Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M47/00—Fuel-injection apparatus operated cyclically with fuel-injection valves actuated by fluid pressure
  • F02M47/02—Fuel-injection apparatus operated cyclically with fuel-injection valves actuated by fluid pressure of accumulator-injector type, i.e. having fuel pressure of accumulator tending to open, and fuel pressure in other chamber tending to close, injection valves and having means for periodically releasing that closing pressure
  • F02M47/027—Electrically actuated valves draining the chamber to release the closing pressure

Definitions

• the invention relates to a fuel injector for injecting fuel held under high pressure into the combustion chamber of an internal combustion engine, as is required in the preamble of claim 1.
• Such a known fuel injector comprises an injector housing and a nozzle needle which has a nozzle needle shaft which is mounted in a longitudinally displaceable manner in a first guide bore formed in the injector housing and a nozzle needle tip which interacts with a valve seat formed in the front end of the injector housing in the sense of opening and closing a valve opening cross section.
• a high-pressure duct is provided for supplying fuel to be injected under high pressure.
• the nozzle needle shaft is preceded by a nozzle antechamber which is acted upon by the fuel to be injected via the high-pressure duct and under high pressure.
• a control chamber acted upon by fuel under high pressure is coupled to the nozzle needle and can be relieved of pressure by means of a control valve in the sense of opening the nozzle needle.
• a control valve in the sense of opening the nozzle needle.
• At the rear of the first guide bore there is a space which receives fuel passing from the nozzle antechamber through the first guide bore.
• a disadvantage of such a fuel injector is that a considerable leakage occurs between the nozzle antechamber and the space arranged at the rear of the first guide bore as well as between the control chamber and this space, which are in the range of up to 20 or 30% of the maximum injection quantity can.
• the object of the invention is to design a fuel injector of the required type so that this leakage is avoided.
• the fuel injector according to the invention is provided for injecting fuel held under high pressure into the combustion chamber of an internal combustion engine.
• the fuel injector comprises an injector housing and a nozzle needle, which has a nozzle needle shaft which is mounted so as to be longitudinally displaceable in a first guide bore formed in the injector housing and a nozzle needle tip which interacts with a valve seat formed in the front end of the injector housing in the sense of opening and closing a valve opening cross section.
• High-pressure duct is used to supply fuel to be injected under high pressure.
• the nozzle needle shaft is preceded by a nozzle antechamber which is acted upon by the fuel to be injected via the high-pressure duct and under high pressure.
• a control chamber acted upon by fuel under high pressure is coupled to the nozzle needle and can be relieved of pressure by means of a control valve in the sense of opening the nozzle needle.
• a space is arranged which receives fuel passing from the nozzle antechamber via the first guide bore or from the control chamber. According to the invention, the space arranged on the rear side of the first guide bore is a high-pressure space acted upon by fuel under high pressure.
• the main advantage of the fuel injector according to the invention is that 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 can occur over it.
• the high-pressure space formed on the rear of the first guide bore is formed by the control space.
• control chamber forming the rear high-pressure chamber contains a return spring which acts on the nozzle needle in the closing direction.
• the return spring is advantageously formed by a plate spring arrangement.
• the return spring is supported at one end by a first abutment provided on the rear side of the nozzle needle shaft and at the other end by a second abutment formed on the rear side of the control chamber.
• control chamber forming the rear high-pressure chamber is formed by a bore running in the longitudinal direction of the injector housing and is limited on its rear by a valve body of the control valve inserted into this bore.
• the control space forming the rear high-pressure space is preferably connected via a throttle duct to the high-pressure duct carrying the fuel to be injected.
• 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.
• the spring chamber is preferably connected via a flow connection to the high-pressure duct carrying the fuel to be injected.
• a second guide bore coaxial with the first guide bore leading the nozzle needle shaft, is formed on the rear side of the spring chamber forming the high-pressure chamber, in which a guide piston coupled to the nozzle needle via a needle stilts is displaceably mounted in the longitudinal direction, which limits the spring space at the back.
• the control chamber is preferably formed on the back of the guide piston, the fuel in the spring chamber under high pressure and the return spring acting on the nozzle needle shaft in the sense of closing the nozzle needle and relieving the pressure on the control chamber by means of the control valve by the control piston by opening the valve piston becomes.
• the first guide bore leading the nozzle needle shaft has a diameter D 1
• the spring chamber is formed by a third bore coaxial with the first guide bore, the diameter D2 of which is larger than the diameter D 1 of the first guide bore, and the control chamber is through that first guide bore and the spring chamber coaxial second guide bore with a diameter DT formed.
• the diameters D 1, D T and D2 are coordinated with one another in such a way that the wagtail is only subjected to tension both when opening and when closing the nozzle needle. This avoids kinking or one-sided contact of the nozzle needle stilts, which could lead to jamming.
• the first guide bore and the second guide bore the same diameter D 1.
• the advantage of this is a simplification in the manufacture of the fuel injector.
• the return spring is supported at one end by a first abutment provided on the rear of the nozzle needle shaft and at the other end by a second abutment formed on the rear of the spring chamber.
• the control chamber preferably has a significantly smaller volume than the spring chamber.
• the injector housing at the rear end contains an individual store, which is connected to the high-pressure channel guiding the fuel to be injected, for holding fuel under high pressure.
• an individual memory is particularly in the fuel injector after the first
• FIG. 1 shows a somewhat schematic longitudinal section through a fuel injector according to a first exemplary embodiment of the invention, in which the high-pressure chamber formed on the rear side of the first guide bore is formed by the control chamber;
• FIG. 2 shows 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;
• 3 shows 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 quantity of fuel that passes from the nozzle chamber via the first guide bore and a fuel quantity that is transferred from the control chamber is discharged as a leak.
• the fuel injector designated as a whole by the reference numeral 300, comprises an injector housing 301 in which a nozzle needle 303 with a nozzle needle shaft 304 is mounted so as to be longitudinally displaceable in a first guide bore 302 formed in the injector housing 301.
• the nozzle needle 303 has a nozzle needle tip 305 which interacts with a valve seat 306 formed in the front end of the injector housing 301 in the sense of opening and closing a valve opening cross section which is provided between the needle tip 305 and the valve seat 306.
• a high-pressure duct 307 is provided for supplying fuel to be injected under high pressure, which is supplied via a pressure connection 329.
• the fuel is stored in an oil-elastic pressure accumulator (common rail) under high pressure, in which it is conveyed from a fuel supply by means of a high-pressure pump (not shown in the figure).
• a nozzle antechamber 308 is provided at the front of the first guide bore 302, in front of the nozzle needle shaft 304 in the injector housing 301, which is acted upon by the fuel to be injected via the high-pressure channel 307 under high pressure.
• a control chamber 309 which is pressurized with fuel under high pressure via a throttle channel 314 connected to the high-pressure channel 307, is via a needle stem 322, which is displaceably mounted in the longitudinal direction of the fuel injector 300 in a guide sleeve 330 arranged in the injector housing 301. coupled to the nozzle needle 303.
• a control valve 310 which is formed by a valve body 312 and a closing body 313, is provided on the rear of the control chamber 309. 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.
• the nozzle needle 303 When the control valve 310 is closed, the nozzle needle 303 is kept closed via the needle stem 322 by the high pressure present in the control chamber 309, while when the control valve 310 is opened, the control chamber 309 can be relieved of pressure by opening the nozzle needle 303 via the needle stem 322. At the back of the first leading the nozzle needle 303
• Guide bore 302 is formed between the nozzle needle 303 and the control chamber 309 and the stilts 322 partially surrounding a low-pressure chamber 331, via which fuel, which passes from the nozzle antechamber 308 via the first guide bore 302 and from the control chamber 309 via the guide sleeve 330, is discharged as a leakage quantity.
• a return spring 316 for closing the nozzle needle 303 is provided in the low-pressure space 331 between a first abutment 320 provided on the back of the nozzle needle 303 and a second abutment 321 provided on the injector housing 301.
• the nozzle needle 303 is opened via the control valve 310 by the fuel pressure acting on the nozzle needle shaft 304 in the nozzle chamber 308.
• the amount of fuel that ends when the pressure in the control chamber 309 is released via the control valve 310 is discharged together with the amount of fuel from the low-pressure chamber 331 via a leakage channel 332.
• Fuel injector for injecting high-pressure fuel into the combustion chamber of an internal combustion engine are described. Similar to the known fuel injector, in the fuel injector shown here, generally designated by the reference numeral 100, a nozzle needle 103 with a nozzle needle shaft 104 is mounted in a longitudinally displaceable manner in a first guide bore 102 formed in the injector housing 101 in an injector housing 101.
• the nozzle needle 103 has at its front end a nozzle needle tip 105 which cooperates with a valve seat 106 formed in the front end of the injector housing 101 in the sense of opening and closing a valve opening cross section which is provided between the nozzle needle tip 105 and the valve seat 106.
• a high-pressure channel 107 is located in the in order to supply fuel to be injected under high pressure Injector housing 101 is formed.
• the fuel to be injected is supplied via a pressure connection 129 from an oil-elastic reservoir (common rail), to which the fuel is conveyed from a fuel supply by means of a high-pressure pump (not shown).
• the nozzle needle shaft 104 is preceded by a nozzle antechamber 108, which is acted upon by the fuel to be injected via the high-pressure channel 107 under high pressure.
• a control chamber 109 is formed in the injector housing 101 after the first guide bore 102 and is acted upon by fuel under high pressure via a throttle duct 114 connected to the high-pressure duct 107.
• the control chamber 109 is formed by a control chamber bore 1 1 1 in the injector housing 101 and is delimited on its rear side by a valve body 1 12 of a control valve 1 10 inserted into the control chamber bore 1 1 1.
• a closing body 111 of the control valve 110 is functionally coupled to a solenoid 126 provided in the rear end of the injector housing 101.
• a return spring 116 is arranged in the control chamber 109, which is supported between a first abutment 120 provided on the rear side of the nozzle needle shaft 104 and a second abutment 121 formed by the front side of the valve body 112 of the control valve 110.
• the nozzle needle 103 is kept closed under the action of the return spring 116 and the fuel present in the control chamber 109 under high pressure.
• the pressure in the control chamber 109 is relieved by means of the control valve 110, the nozzle needle 103 is opened under the action of the fuel present in the nozzle chamber 108 under high pressure, the fuel flowing out of the control chamber 109 via the control valve 110 being discharged through a leakage channel 132.
• FIG. 2 shows a second exemplary embodiment of a fuel injector according to the invention for injecting fuel held under high pressure into the combustion chamber of an internal combustion engine.
• the fuel injector designated as a whole by reference numeral 200, comprises an injector housing 201 in which a nozzle needle 203 with a nozzle needle shaft 204 is mounted so as to be longitudinally displaceable in a first guide bore 201 formed in the injector housing 201.
• the nozzle needle 203 has a nozzle needle tip 205 which interacts with a valve seat 206 formed in the front end of the injector housing 201 in the sense of opening and closing a valve opening cross section which is formed between the nozzle needle tip 205 and the valve seat 206.
• a high-pressure channel 207 for supplying fuel under high pressure is formed in the injector housing 201 and is connected to a pressure connection 229, which is the one to be injected
• Fuel is supplied from an oil-elastic common rail to which the fuel is supplied by a high pressure pump from a fuel supply (not shown).
• a nozzle antechamber 208 is formed in the injector housing 201, which is acted upon by the fuel to be injected via the high-pressure channel 207 under high pressure.
• a control chamber 209 is formed in the rear part of the injector housing 201, which is acted upon by fuel under high pressure via a throttle duct 214 connected to the high-pressure duct 207 and can be relieved of pressure by means of a control valve 207.
• a high-pressure chamber 215 is provided between the nozzle needle 203 and the control chamber 209, which is formed by a spring chamber 215 which contains a return spring 216 which acts on the nozzle needle 203 in the closing direction.
• the spring chamber 215 is separated from the control chamber 209 by a guide piston 219 which is mounted so as to be longitudinally displaceable in a second guide bore 218 which is coaxial with the first guide bore 202.
• the guide piston 219 is coupled to the rear of the nozzle needle 203 via a needle stilts 222, as a result of which the control chamber 209 is coupled to the nozzle needle 203.
• the Guide piston 219 thus delimits the spring space 215 on its rear side.
• the spring chamber 215 is connected via a flow connection 217 to the fuel-carrying high-pressure channel 207 to be injected, so that the same high pressure prevails in the interior of the spring chamber 215 as in the high-pressure channel 207 and thus in the nozzle antechamber 208.
• a flow connection 217 to the fuel-carrying high-pressure channel 207 to be injected, so that the same high pressure prevails in the interior of the spring chamber 215 as in the high-pressure channel 207 and thus in the nozzle antechamber 208.
• Nozzle vestibule 208 via the first guide bore 202 into the space located at the rear of the nozzle needle 203, namely the spring space 215, is not possible.
• the fuel present in the spring chamber 215 under high pressure acts together with the force of the return spring 215 on the nozzle needle shaft 204 in the sense of closing the nozzle needle 203, while the nozzle needle 203 when the control chamber 209 is relieved of pressure by means of the control valve 210 by means of the control piston 210 through the guide piston 219 via the needle stilts 222 im Relieved of opening.
• the control valve 210 includes a valve body 212 and a closing body 213, which is operatively coupled to a solenoid 226 that controls the operation of the fuel injector.
• the return spring 216 arranged in the spring space 215 is at one end by a at the rear of the
• Nozzle needle shaft 204 provided first abutment 220 and supported at the other end by a second abutment 221 formed on the rear of the spring chamber 215.
• the first guide bore 202 leading the nozzle needle shaft 204 has one
• a third bore 228 that forms the spring chamber 215 and is coaxial with the first guide bore 202 has a diameter D2 that is larger than the diameter D1 of the first guide bore 202 and that to the first guide bore 202 and thus simultaneously to that of the spring chamber 215
• the diameter D 1, DT and D2 in the present exemplary embodiment only the two diameters D 1 and D2, are coordinated with one another in such a way that the needle stilts 222 are only subjected to tension when opening and closing the nozzle needle 203 is. In this way, buckling or one-sided contact of the needle stilts 222, which could lead to jamming, is avoided.
• the control chamber 209 has a much smaller volume than the spring chamber 215, which improves the response behavior of the fuel injector.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Fuel-Injection Apparatus (AREA)

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• 1999
  • 1999-04-16 DE DE19917190A patent/DE19917190A1/de not_active Ceased
• 2000
  • 2000-04-13 EP EP00926906A patent/EP1171706B1/fr not_active Expired - Lifetime
  • 2000-04-13 JP JP2000612616A patent/JP2002542427A/ja active Pending
  • 2000-04-13 DE DE2000508236 patent/DE50008236D1/de not_active Expired - Lifetime
  • 2000-04-13 AT AT00926906T patent/ATE279647T1/de active
  • 2000-04-13 WO PCT/EP2000/003319 patent/WO2000063550A1/fr active IP Right Grant
  • 2000-04-13 US US09/958,804 patent/US6622932B1/en not_active Expired - Lifetime

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