Solenoid valve

A solenoid valve for a fuel injection valve with an internal space is disclosed. Fuel is included in the internal space. The solenoid valve includes a magnet coil that forms an electromagnet when energized. The solenoid valve also includes a stator that is magnetized by the electromagnet. The solenoid further includes an armature provided in the internal space that is attracted to and moves toward the stator when the stator is magnetized. The armature includes an attracted surface that faces the stator, a second surface that is opposite the attracted surface, a recess provided in the attracted surface, at least one through hole that extends through the armature from the attracted surface to the second surface, and at least one communication groove that establishes communication between the recess and the at least one through hole.

CROSS REFERENCE TO RELATED APPLICATION(S)

The following is based on and claims priority to Japanese Patent Application No. 2005-251332, filed Aug. 31, 2005, which is hereby incorporated by reference in its entirety.

FIELD

The present invention relates to a solenoid valve for a fuel injection valve.

BACKGROUND

Efforts are being made to reduce emissions of carbon dioxide (CO2) and otherwise purify auto emissions to thereby reduce harmful environmental effects. With respect to diesel engines, for instance, it has been proposed to increase the pressure of injected fuel, inject fuel in multiple stages, and the like to thereby improve emissions. To achieve these purposes, high response and short injection intervals are typically required of the solenoid valves of injectors.

However, conventional solenoid valves suffer from certain disadvantages. For instance, when a magnet coil is energized and to magnetize a stator, an armature is attracted by the stator and moves in fuel at high speed. The armature in conventional solenoid valve meets with the resistance of the fuel (i.e., fluid drag). The fluid drag has an undesirable effect on response.

In partial response to this problem, U.S. Pat. No. 6,648,248 (Japanese Patent Publication No. 2001-304448) discloses a device with passages that establish communication between a valve chamber filled with fuel and a discharge passage of an injector. The passages are provided around an armature. However, the passages are provided in a component other than the solenoid valve. This complicates the construction of the injector, which leads to an increase in cost.

Another technique has been proposed as illustrated inFIG. 7. As shown, notches110are formed in the outer circumferential surface of an armature100. Communication grooves130are also included that establish communication between the notches110and a central recess120formed in the center of the armature100. Fluid drag produced when the armature100is moved in fuel at high speed is thereby reduced.

However, this technique also suffers from certain disadvantages. Specifically, when the armature100is formed of highly magnetic material (e.g. silicon steel) to enhance the solenoid response, the strength of the armature100is relatively low. (For example, silicon steel has highly magnetic properties but it is a low-strength material). Also, the armature100typically includes relatively thin-walled portions, such as between the notches110and the central recess120. Stress concentrations can develop at these thin-walled portions. Therefore, it may be difficult to form the communication grooves130having a sufficient passage area in the thin-walled portions of the armature100if it is made out of relatively low-strength magnetic material.

SUMMARY OF THE INVENTION

A solenoid valve for a fuel injection valve with an internal space is disclosed. Fuel is included in the internal space. The solenoid valve includes a magnet coil that forms an electromagnet when energized. The solenoid valve also includes a stator that is magnetized by the electromagnet. The solenoid further includes an armature provided in the internal space that is attracted to and moves toward the stator when the stator is magnetized. The armature includes an attracted surface that faces the stator, a second surface that is opposite the attracted surface, a recess provided in the attracted surface, at least one through hole that extends through the armature from the attracted surface to the second surface, and at least one communication groove that establishes communication between the recess and the at least one through hole.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring initially toFIGS. 1-3, one embodiment of a solenoid valve6for a fuel injection valve1is illustrated. In one embodiment, the fuel injection valve1is used for a common rail fuel injection system for diesel engines. As illustrated inFIG. 3, the fuel injection valve1includes a nozzle2, a nozzle holder3, a control piston4, an orifice plate5, the solenoid valve6, and the like.

The nozzle2is constructed of a nozzle body7and a needle8to be described in greater detail below. The nozzle2is fixed to the nozzle holder3on an end opposite to the solenoid valve6(i.e., the lower end inFIG. 3) via a retaining nut9.

The nozzle body7includes a guide hole10that houses the needle8, a fuel passage11that guides fuel into the guide hole10, a nozzle hole12through which fuel is injected when the needle8is lifted, and the like.

The guide hole10is drilled from the upper end face of the nozzle body7toward the tip of the nozzle body7, and a conical seat face is formed at the end of the guide hole10. A fuel sump13where the inside diameter is enlarged is formed at a midpoint in the guide hole10.

The upstream end of the fuel passage11is open at the upper end face of the nozzle body7and is in fluid communication with the fuel passage14formed in the nozzle holder3. A downstream end of the fuel passage11is in fluid communication with the fuel sump13.

The needle8includes a sliding portion8athat is slidably disposed in the guide hole10above the fuel sump13and a shank portion8bthat is disposed in the guide hole10beneath the fuel sump13. A gap is included between the sliding portion8aand the shank portion8b. An outer diameter of the shank portion8bis slightly smaller than that of the sliding portion8a. Thus, an annular gap is ensured between the inner surface of the guide hole10and the outer surface of the shank portion8b. (This annular gap is referred to as a fuel passage15.) A seat line is provided at the end of the shank portion8b, and this seat line can seat on the seat face of the nozzle body7and blocks fluid communication between the fuel passage15and the nozzle hole12.

The nozzle holder3is provided with a piping joint16. High-pressure fuel is supplied from a common rail through a fuel pipe (not shown) connected to this piping joint16. A bar filter18for filtering fuel is installed in the internal passage17in the piping joint16.

The nozzle holder3includes a cylindrical hole20for housing the control piston4and a pressure pin19. The above-mentioned fuel passage14is included in the nozzle holder3and guides high-pressure fuel from the piping joint16to the nozzle2. The nozzle holder3also includes a fuel passage21that guides the high-pressure fuel toward the orifice plate5. A cylindrical wall portion22for installing the solenoid valve6is provided at the upper end of the nozzle holder3.

The control piston4is slidably disposed in the cylindrical hole20in the nozzle holder3. Oil pressure in a pressure chamber23, which will be described in greater detail, acts on the upper end face of the control piston4.

The pressure pin19is connected to the lower part of the control piston4(i.e., the side opposite the pressure chamber), and the lower end face of the pressure pin19is abutted against the upper end face of the needle8. The pressure pin19is moved integrally with the control piston4. The pressure pin19presses the needle8toward the valve closing direction (i.e., downward inFIG. 3) due to biasing force from a spring24provided around the lower part of the pressure pin19.

The orifice plate5is disposed on the end face in the cylindrical wall portion22provided in the nozzle holder3. The valve body25is also disposed in the cylindrical wall portion22above the orifice plate5. The orifice plate5is secured by threading and engaging the valve body25with the inner circumferential surface of the cylindrical wall portion22. The orifice plate5, as illustrated inFIG. 1includes the pressure chamber23that communicates with the cylindrical hole20in the nozzle holder3. The orifice plate5also includes an inlet orifice26that communicates with the fuel passage21formed in the nozzle holder3and guides high-pressure fuel into the pressure chamber23. Furthermore, the orifice plate5includes an outlet orifice27(i.e., a fuel passage) that discharges high-pressure fuel from the pressure chamber23when the solenoid valve6is opened.

The solenoid valve6includes a magnet coil28that forms an electromagnet when energized. The solenoid valve6also includes a stator29that forms a magnetic circuit around the magnet coil28. Furthermore, the solenoid valve6includes an armature30that is moved opposite to the stator29. Also, the solenoid valve6includes a ball valve31that is moved with the armature30to open and close the outlet orifice27. The solenoid valve6is fixed on the cylindrical wall portion22in the nozzle holder3via a retaining nut32.

The magnet coil28is wound on a resin bobbin33and is provided in the stator29. The magnet coil28is also at least partially encapsulated with resin material34.

The stator29is formed of a ferromagnetic material such as iron. When the magnet coil28is energized, the stator29is magnetized due to magnetic flux produced. The stator29has a center hole35that extends axially. The center hole35is in fluid communication with the fuel discharge passage37. The fuel discharge passage37is provided in an end housing36provided on a side of the stator29opposite the armature30.

A resin connector38is installed on the end housing36. The terminal39is provided in the connector38, and the magnet coil28is electrically connected to the terminal39via a metal lead terminal40.

In one embodiment, the armature30is formed of a highly magnetic material, such as silicon steel. The armature30is provided in the valve chamber41defined between the stator29and the valve body25inside the cylindrical wall portion22of the nozzle holder3. Further, the armature30includes a shaft portion42that protrudes from a center portion away from the stator29. The armature30includes an attracted surface30hthat faces the stator29and a second surface30jthat is opposite to the attracted surface30h. The shaft portion42is slidably provided in a slide hole in the center of the valve body25.

The valve chamber41is filled with fuel, and communicates with the discharge passage37through the center hole35in the stator29.

The spring43extends through the center hole35in the stator29. The armature30is biased away from the stator29(i.e., downward inFIG. 1) by the spring43. When the magnet coil28is off, a predetermined gap is maintained between the armature30and the stator29. When the magnet coil28is energized and the stator29is thereby magnetized, the armature30is attracted toward the magnetized stator29. Then, the armature30moves toward the stator29to abut against the end face of the stator29.

A communicating hole44is included in the valve body25that communicates with the above-mentioned valve chamber41. An oil passage45is also included in the valve body25that communicates with the outlet orifice27when the ball valve31opens the outlet orifice27. The oil passage45is in fluid communication to the side face of the communicating hole44.

The ball valve31is held at the lower end of the shaft portion42. When the magnet coil28is off, the armature30is biased by the spring43away from the stator29, and as a result, the ball valve31closes the outlet orifice27against the oil pressure in the pressure chamber23. When the magnet coil28is energized, the armature30is attracted toward the magnetized stator29, and the ball valve is forced to open the outlet orifice27by the oil pressure in the pressure chamber23. Also, when the magnet coil28is off (i.e., when the ball valve31has closed the outlet orifice27), a relatively small gap is maintained between the surface of the armature30and the plate46.

As illustrated inFIG. 2, the armature30includes a central recess30ain the axial center of the attracted surface30h(i.e., the surface of the armature30facing the stator29and that is attracted by the magnetized stator29). The armature30also includes a plurality of through holes30bthat extend through the armature30from the attracted surface30hto the second surface30jof the armature30. The armature30further includes a plurality of communication grooves30cthat extend radially on the attracted surface30h. The communication grooves30cestablish communication between the central recess30aand the through holes30b. A chamfer30d(e.g., a chamfer of 45 degrees) is formed at the outer edge of the armature30on the second side30j.

The central recess30aextends axially from the attracted surface30hof the armature30approximately half way through the armature30toward the second surface30j. The central recess30aof the armature30is axially aligned and is in fluid communication with the center hole35of the stator29.

The through holes30bare spaced equally from each other circumferentially. In the embodiment shown, there are three through holes30bspaced 120 degrees apart from each other circumferentially. When the armature30abuts against the stator29, the through holes30bare in fluid communication with the valve chamber41through the chamfer30dof the armature30. Thus, even when the armature30abuts against the stator29, a fluid passage exists between the valve chamber41, the chamfer30d, the through holes30b, the communication grooves30c, the central recess30a, and the center hole35.

The communication grooves30care so formed that they have rectangular shape in a section taken perpendicular to the respective axis. The communication grooves30cestablish fluid communication between the respective through holes30band the central recess30a.

A plurality of notches30eare also included in the armature30between the through holes30b. The notches30eextend radially inward from the outer periphery and are substantially V-shaped. In one embodiment, the notches30eare formed by cutting. The notches30eare equally spaced circumferentially. In the embodiment shown, there are three notches30espaced at intervals of 120 degrees in the circumferential direction.

During operation, when the magnet coil28is off, the ball valve31closes the outlet orifice27. Therefore, the needle8is biased in the valve closing direction because the oil pressure in the pressure chamber23and the force of the spring24is greater than oil pressure force that pushes up the needle8in the valve opening direction. As a result, the seat line of the needle8rests on the seat face to block communication between the fuel passage15and the nozzle hole12, and fuel is not injected.

When the magnet coil28is energized and the electromagnet is formed, the armature30is attracted toward the magnetized stator29and moves toward the stator29against the biasing force of the spring43. As a result, the ball valve31opens the outlet orifice27due to oil pressure in the pressure chamber23.

Thus, the oil pressure in the pressure chamber23is reduced because fluid passes through the outlet orifice27. Also, the needle8moves toward the opening direction. Then, fuel supplied through the fuel passage15is injected from the nozzle hole12.

When power is cut from the magnet coil28, the electromagnet stops functioning, the armature30is biased away from the stator29by the spring43, and the ball valve31closes the outlet orifice27. Thus, the oil pressure in the pressure chamber23rises again. When the force that biases the needle8in the valve closing direction thereby exceeds the oil pressure force that pushes up the needle8in the valve opening direction, the needle8moves toward the closing direction. Thus, the seat line of the needle8rests on the seat face to block communication between the fuel passage15and the nozzle hole12, and injection is thereby terminated.

The solenoid valve6in this embodiment, used in the fuel injection valve1experiences resistance (i.e., fluid drag) due to the armature30moving through fuel in the valve chamber41. As mentioned above, the attracted surface30hof the armature30includes the communication grooves30cthat establish fluid communication between the through holes30band the central recess30a, and the second surface30jof the armature30includes the chamfer30don the peripheral edge. The through holes30band the valve chamber41communicate with each other through the chamfer30d. As such, fuel can flow between the valve chamber41and the center hole35in the stator29via the through holes30b. As a result, the armature30experiences less fluid drag during movement. Thus response of the solenoid valve6is improved.

In one embodiment, the armature30is formed of silicon steel, a highly magnetic but relatively low strength material. The armature30can have improved response due to the silicon steel, but despite the communication grooves30c, the armature30is less likely to fracture or otherwise fail due to the construction described above. Unlike the prior art, the communication grooves30cof the present embodiment establish fluid communication between the through holes30band the central recess30a. Thus, when external force (e.g. impact force produced when the armature collides with the stator29) is applied to the armature30, stress concentration is better distributed (i.e., stress concentrations are unlikely to be concentrated on the communication grooves30c). Therefore, even with an armature30made of silicon steel, the passage area (i.e., depth and groove width) of the communication grooves30cis sufficiently large to reduce fluid drag.

Referring now toFIG. 4, another embodiment of the armature30is illustrated. In this embodiment, the armature30includes first communication grooves30cthat establish fluid communication between the central recess30aand the through holes30b. The armature30in this embodiment also includes second communication grooves30fformed in the attracted surface30h. The second communication grooves establish fluid communication between the notches30eand the central recess30ain the armature30.

Thus, in the embodiment ofFIG. 4, two systems of passages are formed by forming the second communication grooves30f. Fuel can flow between the valve chamber41and the center hole35in the stator29through these passages. Therefore, it is possible to further reduce fluid drag produced when the armature30moves to thereby obtain more stable response.

The depth, width, and the like of the second communication grooves30fcan be appropriately selected to the extent that required strength can be ensured in the armature30.

Referring now toFIG. 5, another embodiment of the solenoid valve6is illustrated. In this embodiment, the solenoid valve6includes an annular groove34aformed in the resin material34that encapsulates the magnet coil28. In this case, the notches30eand through holes30bformed in the armature30communicate with each other through the annular groove34aformed in the resin material34. Therefore, fluid can flow between the valve chamber41and the center hole35in the stator29via the notches30eas well as the through holes30b.

Referring now toFIG. 6, another embodiment of the armature30is shown. In the embodiment shown, the armature30includes a step30ginstead of the chamfer30ddescribed above. Accordingly, in the embodiment shown, the through holes30band the valve chamber41fluidly communicate with each other through this step30g.

In the fuel injection valve1described in the embodiment ofFIGS. 1-3, the fuel discharge passage37is provided in the end housing36and communicates with the center hole35in the stator29. In another embodiment, the discharge passage37is provided in a component other than the end housing36, for example, in the nozzle holder3.

While only the selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the scope of the disclosure as defined in the appended claims. Furthermore, the foregoing description of the embodiments herein is provided for illustration only, and not for the purpose of limiting the disclosure as defined by the appended claims and their equivalents.