DE112019005294T5 - Fuel injection system - Google Patents

Abstract

An injector (20) includes: a control chamber (36, 46) configured to receive high pressure fuel from a pressure manifold (11); a needle valve (31) configured to open and close an injection hole (34) in response to fuel pressure in the control chamber; a fuel drain passage (58) configured to drain the fuel of the control chamber to an outside of the injector; and a pressure control valve (52) configured to enable and break communication between the control chamber and the fuel drain passage, thereby adjusting the fuel pressure in the control chamber without moving the needle valve. A fuel injection system includes a return pipe (65, 65a) connecting the fuel drain passage and a portion of a low pressure fuel passage located on a downstream side of a fuel tank and a downstream side of a fuel filter. The fuel injection system includes a delivery control unit configured to operate the pressure control valve such that the pressure control valve enables communication between the control chamber and the fuel drain passage in a state where the needle valve is in a valve closing position, and thereby the fuel of the control chamber is supplied to the fuel filter through the return pipe without the needle valve being moved from the valve closing position.

Description

Cross reference to similar application

This application is based on Japanese Patent Application No. 2018-199 581 , filed October 23, 2018, which is incorporated herein by reference.

Technical area

The present disclosure relates to a fuel injection system.

State of the art

In a fuel injection system of a diesel engine, diesel fuel (light oil) is used as fuel. In a low temperature environment, a phenomenon called gelling of diesel fuel occurs, and the fuel containing the deposited paraffin (deposit) is filtered through a fuel filter that is in a Fuel supply path is installed. On the other hand, if the amount of paraffin deposited on the fuel filter increases or increases, the fuel filter may become clogged. If the fuel filter becomes clogged, there is a problem that the amount of fuel supplied to the engine becomes insufficient, resulting in a reduction in engine performance. In view of the disadvantage described above, it has been proposed that a fuel heater is provided on the fuel filter, and the fuel to be passed through the fuel filter is heated by the fuel heater (for example, see Patent Literature 1).

List of references

Patent literature

Patent Literature 1: JP 2014-51920 A

Summary of the invention

In the case where the heater is provided on the fuel filter to heat the fuel, there is a problem that the heater consumes more power to dissolve the paraffin of the fuel or a new heater system needs to be installed.

The present disclosure is made in view of the above disadvantages, and it is an object of the present disclosure to provide a fuel injection system that can restrict clogging of a fuel filter caused by gelling of a fuel without using a heater for heating the fuel is needed.

In order to achieve the above object, the following measures are adopted.

• einen Kraftstofffilter, welcher in einem Niederdruckkraftstoffdurchlass installiert ist, der einen Kraftstofftank und eine Hochdruckpumpe verbindet, wobei der Kraftstofffilter dazu konfiguriert ist, Kraftstoff zu filtern;
• ein Sammelrohr, welches dazu konfiguriert ist, ausgehend von der Hochdruckpumpe den Kraftstoff aufzunehmen und den Kraftstoff in einem Hochdruckzustand anzusammeln; und
• ein Einspritzventil, welches dazu konfiguriert ist, einen Hochdruckkraftstoff des Sammelrohrs direkt in einen Zylinder einer Maschine mit interner Verbrennung einzuspritzen, wobei:
  • der Injektor Folgendes beinhaltet:
    • eine Steuerkammer, die dazu konfiguriert ist, ausgehend von dem Sammelrohr den Hochdruckkraftstoff aufzunehmen;
    • ein Nadelventil, das dazu konfiguriert ist, sich als Reaktion auf einen Kraftstoffdruck in der Steuerkammer zwischen einer Ventilöffnungsposition und einer Ventilschließposition hin und her zu bewegen und dadurch ein Einspritzloch zu öffnen und schließen;
    • einen Kraftstoffablaufdurchlass, der dazu konfiguriert ist, den Kraftstoff der Steuerkammer zu einer Außenseite des Injektors abzulassen; und
    • ein Druck-Steuerventil, das dazu konfiguriert ist, eine Verbindung zwischen der Steuerkammer und dem Kraftstoffablaufdurchlass zu ermöglichen und zu unterbrechen, und dadurch den Kraftstoffdruck in der Steuerkammer anzupassen, ohne das Nadelventil zu bewegen;
    • ein Rückführrohr vorgesehen ist, um den Kraftstoffablaufdurchlass und einen Abschnitt des Niederdruckkraftstoffdurchlasses zu verbinden, wobei sich der Abschnitt des Niederdruckkraftstoffdurchlasses auf einer stromabwärtigen Seite des Kraftstofftanks und einer stromabwärtigen Seite des Kraftstofffilters befindet; und
    • das Kraftstoffeinspritzsystem ferner eine Zufuhr-Steuereinheit umfasst, die dazu konfiguriert ist, das Druck-Steuerventil derart zu betreiben, dass das Druck-Steuerventil die Verbindung zwischen der Steuerkammer und dem Kraftstoffablaufdurchlass in einem Zustand ermöglicht, in welchem das Nadelventil in der Ventilschließposition vorliegt, und dadurch wird dem Kraftstofffilter durch das Rückführrohr der Kraftstoff der Steuerkammer zugeführt, ohne dass das Nadelventil von der Ventilschließposition bewegt wird.

In accordance with the present disclosure, there is provided a fuel injection system that includes:

• a fuel filter installed in a low pressure fuel passage connecting a fuel tank and a high pressure pump, the fuel filter configured to filter fuel;
• a manifold configured to receive the fuel from the high pressure pump and to accumulate the fuel in a high pressure state; and
• an injector configured to inject high pressure manifold fuel directly into a cylinder of an internal combustion engine, wherein:
  • the injector includes:
    • a control chamber configured to receive the high pressure fuel from the manifold;
    • a needle valve configured to reciprocate between a valve opening position and a valve closing position in response to fuel pressure in the control chamber, thereby opening and closing an injection hole;
    • a fuel drain passage configured to drain the fuel of the control chamber to an outside of the injector; and
    • a pressure control valve configured to enable and disable communication between the control chamber and the fuel drain passage, thereby adjusting the fuel pressure in the control chamber without moving the needle valve;
    • a return pipe is provided to connect the fuel drain passage and a portion of the low pressure fuel passage, the portion of the low pressure fuel passage being on a downstream side of the fuel tank and a downstream side of the fuel filter; and
    • the fuel injection system further comprises a delivery control unit configured to operate the pressure control valve such that the pressure control valve communicates between the control chamber and the Allows fuel drain passage in a state in which the needle valve is in the valve closing position, and thereby the fuel filter is supplied with the fuel of the control chamber through the return pipe without moving the needle valve from the valve closing position.

The fuel contained in the control chamber of the injector is acted upon by the high pressure pump and thus has the high pressure and the high temperature. In addition, the direct injection injector is located in the cylinder, and the fuel in the control chamber of the injector is heated to the high temperature by the heat of combustion of the internal combustion engine. In view of this point, the fuel filter is heated by supplying the fuel to the fuel filter from the control chamber of the injector. According to this configuration, the fuel filter can be heated with the high temperature fuel supplied from the injector, so that the accumulation of the fuel adhering to the fuel filter can be dissolved, and the generation of the accumulation of the fuel can be restricted. In addition, the clogging of the fuel filter with the accumulation of the fuel, which is caused by the fouling or the fouling of the fuel, can be restricted without the heating device for heating the fuel filter being provided.

Figure list

• 1 ein Diagramm, welches eine schematische Struktur eines Kraftstoffeinspritzsystems zeigt;
• 2 ein Diagramm, welches beispielhafte Einspritzratenmuster eines Injektors zeigt;
• 3 ein Diagramm, welches den Injektor zu einer Ventilschließzeit zeigt;
• 4 ein Diagramm, das einen Betrieb des Injektors in einem Ventilöffnungsmodus mit hoher Geschwindigkeit veranschaulicht;
• 5 ein Diagramm, das einen Betrieb zu einer Zeit veranschaulicht, zu welcher von dem Ventilöffnungsmodus mit hoher Geschwindigkeit zu dem Ventilschließmodus mit hoher Geschwindigkeit geschaltet wird;
• 6 ein Diagramm, das einen Betrieb des Injektors in dem Ventilschließmodus mit hoher Geschwindigkeit veranschaulicht;
• 7 ein Diagramm, das einen Betrieb des Injektors in einem Ventilöffnungsmodus mit niedriger Geschwindigkeit veranschaulicht;
• 8 ein Diagramm, das einen Betrieb des Injektors zu einer Zeit veranschaulicht, zu welcher von dem Ventilöffnungsmodus mit niedriger Geschwindigkeit zu dem Ventilschließmodus mit niedriger Geschwindigkeit geschaltet wird;
• 9 ein Diagramm, das einen Betrieb des Injektors in dem Ventilschließmodus mit niedriger Geschwindigkeit veranschaulicht;
• 10 ein Diagramm, das einen Druckreduzierungsbetrieb durch ein zweites An-Aus-Ventil zeigt;
• 11 ein Diagramm, das einen Betrieb des Injektors und eine Strömung eines Kraftstoffs während einer Filtertemperatur-Erhöhungssteuerung zeigt;
• 12 ein Flussdiagramm, das ein Betriebsverfahren der Filtertemperatur-Erhöhungssteuerung zeigt;
• 13 ein Flussdiagramm, das ein Betriebsverfahren zum Einstellen der Anzahl an Ziel-Zylindern und (eine) Zylinder-ID-Nummer(n) des/der jeweiligen Ziel-Zylinder(s) einstellt, ausgehend von welchem/welchen der Kraftstoff in einer Dauer rückgeführt wird, in welcher die Temperaturerhöhung möglich ist;
• 14 ein Zeitdiagramm, das den Betrieb der Filtertemperatur-Erhöhungssteuerung im Vergleich zu einer normalen Steuerung zeigt, das einen Zustand eines ersten An-/Aus-Ventils, einen Zustand des zweiten An-/Aus-Ventils und einen Zustand eines Nachlaufventils schematisch zeigt;
• 15 ein Zeitdiagramm, das den Betrieb in dem Ventilöffnungsmodus mit niedriger Geschwindigkeit und dem Ventilschließmodus mit hoher Geschwindigkeit zeigt;
• 16 ein Zeitdiagramm, das einen Betrieb zu der Zeit zeigt, zu welcher von dem Ventilöffnungsmodus mit niedriger Geschwindigkeit und dem Ventilschließmodus mit hoher Geschwindigkeit zu dem Ventilschließmodus mit niedriger Geschwindigkeit geschaltet wird;
• 17 ein Zeitdiagramm, das einen Betrieb des Injektors in einem Fall zeigt, bei welchem das zweite An-/Aus-Ventil vor der Zeit geöffnet wird, zu welcher die Kraftstoffeinspritzung ausgeführt wird;
• 18 ein Zeitdiagramm in einem Fall, bei welchem die Filtertemperatur-Erhöhungssteuerung durchgeführt wird, indem eine Dauer, in der die Filtertemperatur-Erhöhungssteuerung ausgeführt wird, mit einer Kraftstoffeinspritzdauer überlappt.

The present disclosure, along with additional objects, features, and advantages thereof, will be best understood from the following description in view of the accompanying drawings. It shows / it shows:

• 1 Fig. 3 is a diagram showing a schematic structure of a fuel injection system;
• 2 a diagram showing exemplary injection rate patterns of an injector;
• 3 a diagram showing the injector at a valve closing time;
• 4th Fig. 13 is a diagram illustrating an operation of the injector in a high speed valve opening mode;
• 5 Fig. 13 is a diagram illustrating an operation at a time when the valve opening mode at high speed is switched to the valve closing mode at high speed;
• 6th Fig. 13 is a diagram illustrating an operation of the injector in the valve closing mode at high speed;
• 7th Fig. 3 is a diagram illustrating an operation of the injector in a low speed valve opening mode;
• 8th Fig. 13 is a diagram illustrating an operation of the injector at a time when switching from the low-speed valve opening mode to the low-speed valve closing mode;
• 9 Fig. 3 is a diagram illustrating an operation of the injector in the low speed valve closing mode;
• 10 a diagram showing a pressure reducing operation by a second on-off valve;
• 11 Fig. 13 is a diagram showing an operation of the injector and a flow of fuel during filter temperature increase control;
• 12th Fig. 13 is a flowchart showing an operation procedure of the filter temperature increase control;
• 13th Fig. 13 is a flowchart setting up an operation method for setting the number of target cylinders and cylinder ID number (s) of the respective target cylinder (s) from which the fuel is returned in a period in which the temperature increase is possible;
• 14th Fig. 13 is a time chart showing the operation of the filter temperature increase control in comparison with a normal control, schematically showing a state of a first on / off valve, a state of the second on / off valve and a state of a follow-up valve;
• 15th Fig. 13 is a timing chart showing the operation in the low-speed valve opening mode and the high-speed valve closing mode;
• 16 Fig. 13 is a timing chart showing an operation at the time of switching from the low speed valve opening mode and the high speed valve closing mode to the low speed valve closing mode;
• 17th Fig. 13 is a time chart showing an operation of the injector in a case where the second on / off valve is opened before the time when fuel injection is carried out;
• 18th a time chart in a case where the filter temperature Increasing control is performed by overlapping a period in which the filter temperature increasing control is executed with a fuel injection period.

Description of the embodiments

Embodiments will be described below with reference to the drawings. In each of the following embodiments, parts that are the same or the same as each other are indicated by the same reference characters in the drawings, and the description thereof is adopted for the parts with the same reference characters.

The present embodiment is implemented in a fuel injection system applied to an on-vehicle multi-cylinder diesel engine which is an internal combustion engine. In this fuel injection system, the fuel injection of the engine is mainly controlled by an electronic control unit (hereinafter referred to as an ECU). As in 1 shown includes the fuel injection system 10 a fuel tank 61 , a high pressure pump 62 , a common rail 11 , a plurality of injectors 20th , and the ECU 90 .

In 1 are a fuel temperature sensor 71 , which is a temperature of the fuel (diesel fuel) in the fuel tank 61 sensed, and a fuel property sensor 72 which senses fuel properties (density and kinetic viscosity of the fuel) on the fuel tank 61 Installed. The fuel tank 61 is through a low pressure fuel pipe 63 with the high pressure pump 62 connected. The high pressure pump 62 is a mechanical pump that repeatedly draws and discharges fuel by moving a plunger in synchronism with rotation of an output shaft (crankshaft) of the engine 70 is moved back and forth. In the present embodiment, the high pressure pump is 62 of the so-called "one pump per fuel injection type" in which the high pressure pump 62 once per fuel injection, which is necessary for one combustion of the machine 70 is set, the fuel pumps ie promotes. The fuel coming from the fuel tank 61 into the high pressure pump 62 is introduced is by operating the high pressure pump 62 applied to a high pressure or high pressure, and this high pressure fuel is starting from the high pressure pump 62 discharged.

A fuel filter 66 filtering the fuel is in the low pressure fuel pipe 63 installed in a location that is on the downstream side of the fuel tank 61 is arranged and on the upstream side of the high pressure pump 62 is arranged. The fuel filter 66 removes foreign objects contained in the fuel. The common rail 11 is through a fuel pipe 64 with the downstream side of the high pressure pump 62 connected. The high-pressure fuel that comes from the high-pressure pump 62 is pumped becomes in the high pressure state in the interior of the common rail 11 held. In this system, the common rail 11 no pressure reducing valve, which reduces the fuel pressure (rail pressure) in the common rail 11 reduced.

The injectors 20th are through high pressure pipes 12th with the common rail 11 connected. Each of the injectors 20th is of the direct injection type, which puts the fuel directly into a corresponding combustion chamber of the engine 70 injects, and the injectors 20th are each installed on a plurality of cylinders (four cylinders in the present embodiment). 1 only shows the injector 20th of one of the cylinders, and the illustration of the injector 20th is omitted from the rest of the cylinders.

The ECU 90 is a microcomputer that includes a CPU, a ROM, a RAM, a drive circuit, an input / output interface, and the like. In addition to the measurement signals based on the fuel temperature sensor 71 and the fuel property sensor 72 described above are received by the ECU 90 in addition, measurement signals from various other sensors, such as a crank angle sensor for sensing a rotational speed of the machine 70 and an accelerator pedal sensor for sensing an operation amount of an accelerator pedal. The ECU 90 determines the optimal fuel injection amount and the optimal injection timing based on engine operation information such as the engine rotation speed and the amount of depression of the accelerator pedal, and then the ECU outputs 90 an injection control signal, which corresponds to the determined optimum fuel injection quantity and the determined optimum injection time, to the injector 20th out. Therefore, the fuel injection of the injector 20th into the combustion chamber of the machine 70 controlled at each of the cylinders. The ECU also controls 90 the operation of the high pressure pump 62 based on the current machine operating status. The ECU 90 functions as an injection control unit and a drive control unit.

Next is the structure of the injector 20th will be described in detail. The injector 20th includes first through fourth main bodies 21-24 , and the first through fourth main bodies 21-24 form an injector main body. The first through fourth main bodies 21-24 are in this order in an axial direction of the injector 20th arranged. The injector 20th injects the fuel, which the first main body 21 starting from the common rail 11 through a plurality of injection holes 34 supplied to the fourth main body 24 are trained. In the following description, the axial direction of the injector 20th can be referred to as a top-down direction. In addition, becomes a direction toward the first main body 21 in the injector 20th may be referred to as an upward direction, and a direction toward the fourth main body 24 in the injector 20th will be referred to as a downward direction.

A first high pressure passage 13th and a low pressure chamber 57 are on the first main body 21 educated. The first high pressure passage 13th extends along the first main body 21 , the second main body 22nd and the third main body 23 and penetrates through the first through third main bodies 21-23 . An end portion of the first high pressure passage 13th which is opposite to the second main body 22nd is arranged, stands with the corresponding high pressure pipe 12th in connection. Hence the first high pressure passage 13th through the high pressure pipe 12th the high pressure fuel of the common rail 11 fed. A fuel temperature sensor 73 which is the temperature of the fuel in the first high pressure passage 13th sensed is at the first high pressure passage 13th Installed. A measurement signal from the fuel temperature sensor 73 gets into the ECU 90 entered.

The low pressure chamber 57 is on a boundary between the first main body 21 and the second main body 22nd in the first main body 21 formed by a surface of the first main body 21 which the second main body 22nd is cut out in the upward direction. The high pressure fuel of the first high pressure passage 13th is through the second main body 22nd , the third main body 23 and the fourth main body 24 and the low pressure chamber 57 takes in the fuel, the pressure of which is reduced through this line. The low pressure chamber 57 is through a low pressure passage 58 with a return pipe 65 and is also connected to the fuel tank 61 connected. Therefore, a portion of the high pressure fuel supplied to the injector 20th is supplied through the return pipe 65 starting from the low pressure chamber 57 to the fuel tank 61 returned. A plurality of on / off valves 50 which control an injection state of the fuel starting from the injector 20th is injected is in the low pressure chamber 57 Installed. The low pressure passage corresponds to a fuel drain passage.

A second high pressure passage 14th , an intermediate chamber 26th , a first passage 25th and a second passage 27 are in the second main body 22nd educated. The second high pressure passage 14th is a branch passage that from the first high pressure passage 13th branches off, and is a fuel passage through which starting from the common rail 11 the high pressure fuel is supplied. A pressure load restraining orifice 14a is in the second high pressure passage 14th educated. The pressure load restriction mouth 14a restricts the flow amount of fuel in the second high pressure passage 14th is directed. At the second high pressure passage 14th is an annular chamber 14b at an end portion of the second high pressure passage 14th formed, which opposite the first high pressure passage 13th is arranged. The annular chamber 14b is a fuel passage portion that is formed in an annular shape and at a boundary between the second main body 22nd and the third main body 23 in the second main body 22nd is trained. The high pressure fuel is passed through the second high pressure passage 14th starting from the first high pressure passage 13th into the annular chamber 14b introduced.

The intermediate chamber 26th is a chamber formed in a cylindrical shape and at the boundary between the second main body 22nd and the third main body 23 is trained. The first passage 25th extends in the axial direction (the top-down direction) of the injector 20th on the inside of the second main body 22nd and penetrates through the second main body 22nd . An end portion of the first passage 25th stands with the low pressure chamber 57 in communication, and the other end portion of the first passage 25th stands with the intermediate chamber 26th in connection. Hence the intermediate chamber 26th through the first passage 25th with the low pressure chamber 57 in connection.

The second passage 27 is on the inside of the second main body 22nd and extends in the same direction (top-to-bottom direction) as the first passage 25th . The second passage 27 thus extends through the second main body 22nd that an end portion of the second passage 27 with the low pressure chamber 57 communicates, and the other end portion of the second passage 27 with the first control chamber 46 of the third main body 23 communicates. A pressure relief restriction orifice 27a is in the second passage 27 formed at a location adjacent to the first main body 21 is arranged. The pressure relief restriction mouth 27a restricts the flow amount of fuel entering the second passage 27 is directed.

The first control chamber 46 and a communication passage 47 are in the third main body 23 educated. The first control chamber 46 is a chamber contained in the injector main body is formed by starting from a surface of the third main body 23 which the second main body 22nd is cut out in the downward direction. The first control chamber 46 stands with the annular chamber 14b in connection. The high pressure fuel becomes the first control chamber 46 starting from the first high pressure passage 13th through the second high pressure passage 14th fed.

A follow-up valve 41 which is in the axial direction (the top-to-bottom direction) of the injector 20th can be moved is in the first control chamber 46 Installed. The follow-up valve 41 is shaped in a cylindrical shape and has a third passage 42 on, which is at a center point of the follow-up valve 41 and is located in the axial direction through the follow-up valve 41 extends. An opening of the third passage 42 which is on the side of the second main body 22nd is to the intermediate chamber 26th opened, and another opening of the third passage 42 which is on the side of the fourth main body 24 is to the inside of the first control chamber 46 open. A pressure relief restriction orifice 42a is in the third passage 42 educated. The pressure relief restriction mouth 42a restricts the amount of flow of fuel flowing into the third passage 42 is directed.

A feather 45 , which is the follow-up valve 41 in the direction (upward direction) toward the second main body 22nd preloaded, is on the follow-up valve 41 Installed. The follow-up valve 41 is caused by the upward force created by the fuel pressure in the first control chamber 46 and the biasing force of the spring 45 is exerted, biased so that this is the lower surface of the second main body 22nd contacted. In this contact state, the follow-up valve interrupts 41 the connection between the annular chamber 14b and the first control chamber 46 , and the intermediate chamber 26th stands through the third passage 42 with the first control chamber 46 in connection. In this state, the fuel can be in the first control chamber 46 through the third passage 42 , the intermediate chamber 26th and the first passage 25th into the low pressure chamber 57 stream.

In the state in which the follow-up valve 41 the lower surface of the second main body 22nd contacted when a sum of the upward force exerted by the fuel pressure in the first control chamber 46 is exercised, as well as the preload force of the spring 45 due to a reduction in fuel pressure in the first control chamber 46 becomes smaller than the downward force exerted by the fuel pressure in the annular chamber 14b and the fuel pressure in the intermediate chamber 26th is exercised, the follow-up valve becomes 41 displaced in a direction from the lower surface of the second main body 22nd runs away. Hence the intermediate chamber 26th with the first control chamber 46 in connection without passing this through the third passage 42 runs, and the annular chamber 14b stands with the first control chamber 46 in connection.

The second passage 27 sets the low pressure chamber 57 directly to the first control chamber 46 in connection. More precisely, there is the first control chamber 46 regardless of the position (stroke state) of the follow-up valve 41 through the second passage 27 with the low pressure chamber 57 in connection. Also is the communication passage 47 , which is based on the first control chamber 46 to the fourth main body 24 extends in the third main body 23 educated. A restriction mouth 47a is in the communication passage 47 is formed and restricts the flow amount of the fuel flowing in the communication passage 47 is directed.

The fourth main body 24 has a cylinder 35 , a needle valve 31 , a high pressure chamber 33 and a second control chamber 36 on. A distal end portion of the fourth main body 24 shows the injection holes 34 for injecting the fuel to the outside. The needle valve 31 is in a way on an inside of the cylinder 35 added showing a reciprocating motion of the needle valve 31 in the top-down direction. A feather 32 showing the needle valve 31 biasing is on an upper surface of the needle valve 31 Installed.

The high pressure chamber 33 is located in the middle of a passage, which is the first high pressure passage 13th and the injection holes 34 contacts. A distal end portion of the needle valve 31 is on the inside of the high pressure chamber 33 placed. The second control chamber 36 is located on one side (upper side of the needle valve 31 ), which is opposite the injection holes 34 is arranged in the interior of the cylinder 35 . The second control chamber 36 stands through the connecting passage 47 with the first control chamber 46 in connection. Hence becomes the second control chamber 36 starting from the first high pressure passage 13th through the first control chamber 46 and the communication passage 47 the high pressure fuel is supplied. The fuel pressure on the inside of the second control chamber 36 and the biasing force of the spring 32 attached to the needle valve 31 installed on the needle valve 31 exercised so that the needle valve 31 in a closing direction (downward direction) to close the injection holes 34 is moved, and this is the injector 20th placed in a valve closing state.

Also, the needle valve 31 in an opening direction (upward direction) to open the injection holes 34 shifted when the fuel pressure on the inside of the high pressure chamber 33 becomes larger than a sum of the fuel pressure inside the second control chamber 36 and the biasing force of the spring 32 , and thereby the injector 20th placed in a valve open state. When the injector 20th is placed in the valve opening state, the high pressure fuel becomes the high pressure chamber 33 starting from the injection holes 34 injected.

Next is the structure of the on / off valves 50 to be discribed. A first on / off valve 51 and a second on / off valve 52 are called the on / off valves 50 on the inside of the low pressure chamber 57 Installed. The first on / off valve 51 is a solenoid valve that connects the low pressure chamber 57 and the first passage 25th enables and interrupts. The second on / off valve 52 is a solenoid valve that connects the low pressure chamber 57 and the second passage 27 enables and interrupts. The ECU 90 independently energizes a first solenoid 53 and a second solenoid 54 so that the ECU 90 enabling and breaking the connection between the first passage 25th and the low pressure chamber 57 through the first on / off valve 51 as well as enabling and breaking the connection between the second passage 27 and the low pressure chamber 57 through the second on / off valve 52 controls independently.

More precisely, it is the first on / off valve 51 by a biasing force of a first spring 55 biased and contacted the second main body 22nd when the first solenoid 53 is not aroused. The first on / off valve is in this contact state 51 placed in a state (valve closing state) in which the first on / off valve 51 the connection between the low pressure chamber 57 and the first passage 25th interrupts. It is also the first on / off valve 51 in the valve closing state of the first on / off valve 51 when the first solenoid 53 is excited, against the biasing force of the first spring 55 moved in the upward direction, and is thereby from the second main body 22nd spaced. The first on / off valve is in this state 51 placed in a state (valve open state) in which the first on / off valve 51 the connection between the low pressure chamber 57 and the first passage 25th allows the flow of fuel starting from the first passage 25th to the low pressure chamber 57 is made possible.

In addition, the second on / off valve is used 52 by a biasing force of a second spring 56 biased and contacted the second main body 22nd when the second solenoid 54 is not aroused. The second on / off valve is in this contact state 52 placed in a state (valve closing state) in which the second on / off valve 52 the connection between the low pressure chamber 57 and the second passage 27 interrupts. In addition, the second on / off valve is used 52 in the valve closing state of the second on / off valve 52 when the second solenoid 54 is excited, against the biasing force of the second spring 56 moved in the upward direction, and is thereby from the second main body 22nd spaced. The second on / off valve is in this state 52 placed in a state (valve open state) in which the second on / off valve 52 the connection between the low pressure chamber 57 and the second passage 27 allows the flow of fuel starting from the second passage 27 to the low pressure chamber 57 is made possible.

With the injector 20th becomes the needle valve 31 moved in such a way that it switches between the valve opening position and the valve closing position when the first on / off valve 51 is controlled or driven in such a way that it switches between the valve opening state and the valve closing state. Hence the operation of the injector 20th between an injection mode, in which the fuel starts from the injection holes 34 is injected, and an injection stop operation in which the injection of the fuel from the injection holes 34 stopped, switched. In addition, by switching the second on / off valve 52 between the valve opening state and the valve closing state in combination with the opening / closing control of the first on / off valve 51 a moving speed of the needle valve 31 controlled between its valve open position and its valve closed position. More precisely, in the case of the injector 20th an inclination of an injection rate of the fuel, more specifically, an increase rate (which is also referred to as an increase speed) of the injection rate and a decrease rate (which is also referred to as a decrease speed) of the injection rate are controlled by opening / closing the first on / off Valve 51 and opening / closing the second on / off valve 52 independently controlled.

2 shows exemplary injection rate patterns of the injector 20th . In all of the injection rate patterns, the first is the on / off valve 51 at the start time of fuel injection of the injector 20th opened, and the first on / off valve (or simply referred to as the first valve) 51 is closed at the end time of fuel injection. The valve opening and valve closing of the second on / off valve (or simply referred to as the second valve) 52 become is controlled according to the rate of increase of the injection rate and the rate of decrease of the injection rate.

More specifically, in a high-speed valve opening mode in which the rate of increase of the injection rate at the start timing of fuel injection is high, the second on / off valve becomes 52 opened (see (a) and (c) of 2 ). In a low-speed valve opening mode in which the rate of increase of the injection rate is low, the second on / off valve becomes 52 closed (see (b) and (d) of 2 ). In addition, in a high-speed valve closing mode in which a drop rate of the injection rate is high at the end time of fuel injection, the second on / off valve becomes 52 closed (see (a) and (b) of 2 ). In a low-speed valve closing mode in which a drop rate of the injection rate is low, the second on / off valve becomes 52 opened (see (c) and (d) of 2 ). In addition, the rate of increase of the injection rate and the rate of decrease of the injection rate can be changed in the middle of the operation. According to the injector 20th it is possible to implement an injection rate pattern in which the operation is changed from the high-speed valve closing mode to the low-speed valve closing mode, such as in (e) of FIG 2 will be shown.

A relationship between the opening / closing states of the first on / off valve 51 and the second on / off valve 52 as well as the operation of the injector 20th is made with reference to the 3 to 8th to be discribed. At the time before the start of injection, the first solenoid will be activated 53 and the second solenoid 54 not energized, so the first on / off valve 51 and the second on / off valve 52 both are closed, as in 3 is shown, thereby breaking the needle valve 31 the connection between the high pressure chamber 33 and the injection holes 34 .

The injection pattern (see (a) of 2 ) for the high speed valve opening mode and the high speed valve closing mode with reference to FIG 3 to 6th will be described. In the state in which the first on / off valve 51 and the second on / off valve 52 both are closed at the time before the start of the injection, the high pressure fuel becomes from the first high pressure passage 13th introduced so that a fuel reservoir (the annular chamber 14b , the intermediate chamber 26th , the first control chamber 46 , the second control chamber 36 and the high pressure chamber 33 ) and the fuel passages (the first passage 25th , the second passage 27 , the third passage 42 and the communication passage 47 ) that are in the second through fourth main bodies 22-24 are maintained in the high pressure state in which the pressure of the fuel accumulator and the fuel passages are equal to the fuel pressure in the first high pressure passage 13th is (see 3 ).

In the state in which the first on / off valve 51 and the second on / off valve 52 both are closed when the first on / off valve 51 and the second on / off valve 52 both are opened by the first solenoid 53 and the second solenoid 54 get excited as in 4th is shown, is the first control chamber 46 through the first passage 25th , the third passage 42 and the second passage 27 with the low pressure chamber 57 in connection. Therefore, the fuel flows into the first control chamber 46 and the fuel of the second control chamber 36 by two paths, that is, one path that goes through the first passage 25th and the third passage 42 and a path extending through the second passage 27 extends into the low pressure chamber 57 . Thus, the fuel pressure of the first control chamber drops 46 and the fuel pressure of the second control chamber 36 at the high rate, and this causes the needle valve 31 shifted at the high speed in the valve opening direction (upward direction). As a result, the fuel gets out from the injection holes 34 injected. In this case, the injection rate increases at the high rate as in (a) of 2 will be shown.

Between the upstream side and the downstream side of the pressure relief restriction orifice 42a a differential pressure or pressure difference is generated, and thereby a sum of the upward acting force caused by the fuel pressure in the first control chamber 46 is exerted, and the biasing force of the spring 45 greater than the downward force exerted by the fuel pressure in the intermediate chamber 26th and the fuel pressure in the annular chamber 14b is exercised. Hence the follow-up valve 41 in the state in which the first on / off valve 51 and the second on / off valve 52 both are open, held in the state in which the follow-up valve 41 the second main body 22nd contacted (see 4th ).

After the injection rate reaches a maximum rate when the first on / off valve 51 is closed, the fuel flows in the first control chamber 46 through the third passage 42 in the intermediate chamber 26th so that the fuel pressure of the intermediate chamber 26th is increased (see 5 ). In addition, the connection between the low pressure chamber 57 and the first control chamber 46 interrupted by the second on / off valve 52 is closed. In this case, the downward force caused by the fuel pressure in the intermediate chamber 26th and the fuel pressure in the annular chamber 14b is exerted greater than the sum of the upward force exerted by the fuel pressure in the first control chamber 46 is exerted, and the biasing force of the spring 45 . Hence the follow-up valve 41 moved in the downward direction (see 6th ). When the follow-up valve 41 is moved in the downward direction, the high pressure fuel of the first high pressure passage flows 13th into the first control chamber 46 .

At this time are the first on / off valve 51 and the second on / off valve 52 both closed, so the fuel pressure in the first control chamber 46 increases at the high rate. The fuel flows through the communication passage 47 starting from the first control chamber 46 into the second control chamber 36 . Then the needle valve begins 31 its downward movement to initiate valve closing operation (see 6th ) when the fuel pressure in the second control chamber 36 becomes higher than a predetermined pressure. In this case, the injection rate falls at the high rate as in (a) of FIG 2 will be shown. After that, the fuel injection of the injector 20th stopped when the injection holes 34 through the needle valve 31 getting closed.

Next, the injection pattern (see (b) of 2 ) for the low-speed valve opening mode and the high-speed valve closing mode. At the time before the start of the injection, the first on / off valves are 51 and the second on / off valve 52 both closed (see 3 ). Then there is the first on / off valve 51 in the state in which the second on / off valve 52 is kept closed, opened, as in 7th will be shown. Therefore, the fuel of the first control chamber flows 46 through the third passage 42 and the first passage 25th in the intermediate chamber 26th . At this time, between the upstream side and the downstream side of the pressure relief restriction orifice 42a a differential pressure or pressure difference is generated, and thereby a sum of the upward acting force caused by the fuel pressure in the first control chamber 46 is exerted, and the biasing force of the spring 45 greater than the downward force exerted by the fuel pressure in the intermediate chamber 26th and the fuel pressure in the annular chamber 14b is exercised. Hence the follow-up valve 41 held in the contact state in which the follower valve 41 the second main body 22nd contacted.

In the state in which the second on / off valve 52 is closed, the flow of fuel is through the second passage 27 interrupted. Therefore, the fuel pressure falls in the first control chamber 46 at the low rate. Thus becomes the needle valve 31 shifted at the low speed in the valve opening direction. In this case, the injection rate increases at the low rate as in (b) of FIG 2 will be shown. More specifically, the rate of increase (inclination) of the injection rate is in the state in which the first on / off valve is 51 is open and the second on / off valve 52 is closed, lower than that in the state in which the first on / off valve 51 and the second on / off valve 52 both are open. After the injection rate reaches the maximum rate, the operation is the same as the operation at the high rate of decrease time shown in (a) of FIG 2 will be shown.

Next, the injection pattern (see (c) of 2 ) for the high-speed valve opening mode and the low-speed valve closing mode. First of all, the operation at the high rate of rise time is the same as the operation at the high rate of rise time shown in (a) of FIG 2 will be shown. After the injection rate reaches the maximum rate, the first on / off valve is 51 in the state in which the second on / off valve 52 is held open, closed, as in 8th will be shown. Thus, the fuel flows in the first control chamber 46 through the third passage 42 in the intermediate chamber 26th so that the fuel pressure of the intermediate chamber 26th is increased. In addition, the fuel of the first control chamber flows 46 through the second passage 27 into the low pressure chamber 57 , as the second on / off valve 52 is open. In response to an increase in fuel pressure in the intermediate chamber 26th becomes the downward force caused by the fuel pressure in the intermediate chamber 26th and the fuel pressure in the annular chamber 14b is exerted greater than the sum of the upward force exerted by the fuel pressure in the first control chamber 46 is exerted, and the biasing force of the spring 45 . Hence the follow-up valve 41 moved in the downward direction (see 9 ). When the follow-up valve 41 is moved in the downward direction, the high pressure fuel of the first high pressure passage flows 13th into the first control chamber 46 .

At this time the second on / off valve becomes 52 kept open so that the fuel pressure in the first control chamber 46 increases at the low rate. The fuel flows through the communication passage 47 starting from the first control chamber 46 into the second control chamber 36 . Then the needle valve begins 31 its downward movement to initiate valve closing operation (see 9 ) when the fuel pressure in the second control chamber 36 becomes higher than the specified pressure. In this case, the injection rate falls at the low rate as in (c) of FIG 2 will be shown. More specifically, the drop rate (slope) of the injection rate is in the state in which the first on / off valve is 51 is closed and the second on / off valve 52 is opened, lower than that in the state in which the first on / off valve 51 and the second on / off valve 52 both are closed. After that, fuel injection is started from the injection holes 34 stopped when the injection holes 34 through the needle valve 31 are closed.

10 FIG. 13 is a diagram showing a pressure reducing operation for reducing the fuel pressure in the common rail 11 through the second on / off valve 52 indicates without the fuel coming from the injector 20th is injected.

As discussed above, in the state in which the first on / off valve 51 and the second on / off valve 52 Both are closed, the fuel pressure in both the second control chamber 36 , the first control chamber 46 as well as the intermediate chamber 26th the same as the fuel pressure in the first high pressure passage 13th , and the follow-up valve 41 contacts the second main body 22nd (please refer 3 ). In the pressure reducing operation, the second on / off valve becomes 52 open based on this state. Therefore, the fuel becomes the first control chamber 46 through the second passage 27 into the low pressure chamber 57 discharged, as in 10 will be shown. Thereafter, in response to a decrease or decrease in pressure in the first control chamber 46 the follow-up valve 41 moved in the downward direction.

Here is with the injector 20th in the state in which the first on / off valve 51 is closed and the second on / off valve 52 is open, the amount of flow of the fuel through the pressure load restricting orifice 14a set so that it is larger than the flow amount of the fuel through the pressure relief restriction orifice 27a . Therefore, in the state in which the first on / off valve 51 is closed and the second on / off valve 52 is open, the amount of fuel emanating from the second high pressure passage 14th into the first control chamber 46 flows, greater than the amount of fuel that emanating from the first control chamber 46 through the second passage 27 is discharged. Thus, in the state in which the first on / off valve 51 is closed and the second on / off valve 52 is open, maintaining the state in which the communication between the high pressure chamber 33 and the injection holes 34 through the needle valve 31 is interrupted, that is, the state in which the fuel is not starting from the injection holes 34 is injected.

In addition, the fuel flows from the common rail 11 through the first high pressure passage 13th and the second high pressure passage 14th into the first control chamber 46 , and this fuel is starting from the first control chamber 46 to the low pressure chamber 57 discharged and returned to the upstream side (the low pressure side) of the fuel injection system. Therefore, the fuel pressure in the common rail decreases 11 . More precisely, the fuel pressure in the common rail decreases 11 in the state in which the fuel is not starting from the injector 20th is injected. Hence the injector 20th a function as a pressure reducing valve for reducing the fuel pressure of the common rail 11 on.

With the injector 20th are a passage cross-sectional area of the pressure relief restriction orifice 42a , a cross-sectional area of an opening of the intermediate chamber 26th that are on the side of the third main body 23 (the side of the first control chamber 46 ) and a cross-sectional area of an opening of the annular chamber 14b that are on one side of the third main body 23 (the side of the first control chamber 46 ), as well as a pretensioning force of the spring 45 adjusted so that the connection between the annular chamber 14b and the first control chamber 46 in the case where the connection between the first passage 25th and the low pressure chamber 57 through the first on / off valve 51 is interrupted by the follow-up valve 41 is interrupted. More specifically, in the state in which the communication between the first passage 25th and the low pressure chamber 57 through the first on / off valve 51 is made possible, enabling the connection between the first control chamber 46 and the intermediate chamber 26th through the third passage 42 through the follow-up valve 41 through the amount restriction settings of the amount of flow of fuel through the pressure relief restriction orifice 42a , an exposed surface area of the follower valve 41 leading to the intermediate chamber 26th is exposed, an exposed surface area of the follower valve 41 leading to the first high pressure passage 13th is exposed, and the biasing force of the spring 45 implemented.

In this way occurs in the low temperature environment in which, for example, the machine 70 cold starts when the temperature of the fuel (diesel fuel) becomes lower than the crystallization point, the phenomenon known as gelling of the fuel. Therefore, solid components are deposited or separated in the fuel. When the fuel, which contains the attached paraffin, passes through the fuel filter 66 passes, the paraffin deposited in the fuel will pass through the fuel filter 66 trapped and adhered to the fuel filter 66 at. When the amount of deposition of the attached paraffin on the fuel filter 66 becomes large, the fuel filter becomes 66 possibly clogged. In such a case it is possible that the machine 70 a sufficient amount of fuel cannot be supplied, resulting in a decrease in the output of the engine 70 results.

In view of the disadvantage described above, in the present system, attention is paid to the fact that the temperature of the fuel, which originates from the fuel tank 61 by the high pressure pump 62 and the common rail 11 into the injector 20th flows, is raised to a high temperature, and it was decided to use the fuel filter 66 to heat up by the upstream side of the fuel filter 66 this fuel is supplied at a high temperature.

More specifically, is the fuel injection system 10 with a return mechanism 69 for returning the fuel starting from the inside or the inside of the injector 20th provided to the low pressure side to raise the filter temperature by the high temperature fuel which is the inside of the injector 20th is fed. As in 1 shown includes the return mechanism 69 a branch pipe 65a and a recirculation valve 67 . The branch pipe 65a is a fuel pipe starting from the return pipe 65 branches off. An end portion of the branch pipe 65a , which opposite a connection of the branch pipe 65a is arranged with the return pipe 65 is connected to a center of the low pressure fuel pipe 63 connected to the fuel tank 61 and the fuel filter 66 connects.

The recirculation valve 67 is in the branch pipe 65a Installed. The recirculation valve 67 is a solenoid valve whose opening degree is controlled based on a drive signal sent from the ECU 90 is issued. The recirculation valve 67 changes a passage cross-sectional area of the branch pipe 65a according to the degree of opening of the return valve 67 . In a valve closing state of the return valve 67 , in which the recirculation valve 67 is closed, the flow of fuel into the branch pipe 65a blocked, and thereby the fuel of the low pressure chamber 57 through the return pipe 65 to the fuel tank 61 returned. In addition, the return valve is in a valve open state 67 , in which the recirculation valve 67 is open, the flow of fuel into the branch pipe 65a allows, and thereby the fuel of the low pressure chamber 57 through the branch pipe 65a into the low pressure fuel pipe 63 introduced.

11 shows the operation of the injector 20th and the flow of fuel in the case where a controller (filter temperature raising control) for raising the temperature of the fuel filter 66 is carried out by recycling the high temperature fuel. In 11 An arrow A indicates the flow of the high temperature fuel returned to the low pressure side. As in 11 is shown, in the filter temperature increase control in the state in which the fuel is not coming from the injection holes 34 is injected by the first on / off valve 51 is closed, the second on / off valve 52 opened, and the return valve 67 will be opened. Therefore, the high temperature fuel flows into the first control chamber 46 through the second passage 27 into the low pressure chamber 57 and is then starting from the low pressure chamber 57 through the return pipe 65 and the branch pipe 65a to the low pressure fuel pipe 63 discharged. After that, the fuel filter 66 this discharged fuel is supplied.

Referring next to a flow chart of FIG 12th an operation method of the filter temperature increase control will be described. This operation is in a situation in which the return of fuel to the fuel filter 66 is stopped by the filter temperature increase control at predetermined intervals by the microcomputer of the ECU 90 executed.

In 12th will at step S101 determines a condition of the fuel in the fuel tank 61 is stored. The fuel property (the density and kinetic viscosity of the fuel) recorded with the fuel property sensor 72 is sensed, and the fuel temperature (hereinafter referred to as a temperature Tb in front of the filter) obtained with the fuel temperature sensor 71 is sensed when the state of the fuel is determined.

The next step S102 it is determined whether a clogging condition (accumulation condition) of the fuel is satisfied. Here, it is determined whether the temperature Tb in front of the filter is equal to or lower than a clogging determination value Tw. In the present embodiment, the clogging determination value Tw is determined according to the fuel property obtained with the fuel property sensor 72 is sensed in view of the fact that a temperature (ie, a crystallization point CP) at which the gasification of the fuel occurs differs depending on the fuel property. More specifically, the crystallization point CP is estimated based on the fuel property obtained with the fuel property sensor 72 is sensed, and the blooming determination value Tw is set based on the estimated crystallization point CP. At this time, the gassing determination value becomes Tw is set to be larger, the higher the crystallization point CP is.

In view of the estimation of the cloud point CP, in the present embodiment, a corresponding relationship between the kinetic viscosity of the fuel and the cloud point CP of the fuel is set in advance in the ROM of the ECU 90 saved. The crystallization point CP of the fuel is determined based on the stored correspondence relationship and the kinetic viscosity obtained with the fuel property sensor 72 is sensed, appreciated. At this time, the higher the kinetic viscosity of the fuel, the higher the value of the crystallization point CP is set. Instead of the above-described configuration in which the dislocation determination value Tw is made variable according to the crystallization point CP, the dislocation determination value Tw may be set to a predetermined constant value. In addition, the clogging determination value Tw may be made variable according to the area in which the vehicle is used, instead of making the clogging determination value Tw variable according to the crystallization point CP.

If the temperature Tb in front of the filter is higher than the clogging determination value Tw and thereby the clogging condition is not satisfied, step S102 NO is returned and the present routine ends. In such a case, the return of the fuel by the filter temperature increase control is not carried out. In contrast, the operation advances to step S103 continues when the temperature Tb in front of the filter is equal to or lower than the clogging determination value Tw, and thereby the clogging condition is satisfied. At step S103 the fuel temperature (which will hereinafter be referred to as a temperature Th after high pressure load) obtained with the fuel temperature sensor is detected 73 is sensed. Also be at step S104 an engine rotation speed and an engine load are determined, and it becomes an injection condition of the injector 20th (an injection time and an injection duration) determined.

In the present system is the fuel temperature sensor 73 in the first high pressure passage 13th installed, but this is sufficient if the fuel temperature is on the downstream side of the high pressure pump 62 can be sensed. Therefore, for example, a temperature which is determined by a sensor for sensing the fuel temperature in the common rail 11 is sensed when used as the temperature Th after high pressure load.

Next up will be at step S105 a temperature increase flow rate Qu and a target rail pressure PtB for increasing the filter temperature are set. The temperature increase flow rate Qu is a flow rate of the fuel which the low pressure fuel pipe 63 starting from the low pressure chamber 57 from one or more injectors 20th installed in the target cylinders through the branch pipe 65a and is required to dissolve the deposit (paraffin) that is on the fuel filter 66 is deposited, and limits the deposition of paraffin. Here, the temperature increase flow rate Qu is set based on the temperature Tb in front of the filter and the temperature Th after a high pressure load. More specifically, the larger the difference between the temperature Tb in front of the filter and the crystallization point CP of the fuel, the larger the value is set as the temperature increase flow amount Qc. Further, the higher the temperature Th after a high pressure load, the smaller the value is set as the temperature increase flow rate Qu.

Instead of the configuration described above in which the temperature increase flow rate Qc is set based on the difference between the temperature Tb in front of the filter and the crystallization point CP of the fuel, the temperature increase flow rate Qc can be set based on a difference between the temperature Tb can be set before the filter and a predetermined determination value.

In expectation that the rail pressure will increase due to the return of the fuel to the fuel filter 66 is decreased, the target rail pressure PtB is set to a higher pressure than the target rail pressure PtA, which is set in the case that the normal control is carried out in which the filter temperature increase control is not carried out becomes. Here, the target rail pressure PtB is used to increase the filter temperature based on the injection amount command value Ki of each corresponding one of the injectors 20th and the temperature increase flow rate Qc is calculated. The larger the injection amount command value Ki or the larger the temperature increase flow amount Qc, the higher the value of the target rail pressure PtB is set.

At step S106 becomes a period (hereinafter referred to as a period Tf in which the temperature increase is possible) during which the second on / off valve 52 can be opened to the filter temperature in one combustion cycle of the machine 70 to increase, based on the determined injection condition. To the influence on the fuel injection of the injectors 20th According to the present embodiment, the duration Tf in which the temperature increase is possible is set such that the duration Tf in which the temperature increase is possible is a duration (a fuel injection duration T # n, where n is the cylinder ID Number is) of the injector 20th any of the cylinders does not overlap, during which one emanating from the injector 20th the fuel is injected, that is, the duration Tf in which the temperature increase is possible is set in a duration during which the fuel does not come from the injector 20th any one of the cylinders is injected.

More specifically, the period Tf in which the temperature increase is possible is set to a period which is after the end of the fuel injection period T # n of any of the cylinders (in other words, after the needle valve 31 is placed in the valve closing position), and before a start of the fuel injection duration T # n of the next combustion cylinder out of the cylinders. That is, the duration Tf, in which the temperature increase is possible, is set in the duration between the fuel injection duration T # n and the fuel injection duration T # n of each two successively injecting cylinders (see FIG 14th ). An end time of the duration Tf, in which the temperature increase is possible, is set in such a way that it is around a predetermined time B1 (eg 20 to 30 ° CA) before the injection start time of the next combustion cylinder. In this way, a period for restoring the rail pressure, which has decreased due to the return of the fuel to increase the filter temperature, to a target pressure is ensured before the start of the next injection. In the case of the 4-cylinder engine, a total of four periods Tf in which the temperature increase is possible are set within one combustion cycle (720 ° CA).

In the present embodiment, the predetermined time becomes B1 set variably according to the engine rotational speed with each crank angle sensor detection. More precisely, it is the allotted time B1 the longer it is set, the higher the machine rotation speed. In a case where the sufficient time is not ensured until the start of fuel injection in the next combustion cylinder, the next fuel injection is carried out in a state in which the follower valve 41 from the second main body 22nd in the first control chamber 46 is arranged spaced, that is, a state in which the fuel pressure with respect to the respective control chambers 46 , 36 is not high enough. In this case, there is a problem that the injection start may be delayed or the injection amount may be insufficient, resulting in insufficient output of the engine 70 results. Taking this point into account, the predetermined time B 1 is set in accordance with the engine rotational speed, as a result of which the rail pressure is sufficiently increased before the start of the next injection.

Next up will be at step S107 the number of target cylinders, the second on / off valve for each of them during the duration Tf in which the temperature increase is possible 52 is opened, and the cylinder ID number (s) of the respective target cylinder (s) is set. The amount of fuel required to prevent the fuel filter from clogging 66 that is caused by the fuel containing the attached paraffin varies depending on the temperature Tb in front of the filter. More specifically, the more fuel it takes to clog the fuel filter 66 to be restricted and eliminated the lower the temperature Tb in front of the filter. Further, the flow rate of the high temperature fuel can be increased from the injector 20th to the fuel filter 66 is returned as the number of target cylinders used to return the fuel is increased by the second on / off valve 52 of the injector 20th which is installed in the respective target cylinders.

With these points in mind, in the present embodiment, the number N of target cylinders (ie, the number of one or more target cylinders), each of which is used for returning the fuel in the duration Tf in which the temperature increase is possible, is set according to the temperature increase flow rate Qu. More specifically, the larger the temperature increase flow rate Qu, the larger the number of target cylinders used for returning the fuel is set. As a result, there may be a deterioration in fuel consumption caused by unnecessarily opening the second on / off valve 52 can be restricted in the case where the temperature of the fuel is not so low and the temperature increase flow rate Qu is small while the fuel filter is clogged 66 is sufficiently limited and eliminated.

In addition, in a case where the temperature increase flow rate Qu is relatively small, and thereby the second on / off valve becomes 52 is only open at one or some of the cylinders, if there are one or more deactivated cylinders in which the combustion in the engine is present 70 is stopped, such deactivated cylinder (s) preferably or preferably selected as the target cylinder (s), with each of them having the second on / off valve 52 during the duration of which Tf, in which the temperature increase is possible, is opened. By preferably using the deactivated cylinder (s) as the target cylinder (s), for each of which, during its duration Tf in which the temperature increase is possible, the second on / off valve 52 is opened, it is possible to minimize an influence on the fuel injection in the remaining activated cylinder (s), ie combustion cylinder (s).

13th Fig. 13 is a flowchart showing an operation method for setting the number N of target cylinder (s) and the cylinder ID number (s) of the respective target cylinder (s) based on which one (s) Fuel is returned for the duration Tf in which the temperature increase is possible. In 13th will at step S201 the number N of target cylinders is set based on the temperature increasing flow rate Qu. Then at step S202 determines whether the number N of target cylinders is less than the total number Ntotal of cylinders of the engine 70 (In the present embodiment, the total number Ntotal is four). When the number N of target cylinders is equal to the total number Ntotal, the operation goes to step S203 away. At step S203 becomes (a) drive cylinder, which is (a) cylinder (s), each of which has the second on / off valve 52 is driven in such a way that it recirculates the fuel during its duration Tf in which the temperature increase is possible, selected from the cylinder (s) (combustion cylinders) in which the combustion is carried out.

In contrast, the operation advances to step S204 if the number N of target cylinders is less than the total number Ntotal. At step S204 it is determined whether there is (a) deactivated cylinder (s) present. If there is no deactivated cylinder, the operation goes to step S203 away. In contrast, the operation advances to step S205 if the deactivated cylinder (s) is / are present. At step S205 the deactivated cylinder (s) is / are preferably selected as the drive cylinder (s). At this time, the shortage is compensated by the combustion cylinder (s) if the number N of target cylinders is greater than the number of deactivated cylinders. The current or current operation is then ended.

Referring back to the description of 12th will at step S108 a temperature increase execution period Tc, which is a period in which the fuel is actually delivered from the injector 20th is returned, set within at least a part of the duration Tf in which the temperature increase is possible. Here, the temperature increase period Tc is set based on the temperature increase flow amount Qc. More specifically, the larger the temperature increase flow rate Qu, the longer the temperature increase execution period Tc is set. By variably setting the temperature increase execution period Tc together with the number N of target cylinders, each of which has the second on / off valve 52 is open, it is possible to adjust the amount of fuel going to the fuel filter 66 should be traced back to adjust exactly.

Next is at step S109 during the temperature increase execution period Tc which is set in advance, the first on / off valve 51 closed, the second on / off valve 52 is opened, and the return valve 67 will be opened. As a result, the fuel filter becomes 66 the high temperature fuel in the injector 20th fed. In the present embodiment, the recirculation valve 67 kept open for the entire duration during which the gulp condition is met. Alternatively, the recirculation valve 67 every time the second on / off valve 52 opened / closed to increase the filter temperature, opened / closed. In addition, it becomes a command value of the fuel delivery amount of the high pressure pump 62 calculated in such a way that the actual rail pressure of the common rail 11 becomes the target rail pressure PtB, which is set to increase the filter temperature. Then the high pressure pump will operate 62 controlled based on the calculated command value.

After the filter temperature raising control starts to recirculate the fuel, step S110 the temperature Tb in front of the filter is determined. Then at step S111 determines whether the clogging condition is lost on the basis of the determined temperature Tb in front of the filter. When the temperature Tb in front of the filter is equal to or lower than the clogging determination value Tw, the operation returns to step S107 back and repeat the steps S107-S111 . At this time, the fuel return can be performed using the injector (s) 20th of the target cylinder (s) set in advance can be performed, or the fuel recirculation may be performed after the number of target cylinders for performing the fuel recirculation is increased or decreased based on the detected temperature Tb in front of the filter.

If it is determined that the failure condition at step S111 is lost, the operation proceeds to step S112 away. At step S112 becomes the recirculation valve 67 closed, and the return of the fuel to the fuel filter 66 by the filter temperature increase control is stopped, and the present routine is ended.

14th Fig. 13 is a time chart showing an example of the filter temperature increase control in comparison with normal control in which the filter temperature increase control is not executed. In 14th shows (a) the cam lift amount, and (b) shows the drive signal of the high pressure pump 62 and (c) shows the fuel delivery rate (pump discharge rate) of the high pressure pump 62 and (d) shows the injection rate of the injector 20th and (e) indicates the amount of fuel returned from the injector 20th to the fuel filter 66 is fed back, and (f) indicates the transition or fluctuation in the actual rail pressure. In (b), (c), (e) and (f) of 14th a solid line indicates a change at the time the filter temperature raising control is carried out, and a chain line indicates a change at the time the normal control is carried out.

As in 14th is indicated, the return of fuel by the filter temperature increase control is carried out in the period during which the return of fuel by the filter temperature increase control does not affect the normal fuel injection of the respective injectors 20th Has. More specifically, the period Tf in which the temperature increase is possible is set within a period between one fuel injection and the next fuel injection performed in each cylinder, and the temperature increase execution period Tc is set within this period Tf in which the Temperature increase is possible to achieve the temperature increase flow rate Qc. The duration Tf in which the temperature increase is possible is set such that it starts from or after the injection end time of each cylinder (that is, the time when the needle valve is opened 31 to the valve closing position is offset or shifted) up to or before the point in time which lasts or lies by the specified time B1 is before the injection start time of the next combustion cylinder.

For example, in a case where the current combustion cylinder is the first cylinder # 1, a duration is from the injection end timing DA of the first cylinder # 1 to the timing around the predetermined time B1 before the injection start timing DB of the next combustion cylinder (the third cylinder # 3 in 14th ) is set as the duration Tf in which the temperature increase is possible of the first cylinder # 1. The temperature increase execution period Tc is set within this period Tf in which the temperature increase is possible. The second on / off valve 52 of the injector 20th installed in the first cylinder # 1 is opened during this temperature increase execution period Tc, so that the fuel from the injector 20th of the first cylinder # 1 is output.

At the time when the normal control is carried out, as in (f) of FIG 14th is shown, the fuel delivery rate of the high pressure pump 62 controlled in such a way that the actual rail pressure follows the target rail pressure PtA. In contrast, at the time the filter temperature increase control is executed, the fuel delivery amount of the high pressure pump becomes 62 to increase the filter temperature to make the rail pressure conform to the return of the fuel from the injector 20th to the fuel filter 66 to increase. At this time, the target rail pressure PtB is set higher, the larger the return amount of the fuel. If the required return amount of the fuel is large and the maximum value of the rail pressure is increased beyond a predetermined pressure (e.g., a maximum allowable pressure), the filter temperature increase control can be stopped.

Next, referring to timing diagrams shown in FIGS 15th and 16 A specific example of the filter temperature increase control according to the injection rate pattern will be described. 15th shows the timing diagram (see (b) of 2 ) indicating the operation in the low-speed valve opening mode and the high-speed valve closing mode. 16 shows the timing diagram (see (e) of 2 ), which indicates the operation at the time of switching from the low-speed valve opening mode and the high-speed valve-closing mode to the low-speed valve closing mode. In the 15th and 16 the operation of a cylinder (e.g. the injector of the first cylinder # 1) out of all cylinders of the engine is displayed. In the 15th and 16 It is assumed that the temperature Tb in front of the filter immediately after the engine start is equal to or lower than the clogging determination value Tw, and the combustion cylinder (s) is / are subjected to the filter temperature increase control.

In 15th At a time point t11, the first on / off valve (the first valve) 51 and the second on / off valve (the second valve) 52 are both closed, and the lift amount of the follower valve 41 is zero, and the fuel pressure in both the control chambers (the first control chamber 46 and the second control chamber 36 ) as well as the intermediate chamber 26th is a high pressure PI, and the lift amount of the needle valve 31 and the injection rate are both zero.

When the first on / off valve 51 based on a fuel injection start command to a Time t12 is opened, the fuel pressure decreases in both the intermediate chamber 26th as well as the control chambers 46 , 36 . At this time, the fuel pressure in the intermediate chamber becomes 26th compared to the fuel pressure in the control chambers 46 , 36 decreased at a higher rate because of the pressure relief restriction orifice 42a in the third passage 42 is provided. The needle valve also starts 31 at a time point t13 when the fuel pressure in the second control chamber 36 becomes lower than the predetermined pressure whose movement in the valve opening direction, and thereby the injection of the fuel starts from the injection holes 34 . At this time, the fuel is in the first control chamber 46 through the first passage 25th to the low pressure chamber 57 discharged. However, the fuel is in the first control chamber 46 not starting from the second passage 27 to the low pressure chamber 57 dissipated as the second on / off valve 52 closed is. Therefore, the fuel pressure of the second control chamber decreases 36 at a low rate. As a result, the needle valve becomes 31 moves in the valve opening direction at the low speed, and thereby the injection rate increases at the low rate.

When the first on / off valve 51 is closed based on a fuel injection end command at a time point t14, the fuel pressure in the intermediate chamber increases 26th due to the supply of the high pressure fuel from the first high pressure passage 13th . In addition, the follow-up valve 41 moved away from the position (contact position) at which the follow-up valve 41 the second main body 22nd contacted when there is a difference between the fuel pressure of the control chambers 46 , 36 and the fuel pressure of the intermediate chamber 26th becomes low at a time point t15. As a result, the high pressure fuel flows from the first high pressure passage 13th into the first control chamber 46 .

After that, the needle valve 31 moves in the valve closing direction (a time point t16) when the fuel pressure in the second control chamber 36 becomes equal to or higher than the predetermined pressure. At this time are the first on / off valve 51 and the second on / off valve 52 both closed, and the fuel pressure in each of the control chambers 46 , 36 increases at the high rate. Hence the needle valve 31 moves at the high speed in the valve closing direction, and thereby the injection rate drops at the high rate. Thereafter, at a time point t17, the lift amount of the needle valve becomes 31 zero, and thereby the fuel is no longer starting from the injection holes 34 injected.

The gulp condition is currently met, and at a point in time 118 is after a specified time has elapsed B2 from time t17 at which the needle valve 31 is moved to the valve closing position, the second on / off valve 52 opened in the state in which the first on / off valve 51 is kept closed. In this case, the fuel is starting from the first control chamber 46 through the second passage 27 to the low pressure chamber 57 discharged without the needle valve 31 moving from the valve closing position (ie while through the needle valve 31 the closed state of the injection holes 34 is retained). As a result, the fuel pressure decreases in both the control chambers 46 , 36 as well as the intermediate chamber 26th to a fuel pressure P2 which is lower than the high pressure P1 and is higher than an intermediate pressure P3 . At this time, the follow-up valve will 41 from the second main body 22nd kept spaced. Then the second on / off valve is activated 52 closed at time t19 after the lapse of the temperature increase execution period Tc from time t18. For the respective target cylinder (s) to be subjected to the filter temperature increase control, the injector instructs 20th the operation that is in 15th is shown so that the fuel starting from the injector 20th is injected, and after that the fuel is starting from the injector 20th returned.

In the case of the high-speed valve closing mode, the moving speed of the needle valve becomes 31 slowed in the valve closing direction (ie changed to the low speed valve closing mode) when the second on / off valve 52 before the time at which the fuel pressure in the control chambers is opened 46 , 36 is increased to the sufficiently high pressure. Thus, the injection rate changes. Therefore, in the valve closing mode at high speed, it becomes the second on / off valve 52 opened to the filter temperature after the specified time has elapsed B2 from the valve closing time (the time t17), which is the time or the timing for closing the needle valve 31 is to increase.

The recirculation valve will be open for the duration of the gulping condition 67 open. Thus, the high temperature fuel which emanates from the low pressure chamber 57 through the low pressure passage 58 is discharged, the fuel filter 66 through the return pipe 65 and the branch pipe 65a fed. By supplying the fuel at a high temperature, the temperature of the fuel filter becomes higher 66 is increased so that the attachment of the solid components of the fuel is restricted, and the attached paraffin of the fuel is dissolved.

Next, referring to FIG 16 the operation at the time will be described which is switched from the low speed valve opening mode and the high speed valve closing mode to the low speed valve closing mode. In 16 are the first on / off valve at a point in time t21 51 and the second on / off valve 52 both closed, and the lift amount of the follower valve 41 is zero, and the fuel pressure in both the control chambers (the first control chamber 46 and the second control chamber 36 ) as well as the intermediate chamber 26th is the high pressure PI, and the lift amount of the needle valve 31 and the injection rate are both zero. When the first on / off valve 51 is opened based on the fuel injection start command at a time point t22, the fuel pressure in the second control chamber decreases 36 at the low rate. As a result, the needle valve becomes 31 moves in the valve opening direction at the low speed, and thereby the injection rate increases at the low rate.

After that, the fuel pressure in the intermediate chamber increases 26th due to the supply of the high pressure fuel from the first high pressure passage 13th when the first on / off valve 51 is closed at a time t23. When there is a difference between the fuel pressure in the control chambers 46 , 36 and the fuel pressure in the intermediate chamber 26th becomes low, the follow-up valve becomes 41 shifted in the direction away from the second main body 22nd runs. As a result, the high pressure fuel flows from the first high pressure passage 13th into the first control chamber 46 . Then the needle valve moves 31 in the valve closing direction (a time point t24) when the fuel pressure in the second control chamber 36 becomes equal to or higher than the predetermined pressure. At this time are the first on / off valve 51 and the second on / off valve 52 both closed, and the fuel pressure in each of the control chambers 46 , 36 increases at the high rate. Thus the needle valve moves 31 at the high speed in the valve closing direction, and the injection rate falls at the high rate.

The second on / off valve 52 is opened at a point of time t25 which is in the midst of the duration from the point of time at which the movement of the needle valve 31 is started in the valve closing direction until the point in time at which the injection holes 34 be closed, lies. Therefore, the fuel is in the first control chamber 46 through the second passage 27 to the low pressure chamber 57 dissipated, and the fuel pressure in the control chambers 46 , 36 is maintained at the given pressure. As a result, the moving speed of the needle valve becomes 31 in the valve closing direction is changed from the high speed to the low speed, and thereby the injection rate falls at the low rate. Thereafter, at a time point t26, the lift amount of the needle valve becomes 31 zero, and thereby the fuel is no longer starting from the injection holes 34 injected. The second on / off valve is also used 52 at time t27 after the lapse of the temperature increase execution period Tc from time t26.

In 16 the failure condition is satisfied, and at time point t26 at which the lift amount of the needle valve 31 becomes zero, the second on / off valve becomes 52 kept open to execute the filter temperature raising control after the end of the fuel injection. Thus, the fuel is starting from the first control chamber 46 to the low pressure chamber 57 discharged without the fuel starting from the injection holes 34 is injected, so that the fuel pressure in the control chambers 46 , 36 and the fuel pressure in the intermediate chamber 26th reduce. In addition, the high temperature fuel becomes the low pressure chamber 57 starting from the low pressure passage 58 discharged and becomes the upstream side of the fuel filter 66 through the return pipe 65 and the branch pipe 65a fed.

The present embodiment described in detail above provides the following advantages.

The feedback mechanism 69 which feeds the fuel from the injector 20th to the low pressure fuel pipe 63 recirculates is provided, and the high temperature fuel in the first control chamber 46 of the injector 20th becomes the upstream side of the fuel filter 66 through the return mechanism 69 supplied so that the temperature of the fuel filter 66 increases or increases. With this configuration, the fuel filter 66 to be heated with the fuel at high temperature starting from the injector 20th is supplied, so that the accumulation of the fuel on the fuel filter 66 adheres, can be dissolved, and generation of attachment of the fuel can be restrained. It can also clog the fuel filter 66 with the accumulation of fuel are limited without the heater to heat the fuel filter 66 is provided.

The injector 20th includes the first on / off valve 51 and the second on / off valve 52 so that the injector 20th can change the injection rate. The injector 20th having this configuration can control the fuel pressure in the control chambers 46 , 36 reduce while the needle valve 31 is held in the valve closing position (ie without the fuel from the injection holes 34 inject) by turning the second on / off valve 52 is opened in the state in which the first On / off valve 51 closed is. Therefore, the injector can 20th as a pressure reducing valve for reducing the fuel pressure of the common rail 11 act. In the present embodiment, this function is used to filter the upstream side of the fuel 66 the high temperature fuel of the control chambers 46 , 36 so that there is no need to use the heater or a complicated mechanism for restricting the clogging of the fuel filter 66 to be provided. Therefore, the system cost can be reduced.

In the state where the clogging condition is satisfied, the filter temperature increase control is carried out to increase the temperature of the fuel filter 66 increase by the first on / off valve 51 closed and the second on / off valve 52 is opened. According to this configuration, the filter temperature increase control can be performed only when the temperature of the fuel filter 66 needs to be increased. As a result, deterioration in fuel consumption caused by the return of the fuel from the injector can be minimized 20th caused.

The fuel injection system is configured such that the temperature increase flow amount Qu is set based on the temperature Tb in front of the filter, and the second on / off valve 52 is driven so the fuel filter 66 the amount of fuel is supplied which corresponds to the set temperature increase flow rate Qu. Since the temperature increase flow rate Qu varies depending on the temperature Tb in front of the filter, this configuration enables the necessary amount of fuel to be supplied to avoid clogging of the fuel filter 66 to restrict.

The fuel injection system is configured such that, at the time the filter temperature increase control is executed, the number of target cylinders each of which has the second on / off valve 52 is driven, is variably set according to the temperature increasing flow rate Qu. According to this configuration, the amount of fuel supplied to the fuel filter 66 is fed back by a simple method of changing the number of target cylinders, each of which has the second on / off valve 52 driven. Therefore, it is possible to limit the complexity of the system.

In the case where the deactivated cylinder (s) exists, the deactivated cylinder (s) is / are preferably used as the target cylinder (s) to carry out the filter temperature increase control. In this way, it is possible to minimize the execution of the filter temperature raising control using the combustion cylinder (s), and thereby it is possible to minimize the influence on the normal fuel injection for generating the torque.

The fuel injection system is configured such that the fuel delivery rate of the high pressure pump 62 depending on the injection amount command value of the injector 20th and the temperature increase flow rate Qu is variably controlled. As the fuel delivery rate of the high pressure pump 62 is increased in accordance with the temperature increase flow rate Qu, it is possible to restrain the actual rail pressure from falling below the target rail pressure at the time the normal fuel injection is carried out.

During the period in which the fuel is coming from the injector 20th to the fuel filter 66 is returned, the fuel may be due to a drop in rail pressure from the injector 20th cannot be injected in the amount that corresponds to the commanded injection amount. In this regard, the fuel injection system of the present embodiment is configured to have the second on / off valve 52 open to the high temperature fuel during the duration of the fuel injection in a combustion cycle of the engine 70 not with all of the injectors 20th is carried out to the fuel filter 66 to return. According to this configuration, the fuel filter can become clogged 66 sufficiently restricted during normal fuel injection through the injector 20th is not affected.

The second on / off valve 52 , which was opened for the purpose of increasing the filter temperature, is closed at the point in time, around the predetermined time B1 after the end of the fuel injection of the current combustion cylinder is before the injection start time of the next combustion cylinder. Therefore, the rail pressure, which has been reduced by the return of fuel to increase the filter temperature, can be increased to the target rail pressure prior to the time the next injection is started.

Other embodiments

The present disclosure is not limited to the above embodiment and can be implemented as follows, for example.

In the above embodiment, the fuel becomes the fuel filter 66 fed back by the second on / off valve 52 during the Duration after the fuel is injected from the injector 20th is opened. Alternatively, the fuel can go to the fuel filter 66 be returned by the second on / off valve 52 during a period prior to the injection of the fuel from the injector 20th is opened. More precisely, in 14th in a case where the current combustion cylinder is the first cylinder # 1, a period which is from the injection end time DA of the first cylinder # 1 to the time around the predetermined time B1 before the injection start timing DB of the next combustion cylinder (the third cylinder # 3 in 14th ) is set as the period Tf in which the temperature increase is possible of the third cylinder # 3. Then the second on / off valve is activated 52 of the injector 20th , which is installed on the third cylinder # 3, is opened for the period Tf in which the temperature increase is possible, to the fuel from the injector 20th of the third cylinder # 3.

17th Fig. 13 is a timing chart showing an operation of the injector 20th (for example, the injector of the third cylinder # 3) in the case where the second on / off valve 52 is opened during the period prior to fuel injection. 17th Fig. 13 shows the operation in the low-speed valve opening mode and the high-speed valve closing mode.

In the state in which the first on / off valve 51 and the second on / off valve 52 both are closed, and the lift amount of the follower valve 41 is zero, and the fuel pressure in both the control chambers and the intermediate chamber 26th the high pressure P1 and the lift amount of the needle valve 31 and the injection rate are both zero when the second on / off valve 52 is open, the fuel is through the second passage 27 starting from the first control chamber 46 to the low pressure chamber 57 discharged while the needle valve 31 is maintained or held at the valve closing position. As a result, the fuel pressure decreases in both the control chambers 46 , 36 as well as the intermediate chamber 26th on the fuel pressure, which is lower than the high pressure P1 and is higher than the intermediate pressure P3 . Then the second on / off valve is activated 52 closed at a time t30. As a result, the fuel pressure in both the control chambers 46 , 36 as well as the intermediate chamber 26th on the high pressure P1 deferred. Thereafter, at a point of time t31 after the lapse of time B1 from time t30 the first on / off valve 51 opened in response to the fuel injection start command. Then, at a point in time t32, it becomes the first on / off valve 51 closed in response to an end fuel injection command. In the operation in the valve opening mode at low speed and the valve closing mode at high speed, the valve closing state of the second on / off valve becomes 52 maintained.

In the above embodiment, the filter temperature increase control is carried out by dividing the period Tf in which the temperature increase is possible in the period in which the fuel is not from the injector 20th any one of the cylinders is injected. Alternatively, in the middle of injecting the fuel at one of the cylinders, the high temperature fuel may be sent to the fuel filter 66 be fed back by the first on / off valve 51 is closed and the second on / off valve 52 on the injector 20th another one of the cylinders is opened. 18th 13 indicates a time chart in a case where the filter temperature increase control is performed by overlapping the period in which the filter temperature increase control is executed with a fuel injection period. In 18th becomes the second on / off valve in the period Tx during which the fuel injection is carried out in the first cylinder # 1 52 of another cylinder (in this case the fourth cylinder # 4) is opened in such a way that the duration in which the second on / off valve 52 of another cylinder (in this case the fourth cylinder # 4) is opened, with the duration Tx overlapping. Hence the fuel filter 66 in the duration Ty the high temperature fuel of the injector 20th installed in the fourth cylinder # 4.

In the case where the filter temperature increase control is carried out in the middle of the injection of the fuel, the rail pressure is decreased during the time when the fuel is injected. Therefore, the filter temperature increase control during the time the fuel is injected is generally prohibited, and the filter temperature increase control during the time the fuel is injected can be combined with the filter temperature increase control during the time the fuel injection is stopped only in the case where the fuel filter 66 needs to be heated quickly, such as at extremely low temperatures. In the case where the filter temperature increase control is carried out in the middle of injecting the fuel, it is recommended that a restriction be set on the amount of rail pressure drop to allow the fuel to reach the fuel filter 66 is fed back while minimizing problems such as smoke deterioration or torque reduction.

The fuel injection system may be configured to assess whether in at least one of the injector 20th or the drive circuit has an error has occurred and to restrict the execution of the filter temperature increase control in the case where it is determined that the failure is in at least one of the injector 20th or the drive circuit has occurred. In this case, if one or more of the cylinders are judged to be defective, the execution of the filter temperature increase control is prohibited for the one or more cylinders judged to be defective and the temperature increase control is prohibited. Flow rate Qu of the injector 20th the remaining normal cylinder (s) is increased. In addition, in the system in which the heater is used to heat the fuel filter 66 is provided, the fuel filter 66 be heated by the heater to prevent clogging of the fuel filter 66 rather than restricting the filter temperature increase control using the injector 20th is performed.

In addition, the heater can be used to heat the fuel filter 66 can be provided such that the filter temperature increase control by the return of the fuel from the injector 20th and the heating control of the fuel filter 66 by the heater can be used in combination. In such a case, the filter temperature increase control is performed by returning the fuel from the injector 20th Priority granted and the heating control of the fuel filter 66 by the heater is used in combination with the filter temperature increase control when the fuel filter 66 cannot be heated sufficiently by recirculating the fuel alone, thereby clogging the fuel filter 66 is restricted.

In the above embodiment, the number N of the target cylinders is made variable according to the temperature increasing flow amount Qu. Alternatively, the fuel injection system can be configured to use the fuel filter 66 to supply the fuel at high temperature by the injectors 20th of all cylinders can be used regardless of the temperature increasing flow rate Qu. In such a case, the fuel injection system can be configured, for example, to adjust the degree of opening of the recirculation valve 67 to change, or according to the temperature increase flow rate Qu, the opening duration of the second on / off valve 52 to vary (ie, to vary the temperature rise execution time Tc).

In the above embodiment, the clogging condition includes that the temperature Tb in front of the filter is equal to or lower than the clogging determination value Tw, and the filter temperature raising control is carried out in which the temperature Tb in front of the filter is equal to or lower than the clogging Determination value is Tw. Alternatively, the fuel injection system can be configured to sense the amount of foreign objects on the fuel filter 66 are deposited, and execute the filter temperature increase control when the sensed amount of foreign objects stuck on the fuel filter 66 are deposited, is above a predetermined value. More specifically, a pressure difference before and after the fuel filter becomes, for example 66 is sensed, and if the pressure difference is over a predetermined value, the filter temperature increase control can be carried out.

In the above embodiment, the filter temperature increase control is carried out when the clogging condition is satisfied. Alternatively, the fuel injection system may be configured to judge whether this is the time of engine start, and each time it is the time of engine start, the filter temperature increase control may always be executed.

In the above embodiment, the description will be given of the case where the injection rate is variably controlled by opening and closing the second on / off valve 52 is controlled. Alternatively, an on / off valve associated with the filter temperature increase can be provided as a pressure control valve that is configured to adjust the fuel pressure in the control chamber without the needle valve 31 to move by allowing and breaking the communication between the control chamber and the fuel drain passage.

The configuration of the injector 20th is not limited to the configuration included in 1 will be shown. For example with the injector 20th of 1 can in the state in which the follow-up valve 41 the connection between the first high pressure passage 13th and the first control chamber 46 interrupts the second passage 27 through another passage, which is in the follow-up valve 41 is formed and extends from the third passage 42 differs, with the first control chamber 46 stay in contact. Alternatively, in the state in which the second passage 27 with the intermediate chamber 26th is in communication and the follow-up valve 41 the connection between the first high pressure passage 13th and the first control chamber 46 interrupts the second passage 27 through the intermediate chamber 26th and the third passage 42 with the first control chamber 46 stay in contact.

In addition, the injector 20th of 1 two or more on / off valves than the second on / off valves 52 to adjust the speed of movement of the needle valve 31 be provided, and the speed of movement of the needle valve 31 can be adjusted more precisely by individually controlling the opening and closing of these two or more on / off valves. In this case, the amount of flow of fuel through the pressure load restricting orifice is 14a is set to be larger than a sum of the amounts of flow of fuel through the pressure relief orifices each provided in two or more fuel passages which are opened and closed by the two or more on / off valves.

The above components are conceptual and are not limited to the above embodiments. For example, the functions of a single component can be distributed across multiple components, or the functions of multiple components can be implemented by a single component.

Although the present disclosure has been described in accordance with the examples, it should not be construed that the present disclosure is limited to such examples or structures. The present disclosure also encompasses various variations and variations within a range of equivalences. In addition, various combinations and shapes, as well as other combinations and shapes including only one element, more or less, are included within the scope and spirit of the present disclosure.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• JP 2018199581 [0001]
• JP 2014051920 A [0004]

Claims (9)

Fuel injection system, comprising: a fuel filter (66) installed in a low pressure fuel passage (63) connecting a fuel tank (61) and a high pressure pump (62), the fuel filter configured to filter fuel; a manifold (11) configured to receive the fuel from the high pressure pump and to accumulate the fuel in a high pressure state; and an injector (20) configured to inject high pressure manifold fuel directly into a cylinder of an internal combustion engine (70), wherein: the injector includes: a control chamber (36, 46) configured to receive the high pressure fuel from the manifold; a needle valve (31) configured to reciprocate between a valve opening position and a valve closing position in response to fuel pressure in the control chamber, thereby opening and closing an injection hole (34); a fuel drain passage (58) configured to drain the fuel of the control chamber to an outside of the injector; and a pressure control valve (52) configured to enable and break communication between the control chamber and the fuel drain passage, thereby adjusting the fuel pressure in the control chamber without moving the needle valve; a return pipe (65, 65a) is provided to connect the fuel drain passage and a portion of the low pressure fuel passage, the portion of the low pressure fuel passage being on a downstream side of the fuel tank and a downstream side of the fuel filter; and the fuel injection system further comprises a delivery control unit configured to operate the pressure control valve such that the pressure control valve enables communication between the control chamber and the fuel drain passage in a state where the needle valve is in the valve closing position, and as a result, the fuel of the control chamber is supplied to the fuel filter through the return pipe without the needle valve being moved from the valve closing position. Fuel injection system according to Claim 1 wherein: the injector includes: a first on / off valve (51) installed on a first passage (25) connecting the control chamber and the fuel drain passage, the first on / off valve configured to do so is to enable and break communication between the control chamber and the fuel drain passage, thereby moving the needle valve to the valve opening position and the valve closing position, respectively; and a second on / off valve (52) installed on a second passage (27) different from the first passage and connecting the control chamber and the fuel drain passage, the second on / off valve being configured to do so is to enable and break communication between the control chamber and the fuel drain passage, thereby adjusting the fuel pressure in the control chamber without moving the needle valve; the pressure control valve is the second on / off valve, the fuel injection system further comprises an injection control unit configured to open and close the first on / off valve and to open and close the second on / off To control valve and thereby variably control an injection rate of the injector; and the supply control unit is configured to control the second on / off valve such that the second on / off valve enables communication between the control chamber and the fuel drain passage through the second passage, and thereby in the state in which the needle valve is placed in the valve closing position by controlling the first on / off valve such that the first on / off valve interrupts communication between the control chamber and the fuel drain passage through the first passage, the fuel filter through the Return pipe the fuel is supplied to the control chamber. Fuel injection system according to Claim 1 or 2 , comprising a condition determination unit configured to determine whether a predetermined accumulation condition for generating accumulation of the fuel is satisfied based on a fuel temperature on an upstream side of the high pressure pump, wherein: the supply control unit is configured to operate in a case where the condition determining unit determines that the predetermined accumulation condition is satisfied to supply the fuel to the fuel filter from the control chamber. Fuel injection system according to one of the Claims 1 to 3 having a flow rate adjustment unit configured to adjust a flow rate of the fuel to be supplied to the fuel filter from the control chamber based on a fuel temperature on an upstream side of the high pressure pump, wherein: the supply control unit is configured to: based on the flow rate of the fuel that is set by the flow rate adjusting unit to supply the fuel to the fuel filter from the control chamber. Fuel injection system according to Claim 4 wherein: the cylinder is one of a plurality of cylinders of the internal combustion engine, and the injector is one of a plurality of injectors each installed on the plurality of cylinders; the fuel injection system further includes a cylinder number setting unit configured to be supplied to the fuel filter from the one or more target cylinders based on the flow amount of the fuel that is set by the flow amount setting unit to set a number of one or more target cylinders from the plurality of cylinders, each of which is supplied with fuel to the fuel filter from the control chamber of a corresponding one of the plurality of injectors; and the supply control unit is configured to control the pressure control valve of the corresponding one of the plurality of injectors in each of the one or more target cylinders, the number of which is set by the number of cylinders setting unit, so that the fuel of the control chamber of the corresponding one of the plurality of injectors is supplied to the fuel filter. Fuel injection system according to Claim 5 further comprising a deactivated cylinder determination unit configured to determine whether the plurality of cylinders have a deactivated cylinder in which combustion of the fuel is stopped, wherein: the supply control unit preferably includes the deactivated cylinder as one of selects the one or more target cylinders in which the fuel is supplied to the control chamber of the corresponding one of the plurality of injectors to the fuel filter when the deactivated cylinder determination unit determines that the deactivated cylinder is present, and the supply control unit then determines the pressure Controls the control valve of the corresponding one of the plurality of injectors installed in the deactivated cylinder so that the fuel is supplied to the control chamber of the corresponding one of the plurality of injectors to the fuel filter. Fuel injection system according to one of the Claims 4 to 6th , further comprising: a delivery amount calculating unit configured based on an injection amount command value of the injector installed in each of the one or more target cylinders and the flow amount of the fuel adjusted by the flow amount adjusting unit is to calculate a fuel delivery amount of the high pressure pump; and a drive control unit configured to control an operation of the high pressure pump based on the fuel delivery amount calculated by the delivery amount calculation unit. Fuel injection system according to one of the Claims 1 to 7th wherein: the cylinder is one of a plurality of cylinders of the internal combustion engine, and the injector is one of a plurality of injectors each installed on the plurality of cylinders; and the supply control unit is configured to supply the fuel of the control chamber of the one of the plurality of injectors to the fuel filter during a period during which the fuel is not injected from the injection holes of one of the plurality of injectors. Fuel injection system according to Claim 8 , wherein the supply control unit is configured to control the pressure control valve of the one of the plurality of injectors after a start of supply of the fuel of the control chamber to the fuel filter such that the pressure control valve opens the connection between the control chamber and the fuel drain passage of the interrupts one of the plurality of injectors at a point in time which is a predetermined time before an injection start point in time of a next combustion cylinder out of the plurality of cylinders.

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