EP1171706B1 - Fuel injector for an internal combustion engine - Google Patents

Abstract

Within an injector housing, a nozzle needle comprising a nozzle needle shaft is accommodated in a first guide boring in a longitudinally displaceable manner. A nozzle prechamber which is arranged in front of the nozzle needle shaft and which is situated on the fore-part of the first guide boring is supplied with fuel via a high pressure channel. A control valve permits a control chamber, which is coupled to the nozzle needle and which is subjected to the action of highly pressurized fuel, to be relieved from pressure by opening the nozzle needle. According to a second embodiment, a spring chamber is configured as a high-pressure chamber on the rear side of the first guide boring that guides the nozzle needle shaft. The spring chamber is separate from the control chamber and contains a readjusting spring that impinges upon the nozzle needle in a direction of closure. This configuration prevents fuel exiting the nozzle prechamber from overflowing over the guide boring which guides the nozzle needle.

Description

The invention relates to a fuel injector for injecting under high pressure available fuel in the combustion chamber of an internal combustion engine, as in The preamble of claim 1 is required (see EP-A-582 993).

Such a known fuel injector comprises an injector housing and a nozzle needle, one in a first guide bore formed in the injector housing longitudinally displaceable nozzle needle shaft and one with one in the front end of the Injector housing trained valve seat in the sense of opening and closing a Has valve opening cross section interacting nozzle needle tip. For feeding high pressure fuel to be injected is a high pressure duct intended. At the front of the first guide bore is the nozzle needle shaft of the fuel to be injected via the high-pressure channel under high Pressure upstream of the nozzle antechamber. With the nozzle needle is one from below high pressure fuel coupled control chamber coupled by means of a control valve in the sense of opening the nozzle needle can be relieved of pressure. At the At the back of the first guide hole there is a space which is separated from the Receives anteroom passing over the first guide bore fuel.

A disadvantage with such a fuel injector is that between the Anteroom and the arranged at the back of the first guide hole Space as well as between the control room and this room a significant leak occurs, which are in the range of up to 20 or 30% of the maximum injection quantity can.

The object of the invention is a fuel injector of the type described above train that this leakage is avoided.

This object is achieved by a fuel injector with the features of claim 1 solved.

Advantageous developments of the fuel injector according to the invention are in the Subclaims marked.

The fuel injector according to the invention is for injecting under high pressure provided fuel is provided in the combustion chamber of an internal combustion engine. The Fuel injector includes an injector housing and a nozzle needle, one in one in the first guide bore formed in the injector housing is longitudinally displaceable mounted nozzle needle shaft and one with one in the front end of the injector housing trained valve seat in the sense of opening and closing a Has valve opening cross section interacting nozzle needle tip. On High-pressure duct is used for supplying those to be injected under high pressure Fuel. At the front of the first guide bore is the nozzle needle shaft of the fuel to be injected via the high-pressure channel under high Pressure upstream of the nozzle antechamber. With the nozzle needle is one from below high pressure fuel coupled control chamber coupled by means of a control valve in the sense of opening the nozzle needle can be relieved of pressure. At the At the back of the first guide hole there is a space which is separated from the Nozzle vestibule via the first guide hole or from the control chamber Absorbs fuel. According to the invention is that on the back of the first Guide hole arranged a high pressure fuel pressurized high pressure room.

The main advantage of the fuel injector according to the invention is that at the There is no space on the back of the first guide bore guiding the nozzle needle which is at a low pressure level so that no leakage occurs over it can.

According to one aspect of the invention, that is at the rear of the first guide bore trained high pressure space formed by the control room. An advantage of this is that due to the high pressure in the control chamber, an overflow of fuel the first guide hole is not possible. Another advantage is that because of the immediate action on the nozzle needle by the one in the control room Pressure a very fast response of the fuel injector is achieved. Because it there is no low-pressure room adjacent to the control room, there is a leak from the Control room not possible.

According to a development of the invention, it contains the rear high-pressure space forming control chamber acting on the nozzle needle in the closing direction Return spring.

The return spring is advantageously formed by a plate spring arrangement.

It is preferably provided that the return spring at one end by a Back of the nozzle needle shaft provided first abutment and at the other end supported by a second abutment formed on the rear of the control room is.

According to an advantageous embodiment of the invention, the rear is Control room forming high-pressure space through a lengthwise direction of the injector housing running hole formed and at its back by a hole in this used valve body of the control valve limited.

The control space forming the rear high-pressure space is preferably above a Throttle channel with the high pressure channel leading the fuel to be injected in Connection.

According to a second aspect of the invention, the rear high-pressure space is through one separate from the control room, one the nozzle needle in the closing direction acting spring-containing spring chamber formed. One advantage of this is it that the return spring can be dimensioned optimally, while at the same time Control room can be made very small, which is the response of the Fuel injector is advantageous.

The spring chamber is preferably in flow communication with the High-pressure channel leading to the fuel to be injected.

According to a particularly advantageous embodiment of this variant of the The fuel injector according to the invention is at the rear of the high-pressure chamber forming the spring chamber coaxially to the first leading the nozzle needle shaft Guide bore extending second guide bore formed in which a a needle stilts with the nozzle needle coupled guide piston in the longitudinal direction is slidably mounted, which limits the spring space at the rear.

The control chamber is preferably formed on the rear of the guide piston, the fuel in the spring chamber under high pressure and the return spring act on the nozzle needle shaft in the sense of closing the nozzle needle and the Nozzle needle when the control chamber is relieved of pressure by means of the control valve Guide piston is relieved in the sense of opening.

The first guide bore leading the nozzle needle shaft preferably has one Diameter D1, and the spring chamber is through a to the first guide bore coaxial third bore formed, the diameter D2 larger than the diameter D1 the first guide hole is, and the control room is through to the first Guide bore and the spring chamber coaxial second guide bore with a Diameter D1 'formed.

According to a preferred embodiment thereof, it is provided that the Diameters D1, D1 'and D2 are coordinated so that the needle stilts both is only subjected to tension when opening and when closing the nozzle needle. This will result in a buckling or a one-sided contact of the nozzle needle stilts, which leads to jamming could be avoided.

According to a preferred embodiment, the first guide bore and the second guide hole the same diameter D1. The advantage of this is one Simplification in the manufacture of the fuel injector.

According to a preferred embodiment, the return spring is at one end by first abutment provided on the rear of the nozzle needle shaft and on the other End by a second abutment formed on the back of the spring chamber supported.

The control chamber preferably has a significantly smaller volume than the spring chamber.

According to an advantageous development of the fuel injector according to the invention, it is provided that the injector housing at the rear end with the High-pressure channel leading to the fuel to be injected Contains individual storage for holding fuel under high pressure. On such an individual store is in particular in the fuel injector after the first Realize embodiment of the invention in which the rear high pressure space is formed by the control room, since in this embodiment an essential measure in terms of overall length, which can be used for the individual storage.

Figur 1

einen etwas schematisierten Längsschnitt durch einen Kraftstoffinjektor gemäß einem ersten Ausführungsbeispiel der Erfindung, bei dem der an der Rückseite der ersten Führungsbohrung ausgebildete Hochdruckraum durch den Steuerraum gebildet ist;

Figur 2

einen etwas schematisierten Längsschnitt durch einen Kraftstoffinjektor gemäß einem zweiten Ausführungsbeispiel der Erfindung, bei dem der rückseitige Hochdruckraum durch einen vom Steuerraum getrennten, eine die Düsennadel in Schließrichtung beaufschlagende Rückstellfeder enthaltenden Federraum gebildet ist; und

Figur 3

einen etwas schematisierten Längsschnitt durch einen Kraftstoffinjektor nach dem Stand der Technik, bei dem zwischen Düsennadel und Steuerraum ein Niederdruckraum ausgebildet ist, über welchen eine vom Düsenvorraum über die erste Führungsbohrung und eine vom Steuerraum übertretende Kraftstoffmenge

als

Leckage abgeführt wird.

Two exemplary embodiments of the fuel injector according to the invention are explained below with reference to the drawing. Show it:

Figure 1

a somewhat schematic longitudinal section through a fuel injector according to a first embodiment of the invention, in which the high-pressure chamber formed on the back of the first guide bore is formed by the control chamber;

Figure 2

a somewhat schematic longitudinal section through a fuel injector according to a second exemplary embodiment of the invention, in which the rear high-pressure chamber is formed by a spring chamber which is separate from the control chamber and contains a return spring which acts on the nozzle needle in the closing direction; and

Figure 3

a somewhat schematic longitudinal section through a fuel injector according to the prior art, in which a low-pressure chamber is formed between the nozzle needle and the control chamber, via which a fuel quantity passing from the nozzle antechamber via the first guide bore and a fuel quantity passing from the control chamber

as

Leakage is discharged.

First of all, a fuel injector for injecting from below high should be based on FIG Fuel pressure is described in the combustion chamber of an internal combustion engine be as it is known in the prior art. The total with the Fuel injector designated by reference numeral 300 comprises an injector housing 301, in which a nozzle needle 303 with a nozzle needle shaft 304 in one in the Injector housing 301 formed first guide bore 302 is longitudinally displaceable is stored. The nozzle needle 303 has a nozzle needle tip 305 which is in contact with an front end of the injector housing 301 formed valve seat 306 in the sense of a Opening and closing a valve opening cross-section that interacts between the needle tip 305 and the valve seat 306 is provided. A high pressure channel 307 is provided for supplying fuel to be injected under high pressure, which is supplied via a pressure connection 329. The fuel comes in one Oil-elastic pressure accumulator (common rail) held under high pressure, in which it is promoted from a fuel supply by means of a high-pressure pump (not in the figure ) Shown. This is at the front of the first guide bore 302 Nozzle needle shaft 304 in front of a nozzle antechamber 308 in the injector housing 301 provided, that of the injected via the high pressure channel 307 to be injected Fuel is pressurized under high pressure. A control room 309 that has a the high-pressure channel 307 connected throttle channel 314 with under high Pressurized fuel is applied via a needle stilts 322, which in a guide sleeve 330 arranged in the injector housing 301 in the longitudinal direction of the Fuel injector 300 is slidably coupled to the nozzle needle 303. On A control valve 310 is provided at the rear of the control chamber 309 Valve body 312 and a closing body 313 is formed. The closing body 313 of the Control valve 310 is operatively coupled to a solenoid 326, through which the control valve 310 is opened and closed. With control valve 310 closed the nozzle needle 303 via the needle stilts 322 through the in the control room 309 pending high pressure is kept closed while opening the control valve 310 the control room 309 in the sense of opening the nozzle needle 303 via the needle stilts 322 can be relieved of pressure. At the back of the first leading the nozzle needle 303 Guide bore 302 is between the nozzle needle 303 and the control chamber 309 and Needle wagtail 322 partially surrounding a low pressure space 331, over which from the nozzle antechamber 308 via the first guide bore 302 and from the control chamber 309 fuel that is transferred via the guide sleeve 330 is discharged as a leakage quantity. Surrounding the front end of the needle stilts 322 is in the low pressure space 331 between a first abutment provided on the back of the nozzle needle 303 320 and a second abutment 321 provided on the injector housing 301 Return spring 316 is provided for closing the nozzle needle 303. The nozzle needle 303 is at pressure relief of the control room 309 via the control valve 310 by the in Antechamber 308 opened on fuel pressure acting on nozzle needle shaft 304. The in the pressure relief of the control chamber 309 via the control valve 310 final The amount of fuel together with the amount of fuel from the low pressure space 331 discharged via a leakage channel 332.

A first exemplary embodiment of an inventive device is now to be described with reference to FIG Fuel injector for injecting high-pressure fuel into the Combustion chamber of an internal combustion engine can be described. Similar to that known fuel injector is in the one shown here, overall with the reference symbol 100 designated fuel injector in an injector housing 101, a nozzle needle 103 with a nozzle needle shaft 104 in a formed in the injector housing 101 first guide bore 102 mounted longitudinally. The nozzle needle 103 is on its front end a nozzle needle tip 105, which is in the front end of the Injector housing 101 formed valve seat 106 in the sense of opening and closing of a valve opening cross-section which interacts between the nozzle needle tip 105 and the valve seat 106 is provided. For feeding under high pressure standing fuel to be injected is a high pressure channel 107 in the Injector housing 101 is formed. The fuel to be injected is a Pressure port 129 supplied from an oil-elastic memory (common rail), too which the fuel from a fuel supply by means of a high pressure pump is promoted (not shown). This is at the front of the first guide bore 102 Nozzle needle shaft 104 in front of a nozzle antechamber 108, which of the over the High pressure channel 107 supplied fuel to be injected under high pressure is acted upon. At the back of the nozzle needle 103 is the first guide hole 102 then a control room 109 is formed in the injector housing 101, which over a throttle channel 114 connected to the high-pressure channel 107 with below high pressure fuel is applied. The control room 109 is through a Control chamber bore 111 is formed in the injector housing 101 and is on its rear side through a valve body 112 inserted into the control chamber bore 111 Control valve 110 limited. A closing body 113 of the control valve 110 is with a rear end of the injector housing 101 provided solenoid 126 functionally coupled. Furthermore, a return spring 116 is arranged in the control chamber 109, which is provided between one on the rear of the nozzle needle shaft 104 first abutment 120 and one through the front of the valve body 112 of the Control valve 110 formed second abutment 121 is supported. When closed Control valve 110, the nozzle needle 103 under the action of the return spring 116 and the closed in the control chamber 109 under high pressure fuel held. When the pressure in the control chamber 109 is relieved by means of the control valve 110 Nozzle needle 103 under the action of the high pressure in the antechamber 108 pending fuel opened, which from the control room 109 via the Control valve 110 flowing fuel is discharged through a leakage channel 132.

As in comparison with the fuel injector shown in Figure 3 according to the state of the Technology can be seen, there is no on the back of the nozzle needle 103 Low-pressure space, over which one from the nozzle antechamber 108 through the first Guide hole 102 leakage amount may occur. The one in the control room 109 fuel under high pressure prevents such a violation of Fuel from the nozzle vestibule 108 via the first guide bore 102 Return spring 116 is in the illustrated embodiment by a Disc spring arrangement formed.

FIG. 2 shows a second exemplary embodiment of a fuel injector according to the invention for injecting high-pressure fuel into the combustion chamber Internal combustion engine shown. The one with the reference numeral 200 Fuel injector comprises an injector housing 201, in which a nozzle needle 203 also a nozzle needle shaft 204 in a first one formed in the injector housing 201 Guide bore 201 is mounted to be longitudinally displaceable. The nozzle needle 203 has one Nozzle needle tip 205, which with a in the front end of the injector housing 201 trained valve seat 206 in the sense of opening and closing one Valve opening cross-section cooperates between the nozzle needle tip 205 and the valve seat 206 is formed. A high pressure channel 207 for feeding from under high Pressure fuel to be injected is formed in the injector housing 201 and communicates with a pressure port 229, which is the one to be injected Fuel is supplied from an oil-elastic storage tank (common rail) to which the Fuel is supplied by a high pressure pump from a fuel supply (not shown). At the front of the first guide bore 202 is in the injector housing 201 a nozzle vestibule 208 is formed, which via the high pressure channel 207 under high Pressure is applied by the fuel to be injected. In the rear part of the Injector housing 201, a control chamber 209 is formed which communicates with the High pressure passage 207 communicating throttle passage 214 with high pressure standing fuel and is depressurized by means of a control valve 207 is. At the rear of the first guide bore 202 is between the nozzle needle 203 and the control chamber 209, a high-pressure chamber 215 is provided, which by a Nozzle needle 203 containing restoring spring 216 acting in the closing direction Spring chamber 215 is formed. The spring chamber 215 is separated from the control chamber 209 by an in a second guide bore which is coaxial with the first guide bore 202 218 guide piston 219 mounted for longitudinal displacement. The guide piston 219 is coupled to the back of the nozzle needle 203 via a needle stilts 222, whereby a coupling of the control chamber 209 with the nozzle needle 203 is established. The Guide piston 219 thus delimits the spring space 215 on its rear side. The Spring chamber 215 is connected to the one to be injected via a flow connection 217 fuel-carrying high pressure channel 207 connected so that inside the spring chamber 215 the same high pressure as in the high pressure channel 207 and thus in the Antechamber 208 prevails. Thus, an overflow of fuel from that Nozzle vestibule 208 via the first guide bore 202 in the at the rear of the Nozzle needle 203 space, namely the spring space 215 not possible. The one in Spring chamber 215 pressurized fuel acting together with the Force of the return spring 215 the nozzle needle shaft 204 in the sense of closing the Nozzle needle 203, while nozzle needle 203 relieves pressure in control chamber 209 by means of the control valve 210 through the guide piston 219 via the needle stilts 222 in Relieved of opening. The control valve 210 includes a valve body 212 and a closing body 213, which is used to operate the fuel injector controlling solenoid 226 is operatively coupled. The in the spring space 215 return spring 216 is arranged at one end by a at the rear of the Nozzle needle shaft 204 provided first abutment 220 and at the other end a second abutment 221 formed on the rear of the spring chamber 215 supported.

The first guide bore 202 leading the nozzle needle shaft 204 has one Diameter D1, which forms the spring space 215 to the first guide bore 202 Coaxial third bore 228 has a diameter D2 that is larger than the diameter D1 of the first guide hole 202, and that to the first guide hole 202 and thus simultaneously coaxial with the third bore 228 forming the spring chamber 215 second guide bore 218, which also has the control chamber 209 in its rear part forms, has a diameter D1 ', which in the illustrated embodiment Diameter D1 of the first guide bore 202 is the same, i.e. D1 '= D1. The Diameter D1, D1 'and D2, in the present embodiment only that Both diameters D1 and D2 are matched to one another so that the needle stilts 222 both when opening and when closing the nozzle needle 203 only under tension is. This causes a buckling or one-sided contact of the needle stilts 222, what could lead to jamming.

The control chamber 209 has a much smaller volume than the spring chamber 215, which improves the response of the fuel injector.

LIST OF REFERENCE NUMBERS

100; 200; 300

fuel injector

101; 201; 301

injector

102; 202; 302

(first) pilot hole

103; 203; 303

nozzle needle

104; 204; 304

Nozzle needle shaft

105: 205; 305

Nozzle needle tip

106; 206; 306

valve seat

107; 207; 307

High pressure passage

108; 208; 308

nozzle antechamber

109; 209; 309

control room

110; 210; 310

control valve

111; 211; 311

Control chamber bore

112; 212; 312

Valve body of the control valve

113; 213; 313

Control valve closing body

114; 214; 314

throttle channel

115; 215; 315

spring chamber

116; 216; 316

Return spring

217

flow connection

218; 318

second guide hole

219

guide piston

120; 220; 320

first abutment

121; 221; 321

second abutment

222; 322

Nadelstelze

323

control rod

324

leakage chamber

325

leakage channel

126; 226; 326

solenoid

127

Single memory

228

Spring chamber bore

129; 229; 329

pressure connection

330

guide sleeve

331

Low-pressure chamber

132; 232; 332

leakage channel

Claims (16)

1. Fuel injector for injecting highly pressurized fuel into the combustion chamber of an internal combustion engine, having an injector housing (101; 201), a nozzle needle (103; 203) which has a nozzle-needle shank (104; 204) which is mounted longitudinally displaceably in a first guide hole (102; 202) formed in the injector housing (101; 201) and a nozzle-needle tip (105; 205) which interacts, in terms of opening and closing a valve opening cross section, with a valve seat (106; 206) formed in the front end of the injector housing (101; 201), having a high-pressure duct (107; 207) for feeding highly pressurized fuel to be injected, a nozzle supply chamber (108; 208) which is mounted ahead of the nozzle-needle shank (104; 204) on the front side of the first guide hole (102; 202) and is acted on at high pressure by the fuel which is to be injected and is supplied via the high-pressure duct (107; 207), having a control chamber (109; 209) which is coupled to the nozzle needle (103; 203), is acted on by highly pressurized fuel and can be relieved of pressure, in terms of opening the nozzle needle (103; 203), by means of a control valve (110; 210), and having a chamber which is arranged on the rear side of the first guide hole (102; 202) and receives fuel which passes from the nozzle supply chamber (108; 208) via the first guide hole (102; 202) or from the control chamber (109; 209), the chamber which is arranged on the rear side of the first guide hole (102; 202) being a high-pressure chamber (109; 215) which is acted on by highly pressurized fuel, characterized in that the injector housing (101) comprises, at the rear end, an individual store (127) for storing highly-pressurized fuel which is connected to the high-pressure duct (107) which conducts the fuel to be injected.
2. Fuel injector according to Claim 1, characterized in that the high-pressure chamber which is configured on the rear side of the first guide hole (102) is formed by the control chamber (109).
3. Fuel injector according to Claim 2, characterized in that the control chamber (109) which forms the rear high-pressure chamber comprises a restoring spring (116) which acts on the nozzle needle (103) in the closing direction.
4. Fuel injector according to Claim 3, characterized in that the restoring spring (116) is formed by a disc-spring arrangement.
5. Fuel injector according to Claim 4, characterized in that the restoring spring (116) is supported at one end by a first abutment (120) which is provided on the rear side of the nozzle-needle shank (104) and at the other end by a second abutment (121) which is configured on the rear side of the control chamber (109).
6. Fuel injector according to one of Claims 2 to 5, characterized in that the control chamber (109) which forms the rear high-pressure chamber is formed by a hole (111) extending in the longitudinal direction of the injector housing (101) and is delimited on its rear side by a valve body (112), which is inserted into the said hole (111), of the control valve (110).
7. Fuel injector according to one of Claims 2 to 6, characterized in that the control chamber (109) which forms the rear high-pressure chamber is connected via a restrictor duct (114) to the high-pressure duct (107) which conducts the fuel to be injected.
8. Fuel injector according to Claim 1, characterized in that the rear high-pressure chamber is formed by a spring chamber (215) which is separate from the control chamber (209) and contains a restoring spring (216) which acts on the nozzle needle (203) in the closing direction.
9. Fuel injector according to Claim 8, characterized in that the spring chamber (215) is connected via a flow connection (217) to the high-pressure duct (207) which conducts the fuel to be injected.
10. Fuel injector according to Claim 8 or 9, characterized in that a second guide hole (218) which extends coaxially to the first guide hole (202) which guides the nozzle-needle shank (207) is configured on the rear side of the spring chamber (215) which forms the high-pressure chamber, in which second guide hole (218) a guide piston (219) which is coupled to the nozzle needle (203) via a needle stilt (222) is displaceably mounted in the longitudinal direction, which guide piston (219) delimits the spring chamber (215) on its rear side.
11. Fuel injector according to Claim 10, characterized in that the control chamber (209) is configured on the rear side of the guide piston (219), the highly-pressurized fuel in the spring chamber (215) and the restoring spring (216) acting on the nozzle-needle shank (204) in terms of closing the nozzle needle (203), and the nozzle needle (203) being relieved by the guide piston (219) via the needle stilt (222) in terms of opening it when the control chamber (209) is relieved of pressure by means of the control valve (210).
12. Fuel injector according to Claim 11, characterized in that the first guide hole (202) which guides the nozzle-needle shank (204) has a diameter D1, in that the spring chamber (215) is formed by a third hole (228) which is coaxial to the first guide hole (202), the diameter D2 of the said third hole (228) being larger than the diameter D1 of the first guide hole (202), and in that the control chamber (209) is formed by the second guide hole (218) which is coaxial to the first guide hole (202) and the spring chamber (215) and has a diameter D1'.
13. Fuel injector according to Claim 12, characterized in that the diameters D1, D1' and D2 are adapted to one another in such a way that the needle stilt (222) is subjected only to tension both when the nozzle needle (203) is opened and when it is closed.
14. Fuel injector according to one of Claims 10 to 13, characterized in that the first guide hole (202) and the second guide hole (218) have the same diameter D1.
15. Fuel injector according to one of Claims 8 to 14, characterized in that the restoring spring (216) is supported at one end by a first abutment (222) which is provided on the rear side of the nozzle-needle shank (204) and at the other end by a second abutment (221) which is configured on the rear side of the spring chamber (215).
16. Fuel injector according to one of Claims 11 to 15, characterized in that the control chamber (209) has a substantially smaller volume than the spring chamber (215).

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