EP2310662A1

EP2310662A1 - Fuel injector

Info

Publication number: EP2310662A1
Application number: EP09779562A
Authority: EP
Inventors: Matthias Burger; Hans-Christoph Magel
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2008-07-24
Filing date: 2009-05-27
Publication date: 2011-04-20
Anticipated expiration: 2029-05-27
Also published as: US20110139906A1; DE102008040680A1; US8864054B2; WO2010009932A1; EP2310662B1

Abstract

The invention relates to a fuel injector (1) and, in particular, to a common-rail injector for injecting fuel into a combustion chamber of an internal combustion engine with a multi-part injection valve element (21), which can be adjusted between an open position and a closed position, wherein a first part (22 ) and a second part (23) of the injection valve element (21) are coupled to one another via a hydraulic coupler (24), which is bounded radially by a first guide (53) for the first part (22) and by a second guide (54) for the second part (23). According to the invention, at least some sections of the first and the second guide (53, 54) are surrounded at their outer radii by fuel under high pressure, and the pressure realized in the hydraulic coupler (24) is lower than the pressure radially outside the guides (53, 54).

Description

description

title

Fuel injector

State of the art

The invention relates to a fuel injector for injecting fuel into a combustion chamber of an internal combustion engine according to the preamble of claim 1.

From DE 10 2006 008 648 Al a trained as a common rail injector fuel injector is known, which has a two-part injection valve element, which via a control valve (servo-valve) can be controlled. The two parts of the injection valve element are coupled together via a hydraulic coupler. In the idle state of the fuel injector prevails in the hydraulic coupler rail pressure. The known fuel injector is low leakage, ie executed without low pressure stage. To achieve a sufficient hydraulic needle-closing force, a closing throttle is introduced in a connection channel supplying fuel to a lower nozzle chamber. A disadvantage of the known fuel injector is that the two parts of the injection valve element do not react as a single part, but delayed in a control of the injection valve element. This can only be compensated by very fast switching control valves, which, however, is associated with higher costs. DISCLOSURE OF THE INVENTION Technical Problem

The invention is therefore based on the object to propose an alternative fuel injector, in which at least two injection valve element parts are coupled together via a low-leakage hydraulic coupler.

Technical solution

This object is achieved with a fuel injector having the features of claim 1. Advantageous developments of the invention are specified in the subclaims. All combinations of at least two features disclosed in the description, the claims and / or the figures fall within the scope of the invention.

The invention is based on the idea of achieving strong compression of the two separate injector element parts coupled by means of the hydraulic coupler in that the hydraulic coupler, more precisely a coupler space of the coupler, in particular permanently, with a low pressure source, in particular a connected to an injector return low pressure region of the injector is connected. Due to the reduced pressure within the hydraulic coupler compared to the high-pressure region of the fuel injector, the injection valve element parts are permanently and substantially interconnected during operation of the fuel injector, so that from a functional point of view they can be considered as one-piece. This effect is of significant advantage especially with multiple injection, since, in comparison with known, not pressure-reduced hydraulic couplers, a negative pressure in the hydraulic coupler does not have to be built up with the Einspritzventilelementhub. In comparison with a one-piece injection valve element, the advantage is achieved that it is possible to fall back on a logistics adapted to current production processes. Moreover, it is possible to form the nozzle needle part of the injection valve element from a different material than the control rod part, whereby the injection valve element parts can be optimally adapted to specific requirements (stiffness / strength). In order to minimize the leakage amount flowing through the hydraulic coupler, more precisely the coupler space, axially delimiting guide gaps, a fuel injector designed according to the concept of the invention provides that both guides are surrounded at least in sections radially outward with fuel under high pressure. In other words, the at least one injector component, which delimits the guide gap radially outwardly, is surrounded by high-pressure fuel in an area radially outward of the respective guide gap formed between the at least one injector component and the injection valve element, thereby expanding the guide gaps by penetrating into the guide gaps High pressure fuel is avoided. In other words, widening of the one or more guide gaps limiting injector component (s) is minimized by the fact that the pressure in the guide gaps at least approximately the same size as outside of the Inj ektorbauteil (e) in a region radially outside the guide gaps , In the manner described, a particularly strong hydraulic coupling of two injection valve element parts with the aid of an Nes, in particular significantly, lower pressure than the rail pressure achieved, without causing particularly large leakage quantities.

In a further development of the invention is advantageously provided that within the hydraulic coupler, a low-pressure stage is realized, which causes a force acting in the closing direction of the injection valve element hydraulic force. As a result, the injection valve element switching time can be accelerated. Since the closing force generated by the low-pressure stage, hydraulic, acting on the injection valve element, closing force is raildruckabhängig, this closing force acts not only during the injection, as in a closing throttle, but permanently. In this case, it is particularly preferred if an additional closing throttle, which reduces the fuel pressure in the region of the injection valve element support in comparison to the fuel pressure in the region of an inlet passage of the fuel injector, is dispensed with. By providing a closing throttle, the effective injection pressure would be reduced by up to 150 bar. This can be dispensed with advantageously due to the provision of a low-pressure stage in the hydraulic coupler. The low-pressure stage is preferably realized by reducing the diameter of the nozzle-hole-adjacent injection valve member member (nozzle needle) as compared to the diameter of the nozzle-hole-remote injector member member in a hydraulic coupler-limiting portion (something). In other words, the guide diameter of the guide facing the nozzle hole arrangement is preferably somewhat smaller than the guide diameter of the other, the hydraulic coupler axially delimiting (in particular upper) guide. Particularly preferred is an embodiment in which the hydraulic coupler is connected via a connecting channel to a low pressure region of the fuel injector. As a result, the pressure in the hydraulic coupler compared to the rail pressure can be significantly reduced. In the event that the connecting channel, at least approximately, throttle-free, prevails within the hydraulic coupler, at least approximately, low pressure, preferably in a pressure range between about 0 and 20 bar.

In a further development of the invention is advantageously provided that at least one of the two, the hydraulic coupler limiting guides is formed by a sleeve-shaped extension of a plate member, said sleeve-shaped extension, at least partially, preferably completely, radially outwardly surrounded by under high pressure fuel is. It is particularly preferred to provide a portion of the connecting channel, in particular as a radial channel, in the plate element, which connects the hydraulic coupler to the low-pressure region of the fuel injector. In the low-pressure region of the fuel injector, not only the named connection channel but also a discharge channel from a control chamber, via which fuel flows out of the control chamber in the direction of the injector return when the control valve is open, preferably discharges.

Particularly preferred is a design variant in which in the plate member at least one, preferably throttle-free, axial channel is provided, can flow through the fuel with the injector element open in the axial direction of the nozzle hole arrangement. It is particularly expedient if the plate element is arranged between an (upper) injector body and a (lower) nozzle nozzle arrangement having a nozzle body, that is clamped between these housing parts. Preferably, the nozzle body is screwed by means of a union nut with an external thread of the injector body.

Particularly preferred is an embodiment in which at least one of the couplers axially delimiting guides is formed by a sleeve arranged in a high-pressure chamber, in particular spring-loaded sleeve. An embodiment in which the sleeve is pressed by the spring in the axial direction against the previously explained plate element is particularly expedient. An embodiment is particularly preferred in which this spring is at the same time the closing spring acting on an injection valve element part in the direction of the nozzle hole arrangement, which is located at one end on the sleeve and at other ends on the injection valve element part, in particular on a circumferential collar or a retaining ring of the injection valve element. element part, supports.

As previously explained, it is possible to place the hydraulic coupler at the low pressure applied to the injector return. However, it is also possible to implement an embodiment in which the pressure in the hydraulic coupler is dimensioned such that it lies under the high pressure of the fuel outside the guides delimiting the hydraulic coupler but above the low pressure in the region of the injector return. For this purpose, at least one throttle is preferably applied in the connecting channel connecting the hydraulic coupler to the low-pressure region. assigns. This is adjusted so that the pressure in the hydraulic coupler is higher than in the area of the injector return. By implementing a higher (low) pressure in the hydraulic coupler compared to the low pressure in the injector return region, the component load in the area of the hydraulic coupler is reduced. Since due to the provision of the throttle in the connecting channel, the pressure in the hydraulic coupler is now load-dependent, it is preferred, in the case of providing such a throttle, to dispense with a low-pressure stage in the hydraulic coupler, so that the hydraulic coupler no longer has the function of a hydraulic Closing force to produce, but only a coupling function. Due to the slightly increased pressure in the hydraulic coupler, the already small amount of leakage, which flows through the guides into the hydraulic coupler and thus into the low-pressure area, is further reduced. Preferably, the throttle is designed so that the pressure in the hydraulic coupler corresponds approximately to half the rail pressure.

In this case, a closing throttle is preferably provided for generating a hydraulic closing force, which is dimensioned such that the pressure in the region of the tip of the injection valve element is lower, preferably by about 50 to 200 bar, than the rail pressure.

An embodiment in which such a closing throttle is arranged in an injector component which delimits a control chamber radially on the inside is structurally particularly elegant. At the same time, an inlet throttle for the control chamber and an outlet throttle from the control chamber and possibly also a filling throttle are preferred in this injector component. Throttle introduced for accelerated refilling the control chamber.

Brief description of the drawings

Further advantages, features and details of the invention will become apparent from the following description

Embodiments and with reference to the drawings. These show in:

Fig. 1 shows a first embodiment of a fuel injector with a connected to a low pressure region of the fuel Inj ector hydraulic coupler with low pressure stage and

Fig. 2 shows an embodiment of a fuel injector with connected to a low pressure region of the fuel injector hydraulic coupler without low pressure stage and arranged in a connecting channel between the hydraulic coupler and the low pressure region throttle for adjusting the pressure in the hydraulic coupler.

Embodiments of the invention

In the figures, the same components and components with the same function with the same reference numerals.

In Fig. 1 is designed as a common rail injector fuel Inj ector 1 for injecting fuel into a combustion chamber, not shown, of an internal combustion engine an presented a motor vehicle. A high pressure pump 2 delivers fuel from a reservoir 3 in a high-pressure fuel storage 4 (Rail). In this fuel, especially diesel or gasoline, under high pressure, stored in this embodiment about 2000 bar.

To the high-pressure fuel accumulator 4, the fuel injector 1 is connected, among other injectors, not shown, via a supply line 5. The supply line 5 opens into a supply channel 6 of the fuel injector 1, which opens into a high-pressure chamber 7 of the fuel injector 1. The high-pressure chamber 7 forms a mini-rail, due to which pressure oscillations are minimized. By means of a return line 8, a low-pressure region 9 of the fuel injector 1 is connected to the reservoir 3. Via an injector return port 10 and the return line 8, a control amount to be explained later as well as a small amount of leakage of fuel from the fuel injector 1 to the reservoir 3 can flow off.

The fuel injector 1 has a housing 11, which has an injector body 12 into which the supply channel 6 is introduced and comprises a lower nozzle body 13. Between the injector body 12 and the nozzle body 13, a plate element 14 to be explained later is clamped, wherein the nozzle body 13 is braced against the plate element 14 by means of a union nut 15 and this in turn against the nozzle body 13. For this purpose, the union nut 15 is screwed to an external thread of the injector body 12. The head part of the housing 11 is formed by a clamping nut 16, which is screwed to the injector body 12, and which clamps a cover element 17, comprising the injector return port 10, against an electromagnet arrangement 18 of an electromagnetic actuator 19 to be explained later. which in turn rests in the axial direction on an inner shoulder 20 of the clamping nut 16.

In the housing 11, more precisely in the injector body 12 and in the duplex body 13, a two-part injection valve element 21 is accommodated. This comprises an upper, first part 22 (control rod) and a lower, second part 23 (nozzle needle). The first and the second part 22, 23 of the injection valve element 21 are coupled to each other via a hydraulic coupler 24 to be explained later and behave like a single component. The second, lower part 23 of the injection valve element 21 is guided in a guide bore 25 in the nozzle body 13. In this case, axial channels 26 are formed on the outer circumference of the second part 23 in an area within the guide bore 25, through which fuel can flow from the high-pressure chamber 7 into a lower annular space 67 when the injection valve element 21 is open, in which substantially the same fuel pressure prevails as in the high-pressure space 7. In order to ensure this, the axial channels 26 designed as bevels and an axial channel 66 in the plate element 14 are (at least approximately) throttle-free. As a result, the fuel pressure in a gap 27 formed between the plate element 14 and the guide bore 25 also corresponds to the fuel pressure within the high-pressure space 7. The closing throttle otherwise required in the prior art is used in the embodiment. Measure Fig. 1 (in contrast to the later still to be explained embodiment of FIG. 2) deliberately omitted.

The injection valve element 21, more precisely the second part 23, has at its tip 28 a closing surface 29 with which the injection valve element 21 can be brought into tight contact with an injection valve element seat 30 (nozzle needle seat) formed inside the nozzle body 13. When the injection valve element 21 abuts against its injection valve element seat 30, i. is in a closed position, the fuel outlet from a Düsenlochanord- tion 31 is locked. If, on the other hand, it is lifted from its injection valve element seat 30 and is in an open position, here fuel can flow from the high-pressure chamber 7 via the intermediate space 27 and the lower annular space 67 past the injection valve element seat 30 to the nozzle hole arrangement 31 and essentially there under high pressure (rail pressure) standing in the combustion chamber are injected.

From an upper end face 32 of the first part 22 of the injection valve element 21 and a lower in the drawing plane sleeve-shaped portion 33 of an injector designed as a throttle component 34 a Steuerkam- mer 35 is limited, via a radially extending in the sleeve-shaped portion 33 inlet throttle 36 with high pressure Stagnant fuel from the high-pressure chamber 7 is supplied. The control chamber 35 is connected to a valve chamber 39 of a control valve 40 (servo-valve) via a drain throttle 38 provided in an upper, plate-shaped section 37 of the injector component 34. The valve chamber 39 is bounded radially outwardly by a sleeve-shaped control valve member 41, which is integral with one with the electromagnetic actuator 19 cooperating armature plate 42 is formed. The sleeve-shaped control valve element 41 is pressure balanced in its closed position in the axial direction. The control chamber 35 is bounded axially upward by a guide pin 43 which is axially supported on the cover member 17 and on the one hand has the task to guide the control valve member 41 during its adjustment and on the other hand to seal the valve chamber 39 in the axial direction upwards. From the valve chamber 39, fuel can flow into the low-pressure region 9 of the fuel injector 1 when the control valve element 41 which can be actuated by the electromagnetic actuator 19 is lifted off its control valve seat 44, which is designed as a flat seat and is arranged on the plate-shaped section 37 of the injector component 34 the control valve 40 is open. When the control valve 40 is open, fuel flows out of the control chamber 35 via the outlet throttle 38. The flow cross sections of the inlet throttle 36 and the outlet throttle 38 are matched to one another such that when the control valve 40 is open, a net outflow of fuel (control quantity) from the control chamber 35 via the valve chamber 39 into the low pressure region 9 of the fuel injector 1 and from there via the return line 8 results in the reservoir 3. As a result, the pressure in the control chamber 35 decreases rapidly, whereby the injection valve element 21 experiences a resulting opening force and abuts in the sequence with an end-side abutment portion 45 on the ceiling of the sleeve-shaped portion 33. The injection valve element 21 thus lifts off from its injection valve element seat 30, so that fuel can flow out through the nozzle hole arrangement 31. To end the injection process, the energization of the solenoid assembly 18 of the electromagnetic actuator 19 is interrupted. As a result, the sleeve-shaped control valve element 41 moves back onto its control valve seat 44. The fuel flowing in through the inlet throttle 36 rapidly increases the pressure in the control chamber 35, as a result of which the injection valve element 21 is supported by the Spring force of a closing spring 47, is moved back to its injection valve element seat 30, which in turn the fuel flow from the Düsenlochan- Regulation 31 is interrupted in the combustion chamber. The filling of the control chamber 35 via the inlet throttle 36 is accelerated via a Fülldrossel 61 which connects the high pressure chamber 7 permanently hydraulically with the valve chamber 39. Possibly. can also be dispensed with this Fülldrossel 61.

The first and second parts 22, 23 of the injection valve element 21 are hydraulically coupled together in the hydraulic coupler 24, more specifically in a coupler space 48, and behave as a single component. This is due to the fact that the hydraulic coupler 24, or the coupler chamber 48 is permanently connected via a multi-part connecting channel 49 with the arranged in the injector low-pressure region 9 of the fuel injector 1, and thus during operation of the fuel injector 1 permanently low pressure. The connecting channel 49 is formed by a radial channel 50 provided in the plate element 14, an annular space 51 radially between the plate element 14 and the union nut 15 and a vertical channel 52 in the injector body 12. The hydraulic coupler 24 is limited in the embodiment shown in the axial direction upward by a first guide 53 for the first part 22 of the injection valve element 21 and in the axial direction down from a second guide 54 for the second, lower part 23 of the injection valve element 21st In this case, the first guide 53 comprises a first guide gap 55 (annular gap) radially between a sleeve-shaped extension 56 of the plate member 14 and a lower portion of the first part 22 of the injection valve element 21. Analogously, the second guide 54 comprises a second guide gap 57 (annular gap) radially between a The closing spring 47 is supported at one end on the lower end face of the sleeve 58 and at the other end on a circumferential collar 59 of the second part 23 of the injection valve element 21 from the closing spring 47 spring-loaded sleeve 58 and an upper portion of the second part 23 of the injection valve element 21.

The guide gaps 55, 57 are comparatively fuel-tight. This is primarily attributable to the fact that the first guide 53, more precisely the sleeve-shaped extension 56, is arranged inside the high-pressure chamber 7, that is to say is surrounded radially on the outside by high-pressure fuel. As a result, the first guide gap 55 experiences no expansion radially outward due to the low leakage flowing through the first guide gap 55 into the coupler space 48. Similarly, the second guide 54, more precisely, the sleeve 58 is disposed within the gap 27, in which approximately the same pressure prevails as in the high-pressure chamber 7, so that the second guide gap 57 is not widened because the sleeve 58 radially outward from under high pressure Fuel is surrounded. As a result, the lever, which flows via the guides 53, 54 into the hydraulic coupler 24, is level, which continues to flow via the connecting channel 49 in the low-pressure region 9, low.

In the embodiment according to FIG. 1, a low-pressure stage 60 is realized in the hydraulic coupler 24, which has a force acting in the closing direction on the injection valve element 21. The low-pressure stage 60 is realized in that the diameter O _{1 of} the first part 21 in the region of the first guide 53 is (slightly) greater than the diameter Du of the second part 23 of the injection valve element 21 in the region of the second guide 54. With the aid of the low-pressure stage 60 a permanently acting, acting in the closing direction force is generated on the injection valve element 21. As a result, the sum of all closing forces acting on the injection valve element 21 is increased, which delays the opening time of the injection valve element 21. This is crucial: For reasons of tolerance, the injection valve element 21 should only open when the control valve 40 can already be operated non-ballistically. Without the realized low-pressure stage 60, the start of injection can be delayed only for a mechanically soft injection valve element 21 or a small drain / inlet throttle ratio. Both measures lead to disadvantages in the injector behavior: While a soft injection valve element 21 leads to a poorer multiple injection suitability, a small drain / feed throttle ratio reduces the increase in the jet force of the injection jet and generally leads to emission disadvantages.

In the following, the embodiment of a fuel injector 1 according to FIG. 2 will be explained. Since essential funktions- and design features with the one shown in Fig. 1 and previously described fuel injector 1, in the following essentially only the differences from the previously shown and described embodiment will be explained. With regard to the common features, reference is made to FIG. 1 and the associated description.

In contrast to the embodiment according to FIG. 1, a throttle 62 is integrated in the connecting channel 49, more precisely in the radial channel 50 between the hydraulic coupler 24 and the low-pressure region 9. This is designed so that approximately half the pressure prevails in the hydraulic coupler 24, more precisely in the coupler chamber 48, as in the high-pressure chamber 7 and in the intermediate space 27. This is achieved by the pressure drop across the guides 53, 54 being approximately equal to the Pressure drop at the throttle 62 corresponds. By compared to the embodiment of FIG. 1 increased pressure in the coupler chamber 48, the effluent via the guide gaps 55, 56 leakage amount is further reduced. In addition, the component load of the plate member 14 and the sleeve 58 is reduced.

In contrast to the embodiment according to FIG. 1, the diameters O ₁ and Du of the first and second part 22, 23 of the injection valve element 21 in the region of the guides 53, 54 are the same size - so it became aware of the realization of a low-pressure stage in the hydraulic coupler 24 omitted, since the pressure in the hydraulic coupler 24 by the provision of the throttle 62 is load-dependent and thus fluctuates during operation, which would result in fluctuating closing forces in the event that a low pressure stage would be provided in the coupler 24. However, it is also conceivable, the embodiment of FIG. 2 with a low pressure stage to equip for certain applications analogous to the embodiment of FIG. Due to the omission of a low-pressure stage, production-related and / or temperature-dependent guide leakage fluctuations on the guides 53, 54 do not affect the injector function.

In order to realize a sufficiently large hydraulic closing force despite the omission of a low-pressure stage, the fuel injector 1 according to FIG. 2 is equipped with an additional closing throttle 63, which is introduced into the sleeve-shaped section 33 of the injector component 34. This connects the high-pressure chamber 7 with an annular, additional inlet chamber 64, which surrounds the sleeve-shaped section 33 radially on the outside in comparison with FIG. 1, and which is sealed by way of an annular sealing element 65 with respect to the high-pressure space 7 serving as a minirail. The closing throttle 63 is designed in the illustrated embodiment so that the pressure in the high-pressure chamber 7 is about 50-200 bar less than the rail pressure in Zulaufräum 64. In contrast to the embodiment of FIG. 1, the inlet throttle 36 and the Fülldrossel 61 do not open the high-pressure chamber 7, but from the inlet chamber 64.

The throttle 62 can, as shown, be designed as a simple throttle bore. Due to the necessary small flow cross sections which are necessary in the throttle 62, a conventional throttle bore, however, is relatively difficult to produce for reasons of tolerance. Therefore, it is preferable to perform the throttle 62 as an annular gap throttle. This can be achieved, for example, by positioning an insert part, for example a pin, in the actual throttle bore, on which the Fuel must flow past radially outside. The advantage of such a construction is the easier manufacturability.

Claims

claims

1. fuel Inj ector, in particular common rail injector, for injecting fuel into a combustion chamber of an internal combustion engine, with an adjustable between an open position and a closed position, multi-part injection valve element (21), wherein a first part (22) and a second Part (23) of the injection valve element (21) via a hydraulic see coupler (24) are coupled together, the axially of a first guide (53) for the first part (22) and of a second guide (54) for the second part (23) is limited

characterized,

the first and the second guide (53, 54) are surrounded radially at least in sections with fuel under high pressure, and that a lower pressure is realized in the hydraulic coupler (24) than radially outside the guides (53, 54) ,

2. Fuel Inj ector according to claim 1, characterized in that in the hydraulic coupler (24) on the injection valve element (21) a closing force causing low pressure stage (60) is realized.

3. Fuel injector according to one of claims 1 or 2, characterized in that the hydraulic coupler (24) via a connecting channel (49) to a low pressure region (9) of the fuel injector (1) is connected.

4. Fuel Inj ector according to claim 3, characterized in that the first and / or the second guide (53, 54) of a sleeve-shaped extension (56) of a plate element (14) are / is formed, in the sections of the connecting channel ( 49), preferably as a radial channel (50) is introduced.

5. Fuel injector according to claim 4, characterized in that in the plate element (14) at least one, preferably throttle-free, axial channel (66) is provided.

6. Fuel injector according to one of claims 4 or 5, characterized in that the plate element (14) between an injector body (12) and a nozzle nozzle arrangement (31) having nozzle body (13) is arranged.

7. Fuel injector according to one of the preceding claims, characterized in that the first and / or the second guide (53, 54) arranged in a high-pressure chamber (7), in particular spring-loaded, sleeve (58) are / is formed.

8. Fuel Inj ector according to one of claims 3 to 7, characterized in that in the connecting channel (49) a throttle (62) is arranged, which is dimensioned such that the Pressure in the hydraulic coupler (24) is lower than the guide (53, 54) enclosing high pressure and higher than the pressure in the low pressure region (9).

9. Fuel Inj ector according to claim 8, characterized in that a closing throttle (63) is provided, which is dimensioned and arranged such that the pressure in the region of a tip (28) of the Einspritzventilele- Mentes (21) is less than that Pressure in a fuel inlet channel of the fuel injector (1).

10. Fuel Inj ector according to claim 9, characterized in that the closing throttle (63) in a control chamber (35) limiting injector component (34) is arranged.