of the movable member 102 is greater than or equal to 0.9 times the total axial cross-sectional area 204 of the housing 103, the magnetic resistance can be reduced and the magnetic attraction force generated in the movable member 102 can be ensured. In addition, when the total area 203 of the outer peripheral side of the movable member 102 is less than or equal to 1.1 times a cross-sectional area in which the magnetic attraction force tends to increase, the magnetic attraction force generated in the movable member 102 can be effectively increased with a smaller than usual magnetomotive force.

[0037] Furthermore, as in Fig. 2, when the radial cross-sectional area 212 of the housing 103 and the radial cross-sectional area 211 of the electromagnetic coil 105 are compared, it is desirable that the radial cross-sectional area 212 of the housing 103 be greater than or equal to twice the radial cross-sectional area 211 of the electromagnetic coil 105.

[0038] In Fig. In Figure 11, the horizontal axis represents the comparison between the radial cross-sectional area 212 of the housing 103 and the radial cross-sectional area 211 of the electromagnetic coil 105, and the vertical axis represents the magnetic attraction force in this case. The increase in the magnetic attraction force usually becomes small when the aspect ratio becomes two or larger. Accordingly, the magnetic resistance in the housing 103 can be reduced and the magnetic attraction force generated between the magnetic core and the movable element 102 can be increased by at least doubling the radial cross-sectional area of ​​the housing 103.

[0039] It is desirable that the cross-sectional area of ​​the magnetic core 107 as the magnetic passage of the fuel injection device according to the present example decreases from the upstream side to the collision surface perpendicular to the axial direction of the valve body 114 and adjoins the nozzle holder 101 in a portion where the cross-sectional area is largest.

[0040] In the present example, as in Fig. As shown in Figure 3, the magnetic core 107 includes, at positions in the axial direction of the electromagnetic coil 105, a first portion 301 having a first horizontal cross-sectional area (large diameter portion), a second portion 302 having a second horizontal cross-sectional area (medium diameter portion), and a third portion 303 having a third horizontal cross-sectional area (small diameter portion). The cross-sectional area of ​​the first portion 301 (large diameter portion) at the upper part is larger than the cross-sectional area of ​​the second portion 302 (medium diameter portion), and the cross-sectional area of ​​the third portion 303 (small diameter portion) is smaller than the cross-sectional area of ​​the second portion 302 (medium diameter portion).

[0041] In Fig. Figure 7 shows the magnetic flux density distribution in the magnetic circuit according to the present example using color gradation. Note that components other than the magnetic core 107 of the magnetic circuit, the housing 103, the nozzle holder 101, the movable element 102, and the solenoid coil 105 are not shown.

[0042] With the above structure, the magnetic flux density distribution in the magnetic core 107 is highest in the third section 303 (small diameter section), second highest in the second section 302 (medium diameter section), and lowest in the first section 301 (large diameter section). Therefore, the magnetic resistance except for the attraction area can be reduced, the magnetic flux density can be reduced, and the diaphragm of the cross-sectional area with respect to the attraction area can promote the increase of the magnetic flux density at the attraction area and can effectively increase the magnetic attraction force. Therefore, a higher magnetic attraction force can be obtained than in the conventional case.

[0043] As in Fig. 3, the magnetic core 107 of the fuel injection device according to the present example is configured such that the third portion 303 (the small diameter portion) has an outer peripheral surface formed at the same position as the outer peripheral surface 403 of the second portion 302 (the medium diameter portion), and an inner peripheral surface 401 of the third portion 303 (the small diameter portion) is formed to expand toward an inner peripheral surface 402 of the second portion 302 (the medium diameter portion) toward the inner peripheral side. In other words, the magnetic core 107 has a gradually decreasing diameter from the end surface on the movable member side to the upstream side in the fuel flow direction, and this inner diameter portion 401 has, for example, a tapered surface.

[0044] With this feature, the effect of increasing the magnetic flux density of the attraction surface of the movable element 102 through the membrane of the cross-sectional area to the attraction surface can be easily obtained. As shown in Fig. As shown in Figure 7, the magnetic attraction force of the third portion 303 (the small-diameter portion) can be improved relative to the magnetic flux density of the second portion 302 (the medium-diameter portion). In addition, the portion of the magnetic core 107 expands in the downstream direction with an increase in the inner diameter, and therefore, a fluid passage can be ensured between the magnetic core 107 and the valve body. If the fluid passage is lacking, a diaphragm is formed when the fluid flows through the magnetic core 107 and the valve body, and pressure loss increases. Therefore, the maximum possible injection flow rate decreases, and it becomes difficult to inject the desired amount of fuel.

[0045] It is desirable to configure the magnetic core 107 such that the inner peripheral surface 402 of the second portion 302 (the medium diameter portion) is formed at the same position as the inner peripheral surface of the first portion 301 (the large diameter portion), and that an outer peripheral surface 404 of the first portion 301 (the large diameter portion) is formed to widen toward the outer peripheral side more than the outer peripheral surface 403 of the second portion 302 (the medium diameter portion).

[0046] In this way, by increasing the area of ​​the portion of the magnetic core where the magnetic fluxes pass through, except for the attraction area of ​​the movable element 102, as shown in Fig. As shown in Figure 7, the magnetic flux density distribution in the magnetic core 107 is highest in the third section 303 (the small diameter section), second highest in the second section 302 (the medium diameter section), and lowest in the first section 301 (the large diameter section). Therefore, the magnetic resistance except in the attraction area of ​​the magnetic core 107 can be reduced, the magnetic flux density except in the attraction area can be reduced, and the magnetic attraction force can be effectively increased.

[0047] As in Fig. 5, in the present example, the first portion 301 (the large diameter portion) of the magnetic core 107 extends to the outer peripheral side of the second portion 302 (the medium diameter portion), and the large diameter cylindrical portion 23 of the nozzle holder 101 covering the outer peripheral side of the movable member 102 abuts against an outer peripheral extension part 502 of the first portion 301 (the large diameter portion) of the magnetic core 107 so as to be fixed.

[0048] Here, in view of the structure of the fuel injection valve, it is necessary for the movable member 102 and the magnetic core 107 to ensure the largest possible attraction area for generating the magnetic attraction force. Therefore, the nozzle holder 101 is desirably thin. On the other hand, strength must be ensured for the fuel under high pressure, so the nozzle holder 101 is formed of a material with high strength. However, since a material with high strength generally has low magnetic properties, the nozzle holder 101 must be formed of a material with such low magnetic properties. In view of this, the first portion 301 (the large-diameter portion) of the magnetic core 107 is extended toward the outer peripheral side of the second portion 302 (the small-diameter portion) so as to be adjacent to the nozzle holder.This allows the magnetic core 107 with excellent magnetic properties to have a larger cross-sectional area in the magnetic passage, and the magnetic resistance of the upstream part of the magnetic core 107 to be reduced. Therefore, the magnetic attraction force can be improved.

[0049] As in Fig. 3, the cross-sectional area of ​​the third section 303 (the small diameter section) is 0.78 to 0.85 times the cross-sectional area of ​​the second section 302 (the medium diameter section). Accordingly, as shown in Fig. As shown in Fig. 7, the magnetic flux density of the attraction surface of the third portion 303 (the small-diameter portion) and the movable member 102 opposite to the third portion 303 is high. Therefore, the magnetic flux density of the attraction surface can be increased while ensuring the cross-sectional area of ​​the attraction surface of the magnetic core 107, and the magnetic attraction force can be improved.

[0050] As in Fig. As shown in Fig. 5, an escape portion 501 may be formed from the first portion 301 (large diameter portion) to the second portion 302 (medium diameter portion) of the magnetic core 107, and the escape portion 501 is used when fitting the nozzle holder 101 by press fitting. When the nozzle holder 101 and the magnetic core 107 are fitted together by press fitting or the like, the upper end surface of the nozzle holder 101 and a corner part of the magnetic core 107 may be rounded by the process, so an escape portion must be formed in the contact part. By providing the magnetic core 107 with the escape portion 501 instead of the nozzle holder 101, the area for the load generated during the press fitting and the strength can be ensured.

[0051] Fig. 8 shows a state in which the movable element 102 is attracted by the magnetic attraction force, and the movable element 102 collides with the lower surface 107B of the magnetic core 107. When current is supplied to the electromagnetic coil 105, the magnetization of the movable element 102 progresses from the inside of the electromagnetic coil 105 to the outside, that is, from the outer peripheral side of the magnetic core 107 to its inner peripheral side, due to the influence of eddy currents. When the magnetic attraction force generated by the current exceeds the sum of the load applied by the spring 110 and the force acting on the valve body 114 due to the fuel pressure, the movable element 102 begins to move upward.

[0052] At this time, the valve body 114 moves upward together with the movable element 102 until the upper end surface of the movable element 102 collides with the lower surface 107B of the magnetic core 107 (G1 = 0). As a result, the seat portion 114B of the valve body 114 is separated from the valve seat 39 of the orifice cup 116, and the supplied fuel is injected from the plurality of injection holes. The number of injection holes may be one.

[0053] With reference to Fig. 9 describes a structure of the drive unit when the power supply to the fuel injector is interrupted and the seat portion 114B of the valve body 114 is located in the valve seat 39. When the power supply to the electromagnetic coil 105 is interrupted and the magnetic attraction force acting between an armature 102 and the fixing core 107 becomes smaller than the driving force of the first spring, the movable portion 106 begins to move in the valve-closing direction. However, alternating currents are generated in the magnetic passageway opposite to a direction in which the magnetic fluxes are canceled even after the power supply to the coil 105 is interrupted, so there is a magnetic delay after the power supply to the electromagnetic coil is interrupted and before the magnetic fluxes and attraction force decrease.After the magnetic deceleration, the magnetic fluxes in the magnetic passage and the magnetic attraction force are also lost. Because the magnetic attraction force acting on the movable element 102 is lost, the valve body 114 is returned to the closed position by the load of the spring 110 and the force exerted by the fuel pressure, where the valve body 114 is in contact with the valve seat 39. Fig. 5 shows a state in which the movable part 106 initiates the valve closing movement when the valve is open, and a gap designated G2 is formed between the movable element and the magnetic core 107. After the stroke G2 reaches a desired value (G2 = G1) during the valve closing process, the valve body 114 moves into the valve closing position, in which the valve body 114 is in contact with the valve seat 39, so that fuel injection ends.

[0054] Note that the fuel injection device according to the present example is particularly desirable for a turbocharger-mounted type, where fuel is directly injected into the engine. The turbocharger-mounted type is desirable because newer engines require smaller sizes. List of reference symbols 10 Fuel injection port 22 cylindrical section of small diameter 23 large diameter cylindrical section 39 Valve seat 54 Setting element 101 nozzle holder 102 anchors 102A upper end surface of the anchor 102 103 housings 104 coil bodies 105 Electromagnetic coil 106 moving part 107 Magnetic core 107B lower end face of the magnetic core 107 107A Inner peripheral surface (through hole) of the magnetic core 107 108 adapters 109 ladders 110 spring 112 zero spring 113 filters 114 valve body 114A movable part of the valve body 114B Seat part of the valve body 118 Fuel supply opening 121 resin molded bodies 130 sealing material 131 Sealing element 201 axial length of the movable element 202 axial length of the housing 203 Side surface of the movable element 204 axial cross-sectional area of ​​the housing 211 radial cross-sectional area of ​​the electromagnetic coil 212 radial cross-sectional area of ​​the housing 213 Membran 301 first section of the magnetic core (large diameter section) 302 second section of the magnetic core (medium diameter section) 303 third section of the magnetic core (small diameter section) 401 inclined section from the third section to the second section of the magnetic core 402 Inner peripheral surface of the first section and the second section of the magnetic core 403 Outer peripheral surface of the second section of the magnetic core 404 Outer peripheral surface of the first section of the magnetic core 501 Avoidance area of ​​the press fit section 502 Connection surface between the magnetic core and the nozzle holder G1 stroke in valve closed state G2 stroke during valve closing

Claims

[1] A fuel injection device comprising a movable element (102) attracted by a magnetic core (107) and a housing (103) provided opposite to the movable element (102) in a direction orthogonal to an axial direction, characterized by , that the movable element (102) is designed such that its axial length (201) is 1.25 to 1.46 times the axial length (202) of the housing (103), the housing (103) is designed such that its radial cross-sectional area (212) is greater than or equal to twice the radial cross-sectional area (211) of an electromagnetic coil (105) accommodated in the housing (103), the fuel injection device comprises a nozzle holder (101) press-fitted to the magnetic core (107) and provided opposite to the movable element (102) in the axial direction, and the magnetic core (107) has, at positions in the axial direction corresponding to the magnetic coil (105) viewed from the top, a first section (301) with a first horizontal cross-sectional area, a second section (302) with a second horizontal cross-sectional area, and a third section (303) with a third horizontal cross-sectional area, wherein the cross-sectional area of ​​the first section (301) is larger than the cross-sectional area of ​​the second section (302) and the cross-sectional area of ​​the third section (303) is smaller than the cross-sectional area of ​​the second section (302). [2] The fuel injection device according to claim 1, wherein the magnetic core (107) is formed such that the outer peripheral surface of the third portion (303) is formed at the same position as the outer peripheral surface (403) of the second portion (302), and the magnetic core (107) extends from the inner peripheral surface (401) of the third portion (303) to the inner peripheral surface (402) of the second portion (302) toward an inner peripheral side. [3] The fuel injection device according to claim 2, wherein the magnetic core (107) is formed such that the inner peripheral surface (402) of the second portion (302) is formed at the same position as the inner peripheral surface of the first portion (301), and the magnetic core (107) extends from the outer peripheral surface (403) of the second portion (302) to the outer peripheral surface (404) of the first portion (301) to an outer peripheral side. [4] The fuel injection device according to claim 1, wherein the magnetic core (107) is formed to extend from an outer peripheral surface (403) of the second portion (302) to an outer peripheral surface (404) of the first portion (301) toward an outer peripheral side, and a nozzle covering the outer peripheral side of the movable member (102) abuts against an extension part of the first portion (301) up to an outer periphery so as to be fixed. [5] The fuel injector according to claim 1, wherein the cross-sectional area of ​​the third portion (303) is 0.78 to 0.85 times the cross-sectional area of ​​the second portion (302). [6] The fuel injection device according to claim 1, wherein the inner diameter of the magnetic core (107) is inclined toward an outer peripheral side to a collision surface with the movable member (102).

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