EP1989436B1 - Fuel injection device for an internal combustion engine - Google Patents

Description

The invention relates to a fuel injection device for an internal combustion engine according to the preamble of claim 1, such as in the document EP 1624181 shown.

From the market known is a fuel injection device with which the fuel can be injected directly into its associated combustion chamber of an internal combustion engine. For this purpose, a valve element is arranged in a housing, which in the region of a fuel outlet opening has a total acting in the opening direction of the valve element pressure surface. At the opposite end of the valve element, a control surface acting in the closing direction is present, which delimits a control chamber. Overall, the control surface acting in the closing direction is larger than the pressure surface acting in the opening direction when the valve element is open.

When the fuel injection device is closed, a high fuel pressure is present at a region of the pressure surface acting in the opening direction and at the control surface acting in the closing direction, as is provided, for example, by a fuel rail. To open the valve element, the pressure applied to the control surface is lowered until the hydraulic force resultant in the opening direction on the pressure surface exceeds the force acting in the closing direction. As a result, opening of the valve element is effected.

Prerequisite for the operation of this fuel injection device is a seal between that area in which the comparatively small acting in the opening direction Pressure surface is present, and that portion of the valve element in which the comparatively large acting in the closing direction control surface is present. Leakage fluid is discharged in the known fuel injection device from the region of the seal via a leakage line.

Object of the present invention is to develop a fuel injection device of the type mentioned so that it is as simple and inexpensive builds and can be used at a very high operating pressure. In addition, the Kraftstoff-Einspritzvomichtung should work safely even in the presence of manufacturing tolerances.

Disclosure of the invention

This object is achieved by a fuel Einspntzvorrichtung with the features of claim 1. Advantageous developments of the invention are specified in subclaims. Further essential features of the invention are given in the following description and in the figures, wherein these features may also be essential in very different combinations for the invention, without being explicitly pointed out.

Advantages of the invention

In the fuel injection device according to the invention, the freedom of design of the fuel injection device is significantly increased by the hydraulic coupling of two separate parts of the valve element, because it can be optimally adapted to the respective location within the fuel injection device, the respective parts of the valve element. For example, the elastic properties of the valve element can be optimally adapted to the intended area of use by an appropriate choice of the material used and the dimensions. Moreover, the manufacture of the valve element as a whole is considerably simplified since parts with a constant diameter are also used. This allows a structure of the fuel injection device with simple parts, which on the one hand facilitates the production and on the other hand allows a small construction. In addition, numerous components of previous devices can continue to be used for realizing the present invention.

Another advantage of the hydraulic coupler is the compensation of tolerances, which simplifies the manufacture and assembly. The coupling of two parts of the valve element by means of a hydraulic coupler also allows the realization of a certain motion damping.

By virtue of the sleeve provided according to the invention, the hydraulic coupler can be easily realized, and work required on the housing side is simplified. By virtue of the guide element separate from the housing according to the invention, a misalignment of the sleeve relative to a housing-side sealing surface cooperating therewith is furthermore minimized. This comes into play particularly when the first part of the valve element is particularly long, and when the sleeve is guided particularly narrow on the first part of the valve element.
Leaks in the coupling space are minimized through or even completely prevented. An elaborate and costly Einmessprozess can therefore be omitted. A wear-related change in the functional properties of the fuel injection device according to the invention is reduced. By the leadership by means of the guide element manufacturing tolerances are compensated, which ensures a secure injector function.

The fuel injection device is particularly simple in construction when the sleeve is supported on the guide element. In this case, a sealing surface on the guide element, on which the sleeve is supported, are formed exactly at right angles to the guide axis of the guide element, so that a slanted position of the sleeve guided on the first part relative to the sealing surface on the guide element is particularly clearly minimized.

In a further development, it is proposed that at least in one part of a guide region of the guide element or a complementary region of the first part of the valve element there is a fluid passage leading from one side to the other side of the guide element. This results in a clear separation of functions insofar as the guide region of the guide element has a pure guiding function and the sleeve has a pure sealing function. Such a separation of the functions allows each an optimal design. In concrete development, the fluid passage can be formed by a guide play between the guide element and the first part of the valve element. This is manufacturing technology particularly easy to implement.

Furthermore, it is proposed in an advantageous development of the fuel injection device according to the invention that the guide element comprises a stroke stop for the second part of the valve element. This is particularly advantageous in those fuel injection devices with which comparatively large amounts of fuel are to be injected, for example in commercial vehicles. In such a fuel injection device could be due to their multi-part design by manufacturing tolerances in the length dimensions to strong stroke tolerances. So far, these have been reduced by the calibration of a setting. It had to be measured prior to assembly of the individual parts of the fuel injector each relevant installation dimension with an influence on the stroke tolerance. From these measured values, the correct stroke value could be set via a selection group of setting elements.

With the now integrated in the guide element stroke stop for the second part of the valve element, such an approach can be avoided, which simplifies the assembly. However, if adjustability of the stroke of the second part of the valve element is necessary due to other requirements, this can continue to be done by the arrangement of a Hubeinstellelements between the second part of the valve element and the stroke stop in or on the guide element.

The production of the fuel injection device is further simplified when the guide element comprises a passage opening, preferably with a flow restrictor, which connects a pressure chamber in the region of the valve seat with a high-pressure chamber.

In order to ensure optimum sealing of the coupling space and the high-pressure chamber or a fluid channel, the guide element between two housing bodies of the fuel injection device may be jammed, with its contact surfaces are designed with the housing bodies so that their centroid at least approximately on a central axis of a guide portion of Guide element is located.

It is also proposed that the sleeve is acted upon by a spring which is supported on a shoulder which is formed on the first part of the valve element. This allows the realization of a preassemblable unit, the at least the first part of the valve element, the Sleeve and the spring and optionally the guide element comprises. In addition to the time savings in the final assembly of the fuel injection device damage to the high-precision guidance between the sleeve and the first part of the valve element during final assembly are thereby avoided. In addition, eliminates the otherwise necessary captive intermediate storage of the sleeve during the assembly and Einmessprozesses the spring. The risk of contamination or damage or even loss of the sleeve due to such intermediate storage is eliminated. In addition, the housing and thus its manufacture is simplified because now a smooth through hole can be provided without grading for receiving the valve element in the housing. This also improves the high-pressure resistance of the fuel injection device, and its larger storage volume (space between the valve element and through-bore in the housing) leads to a reduction of pressure oscillations.

An alternative to this is that the sleeve is acted upon by a first spring, which is supported on a shoulder which is formed on one side of a ring member which is acted upon on the other side by a second spring, at least indirectly on Housing supported, and which is coupled via a coupling element with the valve element in the closing direction.

The guide element can have a centering section, preferably a centering collar, which centers the guide element with respect to a housing body. At least indirectly, this also the valve element and other remote from the coupler areas of the housing are centered to each other.

drawings

Figur 1

eine schematische Darstellung einer Brennkraftmaschine mit einer Kraftstoff-Einspritzvorrichtung;

Figur 2

eine schematisierte und teilweise geschnittene Darstellung einer ersten Ausführungsform der Kraftstoff-Einspritzvorrichtung von Figur 1;

Figur 3

eine detailliertere Darstellung eines Bereichs der Kraftstoff-Einspritzvorrichtung von Figur 2;

Figur 4

eine Draufsicht auf ein Führungselement der Kraftstoff-Einspritzvorrichtung von Figur 3;

Figur 5

einen Schnitt längs der Linie V-V von Figur 4;

Figur 6

eine Darstellung ähnlich Figur 2 eines Bereichs einer zweiten Ausführungsform einer Kraftstoff-Einspritzvorrichtung;

Figur 7

eine Darstellung ähnlich Figur 2 eines Bereichs einer dritten Ausführungsform einer Kraftstoff-Einspritzvorrichtung;

Figur 8

eine Darstellung ähnlich Figur 2 einer vierten Ausführungsform; und

Figur 9

eine Darstellung ähnlich Figur 2 einer fünften Ausführungsform.

Hereinafter, particularly preferred embodiments of the present invention will be explained in more detail with reference to the accompanying drawings. In the drawing show:

FIG. 1

a schematic representation of an internal combustion engine with a fuel injection device;

FIG. 2

a schematic and partially sectioned view of a first embodiment of the fuel injection device of FIG. 1 ;

FIG. 3

a more detailed representation of a portion of the fuel injection device of FIG. 2 ;

FIG. 4

a plan view of a guide element of the fuel injection device of FIG. 3 ;

FIG. 5

a section along the line VV of FIG. 4 ;

FIG. 6

a representation similar FIG. 2 a portion of a second embodiment of a fuel injection device;

FIG. 7

a representation similar FIG. 2 a portion of a third embodiment of a fuel injection device;

FIG. 8

a representation similar FIG. 2 a fourth embodiment; and

FIG. 9

a representation similar FIG. 2 a fifth embodiment.

Description of the embodiments

In FIG. 1 an internal combustion engine carries the reference numeral 10. Overall, it serves to drive a motor vehicle, not shown. A high-pressure conveyor 12 conveys fuel from a fuel reservoir 14 into a fuel pressure accumulator 16 ("rail"). In this fuel - for example, diesel or gasoline - is stored under very high pressure. To the rail 16 a plurality of fuel injection devices 18 are connected by means of a respective high-pressure port 17, which inject the fuel directly into them associated combustion chambers 20. The fuel injectors 18 also each have a low-pressure port 21, via which they are connected to a low-pressure region, present with the fuel reservoir 14.

The fuel injectors 18 may in a first embodiment according to the Figures 2 and 3 be formed: In the present embodiment, the fuel injection device 18 shown therein includes a housing 22 having a nozzle body 24, a main body 26 and an end body 28. Also possible is a one-piece design of main body 26 and end body 28. In the housing 22 is in the longitudinal direction a step-shaped recess 30 is present, in which a needle-like valve element 32 is received. This is in two parts: it consists of a control piston 34 and a nozzle needle 36th

The nozzle needle 36 has pressure surfaces 38 which delimit a pressure chamber 40 and their hydraulic force resulting in the opening direction of the nozzle needle 36 shows. At her in FIG. 2 bottom end, the nozzle needle 36 works in FIG. 2 not shown manner with a housing-side valve seat (without reference numerals) together. In this way, fuel outlet openings 42 can be separated from or connected to the pressure chamber 40. The nozzle needle 36 has a section 44 with a smaller diameter and a section 46 with a larger diameter. With the section 46, the nozzle needle 36 is guided longitudinally displaceable in the nozzle body 24.

The control piston 34 is received in the main body 26. An in FIG. 2 Upper end portion 48 of the control piston 34 is designed as a guide, which is received in a sleeve-like extension of the end body 28 and guided. A spring 50 is supported on a shoulder formed by an annular collar 52 on the control piston 34 and acts on the control piston 34 in the closing direction. In the FIG. 2 upper axial end surface of the control piston 34 forms a hydraulic control surface 54 acting in the closing direction of the valve element 32. It defines, together with the end body 28, a control chamber 56.

The control chamber 56 is connected via an inlet throttle 58, which is present in the sleeve-like extension of the end body 28, with an existing present between the sleeve-like extension of the end body 28 and the main body 26 annular space 60, which in turn is connected to the high pressure port 17. In the main body 26, the annular space 60 is formed by the recesses 30 incorporated therein. The control chamber 56 is also connected to a 2/2-way valve 66 through an outlet throttle 64 provided in the end body 28. Depending on the switching position, this connects or blocks the outlet throttle 64 to the Low pressure port 21 down. The annular space 60 is also connected via at least one channel 68 to the pressure chamber 40.

Between the nozzle body 24 and the main body 26, a guide member 70 is jammed. Its exact structure goes out of the FIGS. 4 and 5 The guide element 70 then comprises a base plate 72 and a cylindrical extension 74 integrally formed thereon, which forms a guide collar which has a centering function. Concentric with the extension 74, a guide bore forming a guide portion 76 is provided in the guide member 70, which in the in the Figures 2 and 3 shown mounting position with a guide on in the Figures 2 and 3 lower end portion 77 of the control piston 34 cooperates. The upper and lower sides of the base plate 72 are formed as high-pressure sealing surfaces 78, in the installed position a secure seal of the housing 22, in particular the annular space 60 and lying within the guide member 70 spaces, with respect to the environment of the fuel injection device 18 is ensured. To represent a good sealing effect, the position of the center of gravity of the center axis also belongs. This is achieved by a corresponding design of the outer contour of the base plate 72, in such a way that the centroid is at least approximately on a central axis (not shown) of the guide bore 76.

In the bottom of the base plate 72, a bore approach 80 is incorporated, which is concentric with the guide bore 76 and has a larger diameter than this. The diameter of the bore extension 80 is also greater than the diameter of the portion 46 of the nozzle needle 36. In this way, the bore extension 80 forms a stroke stop for the nozzle needle 36 in a manner yet to be illustrated. In the base plate 72 of the guide element 70 is also an eccentric passage opening or bore 82 introduced, which is part of the channel 68 in the installed position. In some cases of application of the fuel injector 18 to the engine 10, the port 82 must include a flow restrictor, as in FIG FIG. 2 indicated.

A sealing surface representing an end face 85 of the extension 74 is worked very precisely at right angles to the axis of the guide bore 76. In the in FIG. 2 and 3 shown installation position is based on her via a sealing edge 86 from a sleeve 88, which is guided with little play on the control piston 34. It is by a spring 90 against the guide member 70th in turn, which in turn is supported on the main body 26. The sleeve 88 belongs to a hydraulic coupler 92, through which the first part of the valve element 32, namely the control piston 34, with the second part of the valve element 32, namely the nozzle needle 36 is coupled. For this purpose, the hydraulic coupler 92 comprises a hydraulic coupling space 94 with subspaces 94a and 94b, which is located between the sleeve 88, the guide element 70, which in the Figures 2 and 3 lower end portion of the control piston 34 and in the Figures 2 and 3 upper end portion of the nozzle needle 36 is formed. The volume formed by the guide play between the guide bore 76 and the guide 77 on the control piston 34 is dimensioned so that the subspaces 94a and 94b of the coupling space 94 form a coherent control volume without hydraulic influence. Said volume thus forms a fluid passage from one side to the other of the guide element 70. Alternatively or additionally, the fluid passage could also comprise at least one groove in the guide bore 76 and / or at least one flattening on the control piston 34.

The in the Figures 2 and 3 shown fuel injector 18 operates as follows: In the initial state, when energized switching valve 66, the control chamber 56 is separated from the low pressure port 21 and connected via the inlet throttle 58 to the high pressure port 17 and thus to the rail 16. In the control chamber 56 is thus the same pressure as in the annulus 60. This prevails over the channel 68 in the pressure chamber 40. Due to certain unavoidable leaks by the leadership of the nozzle needle 36 in the nozzle body 24 and the sleeve 88 on the control piston 34 is also in Coupling chamber 94 this pressure on. Overall, in this constellation results in a force acting in the closing direction of the valve element 32, which presses the valve element 32 against the valve seat in the region of the fuel outlet openings 42 and which is exerted by the compression spring 50 on the control piston 34. Fuel can thus not escape through the fuel outlet openings 42.

If the switching valve 66 is energized, the outlet throttle 64 is connected to the low-pressure connection 21. As a result, the pressure in the control chamber 56 decreases. The sum now results in a force acting in the opening direction of the control piston 34 force. This begins now, against the force of the spring 50 in the Figures 2 and 3 to move upwards. As a result of the increase in volume, the pressure in the coupling space 94 drops. As a result of the pressure relationship between the force difference between an end face 96 of the nozzle needle 36 delimiting the coupling space 94 and the pressure surfaces 38, the nozzle needle 36 also moves into the characters 2 and 3 upwards, so it lifts off from its valve seat in the region of the fuel outlet openings 42. Thus, fuel from the rail 16 via the high-pressure port 17, the annular space 60, the channel 68, the pressure chamber 40 and the fuel outlet openings 42 are injected into the combustion chamber 20.

By the guide member 70, the valve member 32 and the control piston 34 is held relative to the sealing surface 86 in position. As a result, an oblique position of the sleeve 88 relative to the sealing surface 85 is prevented. Such an obliquity would lead to leaks between the annulus 60 and coupling space 94 and thus malfunction of the fuel injection device 18. The stroke of the nozzle needle 36 is limited by the stroke stop 80. The stroke of the nozzle needle 36 can, as in the FIGS. 2 to 5 is represented by the processing of the bore approach 80 or by a paragraph processing on the end face 96 of the nozzle needle 36 can be realized. In this case, the sealing surface 78 simultaneously forms the stroke stop for the end face 96 of the nozzle needle 36 (see FIG. 6 ).

The control piston 34 will continue its lifting movement. Therefore, the free lift of the control piston 34 must always be greater than the maximum stroke of the nozzle needle 36. Due to the narrow guide clearance between the sleeve 88 and the control piston 34 and the resulting low leakage into the coupling chamber 94, the control piston 34 is braked so much in its stroke movement, that he can do only a little extra movement.

In an in FIG. 7 illustrated alternative embodiment, a Hubeinstellelement 97 is disposed between the end face 96 and the stroke stop 80, through which in addition an adjustment of a desired stroke of the nozzle needle 36 is possible.

To end an injection, the switching valve 66 is brought back into its closed position, in which the connection of the control chamber 56 is locked to the low pressure port 21. Via the inlet throttle 58, the pressure in the control chamber 56 increases continuously. As a result, the control piston 34 is again moved in the closing direction, since the pressure in the coupling chamber 94 is initially lower than in the control chamber 56. As a result, the pressure in the coupling chamber 94 increases due to the reduction in volume again, resulting in a closing movement of the nozzle needle 36.

In FIG. 8 an alternative embodiment of a fuel injector 18 is shown. It is not only here, but in principle that such elements and areas that have equivalent functions to previously described elements and areas, the same reference numerals and are not explained again in detail. For the sake of simplicity, only those reference signs which are required to explain the differences from a previous exemplary embodiment are essentially entered.

Unlike in the Figures 2 and 3 illustrated embodiment, the spring 90, which is applied to the coupling chamber 94 surrounding sleeve 88 against the guide member 70, not on the main body 26, but on the annular collar 52 and the shoulder formed by this is supported. Both springs 90 and 50 thus act on the same annular collar 52 of the control piston 34. When designing the spring 50, therefore, the force component of the spring 90 acting in the opening direction must be taken into account. Another difference to that. Embodiment of Figures 2 and 3 lies in the two-part end body 28. This was divided so that the outlet throttle 64 in the remaining end body 28 and the inlet throttle 58 is in the now separate sleeve 99. The spring 50 presses the sleeve 99 via the sealing surface or sealing edge (without reference numeral) against the end body 28 and thus generates a sufficient separation of the annular space 60 relative to the control chamber 56th

The advantage of in FIG. 8 shown fuel injection device 18 opposite to that of Figures 2 and 3 is that the control piston 34 with the sleeve 99, the spring 50, the spring 90 and the sleeve 88 may form a preassembled unit, so that in the later assembly of all components of the fuel injection device 18, the sleeves 99 and 88 no longer from Control piston 34 must be disconnected. In addition, the recess 30 in the main body 26 of the housing 22 may be designed as a smooth through-hole, which allows the establishment of a comparatively large annular space 60 and a correspondingly large storage volume for the fuel.

A similar variant shows FIG. 9 In this, instead of an annular collar 52 in the control piston 34, a circumferential groove 100 is provided in which an annular coupling element 102 is inserted, on which in turn, but only in the closing direction of the valve element 32, a ring member 104 is supported. At this attack on the one hand, the spring 90 and on the other hand, the spring 50. Again, the control piston 34 with the sleeve 99, the spring 50, the sleeve 88 and the spring 90th and the coupling element 102 and the ring element 104 form a preassembled unit, which is mounted as such and used in the final assembly in the recess 30 in the main body 26 of the housing 22
can be.

Claims (11)

1. Fuel injection device (18) for an internal combustion engine (10), having a housing (22) and having a valve element (32) which is arranged in the housing (22) and which interacts with a valve seat situated in the region of a fuel outlet opening (42), characterized in that at least one first part (34) and one second part (36) of the valve element (32) are coupled to one another by means of a hydraulic coupler (92) which has a coupler chamber (94) which is delimited at least in regions by a sleeve (88) which is guided on the first part (34), and in that said fuel injection device (18) has a guide element (70) which guides a coupler-side end region (77) of the first part (34) of the valve element (32).
2. Fuel injection device (18) according to Claim 1, characterized in that the sleeve (88) is supported on the guide element (70).
3. Fuel injection device (18) according to Claim 2, characterized in that a fluid passage (76) is provided at least in one part of a guide region (76) of the guide element (70) or in a complementary region of the first part of the valve element (32), which fluid passage (76) leads from one side of the guide element (70) to the other.
4. Fuel injection device (18) according to one of the preceding claims, characterized in that the guide element (70) comprises a stroke stop (80) for the second part (36) of the valve element (32).
5. Fuel injection device (18) according to Claim 4, characterized in that a stroke-adjusting element (97) is arranged between the second part (36) of the valve element (32) and the stroke stop (80).
6. Fuel injection device (18) according to one of the preceding claims, characterized in that the guide element (70) comprises a fluid duct (68) with a through opening (82) which at least indirectly connects a pressure chamber (40) in the region of the valve seat to a high-pressure port (17).
7. Fuel injection device according to Claim 6, characterized in that the through opening comprises a flow throttle (82).
8. Fuel injection device (18) according to one of the preceding claims, characterized in that the guide element (70) is clamped between two housing bodies (24, 26) and those surfaces (78) of said guide element (70) which make contact with the housing bodies (24, 26) are designed such that their centre of area lies at least approximately on a central axis of a guide region (76) of the guide element (70).
9. Fuel injection device (18) according to one of the preceding claims, characterized in that the sleeve (88) is acted on by a spring (90) which is supported on a shoulder (52) formed on the first part (34) of the valve element (32).
10. Fuel injection device (18) according to one of Claims 1 to 8, characterized in that the sleeve (88) is acted on by a first spring (90) which is supported on a shoulder formed on one side of a ring element (104), which ring element (104) is acted on on the other side by a second spring (50) which is supported at least indirectly on the housing (22) and which ring element (104) is coupled by means of a coupling element (102) to the valve element (32) in the closing direction of the latter.
11. Fuel injection device (18) according to one of the preceding claims, characterized in that the guide element (70) has a centring section, preferably a centring collar, which centres the guide element (70) with respect to a housing body (26).

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