EP2462335B1 - Device for high-pressure fuel injection - Google Patents

Description

State of the art

The present invention relates to a device for high-pressure fuel injection, which can be used in particular in internal combustion engines with direct injection in the stratified charge mode.

As devices for high-pressure fuel injection in internal combustion engines with direct injection high-pressure injection valves are used with outwardly opening valve needle, which are particularly suitable for combustion processes with beam-guided stratified operation due to their advantageous spray characteristics due to the annular gap between the valve needle and valve body. However, in injectors with outwardly opening valve needle, due to the larger seat diameter of the valve needle, the hydraulic force generated by the fuel pressure is significantly higher compared to injectors with inwardly opening needle. Because of the high forces and short switching times injectors are therefore usually used with piezo actuators, however, cause an increased cost.

At an in EP 1783 358A1 described concept, an injection valve with outwardly opening valve needle is disclosed, which is actuated by a solenoid actuator and having a guide element on the valve needle, which is guided in a valve housing, wherein the diameters of the guide element and a valve seat of the valve needle are selected so that the valve needle is essentially pressure balanced.

The high-pressure injection valves of the prior art are only insufficiently suitable to a simple and inexpensive to produce device for To provide high pressure injection for internal combustion engines with direct injection in stratified charge mode, which provides a high sealing force between the valve seat and valve needle in the closed state, and can be operated by a solenoid actuator with low actuation force or low power consumption and has a comparable switching dynamics as an injection valve with piezo actuator.

Disclosure of the invention

The valve assembly according to the invention with the features of claim 1 has the advantage that it has a simple and thus more cost-effective design with a solenoid actuator that opens an outwardly opening valve needle due to effective on the valve needle pressure equalization with a significantly reduced operating force. Therefore, in the valve assembly according to the invention solenoid actuators with low power consumption, especially at injection pressures of 20 MPa or higher, can be used, which allow sufficient switching dynamics and reliable sealing of the valve needle valve seat of the valve in the closed state. This is inventively achieved in that when activating an electromagnetic actuator arranged between the high pressure region and low pressure region of the valve assembly control valve is opened in front of an outwardly opening valve needle. By releasing a connection between a pressure chamber in the high pressure region and a pressure chamber in the low pressure region of the valve assembly, a pressure equalization, d. H. a pressure increase in the low pressure region, which causes a hydraulic force on an active surface of a valve element of the control valve in the opening direction of the valve needle and thereby significantly reduces an opening force of the electromagnetic actuator for the valve needle. As a result, an easy and fast switching is possible. The control valve is opened by means of a freely movable magnet armature or a component connected to the magnet armature.

The dependent claims show preferred developments of the invention.

According to a preferred embodiment of the invention, the device according to the invention for high-pressure fuel injection further comprises a driver attached to the valve needle with an armature contact region, wherein the driver is arranged in the starting position at a predetermined distance from the armature and the armature is movably disposed on the valve needle. A closing spring for closing the valve needle also restores the armature. This ensures that upon activation of the electromagnetic actuator whose armature first moves from the starting position to the armature contact region of the driver and thereby opens the control valve for pressure equalization, without operating the valve needle. Only when the magnet armature is applied to the driver, the valve needle is actuated directly via the armature and opened.

Preferably, a ring-cylindrical component is attached to the armature, wherein the valve seat of the control valve is arranged on a free end face of the annular-cylindrical component. As a result, a simple construction of the control valve is achieved with a minimum number of components.

Further preferably, a gap seal is formed between the annular cylindrical component and the valve housing. As a result, a simple and cost-effective seal between the two components is realized with a small amount of leakage.

Particularly preferably, a diameter of the gap seal is formed larger than a diameter of the valve seat of the valve needle. In this way, a resulting hydraulic force is generated in the opening direction of the valve needle with open control valve and pressure equalization and thus reduces the force to be overcome by the armature opening force of the valve needle. When the control valve is closed by the low pressure in the pressure chamber, however, results in a hydraulic force in the closing direction of the valve needle, which causes a reliable seal of the valve.

According to a further preferred embodiment of the invention, the distance from the starting position of the magnet armature to the driver attached to the valve needle is smaller than a total stroke of the magnet armature, ie, there is a residual stroke for opening the valve needle. Through a first partial stroke the magnet armature from the starting position to the driver is a rapid opening of the control valve for pressure equalization and thus a rapid pressure equalization for the easier opening of the valve needle achieved, which is then opened with a second partial stroke. When closing the valve needle, a first partial stroke of the armature is first carried out by the driver to the closed position of the control valve and the control valve thus closed. Here, the valve element of the control valve acts as another actuated by the armature driver for the return of the valve needle. By thus again occurring at the control valve pressure difference between the high pressure region and the low pressure region of the device, the closing of the valve needle can be done faster by a hydraulic force in the closing direction of the valve needle supporting hydraulic force. This makes it possible to use magnetic actuators with low power consumption and to realize the switching dynamics required for gasoline injection during stratified operation of internal combustion engines.

According to a further preferred embodiment of the invention, the device for high-pressure fuel injection between the pressure chamber and the low-pressure region further comprises a throttle. As a result, a quick pressure reduction over an annular gap between the valve needle and the valve housing in the pressure chamber with a closed control valve and thus a high contact pressure and a good sealing effect between the valve needle and the valve seat is achieved in a simple manner.

As an alternative to the throttle, a leakage check valve can be inserted between the pressure chamber and the low-pressure region. As a result, a leakage or return amount of fuel to a fuel return when opening the valve needle is significantly reduced. Thus, the device according to the invention can be used very economically.

Preferably, the leakage check valve has as closure member a collar-like extension formed on the valve needle and a seat which is formed on the valve housing. As a result, a simple construction of the leakage check valve with a minimum number of components can be realized. Furthermore, this can provide a very reliable device.

Short description of the drawing

Figur 1

eine schematisch vereinfachte Schnittdarstellung der erfindungsgemäßen Vorrichtung bei geschlossener Ventilnadel

Figur 2

eine vergrößerte schematische Schnittdarstellung eines Teils der Vorrichtung von Figur 1,

Figur 3

eine schematisch vereinfachte Schnittdarstellung der Vorrichtung von Figur 1 beim Öffnen der Ventilnadel,

Figur 4

eine schematisch vereinfachte Schnittdarstellung der Vorrichtung von Figur 1 bei geöffneter Ventilnadel,

Figur 5

eine vergrößerte schematische Schnittdarstellung eines Teils der Vorrichtung von Figur 4,

Figur 6

eine schematisch vereinfachte Schnittdarstellung der Vorrichtung von Figur 1 beim Schließen der Ventilnadel,

Figur 7

eine schematisch vereinfachte Schnittdarstellung einer zweiten Ausführungsform der Vorrichtung bei geschlossener Ventilnadel,

Figur 8

eine schematisch vereinfachte Schnittdarstellung der Vorrichtung von Figur 7 bei geöffneter Ventilnadel,

Figur 9

eine vergrößerte schematische Schnittdarstellung eines Teils der Vorrichtung von Figur 7 bei geschlossener Ventilnadel, und

Figur 10

eine vergrößerte schematische Schnittdarstellung eines Teils der Vorrichtung von Figur 7 bei geöffneter Ventilnadel.

Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings. In the drawing is:

FIG. 1

a schematically simplified sectional view of the device according to the invention with a closed valve needle

FIG. 2

an enlarged schematic sectional view of a part of the device of FIG. 1 .

FIG. 3

a schematically simplified sectional view of the device of FIG. 1 when opening the valve needle,

FIG. 4

a schematically simplified sectional view of the device of FIG. 1 with open valve needle,

FIG. 5

an enlarged schematic sectional view of a part of the device of FIG. 4 .

FIG. 6

a schematically simplified sectional view of the device of FIG. 1 when closing the valve needle,

FIG. 7

a schematically simplified sectional view of a second embodiment of the device with the valve needle closed,

FIG. 8

a schematically simplified sectional view of the device of FIG. 7 with open valve needle,

FIG. 9

an enlarged schematic sectional view of a part of the device of FIG. 7 with closed valve needle, and

FIG. 10

an enlarged schematic sectional view of a part of the device of FIG. 7 with open valve needle.

The following is with reference to the FIGS. 1 to 6 a device 1 for high-pressure fuel injection according to a first preferred embodiment of the invention described in detail.

FIG. 1 shows a schematically simplified sectional view of the device according to the invention in the closed state. As from the schematic sectional view of FIG. 1 As can be seen, the device 1 comprises a valve housing 2, an outwardly opening valve needle 3, which is arranged in the valve housing 2 in a pressure chamber 4 filled with fuel. This pressure chamber 4, a fuel K is supplied via a fuel inlet 24 under pressure, wherein the valve needle 3 seals on a valve seat 16 on the valve housing 2. Furthermore, the device 1 has a closing spring 5, which returns the valve needle 3 to a starting position, and an electromagnetic actuator 6 with a magnetic coil 63, an inner pole 62, a magnet housing 61 and a movably arranged magnet armature 7, the valve needle 3 via a thereto trained or attached driver 9 is actuated. A control valve 8 having a valve element 10 and a valve seat 11 is arranged on an end region 29 of the valve needle 3 opposite the injection side.

The valve element 10 has a first active surface 13, which faces the pressure chamber 4, and a second active surface 14, which faces a pressure chamber 12, which communicates with a low-pressure region 19. The valve element 10 of the control valve 8 is designed to release and close a connection between the pressure chamber 4 and the pressure chamber 12, the valve seat 11 of the control valve 8 being arranged on an end face of a ring-cylindrical component 17 fastened to the magnet armature 7. Between the outer circumference of the annular cylindrical member 17 and the valve housing 2, a gap seal 18 is formed with a small guide clearance.

How out FIG. 1 Furthermore, 17 flow through openings 30, 31, for the supply of the fuel K are formed in the armature 7 and the annular cylindrical member. Accordingly, when the valve needle 3 is closed and the control valve 8 is closed, the high pressure of the fuel inlet 24 is present supplied fuel in all connected to the pressure chamber 4 interior spaces of the device. In the pressure chamber 12, there is low pressure, since it is connected via a throttle 21 to the fuel return 25 and the control valve 8 is closed.

Since, in the device 1 according to the invention, a diameter ds of the valve seat 16 is selected to be smaller than a diameter d1 of the valve element 10, the valve needle 3 is additionally pressed, in addition to the force of the closing spring 5, into the valve seat 16 by a hydraulic force component resulting from this difference in diameter , As a result, a reliable sealing of the device 1 is ensured when the valve needle 3 is closed.

FIG. 2 shows an enlarged schematic sectional view showing a part of the device 1 of FIG. 1 illustrated in more detail. As from the picture of FIG. 2 can be seen, located in the closed state of the device 1 with a closed control valve 8 and inactivated electromagnetic actuator 6 whose armature 7 in its initial position. The closing spring 5 acts on the armature 7 and is supported on the housing 2 from. In this initial position, the axially freely movable armature 7 due to the spring force of the closing spring 5 a distance A to the driver 9 on the valve needle 3, and a distance H to the inner pole 62.

FIG. 3 shows a schematically simplified sectional view of the device 1 of FIG. 1 When opening the valve needle 3. In this case, the magnetic coil 63 of the electromagnetic actuator 6 is energized (which is illustrated by a lightning-shaped symbol), the armature 7 performs a first partial stroke in the direction of the inner pole 62, which corresponds to the degree of the distance A, until he the driver 9 touched. As a result, the control valve 8 opens so that fuel K flows from the fuel inlet 24 into the pressure chamber 4 and via the flow opening 31 into the pressure chamber 12 (as indicated by an arrow B in FIG FIG. 3 is clarified). As a result, the pressure in the pressure chamber 12 rises directly and causes a force on the valve needle 3, which results from the ratio of the hydraulically effective first and second active surfaces 13 and 14 on the valve element 10, which are each subjected to high pressure. This resulting hydraulic force acts in the open control valve 8 in addition to Magnetic force of the armature 7 in the opening direction of the valve needle 3 and reduces the contact pressure of the valve needle 3 on the valve seat 16. The valve needle 3 can now be taken or moved with little force from the armature 3 via the driver 9 in the opening direction, so that the valve needle 3 opens and the injection process can begin.

FIG. 4 shows a schematically simplified sectional view of the device of FIG. 1 with open valve needle. Due to the continued energization of the solenoid 63, the magnet armature 7 was pulled together with the valve needle 3 in the opening direction of the device 1 and has a second partial stroke to stop at the inner pole 62 executed, and thereby raised the valve needle 3 from the valve seat 16 to the outside and opened. The second partial stroke for opening the valve needle 3 is here designed to be larger than the first partial stroke A for opening the control valve 8. The effluent between the valve needle 3 and the valve housing 2 fuel spray is indicated by small arrows C in the FIG. 4 illustrated.

FIG. 5 shows an enlarged schematic sectional view showing a part of the device 1 of FIG. 4 illustrated in more detail. As from the picture of FIG. 5 can be seen with open control valve 8, a portion of the fuel in the pressure chamber 12 via the throttle 21 (as illustrated by an arrow D) in the fuel return 25 as a leakage amount back. This leakage amount through the throttle 21 is defined or limited to a predetermined value, so that the pressure drop in the pressure chamber 12 after switching off the electromagnetic actuator 6 (closing the valve needle 3) does not take too long and extends the dead times of the switching cycles and thus the switching dynamics deteriorated.

In FIG. 6 is a schematically simplified sectional view of the device of FIG. 1 illustrated when closing the valve needle 3. Here, the state of the device 1 is shown, which adjusts after switching off the solenoid 63 of the electromagnetic actuator 6, wherein first the control valve 8 is closed. Thereafter, the pressure in the pressure chamber 12 drops due to the connection to the fuel return 25 via the throttle 21 again, so that the second effective surface 14 is acted upon only with the low pressure from the fuel return 25. The first active surface 13 is still with the high pressure in the interior of the annular cylindrical member 17 acted upon. As a result, a hydraulic closing force is generated which presses the valve needle 3 in addition to the spring force of the closing spring 5 in the valve seat 16 until the closed state of the valve needle 3 (see. FIG. 1 ) is restored and the injection process is completed. The closing spring 5 acts on the magnet armature 7, the annular cylindrical component 17 and the valve element 10 on the valve needle 3.

The fact that the opening and closing of the valve needle 3 of the device 1 according to the invention for high-pressure fuel injection is hydraulically assisted by using the prevailing inside the device 1 high pressure in conjunction with the arranged on the valve element 10 of the control valve 8 first and second active surfaces 13 and 14, the Device 1 already with relatively low magnetic forces provide a high switching dynamics at the same time high sealing force.

The following is with reference to the FIGS. 7 to 10 a device 1 for high-pressure fuel injection according to a second preferred embodiment of the invention described in detail. Identical or functionally identical parts are denoted by the same reference numerals as in the first embodiment.

FIG. 7 shows a schematically simplified sectional view of a second embodiment of the inventive device 1 for high-pressure fuel injection with the valve needle closed 3. The second embodiment of the device 1 according to the invention differs from the first embodiment described above in that in this case between the pressure chamber 12 and the low pressure region 19 of the fuel return 25, a leakage check valve 26 is arranged. By the leakage check valve 26 is a leakage amount to the fuel return 25, as occurs in the first embodiment in the throttle 21, drastically reduced. The leakage check valve 26 has a collar-like extension 22 of the diameter at the end region 29 of the valve needle 3. In conjunction with a arranged at the output of the pressure chamber 12 stop 23 on the valve housing 2, the leakage check valve 26 closes the pressure chamber 12 from the fuel return 25 in the closed state.

How out FIG. 7 Furthermore, it can be seen, when the valve needle 3 is closed, the control valve 8 is closed and the leakage check valve 26 is opened so that a low pressure prevails in the pressure chamber 12.

FIG. 9 shows an enlarged schematic sectional view of a part of the device of FIG. 7 , which illustrates the pressure conditions when the valve needle 3 is closed. How out FIG. 9 can be seen, an annular groove 27 is formed in the valve housing 2 in a region between the annular cylindrical member 17 and the valve element 10 of the control valve 8 to an unimpeded fuel flow into the pressure chamber 12 with open control valve 8 (see FIG. 10 ). When the valve needle 3 is closed, the control valve 8 is closed and the leakage check valve 26 is opened. Here, behind the closed valve element 10 of the control valve 8, ie in the annular groove 27, the pressure chamber 12 and the adjacent fuel return 25 low pressure present (indicated by the reference numeral 19), while in the remaining interiors of the device 1 to the closed valve element 10 high pressure is applied (indicated by reference numeral 28).

How out FIG. 8 can be seen, which is a schematically simplified sectional view of the second embodiment of FIG. 7 when the valve needle 3 is open, in this state, the leakage check valve 26 is closed and the control valve 8 is opened. In this case, high pressure prevails in the pressure chamber 12, so that the valve needle 3 can be opened with small forces. Since the leakage check valve 26 is closed, no amount of leakage into the fuel return 25 occurs. The collar-like extension 22 of the leakage check valve 26 that adjoins the stop 23 at the same time defines a stroke stop of the opened valve needle 3.

FIG. 10 shows an enlarged schematic sectional view of a part of the device of FIG. 8 , which illustrates the pressure conditions when the valve needle 3 is open. How out FIG. 10 can be seen, in this case the control valve 8 is opened and the leakage check valve 26 is closed. The high-pressure region 28 is in this case both in the control valve 8 and in the leakage check valve 26 formed while only in the fuel return 25 of the low pressure region 19 is formed.

Due to the low forces that are required in the inventive device 1 for high-pressure fuel injection for opening and closing the valve needle 3, the actuation of the valve needle 3 can be done directly by a low-cost electromagnetic actuator, even at high injection pressures of 20 MPa, with a sufficiently high switching dynamics , Because of the correspondingly low power requirement of the electromagnetic actuator, the control of the device 1 can therefore be compared with conventional, d. H. available power amplifiers for solenoid high-pressure injection valves. This contributes to a further cost reduction and thus to increased cost-effectiveness of the inventive device 1 for high-pressure fuel injection.

Claims (9)

1. Device for high-pressure fuel injection, comprising

   - a valve housing (2),

   - an outwardly opening valve needle (3) which is arranged in the valve housing (2) in a fuel-filled pressure space (4) to which fuel (K) is supplied under pressure, wherein the valve needle (3) is sealed off at a valve seat (16),

   - a closing spring (5) which returns the valve needle (3) to a starting position,

   - an electromagnetic actuator (6) with a movably arranged magnet armature (7) for actuating the valve needle (3),

   characterized in that a control valve (8) with a valve element (10) and a valve seat (11) is provided, wherein the valve element (10) has a first active surface (13) and a second active surface (14), wherein the first active surface (13) faces the pressure space (4), the second active surface (14) faces a pressure chamber (12) which is connected to a low-pressure region (19), and the valve element (10) enables and closes a connection between the pressure space (4) and the pressure chamber (12), and the valve seat (11) is arranged on the magnet armature (7) or on a component connected to the magnet armature (7), wherein during an activation of the electromagnetic actuator (6) the control valve (8) opens ahead of the outwardly opening valve needle (3) in order to reduce an opening force for the valve needle (3) by enabling the connection between the pressure space (4) and the pressure chamber (12).
2. Device for high-pressure fuel injection according to Claim 1, further comprising a driver (9) which is fastened to the valve needle (3) and has an armature contact region (20), wherein the driver (9) is arranged at a distance (A) from the magnet armature (7) in the starting position, and the magnet armature (7) is movably arranged on the valve needle (3).
3. Device for high-pressure fuel injection according to Claim 1 or 2, characterized in that an annularly cylindrical component (17) is fastened to the magnet armature (7), wherein the valve seat (11) of the control valve (8) is arranged on a free end face of the annularly cylindrical component (17).
4. Device for high-pressure fuel injection according to Claim 3, characterized in that a gap seal (18) is formed between the outer circumference of the annularly cylindrical component (17) and the valve housing (2).
5. Device for high-pressure fuel injection according to Claim 4, characterized in that a diameter (d1) of the gap seal (18) is greater than a diameter (ds) of the valve seat (16).
6. Device for high-pressure fuel injection according to Claims 2 to 5, characterized in that the distance (A) between driver (9) and magnet armature (7) in the starting position is smaller than a difference of a total travel (H) of the magnet armature (7) and the distance (A).
7. Device for high-pressure fuel injection according to one of the preceding claims, characterized in that a throttle (21) is arranged between the pressure chamber (12) and the low-pressure region (19).
8. Device for high-pressure fuel injection according to one of Claims 1 to 6, characterized in that a leakage shut-off valve (26) is arranged between the pressure chamber (12) and the low-pressure region (19).
9. Device for high-pressure fuel injection according to Claim 8, characterized in that the leakage shut-off valve (26) comprises as closing member a collar-like extension (22) formed on the valve needle (3), and a seat (23) of the leakage shut-off valve (26) is formed on the valve housing (2).

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