JP2007285246A - Fuel injection valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection valve materializing miniaturization of a core while securing wear resistance, corrosion resistance and response of intermittence of fuel injection. <P>SOLUTION: The valve is provided with a movable core 30 reciprocating together with a valve member intermitting fuel injection, a fixed core 44 forming a magnetic circuit together with the movable core 30, and a coil generating magnetic attraction force between the movable core 30 and the fixed core 44 by excitation. Fe-Co alloy containing cobalt material is employed for material of the movable core 30 and the fixed core 44. Corrosion resistant plating layers 302, 442 are formed on whole surface of the both cores 30, 44. Hard plating layer 303, 443 are formed on a movable side contact surface 301 of the movable core 30 and a fixed side contact surface 441 of the fixed core 44. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel injection valve capable of intermittently injecting fuel.

Conventionally, a movable core that reciprocates together with a valve member that interrupts fuel injection and a fixed core that forms a magnetic circuit together with the movable core, and a magnetic attraction force between the movable core and the fixed core by energizing the coil. There is known a fuel injection valve that reciprocally moves a valve member (for example, Patent Documents 1 to 4).
When the movable core moves toward the fixed core, it collides with the fixed core, so both cores are required to have wear resistance. Further, since the fuel comes into contact with both cores, corrosion resistance is required. Conventionally, stainless steel has been adopted as the material for both cores in response to these requirements.

JP 56-66446 A Japanese Patent Laid-Open No. 9-154261 JP 2001-186708 A JP 2002-218712 A

However, in recent years, in addition to the above requirements, further downsizing of the fuel injection valve has been required. If both cores are simply miniaturized in response to the demand for miniaturization, the magnetic flux density generated in both cores when the coil is energized decreases, and the magnetic attractive force decreases. Then, the reciprocating speed of the movable core is slowed, and the responsiveness of intermittent fuel injection by the valve member is deteriorated.
Accordingly, an object of the present invention is to provide a fuel injection valve that realizes a reduction in the size of the core while ensuring wear resistance, corrosion resistance, and intermittent fuel injection response.

In the invention according to any one of claims 1 to 4, at least one of the movable core and the fixed core includes a cobalt-based material, and the entire surface of the at least one core is subjected to corrosion-resistant plating, And the hard plating is given to the part which a movable core and a fixed core mutually contact among said at least one core.
Here, when the cobalt-based material is included in the core, the magnetic flux density generated in the core when the coil is energized increases. Therefore, according to the present invention in which the cobalt-based material is included in at least one of the cores, the core can be reduced in size without reducing the magnetic flux density generated in the core when the coil is energized.

Furthermore, according to the present invention, since the entire surface of the at least one core is subjected to corrosion-resistant plating, it is possible to ensure the corrosion resistance of the core surface while including a cobalt-based material having low corrosion resistance. . In addition, since hard plating is applied to the portion of the at least one core where both the cores are in contact with each other, the portion where both the cores are in contact with each other even though the cobalt-based material has low wear resistance. Can be secured.
As described above, according to the present invention, it is possible to ensure the responsiveness of intermittent fuel injection by avoiding a decrease in magnetic flux density, and it is possible to ensure wear resistance and corrosion resistance, and to realize downsizing of the core.

  In the invention of claim 2, the corrosion-resistant plating contains nickel and phosphorus, and the hard plating contains chromium. According to this, the oxide film generated when nickel-phosphorous plating is applied to the core is removed by chromic acid used as a plating solution when applying chromium plating. Therefore, when the hard plating is laminated on the corrosion-resistant plating, it is possible to easily realize the hard plating that does not easily peel off.

  Here, as illustrated in FIG. 4, the effect of increasing the magnetic flux density by including the cobalt-based material in the core is sufficiently exhibited even when the content of the cobalt-based material is 1 wt%, and the content is 55 wt%. When it exceeds%, it decreases rapidly. In view of this point, in the invention according to claim 3, the content of the cobalt-based material contained in at least one of the cores is set to 1 to 55 wt% with respect to the mass of the entire core. The unit “wt%” means “mass percent” defined by Japanese Industrial Standards, and means the ratio of the mass of the cobalt-based material to the mass of the entire core.

  According to a fourth aspect of the present invention, at least one additive of Si, Al, V, Cr and Fe is added to the at least one core. According to this, since the electrical resistance of the core can be reduced, it is possible to shorten the demagnetization time until the magnetized core changes to the demagnetized state when the coil is switched from on to off. . Therefore, the reciprocating speed of the movable core can be increased when energization of the coil is switched off, and the response of fuel injection can be improved.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
2 is a cross-sectional view showing the entire fuel injection valve according to the present embodiment, and FIG. 3 is an enlarged view of the movable core and the fixed core shown in FIG. 2. First, the fuel injection valve 10 will be described with reference to FIGS. The structure of will be described.

  The fuel injection valve 10 is applied to, for example, a direct injection gasoline engine. When applied to a direct-injection gasoline engine, the fuel injection valve 10 is mounted on a cylinder head. The fuel injection valve 10 may be applied not only to a direct injection type gasoline engine but also to a port injection type gasoline engine that injects fuel into intake air flowing through an intake passage, a diesel engine, or the like.

  As shown in FIG. 2, the valve holder 12, the nonmagnetic member 14, and the connecting member 40 are installed in this order from the fuel injection side, and adjacent members are joined together by welding or the like. In the internal space formed by the valve holder 12, the nonmagnetic member 14, and the connecting member 40, the valve body 20, the valve member 24, the movable core 30, the fixed core 44, the adjusting pipe 46, the spring 48, the fuel filter 64, and the like. Contained.

  The nonmagnetic member 14 as a magnetic diaphragm covers the outer peripheral sides of the movable core 30 and the fixed core 44. The nonmagnetic member 14 prevents the magnetic flux from short-circuiting between the valve holder 12 and the connecting member 40 and prevents the magnetic flux from leaking from the movable core 30 and the fixed core 44 to the outer peripheral side.

  The valve body 20 is fixed to the inside of the nozzle hole side tip of the valve holder 12 by welding. The valve body 20 has a valve seat 21 on the inner peripheral wall on which the valve member 24 can be seated. The nozzle hole plate 22 is fixed to the bottom outer wall of the valve body 20 by welding. The nozzle hole plate 22 is formed in a thin plate shape, and one or a plurality of nozzle holes are formed at the center.

  The valve member 24 is a bottomed cylindrical hollow, and a contact portion 25 is formed on the bottom side of the valve member 24. The contact portion 25 can be seated on a valve seat 21 formed on the valve body 20. When the abutting portion 25 is seated on the valve seat 21, the nozzle hole of the nozzle hole plate 22 is closed and fuel injection is blocked. A plurality of fuel holes 241 penetrating the side wall of the valve member 24 are formed on the upstream side of the contact portion 25. The fuel that has flowed into the valve member 24 passes from the inside to the outside through the fuel hole 241 and travels toward the valve portion formed by the contact portion 25 and the valve seat 21.

The valve member 24 is coupled to the connecting member 28 by welding. As shown in FIG. 3, a flange 26 that extends radially outward is formed at the end of the valve member 24 on the movable core 30 side. The valve member 24 sandwiches the movable core 30 between the flange 26 and the flange 29 of the connecting member 28, and reciprocates together with the movable core 30.
As shown in FIG. 3, the movable core 30 is coupled to the valve member 24 on the side opposite to the valve body 20 with respect to the valve member 24. The spring 48 as an urging member urges the movable core 30 and the valve member 24 in the direction in which the valve member 24 is seated on the valve seat 21.

  The connection member 40 is formed of a magnetic material such as electromagnetic stainless steel by sintering or the like, and has a protruding portion 42 protruding in a cylindrical shape on the movable core 30 side on the outer peripheral side. The protrusion 42 is coupled to the nonmagnetic member 14 in the axial direction. The connecting member 40 accommodates the fixed core 44 on the inner peripheral side of the protrusion 42 and is coupled to the fixed core 44. The connecting member 40 magnetically connects the fixed core 44 and a yoke 52 described later.

  The fixed core 44 is formed in a cylindrical shape, and is accommodated in the protrusion 42 of the connection member 40 and positioned in the radial direction and the axial direction. The fixed core 44 is installed on the side opposite to the valve body 20 with respect to the movable core 30. A part of the fixed core 44 is disposed on the inner peripheral side of the nonmagnetic member 14, and extends to the opposite side of the movable core 30 from the end of the nonmagnetic member 14 opposite to the movable core 30.

  As shown in FIG. 3, a fixed contact surface 441 is formed at the axial end of the fixed core 44, and a movable contact surface 301 is formed at the axial end of the movable core 30. The movable core 30 and the fixed core 44 are arranged coaxially in the axial direction, and are arranged so that the fixed-side contact surface 441 and the movable-side contact surface 301 face each other.

  The movable core 30 and the fixed core 44 are made of a magnetic material by sintering or the like, and an alloy containing a cobalt-based material is adopted as the magnetic material. A specific example of the alloy is an Fe—Co alloy obtained by adding a cobalt-based material to an iron-based metal material. The content rate of cobalt-type material is 1-55 wt% with respect to the mass of the fixed core 44 or the movable core 30 whole, More desirably, it is 5-15 wt%. In addition, at least one additive of Si, Al, V, Cr, and Fe is added to the Fe—Co alloy.

  FIG. 1 is a cross-sectional view schematically showing the movable core 30 and the fixed core 44, and shows a state where the fixed side contact surface 441 and the movable side contact surface 301 are separated by turning off the power to the coil 54. As shown in FIG. 1, the movable core 30 and the fixed core 44 are subjected to corrosion-resistant plating, and corrosion-resistant plating layers 302 and 442 are formed. These corrosion-resistant plating layers 302 and 442 are formed on the entire outer peripheral surface, inner peripheral surface, and axial end surfaces of the movable core 30 and the fixed core 44. Ni-P plating is adopted as the material of the corrosion-resistant plating layers 302 and 442.

  Further, the movable core 30 and the fixed core 44 are subjected to hard plating, and are laminated on the corrosion-resistant plating layers 302 and 442 to form hard plating layers 303 and 443. These hard plating layers 303 and 443 are formed only on the movable contact surface 301 of the movable core 30 and the fixed contact surface 441 of the fixed core 44. Cr plating is adopted as the material of the hard plating layers 303 and 443.

  As shown in FIG. 2, the adjusting pipe 46 is press-fitted into the connecting member 40 and engages one end of the spring 48. The biasing force of the spring 48 is adjusted by adjusting the press-fitting amount of the adjusting pipe 46. The other end of the spring 48 is locked to the flange 26 of the valve member 24 (see FIG. 3). The spring 48 is guided in the extending and contracting direction on at least one inner peripheral surface of the movable core 30 and the fixed core 44.

  The yokes 50 and 52 are magnetically connected to each other and cover the outer periphery of the coil 54. The yoke 50 is magnetically connected to the valve holder 12, and the yoke 52 is magnetically connected to the connecting member 40. The yokes 50 and 52 form a magnetic circuit with the valve holder 12, the movable core 30, the connection member 40, and the fixed core 44.

  The coil 54 is installed on the outer periphery of the nonmagnetic member 14 and the connection member 40. The resin housing 60 insert-molds the coil 54 and the terminal 62. The terminal 62 is electrically connected to the coil 54 and supplies a drive current to the coil 54.

  In the fuel injection valve 10 configured as described above, when energization to the coil 54 is turned off, the urging force of the spring 48 causes the valve member 24 to move downward in FIG. The abutting portion 25 is seated on the valve seat 21, the nozzle hole is closed, and fuel injection is shut off. When such energization is turned off, the movable side contact surface 301 of the movable core 30 and the fixed side contact surface 441 of the fixed core 44 are separated as shown in FIG.

  On the other hand, when energization of the coil 54 is turned on, magnetic flux flows through a magnetic circuit including the valve holder 12, the movable core 30, the connection member 40, the fixed core 44, and the yokes 50 and 52. Magnetic attraction force is generated. Then, together with the movable core 30, the valve member 24 moves toward the fixed core 44 against the urging force of the spring 48, and the contact portion 25 is separated from the valve seat 21. Thereby, fuel is injected from a nozzle hole. When such energization is turned on, the movable side contact surface 301 of the movable core 30 and the fixed side contact surface 441 of the fixed core 44 are in contact as shown in FIG.

  As described above, according to the fuel injection valve 10 of the present embodiment, an Fe—Co alloy containing a cobalt-based material is adopted as the material of the movable core 30 and the fixed core 44. When a cobalt-based material is included, the magnetic flux density generated in both the cores 30 and 44 when the coil 54 is energized is increased. Accordingly, it is possible to reduce the size of both cores 30 and 44 without reducing the magnetic flux density generated in both cores 30 and 44 when energization is turned on. That is, it is possible to reduce the size of both the cores 30 and 44 while ensuring the responsiveness of intermittent fuel injection without reducing the moving speed in the valve opening direction of both the cores 30 and 44 when energization is on.

  FIG. 4 is a graph showing the relationship between the cobalt content Wt% (mass percent) contained in the Fe—Co alloy and the magnetic flux density G (Gauss) generated in the movable core 30 when energization is turned on. The symbol H in the figure represents the magnitude Oe (Oersted) of the magnetic field, and the six curves in the figure indicate the magnetic flux density in the case of H = 17000 Oe, 1500 Oe, 100 Oe, 30 Oe, 10 Oe, 3 Oe in order from the top. It shows a change.

  According to the graph shown in FIG. 4, when H = 100 or less, the magnetic flux density has a peak value when the cobalt content is about 50 wt%, and when the cobalt content exceeds about 50 wt%, the magnetic flux density increases rapidly. It can be seen that the number decreases. Moreover, the higher the cobalt content, the higher the core material cost. In view of these points, the cobalt content is desirably 55 wt% or less. Further, according to the graph shown in FIG. 4, it can be seen that the magnetic flux density is sufficiently high even if the cobalt content is only a few percent. Therefore, the cobalt content is preferably 1 wt% or more. In this embodiment, since the magnetic field H is about 1500 Oe and the cobalt content is about 5 wt%, the magnetic flux density is about 22000 G.

  Further, according to the present embodiment, since the corrosion-resistant plating layers 302 and 442 are formed on the entire surfaces of the movable core 30 and the fixed core 44, both the cores 30, while including a cobalt-based material having low corrosion resistance, Corrosion resistance can be secured for the surface of 44. Moreover, since the hard plating layers 303 and 443 are formed on the movable side contact surface 301 of the movable core 30 and the fixed side contact surface 441 of the fixed core 44, both cores are included while including a cobalt-based material having low wear resistance. Abrasion resistance can be secured for the portion where 30 and 44 contact.

  In the present embodiment, the corrosion-resistant plating layers 302 and 442 include nickel phosphorus, and the hard plating layers 303 and 443 include chromium. According to this, the oxide film produced when nickel phosphorous plating is applied to both the cores 30 and 44 is removed by chromic acid used as a plating solution when applying chromium plating. Therefore, when the hard plating layers 303 and 443 are laminated and formed on the corrosion-resistant plating layers 302 and 442, it is possible to easily form the hard plating layers 303 and 443 that are difficult to peel off.

  In the present embodiment, at least one additive of Si, Al, V, Cr, and Fe is added to the Fe—Co alloy. According to this, since the electrical resistance of both the cores 30 and 44 can be reduced, when the energization to the coil 54 is switched from on to off, both the magnetized cores 30 and 44 change to a demagnetized state. The demagnetization time until it can be shortened. Therefore, when the energization of the coil 54 is switched off, the moving speed of the movable core 30 in the valve closing direction by the spring 48 can be increased, and the response of intermittent fuel injection can be improved.

  As described above, according to the present embodiment, it is possible to ensure the responsiveness of intermittent fuel injection by avoiding a decrease in magnetic flux density, and to ensure wear resistance and corrosion resistance. Can be realized.

(Other embodiments)
In the embodiment described above, the cobalt-based material is included in both the movable core 30 and the fixed core 44, but the cobalt-based material may be included in only one of the cores. In that case, the corrosion-resistant plating layers 302 and 442 and the hard plating layers 303 and 443 may be formed only on the core containing the cobalt-based material.

  In the above-described embodiment, the movable side contact surface 301 and the fixed side contact surface 441 are positioned on the axial end surfaces of both the cores 30 and 44. A stopper surface may be formed in a portion different from the above, and the cores 30 and 44 may be brought into contact with each other at the stopper surface, and the axial end surfaces of the cores 30 and 44 may not be in contact with each other. In that case, the hard plating layers 303 and 443 are formed on the stopper surfaces instead of the axial end surfaces of both cores.

  As described above, the present invention is not limited to the above-described embodiment, and can be applied to various embodiments without departing from the gist thereof.

Sectional drawing which shows typically the movable core and fixed core by one Embodiment of this invention. Sectional drawing which shows the whole fuel-injection valve provided with both the cores of FIG. The elements on larger scale of FIG. The figure which shows the relationship between the cobalt content rate and magnetic flux density in both the cores of FIG.

Explanation of symbols

  10: Fuel injection valve, 24: Valve member, 30: Movable core, 44: Fixed core, 54: Coil, 301: Movable side contact surface, 302, 442: Corrosion-resistant plating layer, 303, 443: Hard plating layer, 441 : Fixed contact surface.

Claims (4)

A valve member for intermittent fuel injection;
A movable core that reciprocates with the valve member;
A fixed core that forms a magnetic circuit with the movable core;
A coil that generates a magnetic attractive force between the movable core and the fixed core by energization;
With
At least one of the movable core and the fixed core includes a cobalt-based material,
A fuel injection valve in which corrosion resistance plating is applied to the entire surface of the at least one core, and hard plating is applied to a portion of the at least one core where the movable core and the fixed core are in contact with each other .   The fuel injection valve according to claim 1, wherein the corrosion-resistant plating contains nickel and phosphorus, and the hard plating contains chromium.   The fuel injection valve according to claim 1 or 2, wherein a content of the cobalt-based material contained in the at least one core is 1 to 55 wt% with respect to a mass of the entire core. The fuel injection valve according to any one of claims 1 to 3, wherein at least one additive of Si, Al, V, Cr, and Fe is added to the at least one core.

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