EP1671029A2

EP1671029A2 - Fuel injection device, especially for a direct injection internal combustion engine

Info

Publication number: EP1671029A2
Application number: EP04762588A
Authority: EP
Inventors: Siegfried Ruthardt; Holger Rapp
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2003-09-23
Filing date: 2004-08-04
Publication date: 2006-06-21
Anticipated expiration: 2024-08-04
Also published as: WO2005038235A2; EP1671029B1; DE10346222A1; DE502004005391D1; WO2005038235A3

Abstract

The invention relates to a fuel injection device (18) comprising a housing (28). The housing is provided with a housing recess (30) in which a valve element (48) is located. At least one fuel outlet channel (32) is associated with said valve element. The device also comprises a sleeve piece (34) that is coaxial to the valve element (48) and that is located on the valve element (48). The fuel injection device (18) is characterized in that it comprises alignment means (38) which radially align the sleeve piece (34) relative to the housing recess (30) and that the valve element (48) is guided in the sleeve piece (34).

Description

Fuel injection device, in particular for an internal combustion engine with direct fuel injection

State of the art

The invention relates to a fuel injection device, in particular for an internal combustion engine with direct fuel injection, with a housing and a valve element arranged in a housing recess, to which at least one fuel outlet channel is assigned, and with a sleeve part which is coaxial with the valve element and which is on the valve element sitting.

A fuel injection device of the type mentioned above is known from DE 101 22 256 AI. This shows a fuel injection device with a nozzle body in which a longitudinal bore is present. In this, an elongated valve element is guided in some areas. The valve element is “stroke-controlled”, that is to say that at its end facing away from a combustion chamber in the installed position it has a control surface which delimits a hydraulic control chamber. If there is high pressure in the hydraulic control room, the valve element is pressed into its closed position. In the event of a pressure drop, the valve element can be opened by an actuating device acting in the opening direction. The control chamber is delimited radially outwards by a sleeve part which is fluid-tight on an end region of the valve element is pushed on and pressed by a spring against a control part opposite the control surface.

In the fuel injection device shown in DE 101 22 256 AI, the valve element has a guide section approximately in its axial center, which cooperates with a corresponding guide section of the longitudinal bore in the housing. As a result, the valve element is guided relative to the housing and prevents it from tilting in relation to the longitudinal axis of the housing during operation. In order to avoid tensioning the valve element, the sleeve part at the end, which radially delimits the control chamber, is not radially fixed in relation to the recess in the housing.

The object of the present invention is to develop a fuel injection device of the type mentioned at the outset in such a way that it can be produced as inexpensively as possible.

This task is

Injection device of the type mentioned at the outset in that it comprises alignment means which radially align the sleeve part with respect to the housing recess, and in that the valve element is guided in the sleeve part.

Advantages of the invention

The radial position and axial alignment of the sleeve part are clearly defined by the alignment means. Therefore, it can very well form one or the only guide for the valve element. On the complex and expensive production of guide surfaces in the wall of the Housing recess can therefore be dispensed with in the fuel injection device according to the invention. It is therefore comparatively inexpensive.

Advantageous developments of the invention are specified in the subclaims.

First, it is proposed that the alignment means comprise at least one peripheral wall on the sleeve part, which abuts the wall of the housing recess. In this particularly simple embodiment of the alignment means, the sleeve part is more or less a fitting ring that is pressed into the housing recess, for example. This is particularly simple, robust and inexpensive.

It is also possible for the alignment means to have a plurality of radially extending webs, each of which abuts the wall of the housing recess with its projecting end. Such webs automatically form free spaces between the webs, which for example can be part of a fluid connection from a high-pressure connection to the fuel outlet channel. This facilitates and simplifies the flow guidance in the fuel injection device according to the invention.

In a further development, it is proposed that the free spaces between the webs be dimensioned such that a desired throttling effect is achieved. In this advantageous embodiment, the sleeve part therefore has a double function, because it also serves to coordinate the dynamics of the valve element during its opening and closing operation. Another particularly preferred embodiment of the fuel injection device according to the invention provides that at the end of the valve element facing away from the combustion chamber in the installed position there is a control surface which acts in the closing direction and which has a hydraulic control surface

Control space limited, and that the sleeve element protrudes beyond this end of the valve element at least when the valve element is closed and is pressed by a pretensioning device against a wall of a counter element opposite the control surface, in such a way that it seals the control space against the counter element. In this development, too, the sleeve part has a double function: in addition to guiding the valve element, it also serves to radially delimit the control chamber and to seal the control chamber from the counter element. The corresponding fuel injection device is therefore comparatively compact.

If the webs mentioned above are present in such a fuel injection device, it is advantageous if these webs are arranged axially offset from the control chamber. This allows additional freedom in the design of the area of the housing recess directly adjacent to the wall of the counter element.

Another particularly preferred embodiment of the fuel injection device according to the invention provides that the alignment means comprise a conical recess in the wall of the counter element in the region of the housing recess, such that the sleeve part is centered by the conical recess. In this way, the sleeve part can be aligned with respect to the housing recess without angular errors between the wall of the counter element and the orientation of the housing recess play a role. This simplifies production and lowers the manufacturing costs of the fuel injection device according to the invention. At the same time, the reliability during operation of the fuel injection device according to the invention is increased, since the sealing of the

Control room is guaranteed even with such angular errors. The correct alignment of the housing and the counter element to one another is carried out by simple and customary measures, for example dowel pins, a centering groove, or the like.

Alternatively, it is also possible for the alignment means to comprise an overall conical wall of the counter element opposite the control surface and a corresponding housing wall which is complementary thereto, such that the sleeve part and the housing are centered by the conical wall. In this way, the centering of the sleeve part with respect to the housing is automatically ensured, without contact between the sleeve part and the housing or other alignment means for aligning the counter element with respect to the housing being required. In particular, the assembly of such a fuel injection device is very simple.

It is possible that the wall of the counter element is conically concave. In principle, however, it is also conceivable that this wall is designed conically convex. In both cases, the wall can be manufactured very easily and ensures that the sleeve part is well centered.

It is further provided according to the invention that, in a preferred embodiment of the fuel injection device, the valve element has a guide section which is guided in the sleeve part and has a larger diameter than an area of the valve element around which the biasing device is arranged. In this way, contact between the pretensioning device and the valve element, which would cause sliding friction during the operation of the fuel injection device, is avoided. This allows even better and more accurate fuel injection.

drawing

Particularly preferred exemplary embodiments of the present invention are explained in more detail below with reference to the accompanying drawing. The drawing shows:

Figure 1 is a schematic representation of a fuel system of an internal combustion engine with a fuel injection device;

FIG. 2 shows a partial section through a first exemplary embodiment of the fuel injection device from FIG. 1;

3 shows a section along the line III-III of Figure 2;

Figure 4 is a partial section similar to Figure 2 of a second embodiment; and

Figure 5 is a partial section similar to Figure 2 of a third embodiment.

Description of the embodiments In FIG. 1, a fuel system of an internal combustion engine bears the reference number 10 overall. It comprises a fuel tank 12, from which a delivery system 14 conveys the fuel to a fuel collecting line (“rail”) 16. The conveyor system 14 can comprise, for example, a prefeed pump and a high-pressure pump.

A plurality of fuel injection devices 18 are connected to the fuel collecting line 16, only one of which is shown in FIG. 1. For this purpose, the fuel injection device 18 has a high-pressure connection 20. The fuel injection device 18 is assigned to a combustion chamber 22 into which it injects the fuel directly. One leads from the fuel injection device 18

Return line 24 back to the fuel tank 12. The return line 24 is connected to the fuel injection device 18 at a low pressure connection 26.

The structure of the fuel injection device 18 will now be explained in more detail with reference to FIGS. 2 and 3:

Thereafter, the fuel injector 18 includes a housing 28 in which a longitudinally extending one

Housing recess 30 is present. The housing 28 is also referred to as a "nozzle body". At the lower end of the housing 28 in FIG. 2, there are fuel outlet channels 32 distributed over the circumference, via which fuel can pass from the housing recess 30 into the combustion chamber 22.

The housing recess 30 comprises a lower portion 30a in FIG. 2 and a conical end 30b and an upper portion 30b which is larger in diameter than section 30a. A sleeve part 34 is inserted into the upper section 30a of the housing recess 30. As can be seen in particular from FIG. 3, this sleeve part 34 has a continuous and radially inner guide section 36, a tapered sealing section 37 and a plurality of webs 38, which are distributed over the circumference of the guide section 36 and extend radially outward.

As can be seen from FIG. 2, the webs 38 are arranged offset somewhat downwards relative to the guide section 36. The webs 38 are formed by semicircular free spaces 40 which are present between the webs 38. The radially projecting end faces 42 of the webs 38 lie on a common one

Cylinder surface, which corresponds approximately to the lateral surface of the upper section 30b of the housing recess 30. In this way, the sleeve part 34 is radially fixed and centered with respect to the housing recess 30.

The sleeve part 34 has a central, continuous guide bore 44. This works together with a guide section 46 of a valve element 48, which is guided in this way in the sleeve part 34 and is thus movable in the housing recess 30 in the axial direction, but is not displaceable in the radial direction. A section 50 adjoins the guide section 46 towards the lower end of the valve element 48 in FIG. 2, which section has a smaller diameter than the guide section 46. Shortly above the transition from

Section 30a to section 30b of the housing recess 30, the section 50 of the valve element 48 has a circumferential collar 52. A helical compression spring 54 is clamped between this collar 52 and the guide section 36 of the sleeve part 34. Above the housing 28, the fuel injection device 18 comprises a plate-shaped counter element 56. This is fastened to the housing 28 in a manner not shown in FIG. 2. It has a flat wall surface 58 toward the housing 28. Against this, the sleeve part 34 is acted upon by the helical compression spring 54. A hydraulic control chamber 60 is formed between the wall surface 58, the sleeve part 34, and the upper end surface of the valve element 58 in FIG. Therefore, the upper end surface of the valve element 48 is also referred to as a control surface. It bears the reference number 62.

Various channels and throttles are accommodated in the plate-shaped counter element 56. Therefore, it will

Counter element 56 also referred to as a throttle plate. A first high-pressure duct 64 connects a high-pressure chamber 66, which is present radially outside of the sleeve part 34, between the valve element 48 and the housing recess 30b, with the high-pressure connection 20. An inlet duct 68 with an inlet throttle 70 leads from the high-pressure connection 20 to the control chamber 60. which contains a discharge throttle 74 leads from the control chamber 60 to a control valve 76. Via this the control chamber 60 can either be connected to or disconnected from the low-pressure connection 26.

The fuel injection device 18 shown in FIGS. 2 and 3 is assembled as follows:

First, the valve element 48 is inserted into the housing recess 30 e and the helical compression spring 54 is threaded onto the valve element 48. Then the sleeve part 34 is pushed onto the guide section 46 of the valve element 48 and in the section 30b of the housing recess 30 centered. Finally, the counter element 56 is attached to the housing 28.

The fuel injection device 18 shown in FIGS. 2 and 3 is operated as follows:

In the initial state, the control valve 76 is closed, and the high pressure prevailing in the fuel collecting line 16 is present at the high-pressure connection 20. The corresponding high fuel pressure is thus also present in the high-pressure channel 64 and in the high-pressure chamber 66. This high fuel pressure is also present at a conical pressure surface 78, which is present at the lower end of the valve element 48 in FIG. 2, so that a hydraulic force acting in the opening direction acts there. At the same time, the high pressure is also transmitted into the control chamber 60 via the inlet channel 68. There is therefore a high fuel pressure in this too.

The hydraulic force acting on the control surface 62 in the closing direction is, however, greater than that which acts on the pressure surface 78 in the opening direction due to the area ratios. The valve element 48 is therefore pressed with a sealing edge 80 against a corresponding housing-side valve seat (without reference numerals). Fuel can therefore not escape through the fuel outlet channels 32.

The control valve 76 is opened for an injection. Fuel can thus from the control room 60 to

Flow out low pressure port 26. The inlet throttle 70 and the outlet throttle 74 are coordinated with one another in such a way that the pressure in the control chamber 60 drops in a certain manner. If the hydraulic force acting on the control surface 62 in the closing direction falls below that in Force acting in the opening direction, which is applied to the pressure surface 78, lifts the sealing edge 80 off the valve seat on the housing side, and the valve element 48 opens.

During this opening movement, it is guided securely by the guide section 46 in the guide bore 44 of the sleeve part 34. At the same time, the close sliding guidance between the guide section 46 and the guide bore 44 ensures a good seal of the control chamber 60 with respect to the high-pressure chamber 66. When the sealing edge 80 lifts off the valve seat on the housing side, fuel can reach the fuel outlet channels 32, so that the fuel injection device 18 injects fuel into the combustion chamber 22.

If the injection is to be ended, the control valve 76 is closed again. The pressure in the control chamber 60 thus rises and the valve element 48 comes into contact with the sealing edge 80 against the valve seat on the housing side.

Because the section 50 of the valve element 48, in the area of which the helical compression spring 54 is arranged, has a comparatively small diameter, no sliding friction can occur during the movement of the valve element 48 between the helical compression spring 54 and the valve element 48. Corresponding wear of the spring 54 and the valve element 48 is thus reduced or completely avoided. Since the valve element 48, as soon as the sealing edge 80 has lifted off the valve seat on the housing side, only via the guide section 46 in FIG

Guide bore 44 of the sleeve part 34 is guided, a complex machining of the housing recess 30 for guiding the valve element 48 is not necessary. The semicircular free spaces 40 between the webs 38 of the sleeve part 34 can be dimensioned such that one Desired throttling effect occurs from the high pressure channel 64 to the fuel outlet channels 32. In an embodiment not shown, the helical compression spring 54 is also completely dispensed with. In this case, the sleeve part 34 is press-fitted into the housing recess 30 in the housing 28.

An alternative embodiment of a fuel injection device is shown in FIG. 4. Elements and areas which have functions equivalent to elements and areas of the exemplary embodiment shown in connection with FIGS. 2 and 3 have the same reference symbols. They are not explained in detail again. For reasons of illustration, not all reference numerals are also entered.

The differences between the fuel injection device 18 shown in FIG. 4 and the previous one relate to the design of the sleeve part 34 and the wall surface 58 of the throttle plate 56. The sleeve part 34 has none

Webs, but only via a guide section 36 and towards the throttle plate 56 via a sealing section 37. The wall surface 58 has a conically concave recess 82 in the region of the housing recess 30. The sealing section 37 of the sleeve part 34 lies on the throttle plate 56 in

Area of this conical recess 82. In this way, the sleeve part 34 is centered relative to the throttle plate 56, against which it is pressed by the helical compression spring 54. Direct centering of the sleeve part 34 with respect to the housing recess 30 can therefore be dispensed with. However, the throttle plate 56 must be positioned very precisely in relation to the housing 28, which is possible, for example, by means of dowel pins or a centering groove (neither of which is shown). A further modified embodiment is shown in FIG. 5. What has been said above applies with regard to functionally equivalent elements and areas.

In the fuel injection device 18 shown in FIG. 5, the wall surface 58 of the throttle plate 56 is generally conically concave. An opposite housing surface 84 is complementary to this, that is, conically convex. In this way, a special positioning of the throttle plate 56 with respect to the housing 28 can be dispensed with, since these virtually center on one another by themselves.

Claims

Expectations

1. Fuel injection device (18), in particular for an internal combustion engine with direct fuel injection, with a housing (20) and a valve element (48) arranged in a housing recess (30), to which at least one fuel outlet channel (32) is assigned, and with a sleeve part (34) which is coaxial with the valve element (48) and which sits on the valve element (48), characterized in that it comprises alignment means (38; 82; 58) which separate the sleeve part (34) from the housing recess (30 ) align radially, and that the valve element (48) is guided in the sleeve part (34).

2. Fuel injection device (18) according to claim 1, characterized in that the alignment means (38) comprise at least one peripheral wall (42) on the sleeve part (34) which bears on the wall of the housing recess (30).

3. Fuel injection device (18) according to one of claims 1 or 2, characterized in that the

Alignment means has a plurality of radially extending webs (38), each of which abuts the wall of the housing recess (30) with its projecting end (42).

4. Fuel injection device (18) according to claim 3, characterized in that the spaces (40) present between the webs (38) are dimensioned such that a desired throttling effect is achieved.

5. Fuel injection device (18) according to one of the preceding claims, characterized in that at the end of the valve element (48) facing away from a combustion chamber (22) in the installed position there is a control surface (62) acting in the closing direction, which has a hydraulic control chamber (60), and that the sleeve element (34), at least when the valve element (48) is closed, projects beyond this end (62) of the valve element (48) and from a pretensioning device (54) against a wall (58) opposite the control surface (62) of a counter element (56) is pressed in such a way that it seals the control chamber (60) with respect to the counter element (56).

6. Fuel injection device (18) according to claim 5 in conjunction with one of claims 3 or 4, characterized in that the webs (38) are arranged axially offset from the control chamber (60).

7. Fuel injection device (18) according to claim 5, characterized in that the alignment means comprise a conical recess (82) in the wall (58) of the counter-element (56) in the region of the housing recess (60), such that the sleeve part ( 34) is centered by the conical recess (82).

8. The fuel injection device (18) according to claim 5, characterized in that the alignment means comprise an overall conical wall (58) of the counter element (56) opposite the control surface (62) and a corresponding housing wall (84) complementary thereto, such that that the sleeve part (34) and the housing (30) are centered by the conical wall (58).

9. Fuel injection device (18) according to one of claims 6 or 7, characterized in that the conical recess (82) or the conical wall (58) of the counter element (56) is concave.

Fuel injection device (18) according to one of the preceding claims, characterized in that the valve element (48) has a guide section (46) which is guided in the sleeve part (34) and has a larger diameter than a region of the valve element (50) around which the pretensioning device (54) is arranged.