Title of Invention

FUEL INJECTION DEVICE HAVING A PRESSURE AMPLIFIER

Abstract

ABSTRACT (115/CHENP/2003) "FUEL INJECTION DEVICE HAVING A PRESSURE AMPLIFIER" A fuel injection device having a pressure amplifier which has a displaceable piston, which can be pressurized via a pressure-amplifying chamber on the low-pressure side, for compressing the fuel, which is to be supplied to an injector, in a pressure-amplifying chamber on the high-pressure side, the stroke of the piston being controllable essentially by the pressure in a differential chamber of the pressure amplifier and being used for influencing the pressure of the fuel supplied to the injector, characterized in that means for cross-sectional control of the discharge cross section from the differential chamber of the pressure amplifier are provided. Figure 1

Full Text

The invention relates to a fuel injection device according to the precharacterizing clause of patent claim 1. A number of terms will be explained in the following for better comprehension of the description and the patent claims: the fuel injection device according to the invention can be designed to be both stroke-controlled and also pressure-controlled. Within the context of the invention, a stroke-controlled fuel injection device is understood as meaning that the opening and closing of the injection opening takes place with the aid of a displaceable nozzle needle on the basis of the hydraulic interaction of the pressures of the fuel in a nozzle chamber and in a control chamber. A reduction in pressure within the control chamber causes a stroke of the nozzle needle. Alternatively, the nozzle needle can be deflected by means of an actuating element (actuator) . In the case of a pressure-controlled fuel injection device according to the invention, the nozzle needle is moved counter to the effect of a closing force (spring) by the pressure of the fuel prevailing in the nozzle chamber of an injector, so that the injection opening is released for injection of the fuel from the nozzle chamber into the cylinder. The pressure with which fuel emerges from the nozzle chamber into a cylinder of an internal combustion engine is referred to as injection pressure while system pressure is understood to be the pressure at which fuel is available or is stored within the fuel injection device. Fuel metering means providing a defined quantity of fuel for injection purposes. Leakage is understood to be an amount of fuel which is produced during operation of the fuel injection device (for example leakage in the guiding means), is not used for the injection and is recycled to the fuel tank. The pressure level of this leakage can be static, the fuel subsequently being depressurized to the pressure level of the fuel tank. Many engine manufacturers require a flat pressure-rising profile at the beginning of the injection. A boot phase is often also desirable in order to reduce emissions. In the case of fuel injection devices having a pressure amplifier, as are known, for example from DE-A1-19910970, the pressure amplifier can be used in order to form the injection profile. The desired injection profile can thus be realized without additional parts, such as, for example, bypass pistons. In this case, the movement of the piston of the pressure amplifier can be used to influence the pressure profile. The stroke-dependent influencing of the admission cross section to the pressure-amplifying chamber on the low-pressure side is known from US-A 5,568,317. The US-A proposes a multistage control of the admission cross section. Advantages of the invention In order to influence the fuel pressure during the injection and in order to obtain a rise in pressure with simple means, a fuel injection device as claimed in patent claim 1 is proposed. If, for example, two discharge cross sections (a larger one and a smaller one) from the differential chamber of the pressure amplifier are released one after the other as a function of the piston stroke of the pressure amplifier, then a "boot injection" can be carried out. Drawing Three exemplary embodiments of the fuel injection device according to the invention are illustrated in the schematic drawing and will be explained in the following description. In the drawing: fig. 1 shows a stroke-controlled fuel injection device having a pressure amplifier with a two-stage discharge cross section; fig. 2 shows a first, stage-free change in the discharge cross section; fig. 3 shows a second, stage-free change in the discharge cross section. Description of the exemplary embodiments In the case of the first exemplary embodiment, which is illustrated in fig. 1, of a stroke-controlled fuel injection device 1, a quantity-controlled fuel pump feeds fuel from a storage tank via a feed line into a central pressure storage chamber (common rail) from which a plurality of pressure lines 2, which correspond to the number of individual cylinders, lead off to the individual injectors 3 (injection device) protruding into the combustion chamber of the internal combustion engine to be supplied. Only one of the injectors 3 is shown in fig. 1. With the aid of the fuel pump a first system pressure is generated and is stored in the pressure storage chamber. This first system pressure is used for the preinjection and, if the need arises, for the postinjection (HC enrichment for aftertreatment of the exhaust gas or reduction in soot) and for depicting an injection profile having a plateau (boot injection). In order to inject fuel at a second, higher system pressure, each injector 3 is respectively assigned a local pressure amplifier 4 having a nonreturn valve 5 and having a displaceable piston 6. Fuel injection devices of this type are known, for example, from DE-A1-19910970. The pressure in the differential chamber 7, which is formed by a transition from a larger to a smaller piston cross section, is used in order to control the pressure amplifier 4. In order to refill and deactivate the pressure amplifier, the differential chamber 7 is charged with a supply pressure (rail pressure). The same pressure ratios (rail pressure) then prevail at all of the pressure surfaces of a piston 6. The piston 6 is pressure-equalized. The piston 6 is pressed into its starting position by an additional spring 8. In order to activate the pressure amplifier 4, the differential chamber 7 is relieved of pressure and the pressure amplifier 4 generates an amplification of the pressure in accordance with the area ratio. The effect achieved by this type of control is that a pressure-amplifying chamber 10 on the low-pressure side does not have to be relieved of pressure in order to reset the pressure amplifier 4 and to refill a pressure chamber 9. With a small, hydraulic transmission ratio, the losses due to depressurization can therefore be sharply reduced. In order to control the pressure amplifier 4, a restrictor 11 and a simple 2/2-port directional control valve 12 can be used instead of a complicated 3/2-port directional control valve. The restrictor 11 connects the differential chamber 7 to fuel, which is under supply pressure, from a pressure storage chamber. The 2/2-port directional control valve 12 connects the differential chamber 7 to a leakage line 13. The restrictor 11 is to be configured to be as small as possible, but nevertheless of a sufficient size that the piston 6 returns into its starting position between the injection cycles. A leakage in the guiding means of the piston 6 may also be used as the restrictor. If the 2/2-port directional control valve 12 is closed, there is no leakage in the guiding means of the piston 6, since the differential chamber 7 is pressurized. The restrictor may also be integrated in the piston. If the 2/2-port directional control valves 12 and 14 are closed, the injector 3 is under the pressure of the pressure storage chamber. The pressure amplifier 4 is in the starting position. An injection at rail pressure can now be carried out by the valve 14. If an injection at higher pressure is desired, the 2/2-port directional control valve 12 is activated (opened) and an amplification of the pressure is therefore achieved. The injection takes place via a fuel-metering means with the aid of a nozzle needle 15 which can be displaced axially in a guide bore and has a conical valve-sealing surface at its one end, with which it interacts with a valve-seat surface on the injector housing of the injector 3. Injection openings are provided on the valve-seat surface of the injector housing. Within a nozzle chamber 16, a pressure surface pointing in the opening direction of the nozzle needle 15 is exposed to the pressure which prevails there and which is supplied to the nozzle chamber 16 via a pressure line. Coaxially with a valve spring 17, a thrust component 18, which, with its end side facing away from the valve-sealing surface, bounds the control chamber 19, also engages on the nozzle needle 15. From the fuel-pressure connection, the control chamber 19 has an admission with a first restrictor and a discharge to a pressure-relief line 20 with a second restrictor which is controlled by the 2/2-port directional control valve 14. Fuel which is under the first or second system pressure continuously fills the nozzle chamber 16 and the control chamber 19. If the 2/2-port directional control valve 14 is actuated (opened) , the pressure in the control chamber 19 can be reduced, so that, in consequence, in the nozzle chamber 16 the pressure force acting on the nozzle needle 15 in the opening direction exceeds the pressure force acting on the nozzle needle 15 in the closing direction. The valve-sealing surface lifts off from the valve-seat surface and fuel is injected. In this case, the pressure-relieving process of the control chamber 19, and therefore the stroke control of the nozzle needle 15, can be influenced via the dimensioning of the restrictors. The end of the injection is initiated by renewed actuation (closing) of the 2/2-port directional control valve 14 which decouples the control chamber 19 again from the leakage line 20, so that a pressure which can move the thrust component 18 in the closing direction builds up again in the control chamber 19. In order to improve the pressure rise, the discharge cross section of the differential chamber 7 is of multi-stage design. In the starting position of the piston 6, only the discharge path 21 is opened. This brings about, when the valve 12 is opened, a slow drop in pressure within the differential chamber 7, a damped movement of the piston 6 and a slow pressure rise in the pressure chamber 9 to an average pressure level. After a stroke h a second, larger discharge path 22 is released by the piston 6. This brings about an amplified drop in pressure within the differential chamber 7 and an undamped movement of the piston 6 with a resulting, maximum pressure level in the pressure chamber 9. After the valve 12 is closed, the piston 6 is moved back into its starting position. The pressure amplifier 4 is deactivated. Instead of the stage-wise increase in cross section of the discharge from the differential chamber 7, a continuous increase in cross section may also be formed (figs. 2 and 3) . A uniform, flat pressure rise without disturbing oscillations in pressure can be achieved. According to fig. 2, the direction of movement 23 of a piston 24 (longitudinal direction of the opening and of the piston) causes, depending on the position of the piston 24, merely a subarea 25 of a slot-shaped opening 26 to be released as far as a control edge 24' and > causes a subarea 27 in the opening 26 to be covered. The opening 26 in the wall surface of the differential chamber produces the connection of the differential chamber 7 (see fig. 1) to the leakage line (see fig. 1) and can be closed by the piston. With increasing piston stroke, a larger discharge cross section is released. According to fig. 3, a slot-shaped opening 28 in the wall surface of a pressure-amplifying chamber has a cross-sectional area which can be varied in the direction of movement 29 of the piston 30. The piston 30 itself has a recess 31 which produces the continuous connection of the differential chamber 7 (see fig. 1) to the leakage line. The recess 31 forms a type of control aperture which slides along the slot 28. The discharge cross section can be varied as desired via the stroke profile of the piston. Alternatively, the slot-shaped opening 28 can also be formed in the piston, and the control edge 24' or a recess 31 can be formed in the wall surface. WE CLAIM: 1. A fuel injection device (1) having a pressure amplifier (4) which has a displaceable piston (6; 24; 30), which can be pressurized via a pressure-amplifying chamber (10) on the low-pressure side, for compressing the fuel, which is to be supplied to an injector (3), in a pressure-amplifying chamber (9) on the high-pressure side, the stroke of the piston (6; 24; 30) being controllable essentially by the pressure in a differential chamber (7) of the pressure amplifier (4) and being used for influencing the pressure of the fuel supplied to the injector (3), characterized in that means (24, 25; 28, 31) for cross-sectional control of the discharge cross section from the differential chamber (7) of the pressure amplifier (4) are provided. 2. The fuel injection device as claimed in claim 1, wherein a first cross section (first stage) which is dependent on the piston stroke (h) and a second cross section (second stage) of the discharge is [sic] provided. 3. The injection device as claimed in claim 1, wherein the means are formed by at least one slot-shaped opening (26; 28) between the differential chamber (7) of the pressure amplifier (4) and a leakage line (21), and by the piston (24; 30) which closes or releases the opening (26; 28). 4. The fuel injection device as claimed in claim 3, wherein the piston (24) has a control edge (24') with the opening (26) being released up to it. 5. The fuel injection device as claimed in Claim 3, wherein the piston (30) has a recess (31) which can be arranged over the opening (28) and defines a released region of the opening (28).

Documents:

0115-chenp-2003 abstract-duplicate.pdf

0115-chenp-2003 abstract.jpg

0115-chenp-2003 abstract.pdf

0115-chenp-2003 claims-duplicate.pdf

0115-chenp-2003 claims.pdf

0115-chenp-2003 correspondence-others.pdf

0115-chenp-2003 correspondence-po.pdf

0115-chenp-2003 description (complete)-duplicate.pdf

0115-chenp-2003 description (complete).pdf

0115-chenp-2003 drawings-duplicate.pdf

0115-chenp-2003 drawings.pdf

0115-chenp-2003 form-1.pdf

0115-chenp-2003 form-18.pdf

0115-chenp-2003 form-26.pdf

0115-chenp-2003 form-3.pdf

0115-chenp-2003 form-5.pdf

0115-chenp-2003 pct.pdf

0115-chenp-2003 petition.pdf