WO2008061842A1

WO2008061842A1 - Fuel injector

Info

Publication number: WO2008061842A1
Application number: PCT/EP2007/060741
Authority: WO
Inventors: Friedrich Boecking
Original assignee: Robert Bosch Gmbh
Priority date: 2006-11-24
Filing date: 2007-10-10
Publication date: 2008-05-29
Also published as: DE102006055487A1

Abstract

The invention relates to a fuel injector (1) for an internal combustion engine having a control chamber (2) connected to a high-pressure side (5). The pressure of the control chamber controls the movement of an injector needle (3). The invention further comprises a control valve (6), which either closes or opens the connection of the control chamber (2) toward a low-pressure side (7). According to the invention, the control valve (6) comprises a force-equilibrating control piston (10), which is displaceably guided in a bore (9a) of a guiding piece (9) between two valve positions. Said control piston closes the connection of a connecting channel (13) coming from the control chamber (2) and ending in the bore (9a) toward the low-pressure side (7) in the closed valve position and releases it in the open valve position, which is displaced in the direction of the injector needle (3).

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: With a force balanced control valve, the dynamics can be improved.

Very compact solution with a force balanced solenoid valve. The concept is suitable for inline use. - By using a compact balanced valve, where the leakage passes through the spool and not over the armature, a nearly vibration free high dynamic valve can be built. A valve seat designed as a flat seat enables a compact valve design that allows very small valve strokes via the flat seat with extremely steep flow behavior, which can considerably increase the dynamics of the valve.

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. - Simplest solution for a piezo inline concept with force balanced

Control valve that opens to the outside in the direction of movement of the piezoelectric actuator. An outward-opening, force-balanced control valve with integrated hydraulic translator that simultaneously reverses the direction of movement, provides a compact solution that allows a very small, narrow piezoelectric actuator.

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

Brief description of the drawings

Various 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:

FIGS. 1 to 6 six different embodiments of the invention

Fuel injector. 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). The injector has in a known 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, which is the connection of the control chamber 2 with a low-pressure chamber

(Low pressure side) 7 opens or locks. The high-pressure feed line 5 is connected to a high-pressure accumulator, not shown (common rail), and the low-pressure chamber 7 is connected to a drain 7a. 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 guide piece 9 with a through-bore 9a and a control piston 10 displaceably guided therein between two valve positions, the upper end of the piston protruding into the low-pressure space 7 in FIG. The valve and guide pieces 8, 9 are arranged in a bore of an injector body 11, wherein the valve member 8 is clamped in the Injektorbohrung by the guide piece 9 screwed therein. The through-hole 9a is closed at the bottom by the valve piece 8. In the valve and guide pieces 8, 9 extending from the control chamber 2 connecting channel 13 which opens into the bore 9a of the guide piece 9, more precisely in an annular groove 14 of the control piston 10, and an outlet throttle (A-throttle) 15 has. In the bore 9a of the guide piece 9, a conical valve seat 16 connects at the bottom of the annular groove 14. The control piston 10 has at its thickened lower end a conical sealing surface which cooperates with the conical valve seat 16. Over a Longitudinal bore (hollow bore) 17 in the control piston 10, the valve seat 16 is connected to the low-pressure chamber 7 above the control piston 10. The control piston 10 is biased by a closing spring 18 supported on the housing side into its closed valve position shown in FIG. 1 and displaceable into its open valve position by means of a magnetic coil 19 whose magnetic field acts on a disk-shaped armature 20 of the control piston 10. The armature 20 is provided at the upper end of the control piston 10. Since the control valve 6 is an outwardly opening valve (A-valve), the magnetic coil 19 is located below the armature 20. The magnetic coil 19 with its magnetic core 21 is arranged inside a magnet sleeve 22 which is fastened to the injector body 11 by means of a magnetic clamping nut 23 ,

The diameter d of the valve seat 16 is equal to the guide diameter D of the guide piece 9, whereby the control piston 10 is force-balanced in its closed valve position shown in Fig. 1 with respect to the pressure prevailing in the annular groove 14 high pressure. In this closed valve position, the connection of the control chamber 2 to the low pressure side 7 is blocked by the control piston 10 and therefore the nozzle needle 3 is closed by the pressure prevailing in the control chamber 2 high pressure. If the solenoid coil 19 is energized, the control piston 10 is pulled from the valve seat 16 in the direction of the nozzle needle 3, that is down, into its open valve position, whereby the pressure in the control chamber 2 is reduced and the nozzle needle 3 opens. The pressure surge occurring during opening of the control piston 10 (Absteuerstoß) is not dissipated via the armature 20, but via the longitudinal bore 17, whereby the control piston 10 is not excited to vibrate. The path of the reduced fuel quantity from the valve seat 16 to the drain 7a is marked with flow arrow 24. Since the control piston 10 is force-balanced, only small forces are required to open the control piston 10. The control piston 10 makes only a very small opening stroke of about 20-30 microns. When the control piston 10 is open, the A-throttle 15 limits the flow. If the energization of the solenoid 19 is released, the control piston 10 is moved back into its closed valve position via the closing spring 18 and the control chamber 2 is filled again via the Z-throttle 4. Via leakage oil bores 25 in the injector body 11 and in the valve and guide pieces 8, 9, the remaining leakage of the injector 1 can also be removed via the control valve 6. The force-balanced control piston 10 and the leakage guide through the Control piston 10 enable an almost vibration-free, highly dynamic control valve. 6

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, so that with regard to their description, 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 armature 20 is disposed at the lower end of the control piston 10 and the valve seat 16 is formed as a flat seat. At the valve seat 16 of the guide piece 9, the low pressure side is followed by a longitudinal bore 26 in the guide piece 9, which opens into the low-pressure chamber 7. The occurring during opening of the control piston 10 pressure surge (Absteuerstoß) is not over the

Anchor 20 and the longitudinal bore 17, but discharged directly over the longitudinal bore 26 of the guide piece 9, whereby the control piston 10 is not excited to vibrate. Furthermore, the valve and guide pieces 8, 9 clamped by a valve clamping screw 12 in the bore of the injector body 11. This injector 1 is a very compact solution with a force-balanced control valve 6, wherein the combination of a flat seat 16 with a force-balanced control piston 10 allows a very high dynamics.

From the injector of Fig. 1, the fuel injector 1 shown in Fig. 3 differs in that here the annular groove 14 is formed in the guide piece 9 and the valve seat 16 connects upwards, ie in the closing direction of the control piston 10, to the annular groove 14. The seat opening of the valve seat 16 is connected to the low pressure chamber 7 via an annular gap 31 located between the control piston 10 and the magnetic core 21. The closing spring 18 is arranged between the valve piece 8 and control piston 10 in a spring chamber 32, which is connected via longitudinal and transverse bores 17, 33 with the low pressure chamber 7 and with the annular gap 31. The connection of the annular groove 14 to the annular gap 31, so the connection of the control chamber 2 to the low-pressure chamber 7 is locked in the closed valve position and released in the open valve position. From the injector of Fig. 1, the fuel injector 1 shown in Fig. 4 differs in that here the control piston 10 via a hydraulic booster 40, which in turn is controlled by a schematically indicated here only as an arrow piezoelectric actuator 41, is opened. The hydraulic booster 40 includes two pistons 43, 44 which are coupled in a synchronized motion with each other through an intermediate fuel-filled booster chamber 42. The piezoactuator 41 acts on the upper piston 43, and the lower piston 44 is formed integrally with the control piston 10. In the closed valve position shown, the piezoelectric actuator 41 is not energized and thus shortened, whereby the upper piston 43 is displaced upwards and thus the lower piston 44 and the control piston 10 are displaced upwards into the closed valve position. If the piezoelectric actuator 41 is energized, it is extended against the action of a tubular spring 45, whereby the upper piston 43 is pushed down and thus the lower piston 44 and the control piston 10 are also moved down into the open valve position. If the piezoelectric actuator 41 is no longer energized, the control piston 10 is moved back to its closed valve position via the closing spring 18 supported on the upper piston 43 and the control chamber 2 is filled again via the Z-throttle 4. Since hardly force is demanded from the piezoelectric actuator 41, it can be made very small in diameter. Through the longitudinal bore 17 and transverse bores 46 in

Control piston 10 and through holes 47 of a common cylinder sleeve 48 flows with open control piston 10 the amount of fuel diverted from the control chamber 2 in the low-pressure chamber 7. The compact control valve 6 is an outwardly opening (A-valve), which opens in the direction of force of the piezoelectric actuator 41 and hydraulically translated controls the force balanced control piston 10, whereby the piezoelectric actuator 31 can be made very narrow.

From the injector of Fig. 3, the fuel injector 1 shown in Fig. 5 differs in that here the control piston 10 is opened directly by a piezoelectric actuator 41 and the valve seat 16 is formed as a flat seat. The piezoelectric actuator 41 is suspended in a housing 51 made of invar, which is fixed in the bore of the injector body 11. The piezoelectric actuator 41 is separated by a membrane 52 from the low-pressure chamber 7 and thus protected from fuel. In the closed valve position shown, the piezoelectric actuator 41 is not energized and thus shortened, whereby the control piston 10th are moved upwards in the closed valve position. If the piezoelectric actuator 41 is energized, it extends against the action of the tubular spring 45, whereby the control piston 10 is moved downward in the open valve position. If the piezoelectric actuator 41 is no longer energized, the control piston 10 is moved back into its closed valve position via the closing spring 18 and the control chamber 2 is filled again via the Z-throttle 4. This compact force-balanced control valve 6, which opens in the direction of force of the piezoelectric actuator 41, makes it possible to reduce the piezoactuator 41 in cross-section and stroke (20-30μm).

From the injector of Fig. 5, the fuel injector 1 shown in Fig. 6 differs in that here the control piston 10 is not opened directly from the piezoelectric actuator 41, but via the hydraulic booster 40 shown in Fig. 4.

Claims

claims

1. fuel injector (1) for internal combustion engines, with a high-pressure side (5) connected to the control chamber (2), via the pressure of 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) locks or opens, characterized in that the control valve (6) in a bore (9 a) of a guide piece (9) between two valve positions displaceably guided guided force-balanced Control piston (10) which blocks the connection of one of the control chamber (2) and opening into the bore (9a) connecting channel (13) to the low pressure side (7) in its closed valve position and in its in the direction of the nozzle needle (3) shifted open valve position releases.

2. Fuel injector according to claim 1, characterized in that the valve piece (9) within its bore (9a) has a valve seat (16) in the opening direction of the control piston (10) opening into the bore (9a) connecting channel (13 ) and at which the

Control piston (10) in its closed valve position is applied, wherein the valve seat (16) to the low pressure side (7) is connected.

3. Fuel injector according to claim 2, characterized in that the valve seat (16) via a longitudinal bore (17) of the control piston (10) to the

Low pressure side (7) is connected.

4. Fuel injector according to claim 1, characterized in that the valve piece (9) within its bore (9 a) has a valve seat (16), in the closing direction of the control piston (10) to the opening into the bore (9a) connecting channel (13) and adjoins the control piston (10) in its closed valve position, wherein the seat opening of the valve seat (16) to the low pressure side (7 ) connected.

5. Fuel injector according to one of the preceding claims, characterized in that the control piston (10) rests in its closed valve position on a valve seat (16) whose seat diameter (d) equal to the guide diameter (D) of the bore (9 a) of the guide piece (9 ).

6. Fuel injector according to one of the preceding claims, characterized in that the connecting channel (13) in an annular groove (14) of the control piston (10) or the guide piece (9) opens.

7. Fuel injector according to one of the preceding claims, characterized in that the control piston (10) by means of an armature (20) in the magnetic field of a magnetic coil (19) is displaceable.

8. Fuel injector according to claim 7, characterized in that the

Magnet coil (19) in the closing direction of the control piston (10) behind the armature (20) is arranged.

9. Fuel injector according to one of claims 1 to 6, characterized in that the control piston (10) by means of a piezoelectric actuator (41) and preferably a hydraulic translator (40) is displaceable.