DE102017112715B4 - fuel injector - Google Patents

Abstract

A fuel injection valve for an internal combustion engine, comprising;a needle (4) serving as a valve member for opening and closing an injection hole (9) for injecting fuel into a combustion chamber of the internal combustion engine;a needle body (5) having a cylindrical shape for movably accommodating the needle (4), the injection hole (9) being formed in the needle body (5);a back pressure chamber (6) for applying a back pressure of the fuel to the needle (4) in an injection hole closing direction;a outflow passage (7) for discharging the fuel from the back pressure chamber (6); anda drive section (8) for opening or closing the outflow passage (7) based on a control signal from a control unit (2) to thereby increase the back pressure for controlling an opening or closing operation of the injection hole (9) by the needle (4) or to lower, wherein the drive section (8) increases the back pressure so that a contacting section (10) at the front end of the needle (4) is moved to a seating position (12) so as to sit on a seating surface (11) arranged at a inner surface of the needle body (5) to thereby close the injection hole (9), the driving section (8) lowering the back pressure to cause the contacting section (10) at the front end of the needle (4) to be lifted from the seated position (12). so as to increase a lifting amount of the needle (4) in its axial direction to thereby open the injection hole (9), the lifting amount of the needle (4) leading to a distance between the contacting portion (10). n end and corresponds to the seated position (12), wherein the needle (4) is operated in either a first mode at a first stroke speed or a second mode at a second stroke speed, the second stroke speed being lower than the first stroke speed, and wherein the lifting speed corresponds to an increase amount of the lifting amount of the needle (4) per unit time, wherein the fuel injection valve further comprises a mode switching section (55) for switching the first mode to the second mode by a lifting movement of the needle (4) in a lifting stroke of the needle (4). mode or vice versa, and wherein a first protruding area of a pressure-receiving surface of the needle (4) on which the back pressure is applied in the first mode is smaller than a second protruding area of the pressure-receiving surface of the needle (4) on which in the second mode the back pressure is applied, the protruding portion being a portion on a plane ne which is perpendicular to the axial direction of the needle (4), an inflow passage (21) being formed so that the fuel is supplied from the inflow passage (21) into the back pressure chamber (6), a control plate member (45) so formed is that this partially defines the back pressure chamber (6), and the control plate member (45) opens the inflow port (21) when the outflow port (7) is closed, while the control plate member (45) closes the inflow port (21) when the outflow port ( 7) is opened, and a restricted portion (51) is formed in the control plate member (45) to restrict an outflow amount of the fuel that outflows from the back pressure chamber (6) to the outflow passage (7) when the outflow passage (7) opens is.

Description

The present disclosure relates to a fuel injector for injecting fuel into a combustion chamber of an internal combustion engine.

A fuel injection valve (hereinafter an injector) composed of a needle, a nozzle body, a back pressure chamber, an inflow passage, an outflow passage, a driving portion and the like is known in the prior art.

The needle is a valve body for opening and closing an injection hole from which fuel is injected into a combustion chamber of an internal combustion engine (hereinafter the engine).

The nozzle body is formed in a cylindrical shape to movably accommodate the needle. The injection hole is formed in the nozzle body.

The back pressure chamber is formed to apply a back pressure of the fuel to the needle in a closing direction of the injection hole.

The inflow passage is formed to supply the fuel into the back pressure chamber. For example, high-pressure fuel, which is charged by a feed pump, is fed from the inflow passage into the back pressure chamber.

The outflow passage is formed so that the fuel is discharged from the back pressure chamber.

The drive section controls an opening and closing operation for the outflow passage in accordance with a control signal from a control unit. More specifically, the back pressure is increased or decreased to control an opening and closing operation of the needle for the injection hole.

In the above injector, when the back pressure is increased, a contacting portion at the front end of the needle sits on a seating surface formed on an inner surface of the nozzle body, so that the injection hole is closed. A lift amount of the needle, which corresponds to a distance between the front-end contacting portion and the seat surface in an axial direction of the needle, is increased as the back pressure is decreased to open the injection hole.

When an increase amount per unit time of the lift amount is defined as a lift speed of the needle in the injector of the above type, it is known in the art to change the lift speed in an injection stroke, such as in the patent publication U.S. 2013/0 233 941 A1 is revealed.

When the stroke speed is changed in an injection stroke, it becomes possible not only to reduce generation of smoke but also to increase an output of the engine as explained below.

According to the injector of the above prior art, two exhaust ports are provided, and a drive portion for opening and closing the exhaust port is provided for each of the exhaust ports. An opening and closing operation is independently performed for each of the outflow passages to increase or decrease an outflow amount of the fuel from a back pressure chamber. As a result, the lifting speed of the needle can be changed.

With the structure of the above prior art, however, it is necessary to provide the driving portion for each of the two outflow ports, respectively. Therefore, there is a problem that a size of the injector becomes larger. In addition, there is another problem that electric power consumption is increased when the plurality of driving sections are operated.

Further prior art is disclosed in the following documents.

JP 2001-221 119A discloses a fuel injection device capable of controlling a fuel injection rate according to an engine operating condition to simultaneously reduce NOx, HC and black smoke and improve fuel consumption performance. A needle receives a force from fuel pressure of a first control chamber in the closing direction of the nozzle hole and receives force from fuel pressure of a fuel accumulating part in the opening direction of the nozzle hole. When a voltage is applied to a piezoelectric element, fuel pressure of the first control chamber and a second control chamber is reduced, so that the needle leaves a valve seat to rise by a lift amount, injecting fuel from a nozzle hole. When the voltage applied to the piezoelectric element drops, the fuel pressure in the second control chamber increases to lift a second piston so that the needle is raised again and abuts a tip seal and is stopped. When applying the voltage to when the piezoelectric element is broken, the fuel pressure of the first control chamber is increased and the force in the closing direction of the nozzle hole becomes large, so that the needle is seated on the valve seat, stopping the fuel injection.

JP H11-173 234A discloses a fuel injector that can shorten the interval between a pilot injection and a main injection while decreasing the initial injection rate of an injector. An orifice forming member divided into a first control chamber that applies hydraulic force to the shoulder part of a spool in the nozzle closing direction and a second control chamber that applies hydraulic force to the head part of the spool in the nozzle closing direction is divided into installed at the rear end of an injector body. The center of an annular portion of the injector body is provided with an opening to connect a fuel supply and discharge passage to the second control chamber. An axial groove formed of a fuel passage having a passage cross-sectional area larger than that of the opening between the inner peripheral surfaces of the injector body is provided on the outer peripheral surface of the annular portion of the opening forming member. As a result, the time from when a control valve opens to when a nozzle needle starts to act in the valve opening direction can be shortened.

DE 10 2010 017 092 A1 discloses a fuel injector. A fuel injector includes a nozzle orifice, a valve portion, an upstream fuel passage, a pressure control chamber, a cylindrical member, an downstream fuel passage, a pressure control valve, a blocking member, a valve member, and a space. A first contact portion faces a first restricting part in the axial direction, and the first contact portion abuts against the first restricting part to restrict displacement of the valve member toward the chamber while a pressure receiving portion is spaced from the blocking member. The space is formed between the cylindrical member and the valve member and communicates with a clearance between the first restricting part and the first contact portion at least when the nozzle opening is closed. When the first restricting piece abuts against the first contact portion, a perimeter of the space is defined by the cylindrical member and the valve member.

DE 10 2007 030 794 A1 discloses a fuel injector with an injector body suitable for high fuel pressures. A fuel injector comprises a nozzle body with a nozzle needle guided in it so that it can be displaced, which controls the injection of fuel from a nozzle chamber of the nozzle body, an injector body on which the nozzle body is held, and a high-pressure fuel line which is located inside the injector body and inside the nozzle body to the nozzle chamber, wherein according to the invention at least one line section of the high-pressure fuel line running in the injector body, in particular the entire high-pressure fuel line running in the injector body, is surrounded by an annular space to which a fuel pressure can be applied.

The present disclosure is made in view of the above problem. It is an object of the present disclosure to provide a fuel injection valve capable of changing a lifting speed of a needle in an injection stroke without providing a plurality of drive sections.

This object is solved by the features of claims 1 and 5. Further advantageous embodiments and further developments are the subject matter of the subsequent claims.

According to one of the features of the present disclosure, a fuel injection valve is composed of a needle (4), a needle body (5), a back pressure chamber (6), an outflow passage (7), a driving portion (8), a mode switching portion (55) and the like.

The needle (4) is a valve member for opening and closing an injection hole (9) for injecting fuel into a combustion chamber of an internal combustion engine.

The needle body (5) is formed in a cylindrical shape to movably accommodate the needle (4), and the injection hole (9) is formed in the needle body (5).

The back pressure chamber (6) is provided in the fuel injection valve for applying a back pressure of the fuel to the needle (4) in an injection hole closing direction.

The outflow passage (7) is designed to discharge the fuel from the back pressure chamber (6).

The drive section (8) opens or closes the outflow passage (7) based on a control signal from a control unit (2) to thereby increase the back pressure for controlling an open opening or closing operation of the injection hole (9) by the needle (4) to increase or decrease.

The driving section (8) increases the back pressure so that a contacting section (10) at the front end of the needle (4) is moved to a seating position (12) so as to be seated on a seating surface (11) formed on an inner surface of the needle body ( 5) is formed to thereby close the injection hole (9).

In addition, the driving section (8) lowers the back pressure so that the contacting section (10) at the front end of the needle (4) is lifted from the seated position (12) so as to increase a lifting amount of the needle (4) in its axial direction thereby opening the injection hole (9) with the amount of lift of the needle (4) corresponding to a distance between the front end contacting portion (10) and the seating position (12).

The needle (4) is operated in either a first mode at a first lifting speed or a second mode at a second lifting speed, the second lifting speed being lower than the first lifting speed and the lifting speed corresponding to an increase in the lifting amount of the needle (4) per unit time is equivalent to.

The mode switching section (55) switches the first mode to the second mode or vice versa by a lifting movement of the needle (4).

A first protruding area of a pressure-receiving surface of the needle (4) on which the back pressure is applied in the first mode is smaller than a second protruding area of the pressure-receiving surface of the needle (4) on which the back pressure is applied in the second mode, where the protruding portion corresponds to a portion on a plane perpendicular to the axial direction of the needle (4).

Furthermore, an inflow passage (21) is formed so that the fuel is supplied from the inflow passage (21) into the back pressure chamber (6). A control plate member (45) is formed to partially define the back pressure chamber (6). The control plate member (45) opens the inflow port (21) when the outflow port (7) is closed, while the control plate member (45) closes the inflow port (21) when the outflow port (7) is opened. A restricted portion (51) is formed in the control plate member (45) to restrict an outflow amount of fuel flowing out of the back pressure chamber (6) to the outflow port (7) when the outflow port (7) is opened

According to the above structure, a volume of fuel per unit lift amount of the needle discharged from the back pressure chamber by the movement of the pressure receiving surface of the needle in the first mode can be made smaller than a volume of fuel per unit lift amount of the needle in the first mode. which is discharged from the back pressure chamber by the movement of the pressure receiving surface of the needle in the second mode, in the second mode. In other words, the lift amount of the needle in the first mode can be made larger than that in the second mode with respect to the outflow amount of the fuel from the back pressure chamber. That is, the lifting speed of the needle in the first mode can be made higher than that in the second mode.

In addition, since the first mode is changed to the second mode by the movement of the needle, more specifically, by an increase in the lifting amount of the needle, it is not necessary to provide an additional drive section. That is, it is not necessary to provide a plurality of drive sections.

Accordingly, it is possible to provide the injector capable of changing the lifting speed of the needle without providing the plurality of driving sections.

According to another feature of the present disclosure, a fuel injection valve has a mode switching section (55).

The mode switching section (55) switches an operation mode of a needle (4) by moving the needle (4) from a first mode to a second mode.

A restricted portion (51, 63, 64, 90, 91, 92, 94, 95) is formed in a fuel passage from a back pressure chamber (6) to an outflow passage (7), through which fuel is discharged from the back pressure chamber (6) to the Outflow passage (7) is discharged. A cross-sectional area of the restricted portion is larger in the first mode than in the second mode, the cross-sectional area corresponding to an area on a plane perpendicular to a fuel flow direction through the restricted portion.

According to the above feature, since in the first mode, an outflow amount of the fuel from the back pressure chamber is large More than that in the second mode, a lift amount of the needle in the first mode is larger than that in the second mode. Accordingly, it is possible to change the lifting speed such that the lifting speed in the first mode is higher than that in the second mode.

Since the first mode is changed to the second mode by the movement of the needle, more specifically, by an increase in the lifting amount of the needle, it is not necessary to provide an additional drive section. That is, it is not necessary to provide a plurality of drive sections.

Accordingly, it is possible to provide the injector capable of changing the lifting speed of the needle without providing the plurality of driving sections.

The above and other objects, features and advantages of the present disclosure will become apparent from the following detailed description with reference to the accompanying drawings.

• 1 eine schematische Querschnittsansicht, die ein Kraftstoffeinspritzventil gemäß einer ersten Ausführungsform der vorliegenden Offenbarung zeigt.
• 2 eine schematisch vergrößerte Querschnittsansicht, die relevante Abschnitte des Kraftstoffeinspritzventils der ersten Ausführungsform zeigt.
• 3A und 3B schematische Querschnittsansichten, die relevante Abschnitte zum Erläutern von Betrieben des Kraftstoffeinspritzventils zeigen, wobei 3A einen Zustand eines ersten Modus zeigt, in welchem eine Hubgeschwindigkeit der Nadel hoch ist, während 3B einen Zustand eines zweiten Modus zeigt, in welchem die Hubgeschwindigkeit der Nadel niedrig ist.
• 4A einen Graphen, der eine Veränderung eines Hubbetrags der Nadel im Hinblick auf die Zeit zeigt, während 4B einen Graphen zeigt, der eine Kraftstoffeinspritzrate im Hinblick auf die Zeit zeigt.
• 5A einen Graphen, der eine Kraftstoffeinspritzrate im Hinblick auf die Zeit zeigt, wenn die Hubgeschwindigkeit hoch ist und wenn die Hubgeschwindigkeit niedrig ist, 5B einen Graphen, der eine Länge eines Kraftstoff-Sprühstrahls im Hinblick auf die Zeit zeigt, und 5C einen Graphen, der eine Rauchmenge zeigt.
• 6A eine pV-Diagrammansicht, die einen theoretischen Zyklus und einen wirklichen Zyklus zeigt, währen sowohl 6B als auch 6C einen Graphen zeigen, der die Kraftstoffeinspritzrate zeigt, wenn die Hubgeschwindigkeit hoch ist und wenn die Hubgeschwindigkeit niedrig ist.
• 7 eine schematische Querschnittsansicht, die ein Kraftstoffeinspritzventil gemäß einer zweiten Ausführungsform der vorliegenden Offenbarung zeigt.
• 8 eine schematisch vergrößerte Querschnittsansicht, die relevante Abschnitte des Kraftstoffeinspritzventils gemäß der zweiten Ausführungsform zeigt.
• 9A und 9B schematische Querschnittsansichten, die relevante Abschnitte zum Erläutern von Betrieben des Kraftstoffeinspritzventils der zweiten Ausführungsform zeigen, wobei 9A einen Zustand des ersten Modus zeigt, während 9B einen Zustand des zweiten Modus zeigt.
• 10 eine schematische Draufsicht eines Bodenabschnitts eines Steuerplattenbauteils, um Stellen von Durchgangslöchern zu zeigen, wenn der Bodenabschnitt ausgehend von der vorderen Endseite betrachtet wird.
• 11A und 11B schematisch vergrößerte Querschnittsansichten, von welchen jede relevante Abschnitte eines Kraftstoffeinspritzventils gemäß einer Modifikation der vorliegenden Offenbarung zeigt.
• 12A eine schematisch vergrößerte Querschnittsansicht, die relevante Abschnitte eines Kraftstoffeinspritzventils gemäß einer anderen Modifikation der vorliegenden Offenbarung zeigt, 12B einen Graphen, der eine Veränderung des Hubbetrags der Nadel im Hinblick auf die Zeit zeigt, und 12C einen Graphen, der die Kraftstoffeinspritzrate im Hinblick auf die Zeit zeigt.
• 13A eine schematisch vergrößerte Querschnittsansicht, die relevante Abschnitte eines Kraftstoffeinspritzventils gemäß einer weiteren Modifikation der vorliegenden Offenbarung zeigt, 13B einen Graphen, der die Veränderung des Hubbetrags der Nadel im Hinblick auf die Zeit zeigt, und 13C einen Graphen, der die Kraftstoffeinspritzrate im Hinblick auf die Zeit zeigt.
• 14A und 14B schematisch vergrößerte Querschnittsansichten, von welchen jede relevante Abschnitte eines Kraftstoffeinspritzventils gemäß noch einer weiteren Modifikation der vorliegenden Offenbarung zeigt.
• 15A eine schematisch vergrößerte Querschnittsansicht, die relevante Abschnitte eines Kraftstoffeinspritzventils gemäß noch einer weiteren Modifikation der vorliegenden Offenbarung zeigt, und 15B eine schematische Draufsicht eines Bodenabschnitts, um Stellen von Durchgangslöchern zu zeigen.
• 16A eine schematisch vergrößerte Querschnittsansicht, die relevante Abschnitte eines Kraftstoffeinspritzventils gemäß noch einer weiteren Modifikation der vorliegenden Offenbarung zeigt, und 16B eine schematische Draufsicht eines Bodenabschnitts, um Stellen von Durchgangslöchern zu zeigen.
• 17A und 17B schematisch vergrößerte Querschnittsansichten, von welchen jede relevante Abschnitte eines Kraftstoffeinspritzventils gemäß noch einer weiteren Modifikation der vorliegenden Offenbarung zeigt; und
• 18A und 18B schematisch vergrößerte Querschnittsansichten, von welchen jede relevante Abschnitte eines Kraftstoffeinspritzventils gemäß noch einer weiteren Modifikation der vorliegenden Offenbarung zeigt.

It shows/shows:

• 1 12 is a schematic cross-sectional view showing a fuel injection valve according to a first embodiment of the present disclosure.
• 2 12 is a schematically enlarged cross-sectional view showing relevant portions of the fuel injection valve of the first embodiment.
• 3A and 3B Schematic cross-sectional views showing relevant portions for explaining operations of the fuel injection valve, wherein 3A 12 shows a state of a first mode in which a lifting speed of the needle is high while FIG 3B Fig. 12 shows a state of a second mode in which the lifting speed of the needle is low.
• 4A Fig. 14 is a graph showing a change in a lift amount of the needle with respect to time while 4B Fig. 12 shows a graph showing fuel injection rate with respect to time.
• 5A a graph showing a fuel injection rate with respect to time when the lift speed is high and when the lift speed is low, 5B a graph showing a length of a fuel spray with respect to time, and 5C a graph showing an amount of smoke.
• 6A a pV diagram view showing a theoretical cycle and a real cycle both during 6B as well as 6C 12 shows a graph showing the fuel injection rate when the lift speed is high and when the lift speed is low.
• 7 12 is a schematic cross-sectional view showing a fuel injection valve according to a second embodiment of the present disclosure.
• 8th 12 is a schematically enlarged cross-sectional view showing relevant portions of the fuel injection valve according to the second embodiment.
• 9A and 9B 12 are schematic cross-sectional views showing relevant portions for explaining operations of the fuel injection valve of the second embodiment, wherein 9A shows a state of the first mode while 9B shows a state of the second mode.
• 10 12 is a schematic plan view of a bottom portion of a control plate member to show through hole locations when the bottom portion is viewed from the front end side.
• 11A and 11B 12 are schematically enlarged cross-sectional views each showing relevant portions of a fuel injection valve according to a modification of the present disclosure.
• 12A 12 is a schematically enlarged cross-sectional view showing relevant portions of a fuel injection valve according to another modification of the present disclosure. 12B a graph showing a change in the lift amount of the needle with respect to time, and 12C Figure 12 is a graph showing fuel injection rate with respect to time.
• 13A 12 is a schematically enlarged cross-sectional view showing relevant portions of a fuel injection valve according to another modification of the present disclosure. 13B a graph showing the change in the lift amount of the needle with respect to time, and 13C Figure 12 is a graph showing fuel injection rate with respect to time.
• 14A and 14B 12 are schematically enlarged cross-sectional views each showing relevant portions of a fuel injection valve according to still another modification of the present disclosure.
• 15A 12 is a schematically enlarged cross-sectional view showing relevant portions of a fuel injection valve according to still another modification of the present disclosure, and 15B Fig. 12 is a schematic plan view of a bottom portion to show through-hole locations.
• 16A 12 is a schematically enlarged cross-sectional view showing relevant portions of a fuel injection valve according to still another modification of the present disclosure, and 16B Fig. 12 is a schematic plan view of a bottom portion to show through-hole locations.
• 17A and 17B 12 are schematically enlarged cross-sectional views each showing relevant portions of a fuel injection valve according to still another modification of the present disclosure; and
• 18A and 18B 12 are schematically enlarged cross-sectional views each showing relevant portions of a fuel injection valve according to still another modification of the present disclosure.

The present disclosure is explained below using a number of embodiments or modifications with reference to the drawings. The same or similar parts or portions in all the embodiments or modifications are denoted by the same reference numerals to avoid redundant explanations.

First embodiment

A structure of a fuel injection valve 1 (hereinafter, an injector 1) of a first embodiment of the present disclosure will be explained with reference to FIG 1 to be discribed.

Each of the injector 1, a feed pump (not shown), a common rail (not shown) and an electronic control unit 2 (ECU 2) are a component of a fuel injection system. The supply pump charges fuel and supplies such high-pressure fuel to the common rail. The common rail temporarily stores the high-pressure fuel from the feed pump. The high-pressure fuel is distributed to each of the injectors 1 from the common rail.

The ECU 2 calculates a fuel injection amount based on a load of an internal combustion engine (hereinafter the engine: unspecified), a rotating speed of the engine, and the like. The ECU 2 further calculates an injection start timing and an injection period, which corresponds to the fuel injection amount, in accordance with a fuel pressure (a common rail pressure) to be supplied to the injector 1 .

The injector 1 is mounted on the engine and injects the high-pressure fuel, for example more than 250 MPa, directly into a combustion chamber of the engine.

The injector 1 is composed of a needle 4, a nozzle body 5, a back pressure chamber 6, an outflow passage 7, a driving portion 8 and the like, as explained below. In the present disclosure, an axial front end side of the injector 1 is referred to as a front end side, while an axial rear end side of the injector 1 is referred to as a rear end side.

The needle 4 is formed in a columnar shape and serves as a valve body for opening and closing injection holes 9 through which the high-pressure fuel is directly injected into the combustion chamber of the engine. The needle 4 has a contacting section 10 at its front end for opening and closing the injection holes 9 .

The nozzle body 5 is formed in a cylindrical shape to movably accommodate the needle 4 therein. The injection holes 9 are formed at a front end of the nozzle body 5 . A seating surface 11 is formed on an inner surface of the nozzle body 5 so that the contacting portion 10 of the needle 4 is seated on or separated from the seating surface 11 of the nozzle body 5 . A position of the needle 4 at which the contacting portion 10 is seated on (or separated from) the seat surface 11 is referred to as a seated position 12 of the needle 4 .

When the contacting portion 10 of the needle 4 is separated from the seated position 12 in an upward axial direction, the injection holes 9 are opened so as to inject the fuel. On the other hand, when the contacting portion 10 of the needle 4 descends to the seating position 12 and sits on the seating surface 11, the injection holes 9 are closed so as to stop fuel injection.

The back pressure chamber 6 is formed on the rear end side of the needle 4 so that a back pressure of the high-pressure fuel is applied to the needle 4 in a direction closing the injection holes 9 .

The outflow passage 7 is a fuel passage through which the fuel is discharged from the back pressure chamber 6 .

The back pressure chamber 6 and the outflow passage 7 will be further explained in more detail below.

The driving section 8 opens and closes the outflow passage 7 based on a control signal from the ECU 2. The driving section 8 increases or decreases the back pressure by opening or closing the outflow passage 7 to control an opening and closing operation of the needle 4 for the injection holes 9.

The drive section 8 is accommodated in a holding member 13 (a housing 13). The nozzle body 5 and the holding member 13 are connected to each other by a holding nut 16 such that metal plate members 14 and 15 (first and second metal plate members 14 and 15) are interposed between the nozzle body 5 and the holding member 13 . High pressure fuel passages 17, 18, 19 and 20 are respectively formed in the holding member 13, the first and second plate members 14 and 15 and the nozzle body 5 to supply the high pressure fuel to the injection holes 9 from the common rail.

The outflow port 7 is formed in the second plate member 15 so as to penetrate through the second plate member 15 in the axial direction. An inflow passage 21 is formed in the second plate member 15 to supply the high pressure fuel into the back pressure chamber 6 . The inflow passage 21 branches from the high-pressure fuel passage 19 so that the high-pressure fuel is supplied into the back pressure chamber 6 . A restricted portion is formed in the inflow passage 21 to restrict a flow amount of fuel supplied into the back pressure chamber 6 .

A low-pressure passage 23 is formed in the first plate member 14 . The first plate member 14 has a valve chamber 26 for movably accommodating the switching valve 25 . The switching valve 25 serves as a valve body which communicates the outflow passage 7 with the low-pressure fuel passage 23 so as to open the outflow passage 7, or which cuts off communication between the outflow passage 7 and the low-pressure fuel passage 23 so as to open the outflow passage 7 close.

The drive section 8 is composed of a piezoelectric actuator having a piezoelectric element 27, a piezoelectric piston 28, a valve piston 29 and the like.

The piezoelectric element 27, the piezoelectric piston 28, and the valve piston 29 are arranged in this order in the axial direction from the rear end side toward the front end side of the injector 1, and housed in the holding member 13 coaxially.

The piezoelectric element 27 is expanded in the axial direction when electric power is applied thereto so as to move the piezoelectric piston 28 and the spool 29 in an axial direction downward toward the front end side.

A displacement transmission shaft 30 is provided between the valve spool 29 and the switching valve 25 so that it is moved downward in the axial direction toward the front end side. When the switching valve 25 is moved downward toward the front end side together with the displacement transmission shaft 30 in the axial direction, a valve body portion of the switching valve 25 is separated from a valve seat portion formed in the first plate member 14 so that the switching valve 25 is opened. When the switching valve 25 is opened, the outflow passage 7 communicates with the low-pressure fuel passage 23 so that the outflow passage 7 is opened to lower the back pressure in the back pressure chamber 6 .

When the back pressure is lowered, the contacting portion 10 of the needle 4 is separated from the seating position 12 (from the seating surface 11 of the nozzle body 5) to thereby open the injection holes 9. In other words, a lift amount of the needle 4, which corresponds to a shift amount of the needle 4 in an upward axial direction, is increased.

A return spring 32 is provided in the valve chamber 26 so as to bias the switching valve 25 in a valve closing direction (upward in the axial direction toward the rear end side).

When electric power supply to the piezoelectric element 27 is cut off, an axial length of the piezoelectric element 27 returns to its original length, that is, the axial length becomes smaller. The switching valve 25 is moved upward in the axial direction toward the rear end side so that the valve body portion of the switching valve 25 is brought into contact with the valve seat portion of the first plate member 14 . When the switching valve 25 is closed, the outflow passage 7 is closed, so as to increase the back pressure in the back pressure chamber 6.

When the back pressure is increased, the contacting portion 10 of the needle 4 is seated on the seating position 12 (the seating surface 11 of the nozzle body 5) to thereby close the injection holes 9.

Characterizing portions of the first embodiment

Characterizing portions of the first embodiment are described with reference to FIG 2 be explained.

The injector 1 includes a cylindrical member 40 having a cup shape (a chamber formation member 40), a pressure receiving member 43 (hereinafter a mode switching member 43), a control plate member 45, a spring 46 (a biasing member), and the like.

The cylindrical member 40 formed in a cylindrical shape with a bottom end 40a forms the back pressure chamber 6. As shown in FIG. A through hole 40b is formed in the bottom end 40a of the cylindrical member 40 . A rear end portion 4a of the needle 4 is movably inserted into the through hole 40b of the cylindrical member 40 so that an outer peripheral surface of the rear end portion 4a and an inner peripheral surface of the through hole 40b contact each other in a slidable manner.

A spring 47 provided between the cylindrical member 40 and the needle 4 biases the cylindrical member 40 upward in the axial direction (in a rearward direction) so that the cylindrical member 40 is in contact with a lower side surface (a front end surface) of the second plate member 15 is.

The mode switching member 43 is formed in a cylindrical shape with a top closed end 48 to partially define the back pressure chamber 6 . The mode switching member 43 is movably fitted to the rear end portion 4a of the needle 4 such that an inner peripheral surface of the mode switching member 43 is in contact with the outer peripheral surface of the rear end portion 4a of the needle 4 in the slidable manner and an outer peripheral surface of the mode switching member 43 is in the slidable manner in Contact with an inner peripheral surface of the cylindrical member 40 is. In the upper-side closed end 48 of the mode switching member 43, a through hole 49 is formed. The through hole 49 penetrates through the mode switching member 43 in the axial direction, so that a first space 6a formed between the mode switching member 43 and the rear end portion 4a communicates via the through hole 49 with a second space 6b formed on an outside of the mode switching member 43 is trained, is connected. The back pressure chamber 6 is composed of the first space 6a and the second space 6b.

The control plate member 45 is formed in a disk shape to partially define the back pressure chamber 6 . The control plate member 45 is located at a position on the rear end side of the mode switching member 43. A through hole 50 is formed at a center of the control plate member 45 in the axial direction so that the back pressure chamber 6 is always in communication with the outflow passage 7.

A cross-sectional area of the through hole 50 on a plane perpendicular to a flow direction of fuel is smaller than that of the through hole 49 on a plane perpendicular to a flow direction of fuel. The through hole 50 serves as an outflow port 51 for restricting a flow amount of the fuel that outflows from the back pressure chamber 6 into the outflow passage 7 .

The spring 46 is interposed between the mode switching member 43 and the control plate member 45 in a compressed state.

Operation of the First Embodiment

An operation of the injector 1 of the first embodiment will be described with reference to FIG 1 , 2 , 3A and 3B be explained.

The switching valve 25 opens the outflow passage 7 (the outflow passage 7 communicates with the low-pressure fuel passage 23) when the electric power is supplied to the piezoelectric element 27 in accordance with the control signal from the ECU 2.

When the fuel starts flowing out of the back pressure chamber 6 via the outflow passage 7, the fuel pressure in the back pressure chamber 6 is lowered.

Then, a fluid force of the high-pressure fuel applied to a front end of the needle 4 (a fluid force for pushing the needle 4 upward in the axial direction) becomes larger than the back pressure. The needle 4 is doing in the Raised in the rearward direction (upward in the axial direction) so that the contacting portion 10 of the needle 4 is separated from the seat surface 11 of the nozzle body 5 to open the injection holes 9 .

The fluid force applied to the front end of the needle 4 before it starts its upward movement (before separating from the seat surface 11) corresponds to a fluid force which presses the needle 4 at a front end surface outside the contacting portion 10 of the needle 4 of FIG absorbs the high-pressure fuel.

In a period of time just after a start of raising movement of the needle 4, only the needle 4 is raised in the reverse direction without moving the mode switching member 43 as shown in FIG 3A will be shown. In other words, the needle 4 is shifted relative to the mode switching member 43, and the first space 6a formed between the mode switching member 43 and the needle 4 serves as the back pressure chamber 6. As a result, a protruding portion of a pressure-receiving surface of the needle 4 corresponds to a cross-sectional area of the rear end portion 4a as in FIG 3A is shown, wherein each of the protruding portion and the cross-sectional area is a portion on a plane perpendicular to the axial direction of the needle 4.

When a lifting amount of the needle 4 becomes larger than a predetermined value, a rear end surface of the needle 4 is brought into contact with the upper-side closed end 48 of the mode switching member 43, as shown in FIG 3B is shown so that the needle 4 and the mode switching member 43 are integrally raised together in the reverse direction. In other words, the second space 6b serves as the back pressure chamber 6. As a result, the projected area of the pressure receiving surface of the needle 4 corresponds to a cross-sectional area of the mode switching member 43 as shown in FIG 3B is shown, wherein both the protruding portion and the cross-sectional area is the portion on the plane perpendicular to the axial direction of the needle 4.

When the outflow port 7 is opened, the control plate member 45 is pressed in the rearward direction by a differential pressure between the outflow port 7 and the back pressure chamber 6 and by a biasing force of the spring 46, so that the control plate member 45 is in contact with the front end surface of the second plate member 15 . As a result, the inflow passage 21 is closed by the control plate member 45 .

In addition, once the outflow port 7 is closed, the differential pressure between the back pressure chamber 6 and the outflow port 7 becomes smaller. Then, in the axial downward direction (a forward direction), a fuel pressure applied to the control plate member 45 becomes larger than a sum of the differential pressure and the biasing force of the spring 46, so that the control plate member 45 is depressed in the forward direction and the high-pressure fuel from the Inflow passage 21 is introduced into the back pressure chamber 6.

The needle 4, the mode switching member 43 and the cylindrical member 40 are arranged so as to satisfy a condition that a first lifting amount "L1" of the needle 4 is smaller than a second lifting amount "L2" of the needle 4 (L1<L2) , where the first lifting amount “L1” is an amount with which the needle 4 is brought into contact with the mode switching member 43 in the axial direction, while the second lifting amount “L2” is a maximum lifting amount of the needle 4. The second lift amount "L2" corresponds to a distance between a front end surface of the cylindrical member 40 and a shoulder portion 4b of the needle 4.

Advantages of the first embodiment

In the present disclosure, the lifting speed is defined as a moving speed of the needle 4, more specifically, an increase amount per unit time for a lifting amount of the needle 4. A first mode is defined as an operation mode in which the needle 4 moves at a first lifting speed. A second mode is defined as an operational mode in which the needle 4 moves at a second stroke speed lower than the first stroke speed. The first mode is also referred to as a high speed mode, while the second mode is referred to as a low speed mode.

As explained above, after the needle 4 starts its lifting movement, the protruding area of the pressure-receiving surface of the needle 4 is increased from a first value (the protruding area shown in 3A shown) to a second value (the salient area shown in 3B shown) which is greater than the first value is changed. When the protruding area of the pressure receiving surface of the needle 4 is small ( 3A ), then the amount of lift of the needle 4 is large in view of the flow rate of the fuel from the back pressure chamber 6. In other words, the lifting speed of the needle 4 is high. On the other hand, as the protruding area of the pressure-receiving surface of the needle 4 becomes larger ( 3B , the lift amount of Needle 4 with respect to the outflow amount of fuel from the back pressure chamber 6 is smaller. That is, the lifting speed of the needle 4 becomes slower.

As above, after the needle 4 starts its lifting movement, the needle 4 is operated first in the first mode (the high speed mode) and then in the second mode (the low speed mode).

The operation mode of the needle 4 is switched from the first mode to the second mode depending on the lifting amount of the needle 4 .

In other words, the operational mode of the needle 4 is switched from the first mode to the second mode or vice versa when a rear end surface 4r of the needle 4 is brought into contact with or separated from a front end surface 48f of the top-side closed end 48 of the mode switching member 43 becomes. Accordingly, the rear end surface 4r of the needle 4 and the front end surface 48f of the top-side closed end 48 have a function as a mode switching portion 55. As shown in FIG.

As above, the injector 1 of the present embodiment is operated in the first mode (the high speed mode) and then in the second mode (the low speed mode), and the lifting speed of the needle 4 in the second mode is lower than that in the first mode.

The mode switching section 55 switches the operation mode of the needle 4 from the first mode to the second mode depending on the lifting amount of the needle 4 .

In addition, in the first mode ( 3A ) smaller than the protruding area of the pressure receiving surface of the needle 4 in the second mode ( 3B ).

Accordingly, it is possible to make the lifting speed of the first mode higher than that of the second mode. In other words, the lifting speed in a lifting stroke of the needle 4 can be changed.

In addition, since the operation mode is changed from the first mode to the second mode depending on the lifting amount of the needle 4, it is not necessary to provide an additional drive section. In other words, it is not necessary to provide a plurality of drive sections.

As a result, it is possible to provide the injector 1 capable of changing the stroke speed without providing the plurality of drive sections.

The 4A and 4B show the lift amount and the injection rate of the fuel with respect to time, respectively.

In the present embodiment, the needle 4 is operated first in the first mode and then in the second mode, the lifting speed of the second mode being lower than that of the first mode.

In the 4A and 4B "1st" is the first mode in which the needle 4 is operated in the high-speed mode, while "2nd" denotes the second mode in which the needle 4 is operated in the low-speed mode.

As in 5A As shown, it is possible to increase the fuel injection rate shortly after the needle 4 starts lifting when the needle 4 is operated in the first mode in which the lifting speed is high. The fuel injection rate corresponds to the fuel injection amount per unit time.

As in 5B as shown, it is thereby possible to make a fuel spray length larger. The fuel spray length corresponds to a distance that the fuel spreads from the injection hole 9 . It is possible to burn the fuel at a position further separated from the injection hole 9 .

As in 5C 1, it is possible to reduce an amount of smoke to be generated because fuel combustion in an area adjacent to the injection hole 9 can be suppressed while oxygen in the area adjacent to the injection hole 9 becomes scarce.

When the lifting speed of the needle 4 is lowered, it is possible to lengthen a fuel injection period to thereby increase the fuel injection amount in accordance with an increase in a volume of the combustion chamber. Thereby, it is possible to increase an area in the combustor for isobaric combustion.

As a result, it is possible to make a combustion cycle closer to a theoretical cycle to manufacture and thereby increase an output of the machine, as in 6A will be shown.

In addition, it is possible to reduce noise generated by rapid fuel supply when a slope of an initial increase in the fuel injection rate or the slope of the initial increase and a peak value of the fuel injection rate are made smaller than those in the case where the lifting speed is high, as in the 6B and 6C will be shown.

Even in a case of an injector in which the stroke speed cannot be changed in one injection stroke, it is possible to reduce the generation of the smoke by setting the stroke speed to a higher value (a fixed value). However, since the peak value of the fuel injection rate is increased as the fuel injection duration is decreased, it is difficult to increase the engine output and suppress the generation of the noise. On the other hand, when the lifting speed is set to a lower value (a fixed value), it becomes possible to increase the output of the machine and suppress the generation of the noise. However, it becomes difficult to reduce the generation of the smoke.

As above, it is not possible to obtain both effects of reducing the generation of the smoke and increasing the engine output and suppressing the noise in the injector with the fixed value for the stroke speed.

However, according to the injector 1 of the present embodiment, since the lifting speed can be changed during a lifting stroke of the needle 4, not only the generation of the smoke can be reduced but also the engine output can be increased and the generation of the noise can be suppressed.

In the injector 1 of the first embodiment, the mode switching member 43 partially defines the back pressure chamber 6. In addition, the mode switching portion 55, which is composed of the front end surface 48f of the mode switching member 43 and the rear end surface 4r of the needle 4, switches from the first mode in which the mode switching member 43 is not moved independently of the movement of the needle 4 (in other words, the needle 4 is shifted relative to the mode switching member 43) to the second mode in which the mode switching member 43 is moved together with the needle 4 to.

As above, since the first mode is switched to the second mode when the needle 4 is brought into contact with the mode switching member 43, it is possible to make the structure of the mode switching portion 55 simpler.

In the injector 1 of the first embodiment, the mode switching member 43 is formed in the cylindrical shape, the inner peripheral surface of which is in contact with the outer peripheral surface of the rear end portion 4a of the needle 4 in the sliding manner and the outer peripheral surface of which is in contact with the inner peripheral surface of the cylindrical member 40. which forms the counter-pressure chamber 6 .

Accordingly, the structure for changing the lifting speed of the needle 4 can be obtained simply by combining the plurality of parts having the cylindrical shape.

In the first mode, the rear end surface 4r of the needle 4 serves as the pressure receiving surface. In the second mode, a rear end surface 43r of the mode switching member 43 serves as the pressure receiving surface.

The injector 1 has the control plate member 45 which partially defines the back pressure chamber 6 and closes the inflow port 21 when the outflow port 7 is opened.

The outflow passage 7 has the outflow port 51 for restricting the amount of fuel that outflows from the back pressure chamber 6 to the outflow passage 7 .

When the outflow port 7 is opened, the communication between the inflow port 21 and the outflow port 7 is blocked, to thereby suppress the consumption of high-pressure fuel. As a result, it is possible to reduce a load on the supply pump. In addition, since the outflow passage 7 can be closed with a small force, it is possible to reduce a size of the driving portion 8 .

Since the orifice 51 is formed in the control plate member 45, it is possible to make use of the differential pressure between the back pressure chamber 6 and the outflow passage 7 when the control plate member 45 is moved in the reverse direction.

In the injector 1 of the present embodiment, the control plate member 45 is biased by the spring 46 in the rearward direction. As a result, a position of the control plate member 45 becomes stable without being affected by gravity to be affected by the fuel pressure.

Second embodiment

A second embodiment of the present disclosure is described with reference to FIG 7 and 8th will be explained by focusing on those portions that are different from those of the first embodiment.

In the second embodiment, the control plate member 45 has an axially extending portion 60 having a cylindrical shape with one end closed on the front end side of the control plate member 45 . The axially extending portion 60 has a bottom portion 62 (the closed end) in which first and second through holes 63 and 64 are formed. Both the first and second through holes 63 and 64 penetrate through the bottom portion 62 in the axial direction and serve as the orifice 51. The first through hole 63 is formed at a midpoint of the bottom portion 62, while the second through hole 64 is formed at a peripheral portion of the Bottom portion 62 is formed.

The cylindrical member 40 (chamber formation member 40) is composed of a cylindrical member having a small-diameter portion 65 on the rear end side and a large-diameter portion 66 on the front end side, an inner diameter of the small-diameter portion 65 diameter is smaller than that of the large-diameter portion 66, so that a step portion is formed on an inner peripheral surface of the cylindrical member 40 at a boundary between the small-diameter portion 65 and the large-diameter portion 66.

An outer peripheral surface of the axially extending portion 60 is movably in contact with an inner peripheral surface of the small-diameter portion 65, while the outer peripheral surface of the rear end portion 4a of the needle 4 is movably in contact with an inner peripheral surface of the large-diameter portion 66.

A switch plate member 67 is interposed between the needle 4 and the control plate member 45 .

The circuit board member 67 is formed in a disc shape and its outer peripheral surface is movably in contact with the inner peripheral surface of the large-diameter portion 66 . The circuit board member 67 has at its center a through hole 68 which penetrates the circuit board member 67 in the axial direction.

The circuit plate member 67 partially defines the back pressure chamber 6 and changes a cross-sectional area of the orifice 51 (63, 64) when the circuit plate member 67 is brought into contact with the bottom portion 62 of the control plate member 45. More specifically, the cross-sectional area of the orifice 51 on a plane perpendicular to a fuel flow direction becomes from a first value, which is converted when the circuit board member 67 is separated from the bottom portion 62, to a second value, which is converted when the circuit board member 67 is brought into contact with the bottom portion 62 is changed.

A spring 69 is interposed between the switch plate member 67 and the needle 4 so that the switch plate member 67 is biased by the spring 69 in the reverse direction. The circuit board member 67 forms a first space 6a between the circuit board member 67 and the needle 4 . A rear end surface of the circuit board member 67 is in contact with a front end surface of the small-diameter portion 65, that is, the step portion of the cylindrical member 40 formed between the small-diameter portion 65 and the large-diameter portion 66.

A spring 70 is interposed between the needle 4 and the second plate member 15 so as to bias the needle 4 in the forward direction. Another spring 71 is further interposed between the control plate member 45 and the cylindrical member 40 to bias the control plate member 45 in the rearward direction and bias the cylindrical member 40 in the forward direction. The cylindrical member 40 is in contact with the needle 4 through the spring 71 so that the cylindrical member 40 is movable together with the needle 4. As shown in FIG.

A positional arrangement among the circuit board member 67, the control board member 45 and the cylindrical member 40 satisfies a relationship of "L1<L2", where "L1" is a first lift amount of the needle 4 with which the circuit board member 67 is brought into contact with the control board member 45 , while “L2” is a second lift amount of the needle 4 with which the cylindrical member 40 is brought into contact with the control plate member 45 as in FIG 8th will be shown.

In addition, when spring forces of the springs 70, 71, and 69 satisfy a relationship of "P1>P2>P3", the relationship of "L1<L2" can be satisfied for the position arrangement where both "P1", "P2" and "P3'' is a load for the springs 70, 71 and 69 in a state where the injection holes 9 are closed.

An inner seat portion 73 and an annular groove 74 are formed on a rear end surface of the control plate member 45 . The inner seat portion 73 is formed in an annular shape so as to surround an open end of the outflow passage 7 on the front end surface of the second plate member 15, and is in contact with an outer circumference of the open end of the outflow passage 7. The annular groove 74 is on an outer circumference of the inner seat portion 73 and receives the fuel pressure from the inflow passage 21 . The inner seat portion 73 and the axially extending portion 60 of the control plate member 45 have a relationship of “r1<r2”, where “r1” is a radius of an outer circle formed by the inner seat portion 73, while “r2” is a radius of an outer circle formed by the axially extending portion 60 .

According to the above structure, the fuel pressure can be applied from the inflow passage 21 to an inside of the control plate member 45 (an inside of the axially extending portion 60) when the outflow port 7 is closed and a differential pressure between the outflow port 7 and the back pressure chamber 6 is reduced . It is thereby possible to quickly move the control plate member 45 in the forward direction. In other words, the back pressure in the back pressure chamber 6 can be quickly increased to speed up a valve closing operation of the needle 4 .

Operation of the second embodiment

An operation of the injector 1 of the second embodiment will be described with reference to FIG 9A and 9B be explained.

In a period of time shortly after the needle 4 starts its rising movement, since the switching plate member 67 is not yet in contact with the bottom portion 62 of the axially extending portion 60 of the control plate member 45, the fuel flows via the orifice 51 composed of the first and the second through holes 63 and 64 consists of the back pressure chamber 6 (a second space 6b formed between the circuit board member 67 and the bottom portion 62) as shown in FIG 9A will be shown.

When the lift amount of the needle 4 is increased, the switch plate member 67 is moved up together with the needle 4, and then the switch plate member 67 is brought into contact with the bottom portion 62 of the control plate member 45 as shown in FIG 9B will be shown. In this situation, the second through hole 64 is closed by the circuit board member 67, while the first through hole 63 is continuous via the through hole 68 formed in the circuit board member 67 in communication with the back pressure chamber 6 (the first space 6a defined between the circuit board member 67 and the needle 4 is formed). In this state, the fuel flows out of the back pressure chamber 6 (the first space 6a) via the outflow port 51 composed of the first through hole 63. The first space 6a of the back pressure chamber 6 is defined by the circuit board member 67 and the rear end portion 4a of the needle 4. As shown in FIG. When the needle 4 is further moved in the reverse direction, the needle 4 is displaced with respect to the circuit board member 67.

As above, the circuit board member 67 changes a cross-sectional area of the orifice 51 depending on the lifting amount of the needle 4. More specifically, the cross-sectional area of the orifice 51 (the first through hole 63) in the case where the circuit board member 67 is brought into contact with the bottom portion 62 , smaller than the cross-sectional area of the outflow port 51 (the first and second through holes 63 and 64) in the case where the circuit board member 67 is separated from the bottom portion 62. As a result, an outflow amount of the fuel from the back pressure chamber 6 in the state where the circuit board member 67 is separated from the bottom portion 62 is larger than that in the state where the circuit board member 67 is brought into contact with the bottom portion 62. Accordingly, the needle 4 is operated in the second mode (the low speed mode) after the first mode (the high speed mode).

In the second embodiment, an outer diameter of the rear end surface of the needle 4 is larger than the outer diameter of the axially extending portion 60 (corresponding to the radius “r2”). Therefore, the lifting speed of the needle 4 in the second mode becomes even lower than that in the first mode.

As in 10 As shown, the first through hole 63 of the control plate member 45 and the through hole 68 of the switch plate member 67 are arranged coaxially with each other with respect to an axis line of the needle 4 . A cross-sectional area of the through hole 68 (a protruding Area on a plane perpendicular to the axial direction) is larger than that of the first through hole 63. The protruding area of the through hole 68 on the plane perpendicular to the axial direction does not overlap with a protruding area of the second through hole 64 on the plane perpendicular to the axial direction. The above relationship regarding the protruding portions for the through holes 63, 64 and 68 is not changed even if the circuit board member 67 is rotated about its central axis. Therefore, the rotation of the circuit board member 67 in the back pressure chamber 6 has no adverse effect on the lifting speed of the needle 4.

Advantages of the second embodiment

In the second embodiment, the cross-sectional area of the orifice 51 on the plane perpendicular to the fuel flow direction is changed from a first value to a second value, which is smaller than the first value.

When the cross-sectional area of the orifice 51 is the first value, the flow rate of the fuel from the back pressure chamber 6 per unit time is large, and the lifting speed of the needle 4 is high. On the other hand, as the cross-sectional area of the orifice 51 decreases (changes to the second value), the outflow amount of fuel from the back pressure chamber 6 per unit time decreases correspondingly, and thereby the lifting speed of the needle 4 decreases.

The needle 4 is first operated in the first mode (the high speed mode) and then in the second mode (the low speed mode).

The operation mode of the needle 4 is switched from the first mode to the second mode depending on the relative movement of the switching plate member 67 to the control plate member 45 in accordance with the upward movement of the needle 4.

Since the first mode is changed to the second mode when the circuit board member 67 is brought into contact with the bottom portion 62 of the control board member 45, a front end surface 62f of the bottom section 62 and a rear end surface 67r of the circuit board member 67 serve as the mode switching portion 55, as in FIG 8th will be shown.

Accordingly, in the second embodiment, it is possible to change the lifting speed of the needle 4 in the same manner as in the first embodiment. More specifically, it is possible to make the lifting speed in the first mode higher than that in the second mode.

In addition, since the first mode is changed to the second mode by the movement of the switching plate member 67 depending on the amount of lift of the needle 4, it is not necessary to provide an additional drive section. In other words, in order to change the lifting speed of the needle 4, it is not necessary to provide a plurality of driving sections.

As above, it is possible to provide the injector 1 capable of changing the stroke speed without providing the plurality of drive sections.

In the second embodiment, like the first embodiment, the needle 4 is first operated in the first mode with the higher lifting speed, and then in the second mode with the lower lifting speed. As a result of changing the lifting speed during a lifting stroke of the needle 4, not only the generation of the smoke can be reduced but also the engine output can be increased and the generation of the noise can be suppressed.

In the injector 1 of the second embodiment, the switching plate member 67 not only defines the back pressure chamber 6, but also changes the cross-sectional area of the orifice 51. More specifically, the cross-sectional area of the orifice 51 (the first and second through holes 63 and 64) in the first mode , in which the circuit board member 67 is separated from the bottom portion 62, is changed to the cross-sectional area of the orifice 51 (the first through hole 63) in the second mode by the mode switching portion 55 (62f and 67r).

As above, since the first mode is changed by the contact-or-non-contact state between the circuit board member 67 and the bottom portion 62, the structure of the mode switching portion 55 can be made simpler.

In the injector 1 of the second embodiment, the needle 4 is operated in the second mode after the first mode. This mode change is performed by changing the cross-sectional area of the orifice 51 in a direction that decreases the cross-sectional area. This is done by closing a part of the orifice 51 (that is, the second through hole 64) with the circuit board member 67. Accordingly, it is possible to make the structure of the injector simpler.

modifications

The present embodiment is not limited to the above embodiments, but can be further modified in various ways without departing from a spirit of the present disclosure.

(M1) In the first embodiment, the mode switching member 43 is formed in the cylindrical shape having the closed end and movably fitted to the rear end portion 4a of the needle 4. As shown in FIG.

However, the mode switching member 43 may be modified to be formed in a cylindrical shape without a closed end as shown in FIG 11A or 11B will be shown. According to a structure of the modification, it is possible to adjust a volume of the back pressure chamber 6 by a rear end portion of the mode switching member 43 . For example, it is possible to improve a response of the needle 4 by reducing the volume of the back pressure chamber 6.

With the modification included in each of the 11A and 11B As shown, the needle 4 has a small-diameter portion 75 and a large-diameter portion 76 on a front end side of the small-diameter portion 75, the small-diameter portion 75 being movably in contact with an inner peripheral surface of the mode switching member 43.

In the present modification, the large-diameter portion 76 in each of the 11A and 11B operatively brought into contact with the mode switching member 43 . More specifically, the needle 4 is moved in the reverse direction relative to the mode switching member 43 until the large-diameter portion 76 is brought into contact with the mode switching member 43 . On the other hand, after the large diameter portion 76 is brought into contact with the mode switching member 43, the mode switching member 43 is moved together with the needle 4 . Accordingly, a front end surface 43f of the mode switching member 43 and a rear end surface 76r of the large-diameter portion 76 serve as the mode switching portion 55.

(M2) In the first embodiment, the needle 4 is operated in the second mode (the low speed mode) after the first mode (the high speed mode).

However, according to another modification contained in 12A As shown, the needle 4 is first operated in the second mode (the low speed mode) and then in the first mode (the high speed mode).

In the modification made in 12A As shown, the rear end portion of the needle 4 has a small-diameter portion 78 and a large-diameter portion 79 on the rear end side of the small-diameter portion 78, a diameter of the large-diameter portion 79 being larger than that of the portion 78 small diameter.

The mode switching member 43 is movably fitted on an outer peripheral surface of the small-diameter portion 78 . The mode switching member 43 is biased in the reverse direction by a spring 80 so that the mode switching member 43 is brought into contact with an outer peripheral portion 81 of the large-diameter portion 79 . An annular projection 82 protruding inward is formed in the chamber formation member 40 .

In a period of time just after the needle 4 starts its raising motion, the needle 4 and the mode switching member 43 are moved together in the reverse direction. After the mode switching member 43 is brought into contact with the annular projection 82, the needle 4 is further moved in the reverse direction relative to the mode switching member 43, so that the pressure receiving surface area becomes smaller.

Accordingly, it is possible to operate the needle 4 first in the second mode (the low-speed mode) and then in the first mode (the high-speed mode), as in FIGS 12B and 12C will be shown. It is thereby possible to precisely control a fuel injection amount of a small amount.

In the present modification, a front end surface 82f of the annular projection 82 and the rear end surface 43r of the mode switching member 43 serve as the mode switching portion 55.

(M3) In the first embodiment, the mode switching component 43 is composed of one piece of parts.

However, as in a modification of 13A As shown, the mode switching component (43a and 43b) may be composed of a plurality of pieces of the parts. In the present modification, the rear end portion of the needle 4 has a small-diameter portion 84 and a large-diameter portion 85 on the rear end side of the small-diameter portion 84, a diameter of the large-diameter portion 85 being larger than that of the Small diameter section 84.

The mode switching member is composed of a first switching member 43a movably fitted to the small-diameter portion 84 and a second switching member 43b movably fitted to the large-diameter portion 85, the second switching member 43b having a rear end of the Section 85 covered with large diameter.

The first switching member 43a is movable relative to the small-diameter portion 84 and is biased by a spring 86 in the reverse direction so that the first switching member 43a contacts an outer peripheral portion 87 of the large-diameter portion 85 . A plurality of through holes 88 are formed in the outer peripheral portion 87 of the large-diameter portion 85 . An annular projection 89 protruding inward is formed in the chamber formation member 40 .

In a period of time just after the needle 4 starts lifting, since the first switching member 43a is moved together with the needle 4, the pressure-receiving surface area is large. When the first switching member 43a is then brought into contact with the annular projection 89, the needle 4 is further moved in the rearward direction relative to the first switching member 43a. As a result, the pressure receiving surface becomes smaller.

When the needle 4 is further raised and the needle 4 is brought into contact with the second switching member 43b, the needle 4 is moved in the reverse direction together with the second switching member 43b. As a result, the pressure receiving surface becomes larger again. As above, since the pressure-receiving surface is changed from a larger value to a smaller value and then from the smaller value to the larger value, the lifting speed of the needle 4 first becomes from a low speed to a high speed and then from changed from high speed to low speed as in 13B will be shown. The fuel injection rate changes as shown in 13C will be shown.

The through hole 88 functions as a fuel passage through which the fuel is supplied into a space formed between the first switching member 43 a and the large-diameter portion 85 .

(M4) In the second embodiment, the spring 70 is provided between the needle 4 and the second plate member 15. As shown in FIG.

However, as in 14A 1, according to a modification of the second embodiment, the needle 4 can be biased only by the spring 71 in the forward direction.

(M5) In addition, in the second embodiment, the inflow passage 21 is formed.

However, according to another modification of the second embodiment, as shown in FIG 14B 1, the inflow passage 21 can be eliminated if a rear end surface of the control plate member 45 is formed with a tapered surface 45t.

According to the present modification, since the fuel pressure of the high-pressure fuel passage 20 can be applied to the control plate member 45 as a force to press the same in the forward direction, it is not necessary to provide the inflow passage 21 of the second embodiment.

In the present modification, the inner seat portion 73 and the axially extending portion 60 of the control plate member 45 also have the relationship of "r1<r2", where "r1" is the radius of the outer circle of the inner seat portion 73, while "r2" is the radius of the outer circle of the axially extending portion 60 is. According to the above structure, since the fuel pressure can be applied from the high-pressure fuel passage 20 to the inside of the control plate member 45 (the inside of the axially extending portion 60), the control plate member 45 can be quickly moved in the forward direction.

(M6) In the second embodiment, in the bottom portion 62 of the control board member 45, two through holes (the first and second through holes 63 and 64) are formed, and in the circuit board member 67, a through hole 68 is formed.

However, according to a further modification of the second embodiment, as shown in FIGS 15A and 15B As shown, a through hole 90 extending in the axial direction may be formed in the bottom portion 62 while two through holes 91 and 92 extending in the axial direction may be formed in the circuit board member 67.

In the present modification, the through hole 90 and the through hole 91 are formed coaxially with each other with respect to the center axis of the needle 4 .

A cross-sectional area of the through hole 90 (a protruding portion on the plane perpendicular to the axial direction) is larger than that of the through hole 91. The protruding portion of the through hole 90 on the plane perpendicular to the axial direction does not overlap either a protruding portion of the through hole 92 on the plane perpendicular to the axial direction. The above relationship regarding the protruding portions for the through holes 90, 91 and 92 is not changed even if the circuit board member 67 is rotated about its central axis.

In addition, the projected areas for the through holes 90, 91 and 92 have a relationship of “S1<(S2+S3)” and a relationship of “S1>S2”, where “S1” is an area for the projected area of the through hole 90 , “S2” is a range for the protruding portion of the through hole 91, and “S3” is a range for the protruding portion of the through hole 92.

According to the above structure, in the present modification, the same advantages as in the second embodiment can be obtained.

(M7) Moreover, the second embodiment can be modified as shown in FIGS 16A and 16B will be shown.

In the present modification, a through hole 94 extending in the axial direction is formed in the bottom portion 62, and a through hole 95 extending in the axial direction is formed in the circuit board member 67, the through hole 94 and the through hole 95 are offset from each other.

In the present embodiment, a protruding portion of the through hole 94 on the plane perpendicular to the axial direction and a protruding portion of the through hole 95 on the plane perpendicular to the axial direction partially overlap each other. The above relationship regarding the protruding portions for the through holes 94 and 95 is not changed even if the circuit board member 67 is rotated about its central axis. An overlapping area between the through holes 94 and 95 is smaller than the protruding area of the through hole 94.

(M8) The second embodiment can be further modified as in 17A will be shown.

In the modification made in 17A As shown, an outer cylindrical member 96 is provided on an outside of the chamber formation member 40 . An inner peripheral surface of the outer cylindrical member 96 is movably in contact with an outer peripheral surface of the chamber formation member 40. The outer cylindrical member 96 is biased by a spring 97 in the rearward direction so as to be in contact with the second plate member 15. At this time, a space S surrounded by the outer cylindrical member 96, the second plate member 15 and the chamber forming member 40 is formed.

According to the above structure, it is possible to adjust the volume of the space S. The inflow amount of fuel flowing into the space S from the inflow passage 21 can also be adjustable by the restricted portion formed in the inflow passage 21 . As a result, it is possible to adjust the moving speed of the needle 4 in the injection hole closing direction.

A rear end surface of the outer cylindrical member 96 is formed with a tapered surface having an inwardly recessed shape. When the lift amount of the needle 4 is increased and thereby a fuel pressure in the space S is increased, the outer cylindrical member 96 is depressed in the forward direction so that the fuel in the space S can flow out.

Alternatively, as in 17B As shown, a small gap may be formed between the axially extending portion 60 and the chamber formation member 40 in the radial direction, the small gap having such a clearance that would not adversely affect the function of the orifice 51 . According to such a configuration, it is possible to secure an escape route for the fuel in the space S, thereby preventing the fuel pressure in the space S from being excessively increased.

(M9) The second embodiment can be further modified as in 18A will be shown.

When modifying 18A are the control plate member 45 and the chamber formation member 40 is integrally formed as an integral member so as to reduce a number of parts for the injector 1.

Additionally, as in 18B is shown, the outer cylindrical member 96 further in the modification of FIG 18A be provided, like the modification contained in 17A will be shown.

Claims (10)

Fuel injector for an internal combustion engine, comprising; a needle (4) serving as a valve member for opening and closing an injection hole (9) for injecting fuel into a combustion chamber of the internal combustion engine; a needle body (5) having a cylindrical shape for movably accommodating the needle (4), the injection hole (9) being formed in the needle body (5); a back pressure chamber (6) for applying a back pressure of the fuel to the needle (4) in an injection hole closing direction; an outflow passage (7) for discharging the fuel from the back pressure chamber (6); and a drive section (8) for opening or closing the outflow passage (7) based on a control signal from a control unit (2) to thereby increase the back pressure for controlling an opening or closing operation of the injection hole (9) by the needle (4), or to lower, wherein the driving section (8) increases the back pressure so that a contacting section (10) at the front end of the needle (4) is moved to a seating position (12) so as to sit on a seating surface (11) which is on an inner surface of the needle body (5) is formed to thereby close the injection hole (9), wherein the driving section (8) decreases the back pressure so that the contacting section (10) at the front end of the needle (4) is lifted from the seated position (12) so as to increase a lifting amount of the needle (4) in its axial direction to thereby opening the injection hole (9) with the amount of lift of the needle (4) corresponding to a distance between the front-end contacting portion (10) and the seating position (12), wherein the needle (4) is operated in either a first mode at a first stroke speed or a second mode at a second stroke speed, the second stroke speed being lower than the first stroke speed, and the stroke speed corresponding to an increase in the amount of stroke of the needle (4) per time unit corresponds to wherein the fuel injection valve further comprises a mode switching portion (55) for switching the first mode to the second mode or vice versa by a lifting motion of the needle (4) in a lifting stroke of the needle (4), and wherein a first protruding area of a pressure-receiving surface of the needle (4) on which the back pressure is applied in the first mode is smaller than a second protruding area of the pressure-receiving surface of the needle (4) on which the back pressure is applied in the second mode, wherein the protruding portion corresponds to a portion on a plane perpendicular to the axial direction of the needle (4), wherein an inflow passage (21) is formed so that the fuel is supplied from the inflow passage (21) into the back pressure chamber (6). , a control plate member (45) is formed to partially define the back pressure chamber (6), and the control plate member (45) opens the inflow port (21) when the outflow port (7) is closed, while the control plate member (45) closes the inflow port (21) when the outflow port (7) is opened, and a restricted portion (51) is formed in the control plate member (45) to restrict an outflow amount of the fuel that outflows from the back pressure chamber (6) to the outflow passage (7) when the outflow passage (7) is opened. Fuel injector according to claim 1 , further comprising; a mode switching member (43, 43a, 43b) to partially define the back pressure chamber (6), wherein in the first mode the needle (4) is moved in a reverse direction relative to the mode switching member (43, 43a) while the mode switching member (43 , 43b) is moved in the reverse direction together with the needle (4) in the second mode, so that the first mode is switched to the second mode. Fuel injector according to claim 2 wherein the back pressure chamber (6) is provided at a rear end side of the needle (4), the mode switching member (43, 43a, 43b) is formed in a cylindrical shape and thus movably fitted to a rear end portion (4a) of the needle (4). that an inner peripheral surface of the mode switching member (43, 43a, 43b) is movably in contact with an outer peripheral surface of the rear end portion (4a), an outer peripheral surface of the mode switching member (43, 43a, 43b) movably with an inner peripheral surface of the chamber forming member (40). a cylindrical shape is in contact, wherein the chamber forming member (40) partially defines the back pressure chamber (6). Fuel injector according to claim 1 wherein the control plate member (45) is biased by a spring (46) in a direction to close the inflow passage (21). Fuel injector for an internal combustion engine, comprising; a needle (4) serving as a valve member for opening and closing an injection hole (9) for injecting fuel into a combustion chamber of the internal combustion engine; a needle body (5) having a cylindrical shape for movably accommodating the needle (4), the injection hole (9) being formed in the needle body (5); a back pressure chamber (6) for applying a back pressure of the fuel to the needle (4) in an injection hole closing direction; an outflow passage (7) for discharging the fuel from the back pressure chamber (6); and a drive section (8) for opening or closing the outflow passage (7) based on a control signal from a control unit (2) to thereby increase the back pressure for controlling an opening or closing operation of the injection hole (9) by the needle (4), or to lower, wherein the driving section (8) increases the back pressure so that a contacting section (10) at the front end of the needle (4) is moved to a seating position (12) so as to sit on a seating surface (11) which is on an inner surface of the needle body (5) is formed to thereby close the injection hole (9), wherein the driving section (8) decreases the back pressure so that the contacting section (10) at the front end of the needle (4) is lifted from the seated position (12) so as to increase a lifting amount of the needle (4) in its axial direction to thereby opening the injection hole (9) with the amount of lift of the needle (4) corresponding to a distance between the front-end contacting portion (10) and the seating position (12), wherein the needle (4) is operated in a first mode at a first stroke speed and in a second mode at a second stroke speed, the second stroke speed being lower than the first stroke speed, and the stroke speed corresponding to an increase in the amount of stroke of the needle (4) per time unit corresponds to wherein the fuel injector further comprises; a mode switching section (55) for switching the first mode to the second mode by a lifting movement of the needle (4) in a lifting stroke of the needle (4); and a restricted portion (51, 63, 64, 90, 91, 92, 94, 95) for restricting an outflow amount of the fuel from the back pressure chamber (6) to the outflow passage (7), wherein a cross-sectional area of the restricted portion (51, 63, 64, 90, 91, 92, 94, 95) on a plane perpendicular to a flow direction of the fuel is larger than that of the restricted portion (63, 91, 94, 95) in the second mode. Fuel injector according to claim 5 , further comprising; a control plate member (45) to partially define the back pressure chamber (6); and a mode switching member (67) to partially define the back pressure chamber (6), the restricted portion (51, 63, 64, 90, 91, 92, 94, 95) being in the control plate member (45) and/or in the mode switching member (67) is formed; and wherein the mode switching member (67) is movable relative to the control plate member (45) when the needle (4) is raised such that the mode switching member (67) is separated from the control plate member (45) in the first mode or the mode switching member (67 ) is brought into contact with the control plate member (45) in the second mode to change the cross-sectional area of the restricted portion (51, 63, 64, 90, 91, 92, 94, 95). Fuel injector according to claim 6 , further comprising; an inflow port (21) for supplying fuel into the back pressure chamber (6), wherein the control plate member (45) opens the inflow port (21) when the outflow port (7) is closed while the control plate member (45) closes the inflow port (21). , when the outflow passage (7) is opened. Fuel injector according to claim 7 wherein the control plate member (45) is biased by a spring (71) in a direction to close the inflow passage (21). Fuel injector according to claim 7 or 8th wherein the back pressure chamber (6) is provided on a rear end side of the needle (4), a chamber formation member (40) having a cylindrical shape and partially defining the back pressure chamber (6), the chamber formation member (40) being such movably fitted to a rear end portion (4a) of the needle (4) such that an inner peripheral surface of the chamber formation member (40) is movably contacted with an outer peripheral surface of the rear end portion (4a), the mode switching member (67) thus moving lich housed in the chamber formation member (40) that an outer peripheral surface of the mode switching member (67) is movably in contact with the inner peripheral surface of the chamber formation member (40), the mode switching member (67) between the mode switching member (67) and a rear end of the needle (4) forms a space (6a) as a part of the back pressure chamber (6), wherein the mode switching member (67) has a through hole (68, 91, 92, 95) through which the space (6a) in communicating with the outflow passage (7), and wherein the cross-sectional area of the restricted portion (51, 63, 64, 90, 91, 92, 94, 95) is changed when the mode switching member (67) in accordance with a lifting motion of the needle ( 4) is brought into contact with the control plate assembly (45). Fuel injection valve according to one of Claims 5 until 9 , wherein the needle (4) is operated in the second mode after the first mode.

Images