WO2008049671A1

WO2008049671A1 - Fuel injector

Info

Publication number: WO2008049671A1
Application number: PCT/EP2007/059028
Authority: WO
Inventors: Friedrich Boecking
Original assignee: Robert Bosch Gmbh
Priority date: 2006-10-27
Filing date: 2007-08-30
Publication date: 2008-05-02
Also published as: DE102006050810A1

Abstract

Disclosed is a fuel injector (1) for internal combustion engines, comprising a control chamber (2) which is connected to a high-pressure side (5) and the pressure of which is used for controlling the movement of a nozzle pin (3), and a control valve (6) that blocks or opens the connection of the control chamber (2) to a low-pressure side (7). According to the invention, the control valve (6) is provided with a stationary valve pin (9) which has an internal relief duct (11) that extends from the control chamber (2) to an annular groove (10) of the valve pin (9). The control valve (6) is also provided with a force-balanced control sleeve (12) that is movably guided along the free end of the valve pin (9) and externally seals the annular groove (10) in the closed valve position while opening the connection of the annular groove (10) to the low-pressure side (7) in the open valve position in which the control sleeve (12) is moved in the direction of the free end of the valve pin (9).

Description

fuel injector

State of the art

The invention relates to a fuel injector according to the preamble of patent claim 1.

Disclosure of the invention

The fuel injector according to the invention with its force-balanced control sleeve has, depending on the design, one or more of the following advantages: By using three components (valve pin, control sleeve with armature and valve disc) results in a very simple solution for the control valve; The high pressure in the valve pin (common rail pressure) reduces the guide clearance between the valve pin and the control sleeve and thus the leakage by up to 50-70%. With open control sleeve, so during the

Valve movement, the guide clearance is increased due to the reduced pressure, which provides additional security against friction; Force balanced control valves with a large valve diameter are well damped and have the advantage of making only small valve strokes. If the Absteuererstoß of the control valve is not guided over the armature, this is not excited to vibrate;

With a force-balanced control valve, the dynamics can be improved; By the armature is displaced downwards on the control sleeve and the control sleeve projects into the electromagnet, a particularly compact force-balanced solenoid valve results;

By using a force balanced valve, a very narrow piezoactuator specially grown for stroke can be used. Since hardly any force is required from the piezoactuator, it can be very small in diameter; - To improve the strength of the transverse bores of the valve pin with respect to its longitudinal bore are offset eccentrically and / or arranged in height. The required high-pressure resistance can be achieved with a significantly smaller valve pin diameter, which reduces the guide leakage on the valve pin square.

Further advantages and advantageous embodiments of the subject invention are the description, the drawings and claims removed.

Brief description of the drawings

Embodiments of the fuel injector according to the invention are illustrated in the drawings and explained in more detail in the following description. The figures are partially broken off, schematically and not to scale. Show it: Fig. 1 shows a first embodiment of the fuel injector according to the invention;

2 shows a second embodiment of the fuel injector according to the invention;

3 shows a third embodiment of the fuel injector according to the invention;

4 shows a fourth embodiment of the fuel injector according to the invention;

5 shows a fifth embodiment of the fuel injector according to the invention;

Fig. 6a-6c modifications to the valve pin of the in Figs. 1 to 5 fuel injectors shown;

Fig. 7 shows a further modification to the valve pin of FIGS. 1 to 5 shown

fuel injectors; and

Fig. 8 shows a sixth embodiment of the fuel injector according to the invention.

Embodiments of the invention

The fuel injector 1 shown in Fig. 1 is usually at a

Internal combustion engine with multiple cylinders used, each of which cylinder is associated with such an injector (fuel injection valve). This injector has in a conventional manner a projecting into a cylinder combustion chamber of the internal combustion engine, not shown here injector and the injector depending on the pressure in a control chamber 2 opening and closing, here indicated only to a small extent nozzle needle 3. The control chamber 2 is connected via an inlet throttle (Z-throttle) 4 permanently to a high-pressure inlet line (high pressure side) 5 of the fuel. For controlling the injection process, a control valve 6 in the form of a 2/2-way valve is provided, that the connection of the control chamber 2 with a low pressure chamber (low pressure side) 7, which is connected to a drain 7a, opens or blocks. The high-pressure feed line 5 may be connected to a high-pressure accumulator (common rail), not shown, and the low-pressure drain line 7 with leak oil. The nozzle needle 3 is guided to form the control chamber 2 in a valve piece 8, in which the Z-throttle 4 is provided.

The control valve 6 has a fixed valve pin 9 with a coming from the control chamber 2 and opening into an annular groove 10 of the valve pin 9 inner discharge channel 11 and surrounded by the low-pressure chamber 7

Control sleeve 12 which is slidably guided on the projecting into the low-pressure chamber 7 free end of the valve pin 9 between two valve positions. The control sleeve 12 closes in one closed valve position shown in Figure 1, the annular groove 10 to the outside and opens in the other, open valve position, the compound of the annular groove 10 to the low pressure side 7. The discharge channel 11 is connected to the control chamber 2 via a valve in the piece. 8 provided outlet throttle (A-throttle) 13 connected and formed in the valve pin 9 by a longitudinal bore 14 and thereof to the annular groove 10 outgoing transverse bores 15. The transverse bores 15 of the valve pin 9 go centric and not offset in height from the longitudinal bore 14 from. The control sleeve 12 is biased by a housing side supported closing spring 16 in its closed valve position and by means of a magnetic coil 17 whose magnetic field acts on a disc-shaped armature 18 of the control sleeve 12, slidable into its open valve position. The armature 18 is provided at the upper end of the control sleeve 12. The valve piece 8 and a valve disc 19 are braced in a bore of an injector body 20 by means of a valve clamping screw 21, whereby the guided in the valve disc 19 valve pin 9, which has an overlapped by the valve disc 19 annular shoulder 22 at the lower end, clamped to the injector body 20 is. The magnetic coil 17 with its magnetic core 23 are arranged in the interior of a magnetic sleeve 24, which is fastened by means of a magnetic clamping nut 25 on the injector 20.

In its closed valve position shown in FIG. 1, the control sleeve 12 bears against a conical valve seat 26 of the valve pin 9. The diameter d of the Valve seat 26 is equal to the guide diameter D of the free end of the valve pin 9, whereby the control sleeve 12 is force-balanced. In this closed valve position, the connection of the control chamber 2 to the low pressure side 7 is closed by the annular groove 10 occluding control sleeve 12 and therefore the nozzle needle 3 closed by the pressure prevailing in the control chamber 2 high pressure. If the magnetic coil 17 is energized, the control sleeve 12 is pulled from the valve seat 26 in the direction of the free end of the valve pin 9 in its open valve position, whereby the pressure in the control chamber 2 is reduced and the nozzle needle 3 opens. Since the control sleeve 12 is force balanced, only small forces are needed to open the control sleeve 12. The control sleeve 12 makes only a very small opening stroke of about 18-25 microns. When the control sleeve 12 is open, the A-throttle 13 limits the flow. If the energization of the solenoid 17 is released, the control sleeve 12 is moved back into its closed valve position via the closing spring 16 and the control chamber 2 is filled again via the Z-throttle 4.

Since the precision of the sealing seat in the valve pin 9 and in the control sleeve 12, both of which are very compact, the valve disc 19 with respect to the valve pin 9 have a fairly large guide clearance 27, if at the annular shoulder 22 cross-edge of the valve disc 19 is sealed exactly ,

The prevailing in the longitudinal bore 14 high pressure causes a widening of the valve pin 9, resulting in a reduction of the guide clearance between the valve pin 9 and control sleeve 12 and a reduced by about 50-70% leakage. For this purpose, the length of the longitudinal bore 14 should make up at least 1/2 to 2/3 of the guide length of the valve pin 9, so that a hydrostatic / dynamic bearing is formed in the region of the guide. With open valve sleeve 12, the pressure in the longitudinal bore 14 is reduced, and therefore the guide clearance is increased during valve movement, which provides additional security against friction.

In the further embodiments of fuel injectors described below, all those elements which are identical to the first embodiment shown in FIG. 1 are provided with the same reference numerals that with respect to the description thereof, reference is made in full to the comments on the first embodiment.

From the injector of Fig. 1, the fuel injector 1 shown in Fig. 2 differs in that here the valve pin 9 in the bore of the injector body 20 between the valve piece 8 and the valve clamping screw 21, the ring shoulder 22 of the valve pin 9 directly, i. without additional valve disc, engages over, is clamped, that the valve pin 9 has a flat valve seat 26 for the force-balanced control sleeve 12 and that the control sleeve 12 has a sealing surface surrounding its annular pressure chamber 28 which is limited by the valve pin 9 inwardly when the control sleeve is closed , Via longitudinal bores 29, the pressure chamber 28 is connected to the low-pressure side 7 above the armature disk 18. The pressure surge occurring during opening of the control sleeve 12 (Absteuerstoß) is not dissipated via the armature disc 18, but via the pressure chamber 28 and the longitudinal bores 29, whereby the control sleeve 12 is not excited to vibrate.

From the injector of Fig. 1, the fuel injector 1 shown in Fig. 3 differs in that here the valve seat 26 is formed flat for the force-balanced control sleeve 12 and not on the valve pin 9, but on the Ventilscheibe19 is provided. Compared to Fig. 1, this valve seat 26 means a very simple solution when the valve disc 19 is clean plan and has a good angularity to the valve pin 9.

From the injector of Fig. 3, the fuel injector 1 shown in Fig. 4 differs in that here the armature disc 18 is not provided at the upper end of the force-balanced control sleeve 12, but in the region of the lower half sleeve and that the valve pin 9 and the control sleeve 12 in the magnet coil 17 or protrude into the magnetic core 23. The control sleeve 12 has at its protruding end on the outside longitudinal slots 30 through which the low-pressure chamber 7 is connected to the drain 7a. This offset anchor plate 18 results in a compact balanced solenoid valve. In the case of the fuel injector 1 shown in FIG. 5, the valve pin 9 is formed integrally with the valve piece 8, which is clamped to the injector body 20 via the valve clamping screw 21. The valve seat 26 for the force-balanced control sleeve 12 is formed flat and provided on the valve piece 8. The control sleeve 12 is opened via a hydraulic translator 31, which in turn is controlled inversely by a piezo actuator 32. The hydraulic booster 31 comprises two pistons 34, 35 which are coupled to one another by a fuel-filled booster chamber 33, wherein the piezoactuator 32 acts on the upper piston 34 and the lower piston 35 is integrally connected to the control sleeve 12. In the closed valve position shown, the piezo-actuator 32 is energized and thus extended, whereby the upper piston 34 is displaced against the action of a Bourdon tube 36 down into the booster chamber 33 and thus also the lower piston 35 and the control sleeve 12 down in the closed valve position are shifted. If the energization is canceled, the piezo actuator 32 is shortened, whereby the upper piston 34 is pushed over the tube spring 36 upwards and thus the lower piston 35 and the control sleeve 12 are moved upwards in the open valve position. Since hardly force is required from the piezo actuator 32, it can be made very small in diameter.

FIGS. FIGS. 6a to 6c show cross sections of modified valve bolts 9, in which one or more transverse bores 15 each depart eccentrically from the longitudinal bore 14. Preferably, the diameter of the longitudinal bore 14 is at least twice as large as the diameter of the transverse bore 15. The two transverse bores 15 shown in FIG. 6a are eccentric and opposed to each other from the longitudinal bore 14. The two transverse bores 15 shown in FIG. 6b descend from the longitudinal bore 14 eccentrically and at an angle of 90 °, wherein an angle greater than 90 ° can also be selected. In Fig. 6c, only a single transverse bore 15 is provided which goes off eccentrically from the longitudinal bore 14. Fig. 7 shows a modified valve pin 9, in which the two transverse bores 15 are offset in height by .DELTA.L. The transverse bores 15 can be centered from the longitudinal bore 14 or analogous to FIGS. 6a to 6c each off eccentrically. By this eccentric and / or offset in height arrangement of the transverse bores 15, the high pressure resistance of the valve pin 9 optimized and thus a significantly smaller valve pin diameter can be achieved, which reduces the guide leakage on the valve pin 9 square.

In the case of the fuel injector 1 shown in FIG. 8, the valve pin 9 is mounted on both sides, namely at the bottom in a bore of the valve piece 8 and at the top in one

Hole of the magnet sleeve 24. In the bore of the valve member 8, a plate spring 37 is arranged, through which the valve pin 9 between the valve member 8 and control sleeve 24 is clamped immovably. If the solenoid 17 is energized, the control sleeve 12 is pulled by the valve seat 26 in the direction of the solenoid 17, whereby the pressure in the control chamber 2 is reduced and the nozzle needle 3 opens. Since the control sleeve 12 is force balanced, only small forces are needed to open the control sleeve 12. When the control sleeve 12 is open, the A-throttle 13 limits the flow. If the energization of the solenoid 17 is released, the control sleeve 12 is moved back into its closed valve position via the closing spring 16 and the control chamber 2 is filled again via the Z-throttle 4.

Claims

claims

1 . Fuel injector (1) for internal combustion engines, with a control chamber (2) connected to a high-pressure side (5), via the pressure of which the movement of a nozzle needle (3) is controlled, and with a control valve

(6), which either the connection of the control chamber (2) to a low pressure side (7) either locks or opens, characterized in that the control valve (6) has a fixed valve pin (9), one from the control chamber (2) coming and in a Ring groove (10) of the valve pin

(9) has an opening inner relief channel (1 1), and on the free end of the valve pin (9) slidably guided, force-balanced control sleeve (12) which closes in its closed valve position, the annular groove (10) to the outside and in their in Direction to the free end of the valve pin (9) shifted open valve position the

Connection of the annular groove (10) to the low pressure side (7) opens.

2. Fuel injector according to claim 1, characterized in that the valve pin (9) in an injector body (20) by means of a valve clamping screw (21) is clamped, either an annular shoulder (22) of the valve pin

(9) overlaps or acts on a ring shoulder (22) of the valve pin (9) cross-valve disc (19).

3. Fuel injector according to claim 1 or 2, characterized in that the valve pin (9) or the valve disc (19) has a conical or a flat valve seat (26) on which the control sleeve (12) rests in its closed valve position.

4. Fuel injector according to claim 3, characterized in that the

Diameter (d) of the valve seat (26) is equal to the guide diameter (D) of the free end of the valve pin (9).

5. Fuel injector according to one of the preceding claims, characterized in that the discharge channel (11) from the control chamber (2) coming longitudinal bore (14) which is at least 1/2 to 2/3 as long as the guide length of the valve pin (9 ) for the control sleeve (12).

6. Fuel injector according to one of the preceding claims, characterized in that the control sleeve (12) by means of an armature (18) in the magnetic field of a magnetic coil (17) is displaceable and has a sealing surface surrounding its annular pressure chamber (28) via bores (29 ) is connected to the low-pressure side (7) above the armature (18) and is limited inwardly when the control sleeve (12) is closed by the valve pin (9).

7. Fuel injector according to one of the preceding claims, characterized in that the control sleeve (12) by means of an armature (18) in the magnetic field of a magnetic coil (17) is displaceable and that the armature (18) in the region of the lower half of the control sleeve (12) is provided and the valve pin (9) and the control sleeve (12) protrude into the magnetic coil (17).

8. Fuel injector according to one of claims 1 to 5, characterized in that the control sleeve (12) by means of a piezoelectric actuator (32) and a hydraulic translator (31) is displaceable.

9. Fuel injector according to one of the preceding claims, characterized in that the discharge channel (11) from the control chamber (2) coming longitudinal bore (14) and one or more in the annular groove (10) of the

Valve pin (9) has opening transverse bores (15) which each eccentrically depart from the longitudinal bore (14).

10. Fuel injector according to claim 9, characterized in that two transverse bores (15) with respect to the longitudinal bore (14) face each other or enclose an angle between 90 ° and 180 °.

11. Fuel injector according to one of the preceding claims, characterized in that the discharge channel (11) from the control chamber (2) coming longitudinal bore (14) and one or more in the annular groove (10) of the valve pin (9) opening transverse bores (15) , which are offset in height to each other.