EP1507972B1 - Fuel injection valve for internal combustion engines - Google Patents

Description

State of the art

The invention is based on fuel injection valves, the have two nested valve needles and otherwise the genus of claim 1 correspond. Such fuel injection valves are for example from the published patent application DE 41 15 477 Al known. The two valve pins control the opening with its combustion chamber end each of at least one injection port and let to control itself so that either only the outer valve needle opens up a part of the injection openings, or both Open valve pins and open all injection openings. In this way, the injection cross section can be set optimally depending on the load of the internal combustion engine. The longitudinal movement of the valve pins in the bore is done by the ratio of acting on the valve needles Opening force and one opposite each Closing force. The opening force results from the hydraulic Pressure on corresponding pressure surfaces on the valve pins, while the closing force in the known fuel injection valves either by springs or likewise generated by hydraulic forces. The known fuel injection valve has the disadvantage that not the opening of both needles in time and duration can be controlled arbitrarily. The outer valve needle opens under pressure control against the force of a recoil spring while the inner valve needle - in addition to the closing force of a Closing spring - a force due to the hydraulic pressure in experiences a control room. By a solenoid valve can be However, so only control whether the inner valve needle at a Injection cycle opens or not. The outer valve needle can not through the solenoid valve in its opening behavior to be influenced. This sets the control of the exact Injection timing and the exact injection amount one Border, which of course also the further optimization of the Combustion difficult.

Advantages of the invention

The fuel injection valve according to the invention with the characterizing Features of claim 1, in contrast the advantage of having a single control valve Opening time and opening duration of both the outer and also the inner valve needle is controllable. For this purpose, the arranged in the housing of the fuel injection valve control valve a valve space in which a valve member is arranged is. The valve member is between two end positions movable, wherein the valve member in the first end position causes both the control room, as well as the control pressure chamber filled with fuel under high pressure, so that both the outer valve needle and the inner valve needle remain in their closed position. Moves the valve member fast in its second end position, so only the control chamber is relieved of pressure in the leakage oil chamber while the Control pressure chamber practically maintains its pressure. hereby only opens the outer valve needle, while the inner valve needle remains in its closed position. Both should Valve needles, so both the inner and the outer Valve needle are turned on, so the valve member moves slightly slower from its first to the second end position, which now also reduces the pressure in the control pressure chamber so far that in addition to the outer valve needle and the inner Valve needle opens. About the switching time of the control valve So it can be adjusted whether the entire injection cross section or only a part of the injection cross section opened becomes. It is a control of the coaxial Vario nozzle possible by means of only a single control valve.

In an advantageous embodiment of the subject of the Invention, the valve member is moved by an actuator, the is preferably electrically operated. Especially advantageous is the training of the actuator as a piezo actuator, since this the Virtue, with almost any speed to be switchable. The valve member moved by the actuator can be so with different speed of the drive first end position in the second end position, wherein itself by the switching speed of the injection cross section can be set.

Further advantages and advantageous embodiments of the subject The invention are the description and the Drawing removable.

drawing

Figur 1

einen Längsschnitt durch ein erfindungsgemäßes Kraftstoffeinspritzventil,

Figur 2

eine Vergrößerung des mit II bezeichneten Ausschnitts von Figur 1,

Figur 3

eine Vergrößerung von Figur 1 im mit III bezeichneten Ausschnitt,

Figur 4

den Zeitverlauf von Druck, Nadelhub und Ventilgliedhub beim Aufsteuern nur der äußeren Ventilnadel und

Figur 5

den zeitlichen Verlauf von Ventilgliedhub, Druck und Nadelhub beim Aufsteuern beider Ventilnadeln.

In the drawing, an embodiment of the fuel injection valve according to the invention is shown. It shows

FIG. 1

a longitudinal section through a fuel injection valve according to the invention,

FIG. 2

an enlargement of the section of FIG. 1 denoted by II,

FIG. 3

an enlargement of FIG. 1 in the detail marked III,

FIG. 4

the time course of pressure, needle lift and Ventilgliedhub when controlling only the outer valve needle and

FIG. 5

the time course of Ventilgliedhub, pressure and needle stroke when controlling both valve pins.

Description of the embodiment

In Figure 1 is a longitudinal section through an inventive Fuel injection valve shown. The fuel injector has a housing 1, which has a holding body 14, a control body 12, an intermediate disc 9, a Intermediate body 7 and a valve body 3 comprises, in abut each other in this order. The individual components of the housing 1 are by a clamping nut 5 against each other pressed and fixed in their position to each other. in the Valve body 3 is formed a bore 16 in which a outer valve needle 20 is arranged longitudinally displaceable. The outer valve needle 20 is in a combustion chamber facing away portion guided in the bore 16 and tapers the Combustion chamber to form a pressure shoulder 27. The outer Valve needle 20 extends to one on the combustion chamber side End of the bore 16 formed seat surface 24, in which a plurality of injection openings 30 are formed, the the seat 24 with the combustion chamber of the internal combustion engine connect. Between the outer valve needle 20 and the wall the bore 16 is an annular channel 28 is formed, of the Seat 24 extends to the height of the pressure shoulder 27. On Height of the pressure shoulder 27, the annular channel 28 widens a pressure chamber 26, in the one in the valve body 3, the intermediate body 7, the washer 9, the control body 12th and the valve holding body 14 extending inlet channel 10th empties. In the pressure chamber 26 and thus also in the annular channel 26 can fuel via the inlet channel 10 under high pressure be introduced. The outer valve needle 20 has a Longitudinal bore 21, in which an inner valve needle 22nd is arranged longitudinally displaceable. To clarify the Control of the injection openings 30 through the valve pins 20, 22, Figure 2 shows the designated II section of Figure 1 enlarged. The seat surface 24 is conical and the injection ports 30 are grouped in two Injection opening rows, namely in an outer row of injection openings 130 and in an inner injection port row 230. The outer valve needle 20 has at its combustion chamber side End of a conical outer valve sealing surface 32, so a sealing edge 34 is formed, with which the outer Valve needle 20 in its closed position on the seat surface 24th comes to the plant. The outer injection port row 130, the consists of at least two injection ports 30, with respect to the longitudinal axis of the bore 16 in a radial plane lie, downstream of this sealing edge 34 are arranged. The inner valve needle 22 has at its combustion chamber side End an inner valve sealing surface 36 and a conical surface 38, wherein at the transition, a sealing edge 37 is formed is, with the inner valve needle 22 on the seat 24 abuts in its Schrießstellung. The inner injection port series 230, which also consists of at least two injection ports exists in a common radial plane are arranged to the longitudinal axis of the bore 16, open downstream of the sealing edge 37 of the inner valve needle 22 in the seat 24.

The interaction of the two valve pins 20, 22 for control the injection openings 30 is as follows: Should only by the outer injection port row 130 fuel in the Combustion chamber of the internal combustion engine are injected, which is particularly advantageous if the internal combustion engine to be operated in a partial load range, so raises for injection only the outer valve needle 20 of the Seat 24 from. This can cause fuel in the annular channel 28 is under high pressure, between the outer valve sealing surface 32 and the seat surface 24 to the outer injection opening row 130 flow and from there into the combustion chamber the internal combustion engine injected. The inner valve needle 22 remains in its closed position, i. in Appendix on the seat 24, so that the inner row of injection openings 230 remains closed. Target through all injection openings Be injected, so also raises the inner Valve needle 22 from the seat 24 from, which also the inner injection port row 230 is released.

For controlling the two valve needles 20, 22 serve the devices, in the intermediate body 7, the intermediate disc 9, the control body 12 and also arranged in the valve holding body 14 are. This designated in Figure 1 with III section is shown in more detail in FIG. In the intermediate body 7 is coaxial with the bore 16, a piston bore 45 is formed, the diameter in the formation of a contact surface 41st is designed graduated. In the receiving bore 35 is a outer pressure piston 40 disposed on the outer valve needle 20 rests and synchronously with this in the longitudinal direction can move. On the outside of the outer pressure piston 40, an annular surface 39 is arranged between the and the contact surface 41 a closing spring 44 under compressive bias is arranged, which formed as a helical compression spring is and surrounds the outer pressure piston 40. By the End face 51 of the outer pressure piston 40, the intermediate disc 9 and the wall of the piston bore 45 becomes a control room 50 limits, via an inlet throttle 70 with the inlet channel 10 connected here as a high pressure room serves, in which always fuel under high pressure. In addition to the force of the closing spring 44 thus acts on the outer Pressure piston 40 and thus on the outer valve needle 20th the hydraulic force on the end face 51 through the Pressure in the control chamber 50 results is applied.

The outer pressure piston 40 has a guide bore 47, in which an inner pressure piston 42 is arranged longitudinally displaceable is. The inner pressure piston 42 is located on the inner valve needle 22 and always moves in sync with this. Through the guide bore 47 and the end face 53 of the inner Pressure piston 42 is a control pressure chamber 52 limited by the pressure of a hydraulic Kraftrauf the Pressure piston 42 and thus also on the inner valve needle 22nd in the direction of the seat 24 results.

In the valve holding body 14, a receiving body 13 is arranged, in which an actuator 46 and an associated with this Pressure piece 48 is located. By the actuator 46, preferably is designed as a piezo actuator, the pressure piece 48 in the longitudinal direction or in the direction of Force of a spring 49 moves between the pressure piece 48th and the receiving body 13 is arranged. The pressure piece 48 is connected to a valve member 60 which is in a valve chamber 68 is arranged, which formed in the control body 12 is and together with a first valve seat 62 and a this opposite second valve seat 64 a Control valve 58 forms. The valve member 60 is substantially formed as a hemisphere, the hemispherical Valve sealing surface 66 cooperates with the first valve seat 62, while the flat side of the valve member 60 with the second valve seat 64 cooperates, which formed as a flat seat is. The valve space 68 has a connection 59 a leakage oil space 78 formed in the valve holding body 14 on, wherein the connection 59 through the valve member 60 through its interaction with the first valve seat 62 is opened and can be closed. In addition, the valve chamber points 68, an outlet throttle 72, the valve space 68th connects to the control room 50. The outlet throttle 72 remains always open, regardless of the position of the valve member 60. By the interaction of the valve member 60 with the second valve seat 64 is controlled a connection channel 74, the connection between the valve chamber 68 and forms the control pressure chamber 52. The connection channel 74 This extends into the intermediate body 7 and opens laterally in the piston bore 45. The connection to the control pressure chamber 52 is via a transverse bore 55 in the outer pressure piston 40 produced. This connection of the control pressure chamber 52 to the connection channel 74 remains at each position of the outer Pressure piston 40 received. In the connection channel 74 is a throttle point 76 is provided which the possible fuel flow can limit through the connecting channel 74 and which can be omitted if necessary.

The operation of the control valve 58 is as follows. At the beginning of the injection cycle, the valve member 60 is in contact with the first valve seat 62, so that the connection 59 of the valve chamber 68 is closed to the leakage oil chamber 78. The connecting channel 74 and the outlet throttle 72 are opened, so that the control pressure chamber 52 and the control chamber 50 are hydraulically connected to the valve chamber 68. By the inlet throttle 70 prevails in the control chamber 50 of the injection pressure P ₀ , which also prevails in the high-pressure passage 10. Of course, the same pressure P ₀ is also present in the control pressure chamber 52 due to the open connections. If fuel is to be injected only through the outer row of injection openings 130, the actuator 46 via the pressure member 48, the valve member 60 very quickly from the first valve seat 62 in abutment against the second valve seat 64. Thus, the connection of the valve chamber 68 is opened to the leakage oil chamber 78 and the Connecting channel 74 closed. Since this switching process happens very quickly, the pressure in the control pressure chamber 52 drops only insignificantly. Due to the now existing connection of the valve chamber 68 to the leakage oil chamber 78, in which there is always a very low fuel pressure, the pressure in the pressure chamber 50 decreases, since the inlet throttle 70 and the outlet throttle 72 are coordinated so that more fuel from the. Through the outlet throttle 72 Control chamber 50 drains as can flow on the inlet throttle 70 from the high-pressure passage 10. As a result, the hydraulic force on the end face 51 of the outer pressure piston 40 is lowered, so that acting on the pressure shoulder 27 hydraulic forces in the pressure chamber 26, the outer valve needle 20 lifts from the seat surface 24, so that the outer injection opening row 130 is released. The movement of the outer valve needle 20 and the outer valve piston 40 is continued until the end face 51 of the outer valve piston 40 comes to rest on the washer 9. Although the volume of the control pressure chamber 52 increases slightly due to the movement of the outer valve piston with respect to the inner valve piston 42, which remains stationary, the pressure in the control pressure chamber does not substantially decrease due to the large volume of control pressure chamber 52 and connection channel 74.

The time course of the valve member path V, the pressure p in the control pressure chamber 52 and the stroke h of the outer valve needle 20 and the inner valve needle 22 is shown in Figure 4. The upper diagram of Figure 4 shows the movement of the valve member 60, which begins at a time t ₀ and which comes at time t ₁ at the second valve seat 64 for conditioning. The middle graph shows the pressure p in the control pressure chamber 52 again, and there is a pressure drop from the injection pressure p ₀ to a pressure level that is above the pressure p ₁ , wherein the pressure p ₁ denotes the pressure at which the inner valve needle 22nd driven by the hydraulic force on the inner valve sealing surface 36 lifts off from the seat surface 24. The outer valve needle 20, the stroke h is shown in the lower diagram of Figure 4, begins their movement shortly after the time t ₀ and continues the movement until it has reached its maximum stroke. At time t ₂ , the control valve 58 switches again and the valve member 60 reaches its original position at the first valve seat 62 at time t _3. The control chamber 50 fills via the inlet throttle 70 with the injection pressure of the high-pressure passage 10 and via the connecting channel 74 also builds up in the Control pressure chamber 52 back to the pressure p ₀ . Due to the increasing pressure in the control chamber 50, the outer valve needle 20 is pushed back into its closed position.

To be injected through all the injection ports 30, the control valve 58 switches more slowly than in the just described injection through the outer injection opening 130. The relatively slow movement of the valve member 60 remains for a certain time when the valve member 60 between the first valve seat 62 and the second valve seat 64 is open, both the connecting channel 74 and the connection to the leakage oil chamber 78, so that the pressure in the control pressure chamber 52 below the opening pressure of the inner valve needle 22, the pressure p ₁ , drops. Thereby moves in the manner described above, the outer pressure piston 40 and also the inner pressure piston 42, so that both the outer valve needle 20 and the inner valve needle 22 lift off from the seat surface 24 and release all the injection ports 30. In FIG. 5, the time course of the governing quantities is shown in the same manner as in FIG. The upper diagram of FIG. 5 shows the slower course of the movement of the valve member 60, wherein the movement back to the starting position on the first valve seat 62 can take place at the same speed as in the partial load injection. The pressure curve of the pressure p in the control pressure chamber 52 shows a drop in pressure below the pressure p ₁ , so that the inner valve needle 22 begins its stroke movement at the time t ₁ . This is shown in the lower diagram of Figure 5 by the dashed line. The closing of the fuel injection valve is analogous to the partial load range by the reconstruction of the pressure in the control chamber 50 and the control pressure chamber 52nd

As actuator 46 is preferably a piezoelectric actuator, the performs a stroke depending on the applied voltage. With a simple voltage regulation it is almost possible each time course in the movement of the valve member 60th realize. In addition to a piezo actuator also other actuators come for example, fast-switching magnetic actuators, their switching speed depends on the magnetic field strength can be controlled.

Claims (7)

1. Fuel injection valve for internal combustion engines having a housing (1), in which a longitudinally displaceable outer valve needle (20) and an inner valve needle (22) which can be longitudinally displaced in the latter are arranged in a bore (16), which needles each control at least one injection opening (30) with their combustion space end, and having a control space (50) which is connected via an inflow throttle (70) to a high-pressure space (10) and by means of whose pressure a closing force is exerted at least indirectly on the outer valve needle (20), and having a control-pressure space (52) by means of whose pressure a closing force is exerted at least indirectly on the inner valve needle (22), and having a leakage oil space (78) in which there always prevails a low fuel pressure, characterized in that a control valve (58) which has a valve space (68) and a valve member (60) arranged therein is arranged in the housing (1), the valve space (68) having a connection (59) to the leakage oil space (78), a continuously open connection (72) to the control space (50) and a connection (74) to the control-pressure space (52), the valve member (60) being able to move in the valve space (68) between two end positions and, in the first end position, closing the connection (59) to the leakage oil space (78) and opening the connection (74) to the control-pressure space (52) and, in the second end position, closing the connection (74) to the control-pressure space (52) and opening the connection (59) to the leakage oil space (78).
2. Fuel injection valve according to Claim 1, characterized in that less fuel flows into the control space (50) via the inflow throttle (70) than flows out of the control space (50) into the leakage oil space (78) via an outflow throttle (72) for a corresponding position of the control valve (58).
3. Fuel injection valve according to Claim 1, characterized in that the valve member (60) is moved by an actuator (46).
4. Fuel injection valve according to Claim 3, characterized in that the actuator (46) can move the valve member (60) at different speeds from the first end position into the second end position.
5. Fuel injection valve according to Claim 3 or 4, characterized in that the actuator (46) is a piezo actuator.
6. Fuel injection valve according to Claim 1, characterized in that all the connections (59; 74; 72) to the valve space (68) are open when the valve member (60) is situated between the first end position and the second end position.
7. Fuel injection valve according to Claim 1, characterized in that the valve member (60) can be moved from the first end position into the second end position at such a speed that the pressure in the control-pressure space (52) decreases only insignificantly in the process.

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