Fuel injection device

The invention has an object for improving response of a fuel injection device. A flow-in recessed portion and a flow-out recessed portion are formed at a press-contacting surface of a floating plate, which is movably accommodated in a pressure control chamber. A flow-in port and a flow-out port are formed at a pressure control surface of a valve body. The flow-in port is opened to the flow-in recessed portion, while the flow-out port is opened to the flow-out recessed portion. When the floating plate is moved upwardly and the press-contacting surface is brought into contact with the pressure control surface, the flow-in port is surely closed.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2009-133362 filed on Jun. 2, 2009 and Japanese Patent Application No. 2010-030544 filed on Feb. 15, 2010, the disclosures of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a fuel injection device, according to which a valve portion is opened and closed in accordance with a control signal from an electronic control unit so that a part of fuel supplied from a fuel supply line to the fuel injection device is injected through injection ports and fuel injection is thereby controlled. According to the fuel injection device, a remaining part of the fuel is discharged to a fuel return line during the fuel injection operation.

BACKGROUND OF THE INVENTION

A fuel injection device is generally known in the art, which is composed of a control body having a pressure control chamber, and a valve member for opening and closing a valve portion in accordance with fuel pressure in the pressure control chamber. According to the fuel injection device of this kind, a fuel inlet port is opened to the pressure control chamber of the control body so that the fuel from the fuel supply line flows into the pressure control chamber, and a fuel outlet port is likewise opened to the pressure control chamber so that the fuel is discharged from the pressure control chamber to the fuel return line. Communication and non-communication (block-off of the communication) between the fuel outlet port and the fuel return line is controlled by a pressure control valve so that the fuel pressure in the pressure control chamber is controlled.

According to a known fuel injection device, for example, as disclosed in Japanese Patent Publication No. H6-108948 or Japanese Patent No. 4054621, the fuel injection device further has a floating member movable in the pressure control chamber. The floating member has a press-contacting surface, which is opposed in an axial direction of the floating member to a pressure control surface exposed to the pressure control chamber. A fuel inlet port as well as a fuel outlet port is opened at the pressure control surface. When a pressure control valve is operated to communicate the fuel outlet port with a fuel return line, the press-contacting surface of the floating member is attracted to the pressure control surface (at which the fuel outlet port is opened) by fuel flow from the pressure control chamber to the fuel outlet port. When the floating member is brought into contact with the pressure control surface, the press-contacting surface of the floating member is pressed against the pressure control surface, so that communication between the fuel inlet port and the pressure control chamber as well as communication between the fuel inlet port and the fuel outlet port is blocked off.

According to the fuel injection device of Japanese Patent No. 4054621, a surface portion of the pressure control surface (surrounding the fuel inlet port) is recessed, while another surface portion of the pressure control surface (surrounding the fuel outlet port) is not recessed but formed in a flat shape. The press-contacting surface of the floating member is also formed in a flat shape.

In the above fuel injection device, when the press-contacting surface of the floating member is pressed against the pressure control surface in order to block off the communication between the fuel injection port and the pressure control chamber, a surface area of the floating member (that is, the press-contacting surface) which is in contact with the pressure control surface is large. Therefore, it is difficult to increase surface pressure (pressing force per unit surface area). As a result, high pressure fuel from the fuel inlet port may pass through a gap between the pressure control surface and the press-contacting surface of the floating member. In other words, it is difficult to surely block off the communication between the fuel inlet port and the pressure control chamber. Therefore, when the fuel outlet port is opened (that is, when the fuel outlet port is communicated to the fuel return line), rapid pressure increase of the fuel in the pressure control chamber may not be realized, and thereby a rapid opening operation of the valve portion may not be possible.

SUMMARY OF THE INVENTION

The present invention is made in view of the above problems. It is an object of the present invention to provide a fuel injection device, in which a response for opening and closing a valve portion in accordance with a control signal from a control unit is increased.

According to a feature of the invention, a fuel injection device has a nozzle body having an injection port and movably accommodating a valve member. A valve portion is provided in the nozzle body for opening and closing the injection port by movement of the valve member in accordance with a control signal from an engine control unit, so that apart of high pressure fuel from a fuel supply system is injected from the injection port and another part of the fuel is discharged into a fuel discharge passage, which is operatively connected to a fuel return line.

The fuel injection device has a pressure control chamber having a flow-in port through which the high pressure fuel is supplied into the pressure control chamber, and a flow-out port through which the fuel is discharged from the pressure control chamber to the fuel discharge passage, wherein the fuel pressure in the pressure control chamber is applied to the valve member so that the valve member is moved up or down depending on the fuel pressure in the pressure control chamber to thereby open or close the injection port.

The fuel injection device has a control body having a valve body, wherein the valve body has a pressure control surface exposed to the pressure control chamber, and the flow-in port and the flow-out port are opened at the pressure control surface.

The fuel injection device has a pressure control valve provided in the fuel discharge passage for changing its valve position in accordance with the control signal, so that the flow-out port is communicated with the fuel return line or the communication between the flow-out port and the fuel return line is blocked off.

The fuel injection device has a floating member movably accommodated in the pressure control chamber and having a press-contacting surface opposing to the pressure control surface in a moving direction of the floating member, the press-contacting surface being pressed against the pressure control surface in order to block off communication between the flow-in port and the pressure control chamber as well as communication between the flow-in port and the flow-out port when the pressure control valve is operated to bring the flow-out port into communication with the fuel return line.

The fuel injection device has a flow-out recessed portion formed at the pressure control surface or the press-contacting surface, so that a first space is formed on the side of the press-contacting surface as a part of the pressure control chamber when the press-contacting surface of the floating member is in contact with the pressure control surface, wherein the flow-out port is opened to the flow-out recessed portion.

The fuel injection device has a flow-in recessed portion formed at the pressure control surface or the press-contacting surface, so that the flow-in recessed portion is isolated from the pressure control chamber when the press-contacting surface of the floating member is in contact with the pressure control surface, wherein the flow-in port is opened to the flow-in recessed portion.

According to another feature of the invention, the flow-in recessed portion is formed in an annular shape and coaxial with the pressure control surface or the press-contacting surface, at which the flow-in recessed portion is formed, and the flow-out recessed portion is formed at a surface portion of the pressure control surface or the press-contacting surface, at which the flow-out recessed portion is formed, the surface portion is located in an inside of flow-in recessed portion of the annular shape.

According to a further feature of the invention, the pressure control surface of the valve body is formed of a circular shape. The flow-out recessed portion is formed at the pressure control surface at a position offset from a center of the pressure control surface. The flow-out recessed portion is surrounded by an annular flow-out-side contacting portion. The flow-in recessed portion is formed at the pressure control surface. The flow-in recessed portion is surrounded by a part of the annular flow-out-side contacting portion and a part of an annular flow-in-side contacting portion. And the other part of the annular flow-out-side contacting portion and the other part of the annular flow-in-side contacting portion are overlapped with each other.

According to a still further feature of the invention, a second space is formed on the other side of the floating member opposite to the press-contacting surface, wherein the second space is another part of the pressure control chamber. The floating member has a communication hole for communicating the first and second spaces with each other, so that the flow-out port is communicated with the second space even when the press-contacting surface of the floating member is in contact with the pressure control surface, and the floating member has a restricted portion in the communication hole.

According to a still further feature of the invention, the control body has a cylinder, one end of which surrounds the pressure control surface, and a cylindrical space of which forms the pressure control chamber so that the floating member is movable in the cylindrical space. The press-contacting surface is moved away from the pressure control surface when the pressure control valve is operated to block off the communication between the flow-out port and the fuel return line.

A first space is formed on a side of the press-contacting surface of the floating member, as a part of the pressure control chamber, and a second space is formed on the other side of the floating member opposite to the press-contacting surface, as another part of the pressure control chamber.

A side wall portion is formed at an outer side wall of the floating member, and a communication passage is formed at the side wall portion for communicating the first and second spaces of the pressure control chamber with each other.

According to a still further feature of the invention, a fuel injection device has a nozzle body having an injection port and movably accommodating a valve member. A valve portion is provided in the nozzle body for opening and closing the injection port by movement of the valve member in accordance with a control signal from an engine control unit, so that a part of high pressure fuel from a fuel supply system is injected from the injection port and another part of the fuel is discharged into a fuel discharge passage, which is operatively connected to a fuel return line.

The fuel injection device has a pressure control chamber having a flow-in port through which the high pressure fuel is supplied into the pressure control chamber, and a flow-out port through which the fuel is discharged from the pressure control chamber to the fuel discharge passage.

The fuel injection device has a control body having a valve body and a cylinder, wherein the valve body has a pressure control surface surrounded by one end of the cylinder and exposed to the pressure control chamber, wherein the flow-in port and the flow-out port are opened at the pressure control surface, wherein one end of the valve member is movably supported in a cylindrical space of the cylinder, wherein the pressure control chamber is defined by the pressure control surface, an inner peripheral wall of the cylinder and a pressure receiving surface formed at one end of the valve member, and wherein the fuel pressure in the pressure control chamber is applied to the pressure receiving surface of the valve member so that the valve member is moved up or down depending on the fuel pressure in the pressure control chamber to thereby open or close the injection port.

The fuel injection device has a pressure control valve provided in the fuel discharge passage for changing its valve position in accordance with the control signal, so that the flow-out port is communicated with the fuel return line or the communication between the flow-out port and the fuel return line is blocked off.

The fuel injection device has a floating member movably accommodated in the pressure control chamber and having a press-contacting surface opposing to the pressure control surface in a moving direction of the floating member, wherein the press-contacting surface is pressed against the pressure control surface in order to block off communication between the flow-in port and the pressure control chamber as well as communication between the flow-in port and the flow-out port when the pressure control valve is operated to bring the flow-out port into communication with the fuel return line, and wherein the press-contacting surface is moved away from the pressure control surface when the pressure control valve is operated to block off the communication between the flow-out port and the fuel return line.

The fuel injection device has a first space formed on a side of the press-contacting surface of the floating member, as a part of the pressure control chamber, and a second space formed on the other side of the floating member opposite to the press-contacting surface, as another part of the pressure control chamber.

The fuel injection device has a side wall portion formed at an outer side wall of the floating member and a communication passage formed at the side wall portion for communicating the first and second spaces of the pressure control chamber with each other.

According to a still further feature of the invention, the side wall portion formed at the outer side wall of the floating member is in a sliding contact with the inner peripheral wall of the cylinder, so that the floating member is movable in the cylinder in its axial direction.

According to a still further feature of the invention, a passage area of the communication passage is larger than an opening area of the flow-in port.

According to a still further feature of the invention, multiple passage wall portions are formed at the side wall portion of the floating member, so that multiple communication passages are formed for communicating the first and second spaces of the pressure control chamber with each other.

According to a still further feature of the invention, the passage wall portion is formed of a flat surface extending in an axial direction of the floating member.

According to a still further feature of the invention, the passage wall portion is formed of a groove, one end of which is opened to the press-contacting surface of the floating member and the other end of which is opened to a side surface of the floating member opposite to the press-contacting surface.

According to a still further feature of the invention, a length of the groove in a circumferential direction of the floating member is made larger than a depth of the groove in a radial direction of the floating member.

According to a still further feature of the invention, the control body has a cylinder, one end of which surrounds the pressure control surface, and a cylindrical space of which forms the pressure control chamber so that the floating member is movable in the cylindrical space. The press-contacting surface is moved away from the pressure control surface when the pressure control valve is operated to block off the communication between the flow-out port and the fuel return line. A first space is formed on a side of the press-contacting surface of the floating member, as a part of the pressure control chamber, and a second space is formed on the other side of the floating member opposite to the press-contacting surface, as another part of the pressure control chamber. A side wall portion is formed at an outer side wall of the floating member, and a communication space is formed at a gap between the side wall portion and an inner peripheral wall of the cylinder for communicating the first and second spaces of the pressure control chamber with each other.

According to a still further feature of the invention, the floating member is formed in a disc shape and movable in the pressure control chamber in an axial direction of the disc shaped floating member, and a diameter of the floating member at the press-contacting surface or a surface of the floating member opposite to the press-contacting surface is made smaller than a diameter of the floating member at a middle portion thereof.

According to a still further feature of the invention, a side wall portion is formed at an outer side wall of the floating member, and the side wall portion has a cross sectional shape, which is outwardly expanded in a radial direction of the floating member.

According to a still further feature of the invention, a stopper portion is formed at an inner peripheral wall of the cylinder, so that a surface of the floating member opposite to the press-contacting surface is brought into contact with the stopper portion so as to limit a movement of the floating member. In addition, a flow limiting groove is formed at the stopper portion or at the surface of the floating member opposite to the press-contacting surface, so that the fuel may flow though the flow limiting groove.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be explained with reference to the drawings. The same reference numerals are used for the same or similar parts and components, so that duplicated explanation will be eliminated.

First Embodiment

FIG. 1shows a fuel supply system10, to which a fuel injection device100according to a first embodiment is applied. The fuel injection device100is a fuel injection valve of a direct injection type, which directly injects fuel into a combustion chamber22of a diesel engine20(an internal combustion engine).

The fuel supply system10is composed of a fuel feed pump12, a high pressure pump13, a common rail14, an engine control unit17, and the fuel injection device100.

The fuel feed pump12is an electrically driven pump and mounted in a fuel tank11. The fuel feed pump12applies a feed pressure to fuel contained in the fuel tank11, wherein the feed pressure is higher than vapor pressure of the fuel. The fuel feed pump12is connected to the high pressure pump13via a fuel pipe12ain order to supply the fuel in liquid phase (to which a certain feed pressure is applied) to the high pressure pump13. A pressure regulating valve (not shown) is provided in the fuel pipe12a, so that fuel pressure of the fuel to be supplied to the high pressure pump13is regulated at a predetermined pressure.

The high pressure pump13is mounted to the diesel engine20, so that it is driven by a driving torque from an output shaft of the diesel engine. The high pressure pump13is connected to the common rail14via a fuel supply pipe13ain order to further pressurized the fuel from the fuel feed pump12and to supply such high pressure fuel to the common rail14. The high pressure pump13has an electromagnetic valve (not shown) electrically connected to the engine control unit17. The electromagnetic valve is controlled by the engine control unit17to open and close, so that the fuel pressure of the fuel to be supplied from the high pressure pump13to the common rail14is controlled at a predetermined value.

The common rail14is formed in a pipe shape made of chrome molybdenum steel and a plurality of branch portions14ais formed. A number of the branch portions14acorresponds to a number of cylinders of the diesel engine20. Each of the branch portions14ais respectively connected to the fuel injection devices100via a fuel pipe forming a fuel supply line14d. The fuel injection devices100as well as the high pressure pump13are connected to a fuel pipe forming a fuel return line14f. According to the above structure, the common rail14temporarily stores the high pressure fuel supplied from the high pressure pump13and distributes the fuel to the respective fuel injection devices100via the fuel supply lines14dwhile keeping the high fuel pressure.

The common rail14further has a common rail sensor14band a pressure regulator14cat respective axial ends. The common rail sensor14bis electrically connected to the engine control unit17. The common rail sensor14bdetects pressure and temperature of the fuel and outputs detected information to the engine control unit17. The pressure regulator14cregulates the pressure of the fuel in the common rail14at a predetermined value and at the same time depressurizes and discharges surplus fuel. The surplus fuel passing through the pressure regulator14creturns to the fuel tank11via a fuel line formed by a fuel pipe14e, which connects the common rail14to the fuel tank11.

The fuel injection device100injects the high pressure fuel from injection ports44, wherein the high pressure fuel is supplied to the respective fuel injection devices100via the branch portions14aof the common rail14. The fuel injection device100opens and closes a valve portion50in accordance with a control signal from the engine control unit17, so that fuel injection of the fuel supplied from the fuel supply line14dand injected through the injection ports44is controlled. A part of the fuel, which has not been injected through the injection ports44, is discharged into the fuel return line14f. As above, the fuel injection is controlled by the fuel injection device100. The fuel injection device100is inserted into and fixed to an injector hole formed in a cylinder head21, which is a part of the diesel engine20forming the combustion chamber22. The fuel injection devices100are arranged to the respective combustion chambers22so as to directly inject the fuel thereinto, for example, at a pressure of 160 to 220 MPa.

The engine control unit17is composed of a micro computer and so on, which is electrically connected not only to the above common rail sensor14bbut also to a rotational speed sensor for detecting a rotational speed of the diesel engine20, a throttle sensor for detecting an opening degree of a throttle valve, an air flow sensor for detecting intake air amount, a pressure sensor for detecting a pressure of a super charger, a temperature sensor for detecting temperature of engine cooling water, an oil temperature sensor for detecting temperature of lubricating oil, and other various sensors. The engine control unit17outputs electrical signals to the electromagnetic valve of the high pressure pump13and the fuel injection devices100for controlling opening and closing operations thereof. The electrical signals are calculated based on the information of the sensors.

A structure of the fuel injection device100will be further explained in detail with reference toFIGS. 2 and 3.

The fuel injection device100is composed of a control valve driving portion30, a control body40, a nozzle needle60, and a floating plate70. Only for the purpose of explanation, a portion (or a side) of the fuel injection device100, such as the valve portion50which is exposed into the combustion chamber22, that is a lower portion of the fuel injection device100in the drawing ofFIG. 2, is referred to as a forward end and/or a forward end side, while an opposite portion (or an opposite side) of the fuel injection device100is referred to as a top end and/or top end side.

The control valve driving portion30is accommodated in the control body40. The control valve driving portion30has a terminal32, a solenoid31, a stator36, a movable member35, a spring34, and a valve seat member33. The terminal32is made of electrically conductive metal material, one end of which is outwardly projected from the control body40and the other end of which is connected to the solenoid31. The solenoid31is a spirally would coil for receiving pulse-formed current from the engine control unit17via the terminal32. The solenoid31generates magnetic field going around in an axial direction, when receiving the current. The stator36is made of magnetic material and formed in a cylindrical shape. The stator36is magnetized in the magnetic field generated by the solenoid31. The movable member35is made of magnetic material and formed in a column shape having a step portion. The movable member35is arranged on the forward end side of the stator36(a lower side of the stator36in the drawing). The movable member35is attracted by the magnetized stator36in a direction toward the top end side of the fuel injection device100(in an upward direction in the drawing). The spring34is a coil spring made of a wire rod spirally wound and biases the movable member35in a direction away from the stator36(in a downward direction in the direction). The valve seat member33forms a pressure control valve80together with a valve seat47aof the control body40(explained below). The valve seat member33is provided at a lower end of the movable member35(that is, an opposite end of the movable member35to the stator36) and being capable of being seated on the valve seat47a. When the magnetic field is not generated by the solenoid31, the valve seat member33is seated on the valve seat47aby the biasing force of the spring34. When the magnetic field is generated by the solenoid31, the valve seat member33is separated (lifted up) from the valve seat47a.

As more clearly shown inFIG. 3, andFIGS. 5A and 5B, the control body40has a nozzle body41, a cylinder56, a first valve body46, a second valve body47, a valve holder48, and a retaining nut49(FIG. 2). A flow-in passage52which is communicated to the common rail14and the high pressure pump13via the fuel supply line14d, a pressure control chamber53into which the fuel flows from the flow-in passage52, and a flow-out passage54for discharging the fuel from the pressure control chamber53, are respectively formed in the control body40. Furthermore, a flow-in port52band a flow-out port54b, each of which is opening to the pressure control chamber53, are provided at a pressure control surface53bof the first valve body46. The pressure control surface53bis a lower surface of the first valve body46and is exposed to the pressure control chamber53and facing to the floating plate70on the top end side. According to the above structure of the control body40, the fuel from the fuel supply line14dflows into the pressure control chamber53through the flow-in port52band the fuel is discharged to the fuel return line14fthrough the flow-out port54b.

As shown inFIG. 2, the nozzle body41is made of chrome molybdenum steel and is formed in a cylindrical shape having a closed bottom end. The nozzle body41has a nozzle-needle accommodating portion43, a valve seat portion45, and the injection ports44. The nozzle-needle accommodating portion43is formed in a direction along an axial direction of the nozzle body41and a longitudinal hole is formed therein for accommodating the nozzle needle60. The high pressure fuel from the high pressure pump13and the common rail14is supplied into the nozzle-needle accommodating portion43. A fuel flow passage43ais formed in the nozzle-needle accommodating portion43, so that the fuel from the fuel supply line14dflows to the injection ports44. The valve seat portion45is formed at the closed bottom end of the nozzle body41(at the forward end of the nozzle-needle accommodating portion43), on or from which a forward end of the nozzle needle60is seated or separated. The injection ports44are formed at the forward end of the nozzle body41, which are located at a further forward side of the valve seat portion45, and composed of multiple micro-holes extending in a radial pattern from the inside of the nozzle body41toward the outside thereof. When the fuel passes through the micro-holes, the fuel is atomized and diffused into the air so that the fuel is easily mixed with the air.

As more clearly shown inFIG. 3, the cylinder56is made of metal and formed in a cylindrical shape. The cylinder56is arranged within and co-axially with the nozzle-needle accommodating portion43and located on the forward end side (the lower side in the drawing) of the first valve body46. The cylinder56surrounds the pressure control surface53bto define the pressure control chamber53. An inner peripheral wall57of the cylinder56forms the pressure control chamber53(which is a cylindrical space) together with a wall surface on the forward end side of the first valve body46(that is, the pressure control surface53b). In addition, the inner peripheral wall of the cylinder56forms on the forward end side (the lower side in the drawing) a cylinder sliding portion59for movably supporting the nozzle needle60, so that the nozzle needle60may reciprocate in the axial direction.

Each of the first and second valve bodies46and47is made of the metal, such as chrome molybdenum steel, and formed in a columnar shape. The second valve body47is held at the forward end side (the lower side in the drawing) of the valve holder48and holds the first valve body46at its forward end side. The first and second valve bodies46and47are interposed between the nozzle body41and the valve holder48, and rotation of the first and second valve bodies46and47around a longitudinal axis of the fuel injection device100is restricted by the valve holder48.

The flow-in passage52as well as a discharge passage47c(which is a part of the flow-out passage54) is formed in the first and second valve bodies46and47. A flow-in side restricted portion52aand a flow-out side restricted portion54aare respectively formed in the flow-in passage52and the discharge passage47c, each of which is formed in the second valve body47, for restricting maximum flow amount in the respective passages. A valve seat portion47ais formed on an upper side (the top end side) surface of the second valve body47so as to form the pressure control valve80together with the valve seat member33of the control valve driving portion30(FIG. 2). A discharge port47bis opened at the valve seat portion47a, which is formed on the upper side (the top end side) surface of the second valve body47, so that the discharge port47bis opened or closed by the pressure control valve80. The pressure control valve80opens or closes the discharge port47bin accordance with the control signal. The communication and non-communication between the flow-out port54band the fuel return line14dis switched over from one condition to the other condition by opening or closing the discharge port47b. The flow-out port54bis opened at a lower end surface of the first valve body46, wherein a part of the lower end surface forms the pressure control surface53band the flow-out port54bis located at a center portion of the pressure control surface53bin a radial direction. The fuel pressure in the pressure control chamber53is controlled by switching the communication and non-communication between the flow-out port54band the fuel return line14d.

As shown inFIG. 2, the valve holder48is made of the metal, such as chrome molybdenum steel, and formed in a cylindrical shape. The valve holder48has longitudinal through-holes48aand48bwhich are formed along the axial direction of the fuel injection device100. The valve holder48further has a socket portion48c. The longitudinal through-hole48aforms a part of the flow-in passage52and is communicated with the flow-in passage52formed in the second valve body47. The other longitudinal through-hole48baccommodates the control valve driving portion30at its forward end side (a lower end side). The socket portion48cis formed at a top end side of the longitudinal through-hole48bso as to close an open end thereof. One end of the terminal32of the control valve driving portion30projects in the inside of the socket portion48c, into which a plug portion (not shown) connected to the engine control unit17will be inserted. It is possible to supply driving current from the engine control unit17to the control valve driving portion30, when the plug portion (not shown) is electrically connected to the socket portion48c.

The retaining nut49is made of metal material and formed in a cylindrical shape having a step portion49a. The retaining nut49accommodates an upper portion of the nozzle body41, the first valve body46, and the second valve body47. An upper end of the retaining nut49is screwed to a forward end (a lower end) of the valve holder48. The step portion49ais formed at an inner periphery of the retaining nut49. The step portion49aurges the nozzle body41and the first and second valve bodies46and47in a direction toward the valve holder48, when the retaining nut49is screwed to the valve holder48.

As shown inFIGS. 2 and 3, the nozzle needle60is made of a metal material, such as high-speed tool steel, and formed in a columnar shape. The nozzle needle60has a seat portion65, a pressure receiving surface61, and a ring member67. The seat portion65is formed at a forward end (lower end) of the nozzle needle60and will be seated on or separated from the valve seat portion45of the nozzle body41. The seat portion65forms the valve portion50together with the valve seat portion45, wherein the communication and non-communication between the injection ports44and the fuel passage formed in the nozzle-needle accommodating portion43for the high pressure fuel are switched over by the valve portion50.

The pressure receiving surface61is formed at a top end (an upper end) surface of the nozzle needle60. The pressure receiving surface61is exposed to the pressure control chamber53, so that the pressure receiving surface61receives the fuel pressure in the pressure control chamber53. The ring member67is arranged at an outer peripheral wall of the nozzle needle60and is held by the nozzle needle60. As above, the pressure control chamber53is defined by the inner peripheral wall57of the cylinder56, the pressure control surface53bof the first valve body46, and the pressure receiving surface61. The pressure control chamber53is separated from the fuel flow passage43a.

The nozzle needle60is biased by a return spring66in a downward direction toward the valve portion50. The return spring66is a coil spring made of metal wire spirally wound, a lower end of which is seated on an upper end surface of the ring member67and an upper end of which is in contact with a lower end surface of the cylinder56. According to the above structure, the nozzle needle60is linearly moved with respect to the control body40in accordance with the fuel pressure in the pressure control chamber53, to thereby open or close the valve portion50.

As more clearly shown inFIGS. 5A and 5B, the floating plate70is a disc shaped member made of metal material and has a communication hole71. The floating plate70is coaxially accommodated in the cylinder56, so that the floating plate70is movable in an axial direction thereof, which is along a reciprocating direction of the nozzle needle60. The floating plate70has a pair of axial end surfaces, one of which is an upper end surface73aopposing to the pressure control surface53band forming a press-contacting surface73, and the other of which is a lower end surface79aforming a pressure receiving surface for receiving the fuel pressure in the pressure control chamber53.

The floating plate70is pressed against the pressure control surface53bby the fuel pressure in the pressure control chamber53, when the pressure control valve80is switched to the communication state between the flow-out port54band the fuel return line14f. Namely, the press-contacting surface73of the floating plate70is pressed against the pressure control surface53bto block off the communication between the flow-in passage52and the pressure control chamber53. The communication hole71is formed in the floating plate70at a center thereof in the axial direction. When the flow-in port52bis closed by the floating plate70, the fuel in the pressure control chamber53is discharged into the flow-out passage54through the communication hole71. A flow passage area of the communication hole71is larger than that of the flow-out side restricted portion54a(FIG. 3). When the pressure control valve80is switched to the non-communication state between the flow-out port54band the fuel return line14f, the floating plate70is urged by the fuel pressure in the flow-in passage52in the direction away from the pressure control surface53b. As a result, the press-contacting surface73of the floating plate70is moved away from the pressure control surface53b, so that the flow-in passage52and the pressure control chamber53are brought into the communication state again.

Characterizing portions of the fuel injection device100will be further explained with reference toFIGS. 3 to 6.

As best shown inFIG. 3, longitudinal through-holes46aand46bare respectively formed in the first valve body46of the control body40in the axial direction. The through-hole46bis a part of the discharge passage47cand its lower end (that is, the flow-out port54b) is opened to the pressure control chamber53in the direction to the communication hole71of the floating plate70. The through-holes46aform a part of the flow-in passage52and four through-holes46aare formed around the through-hole46bat equal distances in a circumferential direction (as shown inFIG. 4). A restricted portion46chaving a smaller passage area is formed at a lower side of each through-hole46a(at a side closer to the pressure control chamber53). A lower end of the each restricted portion46c, that is, the flow-in port52b, is restricted and opened to the pressure control chamber53. A sum of the passage areas of the four restricted portions46cis larger than the passage area of the flow-in side restricted portion52a. As above, the flow-in ports52band the flow-out port54bare formed in the first valve body46on the same surface opposing to the floating plate70, and symmetrically arranged with respect to the axis of the floating plate70for its reciprocal movement (FIG. 4).

According to the above structure for the through-holes46aand46b, the flow-out port54bis formed at the pressure control surface53bin a center of the radial direction (as shown inFIG. 4). The flow-in ports52bare formed at the pressure control surface53bon an outer periphery side of the flow-out port54band arranged at the equal distances in the circumferential direction. As shown inFIG. 5A, a surface portion of the pressure control surface53b, which surrounds the flow-in port52b, is referred to as a flow-in-port surrounding portion. In a similar manner, a surface portion of the pressure control surface53b, which surrounds the flow-out port54b, is referred to as a flow-out-port surrounding portion.

As shown inFIG. 3, a passage portion of the discharge passage47c, which is formed in the second valve body47and connects the flow-out port54band the discharge port47bwith each other, is inclined with respect to the axis of the second valve body47. It is possible to freely design a position of the discharge port47bas well as a position of the valve seat portion47a, which are formed at the upper surface of the second valve body47, when an inclination angle of the discharge passage47cis changed with respect to the axial direction of the second valve body47. This is possible even when the flow-out port54bis formed at the center of the pressure control surface53bof the first valve body46. It is, therefore, possible to locate the pressure control valve80(that is, to decide a position of the discharge port47b) at such a position, at which the pressure control valve80can surely operate. According to the above structure, the pressure control valve80can surely open and close the discharge port47bin accordance with the control signal. In other words, the switching operation for the communication and non-communication between the flow-out port54band the fuel return line14f, which is done by opening or closing the discharge port47b, can be surely performed.

As shown inFIGS. 4 and 5A, the floating plate70further has a flow-in recessed portion72a, a flow-out recessed portion74a, an inner press-contacting portion72, an outer press-contacting portion74, a side wall portion76and a communication passage wall portion77.

The flow-in recessed portion72ais formed by depressing a part of the press-contacting surface73, so that a bottom surface72bis opposed to the flow-in-port surrounding portion52dof the open-side wall surface53bin the axial direction of the floating portion70. The flow-in recessed surface72bis recessed in the direction away from the pressure control surface53b, to thereby form the annular flow-in recessed portion72aat an outer side of the flow-out recessed portion74a. The flow-in recessed portion72aforms a flow-in space83together with the flow-in-port surrounding portion52d, when the press-contacting surface73is in contact with the pressure control surface53b, wherein the fuel flows into the flow-in space83from the plurality of the flow-in ports52b.

The flow-out recessed portion74ais formed by depressing a part of the press-contacting surface73, so that a bottom surface74bis opposed to the flow-out-port surrounding portion54dof the pressure control surface53bin the axial direction of the floating portion70. The flow-out recessed surface74bis recessed in the direction away from the pressure control surface53b, to thereby form the circular flow-out recessed portion74a. The flow-out recessed portion74ais formed in a center of the press-contacting surface73, so that the flow-out recessed portion74ais coaxial with the circular press-contacting surface73and the annular flow-in recessed portion72a, as shown inFIG. 4.

Each of the inner and the outer press-contacting portions72and74is formed in a circular shape on the upper end surface73aof the floating plate70. In other words, the inner and outer press-contacting portions72and74are coaxially formed on the press-contacting surface73and opposed to the pressure control surface53b. The outer press-contacting portion74is formed at an outer peripheral portion of the floating plate70and surrounds the outer periphery of the circular flow-in recessed portion72a. The inner press-contacting portion72is formed inside of the outer press-contacting portion74to define the flow-in and the flow-out recessed portions72aand74a. As above, each of inner and the outer press-contacting portions72and74is a circular projection formed on the upper end surface73a(that is, the press-contacting surface73) of the floating plate70projecting toward the pressure control surface53b.

Since the flow-in recessed portion72ais formed between the inner and outer press-contacting portions72and74, the fuel pressure of the fuel flowing from the flow-in port52binto the flow-in space83is applied to the flow-in recessed portion72a, when the press-contacting surface73is pressed against and in contact with the pressure control surface53b. Likewise, since the flow-out recessed portion74ais surrounded by the inner press-contacting portion72, the fuel pressure of the fuel in the flow-out passage54is applied to the flow-out recessed portion74a, when the press-contacting surface73is pressed against and in contact with the pressure control surface53b.

The side wall portion76and the passage wall portion77are formed at an outer side wall75of the floating plate70. A longitudinal cross sectional shape of the outer side wall75, which is a cross sectional shape on a plane including the axis of the floating plate70, has a curved side wall projecting in a radial outward direction of the floating plate70. A small communication space78, through which the fuel flows, is formed between the side wall portion76of the outer side wall75and the inner peripheral surface57of the cylinder56. The communication space78communicates an upper side space53cand a lower side space53dof the pressure control chamber53with each other. The upper side space53cis a part of the pressure control chamber53, which is formed between the floating plate70and the pressure control surface53b. The lower side space53dis another part of the pressure control chamber53, which is formed between the floating plate70and the nozzle needle60.

The passage wall portion77is formed by cutting away a part of the outer side wall75. The passage wall portion77forms a communication passage77atogether with the inner peripheral wall57, so that the upper side and lower side spaces53cand53dare communicated with each other. The passage wall portion77is formed as a flat surface. A pair of flat surface portions (the passage wall portions77) is formed at opposite sides of the floating plate70in the radial direction. As above, in the present embodiment, the upper side and the lower side spaces53cand53dare communicated with each other not only through the communication passages77abut also through the communication space78.

A sum of the passage areas of the communication passages77aand the communication space78is larger than a sum of the passage areas of the flow-in ports52b. In addition, the sum of the passage areas of the communication passages77aand the communication space78is larger than the passage area of the flow-in side restricted portion52a. The passage area of the flow-in side restricted portion52ais the smallest portion in the flow-in passage52. According to the above structure, restoration of the fuel pressure in the lower side space53dis not limited by the floating plate70. Since the communication passages77aand the communication space78are formed between the outer side wall75(the side wall portion76and the passage wall portion77) of the floating plate70and the inner peripheral wall57of the cylinder56, sufficient amount of the passage area can be obtained at the communication passages77aand the communication space78, without making the diameter of the floating plate70larger or making the area of the pressure receiving surface79smaller. As a result, the surface area of the pressure receiving surface79(the lower side surface of the floating plate70) can be made larger than the surface area of the pressure receiving surface61of the nozzle needle60(the upper side surface thereof), so that a larger fuel pressure can be applied to the floating plate70from the fuel in the pressure control chamber53. Accordingly, a response of the floating plate70to the pressure control valve80can be increased.

Since the passage wall portion77is formed by the flat surface, which is extending in a direction in parallel to the axial direction (the reciprocating direction) of the floating plate70, the passage area of the communication passages77ais maintained at a constant value irrespectively of the displaced position of the floating plate70. Therefore, the fuel can surely flow from the upper side space53cto the lower side space53d, to quickly increase the fuel pressure in the lower side space53d. As a result, a response of the nozzle needle60to the pressure control valve80can be also improved.

Since the communication hole71is formed at the center of the floating plate70, the communication hole71communicates the pressure control chamber53(the lower side space53dthereof) with the flow-out port54b, when the floating plate70is pressed against and in contact with the pressure control surface53b. An upper side opening port71aof the communication hole71is formed at the flow-out recessed portion74a, which is surrounded by the inner press-contacting portion72, and located at the center of the press-contacting surface73. The upper side opening port71ais axially opposed to the flow-out port54b. A lower side opening port (opposite to the upper side opening port71a) is formed at a center of the pressure receiving surface79of the floating plate70.

The communication hole71has a restricted portion71cand a recessed portion71b. The restricted portion71crestricts the passage area of the communication hole71, to thereby regulate flow amount of the fuel flowing through the restricted portion71c. The restricted portion71cis formed in the communication hole71on a side closer to the upper end surface73aof the floating plate70(away from the lower end surface79a). The lower side opening port of the communication hole71is made larger than the upper side opening port71a. A lower part of the communication hole71is recessed (cut away) to form the lower side opening port.

A spring55is arranged between the nozzle needle60and the floating plate70for biasing the floating plate70toward the pressure control surface53b, as shown inFIG. 3. The spring55is a coil spring made of a wire rod spirally wound, one axial end (a lower end) of which is seated on the nozzle needle60and the other end (an upper end) of which is in contact with the lower end surface79aof the floating plate70. The floating plate70is biased by the spring force of the spring55in the direction to the flow-in ports52bso that the press-contacting surface73of the floating plate70is kept in contact with the pressure control surface53b, even when no pressure difference is generated between the upper side space53cand the lower side space53d.

When the communication between the flow-out port54band the fuel return line14fis blocked off by the pressure control valve80, the floating plate70is moved away from the pressure control surface53bby the fuel pressure in the flow-in space83against the spring force of the spring55, as shown inFIG. 5B. The floating plate70is kept away from the pressure control surface53b, until the fuel pressure in the upper side space53cbecomes balanced with the fuel pressure in the lower side space53d.

An operation of the above explained fuel injection device100, in which the valve portion50is opened and closed depending on the driving current from the engine control unit17to thereby inject the fuel, will be explained with reference toFIG. 6together withFIGS. 2 to 5.

When driving current of a pulse shape is supplied from the engine control unit17to the solenoid31at a timing t1(as shown in (a) ofFIG. 6), the magnetic field is generated to operate the pressure control valve80so as to open the valve. When the pressure control valve80is opened, the fuel starts to flow out from the discharge passage47cwhich is brought into the communication with the fuel return line14f. The fuel pressure in the pressure control chamber53is decreased at first in an area neighboring to the flow-out port54b. Then, the floating plate70, which is biased by the spring55to the pressure control surface53b, will be further pushed toward the pressure control surface53b, so that the inner and the outer press-contacting portions72and74are pushed to the pressure control surface53b. As a result, the communication between the flow-in ports52and the pressure control chamber53as well as the communication between the flow-in ports52and the flow-out port54bare blocked off (that is, the blocked-off condition is maintained).

The fuel in the lower side space53dof the pressure control chamber53flows out into the flow-out passage54through the communication hole71of the floating plate70. Since the communication between the pressure control chamber53and the flow-in passage52is blocked off, the fuel pressure of the pressure control chamber53is rapidly decreased. As a result, a sum of the fuel pressure to the pressure receiving surface61of the nozzle needle60and the biasing force of the return spring66will become smaller than the nozzle needle lifting force which is applied by the fuel in the nozzle needle accommodating portion43to the seat portion65of the nozzle needle60. Therefore, the nozzle needle60starts to move up at a high speed in the direction to the pressure control chamber53, at a timing t2(as shown in (e) ofFIG. 6). During upward movement of the nozzle needle60, the fuel pressure in the pressure control chamber53is maintained at almost a constant value, as shown in (c) ofFIG. 6.

When the upward movement of the nozzle needle60to the pressure control chamber53is terminated, the fuel pressure in the pressure control chamber53starts again to further decrease at a timing t3(as shown in (c) ofFIG. 6). Then, the fuel pressure in the pressure control chamber53(in particular, in the lower side space53d) is coming closer to the fuel pressure in the area neighboring to the flow-out port54b(which is the fuel pressure in the flow-out recessed portion74aof the floating plate70). The biasing force for biasing the floating plate70in the upward direction is decreased. And a difference between the fuel pressure in the flow-in recessed portion72aneighboring to the flow-in ports52band the fuel pressure in the pressure control chamber53becomes larger. Therefore, the floating plate70is moved in the downward direction by the fuel pressure in the flow-in recessed portion72aagainst the biasing force of the spring55, at a timing t4(as shown in (d) ofFIG. 6).

When the floating plate70is moved down, the pressure control chamber53is communicated with the flow-in passage52again, so that the high pressure fuel flows into the pressure control chamber53. As a result, a further decrease of the fuel pressure in the pressure control chamber53is terminated, as shown in (c) ofFIG. 6. The fuel, which flows into the upper side space53c, passes through a space between the press-contacting surface73of the floating plate70and the pressure control surface53b. An area, which is calculated by multiplying a length of the outer press-contacting portion74in its circumferential direction by a height of the displacement of the floating plate70, is regarded as a passage area of the passage formed between the floating plate70and the first valve body46. It is, therefore, desirable for the floating plate70to move down by a distance, so that the passage area between the floating plate70and the first valve body46would be larger than the passage area of the flow-in side restricted portion52a.

When the supply of the driving current from the engine control unit17to the solenoid31is terminated, the pressure control valve80starts to close, at a timing t5as shown in (b) ofFIG. 6. When the pressure control valve80is closed at a timing t6ofFIG. 6, the flow-out of the fuel through the flow-out port54bis stopped. The floating plate70is pushed down by the fuel pressure in the flow-in recessed portion72aand kept at the position away from the pressure control surface53b. Since the pressure control chamber53is in communication with the flow-in ports52b, the fuel pressure in the pressure control chamber53is increased, as shown in (c) ofFIG. 6. Then, the sum of the fuel pressure to the pressure receiving surface61of the nozzle needle60and the biasing force of the return spring66will become larger than the nozzle needle lifting force which is applied by the fuel in the nozzle needle accommodating portion43to the seat portion65of the nozzle needle60. The nozzle needle60is thereby moved down at a high speed in the direction to the valve portion50, so that the seat portion65of the nozzle needle60is seated on the valve seat portion45to close the valve portion50, at a timing t7as shown in (e) ofFIG. 6.

When the downward movement of the nozzle needle60is ended (at the timing t7), the fuel pressure in the pressure control chamber53is further increased so that the fuel pressure in the pressure control chamber53becomes equal to the fuel pressure in the flow-in passage52. Since the biasing force applied to the floating plate70, which is caused by the pressure difference of the fuel pressure in the upper side space53cand the lower side space53d, disappears, the biasing force of the spring55is alone applied to the floating plate70. The floating plate70is thereby moved upwardly to the first valve body46, so that the inner and the outer press-contacting portions72and74are brought into contact with the pressure control surface53b, at a timing t8as shown in (d) ofFIG. 6. An actual time for the valve portion50from its opening point (t2) to the closing point (t7) is around 3.0 msec.

Now, a further operation of the fuel injection device, in which the pressure control valve80is closed before the nozzle needle60reaches its maximum stoke (that is, its uppermost position), will be explained.

When the pressure control valve80is closed, the flow-out of the fuel is terminated and thereby the fuel pressure in the flow-out recessed portion74aaround the flow-out port54bwill be restored to its initial pressure, as a result that the fuel flows into the flow-out recessed portion74athrough the communication hole71. The floating plate70is then pushed down in the direction to the valve portion50by the high pressure fuel in the flow-in recessed portion72afrom the flow-in ports52b. The pressure control chamber53is brought into the communication with the flow-in passage52.

When the high pressure fuel flows into the pressure control chamber53, the fuel pressure therein will be restored to the initial pressure so that the nozzle needle60is moved downwardly in the direction to the valve portion50. The nozzle needle60is moved down at the high speed and the seat portion65is seated on the valve seat portion45to close the valve portion50. As already explained above, after the valve portion50is closed, the floating plate70is pushed up in the direction to the first valve body46by the spring force of the spring55. Namely, the inner and the outer press-contacting portions72and74are brought into contact with the pressure control surface53b.

Now, effects of the above explained first embodiment will be explained. According to the first embodiment, each of the areas of the flow-in recessed portions72aand74ais larger than the respective passage areas of the flow-in ports52band the flow-out port54b. The outer and inner press-contacting portions74and72surrounding the flow-in and the flow-out recessed portions72aand74aare so configured as to be in contact with the pressure control surface53b. Therefore, contacting areas between the press-contacting surface73and the pressure control surface53bcan be made smaller. Then, press-contacting force generated at the contacting areas between the outer and the inner press-contacting portions74and72and the pressure control surface53bcan be increased. Accordingly, it is possible to prevent leakage of the fuel from the flow-in ports52binto the pressure control chamber53or from the flow-in ports52to the flow-out port54bthrough any gap between the pressure control surface53band the press-contacting surface73of the floating plate70, when the flow-out port54bis communicated to the fuel return line14fby the pressure control valve80. Namely, the communication between the flow-in ports52band the pressure control chamber53as well as the communication between the flow-in ports52band the flow-out port54bis surely blocked off.

As above, since the fuel flow from the flow-in ports52binto the pressure control chamber53is surely blocked off, the fuel pressure in the pressure control chamber53is rapidly increased immediately after the flow-out passage54is communicated to the fuel return line141. The nozzle needle60is thereby moved up toward the pressure control chamber53at the high speed, the seat portion65is lifted up from the valve seat portion45, and the valve portion50is rapidly opened. Accordingly, it is possible to provide the fuel injection device100, in which the response of the valve portion50to the driving current can be improved.

In addition, according to the first embodiment, the flow-in ports52band the flow-out port54bare formed on the same side of the floating plate70. As a result, a larger press-contacting force can be generated at the contacting areas between the outer and the inner press-contacting portions74and72and the pressure control surface53b. Furthermore, since the outer and the inner press-contacting portions74and72are formed in the circular shape, a sufficient length necessary for the sealing can be obtained.

In addition, the floating plate70is biased in the axial direction to the first valve body46, and the flow-in and the flow-out recessed portions72aand74awhich are symmetric with respect to the center of the floating plate70are formed on the upper end surface thereof. The outer and the inner press-contacting portions74and72as well as the contacting surface areas between the press-contacting surface73and the pressure control surface53bare likewise symmetric with respect to the center of the floating plate70. As a result, the outer and the inner press-contacting portions74and72are equally pressed against the pressure control surface53b. The pressing force for a unit contacting surface area at any portion is equal to that of the any other portions. The sealing performance between the outer and inner press-contacting portions74and72and the pressure control surface is improved.

In addition, according to the first embodiment, multiple flow-in ports52bare formed at the pressure control surface53b, the sum of the passage areas for the flow-in ports52bcan be increased. The flow-in space83can be surely filled with the fuel from the flow-in ports52b. As a result, the movement of the floating plate70in the downward direction away from the pressure control surface53bis surely carried out. A time delay for bringing the pressure control chamber53into communication with the flow-in ports52bcan be made smaller.

In addition, the multiple flow-in ports52bare arranged at equal distances in the circumferential direction around the flow-out port54b. The fuel pressure of the fuel flowing from the flow-in ports52bto the pressure control chamber53is equally applied and distributed to the press-contacting surface73of the floating plate70in the circumferential direction. As a result, an inclination of the press-contacting surface73of the floating plate70with respect to the pressure control surface53bcan be suppressed, so that the floating plate70can be smoothly moved away from the pressure control surface53b. In other words, speed of the smooth movement of the floating plate70can be increased.

It is desirable for the fuel to easily flow from the upper side space53cto the lower side space53dof the floating plate70so that the fuel pressure in the pressure control chamber53is smoothly increased as a whole. According to the first embodiment, the flow-in ports52bare formed at such portions closer to the outer periphery of the pressure control surface53band opposed to the flow-in recessed portion72a(which is formed at an outer peripheral portion of the floating plate70). The fuel from the flow-in ports52bmay not stay in the space between the pressure control surface53band the press-contacting surface73, but easily flow from the upper side space53cto the lower side space53dthrough the communication passages77aformed at the side wall of the floating plate70, as shown inFIG. 5B.

According to the fuel injection device100of the above structure, the floating plate70can be moved at high speed in order to smoothly increase the fuel pressure in the pressure control chamber53as a whole, after the communication between the flow-out port54band the fuel return line14fis blocked off. The response of the valve portion50to the control signal can be surely increased.

In addition, according to the first embodiment, the inner press-contacting portion72of the floating plate70is pressed against the portion of the pressure control surface53bsurrounding the flow-out port54b, to thereby surely decrease the fuel pressure around the flow-out port54b. Furthermore, the fuel may flow out into the flow-out passage54from the pressure control chamber53through the communication hole71formed in the floating plate70. It is, therefore, possible for the floating plate70to optimize the pressure decrease in the pressure control chamber53. The floating plate70is strongly biased in the direction toward the flow-in passage52by the decreased pressure around the flow-out port54b. And when the flow-out port54bis in communication with the fuel return line14f, the floating plate70is moved in the direction away from the pressure control surface53b, so that the fuel pressure in the pressure control chamber53will be increased again due to the high pressure fuel flowing into the pressure control chamber from the flow-in ports52b. When the pressure decrease of the fuel in the pressure control chamber53is adjusted by the communication hole71, it becomes possible to rapidly move the nozzle needle60in the direction to the valve portion50so as to close the valve portion, immediately after the flow-out passage54is closed. It is, therefore, possible to provide the fuel injection device100which has a quick response to the driving current.

In addition, since the communication hole71is formed in the floating plate70for communicating the pressure control chamber53(the lower side space53d) to the flow-out port54b, the floating plate70receives a pressure from the fuel flowing through the communication hole71, when the press-contacting surface73of the floating plate70is pressed against the pressure control surface53b. The communication hole71is formed at the center of the disc shaped floating plate70in the radial direction and extends in the axial direction thereof. The pressure applied to the floating plate70by the fuel flowing through the communication hole71is equally distributed to the press-contacting surface73, so that the floating plate70is equally pressed against the pressure control surface53bin the circumferential direction of the floating plate70. As a result, the flow-in ports52bas well as the flow-out port54bare surely closed by the floating plate70.

Flow amount of the fuel flowing through the communication hole71is decided by the passage area of the restricted portion71c. Therefore, the flow amount can be freely adjusted by changing in advance the passage area of the restricted portion7c. Speed of the fuel pressure decrease in the pressure control chamber53, which takes place (between the timings t3and t4ofFIG. 6) after the press-contacting surface73is pressed against the pressure control surface53b, depends on the passage area of the restricted portion71c. Accordingly, the movement (the moving speed) of the nozzle needle60, which opens and closes the valve portion50depending on the fuel pressure in the pressure control chamber53, can be optimized.

Generally, viscosity of the fuel becomes higher as the temperature becomes lower, and it becomes harder for the fuel to flow through a smaller passage. Therefore, the flow amount of the fuel flowing through the small passage depends more largely on the temperature of the fuel, as the passage area becomes smaller. According to the first embodiment, the recessed portion71bhaving a larger opening area is formed on the lower side surface of the floating plate70, so that variation of the fuel amount flowing through the communication hole71and depending on the fuel temperature can be suppressed. It is possible to suppress variation of the speed of the fuel pressure decrease in the pressure control chamber53, even in the case that the fuel temperature is changed. As a result, it is possible for the fuel injection device100to realize higher accuracy for the fuel injection without being influenced by the temperature change.

The fuel flowing through the communication hole71applies the pressure to the floating plate70, so that the floating plate70may be bent upwardly. According to the first embodiment, the restricted portion71cis formed in the communication hole71at a portion closer to the press-contacting surface73to keep a high rigidity. A possible deformation of the floating plate70is thus suppressed.

As already explained above, the recessed portion71bis formed on the lower side surface of the floating plate70in order to suppress the variation of the flow amount depending on the fuel temperature. Since the recessed portion71bis formed on the lower side surface, a decrease of the rigidity of the floating plate70against the pressure for bending the floating plate70upwardly may be suppressed. As a result, it is possible not only to suppress the variation of the flow amount depending on the fuel temperature but also to decrease the deformation of the floating plate70. Even though the communication hole71is formed in the center of the floating plate70, the inner and outer pres-contacting portions72and74can be surely brought into contact with the pressure control surface53balong their circular shapes. The flow-in ports52bcan be surely blocked off by the floating plate70from the pressure control chamber53and from the flow-out port54b.

As explained above, it is desirable for the fuel to easily flow from the upper side space53cto the lower side space53dof the floating plate70so that the fuel pressure in the pressure control chamber53is smoothly increased as a whole. However, if a gap between the side wall portion76and the inner peripheral wall57of the cylinder56was made larger in order to realize a smooth fuel flow from the upper side space53cto the lower side space53d, it might cause another problem in which the floating plate70may be displaced in the radial direction (that is, the direction along the pressure control surface53b), or in which the floating plate70may be inclined with respect to the axial direction thereof.

According to the first embodiment, the communication passages77aare formed by the passage wall portions77(which are formed at the outer side wall75of the floating plate70) and the inner peripheral wall57of the cylinder56, so that the fuel may smoothly and surely flow from the upper side space53cto the lower side space53d. Accordingly, it is possible to realize a sufficient amount of the fuel flow in the communication passages77a, even though the gap between the side wall portion76and the inner peripheral wall57of the cylinder56was made smaller. As a result of the above structure, a time delay from the timing at which the fuel pressure in the upper side space53cis increased as a result of the communication between the flow-in ports52band the pressure control chamber53to the timing at which the fuel pressure in the lower side space53dis increased can be made shorter.

In addition, since the gap between the side wall portion76and the inner peripheral wall57of the cylinder56is made smaller, it is possible to avoid the above explained problems, in which the floating plate70may be displaced in the radial direction or in which the floating plate70may be inclined with respect to the axial direction thereof. Accordingly, the floating plate70can be surely moved upwardly or downwardly, to thereby communicate the flow-in ports52bto the pressure control chamber53or to block off the communication between the flow-in ports52band the pressure control chamber53(including the communication between the flow-in ports52band the flow-out port54b).

In addition, according to the first embodiment, the communication passages77aare formed at the outer side wall75and the flow-in ports52bare formed at such portions of the pressure control surface53bcloser to the outer periphery of the floating plate70. As a result of the synergy effect of the above structures, the fuel flows more smoothly into the lower side space53d. As shown inFIG. 5B, the fuel flows from the flow-in ports52binto the upper side space53c, and the fuel further flows from the upper side space53cinto the lower side space53dalong the outer side wall75and through the communication passages77aand the communication space78. Since the passage area of the communication passages77aand the communication space78is made larger than the passage area of the flow-in ports52b, the fuel can easily flow from the upper side space53cto the lower side space53d. In addition, since the multiple communication passages77aare formed in the floating plate70, the fuel flows from the upper side space53cinto multiple portions of the lower side space53d. In addition, since the passage wall portion77is formed by the flat wall surface along the axial direction (the reciprocating direction), the communication passage77aextends in the axial direction. It is, therefore, possible to reduce the resistance for the fuel flow from the upper side space53cto the lower side space53d. As above, the fuel surely flows from the upper side space53cto the lower side space53dthrough the communication passage77aand the communication space78.

When the communication between the flow-out port54band the fuel return line14fis blocked off (at the timing t6ofFIG. 6), the fuel pressure of the pressure control chamber53(including the upper and lower side spaces53cand53d) is rapidly increased, so that the nozzle needle60is moved down at the high speed to close the valve portion50and thereby terminate the fuel injection from the injection ports44.

The longitudinal cross sectional shape of the outer side wall75of the floating plate70has the curved side wall projecting in the radial outward direction of the floating plate70. Therefore, even in the case that the floating plate70is inclined with respect to the cylinder56, the curved side wall75is not caught by the inner peripheral wall57of the pressure control chamber53. The floating plate70can be stably maintained in its normal position, so that the movement thereof can be surely done to thereby surely block off the communication between the flow-in ports52band the pressure control chamber53.

Furthermore, according to the first embodiment, the floating plate70is biased by the spring55in the upward direction, so that the inner and outer press-contacting portions72and74are brought into contact with the pressure control surface53b. With such floating plate70biased by the spring55, it is possible to quickly block off the communication between the flow-in ports52band the pressure control chamber53without a substantial displacement (movement) of the floating plate70, immediately when the flow-out port54bis communicated with the fuel return line14fby the pressure control valve80. Accordingly, it is possible to shorten the time period from the timing at which the pressure control valve80is opened (at the timing t1) to the timing at which the fuel pressure in the pressure control chamber53starts to decrease (at the timing t2). This would lead to the effect that the response of the valve portion50with respect to the control signal is improved.

Furthermore, according to the first embodiment, the flow-in recessed portion72aas well as the flow-out recessed portion74ais formed on the same press-contacting surface73. Even when the floating plate70having the press-contacting surface73is displaced with respect to the pressure control surface53b, the relative positions of the flow-in recessed portion72athe flow-out recessed portion74aare not changed. The contacting areas between the press-contacting surface73and the pressure control surface53bare not changed, even when the relative position of the floating plate70to the pressure control surface53bis changed. Therefore, it is possible to surely block off the communication between the flow-in ports52band the flow-out port54b, irrespectively of the relative position of the floating plate70to the pressure control surface53b.

Second Embodiment

A second embodiment of the present invention will be explained with reference toFIGS. 7 to 10, wherein a fuel injection device200is a modification of the fuel injection device100of the first embodiment. Hereinafter, a valve body246, a cylinder256, and a floating plate270of the second embodiment will be explained. An element corresponding to the spring55of the first embodiment is eliminated in the second embodiment.

As shown inFIGS. 7 to 9, the valve body246corresponds to the first and second valve bodies46and47of the first embodiment. Longitudinal through-holes246aand246bextending in a longitudinal direction of the valve body246are formed in the valve body246as a part of a flow-in passage252and a part of a flow-out passage254, respectively. Each of the longitudinal through-holes246aand246bis inclined to the axial direction of the valve body246. The longitudinal through-hole246b(the part of the flow-out passage254) is opened at a pressure control surface253b(of a circular shape) as a flow-out port254b, which is offset from a center of the pressure control surface253b. A restricted portion254ais formed in the longitudinal through-hole246b. The longitudinal through-hole246a(the part of the flow-in passage252) is opened at the pressure control surface253bas a flow-in port252b, which is offset from the center of the pressure control surface253bon an opposite side of the flow-out254b. A restricted portion252ais formed in the longitudinal through-hole246a.

A flow-out recessed portion274aand a flow-in recessed portion272aare formed at the pressure control surface253b(of the circular shape) of the valve body246. The flow-out recessed portion274ais formed by depressing a part of the pressure control surface253bin an upward direction away from a press-contacting surface273of the floating plate270, so that a circular wall254dsurrounding the flow-out port254bis formed (also referred to as a flow-out-port surrounding portion). The circular wall254dis offset from a center of the pressure control surface253b. The flow-out port254bis opened at a center of an area surrounded by the circular wall254d. The flow-in recessed portion272ais likewise formed by depressing a part of the pressure control surface253bin the upward direction away from the press-contacting surface273of the floating plate270, so that a lunate recess is formed. A lunate wall252dsurrounds the flow-in port252b, which is opened at the lunate recess (the flow-in recessed portion272a).

As a result of forming the flow-out recessed portion274aand the flow-in recessed portion272aat the pressure control surface253bof the valve body246, a flow-out-side contacting portion254cand a flow-in-side contacting portion252care formed on the remaining portions of the pressure control surface253b. Those contacting portions254cand252care projections projecting toward the floating plate270and opposed to the press-contacting surface273of the floating plate270, so that the contacting portions254cand252care operatively brought into contact with the floating plate270(the press-contacting surface273). The contacting portion254chas a circular surface surrounding the flow-out recessed portion274aand being in contact with the press-contacting surface273. The contacting portion252clikewise has a circular surface surrounding the flow-in recessed portion272aand being in contact with the press-contacting surface273(the outer periphery of the floating plate270). A part of the contacting portion254cand a part of the contacting portion252care overlapped with each other at a left-hand side inFIG. 8.

A stepped portion258is formed at the inner peripheral wall257of the cylinder256, which defines the pressure control chamber53, as a stopper for limiting a downward movement of the floating plate270(in a direction that the press-contacting surface273is moved away from the pressure control surface253b).

The floating plate270has the press-contacting surface273, a contacting portion275aand multiple flow limiting grooves273a. The press-contacting surface273is a flat surface, which is opposed to the pressure control surface253b. The press-contacting surface273has a flow-out-side surface portion274bopposing to the flow-out recessed portion274aand a flow-in-side surface portion272bopposing to the flow-in recessed portion272a. Each of the surface portions274band272bis brought into contact with and pressed against the respective circular surfaces of the contacting portions252cand254c.

The contacting portion275ais an outer peripheral portion of a lower side surface, which is opposite to the press-contacting surface273of the floating plate270and opposed to the stepped portions258of the cylinder256. The contacting portions275aare brought into contact with the stepped portion258, when the floating plate270is moved downwardly. The flow limiting grooves273aare formed at the lower side surface of the floating plate270, wherein each of the grooves273aextends in a radial direction to the contacting portion275a. According to the above structure, the fuel may flow from the upper side space53cto the lower side space53d, even when the contacting portions275aare in contact with the stepped portion258. When the pressure control valve80is closed, the floating plate270is downwardly moved away from the valve body246so that the contacting portions275aare brought into contact with the stepped portion258.

A side wall portion276and multiple passage wall portions277are formed at an outer side wall275of the floating plate270. The side wall portion276having a curved cross section is in a sliding contact with the inner peripheral wall257of the cylinder256, so that the floating plate270is movably accommodated in the cylinder256.

The passage wall portions277are formed by cutting away portions of the outer side wall275, so that multiple communication passages277aare formed to communicate the upper side space53cand the lower side space53dwith each other. Each of the passage wall portions277is formed in a flat wall extending in a direction parallel to the longitudinal axis of the floating plate270. A pair of passage wall portions277is formed at opposite positions in the radial direction.

According to the second embodiment, the fuel flow from the upper side space53cto the lower side space53is mainly carried out by the fuel flow through the communication passages277a. Namely, the fuel flow through a gap between the side wall portion276and the inner peripheral wall257is negligible. A sum of the passage areas for the communication passages277ais made larger than the passage area of the flow-in port252b(more exactly, the passage area of the restricted portion252aof the flow-in passage252).

An operation of the above explained fuel injection device200, in which the valve portion50is opened and closed depending on the driving current from the engine control unit17(FIG. 1) to thereby inject the fuel, will be explained with reference toFIG. 10in addition toFIGS. 7 to 9.

When the driving current of the pulse shape is supplied from the engine control unit17to the solenoid31(FIG. 2) at a timing t1(as shown in (a) ofFIG. 10), the magnetic field is generated to operate the pressure control valve80so as to open the valve. When the pressure control valve80starts to open (as shown in (b) ofFIG. 10), the fuel starts to flow out from the flow-out port254bwhich is brought into the communication with the fuel return line14f(FIG. 1). The fuel pressure in the pressure control chamber53is decreased at first in an area neighboring to the flow-out port254b. The pressure applied to the flow-out-side surface portion274bof the floating plate270is decreased due to the pressure decrease around the flow-out port254b. Then, the floating plate270starts to move upwardly and the press-contacting surface273is brought into contact with and pressed against the respective circular surfaces of the contacting portions252cand254cof the valve body246, at a timing t2(as shown in (d) ofFIG. 10). The floating plate270blocks off the communication between the flow-in port252band the pressure control chamber53.

The fuel flows from the lower side space53dof the pressure control chamber53into the upper side space53cthrough the communication hole71of the floating plate270, and is discharged from the flow-out port254b. Since the flow-in port252bis closed, the fuel pressure in the pressure control chamber53is rapidly decreased, at a timing t3(as shown in (c) ofFIG. 10). Then, a sum of the fuel pressure applied to the pressure receiving surface61of the nozzle needle60and the biasing force of the spring66immediately becomes smaller than a needle lifting force applied to the seat portion65of the nozzle needle60by the fuel pressure in the nozzle-needle accommodating portion43. The nozzle needle60starts to move upwardly at a high speed in the direction to the pressure control chamber53, at the timing t3as shown in (e) ofFIG. 10. During the upward movement of the nozzle needle60, the fuel pressure in the pressure control chamber53is maintained at a constant value.

When the upward movement of the nozzle needle60in the direction to the pressure control chamber53is terminated, the fuel pressure in the pressure control chamber53is further decreased, at a timing t4(as shown in (c) ofFIG. 10). Then, the fuel pressure in the pressure control chamber53comes down closer to the fuel pressure in the area neighboring to the flow-out port254b, at a timing t5(as shown in (c) ofFIG. 10). The fuel pressure in the flow-out recessed portion274ais applied to the flow-out-side surface portion274bof the floating plate270. As a result, the biasing force applied to the floating plate270by the fuel pressure in the upward direction becomes smaller. Contrary to that, a difference of the fuel pressure between the fuel pressure in the area neighboring to the flow-in port252bapplied to the flow-in-side surface portion272band the fuel pressure in the pressure control chamber53is increased. The floating plate270is thereby pushed down in the direction to the pressure receiving surface61, at the timing t5(as shown in (d) ofFIG. 10).

When the floating plate270is moved downwardly, the flow-in passage252is brought into communication again with the pressure control chamber53, so that the high pressure flows again into the pressure control chamber53. Therefore, the fuel pressure decrease in the pressure control chamber53is stopped, as shown in (c) ofFIG. 10. The lunate flow-in recessed portion272ais surrounded by the contacting portions252cand254c. An integrated value, which is calculated by multiplying a length of the contacting portions252cand254csurrounding the lunate flow-in recessed portion272aby a displaced amount of the floating plate270, corresponds to a passage area for the fuel flow between the floating plate270and the valve body246. It is, therefore, desirable that the floating plate270is moved to such a position, at which the passage area for the fluid flow between the floating plate270and the valve body246becomes larger than the passage area of the restricted portion252aof the flow-in passage252.

When the supply of the driving current from the engine control unit17to the solenoid31is terminated, the pressure control valve80starts to close, at a timing t6as shown in (b) ofFIG. 10. When the pressure control valve80is closed at a timing t7(as shown in (b) ofFIG. 10), the flow-out of the fuel through the flow-out passage254is stopped and thereby the fuel pressure in the pressure control chamber53is immediately increased, as shown in (c) ofFIG. 10. The floating plate270is then further pushed down by the pressure applied to the flow-in-side surface portion272band moved to a position, at which the contacting portions275aare brought into contact with the stopper258, as shown in (d) ofFIG. 10. The sum of the fuel pressure applied to the pressure receiving surface61of the nozzle needle60and the biasing force of the spring66immediately becomes larger than the needle lifting force applied to the seat portion65of the nozzle needle60by the fuel pressure in the nozzle-needle accommodating portion43. The nozzle needle60starts to move downwardly at a high speed in the valve portion50, which is finally closed at a timing t8as shown in (e) ofFIG. 10.

Effects of the Second Embodiment

According to the above explained second embodiment, the floating plate270has a function of fluid sealing between the press-contacting surface273and the flow-in-side and flow-out-side contacting portions252cand254c, so that the communication between the flow-in port252band the pressure control chamber53can be surely blocked off. As a result, it is possible to rapidly decrease the fuel pressure in the pressure control chamber53when the pressure control valve80is opened, to thereby realize the high speed movement of the nozzle needle60. As above, the response of the valve portion50to the driving current can be improved.

Furthermore, according to the second embodiment, the circular wall254dof the flow-out recessed portion274ais offset from the center of the pressure control surface253b, so that the flow-out-side and the flow-in-side contacting portions252cand254care arranged to be neighboring to each other. The contacting areas between the pressure control surface253band the press-contacting surface273can be reduced by arranging the flow-out-side and the flow-in-side contacting portions252cand254cneighboring to each other. The pressing force of the press-contacting surface273to the pressure control surface253bcan be thereby increased, so that the floating plate270can surely block off the communication between the flow-in port252band the pressure control chamber53and the communication between the flow-in port252band the flow-out port254b.

Furthermore, according to the second embodiment, the downward movement of the floating plate270is limited by the stepped portion258, with which the contacting portions275aof the floating plate270are brought into contact. Namely, it is possible to constantly place the floating plate270at a predetermined position, which is separated from the pressure control surface253bby a predetermined distance. As a result, it is possible to maintain a time period, which is a period from the timing at which the flow-out port254bis brought into communication with the fuel return line14f(namely, when the pressure control valve80is opened) to the timing at which the floating plate270blocks off the communication between the flow-in port252band the pressure control chamber53, within a predetermined time. Accordingly, the fuel pressure in the pressure control chamber53can be rapidly decreased.

In addition, according to the second embodiment, since the flow limiting grooves273aare formed at the contacting portions275aof the floating plate270, the fuel may flow from the upper side space53cto the lower side space53deven when the contacting portions275aare in contact with the stepped portion258.

In addition, according to the second embodiment, the flow-out and flow-in recessed portions274aand272aare formed at the pressure control surface253b, and the press-contacting surface273of the floating plate270is formed in the flat surface. As a result, even when the floating plate270is rotated around the axis thereof, the press-contacting surface273of the floating plate270can be surely brought in contact with the contacting portions252cand254c, to thereby surely block off the communication between the flow-in port252band the pressure control chamber53and the communication between the flow-in port252band the flow-out port254b.

In addition, according to the second embodiment, the side wall portion276of the floating plate270is in a sliding contact with the inner peripheral wall257of the cylinder256, so that the floating plate270is movable in the cylinder256. A gap between the side wall portion276of the floating plate270and the inner peripheral wall257of the cylinder256is negligible. A movement of the floating plate270in the radial direction is restricted. A relative displacement of the press-contacting surface273of the floating plate270with respect to the pressure control surface253bis thereby suppressed. If the floating plate270was displaced in the radial direction, the pressure applied to the floating plate270may be disbalanced and thereby local wear-out may occur. However, according to the second embodiment, the displacement of the floating plate270in the radial direction is suppressed to thereby prevent the local wear-out of the press-contacting surface273as well as the pressure control surface253b. As a result, it is possible that the floating plate270demonstrates its sealing effect for a longer time period. Furthermore, a possible inclination of the floating plate270with respect the inner peripheral wall257may be suppressed.

Third Embodiment

A third embodiment of the present invention will be explained with reference toFIGS. 11 to 14, wherein a fuel injection device300is a further modification of the fuel injection device100of the first embodiment. Hereinafter, a valve body346and a floating plate370of the third embodiment will be explained.

The valve body346corresponds to the first and second valve bodies46and47of the first embodiment. As shown inFIG. 11and in a similar manner to the second embodiment, longitudinal through-holes346aand346bextending in a longitudinal direction of the valve body346are formed in the valve body346as a part of a flow-in passage352and a part of a flow-out passage354, respectively. Each of the longitudinal through-holes346aand346bis inclined to the axial direction of the valve body346. The longitudinal through-hole346b(the part of the flow-out passage354) is opened at a pressure control surface353b(of a circular shape) as a flow-out port354b. And the longitudinal through-hole346a(the part of the flow-in passage352) is opened at the pressure control surface353bas a flow-in port352b, which is offset from a center of the pressure control surface353b.

As shown inFIG. 13, a flow-out recessed portion374aand a flow-in recessed portion372aare formed at the pressure control surface353b(of the circular shape) of the valve body346. The flow-out recessed portion374ais formed by depressing a part of the pressure control surface353bin an upward direction away from a press-contacting surface373of the floating plate370, so that a circular bottom surface354dsurrounding the flow-out port354bis formed (also referred to as a flow-out-port surrounding portion). The flow-out port354bof a round shape is opened at a center of an area (that is, the flow-out recessed portion374a) surrounded by the circular bottom surface354d. The flow-in recessed portion372ais likewise formed by depressing a part of the pressure control surface353bin the upward direction away from the press-contacting surface373of the floating plate370, so that an annular recess is formed. An annular bottom surface352dsurrounds the flow-in port352b, which is opened at the annular recess (that is, the flow-in recessed portion372a).

As shown inFIGS. 12 and 13, as a result of forming the flow-out recessed portion374aand the flow-in recessed portion372aat the pressure control surface353bof the valve body346, a flow-out-side contacting portion354cand a flow-in-side contacting portion352care formed on the remaining portions of the pressure control surface353b. Those contacting portions354cand352care projections projecting toward the floating plate370and opposed to the press-contacting surface373of the floating plate370, so that the contacting portions354cand352care operatively brought into contact with the floating plate370(the press-contacting surface373). The contacting portion354chas a circular surface surrounding the flow-out recessed portion374aand being in contact with the press-contacting surface373. The contacting portion352clikewise has a circular surface surrounding the flow-in recessed portion372aand being in contact with the press-contacting surface373(the outer periphery of the floating plate370). The circular contacting portions354cand352care coaxially arranged with the center of the pressure control surface353b.

The press-contacting surface373of the floating plate370is a flat surface, which is opposed to the pressure control surface353b. The press-contacting surface373has a flow-in-side surface portion372bopposing to the flow-in recessed portion372aand a flow-out-side surface portion374bopposing to the flow-out recessed portion374a. Each of the surface portions372band374bis brought into contact with and pressed against the respective circular surfaces of the contacting portions352cand354c.

A side wall portion376and multiple passage wall portions377are formed at an outer side wall375of the floating plate370. The side wall portion376is in a sliding contact with the inner peripheral wall57of the cylinder56, so that the floating plate370is movably accommodated in the cylinder56. A gap between the side wall portion376and the inner peripheral wall57is negligible and fuel may not flow through the gap.

The passage wall portions377are formed at the outer peripheral surface of the side wall portion376by cutting away portions thereof. As shown inFIGS. 14A and 14B, according to the third embodiment, the passage wall portions377form multiple grooves377bat the outer peripheral surface of the side wall portion376, each of which is opened at one end to an upper side of the floating plate370(that is, the side of the press-contacting surface373) and at its other end to a lower side379of the floating plate370(that is, the side to the lower side space53d). Namely, the grooves377bare communication passages377a, which are formed by the passage wall portions377and the inner peripheral wall57and which communicate the upper side space53cand the lower side space53dof the pressure control chamber53with each other. The grooves377bare spirally formed at the outer peripheral surface of the side wall portion376. Therefore, when the floating plate370is projected in the axial direction thereof, as shown inFIG. 14A, an open end of the communication passage377aon the upper side of the floating plate370is displaced in a circumferential direction from the other open end of the same communication passage377aon the opposite (lower) side of the floating plate370. Four communication passages377a(that is, the grooves377b) are formed at equal distances in the circumferential direction at the outer peripheral surface of the side wall portion376.

According to the third embodiment, the fuel flow from the upper side space53cto the lower side space53dof the pressure control chamber53is mainly carried out by the fuel flow through the communication passages377a. In other words, the fuel flow through the gap between the side wall portion376and the inner peripheral wall57is negligible. A sum of the passage areas for the communication passages377ais made larger than the passage area of the flow-in port352b.

According to the first embodiment, the passage wall portions are formed in the flat wall surfaces. However, as in the third embodiment, the communication passages may be formed by spiral grooves377b. In addition, the projected areas of the communication passages377a, which are formed when projecting the floating plate370in the axial direction, can be a part of the pressure receiving surface. Therefore, it is possible with the spiral grooves to suppress the decrease of the pressure receiving surface. The pressing force of the press-contacting surface373to the pressure control surface353bcan be maintained at a high value for the floating plate370having the passage wall portions377.

In addition, according to the third embodiment, the flow-in port352bis offset from the center of the pressure control surface353b, and multiple grooves377bare formed at equal distances in the circumferential direction at the outer periphery of the side wall portion376. Accordingly, even when the floating plate370is rotated with respect to the valve body346, a distance between the flow-in port352band one of the grooves377b(which is nearest to the flow-in port352b) may not be largely changed. As a result, the fuel pressure increase in the lower side space53dof the pressure control chamber53is stably controlled. In other words, it is possible to suppress variation of the response of the valve portion to the driving current, independently from the relative position of the floating plate370to the valve body346.

Fourth and Fifth Embodiments

A fourth and a fifth embodiment of the present invention will be explained with reference toFIGS. 15 and 16, each of which is a modification of the third embodiment. Hereinafter, a floating plate470and570of each embodiment will be explained.

As shown inFIGS. 15A and 15B, according to the fourth embodiment, a side wall portion476and multiple passage wall portions477are formed at an outer side wall475of the floating plate470. The passage wall portions477are formed at the outer peripheral surface of the side wall portion476by cutting away portions thereof. According to the fourth embodiment, the passage wall portions477form multiple grooves (477bto477d) at the outer peripheral surface of the side wall portion476, each of which is opened at one end to an upper side of the floating plate470(that is, the side of the press-contacting surface473) and at its other end to a lower side479of the floating plate470(that is, the pressure receiving surface). The grooves are composed of vertical grooves477band477cextending in the axial direction of the floating plate470and a lateral groove477bextending in a circumferential direction of the floating plate470. Each of the vertical grooves477band477cis opened to the upper and lower side surfaces (473and479) of the floating plate470. The vertical grooves477band477care displaced from each other in the circumferential direction by a length of the circumferential groove477dconnecting the vertical grooves477band477cwith each other.

As shown inFIGS. 16A and 16B, according to the fifth embodiment, a side wall portion576and multiple passage wall portions577are formed at an outer side wall575of the floating plate570. The passage wall portions577are formed at the outer peripheral surface of the side wall portion576by cutting away portions thereof. According to the fifth embodiment, the passage wall portions577form multiple grooves (577bto577f) at the outer peripheral surface of the side wall portion576, each of which is opened at one end to an upper side of the floating plate570(that is, the side of a press-contacting surface573) and at its other end to a lower side579of the floating plate570(that is, the pressure receiving surface). The grooves are composed of vertical grooves577b,577cand577dextending in the axial direction of the floating plate570and lateral grooves577eand577fextending in a circumferential direction of the floating plate570. Each of the vertical grooves577band577cis opened to the upper and lower side surfaces (573and579) of the floating plate570, and arranged at positions which are overlapped in the axial direction of the floating plate570. The vertical grooves577band577care displaced from the vertical grove577din the circumferential direction of the floating plate570. The vertical grooves577band577dare connected with each other by the lateral groove577e, while the vertical grooves577cand577dare connected with each other by the lateral groove577f.

As understood from the fourth and fifth embodiments, the shapes of the grooves formed by the passage wall portions477and577are not limited to the shape (the spiral grooves) of the third embodiment. According to the fourth and fifth embodiments, projected areas of the grooves477and577in the axial direction of the floating plate470and570can be a part of the pressure receiving surface. Therefore, it is possible with the grooves477or577to suppress the decrease of the pressure receiving surface. Accordingly, the pressing force of the press-contacting surface473or573to the pressure control surface of the valve body can be maintained at a high value for the floating plate470or570having the passage wall portions477or577.

Sixth and Seventh Embodiments

A sixth and a seventh embodiment of the present invention will be explained with reference toFIGS. 17 and 18, each of which is a further modification of the third embodiment. Hereinafter, a floating plate670and770as well as a valve body646or746of each embodiment will be explained.

As shown inFIG. 17, according to the sixth embodiment, a flow-in recessed portion672aof an annular shape is formed at a pressure control surface653b(of a circular shape) of the valve body646. The flow-in recessed portion672ais formed by depressing a part of the pressure control surface653bin an upward direction away from a press-contacting surface673of the floating plate670. A flow-in port652bis opened at a bottom surface652dof the flow-in recessed portion672a. A flow-out-port surrounding surface654d, which is a flat surface portion of the pressure control surface653bsurrounding a flow-out port654b, is formed at an inner side of the flow-in recessed portion672a.

According to the sixth embodiment, a flow-out recessed portion674ais formed at a press-contacting surface673(which is an upper side surface of the floating plate670). A bottom surface674bof the flow-out recessed portion674ais opposed to the flow-out-port surrounding surface654dof the pressure control surface653b. The flow-out recessed portion674ais formed by depressing a part of the press-contacting surface673in a downward direction away from the pressure control surface653b. The flow-out recessed portion674ais formed at a center of the press-contacting surface673of a circular shape. In other words, the flow-out recessed portion674ais a circular recess coaxial with the press-contacting surface673. Furthermore, the flow-out recessed portion674ais coaxial with the annular flow-in recessed portion672aformed in the valve body646. An outer peripheral portion672bof the press-contacting surface673, which is formed at an outer side of the flow-out recessed portion674aand is opposed to the flow-in recessed portion672a, is formed in an annular flat surface.

As shown inFIG. 18, according to the seventh embodiment, a flow-out recessed portion774aof a circular shape is formed at a pressure control surface753b(of a circular shape) of the valve body746. The flow-out recessed portion774ais formed by depressing a part of the pressure control surface753bin an upward direction away from a press-contacting surface773of the floating plate770. A flow-out port754bis opened at a bottom surface754dof the flow-out recessed portion774a. The flow-out recessed portion774ais surrounded by a circular flow-in-port surrounding surface752d, which is a remaining part of the pressure control surface753b. The flow-out recessed portion774ais formed at a center of the pressure control surface753b. A flow-in port752bis opened at the flow-in-port surrounding surface752d, which is formed in an annular flat surface.

A flow-in recessed portion772aof an annular shape is formed at the press-contacting surface773of the floating plate770. The flow-in recessed portion772ais formed by depressing a part of the press-contacting surface773in a downward direction away from the pressure control surface753b. The flow-in recessed portion772ais coaxially formed with the press-contacting surface773. A bottom surface772bof the flow-in recessed portion772ais opposed to the annular flow-in-port surrounding surface752d. Furthermore, the flow-in recessed portion772ais coaxial with the flow-out recessed portion774aformed in the valve body746. A portion774bof the press-contacting surface773, which is surrounded by the flow-in recessed portion772aand opposed to the flow-out recessed portion774a, is formed in a circular flat surface.

According to the sixth embodiment (FIG. 17), the flow-in recessed portion672ais formed in the valve body646, while the flow-out recessed portion674ais formed in the floating plate670. On the other hand, according to the seventh embodiment (FIG. 18), the flow-in recessed portion772ais formed in the floating plate770, while the flow-out recessed portion774ais formed in the valve body746. In the fuel injection device, in which the floating plate is provided in order to improve the response of the valve portion to the driving current, the press-contacting surface of the floating plate as well as the pressure control surface should have strength enough to withstand repeated press contacts thereof. However, the strength may be decreased when the flow-in or the flow-out recessed portion is formed. According to the above sixth or seventh embodiment, the flow-in recessed portion (672a,772a) is formed in one of the press-contacting surface (673,773) and the pressure control surface (653b,753b), while the flow-out recessed portion (674a,774a) is formed in the other of the press-contacting surface (673,773) and the pressure control surface (653b,753b). As a result, the sufficient strength for the press-contacting surface and the pressure control surface can be obtained, to thereby assure a stable operation (for example, the block-off of the communication between the flow-in port and the pressure control chamber) of the valve portion for a long period.

Eighth Embodiment

An eighth embodiment of the present invention will be explained with reference toFIG. 19, which is a modification of the first embodiment. Hereinafter, a floating plate870of the eighth embodiment will be explained.

FIG. 19, corresponding toFIG. 4, is a top plan view showing the floating plate870. Multiple flow-in recessed portions872aof an arc shape are formed by depressing respective parts of a press-contacting surface873in a downward direction away from the pressure control surface53b(FIG. 5A) of the valve body. A bottom surface872bof each flow-in recessed portion872ais opposed to the respective flow-in port52b. A flow-out recessed portion874ais formed at the center of the floating plate870(the press-contacting surface873), wherein a bottom surface874bthereof is opposed to the flow-out port54b. The multiple flow-in recessed portions872aform an annular shape as a whole and arranged at an outer side of the flow-out recessed portion874bso as to surround it. The flow-in recessed portions872aare formed in the same shape to each other and arranged at equal distances in a circumferential direction.

At the upper side of the floating plate870, an annular inside contacting portion872is formed between the flow-out recessed portion874aand the flow-in recessed portions872aand an annular outside contacting portion874is formed at an outer peripheral side of the flow-in recessed portions872a, wherein each of the contacting portions872and874are operatively brought into contact with and pressed against the pressure control surface53b. In addition, multiple partitioning portions873bare formed at the upper side of the floating plate870so as to separate the flow-in recessed portions872afrom each other. Each of the partitioning portions873bextends in a radial direction of the floating plate870from the annular inside contacting portion872to the annular outside contacting portion874.

According to the eighth embodiment, multiple flow-in recessed portions872aare formed. In addition, the annular inside and outside contacting portions872and874are connected with each other by the multiple partitioning portions873b, so that the rigidity of the contacting portions872and874can be increased. In addition, the pressing force of the contacting portions872and874are equally applied to the pressure control surface53b, so that the block-off operation of the floating plate870for the communication between the flow-in ports52band the pressure control chamber53(FIG. 5A) as well as the communication between the flow-in ports52band the flow-out port54bcan be surely carried out.

Ninth Embodiment

A ninth embodiment of the present invention will be explained with reference toFIG. 20, which is a further modification of the third embodiment.

A knurled surface976is formed at a side wall975of a floating plate970. The knurled surface976is formed by multiple small grooves extending in the axial direction of the floating plate970, wherein the small grooves are arranged at equal distances in a circumferential direction.

As shown inFIG. 21, a knurled surface may be alternatively formed at the side wall of a floating plate970ain a striped shape, in which multiple small grooves are crossing with each other.

Tenth Embodiment

A tenth embodiment of the present invention will be explained with reference toFIGS. 22 and 23, which is a further modification of the third embodiment. Hereinafter, a floating plate A70of the tenth embodiment will be explained.

A side wall portion A76and multiple passage wall portions A77are formed at an outer side wall A75of the floating plate A70. Each of the passage wall portions A77is formed by cutting away respective portions of the outer side wall A75. Each of the passage wall portions A77forms a groove A77b, one of axial ends of which is opened at an upper side and the other axial end of which is opened at a lower side of the floating plate A70. Multiple (four) grooves A77bextend in an axial direction of the floating plate A70and are arranged at equal distances in a circumferential direction of the floating plate A70. Multiple communication passages A77aare formed by the grooves A77band the inner peripheral wall57of the cylinder56, so that the fuel flows from the flow-in port352binto the pressure control chamber53and further flows from the upper side space53cto the lower side space53dthrough the multiple communication passages A77a, as indicated by solid arrow lines inFIG. 22. A sum of the passage area for the communication passages A77ais made larger than the opening area of the flow-in port352b.

As shown in the tenth embodiment, the communication passages A77amay be formed in the form of the straight grooves A77bextending in the axial direction of the floating plate A70. According to such grooves A77b, the fuel flow between the upper side space53cand the lower side space53dcan be surely obtained.

Eleventh Embodiment

An eleventh embodiment of the present invention will be explained with reference toFIG. 24, which is a modification of the tenth embodiment. Hereinafter, a floating plate B70of the eleventh embodiment will be explained.

Multiple side wall portions B76and multiple passage wall portions B77are formed at an outer side wall B75of the floating plate B70. Each of the communication passage wall portions B77is formed by cutting away respective portions of the outer wall B75. Each of the passage wall portions B77forms a groove B77b, one of axial ends of which is opened at an upper side and the other axial end of which is opened at a lower side of the floating plate B70. The grooves B77bare arranged at equal distances in a circumferential direction of the floating plate B70, and each of the grooves B77bextends in an axial direction of the floating plate B70. In each of the grooves377b, a circumferential length thereof is made larger than a depth of the groove B77bin a radial direction. More exactly, each of the grooves B77bhas an arced shape and an angle of the arc with respect to a center of the floating plate B70is around 90 degrees. Three side wall portions B76between the grooves B77bare formed as sliding surface portions B75b. Each of the sliding surface portions B75bhas an arced surface, an angle of which is around 30 degrees. The sliding surface portions B75bare in a sliding contact with the inner peripheral wall57of the cylinder56, so that the floating plate370is coaxially accommodated in the cylinder56. The groove B77bhas a wider angle in the circumferential direction, so that sliding surface areas between the side wall portions B76and the inner peripheral wall57are reduced to thereby achieve a smooth movement of the floating plate B70.

According to the eleventh embodiment, the depth of the groove377bin the radial direction is made smaller, while the length of the groove B77bin the circumferential direction is made longer, in order that passage area of communication passages B77aformed by the grooves B77bis increased. With the grooves B77bhaving longer length in the circumferential direction, not only a sufficient amount of the passage area for the communication passages377ais obtained, but also a necessary amount for a press-contacting surface (an upper surface of the floating plate570, not shown inFIG. 24) is obtained. A design flexibility for the press-contacting surface can be thus increased.

Twelfth and Thirteenth Embodiments

A twelfth and a thirteenth embodiment of the present invention will be explained with reference toFIGS. 25 and 26, each of which is a modification of the eleventh embodiment. In each of a floating plate C70of the twelfth embodiment (FIG. 25) and a floating plate570of the thirteenth embodiment (FIG. 26), a diameter of an upper side as well as a diameter of a lower side of the floating plate is made smaller than a maximum diameter of a middle portion of the floating plate.

More exactly, as shown inFIG. 25, stepped portions are formed at upper and lower sides of a side wall C75of the floating plate C70. Each of diameters of the upper and lower sides is made smaller than a diameter of the middle portion of the floating plate C70.

In addition, multiple grooves C77b(similar to the grooves B77bof the eleventh embodiment,FIG. 24) are formed at the side wall C75of the floating plate C70. Multiple sliding surface portions C75bare likewise formed between the neighboring grooves C77bin a circumferential direction of the floating plate C70. The sliding surface portions C75bare in a sliding contact with the inner peripheral wall57of the cylinder56, so that the floating plate C70is movably accommodated in the cylinder56. A displacement of the floating plate C70in the cylinder56in the radial direction is suppressed.

According to the floating plate D70of the thirteenth embodiment, as shown inFIG. 26, a cross sectional configuration of a side wall D75is curved, so that a middle portion is expanded in a radial and outward direction. Because of the curved configuration of the side wall D75, each of diameters of the upper and lower sides of the floating plate D70is made smaller than a diameter of the middle portion.

In addition, multiple grooves D77b(similar to the grooves B77bof the eleventh embodiment,FIG. 24) are likewise formed at the side wall D75of the floating plate D70. Multiple sliding surface portions D75bare likewise formed between the neighboring grooves D77bin a circumferential direction of the floating plate D70. The sliding surface portions D75bare in a sliding contact with the inner peripheral wall57of the cylinder56, so that the floating plate D70is movably accommodated in the cylinder56. A displacement of the floating plate D70in the cylinder56in the radial direction is suppressed.

In the twelfth or thirteenth embodiment, even when the floating plate C70or D70is inclined with respect to a longitudinal direction of the fuel injection device, an outer periphery of the upper or lower side of the floating plate may not be brought into contact with the inner peripheral wall57of the cylinder56due to the configuration of the floating plate C70or D70. It is, therefore, possible to avoid such a situation that any of the outer periphery of the upper or lower side of the floating plate may be caught by the inner wall of the cylinder and firmly fixed to the inner wall. As a result, not only accuracy but also reliability for the fuel injection can be realized.

Other Embodiments

The present invention is explained with reference to several embodiments. However, the present invention should not be limited to those of the embodiments, but may be further modified in various ways without departing from the spirit of the invention.

In the above embodiments, the passage wall portion (77) is provided in the floating plate (70) to form the communication passage (77a) for connecting the upper side space (53c) and the lower side space (53d) of the pressure control chamber (53) with each other. The passage wall portion (77) is formed in the shape of the flat surfaces (77,277), the grooves (377,477,577), the stripes or the like. The shape and the number of the passage wall portions are not limited to those explained in the above embodiments, so long as the communication passages (77a) are formed by the passage wall portions and the inner peripheral wall (57) of the cylinder (56) so that the fuel may flow through such communication passages (77a).

For example, as shown inFIG. 27A, multiple passage wall portions1077of a groove-shape may be formed at a side wall1075of a floating plate1070, so that multiple communication passages are formed extending straightly in an axial direction of the floating plate1070. Alternatively, as shown inFIG. 273, multiple passage wall portions1177of a shallow-dish-shape may be formed at a side wall of a floating plate1170, wherein multiple communication passages extend straightly in an axial direction of the floating plate1170.

In the above explained twelfth and thirteenth embodiments, the outer peripheral surface of the floating plate (C70, D70) is in the sliding contact with the inner peripheral wall (57) of the cylinder (56), so that the floating plate (C70, D70) is movable in the cylinder (56). However, at a maximum diameter portion of the floating plate (C70, D70), the gap between the outer peripheral surface of the floating plate (C70, D70) and the inner peripheral wall (57) of the cylinder (56) is negligible, so that substantially no fuel passes through such gap. In other words, the fuel passes only through the communication passages.

However, as a modification thereof, the maximum diameter portion of the floating plate may be reduced in its diameter, so that a gap is formed between the outer peripheral surface of the floating plate and the inner peripheral wall of the cylinder in order that a part of the fuel may pass through such enlarged gap.

In the above twelfth and thirteenth embodiments, the diameters of the upper and lower sides of the floating plate are made smaller. However, the diameter of either the upper or the lower side of the floating plate may be reduced.

According to the above modifications, the same effects to the twelfth or the thirteenth embodiment can be obtained. Namely, it is possible to avoid such a situation that any of the outer periphery of the upper or lower side of the floating plate may be caught by the inner wall of the cylinder and firmly fixed to the inner wall.

In the first embodiment, the inner and outer press-contacting portions72and74(the continuous projecting portions) are formed at the press-contacting surface73of the floating plate70and the pressure control surface53bof the valve body40is formed of the flat surface. On the other hand, in the second embodiment, the flow-in-side and flow-out-side contacting portions252cand254c(the continuous projecting portions) are formed at the pressure control surface253bof the valve body246and the press-contacting surface273is formed of the flat surface. As understood above, in the above first and second embodiments, the flow-in and flow-out recessed portions (72a,74a,272a,274a) are formed either at the pressure control surface of the valve body or at the press-contacting surface of the floating plate.

In the sixth or seventh embodiment, one of the flow-in and the flow-out recessed portions is formed at one of the pressure control surface and the press-contacting surface, and the other of the flow-in and the flow-out recessed portion is formed at the other of the pressure control surface and the press-contacting surface.

It is not always necessary to form the flow-in (and flow-out) recessed portion at only one of the pressure control surface and the press-contacting surface. Namely, the flow-in (and flow-out) recessed portion may be formed at both of the pressure control surface and the press-contacting surface.

In the above embodiments, the flow-in port and the flow-out port are opened to the pressure control chamber at the same side of the floating plate. The relative position of the flow-in and the flow-out ports to the floating plate is not limited to the position of the above embodiments. The positions of the flow-in or the flow-out port may be changed, so long as the communication and non-communication (block-off of the communication) between the flow-in port and the pressure control chamber are carried out by the floating plate by use of the fuel pressure around the flow-out port.

In the above embodiments, the floating plate70is made in the cylindrical shape and the cross sectional shape of the side wall75is outwardly curved in the radial direction. In addition, the passage wall portions77are formed at the outer side wall75of the floating plate70, wherein the passage wall portions77extend in the axial direction. The passage wall portions77may not be always necessary, if the gap between the outer side wall and the inner peripheral wall of the cylinder is enough large so that fuel can easily flows through the gap from the upper side space53cto the lower side space53d. Furthermore, the shape of the outer side wall of the floating plate may not be limited to that shown in the embodiment.

In the above embodiments, the driving portion for the pressure control valve80, which controls fuel pressure in the pressure control chamber53, is composed of the solenoid31and the movable member35driven by the magnetic force generated by the solenoid. The driving portion may be composed of another type actuator, for example, a piezo actuator, which drives the pressure control valve80in accordance with the control signal from the engine control unit17.

In the above embodiments, the pressure control chamber is defined by the pressure control surface of the valve body, the inner peripheral wall of the cylinder, and the pressure receiving surface of the nozzle needle. The present invention may be also applied to the fuel injection device, which does not have an element corresponding to the cylinder, but in which the pressure control chamber is formed by the valve body and the nozzle needle.

In the above embodiments, the fuel injection device is applied to the diesel engine20, in which the fuel is directly injected into combustion chambers22of the engine. The present invention may be also applied to the fuel injection device, which will be mounted in an internal combustion engine of an Otto-cycle engine. The fuel injected by the fuel injection device is not limited to the diesel oil, but other fuel such as, gasoline, liquefied petroleum gas, and so on) may be used. The fuel injection device may be further applied to an external combustion engine.