EP1552135A1

EP1552135A1 - Fuel injection device for an internal combustion engine

Info

Publication number: EP1552135A1
Application number: EP03740026A
Authority: EP
Inventors: Friedrich Boecking
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2002-10-09
Filing date: 2003-05-23
Publication date: 2005-07-13
Anticipated expiration: 2023-05-23
Also published as: DE50303869D1; EP1552135B1; DE10246974A1; WO2004033890A1

Abstract

The invention relates to a fuel injection device (22) for an internal combustion engine, comprising a housing (34, 36, 38). Said housing (34, 36, 38) comprises a recess (40) containing two valve elements (42, 44) which are arranged in a coaxial manner in relation to each other. Said elements cooperate respectively with a corresponding valve seat (46, 50) and at least one fuel injection outlet (48, 52) is associated respectively therewith. At least one control chamber (78, 80) is defined by a pressure surface (66, 76) which is associated with a valve element (42, 44), the force resulting therefrom being directed towards the valve seat (46, 50) of the valve element (42, 44) during operation thereof. The aim of the invention is to produce a fuel injection device (22) which is particularly compact and precise. As a result, at least two control chambers (78, 80) are provided which are associated respectively with a valve element (42, 44) having a pressure surface (66, 76) and the force resulting therefrom is directed towards the valve seat (46, 50) of the valve element (42, 44) during the operation thereof. Said control chambers (78, 80) are arranged in a coaxial manner in relation to each other and at approximately the same axial height.

Description

Fuel injection device for an internal combustion engine

State of the art

The invention relates to a fuel injection device for an internal combustion engine, with a housing, with a recess in the housing, with at least two coaxially arranged in the recess

Valve elements each cooperate with a corresponding valve seat and ^'associated with passage opening where at least a Kraftsto f-stop, and is limited by at least one control space which is assigned by a gauge pressure surface whose

Resulting force is directed towards the valve seat of the valve element during operation.

A fuel injection device of the type mentioned is known from DE 100 58 153 AI. It is an injector that is used in internal combustion engines with direct fuel injection. Two elongated coaxial valve needles are arranged in an elongated housing. The outer Valve needle is pressure controlled. This means that by increasing a pressure in a pressure chamber, which is delimited in some areas by a pressure flank on the outer valve element, the outer valve element is lifted from the corresponding valve seat against the application force by a compression spring. In contrast, the inner valve element is stroke-controlled. This means that a control room is assigned to it, which is normally under high pressure. Due to this high pressure, the valve element is pressed against the valve seat against an application force. The pressure in the control chamber can, however, be briefly reduced, as a result of which the valve element is only subjected to a lower force in the direction of the valve seat. Since there is still an application force that tries to lift the valve element from the valve seat, when the fuel pressure in the control chamber is reduced, the inner valve element moves away from the valve seat.

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 is as compact as possible and can be produced inexpensively.

This task is

Injection device of the type mentioned at the outset in that at least two control spaces are present, each of which is assigned a valve element with a pressure surface, the resultant force of which, in operation, is directed toward the valve seat of the valve element hm, the control spaces being arranged coaxially with one another and approximately at the same axial height are.

Advantages of the invention The fuel injection device according to the invention has the advantage that both valve elements are stroke-controlled and still have a very compact construction. The stroke control of the valve elements by briefly reducing the pressure in the respective control room enables the valve elements to be switched very precisely. The coaxial arrangement and the arrangement at the same height of the control spaces enables a short and narrow construction of the injection device.

Advantageous developments of the invention are specified in subclaims.

In a first development, it is proposed that the control spaces are separated from one another by a sleeve-like separating element. Such a sleeve-like separating element can be produced simply and inexpensively.

In a further development, it is proposed that the sleeve-like separating element is a separate part and is acted upon by a clamping device with a sealing edge against the pressure surface of one of the valve elements. As a separate part, the manufacture of the sleeve-like separating element is further simplified. In the simplest case, the sleeve-like separating element can be a piece of pipe. By applying a tensioning or spring force to the sleeve-like separating element, a secure sealing of the two control rooms located directly next to one another is ensured.

It is particularly advantageous if both or all of the control spaces face outwards through a sleeve-like one Separating element are limited, which is acted upon by a tensioning device. The similar structure simplifies the assembly of the fuel injection seal according to the invention.

Another embodiment of the fuel injection device according to the invention is characterized in that at least one valve element is acted against its sealing seat by a tensioning device which acts on a sleeve-like separating element. In this case, the tensioning device not only serves to act on the sleeve-like separating element in such a way that a secure sealing of the control chamber is ensured, but at the same time it also ensures a certain preload of the valve element against its sealing seat. It is particularly advantageous if the fuel system or the internal combustion engine, in which the fuel injection device is used, is not currently being operated and the corresponding control spaces are therefore more or less depressurized.

This is particularly simple to achieve in the case of the tensioning device which acts on the sleeve-like sealing element which delimits the control chamber of the radially outer valve element to the outside in that the latter

Spanneini xchtung supported on a support ring which is connected to the radially outer valve element.

It is particularly easy to supply the control chamber of the radially outer valve element with fluid under high pressure if the control chamber of the radially outer valve element is connected to a high-pressure connection via a channel m to the sleeve-like separating element, which delimits the control chamber from the outside is. Such a channel can easily be realized through a hole in the wall of the separating element. Its diameter can be selected so that it simultaneously represents or comprises an inflow throttle into the control chamber.

A particularly preferred development of the fuel injection device according to the invention is characterized in that it comprises a 3/3-way valve which is connected to a low-pressure connection and to the two control spaces. The movements of the at least two valve elements can thus be controlled with a single valve. The corresponding fuel injection device is particularly compact in this case and is inexpensive. Installation is also easier because fewer connections have to be connected.

It is again particularly preferred if, in a first switching position of the 3/3-way valve, both valve elements rest on their valve seats, in a second switching position the radially outer valve element is lifted from its valve seat and the radially inner valve element lies on the valve seat, and in one third switching position both valve elements are lifted from their valve seats. This allows all the essentials

Switch positions of the fuel injector are covered.

drawing

A particularly preferred exemplary embodiment of the present invention is explained in detail below with reference to the accompanying drawing. The drawing shows: Figure 1 is a schematic representation of a

Fuel system with multiple fuel injection devices;

Figure 2 is a partial section through one of the

Fuel Einspπtzvorπchtungen of Figure 1; and

FIG. 3 shows an enlarged illustration of a region of the fuel injection device from FIG. 2.

Description of the exemplary embodiment

In Figure 1, a fuel system as a whole carries this

Reference numeral 10. It comprises a fuel tank 12, from which an electric fuel pump 14 requests fuel into a low-pressure fuel line 16. This leads to a high-pressure fuel pump 18. The high-pressure fuel pump 18 is a piston pump which is driven by a camshaft (not shown) of an internal combustion engine (likewise not shown), to which the fuel system 10 belongs. The high-pressure fuel pump 18 compresses the fuel to a very high pressure and prompts it to

Fuel manifold 20. This is also referred to as a "rail". The fuel is stored under high pressure in it.

A plurality of fuel injection devices 22 are connected to the fuel line 20. For this purpose, they have high-pressure connections 24. The fuel injection devices 22 inject the fuel directly into combustion chambers 26 of the internal combustion engine assigned to them. The fuel injection devices 22 each also have a low-pressure connection 28, from which a return line 30 leads back to the fuel tank 12. The operation of the internal combustion engine, the fuel system 10 and, in particular, the fuel injection devices 22 is controlled or regulated by a control and regulating device 32. For this purpose, this is connected to the fuel injection devices 22 via lines (without reference numerals). The fuel system shown in Figure 1 can be used in both gasoline and diesel engines.

The structure of the fuel injection devices 22 will now be explained in detail with reference to FIGS. 2 and 3:

The fuel injection devices 22 comprise a housing which comprises a nozzle body 34, an intermediate piece 36, and an upper end piece 38. A recess 40 is provided in the nozzle body 34, and there are two coaxially arranged valve elements 42 and 44. The outer tubular valve element 42 works together with a valve seat 46, which is present in the lower region of the recess 40 in FIG. 2. Exit openings 48 are also assigned to it. The inner valve element 44 cooperates with a valve seat 50, and fuel outlet openings 52 are assigned to it.

The outer valve element 42 is guided in the recess 40. The inner valve element 44 is guided in the outer valve element 42. The outer jacket pool of the outer valve element 42 has a shoulder 54 in the area of the upper end of the outer valve element 42 in FIG. A support ring 56 bears against this. On the support ring 56 in turn supports one end of a compression spring 58, the other end of which acts on a first sealing sleeve 60 against the intermediate piece 36. The first sealing sleeve 60 is pushed onto the upper end of the outer valve element 42 in a fluid-tight manner. However, the first sealing sleeve 60 and the outer valve element 42 can be moved relative to one another at least in the axial direction.

The first sealing sleeve 60 has a tapering circumferential sealing edge 62 on its upper edge in FIG. 2. In the area of this tapered sealing edge 62, a radial channel 64 is worked through the sealing sleeve at one point of the first sealing sleeve 60. The upper edge of the outer valve element 42 in FIG. 2 forms a flat annular surface, which represents an annular pressure surface 66. Their meaning will be explained in more detail below.

In the intermediate piece 36 there is an annular recess 68 which is open towards the nozzle body 34. At its upper end in FIG. 2, one end of a compression spring 70 is supported, the other end of which acts on an edge of a second annular sealing sleeve 72. The second sealing sleeve 72 is guided in the annular recess 68 in a sliding and fluid-tight manner. Your lower in Figure 2

Analogous to the edge 62 of the first sealing sleeve 60, the edge tapers to a point and forms a sealing edge 74. This lies against an upper end face of the inner valve element 44.

This upper end surface forms a pressure surface 76 in a manner to be explained in more detail below. The diameter of the sealing edge 74 of the second sealing sleeve 72 is somewhat smaller than the outer diameter of the inner valve element 44. The compression spring 58, the first sealing sleeve 60, the compression spring 70, the second sealing sleeve 72 and the two valve elements 42 and 44 are arranged coaxially to one another.

An outer annular control chamber 78 is present between the two sealing sleeves 60 and 72, the pressure surface 66 on the outer valve element 42 and the intermediate piece 36. An inner control space 80 is formed between the circular pressure surface 76 of the inner valve element 44, the second sealing sleeve 72 and the intermediate piece 36.

In the upper end piece 38 of the fuel injection device 22 there is a 3/3-way valve 82. Its valve element 84 is actuated by a piezo actuator 88 via a tappet 86. The valve element 84 is arranged in a control chamber 90 and cooperates with an upper valve seat 92 in FIGS. 2 and 3 and a lower valve seat 94 in FIGS. 2 and 3. A central channel 96 leads from the 3/3-way valve 82 via an outflow throttle 98 to the inner control chamber 80. Furthermore, an off-center channel 100 also leads from the 3/3 way valve 82 via an outflow throttle 102 to the outer annular control chamber 78.

A channel 104 leads from the 3/3-way valve 82 to

Low-pressure connection 28. This is also connected via a leakage channel 106 to the annular recess 68 in the intermediate piece 36. A channel 108 leads from the high-pressure connection 24 in the upper end piece 38 and in the intermediate piece 36 to the recess 40 in the nozzle body 34. Another channel 110 leads obliquely from the high-pressure connection 24 via an inflow throttle 112 to the central channel 96. From the recess 40, one leads to the longitudinal axis of the recess 40 parallel channel 114 to one in the lower area of the Recess 40 existing annular space 116.

The fuel injection device 22 shown in FIGS. 2 and 3 operates as follows:

In the closed rest position, when the fuel injection device 22 is not to inject any fuel into the combustion chamber 26 assigned to it, the valve element 84 of the 3/3-way valve 82 rests on the upper valve seat 92. The connection of the control spaces 78 and 80 to the low-pressure connection 28 is thus interrupted. At the same time, the connection of the control spaces 78 and 80 remains on the one hand via the channel 96, the channel 110 and the flow restrictor 112 and on the other hand via the flow restrictor 64 and the passage 108. In the control spaces 78 and 80 there is therefore the high fuel pressure also acting at the high pressure connection 24. This leads to corresponding forces on the pressure surfaces 76 and 66, by means of which the valve elements 42 and 44 are pressed against the valve seats 46 and 50. These forces on the pressure surfaces 76 and 66 act in the same direction as the forces exerted by the pressure springs 58 and 70.

If fuel is to be injected through the fuel outlet openings 48, the piezo actuator 88 is controlled by the control and regulating device 32 such that the valve element 84 of the 3/3-way valve 82 comes into contact with the lower valve seat 94. In this state, although the fluid connection between the control chamber 80 of the inner valve element 44 and the low-pressure connection 28 is still interrupted, edozh can now use the outflow throttle 102, the flow channel 100, the control chamber 90 and the channel 104 to fuel from the annular control chamber 78 of the outer valve element 42 for low pressure connection 28 flow out.

Thus the pressure in the control chamber 78 and the corresponding force resultant on the pressure surface 66 also decrease. Since the annular space 116 is still a high one

There is fuel pressure and this acts on a pressure surface of the outer valve element 42 which is located radially outward from the valve seat 46 in a direction pointing away from the valve seat 46, the outer valve element 42 is now lifted off the valve seat 46 so that fuel can escape from the fuel outlet openings 48 ,

If fuel is to be injected through both the fuel outlet openings 48 and through the fuel outlet openings 52, the

Piezo actuator 88 is controlled by the control and regulating device 32 such that the valve element 84 is in a middle switching position, that is to say neither in contact with the upper valve seat 92 nor in contact with the lower valve seat 94. In this case, both control spaces 78 and 80 are connected to the low pressure connection 28. Analogously to what has been described above, the amount of the resultant force which acts on the pressure surface 76 of the inner valve element 44 thus decreases, and the inner valve element 44 can move radially outward from the

Lift valve seat 50 off the valve seat 50 at the high pressure acting on its conical tip.

It can easily be seen in particular from FIG. 3 that the two control spaces 78 and 80 are arranged coaxially with one another and at approximately the same axial height. The control spaces 78 and 80 are essentially sealed by the sealing sleeves 60 and 72.

Claims

Expectations

1. Fuel injection device (22) for an internal combustion engine, with a housing (34, 36, 38) ^' , with a recess (40) present in the housing (34, 36, 38), with at least two in the recess (40 ) coaxially arranged valve elements (42, 44), which each cooperate with a corresponding valve seat (46, 50) and to which at least one fuel outlet opening (48, 52) is assigned, and with at least one control chamber (80) which is provided by a valve element (44) associated printing surface (76) is restricted, the net force of the valve member is directed toward (44) in the ^'operation to the valve seat (50), characterized in that at least two control spaces (78, 80) are provided, each of which a valve element (42, 44) is associated with a pressure surface (66, 76), the resultant force of which, during operation, is directed toward the valve seat (46, 50) of the valve element (42, 44), the control spaces (78, 80) being coaxial with one another and are arranged approximately at the same axial height.

2. Fuel injection device (22) according to claim 1, characterized in that the control spaces (78, 80) through a sleeve-like separating element (72) are separated from one another.

3. Fuel injection device (22) according to claim 2, characterized in that the sleeve-like separating element is a separate part (72) and of a tensioning device (70) with a sealing edge (74) against the pressure surface (76) of one of the valve elements (44 ) is applied.

4. Fuel injection device (22) according to one of claims 2 or 3, characterized in that the control spaces (78, 80) are each outwardly delimited by a sleeve-like separating element (60, 72) which is provided by a tensioning device (70, 58 ) is applied.

5. Kra tstoff injection device (22) according to one of claims 2 or 4, characterized in that at least em valve element (42, 44) of a tensioning device (58, 70), which acts em sleeve-like separating element (60, 72) against its valve seat (46, 50) is acted upon.

6. Fuel-Emspr ltzvorπchtung (22) according to claim 5, characterized in that d e Spannemrichtung

(58), which acts on the sleeve-like sealing element (60), which limits the control chamber (78) of the radially outer valve element (42) to the outside, is supported on a support ring (56) which bears on the radially outer valve element (42).

7. Fuel-Emspπtzvorrichtung (22) characterized in that the control chamber (78) of the radially outer valve element (42) via a channel (64) m the sleeve-like separating element (60), which limits it to the outside h, with a high pressure connection ( 24) is connected.

8. Fuel injection device (22) according to one of the preceding claims, characterized in that it comprises a 3/3-way valve (82) which is connected to a low-pressure connection (28) and to the two control rooms (78, 80).

9. Fuel injection device (22) according to claim 8, characterized in that in a first switching position of the 3/3-way valve (82) both valve elements (42, 44) rest on their valve seats (46, 50), in a second switching position the radially outer valve element (42) is lifted from its valve seat (46) and the radially inner valve element (44) bears against its valve seat (50), and in a third switching position both valve elements (42, 44) from their valve seats (46, 50 ) are lifted off.